| blob | 73d141edc0787ff36334da8816355933657b1ba0 |
1 /* Optimize by combining instructions for GNU compiler.
2 Copyright (C) 1987-2015 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 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. */
106 /* Include expr.h after insn-config.h so we get HAVE_conditional_move. */
138 /* Number of attempts to combine instructions in this function. */
142 /* Number of attempts that got as far as substitution in this function. */
146 /* Number of instructions combined with added SETs in this function. */
150 /* Number of instructions combined in this function. */
154 /* Totals over entire compilation. */
158 /* combine_instructions may try to replace the right hand side of the
159 second instruction with the value of an associated REG_EQUAL note
160 before throwing it at try_combine. That is problematic when there
161 is a REG_DEAD note for a register used in the old right hand side
162 and can cause distribute_notes to do wrong things. This is the
163 second instruction if it has been so modified, null otherwise. */
167 /* When I2MOD is nonnull, this is a copy of the old right hand side. */
171 /* When I2MOD is nonnull, this is a copy of the new right hand side. */
174 \f
176 /* Record last point of death of (hard or pseudo) register n. */
179 /* Record last point of modification of (hard or pseudo) register n. */
182 /* The next group of fields allows the recording of the last value assigned
183 to (hard or pseudo) register n. We use this information to see if an
184 operation being processed is redundant given a prior operation performed
185 on the register. For example, an `and' with a constant is redundant if
186 all the zero bits are already known to be turned off.
188 We use an approach similar to that used by cse, but change it in the
189 following ways:
191 (1) We do not want to reinitialize at each label.
192 (2) It is useful, but not critical, to know the actual value assigned
193 to a register. Often just its form is helpful.
195 Therefore, we maintain the following fields:
197 last_set_value the last value assigned
198 last_set_label records the value of label_tick when the
199 register was assigned
200 last_set_table_tick records the value of label_tick when a
201 value using the register is assigned
202 last_set_invalid set to nonzero when it is not valid
203 to use the value of this register in some
204 register's value
206 To understand the usage of these tables, it is important to understand
207 the distinction between the value in last_set_value being valid and
208 the register being validly contained in some other expression in the
209 table.
211 (The next two parameters are out of date).
213 reg_stat[i].last_set_value is valid if it is nonzero, and either
214 reg_n_sets[i] is 1 or reg_stat[i].last_set_label == label_tick.
216 Register I may validly appear in any expression returned for the value
217 of another register if reg_n_sets[i] is 1. It may also appear in the
218 value for register J if reg_stat[j].last_set_invalid is zero, or
219 reg_stat[i].last_set_label < reg_stat[j].last_set_label.
221 If an expression is found in the table containing a register which may
222 not validly appear in an expression, the register is replaced by
223 something that won't match, (clobber (const_int 0)). */
225 /* Record last value assigned to (hard or pseudo) register n. */
227 rtx last_set_value;
229 /* Record the value of label_tick when an expression involving register n
230 is placed in last_set_value. */
234 /* Record the value of label_tick when the value for register n is placed in
235 last_set_value. */
239 /* These fields are maintained in parallel with last_set_value and are
240 used to store the mode in which the register was last set, the bits
241 that were known to be zero when it was last set, and the number of
242 sign bits copies it was known to have when it was last set. */
248 /* Set nonzero if references to register n in expressions should not be
249 used. last_set_invalid is set nonzero when this register is being
250 assigned to and last_set_table_tick == label_tick. */
254 /* Some registers that are set more than once and used in more than one
255 basic block are nevertheless always set in similar ways. For example,
256 a QImode register may be loaded from memory in two places on a machine
257 where byte loads zero extend.
259 We record in the following fields if a register has some leading bits
260 that are always equal to the sign bit, and what we know about the
261 nonzero bits of a register, specifically which bits are known to be
262 zero.
264 If an entry is zero, it means that we don't know anything special. */
270 /* Record the value of the label_tick when the last truncation
271 happened. The field truncated_to_mode is only valid if
272 truncation_label == label_tick. */
276 /* Record the last truncation seen for this register. If truncation
277 is not a nop to this mode we might be able to save an explicit
278 truncation if we know that value already contains a truncated
279 value. */
287 /* One plus the highest pseudo for which we track REG_N_SETS.
288 regstat_init_n_sets_and_refs allocates the array for REG_N_SETS just once,
289 but during combine_split_insns new pseudos can be created. As we don't have
290 updated DF information in that case, it is hard to initialize the array
291 after growing. The combiner only cares about REG_N_SETS (regno) == 1,
292 so instead of growing the arrays, just assume all newly created pseudos
293 during combine might be set multiple times. */
297 /* Record the luid of the last insn that invalidated memory
298 (anything that writes memory, and subroutine calls, but not pushes). */
302 /* Record the luid of the last CALL_INSN
303 so we can tell whether a potential combination crosses any calls. */
307 /* When `subst' is called, this is the insn that is being modified
308 (by combining in a previous insn). The PATTERN of this insn
309 is still the old pattern partially modified and it should not be
310 looked at, but this may be used to examine the successors of the insn
311 to judge whether a simplification is valid. */
315 /* This is the lowest LUID that `subst' is currently dealing with.
316 get_last_value will not return a value if the register was set at or
317 after this LUID. If not for this mechanism, we could get confused if
318 I2 or I1 in try_combine were an insn that used the old value of a register
319 to obtain a new value. In that case, we might erroneously get the
320 new value of the register when we wanted the old one. */
324 /* This contains any hard registers that are used in newpat; reg_dead_at_p
325 must consider all these registers to be always live. */
329 /* This is an insn to which a LOG_LINKS entry has been added. If this
330 insn is the earlier than I2 or I3, combine should rescan starting at
331 that location. */
335 /* Basic block in which we are performing combines. */
339 \f
340 /* Length of the currently allocated uid_insn_cost array. */
344 /* The following array records the insn_rtx_cost for every insn
345 in the instruction stream. */
349 /* The following array records the LOG_LINKS for every insn in the
350 instruction stream as struct insn_link pointers. */
356 };
360 #define INSN_COST(INSN) (uid_insn_cost[INSN_UID (INSN)])
361 #define LOG_LINKS(INSN) (uid_log_links[INSN_UID (INSN)])
363 #define FOR_EACH_LOG_LINK(L, INSN) \
364 for ((L) = LOG_LINKS (INSN); (L); (L) = (L)->next)
366 /* Links for LOG_LINKS are allocated from this obstack. */
370 /* Allocate a link. */
374 {
382 }
384 /* Incremented for each basic block. */
388 /* Reset to label_tick for each extended basic block in scanning order. */
392 /* Mode used to compute significance in reg_stat[].nonzero_bits. It is the
393 largest integer mode that can fit in HOST_BITS_PER_WIDE_INT. */
397 /* Nonzero when reg_stat[].nonzero_bits and reg_stat[].sign_bit_copies can
398 be safely used. It is zero while computing them and after combine has
399 completed. This former test prevents propagating values based on
400 previously set values, which can be incorrect if a variable is modified
401 in a loop. */
405 \f
406 /* Record one modification to rtl structure
407 to be undone by storing old_contents into *where. */
411 struct undo
412 {
417 };
419 /* Record a bunch of changes to be undone, up to MAX_UNDO of them.
420 num_undo says how many are currently recorded.
422 other_insn is nonzero if we have modified some other insn in the process
423 of working on subst_insn. It must be verified too. */
425 struct undobuf
426 {
430 };
434 /* Number of times the pseudo being substituted for
435 was found and replaced. */
440 machine_mode,
444 machine_mode,
516 \f
518 /* It is not safe to use ordinary gen_lowpart in combine.
519 See comments in gen_lowpart_for_combine. */
520 #undef RTL_HOOKS_GEN_LOWPART
521 #define RTL_HOOKS_GEN_LOWPART gen_lowpart_for_combine
523 /* Our implementation of gen_lowpart never emits a new pseudo. */
524 #undef RTL_HOOKS_GEN_LOWPART_NO_EMIT
525 #define RTL_HOOKS_GEN_LOWPART_NO_EMIT gen_lowpart_for_combine
527 #undef RTL_HOOKS_REG_NONZERO_REG_BITS
528 #define RTL_HOOKS_REG_NONZERO_REG_BITS reg_nonzero_bits_for_combine
530 #undef RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES
531 #define RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES reg_num_sign_bit_copies_for_combine
533 #undef RTL_HOOKS_REG_TRUNCATED_TO_MODE
534 #define RTL_HOOKS_REG_TRUNCATED_TO_MODE reg_truncated_to_mode
538 \f
539 /* Convenience wrapper for the canonicalize_comparison target hook.
540 Target hooks cannot use enum rtx_code. */
544 {
548 }
550 /* Try to split PATTERN found in INSN. This returns NULL_RTX if
551 PATTERN can not be split. Otherwise, it returns an insn sequence.
552 This is a wrapper around split_insns which ensures that the
553 reg_stat vector is made larger if the splitter creates a new
554 register. */
558 {
567 }
569 /* This is used by find_single_use to locate an rtx in LOC that
570 contains exactly one use of DEST, which is typically either a REG
571 or CC0. It returns a pointer to the innermost rtx expression
572 containing DEST. Appearances of DEST that are being used to
573 totally replace it are not counted. */
577 {
586 {
590 CASE_CONST_ANY:
595 /* If the destination is anything other than CC0, PC, a REG or a SUBREG
596 of a REG that occupies all of the REG, the insn uses DEST if
597 it is mentioned in the destination or the source. Otherwise, we
598 need just check the source. */
618 }
620 /* If it wasn't one of the common cases above, check each expression and
621 vector of this code. Look for a unique usage of DEST. */
625 {
627 {
632 else
638 /* Duplicate usage. */
640 }
642 {
646 {
652 else
659 }
660 }
661 }
664 }
667 /* See if DEST, produced in INSN, is used only a single time in the
668 sequel. If so, return a pointer to the innermost rtx expression in which
669 it is used.
671 If PLOC is nonzero, *PLOC is set to the insn containing the single use.
673 If DEST is cc0_rtx, we look only at the next insn. In that case, we don't
674 care about REG_DEAD notes or LOG_LINKS.
676 Otherwise, we find the single use by finding an insn that has a
677 LOG_LINKS pointing at INSN and has a REG_DEAD note for DEST. If DEST is
678 only referenced once in that insn, we know that it must be the first
679 and last insn referencing DEST. */
683 {
684 basic_block bb;
690 {
700 }
710 {
716 {
721 }
722 }
725 }
726 \f
727 /* Substitute NEWVAL, an rtx expression, into INTO, a place in some
728 insn. The substitution can be undone by undo_all. If INTO is already
729 set to NEWVAL, do not record this change. Because computing NEWVAL might
730 also call SUBST, we have to compute it before we put anything into
731 the undo table. */
733 static void
735 {
742 /* We'd like to catch as many invalid transformations here as
743 possible. Unfortunately, there are way too many mode changes
744 that are perfectly valid, so we'd waste too much effort for
745 little gain doing the checks here. Focus on catching invalid
746 transformations involving integer constants. */
749 {
750 /* Sanity check that we're replacing oldval with a CONST_INT
751 that is a valid sign-extension for the original mode. */
755 /* Replacing the operand of a SUBREG or a ZERO_EXTEND with a
756 CONST_INT is not valid, because after the replacement, the
757 original mode would be gone. Unfortunately, we can't tell
758 when do_SUBST is called to replace the operand thereof, so we
759 perform this test on oldval instead, checking whether an
760 invalid replacement took place before we got here. */
765 }
769 else
778 }
780 #define SUBST(INTO, NEWVAL) do_SUBST (&(INTO), (NEWVAL))
782 /* Similar to SUBST, but NEWVAL is an int expression. Note that substitution
783 for the value of a HOST_WIDE_INT value (including CONST_INT) is
784 not safe. */
786 static void
788 {
797 else
806 }
808 #define SUBST_INT(INTO, NEWVAL) do_SUBST_INT (&(INTO), (NEWVAL))
810 /* Similar to SUBST, but just substitute the mode. This is used when
811 changing the mode of a pseudo-register, so that any other
812 references to the entry in the regno_reg_rtx array will change as
813 well. */
815 static void
817 {
826 else
835 }
837 #define SUBST_MODE(INTO, NEWVAL) do_SUBST_MODE (&(INTO), (NEWVAL))
839 #if !HAVE_cc0
840 /* Similar to SUBST, but NEWVAL is a LOG_LINKS expression. */
842 static void
844 {
853 else
862 }
864 #define SUBST_LINK(oldval, newval) do_SUBST_LINK (&oldval, newval)
865 #endif
866 \f
867 /* Subroutine of try_combine. Determine whether the replacement patterns
868 NEWPAT, NEWI2PAT and NEWOTHERPAT are cheaper according to insn_rtx_cost
869 than the original sequence I0, I1, I2, I3 and undobuf.other_insn. Note
870 that I0, I1 and/or NEWI2PAT may be NULL_RTX. Similarly, NEWOTHERPAT and
871 undobuf.other_insn may also both be NULL_RTX. Return false if the cost
872 of all the instructions can be estimated and the replacements are more
873 expensive than the original sequence. */
875 static bool
878 {
883 /* Lookup the original insn_rtx_costs. */
888 {
891 {
895 }
896 else
897 {
901 }
902 }
903 else
904 {
907 }
909 /* If we have split a PARALLEL I2 to I1,I2, we have counted its cost twice;
910 correct that. */
915 /* Calculate the replacement insn_rtx_costs. */
918 {
922 }
923 else
924 {
927 }
930 {
936 {
939 }
940 else
942 }
944 /* Disallow this combination if both new_cost and old_cost are greater than
945 zero, and new_cost is greater than old cost. */
949 {
968 else
970 }
975 /* Update the uid_insn_cost array with the replacement costs. */
979 {
983 }
986 }
989 /* Delete any insns that copy a register to itself. */
991 static void
993 {
995 basic_block bb;
998 {
1000 {
1003 {
1008 }
1009 }
1010 }
1011 }
1013 \f
1014 /* Return false if we do not want to (or cannot) combine DEF. */
1015 static bool
1017 {
1018 /* Do not consider if it is pre/post modification in MEM. */
1024 /* Do not combine frame pointer adjustments. */
1027 #if !HARD_FRAME_POINTER_IS_FRAME_POINTER
1030 #endif
1036 }
1038 /* Return false if we do not want to (or cannot) combine USE. */
1039 static bool
1041 {
1042 /* Do not consider the usage of the stack pointer by function call. */
1047 }
1049 /* Fill in log links field for all insns. */
1051 static void
1053 {
1054 basic_block bb;
1061 /* Pass through each block from the end, recording the uses of each
1062 register and establishing log links when def is encountered.
1063 Note that we do not clear next_use array in order to save time,
1064 so we have to test whether the use is in the same basic block as def.
1066 There are a few cases below when we do not consider the definition or
1067 usage -- these are taken from original flow.c did. Don't ask me why it is
1068 done this way; I don't know and if it works, I don't want to know. */
1071 {
1073 {
1077 /* Log links are created only once. */
1081 {
1097 /* flow.c claimed:
1099 We don't build a LOG_LINK for hard registers contained
1100 in ASM_OPERANDs. If these registers get replaced,
1101 we might wind up changing the semantics of the insn,
1102 even if reload can make what appear to be valid
1103 assignments later. */
1108 /* Don't add duplicate links between instructions. */
1117 }
1122 }
1123 }
1126 }
1128 /* Walk the LOG_LINKS of insn B to see if we find a reference to A. Return
1129 true if we found a LOG_LINK that proves that A feeds B. This only works
1130 if there are no instructions between A and B which could have a link
1131 depending on A, since in that case we would not record a link for B.
1132 We also check the implicit dependency created by a cc0 setter/user
1133 pair. */
1135 static bool
1137 {
1145 }
1146 \f
1147 /* Main entry point for combiner. F is the first insn of the function.
1148 NREGS is the first unused pseudo-reg number.
1150 Return nonzero if the combiner has turned an indirect jump
1151 instruction into a direct jump. */
1152 static int
1154 {
1156 #if HAVE_cc0
1158 #endif
1161 basic_block last_bb;
1181 /* Allocate array for insn info. */
1189 /* Don't use reg_stat[].nonzero_bits when computing it. This can cause
1190 problems when, for example, we have j <<= 1 in a loop. */
1195 /* Scan all SETs and see if we can deduce anything about what
1196 bits are known to be zero for some registers and how many copies
1197 of the sign bit are known to exist for those registers.
1199 Also set any known values so that we can use it while searching
1200 for what bits are known to be set. */
1203 /* Allow the entry block and the first block to fall into the same EBB.
1204 Conceptually the incoming promotions are assigned to the entry block. */
1209 {
1214 label_tick++;
1222 {
1223 #ifdef AUTO_INC_DEC
1224 rtx links;
1225 #endif
1231 insn);
1234 #ifdef AUTO_INC_DEC
1238 insn);
1239 #endif
1241 /* Record the current insn_rtx_cost of this instruction. */
1244 optimize_this_for_speed_p);
1248 }
1249 }
1253 /* Now scan all the insns in forward order. */
1261 {
1267 label_tick++;
1277 {
1291 /* See if we know about function return values before this
1292 insn based upon SUBREG flags. */
1295 /* See if we can find hardregs and subreg of pseudos in
1296 narrower modes. This could help turning TRUNCATEs
1297 into SUBREGs. */
1300 /* Try this insn with each insn it links back to. */
1306 {
1309 }
1311 /* Try each sequence of three linked insns ending with this one. */
1315 {
1318 /* If the linked insn has been replaced by a note, then there
1319 is no point in pursuing this chain any further. */
1327 {
1330 }
1331 }
1333 #if HAVE_cc0
1334 /* Try to combine a jump insn that uses CC0
1335 with a preceding insn that sets CC0, and maybe with its
1336 logical predecessor as well.
