| blob | 39ef3c6ecb82e364ca41e12877559252d67b4fe9 |
1 /* Optimize by combining instructions for GNU compiler.
2 Copyright (C) 1987-2017 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 use_crosses_set_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 /* Basic block in which we are performing combines. */
309 \f
310 /* Length of the currently allocated uid_insn_cost array. */
314 /* The following array records the insn_rtx_cost for every insn
315 in the instruction stream. */
319 /* The following array records the LOG_LINKS for every insn in the
320 instruction stream as struct insn_link pointers. */
326 };
332 {
336 }
338 #define INSN_COST(INSN) (uid_insn_cost[insn_uid_check (INSN)])
339 #define LOG_LINKS(INSN) (uid_log_links[insn_uid_check (INSN)])
341 #define FOR_EACH_LOG_LINK(L, INSN) \
342 for ((L) = LOG_LINKS (INSN); (L); (L) = (L)->next)
344 /* Links for LOG_LINKS are allocated from this obstack. */
348 /* Allocate a link. */
352 {
360 }
362 /* Incremented for each basic block. */
366 /* Reset to label_tick for each extended basic block in scanning order. */
370 /* Mode used to compute significance in reg_stat[].nonzero_bits. It is the
371 largest integer mode that can fit in HOST_BITS_PER_WIDE_INT. */
375 /* Nonzero when reg_stat[].nonzero_bits and reg_stat[].sign_bit_copies can
376 be safely used. It is zero while computing them and after combine has
377 completed. This former test prevents propagating values based on
378 previously set values, which can be incorrect if a variable is modified
379 in a loop. */
383 \f
384 /* Record one modification to rtl structure
385 to be undone by storing old_contents into *where. */
389 struct undo
390 {
395 };
397 /* Record a bunch of changes to be undone, up to MAX_UNDO of them.
398 num_undo says how many are currently recorded.
400 other_insn is nonzero if we have modified some other insn in the process
401 of working on subst_insn. It must be verified too. */
403 struct undobuf
404 {
408 };
412 /* Number of times the pseudo being substituted for
413 was found and replaced. */
418 machine_mode,
422 machine_mode,
494 \f
496 /* It is not safe to use ordinary gen_lowpart in combine.
497 See comments in gen_lowpart_for_combine. */
498 #undef RTL_HOOKS_GEN_LOWPART
499 #define RTL_HOOKS_GEN_LOWPART gen_lowpart_for_combine
501 /* Our implementation of gen_lowpart never emits a new pseudo. */
502 #undef RTL_HOOKS_GEN_LOWPART_NO_EMIT
503 #define RTL_HOOKS_GEN_LOWPART_NO_EMIT gen_lowpart_for_combine
505 #undef RTL_HOOKS_REG_NONZERO_REG_BITS
506 #define RTL_HOOKS_REG_NONZERO_REG_BITS reg_nonzero_bits_for_combine
508 #undef RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES
509 #define RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES reg_num_sign_bit_copies_for_combine
511 #undef RTL_HOOKS_REG_TRUNCATED_TO_MODE
512 #define RTL_HOOKS_REG_TRUNCATED_TO_MODE reg_truncated_to_mode
516 \f
517 /* Convenience wrapper for the canonicalize_comparison target hook.
518 Target hooks cannot use enum rtx_code. */
522 {
526 }
528 /* Try to split PATTERN found in INSN. This returns NULL_RTX if
529 PATTERN can not be split. Otherwise, it returns an insn sequence.
530 This is a wrapper around split_insns which ensures that the
531 reg_stat vector is made larger if the splitter creates a new
532 register. */
536 {
545 }
547 /* This is used by find_single_use to locate an rtx in LOC that
548 contains exactly one use of DEST, which is typically either a REG
549 or CC0. It returns a pointer to the innermost rtx expression
550 containing DEST. Appearances of DEST that are being used to
551 totally replace it are not counted. */
555 {
564 {
568 CASE_CONST_ANY:
573 /* If the destination is anything other than CC0, PC, a REG or a SUBREG
574 of a REG that occupies all of the REG, the insn uses DEST if
575 it is mentioned in the destination or the source. Otherwise, we
576 need just check the source. */
596 }
598 /* If it wasn't one of the common cases above, check each expression and
599 vector of this code. Look for a unique usage of DEST. */
603 {
605 {
610 else
616 /* Duplicate usage. */
618 }
620 {
624 {
630 else
637 }
638 }
639 }
642 }
645 /* See if DEST, produced in INSN, is used only a single time in the
646 sequel. If so, return a pointer to the innermost rtx expression in which
647 it is used.
649 If PLOC is nonzero, *PLOC is set to the insn containing the single use.
651 If DEST is cc0_rtx, we look only at the next insn. In that case, we don't
652 care about REG_DEAD notes or LOG_LINKS.
654 Otherwise, we find the single use by finding an insn that has a
655 LOG_LINKS pointing at INSN and has a REG_DEAD note for DEST. If DEST is
656 only referenced once in that insn, we know that it must be the first
657 and last insn referencing DEST. */
661 {
662 basic_block bb;
668 {
678 }
688 {
694 {
699 }
700 }
703 }
704 \f
705 /* Substitute NEWVAL, an rtx expression, into INTO, a place in some
706 insn. The substitution can be undone by undo_all. If INTO is already
707 set to NEWVAL, do not record this change. Because computing NEWVAL might
708 also call SUBST, we have to compute it before we put anything into
709 the undo table. */
711 static void
713 {
720 /* We'd like to catch as many invalid transformations here as
721 possible. Unfortunately, there are way too many mode changes
722 that are perfectly valid, so we'd waste too much effort for
723 little gain doing the checks here. Focus on catching invalid
724 transformations involving integer constants. */
727 {
728 /* Sanity check that we're replacing oldval with a CONST_INT
729 that is a valid sign-extension for the original mode. */
733 /* Replacing the operand of a SUBREG or a ZERO_EXTEND with a
734 CONST_INT is not valid, because after the replacement, the
735 original mode would be gone. Unfortunately, we can't tell
736 when do_SUBST is called to replace the operand thereof, so we
737 perform this test on oldval instead, checking whether an
738 invalid replacement took place before we got here. */
743 }
747 else
756 }
758 #define SUBST(INTO, NEWVAL) do_SUBST (&(INTO), (NEWVAL))
760 /* Similar to SUBST, but NEWVAL is an int expression. Note that substitution
761 for the value of a HOST_WIDE_INT value (including CONST_INT) is
762 not safe. */
764 static void
766 {
775 else
784 }
786 #define SUBST_INT(INTO, NEWVAL) do_SUBST_INT (&(INTO), (NEWVAL))
788 /* Similar to SUBST, but just substitute the mode. This is used when
789 changing the mode of a pseudo-register, so that any other
790 references to the entry in the regno_reg_rtx array will change as
791 well. */
793 static void
795 {
804 else
813 }
815 #define SUBST_MODE(INTO, NEWVAL) do_SUBST_MODE (&(INTO), (NEWVAL))
817 /* Similar to SUBST, but NEWVAL is a LOG_LINKS expression. */
819 static void
821 {
830 else
839 }
841 #define SUBST_LINK(oldval, newval) do_SUBST_LINK (&oldval, newval)
842 \f
843 /* Subroutine of try_combine. Determine whether the replacement patterns
844 NEWPAT, NEWI2PAT and NEWOTHERPAT are cheaper according to insn_rtx_cost
845 than the original sequence I0, I1, I2, I3 and undobuf.other_insn. Note
846 that I0, I1 and/or NEWI2PAT may be NULL_RTX. Similarly, NEWOTHERPAT and
847 undobuf.other_insn may also both be NULL_RTX. Return false if the cost
848 of all the instructions can be estimated and the replacements are more
849 expensive than the original sequence. */
851 static bool
854 {
859 /* Lookup the original insn_rtx_costs. */
864 {
867 {
871 }
872 else
873 {
877 }
878 }
879 else
880 {
883 }
885 /* If we have split a PARALLEL I2 to I1,I2, we have counted its cost twice;
886 correct that. */
891 /* Calculate the replacement insn_rtx_costs. */
894 {
898 }
899 else
900 {
903 }
906 {
912 {
915 }
916 else
918 }
920 /* Disallow this combination if both new_cost and old_cost are greater than
921 zero, and new_cost is greater than old cost. */
925 {
944 else
946 }
951 /* Update the uid_insn_cost array with the replacement costs. */
955 {
959 }
962 }
965 /* Delete any insns that copy a register to itself. */
967 static void
969 {
971 basic_block bb;
974 {
976 {
979 {
984 }
985 }
986 }
987 }
989 \f
990 /* Return false if we do not want to (or cannot) combine DEF. */
991 static bool
993 {
994 /* Do not consider if it is pre/post modification in MEM. */
1000 /* Do not combine frame pointer adjustments. */
1003 || (!HARD_FRAME_POINTER_IS_FRAME_POINTER
1011 }
1013 /* Return false if we do not want to (or cannot) combine USE. */
1014 static bool
1016 {
1017 /* Do not consider the usage of the stack pointer by function call. */
1022 }
1024 /* Fill in log links field for all insns. */
1026 static void
1028 {
1029 basic_block bb;
1036 /* Pass through each block from the end, recording the uses of each
1037 register and establishing log links when def is encountered.
1038 Note that we do not clear next_use array in order to save time,
1039 so we have to test whether the use is in the same basic block as def.
1041 There are a few cases below when we do not consider the definition or
1042 usage -- these are taken from original flow.c did. Don't ask me why it is
1043 done this way; I don't know and if it works, I don't want to know. */
1046 {
1048 {
1052 /* Log links are created only once. */
1056 {
1072 /* flow.c claimed:
1074 We don't build a LOG_LINK for hard registers contained
1075 in ASM_OPERANDs. If these registers get replaced,
1076 we might wind up changing the semantics of the insn,
1077 even if reload can make what appear to be valid
1078 assignments later. */
1083 /* Don't add duplicate links between instructions. */
1092 }
1097 }
1098 }
1101 }
1103 /* Walk the LOG_LINKS of insn B to see if we find a reference to A. Return
1104 true if we found a LOG_LINK that proves that A feeds B. This only works
1105 if there are no instructions between A and B which could have a link
1106 depending on A, since in that case we would not record a link for B.
1107 We also check the implicit dependency created by a cc0 setter/user
1108 pair. */
1110 static bool
1112 {
1120 }
1121 \f
1122 /* Main entry point for combiner. F is the first insn of the function.
1123 NREGS is the first unused pseudo-reg number.
1125 Return nonzero if the combiner has turned an indirect jump
1126 instruction into a direct jump. */
1127 static int
1129 {
1134 basic_block last_bb;
1154 /* Allocate array for insn info. */
1162 /* Don't use reg_stat[].nonzero_bits when computing it. This can cause
1163 problems when, for example, we have j <<= 1 in a loop. */
1168 /* Scan all SETs and see if we can deduce anything about what
1169 bits are known to be zero for some registers and how many copies
1170 of the sign bit are known to exist for those registers.
1172 Also set any known values so that we can use it while searching
1173 for what bits are known to be set. */
1176 /* Allow the entry block and the first block to fall into the same EBB.
1177 Conceptually the incoming promotions are assigned to the entry block. */
1182 {
1187 label_tick++;
1195 {
1196 rtx links;
1202 insn);
1209 insn);
1211 /* Record the current insn_rtx_cost of this instruction. */
1214 optimize_this_for_speed_p);
1218 }
1219 }
1223 /* Now scan all the insns in forward order. */
1231 {
1237 label_tick++;
1247 {
1261 /* See if we know about function return values before this
1262 insn based upon SUBREG flags. */
1265 /* See if we can find hardregs and subreg of pseudos in
1266 narrower modes. This could help turning TRUNCATEs
1267 into SUBREGs. */
1270 /* Try this insn with each insn it links back to. */
1276 {
1279 }
1281 /* Try each sequence of three linked insns ending with this one. */
1285 {
1288 /* If the linked insn has been replaced by a note, then there
1289 is no point in pursuing this chain any further. */
1297 {
1300 }
1301 }
1303 /* Try to combine a jump insn that uses CC0
1304 with a preceding insn that sets CC0, and maybe with its
1305 logical predecessor as well.
1306 This is how we make decrement-and-branch insns.
1307 We need this special code because data flow connections
1308 via CC0 do not get entered in LOG_LINKS. */
1315 {
1326 }
1328 /* Do the same for an insn that explicitly references CC0. */
1335 {
1346 }
1348 /* Finally, see if any of the insns that this insn links to
1349 explicitly references CC0. If so, try this insn, that insn,
1350 and its predecessor if it sets CC0. */
1352 {
1364 }
1366 /* Try combining an insn with two different insns whose results it
1367 uses. */
1377 {
1380 }
1382 /* Try four-instruction combinations. */
1385 {
1389 /* If the linked insn has been replaced by a note, then there
1390 is no point in pursuing this chain any further. */
1395 {
1399 /* I0 -> I1 -> I2 -> I3. */
1405 {
1408 }
1409 /* I0, I1 -> I2, I2 -> I3. */
1416 {
1419 }
1420 }
1423 {
1427 /* I0 -> I2; I1, I2 -> I3. */
1433 {
1436 }
1437 /* I0 -> I1; I1, I2 -> I3. */
1443 {
1446 }
1447 }
1448 }
1450 /* Try this insn with each REG_EQUAL note it links back to. */
1452 {
1458 /* Avoid using a register that may already been marked
1459 dead by an earlier instruction. */
1467 {
1468 /* Temporarily replace the set's source with the
1469 contents of the REG_EQUAL note. The insn will
1470 be deleted or recognized by try_combine. */
1481 last_combined_insn);
1484 {
1487 }
1490 }
1491 }
1496 retry:
1497 ;
1498 }
1499 }
1506 /* Clean up. */
1512 {
1515 {
1518 }
1520 }
1530 /* Make recognizer allow volatile MEMs again. */
1534 }
1536 /* Wipe the last_xxx fields of reg_stat in preparation for another pass. */
1538 static void
1540 {
1546 }
1547 \f
1548 /* Set up any promoted values for incoming argument registers. */
1550 static void
1552 {
1553 tree arg;
1558 {
1563 /* Only continue if the incoming argument is in a register. */
1567 /* Determine, if possible, whether all call sites of the current
1568 function lie within the current compilation unit. (This does
1569 take into account the exporting of a function via taking its
1570 address, and so forth.) */
1573 /* The mode and signedness of the argument before any promotions happen
1574 (equal to the mode of the pseudo holding it at that stage). */
1578 /* The mode and signedness of the argument after any source language and
1579 TARGET_PROMOTE_PROTOTYPES-driven promotions. */
1583 /* The mode and signedness of the argument as it is actually passed,
1584 see assign_parm_setup_reg in function.c. */
1588 /* The mode of the register in which the argument is being passed. */
1591 /* Eliminate sign extensions in the callee when:
1592 (a) A mode promotion has occurred; */
1595 /* (b) The mode of the register is the same as the mode of
1596 the argument as it is passed; */
1599 /* (c) There's no language level extension; */
1601 ;
1602 /* (c.1) All callers are from the current compilation unit. If that's
1603 the case we don't have to rely on an ABI, we only have to know
1604 what we're generating right now, and we know that we will do the
1605 mode1 to mode2 promotion with the given sign. */
1608 /* (c.2) The combination of the two promotions is useful. This is
1609 true when the signs match, or if the first promotion is unsigned.
1610 In the later case, (sign_extend (zero_extend x)) is the same as
1611 (zero_extend (zero_extend x)), so make sure to force UNS3 true. */
1617 /* Record that the value was promoted from mode1 to mode3,
1618 so that any sign extension at the head of the current
1619 function may be eliminated. */
1623 }
1624 }
1626 /* If MODE has a precision lower than PREC and SRC is a non-negative constant
1627 that would appear negative in MODE, sign-extend SRC for use in nonzero_bits
1628 because some machines (maybe most) will actually do the sign-extension and
1629 this is the conservative approach.
1631 ??? For 2.5, try to tighten up the MD files in this regard instead of this
1632 kludge. */
1634 static rtx
1636 {
1644 }
1646 /* Update RSP for pseudo-register X from INSN's REG_EQUAL note (if one exists)
1647 and SET. */
1649 static void
1651 rtx x)
1652 {
1662 {
1666 }
1668 /* Don't call nonzero_bits if it cannot change anything. */
1670 {
1675 }
1677 /* Don't call num_sign_bit_copies if it cannot change anything. */
1679 {
1682 {
1686 }
1689 }
1690 }
1692 /* Called via note_stores. If X is a pseudo that is narrower than
1693 HOST_BITS_PER_WIDE_INT and is being set, record what bits are known zero.
1695 If we are setting only a portion of X and we can't figure out what
1696 portion, assume all bits will be used since we don't know what will
1697 be happening.
1699 Similarly, set how many bits of X are known to be copies of the sign bit
1700 at all locations in the function. This is the smallest number implied
1701 by any set of X. */
1703 static void
1705 {
1710 /* If this register is undefined at the start of the file, we can't
1711 say what its contents were. */
1712 && ! REGNO_REG_SET_P
1715 {
1719 {
1723 }
1725 /* If this register is being initialized using itself, and the
1726 register is uninitialized in this basic block, and there are
1727 no LOG_LINKS which set the register, then part of the
1728 register is uninitialized. In that case we can't assume
1729 anything about the number of nonzero bits.
1731 ??? We could do better if we checked this in
1732 reg_{nonzero_bits,num_sign_bit_copies}_for_combine. Then we
1733 could avoid making assumptions about the insn which initially
1734 sets the register, while still using the information in other
1735 insns. We would have to be careful to check every insn
1736 involved in the combination. */
1742 {
1749 {
1753 }
1754 }
1756 /* If this is a complex assignment, see if we can convert it into a
1757 simple assignment. */
1760 /* If this is a simple assignment, or we have a paradoxical SUBREG,
1761 set what we know about X. */
1767 else
1768 {
1771 }
1772 }
1773 }
1774 \f
1775 /* See if INSN can be combined into I3. PRED, PRED2, SUCC and SUCC2 are
1776 optionally insns that were previously combined into I3 or that will be
1777 combined into the merger of INSN and I3. The order is PRED, PRED2,
1778 INSN, SUCC, SUCC2, I3.
1780 Return 0 if the combination is not allowed for any reason.
1782 If the combination is allowed, *PDEST will be set to the single
1783 destination of INSN and *PSRC to the single source, and this function
1784 will return 1. */
1786 static int
1790 {
1795 rtx link;
1800 {
1802 {
1807 }
1812 }
1816 /* Can combine only if previous insn is a SET of a REG, a SUBREG or CC0.
1817 or a PARALLEL consisting of such a SET and CLOBBERs.
1819 If INSN has CLOBBER parallel parts, ignore them for our processing.
1820 By definition, these happen during the execution of the insn. When it
1821 is merged with another insn, all bets are off. If they are, in fact,
1822 needed and aren't also supplied in I3, they may be added by
1823 recog_for_combine. Otherwise, it won't match.
1825 We can also ignore a SET whose SET_DEST is mentioned in a REG_UNUSED
1826 note.
1828 Get the source and destination of INSN. If more than one, can't
1829 combine. */
1835 {
1837 {
1841 {
1842 /* This is important to combine floating point insns
1843 for the SH4 port. */
1845 /* Combining an isolated USE doesn't make sense.
1846 We depend here on combinable_i3pat to reject them. */
1847 /* The code below this loop only verifies that the inputs of
1848 the SET in INSN do not change. We call reg_set_between_p
1849 to verify that the REG in the USE does not change between
1850 I3 and INSN.
1851 If the USE in INSN was for a pseudo register, the matching
1852 insn pattern will likely match any register; combining this
1853 with any other USE would only be safe if we knew that the
1854 used registers have identical values, or if there was
1855 something to tell them apart, e.g. different modes. For
1856 now, we forgo such complicated tests and simply disallow
1857 combining of USES of pseudo registers with any other USE. */
1860 {
1865 do
1866 {
1876 }
1878 }
1881 /* We can ignore CLOBBERs. */
1886 /* Ignore SETs whose result isn't used but not those that
1887 have side-effects. */
1893 /* If we have already found a SET, this is a second one and
1894 so we cannot combine with this insn. */
1902 /* Anything else means we can't combine. */
1904 }
1905 }
1908 /* If SET_SRC is an ASM_OPERANDS we can't throw away these CLOBBERs,
1909 so don't do anything with it. */
1912 }
1913 else
1919 /* The simplification in expand_field_assignment may call back to
1920 get_last_value, so set safe guard here. */
1926 /* Do not eliminate user-specified register if it is in an
1927 asm input because we may break the register asm usage defined
1928 in GCC manual if allow to do so.
1929 Be aware that this may cover more cases than we expect but this
1930 should be harmless. */
1935 /* Don't eliminate a store in the stack pointer. */
1937 /* Don't combine with an insn that sets a register to itself if it has
1938 a REG_EQUAL note. This may be part of a LIBCALL sequence. */
1940 /* Can't merge an ASM_OPERANDS. */
1942 /* Can't merge a function call. */
1944 /* Don't eliminate a function call argument. */
1950 /* Don't substitute into an incremented register. */
1954 /* Don't substitute into a non-local goto, this confuses CFG. */
1956 /* Make sure that DEST is not used after INSN but before SUCC, or
1957 after SUCC and before SUCC2, or after SUCC2 but before I3. */
1958 || (!all_adjacent
1959 && ((succ2
1963 || (succ
1964 /* SUCC and SUCC2 can be split halves from a PARALLEL; in
1965 that case SUCC is not in the insn stream, so use SUCC2
1966 instead for this test. */
1968 succ2
1971 /* Make sure that the value that is to be substituted for the register
1972 does not use any registers whose values alter in between. However,
1973 If the insns are adjacent, a use can't cross a set even though we
1974 think it might (this can happen for a sequence of insns each setting
1975 the same destination; last_set of that register might point to
1976 a NOTE). If INSN has a REG_EQUIV note, the register is always
1977 equivalent to the memory so the substitution is valid even if there
1978 are intervening stores. Also, don't move a volatile asm or
1979 UNSPEC_VOLATILE across any other insns. */
1980 || (! all_adjacent
1986 /* Don't combine across a CALL_INSN, because that would possibly
1987 change whether the life span of some REGs crosses calls or not,
1988 and it is a pain to update that information.
1989 Exception: if source is a constant, moving it later can't hurt.
1990 Accept that as a special case. */
1994 /* DEST must either be a REG or CC0. */
1996 {
1997 /* If register alignment is being enforced for multi-word items in all
1998 cases except for parameters, it is possible to have a register copy
1999 insn referencing a hard register that is not allowed to contain the
2000 mode being copied and which would not be valid as an operand of most
2001 insns. Eliminate this problem by not combining with such an insn.
2003 Also, on some machines we don't want to extend the life of a hard
2004 register. */
2009 /* Don't extend the life of a hard register unless it is
2010 user variable (if we have few registers) or it can't
2011 fit into the desired register (meaning something special
2012 is going on).
2013 Also avoid substituting a return register into I3, because
2014 reload can't handle a conflict with constraints of other
2015 inputs. */
2019 }
2027 {
2030 /* If the clobber represents an earlyclobber operand, we must not
2031 substitute an expression containing the clobbered register.
2032 As we do not analyze the constraint strings here, we have to
2033 make the conservative assumption. However, if the register is
2034 a fixed hard reg, the clobber cannot represent any operand;
2035 we leave it up to the machine description to either accept or
2036 reject use-and-clobber patterns. */
2042 }
2044 /* If INSN contains anything volatile, or is an `asm' (whether volatile
2045 or not), reject, unless nothing volatile comes between it and I3 */
2048 {
2049 /* Make sure neither succ nor succ2 contains a volatile reference. */
2054 /* We'll check insns between INSN and I3 below. */
2055 }
2057 /* If INSN is an asm, and DEST is a hard register, reject, since it has
2058 to be an explicit register variable, and was chosen for a reason. */
2064 /* If INSN contains volatile references (specifically volatile MEMs),
2065 we cannot combine across any other volatile references.
2066 Even if INSN doesn't contain volatile references, any intervening
2067 volatile insn might affect machine state. */
2070 ? volatile_refs_p
2077 /* If INSN contains an autoincrement or autodecrement, make sure that
2078 register is not used between there and I3, and not already used in
2079 I3 either. Neither must it be used in PRED or SUCC, if they exist.
2080 Also insist that I3 not be a jump; if it were one
2081 and the incremented register were spilled, we would lose. */
2099 /* Don't combine an insn that follows a CC0-setting insn.
2100 An insn that uses CC0 must not be separated from the one that sets it.
2101 We do, however, allow I2 to follow a CC0-setting insn if that insn
2102 is passed as I1; in that case it will be deleted also.
