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1 /* Optimize by combining instructions for GNU compiler.
2 Copyright (C) 1987-2018 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
9 version.
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
20 /* This module is essentially the "combiner" phase of the U. of Arizona
21 Portable Optimizer, but redone to work on our list-structured
22 representation for RTL instead of their string representation.
24 The LOG_LINKS of each insn identify the most recent assignment
25 to each REG used in the insn. It is a list of previous insns,
26 each of which contains a SET for a REG that is used in this insn
27 and not used or set in between. LOG_LINKs never cross basic blocks.
28 They were set up by the preceding pass (lifetime analysis).
30 We try to combine each pair of insns joined by a logical link.
31 We also try to combine triplets of insns A, B and C when C has
32 a link back to B and B has a link back to A. Likewise for a
33 small number of quadruplets of insns A, B, C and D for which
34 there's high likelihood of success.
36 LOG_LINKS does not have links for use of the CC0. They don't
37 need to, because the insn that sets the CC0 is always immediately
38 before the insn that tests it. So we always regard a branch
39 insn as having a logical link to the preceding insn. The same is true
40 for an insn explicitly using CC0.
42 We check (with modified_between_p) to avoid combining in such a way
43 as to move a computation to a place where its value would be different.
45 Combination is done by mathematically substituting the previous
46 insn(s) values for the regs they set into the expressions in
47 the later insns that refer to these regs. If the result is a valid insn
48 for our target machine, according to the machine description,
49 we install it, delete the earlier insns, and update the data flow
50 information (LOG_LINKS and REG_NOTES) for what we did.
52 There are a few exceptions where the dataflow information isn't
53 completely updated (however this is only a local issue since it is
54 regenerated before the next pass that uses it):
56 - reg_live_length is not updated
57 - reg_n_refs is not adjusted in the rare case when a register is
58 no longer required in a computation
59 - there are extremely rare cases (see distribute_notes) when a
60 REG_DEAD note is lost
61 - a LOG_LINKS entry that refers to an insn with multiple SETs may be
62 removed because there is no way to know which register it was
63 linking
65 To simplify substitution, we combine only when the earlier insn(s)
66 consist of only a single assignment. To simplify updating afterward,
67 we never combine when a subroutine call appears in the middle.
69 Since we do not represent assignments to CC0 explicitly except when that
70 is all an insn does, there is no LOG_LINKS entry in an insn that uses
71 the condition code for the insn that set the condition code.
72 Fortunately, these two insns must be consecutive.
73 Therefore, every JUMP_INSN is taken to have an implicit logical link
74 to the preceding insn. This is not quite right, since non-jumps can
75 also use the condition code; but in practice such insns would not
76 combine anyway. */
98 /* Include expr.h after insn-config.h so we get HAVE_conditional_move. */
108 /* Number of attempts to combine instructions in this function. */
112 /* Number of attempts that got as far as substitution in this function. */
116 /* Number of instructions combined with added SETs in this function. */
120 /* Number of instructions combined in this function. */
124 /* Totals over entire compilation. */
128 /* combine_instructions may try to replace the right hand side of the
129 second instruction with the value of an associated REG_EQUAL note
130 before throwing it at try_combine. That is problematic when there
131 is a REG_DEAD note for a register used in the old right hand side
132 and can cause distribute_notes to do wrong things. This is the
133 second instruction if it has been so modified, null otherwise. */
137 /* When I2MOD is nonnull, this is a copy of the old right hand side. */
141 /* When I2MOD is nonnull, this is a copy of the new right hand side. */
144 \f
146 /* Record last point of death of (hard or pseudo) register n. */
149 /* Record last point of modification of (hard or pseudo) register n. */
152 /* The next group of fields allows the recording of the last value assigned
153 to (hard or pseudo) register n. We use this information to see if an
154 operation being processed is redundant given a prior operation performed
155 on the register. For example, an `and' with a constant is redundant if
156 all the zero bits are already known to be turned off.
158 We use an approach similar to that used by cse, but change it in the
159 following ways:
161 (1) We do not want to reinitialize at each label.
162 (2) It is useful, but not critical, to know the actual value assigned
163 to a register. Often just its form is helpful.
165 Therefore, we maintain the following fields:
167 last_set_value the last value assigned
168 last_set_label records the value of label_tick when the
169 register was assigned
170 last_set_table_tick records the value of label_tick when a
171 value using the register is assigned
172 last_set_invalid set to nonzero when it is not valid
173 to use the value of this register in some
174 register's value
176 To understand the usage of these tables, it is important to understand
177 the distinction between the value in last_set_value being valid and
178 the register being validly contained in some other expression in the
179 table.
181 (The next two parameters are out of date).
183 reg_stat[i].last_set_value is valid if it is nonzero, and either
184 reg_n_sets[i] is 1 or reg_stat[i].last_set_label == label_tick.
186 Register I may validly appear in any expression returned for the value
187 of another register if reg_n_sets[i] is 1. It may also appear in the
188 value for register J if reg_stat[j].last_set_invalid is zero, or
189 reg_stat[i].last_set_label < reg_stat[j].last_set_label.
191 If an expression is found in the table containing a register which may
192 not validly appear in an expression, the register is replaced by
193 something that won't match, (clobber (const_int 0)). */
195 /* Record last value assigned to (hard or pseudo) register n. */
197 rtx last_set_value;
199 /* Record the value of label_tick when an expression involving register n
200 is placed in last_set_value. */
204 /* Record the value of label_tick when the value for register n is placed in
205 last_set_value. */
209 /* These fields are maintained in parallel with last_set_value and are
210 used to store the mode in which the register was last set, the bits
211 that were known to be zero when it was last set, and the number of
212 sign bits copies it was known to have when it was last set. */
218 /* Set nonzero if references to register n in expressions should not be
219 used. last_set_invalid is set nonzero when this register is being
220 assigned to and last_set_table_tick == label_tick. */
224 /* Some registers that are set more than once and used in more than one
225 basic block are nevertheless always set in similar ways. For example,
226 a QImode register may be loaded from memory in two places on a machine
227 where byte loads zero extend.
229 We record in the following fields if a register has some leading bits
230 that are always equal to the sign bit, and what we know about the
231 nonzero bits of a register, specifically which bits are known to be
232 zero.
234 If an entry is zero, it means that we don't know anything special. */
240 /* Record the value of the label_tick when the last truncation
241 happened. The field truncated_to_mode is only valid if
242 truncation_label == label_tick. */
246 /* Record the last truncation seen for this register. If truncation
247 is not a nop to this mode we might be able to save an explicit
248 truncation if we know that value already contains a truncated
249 value. */
252 };
257 /* One plus the highest pseudo for which we track REG_N_SETS.
258 regstat_init_n_sets_and_refs allocates the array for REG_N_SETS just once,
259 but during combine_split_insns new pseudos can be created. As we don't have
260 updated DF information in that case, it is hard to initialize the array
261 after growing. The combiner only cares about REG_N_SETS (regno) == 1,
262 so instead of growing the arrays, just assume all newly created pseudos
263 during combine might be set multiple times. */
267 /* Record the luid of the last insn that invalidated memory
268 (anything that writes memory, and subroutine calls, but not pushes). */
272 /* Record the luid of the last CALL_INSN
273 so we can tell whether a potential combination crosses any calls. */
277 /* When `subst' is called, this is the insn that is being modified
278 (by combining in a previous insn). The PATTERN of this insn
279 is still the old pattern partially modified and it should not be
280 looked at, but this may be used to examine the successors of the insn
281 to judge whether a simplification is valid. */
285 /* This is the lowest LUID that `subst' is currently dealing with.
286 get_last_value will not return a value if the register was set at or
287 after this LUID. If not for this mechanism, we could get confused if
288 I2 or I1 in try_combine were an insn that used the old value of a register
289 to obtain a new value. In that case, we might erroneously get the
290 new value of the register when we wanted the old one. */
294 /* This contains any hard registers that are used in newpat; reg_dead_at_p
295 must consider all these registers to be always live. */
299 /* This is an insn to which a LOG_LINKS entry has been added. If this
300 insn is the earlier than I2 or I3, combine should rescan starting at
301 that location. */
305 /* And similarly, for notes. */
309 /* Basic block in which we are performing combines. */
313 \f
314 /* Length of the currently allocated uid_insn_cost array. */
318 /* The following array records the insn_cost for every insn
319 in the instruction stream. */
323 /* The following array records the LOG_LINKS for every insn in the
324 instruction stream as struct insn_link pointers. */
330 };
336 {
340 }
342 #define INSN_COST(INSN) (uid_insn_cost[insn_uid_check (INSN)])
343 #define LOG_LINKS(INSN) (uid_log_links[insn_uid_check (INSN)])
345 #define FOR_EACH_LOG_LINK(L, INSN) \
346 for ((L) = LOG_LINKS (INSN); (L); (L) = (L)->next)
348 /* Links for LOG_LINKS are allocated from this obstack. */
352 /* Allocate a link. */
356 {
364 }
366 /* Incremented for each basic block. */
370 /* Reset to label_tick for each extended basic block in scanning order. */
374 /* Mode used to compute significance in reg_stat[].nonzero_bits. It is the
375 largest integer mode that can fit in HOST_BITS_PER_WIDE_INT. */
379 /* Nonzero when reg_stat[].nonzero_bits and reg_stat[].sign_bit_copies can
380 be safely used. It is zero while computing them and after combine has
381 completed. This former test prevents propagating values based on
382 previously set values, which can be incorrect if a variable is modified
383 in a loop. */
387 \f
388 /* Record one modification to rtl structure
389 to be undone by storing old_contents into *where. */
393 struct undo
394 {
399 };
401 /* Record a bunch of changes to be undone, up to MAX_UNDO of them.
402 num_undo says how many are currently recorded.
404 other_insn is nonzero if we have modified some other insn in the process
405 of working on subst_insn. It must be verified too. */
407 struct undobuf
408 {
412 };
416 /* Number of times the pseudo being substituted for
417 was found and replaced. */
422 scalar_int_mode,
425 scalar_int_mode,
497 \f
499 /* It is not safe to use ordinary gen_lowpart in combine.
500 See comments in gen_lowpart_for_combine. */
501 #undef RTL_HOOKS_GEN_LOWPART
502 #define RTL_HOOKS_GEN_LOWPART gen_lowpart_for_combine
504 /* Our implementation of gen_lowpart never emits a new pseudo. */
505 #undef RTL_HOOKS_GEN_LOWPART_NO_EMIT
506 #define RTL_HOOKS_GEN_LOWPART_NO_EMIT gen_lowpart_for_combine
508 #undef RTL_HOOKS_REG_NONZERO_REG_BITS
509 #define RTL_HOOKS_REG_NONZERO_REG_BITS reg_nonzero_bits_for_combine
511 #undef RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES
512 #define RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES reg_num_sign_bit_copies_for_combine
514 #undef RTL_HOOKS_REG_TRUNCATED_TO_MODE
515 #define RTL_HOOKS_REG_TRUNCATED_TO_MODE reg_truncated_to_mode
519 \f
520 /* Convenience wrapper for the canonicalize_comparison target hook.
521 Target hooks cannot use enum rtx_code. */
525 {
529 }
531 /* Try to split PATTERN found in INSN. This returns NULL_RTX if
532 PATTERN can not be split. Otherwise, it returns an insn sequence.
533 This is a wrapper around split_insns which ensures that the
534 reg_stat vector is made larger if the splitter creates a new
535 register. */
539 {
548 }
550 /* This is used by find_single_use to locate an rtx in LOC that
551 contains exactly one use of DEST, which is typically either a REG
552 or CC0. It returns a pointer to the innermost rtx expression
553 containing DEST. Appearances of DEST that are being used to
554 totally replace it are not counted. */
558 {
567 {
571 CASE_CONST_ANY:
577 /* If the destination is anything other than CC0, PC, a REG or a SUBREG
578 of a REG that occupies all of the REG, the insn uses DEST if
579 it is mentioned in the destination or the source. Otherwise, we
580 need just check the source. */
597 }
599 /* If it wasn't one of the common cases above, check each expression and
600 vector of this code. Look for a unique usage of DEST. */
604 {
606 {
611 else
617 /* Duplicate usage. */
619 }
621 {
625 {
631 else
638 }
639 }
640 }
643 }
646 /* See if DEST, produced in INSN, is used only a single time in the
647 sequel. If so, return a pointer to the innermost rtx expression in which
648 it is used.
650 If PLOC is nonzero, *PLOC is set to the insn containing the single use.
652 If DEST is cc0_rtx, we look only at the next insn. In that case, we don't
653 care about REG_DEAD notes or LOG_LINKS.
655 Otherwise, we find the single use by finding an insn that has a
656 LOG_LINKS pointing at INSN and has a REG_DEAD note for DEST. If DEST is
657 only referenced once in that insn, we know that it must be the first
658 and last insn referencing DEST. */
662 {
663 basic_block bb;
669 {
679 }
689 {
695 {
700 }
701 }
704 }
705 \f
706 /* Substitute NEWVAL, an rtx expression, into INTO, a place in some
707 insn. The substitution can be undone by undo_all. If INTO is already
708 set to NEWVAL, do not record this change. Because computing NEWVAL might
709 also call SUBST, we have to compute it before we put anything into
710 the undo table. */
712 static void
714 {
721 /* We'd like to catch as many invalid transformations here as
722 possible. Unfortunately, there are way too many mode changes
723 that are perfectly valid, so we'd waste too much effort for
724 little gain doing the checks here. Focus on catching invalid
725 transformations involving integer constants. */
728 {
729 /* Sanity check that we're replacing oldval with a CONST_INT
730 that is a valid sign-extension for the original mode. */
734 /* Replacing the operand of a SUBREG or a ZERO_EXTEND with a
735 CONST_INT is not valid, because after the replacement, the
736 original mode would be gone. Unfortunately, we can't tell
737 when do_SUBST is called to replace the operand thereof, so we
738 perform this test on oldval instead, checking whether an
739 invalid replacement took place before we got here. */
744 }
748 else
757 }
759 #define SUBST(INTO, NEWVAL) do_SUBST (&(INTO), (NEWVAL))
761 /* Similar to SUBST, but NEWVAL is an int expression. Note that substitution
762 for the value of a HOST_WIDE_INT value (including CONST_INT) is
763 not safe. */
765 static void
767 {
776 else
785 }
787 #define SUBST_INT(INTO, NEWVAL) do_SUBST_INT (&(INTO), (NEWVAL))
789 /* Similar to SUBST, but just substitute the mode. This is used when
790 changing the mode of a pseudo-register, so that any other
791 references to the entry in the regno_reg_rtx array will change as
792 well. */
794 static void
796 {
805 else
814 }
816 #define SUBST_MODE(INTO, NEWVAL) do_SUBST_MODE (&(INTO), (NEWVAL))
818 /* Similar to SUBST, but NEWVAL is a LOG_LINKS expression. */
820 static void
822 {
831 else
840 }
842 #define SUBST_LINK(oldval, newval) do_SUBST_LINK (&oldval, newval)
843 \f
844 /* Subroutine of try_combine. Determine whether the replacement patterns
845 NEWPAT, NEWI2PAT and NEWOTHERPAT are cheaper according to insn_cost
846 than the original sequence I0, I1, I2, I3 and undobuf.other_insn. Note
847 that I0, I1 and/or NEWI2PAT may be NULL_RTX. Similarly, NEWOTHERPAT and
848 undobuf.other_insn may also both be NULL_RTX. Return false if the cost
849 of all the instructions can be estimated and the replacements are more
850 expensive than the original sequence. */
852 static bool
855 {
860 /* Lookup the original insn_costs. */
865 {
868 {
872 }
873 else
874 {
878 }
879 }
880 else
881 {
884 }
886 /* If we have split a PARALLEL I2 to I1,I2, we have counted its cost twice;
887 correct that. */
892 /* Calculate the replacement insn_costs. */
901 {
911 }
912 else
913 {
916 }
919 {
928 optimize_this_for_speed_p);
932 {
935 }
936 else
938 }
940 /* Disallow this combination if both new_cost and old_cost are greater than
941 zero, and new_cost is greater than old cost. */
945 {
964 else
966 }
971 /* Update the uid_insn_cost array with the replacement costs. */
975 {
979 }
982 }
985 /* Delete any insns that copy a register to itself. */
987 static void
989 {
991 basic_block bb;
994 {
996 {
999 {
1004 }
1005 }
1006 }
1007 }
1009 \f
1010 /* Return false if we do not want to (or cannot) combine DEF. */
1011 static bool
1013 {
1014 /* Do not consider if it is pre/post modification in MEM. */
1020 /* Do not combine frame pointer adjustments. */
1023 || (!HARD_FRAME_POINTER_IS_FRAME_POINTER
1031 }
1033 /* Return false if we do not want to (or cannot) combine USE. */
1034 static bool
1036 {
1037 /* Do not consider the usage of the stack pointer by function call. */
1042 }
1044 /* Fill in log links field for all insns. */
1046 static void
1048 {
1049 basic_block bb;
1056 /* Pass through each block from the end, recording the uses of each
1057 register and establishing log links when def is encountered.
1058 Note that we do not clear next_use array in order to save time,
1059 so we have to test whether the use is in the same basic block as def.
1061 There are a few cases below when we do not consider the definition or
1062 usage -- these are taken from original flow.c did. Don't ask me why it is
1063 done this way; I don't know and if it works, I don't want to know. */
1066 {
1068 {
1072 /* Log links are created only once. */
1076 {
1092 /* flow.c claimed:
1094 We don't build a LOG_LINK for hard registers contained
1095 in ASM_OPERANDs. If these registers get replaced,
1096 we might wind up changing the semantics of the insn,
1097 even if reload can make what appear to be valid
1098 assignments later. */
1103 /* Don't add duplicate links between instructions. */
1112 }
1117 }
1118 }
1121 }
1123 /* Walk the LOG_LINKS of insn B to see if we find a reference to A. Return
1124 true if we found a LOG_LINK that proves that A feeds B. This only works
1125 if there are no instructions between A and B which could have a link
1126 depending on A, since in that case we would not record a link for B.
1127 We also check the implicit dependency created by a cc0 setter/user
1128 pair. */
1130 static bool
1132 {
1140 }
1141 \f
1142 /* Main entry point for combiner. F is the first insn of the function.
1143 NREGS is the first unused pseudo-reg number.
1145 Return nonzero if the combiner has turned an indirect jump
1146 instruction into a direct jump. */
1147 static int
1149 {
1154 basic_block last_bb;
1174 /* Allocate array for insn info. */
1182 /* Don't use reg_stat[].nonzero_bits when computing it. This can cause
1183 problems when, for example, we have j <<= 1 in a loop. */
1188 /* Scan all SETs and see if we can deduce anything about what
1189 bits are known to be zero for some registers and how many copies
1190 of the sign bit are known to exist for those registers.
1192 Also set any known values so that we can use it while searching
1193 for what bits are known to be set. */
1196 /* Allow the entry block and the first block to fall into the same EBB.
1197 Conceptually the incoming promotions are assigned to the entry block. */
1202 {
1207 label_tick++;
1215 {
1216 rtx links;
1222 insn);
1229 insn);
1231 /* Record the current insn_cost of this instruction. */
1235 {
1238 }
1239 }
1240 }
1244 /* Now scan all the insns in forward order. */
1252 {
1255 /* Ignore instruction combination in basic blocks that are going to
1256 be removed as unreachable anyway. See PR82386. */
1264 label_tick++;
1274 {
1288 /* See if we know about function return values before this
1289 insn based upon SUBREG flags. */
1292 /* See if we can find hardregs and subreg of pseudos in
1293 narrower modes. This could help turning TRUNCATEs
1294 into SUBREGs. */
1297 /* Try this insn with each insn it links back to. */
1303 {
1306 }
1308 /* Try each sequence of three linked insns ending with this one. */
1312 {
1315 /* If the linked insn has been replaced by a note, then there
1316 is no point in pursuing this chain any further. */
1324 {
1327 }
1328 }
1330 /* Try to combine a jump insn that uses CC0
1331 with a preceding insn that sets CC0, and maybe with its
1332 logical predecessor as well.
1333 This is how we make decrement-and-branch insns.
1334 We need this special code because data flow connections
1335 via CC0 do not get entered in LOG_LINKS. */
1342 {
1353 }
1355 /* Do the same for an insn that explicitly references CC0. */
1362 {
1373 }
1375 /* Finally, see if any of the insns that this insn links to
1376 explicitly references CC0. If so, try this insn, that insn,
1377 and its predecessor if it sets CC0. */
1379 {
1391 }
1393 /* Try combining an insn with two different insns whose results it
1394 uses. */
1404 {
1407 }
1409 /* Try four-instruction combinations. */
1412 {
1416 /* If the linked insn has been replaced by a note, then there
1417 is no point in pursuing this chain any further. */
1422 {
1426 /* I0 -> I1 -> I2 -> I3. */
1432 {
1435 }
1436 /* I0, I1 -> I2, I2 -> I3. */
1443 {
1446 }
1447 }
1450 {
1454 /* I0 -> I2; I1, I2 -> I3. */
1460 {
1463 }
1464 /* I0 -> I1; I1, I2 -> I3. */
1470 {
1473 }
1474 }
1475 }
1477 /* Try this insn with each REG_EQUAL note it links back to. */
1479 {
1485 /* Avoid using a register that may already been marked
1486 dead by an earlier instruction. */
1494 {
1495 /* Temporarily replace the set's source with the
1496 contents of the REG_EQUAL note. The insn will
1497 be deleted or recognized by try_combine. */
1508 last_combined_insn);
1511 {
1514 }
1517 }
1518 }
1523 retry:
1524 ;
1525 }
1526 }
1533 /* Clean up. */
1539 {
1542 {
1545 }
1547 }
1557 /* Make recognizer allow volatile MEMs again. */
1561 }
1563 /* Wipe the last_xxx fields of reg_stat in preparation for another pass. */
1565 static void
1567 {
1573 }
1574 \f
1575 /* Set up any promoted values for incoming argument registers. */
1577 static void
1579 {
1580 tree arg;
1585 {
1590 /* Only continue if the incoming argument is in a register. */
1594 /* Determine, if possible, whether all call sites of the current
1595 function lie within the current compilation unit. (This does
1596 take into account the exporting of a function via taking its
1597 address, and so forth.) */
1600 /* The mode and signedness of the argument before any promotions happen
1601 (equal to the mode of the pseudo holding it at that stage). */
1605 /* The mode and signedness of the argument after any source language and
1606 TARGET_PROMOTE_PROTOTYPES-driven promotions. */
1610 /* The mode and signedness of the argument as it is actually passed,
1611 see assign_parm_setup_reg in function.c. */
1615 /* The mode of the register in which the argument is being passed. */
1618 /* Eliminate sign extensions in the callee when:
1619 (a) A mode promotion has occurred; */
1622 /* (b) The mode of the register is the same as the mode of
1623 the argument as it is passed; */
1626 /* (c) There's no language level extension; */
1628 ;
1629 /* (c.1) All callers are from the current compilation unit. If that's
1630 the case we don't have to rely on an ABI, we only have to know
1631 what we're generating right now, and we know that we will do the
1632 mode1 to mode2 promotion with the given sign. */
1635 /* (c.2) The combination of the two promotions is useful. This is
1636 true when the signs match, or if the first promotion is unsigned.
1637 In the later case, (sign_extend (zero_extend x)) is the same as
1638 (zero_extend (zero_extend x)), so make sure to force UNS3 true. */
1644 /* Record that the value was promoted from mode1 to mode3,
1645 so that any sign extension at the head of the current
1646 function may be eliminated. */
1650 }
1651 }
1653 /* If MODE has a precision lower than PREC and SRC is a non-negative constant
1654 that would appear negative in MODE, sign-extend SRC for use in nonzero_bits
1655 because some machines (maybe most) will actually do the sign-extension and
1656 this is the conservative approach.
1658 ??? For 2.5, try to tighten up the MD files in this regard instead of this
1659 kludge. */
1661 static rtx
1663 {
1664 scalar_int_mode int_mode;
1673 }
1675 /* Update RSP for pseudo-register X from INSN's REG_EQUAL note (if one exists)
1676 and SET. */
1678 static void
1680 rtx x)
1681 {
1691 {
1695 }
1697 /* Don't call nonzero_bits if it cannot change anything. */
1699 {
1704 }
1706 /* Don't call num_sign_bit_copies if it cannot change anything. */
1708 {
1711 {
1715 }
1718 }
1719 }
1721 /* Called via note_stores. If X is a pseudo that is narrower than
1722 HOST_BITS_PER_WIDE_INT and is being set, record what bits are known zero.
1724 If we are setting only a portion of X and we can't figure out what
1725 portion, assume all bits will be used since we don't know what will
1726 be happening.
1728 Similarly, set how many bits of X are known to be copies of the sign bit
1729 at all locations in the function. This is the smallest number implied
1730 by any set of X. */
1732 static void
1734 {
1736 scalar_int_mode mode;
1740 /* If this register is undefined at the start of the file, we can't
1741 say what its contents were. */
1742 && ! REGNO_REG_SET_P
1746 {
1750 {
1754 }
1756 /* Should not happen as we only using pseduo registers. */
1759 /* If this register is being initialized using itself, and the
1760 register is uninitialized in this basic block, and there are
1761 no LOG_LINKS which set the register, then part of the
1762 register is uninitialized. In that case we can't assume
1763 anything about the number of nonzero bits.
1765 ??? We could do better if we checked this in
1766 reg_{nonzero_bits,num_sign_bit_copies}_for_combine. Then we
1767 could avoid making assumptions about the insn which initially
1768 sets the register, while still using the information in other
1769 insns. We would have to be careful to check every insn
1770 involved in the combination. */
1776 {
1783 {
1787 }
1788 }
1790 /* If this is a complex assignment, see if we can convert it into a
1791 simple assignment. */
1794 /* If this is a simple assignment, or we have a paradoxical SUBREG,
1795 set what we know about X. */
1801 else
1802 {
1805 }
1806 }
1807 }
1808 \f
1809 /* See if INSN can be combined into I3. PRED, PRED2, SUCC and SUCC2 are
1810 optionally insns that were previously combined into I3 or that will be
1811 combined into the merger of INSN and I3. The order is PRED, PRED2,
1812 INSN, SUCC, SUCC2, I3.
1814 Return 0 if the combination is not allowed for any reason.
1816 If the combination is allowed, *PDEST will be set to the single
1817 destination of INSN and *PSRC to the single source, and this function
1818 will return 1. */
1820 static int
1824 {
1829 rtx link;
1834 {
1836 {
1841 }
1846 }
1850 /* Can combine only if previous insn is a SET of a REG, a SUBREG or CC0.