1337 This is how we make decrement-and-branch insns.
1338 We need this special code because data flow connections
1339 via CC0 do not get entered in LOG_LINKS. */
1345 {
1356 }
1358 /* Do the same for an insn that explicitly references CC0. */
1365 {
1376 }
1378 /* Finally, see if any of the insns that this insn links to
1379 explicitly references CC0. If so, try this insn, that insn,
1380 and its predecessor if it sets CC0. */
1392 #endif
1394 /* Try combining an insn with two different insns whose results it
1395 uses. */
1405 {
1408 }
1410 /* Try four-instruction combinations. */
1413 {
1417 /* If the linked insn has been replaced by a note, then there
1418 is no point in pursuing this chain any further. */
1423 {
1427 /* I0 -> I1 -> I2 -> I3. */
1433 {
1436 }
1437 /* I0, I1 -> I2, I2 -> I3. */
1444 {
1447 }
1448 }
1451 {
1455 /* I0 -> I2; I1, I2 -> I3. */
1461 {
1464 }
1465 /* I0 -> I1; I1, I2 -> I3. */
1471 {
1474 }
1475 }
1476 }
1478 /* Try this insn with each REG_EQUAL note it links back to. */
1480 {
1486 /* Avoid using a register that may already been marked
1487 dead by an earlier instruction. */
1492 {
1493 /* Temporarily replace the set's source with the
1494 contents of the REG_EQUAL note. The insn will
1495 be deleted or recognized by try_combine. */
1503 last_combined_insn);
1506 {
1509 }
1511 }
1512 }
1517 retry:
1518 ;
1519 }
1520 }
1527 /* Clean up. */
1533 {
1536 {
1539 }
1541 }
1551 /* Make recognizer allow volatile MEMs again. */
1555 }
1557 /* Wipe the last_xxx fields of reg_stat in preparation for another pass. */
1559 static void
1561 {
1567 }
1568 \f
1569 /* Set up any promoted values for incoming argument registers. */
1571 static void
1573 {
1574 tree arg;
1579 {
1584 /* Only continue if the incoming argument is in a register. */
1588 /* Determine, if possible, whether all call sites of the current
1589 function lie within the current compilation unit. (This does
1590 take into account the exporting of a function via taking its
1591 address, and so forth.) */
1594 /* The mode and signedness of the argument before any promotions happen
1595 (equal to the mode of the pseudo holding it at that stage). */
1599 /* The mode and signedness of the argument after any source language and
1600 TARGET_PROMOTE_PROTOTYPES-driven promotions. */
1604 /* The mode and signedness of the argument as it is actually passed,
1605 see assign_parm_setup_reg in function.c. */
1609 /* The mode of the register in which the argument is being passed. */
1612 /* Eliminate sign extensions in the callee when:
1613 (a) A mode promotion has occurred; */
1616 /* (b) The mode of the register is the same as the mode of
1617 the argument as it is passed; */
1620 /* (c) There's no language level extension; */
1622 ;
1623 /* (c.1) All callers are from the current compilation unit. If that's
1624 the case we don't have to rely on an ABI, we only have to know
1625 what we're generating right now, and we know that we will do the
1626 mode1 to mode2 promotion with the given sign. */
1629 /* (c.2) The combination of the two promotions is useful. This is
1630 true when the signs match, or if the first promotion is unsigned.
1631 In the later case, (sign_extend (zero_extend x)) is the same as
1632 (zero_extend (zero_extend x)), so make sure to force UNS3 true. */
1638 /* Record that the value was promoted from mode1 to mode3,
1639 so that any sign extension at the head of the current
1640 function may be eliminated. */
1644 }
1645 }
1647 #ifdef SHORT_IMMEDIATES_SIGN_EXTEND
1648 /* If MODE has a precision lower than PREC and SRC is a non-negative constant
1649 that would appear negative in MODE, sign-extend SRC for use in nonzero_bits
1650 because some machines (maybe most) will actually do the sign-extension and
1651 this is the conservative approach.
1653 ??? For 2.5, try to tighten up the MD files in this regard instead of this
1654 kludge. */
1656 static rtx
1658 {
1666 }
1667 #endif
1669 /* Update RSP for pseudo-register X from INSN's REG_EQUAL note (if one exists)
1670 and SET. */
1672 static void
1674 rtx x)
1675 {
1684 #ifdef SHORT_IMMEDIATES_SIGN_EXTEND
1688 #endif
1690 /* Don't call nonzero_bits if it cannot change anything. */
1692 {
1697 }
1699 /* Don't call num_sign_bit_copies if it cannot change anything. */
1701 {
1704 {
1708 }
1711 }
1712 }
1714 /* Called via note_stores. If X is a pseudo that is narrower than
1715 HOST_BITS_PER_WIDE_INT and is being set, record what bits are known zero.
1717 If we are setting only a portion of X and we can't figure out what
1718 portion, assume all bits will be used since we don't know what will
1719 be happening.
1721 Similarly, set how many bits of X are known to be copies of the sign bit
1722 at all locations in the function. This is the smallest number implied
1723 by any set of X. */
1725 static void
1727 {
1732 /* If this register is undefined at the start of the file, we can't
1733 say what its contents were. */
1734 && ! REGNO_REG_SET_P
1737 {
1741 {
1745 }
1747 /* If this register is being initialized using itself, and the
1748 register is uninitialized in this basic block, and there are
1749 no LOG_LINKS which set the register, then part of the
1750 register is uninitialized. In that case we can't assume
1751 anything about the number of nonzero bits.
1753 ??? We could do better if we checked this in
1754 reg_{nonzero_bits,num_sign_bit_copies}_for_combine. Then we
1755 could avoid making assumptions about the insn which initially
1756 sets the register, while still using the information in other
1757 insns. We would have to be careful to check every insn
1758 involved in the combination. */
1764 {
1771 {
1775 }
1776 }
1778 /* If this is a complex assignment, see if we can convert it into a
1779 simple assignment. */
1782 /* If this is a simple assignment, or we have a paradoxical SUBREG,
1783 set what we know about X. */
1789 else
1790 {
1793 }
1794 }
1795 }
1796 \f
1797 /* See if INSN can be combined into I3. PRED, PRED2, SUCC and SUCC2 are
1798 optionally insns that were previously combined into I3 or that will be
1799 combined into the merger of INSN and I3. The order is PRED, PRED2,
1800 INSN, SUCC, SUCC2, I3.
1802 Return 0 if the combination is not allowed for any reason.
1804 If the combination is allowed, *PDEST will be set to the single
1805 destination of INSN and *PSRC to the single source, and this function
1806 will return 1. */
1808 static int
1812 {
1817 #ifdef AUTO_INC_DEC
1818 rtx link;
1819 #endif
1824 {
1826 {
1831 }
1836 }
1840 /* Can combine only if previous insn is a SET of a REG, a SUBREG or CC0.
1841 or a PARALLEL consisting of such a SET and CLOBBERs.
1843 If INSN has CLOBBER parallel parts, ignore them for our processing.
1844 By definition, these happen during the execution of the insn. When it
1845 is merged with another insn, all bets are off. If they are, in fact,
1846 needed and aren't also supplied in I3, they may be added by
1847 recog_for_combine. Otherwise, it won't match.
1849 We can also ignore a SET whose SET_DEST is mentioned in a REG_UNUSED
1850 note.
1852 Get the source and destination of INSN. If more than one, can't
1853 combine. */
1859 {
1861 {
1865 {
1866 /* This is important to combine floating point insns
1867 for the SH4 port. */
1869 /* Combining an isolated USE doesn't make sense.
1870 We depend here on combinable_i3pat to reject them. */
1871 /* The code below this loop only verifies that the inputs of
1872 the SET in INSN do not change. We call reg_set_between_p
1873 to verify that the REG in the USE does not change between
1874 I3 and INSN.
1875 If the USE in INSN was for a pseudo register, the matching
1876 insn pattern will likely match any register; combining this
1877 with any other USE would only be safe if we knew that the
1878 used registers have identical values, or if there was
1879 something to tell them apart, e.g. different modes. For
1880 now, we forgo such complicated tests and simply disallow
1881 combining of USES of pseudo registers with any other USE. */
1884 {
1889 do
1890 {
1900 }
1902 }
1905 /* We can ignore CLOBBERs. */
1910 /* Ignore SETs whose result isn't used but not those that
1911 have side-effects. */
1917 /* If we have already found a SET, this is a second one and
1918 so we cannot combine with this insn. */
1926 /* Anything else means we can't combine. */
1928 }
1929 }
1932 /* If SET_SRC is an ASM_OPERANDS we can't throw away these CLOBBERs,
1933 so don't do anything with it. */
1936 }
1937 else
1943 /* The simplification in expand_field_assignment may call back to
1944 get_last_value, so set safe guard here. */
1950 /* Do not eliminate user-specified register if it is in an
1951 asm input because we may break the register asm usage defined
1952 in GCC manual if allow to do so.
1953 Be aware that this may cover more cases than we expect but this
1954 should be harmless. */
1959 /* Don't eliminate a store in the stack pointer. */
1961 /* Don't combine with an insn that sets a register to itself if it has
1962 a REG_EQUAL note. This may be part of a LIBCALL sequence. */
1964 /* Can't merge an ASM_OPERANDS. */
1966 /* Can't merge a function call. */
1968 /* Don't eliminate a function call argument. */
1974 /* Don't substitute into an incremented register. */
1978 /* Don't substitute into a non-local goto, this confuses CFG. */
1980 /* Make sure that DEST is not used after SUCC but before I3. */
1981 || (!all_adjacent
1982 && ((succ2
1986 /* Make sure that the value that is to be substituted for the register
1987 does not use any registers whose values alter in between. However,
1988 If the insns are adjacent, a use can't cross a set even though we
1989 think it might (this can happen for a sequence of insns each setting
1990 the same destination; last_set of that register might point to
1991 a NOTE). If INSN has a REG_EQUIV note, the register is always
1992 equivalent to the memory so the substitution is valid even if there
1993 are intervening stores. Also, don't move a volatile asm or
1994 UNSPEC_VOLATILE across any other insns. */
1995 || (! all_adjacent
2001 /* Don't combine across a CALL_INSN, because that would possibly
2002 change whether the life span of some REGs crosses calls or not,
2003 and it is a pain to update that information.
2004 Exception: if source is a constant, moving it later can't hurt.
2005 Accept that as a special case. */
2009 /* DEST must either be a REG or CC0. */
2011 {
2012 /* If register alignment is being enforced for multi-word items in all
2013 cases except for parameters, it is possible to have a register copy
2014 insn referencing a hard register that is not allowed to contain the
2015 mode being copied and which would not be valid as an operand of most
2016 insns. Eliminate this problem by not combining with such an insn.
2018 Also, on some machines we don't want to extend the life of a hard
2019 register. */
2024 /* Don't extend the life of a hard register unless it is
2025 user variable (if we have few registers) or it can't
2026 fit into the desired register (meaning something special
2027 is going on).
2028 Also avoid substituting a return register into I3, because
2029 reload can't handle a conflict with constraints of other
2030 inputs. */
2034 }
2042 {
2045 /* If the clobber represents an earlyclobber operand, we must not
2046 substitute an expression containing the clobbered register.
2047 As we do not analyze the constraint strings here, we have to
2048 make the conservative assumption. However, if the register is
2049 a fixed hard reg, the clobber cannot represent any operand;
2050 we leave it up to the machine description to either accept or
2051 reject use-and-clobber patterns. */
2057 }
2059 /* If INSN contains anything volatile, or is an `asm' (whether volatile
2060 or not), reject, unless nothing volatile comes between it and I3 */
2063 {
2064 /* Make sure neither succ nor succ2 contains a volatile reference. */
2069 /* We'll check insns between INSN and I3 below. */
2070 }
2072 /* If INSN is an asm, and DEST is a hard register, reject, since it has
2073 to be an explicit register variable, and was chosen for a reason. */
2079 /* If INSN contains volatile references (specifically volatile MEMs),
2080 we cannot combine across any other volatile references.
2081 Even if INSN doesn't contain volatile references, any intervening
2082 volatile insn might affect machine state. */
2085 ? volatile_refs_p
2092 /* If INSN contains an autoincrement or autodecrement, make sure that
2093 register is not used between there and I3, and not already used in
2094 I3 either. Neither must it be used in PRED or SUCC, if they exist.
2095 Also insist that I3 not be a jump; if it were one
2096 and the incremented register were spilled, we would lose. */
2098 #ifdef AUTO_INC_DEC
2113 #endif
2115 /* Don't combine an insn that follows a CC0-setting insn.
2116 An insn that uses CC0 must not be separated from the one that sets it.
2117 We do, however, allow I2 to follow a CC0-setting insn if that insn
2118 is passed as I1; in that case it will be deleted also.
2119 We also allow combining in this case if all the insns are adjacent
2120 because that would leave the two CC0 insns adjacent as well.
2121 It would be more logical to test whether CC0 occurs inside I1 or I2,
2122 but that would be much slower, and this ought to be equivalent. */
2125 {
2130 }
2132 /* If we get here, we have passed all the tests and the combination is
2133 to be allowed. */
2139 }
2140 \f
2141 /* LOC is the location within I3 that contains its pattern or the component
2142 of a PARALLEL of the pattern. We validate that it is valid for combining.
2144 One problem is if I3 modifies its output, as opposed to replacing it
2145 entirely, we can't allow the output to contain I2DEST, I1DEST or I0DEST as
2146 doing so would produce an insn that is not equivalent to the original insns.
2148 Consider:
2150 (set (reg:DI 101) (reg:DI 100))
2151 (set (subreg:SI (reg:DI 101) 0) <foo>)
2153 This is NOT equivalent to:
2155 (parallel [(set (subreg:SI (reg:DI 100) 0) <foo>)
2156 (set (reg:DI 101) (reg:DI 100))])
2158 Not only does this modify 100 (in which case it might still be valid
2159 if 100 were dead in I2), it sets 101 to the ORIGINAL value of 100.
2161 We can also run into a problem if I2 sets a register that I1
2162 uses and I1 gets directly substituted into I3 (not via I2). In that
2163 case, we would be getting the wrong value of I2DEST into I3, so we
2164 must reject the combination. This case occurs when I2 and I1 both
2165 feed into I3, rather than when I1 feeds into I2, which feeds into I3.
2166 If I1_NOT_IN_SRC is nonzero, it means that finding I1 in the source
2167 of a SET must prevent combination from occurring. The same situation
2168 can occur for I0, in which case I0_NOT_IN_SRC is set.
2170 Before doing the above check, we first try to expand a field assignment
2171 into a set of logical operations.
2173 If PI3_DEST_KILLED is nonzero, it is a pointer to a location in which
2174 we place a register that is both set and used within I3. If more than one
2175 such register is detected, we fail.
2177 Return 1 if the combination is valid, zero otherwise. */
2179 static int
2182 {
2186 {
2191 rtx subdest;
2198 /* Check for the case where I3 modifies its output, as discussed
2199 above. We don't want to prevent pseudos from being combined
2200 into the address of a MEM, so only prevent the combination if
2201 i1 or i2 set the same MEM. */
2211 /* This is the same test done in can_combine_p except we can't test
2212 all_adjacent; we don't have to, since this instruction will stay
2213 in place, thus we are not considering increasing the lifetime of
2214 INNER_DEST.
2216 Also, if this insn sets a function argument, combining it with
2217 something that might need a spill could clobber a previous
2218 function argument; the all_adjacent test in can_combine_p also
2219 checks this; here, we do a more specific test for this case. */
2229 /* If DEST is used in I3, it is being killed in this insn, so
2230 record that for later. We have to consider paradoxical
2231 subregs here, since they kill the whole register, but we
2232 ignore partial subregs, STRICT_LOW_PART, etc.
2233 Never add REG_DEAD notes for the FRAME_POINTER_REGNUM or the
2234 STACK_POINTER_REGNUM, since these are always considered to be
2235 live. Similarly for ARG_POINTER_REGNUM if it is fixed. */
2245 #if !HARD_FRAME_POINTER_IS_FRAME_POINTER
2247 #endif
2252 {
2257 }
2258 }
2261 {
2268 }
2271 }
2272 \f
2273 /* Return 1 if X is an arithmetic expression that contains a multiplication
2274 and division. We don't count multiplications by powers of two here. */
2276 static int
2278 {
2280 {
2296 }
2297 }
2298 \f
2299 /* Determine whether INSN can be used in a combination. Return nonzero if
2300 not. This is used in try_combine to detect early some cases where we
2301 can't perform combinations. */
2303 static int
2305 {
2306 rtx set;
2309 /* If this isn't really an insn, we can't do anything.
2310 This can occur when flow deletes an insn that it has merged into an
2311 auto-increment address. */
2315 /* Never combine loads and stores involving hard regs that are likely
2316 to be spilled. The register allocator can usually handle such
2317 reg-reg moves by tying. If we allow the combiner to make
2318 substitutions of likely-spilled regs, reload might die.
2319 As an exception, we allow combinations involving fixed regs; these are
2320 not available to the register allocator so there's no risk involved. */
2341 }
2343 struct likely_spilled_retval_info
2344 {
2347 };
2349 /* Called via note_stores by likely_spilled_retval_p. Remove from info->mask
2350 hard registers that are known to be written to / clobbered in full. */
2351 static void
2353 {
2370 else
2373 }
2375 /* Return nonzero iff part of the return value is live during INSN, and
2376 it is likely spilled. This can happen when more than one insn is needed
2377 to copy the return value, e.g. when we consider to combine into the
2378 second copy insn for a complex value. */
2380 static int
2382 {
2384 rtx reg;
2387 /* We assume here that no machine mode needs more than
2388 32 hard registers when the value overlaps with a register
2389 for which TARGET_FUNCTION_VALUE_REGNO_P is true. */
2404 /* Disregard parts of the return value that are set later. */
2413 /* Check if any of the (probably) live return value registers is
2414 likely spilled. */
2415 nregs --;
2416 do
2417 {
2423 }
2425 /* Adjust INSN after we made a change to its destination.
2427 Changing the destination can invalidate notes that say something about
2428 the results of the insn and a LOG_LINK pointing to the insn. */
2430 static void
2432 {
2433 /* For notes, be conservative and simply remove them. */
2436 /* The new insn will have a destination that was previously the destination
2437 of an insn just above it. Call distribute_links to make a LOG_LINK from
2438 the next use of that destination. */
2454 }
2456 /* Return TRUE if combine can reuse reg X in mode MODE.
2457 ADDED_SETS is nonzero if the original set is still required. */
2458 static bool
2460 {
2467 /* Allow hard registers if the new mode is legal, and occupies no more
2468 registers than the old mode. */
2473 /* Or a pseudo that is only used once. */
2476 && !added_sets
2478 }
2481 /* Check whether X, the destination of a set, refers to part of
2482 the register specified by REG. */
2484 static bool
2486 {
2487 /* Check that reg is an integer mode register. */
2498 }
2500 /* Delete the unconditional jump INSN and adjust the CFG correspondingly.
2501 Note that the INSN should be deleted *after* removing dead edges, so
2502 that the kept edge is the fallthrough edge for a (set (pc) (pc))
2503 but not for a (set (pc) (label_ref FOO)). */
2505 static void
2507 {
2515 {
2520 /* Remove barriers from the footer if there are any. */
2523 {
2526 else
2530 }
2533 }
2534 }
2536 /* Return whether PAT is a PARALLEL of exactly N register SETs followed
2537 by an arbitrary number of CLOBBERs. */
2538 static bool
2540 {
2558 }
2560 #if !HAVE_cc0
2561 /* Return whether INSN, a PARALLEL of N register SETs (and maybe some
2562 CLOBBERs), can be split into individual SETs in that order, without
2563 changing semantics. */
2564 static bool
2566 {
2574 {
2583 }
2586 }
2587 #endif
2589 /* Try to combine the insns I0, I1 and I2 into I3.
2590 Here I0, I1 and I2 appear earlier than I3.
2591 I0 and I1 can be zero; then we combine just I2 into I3, or I1 and I2 into
2592 I3.
2594 If we are combining more than two insns and the resulting insn is not
2595 recognized, try splitting it into two insns. If that happens, I2 and I3
2596 are retained and I1/I0 are pseudo-deleted by turning them into a NOTE.
2597 Otherwise, I0, I1 and I2 are pseudo-deleted.
2599 Return 0 if the combination does not work. Then nothing is changed.
2600 If we did the combination, return the insn at which combine should
2601 resume scanning.
2603 Set NEW_DIRECT_JUMP_P to a nonzero value if try_combine creates a
2604 new direct jump instruction.