2103 We also allow combining in this case if all the insns are adjacent
2104 because that would leave the two CC0 insns adjacent as well.
2105 It would be more logical to test whether CC0 occurs inside I1 or I2,
2106 but that would be much slower, and this ought to be equivalent. */
2109 {
2114 }
2116 /* If we get here, we have passed all the tests and the combination is
2117 to be allowed. */
2123 }
2124 \f
2125 /* LOC is the location within I3 that contains its pattern or the component
2126 of a PARALLEL of the pattern. We validate that it is valid for combining.
2128 One problem is if I3 modifies its output, as opposed to replacing it
2129 entirely, we can't allow the output to contain I2DEST, I1DEST or I0DEST as
2130 doing so would produce an insn that is not equivalent to the original insns.
2132 Consider:
2134 (set (reg:DI 101) (reg:DI 100))
2135 (set (subreg:SI (reg:DI 101) 0) <foo>)
2137 This is NOT equivalent to:
2139 (parallel [(set (subreg:SI (reg:DI 100) 0) <foo>)
2140 (set (reg:DI 101) (reg:DI 100))])
2142 Not only does this modify 100 (in which case it might still be valid
2143 if 100 were dead in I2), it sets 101 to the ORIGINAL value of 100.
2145 We can also run into a problem if I2 sets a register that I1
2146 uses and I1 gets directly substituted into I3 (not via I2). In that
2147 case, we would be getting the wrong value of I2DEST into I3, so we
2148 must reject the combination. This case occurs when I2 and I1 both
2149 feed into I3, rather than when I1 feeds into I2, which feeds into I3.
2150 If I1_NOT_IN_SRC is nonzero, it means that finding I1 in the source
2151 of a SET must prevent combination from occurring. The same situation
2152 can occur for I0, in which case I0_NOT_IN_SRC is set.
2154 Before doing the above check, we first try to expand a field assignment
2155 into a set of logical operations.
2157 If PI3_DEST_KILLED is nonzero, it is a pointer to a location in which
2158 we place a register that is both set and used within I3. If more than one
2159 such register is detected, we fail.
2161 Return 1 if the combination is valid, zero otherwise. */
2163 static int
2166 {
2170 {
2175 rtx subdest;
2182 /* Check for the case where I3 modifies its output, as discussed
2183 above. We don't want to prevent pseudos from being combined
2184 into the address of a MEM, so only prevent the combination if
2185 i1 or i2 set the same MEM. */
2195 /* This is the same test done in can_combine_p except we can't test
2196 all_adjacent; we don't have to, since this instruction will stay
2197 in place, thus we are not considering increasing the lifetime of
2198 INNER_DEST.
2200 Also, if this insn sets a function argument, combining it with
2201 something that might need a spill could clobber a previous
2202 function argument; the all_adjacent test in can_combine_p also
2203 checks this; here, we do a more specific test for this case. */
2213 /* If DEST is used in I3, it is being killed in this insn, so
2214 record that for later. We have to consider paradoxical
2215 subregs here, since they kill the whole register, but we
2216 ignore partial subregs, STRICT_LOW_PART, etc.
2217 Never add REG_DEAD notes for the FRAME_POINTER_REGNUM or the
2218 STACK_POINTER_REGNUM, since these are always considered to be
2219 live. Similarly for ARG_POINTER_REGNUM if it is fixed. */
2229 && (HARD_FRAME_POINTER_IS_FRAME_POINTER
2235 {
2240 }
2241 }
2244 {
2251 }
2254 }
2255 \f
2256 /* Return 1 if X is an arithmetic expression that contains a multiplication
2257 and division. We don't count multiplications by powers of two here. */
2259 static int
2261 {
2263 {
2279 }
2280 }
2281 \f
2282 /* Determine whether INSN can be used in a combination. Return nonzero if
2283 not. This is used in try_combine to detect early some cases where we
2284 can't perform combinations. */
2286 static int
2288 {
2289 rtx set;
2292 /* If this isn't really an insn, we can't do anything.
2293 This can occur when flow deletes an insn that it has merged into an
2294 auto-increment address. */
2298 /* Never combine loads and stores involving hard regs that are likely
2299 to be spilled. The register allocator can usually handle such
2300 reg-reg moves by tying. If we allow the combiner to make
2301 substitutions of likely-spilled regs, reload might die.
2302 As an exception, we allow combinations involving fixed regs; these are
2303 not available to the register allocator so there's no risk involved. */
2324 }
2326 struct likely_spilled_retval_info
2327 {
2330 };
2332 /* Called via note_stores by likely_spilled_retval_p. Remove from info->mask
2333 hard registers that are known to be written to / clobbered in full. */
2334 static void
2336 {
2353 else
2356 }
2358 /* Return nonzero iff part of the return value is live during INSN, and
2359 it is likely spilled. This can happen when more than one insn is needed
2360 to copy the return value, e.g. when we consider to combine into the
2361 second copy insn for a complex value. */
2363 static int
2365 {
2367 rtx reg;
2370 /* We assume here that no machine mode needs more than
2371 32 hard registers when the value overlaps with a register
2372 for which TARGET_FUNCTION_VALUE_REGNO_P is true. */
2387 /* Disregard parts of the return value that are set later. */
2396 /* Check if any of the (probably) live return value registers is
2397 likely spilled. */
2398 nregs --;
2399 do
2400 {
2406 }
2408 /* Adjust INSN after we made a change to its destination.
2410 Changing the destination can invalidate notes that say something about
2411 the results of the insn and a LOG_LINK pointing to the insn. */
2413 static void
2415 {
2416 /* For notes, be conservative and simply remove them. */
2419 /* The new insn will have a destination that was previously the destination
2420 of an insn just above it. Call distribute_links to make a LOG_LINK from
2421 the next use of that destination. */
2437 }
2439 /* Return TRUE if combine can reuse reg X in mode MODE.
2440 ADDED_SETS is nonzero if the original set is still required. */
2441 static bool
2443 {
2450 /* Allow hard registers if the new mode is legal, and occupies no more
2451 registers than the old mode. */
2456 /* Or a pseudo that is only used once. */
2459 && !added_sets
2461 }
2464 /* Check whether X, the destination of a set, refers to part of
2465 the register specified by REG. */
2467 static bool
2469 {
2470 /* Check that reg is an integer mode register. */
2481 }
2483 /* Delete the unconditional jump INSN and adjust the CFG correspondingly.
2484 Note that the INSN should be deleted *after* removing dead edges, so
2485 that the kept edge is the fallthrough edge for a (set (pc) (pc))
2486 but not for a (set (pc) (label_ref FOO)). */
2488 static void
2490 {
2498 {
2503 /* Remove barriers from the footer if there are any. */
2506 {
2509 else
2513 }
2516 }
2517 }
2519 /* Return whether PAT is a PARALLEL of exactly N register SETs followed
2520 by an arbitrary number of CLOBBERs. */
2521 static bool
2523 {
2542 }
2544 /* Return whether INSN, a PARALLEL of N register SETs (and maybe some
2545 CLOBBERs), can be split into individual SETs in that order, without
2546 changing semantics. */
2547 static bool
2549 {
2557 {
2566 }
2569 }
2571 /* Try to combine the insns I0, I1 and I2 into I3.
2572 Here I0, I1 and I2 appear earlier than I3.
2573 I0 and I1 can be zero; then we combine just I2 into I3, or I1 and I2 into
2574 I3.
2576 If we are combining more than two insns and the resulting insn is not
2577 recognized, try splitting it into two insns. If that happens, I2 and I3
2578 are retained and I1/I0 are pseudo-deleted by turning them into a NOTE.
2579 Otherwise, I0, I1 and I2 are pseudo-deleted.
2581 Return 0 if the combination does not work. Then nothing is changed.
2582 If we did the combination, return the insn at which combine should
2583 resume scanning.
2585 Set NEW_DIRECT_JUMP_P to a nonzero value if try_combine creates a
2586 new direct jump instruction.
2588 LAST_COMBINED_INSN is either I3, or some insn after I3 that has
2589 been I3 passed to an earlier try_combine within the same basic
2590 block. */
2595 {
2596 /* New patterns for I3 and I2, respectively. */
2600 /* Indicates need to preserve SET in I0, I1 or I2 in I3 if it is not
2601 dead. */
2603 /* Total number of SETs to put into I3. */
2605 /* Nonzero if I2's or I1's body now appears in I3. */
2607 /* INSN_CODEs for new I3, new I2, and user of condition code. */
2609 /* Contains I3 if the destination of I3 is used in its source, which means
2610 that the old life of I3 is being killed. If that usage is placed into
2611 I2 and not in I3, a REG_DEAD note must be made. */
2613 /* SET_DEST and SET_SRC of I2, I1 and I0. */
2615 /* Copy of SET_SRC of I1 and I0, if needed. */
2617 /* Set if I2DEST was reused as a scratch register. */
2619 /* The PATTERNs of I0, I1, and I2, or a copy of them in certain cases. */
2621 /* Indicates if I2DEST or I1DEST is in I2SRC or I1_SRC. */
2626 /* Notes that must be added to REG_NOTES in I3 and I2. */
2628 /* Notes that we substituted I3 into I2 instead of the normal case. */
2630 /* Notes that I1, I2 or I3 is a MULT operation. */
2637 rtx temp_expr;
2640 rtx new_other_notes;
2643 /* Immediately return if any of I0,I1,I2 are the same insn (I3 can
2644 never be). */
2648 /* Only try four-insn combinations when there's high likelihood of
2649 success. Look for simple insns, such as loads of constants or
2650 binary operations involving a constant. */
2652 {
2662 {
2665 rtx src;
2670 {
2673 }
2675 ngood++;
2678 nshift++;
2679 }
2681 /* If I0 loads a memory and I3 sets the same memory, then I1 and I2
2682 are likely manipulating its value. Ideally we'll be able to combine
2683 all four insns into a bitfield insertion of some kind.
2685 Note the source in I0 might be inside a sign/zero extension and the
2686 memory modes in I0 and I3 might be different. So extract the address
2687 from the destination of I3 and search for it in the source of I0.
2689 In the event that there's a match but the source/dest do not actually
2690 refer to the same memory, the worst that happens is we try some
2691 combinations that we wouldn't have otherwise. */
2693 /* Ensure the source of SET0 is a MEM, possibly buried inside
2694 an extension. */
2700 /* Ensure the destination of SET3 is a MEM. */
2702 /* Would it be better to extract the base address for the MEM
2703 in SET3 and look for that? I don't have cases where it matters
2704 but I could envision such cases. */
2710 }
2712 /* Exit early if one of the insns involved can't be used for
2713 combinations. */
2724 combine_attempts++;
2727 /* Reset the hard register usage information. */
2731 {
2738 else
2741 }
2743 /* If multiple insns feed into one of I2 or I3, they can be in any
2744 order. To simplify the code below, reorder them in sequence. */
2754 /* First check for one important special case that the code below will
2755 not handle. Namely, the case where I1 is zero, I2 is a PARALLEL
2756 and I3 is a SET whose SET_SRC is a SET_DEST in I2. In that case,
2757 we may be able to replace that destination with the destination of I3.
2758 This occurs in the common code where we compute both a quotient and
2759 remainder into a structure, in which case we want to do the computation
2760 directly into the structure to avoid register-register copies.
2762 Note that this case handles both multiple sets in I2 and also cases
2763 where I2 has a number of CLOBBERs inside the PARALLEL.
2765 We make very conservative checks below and only try to handle the
2766 most common cases of this. For example, we only handle the case
2767 where I2 and I3 are adjacent to avoid making difficult register
2768 usage tests. */
2776 /* If the dest of I3 is a ZERO_EXTRACT or STRICT_LOW_PART, the code
2777 below would need to check what is inside (and reg_overlap_mentioned_p
2778 doesn't support those codes anyway). Don't allow those destinations;
2779 the resulting insn isn't likely to be recognized anyway. */
2785 {
2788 /* Make sure that the destination of I3,
2789 which we are going to substitute into one output of I2,
2790 is not used within another output of I2. We must avoid making this:
2791 (parallel [(set (mem (reg 69)) ...)
2792 (set (reg 69) ...)])
2793 which is not well-defined as to order of actions.
2794 (Besides, reload can't handle output reloads for this.)
2796 The problem can also happen if the dest of I3 is a memory ref,
2797 if another dest in I2 is an indirect memory ref.
2799 Neither can this PARALLEL be an asm. We do not allow combining
2800 that usually (see can_combine_p), so do not here either. */
2803 {
2812 }
2818 {
2819 combine_merges++;
2829 /* Replace the dest in I2 with our dest and make the resulting
2830 insn the new pattern for I3. Then skip to where we validate
2831 the pattern. Everything was set up above. */
2836 }
2837 }
2839 /* If I2 is setting a pseudo to a constant and I3 is setting some
2840 sub-part of it to another constant, merge them by making a new
2841 constant. */
2848 {
2854 {
2857 {
2863 }
2864 }
2865 else
2866 {
2871 }
2874 {
2875 /* If this is the low part, we're done. */
2877 ;
2878 /* Handle the case where inner is twice the size of outer. */
2882 /* Otherwise give up for now. */
2883 else
2885 }
2888 {
2892 wide_int o
2897 combine_merges++;
2904 /* Replace the source in I2 with the new constant and make the
2905 resulting insn the new pattern for I3. Then skip to where we
2906 validate the pattern. Everything was set up above. */
2912 /* The dest of I3 has been replaced with the dest of I2. */
2915 }
2916 }
2918 /* If we have no I1 and I2 looks like:
2919 (parallel [(set (reg:CC X) (compare:CC OP (const_int 0)))
2920 (set Y OP)])
2921 make up a dummy I1 that is
2922 (set Y OP)
2923 and change I2 to be
2924 (set (reg:CC X) (compare:CC Y (const_int 0)))
2926 (We can ignore any trailing CLOBBERs.)
2928 This undoes a previous combination and allows us to match a branch-and-
2929 decrement insn. */
2941 {
2942 /* We make I1 with the same INSN_UID as I2. This gives it
2943 the same DF_INSN_LUID for value tracking. Our fake I1 will
2944 never appear in the insn stream so giving it the same INSN_UID
2945 as I2 will not cause a problem. */
2958 }
2960 /* If I2 is a PARALLEL of two SETs of REGs (and perhaps some CLOBBERs),
2961 make those two SETs separate I1 and I2 insns, and make an I0 that is
2962 the original I1. */
2968 {
2969 /* If there is no I1, there is no I0 either. */
2972 /* We make I1 with the same INSN_UID as I2. This gives it
2973 the same DF_INSN_LUID for value tracking. Our fake I1 will
2974 never appear in the insn stream so giving it the same INSN_UID
2975 as I2 will not cause a problem. */
2983 }
2985 /* Verify that I2 and I1 are valid for combining. */
2991 {
2994 }
2996 /* Record whether I2DEST is used in I2SRC and similarly for the other
2997 cases. Knowing this will help in register status updating below. */
3008 /* For the earlier insns, determine which of the subsequent ones they
3009 feed. */
3016 /* Ensure that I3's pattern can be the destination of combines. */
3022 {
3025 }
3027 /* See if any of the insns is a MULT operation. Unless one is, we will
3028 reject a combination that is, since it must be slower. Be conservative
3029 here. */
3037 /* If I3 has an inc, then give up if I1 or I2 uses the reg that is inc'd.
3038 We used to do this EXCEPT in one case: I3 has a post-inc in an
3039 output operand. However, that exception can give rise to insns like
3040 mov r3,(r3)+
3041 which is a famous insn on the PDP-11 where the value of r3 used as the
3042 source was model-dependent. Avoid this sort of thing. */
3044 #if 0
3050 /* It's not the exception. */
3051 #endif
3053 {
3054 rtx link;
3060 {
3063 }
3064 }
3066 /* See if the SETs in I1 or I2 need to be kept around in the merged
3067 instruction: whenever the value set there is still needed past I3.
3068 For the SET in I2, this is easy: we see if I2DEST dies or is set in I3.
3070 For the SET in I1, we have two cases: if I1 and I2 independently feed
3071 into I3, the set in I1 needs to be kept around unless I1DEST dies
3072 or is set in I3. Otherwise (if I1 feeds I2 which feeds I3), the set
3073 in I1 needs to be kept around unless I1DEST dies or is set in either
3074 I2 or I3. The same considerations apply to I0. */
3081 else
3089 else
3092 /* We are about to copy insns for the case where they need to be kept
3093 around. Check that they can be copied in the merged instruction. */
3099 {
3102 }
3104 /* If the set in I2 needs to be kept around, we must make a copy of
3105 PATTERN (I2), so that when we substitute I1SRC for I1DEST in
3106 PATTERN (I2), we are only substituting for the original I1DEST, not into
3107 an already-substituted copy. This also prevents making self-referential
3108 rtx. If I2 is a PARALLEL, we just need the piece that assigns I2SRC to
3109 I2DEST. */
3112 {
3115 else
3117 }
3120 {
3123 else
3125 }
3128 {
3131 else
3133 }
3135 combine_merges++;
3137 /* Substitute in the latest insn for the regs set by the earlier ones. */
3143 /* Many machines that don't use CC0 have insns that can both perform an
3144 arithmetic operation and set the condition code. These operations will
3145 be represented as a PARALLEL with the first element of the vector
3146 being a COMPARE of an arithmetic operation with the constant zero.
3147 The second element of the vector will set some pseudo to the result
3148 of the same arithmetic operation. If we simplify the COMPARE, we won't
3149 match such a pattern and so will generate an extra insn. Here we test
3150 for this case, where both the comparison and the operation result are
3151 needed, and make the PARALLEL by just replacing I2DEST in I3SRC with
3152 I2SRC. Later we will make the PARALLEL that contains I2. */
3158 {
3159 rtx newpat_dest;
3173 {
3178 }
3180 /* Do the rest only if op1 is const0_rtx, which may be the
3181 result of simplification. */
3183 {
3184 /* If a single use of the CC is found, prepare to modify it
3185 when SELECT_CC_MODE returns a new CC-class mode, or when
3186 the above simplify_compare_const() returned a new comparison
3187 operator. undobuf.other_insn is assigned the CC use insn
3188 when modifying it. */
3190 {
3191 #ifdef SELECT_CC_MODE
3192 machine_mode new_mode
3197 {
3202 else
3203 {
3206 }
3207 }
3208 #endif
3209 /* Cases for modifying the CC-using comparison. */
3211 /* ??? Do we need to verify the zero rtx? */
3213 {
3214 /* Replace cc_use_loc with entire new RTX. */
3219 }
3221 {
3222 /* Just replace the CC reg with a new mode. */
3225 }
3226 }
3228 /* Now we modify the current newpat:
3229 First, SET_DEST(newpat) is updated if the CC mode has been
3230 altered. For targets without SELECT_CC_MODE, this should be
3231 optimized away. */
3234 /* This is always done to propagate i2src into newpat. */
3237 /* Create new version of i2pat if needed; the below PARALLEL
3238 creation needs this to work correctly. */
3242 }
3243 }
3246 {
3247 /* It is possible that the source of I2 or I1 may be performing
3248 an unneeded operation, such as a ZERO_EXTEND of something
3249 that is known to have the high part zero. Handle that case
3250 by letting subst look at the inner insns.
3252 Another way to do this would be to have a function that tries
3253 to simplify a single insn instead of merging two or more
3254 insns. We don't do this because of the potential of infinite
3255 loops and because of the potential extra memory required.
3256 However, doing it the way we are is a bit of a kludge and
3257 doesn't catch all cases.
3259 But only do this if -fexpensive-optimizations since it slows
3260 things down and doesn't usually win.
3262 This is not done in the COMPARE case above because the
3263 unmodified I2PAT is used in the PARALLEL and so a pattern
3264 with a modified I2SRC would not match. */
3267 {
3268 /* Pass pc_rtx so no substitutions are done, just
3269 simplifications. */
3271 {
3274 }
3278 }
3283 /* If I1 feeds into I2 and I1DEST is in I1SRC, we need to make a unique
3284 copy of I2SRC each time we substitute it, in order to avoid creating
3285 self-referential RTL when we will be substituting I1SRC for I1DEST
3286 later. Likewise if I0 feeds into I2, either directly or indirectly
3287 through I1, and I0DEST is in I0SRC. */
3294 /* Record whether I2's body now appears within I3's body. */
3296 }
3298 /* If we already got a failure, don't try to do more. Otherwise, try to
3299 substitute I1 if we have it. */
3302 {
3303 /* Check that an autoincrement side-effect on I1 has not been lost.
3304 This happens if I1DEST is mentioned in I2 and dies there, and
3305 has disappeared from the new pattern. */
3307 && i1_feeds_i2_n
3310 /* Before we can do this substitution, we must redo the test done
3311 above (see detailed comments there) that ensures I1DEST isn't
3312 mentioned in any SETs in NEWPAT that are field assignments. */
3315 {
3318 }
3323 /* If the following substitution will modify I1SRC, make a copy of it
3324 for the case where it is substituted for I1DEST in I2PAT later. */
3328 /* If I0 feeds into I1 and I0DEST is in I0SRC, we need to make a unique
3329 copy of I1SRC each time we substitute it, in order to avoid creating
3330 self-referential RTL when we will be substituting I0SRC for I0DEST
3331 later. */
3336 /* Record whether I1's body now appears within I3's body. */
3338 }
3340 /* Likewise for I0 if we have it. */
3343 {
3350 {
3353 }
3355 /* If the following substitution will modify I0SRC, make a copy of it
3356 for the case where it is substituted for I0DEST in I1PAT later. */
3359 /* And a copy for I0DEST in I2PAT substitution. */
3368 }
3370 /* Fail if an autoincrement side-effect has been duplicated. Be careful
3371 to count all the ways that I2SRC and I1SRC can be used. */
3382 /* Fail if we tried to make a new register. */
3384 /* Fail if we couldn't do something and have a CLOBBER. */
3386 /* Fail if this new pattern is a MULT and we didn't have one before
3387 at the outer level. */
3390 {
3393 }
3395 /* If the actions of the earlier insns must be kept
3396 in addition to substituting them into the latest one,
3397 we must make a new PARALLEL for the latest insn
3398 to hold additional the SETs. */
3401 {
3403 combine_extras++;
3406 {
3412 }
3413 else
3414 {
3419 }
3425 {
3431 }
3433 {
3442 }
3443 }
3445 validate_replacement:
3447 /* Note which hard regs this insn has as inputs. */
3450 /* If recog_for_combine fails, it strips existing clobbers. If we'll
3451 consider splitting this pattern, we might need these clobbers. */
3454 {
3460 }
3462 /* We have recognized nothing yet. */
3465 /* See if this is a PARALLEL of two SETs where one SET's destination is
3466 a register that is unused and this isn't marked as an instruction that
3467 might trap in an EH region. In that case, we just need the other SET.
3468 We prefer this over the PARALLEL.
3470 This can occur when simplifying a divmod insn. We *must* test for this
3471 case here because the code below that splits two independent SETs doesn't
3472 handle this case correctly when it updates the register status.
3474 It's pointless doing this if we originally had two sets, one from
3475 i3, and one from i2. Combining then splitting the parallel results
3476 in the original i2 again plus an invalid insn (which we delete).
3477 The net effect is only to move instructions around, which makes
3478 debug info less accurate. */
3483 {
3494 {
3497 }
3506 {
3512 }
3516 }
3518 /* Is the result of combination a valid instruction? */
3522 /* If we were combining three insns and the result is a simple SET
3523 with no ASM_OPERANDS that wasn't recognized, try to split it into two
3524 insns. There are two ways to do this. It can be split using a
3525 machine-specific method (like when you have an addition of a large
3526 constant) or by combine in the function find_split_point. */
3530 {
3534 /* See if the MD file can split NEWPAT. If it can't, see if letting it
3535 use I2DEST as a scratch register will help. In the latter case,
3536 convert I2DEST to the mode of the source of NEWPAT if we can. */
3540 /* We can only use I2DEST as a scratch reg if it doesn't overlap any
3541 inputs of NEWPAT. */
3543 /* ??? If I2DEST is not safe, and I1DEST exists, then it would be
3544 possible to try that as a scratch reg. This would require adding
3545 more code to make it work though. */
3548 {
3551 /* ??? Reusing i2dest without resetting the reg_stat entry for it
3552 (temporarily, until we are committed to this instruction
3553 combination) does not work: for example, any call to nonzero_bits
3554 on the register (from a splitter in the MD file, for example)
3555 will get the old information, which is invalid.