1851 or a PARALLEL consisting of such a SET and CLOBBERs.
1853 If INSN has CLOBBER parallel parts, ignore them for our processing.
1854 By definition, these happen during the execution of the insn. When it
1855 is merged with another insn, all bets are off. If they are, in fact,
1856 needed and aren't also supplied in I3, they may be added by
1857 recog_for_combine. Otherwise, it won't match.
1859 We can also ignore a SET whose SET_DEST is mentioned in a REG_UNUSED
1860 note.
1862 Get the source and destination of INSN. If more than one, can't
1863 combine. */
1869 {
1871 {
1875 {
1876 /* This is important to combine floating point insns
1877 for the SH4 port. */
1879 /* Combining an isolated USE doesn't make sense.
1880 We depend here on combinable_i3pat to reject them. */
1881 /* The code below this loop only verifies that the inputs of
1882 the SET in INSN do not change. We call reg_set_between_p
1883 to verify that the REG in the USE does not change between
1884 I3 and INSN.
1885 If the USE in INSN was for a pseudo register, the matching
1886 insn pattern will likely match any register; combining this
1887 with any other USE would only be safe if we knew that the
1888 used registers have identical values, or if there was
1889 something to tell them apart, e.g. different modes. For
1890 now, we forgo such complicated tests and simply disallow
1891 combining of USES of pseudo registers with any other USE. */
1894 {
1899 do
1900 {
1910 }
1912 }
1915 /* We can ignore CLOBBERs. */
1921 /* Ignore SETs whose result isn't used but not those that
1922 have side-effects. */
1928 /* If we have already found a SET, this is a second one and
1929 so we cannot combine with this insn. */
1937 /* Anything else means we can't combine. */
1939 }
1940 }
1943 /* If SET_SRC is an ASM_OPERANDS we can't throw away these CLOBBERs,
1944 so don't do anything with it. */
1947 }
1948 else
1954 /* The simplification in expand_field_assignment may call back to
1955 get_last_value, so set safe guard here. */
1961 /* Do not eliminate user-specified register if it is in an
1962 asm input because we may break the register asm usage defined
1963 in GCC manual if allow to do so.
1964 Be aware that this may cover more cases than we expect but this
1965 should be harmless. */
1970 /* Don't eliminate a store in the stack pointer. */
1972 /* Don't combine with an insn that sets a register to itself if it has
1973 a REG_EQUAL note. This may be part of a LIBCALL sequence. */
1975 /* Can't merge an ASM_OPERANDS. */
1977 /* Can't merge a function call. */
1979 /* Don't eliminate a function call argument. */
1985 /* Don't substitute into an incremented register. */
1989 /* Don't substitute into a non-local goto, this confuses CFG. */
1991 /* Make sure that DEST is not used after INSN but before SUCC, or
1992 after SUCC and before SUCC2, or after SUCC2 but before I3. */
1993 || (!all_adjacent
1994 && ((succ2
1999 || (succ
2000 /* SUCC and SUCC2 can be split halves from a PARALLEL; in
2001 that case SUCC is not in the insn stream, so use SUCC2
2002 instead for this test. */
2004 succ2
2007 /* Make sure that the value that is to be substituted for the register
2008 does not use any registers whose values alter in between. However,
2009 If the insns are adjacent, a use can't cross a set even though we
2010 think it might (this can happen for a sequence of insns each setting
2011 the same destination; last_set of that register might point to
2012 a NOTE). If INSN has a REG_EQUIV note, the register is always
2013 equivalent to the memory so the substitution is valid even if there
2014 are intervening stores. Also, don't move a volatile asm or
2015 UNSPEC_VOLATILE across any other insns. */
2016 || (! all_adjacent
2022 /* Don't combine across a CALL_INSN, because that would possibly
2023 change whether the life span of some REGs crosses calls or not,
2024 and it is a pain to update that information.
2025 Exception: if source is a constant, moving it later can't hurt.
2026 Accept that as a special case. */
2030 /* DEST must either be a REG or CC0. */
2032 {
2033 /* If register alignment is being enforced for multi-word items in all
2034 cases except for parameters, it is possible to have a register copy
2035 insn referencing a hard register that is not allowed to contain the
2036 mode being copied and which would not be valid as an operand of most
2037 insns. Eliminate this problem by not combining with such an insn.
2039 Also, on some machines we don't want to extend the life of a hard
2040 register. */
2045 /* Don't extend the life of a hard register unless it is
2046 user variable (if we have few registers) or it can't
2047 fit into the desired register (meaning something special
2048 is going on).
2049 Also avoid substituting a return register into I3, because
2050 reload can't handle a conflict with constraints of other
2051 inputs. */
2056 }
2064 {
2067 /* If the clobber represents an earlyclobber operand, we must not
2068 substitute an expression containing the clobbered register.
2069 As we do not analyze the constraint strings here, we have to
2070 make the conservative assumption. However, if the register is
2071 a fixed hard reg, the clobber cannot represent any operand;
2072 we leave it up to the machine description to either accept or
2073 reject use-and-clobber patterns. */
2079 }
2081 /* If INSN contains anything volatile, or is an `asm' (whether volatile
2082 or not), reject, unless nothing volatile comes between it and I3 */
2085 {
2086 /* Make sure neither succ nor succ2 contains a volatile reference. */
2091 /* We'll check insns between INSN and I3 below. */
2092 }
2094 /* If INSN is an asm, and DEST is a hard register, reject, since it has
2095 to be an explicit register variable, and was chosen for a reason. */
2101 /* If INSN contains volatile references (specifically volatile MEMs),
2102 we cannot combine across any other volatile references.
2103 Even if INSN doesn't contain volatile references, any intervening
2104 volatile insn might affect machine state. */
2107 ? volatile_refs_p
2114 /* If INSN contains an autoincrement or autodecrement, make sure that
2115 register is not used between there and I3, and not already used in
2116 I3 either. Neither must it be used in PRED or SUCC, if they exist.
2117 Also insist that I3 not be a jump; if it were one
2118 and the incremented register were spilled, we would lose. */
2136 /* Don't combine an insn that follows a CC0-setting insn.
2137 An insn that uses CC0 must not be separated from the one that sets it.
2138 We do, however, allow I2 to follow a CC0-setting insn if that insn
2139 is passed as I1; in that case it will be deleted also.
2140 We also allow combining in this case if all the insns are adjacent
2141 because that would leave the two CC0 insns adjacent as well.
2142 It would be more logical to test whether CC0 occurs inside I1 or I2,
2143 but that would be much slower, and this ought to be equivalent. */
2146 {
2151 }
2153 /* If we get here, we have passed all the tests and the combination is
2154 to be allowed. */
2160 }
2161 \f
2162 /* LOC is the location within I3 that contains its pattern or the component
2163 of a PARALLEL of the pattern. We validate that it is valid for combining.
2165 One problem is if I3 modifies its output, as opposed to replacing it
2166 entirely, we can't allow the output to contain I2DEST, I1DEST or I0DEST as
2167 doing so would produce an insn that is not equivalent to the original insns.
2169 Consider:
2171 (set (reg:DI 101) (reg:DI 100))
2172 (set (subreg:SI (reg:DI 101) 0) <foo>)
2174 This is NOT equivalent to:
2176 (parallel [(set (subreg:SI (reg:DI 100) 0) <foo>)
2177 (set (reg:DI 101) (reg:DI 100))])
2179 Not only does this modify 100 (in which case it might still be valid
2180 if 100 were dead in I2), it sets 101 to the ORIGINAL value of 100.
2182 We can also run into a problem if I2 sets a register that I1
2183 uses and I1 gets directly substituted into I3 (not via I2). In that
2184 case, we would be getting the wrong value of I2DEST into I3, so we
2185 must reject the combination. This case occurs when I2 and I1 both
2186 feed into I3, rather than when I1 feeds into I2, which feeds into I3.
2187 If I1_NOT_IN_SRC is nonzero, it means that finding I1 in the source
2188 of a SET must prevent combination from occurring. The same situation
2189 can occur for I0, in which case I0_NOT_IN_SRC is set.
2191 Before doing the above check, we first try to expand a field assignment
2192 into a set of logical operations.
2194 If PI3_DEST_KILLED is nonzero, it is a pointer to a location in which
2195 we place a register that is both set and used within I3. If more than one
2196 such register is detected, we fail.
2198 Return 1 if the combination is valid, zero otherwise. */
2200 static int
2203 {
2207 {
2212 rtx subdest;
2219 /* Check for the case where I3 modifies its output, as discussed
2220 above. We don't want to prevent pseudos from being combined
2221 into the address of a MEM, so only prevent the combination if
2222 i1 or i2 set the same MEM. */
2232 /* This is the same test done in can_combine_p except we can't test
2233 all_adjacent; we don't have to, since this instruction will stay
2234 in place, thus we are not considering increasing the lifetime of
2235 INNER_DEST.
2237 Also, if this insn sets a function argument, combining it with
2238 something that might need a spill could clobber a previous
2239 function argument; the all_adjacent test in can_combine_p also
2240 checks this; here, we do a more specific test for this case. */
2250 /* If DEST is used in I3, it is being killed in this insn, so
2251 record that for later. We have to consider paradoxical
2252 subregs here, since they kill the whole register, but we
2253 ignore partial subregs, STRICT_LOW_PART, etc.
2254 Never add REG_DEAD notes for the FRAME_POINTER_REGNUM or the
2255 STACK_POINTER_REGNUM, since these are always considered to be
2256 live. Similarly for ARG_POINTER_REGNUM if it is fixed. */
2264 && (HARD_FRAME_POINTER_IS_FRAME_POINTER
2270 {
2275 }
2276 }
2279 {
2286 }
2289 }
2290 \f
2291 /* Return 1 if X is an arithmetic expression that contains a multiplication
2292 and division. We don't count multiplications by powers of two here. */
2294 static int
2296 {
2298 {
2314 }
2315 }
2316 \f
2317 /* Determine whether INSN can be used in a combination. Return nonzero if
2318 not. This is used in try_combine to detect early some cases where we
2319 can't perform combinations. */
2321 static int
2323 {
2324 rtx set;
2327 /* If this isn't really an insn, we can't do anything.
2328 This can occur when flow deletes an insn that it has merged into an
2329 auto-increment address. */
2333 /* Never combine loads and stores involving hard regs that are likely
2334 to be spilled. The register allocator can usually handle such
2335 reg-reg moves by tying. If we allow the combiner to make
2336 substitutions of likely-spilled regs, reload might die.
2337 As an exception, we allow combinations involving fixed regs; these are
2338 not available to the register allocator so there's no risk involved. */
2359 }
2361 struct likely_spilled_retval_info
2362 {
2365 };
2367 /* Called via note_stores by likely_spilled_retval_p. Remove from info->mask
2368 hard registers that are known to be written to / clobbered in full. */
2369 static void
2371 {
2388 else
2391 }
2393 /* Return nonzero iff part of the return value is live during INSN, and
2394 it is likely spilled. This can happen when more than one insn is needed
2395 to copy the return value, e.g. when we consider to combine into the
2396 second copy insn for a complex value. */
2398 static int
2400 {
2402 rtx reg;
2405 /* We assume here that no machine mode needs more than
2406 32 hard registers when the value overlaps with a register
2407 for which TARGET_FUNCTION_VALUE_REGNO_P is true. */
2422 /* Disregard parts of the return value that are set later. */
2431 /* Check if any of the (probably) live return value registers is
2432 likely spilled. */
2433 nregs --;
2434 do
2435 {
2441 }
2443 /* Adjust INSN after we made a change to its destination.
2445 Changing the destination can invalidate notes that say something about
2446 the results of the insn and a LOG_LINK pointing to the insn. */
2448 static void
2450 {
2451 /* For notes, be conservative and simply remove them. */
2454 /* The new insn will have a destination that was previously the destination
2455 of an insn just above it. Call distribute_links to make a LOG_LINK from
2456 the next use of that destination. */
2472 }
2474 /* Return TRUE if combine can reuse reg X in mode MODE.
2475 ADDED_SETS is nonzero if the original set is still required. */
2476 static bool
2478 {
2484 /* Don't change between modes with different underlying register sizes,
2485 since this could lead to invalid subregs. */
2491 /* Allow hard registers if the new mode is legal, and occupies no more
2492 registers than the old mode. */
2497 /* Or a pseudo that is only used once. */
2500 && !added_sets
2502 }
2505 /* Check whether X, the destination of a set, refers to part of
2506 the register specified by REG. */
2508 static bool
2510 {
2511 /* Check that reg is an integer mode register. */
2522 }
2524 /* Delete the unconditional jump INSN and adjust the CFG correspondingly.
2525 Note that the INSN should be deleted *after* removing dead edges, so
2526 that the kept edge is the fallthrough edge for a (set (pc) (pc))
2527 but not for a (set (pc) (label_ref FOO)). */
2529 static void
2531 {
2539 {
2544 /* Remove barriers from the footer if there are any. */
2547 {
2550 else
2554 }
2557 }
2558 }
2560 /* Return whether PAT is a PARALLEL of exactly N register SETs followed
2561 by an arbitrary number of CLOBBERs. */
2562 static bool
2564 {
2579 {
2588 }
2590 }
2592 /* Return whether INSN, a PARALLEL of N register SETs (and maybe some
2593 CLOBBERs), can be split into individual SETs in that order, without
2594 changing semantics. */
2595 static bool
2597 {
2605 {
2614 }
2617 }
2619 /* Return whether X is just a single set, with the source
2620 a general_operand. */
2621 static bool
2623 {
2628 }
2630 /* Try to combine the insns I0, I1 and I2 into I3.
2631 Here I0, I1 and I2 appear earlier than I3.
2632 I0 and I1 can be zero; then we combine just I2 into I3, or I1 and I2 into
2633 I3.
2635 If we are combining more than two insns and the resulting insn is not
2636 recognized, try splitting it into two insns. If that happens, I2 and I3
2637 are retained and I1/I0 are pseudo-deleted by turning them into a NOTE.
2638 Otherwise, I0, I1 and I2 are pseudo-deleted.
2640 Return 0 if the combination does not work. Then nothing is changed.
2641 If we did the combination, return the insn at which combine should
2642 resume scanning.
2644 Set NEW_DIRECT_JUMP_P to a nonzero value if try_combine creates a
2645 new direct jump instruction.
2647 LAST_COMBINED_INSN is either I3, or some insn after I3 that has
2648 been I3 passed to an earlier try_combine within the same basic
2649 block. */
2654 {
2655 /* New patterns for I3 and I2, respectively. */
2659 /* Indicates need to preserve SET in I0, I1 or I2 in I3 if it is not
2660 dead. */
2662 /* Total number of SETs to put into I3. */
2664 /* Nonzero if I2's or I1's body now appears in I3. */
2666 /* INSN_CODEs for new I3, new I2, and user of condition code. */
2668 /* Contains I3 if the destination of I3 is used in its source, which means
2669 that the old life of I3 is being killed. If that usage is placed into
2670 I2 and not in I3, a REG_DEAD note must be made. */
2672 /* SET_DEST and SET_SRC of I2, I1 and I0. */
2674 /* Copy of SET_SRC of I1 and I0, if needed. */
2676 /* Set if I2DEST was reused as a scratch register. */
2678 /* The PATTERNs of I0, I1, and I2, or a copy of them in certain cases. */
2680 /* Indicates if I2DEST or I1DEST is in I2SRC or I1_SRC. */
2685 /* Notes that must be added to REG_NOTES in I3 and I2. */
2687 /* Notes that we substituted I3 into I2 instead of the normal case. */
2689 /* Notes that I1, I2 or I3 is a MULT operation. */
2698 rtx temp_expr;
2701 rtx new_other_notes;
2705 /* Immediately return if any of I0,I1,I2 are the same insn (I3 can
2706 never be). */
2710 /* Only try four-insn combinations when there's high likelihood of
2711 success. Look for simple insns, such as loads of constants or
2712 binary operations involving a constant. */
2714 {
2724 {
2727 rtx src;
2732 {
2735 }
2737 ngood++;
2740 nshift++;
2741 }
2743 /* If I0 loads a memory and I3 sets the same memory, then I1 and I2
2744 are likely manipulating its value. Ideally we'll be able to combine
2745 all four insns into a bitfield insertion of some kind.
2747 Note the source in I0 might be inside a sign/zero extension and the
2748 memory modes in I0 and I3 might be different. So extract the address
2749 from the destination of I3 and search for it in the source of I0.
2751 In the event that there's a match but the source/dest do not actually
2752 refer to the same memory, the worst that happens is we try some
2753 combinations that we wouldn't have otherwise. */
2755 /* Ensure the source of SET0 is a MEM, possibly buried inside
2756 an extension. */
2762 /* Ensure the destination of SET3 is a MEM. */
2764 /* Would it be better to extract the base address for the MEM
2765 in SET3 and look for that? I don't have cases where it matters
2766 but I could envision such cases. */
2772 }
2774 /* Exit early if one of the insns involved can't be used for
2775 combinations. */
2786 combine_attempts++;
2789 /* Reset the hard register usage information. */
2793 {
2800 else
2810 }
2812 /* If multiple insns feed into one of I2 or I3, they can be in any
2813 order. To simplify the code below, reorder them in sequence. */
2824 /* First check for one important special case that the code below will
2825 not handle. Namely, the case where I1 is zero, I2 is a PARALLEL
2826 and I3 is a SET whose SET_SRC is a SET_DEST in I2. In that case,
2827 we may be able to replace that destination with the destination of I3.
2828 This occurs in the common code where we compute both a quotient and
2829 remainder into a structure, in which case we want to do the computation
2830 directly into the structure to avoid register-register copies.
2832 Note that this case handles both multiple sets in I2 and also cases
2833 where I2 has a number of CLOBBERs inside the PARALLEL.
2835 We make very conservative checks below and only try to handle the
2836 most common cases of this. For example, we only handle the case
2837 where I2 and I3 are adjacent to avoid making difficult register
2838 usage tests. */
2846 /* If the dest of I3 is a ZERO_EXTRACT or STRICT_LOW_PART, the code
2847 below would need to check what is inside (and reg_overlap_mentioned_p
2848 doesn't support those codes anyway). Don't allow those destinations;
2849 the resulting insn isn't likely to be recognized anyway. */
2855 {
2858 /* Make sure that the destination of I3,
2859 which we are going to substitute into one output of I2,
2860 is not used within another output of I2. We must avoid making this:
2861 (parallel [(set (mem (reg 69)) ...)
2862 (set (reg 69) ...)])
2863 which is not well-defined as to order of actions.
2864 (Besides, reload can't handle output reloads for this.)
2866 The problem can also happen if the dest of I3 is a memory ref,
2867 if another dest in I2 is an indirect memory ref.
2869 Neither can this PARALLEL be an asm. We do not allow combining
2870 that usually (see can_combine_p), so do not here either. */
2873 {
2883 }
2889 {
2890 combine_merges++;
2900 /* Replace the dest in I2 with our dest and make the resulting
2901 insn the new pattern for I3. Then skip to where we validate
2902 the pattern. Everything was set up above. */
2907 }
2908 }
2910 /* If I2 is setting a pseudo to a constant and I3 is setting some
2911 sub-part of it to another constant, merge them by making a new
2912 constant. */
2920 {
2927 {
2932 {
2938 }
2939 }
2940 else
2941 {
2945 {
2948 }
2949 }
2952 {
2953 /* If this is the low part, we're done. */
2955 ;
2956 /* Handle the case where inner is twice the size of outer. */
2960 /* Otherwise give up for now. */
2961 else
2963 }
2966 {
2974 combine_merges++;
2981 /* Replace the source in I2 with the new constant and make the
2982 resulting insn the new pattern for I3. Then skip to where we
2983 validate the pattern. Everything was set up above. */
2989 /* The dest of I3 has been replaced with the dest of I2. */
2992 }
2993 }
2995 /* If we have no I1 and I2 looks like:
2996 (parallel [(set (reg:CC X) (compare:CC OP (const_int 0)))
2997 (set Y OP)])
2998 make up a dummy I1 that is
2999 (set Y OP)
3000 and change I2 to be
3001 (set (reg:CC X) (compare:CC Y (const_int 0)))
3003 (We can ignore any trailing CLOBBERs.)
3005 This undoes a previous combination and allows us to match a branch-and-
3006 decrement insn. */
3018 {
3019 /* We make I1 with the same INSN_UID as I2. This gives it
3020 the same DF_INSN_LUID for value tracking. Our fake I1 will
3021 never appear in the insn stream so giving it the same INSN_UID
3022 as I2 will not cause a problem. */
3035 }
3037 /* If I2 is a PARALLEL of two SETs of REGs (and perhaps some CLOBBERs),
3038 make those two SETs separate I1 and I2 insns, and make an I0 that is
3039 the original I1. */
3047 {
3048 /* If there is no I1, there is no I0 either. */
3051 /* We make I1 with the same INSN_UID as I2. This gives it
3052 the same DF_INSN_LUID for value tracking. Our fake I1 will
3053 never appear in the insn stream so giving it the same INSN_UID
3054 as I2 will not cause a problem. */
3062 }
3064 /* Verify that I2 and maybe I1 and I0 can be combined into I3. */
3066 {
3071 }
3073 {
3078 }
3080 {
3085 }
3087 /* Record whether i2 and i3 are trivial moves. */
3091 /* Record whether I2DEST is used in I2SRC and similarly for the other
3092 cases. Knowing this will help in register status updating below. */
3103 /* For the earlier insns, determine which of the subsequent ones they
3104 feed. */
3111 /* Ensure that I3's pattern can be the destination of combines. */
3117 {
3120 }
3122 /* See if any of the insns is a MULT operation. Unless one is, we will
3123 reject a combination that is, since it must be slower. Be conservative
3124 here. */
3132 /* If I3 has an inc, then give up if I1 or I2 uses the reg that is inc'd.
3133 We used to do this EXCEPT in one case: I3 has a post-inc in an
3134 output operand. However, that exception can give rise to insns like
3135 mov r3,(r3)+
3136 which is a famous insn on the PDP-11 where the value of r3 used as the
3137 source was model-dependent. Avoid this sort of thing. */
3139 #if 0
3145 /* It's not the exception. */
3146 #endif
3148 {
3149 rtx link;
3155 {
3158 }
3159 }
3161 /* See if the SETs in I1 or I2 need to be kept around in the merged
3162 instruction: whenever the value set there is still needed past I3.
3163 For the SET in I2, this is easy: we see if I2DEST dies or is set in I3.
3165 For the SET in I1, we have two cases: if I1 and I2 independently feed
3166 into I3, the set in I1 needs to be kept around unless I1DEST dies
3167 or is set in I3. Otherwise (if I1 feeds I2 which feeds I3), the set
3168 in I1 needs to be kept around unless I1DEST dies or is set in either
3169 I2 or I3. The same considerations apply to I0. */
3176 else
3184 else
3187 /* We are about to copy insns for the case where they need to be kept
3188 around. Check that they can be copied in the merged instruction. */
3194 {
3197 }
3199 /* If the set in I2 needs to be kept around, we must make a copy of
3200 PATTERN (I2), so that when we substitute I1SRC for I1DEST in
3201 PATTERN (I2), we are only substituting for the original I1DEST, not into
3202 an already-substituted copy. This also prevents making self-referential
3203 rtx. If I2 is a PARALLEL, we just need the piece that assigns I2SRC to
3204 I2DEST. */
3207 {
3210 else
3212 }
3215 {
3218 else
3220 }
3223 {
3226 else
3228 }
3230 combine_merges++;
3232 /* Substitute in the latest insn for the regs set by the earlier ones. */
3238 /* Many machines that don't use CC0 have insns that can both perform an
3239 arithmetic operation and set the condition code. These operations will
3240 be represented as a PARALLEL with the first element of the vector
3241 being a COMPARE of an arithmetic operation with the constant zero.
3242 The second element of the vector will set some pseudo to the result
3243 of the same arithmetic operation. If we simplify the COMPARE, we won't
3244 match such a pattern and so will generate an extra insn. Here we test
3245 for this case, where both the comparison and the operation result are
3246 needed, and make the PARALLEL by just replacing I2DEST in I3SRC with
3247 I2SRC. Later we will make the PARALLEL that contains I2. */
3253 {
3254 rtx newpat_dest;
3260 scalar_int_mode mode;
3269 {
3275 }
3277 /* Do the rest only if op1 is const0_rtx, which may be the
3278 result of simplification. */
3280 {
3281 /* If a single use of the CC is found, prepare to modify it
3282 when SELECT_CC_MODE returns a new CC-class mode, or when
3283 the above simplify_compare_const() returned a new comparison
3284 operator. undobuf.other_insn is assigned the CC use insn
3285 when modifying it. */
3287 {
3288 #ifdef SELECT_CC_MODE
3289 machine_mode new_mode
3294 {
3299 else
3300 {
3303 }
3304 }
3305 #endif
3306 /* Cases for modifying the CC-using comparison. */
3308 /* ??? Do we need to verify the zero rtx? */
3310 {
3311 /* Replace cc_use_loc with entire new RTX. */
3316 }
3318 {
3319 /* Just replace the CC reg with a new mode. */
3322 }
3323 }
3325 /* Now we modify the current newpat:
3326 First, SET_DEST(newpat) is updated if the CC mode has been
3327 altered. For targets without SELECT_CC_MODE, this should be
3328 optimized away. */
3331 /* This is always done to propagate i2src into newpat. */
3334 /* Create new version of i2pat if needed; the below PARALLEL
3335 creation needs this to work correctly. */
3339 }
3340 }
3343 {
3344 /* It is possible that the source of I2 or I1 may be performing
3345 an unneeded operation, such as a ZERO_EXTEND of something
3346 that is known to have the high part zero. Handle that case
3347 by letting subst look at the inner insns.
3349 Another way to do this would be to have a function that tries
3350 to simplify a single insn instead of merging two or more
3351 insns. We don't do this because of the potential of infinite
3352 loops and because of the potential extra memory required.