2606 LAST_COMBINED_INSN is either I3, or some insn after I3 that has
2607 been I3 passed to an earlier try_combine within the same basic
2608 block. */
2613 {
2614 /* New patterns for I3 and I2, respectively. */
2618 /* Indicates need to preserve SET in I0, I1 or I2 in I3 if it is not
2619 dead. */
2621 /* Total number of SETs to put into I3. */
2623 /* Nonzero if I2's or I1's body now appears in I3. */
2625 /* INSN_CODEs for new I3, new I2, and user of condition code. */
2627 /* Contains I3 if the destination of I3 is used in its source, which means
2628 that the old life of I3 is being killed. If that usage is placed into
2629 I2 and not in I3, a REG_DEAD note must be made. */
2631 /* SET_DEST and SET_SRC of I2, I1 and I0. */
2633 /* Copy of SET_SRC of I1 and I0, if needed. */
2635 /* Set if I2DEST was reused as a scratch register. */
2637 /* The PATTERNs of I0, I1, and I2, or a copy of them in certain cases. */
2639 /* Indicates if I2DEST or I1DEST is in I2SRC or I1_SRC. */
2644 /* Notes that must be added to REG_NOTES in I3 and I2. */
2646 /* Notes that we substituted I3 into I2 instead of the normal case. */
2648 /* Notes that I1, I2 or I3 is a MULT operation. */
2655 rtx temp_expr;
2658 rtx new_other_notes;
2661 /* Immediately return if any of I0,I1,I2 are the same insn (I3 can
2662 never be). */
2666 /* Only try four-insn combinations when there's high likelihood of
2667 success. Look for simple insns, such as loads of constants or
2668 binary operations involving a constant. */
2670 {
2680 {
2683 rtx src;
2688 {
2691 }
2693 ngood++;
2696 nshift++;
2697 }
2699 /* If I0 loads a memory and I3 sets the same memory, then I1 and I2
2700 are likely manipulating its value. Ideally we'll be able to combine
2701 all four insns into a bitfield insertion of some kind.
2703 Note the source in I0 might be inside a sign/zero extension and the
2704 memory modes in I0 and I3 might be different. So extract the address
2705 from the destination of I3 and search for it in the source of I0.
2707 In the event that there's a match but the source/dest do not actually
2708 refer to the same memory, the worst that happens is we try some
2709 combinations that we wouldn't have otherwise. */
2711 /* Ensure the source of SET0 is a MEM, possibly buried inside
2712 an extension. */
2718 /* Ensure the destination of SET3 is a MEM. */
2720 /* Would it be better to extract the base address for the MEM
2721 in SET3 and look for that? I don't have cases where it matters
2722 but I could envision such cases. */
2728 }
2730 /* Exit early if one of the insns involved can't be used for
2731 combinations. */
2742 combine_attempts++;
2745 /* Reset the hard register usage information. */
2749 {
2756 else
2759 }
2761 /* If multiple insns feed into one of I2 or I3, they can be in any
2762 order. To simplify the code below, reorder them in sequence. */
2772 /* First check for one important special case that the code below will
2773 not handle. Namely, the case where I1 is zero, I2 is a PARALLEL
2774 and I3 is a SET whose SET_SRC is a SET_DEST in I2. In that case,
2775 we may be able to replace that destination with the destination of I3.
2776 This occurs in the common code where we compute both a quotient and
2777 remainder into a structure, in which case we want to do the computation
2778 directly into the structure to avoid register-register copies.
2780 Note that this case handles both multiple sets in I2 and also cases
2781 where I2 has a number of CLOBBERs inside the PARALLEL.
2783 We make very conservative checks below and only try to handle the
2784 most common cases of this. For example, we only handle the case
2785 where I2 and I3 are adjacent to avoid making difficult register
2786 usage tests. */
2794 /* If the dest of I3 is a ZERO_EXTRACT or STRICT_LOW_PART, the code
2795 below would need to check what is inside (and reg_overlap_mentioned_p
2796 doesn't support those codes anyway). Don't allow those destinations;
2797 the resulting insn isn't likely to be recognized anyway. */
2803 {
2806 /* Make sure that the destination of I3,
2807 which we are going to substitute into one output of I2,
2808 is not used within another output of I2. We must avoid making this:
2809 (parallel [(set (mem (reg 69)) ...)
2810 (set (reg 69) ...)])
2811 which is not well-defined as to order of actions.
2812 (Besides, reload can't handle output reloads for this.)
2814 The problem can also happen if the dest of I3 is a memory ref,
2815 if another dest in I2 is an indirect memory ref. */
2823 /* Make sure this PARALLEL is not an asm. We do not allow combining
2824 that usually (see can_combine_p), so do not here either. */
2834 {
2835 combine_merges++;
2845 /* Replace the dest in I2 with our dest and make the resulting
2846 insn the new pattern for I3. Then skip to where we validate
2847 the pattern. Everything was set up above. */
2852 }
2853 }
2855 /* If I2 is setting a pseudo to a constant and I3 is setting some
2856 sub-part of it to another constant, merge them by making a new
2857 constant. */
2864 {
2870 {
2873 {
2879 }
2880 }
2881 else
2882 {
2887 }
2890 {
2891 /* If this is the low part, we're done. */
2893 ;
2894 /* Handle the case where inner is twice the size of outer. */
2898 /* Otherwise give up for now. */
2899 else
2901 }
2904 {
2908 wide_int o
2913 combine_merges++;
2920 /* Replace the source in I2 with the new constant and make the
2921 resulting insn the new pattern for I3. Then skip to where we
2922 validate the pattern. Everything was set up above. */
2928 /* The dest of I3 has been replaced with the dest of I2. */
2931 }
2932 }
2934 #if !HAVE_cc0
2935 /* If we have no I1 and I2 looks like:
2936 (parallel [(set (reg:CC X) (compare:CC OP (const_int 0)))
2937 (set Y OP)])
2938 make up a dummy I1 that is
2939 (set Y OP)
2940 and change I2 to be
2941 (set (reg:CC X) (compare:CC Y (const_int 0)))
2943 (We can ignore any trailing CLOBBERs.)
2945 This undoes a previous combination and allows us to match a branch-and-
2946 decrement insn. */
2958 {
2959 /* We make I1 with the same INSN_UID as I2. This gives it
2960 the same DF_INSN_LUID for value tracking. Our fake I1 will
2961 never appear in the insn stream so giving it the same INSN_UID
2962 as I2 will not cause a problem. */
2975 }
2977 /* If I2 is a PARALLEL of two SETs of REGs (and perhaps some CLOBBERs),
2978 make those two SETs separate I1 and I2 insns, and make an I0 that is
2979 the original I1. */
2985 {
2986 /* If there is no I1, there is no I0 either. */
2989 /* We make I1 with the same INSN_UID as I2. This gives it
2990 the same DF_INSN_LUID for value tracking. Our fake I1 will
2991 never appear in the insn stream so giving it the same INSN_UID
2992 as I2 will not cause a problem. */
3000 }
3001 #endif
3003 /* Verify that I2 and I1 are valid for combining. */
3009 {
3012 }
3014 /* Record whether I2DEST is used in I2SRC and similarly for the other
3015 cases. Knowing this will help in register status updating below. */
3026 /* For the earlier insns, determine which of the subsequent ones they
3027 feed. */
3034 /* Ensure that I3's pattern can be the destination of combines. */
3040 {
3043 }
3045 /* See if any of the insns is a MULT operation. Unless one is, we will
3046 reject a combination that is, since it must be slower. Be conservative
3047 here. */
3055 /* If I3 has an inc, then give up if I1 or I2 uses the reg that is inc'd.
3056 We used to do this EXCEPT in one case: I3 has a post-inc in an
3057 output operand. However, that exception can give rise to insns like
3058 mov r3,(r3)+
3059 which is a famous insn on the PDP-11 where the value of r3 used as the
3060 source was model-dependent. Avoid this sort of thing. */
3062 #if 0
3068 /* It's not the exception. */
3069 #endif
3070 #ifdef AUTO_INC_DEC
3071 {
3072 rtx link;
3078 {
3081 }
3082 }
3083 #endif
3085 /* See if the SETs in I1 or I2 need to be kept around in the merged
3086 instruction: whenever the value set there is still needed past I3.
3087 For the SET in I2, this is easy: we see if I2DEST dies or is set in I3.
3089 For the SET in I1, we have two cases: if I1 and I2 independently feed
3090 into I3, the set in I1 needs to be kept around unless I1DEST dies
3091 or is set in I3. Otherwise (if I1 feeds I2 which feeds I3), the set
3092 in I1 needs to be kept around unless I1DEST dies or is set in either
3093 I2 or I3. The same considerations apply to I0. */
3100 else
3108 else
3111 /* We are about to copy insns for the case where they need to be kept
3112 around. Check that they can be copied in the merged instruction. */
3118 {
3121 }
3123 /* If the set in I2 needs to be kept around, we must make a copy of
3124 PATTERN (I2), so that when we substitute I1SRC for I1DEST in
3125 PATTERN (I2), we are only substituting for the original I1DEST, not into
3126 an already-substituted copy. This also prevents making self-referential
3127 rtx. If I2 is a PARALLEL, we just need the piece that assigns I2SRC to
3128 I2DEST. */
3131 {
3134 else
3136 }
3139 {
3142 else
3144 }
3147 {
3150 else
3152 }
3154 combine_merges++;
3156 /* Substitute in the latest insn for the regs set by the earlier ones. */
3162 /* Many machines that don't use CC0 have insns that can both perform an
3163 arithmetic operation and set the condition code. These operations will
3164 be represented as a PARALLEL with the first element of the vector
3165 being a COMPARE of an arithmetic operation with the constant zero.
3166 The second element of the vector will set some pseudo to the result
3167 of the same arithmetic operation. If we simplify the COMPARE, we won't
3168 match such a pattern and so will generate an extra insn. Here we test
3169 for this case, where both the comparison and the operation result are
3170 needed, and make the PARALLEL by just replacing I2DEST in I3SRC with
3171 I2SRC. Later we will make the PARALLEL that contains I2. */
3177 {
3178 rtx newpat_dest;
3192 {
3197 }
3199 /* Do the rest only if op1 is const0_rtx, which may be the
3200 result of simplification. */
3202 {
3203 /* If a single use of the CC is found, prepare to modify it
3204 when SELECT_CC_MODE returns a new CC-class mode, or when
3205 the above simplify_compare_const() returned a new comparison
3206 operator. undobuf.other_insn is assigned the CC use insn
3207 when modifying it. */
3209 {
3210 #ifdef SELECT_CC_MODE
3211 machine_mode new_mode
3216 {
3221 else
3222 {
3225 }
3226 }
3227 #endif
3228 /* Cases for modifying the CC-using comparison. */
3230 /* ??? Do we need to verify the zero rtx? */
3232 {
3233 /* Replace cc_use_loc with entire new RTX. */
3238 }
3240 {
3241 /* Just replace the CC reg with a new mode. */
3244 }
3245 }
3247 /* Now we modify the current newpat:
3248 First, SET_DEST(newpat) is updated if the CC mode has been
3249 altered. For targets without SELECT_CC_MODE, this should be
3250 optimized away. */
3253 /* This is always done to propagate i2src into newpat. */
3256 /* Create new version of i2pat if needed; the below PARALLEL
3257 creation needs this to work correctly. */
3261 }
3262 }
3265 {
3266 /* It is possible that the source of I2 or I1 may be performing
3267 an unneeded operation, such as a ZERO_EXTEND of something
3268 that is known to have the high part zero. Handle that case
3269 by letting subst look at the inner insns.
3271 Another way to do this would be to have a function that tries
3272 to simplify a single insn instead of merging two or more
3273 insns. We don't do this because of the potential of infinite
3274 loops and because of the potential extra memory required.
3275 However, doing it the way we are is a bit of a kludge and
3276 doesn't catch all cases.
3278 But only do this if -fexpensive-optimizations since it slows
3279 things down and doesn't usually win.
3281 This is not done in the COMPARE case above because the
3282 unmodified I2PAT is used in the PARALLEL and so a pattern
3283 with a modified I2SRC would not match. */
3286 {
3287 /* Pass pc_rtx so no substitutions are done, just
3288 simplifications. */
3290 {
3293 }
3297 }
3302 /* If I1 feeds into I2 and I1DEST is in I1SRC, we need to make a unique
3303 copy of I2SRC each time we substitute it, in order to avoid creating
3304 self-referential RTL when we will be substituting I1SRC for I1DEST
3305 later. Likewise if I0 feeds into I2, either directly or indirectly
3306 through I1, and I0DEST is in I0SRC. */
3313 /* Record whether I2's body now appears within I3's body. */
3315 }
3317 /* If we already got a failure, don't try to do more. Otherwise, try to
3318 substitute I1 if we have it. */
3321 {
3322 /* Check that an autoincrement side-effect on I1 has not been lost.
3323 This happens if I1DEST is mentioned in I2 and dies there, and
3324 has disappeared from the new pattern. */
3326 && i1_feeds_i2_n
3329 /* Before we can do this substitution, we must redo the test done
3330 above (see detailed comments there) that ensures I1DEST isn't
3331 mentioned in any SETs in NEWPAT that are field assignments. */
3334 {
3337 }
3342 /* If the following substitution will modify I1SRC, make a copy of it
3343 for the case where it is substituted for I1DEST in I2PAT later. */
3347 /* If I0 feeds into I1 and I0DEST is in I0SRC, we need to make a unique
3348 copy of I1SRC each time we substitute it, in order to avoid creating
3349 self-referential RTL when we will be substituting I0SRC for I0DEST
3350 later. */
3355 /* Record whether I1's body now appears within I3's body. */
3357 }
3359 /* Likewise for I0 if we have it. */
3362 {
3369 {
3372 }
3374 /* If the following substitution will modify I0SRC, make a copy of it
3375 for the case where it is substituted for I0DEST in I1PAT later. */
3378 /* And a copy for I0DEST in I2PAT substitution. */
3387 }
3389 /* Fail if an autoincrement side-effect has been duplicated. Be careful
3390 to count all the ways that I2SRC and I1SRC can be used. */
3401 /* Fail if we tried to make a new register. */
3403 /* Fail if we couldn't do something and have a CLOBBER. */
3405 /* Fail if this new pattern is a MULT and we didn't have one before
3406 at the outer level. */
3409 {
3412 }
3414 /* If the actions of the earlier insns must be kept
3415 in addition to substituting them into the latest one,
3416 we must make a new PARALLEL for the latest insn
3417 to hold additional the SETs. */
3420 {
3422 combine_extras++;
3425 {
3431 }
3432 else
3433 {
3438 }
3444 {
3450 }
3452 {
3461 }
3462 }
3464 validate_replacement:
3466 /* Note which hard regs this insn has as inputs. */
3469 /* If recog_for_combine fails, it strips existing clobbers. If we'll
3470 consider splitting this pattern, we might need these clobbers. */
3473 {
3479 }
3481 /* We have recognized nothing yet. */
3484 /* See if this is a PARALLEL of two SETs where one SET's destination is
3485 a register that is unused and this isn't marked as an instruction that
3486 might trap in an EH region. In that case, we just need the other SET.
3487 We prefer this over the PARALLEL.
3489 This can occur when simplifying a divmod insn. We *must* test for this
3490 case here because the code below that splits two independent SETs doesn't
3491 handle this case correctly when it updates the register status.
3493 It's pointless doing this if we originally had two sets, one from
3494 i3, and one from i2. Combining then splitting the parallel results
3495 in the original i2 again plus an invalid insn (which we delete).
3496 The net effect is only to move instructions around, which makes
3497 debug info less accurate. */
3502 {
3513 {
3516 }
3525 {
3531 }
3535 }
3537 /* Is the result of combination a valid instruction? */
3541 /* If we were combining three insns and the result is a simple SET
3542 with no ASM_OPERANDS that wasn't recognized, try to split it into two
3543 insns. There are two ways to do this. It can be split using a
3544 machine-specific method (like when you have an addition of a large
3545 constant) or by combine in the function find_split_point. */
3549 {
3553 /* See if the MD file can split NEWPAT. If it can't, see if letting it
3554 use I2DEST as a scratch register will help. In the latter case,
3555 convert I2DEST to the mode of the source of NEWPAT if we can. */
3559 /* We can only use I2DEST as a scratch reg if it doesn't overlap any
3560 inputs of NEWPAT. */
3562 /* ??? If I2DEST is not safe, and I1DEST exists, then it would be
3563 possible to try that as a scratch reg. This would require adding
3564 more code to make it work though. */
3567 {
3570 /* First try to split using the original register as a
3571 scratch register. */
3575 i2dest)));
3578 /* If that didn't work, try changing the mode of I2DEST if
3579 we can. */
3584 {
3586 rtx ni2dest;
3590 else
3591 {
3594 }
3596 parallel = (gen_rtx_PARALLEL
3600 ni2dest))));
3605 {
3613 }
3614 }
3617 }
3619 /* If recog_for_combine has discarded clobbers, try to use them
3620 again for the split. */
3622 {
3625 }
3628 {
3633 }
3637 {
3647 /* If I2 or I3 has multiple SETs, we won't know how to track
3648 register status, so don't use these insns. If I2's destination
3649 is used between I2 and I3, we also can't use these insns. */
3659 /* It is possible that both insns now set the destination of I3.
3660 If so, we must show an extra use of it. */
3663 {
3682 }
3683 }
3685 /* If we can split it and use I2DEST, go ahead and see if that
3686 helps things be recognized. Verify that none of the registers
3687 are set between I2 and I3. */
3691 /* We need I2DEST in the proper mode. If it is a hard register
3692 or the only use of a pseudo, we can change its mode.
3693 Make sure we don't change a hard register to have a mode that
3694 isn't valid for it, or change the number of registers. */
3701 /* We can't overwrite I2DEST if its value is still used by
3702 NEWPAT. */
3704 {
3713 /* *SPLIT may be part of I2SRC, so make sure we have the
3714 original expression around for later debug processing.
3715 We should not need I2SRC any more in other cases. */
3718 else
3721 /* Get NEWDEST as a register in the proper mode. We have already
3722 validated that we can do this. */
3724 {
3727 else
3728 {
3731 }
3732 }
3734 /* If *SPLIT is a (mult FOO (const_int pow2)), convert it to
3735 an ASHIFT. This can occur if it was inside a PLUS and hence
3736 appeared to be a memory address. This is a kludge. */
3741 {
3744 /* Update split_code because we may not have a multiply
3745 anymore. */
3747 }
3749 /* Similarly for (plus (mult FOO (const_int pow2))). */
3755 {
3759 /* Update split_code because we may not have a multiply
3760 anymore. */
3762 }
3764 #ifdef INSN_SCHEDULING
3765 /* If *SPLIT is a paradoxical SUBREG, when we split it, it should
3766 be written as a ZERO_EXTEND. */
3768 {
3769 #ifdef LOAD_EXTEND_OP
3770 /* Or as a SIGN_EXTEND if LOAD_EXTEND_OP says that that's
3771 what it really is. */
3776 else
3777 #endif
3780 }
3781 #endif
3783 /* Attempt to split binary operators using arithmetic identities. */
3787 {
3794 /* Split "X = Y op Y" as "Z = Y; X = Z op Z". */
3796 {
3801 }
3802 /* Split "((P op Q) op R) op S" where op is PLUS or MULT. */
3809 {
3815 /* Split both "((X op Y) op X) op Y" and
3816 "((X op Y) op Y) op X" as "T op T" where T is
3817 "X op Y". */
3820 {
3825 }
3826 /* Split "((X op X) op Y) op Y)" as "T op T" where
3827 T is "X op Y". */
3829 {
3835 }
3836 }
3837 }
3840 {
3843 }
3847 /* recog_for_combine might have added CLOBBERs to newi2pat.