3557 Since nowadays we can create registers during combine just fine,
3558 we should just create a new one here, not reuse i2dest. */
3560 /* First try to split using the original register as a
3561 scratch register. */
3565 i2dest)));
3568 /* If that didn't work, try changing the mode of I2DEST if
3569 we can. */
3574 {
3576 rtx ni2dest;
3580 else
3581 {
3584 }
3586 parallel = (gen_rtx_PARALLEL
3590 ni2dest))));
3595 {
3603 }
3604 }
3607 }
3609 /* If recog_for_combine has discarded clobbers, try to use them
3610 again for the split. */
3612 {
3615 }
3618 {
3623 }
3627 {
3637 /* If I2 or I3 has multiple SETs, we won't know how to track
3638 register status, so don't use these insns. If I2's destination
3639 is used between I2 and I3, we also can't use these insns. */
3649 /* It is possible that both insns now set the destination of I3.
3650 If so, we must show an extra use of it. */
3653 {
3672 }
3673 }
3675 /* If we can split it and use I2DEST, go ahead and see if that
3676 helps things be recognized. Verify that none of the registers
3677 are set between I2 and I3. */
3681 /* We need I2DEST in the proper mode. If it is a hard register
3682 or the only use of a pseudo, we can change its mode.
3683 Make sure we don't change a hard register to have a mode that
3684 isn't valid for it, or change the number of registers. */
3691 /* We can't overwrite I2DEST if its value is still used by
3692 NEWPAT. */
3694 {
3703 /* *SPLIT may be part of I2SRC, so make sure we have the
3704 original expression around for later debug processing.
3705 We should not need I2SRC any more in other cases. */
3708 else
3711 /* Get NEWDEST as a register in the proper mode. We have already
3712 validated that we can do this. */
3714 {
3717 else
3718 {
3721 }
3722 }
3724 /* If *SPLIT is a (mult FOO (const_int pow2)), convert it to
3725 an ASHIFT. This can occur if it was inside a PLUS and hence
3726 appeared to be a memory address. This is a kludge. */
3731 {
3734 /* Update split_code because we may not have a multiply
3735 anymore. */
3737 }
3739 /* Similarly for (plus (mult FOO (const_int pow2))). */
3745 {
3749 /* Update split_code because we may not have a multiply
3750 anymore. */
3752 }
3754 #ifdef INSN_SCHEDULING
3755 /* If *SPLIT is a paradoxical SUBREG, when we split it, it should
3756 be written as a ZERO_EXTEND. */
3758 {
3759 /* Or as a SIGN_EXTEND if LOAD_EXTEND_OP says that that's
3760 what it really is. */
3765 else
3768 }
3769 #endif
3771 /* Attempt to split binary operators using arithmetic identities. */
3775 {
3782 /* Split "X = Y op Y" as "Z = Y; X = Z op Z". */
3784 {
3789 }
3790 /* Split "((P op Q) op R) op S" where op is PLUS or MULT. */
3797 {
3803 /* Split both "((X op Y) op X) op Y" and
3804 "((X op Y) op Y) op X" as "T op T" where T is
3805 "X op Y". */
3808 {
3813 }
3814 /* Split "((X op X) op Y) op Y)" as "T op T" where
3815 T is "X op Y". */
3817 {
3823 }
3824 }
3825 }
3828 {
3831 }
3835 /* recog_for_combine might have added CLOBBERs to newi2pat.
3836 Make sure NEWPAT does not depend on the clobbered regs. */
3840 {
3843 {
3846 }
3847 }
3849 /* If the split point was a MULT and we didn't have one before,
3850 don't use one now. */
3853 }
3854 }
3856 /* Check for a case where we loaded from memory in a narrow mode and
3857 then sign extended it, but we need both registers. In that case,
3858 we have a PARALLEL with both loads from the same memory location.
3859 We can split this into a load from memory followed by a register-register
3860 copy. This saves at least one insn, more if register allocation can
3861 eliminate the copy.
3863 We cannot do this if the destination of the first assignment is a
3864 condition code register or cc0. We eliminate this case by making sure
3865 the SET_DEST and SET_SRC have the same mode.
3867 We cannot do this if the destination of the second assignment is
3868 a register that we have already assumed is zero-extended. Similarly
3869 for a SUBREG of such a register. */
3904 {
3905 rtx ni2dest;
3919 }
3921 /* Similarly, check for a case where we have a PARALLEL of two independent
3922 SETs but we started with three insns. In this case, we can do the sets
3923 as two separate insns. This case occurs when some SET allows two
3924 other insns to combine, but the destination of that SET is still live.
3926 Also do this if we started with two insns and (at least) one of the
3927 resulting sets is a noop; this noop will be deleted later. */
3946 {
3950 /* Normally, it doesn't matter which of the two is done first,
3951 but the one that references cc0 can't be the second, and
3952 one which uses any regs/memory set in between i2 and i3 can't
3953 be first. The PARALLEL might also have been pre-existing in i3,
3954 so we need to make sure that we won't wrongly hoist a SET to i2
3955 that would conflict with a death note present in there. */
3963 /* If I3 is a jump, ensure that set0 is a jump so that
3964 we do not create invalid RTL. */
3966 )
3967 {
3970 }
3978 /* If I3 is a jump, ensure that set1 is a jump so that
3979 we do not create invalid RTL. */
3981 )
3982 {
3985 }
3986 else
3987 {
3990 }
3995 {
3996 /* recog_for_combine might have added CLOBBERs to newi2pat.
3997 Make sure NEWPAT does not depend on the clobbered regs. */
3999 {
4002 {
4005 {
4008 }
4009 }
4010 }
4013 }
4014 }
4016 /* If it still isn't recognized, fail and change things back the way they
4017 were. */
4019 /* Is the result a reasonable ASM_OPERANDS? */
4021 {
4024 }
4026 /* If we had to change another insn, make sure it is valid also. */
4028 {
4036 {
4039 }
4040 }
4042 /* If I2 is the CC0 setter and I3 is the CC0 user then check whether
4043 they are adjacent to each other or not. */
4045 {
4049 {
4052 }
4053 }
4055 /* Only allow this combination if insn_rtx_costs reports that the
4056 replacement instructions are cheaper than the originals. */
4058 {
4061 }
4064 {
4069 {
4074 /* Temporarily revert mode back. */
4078 {
4079 /* If we used i2dest as a scratch register with a
4080 different mode, substitute it for the original
4081 i2src while its original mode is temporarily
4082 restored, and then clear i2scratch so that we don't
4083 do it again later. */
4085 this_basic_block);
4087 /* Put back the new mode. */
4089 }
4090 else
4091 {
4096 {
4099 }
4100 else
4101 {
4108 }
4110 /* We're dealing with a reg that changed mode but not
4111 meaning, so we want to turn it into a subreg for
4112 the new mode. However, because of REG sharing and
4113 because its mode had already changed, we have to do
4114 it in two steps. First, replace any debug uses of
4115 reg, with its original mode temporarily restored,
4116 with this copy we have created; then, replace the
4117 copy with the SUBREG of the original shared reg,
4118 once again changed to the new mode. */
4120 this_basic_block);
4124 this_basic_block);
4125 }
4126 }
4127 }
4129 /* If we will be able to accept this, we have made a
4130 change to the destination of I3. This requires us to
4131 do a few adjustments. */
4134 {
4137 }
4139 /* We now know that we can do this combination. Merge the insns and
4140 update the status of registers and LOG_LINKS. */
4143 {
4148 /* If any of the notes in OTHER_INSN were REG_DEAD or REG_UNUSED,
4149 ensure that they are still valid. Then add any non-duplicate
4150 notes added by recog_for_combine. */
4152 {
4161 /* Simply drop equal note since it may be no longer valid
4162 for other_insn. It may be possible to record that CC
4163 register is changed and only discard those notes, but
4164 in practice it's unnecessary complication and doesn't
4165 give any meaningful improvement.
4167 See PR78559. */
4171 }
4175 NULL_RTX);
4176 }
4179 {
4182 rtx ni2dest;
4184 /* I3 now uses what used to be its destination and which is now
4185 I2's destination. This requires us to do a few adjustments. */
4189 /* We need a LOG_LINK from I3 to I2. But we used to have one,
4190 so we still will.
4192 However, some later insn might be using I2's dest and have
4193 a LOG_LINK pointing at I3. We must remove this link.
4194 The simplest way to remove the link is to point it at I1,
4195 which we know will be a NOTE. */
4197 /* newi2pat is usually a SET here; however, recog_for_combine might
4198 have added some clobbers. */
4201 else
4208 {
4211 {
4217 }
4218 }
4219 }
4221 {
4226 /* Compute which registers we expect to eliminate. newi2pat may be setting
4227 either i3dest or i2dest, so we must check it. */
4230 || !i2dest_killed
4232 /* For i1, we need to compute both local elimination and global
4233 elimination information with respect to newi2pat because i1dest
4234 may be the same as i3dest, in which case newi2pat may be setting
4235 i1dest. Global information is used when distributing REG_DEAD
4236 note for i2 and i3, in which case it does matter if newi2pat sets
4237 i1dest or not.
4239 Local information is used when distributing REG_DEAD note for i1,
4240 in which case it doesn't matter if newi2pat sets i1dest or not.
4241 See PR62151, if we have four insns combination:
4242 i0: r0 <- i0src
4243 i1: r1 <- i1src (using r0)
4244 REG_DEAD (r0)
4245 i2: r0 <- i2src (using r1)
4246 i3: r3 <- i3src (using r0)
4247 ix: using r0
4248 From i1's point of view, r0 is eliminated, no matter if it is set
4249 by newi2pat or not. In other words, REG_DEAD info for r0 in i1
4250 should be discarded.
4252 Note local information only affects cases in forms like "I1->I2->I3",
4253 "I0->I1->I2->I3" or "I0&I1->I2, I2->I3". For other cases like
4254 "I0->I1, I1&I2->I3" or "I1&I2->I3", newi2pat won't set i1dest or
4255 i0dest anyway. */
4257 || !i1dest_killed
4262 /* Same case as i1. */
4269 /* Get the old REG_NOTES and LOG_LINKS from all our insns and
4270 clear them. */
4278 /* Ensure that we do not have something that should not be shared but
4279 occurs multiple times in the new insns. Check this by first
4280 resetting all the `used' flags and then copying anything is shared. */
4304 {
4307 {
4309 {
4310 /* I2SRC must still be meaningful at this point. Some
4311 splitting operations can invalidate I2SRC, but those
4312 operations do not apply to calls. */
4316 }
4323 }
4324 }
4329 /* We had one special case above where I2 had more than one set and
4330 we replaced a destination of one of those sets with the destination
4331 of I3. In that case, we have to update LOG_LINKS of insns later
4332 in this basic block. Note that this (expensive) case is rare.
4334 Also, in this case, we must pretend that all REG_NOTEs for I2
4335 actually came from I3, so that REG_UNUSED notes from I2 will be
4336 properly handled. */
4339 {
4348 temp_insn
4358 {
4363 }
4364 else
4367 }
4375 {
4378 this_basic_block);
4381 }
4382 else
4383 {
4386 this_basic_block);
4388 }
4391 {
4396 this_basic_block);
4398 }
4401 {
4406 this_basic_block);
4408 }
4410 /* Get death notes for everything that is now used in either I3 or
4411 I2 and used to die in a previous insn. If we built two new
4412 patterns, move from I1 to I2 then I2 to I3 so that we get the
4413 proper movement on registers that I2 modifies. */
4419 else
4425 /* Distribute all the LOG_LINKS and REG_NOTES from I1, I2, and I3. */
4442 /* Distribute any notes added to I2 or I3 by recog_for_combine. We
4443 know these are REG_UNUSED and want them to go to the desired insn,
4444 so we always pass it as i3. */
4448 NULL_RTX);
4452 NULL_RTX);
4454 /* If I3DEST was used in I3SRC, it really died in I3. We may need to
4455 put a REG_DEAD note for it somewhere. If NEWI2PAT exists and sets
4456 I3DEST, the death must be somewhere before I2, not I3. If we passed I3
4457 in that case, it might delete I2. Similarly for I2 and I1.
4458 Show an additional death due to the REG_DEAD note we make here. If
4459 we discard it in distribute_notes, we will decrement it again. */
4462 {
4467 else
4470 }
4473 {
4478 else
4481 }
4484 {
4489 else
4492 }
4495 {
4500 else
4503 }
4511 {
4516 /* The insn that used to set this register doesn't exist, and
4517 this life of the register may not exist either. See if one of
4518 I3's links points to an insn that sets I2DEST. If it does,
4519 that is now the last known value for I2DEST. If we don't update
4520 this and I2 set the register to a value that depended on its old
4521 contents, we will get confused. If this insn is used, thing
4522 will be set correctly in combine_instructions. */
4530 /* If the reg formerly set in I2 died only once and that was in I3,
4531 zero its use count so it won't make `reload' do any work. */
4534 && ! i2dest_in_i2src
4537 }
4540 {
4553 && ! i1dest_in_i1src
4556 }
4559 {
4572 && ! i0dest_in_i0src
4575 }
4577 /* Update reg_stat[].nonzero_bits et al for any changes that may have
4578 been made to this insn. The order is important, because newi2pat
4579 can affect nonzero_bits of newpat. */
4583 }
4586 {
4588 {
4591 }
4593 }
4596 {
4598 {
4601 }
4603 }
4606 {
4608 {
4611 }
4613 }
4616 {
4618 {
4621 }
4623 }
4626 {
4628 {
4631 }
4633 }
4635 /* Set new_direct_jump_p if a new return or simple jump instruction
4636 has been created. Adjust the CFG accordingly. */
4638 {
4642 }
4647 {
4650 }
4654 {
4660 }
4665 {
4671 }
4673 /* A noop might also need cleaning up of CFG, if it comes from the
4674 simplification of a jump. */
4679 {
4682 }
4689 {
4692 }
4694 combine_successes++;
4701 else
4703 }
4704 \f
4705 /* Get a marker for undoing to the current state. */
4709 {
4711 }
4713 /* Undo the modifications up to the marker. */
4715 static void
4717 {
4721 {
4726 {
4741 }
4745 }
4748 }
4750 /* Undo all the modifications recorded in undobuf. */
4752 static void
4754 {
4756 }
4758 /* We've committed to accepting the changes we made. Move all
4759 of the undos to the free list. */
4761 static void
4763 {
4767 {
4771 }
4773 }
4774 \f
4775 /* Find the innermost point within the rtx at LOC, possibly LOC itself,
4776 where we have an arithmetic expression and return that point. LOC will
4777 be inside INSN.
4779 try_combine will call this function to see if an insn can be split into
4780 two insns. */
4784 {
4793 /* First special-case some codes. */
4795 {
4797 #ifdef INSN_SCHEDULING
4798 /* If we are making a paradoxical SUBREG invalid, it becomes a split
4799 point. */
4802 #endif
4806 /* If we have (mem (const ..)) or (mem (symbol_ref ...)), split it
4807 using LO_SUM and HIGH. */
4810 {
4818 }
4820 /* If we have a PLUS whose second operand is a constant and the
4821 address is not valid, perhaps will can split it up using
4822 the machine-specific way to split large constants. We use
4823 the first pseudo-reg (one of the virtual regs) as a placeholder;
4824 it will not remain in the result. */
4829 {
4832 subst_insn);
4834 /* This should have produced two insns, each of which sets our
4835 placeholder. If the source of the second is a valid address,
4836 we can make put both sources together and make a split point
4837 in the middle. */
4850 && memory_address_addr_space_p
4853 {
4857 /* Replace the placeholder in SRC2 with SRC1. If we can
4858 find where in SRC2 it was placed, that can become our
4859 split point and we can replace this address with SRC2.
4860 Just try two obvious places. */
4871 {
4874 }
4875 }
4877 /* If that didn't work, perhaps the first operand is complex and
4878 needs to be computed separately, so make a split point there.
4879 This will occur on machines that just support REG + CONST
4880 and have a constant moved through some previous computation. */
4886 }
4888 /* If we have a PLUS whose first operand is complex, try computing it
4889 separately by making a split there. */
4900 /* If SET_DEST is CC0 and SET_SRC is not an operand, a COMPARE, or a
4901 ZERO_EXTRACT, the most likely reason why this doesn't match is that
4902 we need to put the operand into a register. So split at that
4903 point. */
4913 /* See if we can split SET_SRC as it stands. */
4918 /* See if we can split SET_DEST as it stands. */
4923 /* See if this is a bitfield assignment with everything constant. If
4924 so, this is an IOR of an AND, so split it into that. */
4934 {
4940 unsigned HOST_WIDE_INT mask
4942 rtx or_mask;
4951 else
4952 {
4958 or_mask));
4959 }
4966 }
4968 /* Otherwise, see if this is an operation that we can split into two.
4969 If so, try to split that. */
4973 {
4975 /* If we are AND'ing with a large constant that is only a single
4976 bit and the result is only being used in a context where we
4977 need to know if it is zero or nonzero, replace it with a bit
4978 extraction. This will avoid the large constant, which might
4979 have taken more than one insn to make. If the constant were
4980 not a valid argument to the AND but took only one insn to make,
4981 this is no worse, but if it took more than one insn, it will
4982 be better. */
4992 {
4997 {
5000 }
5001 }
5005 /* If STORE_FLAG_VALUE is -1, this is (NE X 0) and only one bit of X
5006 is known to be on, this can be converted into a NEG of a shift. */
5012 {
5024 }
5030 /* We can't optimize if either mode is a partial integer
5031 mode as we don't know how many bits are significant
5032 in those modes. */
5046 {
5054 }
5059 }
5063 {
5066 /* For unsigned, we have a choice of a shift followed by an
5067 AND or two shifts. Use two shifts for field sizes where the
5068 constant might be too large. We assume here that we can
5069 always at least get 8-bit constants in an AND insn, which is
5070 true for every current RISC. */
5073 {
5074 unsigned HOST_WIDE_INT mask
5078 gen_rtx_LSHIFTRT
5086 }
5087 else
5088 {
5090 gen_rtx_fmt_ee
5101 }
5102 }
5104 /* See if this is a simple operation with a constant as the second
5105 operand. It might be that this constant is out of range and hence
5106 could be used as a split point. */
5114 /* Finally, see if this is a simple operation with its first operand
5115 not in a register. The operation might require this operand in a
5116 register, so return it as a split point. We can always do this
5117 because if the first operand were another operation, we would have
5118 already found it as a split point. */
5127 /* We write NOR as (and (not A) (not B)), but if we don't have a NOR,
5128 it is better to write this as (not (ior A B)) so we can split it.
5129 Similarly for IOR. */
5131 {
5139 }
5141 /* Many RISC machines have a large set of logical insns. If the
5142 second operand is a NOT, put it first so we will try to split the
5143 other operand first. */
5145 {
5149 }
5154 /* Canonicalization can produce (minus A (mult B C)), where C is a
5155 constant. It may be better to try splitting (plus (mult B -C) A)
5156 instead if this isn't a multiply by a power of two. */
5160 {
5168 mode)),
5171 }
5173 /* Split at a multiply-accumulate instruction. However if this is
5174 the SET_SRC, we likely do not have such an instruction and it's
5175 worthless to try this split. */
5184 }
5186 /* Otherwise, select our actions depending on our rtx class. */
5188 {
5194 /* fall through */
5202 /* fall through */
5204 /* Some machines have (and (shift ...) ...) insns. If X is not
5205 an AND, but XEXP (X, 0) is, use it as our split point. */
5215 /* Otherwise, we don't have a split point. */
5217 }
5218 }
5219 \f
5220 /* Throughout X, replace FROM with TO, and return the result.
5221 The result is TO if X is FROM;
5222 otherwise the result is X, but its contents may have been modified.
5223 If they were modified, a record was made in undobuf so that
5224 undo_all will (among other things) return X to its original state.
5226 If the number of changes necessary is too much to record to undo,
5227 the excess changes are not made, so the result is invalid.
5228 The changes already made can still be undone.
5229 undobuf.num_undo is incremented for such changes, so by testing that
5230 the caller can tell whether the result is valid.
5232 `n_occurrences' is incremented each time FROM is replaced.
5234 IN_DEST is nonzero if we are processing the SET_DEST of a SET.
5236 IN_COND is nonzero if we are at the top level of a condition.
5238 UNIQUE_COPY is nonzero if each substitution must be unique. We do this
5239 by copying if `n_occurrences' is nonzero. */
5241 static rtx
5243 {
5248 rtx new_rtx;
5250 /* Two expressions are equal if they are identical copies of a shared
5251 RTX or if they are both registers with the same register number
5252 and mode. */
5254 #define COMBINE_RTX_EQUAL_P(X,Y) \
5255 ((X) == (Y) \
5256 || (REG_P (X) && REG_P (Y) \
5257 && REGNO (X) == REGNO (Y) && GET_MODE (X) == GET_MODE (Y)))
5259 /* Do not substitute into clobbers of regs -- this will never result in
5260 valid RTL. */
5265 {
5266 n_occurrences++;
5268 }
5270 /* If X and FROM are the same register but different modes, they
5271 will not have been seen as equal above. However, the log links code
5272 will make a LOG_LINKS entry for that case. If we do nothing, we
5273 will try to rerecognize our original insn and, when it succeeds,
5274 we will delete the feeding insn, which is incorrect.
5276 So force this insn not to match in this (rare) case. */
5281 /* If this is an object, we are done unless it is a MEM or LO_SUM, both
5282 of which may contain things that can be combined. */
5286 /* It is possible to have a subexpression appear twice in the insn.
5287 Suppose that FROM is a register that appears within TO.
5288 Then, after that subexpression has been scanned once by `subst',
5289 the second time it is scanned, TO may be found. If we were
5290 to scan TO here, we would find FROM within it and create a
5291 self-referent rtl structure which is completely wrong. */
5295 /* Parallel asm_operands need special attention because all of the
5296 inputs are shared across the arms. Furthermore, unsharing the
5297 rtl results in recognition failures. Failure to handle this case
5298 specially can result in circular rtl.
5300 Solve this by doing a normal pass across the first entry of the
5301 parallel, and only processing the SET_DESTs of the subsequent
5302 entries. Ug. */
5307 {
5310 /* If this substitution failed, this whole thing fails. */
5318 {
5324 {
5327 /* If this substitution failed, this whole thing fails. */
5333 }
5334 }
5335 }
5336 else
5337 {
5341 /* We don't need to process a SET_DEST that is a register, CC0,
5342 or PC, so set up to skip this common case. All other cases
5343 where we want to suppress replacing something inside a
5344 SET_SRC are handled via the IN_DEST operand. */
5351 /* Trying to simplify the operands of a widening MULT is not likely
5352 to create RTL matching a machine insn. */
5364 /* Get the mode of operand 0 in case X is now a SIGN_EXTEND of a
5365 constant. */
5370 {
5372 {
5375 {
5377 {
5380 n_occurrences++;
5381 }
5382 else
5383 {
5385 unique_copy);
5387 /* If this substitution failed, this whole thing
5388 fails. */
5392 }
5395 }
5396 }
5398 {
5399 /* If this is a register being set, ignore it. */
5406 ;
5409 {
5410 /* In general, don't install a subreg involving two
5411 modes not tieable. It can worsen register
5412 allocation, and can even make invalid reload
5413 insns, since the reg inside may need to be copied
5414 from in the outside mode, and that may be invalid
5415 if it is an fp reg copied in integer mode.
5417 We allow two exceptions to this: It is valid if
5418 it is inside another SUBREG and the mode of that
5419 SUBREG and the mode of the inside of TO is
5420 tieable and it is valid if X is a SET that copies
5421 FROM to CC0. */
5429 && (!HAVE_cc0
5444 n_occurrences++;
5445 }
5446 else
5447 /* If we are in a SET_DEST, suppress most cases unless we
5448 have gone inside a MEM, in which case we want to
5449 simplify the address. We assume here that things that
5450 are actually part of the destination have their inner
5451 parts in the first expression. This is true for SUBREG,
5452 STRICT_LOW_PART, and ZERO_EXTRACT, which are the only
5453 things aside from REG and MEM that should appear in a
5454 SET_DEST. */
5456 (((in_dest
5462 unique_copy);
5464 /* If we found that we will have to reject this combination,
5465 indicate that by returning the CLOBBER ourselves, rather than
5466 an expression containing it. This will speed things up as
5467 well as prevent accidents where two CLOBBERs are considered
5468 to be equal, thus producing an incorrect simplification. */
5474 {
5482 }
5485 {
5489 }
5490 else
5492 }
5493 }
5494 }
5496 /* Check if we are loading something from the constant pool via float
5497 extension; in this case we would undo compress_float_constant
5498 optimization and degenerate constant load to an immediate value. */
5502 {
5506 }
5508 /* Try to simplify X. If the simplification changed the code, it is likely
5509 that further simplification will help, so loop, but limit the number
5510 of repetitions that will be performed. */
5513 {
5514 /* If X is sufficiently simple, don't bother trying to do anything
5515 with it. */
5524 /* We no longer know the original mode of operand 0 since we
5525 have changed the form of X) */
5527 }
5530 }
5531 \f
5532 /* If X is a commutative operation whose operands are not in the canonical
5533 order, use substitutions to swap them. */
5535 static void
5537 {
5540 {
5544 }
5545 }
5547 /* Simplify X, a piece of RTL. We just operate on the expression at the
5548 outer level; call `subst' to simplify recursively. Return the new
5549 expression.