3353 However, doing it the way we are is a bit of a kludge and
3354 doesn't catch all cases.
3356 But only do this if -fexpensive-optimizations since it slows
3357 things down and doesn't usually win.
3359 This is not done in the COMPARE case above because the
3360 unmodified I2PAT is used in the PARALLEL and so a pattern
3361 with a modified I2SRC would not match. */
3364 {
3365 /* Pass pc_rtx so no substitutions are done, just
3366 simplifications. */
3368 {
3371 }
3375 }
3380 /* If I1 feeds into I2 and I1DEST is in I1SRC, we need to make a unique
3381 copy of I2SRC each time we substitute it, in order to avoid creating
3382 self-referential RTL when we will be substituting I1SRC for I1DEST
3383 later. Likewise if I0 feeds into I2, either directly or indirectly
3384 through I1, and I0DEST is in I0SRC. */
3391 /* Record whether I2's body now appears within I3's body. */
3393 }
3395 /* If we already got a failure, don't try to do more. Otherwise, try to
3396 substitute I1 if we have it. */
3399 {
3400 /* Check that an autoincrement side-effect on I1 has not been lost.
3401 This happens if I1DEST is mentioned in I2 and dies there, and
3402 has disappeared from the new pattern. */
3404 && i1_feeds_i2_n
3407 /* Before we can do this substitution, we must redo the test done
3408 above (see detailed comments there) that ensures I1DEST isn't
3409 mentioned in any SETs in NEWPAT that are field assignments. */
3412 {
3415 }
3420 /* If the following substitution will modify I1SRC, make a copy of it
3421 for the case where it is substituted for I1DEST in I2PAT later. */
3425 /* If I0 feeds into I1 and I0DEST is in I0SRC, we need to make a unique
3426 copy of I1SRC each time we substitute it, in order to avoid creating
3427 self-referential RTL when we will be substituting I0SRC for I0DEST
3428 later. */
3433 /* Record whether I1's body now appears within I3's body. */
3435 }
3437 /* Likewise for I0 if we have it. */
3440 {
3447 {
3450 }
3452 /* If the following substitution will modify I0SRC, make a copy of it
3453 for the case where it is substituted for I0DEST in I1PAT later. */
3456 /* And a copy for I0DEST in I2PAT substitution. */
3465 }
3467 /* Fail if an autoincrement side-effect has been duplicated. Be careful
3468 to count all the ways that I2SRC and I1SRC can be used. */
3479 /* Fail if we tried to make a new register. */
3481 /* Fail if we couldn't do something and have a CLOBBER. */
3483 /* Fail if this new pattern is a MULT and we didn't have one before
3484 at the outer level. */
3487 {
3490 }
3492 /* If the actions of the earlier insns must be kept
3493 in addition to substituting them into the latest one,
3494 we must make a new PARALLEL for the latest insn
3495 to hold additional the SETs. */
3498 {
3500 combine_extras++;
3503 {
3509 }
3510 else
3511 {
3516 }
3522 {
3528 }
3530 {
3539 }
3540 }
3542 validate_replacement:
3544 /* Note which hard regs this insn has as inputs. */
3547 /* If recog_for_combine fails, it strips existing clobbers. If we'll
3548 consider splitting this pattern, we might need these clobbers. */
3551 {
3557 }
3559 /* We have recognized nothing yet. */
3562 /* See if this is a PARALLEL of two SETs where one SET's destination is
3563 a register that is unused and this isn't marked as an instruction that
3564 might trap in an EH region. In that case, we just need the other SET.
3565 We prefer this over the PARALLEL.
3567 This can occur when simplifying a divmod insn. We *must* test for this
3568 case here because the code below that splits two independent SETs doesn't
3569 handle this case correctly when it updates the register status.
3571 It's pointless doing this if we originally had two sets, one from
3572 i3, and one from i2. Combining then splitting the parallel results
3573 in the original i2 again plus an invalid insn (which we delete).
3574 The net effect is only to move instructions around, which makes
3575 debug info less accurate.
3577 If the remaining SET came from I2 its destination should not be used
3578 between I2 and I3. See PR82024. */
3583 {
3594 {
3597 }
3606 {
3611 {
3617 }
3618 }
3622 }
3624 /* Is the result of combination a valid instruction? */
3628 /* If we were combining three insns and the result is a simple SET
3629 with no ASM_OPERANDS that wasn't recognized, try to split it into two
3630 insns. There are two ways to do this. It can be split using a
3631 machine-specific method (like when you have an addition of a large
3632 constant) or by combine in the function find_split_point. */
3636 {
3640 /* See if the MD file can split NEWPAT. If it can't, see if letting it
3641 use I2DEST as a scratch register will help. In the latter case,
3642 convert I2DEST to the mode of the source of NEWPAT if we can. */
3646 /* We can only use I2DEST as a scratch reg if it doesn't overlap any
3647 inputs of NEWPAT. */
3649 /* ??? If I2DEST is not safe, and I1DEST exists, then it would be
3650 possible to try that as a scratch reg. This would require adding
3651 more code to make it work though. */
3654 {
3657 /* ??? Reusing i2dest without resetting the reg_stat entry for it
3658 (temporarily, until we are committed to this instruction
3659 combination) does not work: for example, any call to nonzero_bits
3660 on the register (from a splitter in the MD file, for example)
3661 will get the old information, which is invalid.
3663 Since nowadays we can create registers during combine just fine,
3664 we should just create a new one here, not reuse i2dest. */
3666 /* First try to split using the original register as a
3667 scratch register. */
3671 i2dest)));
3674 /* If that didn't work, try changing the mode of I2DEST if
3675 we can. */
3680 {
3682 rtx ni2dest;
3686 else
3687 {
3690 }
3692 parallel = (gen_rtx_PARALLEL
3696 ni2dest))));
3701 {
3709 }
3710 }
3713 }
3715 /* If recog_for_combine has discarded clobbers, try to use them
3716 again for the split. */
3718 {
3721 }
3724 {
3729 }
3733 {
3743 /* If I2 or I3 has multiple SETs, we won't know how to track
3744 register status, so don't use these insns. If I2's destination
3745 is used between I2 and I3, we also can't use these insns. */
3755 /* It is possible that both insns now set the destination of I3.
3756 If so, we must show an extra use of it. */
3759 {
3778 }
3779 }
3781 /* If we can split it and use I2DEST, go ahead and see if that
3782 helps things be recognized. Verify that none of the registers
3783 are set between I2 and I3. */
3787 /* We need I2DEST in the proper mode. If it is a hard register
3788 or the only use of a pseudo, we can change its mode.
3789 Make sure we don't change a hard register to have a mode that
3790 isn't valid for it, or change the number of registers. */
3797 /* We can't overwrite I2DEST if its value is still used by
3798 NEWPAT. */
3800 {
3809 /* *SPLIT may be part of I2SRC, so make sure we have the
3810 original expression around for later debug processing.
3811 We should not need I2SRC any more in other cases. */
3814 else
3817 /* Get NEWDEST as a register in the proper mode. We have already
3818 validated that we can do this. */
3820 {
3823 else
3824 {
3827 }
3828 }
3830 /* If *SPLIT is a (mult FOO (const_int pow2)), convert it to
3831 an ASHIFT. This can occur if it was inside a PLUS and hence
3832 appeared to be a memory address. This is a kludge. */
3837 {
3841 /* Update split_code because we may not have a multiply
3842 anymore. */
3844 }
3846 /* Similarly for (plus (mult FOO (const_int pow2))). */
3852 {
3857 i_rtx));
3858 /* Update split_code because we may not have a multiply
3859 anymore. */
3861 }
3863 #ifdef INSN_SCHEDULING
3864 /* If *SPLIT is a paradoxical SUBREG, when we split it, it should
3865 be written as a ZERO_EXTEND. */
3867 {
3868 /* Or as a SIGN_EXTEND if LOAD_EXTEND_OP says that that's
3869 what it really is. */
3874 else
3877 }
3878 #endif
3880 /* Attempt to split binary operators using arithmetic identities. */
3884 {
3891 /* Split "X = Y op Y" as "Z = Y; X = Z op Z". */
3893 {
3898 }
3899 /* Split "((P op Q) op R) op S" where op is PLUS or MULT. */
3906 {
3912 /* Split both "((X op Y) op X) op Y" and
3913 "((X op Y) op Y) op X" as "T op T" where T is
3914 "X op Y". */
3917 {
3922 }
3923 /* Split "((X op X) op Y) op Y)" as "T op T" where
3924 T is "X op Y". */
3926 {
3932 }
3933 }
3934 }
3937 {
3940 }
3944 /* recog_for_combine might have added CLOBBERs to newi2pat.
3945 Make sure NEWPAT does not depend on the clobbered regs. */
3949 {
3952 {
3955 }
3956 }
3958 /* If the split point was a MULT and we didn't have one before,
3959 don't use one now. */
3962 }
3963 }
3965 /* Check for a case where we loaded from memory in a narrow mode and
3966 then sign extended it, but we need both registers. In that case,
3967 we have a PARALLEL with both loads from the same memory location.
3968 We can split this into a load from memory followed by a register-register
3969 copy. This saves at least one insn, more if register allocation can
3970 eliminate the copy.
3972 We cannot do this if the destination of the first assignment is a
3973 condition code register or cc0. We eliminate this case by making sure
3974 the SET_DEST and SET_SRC have the same mode.
3976 We cannot do this if the destination of the second assignment is
3977 a register that we have already assumed is zero-extended. Similarly
3978 for a SUBREG of such a register. */
3997 BITS_PER_WORD)
3999 HOST_BITS_PER_INT)
4007 BITS_PER_WORD)
4009 HOST_BITS_PER_INT)
4016 {
4017 rtx ni2dest;
4031 }
4033 /* Similarly, check for a case where we have a PARALLEL of two independent
4034 SETs but we started with three insns. In this case, we can do the sets
4035 as two separate insns. This case occurs when some SET allows two
4036 other insns to combine, but the destination of that SET is still live.
4038 Also do this if we started with two insns and (at least) one of the
4039 resulting sets is a noop; this noop will be deleted later.
4041 Also do this if we started with two insns neither of which was a simple
4042 move. */
4049 && (i1
4063 {
4067 /* Normally, it doesn't matter which of the two is done first,
4068 but the one that references cc0 can't be the second, and
4069 one which uses any regs/memory set in between i2 and i3 can't
4070 be first. The PARALLEL might also have been pre-existing in i3,
4071 so we need to make sure that we won't wrongly hoist a SET to i2
4072 that would conflict with a death note present in there, or would
4073 have its dest modified between i2 and i3. */
4082 /* If I3 is a jump, ensure that set0 is a jump so that
4083 we do not create invalid RTL. */
4085 )
4086 {
4089 }
4098 /* If I3 is a jump, ensure that set1 is a jump so that
4099 we do not create invalid RTL. */
4101 )
4102 {
4105 }
4106 else
4107 {
4110 }
4115 {
4116 /* recog_for_combine might have added CLOBBERs to newi2pat.
4117 Make sure NEWPAT does not depend on the clobbered regs. */
4119 {
4122 {
4125 {
4128 }
4129 }
4130 }
4136 }
4137 }
4139 /* If it still isn't recognized, fail and change things back the way they
4140 were. */
4142 /* Is the result a reasonable ASM_OPERANDS? */
4144 {
4147 }
4149 /* If we had to change another insn, make sure it is valid also. */
4151 {
4159 {
4162 }
4163 }
4165 /* If I2 is the CC0 setter and I3 is the CC0 user then check whether
4166 they are adjacent to each other or not. */
4168 {
4172 {
4175 }
4176 }
4178 /* Only allow this combination if insn_cost reports that the
4179 replacement instructions are cheaper than the originals. */
4181 {
4184 }
4187 {
4192 {
4197 /* Temporarily revert mode back. */
4201 {
4202 /* If we used i2dest as a scratch register with a
4203 different mode, substitute it for the original
4204 i2src while its original mode is temporarily
4205 restored, and then clear i2scratch so that we don't
4206 do it again later. */
4208 this_basic_block);
4210 /* Put back the new mode. */
4212 }
4213 else
4214 {
4219 {
4222 }
4223 else
4224 {
4231 }
4233 /* We're dealing with a reg that changed mode but not
4234 meaning, so we want to turn it into a subreg for
4235 the new mode. However, because of REG sharing and
4236 because its mode had already changed, we have to do
4237 it in two steps. First, replace any debug uses of
4238 reg, with its original mode temporarily restored,
4239 with this copy we have created; then, replace the
4240 copy with the SUBREG of the original shared reg,
4241 once again changed to the new mode. */
4243 this_basic_block);
4247 this_basic_block);
4248 }
4249 }
4250 }
4252 /* If we will be able to accept this, we have made a
4253 change to the destination of I3. This requires us to
4254 do a few adjustments. */
4257 {
4260 }
4262 /* We now know that we can do this combination. Merge the insns and
4263 update the status of registers and LOG_LINKS. */
4266 {
4271 /* If any of the notes in OTHER_INSN were REG_DEAD or REG_UNUSED,
4272 ensure that they are still valid. Then add any non-duplicate
4273 notes added by recog_for_combine. */
4275 {
4284 /* Simply drop equal note since it may be no longer valid
4285 for other_insn. It may be possible to record that CC
4286 register is changed and only discard those notes, but
4287 in practice it's unnecessary complication and doesn't
4288 give any meaningful improvement.
4290 See PR78559. */
4294 }
4298 NULL_RTX);
4299 }
4302 {
4303 /* I3 now uses what used to be its destination and which is now
4304 I2's destination. This requires us to do a few adjustments. */
4307 }
4310 {
4311 /* We might need a LOG_LINK from I3 to I2. But then we used to
4312 have one, so we still will.
4314 However, some later insn might be using I2's dest and have
4315 a LOG_LINK pointing at I3. We should change it to point at
4316 I2 instead. */
4318 /* newi2pat is usually a SET here; however, recog_for_combine might
4319 have added some clobbers. */
4324 /* It can only be a SET of a REG or of a SUBREG of a REG. */
4329 !done
4330 && insn
4334 {
4338 {
4342 }
4343 }
4344 }
4346 {
4351 /* Compute which registers we expect to eliminate. newi2pat may be setting
4352 either i3dest or i2dest, so we must check it. */
4355 || !i2dest_killed
4357 /* For i1, we need to compute both local elimination and global
4358 elimination information with respect to newi2pat because i1dest
4359 may be the same as i3dest, in which case newi2pat may be setting
4360 i1dest. Global information is used when distributing REG_DEAD
4361 note for i2 and i3, in which case it does matter if newi2pat sets
4362 i1dest or not.
4364 Local information is used when distributing REG_DEAD note for i1,
4365 in which case it doesn't matter if newi2pat sets i1dest or not.
4366 See PR62151, if we have four insns combination:
4367 i0: r0 <- i0src
4368 i1: r1 <- i1src (using r0)
4369 REG_DEAD (r0)
4370 i2: r0 <- i2src (using r1)
4371 i3: r3 <- i3src (using r0)
4372 ix: using r0
4373 From i1's point of view, r0 is eliminated, no matter if it is set
4374 by newi2pat or not. In other words, REG_DEAD info for r0 in i1
4375 should be discarded.
4377 Note local information only affects cases in forms like "I1->I2->I3",
4378 "I0->I1->I2->I3" or "I0&I1->I2, I2->I3". For other cases like
4379 "I0->I1, I1&I2->I3" or "I1&I2->I3", newi2pat won't set i1dest or
4380 i0dest anyway. */
4382 || !i1dest_killed
4387 /* Same case as i1. */
4394 /* Get the old REG_NOTES and LOG_LINKS from all our insns and
4395 clear them. */
4403 /* Ensure that we do not have something that should not be shared but
4404 occurs multiple times in the new insns. Check this by first
4405 resetting all the `used' flags and then copying anything is shared. */
4429 {
4432 {
4434 {
4435 /* I2SRC must still be meaningful at this point. Some
4436 splitting operations can invalidate I2SRC, but those
4437 operations do not apply to calls. */
4441 }
4448 }
4449 }
4454 /* We had one special case above where I2 had more than one set and
4455 we replaced a destination of one of those sets with the destination
4456 of I3. In that case, we have to update LOG_LINKS of insns later
4457 in this basic block. Note that this (expensive) case is rare.
4459 Also, in this case, we must pretend that all REG_NOTEs for I2
4460 actually came from I3, so that REG_UNUSED notes from I2 will be
4461 properly handled. */
4464 {
4473 temp_insn
4483 {
4488 }
4489 else
4492 }
4500 {
4503 this_basic_block);
4506 }
4507 else
4508 {
4511 this_basic_block);
4513 }
4516 {
4521 this_basic_block);
4523 }
4526 {
4531 this_basic_block);
4533 }
4535 /* Get death notes for everything that is now used in either I3 or
4536 I2 and used to die in a previous insn. If we built two new
4537 patterns, move from I1 to I2 then I2 to I3 so that we get the
4538 proper movement on registers that I2 modifies. */
4544 else
4550 /* Distribute all the LOG_LINKS and REG_NOTES from I1, I2, and I3. */
4567 /* Distribute any notes added to I2 or I3 by recog_for_combine. We
4568 know these are REG_UNUSED and want them to go to the desired insn,
4569 so we always pass it as i3. */
4573 NULL_RTX);
4577 NULL_RTX);
4579 /* If I3DEST was used in I3SRC, it really died in I3. We may need to
4580 put a REG_DEAD note for it somewhere. If NEWI2PAT exists and sets
4581 I3DEST, the death must be somewhere before I2, not I3. If we passed I3
4582 in that case, it might delete I2. Similarly for I2 and I1.
4583 Show an additional death due to the REG_DEAD note we make here. If
4584 we discard it in distribute_notes, we will decrement it again. */
4587 {
4592 else
4595 }
4598 {
4603 else
4606 }
4609 {
4614 else
4617 }
4620 {
4625 else
4628 }
4636 {
4641 /* The insn that used to set this register doesn't exist, and
4642 this life of the register may not exist either. See if one of
4643 I3's links points to an insn that sets I2DEST. If it does,
4644 that is now the last known value for I2DEST. If we don't update
4645 this and I2 set the register to a value that depended on its old
4646 contents, we will get confused. If this insn is used, thing
4647 will be set correctly in combine_instructions. */
4655 /* If the reg formerly set in I2 died only once and that was in I3,
4656 zero its use count so it won't make `reload' do any work. */
4659 && ! i2dest_in_i2src
4662 }
4665 {
4678 && ! i1dest_in_i1src
4681 }
4684 {
4697 && ! i0dest_in_i0src
4700 }
4702 /* Update reg_stat[].nonzero_bits et al for any changes that may have
4703 been made to this insn. The order is important, because newi2pat
4704 can affect nonzero_bits of newpat. */
4708 }
4711 {
4713 {
4716 }
4718 }
4721 {
4723 {
4726 }
4728 }
4731 {
4733 {
4736 }
4738 }
4741 {
4743 {
4746 }
4748 }
4751 {
4753 {
4756 }
4758 }
4760 /* Set new_direct_jump_p if a new return or simple jump instruction
4761 has been created. Adjust the CFG accordingly. */
4763 {
4767 }
4772 {
4775 }
4779 {
4785 }
4790 {
4796 }
4798 /* A noop might also need cleaning up of CFG, if it comes from the
4799 simplification of a jump. */
4804 {
4807 }
4814 {
4817 }
4819 combine_successes++;
4829 }
4830 \f
4831 /* Get a marker for undoing to the current state. */
4835 {
4837 }
4839 /* Undo the modifications up to the marker. */
4841 static void
4843 {
4847 {
4852 {
4867 }
4871 }
4874 }
4876 /* Undo all the modifications recorded in undobuf. */
4878 static void
4880 {
4882 }
4884 /* We've committed to accepting the changes we made. Move all
4885 of the undos to the free list. */
4887 static void
4889 {
4893 {
4897 }
4899 }
4900 \f
4901 /* Find the innermost point within the rtx at LOC, possibly LOC itself,
4902 where we have an arithmetic expression and return that point. LOC will
4903 be inside INSN.
4905 try_combine will call this function to see if an insn can be split into
4906 two insns. */
4910 {
4920 /* First special-case some codes. */
4922 {
4924 #ifdef INSN_SCHEDULING
4925 /* If we are making a paradoxical SUBREG invalid, it becomes a split
4926 point. */
4929 #endif
4933 /* If we have (mem (const ..)) or (mem (symbol_ref ...)), split it
4934 using LO_SUM and HIGH. */
4937 {
4945 }
4947 /* If we have a PLUS whose second operand is a constant and the
4948 address is not valid, perhaps will can split it up using
4949 the machine-specific way to split large constants. We use
4950 the first pseudo-reg (one of the virtual regs) as a placeholder;
4951 it will not remain in the result. */
4956 {
4959 subst_insn);
4961 /* This should have produced two insns, each of which sets our
4962 placeholder. If the source of the second is a valid address,
4963 we can make put both sources together and make a split point
4964 in the middle. */
4977 && memory_address_addr_space_p
4980 {
4984 /* Replace the placeholder in SRC2 with SRC1. If we can
4985 find where in SRC2 it was placed, that can become our
4986 split point and we can replace this address with SRC2.
4987 Just try two obvious places. */
4998 {
5001 }
5002 }
5004 /* If that didn't work, perhaps the first operand is complex and
5005 needs to be computed separately, so make a split point there.
5006 This will occur on machines that just support REG + CONST
5007 and have a constant moved through some previous computation. */
5013 }
5015 /* If we have a PLUS whose first operand is complex, try computing it
5016 separately by making a split there. */
5027 /* If SET_DEST is CC0 and SET_SRC is not an operand, a COMPARE, or a
5028 ZERO_EXTRACT, the most likely reason why this doesn't match is that
5029 we need to put the operand into a register. So split at that
5030 point. */
5040 /* See if we can split SET_SRC as it stands. */
5045 /* See if we can split SET_DEST as it stands. */
5050 /* See if this is a bitfield assignment with everything constant. If
5051 so, this is an IOR of an AND, so split it into that. */
5063 {
5068 unsigned HOST_WIDE_INT mask
5070 rtx or_mask;
5079 else
5080 {
5086 or_mask));
5087 }
5094 }
5096 /* Otherwise, see if this is an operation that we can split into two.
5097 If so, try to split that. */
5101 {
5103 /* If we are AND'ing with a large constant that is only a single
5104 bit and the result is only being used in a context where we
5105 need to know if it is zero or nonzero, replace it with a bit
5106 extraction. This will avoid the large constant, which might
5107 have taken more than one insn to make. If the constant were
5108 not a valid argument to the AND but took only one insn to make,
5109 this is no worse, but if it took more than one insn, it will
5110 be better. */
5120 {
5125 {
5128 }
5129 }
5133 /* If STORE_FLAG_VALUE is -1, this is (NE X 0) and only one bit of X
5134 is known to be on, this can be converted into a NEG of a shift. */
5140 {
5147 pos_rtx)));
5152 }
5158 /* We can't optimize if either mode is a partial integer
5159 mode as we don't know how many bits are significant
5160 in those modes. */
5176 {
5184 }
5189 }
5195 {
5196 /* For unsigned, we have a choice of a shift followed by an
5197 AND or two shifts. Use two shifts for field sizes where the
5198 constant might be too large. We assume here that we can
5199 always at least get 8-bit constants in an AND insn, which is
5200 true for every current RISC. */
5203 {
5204 unsigned HOST_WIDE_INT mask
5209 gen_rtx_LSHIFTRT
5216 }
5217 else
5218 {
5222 gen_rtx_fmt_ee
5232 }
5233 }
5235 /* See if this is a simple operation with a constant as the second
5236 operand. It might be that this constant is out of range and hence
5237 could be used as a split point. */
5245 /* Finally, see if this is a simple operation with its first operand
5246 not in a register. The operation might require this operand in a
5247 register, so return it as a split point. We can always do this
5248 because if the first operand were another operation, we would have
5249 already found it as a split point. */
5258 /* We write NOR as (and (not A) (not B)), but if we don't have a NOR,
5259 it is better to write this as (not (ior A B)) so we can split it.
5260 Similarly for IOR. */
5262 {
5270 }
5272 /* Many RISC machines have a large set of logical insns. If the
5273 second operand is a NOT, put it first so we will try to split the
5274 other operand first. */
5276 {
5280 }
5285 /* Canonicalization can produce (minus A (mult B C)), where C is a
5286 constant. It may be better to try splitting (plus (mult B -C) A)
5287 instead if this isn't a multiply by a power of two. */
5291 {
5299 mode)),
5302 }
5304 /* Split at a multiply-accumulate instruction. However if this is
5305 the SET_SRC, we likely do not have such an instruction and it's
5306 worthless to try this split. */
5315 }
5317 /* Otherwise, select our actions depending on our rtx class. */
5319 {
5325 /* fall through */
5333 /* fall through */
5335 /* Some machines have (and (shift ...) ...) insns. If X is not
5336 an AND, but XEXP (X, 0) is, use it as our split point. */
5346 /* Otherwise, we don't have a split point. */
5348 }
5349 }
5350 \f
5351 /* Throughout X, replace FROM with TO, and return the result.
5352 The result is TO if X is FROM;
5353 otherwise the result is X, but its contents may have been modified.
5354 If they were modified, a record was made in undobuf so that
5355 undo_all will (among other things) return X to its original state.
5357 If the number of changes necessary is too much to record to undo,
5358 the excess changes are not made, so the result is invalid.
5359 The changes already made can still be undone.
5360 undobuf.num_undo is incremented for such changes, so by testing that
5361 the caller can tell whether the result is valid.
5363 `n_occurrences' is incremented each time FROM is replaced.
5365 IN_DEST is nonzero if we are processing the SET_DEST of a SET.
5367 IN_COND is nonzero if we are at the top level of a condition.
5369 UNIQUE_COPY is nonzero if each substitution must be unique. We do this
5370 by copying if `n_occurrences' is nonzero. */
5372 static rtx
5374 {
5379 rtx new_rtx;
5381 /* Two expressions are equal if they are identical copies of a shared
5382 RTX or if they are both registers with the same register number
5383 and mode. */
5385 #define COMBINE_RTX_EQUAL_P(X,Y) \
5386 ((X) == (Y) \
5387 || (REG_P (X) && REG_P (Y) \
5388 && REGNO (X) == REGNO (Y) && GET_MODE (X) == GET_MODE (Y)))
5390 /* Do not substitute into clobbers of regs -- this will never result in
5391 valid RTL. */
5396 {
5397 n_occurrences++;
5399 }
5401 /* If X and FROM are the same register but different modes, they
5402 will not have been seen as equal above. However, the log links code
5403 will make a LOG_LINKS entry for that case. If we do nothing, we
5404 will try to rerecognize our original insn and, when it succeeds,
5405 we will delete the feeding insn, which is incorrect.