3848 Make sure NEWPAT does not depend on the clobbered regs. */
3852 {
3855 {
3858 }
3859 }
3861 /* If the split point was a MULT and we didn't have one before,
3862 don't use one now. */
3865 }
3866 }
3868 /* Check for a case where we loaded from memory in a narrow mode and
3869 then sign extended it, but we need both registers. In that case,
3870 we have a PARALLEL with both loads from the same memory location.
3871 We can split this into a load from memory followed by a register-register
3872 copy. This saves at least one insn, more if register allocation can
3873 eliminate the copy.
3875 We cannot do this if the destination of the first assignment is a
3876 condition code register or cc0. We eliminate this case by making sure
3877 the SET_DEST and SET_SRC have the same mode.
3879 We cannot do this if the destination of the second assignment is
3880 a register that we have already assumed is zero-extended. Similarly
3881 for a SUBREG of such a register. */
3916 {
3917 rtx ni2dest;
3931 }
3933 /* Similarly, check for a case where we have a PARALLEL of two independent
3934 SETs but we started with three insns. In this case, we can do the sets
3935 as two separate insns. This case occurs when some SET allows two
3936 other insns to combine, but the destination of that SET is still live.
3938 Also do this if we started with two insns and (at least) one of the
3939 resulting sets is a noop; this noop will be deleted later. */
3958 {
3962 /* Normally, it doesn't matter which of the two is done first,
3963 but the one that references cc0 can't be the second, and
3964 one which uses any regs/memory set in between i2 and i3 can't
3965 be first. The PARALLEL might also have been pre-existing in i3,
3966 so we need to make sure that we won't wrongly hoist a SET to i2
3967 that would conflict with a death note present in there. */
3975 /* If I3 is a jump, ensure that set0 is a jump so that
3976 we do not create invalid RTL. */
3978 )
3979 {
3982 }
3990 /* If I3 is a jump, ensure that set1 is a jump so that
3991 we do not create invalid RTL. */
3993 )
3994 {
3997 }
3998 else
3999 {
4002 }
4007 {
4008 /* recog_for_combine might have added CLOBBERs to newi2pat.
4009 Make sure NEWPAT does not depend on the clobbered regs. */
4011 {
4014 {
4017 {
4020 }
4021 }
4022 }
4025 }
4026 }
4028 /* If it still isn't recognized, fail and change things back the way they
4029 were. */
4031 /* Is the result a reasonable ASM_OPERANDS? */
4033 {
4036 }
4038 /* If we had to change another insn, make sure it is valid also. */
4040 {
4048 {
4051 }
4052 }
4054 /* If I2 is the CC0 setter and I3 is the CC0 user then check whether
4055 they are adjacent to each other or not. */
4057 {
4061 {
4064 }
4065 }
4067 /* Only allow this combination if insn_rtx_costs reports that the
4068 replacement instructions are cheaper than the originals. */
4070 {
4073 }
4076 {
4081 {
4086 /* Temporarily revert mode back. */
4090 {
4091 /* If we used i2dest as a scratch register with a
4092 different mode, substitute it for the original
4093 i2src while its original mode is temporarily
4094 restored, and then clear i2scratch so that we don't
4095 do it again later. */
4097 this_basic_block);
4099 /* Put back the new mode. */
4101 }
4102 else
4103 {
4108 {
4111 }
4112 else
4113 {
4120 }
4122 /* We're dealing with a reg that changed mode but not
4123 meaning, so we want to turn it into a subreg for
4124 the new mode. However, because of REG sharing and
4125 because its mode had already changed, we have to do
4126 it in two steps. First, replace any debug uses of
4127 reg, with its original mode temporarily restored,
4128 with this copy we have created; then, replace the
4129 copy with the SUBREG of the original shared reg,
4130 once again changed to the new mode. */
4132 this_basic_block);
4136 this_basic_block);
4137 }
4138 }
4139 }
4141 /* If we will be able to accept this, we have made a
4142 change to the destination of I3. This requires us to
4143 do a few adjustments. */
4146 {
4149 }
4151 /* We now know that we can do this combination. Merge the insns and
4152 update the status of registers and LOG_LINKS. */
4155 {
4160 /* If any of the notes in OTHER_INSN were REG_DEAD or REG_UNUSED,
4161 ensure that they are still valid. Then add any non-duplicate
4162 notes added by recog_for_combine. */
4164 {
4174 }
4178 NULL_RTX);
4179 }
4182 {
4185 rtx ni2dest;
4187 /* I3 now uses what used to be its destination and which is now
4188 I2's destination. This requires us to do a few adjustments. */
4192 /* We need a LOG_LINK from I3 to I2. But we used to have one,
4193 so we still will.
4195 However, some later insn might be using I2's dest and have
4196 a LOG_LINK pointing at I3. We must remove this link.
4197 The simplest way to remove the link is to point it at I1,
4198 which we know will be a NOTE. */
4200 /* newi2pat is usually a SET here; however, recog_for_combine might
4201 have added some clobbers. */
4204 else
4211 {
4213 {
4219 }
4220 }
4221 }
4223 {
4228 /* Compute which registers we expect to eliminate. newi2pat may be setting
4229 either i3dest or i2dest, so we must check it. */
4232 || !i2dest_killed
4234 /* For i1, we need to compute both local elimination and global
4235 elimination information with respect to newi2pat because i1dest
4236 may be the same as i3dest, in which case newi2pat may be setting
4237 i1dest. Global information is used when distributing REG_DEAD
4238 note for i2 and i3, in which case it does matter if newi2pat sets
4239 i1dest or not.
4241 Local information is used when distributing REG_DEAD note for i1,
4242 in which case it doesn't matter if newi2pat sets i1dest or not.
4243 See PR62151, if we have four insns combination:
4244 i0: r0 <- i0src
4245 i1: r1 <- i1src (using r0)
4246 REG_DEAD (r0)
4247 i2: r0 <- i2src (using r1)
4248 i3: r3 <- i3src (using r0)
4249 ix: using r0
4250 From i1's point of view, r0 is eliminated, no matter if it is set
4251 by newi2pat or not. In other words, REG_DEAD info for r0 in i1
4252 should be discarded.
4254 Note local information only affects cases in forms like "I1->I2->I3",
4255 "I0->I1->I2->I3" or "I0&I1->I2, I2->I3". For other cases like
4256 "I0->I1, I1&I2->I3" or "I1&I2->I3", newi2pat won't set i1dest or
4257 i0dest anyway. */
4259 || !i1dest_killed
4264 /* Same case as i1. */
4271 /* Get the old REG_NOTES and LOG_LINKS from all our insns and
4272 clear them. */
4280 /* Ensure that we do not have something that should not be shared but
4281 occurs multiple times in the new insns. Check this by first
4282 resetting all the `used' flags and then copying anything is shared. */
4306 {
4313 {
4314 /* I2SRC must still be meaningful at this point. Some splitting
4315 operations can invalidate I2SRC, but those operations do not
4316 apply to calls. */
4319 }
4327 }
4332 /* We had one special case above where I2 had more than one set and
4333 we replaced a destination of one of those sets with the destination
4334 of I3. In that case, we have to update LOG_LINKS of insns later
4335 in this basic block. Note that this (expensive) case is rare.
4337 Also, in this case, we must pretend that all REG_NOTEs for I2
4338 actually came from I3, so that REG_UNUSED notes from I2 will be
4339 properly handled. */
4342 {
4351 temp_insn
4361 {
4366 }
4367 else
4370 }
4378 {
4381 this_basic_block);
4384 }
4385 else
4386 {
4389 this_basic_block);
4391 }
4394 {
4399 this_basic_block);
4401 }
4404 {
4409 this_basic_block);
4411 }
4413 /* Get death notes for everything that is now used in either I3 or
4414 I2 and used to die in a previous insn. If we built two new
4415 patterns, move from I1 to I2 then I2 to I3 so that we get the
4416 proper movement on registers that I2 modifies. */
4422 else
4428 /* Distribute all the LOG_LINKS and REG_NOTES from I1, I2, and I3. */
4445 /* Distribute any notes added to I2 or I3 by recog_for_combine. We
4446 know these are REG_UNUSED and want them to go to the desired insn,
4447 so we always pass it as i3. */
4451 NULL_RTX);
4455 NULL_RTX);
4457 /* If I3DEST was used in I3SRC, it really died in I3. We may need to
4458 put a REG_DEAD note for it somewhere. If NEWI2PAT exists and sets
4459 I3DEST, the death must be somewhere before I2, not I3. If we passed I3
4460 in that case, it might delete I2. Similarly for I2 and I1.
4461 Show an additional death due to the REG_DEAD note we make here. If
4462 we discard it in distribute_notes, we will decrement it again. */
4465 {
4470 else
4473 }
4476 {
4481 else
4484 }
4487 {
4492 else
4495 }
4498 {
4503 else
4506 }
4514 {
4519 /* The insn that used to set this register doesn't exist, and
4520 this life of the register may not exist either. See if one of
4521 I3's links points to an insn that sets I2DEST. If it does,
4522 that is now the last known value for I2DEST. If we don't update
4523 this and I2 set the register to a value that depended on its old
4524 contents, we will get confused. If this insn is used, thing
4525 will be set correctly in combine_instructions. */
4533 /* If the reg formerly set in I2 died only once and that was in I3,
4534 zero its use count so it won't make `reload' do any work. */
4537 && ! i2dest_in_i2src
4540 }
4543 {
4556 && ! i1dest_in_i1src
4559 }
4562 {
4575 && ! i0dest_in_i0src
4578 }
4580 /* Update reg_stat[].nonzero_bits et al for any changes that may have
4581 been made to this insn. The order is important, because newi2pat
4582 can affect nonzero_bits of newpat. */
4586 }
4589 {
4591 {
4594 }
4596 }
4599 {
4601 {
4604 }
4606 }
4609 {
4611 {
4614 }
4616 }
4619 {
4621 {
4624 }
4626 }
4629 {
4631 {
4634 }
4636 }
4638 /* Set new_direct_jump_p if a new return or simple jump instruction
4639 has been created. Adjust the CFG accordingly. */
4641 {
4645 }
4650 {
4653 }
4655 /* A noop might also need cleaning up of CFG, if it comes from the
4656 simplification of a jump. */
4661 {
4664 }
4671 {
4674 }
4676 combine_successes++;
4683 else
4685 }
4686 \f
4687 /* Get a marker for undoing to the current state. */
4691 {
4693 }
4695 /* Undo the modifications up to the marker. */
4697 static void
4699 {
4703 {
4708 {
4723 }
4727 }
4730 }
4732 /* Undo all the modifications recorded in undobuf. */
4734 static void
4736 {
4738 }
4740 /* We've committed to accepting the changes we made. Move all
4741 of the undos to the free list. */
4743 static void
4745 {
4749 {
4753 }
4755 }
4756 \f
4757 /* Find the innermost point within the rtx at LOC, possibly LOC itself,
4758 where we have an arithmetic expression and return that point. LOC will
4759 be inside INSN.
4761 try_combine will call this function to see if an insn can be split into
4762 two insns. */
4766 {
4775 /* First special-case some codes. */
4777 {
4779 #ifdef INSN_SCHEDULING
4780 /* If we are making a paradoxical SUBREG invalid, it becomes a split
4781 point. */
4784 #endif
4788 /* If we have (mem (const ..)) or (mem (symbol_ref ...)), split it
4789 using LO_SUM and HIGH. */
4792 {
4800 }
4802 /* If we have a PLUS whose second operand is a constant and the
4803 address is not valid, perhaps will can split it up using
4804 the machine-specific way to split large constants. We use
4805 the first pseudo-reg (one of the virtual regs) as a placeholder;
4806 it will not remain in the result. */
4811 {
4814 subst_insn);
4816 /* This should have produced two insns, each of which sets our
4817 placeholder. If the source of the second is a valid address,
4818 we can make put both sources together and make a split point
4819 in the middle. */
4832 && memory_address_addr_space_p
4835 {
4839 /* Replace the placeholder in SRC2 with SRC1. If we can
4840 find where in SRC2 it was placed, that can become our
4841 split point and we can replace this address with SRC2.
4842 Just try two obvious places. */
4853 {
4856 }
4857 }
4859 /* If that didn't work, perhaps the first operand is complex and
4860 needs to be computed separately, so make a split point there.
4861 This will occur on machines that just support REG + CONST
4862 and have a constant moved through some previous computation. */
4868 }
4870 /* If we have a PLUS whose first operand is complex, try computing it
4871 separately by making a split there. */
4882 /* If SET_DEST is CC0 and SET_SRC is not an operand, a COMPARE, or a
4883 ZERO_EXTRACT, the most likely reason why this doesn't match is that
4884 we need to put the operand into a register. So split at that
4885 point. */
4895 /* See if we can split SET_SRC as it stands. */
4900 /* See if we can split SET_DEST as it stands. */
4905 /* See if this is a bitfield assignment with everything constant. If
4906 so, this is an IOR of an AND, so split it into that. */
4916 {
4922 unsigned HOST_WIDE_INT mask
4924 rtx or_mask;
4933 else
4934 {
4940 or_mask));
4941 }
4948 }
4950 /* Otherwise, see if this is an operation that we can split into two.
4951 If so, try to split that. */
4955 {
4957 /* If we are AND'ing with a large constant that is only a single
4958 bit and the result is only being used in a context where we
4959 need to know if it is zero or nonzero, replace it with a bit
4960 extraction. This will avoid the large constant, which might
4961 have taken more than one insn to make. If the constant were
4962 not a valid argument to the AND but took only one insn to make,
4963 this is no worse, but if it took more than one insn, it will
4964 be better. */
4974 {
4979 {
4982 }
4983 }
4987 /* If STORE_FLAG_VALUE is -1, this is (NE X 0) and only one bit of X
4988 is known to be on, this can be converted into a NEG of a shift. */
4994 {
5006 }
5012 /* We can't optimize if either mode is a partial integer
5013 mode as we don't know how many bits are significant
5014 in those modes. */
5028 {
5036 }
5041 }
5045 {
5048 /* For unsigned, we have a choice of a shift followed by an
5049 AND or two shifts. Use two shifts for field sizes where the
5050 constant might be too large. We assume here that we can
5051 always at least get 8-bit constants in an AND insn, which is
5052 true for every current RISC. */
5055 {
5056 unsigned HOST_WIDE_INT mask
5060 gen_rtx_LSHIFTRT
5068 }
5069 else
5070 {
5072 gen_rtx_fmt_ee
5083 }
5084 }
5086 /* See if this is a simple operation with a constant as the second
5087 operand. It might be that this constant is out of range and hence
5088 could be used as a split point. */
5096 /* Finally, see if this is a simple operation with its first operand
5097 not in a register. The operation might require this operand in a
5098 register, so return it as a split point. We can always do this
5099 because if the first operand were another operation, we would have
5100 already found it as a split point. */
5109 /* We write NOR as (and (not A) (not B)), but if we don't have a NOR,
5110 it is better to write this as (not (ior A B)) so we can split it.
5111 Similarly for IOR. */
5113 {
5121 }
5123 /* Many RISC machines have a large set of logical insns. If the
5124 second operand is a NOT, put it first so we will try to split the
5125 other operand first. */
5127 {
5131 }
5136 /* Canonicalization can produce (minus A (mult B C)), where C is a
5137 constant. It may be better to try splitting (plus (mult B -C) A)
5138 instead if this isn't a multiply by a power of two. */
5142 {
5150 mode)),
5153 }
5155 /* Split at a multiply-accumulate instruction. However if this is
5156 the SET_SRC, we likely do not have such an instruction and it's
5157 worthless to try this split. */
5165 }
5167 /* Otherwise, select our actions depending on our rtx class. */
5169 {
5175 /* ... fall through ... */
5183 /* ... fall through ... */
5185 /* Some machines have (and (shift ...) ...) insns. If X is not
5186 an AND, but XEXP (X, 0) is, use it as our split point. */
5196 /* Otherwise, we don't have a split point. */
5198 }
5199 }
5200 \f
5201 /* Throughout X, replace FROM with TO, and return the result.
5202 The result is TO if X is FROM;
5203 otherwise the result is X, but its contents may have been modified.
5204 If they were modified, a record was made in undobuf so that
5205 undo_all will (among other things) return X to its original state.
5207 If the number of changes necessary is too much to record to undo,
5208 the excess changes are not made, so the result is invalid.
5209 The changes already made can still be undone.
5210 undobuf.num_undo is incremented for such changes, so by testing that
5211 the caller can tell whether the result is valid.
5213 `n_occurrences' is incremented each time FROM is replaced.
5215 IN_DEST is nonzero if we are processing the SET_DEST of a SET.
5217 IN_COND is nonzero if we are at the top level of a condition.
5219 UNIQUE_COPY is nonzero if each substitution must be unique. We do this
5220 by copying if `n_occurrences' is nonzero. */
5222 static rtx
5224 {
5229 rtx new_rtx;
5231 /* Two expressions are equal if they are identical copies of a shared
5232 RTX or if they are both registers with the same register number
5233 and mode. */
5235 #define COMBINE_RTX_EQUAL_P(X,Y) \
5236 ((X) == (Y) \
5237 || (REG_P (X) && REG_P (Y) \
5238 && REGNO (X) == REGNO (Y) && GET_MODE (X) == GET_MODE (Y)))
5240 /* Do not substitute into clobbers of regs -- this will never result in
5241 valid RTL. */
5246 {
5247 n_occurrences++;
5249 }
5251 /* If X and FROM are the same register but different modes, they
5252 will not have been seen as equal above. However, the log links code
5253 will make a LOG_LINKS entry for that case. If we do nothing, we
5254 will try to rerecognize our original insn and, when it succeeds,
5255 we will delete the feeding insn, which is incorrect.
5257 So force this insn not to match in this (rare) case. */
5262 /* If this is an object, we are done unless it is a MEM or LO_SUM, both
5263 of which may contain things that can be combined. */
5267 /* It is possible to have a subexpression appear twice in the insn.
5268 Suppose that FROM is a register that appears within TO.
5269 Then, after that subexpression has been scanned once by `subst',
5270 the second time it is scanned, TO may be found. If we were
5271 to scan TO here, we would find FROM within it and create a
5272 self-referent rtl structure which is completely wrong. */
5276 /* Parallel asm_operands need special attention because all of the
5277 inputs are shared across the arms. Furthermore, unsharing the
5278 rtl results in recognition failures. Failure to handle this case
5279 specially can result in circular rtl.