5551 OP0_MODE is the original mode of XEXP (x, 0). IN_DEST is nonzero
5552 if we are inside a SET_DEST. IN_COND is nonzero if we are at the top level
5553 of a condition. */
5555 static rtx
5558 {
5561 rtx temp;
5564 /* If this is a commutative operation, put a constant last and a complex
5565 expression first. We don't need to do this for comparisons here. */
5568 /* Try to fold this expression in case we have constants that weren't
5569 present before. */
5572 {
5580 {
5583 {
5587 }
5590 }
5603 }
5606 {
5611 }
5613 /* If this is a simple operation applied to an IF_THEN_ELSE, try
5614 applying it to the arms of the IF_THEN_ELSE. This often simplifies
5615 things. Check for cases where both arms are testing the same
5616 condition.
5618 Don't do anything if all operands are very simple. */
5631 {
5636 /* If everything is a comparison, what we have is highly unlikely
5637 to be simpler, so don't use it. */
5640 {
5647 /* Simplify the alternative arms; this may collapse the true and
5648 false arms to store-flag values. Be careful to use copy_rtx
5649 here since true_rtx or false_rtx might share RTL with x as a
5650 result of the if_then_else_cond call above. */
5654 /* If true_rtx and false_rtx are not general_operands, an if_then_else
5655 is unlikely to be simpler. */
5658 {
5661 /* Restarting if we generate a store-flag expression will cause
5662 us to loop. Just drop through in this case. */
5664 /* If the result values are STORE_FLAG_VALUE and zero, we can
5665 just make the comparison operation. */
5676 /* Likewise, we can make the negate of a comparison operation
5677 if the result values are - STORE_FLAG_VALUE and zero. */
5685 mode);
5696 mode);
5697 else
5700 mode,
5701 VOIDmode,
5702 cond,
5703 cop1),
5708 }
5709 }
5710 }
5712 /* First see if we can apply the inverse distributive law. */
5715 {
5719 }
5721 /* If CODE is an associative operation not otherwise handled, see if we
5722 can associate some operands. This can win if they are constants or
5723 if they are logically related (i.e. (a & b) & a). */
5729 {
5731 {
5735 rtx inner;
5737 /* Make sure we pass the constant operand if any as the second
5738 one if this is a commutative operation. */
5746 /* For commutative operations, try the other pair if that one
5747 didn't simplify. */
5749 {
5754 }
5758 }
5759 }
5761 /* A little bit of algebraic simplification here. */
5763 {
5765 /* Ensure that our address has any ASHIFTs converted to MULT in case
5766 address-recognizing predicates are called later. */
5775 /* See if this can be moved to simplify_subreg. */
5778 /* Don't call gen_lowpart if the inner mode
5779 is VOIDmode and we cannot simplify it, as SUBREG without
5780 inner mode is invalid. */
5787 {
5788 rtx temp;
5794 /* If op is known to have all lower bits zero, the result is zero. */
5804 }
5806 /* Don't change the mode of the MEM if that would change the meaning
5807 of the address. */
5814 /* Note that we cannot do any narrowing for non-constants since
5815 we might have been counting on using the fact that some bits were
5816 zero. We now do this in the SET. */
5823 /* For C equal to the width of MODE minus 1, (neg (ashiftrt X C)) can be
5824 replaced by (lshiftrt X C). This will convert
5825 (neg (sign_extract X 1 Y)) to (zero_extract X 1 Y). */
5833 /* If X has only a single bit that might be nonzero, say, bit I, convert
5834 (neg X) to (ashiftrt (ashift X C-I) C-I) where C is the bitsize of
5835 MODE minus 1. This will convert (neg (zero_extract X 1 Y)) to
5836 (sign_extract X 1 Y). But only do this if TEMP isn't a register
5837 or a SUBREG of one since we'd be making the expression more
5838 complex if it was just a register. */
5844 {
5845 rtx temp1 = simplify_shift_const
5851 /* If all we did was surround TEMP with the two shifts, we
5852 haven't improved anything, so don't use it. Otherwise,
5853 we are better off with TEMP1. */
5858 }
5862 /* We can't handle truncation to a partial integer mode here
5863 because we don't know the real bitsize of the partial
5864 integer mode. */
5873 /* We can truncate a constant value and return it. */
5877 /* Similarly to what we do in simplify-rtx.c, a truncate of a register
5878 whose value is a comparison can be replaced with a subreg if
5879 STORE_FLAG_VALUE permits. */
5888 /* (const (const X)) can become (const X). Do it this way rather than
5889 returning the inner CONST since CONST can be shared with a
5890 REG_EQUAL note. */
5896 /* Convert (lo_sum (high FOO) FOO) to FOO. This is necessary so we
5897 can add in an offset. find_split_point will split this address up
5898 again if it doesn't match. */
5905 /* (plus (xor (and <foo> (const_int pow2 - 1)) <c>) <-c>)
5906 when c is (const_int (pow2 + 1) / 2) is a sign extension of a
5907 bit-field and can be replaced by either a sign_extend or a
5908 sign_extract. The `and' may be a zero_extend and the two
5909 <c>, -<c> constants may be reversed. */
5924 return simplify_shift_const
5931 /* If only the low-order bit of X is possibly nonzero, (plus x -1)
5932 can become (ashiftrt (ashift (xor x 1) C) C) where C is
5933 the bitsize of the mode - 1. This allows simplification of
5934 "a = (b & 8) == 0;" */
5946 /* If we are adding two things that have no bits in common, convert
5947 the addition into an IOR. This will often be further simplified,
5948 for example in cases like ((a & 1) + (a & 2)), which can
5949 become a & 3. */
5954 {
5955 /* Try to simplify the expression further. */
5959 /* If we could, great. If not, do not go ahead with the IOR
5960 replacement, since PLUS appears in many special purpose
5961 address arithmetic instructions. */
5969 }
5971 /* Canonicalize x + x into x << 1. */
5980 /* (minus <foo> (and <foo> (const_int -pow2))) becomes
5981 (and <foo> (const_int pow2-1)) */
5991 /* If we have (mult (plus A B) C), apply the distributive law and then
5992 the inverse distributive law to see if things simplify. This
5993 occurs mostly in addresses, often when unrolling loops. */
5996 {
6000 }
6002 /* Try simplify a*(b/c) as (a*b)/c. */
6005 {
6011 }
6015 /* If this is a divide by a power of two, treat it as a shift if
6016 its first operand is a shift. */
6034 /* If the first operand is a condition code, we can't do anything
6035 with it. */
6039 {
6047 /* Simplify our comparison, if possible. */
6050 /* If STORE_FLAG_VALUE is 1, we can convert (ne x 0) to simply X
6051 if only the low-order bit is possibly nonzero in X (such as when
6052 X is a ZERO_EXTRACT of one bit). Similarly, we can convert EQ to
6053 (xor X 1) or (minus 1 X); we use the former. Finally, if X is
6054 known to be either 0 or -1, NE becomes a NEG and EQ becomes
6055 (plus X 1).
6057 Remove any ZERO_EXTRACT we made when thinking this was a
6058 comparison. It may now be simpler to use, e.g., an AND. If a
6059 ZERO_EXTRACT is indeed appropriate, it will be placed back by
6060 the call to make_compound_operation in the SET case.
6062 Don't apply these optimizations if the caller would
6063 prefer a comparison rather than a value.
6064 E.g., for the condition in an IF_THEN_ELSE most targets need
6065 an explicit comparison. */
6068 ;
6084 {
6088 mode);
6089 }
6096 {
6100 const1_rtx);
6101 }
6109 {
6112 }
6114 /* If STORE_FLAG_VALUE is -1, we have cases similar to
6115 those above. */
6117 ;
6133 {
6137 mode);
6138 }
6146 {
6150 mode);
6151 }
6153 /* If X is 0/1, (eq X 0) is X-1. */
6159 {
6162 }
6164 /* If STORE_FLAG_VALUE says to just test the sign bit and X has just
6165 one bit that might be nonzero, we can convert (ne x 0) to
6166 (ashift x c) where C puts the bit in the sign bit. Remove any
6167 AND with STORE_FLAG_VALUE when we are done, since we are only
6168 going to test the sign bit. */
6175 {
6181 else
6183 }
6185 /* If the code changed, return a whole new comparison.
6186 We also need to avoid using SUBST in cases where
6187 simplify_comparison has widened a comparison with a CONST_INT,
6188 since in that case the wider CONST_INT may fail the sanity
6189 checks in do_SUBST. */
6196 /* Otherwise, keep this operation, but maybe change its operands.
6197 This also converts (ne (compare FOO BAR) 0) to (ne FOO BAR). */
6200 }
6210 /* If we are processing SET_DEST, we are done. */
6228 /* If this is a shift by a constant amount, simplify it. */
6236 (HOST_WIDE_INT_1U
6244 }
6247 }
6248 \f
6249 /* Simplify X, an IF_THEN_ELSE expression. Return the new expression. */
6251 static rtx
6253 {
6260 rtx temp;
6263 rtx reversed;
6265 /* Simplify storing of the truth value. */
6270 /* Also when the truth value has to be reversed. */
6276 /* Sometimes we can simplify the arm of an IF_THEN_ELSE if a register used
6277 in it is being compared against certain values. Get the true and false
6278 comparisons and see if that says anything about the value of each arm. */
6284 {
6285 HOST_WIDE_INT nzb;
6291 /* If FALSE_CODE is EQ, swap the codes and arms. */
6294 {
6297 }
6299 /* If we are comparing against zero and the expression being tested has
6300 only a single bit that might be nonzero, that is its value when it is
6301 not equal to zero. Similarly if it is known to be -1 or 0. */
6305 {
6308 }
6312 {
6315 }
6317 /* Now simplify an arm if we know the value of the register in the
6318 branch and it is used in the arm. Be careful due to the potential
6319 of locally-shared RTL. */
6336 }
6338 /* If we have (if_then_else FOO (pc) (label_ref BAR)) and FOO can be
6339 reversed, do so to avoid needing two sets of patterns for
6340 subtract-and-branch insns. Similarly if we have a constant in the true
6341 arm, the false arm is the same as the first operand of the comparison, or
6342 the false arm is more complicated than the true arm. */
6355 {
6364 /* It is possible that the conditional has been simplified out. */
6367 }
6369 /* If the two arms are identical, we don't need the comparison. */
6374 /* Convert a == b ? b : a to "a". */
6386 /* Look for cases where we have (abs x) or (neg (abs X)). */
6389 && comparison_p
6396 {
6402 return
6405 mode);
6408 }
6410 /* Look for MIN or MAX. */
6413 && comparison_p
6418 {
6433 }
6435 /* If we have (if_then_else COND (OP Z C1) Z) and OP is an identity when its
6436 second operand is zero, this can be done as (OP Z (mult COND C2)) where
6437 C2 = C1 * STORE_FLAG_VALUE. Similarly if OP has an outer ZERO_EXTEND or
6438 SIGN_EXTEND as long as Z is already extended (so we don't destroy it).
6439 We can do this kind of thing in some cases when STORE_FLAG_VALUE is
6440 neither 1 or -1, but it isn't worth checking for. */
6443 && comparison_p
6446 {
6462 /* If an identity-zero op is commutative, check whether there
6463 would be a match if we swapped the operands. */
6483 {
6487 }
6499 {
6503 }
6519 {
6523 }
6535 {
6539 }
6542 {
6548 const_true_rtx));
6556 }
6557 }
6559 /* If we have (if_then_else (ne A 0) C1 0) and either A is known to be 0 or
6560 1 and C1 is a single bit or A is known to be 0 or -1 and C1 is the
6561 negation of a single bit, we can convert this operation to a shift. We
6562 can actually do this more generally, but it doesn't seem worth it. */
6571 return
6575 /* (IF_THEN_ELSE (NE A 0) C1 0) is A or a zero-extend of A if the only
6576 non-zero bit in A is C1. */
6583 {
6590 }
6593 }
6594 \f
6595 /* Simplify X, a SET expression. Return the new expression. */
6597 static rtx
6599 {
6602 machine_mode mode
6607 /* (set (pc) (return)) gets written as (return). */
6611 /* Now that we know for sure which bits of SRC we are using, see if we can
6612 simplify the expression for the object knowing that we only need the
6613 low-order bits. */
6616 {
6619 }
6621 /* If we are setting CC0 or if the source is a COMPARE, look for the use of
6622 the comparison result and try to simplify it unless we already have used
6623 undobuf.other_insn. */
6631 {
6640 {
6643 {
6646 }
6647 }
6648 else
6656 {
6660 }
6661 else
6662 {
6667 /* Attempt to simplify CC user. */
6669 {
6673 }
6675 /* Convert X into a no-op move. */
6679 }
6681 /* Simplify our comparison, if possible. */
6684 #ifdef SELECT_CC_MODE
6685 /* If this machine has CC modes other than CCmode, check to see if we
6686 need to use a different CC mode here. */
6695 else
6698 /* If the mode changed, we have to change SET_DEST, the mode in the
6699 compare, and the mode in the place SET_DEST is used. If SET_DEST is
6700 a hard register, just build new versions with the proper mode. If it
6701 is a pseudo, we lose unless it is only time we set the pseudo, in
6702 which case we can safely change its mode. */
6704 {
6706 {
6708 rtx new_dest;
6712 else
6713 {
6716 }
6723 }
6724 }
6727 /* If the code changed, we have to build a new comparison in
6728 undobuf.other_insn. */
6730 {
6739 /* If the only change we made was to change an EQ into an NE or
6740 vice versa, OP0 has only one bit that might be nonzero, and OP1
6741 is zero, check if changing the user of the condition code will
6742 produce a valid insn. If it won't, we can keep the original code
6743 in that insn by surrounding our operation with an XOR. */
6750 {
6755 {
6762 }
6763 }
6764 }
6769 /* Don't generate a compare of a CC with 0, just use that CC. */
6771 {
6774 }
6775 /* Otherwise, if we didn't previously have the same COMPARE we
6776 want, create it from scratch. */
6779 {
6782 }
6783 }
6784 else
6785 {
6786 /* Get SET_SRC in a form where we have placed back any
6787 compound expressions. Then do the checks below. */
6790 }
6792 /* If we have (set x (subreg:m1 (op:m2 ...) 0)) with OP being some operation,
6793 and X being a REG or (subreg (reg)), we may be able to convert this to
6794 (set (subreg:m2 x) (op)).
6796 We can always do this if M1 is narrower than M2 because that means that
6797 we only care about the low bits of the result.
6799 However, on machines without WORD_REGISTER_OPERATIONS defined, we cannot
6800 perform a narrower operation than requested since the high-order bits will
6801 be undefined. On machine where it is defined, this transformation is safe
6802 as long as M1 and M2 have the same number of words. */
6810 && (WORD_REGISTER_OPERATIONS
6813 #ifdef CANNOT_CHANGE_MODE_CLASS
6818 #endif
6822 {
6825 dest));
6829 }
6831 /* If we have (set (cc0) (subreg ...)), we try to remove the subreg
6832 in SRC. */
6838 {
6842 /* Here we make sure that we don't have a sign bit on. */
6845 {
6848 }
6849 }
6851 /* If we have (set FOO (subreg:M (mem:N BAR) 0)) with M wider than N, this
6852 would require a paradoxical subreg. Replace the subreg with a
6853 zero_extend to avoid the reload that would otherwise be required. */
6859 {
6864 }
6866 /* If we don't have a conditional move, SET_SRC is an IF_THEN_ELSE, and we
6867 are comparing an item known to be 0 or -1 against 0, use a logical
6868 operation instead. Check for one of the arms being an IOR of the other
6869 arm with some value. We compute three terms to be IOR'ed together. In
6870 practice, at most two will be nonzero. Then we do the IOR's. */
6878 && (!HAVE_conditional_move
6884 {
6910 false_rtx);
6916 term3));
6919 }
6921 /* If either SRC or DEST is a CLOBBER of (const_int 0), make this
6922 whole thing fail. */
6927 else
6928 /* Convert this into a field assignment operation, if possible. */
6930 }
6931 \f
6932 /* Simplify, X, and AND, IOR, or XOR operation, and return the simplified
6933 result. */
6935 static rtx
6937 {
6943 {
6945 /* We can call simplify_and_const_int only if we don't lose
6946 any (sign) bits when converting INTVAL (op1) to
6947 "unsigned HOST_WIDE_INT". */
6951 {
6958 }
6960 /* If we have any of (and (ior A B) C) or (and (xor A B) C),
6961 apply the distributive law and then the inverse distributive
6962 law to see if things simplify. */
6964 {
6968 }
6970 {
6974 }
6978 /* If we have (ior (and A B) C), apply the distributive law and then
6979 the inverse distributive law to see if things simplify. */
6982 {
6986 }
6989 {
6993 }
6998 }
7001 }
7002 \f
7003 /* We consider ZERO_EXTRACT, SIGN_EXTRACT, and SIGN_EXTEND as "compound
7004 operations" because they can be replaced with two more basic operations.
7005 ZERO_EXTEND is also considered "compound" because it can be replaced with
7006 an AND operation, which is simpler, though only one operation.
7008 The function expand_compound_operation is called with an rtx expression
7009 and will convert it to the appropriate shifts and AND operations,
7010 simplifying at each stage.
7012 The function make_compound_operation is called to convert an expression
7013 consisting of shifts and ANDs into the equivalent compound expression.
7014 It is the inverse of this function, loosely speaking. */
7016 static rtx
7018 {
7022 rtx tem;
7025 {
7028 /* FALLTHRU */
7030 /* We can't necessarily use a const_int for a multiword mode;
7031 it depends on implicitly extending the value.
7032 Since we don't know the right way to extend it,
7033 we can't tell whether the implicit way is right.
7035 Even for a mode that is no wider than a const_int,
7036 we can't win, because we need to sign extend one of its bits through
7037 the rest of it, and we don't know which bit. */
7041 /* Return if (subreg:MODE FROM 0) is not a safe replacement for
7042 (zero_extend:MODE FROM) or (sign_extend:MODE FROM). It is for any MEM
7043 because (SUBREG (MEM...)) is guaranteed to cause the MEM to be
7044 reloaded. If not for that, MEM's would very rarely be safe.
7046 Reject MODEs bigger than a word, because we might not be able
7047 to reference a two-register group starting with an arbitrary register
7048 (and currently gen_lowpart might crash for a SUBREG). */
7053 /* Reject MODEs that aren't scalar integers because turning vector
7054 or complex modes into shifts causes problems. */
7060 /* If the inner object has VOIDmode (the only way this can happen
7061 is if it is an ASM_OPERANDS), we can't do anything since we don't
7062 know how much masking to do. */
7071 /* fall through */
7074 /* If the operand is a CLOBBER, just return it. */
7083 /* Reject MODEs that aren't scalar integers because turning vector
7084 or complex modes into shifts causes problems. */
7092 /* This should stay within the object being extracted, fail otherwise. */
7103 }
7104 /* Convert sign extension to zero extension, if we know that the high
7105 bit is not set, as this is easier to optimize. It will be converted
7106 back to cheaper alternative in make_extraction. */
7114 {
7119 /* Make sure this is a profitable operation. */
7126 else
7128 }
7130 /* We can optimize some special cases of ZERO_EXTEND. */
7132 {
7133 /* (zero_extend:DI (truncate:SI foo:DI)) is just foo:DI if we
7134 know that the last value didn't have any inappropriate bits
7135 set. */
7143 /* Likewise for (zero_extend:DI (subreg:SI foo:DI 0)). */
7152 /* (zero_extend:DI (truncate:SI foo:DI)) is just foo:DI when foo
7153 is a comparison and STORE_FLAG_VALUE permits. This is like
7154 the first case, but it works even when GET_MODE (x) is larger
7155 than HOST_WIDE_INT. */
7164 /* Likewise for (zero_extend:DI (subreg:SI foo:DI 0)). */
7174 }
7176 /* If we reach here, we want to return a pair of shifts. The inner
7177 shift is a left shift of BITSIZE - POS - LEN bits. The outer
7178 shift is a right shift of BITSIZE - LEN bits. It is arithmetic or
7179 logical depending on the value of UNSIGNEDP.
7181 If this was a ZERO_EXTEND or ZERO_EXTRACT, this pair of shifts will be
7182 converted into an AND of a shift.
7184 We must check for the case where the left shift would have a negative
7185 count. This can happen in a case like (x >> 31) & 255 on machines
7186 that can't shift by a constant. On those machines, we would first
7187 combine the shift with the AND to produce a variable-position
7188 extraction. Then the constant of 31 would be substituted in
7189 to produce such a position. */
7193 {
7202 }
7209 else
7210 /* Any other cases we can't handle. */
7213 /* If we couldn't do this for some reason, return the original
7214 expression. */
7219 }
7220 \f
7221 /* X is a SET which contains an assignment of one object into
7222 a part of another (such as a bit-field assignment, STRICT_LOW_PART,
7223 or certain SUBREGS). If possible, convert it into a series of
7224 logical operations.
7226 We half-heartedly support variable positions, but do not at all
7227 support variable lengths. */
7229 static const_rtx
7231 {
7232 rtx inner;
7236 machine_mode compute_mode;
7238 /* Loop until we find something we can't simplify. */
7240 {
7243 {
7247 }
7250 {
7255 /* A constant position should stay within the width of INNER. */
7261 {
7269 /* If position is ADJUST - X, new position is X. */
7271 else
7272 {
7277 pos);
7278 }
7279 }
7280 }
7282 /* A SUBREG between two modes that occupy the same numbers of words
7283 can be done by moving the SUBREG to the source. */
7285 /* We need SUBREGs to compute nonzero_bits properly. */
7286 && nonzero_sign_valid
7291 {
7293 gen_lowpart
7297 }
7298 else
7306 /* Don't attempt bitwise arithmetic on non scalar integer modes. */
7308 {
7309 machine_mode imode;
7311 /* Don't do anything for vector or complex integral types. */
7315 /* Try to find an integral mode to pun with. */
7322 }
7324 /* Compute a mask of LEN bits, if we can do this on the host machine. */
7328 /* Don't try to compute in too wide unsupported modes. */
7332 /* Now compute the equivalent expression. Make a copy of INNER
7333 for the SET_DEST in case it is a MEM into which we will substitute;
7334 we don't want shared RTL in that case. */
7336 compute_mode);
7340 compute_mode,
7342 compute_mode),
7343 inner);
7348 mask),
7349 pos);
7354 }
7357 }
7358 \f
7359 /* Return an RTX for a reference to LEN bits of INNER. If POS_RTX is nonzero,
7360 it is an RTX that represents the (variable) starting position; otherwise,
7361 POS is the (constant) starting bit position. Both are counted from the LSB.
7363 UNSIGNEDP is nonzero for an unsigned reference and zero for a signed one.
7365 IN_DEST is nonzero if this is a reference in the destination of a SET.
7366 This is used when a ZERO_ or SIGN_EXTRACT isn't needed. If nonzero,
7367 a STRICT_LOW_PART will be used, if zero, ZERO_EXTEND or SIGN_EXTEND will
7368 be used.
7370 IN_COMPARE is nonzero if we are in a COMPARE. This means that a
7371 ZERO_EXTRACT should be built even for bits starting at bit 0.
7373 MODE is the desired mode of the result (if IN_DEST == 0).
7375 The result is an RTX for the extraction or NULL_RTX if the target
7376 can't handle it. */
7378 static rtx
7382 {
7383 /* This mode describes the size of the storage area
7384 to fetch the overall value from. Within that, we
7385 ignore the POS lowest bits, etc. */
7387 machine_mode inner_mode;
7388 machine_mode wanted_inner_mode;
7395 HOST_WIDE_INT orig_pos;
7401 {
7402 /* If going from (subreg:SI (mem:QI ...)) to (mem:QI ...),
7403 consider just the QI as the memory to extract from.
7404 The subreg adds or removes high bits; its mode is
7405 irrelevant to the meaning of this extraction,
7406 since POS and LEN count from the lsb. */
7410 }
7415 {
7416 /* We're extracting the least significant bits of an rtx
7417 (ashift X (const_int C)), where LEN > C. Extract the
7418 least significant (LEN - C) bits of X, giving an rtx
7419 whose mode is MODE, then shift it left C times. */
7425 }
7431 /* See if this can be done without an extraction. We never can if the
7432 width of the field is not the same as that of some integer mode. For
7433 registers, we can only avoid the extraction if the position is at the
7434 low-order bit and this is either not in the destination or we have the
7435 appropriate STRICT_LOW_PART operation available.