5407 So force this insn not to match in this (rare) case. */
5412 /* If this is an object, we are done unless it is a MEM or LO_SUM, both
5413 of which may contain things that can be combined. */
5417 /* It is possible to have a subexpression appear twice in the insn.
5418 Suppose that FROM is a register that appears within TO.
5419 Then, after that subexpression has been scanned once by `subst',
5420 the second time it is scanned, TO may be found. If we were
5421 to scan TO here, we would find FROM within it and create a
5422 self-referent rtl structure which is completely wrong. */
5426 /* Parallel asm_operands need special attention because all of the
5427 inputs are shared across the arms. Furthermore, unsharing the
5428 rtl results in recognition failures. Failure to handle this case
5429 specially can result in circular rtl.
5431 Solve this by doing a normal pass across the first entry of the
5432 parallel, and only processing the SET_DESTs of the subsequent
5433 entries. Ug. */
5438 {
5441 /* If this substitution failed, this whole thing fails. */
5449 {
5455 {
5458 /* If this substitution failed, this whole thing fails. */
5464 }
5465 }
5466 }
5467 else
5468 {
5472 /* We don't need to process a SET_DEST that is a register, CC0,
5473 or PC, so set up to skip this common case. All other cases
5474 where we want to suppress replacing something inside a
5475 SET_SRC are handled via the IN_DEST operand. */
5482 /* Trying to simplify the operands of a widening MULT is not likely
5483 to create RTL matching a machine insn. */
5495 /* Get the mode of operand 0 in case X is now a SIGN_EXTEND of a
5496 constant. */
5501 {
5503 {
5506 {
5508 {
5511 n_occurrences++;
5512 }
5513 else
5514 {
5516 unique_copy);
5518 /* If this substitution failed, this whole thing
5519 fails. */
5523 }
5526 }
5527 }
5529 {
5530 /* If this is a register being set, ignore it. */
5537 ;
5540 {
5541 /* In general, don't install a subreg involving two
5542 modes not tieable. It can worsen register
5543 allocation, and can even make invalid reload
5544 insns, since the reg inside may need to be copied
5545 from in the outside mode, and that may be invalid
5546 if it is an fp reg copied in integer mode.
5548 We allow two exceptions to this: It is valid if
5549 it is inside another SUBREG and the mode of that
5550 SUBREG and the mode of the inside of TO is
5551 tieable and it is valid if X is a SET that copies
5552 FROM to CC0. */
5560 && (!HAVE_cc0
5575 n_occurrences++;
5576 }
5577 else
5578 /* If we are in a SET_DEST, suppress most cases unless we
5579 have gone inside a MEM, in which case we want to
5580 simplify the address. We assume here that things that
5581 are actually part of the destination have their inner
5582 parts in the first expression. This is true for SUBREG,
5583 STRICT_LOW_PART, and ZERO_EXTRACT, which are the only
5584 things aside from REG and MEM that should appear in a
5585 SET_DEST. */
5587 (((in_dest
5593 unique_copy);
5595 /* If we found that we will have to reject this combination,
5596 indicate that by returning the CLOBBER ourselves, rather than
5597 an expression containing it. This will speed things up as
5598 well as prevent accidents where two CLOBBERs are considered
5599 to be equal, thus producing an incorrect simplification. */
5605 {
5613 }
5618 {
5620 new_rtx,
5624 }
5625 else
5627 }
5628 }
5629 }
5631 /* Check if we are loading something from the constant pool via float
5632 extension; in this case we would undo compress_float_constant
5633 optimization and degenerate constant load to an immediate value. */
5637 {
5641 }
5643 /* Try to simplify X. If the simplification changed the code, it is likely
5644 that further simplification will help, so loop, but limit the number
5645 of repetitions that will be performed. */
5648 {
5649 /* If X is sufficiently simple, don't bother trying to do anything
5650 with it. */
5659 /* We no longer know the original mode of operand 0 since we
5660 have changed the form of X) */
5662 }
5665 }
5666 \f
5667 /* If X is a commutative operation whose operands are not in the canonical
5668 order, use substitutions to swap them. */
5670 static void
5672 {
5675 {
5679 }
5680 }
5682 /* Simplify X, a piece of RTL. We just operate on the expression at the
5683 outer level; call `subst' to simplify recursively. Return the new
5684 expression.
5686 OP0_MODE is the original mode of XEXP (x, 0). IN_DEST is nonzero
5687 if we are inside a SET_DEST. IN_COND is nonzero if we are at the top level
5688 of a condition. */
5690 static rtx
5693 {
5696 scalar_int_mode int_mode;
5697 rtx temp;
5700 /* If this is a commutative operation, put a constant last and a complex
5701 expression first. We don't need to do this for comparisons here. */
5704 /* Try to fold this expression in case we have constants that weren't
5705 present before. */
5708 {
5716 {
5719 {
5723 }
5726 }
5739 }
5742 {
5747 }
5749 /* If this is a simple operation applied to an IF_THEN_ELSE, try
5750 applying it to the arms of the IF_THEN_ELSE. This often simplifies
5751 things. Check for cases where both arms are testing the same
5752 condition.
5754 Don't do anything if all operands are very simple. */
5767 {
5772 /* If everything is a comparison, what we have is highly unlikely
5773 to be simpler, so don't use it. */
5776 /* Similarly, if we end up with one of the expressions the same
5777 as the original, it is certainly not simpler. */
5780 {
5787 /* Simplify the alternative arms; this may collapse the true and
5788 false arms to store-flag values. Be careful to use copy_rtx
5789 here since true_rtx or false_rtx might share RTL with x as a
5790 result of the if_then_else_cond call above. */
5794 /* If true_rtx and false_rtx are not general_operands, an if_then_else
5795 is unlikely to be simpler. */
5798 {
5801 /* Restarting if we generate a store-flag expression will cause
5802 us to loop. Just drop through in this case. */
5804 /* If the result values are STORE_FLAG_VALUE and zero, we can
5805 just make the comparison operation. */
5816 /* Likewise, we can make the negate of a comparison operation
5817 if the result values are - STORE_FLAG_VALUE and zero. */
5825 mode);
5836 mode);
5837 else
5840 mode,
5841 VOIDmode,
5842 cond,
5843 cop1),
5848 }
5849 }
5850 }
5852 /* First see if we can apply the inverse distributive law. */
5855 {
5859 }
5861 /* If CODE is an associative operation not otherwise handled, see if we
5862 can associate some operands. This can win if they are constants or
5863 if they are logically related (i.e. (a & b) & a). */
5869 {
5871 {
5875 rtx inner;
5877 /* Make sure we pass the constant operand if any as the second
5878 one if this is a commutative operation. */
5886 /* For commutative operations, try the other pair if that one
5887 didn't simplify. */
5889 {
5894 }
5898 }
5899 }
5901 /* A little bit of algebraic simplification here. */
5903 {
5905 /* Ensure that our address has any ASHIFTs converted to MULT in case
5906 address-recognizing predicates are called later. */
5915 /* See if this can be moved to simplify_subreg. */
5918 /* Don't call gen_lowpart if the inner mode
5919 is VOIDmode and we cannot simplify it, as SUBREG without
5920 inner mode is invalid. */
5927 {
5928 rtx temp;
5934 /* If op is known to have all lower bits zero, the result is zero. */
5947 }
5949 /* Don't change the mode of the MEM if that would change the meaning
5950 of the address. */
5957 /* Note that we cannot do any narrowing for non-constants since
5958 we might have been counting on using the fact that some bits were
5959 zero. We now do this in the SET. */
5966 /* For C equal to the width of MODE minus 1, (neg (ashiftrt X C)) can be
5967 replaced by (lshiftrt X C). This will convert
5968 (neg (sign_extract X 1 Y)) to (zero_extract X 1 Y). */
5976 /* If X has only a single bit that might be nonzero, say, bit I, convert
5977 (neg X) to (ashiftrt (ashift X C-I) C-I) where C is the bitsize of
5978 MODE minus 1. This will convert (neg (zero_extract X 1 Y)) to
5979 (sign_extract X 1 Y). But only do this if TEMP isn't a register
5980 or a SUBREG of one since we'd be making the expression more
5981 complex if it was just a register. */
5988 {
5989 rtx temp1 = simplify_shift_const
5995 /* If all we did was surround TEMP with the two shifts, we
5996 haven't improved anything, so don't use it. Otherwise,
5997 we are better off with TEMP1. */
6002 }
6006 /* We can't handle truncation to a partial integer mode here
6007 because we don't know the real bitsize of the partial
6008 integer mode. */
6017 /* We can truncate a constant value and return it. */
6018 {
6019 poly_int64 c;
6022 }
6024 /* Similarly to what we do in simplify-rtx.c, a truncate of a register
6025 whose value is a comparison can be replaced with a subreg if
6026 STORE_FLAG_VALUE permits. */
6035 /* (const (const X)) can become (const X). Do it this way rather than
6036 returning the inner CONST since CONST can be shared with a
6037 REG_EQUAL note. */
6043 /* Convert (lo_sum (high FOO) FOO) to FOO. This is necessary so we
6044 can add in an offset. find_split_point will split this address up
6045 again if it doesn't match. */
6052 /* (plus (xor (and <foo> (const_int pow2 - 1)) <c>) <-c>)
6053 when c is (const_int (pow2 + 1) / 2) is a sign extension of a
6054 bit-field and can be replaced by either a sign_extend or a
6055 sign_extract. The `and' may be a zero_extend and the two
6056 <c>, -<c> constants may be reversed. */
6073 return simplify_shift_const
6080 /* If only the low-order bit of X is possibly nonzero, (plus x -1)
6081 can become (ashiftrt (ashift (xor x 1) C) C) where C is
6082 the bitsize of the mode - 1. This allows simplification of
6083 "a = (b & 8) == 0;" */
6090 return simplify_shift_const
6094 const1_rtx),
6098 /* If we are adding two things that have no bits in common, convert
6099 the addition into an IOR. This will often be further simplified,
6100 for example in cases like ((a & 1) + (a & 2)), which can
6101 become a & 3. */
6106 {
6107 /* Try to simplify the expression further. */
6111 /* If we could, great. If not, do not go ahead with the IOR
6112 replacement, since PLUS appears in many special purpose
6113 address arithmetic instructions. */
6121 }
6123 /* Canonicalize x + x into x << 1. */
6132 /* (minus <foo> (and <foo> (const_int -pow2))) becomes
6133 (and <foo> (const_int pow2-1)) */
6144 /* If we have (mult (plus A B) C), apply the distributive law and then
6145 the inverse distributive law to see if things simplify. This
6146 occurs mostly in addresses, often when unrolling loops. */
6149 {
6153 }
6155 /* Try simplify a*(b/c) as (a*b)/c. */
6158 {
6164 }
6168 /* If this is a divide by a power of two, treat it as a shift if
6169 its first operand is a shift. */
6189 /* If the first operand is a condition code, we can't do anything
6190 with it. */
6194 {
6202 /* Simplify our comparison, if possible. */
6205 /* If STORE_FLAG_VALUE is 1, we can convert (ne x 0) to simply X
6206 if only the low-order bit is possibly nonzero in X (such as when
6207 X is a ZERO_EXTRACT of one bit). Similarly, we can convert EQ to
6208 (xor X 1) or (minus 1 X); we use the former. Finally, if X is
6209 known to be either 0 or -1, NE becomes a NEG and EQ becomes
6210 (plus X 1).
6212 Remove any ZERO_EXTRACT we made when thinking this was a
6213 comparison. It may now be simpler to use, e.g., an AND. If a
6214 ZERO_EXTRACT is indeed appropriate, it will be placed back by
6215 the call to make_compound_operation in the SET case.
6217 Don't apply these optimizations if the caller would
6218 prefer a comparison rather than a value.
6219 E.g., for the condition in an IF_THEN_ELSE most targets need
6220 an explicit comparison. */
6223 ;
6241 {
6245 int_mode);
6246 }
6254 {
6258 const1_rtx);
6259 }
6268 {
6271 }
6273 /* If STORE_FLAG_VALUE is -1, we have cases similar to
6274 those above. */
6276 ;
6293 {
6297 int_mode);
6298 }
6307 {
6311 int_mode);
6312 }
6314 /* If X is 0/1, (eq X 0) is X-1. */
6321 {
6324 }
6326 /* If STORE_FLAG_VALUE says to just test the sign bit and X has just
6327 one bit that might be nonzero, we can convert (ne x 0) to
6328 (ashift x c) where C puts the bit in the sign bit. Remove any
6329 AND with STORE_FLAG_VALUE when we are done, since we are only
6330 going to test the sign bit. */
6338 {
6344 else
6346 }
6348 /* If the code changed, return a whole new comparison.
6349 We also need to avoid using SUBST in cases where
6350 simplify_comparison has widened a comparison with a CONST_INT,
6351 since in that case the wider CONST_INT may fail the sanity
6352 checks in do_SUBST. */
6359 /* Otherwise, keep this operation, but maybe change its operands.
6360 This also converts (ne (compare FOO BAR) 0) to (ne FOO BAR). */
6363 }
6373 /* If we are processing SET_DEST, we are done. */
6391 /* If this is a shift by a constant amount, simplify it. */
6399 (HOST_WIDE_INT_1U
6408 }
6411 }
6412 \f
6413 /* Simplify X, an IF_THEN_ELSE expression. Return the new expression. */
6415 static rtx
6417 {
6424 rtx temp;
6427 rtx reversed;
6430 /* Simplify storing of the truth value. */
6435 /* Also when the truth value has to be reversed. */
6441 /* Sometimes we can simplify the arm of an IF_THEN_ELSE if a register used
6442 in it is being compared against certain values. Get the true and false
6443 comparisons and see if that says anything about the value of each arm. */
6449 {
6450 HOST_WIDE_INT nzb;
6456 /* If FALSE_CODE is EQ, swap the codes and arms. */
6459 {
6462 }
6464 scalar_int_mode from_mode;
6466 {
6467 /* If we are comparing against zero and the expression being
6468 tested has only a single bit that might be nonzero, that is
6469 its value when it is not equal to zero. Similarly if it is
6470 known to be -1 or 0. */
6474 {
6477 }
6482 {
6485 }
6486 }
6488 /* Now simplify an arm if we know the value of the register in the
6489 branch and it is used in the arm. Be careful due to the potential
6490 of locally-shared RTL. */
6507 }
6509 /* If we have (if_then_else FOO (pc) (label_ref BAR)) and FOO can be
6510 reversed, do so to avoid needing two sets of patterns for
6511 subtract-and-branch insns. Similarly if we have a constant in the true
6512 arm, the false arm is the same as the first operand of the comparison, or
6513 the false arm is more complicated than the true arm. */
6526 {
6535 /* It is possible that the conditional has been simplified out. */
6538 }
6540 /* If the two arms are identical, we don't need the comparison. */
6545 /* Convert a == b ? b : a to "a". */
6557 /* Look for cases where we have (abs x) or (neg (abs X)). */
6560 && comparison_p
6567 {
6573 return
6576 mode);
6579 }
6581 /* Look for MIN or MAX. */
6584 && comparison_p
6589 {
6604 }
6606 /* If we have (if_then_else COND (OP Z C1) Z) and OP is an identity when its
6607 second operand is zero, this can be done as (OP Z (mult COND C2)) where
6608 C2 = C1 * STORE_FLAG_VALUE. Similarly if OP has an outer ZERO_EXTEND or
6609 SIGN_EXTEND as long as Z is already extended (so we don't destroy it).
6610 We can do this kind of thing in some cases when STORE_FLAG_VALUE is
6611 neither 1 or -1, but it isn't worth checking for. */
6614 && comparison_p
6617 {
6633 /* If an identity-zero op is commutative, check whether there
6634 would be a match if we swapped the operands. */
6655 {
6659 }
6672 {
6676 }
6693 {
6697 }
6710 {
6714 }
6717 {
6727 const_true_rtx));
6735 }
6736 }
6738 /* If we have (if_then_else (ne A 0) C1 0) and either A is known to be 0 or
6739 1 and C1 is a single bit or A is known to be 0 or -1 and C1 is the
6740 negation of a single bit, we can convert this operation to a shift. We
6741 can actually do this more generally, but it doesn't seem worth it. */
6753 return
6757 /* (IF_THEN_ELSE (NE A 0) C1 0) is A or a zero-extend of A if the only
6758 non-zero bit in A is C1. */
6766 {
6772 }
6775 }
6776 \f
6777 /* Simplify X, a SET expression. Return the new expression. */
6779 static rtx
6781 {
6784 machine_mode mode
6788 scalar_int_mode int_mode;
6790 /* (set (pc) (return)) gets written as (return). */
6794 /* Now that we know for sure which bits of SRC we are using, see if we can
6795 simplify the expression for the object knowing that we only need the
6796 low-order bits. */
6799 {
6802 }
6804 /* If we are setting CC0 or if the source is a COMPARE, look for the use of
6805 the comparison result and try to simplify it unless we already have used
6806 undobuf.other_insn. */
6814 {
6823 {
6826 {
6829 }
6830 }
6831 else
6839 {
6843 }
6844 else
6845 {
6850 /* Attempt to simplify CC user. */
6852 {
6856 }
6858 /* Convert X into a no-op move. */
6862 }
6864 /* Simplify our comparison, if possible. */
6867 #ifdef SELECT_CC_MODE
6868 /* If this machine has CC modes other than CCmode, check to see if we
6869 need to use a different CC mode here. */
6878 else
6881 /* If the mode changed, we have to change SET_DEST, the mode in the
6882 compare, and the mode in the place SET_DEST is used. If SET_DEST is
6883 a hard register, just build new versions with the proper mode. If it
6884 is a pseudo, we lose unless it is only time we set the pseudo, in
6885 which case we can safely change its mode. */
6887 {
6889 {
6891 rtx new_dest;
6895 else
6896 {
6899 }
6906 }
6907 }
6910 /* If the code changed, we have to build a new comparison in
6911 undobuf.other_insn. */
6913 {
6922 /* If the only change we made was to change an EQ into an NE or
6923 vice versa, OP0 has only one bit that might be nonzero, and OP1
6924 is zero, check if changing the user of the condition code will
6925 produce a valid insn. If it won't, we can keep the original code
6926 in that insn by surrounding our operation with an XOR. */
6933 {
6938 {
6945 }
6946 }
6947 }
6952 /* Don't generate a compare of a CC with 0, just use that CC. */
6954 {
6957 }
6958 /* Otherwise, if we didn't previously have the same COMPARE we
6959 want, create it from scratch. */
6962 {
6965 }
6966 }
6967 else
6968 {
6969 /* Get SET_SRC in a form where we have placed back any
6970 compound expressions. Then do the checks below. */
6973 }
6975 /* If we have (set x (subreg:m1 (op:m2 ...) 0)) with OP being some operation,
6976 and X being a REG or (subreg (reg)), we may be able to convert this to
6977 (set (subreg:m2 x) (op)).
6979 We can always do this if M1 is narrower than M2 because that means that
6980 we only care about the low bits of the result.
6982 However, on machines without WORD_REGISTER_OPERATIONS defined, we cannot
6983 perform a narrower operation than requested since the high-order bits will
6984 be undefined. On machine where it is defined, this transformation is safe
6985 as long as M1 and M2 have the same number of words. */
6989 && (known_equal_after_align_up
6992 UNITS_PER_WORD))
7001 {
7004 dest));
7008 }
7010 /* If we have (set (cc0) (subreg ...)), we try to remove the subreg
7011 in SRC. */
7015 {
7019 /* Here we make sure that we don't have a sign bit on. */
7022 {
7025 }
7026 }
7028 /* If we have (set FOO (subreg:M (mem:N BAR) 0)) with M wider than N, this
7029 would require a paradoxical subreg. Replace the subreg with a
7030 zero_extend to avoid the reload that would otherwise be required.
7031 Don't do this unless we have a scalar integer mode, otherwise the
7032 transformation is incorrect. */
7039 {
7044 }
7046 /* If we don't have a conditional move, SET_SRC is an IF_THEN_ELSE, and we
7047 are comparing an item known to be 0 or -1 against 0, use a logical
7048 operation instead. Check for one of the arms being an IOR of the other
7049 arm with some value. We compute three terms to be IOR'ed together. In
7050 practice, at most two will be nonzero. Then we do the IOR's. */
7058 && (!HAVE_conditional_move
7063 {
7088 int_mode),
7089 false_rtx);
7095 term3));
7098 }
7100 /* If either SRC or DEST is a CLOBBER of (const_int 0), make this
7101 whole thing fail. */
7106 else
7107 /* Convert this into a field assignment operation, if possible. */
7109 }
7110 \f
7111 /* Simplify, X, and AND, IOR, or XOR operation, and return the simplified
7112 result. */
7114 static rtx
7116 {
7119 scalar_int_mode mode;
7122 {
7124 /* We can call simplify_and_const_int only if we don't lose
7125 any (sign) bits when converting INTVAL (op1) to
7126 "unsigned HOST_WIDE_INT". */
7131 {
7138 }
7140 /* If we have any of (and (ior A B) C) or (and (xor A B) C),
7141 apply the distributive law and then the inverse distributive
7142 law to see if things simplify. */
7144 {
7148 }
7150 {
7154 }
7158 /* If we have (ior (and A B) C), apply the distributive law and then
7159 the inverse distributive law to see if things simplify. */
7162 {
7166 }
7169 {
7173 }
7178 }
7181 }
7182 \f
7183 /* We consider ZERO_EXTRACT, SIGN_EXTRACT, and SIGN_EXTEND as "compound
7184 operations" because they can be replaced with two more basic operations.
7185 ZERO_EXTEND is also considered "compound" because it can be replaced with
7186 an AND operation, which is simpler, though only one operation.
7188 The function expand_compound_operation is called with an rtx expression
7189 and will convert it to the appropriate shifts and AND operations,
7190 simplifying at each stage.
7192 The function make_compound_operation is called to convert an expression
7193 consisting of shifts and ANDs into the equivalent compound expression.
7194 It is the inverse of this function, loosely speaking. */
7196 static rtx
7198 {
7202 rtx tem;
7203 scalar_int_mode inner_mode;
7206 {
7209 /* FALLTHRU */
7211 /* We can't necessarily use a const_int for a multiword mode;
7212 it depends on implicitly extending the value.
7213 Since we don't know the right way to extend it,
7214 we can't tell whether the implicit way is right.
7216 Even for a mode that is no wider than a const_int,
7217 we can't win, because we need to sign extend one of its bits through
7218 the rest of it, and we don't know which bit. */
7222 /* Reject modes that aren't scalar integers because turning vector
7223 or complex modes into shifts causes problems. */
7227 /* Return if (subreg:MODE FROM 0) is not a safe replacement for
7228 (zero_extend:MODE FROM) or (sign_extend:MODE FROM). It is for any MEM
7229 because (SUBREG (MEM...)) is guaranteed to cause the MEM to be
7230 reloaded. If not for that, MEM's would very rarely be safe.
7232 Reject modes bigger than a word, because we might not be able
7233 to reference a two-register group starting with an arbitrary register
7234 (and currently gen_lowpart might crash for a SUBREG). */
7240 /* If the inner object has VOIDmode (the only way this can happen
7241 is if it is an ASM_OPERANDS), we can't do anything since we don't
7242 know how much masking to do. */
7251 /* fall through */
7254 /* If the operand is a CLOBBER, just return it. */
7262 /* Reject modes that aren't scalar integers because turning vector
7263 or complex modes into shifts causes problems. */
7270 /* This should stay within the object being extracted, fail otherwise. */
7281 }
7283 /* We've rejected non-scalar operations by now. */
7286 /* Convert sign extension to zero extension, if we know that the high
7287 bit is not set, as this is easier to optimize. It will be converted
7288 back to cheaper alternative in make_extraction. */
7294 {
7298 /* Make sure this is a profitable operation. */
7305 else
7307 }
7309 /* We can optimize some special cases of ZERO_EXTEND. */
7311 {
7312 /* (zero_extend:DI (truncate:SI foo:DI)) is just foo:DI if we
7313 know that the last value didn't have any inappropriate bits
7314 set. */
7322 /* Likewise for (zero_extend:DI (subreg:SI foo:DI 0)). */
7331 /* (zero_extend:DI (truncate:SI foo:DI)) is just foo:DI when foo
7332 is a comparison and STORE_FLAG_VALUE permits. This is like
7333 the first case, but it works even when MODE is larger
7334 than HOST_WIDE_INT. */
7342 /* Likewise for (zero_extend:DI (subreg:SI foo:DI 0)). */
7351 }
7353 /* If we reach here, we want to return a pair of shifts. The inner
7354 shift is a left shift of BITSIZE - POS - LEN bits. The outer
7355 shift is a right shift of BITSIZE - LEN bits. It is arithmetic or
7356 logical depending on the value of UNSIGNEDP.
7358 If this was a ZERO_EXTEND or ZERO_EXTRACT, this pair of shifts will be
7359 converted into an AND of a shift.
7361 We must check for the case where the left shift would have a negative
7362 count. This can happen in a case like (x >> 31) & 255 on machines
7363 that can't shift by a constant. On those machines, we would first
7364 combine the shift with the AND to produce a variable-position
7365 extraction. Then the constant of 31 would be substituted in
7366 to produce such a position. */
7370 {
7378 }
7383 pos),
7385 else
7386 /* Any other cases we can't handle. */
7389 /* If we couldn't do this for some reason, return the original
7390 expression. */
7395 }
7396 \f
7397 /* X is a SET which contains an assignment of one object into
7398 a part of another (such as a bit-field assignment, STRICT_LOW_PART,
7399 or certain SUBREGS). If possible, convert it into a series of
7400 logical operations.