5281 Solve this by doing a normal pass across the first entry of the
5282 parallel, and only processing the SET_DESTs of the subsequent
5283 entries. Ug. */
5288 {
5291 /* If this substitution failed, this whole thing fails. */
5299 {
5305 {
5308 /* If this substitution failed, this whole thing fails. */
5314 }
5315 }
5316 }
5317 else
5318 {
5322 /* We don't need to process a SET_DEST that is a register, CC0,
5323 or PC, so set up to skip this common case. All other cases
5324 where we want to suppress replacing something inside a
5325 SET_SRC are handled via the IN_DEST operand. */
5332 /* Get the mode of operand 0 in case X is now a SIGN_EXTEND of a
5333 constant. */
5338 {
5340 {
5343 {
5345 {
5348 n_occurrences++;
5349 }
5350 else
5351 {
5353 unique_copy);
5355 /* If this substitution failed, this whole thing
5356 fails. */
5360 }
5363 }
5364 }
5366 {
5367 /* If this is a register being set, ignore it. */
5374 ;
5377 {
5378 /* In general, don't install a subreg involving two
5379 modes not tieable. It can worsen register
5380 allocation, and can even make invalid reload
5381 insns, since the reg inside may need to be copied
5382 from in the outside mode, and that may be invalid
5383 if it is an fp reg copied in integer mode.
5385 We allow two exceptions to this: It is valid if
5386 it is inside another SUBREG and the mode of that
5387 SUBREG and the mode of the inside of TO is
5388 tieable and it is valid if X is a SET that copies
5389 FROM to CC0. */
5397 #if HAVE_cc0
5399 #endif
5400 )
5412 n_occurrences++;
5413 }
5414 else
5415 /* If we are in a SET_DEST, suppress most cases unless we
5416 have gone inside a MEM, in which case we want to
5417 simplify the address. We assume here that things that
5418 are actually part of the destination have their inner
5419 parts in the first expression. This is true for SUBREG,
5420 STRICT_LOW_PART, and ZERO_EXTRACT, which are the only
5421 things aside from REG and MEM that should appear in a
5422 SET_DEST. */
5424 (((in_dest
5430 unique_copy);
5432 /* If we found that we will have to reject this combination,
5433 indicate that by returning the CLOBBER ourselves, rather than
5434 an expression containing it. This will speed things up as
5435 well as prevent accidents where two CLOBBERs are considered
5436 to be equal, thus producing an incorrect simplification. */
5442 {
5450 }
5453 {
5457 }
5458 else
5460 }
5461 }
5462 }
5464 /* Check if we are loading something from the constant pool via float
5465 extension; in this case we would undo compress_float_constant
5466 optimization and degenerate constant load to an immediate value. */
5470 {
5474 }
5476 /* Try to simplify X. If the simplification changed the code, it is likely
5477 that further simplification will help, so loop, but limit the number
5478 of repetitions that will be performed. */
5481 {
5482 /* If X is sufficiently simple, don't bother trying to do anything
5483 with it. */
5492 /* We no longer know the original mode of operand 0 since we
5493 have changed the form of X) */
5495 }
5498 }
5499 \f
5500 /* Simplify X, a piece of RTL. We just operate on the expression at the
5501 outer level; call `subst' to simplify recursively. Return the new
5502 expression.
5504 OP0_MODE is the original mode of XEXP (x, 0). IN_DEST is nonzero
5505 if we are inside a SET_DEST. IN_COND is nonzero if we are at the top level
5506 of a condition. */
5508 static rtx
5511 {
5514 rtx temp;
5517 /* If this is a commutative operation, put a constant last and a complex
5518 expression first. We don't need to do this for comparisons here. */
5521 {
5525 }
5527 /* If this is a simple operation applied to an IF_THEN_ELSE, try
5528 applying it to the arms of the IF_THEN_ELSE. This often simplifies
5529 things. Check for cases where both arms are testing the same
5530 condition.
5532 Don't do anything if all operands are very simple. */
5545 {
5550 /* If everything is a comparison, what we have is highly unlikely
5551 to be simpler, so don't use it. */
5554 {
5561 /* Simplify the alternative arms; this may collapse the true and
5562 false arms to store-flag values. Be careful to use copy_rtx
5563 here since true_rtx or false_rtx might share RTL with x as a
5564 result of the if_then_else_cond call above. */
5568 /* If true_rtx and false_rtx are not general_operands, an if_then_else
5569 is unlikely to be simpler. */
5572 {
5575 /* Restarting if we generate a store-flag expression will cause
5576 us to loop. Just drop through in this case. */
5578 /* If the result values are STORE_FLAG_VALUE and zero, we can
5579 just make the comparison operation. */
5590 /* Likewise, we can make the negate of a comparison operation
5591 if the result values are - STORE_FLAG_VALUE and zero. */
5599 mode);
5610 mode);
5611 else
5614 mode,
5615 VOIDmode,
5616 cond,
5617 cop1),
5622 }
5623 }
5624 }
5626 /* Try to fold this expression in case we have constants that weren't
5627 present before. */
5630 {
5638 {
5641 {
5645 }
5648 }
5661 }
5664 {
5669 }
5671 /* First see if we can apply the inverse distributive law. */
5674 {
5678 }
5680 /* If CODE is an associative operation not otherwise handled, see if we
5681 can associate some operands. This can win if they are constants or
5682 if they are logically related (i.e. (a & b) & a). */
5688 {
5690 {
5694 rtx inner;
5696 /* Make sure we pass the constant operand if any as the second
5697 one if this is a commutative operation. */
5699 {
5703 }
5709 /* For commutative operations, try the other pair if that one
5710 didn't simplify. */
5712 {
5717 }
5721 }
5722 }
5724 /* A little bit of algebraic simplification here. */
5726 {
5728 /* Ensure that our address has any ASHIFTs converted to MULT in case
5729 address-recognizing predicates are called later. */
5738 /* See if this can be moved to simplify_subreg. */
5741 /* Don't call gen_lowpart if the inner mode
5742 is VOIDmode and we cannot simplify it, as SUBREG without
5743 inner mode is invalid. */
5750 {
5751 rtx temp;
5757 /* If op is known to have all lower bits zero, the result is zero. */
5767 }
5769 /* Don't change the mode of the MEM if that would change the meaning
5770 of the address. */
5777 /* Note that we cannot do any narrowing for non-constants since
5778 we might have been counting on using the fact that some bits were
5779 zero. We now do this in the SET. */
5786 /* For C equal to the width of MODE minus 1, (neg (ashiftrt X C)) can be
5787 replaced by (lshiftrt X C). This will convert
5788 (neg (sign_extract X 1 Y)) to (zero_extract X 1 Y). */
5796 /* If X has only a single bit that might be nonzero, say, bit I, convert
5797 (neg X) to (ashiftrt (ashift X C-I) C-I) where C is the bitsize of
5798 MODE minus 1. This will convert (neg (zero_extract X 1 Y)) to
5799 (sign_extract X 1 Y). But only do this if TEMP isn't a register
5800 or a SUBREG of one since we'd be making the expression more
5801 complex if it was just a register. */
5807 {
5808 rtx temp1 = simplify_shift_const
5814 /* If all we did was surround TEMP with the two shifts, we
5815 haven't improved anything, so don't use it. Otherwise,
5816 we are better off with TEMP1. */
5821 }
5825 /* We can't handle truncation to a partial integer mode here
5826 because we don't know the real bitsize of the partial
5827 integer mode. */
5836 /* We can truncate a constant value and return it. */
5840 /* Similarly to what we do in simplify-rtx.c, a truncate of a register
5841 whose value is a comparison can be replaced with a subreg if
5842 STORE_FLAG_VALUE permits. */
5851 /* (const (const X)) can become (const X). Do it this way rather than
5852 returning the inner CONST since CONST can be shared with a
5853 REG_EQUAL note. */
5859 /* Convert (lo_sum (high FOO) FOO) to FOO. This is necessary so we
5860 can add in an offset. find_split_point will split this address up
5861 again if it doesn't match. */
5868 /* (plus (xor (and <foo> (const_int pow2 - 1)) <c>) <-c>)
5869 when c is (const_int (pow2 + 1) / 2) is a sign extension of a
5870 bit-field and can be replaced by either a sign_extend or a
5871 sign_extract. The `and' may be a zero_extend and the two
5872 <c>, -<c> constants may be reversed. */
5887 return simplify_shift_const
5894 /* If only the low-order bit of X is possibly nonzero, (plus x -1)
5895 can become (ashiftrt (ashift (xor x 1) C) C) where C is
5896 the bitsize of the mode - 1. This allows simplification of
5897 "a = (b & 8) == 0;" */
5909 /* If we are adding two things that have no bits in common, convert
5910 the addition into an IOR. This will often be further simplified,
5911 for example in cases like ((a & 1) + (a & 2)), which can
5912 become a & 3. */
5917 {
5918 /* Try to simplify the expression further. */
5922 /* If we could, great. If not, do not go ahead with the IOR
5923 replacement, since PLUS appears in many special purpose
5924 address arithmetic instructions. */
5932 }
5936 /* (minus <foo> (and <foo> (const_int -pow2))) becomes
5937 (and <foo> (const_int pow2-1)) */
5947 /* If we have (mult (plus A B) C), apply the distributive law and then
5948 the inverse distributive law to see if things simplify. This
5949 occurs mostly in addresses, often when unrolling loops. */
5952 {
5956 }
5958 /* Try simplify a*(b/c) as (a*b)/c. */
5961 {
5967 }
5971 /* If this is a divide by a power of two, treat it as a shift if
5972 its first operand is a shift. */
5990 /* If the first operand is a condition code, we can't do anything
5991 with it. */
5995 {
6003 /* Simplify our comparison, if possible. */
6006 /* If STORE_FLAG_VALUE is 1, we can convert (ne x 0) to simply X
6007 if only the low-order bit is possibly nonzero in X (such as when
6008 X is a ZERO_EXTRACT of one bit). Similarly, we can convert EQ to
6009 (xor X 1) or (minus 1 X); we use the former. Finally, if X is
6010 known to be either 0 or -1, NE becomes a NEG and EQ becomes
6011 (plus X 1).
6013 Remove any ZERO_EXTRACT we made when thinking this was a
6014 comparison. It may now be simpler to use, e.g., an AND. If a
6015 ZERO_EXTRACT is indeed appropriate, it will be placed back by
6016 the call to make_compound_operation in the SET case.
6018 Don't apply these optimizations if the caller would
6019 prefer a comparison rather than a value.
6020 E.g., for the condition in an IF_THEN_ELSE most targets need
6021 an explicit comparison. */
6024 ;
6040 {
6044 mode);
6045 }
6052 {
6056 const1_rtx);
6057 }
6065 {
6068 }
6070 /* If STORE_FLAG_VALUE is -1, we have cases similar to
6071 those above. */
6073 ;
6089 {
6093 mode);
6094 }
6102 {
6106 mode);
6107 }
6109 /* If X is 0/1, (eq X 0) is X-1. */
6115 {
6118 }
6120 /* If STORE_FLAG_VALUE says to just test the sign bit and X has just
6121 one bit that might be nonzero, we can convert (ne x 0) to
6122 (ashift x c) where C puts the bit in the sign bit. Remove any
6123 AND with STORE_FLAG_VALUE when we are done, since we are only
6124 going to test the sign bit. */
6131 {
6137 else
6139 }
6141 /* If the code changed, return a whole new comparison.
6142 We also need to avoid using SUBST in cases where
6143 simplify_comparison has widened a comparison with a CONST_INT,
6144 since in that case the wider CONST_INT may fail the sanity
6145 checks in do_SUBST. */
6152 /* Otherwise, keep this operation, but maybe change its operands.
6153 This also converts (ne (compare FOO BAR) 0) to (ne FOO BAR). */
6156 }
6166 /* If we are processing SET_DEST, we are done. */
6184 /* If this is a shift by a constant amount, simplify it. */
6200 }
6203 }
6204 \f
6205 /* Simplify X, an IF_THEN_ELSE expression. Return the new expression. */
6207 static rtx
6209 {
6216 rtx temp;
6219 rtx reversed;
6221 /* Simplify storing of the truth value. */
6226 /* Also when the truth value has to be reversed. */
6232 /* Sometimes we can simplify the arm of an IF_THEN_ELSE if a register used
6233 in it is being compared against certain values. Get the true and false
6234 comparisons and see if that says anything about the value of each arm. */
6240 {
6241 HOST_WIDE_INT nzb;
6247 /* If FALSE_CODE is EQ, swap the codes and arms. */
6250 {
6253 }
6255 /* If we are comparing against zero and the expression being tested has
6256 only a single bit that might be nonzero, that is its value when it is
6257 not equal to zero. Similarly if it is known to be -1 or 0. */
6261 {
6264 }
6268 {
6271 }
6273 /* Now simplify an arm if we know the value of the register in the
6274 branch and it is used in the arm. Be careful due to the potential
6275 of locally-shared RTL. */
6292 }
6294 /* If we have (if_then_else FOO (pc) (label_ref BAR)) and FOO can be
6295 reversed, do so to avoid needing two sets of patterns for
6296 subtract-and-branch insns. Similarly if we have a constant in the true
6297 arm, the false arm is the same as the first operand of the comparison, or
6298 the false arm is more complicated than the true arm. */
6311 {
6320 /* It is possible that the conditional has been simplified out. */
6323 }
6325 /* If the two arms are identical, we don't need the comparison. */
6330 /* Convert a == b ? b : a to "a". */
6342 /* Look for cases where we have (abs x) or (neg (abs X)). */
6345 && comparison_p
6352 {
6358 return
6361 mode);
6364 }
6366 /* Look for MIN or MAX. */
6369 && comparison_p
6374 {
6389 }
6391 /* If we have (if_then_else COND (OP Z C1) Z) and OP is an identity when its
6392 second operand is zero, this can be done as (OP Z (mult COND C2)) where
6393 C2 = C1 * STORE_FLAG_VALUE. Similarly if OP has an outer ZERO_EXTEND or
6394 SIGN_EXTEND as long as Z is already extended (so we don't destroy it).
6395 We can do this kind of thing in some cases when STORE_FLAG_VALUE is
6396 neither 1 or -1, but it isn't worth checking for. */
6399 && comparison_p
6402 {
6418 /* If an identity-zero op is commutative, check whether there
6419 would be a match if we swapped the operands. */
6439 {
6443 }
6455 {
6459 }
6475 {
6479 }
6491 {
6495 }
6498 {
6504 const_true_rtx));
6512 }
6513 }
6515 /* If we have (if_then_else (ne A 0) C1 0) and either A is known to be 0 or
6516 1 and C1 is a single bit or A is known to be 0 or -1 and C1 is the
6517 negation of a single bit, we can convert this operation to a shift. We
6518 can actually do this more generally, but it doesn't seem worth it. */
6527 return
6531 /* (IF_THEN_ELSE (NE REG 0) (0) (8)) is REG for nonzero_bits (REG) == 8. */
6541 }
6542 \f
6543 /* Simplify X, a SET expression. Return the new expression. */
6545 static rtx
6547 {
6550 machine_mode mode
6555 /* (set (pc) (return)) gets written as (return). */
6559 /* Now that we know for sure which bits of SRC we are using, see if we can
6560 simplify the expression for the object knowing that we only need the
6561 low-order bits. */
6564 {
6567 }
6569 /* If we are setting CC0 or if the source is a COMPARE, look for the use of
6570 the comparison result and try to simplify it unless we already have used
6571 undobuf.other_insn. */
6579 {
6588 {
6591 {
6594 }
6595 }
6596 else
6604 {
6608 }
6609 else
6610 {
6615 /* Attempt to simplify CC user. */
6617 {
6621 }
6623 /* Convert X into a no-op move. */
6627 }
6629 /* Simplify our comparison, if possible. */
6632 #ifdef SELECT_CC_MODE
6633 /* If this machine has CC modes other than CCmode, check to see if we
6634 need to use a different CC mode here. */
6643 else
6646 /* If the mode changed, we have to change SET_DEST, the mode in the
6647 compare, and the mode in the place SET_DEST is used. If SET_DEST is
6648 a hard register, just build new versions with the proper mode. If it
6649 is a pseudo, we lose unless it is only time we set the pseudo, in
6650 which case we can safely change its mode. */
6652 {
6654 {
6656 rtx new_dest;
6660 else
6661 {
6664 }
6671 }
6672 }
6675 /* If the code changed, we have to build a new comparison in
6676 undobuf.other_insn. */
6678 {
6687 /* If the only change we made was to change an EQ into an NE or
6688 vice versa, OP0 has only one bit that might be nonzero, and OP1
6689 is zero, check if changing the user of the condition code will
6690 produce a valid insn. If it won't, we can keep the original code
6691 in that insn by surrounding our operation with an XOR. */
6698 {
6703 {
6710 }
6711 }
6712 }
6717 /* Don't generate a compare of a CC with 0, just use that CC. */
6719 {
6722 }
6723 /* Otherwise, if we didn't previously have the same COMPARE we
6724 want, create it from scratch. */
6727 {
6730 }
6731 }
6732 else
6733 {
6734 /* Get SET_SRC in a form where we have placed back any
6735 compound expressions. Then do the checks below. */
6738 }
6740 /* If we have (set x (subreg:m1 (op:m2 ...) 0)) with OP being some operation,
6741 and X being a REG or (subreg (reg)), we may be able to convert this to
6742 (set (subreg:m2 x) (op)).
6744 We can always do this if M1 is narrower than M2 because that means that
6745 we only care about the low bits of the result.
6747 However, on machines without WORD_REGISTER_OPERATIONS defined, we cannot
6748 perform a narrower operation than requested since the high-order bits will
6749 be undefined. On machine where it is defined, this transformation is safe
6750 as long as M1 and M2 have the same number of words. */
6758 #ifndef WORD_REGISTER_OPERATIONS
6761 #endif
6762 #ifdef CANNOT_CHANGE_MODE_CLASS
6767 #endif
6771 {
6774 dest));
6778 }
6780 /* If we have (set (cc0) (subreg ...)), we try to remove the subreg
6781 in SRC. */
6787 {
6791 /* Here we make sure that we don't have a sign bit on. */
6794 {
6797 }
6798 }
6800 #ifdef LOAD_EXTEND_OP
6801 /* If we have (set FOO (subreg:M (mem:N BAR) 0)) with M wider than N, this
6802 would require a paradoxical subreg. Replace the subreg with a
6803 zero_extend to avoid the reload that would otherwise be required. */
6811 {
6817 }
6818 #endif
6820 /* If we don't have a conditional move, SET_SRC is an IF_THEN_ELSE, and we
6821 are comparing an item known to be 0 or -1 against 0, use a logical
6822 operation instead. Check for one of the arms being an IOR of the other
6823 arm with some value. We compute three terms to be IOR'ed together. In
6824 practice, at most two will be nonzero. Then we do the IOR's. */
6832 && (!HAVE_conditional_move
6838 {
6864 false_rtx);
6870 term3));
6873 }
6875 /* If either SRC or DEST is a CLOBBER of (const_int 0), make this
6876 whole thing fail. */
6881 else
6882 /* Convert this into a field assignment operation, if possible. */
6884 }
6885 \f
6886 /* Simplify, X, and AND, IOR, or XOR operation, and return the simplified
6887 result. */
6889 static rtx
6891 {
6897 {
6899 /* We can call simplify_and_const_int only if we don't lose
6900 any (sign) bits when converting INTVAL (op1) to
6901 "unsigned HOST_WIDE_INT". */
6905 {
6912 }
6914 /* If we have any of (and (ior A B) C) or (and (xor A B) C),
6915 apply the distributive law and then the inverse distributive
6916 law to see if things simplify. */
6918 {
6922 }
6924 {
6928 }
6932 /* If we have (ior (and A B) C), apply the distributive law and then
6933 the inverse distributive law to see if things simplify. */
6936 {
6940 }
6943 {
6947 }
6952 }
6955 }
6956 \f
6957 /* We consider ZERO_EXTRACT, SIGN_EXTRACT, and SIGN_EXTEND as "compound
6958 operations" because they can be replaced with two more basic operations.