7437 For MEM, we can avoid an extract if the field starts on an appropriate
7438 boundary and we can change the mode of the memory reference. */
7448 && (! in_dest
7452 && (pos
7455 /* We can't do this if we are widening INNER_MODE (it
7456 may not be aligned, for one thing). */
7462 {
7463 /* If INNER is a MEM, make a new MEM that encompasses just the desired
7464 field. If the original and current mode are the same, we need not
7465 adjust the offset. Otherwise, we do if bytes big endian.
7467 If INNER is not a MEM, get a piece consisting of just the field
7468 of interest (in this case POS % BITS_PER_WORD must be 0). */
7471 {
7472 HOST_WIDE_INT offset;
7474 /* POS counts from lsb, but make OFFSET count in memory order. */
7477 else
7481 }
7483 {
7485 {
7486 /* We can't call gen_lowpart in a DEST since we
7487 always want a SUBREG (see below) and it would sometimes
7488 return a new hard register. */
7490 {
7505 /* Avoid creating invalid subregs, for example when
7506 simplifying (x>>32)&255. */
7511 }
7512 else
7514 }
7515 else
7517 }
7518 else
7520 len >= HOST_BITS_PER_WIDE_INT
7521 ? HOST_WIDE_INT_M1U
7524 /* If this extraction is going into the destination of a SET,
7525 make a STRICT_LOW_PART unless we made a MEM. */
7540 /* If we know that no extraneous bits are set, and that the high
7541 bit is not set, convert the extraction to the cheaper of
7542 sign and zero extension, that are equivalent in these cases. */
7548 {
7552 /* Prefer ZERO_EXTENSION, since it gives more information to
7553 backends. */
7558 }
7560 /* Otherwise, sign- or zero-extend unless we already are in the
7561 proper mode. */
7565 }
7567 /* Unless this is a COMPARE or we have a funny memory reference,
7568 don't do anything with zero-extending field extracts starting at
7569 the low-order bit since they are simple AND operations. */
7574 /* Unless INNER is not MEM, reject this if we would be spanning bytes or
7575 if the position is not a constant and the length is not 1. In all
7576 other cases, we would only be going outside our object in cases when
7577 an original shift would have been undefined. */
7586 /* If INNER is not from memory, we want it to have the mode of a register
7587 extraction pattern's structure operand, or word_mode if there is no
7588 such pattern. The same applies to extraction_mode and pos_mode
7589 and their respective operands.
7591 For memory, assume that the desired extraction_mode and pos_mode
7592 are the same as for a register operation, since at present we don't
7593 have named patterns for aligned memory structures. */
7597 {
7601 }
7603 /* Never narrow an object, since that might not be safe. */
7611 else
7612 {
7613 /* Be careful not to go beyond the extracted object and maintain the
7614 natural alignment of the memory. */
7618 {
7621 }
7622 }
7627 {
7628 /* POS is passed as if BITS_BIG_ENDIAN == 0, so we need to convert it to
7629 BITS_BIG_ENDIAN style. If position is constant, compute new
7630 position. Otherwise, build subtraction.
7631 Note that POS is relative to the mode of the original argument.
7632 If it's a MEM we need to recompute POS relative to that.
7633 However, if we're extracting from (or inserting into) a register,
7634 we want to recompute POS relative to wanted_inner_mode. */
7641 else
7642 pos_rtx
7645 pos_rtx);
7646 /* POS may be less than 0 now, but we check for that below.
7647 Note that it can only be less than 0 if !MEM_P (inner). */
7648 }
7650 /* If INNER has a wider mode, and this is a constant extraction, try to
7651 make it smaller and adjust the byte to point to the byte containing
7652 the value. */
7655 && ! pos_rtx
7660 {
7663 /* The computations below will be correct if the machine is big
7664 endian in both bits and bytes or little endian in bits and bytes.
7665 If it is mixed, we must adjust. */
7667 /* If bytes are big endian and we had a paradoxical SUBREG, we must
7668 adjust OFFSET to compensate. */
7673 /* We can now move to the desired byte. */
7684 }
7686 /* If INNER is not memory, get it into the proper mode. If we are changing
7687 its mode, POS must be a constant and smaller than the size of the new
7688 mode. */
7690 {
7691 /* On the LHS, don't create paradoxical subregs implicitely truncating
7692 the register unless TRULY_NOOP_TRUNCATION. */
7695 wanted_inner_mode))
7707 pos_rtx
7709 ? HOST_WIDE_INT_M1U
7713 }
7715 /* Adjust mode of POS_RTX, if needed. If we want a wider mode, we
7716 have to zero extend. Otherwise, we can just use a SUBREG. */
7719 {
7723 /* If we know that no extraneous bits are set, and that the high
7724 bit is not set, convert extraction to cheaper one - either
7725 SIGN_EXTENSION or ZERO_EXTENSION, that are equivalent in these
7726 cases. */
7734 {
7738 /* Prefer ZERO_EXTENSION, since it gives more information to
7739 backends. */
7743 }
7745 }
7747 /* Make POS_RTX unless we already have it and it is correct. If we don't
7748 have a POS_RTX but we do have an ORIG_POS_RTX, the latter must
7749 be a CONST_INT. */
7756 /* Make the required operation. See if we can use existing rtx. */
7763 }
7764 \f
7765 /* See if X contains an ASHIFT of COUNT or more bits that can be commuted
7766 with any other operations in X. Return X without that shift if so. */
7768 static rtx
7770 {
7773 rtx tem;
7776 {
7778 /* This is the shift itself. If it is wide enough, we will return
7779 either the value being shifted if the shift count is equal to
7780 COUNT or a shift for the difference. */
7794 /* If we can safely shift this constant and we find the inner shift,
7795 make a new operation. */
7800 {
7804 }
7809 }
7812 }
7813 \f
7814 /* Subroutine of make_compound_operation. *X_PTR is the rtx at the current
7815 level of the expression and MODE is its mode. IN_CODE is as for
7816 make_compound_operation. *NEXT_CODE_PTR is the value of IN_CODE
7817 that should be used when recursing on operands of *X_PTR.
7819 There are two possible actions:
7821 - Return null. This tells the caller to recurse on *X_PTR with IN_CODE
7822 equal to *NEXT_CODE_PTR, after which *X_PTR holds the final value.
7824 - Return a new rtx, which the caller returns directly. */
7826 static rtx
7830 {
7838 rtx tem;
7842 {
7845 }
7847 /* Process depending on the code of this operation. If NEW is set
7848 nonzero, it will be returned. */
7851 {
7853 /* Convert shifts by constants into multiplications if inside
7854 an address. */
7858 {
7864 {
7867 }
7870 }
7879 {
7883 }
7886 {
7890 mode));
7892 }
7893 else
7894 {
7897 }
7907 {
7911 }
7914 {
7918 mode));
7920 }
7921 else
7922 {
7926 }
7929 /* If the second operand is not a constant, we can't do anything
7930 with it. */
7934 /* If the constant is a power of two minus one and the first operand
7935 is a logical right shift, make an extraction. */
7938 {
7942 }
7944 /* Same as previous, but for (subreg (lshiftrt ...)) in first op. */
7949 {
7958 {
7959 /* If we narrowed the mode when dropping the subreg, then
7960 we must zero-extend to keep the semantics of the AND. */
7962 ;
7966 else
7968 }
7970 /* If that didn't give anything, see if the AND simplifies on
7971 its own. */
7973 {
7977 }
7978 }
7979 /* Same as previous, but for (xor/ior (lshiftrt...) (lshiftrt...)). */
7985 {
7986 /* Apply the distributive law, and then try to make extractions. */
7993 }
7995 /* If we are have (and (rotate X C) M) and C is larger than the number
7996 of bits in M, this is an extraction. */
8002 {
8008 }
8010 /* On machines without logical shifts, if the operand of the AND is
8011 a logical shift and our mask turns off all the propagated sign
8012 bits, we can replace the logical shift with an arithmetic shift. */
8020 {
8027 make_compound_operation
8030 }
8032 /* If the constant is one less than a power of two, this might be
8033 representable by an extraction even if no shift is present.
8034 If it doesn't end up being a ZERO_EXTEND, we will ignore it unless
8035 we are in a COMPARE. */
8039 next_code),
8042 /* If we are in a comparison and this is an AND with a power of two,
8043 convert this into the appropriate bit extract. */
8049 next_code),
8052 /* If the one operand is a paradoxical subreg of a register or memory and
8053 the constant (limited to the smaller mode) has only zero bits where
8054 the sub expression has known zero bits, this can be expressed as
8055 a zero_extend. */
8057 {
8058 rtx sub;
8064 {
8068 /* original AND constant with all the known zero bits set */
8071 {
8076 }
8077 }
8078 }
8083 /* If the sign bit is known to be zero, replace this with an
8084 arithmetic shift. */
8089 {
8092 next_code),
8095 }
8097 /* fall through */
8103 /* If we have (ashiftrt (ashift foo C1) C2) with C2 >= C1,
8104 this is a SIGN_EXTRACT. */
8111 {
8118 }
8120 /* See if we have operations between an ASHIFTRT and an ASHIFT.
8121 If so, try to merge the shifts into a SIGN_EXTEND. We could
8122 also do this for some cases of SIGN_EXTRACT, but it doesn't
8123 seem worth the effort; the case checked for occurs on Alpha. */
8140 /* Call ourselves recursively on the inner expression. If we are
8141 narrowing the object and it has a different RTL code from
8142 what it originally did, do this SUBREG as a force_to_mode. */
8143 {
8147 /* If the SUBREG is masking of a logical right shift,
8148 make an extraction. */
8155 {
8164 }
8166 /* If in_code is COMPARE, it isn't always safe to pass it through
8167 to the recursive make_compound_operation call. */
8171 /* (subreg:SI (and:DI (reg:DI) (const_int 0x800000000)) 0)
8172 is (const_int 0), rather than
8173 (subreg:SI (lshiftrt:DI (reg:DI) (const_int 35)) 0).
8174 Similarly (subreg:QI (and:SI (reg:SI) (const_int 0x80)) 0)
8175 for non-equality comparisons against 0 is not equivalent
8176 to (subreg:QI (lshiftrt:SI (reg:SI) (const_int 7)) 0). */
8186 simplified
8194 {
8195 rtx newer
8198 /* If we have something other than a SUBREG, we might have
8199 done an expansion, so rerun ourselves. */
8203 /* force_to_mode can expand compounds. If it just re-expanded the
8204 compound, use gen_lowpart to convert to the desired mode. */
8206 /* Likewise if it re-expanded the compound only partially.
8207 This happens for SUBREG of ZERO_EXTRACT if they extract
8208 the same number of bits. */
8217 }
8221 }
8226 }
8232 }
8234 /* Look at the expression rooted at X. Look for expressions
8235 equivalent to ZERO_EXTRACT, SIGN_EXTRACT, ZERO_EXTEND, SIGN_EXTEND.
8236 Form these expressions.
8238 Return the new rtx, usually just X.
8240 Also, for machines like the VAX that don't have logical shift insns,
8241 try to convert logical to arithmetic shift operations in cases where
8242 they are equivalent. This undoes the canonicalizations to logical
8243 shifts done elsewhere.
8245 We try, as much as possible, to re-use rtl expressions to save memory.
8247 IN_CODE says what kind of expression we are processing. Normally, it is
8248 SET. In a memory address it is MEM. When processing the arguments of
8249 a comparison or a COMPARE against zero, it is COMPARE, or EQ if more
8250 precisely it is an equality comparison against zero. */
8252 rtx
8254 {
8261 /* Select the code to be used in recursive calls. Once we are inside an
8262 address, we stay there. If we have a comparison, set to COMPARE,
8263 but once inside, go back to our default of SET. */
8271 {
8277 }
8279 /* Now recursively process each operand of this operation. We need to
8280 handle ZERO_EXTEND specially so that we don't lose track of the
8281 inner mode. */
8283 {
8291 }
8296 {
8299 }
8302 {
8305 }
8309 }
8310 \f
8311 /* Given M see if it is a value that would select a field of bits
8312 within an item, but not the entire word. Return -1 if not.
8313 Otherwise, return the starting position of the field, where 0 is the
8314 low-order bit.
8316 *PLEN is set to the length of the field. */
8318 static int
8320 {
8321 /* Get the bit number of the first 1 bit from the right, -1 if none. */
8326 /* Now shift off the low-order zero bits and see if we have a
8327 power of two minus 1. */
8335 }
8336 \f
8337 /* If X refers to a register that equals REG in value, replace these
8338 references with REG. */
8339 static rtx
8341 {
8349 {
8382 /* FALLTHRU */
8386 {
8390 else
8392 }
8394 /* fall through */
8401 {
8404 {
8406 {
8409 }
8411 }
8412 }
8414 {
8417 {
8420 {
8422 {
8425 }
8427 }
8428 }
8429 }
8432 }
8435 }
8437 /* Return X converted to MODE. If the value is already truncated to
8438 MODE we can just return a subreg even though in the general case we
8439 would need an explicit truncation. */
8441 static rtx
8443 {
8448 {
8449 /* Bit-cast X into an integer mode. */
8454 }
8457 }
8459 /* See if X can be simplified knowing that we will only refer to it in
8460 MODE and will only refer to those bits that are nonzero in MASK.
8461 If other bits are being computed or if masking operations are done
8462 that select a superset of the bits in MASK, they can sometimes be
8463 ignored.
8465 Return a possibly simplified expression, but always convert X to
8466 MODE. If X is a CONST_INT, AND the CONST_INT with MASK.
8468 If JUST_SELECT is nonzero, don't optimize by noticing that bits in MASK
8469 are all off in X. This is used when X will be complemented, by either
8470 NOT, NEG, or XOR. */
8472 static rtx
8475 {
8478 machine_mode op_mode;
8482 /* If this is a CALL or ASM_OPERANDS, don't do anything. Some of the
8483 code below will do the wrong thing since the mode of such an
8484 expression is VOIDmode.
8486 Also do nothing if X is a CLOBBER; this can happen if X was
8487 the return value from a call to gen_lowpart. */
8491 /* We want to perform the operation in its present mode unless we know
8492 that the operation is valid in MODE, in which case we do the operation
8493 in MODE. */
8498 /* It is not valid to do a right-shift in a narrower mode
8499 than the one it came in with. */
8504 /* Truncate MASK to fit OP_MODE. */
8508 /* When we have an arithmetic operation, or a shift whose count we
8509 do not know, we need to assume that all bits up to the highest-order
8510 bit in MASK will be needed. This is how we form such a mask. */
8513 else
8517 /* Determine what bits of X are guaranteed to be (non)zero. */
8520 /* If none of the bits in X are needed, return a zero. */
8524 /* If X is a CONST_INT, return a new one. Do this here since the
8525 test below will fail. */
8527 {
8530 else
8531 {
8534 }
8535 }
8537 /* If X is narrower than MODE and we want all the bits in X's mode, just
8538 get X in the proper mode. */
8543 /* We can ignore the effect of a SUBREG if it narrows the mode or
8544 if the constant masks to zero all the bits the mode doesn't have. */
8554 /* The arithmetic simplifications here only work for scalar integer modes. */
8559 {
8561 /* If X is a (clobber (const_int)), return it since we know we are
8562 generating something that won't match. */
8575 /* Similarly for a truncate. */
8579 /* If this is an AND with a constant, convert it into an AND
8580 whose constant is the AND of that constant with MASK. If it
8581 remains an AND of MASK, delete it since it is redundant. */
8584 {
8588 /* If X is still an AND, see if it is an AND with a mask that
8589 is just some low-order bits. If so, and it is MASK, we don't
8590 need it. */
8597 /* If it remains an AND, try making another AND with the bits
8598 in the mode mask that aren't in MASK turned on. If the
8599 constant in the AND is wide enough, this might make a
8600 cheaper constant. */
8605 {
8606 unsigned HOST_WIDE_INT cval
8609 rtx y;
8616 }
8619 }
8624 /* In (and (plus FOO C1) M), if M is a mask that just turns off
8625 low-order bits (as in an alignment operation) and FOO is already
8626 aligned to that boundary, mask C1 to that boundary as well.
8627 This may eliminate that PLUS and, later, the AND. */
8629 {
8633 /* If MODE is narrower than HOST_WIDE_INT and mask is a negative
8634 number, sign extend it. */
8647 }
8649 /* fall through */
8652 /* Substituting into the operands of a widening MULT is not likely to
8653 create RTL matching a machine insn. */
8663 /* For PLUS, MINUS and MULT, we need any bits less significant than the
8664 most significant bit in MASK since carries from those bits will
8665 affect the bits we are interested in. */
8670 /* If X is (minus C Y) where C's least set bit is larger than any bit
8671 in the mask, then we may replace with (neg Y). */
8674 {
8678 }
8680 /* Similarly, if C contains every bit in the fuller_mask, then we may
8681 replace with (not Y). */
8684 {
8688 }
8695 /* If X is (ior (lshiftrt FOO C1) C2), try to commute the IOR and
8696 LSHIFTRT so we end up with an (and (lshiftrt (ior ...) ...) ...)
8697 operation which may be a bitfield extraction. Ensure that the
8698 constant we form is not wider than the mode of X. */
8710 {
8719 }
8721 binop:
8722 /* For most binary operations, just propagate into the operation and
8723 change the mode if we have an operation of that mode. */
8728 /* If we ended up truncating both operands, truncate the result of the
8729 operation instead. */
8732 {
8735 }
8745 /* For left shifts, do the same, but just for the first operand.
8746 However, we cannot do anything with shifts where we cannot
8747 guarantee that the counts are smaller than the size of the mode
8748 because such a count will have a different meaning in a
8749 wider mode. */
8759 /* If the shift count is a constant and we can do arithmetic in
8760 the mode of the shift, refine which bits we need. Otherwise, use the
8761 conservative form of the mask. */
8767 else
8779 /* Here we can only do something if the shift count is a constant,
8780 this shift constant is valid for the host, and we can do arithmetic
8781 in OP_MODE. */
8787 {
8791 /* Select the mask of the bits we need for the shift operand. */
8794 /* We can only change the mode of the shift if we can do arithmetic
8795 in the mode of the shift and INNER_MASK is no wider than the
8796 width of X's mode. */
8804 }
8806 /* If we have (and (lshiftrt FOO C1) C2) where the combination of the
8807 shift and AND produces only copies of the sign bit (C2 is one less
8808 than a power of two), we can do this with just a shift. */
8812 /* The shift puts one of the sign bit copies in the least significant
8813 bit. */
8818 /* Number of bits left after the shift must be more than the mask
8819 needs. */
8822 /* Must be more sign bit copies than the mask needs. */
8832 /* If we are just looking for the sign bit, we don't need this shift at
8833 all, even if it has a variable count. */
8837 /* If this is a shift by a constant, get a mask that contains those bits
8838 that are not copies of the sign bit. We then have two cases: If
8839 MASK only includes those bits, this can be a logical shift, which may
8840 allow simplifications. If MASK is a single-bit field not within
8841 those bits, we are requesting a copy of the sign bit and hence can
8842 shift the sign bit to the appropriate location. */
8846 {
8849 /* If the considered data is wider than HOST_WIDE_INT, we can't
8850 represent a mask for all its bits in a single scalar.
8851 But we only care about the lower bits, so calculate these. */
8854 {
8857 /* GET_MODE_PRECISION (GET_MODE (x)) - INTVAL (XEXP (x, 1))
8858 is the number of bits a full-width mask would have set.
8859 We need only shift if these are fewer than nonzero can
8860 hold. If not, we must keep all bits set in nonzero. */
8865 + HOST_BITS_PER_WIDE_INT
8867 }
8868 else
8869 {
8872 }
8875 {
8880 }
8883 {
8884 x = simplify_shift_const
8890 }
8891 }
8893 /* If MASK is 1, convert this to an LSHIFTRT. This can be done
8894 even if the shift count isn't a constant. */
8899 shiftrt:
8901 /* If this is a zero- or sign-extension operation that just affects bits
8902 we don't care about, remove it. Be sure the call above returned
8903 something that is still a shift. */
8913 next_select);
8919 /* If the shift count is constant and we can do computations
8920 in the mode of X, compute where the bits we care about are.
8921 Otherwise, we can't do anything. Don't change the mode of
8922 the shift or propagate MODE into the shift, though. */
8925 {
8935 }
8939 /* If we just want the low-order bit, the NEG isn't needed since it
8940 won't change the low-order bit. */
8944 /* We need any bits less significant than the most significant bit in
8945 MASK since carries from those bits will affect the bits we are
8946 interested in. */
8951 /* (not FOO) is (xor FOO CONST), so if FOO is an LSHIFTRT, we can do the
8952 same as the XOR case above. Ensure that the constant we form is not
8953 wider than the mode of X. */
8961 {
8970 }
8972 /* (and (not FOO) CONST) is (not (or FOO (not CONST))), so we must
8973 use the full mask inside the NOT. */
8976 unop:
8979 next_select));
8985 /* (and (ne FOO 0) CONST) can be (and FOO CONST) if CONST is included
8986 in STORE_FLAG_VALUE and FOO has a single bit that might be nonzero,
8987 which is equal to STORE_FLAG_VALUE. */
8999 /* We have no way of knowing if the IF_THEN_ELSE can itself be
9000 written in a narrower mode. We play it safe and do not do so. */
9016 }
9018 /* Ensure we return a value of the proper mode. */
9020 }
9021 \f
9022 /* Return nonzero if X is an expression that has one of two values depending on
9023 whether some other value is zero or nonzero. In that case, we return the
9024 value that is being tested, *PTRUE is set to the value if the rtx being
9025 returned has a nonzero value, and *PFALSE is set to the other alternative.
9027 If we return zero, we set *PTRUE and *PFALSE to X. */
9029 static rtx
9031 {
9037 /* If we are comparing a value against zero, we are done. */
9040 {
9044 }
9046 /* If this is a unary operation whose operand has one of two values, apply
9047 our opcode to compute those values. */
9050 {
9055 }
9057 /* If this is a COMPARE, do nothing, since the IF_THEN_ELSE we would
9058 make can't possibly match and would suppress other optimizations. */
9060 ;
9062 /* If this is a binary operation, see if either side has only one of two
9063 values. If either one does or if both do and they are conditional on
9064 the same value, compute the new true and false values. */
9066 {
9074 {
9075 /* Try to enable a simplification by undoing work done by
9076 if_then_else_cond if it converted a REG into something more
9077 complex. */
9079 {
9082 }
9083 else
9084 {
9087 }
9088 }
9092 {
9093 /* If if_then_else_cond returned zero, then true/false are the
9094 same rtl. We must copy one of them to prevent invalid rtl
9095 sharing. */
9102 {
9107 }
9108 else
9109 {
9112 }
9115 }
9117 /* See if we have PLUS, IOR, XOR, MINUS or UMAX, where one of the
9118 operands is zero when the other is nonzero, and vice-versa,
9119 and STORE_FLAG_VALUE is 1 or -1. */
9125 {
9142 {
9149 const_true_rtx);
9151 }
9152 }
9154 /* Similarly for MULT, AND and UMIN, except that for these the result
9155 is always zero. */
9159 {
9173 {
9176 }
9177 }
9178 }
9181 {
9182 /* If we have IF_THEN_ELSE already, extract the condition and
9183 canonicalize it if it is NE or EQ. */
9189 {
9192 }
9193 else
9195 }
9197 /* If X is a SUBREG, we can narrow both the true and false values
9198 if the inner expression, if there is a condition. */
9202 {
9208 {
9212 }
9213 }
9215 /* If X is a constant, this isn't special and will cause confusions
9216 if we treat it as such. Likewise if it is equivalent to a constant. */
9219 ;
9221 /* If we're in BImode, canonicalize on 0 and STORE_FLAG_VALUE, as that
9222 will be least confusing to the rest of the compiler. */
9224 {
9227 }
9229 /* If X is known to be either 0 or -1, those are the true and
9230 false values when testing X. */
9234 {
9237 }
9239 /* Likewise for 0 or a single bit. */
9242 {
9245 }
9247 /* Otherwise fail; show no condition with true and false values the same. */
9250 }
9251 \f
9252 /* Return the value of expression X given the fact that condition COND
9253 is known to be true when applied to REG as its first operand and VAL
9254 as its second. X is known to not be shared and so can be modified in
9255 place.