7402 We half-heartedly support variable positions, but do not at all
7403 support variable lengths. */
7405 static const_rtx
7407 {
7408 rtx inner;
7412 scalar_int_mode compute_mode;
7414 /* Loop until we find something we can't simplify. */
7416 {
7419 {
7425 MAX_MODE_INT);
7426 }
7429 {
7437 /* A constant position should stay within the width of INNER. */
7442 {
7448 /* If position is ADJUST - X, new position is X. */
7450 else
7454 pos);
7455 }
7456 }
7458 /* If the destination is a subreg that overwrites the whole of the inner
7459 register, we can move the subreg to the source. */
7461 /* We need SUBREGs to compute nonzero_bits properly. */
7462 && nonzero_sign_valid
7464 {
7466 gen_lowpart
7470 }
7471 else
7477 /* Don't attempt bitwise arithmetic on non scalar integer modes. */
7479 {
7480 /* Don't do anything for vector or complex integral types. */
7484 /* Try to find an integral mode to pun with. */
7490 }
7492 /* Compute a mask of LEN bits, if we can do this on the host machine. */
7496 /* Don't try to compute in too wide unsupported modes. */
7500 /* Now compute the equivalent expression. Make a copy of INNER
7501 for the SET_DEST in case it is a MEM into which we will substitute;
7502 we don't want shared RTL in that case. */
7504 compute_mode);
7508 compute_mode,
7510 compute_mode),
7511 inner);
7516 mask),
7517 pos);
7522 }
7525 }
7526 \f
7527 /* Return an RTX for a reference to LEN bits of INNER. If POS_RTX is nonzero,
7528 it is an RTX that represents the (variable) starting position; otherwise,
7529 POS is the (constant) starting bit position. Both are counted from the LSB.
7531 UNSIGNEDP is nonzero for an unsigned reference and zero for a signed one.
7533 IN_DEST is nonzero if this is a reference in the destination of a SET.
7534 This is used when a ZERO_ or SIGN_EXTRACT isn't needed. If nonzero,
7535 a STRICT_LOW_PART will be used, if zero, ZERO_EXTEND or SIGN_EXTEND will
7536 be used.
7538 IN_COMPARE is nonzero if we are in a COMPARE. This means that a
7539 ZERO_EXTRACT should be built even for bits starting at bit 0.
7541 MODE is the desired mode of the result (if IN_DEST == 0).
7543 The result is an RTX for the extraction or NULL_RTX if the target
7544 can't handle it. */
7546 static rtx
7550 {
7551 /* This mode describes the size of the storage area
7552 to fetch the overall value from. Within that, we
7553 ignore the POS lowest bits, etc. */
7555 machine_mode inner_mode;
7556 scalar_int_mode wanted_inner_mode;
7562 HOST_WIDE_INT orig_pos;
7570 /* If trying or potentionally trying to extract
7571 bits outside of is_mode, don't look through
7572 non-paradoxical SUBREGs. See PR82192. */
7575 {
7576 /* If going from (subreg:SI (mem:QI ...)) to (mem:QI ...),
7577 consider just the QI as the memory to extract from.
7578 The subreg adds or removes high bits; its mode is
7579 irrelevant to the meaning of this extraction,
7580 since POS and LEN count from the lsb. */
7584 }
7589 {
7590 /* We're extracting the least significant bits of an rtx
7591 (ashift X (const_int C)), where LEN > C. Extract the
7592 least significant (LEN - C) bits of X, giving an rtx
7593 whose mode is MODE, then shift it left C times. */
7599 }
7601 /* If trying or potentionally trying to extract
7602 bits outside of is_mode, don't look through
7603 TRUNCATE. See PR82192. */
7610 /* See if this can be done without an extraction. We never can if the
7611 width of the field is not the same as that of some integer mode. For
7612 registers, we can only avoid the extraction if the position is at the
7613 low-order bit and this is either not in the destination or we have the
7614 appropriate STRICT_LOW_PART operation available.
7616 For MEM, we can avoid an extract if the field starts on an appropriate
7617 boundary and we can change the mode of the memory reference. */
7619 scalar_int_mode tmode;
7628 && (! in_dest
7632 && (pos
7635 /* We can't do this if we are widening INNER_MODE (it
7636 may not be aligned, for one thing). */
7642 {
7643 /* If INNER is a MEM, make a new MEM that encompasses just the desired
7644 field. If the original and current mode are the same, we need not
7645 adjust the offset. Otherwise, we do if bytes big endian.
7647 If INNER is not a MEM, get a piece consisting of just the field
7648 of interest (in this case POS % BITS_PER_WORD must be 0). */
7651 {
7652 poly_int64 offset;
7654 /* POS counts from lsb, but make OFFSET count in memory order. */
7658 else
7662 }
7664 {
7666 {
7667 /* We can't call gen_lowpart in a DEST since we
7668 always want a SUBREG (see below) and it would sometimes
7669 return a new hard register. */
7671 {
7672 poly_uint64 offset
7675 /* Avoid creating invalid subregs, for example when
7676 simplifying (x>>32)&255. */
7681 }
7682 else
7684 }
7685 else
7687 }
7688 else
7690 len >= HOST_BITS_PER_WIDE_INT
7691 ? HOST_WIDE_INT_M1U
7694 /* If this extraction is going into the destination of a SET,
7695 make a STRICT_LOW_PART unless we made a MEM. */
7710 /* If we know that no extraneous bits are set, and that the high
7711 bit is not set, convert the extraction to the cheaper of
7712 sign and zero extension, that are equivalent in these cases. */
7718 {
7722 /* Prefer ZERO_EXTENSION, since it gives more information to
7723 backends. */
7728 }
7730 /* Otherwise, sign- or zero-extend unless we already are in the
7731 proper mode. */
7735 }
7737 /* Unless this is a COMPARE or we have a funny memory reference,
7738 don't do anything with zero-extending field extracts starting at
7739 the low-order bit since they are simple AND operations. */
7744 /* Unless INNER is not MEM, reject this if we would be spanning bytes or
7745 if the position is not a constant and the length is not 1. In all
7746 other cases, we would only be going outside our object in cases when
7747 an original shift would have been undefined. */
7756 /* If INNER is not from memory, we want it to have the mode of a register
7757 extraction pattern's structure operand, or word_mode if there is no
7758 such pattern. The same applies to extraction_mode and pos_mode
7759 and their respective operands.
7761 For memory, assume that the desired extraction_mode and pos_mode
7762 are the same as for a register operation, since at present we don't
7763 have named patterns for aligned memory structures. */
7768 {
7772 }
7774 /* Never narrow an object, since that might not be safe. */
7782 else
7783 {
7784 /* Be careful not to go beyond the extracted object and maintain the
7785 natural alignment of the memory. */
7790 }
7795 {
7796 /* POS is passed as if BITS_BIG_ENDIAN == 0, so we need to convert it to
7797 BITS_BIG_ENDIAN style. If position is constant, compute new
7798 position. Otherwise, build subtraction.
7799 Note that POS is relative to the mode of the original argument.
7800 If it's a MEM we need to recompute POS relative to that.
7801 However, if we're extracting from (or inserting into) a register,
7802 we want to recompute POS relative to wanted_inner_mode. */
7811 else
7812 pos_rtx
7815 pos_rtx);
7816 /* POS may be less than 0 now, but we check for that below.
7817 Note that it can only be less than 0 if !MEM_P (inner). */
7818 }
7820 /* If INNER has a wider mode, and this is a constant extraction, try to
7821 make it smaller and adjust the byte to point to the byte containing
7822 the value. */
7825 && ! pos_rtx
7830 {
7833 /* The computations below will be correct if the machine is big
7834 endian in both bits and bytes or little endian in bits and bytes.
7835 If it is mixed, we must adjust. */
7837 /* If bytes are big endian and we had a paradoxical SUBREG, we must
7838 adjust OFFSET to compensate. */
7843 /* We can now move to the desired byte. */
7854 }
7856 /* If INNER is not memory, get it into the proper mode. If we are changing
7857 its mode, POS must be a constant and smaller than the size of the new
7858 mode. */
7860 {
7861 /* On the LHS, don't create paradoxical subregs implicitely truncating
7862 the register unless TARGET_TRULY_NOOP_TRUNCATION. */
7865 wanted_inner_mode))
7877 pos_rtx
7879 ? HOST_WIDE_INT_M1U
7883 }
7885 /* Adjust mode of POS_RTX, if needed. If we want a wider mode, we
7886 have to zero extend. Otherwise, we can just use a SUBREG.
7888 We dealt with constant rtxes earlier, so pos_rtx cannot
7889 have VOIDmode at this point. */
7893 {
7897 /* If we know that no extraneous bits are set, and that the high
7898 bit is not set, convert extraction to cheaper one - either
7899 SIGN_EXTENSION or ZERO_EXTENSION, that are equivalent in these
7900 cases. */
7908 {
7912 /* Prefer ZERO_EXTENSION, since it gives more information to
7913 backends. */
7917 }
7919 }
7921 /* Make POS_RTX unless we already have it and it is correct. If we don't
7922 have a POS_RTX but we do have an ORIG_POS_RTX, the latter must
7923 be a CONST_INT. */
7930 /* Make the required operation. See if we can use existing rtx. */
7937 }
7938 \f
7939 /* See if X (of mode MODE) contains an ASHIFT of COUNT or more bits that
7940 can be commuted with any other operations in X. Return X without
7941 that shift if so. */
7943 static rtx
7945 {
7947 rtx tem;
7950 {
7952 /* This is the shift itself. If it is wide enough, we will return
7953 either the value being shifted if the shift count is equal to
7954 COUNT or a shift for the difference. */
7968 /* If we can safely shift this constant and we find the inner shift,
7969 make a new operation. */
7974 {
7978 }
7983 }
7986 }
7987 \f
7988 /* Subroutine of make_compound_operation. *X_PTR is the rtx at the current
7989 level of the expression and MODE is its mode. IN_CODE is as for
7990 make_compound_operation. *NEXT_CODE_PTR is the value of IN_CODE
7991 that should be used when recursing on operands of *X_PTR.
7993 There are two possible actions:
7995 - Return null. This tells the caller to recurse on *X_PTR with IN_CODE
7996 equal to *NEXT_CODE_PTR, after which *X_PTR holds the final value.
7998 - Return a new rtx, which the caller returns directly. */
8000 static rtx
8004 {
8012 rtx tem;
8013 scalar_int_mode inner_mode;
8017 {
8020 }
8022 /* Process depending on the code of this operation. If NEW is set
8023 nonzero, it will be returned. */
8026 {
8028 /* Convert shifts by constants into multiplications if inside
8029 an address. */
8033 {
8039 {
8042 }
8045 }
8054 {
8058 }
8061 {
8065 mode));
8067 }
8068 else
8069 {
8072 }
8082 {
8086 }
8089 {
8093 mode));
8095 }
8096 else
8097 {
8101 }
8104 /* If the second operand is not a constant, we can't do anything
8105 with it. */
8109 /* If the constant is a power of two minus one and the first operand
8110 is a logical right shift, make an extraction. */
8113 {
8117 }
8119 /* Same as previous, but for (subreg (lshiftrt ...)) in first op. */
8126 {
8133 /* If we narrowed the mode when dropping the subreg, then we lose. */
8137 /* If that didn't give anything, see if the AND simplifies on
8138 its own. */
8140 {
8144 }
8145 }
8146 /* Same as previous, but for (xor/ior (lshiftrt...) (lshiftrt...)). */
8152 {
8153 /* Apply the distributive law, and then try to make extractions. */
8160 }
8162 /* If we are have (and (rotate X C) M) and C is larger than the number
8163 of bits in M, this is an extraction. */
8169 {
8175 }
8177 /* On machines without logical shifts, if the operand of the AND is
8178 a logical shift and our mask turns off all the propagated sign
8179 bits, we can replace the logical shift with an arithmetic shift. */
8187 {
8197 next_code),
8199 }
8201 /* If the constant is one less than a power of two, this might be
8202 representable by an extraction even if no shift is present.
8203 If it doesn't end up being a ZERO_EXTEND, we will ignore it unless
8204 we are in a COMPARE. */
8208 next_code),
8211 /* If we are in a comparison and this is an AND with a power of two,
8212 convert this into the appropriate bit extract. */
8218 next_code),
8221 /* If the one operand is a paradoxical subreg of a register or memory and
8222 the constant (limited to the smaller mode) has only zero bits where
8223 the sub expression has known zero bits, this can be expressed as
8224 a zero_extend. */
8226 {
8227 rtx sub;
8235 {
8239 /* original AND constant with all the known zero bits set */
8242 {
8246 }
8247 }
8248 }
8253 /* If the sign bit is known to be zero, replace this with an
8254 arithmetic shift. */
8259 {
8262 next_code),
8265 }
8267 /* fall through */
8273 /* If we have (ashiftrt (ashift foo C1) C2) with C2 >= C1,
8274 this is a SIGN_EXTRACT. */
8281 {
8288 }
8290 /* See if we have operations between an ASHIFTRT and an ASHIFT.
8291 If so, try to merge the shifts into a SIGN_EXTEND. We could
8292 also do this for some cases of SIGN_EXTRACT, but it doesn't
8293 seem worth the effort; the case checked for occurs on Alpha. */
8304 next_code),
8311 /* Call ourselves recursively on the inner expression. If we are
8312 narrowing the object and it has a different RTL code from
8313 what it originally did, do this SUBREG as a force_to_mode. */
8314 {
8318 /* If the SUBREG is masking of a logical right shift,
8319 make an extraction. */
8326 {
8335 }
8337 /* If in_code is COMPARE, it isn't always safe to pass it through
8338 to the recursive make_compound_operation call. */
8342 /* (subreg:SI (and:DI (reg:DI) (const_int 0x800000000)) 0)
8343 is (const_int 0), rather than
8344 (subreg:SI (lshiftrt:DI (reg:DI) (const_int 35)) 0).
8345 Similarly (subreg:QI (and:SI (reg:SI) (const_int 0x80)) 0)
8346 for non-equality comparisons against 0 is not equivalent
8347 to (subreg:QI (lshiftrt:SI (reg:SI) (const_int 7)) 0). */
8357 simplified
8365 {
8366 rtx newer
8369 /* If we have something other than a SUBREG, we might have
8370 done an expansion, so rerun ourselves. */
8374 /* force_to_mode can expand compounds. If it just re-expanded
8375 the compound, use gen_lowpart to convert to the desired
8376 mode. */
8378 /* Likewise if it re-expanded the compound only partially.
8379 This happens for SUBREG of ZERO_EXTRACT if they extract
8380 the same number of bits. */
8389 }
8393 }
8398 }
8404 }
8406 /* Look at the expression rooted at X. Look for expressions
8407 equivalent to ZERO_EXTRACT, SIGN_EXTRACT, ZERO_EXTEND, SIGN_EXTEND.
8408 Form these expressions.
8410 Return the new rtx, usually just X.
8412 Also, for machines like the VAX that don't have logical shift insns,
8413 try to convert logical to arithmetic shift operations in cases where
8414 they are equivalent. This undoes the canonicalizations to logical
8415 shifts done elsewhere.
8417 We try, as much as possible, to re-use rtl expressions to save memory.
8419 IN_CODE says what kind of expression we are processing. Normally, it is
8420 SET. In a memory address it is MEM. When processing the arguments of
8421 a comparison or a COMPARE against zero, it is COMPARE, or EQ if more
8422 precisely it is an equality comparison against zero. */
8424 rtx
8426 {
8433 /* Select the code to be used in recursive calls. Once we are inside an
8434 address, we stay there. If we have a comparison, set to COMPARE,
8435 but once inside, go back to our default of SET. */
8442 scalar_int_mode mode;
8444 {
8450 }
8452 /* Now recursively process each operand of this operation. We need to
8453 handle ZERO_EXTEND specially so that we don't lose track of the
8454 inner mode. */
8456 {
8464 }
8469 {
8472 }
8475 {
8478 }
8482 }
8483 \f
8484 /* Given M see if it is a value that would select a field of bits
8485 within an item, but not the entire word. Return -1 if not.
8486 Otherwise, return the starting position of the field, where 0 is the
8487 low-order bit.
8489 *PLEN is set to the length of the field. */
8491 static int
8493 {
8494 /* Get the bit number of the first 1 bit from the right, -1 if none. */
8499 /* Now shift off the low-order zero bits and see if we have a
8500 power of two minus 1. */
8508 }
8509 \f
8510 /* If X refers to a register that equals REG in value, replace these
8511 references with REG. */
8512 static rtx
8514 {
8522 {
8555 /* FALLTHRU */
8559 {
8563 else
8565 }
8567 /* fall through */
8574 {
8577 {
8579 {
8582 }
8584 }
8585 }
8587 {
8590 {
8593 {
8595 {
8598 }
8600 }
8601 }
8602 }
8605 }
8608 }
8610 /* Return X converted to MODE. If the value is already truncated to
8611 MODE we can just return a subreg even though in the general case we
8612 would need an explicit truncation. */
8614 static rtx
8616 {
8621 {
8622 /* Bit-cast X into an integer mode. */
8627 }
8630 }
8632 /* See if X can be simplified knowing that we will only refer to it in
8633 MODE and will only refer to those bits that are nonzero in MASK.
8634 If other bits are being computed or if masking operations are done
8635 that select a superset of the bits in MASK, they can sometimes be
8636 ignored.
8638 Return a possibly simplified expression, but always convert X to
8639 MODE. If X is a CONST_INT, AND the CONST_INT with MASK.
8641 If JUST_SELECT is nonzero, don't optimize by noticing that bits in MASK
8642 are all off in X. This is used when X will be complemented, by either
8643 NOT, NEG, or XOR. */
8645 static rtx
8648 {
8651 machine_mode op_mode;
8654 /* If this is a CALL or ASM_OPERANDS, don't do anything. Some of the
8655 code below will do the wrong thing since the mode of such an
8656 expression is VOIDmode.
8658 Also do nothing if X is a CLOBBER; this can happen if X was
8659 the return value from a call to gen_lowpart. */
8663 /* We want to perform the operation in its present mode unless we know
8664 that the operation is valid in MODE, in which case we do the operation
8665 in MODE. */
8670 /* It is not valid to do a right-shift in a narrower mode
8671 than the one it came in with. */
8676 /* Truncate MASK to fit OP_MODE. */
8680 /* Determine what bits of X are guaranteed to be (non)zero. */
8683 /* If none of the bits in X are needed, return a zero. */
8687 /* If X is a CONST_INT, return a new one. Do this here since the
8688 test below will fail. */
8690 {
8693 else
8694 {
8697 }
8698 }
8700 /* If X is narrower than MODE and we want all the bits in X's mode, just
8701 get X in the proper mode. */
8706 /* We can ignore the effect of a SUBREG if it narrows the mode or
8707 if the constant masks to zero all the bits the mode doesn't have. */
8711 || (mask
8719 /* OP_MODE is either MODE or XMODE, so it must be a scalar
8720 integer too. */
8726 }
8728 /* Subroutine of force_to_mode that handles cases in which both X and
8729 the result are scalar integers. MODE is the mode of the result,
8730 XMODE is the mode of X, and OP_MODE says which of MODE or XMODE
8731 is preferred for simplified versions of X. The other arguments
8732 are as for force_to_mode. */
8734 static rtx
8738 {
8743 poly_int64 const_op0;
8745 /* When we have an arithmetic operation, or a shift whose count we
8746 do not know, we need to assume that all bits up to the highest-order
8747 bit in MASK will be needed. This is how we form such a mask. */
8750 else
8755 {
8757 /* If X is a (clobber (const_int)), return it since we know we are
8758 generating something that won't match. */
8771 /* Similarly for a truncate. */
8775 /* If this is an AND with a constant, convert it into an AND
8776 whose constant is the AND of that constant with MASK. If it
8777 remains an AND of MASK, delete it since it is redundant. */
8780 {
8785 /* If X is still an AND, see if it is an AND with a mask that
8786 is just some low-order bits. If so, and it is MASK, we don't
8787 need it. */
8793 /* If it remains an AND, try making another AND with the bits
8794 in the mode mask that aren't in MASK turned on. If the
8795 constant in the AND is wide enough, this might make a
8796 cheaper constant. */
8801 {
8802 unsigned HOST_WIDE_INT cval
8804 rtx y;
8811 }
8814 }
8819 /* In (and (plus FOO C1) M), if M is a mask that just turns off
8820 low-order bits (as in an alignment operation) and FOO is already
8821 aligned to that boundary, mask C1 to that boundary as well.
8822 This may eliminate that PLUS and, later, the AND. */
8824 {
8828 /* If MODE is narrower than HOST_WIDE_INT and mask is a negative
8829 number, sign extend it. */
8842 }
8844 /* fall through */
8847 /* Substituting into the operands of a widening MULT is not likely to
8848 create RTL matching a machine insn. */
8858 /* For PLUS, MINUS and MULT, we need any bits less significant than the
8859 most significant bit in MASK since carries from those bits will
8860 affect the bits we are interested in. */
8865 /* If X is (minus C Y) where C's least set bit is larger than any bit
8866 in the mask, then we may replace with (neg Y). */
8869 {
8872 }
8874 /* Similarly, if C contains every bit in the fuller_mask, then we may
8875 replace with (not Y). */
8878 {
8881 }
8888 /* If X is (ior (lshiftrt FOO C1) C2), try to commute the IOR and
8889 LSHIFTRT so we end up with an (and (lshiftrt (ior ...) ...) ...)
8890 operation which may be a bitfield extraction. Ensure that the
8891 constant we form is not wider than the mode of X. */
8903 {
8906 xmode);
8912 }
8914 binop:
8915 /* For most binary operations, just propagate into the operation and
8916 change the mode if we have an operation of that mode. */
8921 /* If we ended up truncating both operands, truncate the result of the
8922 operation instead. */
8925 {
8928 }
8934 {
8937 }
8941 /* For left shifts, do the same, but just for the first operand.
8942 However, we cannot do anything with shifts where we cannot
8943 guarantee that the counts are smaller than the size of the mode
8944 because such a count will have a different meaning in a
8945 wider mode. */
8955 /* If the shift count is a constant and we can do arithmetic in
8956 the mode of the shift, refine which bits we need. Otherwise, use the
8957 conservative form of the mask. */
8963 else
8971 {
8974 }
8978 /* Here we can only do something if the shift count is a constant,
8979 this shift constant is valid for the host, and we can do arithmetic
8980 in OP_MODE. */
8986 {
8990 /* Select the mask of the bits we need for the shift operand. */
8993 /* We can only change the mode of the shift if we can do arithmetic
8994 in the mode of the shift and INNER_MASK is no wider than the
8995 width of X's mode. */
9002 {
9005 }
9006 }
9008 /* If we have (and (lshiftrt FOO C1) C2) where the combination of the
9009 shift and AND produces only copies of the sign bit (C2 is one less
9010 than a power of two), we can do this with just a shift. */
9014 /* The shift puts one of the sign bit copies in the least significant
9015 bit. */
9020 /* Number of bits left after the shift must be more than the mask
9021 needs. */
9024 /* Must be more sign bit copies than the mask needs. */
9027 {
9031 }
9035 /* If we are just looking for the sign bit, we don't need this shift at
9036 all, even if it has a variable count. */
9040 /* If this is a shift by a constant, get a mask that contains those bits
9041 that are not copies of the sign bit. We then have two cases: If
9042 MASK only includes those bits, this can be a logical shift, which may
9043 allow simplifications. If MASK is a single-bit field not within
9044 those bits, we are requesting a copy of the sign bit and hence can
9045 shift the sign bit to the appropriate location. */
9049 {
9053 /* If the considered data is wider than HOST_WIDE_INT, we can't
9054 represent a mask for all its bits in a single scalar.
9055 But we only care about the lower bits, so calculate these. */
9058 {
9061 /* GET_MODE_PRECISION (GET_MODE (x)) - INTVAL (XEXP (x, 1))
9062 is the number of bits a full-width mask would have set.
9063 We need only shift if these are fewer than nonzero can
9064 hold. If not, we must keep all bits set in nonzero. */
9069 + HOST_BITS_PER_WIDE_INT
9071 }
9072 else
9073 {
9076 }
9079 {
9084 }
9087 {
9088 x = simplify_shift_const
9094 }
9095 }
9097 /* If MASK is 1, convert this to an LSHIFTRT. This can be done
9098 even if the shift count isn't a constant. */
9102 shiftrt:
9104 /* If this is a zero- or sign-extension operation that just affects bits
9105 we don't care about, remove it. Be sure the call above returned
9106 something that is still a shift. */
9116 next_select);
9122 /* If the shift count is constant and we can do computations
9123 in the mode of X, compute where the bits we care about are.
9124 Otherwise, we can't do anything. Don't change the mode of
9125 the shift or propagate MODE into the shift, though. */
9128 {
9137 }
9141 /* If we just want the low-order bit, the NEG isn't needed since it
9142 won't change the low-order bit. */
9146 /* We need any bits less significant than the most significant bit in
9147 MASK since carries from those bits will affect the bits we are
9148 interested in. */
9153 /* (not FOO) is (xor FOO CONST), so if FOO is an LSHIFTRT, we can do the
9154 same as the XOR case above. Ensure that the constant we form is not
9155 wider than the mode of X. */
9163 {
9170 }
9172 /* (and (not FOO) CONST) is (not (or FOO (not CONST))), so we must
9173 use the full mask inside the NOT. */
9176 unop:
9179 next_select));
9181 {
9184 }
9188 /* (and (ne FOO 0) CONST) can be (and FOO CONST) if CONST is included
9189 in STORE_FLAG_VALUE and FOO has a single bit that might be nonzero,
9190 which is equal to STORE_FLAG_VALUE. */
9202 /* We have no way of knowing if the IF_THEN_ELSE can itself be
9203 written in a narrower mode. We play it safe and do not do so. */
9219 }
9221 /* Ensure we return a value of the proper mode. */
9223 }
9224 \f
9225 /* Return nonzero if X is an expression that has one of two values depending on
9226 whether some other value is zero or nonzero. In that case, we return the
9227 value that is being tested, *PTRUE is set to the value if the rtx being
9228 returned has a nonzero value, and *PFALSE is set to the other alternative.