6959 ZERO_EXTEND is also considered "compound" because it can be replaced with
6960 an AND operation, which is simpler, though only one operation.
6962 The function expand_compound_operation is called with an rtx expression
6963 and will convert it to the appropriate shifts and AND operations,
6964 simplifying at each stage.
6966 The function make_compound_operation is called to convert an expression
6967 consisting of shifts and ANDs into the equivalent compound expression.
6968 It is the inverse of this function, loosely speaking. */
6970 static rtx
6972 {
6976 rtx tem;
6979 {
6983 /* We can't necessarily use a const_int for a multiword mode;
6984 it depends on implicitly extending the value.
6985 Since we don't know the right way to extend it,
6986 we can't tell whether the implicit way is right.
6988 Even for a mode that is no wider than a const_int,
6989 we can't win, because we need to sign extend one of its bits through
6990 the rest of it, and we don't know which bit. */
6994 /* Return if (subreg:MODE FROM 0) is not a safe replacement for
6995 (zero_extend:MODE FROM) or (sign_extend:MODE FROM). It is for any MEM
6996 because (SUBREG (MEM...)) is guaranteed to cause the MEM to be
6997 reloaded. If not for that, MEM's would very rarely be safe.
6999 Reject MODEs bigger than a word, because we might not be able
7000 to reference a two-register group starting with an arbitrary register
7001 (and currently gen_lowpart might crash for a SUBREG). */
7006 /* Reject MODEs that aren't scalar integers because turning vector
7007 or complex modes into shifts causes problems. */
7013 /* If the inner object has VOIDmode (the only way this can happen
7014 is if it is an ASM_OPERANDS), we can't do anything since we don't
7015 know how much masking to do. */
7024 /* ... fall through ... */
7027 /* If the operand is a CLOBBER, just return it. */
7036 /* Reject MODEs that aren't scalar integers because turning vector
7037 or complex modes into shifts causes problems. */
7045 /* This should stay within the object being extracted, fail otherwise. */
7056 }
7057 /* Convert sign extension to zero extension, if we know that the high
7058 bit is not set, as this is easier to optimize. It will be converted
7059 back to cheaper alternative in make_extraction. */
7067 {
7071 /* Make sure this is a profitable operation. */
7078 else
7080 }
7082 /* We can optimize some special cases of ZERO_EXTEND. */
7084 {
7085 /* (zero_extend:DI (truncate:SI foo:DI)) is just foo:DI if we
7086 know that the last value didn't have any inappropriate bits
7087 set. */
7095 /* Likewise for (zero_extend:DI (subreg:SI foo:DI 0)). */
7104 /* (zero_extend:DI (truncate:SI foo:DI)) is just foo:DI when foo
7105 is a comparison and STORE_FLAG_VALUE permits. This is like
7106 the first case, but it works even when GET_MODE (x) is larger
7107 than HOST_WIDE_INT. */
7116 /* Likewise for (zero_extend:DI (subreg:SI foo:DI 0)). */
7126 }
7128 /* If we reach here, we want to return a pair of shifts. The inner
7129 shift is a left shift of BITSIZE - POS - LEN bits. The outer
7130 shift is a right shift of BITSIZE - LEN bits. It is arithmetic or
7131 logical depending on the value of UNSIGNEDP.
7133 If this was a ZERO_EXTEND or ZERO_EXTRACT, this pair of shifts will be
7134 converted into an AND of a shift.
7136 We must check for the case where the left shift would have a negative
7137 count. This can happen in a case like (x >> 31) & 255 on machines
7138 that can't shift by a constant. On those machines, we would first
7139 combine the shift with the AND to produce a variable-position
7140 extraction. Then the constant of 31 would be substituted in
7141 to produce such a position. */
7145 {
7154 }
7161 else
7162 /* Any other cases we can't handle. */
7165 /* If we couldn't do this for some reason, return the original
7166 expression. */
7171 }
7172 \f
7173 /* X is a SET which contains an assignment of one object into
7174 a part of another (such as a bit-field assignment, STRICT_LOW_PART,
7175 or certain SUBREGS). If possible, convert it into a series of
7176 logical operations.
7178 We half-heartedly support variable positions, but do not at all
7179 support variable lengths. */
7181 static const_rtx
7183 {
7184 rtx inner;
7188 machine_mode compute_mode;
7190 /* Loop until we find something we can't simplify. */
7192 {
7195 {
7199 }
7202 {
7207 /* A constant position should stay within the width of INNER. */
7213 {
7221 /* If position is ADJUST - X, new position is X. */
7223 else
7224 {
7229 pos);
7230 }
7231 }
7232 }
7234 /* A SUBREG between two modes that occupy the same numbers of words
7235 can be done by moving the SUBREG to the source. */
7237 /* We need SUBREGs to compute nonzero_bits properly. */
7238 && nonzero_sign_valid
7243 {
7245 gen_lowpart
7249 }
7250 else
7258 /* Don't attempt bitwise arithmetic on non scalar integer modes. */
7260 {
7261 machine_mode imode;
7263 /* Don't do anything for vector or complex integral types. */
7267 /* Try to find an integral mode to pun with. */
7274 }
7276 /* Compute a mask of LEN bits, if we can do this on the host machine. */
7280 /* Now compute the equivalent expression. Make a copy of INNER
7281 for the SET_DEST in case it is a MEM into which we will substitute;
7282 we don't want shared RTL in that case. */
7284 compute_mode);
7288 compute_mode,
7290 compute_mode),
7291 inner);
7296 mask),
7297 pos);
7302 }
7305 }
7306 \f
7307 /* Return an RTX for a reference to LEN bits of INNER. If POS_RTX is nonzero,
7308 it is an RTX that represents the (variable) starting position; otherwise,
7309 POS is the (constant) starting bit position. Both are counted from the LSB.
7311 UNSIGNEDP is nonzero for an unsigned reference and zero for a signed one.
7313 IN_DEST is nonzero if this is a reference in the destination of a SET.
7314 This is used when a ZERO_ or SIGN_EXTRACT isn't needed. If nonzero,
7315 a STRICT_LOW_PART will be used, if zero, ZERO_EXTEND or SIGN_EXTEND will
7316 be used.
7318 IN_COMPARE is nonzero if we are in a COMPARE. This means that a
7319 ZERO_EXTRACT should be built even for bits starting at bit 0.
7321 MODE is the desired mode of the result (if IN_DEST == 0).
7323 The result is an RTX for the extraction or NULL_RTX if the target
7324 can't handle it. */
7326 static rtx
7330 {
7331 /* This mode describes the size of the storage area
7332 to fetch the overall value from. Within that, we
7333 ignore the POS lowest bits, etc. */
7335 machine_mode inner_mode;
7336 machine_mode wanted_inner_mode;
7343 HOST_WIDE_INT orig_pos;
7349 {
7350 /* If going from (subreg:SI (mem:QI ...)) to (mem:QI ...),
7351 consider just the QI as the memory to extract from.
7352 The subreg adds or removes high bits; its mode is
7353 irrelevant to the meaning of this extraction,
7354 since POS and LEN count from the lsb. */
7358 }
7363 {
7364 /* We're extracting the least significant bits of an rtx
7365 (ashift X (const_int C)), where LEN > C. Extract the
7366 least significant (LEN - C) bits of X, giving an rtx
7367 whose mode is MODE, then shift it left C times. */
7373 }
7379 /* See if this can be done without an extraction. We never can if the
7380 width of the field is not the same as that of some integer mode. For
7381 registers, we can only avoid the extraction if the position is at the
7382 low-order bit and this is either not in the destination or we have the
7383 appropriate STRICT_LOW_PART operation available.
7385 For MEM, we can avoid an extract if the field starts on an appropriate
7386 boundary and we can change the mode of the memory reference. */
7395 && (! in_dest
7399 && (pos
7402 /* We can't do this if we are widening INNER_MODE (it
7403 may not be aligned, for one thing). */
7409 {
7410 /* If INNER is a MEM, make a new MEM that encompasses just the desired
7411 field. If the original and current mode are the same, we need not
7412 adjust the offset. Otherwise, we do if bytes big endian.
7414 If INNER is not a MEM, get a piece consisting of just the field
7415 of interest (in this case POS % BITS_PER_WORD must be 0). */
7418 {
7419 HOST_WIDE_INT offset;
7421 /* POS counts from lsb, but make OFFSET count in memory order. */
7424 else
7428 }
7430 {
7432 {
7433 /* We can't call gen_lowpart in a DEST since we
7434 always want a SUBREG (see below) and it would sometimes
7435 return a new hard register. */
7437 {
7452 /* Avoid creating invalid subregs, for example when
7453 simplifying (x>>32)&255. */
7458 }
7459 else
7461 }
7462 else
7464 }
7465 else
7467 len >= HOST_BITS_PER_WIDE_INT
7472 /* If this extraction is going into the destination of a SET,
7473 make a STRICT_LOW_PART unless we made a MEM. */
7488 /* If we know that no extraneous bits are set, and that the high
7489 bit is not set, convert the extraction to the cheaper of
7490 sign and zero extension, that are equivalent in these cases. */
7496 {
7500 /* Prefer ZERO_EXTENSION, since it gives more information to
7501 backends. */
7506 }
7508 /* Otherwise, sign- or zero-extend unless we already are in the
7509 proper mode. */
7513 }
7515 /* Unless this is a COMPARE or we have a funny memory reference,
7516 don't do anything with zero-extending field extracts starting at
7517 the low-order bit since they are simple AND operations. */
7522 /* Unless INNER is not MEM, reject this if we would be spanning bytes or
7523 if the position is not a constant and the length is not 1. In all
7524 other cases, we would only be going outside our object in cases when
7525 an original shift would have been undefined. */
7534 /* If INNER is not from memory, we want it to have the mode of a register
7535 extraction pattern's structure operand, or word_mode if there is no
7536 such pattern. The same applies to extraction_mode and pos_mode
7537 and their respective operands.
7539 For memory, assume that the desired extraction_mode and pos_mode
7540 are the same as for a register operation, since at present we don't
7541 have named patterns for aligned memory structures. */
7545 {
7549 }
7551 /* Never narrow an object, since that might not be safe. */
7559 else
7560 {
7561 /* Be careful not to go beyond the extracted object and maintain the
7562 natural alignment of the memory. */
7566 {
7569 }
7570 }
7575 {
7576 /* POS is passed as if BITS_BIG_ENDIAN == 0, so we need to convert it to
7577 BITS_BIG_ENDIAN style. If position is constant, compute new
7578 position. Otherwise, build subtraction.
7579 Note that POS is relative to the mode of the original argument.
7580 If it's a MEM we need to recompute POS relative to that.
7581 However, if we're extracting from (or inserting into) a register,
7582 we want to recompute POS relative to wanted_inner_mode. */
7589 else
7590 pos_rtx
7593 pos_rtx);
7594 /* POS may be less than 0 now, but we check for that below.
7595 Note that it can only be less than 0 if !MEM_P (inner). */
7596 }
7598 /* If INNER has a wider mode, and this is a constant extraction, try to
7599 make it smaller and adjust the byte to point to the byte containing
7600 the value. */
7603 && ! pos_rtx
7608 {
7611 /* The computations below will be correct if the machine is big
7612 endian in both bits and bytes or little endian in bits and bytes.
7613 If it is mixed, we must adjust. */
7615 /* If bytes are big endian and we had a paradoxical SUBREG, we must
7616 adjust OFFSET to compensate. */
7621 /* We can now move to the desired byte. */
7632 }
7634 /* If INNER is not memory, get it into the proper mode. If we are changing
7635 its mode, POS must be a constant and smaller than the size of the new
7636 mode. */
7638 {
7639 /* On the LHS, don't create paradoxical subregs implicitely truncating
7640 the register unless TRULY_NOOP_TRUNCATION. */
7643 wanted_inner_mode))
7655 pos_rtx
7661 }
7663 /* Adjust mode of POS_RTX, if needed. If we want a wider mode, we
7664 have to zero extend. Otherwise, we can just use a SUBREG. */
7667 {
7671 /* If we know that no extraneous bits are set, and that the high
7672 bit is not set, convert extraction to cheaper one - either
7673 SIGN_EXTENSION or ZERO_EXTENSION, that are equivalent in these
7674 cases. */
7682 {
7686 /* Prefer ZERO_EXTENSION, since it gives more information to
7687 backends. */
7691 }
7693 }
7695 /* Make POS_RTX unless we already have it and it is correct. If we don't
7696 have a POS_RTX but we do have an ORIG_POS_RTX, the latter must
7697 be a CONST_INT. */
7704 /* Make the required operation. See if we can use existing rtx. */
7711 }
7712 \f
7713 /* See if X contains an ASHIFT of COUNT or more bits that can be commuted
7714 with any other operations in X. Return X without that shift if so. */
7716 static rtx
7718 {
7721 rtx tem;
7724 {
7726 /* This is the shift itself. If it is wide enough, we will return
7727 either the value being shifted if the shift count is equal to
7728 COUNT or a shift for the difference. */
7742 /* If we can safely shift this constant and we find the inner shift,
7743 make a new operation. */
7748 {
7752 }
7757 }
7760 }
7761 \f
7762 /* Look at the expression rooted at X. Look for expressions
7763 equivalent to ZERO_EXTRACT, SIGN_EXTRACT, ZERO_EXTEND, SIGN_EXTEND.
7764 Form these expressions.
7766 Return the new rtx, usually just X.
7768 Also, for machines like the VAX that don't have logical shift insns,
7769 try to convert logical to arithmetic shift operations in cases where
7770 they are equivalent. This undoes the canonicalizations to logical
7771 shifts done elsewhere.
7773 We try, as much as possible, to re-use rtl expressions to save memory.
7775 IN_CODE says what kind of expression we are processing. Normally, it is
7776 SET. In a memory address it is MEM. When processing the arguments of
7777 a comparison or a COMPARE against zero, it is COMPARE. */
7779 rtx
7781 {
7789 rtx tem;
7792 /* Select the code to be used in recursive calls. Once we are inside an
7793 address, we stay there. If we have a comparison, set to COMPARE,
7794 but once inside, go back to our default of SET. */
7801 /* Process depending on the code of this operation. If NEW is set
7802 nonzero, it will be returned. */
7805 {
7807 /* Convert shifts by constants into multiplications if inside
7808 an address. */
7813 {
7819 {
7822 }
7825 }
7835 {
7839 }
7842 {
7846 mode));
7848 }
7849 else
7850 {
7854 }
7865 {
7869 }
7872 {
7876 mode));
7878 }
7879 else
7880 {
7884 }
7888 /* If the second operand is not a constant, we can't do anything
7889 with it. */
7893 /* If the constant is a power of two minus one and the first operand
7894 is a logical right shift, make an extraction. */
7897 {
7901 }
7903 /* Same as previous, but for (subreg (lshiftrt ...)) in first op. */
7908 {
7910 next_code);
7914 }
7915 /* Same as previous, but for (xor/ior (lshiftrt...) (lshiftrt...)). */
7921 {
7922 /* Apply the distributive law, and then try to make extractions. */
7929 }
7931 /* If we are have (and (rotate X C) M) and C is larger than the number
7932 of bits in M, this is an extraction. */
7938 {
7944 }
7946 /* On machines without logical shifts, if the operand of the AND is
7947 a logical shift and our mask turns off all the propagated sign
7948 bits, we can replace the logical shift with an arithmetic shift. */
7956 {
7963 make_compound_operation
7966 }
7968 /* If the constant is one less than a power of two, this might be
7969 representable by an extraction even if no shift is present.
7970 If it doesn't end up being a ZERO_EXTEND, we will ignore it unless
7971 we are in a COMPARE. */
7975 next_code),
7978 /* If we are in a comparison and this is an AND with a power of two,
7979 convert this into the appropriate bit extract. */
7984 next_code),
7990 /* If the sign bit is known to be zero, replace this with an
7991 arithmetic shift. */
7996 {
7999 next_code),
8002 }
8004 /* ... fall through ... */
8010 /* If we have (ashiftrt (ashift foo C1) C2) with C2 >= C1,
8011 this is a SIGN_EXTRACT. */
8018 {
8025 }
8027 /* See if we have operations between an ASHIFTRT and an ASHIFT.
8028 If so, try to merge the shifts into a SIGN_EXTEND. We could
8029 also do this for some cases of SIGN_EXTRACT, but it doesn't
8030 seem worth the effort; the case checked for occurs on Alpha. */
8046 /* Call ourselves recursively on the inner expression. If we are
8047 narrowing the object and it has a different RTL code from
8048 what it originally did, do this SUBREG as a force_to_mode. */
8049 {
8053 /* If in_code is COMPARE, it isn't always safe to pass it through
8054 to the recursive make_compound_operation call. */
8058 /* (subreg:SI (and:DI (reg:DI) (const_int 0x800000000)) 0)
8059 is (const_int 0), rather than
8060 (subreg:SI (lshiftrt:DI (reg:DI) (const_int 35)) 0). */
8070 simplified
8078 {
8079 rtx newer
8082 /* If we have something other than a SUBREG, we might have
8083 done an expansion, so rerun ourselves. */
8087 /* force_to_mode can expand compounds. If it just re-expanded the
8088 compound, use gen_lowpart to convert to the desired mode. */
8090 /* Likewise if it re-expanded the compound only partially.
8091 This happens for SUBREG of ZERO_EXTRACT if they extract
8092 the same number of bits. */
8101 }
8105 }
8110 }
8113 {
8116 }
8118 /* Now recursively process each operand of this operation. We need to
8119 handle ZERO_EXTEND specially so that we don't lose track of the
8120 inner mode. */
8122 {
8130 }
8135 {
8138 }
8141 {
8144 }
8146 maybe_swap:
8147 /* If this is a commutative operation, the changes to the operands
8148 may have made it noncanonical. */
8151 {
8155 }
8158 }
8159 \f
8160 /* Given M see if it is a value that would select a field of bits
8161 within an item, but not the entire word. Return -1 if not.
8162 Otherwise, return the starting position of the field, where 0 is the
8163 low-order bit.
8165 *PLEN is set to the length of the field. */
8167 static int
8169 {
8170 /* Get the bit number of the first 1 bit from the right, -1 if none. */
8175 /* Now shift off the low-order zero bits and see if we have a
8176 power of two minus 1. */
8184 }
8185 \f
8186 /* If X refers to a register that equals REG in value, replace these
8187 references with REG. */
8188 static rtx
8190 {
8198 {
8234 {
8238 else
8240 }
8242 /* fall through */
8249 {
8252 {
8254 {
8257 }
8259 }
8260 }
8262 {
8265 {
8268 {
8270 {
8273 }
8275 }
8276 }
8277 }
8280 }
8283 }
8285 /* Return X converted to MODE. If the value is already truncated to
8286 MODE we can just return a subreg even though in the general case we
8287 would need an explicit truncation. */
8289 static rtx
8291 {
8296 {
8297 /* Bit-cast X into an integer mode. */
8302 }
8305 }
8307 /* See if X can be simplified knowing that we will only refer to it in
8308 MODE and will only refer to those bits that are nonzero in MASK.
8309 If other bits are being computed or if masking operations are done
8310 that select a superset of the bits in MASK, they can sometimes be
8311 ignored.