9257 We only handle the simplest cases, and specifically those cases that
9258 arise with IF_THEN_ELSE expressions. */
9260 static rtx
9262 {
9270 /* If either operand of the condition is a floating point value,
9271 then we have to avoid collapsing an EQ comparison. */
9281 /* If X is (abs REG) and we know something about REG's relationship
9282 with zero, we may be able to simplify this. */
9286 {
9295 }
9297 /* The only other cases we handle are MIN, MAX, and comparisons if the
9298 operands are the same as REG and VAL. */
9301 {
9303 {
9306 }
9309 {
9311 {
9319 else
9321 }
9324 {
9327 /* Do not reverse the condition when it is NE or EQ.
9328 This is because we cannot conclude anything about
9329 the value of 'SMAX (x, y)' when x is not equal to y,
9330 but we can when x equals y. */
9336 {
9347 }
9348 }
9349 }
9350 }
9352 {
9357 {
9358 /* We must simplify subreg here, before we lose track of the
9359 original inner_mode. */
9364 else
9366 }
9369 }
9370 /* We don't have to handle SIGN_EXTEND here, because even in the
9371 case of replacing something with a modeless CONST_INT, a
9372 CONST_INT is already (supposed to be) a valid sign extension for
9373 its narrower mode, which implies it's already properly
9374 sign-extended for the wider mode. Now, for ZERO_EXTEND, the
9375 story is different. */
9377 {
9382 {
9383 /* We must simplify the zero_extend here, before we lose
9384 track of the original inner_mode. */
9389 else
9391 }
9394 }
9398 {
9405 }
9408 }
9409 \f
9410 /* See if X and Y are equal for the purposes of seeing if we can rewrite an
9411 assignment as a field assignment. */
9413 static int
9415 {
9417 {
9422 /* For big endian, adjust the memory offset. */
9427 else
9429 }
9437 /* Check for a paradoxical SUBREG of a MEM compared with the MEM.
9438 Note that all SUBREGs of MEM are paradoxical; otherwise they
9439 would have been rewritten. */
9452 /* We used to see if get_last_value of X and Y were the same but that's
9453 not correct. In one direction, we'll cause the assignment to have
9454 the wrong destination and in the case, we'll import a register into this
9455 insn that might have already have been dead. So fail if none of the
9456 above cases are true. */
9458 }
9459 \f
9460 /* See if X, a SET operation, can be rewritten as a bit-field assignment.
9461 Return that assignment if so.
9463 We only handle the most common cases. */
9465 static rtx
9467 {
9470 rtx assign;
9472 HOST_WIDE_INT c1;
9473 HOST_WIDE_INT pos;
9475 rtx other;
9476 machine_mode mode;
9478 /* If SRC was (and (not (ashift (const_int 1) POS)) DEST), this is
9479 a clear of a one-bit field. We will have changed it to
9480 (and (rotate (const_int -2) POS) DEST), so check for that. Also check
9481 for a SUBREG. */
9487 {
9493 }
9503 {
9510 }
9512 /* If SRC is (ior (ashift (const_int 1) POS) DEST), this is a set of a
9513 one-bit field. */
9517 {
9523 }
9525 /* If DEST is already a field assignment, i.e. ZERO_EXTRACT, and the
9526 SRC is an AND with all bits of that field set, then we can discard
9527 the AND. */
9532 {
9539 else
9542 /* Complete overlap. We can remove the source AND. */
9546 /* Partial overlap. We can reduce the source AND. */
9548 {
9553 }
9554 }
9556 /* The other case we handle is assignments into a constant-position
9557 field. They look like (ior/xor (and DEST C1) OTHER). If C1 represents
9558 a mask that has all one bits except for a group of zero bits and
9559 OTHER is known to have zeros where C1 has ones, this is such an
9560 assignment. Compute the position and length from C1. Shift OTHER
9561 to the appropriate position, force it to the required mode, and
9562 make the extraction. Check for the AND in both operands. */
9564 /* One or more SUBREGs might obscure the constant-position field
9565 assignment. The first one we are likely to encounter is an outer
9566 narrowing SUBREG, which we can just strip for the purposes of
9567 identifying the constant-field assignment. */
9581 /* The second SUBREG that might get in the way is a paradoxical
9582 SUBREG around the first operand of the AND. We want to
9583 pretend the operand is as wide as the destination here. We
9584 do this by adjusting the MEM to wider mode for the sole
9585 purpose of the call to rtx_equal_for_field_assignment_p. Also
9586 note this trick only works for MEMs. */
9598 /* The second SUBREG that might get in the way is a paradoxical
9599 SUBREG around the first operand of the AND. We want to
9600 pretend the operand is as wide as the destination here. We
9601 do this by adjusting the MEM to wider mode for the sole
9602 purpose of the call to rtx_equal_for_field_assignment_p. Also
9603 note this trick only works for MEMs. */
9611 else
9624 /* The mode to use for the source is the mode of the assignment, or of
9625 what is inside a possible STRICT_LOW_PART. */
9629 /* Shift OTHER right POS places and make it the source, restricting it
9630 to the proper length and mode. */
9635 dest);
9638 ? HOST_WIDE_INT_M1U
9642 /* If SRC is masked by an AND that does not make a difference in
9643 the value being stored, strip it. */
9654 }
9655 \f
9656 /* See if X is of the form (+ (* a c) (* b c)) and convert to (* (+ a b) c)
9657 if so. */
9659 static rtx
9661 {
9665 rtx tem;
9667 /* Distributivity is not true for floating point as it can change the
9668 value. So we don't do it unless -funsafe-math-optimizations. */
9673 /* The outer operation can only be one of the following: */
9681 /* If either operand is a primitive we can't do anything, so get out
9682 fast. */
9692 /* See if the inner and outer operations distribute. */
9694 {
9699 /* These all distribute except over PLUS. */
9710 /* This is also a multiply, so it distributes over everything. */
9713 /* This used to handle SUBREG, but this turned out to be counter-
9714 productive, since (subreg (op ...)) usually is not handled by
9715 insn patterns, and this "optimization" therefore transformed
9716 recognizable patterns into unrecognizable ones. Therefore the
9717 SUBREG case was removed from here.
9719 It is possible that distributing SUBREG over arithmetic operations
9720 leads to an intermediate result than can then be optimized further,
9721 e.g. by moving the outer SUBREG to the other side of a SET as done
9722 in simplify_set. This seems to have been the original intent of
9723 handling SUBREGs here.
9725 However, with current GCC this does not appear to actually happen,
9726 at least on major platforms. If some case is found where removing
9727 the SUBREG case here prevents follow-on optimizations, distributing
9728 SUBREGs ought to be re-added at that place, e.g. in simplify_set. */
9732 }
9734 /* Set LHS and RHS to the inner operands (A and B in the example
9735 above) and set OTHER to the common operand (C in the example).
9736 There is only one way to do this unless the inner operation is
9737 commutative. */
9749 else
9752 /* Form the new inner operation, seeing if it simplifies first. */
9755 /* There is one exception to the general way of distributing:
9756 (a | c) ^ (b | c) -> (a ^ b) & ~c */
9758 {
9761 }
9763 /* We may be able to continuing distributing the result, so call
9764 ourselves recursively on the inner operation before forming the
9765 outer operation, which we return. */
9768 }
9770 /* See if X is of the form (* (+ A B) C), and if so convert to
9771 (+ (* A C) (* B C)) and try to simplify.
9773 Most of the time, this results in no change. However, if some of
9774 the operands are the same or inverses of each other, simplifications
9775 will result.
9777 For example, (and (ior A B) (not B)) can occur as the result of
9778 expanding a bit field assignment. When we apply the distributive
9779 law to this, we get (ior (and (A (not B))) (and (B (not B)))),
9780 which then simplifies to (and (A (not B))).
9782 Note that no checks happen on the validity of applying the inverse
9783 distributive law. This is pointless since we can do it in the
9784 few places where this routine is called.
9786 N is the index of the term that is decomposed (the arithmetic operation,
9787 i.e. (+ A B) in the first example above). !N is the index of the term that
9788 is distributed, i.e. of C in the first example above. */
9789 static rtx
9791 {
9792 machine_mode mode;
9796 /* Distributivity is not true for floating point as it can change the
9797 value. So we don't do it unless -funsafe-math-optimizations. */
9814 /* Special case (and (xor B C) (not A)), which is equivalent to
9815 (xor (ior A B) (ior A C)) */
9817 {
9820 }
9823 {
9824 /* Distribute the second term. */
9827 }
9828 else
9829 {
9830 /* Distribute the first term. */
9833 }
9843 }
9844 \f
9845 /* Simplify a logical `and' of VAROP with the constant CONSTOP, to be done
9846 in MODE. Return an equivalent form, if different from (and VAROP
9847 (const_int CONSTOP)). Otherwise, return NULL_RTX. */
9849 static rtx
9852 {
9855 rtx orig_varop;
9863 /* Simplify VAROP knowing that we will be only looking at some of the
9864 bits in it.
9866 Note by passing in CONSTOP, we guarantee that the bits not set in
9867 CONSTOP are not significant and will never be examined. We must
9868 ensure that is the case by explicitly masking out those bits
9869 before returning. */
9872 /* If VAROP is a CLOBBER, we will fail so return it. */
9876 /* If VAROP is a CONST_INT, then we need to apply the mask in CONSTOP
9877 to VAROP and return the new constant. */
9881 /* See what bits may be nonzero in VAROP. Unlike the general case of
9882 a call to nonzero_bits, here we don't care about bits outside
9883 MODE. */
9887 /* Turn off all bits in the constant that are known to already be zero.
9888 Thus, if the AND isn't needed at all, we will have CONSTOP == NONZERO_BITS
9889 which is tested below. */
9893 /* If we don't have any bits left, return zero. */
9897 /* If VAROP is a NEG of something known to be zero or 1 and CONSTOP is
9898 a power of two, we can replace this with an ASHIFT. */
9903 /* If VAROP is an IOR or XOR, apply the AND to both branches of the IOR
9904 or XOR, then try to apply the distributive law. This may eliminate
9905 operations if either branch can be simplified because of the AND.
9906 It may also make some cases more complex, but those cases probably
9907 won't match a pattern either with or without this. */
9910 return
9911 gen_lowpart
9913 apply_distributive_law
9918 constop),
9922 constop))));
9924 /* If VAROP is PLUS, and the constant is a mask of low bits, distribute
9925 the AND and see if one of the operands simplifies to zero. If so, we
9926 may eliminate it. */
9930 {
9939 }
9941 /* Make a SUBREG if necessary. If we can't make it, fail. */
9946 /* If we are only masking insignificant bits, return VAROP. */
9953 /* Otherwise, return an AND. */
9955 }
9958 /* We have X, a logical `and' of VAROP with the constant CONSTOP, to be done
9959 in MODE.
9961 Return an equivalent form, if different from X. Otherwise, return X. If
9962 X is zero, we are to always construct the equivalent form. */
9964 static rtx
9967 {
9978 }
9979 \f
9980 /* Given a REG, X, compute which bits in X can be nonzero.
9981 We don't care about bits outside of those defined in MODE.
9983 For most X this is simply GET_MODE_MASK (GET_MODE (MODE)), but if X is
9984 a shift, AND, or zero_extract, we can do better. */
9986 static rtx
9988 const_rtx known_x ATTRIBUTE_UNUSED,
9989 machine_mode known_mode ATTRIBUTE_UNUSED,
9992 {
9993 rtx tem;
9996 /* If X is a register whose nonzero bits value is current, use it.
9997 Otherwise, if X is a register whose value we can find, use that
9998 value. Otherwise, use the previously-computed global nonzero bits
9999 for this register. */
10013 && !REGNO_REG_SET_P
10016 {
10017 /* Note that, even if the precision of last_set_mode is lower than that
10018 of mode, record_value_for_reg invoked nonzero_bits on the register
10019 with nonzero_bits_mode (because last_set_mode is necessarily integral
10020 and HWI_COMPUTABLE_MODE_P in this case) so bits in nonzero_bits_mode
10021 are all valid, hence in mode too since nonzero_bits_mode is defined
10022 to the largest HWI_COMPUTABLE_MODE_P mode. */
10025 }
10029 {
10035 }
10038 {
10042 /* We don't know anything about the upper bits. */
10046 }
10049 }
10051 /* Return the number of bits at the high-order end of X that are known to
10052 be equal to the sign bit. X will be used in mode MODE; if MODE is
10053 VOIDmode, X will be used in its own mode. The returned value will always
10054 be between 1 and the number of bits in MODE. */
10056 static rtx
10058 const_rtx known_x ATTRIBUTE_UNUSED,
10059 machine_mode known_mode
10060 ATTRIBUTE_UNUSED,
10063 {
10064 rtx tem;
10077 && !REGNO_REG_SET_P
10080 {
10083 }
10094 }
10095 \f
10096 /* Return the number of "extended" bits there are in X, when interpreted
10097 as a quantity in MODE whose signedness is indicated by UNSIGNEDP. For
10098 unsigned quantities, this is the number of high-order zero bits.
10099 For signed quantities, this is the number of copies of the sign bit
10100 minus 1. In both case, this function returns the number of "spare"
10101 bits. For example, if two quantities for which this function returns
10102 at least 1 are added, the addition is known not to overflow.
10104 This function will always return 0 unless called during combine, which
10105 implies that it must be called from a define_split. */
10107 unsigned int
10109 {
10119 }
10121 /* This function is called from `simplify_shift_const' to merge two
10122 outer operations. Specifically, we have already found that we need
10123 to perform operation *POP0 with constant *PCONST0 at the outermost
10124 position. We would now like to also perform OP1 with constant CONST1
10125 (with *POP0 being done last).
10127 Return 1 if we can do the operation and update *POP0 and *PCONST0 with
10128 the resulting operation. *PCOMP_P is set to 1 if we would need to
10129 complement the innermost operand, otherwise it is unchanged.
10131 MODE is the mode in which the operation will be done. No bits outside
10132 the width of this mode matter. It is assumed that the width of this mode
10133 is smaller than or equal to HOST_BITS_PER_WIDE_INT.
10135 If *POP0 or OP1 are UNKNOWN, it means no operation is required. Only NEG, PLUS,
10136 IOR, XOR, and AND are supported. We may set *POP0 to SET if the proper
10137 result is simply *PCONST0.
10139 If the resulting operation cannot be expressed as one operation, we
10140 return 0 and do not change *POP0, *PCONST0, and *PCOMP_P. */
10142 static int
10143 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)
10144 {
10151 /* If OP0 is an AND, clear unimportant bits in CONST1. */
10155 /* If OP0 or OP1 is UNKNOWN, this is easy. Similarly if they are the same or
10156 if OP0 is SET. */
10165 {
10167 {
10185 }
10186 }
10188 /* Otherwise, if either is a PLUS or NEG, we can't do anything. */
10192 /* If the two constants aren't the same, we can't do anything. The
10193 remaining six cases can all be done. */
10197 else
10199 {
10202 /* (a & b) | b == b */
10205 /* (a ^ b) | b == a | b */
10206 {;}
10211 /* (a & b) ^ b == (~a) & b */
10214 /* (a | b) ^ b == a & ~b */
10220 /* (a | b) & b == b */
10223 /* (a ^ b) & b) == (~a) & b */
10228 }
10230 /* Check for NO-OP cases. */
10243 /* ??? Slightly redundant with the above mask, but not entirely.
10244 Moving this above means we'd have to sign-extend the mode mask
10245 for the final test. */
10250 }
10251 \f
10252 /* A helper to simplify_shift_const_1 to determine the mode we can perform
10253 the shift in. The original shift operation CODE is performed on OP in
10254 ORIG_MODE. Return the wider mode MODE if we can perform the operation
10255 in that mode. Return ORIG_MODE otherwise. We can also assume that the
10256 result of the shift is subject to operation OUTER_CODE with operand
10257 OUTER_CONST. */
10259 static machine_mode
10263 {
10268 /* In general we can't perform in wider mode for right shift and rotate. */
10270 {
10272 /* We can still widen if the bits brought in from the left are identical
10273 to the sign bit of ORIG_MODE. */
10281 /* Similarly here but with zero bits. */
10286 /* We can also widen if the bits brought in will be masked off. This
10287 operation is performed in ORIG_MODE. */
10289 {
10295 }
10296 /* fall through */
10306 }
10307 }
10309 /* Simplify a shift of VAROP by ORIG_COUNT bits. CODE says what kind
10310 of shift. The result of the shift is RESULT_MODE. Return NULL_RTX
10311 if we cannot simplify it. Otherwise, return a simplified value.
10313 The shift is normally computed in the widest mode we find in VAROP, as
10314 long as it isn't a different number of words than RESULT_MODE. Exceptions
10315 are ASHIFTRT and ROTATE, which are always done in their original mode. */
10317 static rtx
10320 {
10326 unsigned int mode_words
10328 /* We form (outer_op (code varop count) (outer_const)). */
10334 /* Make sure and truncate the "natural" shift on the way in. We don't
10335 want to do this inside the loop as it makes it more difficult to
10336 combine shifts. */
10340 /* If we were given an invalid count, don't do anything except exactly
10341 what was requested. */
10348 /* Unless one of the branches of the `if' in this loop does a `continue',
10349 we will `break' the loop after the `if'. */
10352 {
10353 /* If we have an operand of (clobber (const_int 0)), fail. */
10357 /* Convert ROTATERT to ROTATE. */
10359 {
10363 }
10369 /* Handle cases where the count is greater than the size of the mode
10370 minus 1. For ASHIFT, use the size minus one as the count (this can
10371 occur when simplifying (lshiftrt (ashiftrt ..))). For rotates,
10372 take the count modulo the size. For other shifts, the result is
10373 zero.
10375 Since these shifts are being produced by the compiler by combining
10376 multiple operations, each of which are defined, we know what the
10377 result is supposed to be. */
10380 {
10385 else
10386 {
10387 /* We can't simply return zero because there may be an
10388 outer op. */
10392 }
10393 }
10395 /* If we discovered we had to complement VAROP, leave. Making a NOT
10396 here would cause an infinite loop. */
10401 {
10402 /* An arithmetic right shift of a quantity known to be -1 or 0
10403 is a no-op. */
10407 {
10410 }
10412 /* If we are doing an arithmetic right shift and discarding all but
10413 the sign bit copies, this is equivalent to doing a shift by the
10414 bitsize minus one. Convert it into that shift because it will
10415 often allow other simplifications. */
10422 /* We simplify the tests below and elsewhere by converting
10423 ASHIFTRT to LSHIFTRT if we know the sign bit is clear.
10424 `make_compound_operation' will convert it to an ASHIFTRT for
10425 those machines (such as VAX) that don't have an LSHIFTRT. */
10430 shift_unit_mode)))
10442 }
10445 {
10452 {
10455 }
10459 /* The following rules apply only to scalars. */
10463 /* If we have (xshiftrt (mem ...) C) and C is MODE_WIDTH
10464 minus the width of a smaller mode, we can do this with a
10465 SIGN_EXTEND or ZERO_EXTEND from the narrower memory location. */
10472 {
10481 }
10485 /* The following rules apply only to scalars. */
10489 /* If VAROP is a SUBREG, strip it as long as the inner operand has
10490 the same number of words as what we've seen so far. Then store
10491 the widest mode in MODE. */
10497 == mode_words
10500 {
10505 }
10509 /* Some machines use MULT instead of ASHIFT because MULT
10510 is cheaper. But it is still better on those machines to
10511 merge two shifts into one. */
10514 {
10515 varop
10521 }
10525 /* Similar, for when divides are cheaper. */
10528 {
10529 varop
10535 }
10539 /* If we are extracting just the sign bit of an arithmetic
10540 right shift, that shift is not needed. However, the sign
10541 bit of a wider mode may be different from what would be
10542 interpreted as the sign bit in a narrower mode, so, if
10543 the result is narrower, don't discard the shift. */
10548 {
10551 }
10553 /* fall through */
10558 /* The following rules apply only to scalars. */
10562 /* Here we have two nested shifts. The result is usually the
10563 AND of a new shift with a mask. We compute the result below. */
10569 {
10573 rtx mask_rtx;
10575 /* We have one common special case. We can't do any merging if
10576 the inner code is an ASHIFTRT of a smaller mode. However, if
10577 we have (ashift:M1 (subreg:M1 (ashiftrt:M2 FOO C1) 0) C2)
10578 with C2 == GET_MODE_BITSIZE (M1) - GET_MODE_BITSIZE (M2),
10579 we can convert it to
10580 (ashiftrt:M1 (ashift:M1 (and:M1 (subreg:M1 FOO 0) C3) C2) C1).
10581 This simplifies certain SIGN_EXTEND operations. */
10585 {
10586 /* C3 has the low-order C1 bits zero. */
10598 }
10600 /* If this was (ashiftrt (ashift foo C1) C2) and FOO has more
10601 than C1 high-order bits equal to the sign bit, we can convert
10602 this to either an ASHIFT or an ASHIFTRT depending on the
10603 two counts.
10605 We cannot do this if VAROP's mode is not SHIFT_MODE. */
10611 {
10615 {
10618 }
10621 }
10623 /* There are some cases we can't do. If CODE is ASHIFTRT,
10624 we can only do this if FIRST_CODE is also ASHIFTRT.
10626 We can't do the case when CODE is ROTATE and FIRST_CODE is
10627 ASHIFTRT.
10629 If the mode of this shift is not the mode of the outer shift,
10630 we can't do this if either shift is a right shift or ROTATE.
10632 Finally, we can't do any of these if the mode is too wide
10633 unless the codes are the same.
10635 Handle the case where the shift codes are the same
10636 first. */
10639 {
10648 }
10659 /* To compute the mask to apply after the shift, shift the
10660 nonzero bits of the inner shift the same way the
10661 outer shift will. */
10664 result_mode);
10666 mask_rtx
10670 /* Give up if we can't compute an outer operation to use. */
10678 /* If the shifts are in the same direction, we add the
10679 counts. Otherwise, we subtract them. */
10683 else
10686 /* If COUNT is positive, the new shift is usually CODE,
10687 except for the two exceptions below, in which case it is
10688 FIRST_CODE. If the count is negative, FIRST_CODE should
10689 always be used */
10699 }
10701 /* If we have (A << B << C) for any shift, we can convert this to
10702 (A << C << B). This wins if A is a constant. Only try this if
10703 B is not a constant. */
10708 {
10709 /* For ((unsigned) (cstULL >> count)) >> cst2 we have to make
10710 sure the result will be masked. See PR70222. */
10718 /* For ((int) (cstLL >> count)) >> cst2 just give up. Queuing
10719 up outer sign extension (often left and right shift) is
10720 hardly more efficient than the original. See PR70429. */
10730 }
10734 /* The following rules apply only to scalars. */
10738 /* Make this fit the case below. */
10745 /* The following rules apply only to scalars. */
10749 /* If we have (xshiftrt (ior (plus X (const_int -1)) X) C)
10750 with C the size of VAROP - 1 and the shift is logical if
10751 STORE_FLAG_VALUE is 1 and arithmetic if STORE_FLAG_VALUE is -1,
10752 we have an (le X 0) operation. If we have an arithmetic shift
10753 and STORE_FLAG_VALUE is 1 or we have a logical shift with
10754 STORE_FLAG_VALUE of -1, we have a (neg (le X 0)) operation. */
10762 {
10765 const0_rtx);
10771 }
10773 /* If we have (shift (logical)), move the logical to the outside
10774 to allow it to possibly combine with another logical and the
10775 shift to combine with another shift. This also canonicalizes to
10776 what a ZERO_EXTRACT looks like. Also, some machines have
10777 (and (shift)) insns. */
10780 /* We can't do this if we have (ashiftrt (xor)) and the
10781 constant has its sign bit set in shift_mode with shift_mode
10782 wider than result_mode. */
10786 shift_mode))
10794 {
10797 }
10799 /* If we can't do that, try to simplify the shift in each arm of the
10800 logical expression, make a new logical expression, and apply
10801 the inverse distributive law. This also can't be done for
10802 (ashiftrt (xor)) where we've widened the shift and the constant
10803 changes the sign bit. */
10808 shift_mode)))
10809 {
10821 }
10825 /* The following rules apply only to scalars. */
10829 /* Convert (lshiftrt (eq FOO 0) C) to (xor FOO 1) if STORE_FLAG_VALUE
10830 says that the sign bit can be tested, FOO has mode MODE, C is
10831 GET_MODE_PRECISION (MODE) - 1, and FOO has only its low-order bit
10832 that may be nonzero. */
10842 {
10846 }
10850 /* The following rules apply only to scalars. */
10854 /* (lshiftrt (neg A) C) where A is either 0 or 1 and C is one less
10855 than the number of bits in the mode is equivalent to A. */
10859 {
10863 }
10865 /* NEG commutes with ASHIFT since it is multiplication. Move the
10866 NEG outside to allow shifts to combine. */
10870 {
10873 }
10877 /* The following rules apply only to scalars. */
10881 /* (lshiftrt (plus A -1) C) where A is either 0 or 1 and C
10882 is one less than the number of bits in the mode is
10883 equivalent to (xor A 1). */
10890 {
10894 }
10896 /* If we have (xshiftrt (plus FOO BAR) C), and the only bits
10897 that might be nonzero in BAR are those being shifted out and those
10898 bits are known zero in FOO, we can replace the PLUS with FOO.