9230 If we return zero, we set *PTRUE and *PFALSE to X. */
9232 static rtx
9234 {
9239 scalar_int_mode int_mode;
9241 /* If we are comparing a value against zero, we are done. */
9244 {
9248 }
9250 /* If this is a unary operation whose operand has one of two values, apply
9251 our opcode to compute those values. */
9254 {
9259 }
9261 /* If this is a COMPARE, do nothing, since the IF_THEN_ELSE we would
9262 make can't possibly match and would suppress other optimizations. */
9264 ;
9266 /* If this is a binary operation, see if either side has only one of two
9267 values. If either one does or if both do and they are conditional on
9268 the same value, compute the new true and false values. */
9270 {
9278 {
9279 /* Try to enable a simplification by undoing work done by
9280 if_then_else_cond if it converted a REG into something more
9281 complex. */
9283 {
9286 }
9287 else
9288 {
9291 }
9292 }
9296 {
9297 /* If if_then_else_cond returned zero, then true/false are the
9298 same rtl. We must copy one of them to prevent invalid rtl
9299 sharing. */
9306 {
9311 }
9312 else
9313 {
9316 }
9319 }
9321 /* See if we have PLUS, IOR, XOR, MINUS or UMAX, where one of the
9322 operands is zero when the other is nonzero, and vice-versa,
9323 and STORE_FLAG_VALUE is 1 or -1. */
9329 {
9347 {
9354 const_true_rtx);
9356 }
9357 }
9359 /* Similarly for MULT, AND and UMIN, except that for these the result
9360 is always zero. */
9364 {
9378 {
9381 }
9382 }
9383 }
9386 {
9387 /* If we have IF_THEN_ELSE already, extract the condition and
9388 canonicalize it if it is NE or EQ. */
9394 {
9397 }
9398 else
9400 }
9402 /* If X is a SUBREG, we can narrow both the true and false values
9403 if the inner expression, if there is a condition. */
9407 {
9413 {
9417 }
9418 }
9420 /* If X is a constant, this isn't special and will cause confusions
9421 if we treat it as such. Likewise if it is equivalent to a constant. */
9424 ;
9426 /* If we're in BImode, canonicalize on 0 and STORE_FLAG_VALUE, as that
9427 will be least confusing to the rest of the compiler. */
9429 {
9432 }
9434 /* If X is known to be either 0 or -1, those are the true and
9435 false values when testing X. */
9440 {
9443 }
9445 /* Likewise for 0 or a single bit. */
9448 {
9451 }
9453 /* Otherwise fail; show no condition with true and false values the same. */
9456 }
9457 \f
9458 /* Return the value of expression X given the fact that condition COND
9459 is known to be true when applied to REG as its first operand and VAL
9460 as its second. X is known to not be shared and so can be modified in
9461 place.
9463 We only handle the simplest cases, and specifically those cases that
9464 arise with IF_THEN_ELSE expressions. */
9466 static rtx
9468 {
9476 /* If either operand of the condition is a floating point value,
9477 then we have to avoid collapsing an EQ comparison. */
9487 /* If X is (abs REG) and we know something about REG's relationship
9488 with zero, we may be able to simplify this. */
9492 {
9501 }
9503 /* The only other cases we handle are MIN, MAX, and comparisons if the
9504 operands are the same as REG and VAL. */
9507 {
9509 {
9512 }
9515 {
9517 {
9525 else
9527 }
9530 {
9533 /* Do not reverse the condition when it is NE or EQ.
9534 This is because we cannot conclude anything about
9535 the value of 'SMAX (x, y)' when x is not equal to y,
9536 but we can when x equals y. */
9542 {
9553 }
9554 }
9555 }
9556 }
9558 {
9563 {
9564 /* We must simplify subreg here, before we lose track of the
9565 original inner_mode. */
9570 else
9572 }
9575 }
9576 /* We don't have to handle SIGN_EXTEND here, because even in the
9577 case of replacing something with a modeless CONST_INT, a
9578 CONST_INT is already (supposed to be) a valid sign extension for
9579 its narrower mode, which implies it's already properly
9580 sign-extended for the wider mode. Now, for ZERO_EXTEND, the
9581 story is different. */
9583 {
9588 {
9589 /* We must simplify the zero_extend here, before we lose
9590 track of the original inner_mode. */
9595 else
9597 }
9600 }
9604 {
9611 }
9614 }
9615 \f
9616 /* See if X and Y are equal for the purposes of seeing if we can rewrite an
9617 assignment as a field assignment. */
9619 static int
9621 {
9623 {
9631 }
9639 /* Check for a paradoxical SUBREG of a MEM compared with the MEM.
9640 Note that all SUBREGs of MEM are paradoxical; otherwise they
9641 would have been rewritten. */
9654 /* We used to see if get_last_value of X and Y were the same but that's
9655 not correct. In one direction, we'll cause the assignment to have
9656 the wrong destination and in the case, we'll import a register into this
9657 insn that might have already have been dead. So fail if none of the
9658 above cases are true. */
9660 }
9661 \f
9662 /* See if X, a SET operation, can be rewritten as a bit-field assignment.
9663 Return that assignment if so.
9665 We only handle the most common cases. */
9667 static rtx
9669 {
9672 rtx assign;
9674 HOST_WIDE_INT c1;
9675 HOST_WIDE_INT pos;
9677 rtx other;
9679 /* All the rules in this function are specific to scalar integers. */
9680 scalar_int_mode mode;
9684 /* If SRC was (and (not (ashift (const_int 1) POS)) DEST), this is
9685 a clear of a one-bit field. We will have changed it to
9686 (and (rotate (const_int -2) POS) DEST), so check for that. Also check
9687 for a SUBREG. */
9693 {
9699 }
9708 {
9715 }
9717 /* If SRC is (ior (ashift (const_int 1) POS) DEST), this is a set of a
9718 one-bit field. */
9722 {
9728 }
9730 /* If DEST is already a field assignment, i.e. ZERO_EXTRACT, and the
9731 SRC is an AND with all bits of that field set, then we can discard
9732 the AND. */
9737 {
9744 else
9747 /* Complete overlap. We can remove the source AND. */
9751 /* Partial overlap. We can reduce the source AND. */
9753 {
9757 }
9758 }
9760 /* The other case we handle is assignments into a constant-position
9761 field. They look like (ior/xor (and DEST C1) OTHER). If C1 represents
9762 a mask that has all one bits except for a group of zero bits and
9763 OTHER is known to have zeros where C1 has ones, this is such an
9764 assignment. Compute the position and length from C1. Shift OTHER
9765 to the appropriate position, force it to the required mode, and
9766 make the extraction. Check for the AND in both operands. */
9768 /* One or more SUBREGs might obscure the constant-position field
9769 assignment. The first one we are likely to encounter is an outer
9770 narrowing SUBREG, which we can just strip for the purposes of
9771 identifying the constant-field assignment. */
9788 /* The second SUBREG that might get in the way is a paradoxical
9789 SUBREG around the first operand of the AND. We want to
9790 pretend the operand is as wide as the destination here. We
9791 do this by adjusting the MEM to wider mode for the sole
9792 purpose of the call to rtx_equal_for_field_assignment_p. Also
9793 note this trick only works for MEMs. */
9805 /* The second SUBREG that might get in the way is a paradoxical
9806 SUBREG around the first operand of the AND. We want to
9807 pretend the operand is as wide as the destination here. We
9808 do this by adjusting the MEM to wider mode for the sole
9809 purpose of the call to rtx_equal_for_field_assignment_p. Also
9810 note this trick only works for MEMs. */
9818 else
9832 /* The mode to use for the source is the mode of the assignment, or of
9833 what is inside a possible STRICT_LOW_PART. */
9837 /* Shift OTHER right POS places and make it the source, restricting it
9838 to the proper length and mode. */
9842 dest);
9844 len >= HOST_BITS_PER_WIDE_INT
9845 ? HOST_WIDE_INT_M1U
9849 /* If SRC is masked by an AND that does not make a difference in
9850 the value being stored, strip it. */
9861 }
9862 \f
9863 /* See if X is of the form (+ (* a c) (* b c)) and convert to (* (+ a b) c)
9864 if so. */
9866 static rtx
9868 {
9872 rtx tem;
9874 /* Distributivity is not true for floating point as it can change the
9875 value. So we don't do it unless -funsafe-math-optimizations. */
9880 /* The outer operation can only be one of the following: */
9888 /* If either operand is a primitive we can't do anything, so get out
9889 fast. */
9899 /* See if the inner and outer operations distribute. */
9901 {
9906 /* These all distribute except over PLUS. */
9917 /* This is also a multiply, so it distributes over everything. */
9920 /* This used to handle SUBREG, but this turned out to be counter-
9921 productive, since (subreg (op ...)) usually is not handled by
9922 insn patterns, and this "optimization" therefore transformed
9923 recognizable patterns into unrecognizable ones. Therefore the
9924 SUBREG case was removed from here.
9926 It is possible that distributing SUBREG over arithmetic operations
9927 leads to an intermediate result than can then be optimized further,
9928 e.g. by moving the outer SUBREG to the other side of a SET as done
9929 in simplify_set. This seems to have been the original intent of
9930 handling SUBREGs here.
9932 However, with current GCC this does not appear to actually happen,
9933 at least on major platforms. If some case is found where removing
9934 the SUBREG case here prevents follow-on optimizations, distributing
9935 SUBREGs ought to be re-added at that place, e.g. in simplify_set. */
9939 }
9941 /* Set LHS and RHS to the inner operands (A and B in the example
9942 above) and set OTHER to the common operand (C in the example).
9943 There is only one way to do this unless the inner operation is
9944 commutative. */
9956 else
9959 /* Form the new inner operation, seeing if it simplifies first. */
9962 /* There is one exception to the general way of distributing:
9963 (a | c) ^ (b | c) -> (a ^ b) & ~c */
9965 {
9968 }
9970 /* We may be able to continuing distributing the result, so call
9971 ourselves recursively on the inner operation before forming the
9972 outer operation, which we return. */
9975 }
9977 /* See if X is of the form (* (+ A B) C), and if so convert to
9978 (+ (* A C) (* B C)) and try to simplify.
9980 Most of the time, this results in no change. However, if some of
9981 the operands are the same or inverses of each other, simplifications
9982 will result.
9984 For example, (and (ior A B) (not B)) can occur as the result of
9985 expanding a bit field assignment. When we apply the distributive
9986 law to this, we get (ior (and (A (not B))) (and (B (not B)))),
9987 which then simplifies to (and (A (not B))).
9989 Note that no checks happen on the validity of applying the inverse
9990 distributive law. This is pointless since we can do it in the
9991 few places where this routine is called.
9993 N is the index of the term that is decomposed (the arithmetic operation,
9994 i.e. (+ A B) in the first example above). !N is the index of the term that
9995 is distributed, i.e. of C in the first example above. */
9996 static rtx
9998 {
9999 machine_mode mode;
10003 /* Distributivity is not true for floating point as it can change the
10004 value. So we don't do it unless -funsafe-math-optimizations. */
10021 /* Special case (and (xor B C) (not A)), which is equivalent to
10022 (xor (ior A B) (ior A C)) */
10024 {
10027 }
10030 {
10031 /* Distribute the second term. */
10034 }
10035 else
10036 {
10037 /* Distribute the first term. */
10040 }
10050 }
10051 \f
10052 /* Simplify a logical `and' of VAROP with the constant CONSTOP, to be done
10053 in MODE. Return an equivalent form, if different from (and VAROP
10054 (const_int CONSTOP)). Otherwise, return NULL_RTX. */
10056 static rtx
10059 {
10062 rtx orig_varop;
10070 /* Simplify VAROP knowing that we will be only looking at some of the
10071 bits in it.
10073 Note by passing in CONSTOP, we guarantee that the bits not set in
10074 CONSTOP are not significant and will never be examined. We must
10075 ensure that is the case by explicitly masking out those bits
10076 before returning. */
10079 /* If VAROP is a CLOBBER, we will fail so return it. */
10083 /* If VAROP is a CONST_INT, then we need to apply the mask in CONSTOP
10084 to VAROP and return the new constant. */
10088 /* See what bits may be nonzero in VAROP. Unlike the general case of
10089 a call to nonzero_bits, here we don't care about bits outside
10090 MODE. */
10094 /* Turn off all bits in the constant that are known to already be zero.
10095 Thus, if the AND isn't needed at all, we will have CONSTOP == NONZERO_BITS
10096 which is tested below. */
10100 /* If we don't have any bits left, return zero. */
10104 /* If VAROP is a NEG of something known to be zero or 1 and CONSTOP is
10105 a power of two, we can replace this with an ASHIFT. */
10110 /* If VAROP is an IOR or XOR, apply the AND to both branches of the IOR
10111 or XOR, then try to apply the distributive law. This may eliminate
10112 operations if either branch can be simplified because of the AND.
10113 It may also make some cases more complex, but those cases probably
10114 won't match a pattern either with or without this. */
10117 {
10119 return
10120 gen_lowpart
10122 apply_distributive_law
10126 constop),
10129 constop))));
10130 }
10132 /* If VAROP is PLUS, and the constant is a mask of low bits, distribute
10133 the AND and see if one of the operands simplifies to zero. If so, we
10134 may eliminate it. */
10138 {
10147 }
10149 /* Make a SUBREG if necessary. If we can't make it, fail. */
10154 /* If we are only masking insignificant bits, return VAROP. */
10161 /* Otherwise, return an AND. */
10163 }
10166 /* We have X, a logical `and' of VAROP with the constant CONSTOP, to be done
10167 in MODE.
10169 Return an equivalent form, if different from X. Otherwise, return X. If
10170 X is zero, we are to always construct the equivalent form. */
10172 static rtx
10175 {
10186 }
10187 \f
10188 /* Given a REG X of mode XMODE, compute which bits in X can be nonzero.
10189 We don't care about bits outside of those defined in MODE.
10191 For most X this is simply GET_MODE_MASK (GET_MODE (MODE)), but if X is
10192 a shift, AND, or zero_extract, we can do better. */
10194 static rtx
10196 scalar_int_mode mode,
10198 {
10199 rtx tem;
10202 /* If X is a register whose nonzero bits value is current, use it.
10203 Otherwise, if X is a register whose value we can find, use that
10204 value. Otherwise, use the previously-computed global nonzero bits
10205 for this register. */
10220 && !REGNO_REG_SET_P
10223 {
10224 /* Note that, even if the precision of last_set_mode is lower than that
10225 of mode, record_value_for_reg invoked nonzero_bits on the register
10226 with nonzero_bits_mode (because last_set_mode is necessarily integral
10227 and HWI_COMPUTABLE_MODE_P in this case) so bits in nonzero_bits_mode
10228 are all valid, hence in mode too since nonzero_bits_mode is defined
10229 to the largest HWI_COMPUTABLE_MODE_P mode. */
10232 }
10236 {
10241 }
10244 {
10248 /* We don't know anything about the upper bits. */
10252 }
10255 }
10257 /* Given a reg X of mode XMODE, return the number of bits at the high-order
10258 end of X that are known to be equal to the sign bit. X will be used
10259 in mode MODE; the returned value will always be between 1 and the
10260 number of bits in MODE. */
10262 static rtx
10264 scalar_int_mode mode,
10266 {
10267 rtx tem;
10280 && !REGNO_REG_SET_P
10283 {
10286 }
10297 }
10298 \f
10299 /* Return the number of "extended" bits there are in X, when interpreted
10300 as a quantity in MODE whose signedness is indicated by UNSIGNEDP. For
10301 unsigned quantities, this is the number of high-order zero bits.
10302 For signed quantities, this is the number of copies of the sign bit
10303 minus 1. In both case, this function returns the number of "spare"
10304 bits. For example, if two quantities for which this function returns
10305 at least 1 are added, the addition is known not to overflow.
10307 This function will always return 0 unless called during combine, which
10308 implies that it must be called from a define_split. */
10310 unsigned int
10312 {
10316 scalar_int_mode int_mode;
10324 }
10326 /* This function is called from `simplify_shift_const' to merge two
10327 outer operations. Specifically, we have already found that we need
10328 to perform operation *POP0 with constant *PCONST0 at the outermost
10329 position. We would now like to also perform OP1 with constant CONST1
10330 (with *POP0 being done last).
10332 Return 1 if we can do the operation and update *POP0 and *PCONST0 with
10333 the resulting operation. *PCOMP_P is set to 1 if we would need to
10334 complement the innermost operand, otherwise it is unchanged.
10336 MODE is the mode in which the operation will be done. No bits outside
10337 the width of this mode matter. It is assumed that the width of this mode
10338 is smaller than or equal to HOST_BITS_PER_WIDE_INT.
10340 If *POP0 or OP1 are UNKNOWN, it means no operation is required. Only NEG, PLUS,
10341 IOR, XOR, and AND are supported. We may set *POP0 to SET if the proper
10342 result is simply *PCONST0.
10344 If the resulting operation cannot be expressed as one operation, we
10345 return 0 and do not change *POP0, *PCONST0, and *PCOMP_P. */
10347 static int
10348 merge_outer_ops (enum rtx_code *pop0, HOST_WIDE_INT *pconst0, enum rtx_code op1, HOST_WIDE_INT const1, machine_mode mode, int *pcomp_p)
10349 {
10356 /* If OP0 is an AND, clear unimportant bits in CONST1. */
10360 /* If OP0 or OP1 is UNKNOWN, this is easy. Similarly if they are the same or
10361 if OP0 is SET. */
10370 {
10372 {
10390 }
10391 }
10393 /* Otherwise, if either is a PLUS or NEG, we can't do anything. */
10397 /* If the two constants aren't the same, we can't do anything. The
10398 remaining six cases can all be done. */
10402 else
10404 {
10407 /* (a & b) | b == b */
10410 /* (a ^ b) | b == a | b */
10411 {;}
10416 /* (a & b) ^ b == (~a) & b */
10419 /* (a | b) ^ b == a & ~b */
10425 /* (a | b) & b == b */
10428 /* (a ^ b) & b) == (~a) & b */
10433 }
10435 /* Check for NO-OP cases. */
10448 /* ??? Slightly redundant with the above mask, but not entirely.
10449 Moving this above means we'd have to sign-extend the mode mask
10450 for the final test. */
10455 }
10456 \f
10457 /* A helper to simplify_shift_const_1 to determine the mode we can perform
10458 the shift in. The original shift operation CODE is performed on OP in
10459 ORIG_MODE. Return the wider mode MODE if we can perform the operation
10460 in that mode. Return ORIG_MODE otherwise. We can also assume that the
10461 result of the shift is subject to operation OUTER_CODE with operand
10462 OUTER_CONST. */
10464 static scalar_int_mode
10468 {
10471 /* In general we can't perform in wider mode for right shift and rotate. */
10473 {
10475 /* We can still widen if the bits brought in from the left are identical
10476 to the sign bit of ORIG_MODE. */
10484 /* Similarly here but with zero bits. */
10489 /* We can also widen if the bits brought in will be masked off. This
10490 operation is performed in ORIG_MODE. */
10492 {
10498 }
10499 /* fall through */
10509 }
10510 }
10512 /* Simplify a shift of VAROP by ORIG_COUNT bits. CODE says what kind
10513 of shift. The result of the shift is RESULT_MODE. Return NULL_RTX
10514 if we cannot simplify it. Otherwise, return a simplified value.
10516 The shift is normally computed in the widest mode we find in VAROP, as
10517 long as it isn't a different number of words than RESULT_MODE. Exceptions
10518 are ASHIFTRT and ROTATE, which are always done in their original mode. */
10520 static rtx
10523 {
10528 machine_mode shift_mode;
10530 /* We form (outer_op (code varop count) (outer_const)). */
10536 /* Make sure and truncate the "natural" shift on the way in. We don't
10537 want to do this inside the loop as it makes it more difficult to
10538 combine shifts. */
10542 /* If we were given an invalid count, don't do anything except exactly
10543 what was requested. */
10550 /* Unless one of the branches of the `if' in this loop does a `continue',
10551 we will `break' the loop after the `if'. */
10554 {
10555 /* If we have an operand of (clobber (const_int 0)), fail. */
10559 /* Convert ROTATERT to ROTATE. */
10561 {
10565 }
10569 {
10570 /* We only change the modes of scalar shifts. */
10576 }
10578 scalar_int_mode shift_unit_mode
10581 /* Handle cases where the count is greater than the size of the mode
10582 minus 1. For ASHIFT, use the size minus one as the count (this can
10583 occur when simplifying (lshiftrt (ashiftrt ..))). For rotates,
10584 take the count modulo the size. For other shifts, the result is
10585 zero.
10587 Since these shifts are being produced by the compiler by combining
10588 multiple operations, each of which are defined, we know what the
10589 result is supposed to be. */
10592 {
10597 else
10598 {
10599 /* We can't simply return zero because there may be an
10600 outer op. */
10604 }
10605 }
10607 /* If we discovered we had to complement VAROP, leave. Making a NOT
10608 here would cause an infinite loop. */
10613 {
10614 /* An arithmetic right shift of a quantity known to be -1 or 0
10615 is a no-op. */
10619 {
10622 }
10624 /* If we are doing an arithmetic right shift and discarding all but
10625 the sign bit copies, this is equivalent to doing a shift by the
10626 bitsize minus one. Convert it into that shift because it will
10627 often allow other simplifications. */
10634 /* We simplify the tests below and elsewhere by converting
10635 ASHIFTRT to LSHIFTRT if we know the sign bit is clear.
10636 `make_compound_operation' will convert it to an ASHIFTRT for
10637 those machines (such as VAX) that don't have an LSHIFTRT. */
10642 shift_unit_mode)))
10654 }
10657 {
10664 {
10667 }
10671 /* The following rules apply only to scalars. */
10676 /* If we have (xshiftrt (mem ...) C) and C is MODE_WIDTH
10677 minus the width of a smaller mode, we can do this with a
10678 SIGN_EXTEND or ZERO_EXTEND from the narrower memory location. */
10685 {
10694 }
10698 /* The following rules apply only to scalars. */
10704 /* If VAROP is a SUBREG, strip it as long as the inner operand has
10705 the same number of words as what we've seen so far. Then store
10706 the widest mode in MODE. */
10713 {
10718 }
10722 /* Some machines use MULT instead of ASHIFT because MULT
10723 is cheaper. But it is still better on those machines to
10724 merge two shifts into one. */
10727 {
10732 }
10736 /* Similar, for when divides are cheaper. */
10739 {
10744 }
10748 /* If we are extracting just the sign bit of an arithmetic
10749 right shift, that shift is not needed. However, the sign
10750 bit of a wider mode may be different from what would be
10751 interpreted as the sign bit in a narrower mode, so, if
10752 the result is narrower, don't discard the shift. */
10757 {
10760 }
10762 /* fall through */
10767 /* The following rules apply only to scalars. */
10774 /* Here we have two nested shifts. The result is usually the
10775 AND of a new shift with a mask. We compute the result below. */
10781 {
10785 rtx mask_rtx;
10787 /* We have one common special case. We can't do any merging if
10788 the inner code is an ASHIFTRT of a smaller mode. However, if
10789 we have (ashift:M1 (subreg:M1 (ashiftrt:M2 FOO C1) 0) C2)
10790 with C2 == GET_MODE_BITSIZE (M1) - GET_MODE_BITSIZE (M2),
10791 we can convert it to
10792 (ashiftrt:M1 (ashift:M1 (and:M1 (subreg:M1 FOO 0) C3) C2) C1).
10793 This simplifies certain SIGN_EXTEND operations. */
10797 {
10798 /* C3 has the low-order C1 bits zero. */
10810 }
10812 /* If this was (ashiftrt (ashift foo C1) C2) and FOO has more
10813 than C1 high-order bits equal to the sign bit, we can convert
10814 this to either an ASHIFT or an ASHIFTRT depending on the
10815 two counts.
10817 We cannot do this if VAROP's mode is not SHIFT_UNIT_MODE. */
10823 {
10827 {
10830 }
10833 }
10835 /* There are some cases we can't do. If CODE is ASHIFTRT,
10836 we can only do this if FIRST_CODE is also ASHIFTRT.
10838 We can't do the case when CODE is ROTATE and FIRST_CODE is
10839 ASHIFTRT.
10841 If the mode of this shift is not the mode of the outer shift,
10842 we can't do this if either shift is a right shift or ROTATE.
10844 Finally, we can't do any of these if the mode is too wide
10845 unless the codes are the same.
10847 Handle the case where the shift codes are the same
10848 first. */
10851 {
10860 }
10871 /* To compute the mask to apply after the shift, shift the
10872 nonzero bits of the inner shift the same way the
10873 outer shift will. */
10876 int_result_mode);
10878 mask_rtx
10882 /* Give up if we can't compute an outer operation to use. */
10890 /* If the shifts are in the same direction, we add the
10891 counts. Otherwise, we subtract them. */
10895 else
10898 /* If COUNT is positive, the new shift is usually CODE,
10899 except for the two exceptions below, in which case it is
10900 FIRST_CODE. If the count is negative, FIRST_CODE should
10901 always be used */
10911 }
10913 /* If we have (A << B << C) for any shift, we can convert this to
10914 (A << C << B). This wins if A is a constant. Only try this if
10915 B is not a constant. */
10920 {
10921 /* For ((unsigned) (cstULL >> count)) >> cst2 we have to make
10922 sure the result will be masked. See PR70222. */
10930 /* For ((int) (cstLL >> count)) >> cst2 just give up. Queuing
10931 up outer sign extension (often left and right shift) is
10932 hardly more efficient than the original. See PR70429. */
10939 count_rtx);
10943 }
10947 /* The following rules apply only to scalars. */
10951 /* Make this fit the case below. */
10958 /* The following rules apply only to scalars. */
10964 /* If we have (xshiftrt (ior (plus X (const_int -1)) X) C)
10965 with C the size of VAROP - 1 and the shift is logical if
10966 STORE_FLAG_VALUE is 1 and arithmetic if STORE_FLAG_VALUE is -1,
10967 we have an (le X 0) operation. If we have an arithmetic shift
10968 and STORE_FLAG_VALUE is 1 or we have a logical shift with
10969 STORE_FLAG_VALUE of -1, we have a (neg (le X 0)) operation. */
10977 {
10980 const0_rtx);
10986 }
10988 /* If we have (shift (logical)), move the logical to the outside
10989 to allow it to possibly combine with another logical and the
10990 shift to combine with another shift. This also canonicalizes to
10991 what a ZERO_EXTRACT looks like. Also, some machines have
10992 (and (shift)) insns. */
10995 /* We can't do this if we have (ashiftrt (xor)) and the
10996 constant has its sign bit set in shift_unit_mode with
10997 shift_unit_mode wider than result_mode. */
11010 {
11013 }
11015 /* If we can't do that, try to simplify the shift in each arm of the
11016 logical expression, make a new logical expression, and apply
11017 the inverse distributive law. This also can't be done for
11018 (ashiftrt (xor)) where we've widened the shift and the constant
11019 changes the sign bit. */
11025 {
11037 }
11041 /* The following rules apply only to scalars. */
11046 /* Convert (lshiftrt (eq FOO 0) C) to (xor FOO 1) if STORE_FLAG_VALUE
11047 says that the sign bit can be tested, FOO has mode MODE, C is
11048 GET_MODE_PRECISION (MODE) - 1, and FOO has only its low-order bit
11049 that may be nonzero. */
11059 {
11063 }
11067 /* The following rules apply only to scalars. */
11072 /* (lshiftrt (neg A) C) where A is either 0 or 1 and C is one less
11073 than the number of bits in the mode is equivalent to A. */
11077 {
11081 }
11083 /* NEG commutes with ASHIFT since it is multiplication. Move the
11084 NEG outside to allow shifts to combine. */
11088 {
11091 }
11095 /* The following rules apply only to scalars. */
11100 /* (lshiftrt (plus A -1) C) where A is either 0 or 1 and C
11101 is one less than the number of bits in the mode is
11102 equivalent to (xor A 1). */
11109 {
11113 }
11115 /* If we have (xshiftrt (plus FOO BAR) C), and the only bits
11116 that might be nonzero in BAR are those being shifted out and those
11117 bits are known zero in FOO, we can replace the PLUS with FOO.