8313 Return a possibly simplified expression, but always convert X to
8314 MODE. If X is a CONST_INT, AND the CONST_INT with MASK.
8316 If JUST_SELECT is nonzero, don't optimize by noticing that bits in MASK
8317 are all off in X. This is used when X will be complemented, by either
8318 NOT, NEG, or XOR. */
8320 static rtx
8323 {
8326 machine_mode op_mode;
8330 /* If this is a CALL or ASM_OPERANDS, don't do anything. Some of the
8331 code below will do the wrong thing since the mode of such an
8332 expression is VOIDmode.
8334 Also do nothing if X is a CLOBBER; this can happen if X was
8335 the return value from a call to gen_lowpart. */
8339 /* We want to perform the operation in its present mode unless we know
8340 that the operation is valid in MODE, in which case we do the operation
8341 in MODE. */
8346 /* It is not valid to do a right-shift in a narrower mode
8347 than the one it came in with. */
8352 /* Truncate MASK to fit OP_MODE. */
8356 /* When we have an arithmetic operation, or a shift whose count we
8357 do not know, we need to assume that all bits up to the highest-order
8358 bit in MASK will be needed. This is how we form such a mask. */
8361 else
8365 /* Determine what bits of X are guaranteed to be (non)zero. */
8368 /* If none of the bits in X are needed, return a zero. */
8372 /* If X is a CONST_INT, return a new one. Do this here since the
8373 test below will fail. */
8375 {
8378 else
8379 {
8382 }
8383 }
8385 /* If X is narrower than MODE and we want all the bits in X's mode, just
8386 get X in the proper mode. */
8391 /* We can ignore the effect of a SUBREG if it narrows the mode or
8392 if the constant masks to zero all the bits the mode doesn't have. */
8402 /* The arithmetic simplifications here only work for scalar integer modes. */
8407 {
8409 /* If X is a (clobber (const_int)), return it since we know we are
8410 generating something that won't match. */
8423 /* Similarly for a truncate. */
8427 /* If this is an AND with a constant, convert it into an AND
8428 whose constant is the AND of that constant with MASK. If it
8429 remains an AND of MASK, delete it since it is redundant. */
8432 {
8436 /* If X is still an AND, see if it is an AND with a mask that
8437 is just some low-order bits. If so, and it is MASK, we don't
8438 need it. */
8445 /* If it remains an AND, try making another AND with the bits
8446 in the mode mask that aren't in MASK turned on. If the
8447 constant in the AND is wide enough, this might make a
8448 cheaper constant. */
8453 {
8454 unsigned HOST_WIDE_INT cval
8457 rtx y;
8464 }
8467 }
8472 /* In (and (plus FOO C1) M), if M is a mask that just turns off
8473 low-order bits (as in an alignment operation) and FOO is already
8474 aligned to that boundary, mask C1 to that boundary as well.
8475 This may eliminate that PLUS and, later, the AND. */
8477 {
8481 /* If MODE is narrower than HOST_WIDE_INT and mask is a negative
8482 number, sign extend it. */
8495 }
8497 /* ... fall through ... */
8500 /* For PLUS, MINUS and MULT, we need any bits less significant than the
8501 most significant bit in MASK since carries from those bits will
8502 affect the bits we are interested in. */
8507 /* If X is (minus C Y) where C's least set bit is larger than any bit
8508 in the mask, then we may replace with (neg Y). */
8511 {
8515 }
8517 /* Similarly, if C contains every bit in the fuller_mask, then we may
8518 replace with (not Y). */
8521 {
8525 }
8532 /* If X is (ior (lshiftrt FOO C1) C2), try to commute the IOR and
8533 LSHIFTRT so we end up with an (and (lshiftrt (ior ...) ...) ...)
8534 operation which may be a bitfield extraction. Ensure that the
8535 constant we form is not wider than the mode of X. */
8547 {
8556 }
8558 binop:
8559 /* For most binary operations, just propagate into the operation and
8560 change the mode if we have an operation of that mode. */
8565 /* If we ended up truncating both operands, truncate the result of the
8566 operation instead. */
8569 {
8572 }
8582 /* For left shifts, do the same, but just for the first operand.
8583 However, we cannot do anything with shifts where we cannot
8584 guarantee that the counts are smaller than the size of the mode
8585 because such a count will have a different meaning in a
8586 wider mode. */
8596 /* If the shift count is a constant and we can do arithmetic in
8597 the mode of the shift, refine which bits we need. Otherwise, use the
8598 conservative form of the mask. */
8604 else
8616 /* Here we can only do something if the shift count is a constant,
8617 this shift constant is valid for the host, and we can do arithmetic
8618 in OP_MODE. */
8624 {
8628 /* Select the mask of the bits we need for the shift operand. */
8631 /* We can only change the mode of the shift if we can do arithmetic
8632 in the mode of the shift and INNER_MASK is no wider than the
8633 width of X's mode. */
8641 }
8643 /* If we have (and (lshiftrt FOO C1) C2) where the combination of the
8644 shift and AND produces only copies of the sign bit (C2 is one less
8645 than a power of two), we can do this with just a shift. */
8649 /* The shift puts one of the sign bit copies in the least significant
8650 bit. */
8655 /* Number of bits left after the shift must be more than the mask
8656 needs. */
8659 /* Must be more sign bit copies than the mask needs. */
8669 /* If we are just looking for the sign bit, we don't need this shift at
8670 all, even if it has a variable count. */
8674 /* If this is a shift by a constant, get a mask that contains those bits
8675 that are not copies of the sign bit. We then have two cases: If
8676 MASK only includes those bits, this can be a logical shift, which may
8677 allow simplifications. If MASK is a single-bit field not within
8678 those bits, we are requesting a copy of the sign bit and hence can
8679 shift the sign bit to the appropriate location. */
8683 {
8686 /* If the considered data is wider than HOST_WIDE_INT, we can't
8687 represent a mask for all its bits in a single scalar.
8688 But we only care about the lower bits, so calculate these. */
8691 {
8694 /* GET_MODE_PRECISION (GET_MODE (x)) - INTVAL (XEXP (x, 1))
8695 is the number of bits a full-width mask would have set.
8696 We need only shift if these are fewer than nonzero can
8697 hold. If not, we must keep all bits set in nonzero. */
8702 + HOST_BITS_PER_WIDE_INT
8704 }
8705 else
8706 {
8709 }
8712 {
8717 }
8720 {
8721 x = simplify_shift_const
8727 }
8728 }
8730 /* If MASK is 1, convert this to an LSHIFTRT. This can be done
8731 even if the shift count isn't a constant. */
8736 shiftrt:
8738 /* If this is a zero- or sign-extension operation that just affects bits
8739 we don't care about, remove it. Be sure the call above returned
8740 something that is still a shift. */
8750 next_select);
8756 /* If the shift count is constant and we can do computations
8757 in the mode of X, compute where the bits we care about are.
8758 Otherwise, we can't do anything. Don't change the mode of
8759 the shift or propagate MODE into the shift, though. */
8762 {
8772 }
8776 /* If we just want the low-order bit, the NEG isn't needed since it
8777 won't change the low-order bit. */
8781 /* We need any bits less significant than the most significant bit in
8782 MASK since carries from those bits will affect the bits we are
8783 interested in. */
8788 /* (not FOO) is (xor FOO CONST), so if FOO is an LSHIFTRT, we can do the
8789 same as the XOR case above. Ensure that the constant we form is not
8790 wider than the mode of X. */
8798 {
8807 }
8809 /* (and (not FOO) CONST) is (not (or FOO (not CONST))), so we must
8810 use the full mask inside the NOT. */
8813 unop:
8816 next_select));
8822 /* (and (ne FOO 0) CONST) can be (and FOO CONST) if CONST is included
8823 in STORE_FLAG_VALUE and FOO has a single bit that might be nonzero,
8824 which is equal to STORE_FLAG_VALUE. */
8836 /* We have no way of knowing if the IF_THEN_ELSE can itself be
8837 written in a narrower mode. We play it safe and do not do so. */
8853 }
8855 /* Ensure we return a value of the proper mode. */
8857 }
8858 \f
8859 /* Return nonzero if X is an expression that has one of two values depending on
8860 whether some other value is zero or nonzero. In that case, we return the
8861 value that is being tested, *PTRUE is set to the value if the rtx being
8862 returned has a nonzero value, and *PFALSE is set to the other alternative.
8864 If we return zero, we set *PTRUE and *PFALSE to X. */
8866 static rtx
8868 {
8874 /* If we are comparing a value against zero, we are done. */
8877 {
8881 }
8883 /* If this is a unary operation whose operand has one of two values, apply
8884 our opcode to compute those values. */
8887 {
8892 }
8894 /* If this is a COMPARE, do nothing, since the IF_THEN_ELSE we would
8895 make can't possibly match and would suppress other optimizations. */
8897 ;
8899 /* If this is a binary operation, see if either side has only one of two
8900 values. If either one does or if both do and they are conditional on
8901 the same value, compute the new true and false values. */
8903 {
8909 {
8910 /* If if_then_else_cond returned zero, then true/false are the
8911 same rtl. We must copy one of them to prevent invalid rtl
8912 sharing. */
8919 {
8924 }
8925 else
8926 {
8929 }
8932 }
8934 /* See if we have PLUS, IOR, XOR, MINUS or UMAX, where one of the
8935 operands is zero when the other is nonzero, and vice-versa,
8936 and STORE_FLAG_VALUE is 1 or -1. */
8942 {
8959 {
8966 const_true_rtx);
8968 }
8969 }
8971 /* Similarly for MULT, AND and UMIN, except that for these the result
8972 is always zero. */
8976 {
8990 {
8993 }
8994 }
8995 }
8998 {
8999 /* If we have IF_THEN_ELSE already, extract the condition and
9000 canonicalize it if it is NE or EQ. */
9006 {
9009 }
9010 else
9012 }
9014 /* If X is a SUBREG, we can narrow both the true and false values
9015 if the inner expression, if there is a condition. */
9019 {
9025 {
9029 }
9030 }
9032 /* If X is a constant, this isn't special and will cause confusions
9033 if we treat it as such. Likewise if it is equivalent to a constant. */
9036 ;
9038 /* If we're in BImode, canonicalize on 0 and STORE_FLAG_VALUE, as that
9039 will be least confusing to the rest of the compiler. */
9041 {
9044 }
9046 /* If X is known to be either 0 or -1, those are the true and
9047 false values when testing X. */
9051 {
9054 }
9056 /* Likewise for 0 or a single bit. */
9059 {
9062 }
9064 /* Otherwise fail; show no condition with true and false values the same. */
9067 }
9068 \f
9069 /* Return the value of expression X given the fact that condition COND
9070 is known to be true when applied to REG as its first operand and VAL
9071 as its second. X is known to not be shared and so can be modified in
9072 place.
9074 We only handle the simplest cases, and specifically those cases that
9075 arise with IF_THEN_ELSE expressions. */
9077 static rtx
9079 {
9087 /* If either operand of the condition is a floating point value,
9088 then we have to avoid collapsing an EQ comparison. */
9098 /* If X is (abs REG) and we know something about REG's relationship
9099 with zero, we may be able to simplify this. */
9103 {
9112 }
9114 /* The only other cases we handle are MIN, MAX, and comparisons if the
9115 operands are the same as REG and VAL. */
9118 {
9120 {
9123 }
9126 {
9128 {
9136 else
9138 }
9141 {
9144 /* Do not reverse the condition when it is NE or EQ.
9145 This is because we cannot conclude anything about
9146 the value of 'SMAX (x, y)' when x is not equal to y,
9147 but we can when x equals y. */
9153 {
9164 }
9165 }
9166 }
9167 }
9169 {
9174 {
9175 /* We must simplify subreg here, before we lose track of the
9176 original inner_mode. */
9181 else
9183 }
9186 }
9187 /* We don't have to handle SIGN_EXTEND here, because even in the
9188 case of replacing something with a modeless CONST_INT, a
9189 CONST_INT is already (supposed to be) a valid sign extension for
9190 its narrower mode, which implies it's already properly
9191 sign-extended for the wider mode. Now, for ZERO_EXTEND, the
9192 story is different. */
9194 {
9199 {
9200 /* We must simplify the zero_extend here, before we lose
9201 track of the original inner_mode. */
9206 else
9208 }
9211 }
9215 {
9222 }
9225 }
9226 \f
9227 /* See if X and Y are equal for the purposes of seeing if we can rewrite an
9228 assignment as a field assignment. */
9230 static int
9232 {
9234 {
9239 /* For big endian, adjust the memory offset. */
9244 else
9246 }
9254 /* Check for a paradoxical SUBREG of a MEM compared with the MEM.
9255 Note that all SUBREGs of MEM are paradoxical; otherwise they
9256 would have been rewritten. */
9269 /* We used to see if get_last_value of X and Y were the same but that's
9270 not correct. In one direction, we'll cause the assignment to have
9271 the wrong destination and in the case, we'll import a register into this
9272 insn that might have already have been dead. So fail if none of the
9273 above cases are true. */
9275 }
9276 \f
9277 /* See if X, a SET operation, can be rewritten as a bit-field assignment.
9278 Return that assignment if so.
9280 We only handle the most common cases. */
9282 static rtx
9284 {
9287 rtx assign;
9289 HOST_WIDE_INT c1;
9290 HOST_WIDE_INT pos;
9292 rtx other;
9293 machine_mode mode;
9295 /* If SRC was (and (not (ashift (const_int 1) POS)) DEST), this is
9296 a clear of a one-bit field. We will have changed it to
9297 (and (rotate (const_int -2) POS) DEST), so check for that. Also check
9298 for a SUBREG. */
9304 {
9310 }
9320 {
9327 }
9329 /* If SRC is (ior (ashift (const_int 1) POS) DEST), this is a set of a
9330 one-bit field. */
9334 {
9340 }
9342 /* If DEST is already a field assignment, i.e. ZERO_EXTRACT, and the
9343 SRC is an AND with all bits of that field set, then we can discard
9344 the AND. */
9349 {
9356 else
9359 /* Complete overlap. We can remove the source AND. */
9363 /* Partial overlap. We can reduce the source AND. */
9365 {
9370 }
9371 }
9373 /* The other case we handle is assignments into a constant-position
9374 field. They look like (ior/xor (and DEST C1) OTHER). If C1 represents
9375 a mask that has all one bits except for a group of zero bits and
9376 OTHER is known to have zeros where C1 has ones, this is such an
9377 assignment. Compute the position and length from C1. Shift OTHER
9378 to the appropriate position, force it to the required mode, and
9379 make the extraction. Check for the AND in both operands. */
9381 /* One or more SUBREGs might obscure the constant-position field
9382 assignment. The first one we are likely to encounter is an outer
9383 narrowing SUBREG, which we can just strip for the purposes of
9384 identifying the constant-field assignment. */
9398 /* The second SUBREG that might get in the way is a paradoxical
9399 SUBREG around the first operand of the AND. We want to
9400 pretend the operand is as wide as the destination here. We
9401 do this by adjusting the MEM to wider mode for the sole
9402 purpose of the call to rtx_equal_for_field_assignment_p. Also
9403 note this trick only works for MEMs. */
9415 /* The second SUBREG that might get in the way is a paradoxical
9416 SUBREG around the first operand of the AND. We want to
9417 pretend the operand is as wide as the destination here. We
9418 do this by adjusting the MEM to wider mode for the sole
9419 purpose of the call to rtx_equal_for_field_assignment_p. Also
9420 note this trick only works for MEMs. */
9428 else
9441 /* The mode to use for the source is the mode of the assignment, or of
9442 what is inside a possible STRICT_LOW_PART. */
9446 /* Shift OTHER right POS places and make it the source, restricting it
9447 to the proper length and mode. */
9452 dest);
9459 /* If SRC is masked by an AND that does not make a difference in
9460 the value being stored, strip it. */
9471 }
9472 \f
9473 /* See if X is of the form (+ (* a c) (* b c)) and convert to (* (+ a b) c)
9474 if so. */
9476 static rtx
9478 {
9482 rtx tem;
9484 /* Distributivity is not true for floating point as it can change the
9485 value. So we don't do it unless -funsafe-math-optimizations. */
9490 /* The outer operation can only be one of the following: */
9498 /* If either operand is a primitive we can't do anything, so get out
9499 fast. */
9509 /* See if the inner and outer operations distribute. */
9511 {
9516 /* These all distribute except over PLUS. */
9527 /* This is also a multiply, so it distributes over everything. */
9530 /* This used to handle SUBREG, but this turned out to be counter-
9531 productive, since (subreg (op ...)) usually is not handled by
9532 insn patterns, and this "optimization" therefore transformed
9533 recognizable patterns into unrecognizable ones. Therefore the
9534 SUBREG case was removed from here.
9536 It is possible that distributing SUBREG over arithmetic operations
9537 leads to an intermediate result than can then be optimized further,
9538 e.g. by moving the outer SUBREG to the other side of a SET as done
9539 in simplify_set. This seems to have been the original intent of
9540 handling SUBREGs here.
9542 However, with current GCC this does not appear to actually happen,
9543 at least on major platforms. If some case is found where removing
9544 the SUBREG case here prevents follow-on optimizations, distributing
9545 SUBREGs ought to be re-added at that place, e.g. in simplify_set. */
9549 }
9551 /* Set LHS and RHS to the inner operands (A and B in the example
9552 above) and set OTHER to the common operand (C in the example).
9553 There is only one way to do this unless the inner operation is
9554 commutative. */
9566 else
9569 /* Form the new inner operation, seeing if it simplifies first. */
9572 /* There is one exception to the general way of distributing:
9573 (a | c) ^ (b | c) -> (a ^ b) & ~c */
9575 {
9578 }
9580 /* We may be able to continuing distributing the result, so call
9581 ourselves recursively on the inner operation before forming the
9582 outer operation, which we return. */
9585 }
9587 /* See if X is of the form (* (+ A B) C), and if so convert to
9588 (+ (* A C) (* B C)) and try to simplify.
9590 Most of the time, this results in no change. However, if some of
9591 the operands are the same or inverses of each other, simplifications
9592 will result.
9594 For example, (and (ior A B) (not B)) can occur as the result of
9595 expanding a bit field assignment. When we apply the distributive
9596 law to this, we get (ior (and (A (not B))) (and (B (not B)))),
9597 which then simplifies to (and (A (not B))).
9599 Note that no checks happen on the validity of applying the inverse
9600 distributive law. This is pointless since we can do it in the
9601 few places where this routine is called.