10899 Similarly in the other operand order. This code occurs when
10900 we are computing the size of a variable-size array. */
10907 {
10910 }
10918 result_mode)))
10919 {
10922 }
10924 /* (ashift (plus foo C) N) is (plus (ashift foo N) C'). */
10934 {
10937 }
10939 /* Check for 'PLUS signbit', which is the canonical form of 'XOR
10940 signbit', and attempt to change the PLUS to an XOR and move it to
10941 the outer operation as is done above in the AND/IOR/XOR case
10942 leg for shift(logical). See details in logical handling above
10943 for reasoning in doing so. */
10954 {
10957 }
10962 /* The following rules apply only to scalars. */
10966 /* If we have (xshiftrt (minus (ashiftrt X C)) X) C)
10967 with C the size of VAROP - 1 and the shift is logical if
10968 STORE_FLAG_VALUE is 1 and arithmetic if STORE_FLAG_VALUE is -1,
10969 we have a (gt X 0) operation. If the shift is arithmetic with
10970 STORE_FLAG_VALUE of 1 or logical with STORE_FLAG_VALUE == -1,
10971 we have a (neg (gt X 0)) operation. */
10980 {
10983 const0_rtx);
10989 }
10993 /* Change (lshiftrt (truncate (lshiftrt))) to (truncate (lshiftrt))
10994 if the truncate does not affect the value. */
11001 {
11004 varop_inner
11007 GEN_INT
11012 }
11017 }
11020 }
11025 /* We have now finished analyzing the shift. The result should be
11026 a shift of type CODE with SHIFT_MODE shifting VAROP COUNT places. If
11027 OUTER_OP is non-UNKNOWN, it is an operation that needs to be applied
11028 to the result of the shift. OUTER_CONST is the relevant constant,
11029 but we must turn off all bits turned off in the shift. */
11037 /* Make a SUBREG if necessary. If we can't make it, fail. */
11042 /* If we have an outer operation and we just made a shift, it is
11043 possible that we could have simplified the shift were it not
11044 for the outer operation. So try to do the simplification
11045 recursively. */
11049 else
11055 /* If we were doing an LSHIFTRT in a wider mode than it was originally,
11056 turn off all the bits that the shift would have turned off. */
11061 /* Do the remainder of the processing in RESULT_MODE. */
11064 /* If COMPLEMENT_P is set, we have to complement X before doing the outer
11065 operation. */
11070 {
11078 {
11079 /* This means that we have determined that the result is
11080 equivalent to a constant. This should be rare. */
11083 }
11086 else
11089 }
11092 }
11094 /* Simplify a shift of VAROP by COUNT bits. CODE says what kind of shift.
11095 The result of the shift is RESULT_MODE. If we cannot simplify it,
11096 return X or, if it is NULL, synthesize the expression with
11097 simplify_gen_binary. Otherwise, return a simplified value.
11099 The shift is normally computed in the widest mode we find in VAROP, as
11100 long as it isn't a different number of words than RESULT_MODE. Exceptions
11101 are ASHIFTRT and ROTATE, which are always done in their original mode. */
11103 static rtx
11106 {
11116 }
11118 \f
11119 /* A subroutine of recog_for_combine. See there for arguments and
11120 return value. */
11122 static int
11124 {
11126 rtx pat_without_clobbers;
11134 /* If PAT is a PARALLEL, check to see if it contains the CLOBBER
11135 we use to indicate that something didn't match. If we find such a
11136 thing, force rejection. */
11150 {
11153 else
11156 }
11158 /* If it isn't, there is the possibility that we previously had an insn
11159 that clobbered some register as a side effect, but the combined
11160 insn doesn't need to do that. So try once more without the clobbers
11161 unless this represents an ASM insn. */
11165 {
11170 {
11173 pos++;
11174 }
11184 {
11187 else
11190 }
11191 }
11198 /* Recognize all noop sets, these will be killed by followup pass. */
11202 /* If we had any clobbers to add, make a new pattern than contains
11203 them. Then check to make sure that all of them are dead. */
11205 {
11215 else
11222 {
11227 {
11231 }
11232 }
11234 }
11238 {
11246 /* Allow targets to reject combined insn. */
11248 {
11251 dump_file);
11253 /* Callers expect recog_for_combine to strip
11254 clobbers from the pattern on failure. */
11259 }
11264 }
11270 }
11272 /* Change every ZERO_EXTRACT and ZERO_EXTEND of a SUBREG that can be
11273 expressed as an AND and maybe an LSHIFTRT, to that formulation.
11274 Return whether anything was so changed. */
11276 static bool
11278 {
11284 {
11295 {
11306 else
11310 }
11317 {
11322 }
11328 {
11331 }
11332 else
11338 {
11341 }
11345 }
11356 {
11371 else
11379 }
11382 }
11384 /* Like recog, but we receive the address of a pointer to a new pattern.
11385 We try to match the rtx that the pointer points to.
11386 If that fails, we may try to modify or replace the pattern,
11387 storing the replacement into the same pointer object.
11389 Modifications include deletion or addition of CLOBBERs. If the
11390 instruction will still not match, we change ZERO_EXTEND and ZERO_EXTRACT
11391 to the equivalent AND and perhaps LSHIFTRT patterns, and try with that
11392 (and undo if that fails).
11394 PNOTES is a pointer to a location where any REG_UNUSED notes added for
11395 the CLOBBERs are placed.
11397 The value is the final insn code from the pattern ultimately matched,
11398 or -1. */
11400 static int
11402 {
11414 {
11417 {
11421 }
11422 }
11425 {
11430 }
11433 }
11434 \f
11435 /* Like gen_lowpart_general but for use by combine. In combine it
11436 is not possible to create any new pseudoregs. However, it is
11437 safe to create invalid memory addresses, because combine will
11438 try to recognize them and all they will do is make the combine
11439 attempt fail.
11441 If for some reason this cannot do its job, an rtx
11442 (clobber (const_int 0)) is returned.
11443 An insn containing that will not be recognized. */
11445 static rtx
11447 {
11451 rtx result;
11456 /* We can only support MODE being wider than a word if X is a
11457 constant integer or has a mode the same size. */
11462 /* X might be a paradoxical (subreg (mem)). In that case, gen_lowpart
11463 won't know what to do. So we will strip off the SUBREG here and
11464 process normally. */
11466 {
11469 /* For use in case we fall down into the address adjustments
11470 further below, we need to adjust the known mode and size of
11471 x; imode and isize, since we just adjusted x. */
11478 }
11486 {
11489 /* Refuse to work on a volatile memory ref or one with a mode-dependent
11490 address. */
11495 /* If we want to refer to something bigger than the original memref,
11496 generate a paradoxical subreg instead. That will force a reload
11497 of the original memref X. */
11504 /* Adjust the address so that the address-after-the-data is
11505 unchanged. */
11510 }
11512 /* If X is a comparison operator, rewrite it in a new mode. This
11513 probably won't match, but may allow further simplifications. */
11517 /* If we couldn't simplify X any other way, just enclose it in a
11518 SUBREG. Normally, this SUBREG won't match, but some patterns may
11519 include an explicit SUBREG or we may simplify it further in combine. */
11520 else
11521 {
11522 rtx res;
11525 {
11530 }
11534 }
11536 fail:
11538 }
11539 \f
11540 /* Try to simplify a comparison between OP0 and a constant OP1,
11541 where CODE is the comparison code that will be tested, into a
11542 (CODE OP0 const0_rtx) form.
11544 The result is a possibly different comparison code to use.
11545 *POP1 may be updated. */
11547 static enum rtx_code
11550 {
11554 /* Get the constant we are comparing against and turn off all bits
11555 not on in our mode. */
11559 /* If we are comparing against a constant power of two and the value
11560 being compared can only have that single bit nonzero (e.g., it was
11561 `and'ed with that bit), we can replace this with a comparison
11562 with zero. */
11570 {
11573 }
11575 /* Similarly, if we are comparing a value known to be either -1 or
11576 0 with -1, change it to the opposite comparison against zero. */
11581 {
11584 }
11586 /* Do some canonicalizations based on the comparison code. We prefer
11587 comparisons against zero and then prefer equality comparisons.
11588 If we can reduce the size of a constant, we will do that too. */
11590 {
11592 /* < C is equivalent to <= (C - 1) */
11594 {
11597 /* ... fall through to LE case below. */
11599 }
11600 else
11604 /* <= C is equivalent to < (C + 1); we do this for C < 0 */
11606 {
11609 }
11611 /* If we are doing a <= 0 comparison on a value known to have
11612 a zero sign bit, we can replace this with == 0. */
11622 /* >= C is equivalent to > (C - 1). */
11624 {
11627 /* ... fall through to GT below. */
11629 }
11630 else
11634 /* > C is equivalent to >= (C + 1); we do this for C < 0. */
11636 {
11639 }
11641 /* If we are doing a > 0 comparison on a value known to have
11642 a zero sign bit, we can replace this with != 0. */
11652 /* < C is equivalent to <= (C - 1). */
11654 {
11657 /* ... fall through ... */
11658 }
11659 /* (unsigned) < 0x80000000 is equivalent to >= 0. */
11663 {
11667 }
11668 else
11672 /* unsigned <= 0 is equivalent to == 0 */
11675 /* (unsigned) <= 0x7fffffff is equivalent to >= 0. */
11679 {
11682 }
11686 /* >= C is equivalent to > (C - 1). */
11688 {
11691 /* ... fall through ... */
11692 }
11694 /* (unsigned) >= 0x80000000 is equivalent to < 0. */
11698 {
11702 }
11703 else
11707 /* unsigned > 0 is equivalent to != 0 */
11710 /* (unsigned) > 0x7fffffff is equivalent to < 0. */
11714 {
11717 }
11722 }
11726 }
11727 \f
11728 /* Simplify a comparison between *POP0 and *POP1 where CODE is the
11729 comparison code that will be tested.
11731 The result is a possibly different comparison code to use. *POP0 and
11732 *POP1 may be updated.
11734 It is possible that we might detect that a comparison is either always
11735 true or always false. However, we do not perform general constant
11736 folding in combine, so this knowledge isn't useful. Such tautologies
11737 should have been detected earlier. Hence we ignore all such cases. */
11739 static enum rtx_code
11741 {
11748 /* Try a few ways of applying the same transformation to both operands. */
11750 {
11751 /* The test below this one won't handle SIGN_EXTENDs on these machines,
11752 so check specially. */
11768 - (GET_MODE_PRECISION
11770 {
11773 }
11775 /* If both operands are the same constant shift, see if we can ignore the
11776 shift. We can if the shift is a rotate or if the bits shifted out of
11777 this shift are known to be zero for both inputs and if the type of
11778 comparison is compatible with the shift. */
11791 {
11804 else
11806 }
11808 /* If both operands are AND's of a paradoxical SUBREG by constant, the
11809 SUBREGs are of the same mode, and, in both cases, the AND would
11810 be redundant if the comparison was done in the narrower mode,
11811 do the comparison in the narrower mode (e.g., we are AND'ing with 1
11812 and the operand's possibly nonzero bits are 0xffffff01; in that case
11813 if we only care about QImode, we don't need the AND). This case
11814 occurs if the output mode of an scc insn is not SImode and
11815 STORE_FLAG_VALUE == 1 (e.g., the 386).
11817 Similarly, check for a case where the AND's are ZERO_EXTEND
11818 operations from some narrower mode even though a SUBREG is not
11819 present. */
11824 {
11841 {
11845 /* The resulting comparison is always unsigned since we masked
11846 off the original sign bit. */
11850 }
11857 {
11863 }
11867 }
11869 /* If both operands are NOT, we can strip off the outer operation
11870 and adjust the comparison code for swapped operands; similarly for
11871 NEG, except that this must be an equality comparison. */
11877 else
11879 }
11881 /* If the first operand is a constant, swap the operands and adjust the
11882 comparison code appropriately, but don't do this if the second operand
11883 is already a constant integer. */
11885 {
11888 }
11890 /* We now enter a loop during which we will try to simplify the comparison.
11891 For the most part, we only are concerned with comparisons with zero,
11892 but some things may really be comparisons with zero but not start
11893 out looking that way. */
11896 {
11903 HOST_WIDE_INT const_op;
11905 /* We only want to handle integral modes. This catches VOIDmode,
11906 CCmode, and the floating-point modes. An exception is that we
11907 can handle VOIDmode if OP0 is a COMPARE or a comparison
11908 operation. */
11915 /* Try to simplify the compare to constant, possibly changing the
11916 comparison op, and/or changing op1 to zero. */
11920 /* Compute some predicates to simplify code below. */
11927 /* If this is a sign bit comparison and we can do arithmetic in
11928 MODE, say that we will only be needing the sign bit of OP0. */
11931 HOST_WIDE_INT_1U
11935 /* Now try cases based on the opcode of OP0. If none of the cases
11936 does a "continue", we exit this loop immediately after the
11937 switch. */
11940 {
11942 /* If we are extracting a single bit from a variable position in
11943 a constant that has only a single bit set and are comparing it
11944 with zero, we can convert this into an equality comparison
11945 between the position and the location of the single bit. */
11946 /* Except we can't if SHIFT_COUNT_TRUNCATED is set, since we might
11947 have already reduced the shift count modulo the word size. */
11953 {
11961 /* Result is nonzero iff shift count is equal to I. */
11964 }
11966 /* fall through */
11971 {
11974 }
11978 /* If testing for equality, we can take the NOT of the constant. */
11981 {
11985 }
11987 /* If just looking at the sign bit, reverse the sense of the
11988 comparison. */
11990 {
11994 }
11998 /* If testing for equality, we can take the NEG of the constant. */
12001 {
12005 }
12007 /* The remaining cases only apply to comparisons with zero. */
12011 /* When X is ABS or is known positive,
12012 (neg X) is < 0 if and only if X != 0. */
12020 {
12024 }
12026 /* If we have NEG of something whose two high-order bits are the
12027 same, we know that "(-a) < 0" is equivalent to "a > 0". */
12029 {
12033 }
12037 /* If we are testing equality and our count is a constant, we
12038 can perform the inverse operation on our RHS. */
12042 {
12046 }
12048 /* If we are doing a < 0 or >= 0 comparison, it means we are testing
12049 a particular bit. Convert it to an AND of a constant of that
12050 bit. This will be converted into a ZERO_EXTRACT. */
12054 {
12056 (HOST_WIDE_INT_1U
12061 }
12063 /* Fall through. */
12066 /* ABS is ignorable inside an equality comparison with zero. */
12068 {
12071 }
12075 /* Can simplify (compare (zero/sign_extend FOO) CONST) to
12076 (compare FOO CONST) if CONST fits in FOO's mode and we
12077 are either testing inequality or have an unsigned
12078 comparison with ZERO_EXTEND or a signed comparison with
12079 SIGN_EXTEND. But don't do it if we don't have a compare
12080 insn of the given mode, since we'd have to revert it
12081 later on, and then we wouldn't know whether to sign- or
12082 zero-extend. */
12085 && ! unsigned_comparison_p
12089 {
12092 }
12096 /* Check for the case where we are comparing A - C1 with C2, that is
12098 (subreg:MODE (plus (A) (-C1))) op (C2)
12100 with C1 a constant, and try to lift the SUBREG, i.e. to do the
12101 comparison in the wider mode. One of the following two conditions
12102 must be true in order for this to be valid:
12104 1. The mode extension results in the same bit pattern being added
12105 on both sides and the comparison is equality or unsigned. As
12106 C2 has been truncated to fit in MODE, the pattern can only be
12107 all 0s or all 1s.
12109 2. The mode extension results in the sign bit being copied on
12110 each side.
12112 The difficulty here is that we have predicates for A but not for
12113 (A - C1) so we need to check that C1 is within proper bounds so
12114 as to perturbate A as little as possible. */
12121 {
12130 /* (A - C1) zero-extends if it is positive and sign-extends
12131 if it is negative, C2 both zero- and sign-extends. */
12135 /* (A - C1) sign-extends if it is positive and 1-extends
12136 if it is negative, C2 both sign- and 1-extends. */
12143 /* (A - C1) always sign-extends, like C2. */
12147 {
12150 }
12151 }
12153 /* If the inner mode is narrower and we are extracting the low part,
12154 we can treat the SUBREG as if it were a ZERO_EXTEND. */
12157 ;
12168 {
12169 /* Remove outer subregs that don't do anything. */
12174 {
12178 }
12180 }
12181 else
12184 /* FALLTHROUGH */
12194 {
12197 }
12201 /* (eq (plus X A) B) -> (eq X (minus B A)). We can only do
12202 this for equality comparisons due to pathological cases involving
12203 overflows. */
12207 {
12211 }
12213 /* (plus (abs X) (const_int -1)) is < 0 if and only if X == 0. */
12216 {
12220 }
12224 /* We used to optimize signed comparisons against zero, but that
12225 was incorrect. Unsigned comparisons against zero (GTU, LEU)
12226 arrive here as equality comparisons, or (GEU, LTU) are
12227 optimized away. No need to special-case them. */
12229 /* (eq (minus A B) C) -> (eq A (plus B C)) or
12230 (eq B (minus A C)), whichever simplifies. We can only do
12231 this for equality comparisons due to pathological cases involving
12232 overflows. */
12236 {
12240 }
12245 {
12249 }
12251 /* The sign bit of (minus (ashiftrt X C) X), where C is the number
12252 of bits in X minus 1, is one iff X > 0. */
12257 {
12261 }
12265 /* (eq (xor A B) C) -> (eq A (xor B C)). This is a simplification
12266 if C is zero or B is a constant. */
12270 {
12274 }
12282 /* We can't do anything if OP0 is a condition code value, rather
12283 than an actual data value. */
12289 /* Get the two operands being compared. */
12292 else
12295 /* Check for the cases where we simply want the result of the
12296 earlier test or the opposite of that result. */
12300 {
12304 else
12308 {
12313 }
12314 }
12318 /* The sign bit of (ior (plus X (const_int -1)) X) is nonzero
12319 iff X <= 0. */
12323 {
12327 }
12331 /* Convert (and (xshift 1 X) Y) to (and (lshiftrt Y X) 1). This
12332 will be converted to a ZERO_EXTRACT later. */
12336 {
12341 }
12343 /* If we are comparing (and (lshiftrt X C1) C2) for equality with
12344 zero and X is a comparison and C1 and C2 describe only bits set
12345 in STORE_FLAG_VALUE, we can compare with X. */
12353 {
12360 {
12363 }
12364 }
12366 /* If we are doing an equality comparison of an AND of a bit equal
12367 to the sign bit, replace this with a LT or GE comparison of
12368 the underlying value. */
12375 {
12379 }
12381 /* If this AND operation is really a ZERO_EXTEND from a narrower
12382 mode, the constant fits within that mode, and this is either an
12383 equality or unsigned comparison, try to do this comparison in
12384 the narrower mode.
12386 Note that in:
12388 (ne:DI (and:DI (reg:DI 4) (const_int 0xffffffff)) (const_int 0))
12389 -> (ne:DI (reg:SI 4) (const_int 0))
12391 unless TRULY_NOOP_TRUNCATION allows it or the register is
12392 known to hold a value of the required mode the
12393 transformation is invalid. */
12401 {
12404 }
12406 /* If this is (and:M1 (subreg:M1 X:M2 0) (const_int C1)) where C1
12407 fits in both M1 and M2 and the SUBREG is either paradoxical
12408 or represents the low part, permute the SUBREG and the AND
12409 and try again. */
12412 {
12415 /* Require an integral mode, to avoid creating something like
12416 (AND:SF ...). */
12418 /* It is unsafe to commute the AND into the SUBREG if the
12419 SUBREG is paradoxical and WORD_REGISTER_OPERATIONS is
12420 not defined. As originally written the upper bits
12421 have a defined value due to the AND operation.
12422 However, if we commute the AND inside the SUBREG then
12423 they no longer have defined values and the meaning of
12424 the code has been changed.
12425 Also C1 should not change value in the smaller mode,
12426 see PR67028 (a positive C1 can become negative in the
12427 smaller mode, so that the AND does no longer mask the
12428 upper bits). */
12429 && ((WORD_REGISTER_OPERATIONS
12441 {
12447 }
12448 }
12450 /* Convert (ne (and (not X) 1) 0) to (eq (and X 1) 0). */
12454 {
12459 }
12461 /* Convert (ne (and (lshiftrt (not X)) 1) 0) to
12462 (eq (and (lshiftrt X) 1) 0).
12463 Also handle the case where (not X) is expressed using xor. */
12467 {
12477 == HOST_WIDE_INT_1U
12479 {
12480 op0
12485 }
12486 }
12490 /* If we have (compare (ashift FOO N) (const_int C)) and
12491 the high order N bits of FOO (N+1 if an inequality comparison)
12492 are known to be zero, we can do this by comparing FOO with C
12493 shifted right N bits so long as the low-order N bits of C are
12494 zero. */
12506 {
12507 /* We must perform a logical shift, not an arithmetic one,
12508 as we want the top N bits of C to be zero. */
12515 }
12517 /* If we are doing a sign bit comparison, it means we are testing
12518 a particular bit. Convert it to the appropriate AND. */
12521 {
12523 (HOST_WIDE_INT_1U
12528 }
12530 /* If this an equality comparison with zero and we are shifting
12531 the low bit to the sign bit, we can convert this to an AND of the
12532 low-order bit. */
12536 {
12539 }
12543 /* If this is an equality comparison with zero, we can do this
12544 as a logical shift, which might be much simpler. */
12547 {
12552 }
12554 /* If OP0 is a sign extension and CODE is not an unsigned comparison,
12555 do the comparison in a narrower mode. */
12565 {
12568 }
12570 /* Likewise if OP0 is a PLUS of a sign extension with a
12571 constant, which is usually represented with the PLUS
12572 between the shifts. */
12584 {
12592 new_const);
12594 }
12596 /* FALLTHROUGH */
12598 /* If we have (compare (xshiftrt FOO N) (const_int C)) and
12599 the low order N bits of FOO are known to be zero, we can do this
12600 by comparing FOO with C shifted left N bits so long as no
12601 overflow occurs. Even if the low order N bits of FOO aren't known
12602 to be zero, if the comparison is >= or < we can use the same
12603 optimization and for > or <= by setting all the low
12604 order N bits in the comparison constant. */
12615 {
12616 unsigned HOST_WIDE_INT low_bits
12618 & ((HOST_WIDE_INT_1U
12621 {
12622 /* If the shift was logical, then we must make the condition
12623 unsigned. */
12632 const_op
12637 }
12638 }
12640 /* If we are using this shift to extract just the sign bit, we
12641 can replace this with an LT or GE comparison. */
12646 {
12650 }
12655 }
12658 }
12660 /* Now make any compound operations involved in this comparison. Then,
12661 check for an outmost SUBREG on OP0 that is not doing anything or is
12662 paradoxical. The latter transformation must only be performed when
12663 it is known that the "extra" bits will be the same in op0 and op1 or
12664 that they don't matter. There are three cases to consider:
12666 1. SUBREG_REG (op0) is a register. In this case the bits are don't
12667 care bits and we can assume they have any convenient value. So
12668 making the transformation is safe.
12670 2. SUBREG_REG (op0) is a memory and LOAD_EXTEND_OP is UNKNOWN.
12671 In this case the upper bits of op0 are undefined. We should not make
12672 the simplification in that case as we do not know the contents of
12673 those bits.
12675 3. SUBREG_REG (op0) is a memory and LOAD_EXTEND_OP is not UNKNOWN.
12676 In that case we know those bits are zeros or ones. We must also be
12677 sure that they are the same as the upper bits of op1.