11118 Similarly in the other operand order. This code occurs when
11119 we are computing the size of a variable-size array. */
11126 {
11129 }
11137 {
11140 }
11142 /* (ashift (plus foo C) N) is (plus (ashift foo N) C'). */
11153 {
11156 }
11158 /* Check for 'PLUS signbit', which is the canonical form of 'XOR
11159 signbit', and attempt to change the PLUS to an XOR and move it to
11160 the outer operation as is done above in the AND/IOR/XOR case
11161 leg for shift(logical). See details in logical handling above
11162 for reasoning in doing so. */
11174 {
11177 }
11182 /* The following rules apply only to scalars. */
11187 /* If we have (xshiftrt (minus (ashiftrt X C)) X) C)
11188 with C the size of VAROP - 1 and the shift is logical if
11189 STORE_FLAG_VALUE is 1 and arithmetic if STORE_FLAG_VALUE is -1,
11190 we have a (gt X 0) operation. If the shift is arithmetic with
11191 STORE_FLAG_VALUE of 1 or logical with STORE_FLAG_VALUE == -1,
11192 we have a (neg (gt X 0)) operation. */
11201 {
11204 const0_rtx);
11210 }
11214 /* Change (lshiftrt (truncate (lshiftrt))) to (truncate (lshiftrt))
11215 if the truncate does not affect the value. */
11222 {
11226 new_count);
11229 new_count_rtx);
11233 }
11238 }
11241 }
11245 {
11246 /* We only change the modes of scalar shifts. */
11251 }
11253 /* We have now finished analyzing the shift. The result should be
11254 a shift of type CODE with SHIFT_MODE shifting VAROP COUNT places. If
11255 OUTER_OP is non-UNKNOWN, it is an operation that needs to be applied
11256 to the result of the shift. OUTER_CONST is the relevant constant,
11257 but we must turn off all bits turned off in the shift. */
11265 /* Make a SUBREG if necessary. If we can't make it, fail. */
11270 /* If we have an outer operation and we just made a shift, it is
11271 possible that we could have simplified the shift were it not
11272 for the outer operation. So try to do the simplification
11273 recursively. */
11277 else
11284 /* If we were doing an LSHIFTRT in a wider mode than it was originally,
11285 turn off all the bits that the shift would have turned off. */
11287 /* We only change the modes of scalar shifts. */
11291 /* Do the remainder of the processing in RESULT_MODE. */
11294 /* If COMPLEMENT_P is set, we have to complement X before doing the outer
11295 operation. */
11300 {
11310 {
11311 /* This means that we have determined that the result is
11312 equivalent to a constant. This should be rare. */
11315 }
11318 else
11321 }
11324 }
11326 /* Simplify a shift of VAROP by COUNT bits. CODE says what kind of shift.
11327 The result of the shift is RESULT_MODE. If we cannot simplify it,
11328 return X or, if it is NULL, synthesize the expression with
11329 simplify_gen_binary. Otherwise, return a simplified value.
11331 The shift is normally computed in the widest mode we find in VAROP, as
11332 long as it isn't a different number of words than RESULT_MODE. Exceptions
11333 are ASHIFTRT and ROTATE, which are always done in their original mode. */
11335 static rtx
11338 {
11349 }
11351 \f
11352 /* A subroutine of recog_for_combine. See there for arguments and
11353 return value. */
11355 static int
11357 {
11359 rtx pat_without_clobbers;
11367 /* If PAT is a PARALLEL, check to see if it contains the CLOBBER
11368 we use to indicate that something didn't match. If we find such a
11369 thing, force rejection. */
11383 {
11386 else
11389 }
11391 /* If it isn't, there is the possibility that we previously had an insn
11392 that clobbered some register as a side effect, but the combined
11393 insn doesn't need to do that. So try once more without the clobbers
11394 unless this represents an ASM insn. */
11398 {
11403 {
11406 pos++;
11407 }
11417 {
11420 else
11423 }
11424 }
11431 /* Recognize all noop sets, these will be killed by followup pass. */
11435 /* If we had any clobbers to add, make a new pattern than contains
11436 them. Then check to make sure that all of them are dead. */
11438 {
11448 else
11455 {
11460 {
11464 }
11465 }
11467 }
11471 {
11479 /* Allow targets to reject combined insn. */
11481 {
11484 dump_file);
11486 /* Callers expect recog_for_combine to strip
11487 clobbers from the pattern on failure. */
11492 }
11497 }
11503 }
11505 /* Change every ZERO_EXTRACT and ZERO_EXTEND of a SUBREG that can be
11506 expressed as an AND and maybe an LSHIFTRT, to that formulation.
11507 Return whether anything was so changed. */
11509 static bool
11511 {
11517 {
11529 {
11539 else
11543 {
11549 }
11550 }
11556 {
11561 {
11567 }
11568 }
11573 {
11577 }
11578 else
11584 {
11587 }
11591 }
11598 scalar_int_mode mode;
11604 {
11618 else
11626 }
11629 }
11631 /* Like recog, but we receive the address of a pointer to a new pattern.
11632 We try to match the rtx that the pointer points to.
11633 If that fails, we may try to modify or replace the pattern,
11634 storing the replacement into the same pointer object.
11636 Modifications include deletion or addition of CLOBBERs. If the
11637 instruction will still not match, we change ZERO_EXTEND and ZERO_EXTRACT
11638 to the equivalent AND and perhaps LSHIFTRT patterns, and try with that
11639 (and undo if that fails).
11641 PNOTES is a pointer to a location where any REG_UNUSED notes added for
11642 the CLOBBERs are placed.
11644 The value is the final insn code from the pattern ultimately matched,
11645 or -1. */
11647 static int
11649 {
11661 {
11664 {
11668 }
11669 }
11672 {
11677 }
11680 }
11681 \f
11682 /* Like gen_lowpart_general but for use by combine. In combine it
11683 is not possible to create any new pseudoregs. However, it is
11684 safe to create invalid memory addresses, because combine will
11685 try to recognize them and all they will do is make the combine
11686 attempt fail.
11688 If for some reason this cannot do its job, an rtx
11689 (clobber (const_int 0)) is returned.
11690 An insn containing that will not be recognized. */
11692 static rtx
11694 {
11696 rtx result;
11701 /* We can only support MODE being wider than a word if X is a
11702 constant integer or has a mode the same size. */
11708 /* X might be a paradoxical (subreg (mem)). In that case, gen_lowpart
11709 won't know what to do. So we will strip off the SUBREG here and
11710 process normally. */
11712 {
11715 /* For use in case we fall down into the address adjustments
11716 further below, we need to adjust the known mode and size of
11717 x; imode and isize, since we just adjusted x. */
11722 }
11730 {
11731 /* Refuse to work on a volatile memory ref or one with a mode-dependent
11732 address. */
11737 /* If we want to refer to something bigger than the original memref,
11738 generate a paradoxical subreg instead. That will force a reload
11739 of the original memref X. */
11745 }
11747 /* If X is a comparison operator, rewrite it in a new mode. This
11748 probably won't match, but may allow further simplifications. */
11752 /* If we couldn't simplify X any other way, just enclose it in a
11753 SUBREG. Normally, this SUBREG won't match, but some patterns may
11754 include an explicit SUBREG or we may simplify it further in combine. */
11755 else
11756 {
11757 rtx res;
11760 {
11765 }
11769 }
11771 fail:
11773 }
11774 \f
11775 /* Try to simplify a comparison between OP0 and a constant OP1,
11776 where CODE is the comparison code that will be tested, into a
11777 (CODE OP0 const0_rtx) form.
11779 The result is a possibly different comparison code to use.
11780 *POP1 may be updated. */
11782 static enum rtx_code
11785 {
11786 scalar_int_mode int_mode;
11789 /* Get the constant we are comparing against and turn off all bits
11790 not on in our mode. */
11794 /* If we are comparing against a constant power of two and the value
11795 being compared can only have that single bit nonzero (e.g., it was
11796 `and'ed with that bit), we can replace this with a comparison
11797 with zero. */
11806 {
11809 }
11811 /* Similarly, if we are comparing a value known to be either -1 or
11812 0 with -1, change it to the opposite comparison against zero. */
11818 {
11821 }
11823 /* Do some canonicalizations based on the comparison code. We prefer
11824 comparisons against zero and then prefer equality comparisons.
11825 If we can reduce the size of a constant, we will do that too. */
11827 {
11829 /* < C is equivalent to <= (C - 1) */
11831 {
11834 /* ... fall through to LE case below. */
11836 }
11837 else
11841 /* <= C is equivalent to < (C + 1); we do this for C < 0 */
11843 {
11846 }
11848 /* If we are doing a <= 0 comparison on a value known to have
11849 a zero sign bit, we can replace this with == 0. */
11860 /* >= C is equivalent to > (C - 1). */
11862 {
11865 /* ... fall through to GT below. */
11867 }
11868 else
11872 /* > C is equivalent to >= (C + 1); we do this for C < 0. */
11874 {
11877 }
11879 /* If we are doing a > 0 comparison on a value known to have
11880 a zero sign bit, we can replace this with != 0. */
11891 /* < C is equivalent to <= (C - 1). */
11893 {
11896 /* ... fall through ... */
11898 }
11899 /* (unsigned) < 0x80000000 is equivalent to >= 0. */
11904 {
11908 }
11909 else
11913 /* unsigned <= 0 is equivalent to == 0 */
11916 /* (unsigned) <= 0x7fffffff is equivalent to >= 0. */
11920 == ((HOST_WIDE_INT_1U
11922 {
11925 }
11929 /* >= C is equivalent to > (C - 1). */
11931 {
11934 /* ... fall through ... */
11936 }
11938 /* (unsigned) >= 0x80000000 is equivalent to < 0. */
11943 {
11947 }
11948 else
11952 /* unsigned > 0 is equivalent to != 0 */
11955 /* (unsigned) > 0x7fffffff is equivalent to < 0. */
11959 == (HOST_WIDE_INT_1U
11961 {
11964 }
11969 }
11973 }
11974 \f
11975 /* Simplify a comparison between *POP0 and *POP1 where CODE is the
11976 comparison code that will be tested.
11978 The result is a possibly different comparison code to use. *POP0 and
11979 *POP1 may be updated.
11981 It is possible that we might detect that a comparison is either always
11982 true or always false. However, we do not perform general constant
11983 folding in combine, so this knowledge isn't useful. Such tautologies
11984 should have been detected earlier. Hence we ignore all such cases. */
11986 static enum rtx_code
11988 {
11994 opt_scalar_int_mode tmode_iter;
11996 /* Try a few ways of applying the same transformation to both operands. */
11998 {
11999 /* The test below this one won't handle SIGN_EXTENDs on these machines,
12000 so check specially. */
12019 {
12022 }
12024 /* If both operands are the same constant shift, see if we can ignore the
12025 shift. We can if the shift is a rotate or if the bits shifted out of
12026 this shift are known to be zero for both inputs and if the type of
12027 comparison is compatible with the shift. */
12040 {
12053 else
12055 }
12057 /* If both operands are AND's of a paradoxical SUBREG by constant, the
12058 SUBREGs are of the same mode, and, in both cases, the AND would
12059 be redundant if the comparison was done in the narrower mode,
12060 do the comparison in the narrower mode (e.g., we are AND'ing with 1
12061 and the operand's possibly nonzero bits are 0xffffff01; in that case
12062 if we only care about QImode, we don't need the AND). This case
12063 occurs if the output mode of an scc insn is not SImode and
12064 STORE_FLAG_VALUE == 1 (e.g., the 386).
12066 Similarly, check for a case where the AND's are ZERO_EXTEND
12067 operations from some narrower mode even though a SUBREG is not
12068 present. */
12073 {
12089 {
12093 /* The resulting comparison is always unsigned since we masked
12094 off the original sign bit. */
12098 }
12104 {
12110 }
12114 }
12116 /* If both operands are NOT, we can strip off the outer operation
12117 and adjust the comparison code for swapped operands; similarly for
12118 NEG, except that this must be an equality comparison. */
12124 else
12126 }
12128 /* If the first operand is a constant, swap the operands and adjust the
12129 comparison code appropriately, but don't do this if the second operand
12130 is already a constant integer. */
12132 {
12135 }
12137 /* We now enter a loop during which we will try to simplify the comparison.
12138 For the most part, we only are concerned with comparisons with zero,
12139 but some things may really be comparisons with zero but not start
12140 out looking that way. */
12143 {
12145 scalar_int_mode int_mode;
12149 HOST_WIDE_INT const_op;
12151 /* We only want to handle integral modes. This catches VOIDmode,
12152 CCmode, and the floating-point modes. An exception is that we
12153 can handle VOIDmode if OP0 is a COMPARE or a comparison
12154 operation. */
12161 /* Try to simplify the compare to constant, possibly changing the
12162 comparison op, and/or changing op1 to zero. */
12166 /* Compute some predicates to simplify code below. */
12173 /* If this is a sign bit comparison and we can do arithmetic in
12174 MODE, say that we will only be needing the sign bit of OP0. */
12179 HOST_WIDE_INT_1U
12184 {
12185 /* We can't do anything if OP0 is a condition code value, rather
12186 than an actual data value. */
12192 /* Get the two operands being compared. */
12195 else
12198 /* Check for the cases where we simply want the result of the
12199 earlier test or the opposite of that result. */
12203 {
12207 else
12211 {
12216 }
12217 }
12219 }
12225 /* Now try cases based on the opcode of OP0. If none of the cases
12226 does a "continue", we exit this loop immediately after the
12227 switch. */
12232 {
12234 /* If we are extracting a single bit from a variable position in
12235 a constant that has only a single bit set and are comparing it
12236 with zero, we can convert this into an equality comparison
12237 between the position and the location of the single bit. */
12238 /* Except we can't if SHIFT_COUNT_TRUNCATED is set, since we might
12239 have already reduced the shift count modulo the word size. */
12245 {
12253 /* Result is nonzero iff shift count is equal to I. */
12256 }
12258 /* fall through */
12263 {
12266 }
12270 /* If testing for equality, we can take the NOT of the constant. */
12273 {
12277 }
12279 /* If just looking at the sign bit, reverse the sense of the
12280 comparison. */
12282 {
12286 }
12290 /* If testing for equality, we can take the NEG of the constant. */
12293 {
12297 }
12299 /* The remaining cases only apply to comparisons with zero. */
12303 /* When X is ABS or is known positive,
12304 (neg X) is < 0 if and only if X != 0. */
12312 {
12316 }
12318 /* If we have NEG of something whose two high-order bits are the
12319 same, we know that "(-a) < 0" is equivalent to "a > 0". */
12321 {
12325 }
12329 /* If we are testing equality and our count is a constant, we
12330 can perform the inverse operation on our RHS. */
12334 {
12338 }
12340 /* If we are doing a < 0 or >= 0 comparison, it means we are testing
12341 a particular bit. Convert it to an AND of a constant of that
12342 bit. This will be converted into a ZERO_EXTRACT. */
12346 {
12348 (HOST_WIDE_INT_1U
12353 }
12355 /* Fall through. */
12358 /* ABS is ignorable inside an equality comparison with zero. */
12360 {
12363 }
12367 /* Can simplify (compare (zero/sign_extend FOO) CONST) to
12368 (compare FOO CONST) if CONST fits in FOO's mode and we
12369 are either testing inequality or have an unsigned
12370 comparison with ZERO_EXTEND or a signed comparison with
12371 SIGN_EXTEND. But don't do it if we don't have a compare
12372 insn of the given mode, since we'd have to revert it
12373 later on, and then we wouldn't know whether to sign- or
12374 zero-extend. */
12376 && ! unsigned_comparison_p
12380 {
12383 }
12387 /* Check for the case where we are comparing A - C1 with C2, that is
12389 (subreg:MODE (plus (A) (-C1))) op (C2)
12391 with C1 a constant, and try to lift the SUBREG, i.e. to do the
12392 comparison in the wider mode. One of the following two conditions
12393 must be true in order for this to be valid:
12395 1. The mode extension results in the same bit pattern being added
12396 on both sides and the comparison is equality or unsigned. As
12397 C2 has been truncated to fit in MODE, the pattern can only be
12398 all 0s or all 1s.
12400 2. The mode extension results in the sign bit being copied on
12401 each side.
12403 The difficulty here is that we have predicates for A but not for
12404 (A - C1) so we need to check that C1 is within proper bounds so
12405 as to perturbate A as little as possible. */
12414 {
12422 /* (A - C1) zero-extends if it is positive and sign-extends
12423 if it is negative, C2 both zero- and sign-extends. */
12427 /* (A - C1) sign-extends if it is positive and 1-extends
12428 if it is negative, C2 both sign- and 1-extends. */
12435 /* (A - C1) always sign-extends, like C2. */
12439 {
12442 }
12443 }
12445 /* If the inner mode is narrower and we are extracting the low part,
12446 we can treat the SUBREG as if it were a ZERO_EXTEND. */
12448 ;
12457 {
12458 /* Remove outer subregs that don't do anything. */
12463 {
12467 }
12469 }
12470 else
12473 /* FALLTHROUGH */
12482 {
12485 }
12489 /* (eq (plus X A) B) -> (eq X (minus B A)). We can only do
12490 this for equality comparisons due to pathological cases involving
12491 overflows. */
12495 {
12499 }
12501 /* (plus (abs X) (const_int -1)) is < 0 if and only if X == 0. */
12504 {
12508 }
12512 /* We used to optimize signed comparisons against zero, but that
12513 was incorrect. Unsigned comparisons against zero (GTU, LEU)
12514 arrive here as equality comparisons, or (GEU, LTU) are
12515 optimized away. No need to special-case them. */
12517 /* (eq (minus A B) C) -> (eq A (plus B C)) or
12518 (eq B (minus A C)), whichever simplifies. We can only do
12519 this for equality comparisons due to pathological cases involving
12520 overflows. */
12524 {
12528 }
12533 {
12537 }
12539 /* The sign bit of (minus (ashiftrt X C) X), where C is the number
12540 of bits in X minus 1, is one iff X > 0. */
12545 {
12549 }
12553 /* (eq (xor A B) C) -> (eq A (xor B C)). This is a simplification
12554 if C is zero or B is a constant. */
12558 {
12562 }
12567 /* The sign bit of (ior (plus X (const_int -1)) X) is nonzero
12568 iff X <= 0. */
12572 {
12576 }
12580 /* Convert (and (xshift 1 X) Y) to (and (lshiftrt Y X) 1). This
12581 will be converted to a ZERO_EXTRACT later. */
12585 {
12590 }
12592 /* If we are comparing (and (lshiftrt X C1) C2) for equality with
12593 zero and X is a comparison and C1 and C2 describe only bits set
12594 in STORE_FLAG_VALUE, we can compare with X. */
12602 {
12609 {
12612 }
12613 }
12615 /* If we are doing an equality comparison of an AND of a bit equal
12616 to the sign bit, replace this with a LT or GE comparison of
12617 the underlying value. */
12624 {
12628 }
12630 /* If this AND operation is really a ZERO_EXTEND from a narrower
12631 mode, the constant fits within that mode, and this is either an
12632 equality or unsigned comparison, try to do this comparison in
12633 the narrower mode.
12635 Note that in:
12637 (ne:DI (and:DI (reg:DI 4) (const_int 0xffffffff)) (const_int 0))
12638 -> (ne:DI (reg:SI 4) (const_int 0))
12640 unless TARGET_TRULY_NOOP_TRUNCATION allows it or the register is
12641 known to hold a value of the required mode the
12642 transformation is invalid. */
12650 {
12653 }
12655 /* If this is (and:M1 (subreg:M1 X:M2 0) (const_int C1)) where C1
12656 fits in both M1 and M2 and the SUBREG is either paradoxical
12657 or represents the low part, permute the SUBREG and the AND
12658 and try again. */
12661 {
12663 /* Require an integral mode, to avoid creating something like
12664 (AND:SF ...). */
12667 /* It is unsafe to commute the AND into the SUBREG if the
12668 SUBREG is paradoxical and WORD_REGISTER_OPERATIONS is
12669 not defined. As originally written the upper bits
12670 have a defined value due to the AND operation.
12671 However, if we commute the AND inside the SUBREG then
12672 they no longer have defined values and the meaning of
12673 the code has been changed.
12674 Also C1 should not change value in the smaller mode,
12675 see PR67028 (a positive C1 can become negative in the
12676 smaller mode, so that the AND does no longer mask the
12677 upper bits). */
12678 && ((WORD_REGISTER_OPERATIONS
12690 {
12696 }
12697 }
12699 /* Convert (ne (and (not X) 1) 0) to (eq (and X 1) 0). */
12703 {
12708 }
12710 /* Convert (ne (and (lshiftrt (not X)) 1) 0) to
12711 (eq (and (lshiftrt X) 1) 0).
12712 Also handle the case where (not X) is expressed using xor. */
12716 {
12726 == HOST_WIDE_INT_1U
12728 {
12729 op0
12734 }
12735 }
12739 /* If we have (compare (ashift FOO N) (const_int C)) and
12740 the high order N bits of FOO (N+1 if an inequality comparison)
12741 are known to be zero, we can do this by comparing FOO with C
12742 shifted right N bits so long as the low-order N bits of C are
12743 zero. */
12755 {
12756 /* We must perform a logical shift, not an arithmetic one,
12757 as we want the top N bits of C to be zero. */
12764 }
12766 /* If we are doing a sign bit comparison, it means we are testing
12767 a particular bit. Convert it to the appropriate AND. */
12770 {
12772 (HOST_WIDE_INT_1U
12777 }
12779 /* If this an equality comparison with zero and we are shifting
12780 the low bit to the sign bit, we can convert this to an AND of the
12781 low-order bit. */
12785 {
12788 }
12792 /* If this is an equality comparison with zero, we can do this
12793 as a logical shift, which might be much simpler. */
12796 {
12801 }
12803 /* If OP0 is a sign extension and CODE is not an unsigned comparison,
12804 do the comparison in a narrower mode. */
12814 {
12817 }
12819 /* Likewise if OP0 is a PLUS of a sign extension with a
12820 constant, which is usually represented with the PLUS
12821 between the shifts. */
12833 {
12841 new_const);
12843 }
12845 /* FALLTHROUGH */
12847 /* If we have (compare (xshiftrt FOO N) (const_int C)) and
12848 the low order N bits of FOO are known to be zero, we can do this
12849 by comparing FOO with C shifted left N bits so long as no
12850 overflow occurs. Even if the low order N bits of FOO aren't known
12851 to be zero, if the comparison is >= or < we can use the same
12852 optimization and for > or <= by setting all the low
12853 order N bits in the comparison constant. */
12864 {
12865 unsigned HOST_WIDE_INT low_bits
12867 & ((HOST_WIDE_INT_1U
12870 {
12871 /* If the shift was logical, then we must make the condition
12872 unsigned. */
12881 const_op
12886 }
12887 }
12889 /* If we are using this shift to extract just the sign bit, we
12890 can replace this with an LT or GE comparison. */
12895 {
12899 }
12904 }
12907 }
12909 /* Now make any compound operations involved in this comparison. Then,
12910 check for an outmost SUBREG on OP0 that is not doing anything or is
12911 paradoxical. The latter transformation must only be performed when
12912 it is known that the "extra" bits will be the same in op0 and op1 or
12913 that they don't matter. There are three cases to consider:
12915 1. SUBREG_REG (op0) is a register. In this case the bits are don't
12916 care bits and we can assume they have any convenient value. So
12917 making the transformation is safe.
12919 2. SUBREG_REG (op0) is a memory and LOAD_EXTEND_OP is UNKNOWN.
12920 In this case the upper bits of op0 are undefined. We should not make
12921 the simplification in that case as we do not know the contents of
12922 those bits.
12924 3. SUBREG_REG (op0) is a memory and LOAD_EXTEND_OP is not UNKNOWN.
12925 In that case we know those bits are zeros or ones. We must also be
12926 sure that they are the same as the upper bits of op1.
12928 We can never remove a SUBREG for a non-equality comparison because
12929 the sign bit is in a different place in the underlying object. */
12942 {
12944 {
12945 /* For paradoxical subregs, allow case 1 as above. Case 3 isn't
12946 implemented. */
12948 {
12951 }
12952 }
12956 {
12961 }
12962 }
12964 /* We now do the opposite procedure: Some machines don't have compare
12965 insns in all modes. If OP0's mode is an integer mode smaller than a
12966 word and we can't do a compare in that mode, see if there is a larger
12967 mode for which we can do the compare. There are a number of cases in
12968 which we can use the wider mode. */
12974 {
12979 {
12982 /* If this is a test for negative, we can make an explicit
12983 test of the sign bit. Test this first so we can use
12984 a paradoxical subreg to extend OP0. */
12988 {
12989 unsigned HOST_WIDE_INT sign
12996 }
12998 /* If the only nonzero bits in OP0 and OP1 are those in the
12999 narrower mode and this is an equality or unsigned comparison,
13000 we can use the wider mode. Similarly for sign-extended
13001 values, in which case it is true for all comparisons. */
13018 {
13019 /* If OP0 is an AND and we don't have an AND in MODE either,
13020 make a new AND in the proper mode. */
13028 else
13029 {
13031 {
13036 }
13037 else
13038 {
13043 }
13045 }
13046 }
13047 }
13048 }
13050 /* We may have changed the comparison operands. Re-canonicalize. */
13052 {
13055 }
13057 /* If this machine only supports a subset of valid comparisons, see if we
13058 can convert an unsupported one into a supported one. */
13065 }
13066 \f
13067 /* Utility function for record_value_for_reg. Count number of
13068 rtxs in X. */
13069 static int
13071 {
13078 {
13098 }
13109 }
13110 \f
13111 /* Utility function for following routine. Called when X is part of a value
13112 being stored into last_set_value. Sets last_set_table_tick
13113 for each register mentioned. Similar to mention_regs in cse.c */
13115 static void
13117 {
13123 {
13129 {
13132 }
13135 }
13139 {
13140 /* Check for identical subexpressions. If x contains
13141 identical subexpression we only have to traverse one of
13142 them. */
13144 {
13145 /* Note that at this point x1 has already been
13146 processed. */
13150 /* If x0 and x1 are identical then there is no need to
13151 process x0. */
13155 /* If x0 is identical to a subexpression of x1 then while
13156 processing x1, x0 has already been processed. Thus we
13157 are done with x. */
13162 /* If x1 is identical to a subexpression of x0 then we
13163 still have to process the rest of x0. */
13166 {
13169 }
13170 }
13173 }
13177 }
13179 /* Record that REG is set to VALUE in insn INSN. If VALUE is zero, we
13180 are saying that the register is clobbered and we no longer know its
13181 value. If INSN is zero, don't update reg_stat[].last_set; this is
13182 only permitted with VALUE also zero and is used to invalidate the
13183 register. */
13185 static void
13187 {
13193 /* If VALUE contains REG and we have a previous value for REG, substitute
13194 the previous value. */
13196 {
13197 rtx tem;
13199 /* Set things up so get_last_value is allowed to see anything set up to
13200 our insn. */
13204 /* If TEM is simply a binary operation with two CLOBBERs as operands,
13205 it isn't going to be useful and will take a lot of time to process,
13206 so just use the CLOBBER. */
13209 {
13215 {
13216 /* If there are two or more occurrences of REG in VALUE,
13217 prevent the value from growing too much. */
13220 }
13223 }
13224 }
13226 /* For each register modified, show we don't know its value, that
13227 we don't know about its bitwise content, that its value has been
13228 updated, and that we don't know the location of the death of the
13229 register. */
13231 {
13243 }
13245 /* Mark registers that are being referenced in this value. */
13249 /* Now update the status of each register being set.
13250 If someone is using this register in this block, set this register
13251 to invalid since we will get confused between the two lives in this
13252 basic block. This makes using this register always invalid. In cse, we
13253 scan the table to invalidate all entries using this register, but this
13254 is too much work for us. */
13257 {
13263 else
13265 }
13267 /* The value being assigned might refer to X (like in "x++;"). In that
13268 case, we must replace it with (clobber (const_int 0)) to prevent
13269 infinite loops. */
13272 {
13276 }
13278 /* For the main register being modified, update the value, the mode, the
13279 nonzero bits, and the number of sign bit copies. */
13284 {
13292 rsp->last_set_sign_bit_copies
13294 }
13295 }
13297 /* Called via note_stores from record_dead_and_set_regs to handle one
13298 SET or CLOBBER in an insn. DATA is the instruction in which the
13299 set is occurring. */
13301 static void
13303 {
13310 {
13314 }
13317 {
13318 /* If we are setting the whole register, we know its value. Otherwise
13319 show that we don't know the value. We can handle a SUBREG if it's
13320 the low part, but we must be careful with paradoxical SUBREGs on
13321 RISC architectures because we cannot strip e.g. an extension around
13322 a load and record the naked load since the RTL middle-end considers
13323 that the upper bits are defined according to LOAD_EXTEND_OP. */
13330 BITS_PER_WORD)
13333 WORD_REGISTER_OPERATIONS
13339 {
13342 && reg_is_clobbered_by_clobber_high
13346 }
13347 else
13349 }
13351 /* Ignore pushes, they clobber nothing. */
13354 }
13356 /* Update the records of when each REG was most recently set or killed
13357 for the things done by INSN. This is the last thing done in processing
13358 INSN in the combiner loop.
13360 We update reg_stat[], in particular fields last_set, last_set_value,
13361 last_set_mode, last_set_nonzero_bits, last_set_sign_bit_copies,
13362 last_death, and also the similar information mem_last_set (which insn
13363 most recently modified memory) and last_call_luid (which insn was the
13364 most recent subroutine call). */
13366 static void
13368 {
13369 rtx link;
13373 {
13376 {
13381 {
13386 }
13387 }
13390 }
13393 {
13394 hard_reg_set_iterator hrsi;
13396 {
13408 }
13412 /* We can't combine into a call pattern. Remember, though, that
13413 the return value register is set at this LUID. We could
13414 still replace a register with the return value from the
13415 wrong subroutine call! */
13417 }
13418 else
13420 }
13422 /* If a SUBREG has the promoted bit set, it is in fact a property of the
13423 register present in the SUBREG, so for each such SUBREG go back and
13424 adjust nonzero and sign bit information of the registers that are
13425 known to have some zero/sign bits set.
13427 This is needed because when combine blows the SUBREGs away, the
13428 information on zero/sign bits is lost and further combines can be
13429 missed because of that. */
13431 static void
13433 {
13435 rtx set;
13443 {
13452 {
13455 }
13459 {
13462 }
13465 {
13468 }
13469 else
13471 }
13472 }
13474 /* Check if X, a register, is known to contain a value already
13475 truncated to MODE. In this case we can use a subreg to refer to
13476 the truncated value even though in the generic case we would need
13477 an explicit truncation. */
13479 static bool
13481 {
13493 }
13495 /* If X is a hard reg or a subreg record the mode that the register is
13496 accessed in. For non-TARGET_TRULY_NOOP_TRUNCATION targets we might be
13497 able to turn a truncate into a subreg using this information. Return true
13498 if traversing X is complete. */
13500 static bool
13502 {
13503 machine_mode truncated_mode;
13507 {
13519 }
13520 /* ??? For hard-regs we now record everything. We might be able to
13521 optimize this using last_set_mode. */
13524 else
13531 {
13534 }
13537 }
13539 /* Callback for note_uses. Find hardregs and subregs of pseudos and
13540 the modes they are used in. This can help truning TRUNCATEs into
13541 SUBREGs. */
13543 static void
13545 {
13550 }
13552 /* Scan X for promoted SUBREGs. For each one found,
13553 note what it implies to the registers used in it. */
13555 static void
13557 {
13562 else
13563 {
13569 {
13579 }
13580 }
13581 }
13582 \f
13583 /* Verify that all the registers and memory references mentioned in *LOC are
13584 still valid. *LOC was part of a value set in INSN when label_tick was
13585 equal to TICK. Return 0 if some are not. If REPLACE is nonzero, replace
13586 the invalid references with (clobber (const_int 0)) and return 1. This
13587 replacement is useful because we often can get useful information about
13588 the form of a value (e.g., if it was produced by a shift that always
13589 produces -1 or 0) even though we don't know exactly what registers it
13590 was produced from. */
13592 static int
13594 {
13601 {
13607 {
13610 /* If this is a pseudo-register that was only set once and not
13611 live at the beginning of the function, it is always valid. */
13615 && (!REGNO_REG_SET_P
13617 regno)))
13619 {
13623 }
13624 }
13627 }
13628 /* If this is a memory reference, make sure that there were no stores after
13629 it that might have clobbered the value. We don't have alias info, so we
13630 assume any store invalidates it. Moreover, we only have local UIDs, so
13631 we also assume that there were stores in the intervening basic blocks. */
13634 {
13638 }
13641 {
13643 {
13644 /* Check for identical subexpressions. If x contains
13645 identical subexpression we only have to traverse one of
13646 them. */
13648 {
13649 /* Note that at this point x0 has already been checked
13650 and found valid. */
13654 /* If x0 and x1 are identical then x is also valid. */
13658 /* If x1 is identical to a subexpression of x0 then
13659 while checking x0, x1 has already been checked. Thus
13660 it is valid and so as x. */
13665 /* If x0 is identical to a subexpression of x1 then x is
13666 valid iff the rest of x1 is valid. */
13669 return
13673 }
13678 }
13684 }
13686 /* If we haven't found a reason for it to be invalid, it is valid. */
13688 }
13690 /* Get the last value assigned to X, if known. Some registers
13691 in the value may be replaced with (clobber (const_int 0)) if their value
13692 is known longer known reliably. */
13694 static rtx
13696 {
13698 rtx value;
13701 /* If this is a non-paradoxical SUBREG, get the value of its operand and
13702 then convert it to the desired mode. If this is a paradoxical SUBREG,
13703 we cannot predict what values the "extra" bits might have. */
13717 /* If we don't have a value, or if it isn't for this basic block and
13718 it's either a hard register, set more than once, or it's a live
13719 at the beginning of the function, return 0.
13721 Because if it's not live at the beginning of the function then the reg
13722 is always set before being used (is never used without being set).
13723 And, if it's set only once, and it's always set before use, then all
13724 uses must have the same last value, even if it's not from this basic
13725 block. */
13732 || REGNO_REG_SET_P
13736 /* If the value was set in a later insn than the ones we are processing,
13737 we can't use it even if the register was only set once. */
13742 /* If fewer bits were set than what we are asked for now, we cannot use
13743 the value. */
13748 /* If the value has all its registers valid, return it. */
13752 /* Otherwise, make a copy and replace any invalid register with
13753 (clobber (const_int 0)). If that fails for some reason, return 0. */
13760 }
13761 \f
13762 /* Define three variables used for communication between the following
13763 routines. */
13767 rtx reg_dead_reg;
13769 /* Function called via note_stores from reg_dead_at_p.
13771 If DEST is within [reg_dead_regno, reg_dead_endregno), set
13772 reg_dead_flag to 1 if X is a CLOBBER and to -1 it is a SET. */
13774 static void
13776 {
13790 }
13792 /* Return nonzero if REG is known to be dead at INSN.
13794 We scan backwards from INSN. If we hit a REG_DEAD note or a CLOBBER
13795 referencing REG, it is dead. If we hit a SET referencing REG, it is
13796 live. Otherwise, see if it is live or dead at the start of the basic
13797 block we are in. Hard regs marked as being live in NEWPAT_USED_REGS
13798 must be assumed to be always live. */
13800 static int
13802 {
13803 basic_block block;
13806 /* Set variables for reg_dead_at_p_1. */
13813 /* Check that reg isn't mentioned in NEWPAT_USED_REGS. For fixed registers
13814 we allow the machine description to decide whether use-and-clobber
13815 patterns are OK. */
13817 {
13821 }
13823 /* Scan backwards until we find a REG_DEAD note, SET, CLOBBER, or
13824 beginning of basic block. */
13827 {
13829 {
13839 }
13845 }
13847 /* Look at live-in sets for the basic block that we were in. */
13853 }
13854 \f
13855 /* Note hard registers in X that are used. */
13857 static void
13859 {
13865 {
13869 CASE_CONST_ANY:
13874 /* CC0 must die in the insn after it is set, so we don't need to take
13875 special note of it here. */
13880 /* If we are clobbering a MEM, mark any hard registers inside the
13881 address as used. */
13888 /* A hard reg in a wide mode may really be multiple registers.
13889 If so, mark all of them just like the first. */
13891 {
13892 /* None of this applies to the stack, frame or arg pointers. */
13894 || (!HARD_FRAME_POINTER_IS_FRAME_POINTER
13902 }
13906 {
13907 /* If setting a MEM, or a SUBREG of a MEM, then note any hard regs in
13908 the address. */
13920 }
13925 }
13927 /* Recursively scan the operands of this expression. */
13929 {
13933 {
13937 {
13942 }
13943 }
13944 }
13945 }
13946 \f
13947 /* Remove register number REGNO from the dead registers list of INSN.
13949 Return the note used to record the death, if there was one. */
13951 rtx
13953 {
13960 }
13962 /* For each register (hardware or pseudo) used within expression X, if its
13963 death is in an instruction with luid between FROM_LUID (inclusive) and
13964 TO_INSN (exclusive), put a REG_DEAD note for that register in the
13965 list headed by PNOTES.
13967 That said, don't move registers killed by maybe_kill_insn.
13969 This is done when X is being merged by combination into TO_INSN. These
13970 notes will then be distributed as needed. */
13972 static void
13975 {
13981 {
13985 /* If we do not know where the register died, it may still die between
13986 FROM_LUID and TO_INSN. If so, find it. This is PR83304. */
13988 {
13993 {
13995 {
13999 }
14002 }
14003 }
14005 /* Don't move the register if it gets killed in between from and to. */
14014 {
14017 /* It is possible for the call above to return 0. This can occur
14018 when last_death points to I2 or I1 that we combined with.
14019 In that case make a new note.
14021 We must also check for the case where X is a hard register
14022 and NOTE is a death note for a range of hard registers
14023 including X. In that case, we must put REG_DEAD notes for
14024 the remaining registers in place of NOTE. */
14028 {
14037 }
14039 /* If we didn't find any note, or if we found a REG_DEAD note that
14040 covers only part of the given reg, and we have a multi-reg hard
14041 register, then to be safe we must check for REG_DEAD notes
14042 for each register other than the first. They could have
14043 their own REG_DEAD notes lying around. */
14050 {
14057 else
14063 }
14066 {
14069 }
14070 else
14072 }
14075 }
14078 {
14083 /* In the case of a ZERO_EXTRACT, a STRICT_LOW_PART, or a SUBREG
14084 that accesses one word of a multi-word item, some
14085 piece of everything register in the expression is used by
14086 this insn, so remove any old death. */
14087 /* ??? So why do we test for equality of the sizes? */
14093 {
14096 }
14098 /* If this is some other SUBREG, we know it replaces the entire
14099 value, so use that as the destination. */
14103 /* If this is a MEM, adjust deaths of anything used in the address.
14104 For a REG (the only other possibility), the entire value is
14105 being replaced so the old value is not used in this insn. */
14111 }
14120 {
14122 {
14127 }
14130 }
14131 }
14132 \f
14133 /* Return 1 if X is the target of a bit-field assignment in BODY, the
14134 pattern of an insn. X must be a REG. */
14136 static int
14138 {
14142 {
14144 rtx target;
14151 else
14168 }
14176 }
14177 \f
14178 /* Given a chain of REG_NOTES originally from FROM_INSN, try to place them
14179 as appropriate. I3 and I2 are the insns resulting from the combination
14180 insns including FROM (I2 may be zero).
14182 ELIM_I2 and ELIM_I1 are either zero or registers that we know will
14183 not need REG_DEAD notes because they are being substituted for. This
14184 saves searching in the most common cases.
14186 Each note in the list is either ignored or placed on some insns, depending
14187 on the type of note. */
14189 static void
14192 {
14194 rtx tem_note;
14198 {
14203 {
14206 /* Doesn't matter much where we put this, as long as it's somewhere.
14207 It is preferable to keep these notes on branches, which is most
14208 likely to be i3. */
14215 else
14216 {
14219 }
14223 /* These notes must remain with the call or trapping instruction. */
14228 else
14229 {
14235 /* ??? Otherwise assume we've combined things such that we
14236 can now prove that the instructions can't trap. Drop the
14237 note in this case. */
14238 }
14242 /* ??? How to distribute between i3-i1. Assume i3 contains the
14243 entire adjustment. Assert i3 contains at least some adjust. */
14245 {
14247 /* fixup_args_size_notes looks at REG_NORETURN note,
14248 so ensure the note is placed there first. */
14250 {
14254 {
14260 }
14261 }
14263 /* emit_call_1 adds for !ACCUMULATE_OUTGOING_ARGS
14264 REG_ARGS_SIZE note to all noreturn calls, allow that here. */
14267 && !ACCUMULATE_OUTGOING_ARGS
14269 }
14277 /* These notes must remain with the call. It should not be
14278 possible for both I2 and I3 to be a call. */
14281 else
14282 {
14285 }
14289 /* Any clobbers for i3 may still exist, and so we must process
14290 REG_UNUSED notes from that insn.
14292 Any clobbers from i2 or i1 can only exist if they were added by
14293 recog_for_combine. In that case, recog_for_combine created the
14294 necessary REG_UNUSED notes. Trying to keep any original
14295 REG_UNUSED notes from these insns can cause incorrect output
14296 if it is for the same register as the original i3 dest.
14297 In that case, we will notice that the register is set in i3,
14298 and then add a REG_UNUSED note for the destination of i3, which
14299 is wrong. However, it is possible to have REG_UNUSED notes from
14300 i2 or i1 for register which were both used and clobbered, so
14301 we keep notes from i2 or i1 if they will turn into REG_DEAD
14302 notes. */
14304 /* If this register is set or clobbered in I3, put the note there
14305 unless there is one already. */
14307 {
14315 }
14316 /* Otherwise, if this register is used by I3, then this register
14317 now dies here, so we must put a REG_DEAD note here unless there
14318 is one already. */
14324 {
14327 }
14329 /* A SET or CLOBBER of the REG_UNUSED reg has been removed,
14330 but we can't tell which at this point. We must reset any
14331 expectations we had about the value that was previously
14332 stored in the reg. ??? Ideally, we'd adjust REG_N_SETS
14333 and, if appropriate, restore its previous value, but we
14334 don't have enough information for that at this point. */
14335 else
14336 {
14339 /* Otherwise, if this register is now referenced in i2
14340 then the register used to be modified in one of the
14341 original insns. If it was i3 (say, in an unused
14342 parallel), it's now completely gone, so the note can
14343 be discarded. But if it was modified in i2, i1 or i0
14344 and we still reference it in i2, then we're
14345 referencing the previous value, and since the
14346 register was modified and REG_UNUSED, we know that
14347 the previous value is now dead. So, if we only
14348 reference the register in i2, we change the note to
14349 REG_DEAD, to reflect the previous value. However, if
14350 we're also setting or clobbering the register as
14351 scratch, we know (because the register was not
14352 referenced in i3) that it's unused, just as it was
14353 unused before, and we place the note in i2. */
14356 {
14365 }
14366 }
14373 /* These notes say something about results of an insn. We can
14374 only support them if they used to be on I3 in which case they
14375 remain on I3. Otherwise they are ignored.
14377 If the note refers to an expression that is not a constant, we
14378 must also ignore the note since we cannot tell whether the
14379 equivalence is still true. It might be possible to do
14380 slightly better than this (we only have a problem if I2DEST
14381 or I1DEST is present in the expression), but it doesn't
14382 seem worth the trouble. */
14390 /* These notes say something about how a register is used. They must
14391 be present on any use of the register in I2 or I3. */
14396 {
14399 else
14401 }
14406 /* This can show up in several ways -- either directly in the
14407 pattern, or hidden off in the constant pool with (or without?)
14408 a REG_EQUAL note. */
14409 /* ??? Ignore the without-reg_equal-note problem for now. */
14421 {
14424 else
14426 }
14428 /* For REG_LABEL_TARGET on a JUMP_P, we prefer to put the note
14429 as a JUMP_LABEL or decrement LABEL_NUSES if it's already
14430 there. */
14435 {
14442 }
14448 {
14456 }
14460 /* This note says something about the value of a register prior
14461 to the execution of an insn. It is too much trouble to see
14462 if the note is still correct in all situations. It is better
14463 to simply delete it. */
14467 /* If we replaced the right hand side of FROM_INSN with a
14468 REG_EQUAL note, the original use of the dying register
14469 will not have been combined into I3 and I2. In such cases,
14470 FROM_INSN is guaranteed to be the first of the combined
14471 instructions, so we simply need to search back before
14472 FROM_INSN for the previous use or set of this register,
14473 then alter the notes there appropriately.
14475 If the register is used as an input in I3, it dies there.
14476 Similarly for I2, if it is nonzero and adjacent to I3.
14478 If the register is not used as an input in either I3 or I2
14479 and it is not one of the registers we were supposed to eliminate,
14480 there are two possibilities. We might have a non-adjacent I2
14481 or we might have somehow eliminated an additional register
14482 from a computation. For example, we might have had A & B where
14483 we discover that B will always be zero. In this case we will
14484 eliminate the reference to A.
14486 In both cases, we must search to see if we can find a previous
14487 use of A and put the death note there. */
14493 else
14494 {
14500 {
14501 /* If the new I2 sets the same register that is marked
14502 dead in the note, we do not in general know where to
14503 put the note. One important case we _can_ handle is
14504 when the note comes from I3. */
14507 else
14509 }
14516 && !(i2mod
14518 i2mod_old_rhs)))
14523 }
14526 {
14530 {
14532 {
14536 }
14538 /* If the register is being set at TEM_INSN, see if that is all
14539 TEM_INSN is doing. If so, delete TEM_INSN. Otherwise, make this
14540 into a REG_UNUSED note instead. Don't delete sets to
14541 global register vars. */
14545 {
14556 ;
14558 /* Verify that it was the set, and not a clobber that
14559 modified the register.
14561 CC0 targets must be careful to maintain setter/user
14562 pairs. If we cannot delete the setter due to side
14563 effects, mark the user with an UNUSED note instead
14564 of deleting it. */
14568 && (!HAVE_cc0
14572 {
14573 /* Move the notes and links of TEM_INSN elsewhere.
14574 This might delete other dead insns recursively.
14575 First set the pattern to something that won't use
14576 any register. */
14595 /* Delete the setter too. */
14597 {
14610 }
14611 }
14612 else
14613 {
14616 /* If there isn't already a REG_UNUSED note, put one
14617 here. Do not place a REG_DEAD note, even if
14618 the register is also used here; that would not
14619 match the algorithm used in lifetime analysis
14620 and can cause the consistency check in the
14621 scheduler to fail. */
14626 }
14627 }
14631 {
14634 /* If we are doing a 3->2 combination, and we have a
14635 register which formerly died in i3 and was not used
14636 by i2, which now no longer dies in i3 and is used in
14637 i2 but does not die in i2, and place is between i2
14638 and i3, then we may need to move a link from place to
14639 i2. */
14641 && from_insn
14644 {
14648 }
14650 }
14654 }
14656 }
14658 /* If the register is set or already dead at PLACE, we needn't do
14659 anything with this note if it is still a REG_DEAD note.
14660 We check here if it is set at all, not if is it totally replaced,
14661 which is what `dead_or_set_p' checks, so also check for it being
14662 set partially. */
14665 {
14671 {
14672 /* Unless the register previously died in PLACE, clear
14673 last_death. [I no longer understand why this is
14674 being done.] */
14678 }
14679 else
14682 /* If this is a death note for a hard reg that is occupying
14683 multiple registers, ensure that we are still using all
14684 parts of the object. If we find a piece of the object
14685 that is unused, we must arrange for an appropriate REG_DEAD
14686 note to be added for it. However, we can't just emit a USE
14687 and tag the note to it, since the register might actually
14688 be dead; so we recourse, and the recursive call then finds
14689 the previous insn that used this register. */
14692 {
14701 {
14704 }
14707 {
14708 /* Put only REG_DEAD notes for pieces that are
14709 not already dead or set. */
14713 {
14720 {
14722 NULL_RTX);
14726 NULL_RTX);
14727 }
14732 {
14734 {
14738 }
14742 {
14745 }
14746 }
14747 }
14750 }
14751 }
14752 }
14756 /* Any other notes should not be present at this point in the
14757 compilation. */
14759 }
14762 {
14766 /* Set added_notes_insn to the earliest insn we added a note to. */
14770 }
14773 {
14776 /* Set added_notes_insn to the earliest insn we added a note to. */
14780 }
14781 }
14782 }
14783 \f
14784 /* Similarly to above, distribute the LOG_LINKS that used to be present on
14785 I3, I2, and I1 to new locations. This is also called to add a link
14786 pointing at I3 when I3's destination is changed. */
14788 static void
14790 {
14794 {
14801 /* If the insn that this link points to is a NOTE, ignore it. */
14810 {
14813 {
14829 }
14832 }
14833 else
14846 /* A LOG_LINK is defined as being placed on the first insn that uses
14847 a register and points to the insn that sets the register. Start
14848 searching at the next insn after the target of the link and stop
14849 when we reach a set of the register or the end of the basic block.
14851 Note that this correctly handles the link that used to point from
14852 I3 to I2. Also note that not much searching is typically done here
14853 since most links don't point very far away. */
14862 {
14866 }
14869 {
14872 }
14876 /* If we found a place to put the link, place it there unless there
14877 is already a link to the same insn as LINK at that point. */
14880 {
14888 {
14892 /* Set added_links_insn to the earliest insn we added a
14893 link to. */
14897 }
14898 }
14899 }
14900 }
14901 \f
14902 /* Check for any register or memory mentioned in EQUIV that is not
14903 mentioned in EXPR. This is used to restrict EQUIV to "specializations"
14904 of EXPR where some registers may have been replaced by constants. */
14906 static bool
14908 {
14911 {
14916 }
14918 }
14919 \f
14920 DEBUG_FUNCTION void
14922 {
14923 fprintf
14925 ";; Combiner statistics: %d attempts, %d substitutions (%d requiring new space),\n;; %d successes.\n\n",
14927 }
14929 void
14931 {
14932 fprintf
14934 "\n;; Combiner totals: %d attempts, %d substitutions (%d requiring new space),\n;; %d successes.\n",
14936 }
14937 \f
14938 /* Try combining insns through substitution. */
14939 static unsigned int
14941 {
14951 rebuild_jump_labels_after_combine
14954 /* Combining insns may have turned an indirect jump into a
14955 direct jump. Rebuild the JUMP_LABEL fields of jumping
14956 instructions. */
14958 {
14965 }
14969 }
14974 {
14984 };
14987 {
14991 {}
14993 /* opt_pass methods: */
14996 {
14998 }
15004 rtl_opt_pass *
15006 {
15008 }