12679 We can never remove a SUBREG for a non-equality comparison because
12680 the sign bit is in a different place in the underlying object. */
12693 {
12695 {
12696 /* For paradoxical subregs, allow case 1 as above. Case 3 isn't
12697 implemented. */
12699 {
12702 }
12703 }
12709 {
12715 }
12716 }
12718 /* We now do the opposite procedure: Some machines don't have compare
12719 insns in all modes. If OP0's mode is an integer mode smaller than a
12720 word and we can't do a compare in that mode, see if there is a larger
12721 mode for which we can do the compare. There are a number of cases in
12722 which we can use the wider mode. */
12732 {
12735 /* If this is a test for negative, we can make an explicit
12736 test of the sign bit. Test this first so we can use
12737 a paradoxical subreg to extend OP0. */
12741 {
12742 unsigned HOST_WIDE_INT sign
12749 }
12751 /* If the only nonzero bits in OP0 and OP1 are those in the
12752 narrower mode and this is an equality or unsigned comparison,
12753 we can use the wider mode. Similarly for sign-extended
12754 values, in which case it is true for all comparisons. */
12771 {
12772 /* If OP0 is an AND and we don't have an AND in MODE either,
12773 make a new AND in the proper mode. */
12781 else
12782 {
12784 {
12787 }
12788 else
12789 {
12792 }
12794 }
12795 }
12796 }
12798 /* We may have changed the comparison operands. Re-canonicalize. */
12800 {
12803 }
12805 /* If this machine only supports a subset of valid comparisons, see if we
12806 can convert an unsupported one into a supported one. */
12813 }
12814 \f
12815 /* Utility function for record_value_for_reg. Count number of
12816 rtxs in X. */
12817 static int
12819 {
12826 {
12846 }
12857 }
12858 \f
12859 /* Utility function for following routine. Called when X is part of a value
12860 being stored into last_set_value. Sets last_set_table_tick
12861 for each register mentioned. Similar to mention_regs in cse.c */
12863 static void
12865 {
12871 {
12877 {
12880 }
12883 }
12887 {
12888 /* Check for identical subexpressions. If x contains
12889 identical subexpression we only have to traverse one of
12890 them. */
12892 {
12893 /* Note that at this point x1 has already been
12894 processed. */
12898 /* If x0 and x1 are identical then there is no need to
12899 process x0. */
12903 /* If x0 is identical to a subexpression of x1 then while
12904 processing x1, x0 has already been processed. Thus we
12905 are done with x. */
12910 /* If x1 is identical to a subexpression of x0 then we
12911 still have to process the rest of x0. */
12914 {
12917 }
12918 }
12921 }
12925 }
12927 /* Record that REG is set to VALUE in insn INSN. If VALUE is zero, we
12928 are saying that the register is clobbered and we no longer know its
12929 value. If INSN is zero, don't update reg_stat[].last_set; this is
12930 only permitted with VALUE also zero and is used to invalidate the
12931 register. */
12933 static void
12935 {
12941 /* If VALUE contains REG and we have a previous value for REG, substitute
12942 the previous value. */
12944 {
12945 rtx tem;
12947 /* Set things up so get_last_value is allowed to see anything set up to
12948 our insn. */
12952 /* If TEM is simply a binary operation with two CLOBBERs as operands,
12953 it isn't going to be useful and will take a lot of time to process,
12954 so just use the CLOBBER. */
12957 {
12963 {
12964 /* If there are two or more occurrences of REG in VALUE,
12965 prevent the value from growing too much. */
12968 }
12971 }
12972 }
12974 /* For each register modified, show we don't know its value, that
12975 we don't know about its bitwise content, that its value has been
12976 updated, and that we don't know the location of the death of the
12977 register. */
12979 {
12991 }
12993 /* Mark registers that are being referenced in this value. */
12997 /* Now update the status of each register being set.
12998 If someone is using this register in this block, set this register
12999 to invalid since we will get confused between the two lives in this
13000 basic block. This makes using this register always invalid. In cse, we
13001 scan the table to invalidate all entries using this register, but this
13002 is too much work for us. */
13005 {
13011 else
13013 }
13015 /* The value being assigned might refer to X (like in "x++;"). In that
13016 case, we must replace it with (clobber (const_int 0)) to prevent
13017 infinite loops. */
13020 {
13024 }
13026 /* For the main register being modified, update the value, the mode, the
13027 nonzero bits, and the number of sign bit copies. */
13032 {
13040 rsp->last_set_sign_bit_copies
13042 }
13043 }
13045 /* Called via note_stores from record_dead_and_set_regs to handle one
13046 SET or CLOBBER in an insn. DATA is the instruction in which the
13047 set is occurring. */
13049 static void
13051 {
13058 {
13062 }
13065 {
13066 /* If we are setting the whole register, we know its value. Otherwise
13067 show that we don't know the value. We can handle SUBREG in
13068 some cases. */
13079 else
13081 }
13083 /* Ignore pushes, they clobber nothing. */
13086 }
13088 /* Update the records of when each REG was most recently set or killed
13089 for the things done by INSN. This is the last thing done in processing
13090 INSN in the combiner loop.
13092 We update reg_stat[], in particular fields last_set, last_set_value,
13093 last_set_mode, last_set_nonzero_bits, last_set_sign_bit_copies,
13094 last_death, and also the similar information mem_last_set (which insn
13095 most recently modified memory) and last_call_luid (which insn was the
13096 most recent subroutine call). */
13098 static void
13100 {
13101 rtx link;
13105 {
13108 {
13113 {
13118 }
13119 }
13122 }
13125 {
13126 hard_reg_set_iterator hrsi;
13128 {
13140 }
13144 /* We can't combine into a call pattern. Remember, though, that
13145 the return value register is set at this LUID. We could
13146 still replace a register with the return value from the
13147 wrong subroutine call! */
13149 }
13150 else
13152 }
13154 /* If a SUBREG has the promoted bit set, it is in fact a property of the
13155 register present in the SUBREG, so for each such SUBREG go back and
13156 adjust nonzero and sign bit information of the registers that are
13157 known to have some zero/sign bits set.
13159 This is needed because when combine blows the SUBREGs away, the
13160 information on zero/sign bits is lost and further combines can be
13161 missed because of that. */
13163 static void
13165 {
13167 rtx set;
13175 {
13184 {
13187 }
13191 {
13194 }
13197 {
13200 }
13201 else
13203 }
13204 }
13206 /* Check if X, a register, is known to contain a value already
13207 truncated to MODE. In this case we can use a subreg to refer to
13208 the truncated value even though in the generic case we would need
13209 an explicit truncation. */
13211 static bool
13213 {
13225 }
13227 /* If X is a hard reg or a subreg record the mode that the register is
13228 accessed in. For non-TRULY_NOOP_TRUNCATION targets we might be able
13229 to turn a truncate into a subreg using this information. Return true
13230 if traversing X is complete. */
13232 static bool
13234 {
13235 machine_mode truncated_mode;
13239 {
13250 }
13251 /* ??? For hard-regs we now record everything. We might be able to
13252 optimize this using last_set_mode. */
13255 else
13263 {
13266 }
13269 }
13271 /* Callback for note_uses. Find hardregs and subregs of pseudos and
13272 the modes they are used in. This can help truning TRUNCATEs into
13273 SUBREGs. */
13275 static void
13277 {
13282 }
13284 /* Scan X for promoted SUBREGs. For each one found,
13285 note what it implies to the registers used in it. */
13287 static void
13289 {
13294 else
13295 {
13301 {
13311 }
13312 }
13313 }
13314 \f
13315 /* Verify that all the registers and memory references mentioned in *LOC are
13316 still valid. *LOC was part of a value set in INSN when label_tick was
13317 equal to TICK. Return 0 if some are not. If REPLACE is nonzero, replace
13318 the invalid references with (clobber (const_int 0)) and return 1. This
13319 replacement is useful because we often can get useful information about
13320 the form of a value (e.g., if it was produced by a shift that always
13321 produces -1 or 0) even though we don't know exactly what registers it
13322 was produced from. */
13324 static int
13326 {
13333 {
13339 {
13342 /* If this is a pseudo-register that was only set once and not
13343 live at the beginning of the function, it is always valid. */
13347 && (!REGNO_REG_SET_P
13349 regno)))
13351 {
13355 }
13356 }
13359 }
13360 /* If this is a memory reference, make sure that there were no stores after
13361 it that might have clobbered the value. We don't have alias info, so we
13362 assume any store invalidates it. Moreover, we only have local UIDs, so
13363 we also assume that there were stores in the intervening basic blocks. */
13366 {
13370 }
13373 {
13375 {
13376 /* Check for identical subexpressions. If x contains
13377 identical subexpression we only have to traverse one of
13378 them. */
13380 {
13381 /* Note that at this point x0 has already been checked
13382 and found valid. */
13386 /* If x0 and x1 are identical then x is also valid. */
13390 /* If x1 is identical to a subexpression of x0 then
13391 while checking x0, x1 has already been checked. Thus
13392 it is valid and so as x. */
13397 /* If x0 is identical to a subexpression of x1 then x is
13398 valid iff the rest of x1 is valid. */
13401 return
13405 }
13410 }
13416 }
13418 /* If we haven't found a reason for it to be invalid, it is valid. */
13420 }
13422 /* Get the last value assigned to X, if known. Some registers
13423 in the value may be replaced with (clobber (const_int 0)) if their value
13424 is known longer known reliably. */
13426 static rtx
13428 {
13430 rtx value;
13433 /* If this is a non-paradoxical SUBREG, get the value of its operand and
13434 then convert it to the desired mode. If this is a paradoxical SUBREG,
13435 we cannot predict what values the "extra" bits might have. */
13449 /* If we don't have a value, or if it isn't for this basic block and
13450 it's either a hard register, set more than once, or it's a live
13451 at the beginning of the function, return 0.
13453 Because if it's not live at the beginning of the function then the reg
13454 is always set before being used (is never used without being set).
13455 And, if it's set only once, and it's always set before use, then all
13456 uses must have the same last value, even if it's not from this basic
13457 block. */
13464 || REGNO_REG_SET_P
13468 /* If the value was set in a later insn than the ones we are processing,
13469 we can't use it even if the register was only set once. */
13474 /* If fewer bits were set than what we are asked for now, we cannot use
13475 the value. */
13480 /* If the value has all its registers valid, return it. */
13484 /* Otherwise, make a copy and replace any invalid register with
13485 (clobber (const_int 0)). If that fails for some reason, return 0. */
13492 }
13493 \f
13494 /* Return nonzero if expression X refers to a REG or to memory
13495 that is set in an instruction more recent than FROM_LUID. */
13497 static int
13499 {
13505 {
13509 #ifdef PUSH_ROUNDING
13510 /* Don't allow uses of the stack pointer to be moved,
13511 because we don't know whether the move crosses a push insn. */
13514 #endif
13516 {
13522 }
13524 }
13532 {
13534 {
13539 }
13543 }
13545 }
13546 \f
13547 /* Define three variables used for communication between the following
13548 routines. */
13553 /* Function called via note_stores from reg_dead_at_p.
13555 If DEST is within [reg_dead_regno, reg_dead_endregno), set
13556 reg_dead_flag to 1 if X is a CLOBBER and to -1 it is a SET. */
13558 static void
13560 {
13570 }
13572 /* Return nonzero if REG is known to be dead at INSN.
13574 We scan backwards from INSN. If we hit a REG_DEAD note or a CLOBBER
13575 referencing REG, it is dead. If we hit a SET referencing REG, it is
13576 live. Otherwise, see if it is live or dead at the start of the basic
13577 block we are in. Hard regs marked as being live in NEWPAT_USED_REGS
13578 must be assumed to be always live. */
13580 static int
13582 {
13583 basic_block block;
13586 /* Set variables for reg_dead_at_p_1. */
13592 /* Check that reg isn't mentioned in NEWPAT_USED_REGS. For fixed registers
13593 we allow the machine description to decide whether use-and-clobber
13594 patterns are OK. */
13596 {
13600 }
13602 /* Scan backwards until we find a REG_DEAD note, SET, CLOBBER, or
13603 beginning of basic block. */
13606 {
13608 {
13618 }
13624 }
13626 /* Look at live-in sets for the basic block that we were in. */
13632 }
13633 \f
13634 /* Note hard registers in X that are used. */
13636 static void
13638 {
13644 {
13648 CASE_CONST_ANY:
13653 /* CC0 must die in the insn after it is set, so we don't need to take
13654 special note of it here. */
13659 /* If we are clobbering a MEM, mark any hard registers inside the
13660 address as used. */
13667 /* A hard reg in a wide mode may really be multiple registers.
13668 If so, mark all of them just like the first. */
13670 {
13671 /* None of this applies to the stack, frame or arg pointers. */
13673 || (!HARD_FRAME_POINTER_IS_FRAME_POINTER
13681 }
13685 {
13686 /* If setting a MEM, or a SUBREG of a MEM, then note any hard regs in
13687 the address. */
13699 }
13704 }
13706 /* Recursively scan the operands of this expression. */
13708 {
13712 {
13716 {
13721 }
13722 }
13723 }
13724 }
13725 \f
13726 /* Remove register number REGNO from the dead registers list of INSN.
13728 Return the note used to record the death, if there was one. */
13730 rtx
13732 {
13739 }
13741 /* For each register (hardware or pseudo) used within expression X, if its
13742 death is in an instruction with luid between FROM_LUID (inclusive) and
13743 TO_INSN (exclusive), put a REG_DEAD note for that register in the
13744 list headed by PNOTES.
13746 That said, don't move registers killed by maybe_kill_insn.
13748 This is done when X is being merged by combination into TO_INSN. These
13749 notes will then be distributed as needed. */
13751 static void
13754 {
13760 {
13764 /* Don't move the register if it gets killed in between from and to. */
13773 {
13776 /* It is possible for the call above to return 0. This can occur
13777 when last_death points to I2 or I1 that we combined with.
13778 In that case make a new note.
13780 We must also check for the case where X is a hard register
13781 and NOTE is a death note for a range of hard registers
13782 including X. In that case, we must put REG_DEAD notes for
13783 the remaining registers in place of NOTE. */
13788 {
13797 }
13799 /* If we didn't find any note, or if we found a REG_DEAD note that
13800 covers only part of the given reg, and we have a multi-reg hard
13801 register, then to be safe we must check for REG_DEAD notes
13802 for each register other than the first. They could have
13803 their own REG_DEAD notes lying around. */
13810 {
13817 else
13823 }
13826 {
13829 }
13830 else
13832 }
13835 }
13838 {
13843 /* In the case of a ZERO_EXTRACT, a STRICT_LOW_PART, or a SUBREG
13844 that accesses one word of a multi-word item, some
13845 piece of everything register in the expression is used by
13846 this insn, so remove any old death. */
13847 /* ??? So why do we test for equality of the sizes? */
13856 {
13859 }
13861 /* If this is some other SUBREG, we know it replaces the entire
13862 value, so use that as the destination. */
13866 /* If this is a MEM, adjust deaths of anything used in the address.
13867 For a REG (the only other possibility), the entire value is
13868 being replaced so the old value is not used in this insn. */
13874 }
13883 {
13885 {
13890 }
13893 }
13894 }
13895 \f
13896 /* Return 1 if X is the target of a bit-field assignment in BODY, the
13897 pattern of an insn. X must be a REG. */
13899 static int
13901 {
13905 {
13907 rtx target;
13914 else
13931 }
13939 }
13940 \f
13941 /* Given a chain of REG_NOTES originally from FROM_INSN, try to place them
13942 as appropriate. I3 and I2 are the insns resulting from the combination
13943 insns including FROM (I2 may be zero).
13945 ELIM_I2 and ELIM_I1 are either zero or registers that we know will
13946 not need REG_DEAD notes because they are being substituted for. This
13947 saves searching in the most common cases.
13949 Each note in the list is either ignored or placed on some insns, depending
13950 on the type of note. */
13952 static void
13955 {
13957 rtx tem_note;
13961 {
13966 {
13969 /* Doesn't matter much where we put this, as long as it's somewhere.
13970 It is preferable to keep these notes on branches, which is most
13971 likely to be i3. */
13978 else
13979 {
13982 }
13986 /* These notes must remain with the call or trapping instruction. */
13991 else
13992 {
13998 /* ??? Otherwise assume we've combined things such that we
13999 can now prove that the instructions can't trap. Drop the
14000 note in this case. */
14001 }
14005 /* ??? How to distribute between i3-i1. Assume i3 contains the
14006 entire adjustment. Assert i3 contains at least some adjust. */
14008 {
14010 /* fixup_args_size_notes looks at REG_NORETURN note,
14011 so ensure the note is placed there first. */
14013 {
14017 {
14023 }
14024 }
14026 /* emit_call_1 adds for !ACCUMULATE_OUTGOING_ARGS
14027 REG_ARGS_SIZE note to all noreturn calls, allow that here. */
14030 && !ACCUMULATE_OUTGOING_ARGS
14032 }
14039 /* These notes must remain with the call. It should not be
14040 possible for both I2 and I3 to be a call. */
14043 else
14044 {
14047 }
14051 /* Any clobbers for i3 may still exist, and so we must process
14052 REG_UNUSED notes from that insn.
14054 Any clobbers from i2 or i1 can only exist if they were added by
14055 recog_for_combine. In that case, recog_for_combine created the
14056 necessary REG_UNUSED notes. Trying to keep any original
14057 REG_UNUSED notes from these insns can cause incorrect output
14058 if it is for the same register as the original i3 dest.
14059 In that case, we will notice that the register is set in i3,
14060 and then add a REG_UNUSED note for the destination of i3, which
14061 is wrong. However, it is possible to have REG_UNUSED notes from
14062 i2 or i1 for register which were both used and clobbered, so
14063 we keep notes from i2 or i1 if they will turn into REG_DEAD
14064 notes. */
14066 /* If this register is set or clobbered in I3, put the note there
14067 unless there is one already. */
14069 {
14077 }
14078 /* Otherwise, if this register is used by I3, then this register
14079 now dies here, so we must put a REG_DEAD note here unless there
14080 is one already. */
14086 {
14089 }
14095 /* These notes say something about results of an insn. We can
14096 only support them if they used to be on I3 in which case they
14097 remain on I3. Otherwise they are ignored.
14099 If the note refers to an expression that is not a constant, we
14100 must also ignore the note since we cannot tell whether the
14101 equivalence is still true. It might be possible to do
14102 slightly better than this (we only have a problem if I2DEST
14103 or I1DEST is present in the expression), but it doesn't
14104 seem worth the trouble. */
14112 /* These notes say something about how a register is used. They must
14113 be present on any use of the register in I2 or I3. */
14118 {
14121 else
14123 }
14128 /* This can show up in several ways -- either directly in the
14129 pattern, or hidden off in the constant pool with (or without?)
14130 a REG_EQUAL note. */
14131 /* ??? Ignore the without-reg_equal-note problem for now. */
14143 {
14146 else
14148 }
14150 /* For REG_LABEL_TARGET on a JUMP_P, we prefer to put the note
14151 as a JUMP_LABEL or decrement LABEL_NUSES if it's already
14152 there. */
14157 {
14164 }
14170 {
14178 }
14182 /* This note says something about the value of a register prior
14183 to the execution of an insn. It is too much trouble to see
14184 if the note is still correct in all situations. It is better
14185 to simply delete it. */
14189 /* If we replaced the right hand side of FROM_INSN with a
14190 REG_EQUAL note, the original use of the dying register
14191 will not have been combined into I3 and I2. In such cases,
14192 FROM_INSN is guaranteed to be the first of the combined
14193 instructions, so we simply need to search back before
14194 FROM_INSN for the previous use or set of this register,
14195 then alter the notes there appropriately.
14197 If the register is used as an input in I3, it dies there.
14198 Similarly for I2, if it is nonzero and adjacent to I3.
14200 If the register is not used as an input in either I3 or I2
14201 and it is not one of the registers we were supposed to eliminate,
14202 there are two possibilities. We might have a non-adjacent I2
14203 or we might have somehow eliminated an additional register
14204 from a computation. For example, we might have had A & B where
14205 we discover that B will always be zero. In this case we will
14206 eliminate the reference to A.
14208 In both cases, we must search to see if we can find a previous
14209 use of A and put the death note there. */
14215 else
14216 {
14227 && !(i2mod
14229 i2mod_old_rhs)))
14234 /* If the new I2 sets the same register that is marked dead
14235 in the note, we do not know where to put the note.
14236 Give up. */
14239 }
14242 {
14246 {
14248 {
14252 }
14254 /* If the register is being set at TEM_INSN, see if that is all
14255 TEM_INSN is doing. If so, delete TEM_INSN. Otherwise, make this
14256 into a REG_UNUSED note instead. Don't delete sets to
14257 global register vars. */
14261 {
14272 ;
14274 /* Verify that it was the set, and not a clobber that
14275 modified the register.
14277 CC0 targets must be careful to maintain setter/user
14278 pairs. If we cannot delete the setter due to side
14279 effects, mark the user with an UNUSED note instead
14280 of deleting it. */
14284 && (!HAVE_cc0
14288 {
14289 /* Move the notes and links of TEM_INSN elsewhere.
14290 This might delete other dead insns recursively.
14291 First set the pattern to something that won't use
14292 any register. */
14311 /* Delete the setter too. */
14313 {
14326 }
14327 }
14328 else
14329 {
14332 /* If there isn't already a REG_UNUSED note, put one
14333 here. Do not place a REG_DEAD note, even if
14334 the register is also used here; that would not
14335 match the algorithm used in lifetime analysis
14336 and can cause the consistency check in the
14337 scheduler to fail. */
14342 }
14343 }
14347 {
14350 /* If we are doing a 3->2 combination, and we have a
14351 register which formerly died in i3 and was not used
14352 by i2, which now no longer dies in i3 and is used in
14353 i2 but does not die in i2, and place is between i2
14354 and i3, then we may need to move a link from place to
14355 i2. */
14357 && from_insn
14360 {
14364 }
14366 }
14370 }
14372 }
14374 /* If the register is set or already dead at PLACE, we needn't do
14375 anything with this note if it is still a REG_DEAD note.
14376 We check here if it is set at all, not if is it totally replaced,
14377 which is what `dead_or_set_p' checks, so also check for it being
14378 set partially. */
14381 {
14387 {
14388 /* Unless the register previously died in PLACE, clear
14389 last_death. [I no longer understand why this is
14390 being done.] */
14394 }
14395 else
14398 /* If this is a death note for a hard reg that is occupying
14399 multiple registers, ensure that we are still using all
14400 parts of the object. If we find a piece of the object
14401 that is unused, we must arrange for an appropriate REG_DEAD
14402 note to be added for it. However, we can't just emit a USE
14403 and tag the note to it, since the register might actually
14404 be dead; so we recourse, and the recursive call then finds
14405 the previous insn that used this register. */
14408 {
14417 {
14420 }
14423 {
14424 /* Put only REG_DEAD notes for pieces that are
14425 not already dead or set. */
14429 {
14436 {
14438 NULL_RTX);
14442 NULL_RTX);
14443 }
14448 {
14450 {
14454 }
14458 {
14461 }
14462 }
14463 }
14466 }
14467 }
14468 }
14472 /* Any other notes should not be present at this point in the
14473 compilation. */
14475 }
14478 {
14481 }
14485 }
14486 }
14487 \f
14488 /* Similarly to above, distribute the LOG_LINKS that used to be present on
14489 I3, I2, and I1 to new locations. This is also called to add a link
14490 pointing at I3 when I3's destination is changed. */
14492 static void
14494 {
14498 {
14505 /* If the insn that this link points to is a NOTE, ignore it. */
14514 {
14517 {
14533 }
14536 }
14537 else
14547 /* A LOG_LINK is defined as being placed on the first insn that uses
14548 a register and points to the insn that sets the register. Start
14549 searching at the next insn after the target of the link and stop
14550 when we reach a set of the register or the end of the basic block.
14552 Note that this correctly handles the link that used to point from
14553 I3 to I2. Also note that not much searching is typically done here
14554 since most links don't point very far away. */
14563 {
14567 }
14570 {
14573 }
14577 /* If we found a place to put the link, place it there unless there
14578 is already a link to the same insn as LINK at that point. */
14581 {
14589 {
14593 /* Set added_links_insn to the earliest insn we added a
14594 link to. */
14598 }
14599 }
14600 }
14601 }
14602 \f
14603 /* Check for any register or memory mentioned in EQUIV that is not
14604 mentioned in EXPR. This is used to restrict EQUIV to "specializations"
14605 of EXPR where some registers may have been replaced by constants. */
14607 static bool
14609 {
14612 {
14617 }
14619 }
14620 \f
14621 DEBUG_FUNCTION void
14623 {
14624 fprintf
14626 ";; Combiner statistics: %d attempts, %d substitutions (%d requiring new space),\n;; %d successes.\n\n",
14628 }
14630 void
14632 {
14633 fprintf
14635 "\n;; Combiner totals: %d attempts, %d substitutions (%d requiring new space),\n;; %d successes.\n",
14637 }
14638 \f
14639 /* Try combining insns through substitution. */
14640 static unsigned int
14642 {
14652 rebuild_jump_labels_after_combine
14655 /* Combining insns may have turned an indirect jump into a
14656 direct jump. Rebuild the JUMP_LABEL fields of jumping
14657 instructions. */
14659 {
14666 }
14670 }
14675 {
14685 };
14688 {
14692 {}
14694 /* opt_pass methods: */
14697 {
14699 }
14705 rtl_opt_pass *
14707 {
14709 }