9603 N is the index of the term that is decomposed (the arithmetic operation,
9604 i.e. (+ A B) in the first example above). !N is the index of the term that
9605 is distributed, i.e. of C in the first example above. */
9606 static rtx
9608 {
9609 machine_mode mode;
9613 /* Distributivity is not true for floating point as it can change the
9614 value. So we don't do it unless -funsafe-math-optimizations. */
9631 /* Special case (and (xor B C) (not A)), which is equivalent to
9632 (xor (ior A B) (ior A C)) */
9634 {
9637 }
9640 {
9641 /* Distribute the second term. */
9644 }
9645 else
9646 {
9647 /* Distribute the first term. */
9650 }
9660 }
9661 \f
9662 /* Simplify a logical `and' of VAROP with the constant CONSTOP, to be done
9663 in MODE. Return an equivalent form, if different from (and VAROP
9664 (const_int CONSTOP)). Otherwise, return NULL_RTX. */
9666 static rtx
9669 {
9672 rtx orig_varop;
9680 /* Simplify VAROP knowing that we will be only looking at some of the
9681 bits in it.
9683 Note by passing in CONSTOP, we guarantee that the bits not set in
9684 CONSTOP are not significant and will never be examined. We must
9685 ensure that is the case by explicitly masking out those bits
9686 before returning. */
9689 /* If VAROP is a CLOBBER, we will fail so return it. */
9693 /* If VAROP is a CONST_INT, then we need to apply the mask in CONSTOP
9694 to VAROP and return the new constant. */
9698 /* See what bits may be nonzero in VAROP. Unlike the general case of
9699 a call to nonzero_bits, here we don't care about bits outside
9700 MODE. */
9704 /* Turn off all bits in the constant that are known to already be zero.
9705 Thus, if the AND isn't needed at all, we will have CONSTOP == NONZERO_BITS
9706 which is tested below. */
9710 /* If we don't have any bits left, return zero. */
9714 /* If VAROP is a NEG of something known to be zero or 1 and CONSTOP is
9715 a power of two, we can replace this with an ASHIFT. */
9720 /* If VAROP is an IOR or XOR, apply the AND to both branches of the IOR
9721 or XOR, then try to apply the distributive law. This may eliminate
9722 operations if either branch can be simplified because of the AND.
9723 It may also make some cases more complex, but those cases probably
9724 won't match a pattern either with or without this. */
9727 return
9728 gen_lowpart
9730 apply_distributive_law
9735 constop),
9739 constop))));
9741 /* If VAROP is PLUS, and the constant is a mask of low bits, distribute
9742 the AND and see if one of the operands simplifies to zero. If so, we
9743 may eliminate it. */
9747 {
9756 }
9758 /* Make a SUBREG if necessary. If we can't make it, fail. */
9763 /* If we are only masking insignificant bits, return VAROP. */
9770 /* Otherwise, return an AND. */
9772 }
9775 /* We have X, a logical `and' of VAROP with the constant CONSTOP, to be done
9776 in MODE.
9778 Return an equivalent form, if different from X. Otherwise, return X. If
9779 X is zero, we are to always construct the equivalent form. */
9781 static rtx
9784 {
9795 }
9796 \f
9797 /* Given a REG, X, compute which bits in X can be nonzero.
9798 We don't care about bits outside of those defined in MODE.
9800 For most X this is simply GET_MODE_MASK (GET_MODE (MODE)), but if X is
9801 a shift, AND, or zero_extract, we can do better. */
9803 static rtx
9805 const_rtx known_x ATTRIBUTE_UNUSED,
9806 machine_mode known_mode ATTRIBUTE_UNUSED,
9809 {
9810 rtx tem;
9813 /* If X is a register whose nonzero bits value is current, use it.
9814 Otherwise, if X is a register whose value we can find, use that
9815 value. Otherwise, use the previously-computed global nonzero bits
9816 for this register. */
9830 && !REGNO_REG_SET_P
9833 {
9837 /* We don't know anything about the upper bits. */
9842 }
9847 {
9848 #ifdef SHORT_IMMEDIATES_SIGN_EXTEND
9851 #endif
9853 }
9855 {
9859 /* We don't know anything about the upper bits. */
9863 }
9866 }
9868 /* Return the number of bits at the high-order end of X that are known to
9869 be equal to the sign bit. X will be used in mode MODE; if MODE is
9870 VOIDmode, X will be used in its own mode. The returned value will always
9871 be between 1 and the number of bits in MODE. */
9873 static rtx
9875 const_rtx known_x ATTRIBUTE_UNUSED,
9876 machine_mode known_mode
9877 ATTRIBUTE_UNUSED,
9880 {
9881 rtx tem;
9894 && !REGNO_REG_SET_P
9897 {
9900 }
9911 }
9912 \f
9913 /* Return the number of "extended" bits there are in X, when interpreted
9914 as a quantity in MODE whose signedness is indicated by UNSIGNEDP. For
9915 unsigned quantities, this is the number of high-order zero bits.
9916 For signed quantities, this is the number of copies of the sign bit
9917 minus 1. In both case, this function returns the number of "spare"
9918 bits. For example, if two quantities for which this function returns
9919 at least 1 are added, the addition is known not to overflow.
9921 This function will always return 0 unless called during combine, which
9922 implies that it must be called from a define_split. */
9924 unsigned int
9926 {
9936 }
9938 /* This function is called from `simplify_shift_const' to merge two
9939 outer operations. Specifically, we have already found that we need
9940 to perform operation *POP0 with constant *PCONST0 at the outermost
9941 position. We would now like to also perform OP1 with constant CONST1
9942 (with *POP0 being done last).
9944 Return 1 if we can do the operation and update *POP0 and *PCONST0 with
9945 the resulting operation. *PCOMP_P is set to 1 if we would need to
9946 complement the innermost operand, otherwise it is unchanged.
9948 MODE is the mode in which the operation will be done. No bits outside
9949 the width of this mode matter. It is assumed that the width of this mode
9950 is smaller than or equal to HOST_BITS_PER_WIDE_INT.
9952 If *POP0 or OP1 are UNKNOWN, it means no operation is required. Only NEG, PLUS,
9953 IOR, XOR, and AND are supported. We may set *POP0 to SET if the proper
9954 result is simply *PCONST0.
9956 If the resulting operation cannot be expressed as one operation, we
9957 return 0 and do not change *POP0, *PCONST0, and *PCOMP_P. */
9959 static int
9960 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)
9961 {
9968 /* If OP0 is an AND, clear unimportant bits in CONST1. */
9972 /* If OP0 or OP1 is UNKNOWN, this is easy. Similarly if they are the same or
9973 if OP0 is SET. */
9982 {
9984 {
10002 }
10003 }
10005 /* Otherwise, if either is a PLUS or NEG, we can't do anything. */
10009 /* If the two constants aren't the same, we can't do anything. The
10010 remaining six cases can all be done. */
10014 else
10016 {
10019 /* (a & b) | b == b */
10022 /* (a ^ b) | b == a | b */
10023 {;}
10028 /* (a & b) ^ b == (~a) & b */
10031 /* (a | b) ^ b == a & ~b */
10037 /* (a | b) & b == b */
10040 /* (a ^ b) & b) == (~a) & b */
10045 }
10047 /* Check for NO-OP cases. */
10060 /* ??? Slightly redundant with the above mask, but not entirely.
10061 Moving this above means we'd have to sign-extend the mode mask
10062 for the final test. */
10067 }
10068 \f
10069 /* A helper to simplify_shift_const_1 to determine the mode we can perform
10070 the shift in. The original shift operation CODE is performed on OP in
10071 ORIG_MODE. Return the wider mode MODE if we can perform the operation
10072 in that mode. Return ORIG_MODE otherwise. We can also assume that the
10073 result of the shift is subject to operation OUTER_CODE with operand
10074 OUTER_CONST. */
10076 static machine_mode
10080 {
10085 /* In general we can't perform in wider mode for right shift and rotate. */
10087 {
10089 /* We can still widen if the bits brought in from the left are identical
10090 to the sign bit of ORIG_MODE. */
10098 /* Similarly here but with zero bits. */
10103 /* We can also widen if the bits brought in will be masked off. This
10104 operation is performed in ORIG_MODE. */
10106 {
10112 }
10113 /* fall through */
10123 }
10124 }
10126 /* Simplify a shift of VAROP by ORIG_COUNT bits. CODE says what kind
10127 of shift. The result of the shift is RESULT_MODE. Return NULL_RTX
10128 if we cannot simplify it. Otherwise, return a simplified value.
10130 The shift is normally computed in the widest mode we find in VAROP, as
10131 long as it isn't a different number of words than RESULT_MODE. Exceptions
10132 are ASHIFTRT and ROTATE, which are always done in their original mode. */
10134 static rtx
10137 {
10143 unsigned int mode_words
10145 /* We form (outer_op (code varop count) (outer_const)). */
10151 /* Make sure and truncate the "natural" shift on the way in. We don't
10152 want to do this inside the loop as it makes it more difficult to
10153 combine shifts. */
10157 /* If we were given an invalid count, don't do anything except exactly
10158 what was requested. */
10165 /* Unless one of the branches of the `if' in this loop does a `continue',
10166 we will `break' the loop after the `if'. */
10169 {
10170 /* If we have an operand of (clobber (const_int 0)), fail. */
10174 /* Convert ROTATERT to ROTATE. */
10176 {
10181 else
10183 }
10188 /* Handle cases where the count is greater than the size of the mode
10189 minus 1. For ASHIFT, use the size minus one as the count (this can
10190 occur when simplifying (lshiftrt (ashiftrt ..))). For rotates,
10191 take the count modulo the size. For other shifts, the result is
10192 zero.
10194 Since these shifts are being produced by the compiler by combining
10195 multiple operations, each of which are defined, we know what the
10196 result is supposed to be. */
10199 {
10204 else
10205 {
10206 /* We can't simply return zero because there may be an
10207 outer op. */
10211 }
10212 }
10214 /* If we discovered we had to complement VAROP, leave. Making a NOT
10215 here would cause an infinite loop. */
10219 /* An arithmetic right shift of a quantity known to be -1 or 0
10220 is a no-op. */
10224 {
10227 }
10229 /* If we are doing an arithmetic right shift and discarding all but
10230 the sign bit copies, this is equivalent to doing a shift by the
10231 bitsize minus one. Convert it into that shift because it will often
10232 allow other simplifications. */
10239 /* We simplify the tests below and elsewhere by converting
10240 ASHIFTRT to LSHIFTRT if we know the sign bit is clear.
10241 `make_compound_operation' will convert it to an ASHIFTRT for
10242 those machines (such as VAX) that don't have an LSHIFTRT. */
10259 {
10266 {
10269 }
10273 /* If we have (xshiftrt (mem ...) C) and C is MODE_WIDTH
10274 minus the width of a smaller mode, we can do this with a
10275 SIGN_EXTEND or ZERO_EXTEND from the narrower memory location. */
10282 {
10291 }
10295 /* If VAROP is a SUBREG, strip it as long as the inner operand has
10296 the same number of words as what we've seen so far. Then store
10297 the widest mode in MODE. */
10303 == mode_words
10306 {
10311 }
10315 /* Some machines use MULT instead of ASHIFT because MULT
10316 is cheaper. But it is still better on those machines to
10317 merge two shifts into one. */
10320 {
10321 varop
10327 }
10331 /* Similar, for when divides are cheaper. */
10334 {
10335 varop
10341 }
10345 /* If we are extracting just the sign bit of an arithmetic
10346 right shift, that shift is not needed. However, the sign
10347 bit of a wider mode may be different from what would be
10348 interpreted as the sign bit in a narrower mode, so, if
10349 the result is narrower, don't discard the shift. */
10354 {
10357 }
10359 /* ... fall through ... */
10364 /* Here we have two nested shifts. The result is usually the
10365 AND of a new shift with a mask. We compute the result below. */
10372 {
10376 rtx mask_rtx;
10378 /* We have one common special case. We can't do any merging if
10379 the inner code is an ASHIFTRT of a smaller mode. However, if
10380 we have (ashift:M1 (subreg:M1 (ashiftrt:M2 FOO C1) 0) C2)
10381 with C2 == GET_MODE_BITSIZE (M1) - GET_MODE_BITSIZE (M2),
10382 we can convert it to
10383 (ashiftrt:M1 (ashift:M1 (and:M1 (subreg:M1 FOO 0) C3) C2) C1).
10384 This simplifies certain SIGN_EXTEND operations. */
10388 {
10389 /* C3 has the low-order C1 bits zero. */
10401 }
10403 /* If this was (ashiftrt (ashift foo C1) C2) and FOO has more
10404 than C1 high-order bits equal to the sign bit, we can convert
10405 this to either an ASHIFT or an ASHIFTRT depending on the
10406 two counts.
10408 We cannot do this if VAROP's mode is not SHIFT_MODE. */
10414 {
10418 {
10421 }
10424 }
10426 /* There are some cases we can't do. If CODE is ASHIFTRT,
10427 we can only do this if FIRST_CODE is also ASHIFTRT.
10429 We can't do the case when CODE is ROTATE and FIRST_CODE is
10430 ASHIFTRT.
10432 If the mode of this shift is not the mode of the outer shift,
10433 we can't do this if either shift is a right shift or ROTATE.
10435 Finally, we can't do any of these if the mode is too wide
10436 unless the codes are the same.
10438 Handle the case where the shift codes are the same
10439 first. */
10442 {
10451 }
10462 /* To compute the mask to apply after the shift, shift the
10463 nonzero bits of the inner shift the same way the
10464 outer shift will. */
10467 result_mode);
10469 mask_rtx
10473 /* Give up if we can't compute an outer operation to use. */
10481 /* If the shifts are in the same direction, we add the
10482 counts. Otherwise, we subtract them. */
10486 else
10489 /* If COUNT is positive, the new shift is usually CODE,
10490 except for the two exceptions below, in which case it is
10491 FIRST_CODE. If the count is negative, FIRST_CODE should
10492 always be used */
10502 }
10504 /* If we have (A << B << C) for any shift, we can convert this to
10505 (A << C << B). This wins if A is a constant. Only try this if
10506 B is not a constant. */
10511 {
10518 }
10525 /* Make this fit the case below. */
10532 /* If we have (xshiftrt (ior (plus X (const_int -1)) X) C)
10533 with C the size of VAROP - 1 and the shift is logical if
10534 STORE_FLAG_VALUE is 1 and arithmetic if STORE_FLAG_VALUE is -1,
10535 we have an (le X 0) operation. If we have an arithmetic shift
10536 and STORE_FLAG_VALUE is 1 or we have a logical shift with
10537 STORE_FLAG_VALUE of -1, we have a (neg (le X 0)) operation. */
10545 {
10548 const0_rtx);
10554 }
10556 /* If we have (shift (logical)), move the logical to the outside
10557 to allow it to possibly combine with another logical and the
10558 shift to combine with another shift. This also canonicalizes to
10559 what a ZERO_EXTRACT looks like. Also, some machines have
10560 (and (shift)) insns. */
10563 /* We can't do this if we have (ashiftrt (xor)) and the
10564 constant has its sign bit set in shift_mode with shift_mode
10565 wider than result_mode. */
10569 shift_mode))
10577 {
10580 }
10582 /* If we can't do that, try to simplify the shift in each arm of the
10583 logical expression, make a new logical expression, and apply
10584 the inverse distributive law. This also can't be done for
10585 (ashiftrt (xor)) where we've widened the shift and the constant
10586 changes the sign bit. */
10591 shift_mode)))
10592 {
10604 }
10608 /* Convert (lshiftrt (eq FOO 0) C) to (xor FOO 1) if STORE_FLAG_VALUE
10609 says that the sign bit can be tested, FOO has mode MODE, C is
10610 GET_MODE_PRECISION (MODE) - 1, and FOO has only its low-order bit
10611 that may be nonzero. */
10621 {
10625 }
10629 /* (lshiftrt (neg A) C) where A is either 0 or 1 and C is one less
10630 than the number of bits in the mode is equivalent to A. */
10634 {
10638 }
10640 /* NEG commutes with ASHIFT since it is multiplication. Move the
10641 NEG outside to allow shifts to combine. */
10645 {
10648 }
10652 /* (lshiftrt (plus A -1) C) where A is either 0 or 1 and C
10653 is one less than the number of bits in the mode is
10654 equivalent to (xor A 1). */
10661 {
10665 }
10667 /* If we have (xshiftrt (plus FOO BAR) C), and the only bits
10668 that might be nonzero in BAR are those being shifted out and those
10669 bits are known zero in FOO, we can replace the PLUS with FOO.
10670 Similarly in the other operand order. This code occurs when
10671 we are computing the size of a variable-size array. */
10678 {
10681 }
10689 result_mode)))
10690 {
10693 }
10695 /* (ashift (plus foo C) N) is (plus (ashift foo N) C'). */
10705 {
10708 }
10710 /* Check for 'PLUS signbit', which is the canonical form of 'XOR
10711 signbit', and attempt to change the PLUS to an XOR and move it to
10712 the outer operation as is done above in the AND/IOR/XOR case
10713 leg for shift(logical). See details in logical handling above
10714 for reasoning in doing so. */
10725 {
10728 }
10733 /* If we have (xshiftrt (minus (ashiftrt X C)) X) C)
10734 with C the size of VAROP - 1 and the shift is logical if
10735 STORE_FLAG_VALUE is 1 and arithmetic if STORE_FLAG_VALUE is -1,
10736 we have a (gt X 0) operation. If the shift is arithmetic with
10737 STORE_FLAG_VALUE of 1 or logical with STORE_FLAG_VALUE == -1,
10738 we have a (neg (gt X 0)) operation. */
10747 {
10750 const0_rtx);
10756 }
10760 /* Change (lshiftrt (truncate (lshiftrt))) to (truncate (lshiftrt))
10761 if the truncate does not affect the value. */
10768 {
10771 varop_inner
10774 GEN_INT
10779 }
10784 }
10787 }
10792 /* We have now finished analyzing the shift. The result should be
10793 a shift of type CODE with SHIFT_MODE shifting VAROP COUNT places. If
10794 OUTER_OP is non-UNKNOWN, it is an operation that needs to be applied
10795 to the result of the shift. OUTER_CONST is the relevant constant,
10796 but we must turn off all bits turned off in the shift. */
10804 /* Make a SUBREG if necessary. If we can't make it, fail. */
10809 /* If we have an outer operation and we just made a shift, it is
10810 possible that we could have simplified the shift were it not
10811 for the outer operation. So try to do the simplification
10812 recursively. */
10816 else
10822 /* If we were doing an LSHIFTRT in a wider mode than it was originally,
10823 turn off all the bits that the shift would have turned off. */
10828 /* Do the remainder of the processing in RESULT_MODE. */
10831 /* If COMPLEMENT_P is set, we have to complement X before doing the outer
10832 operation. */
10837 {
10845 {
10846 /* This means that we have determined that the result is
10847 equivalent to a constant. This should be rare. */
10850 }
10853 else
10856 }
10859 }
10861 /* Simplify a shift of VAROP by COUNT bits. CODE says what kind of shift.
10862 The result of the shift is RESULT_MODE. If we cannot simplify it,
10863 return X or, if it is NULL, synthesize the expression with
10864 simplify_gen_binary. Otherwise, return a simplified value.
10866 The shift is normally computed in the widest mode we find in VAROP, as
10867 long as it isn't a different number of words than RESULT_MODE. Exceptions
10868 are ASHIFTRT and ROTATE, which are always done in their original mode. */
10870 static rtx
10873 {
10883 }
10885 \f
10886 /* A subroutine of recog_for_combine. See there for arguments and
10887 return value. */
10889 static int
10891 {
10893 rtx pat_without_clobbers;
10901 /* If PAT is a PARALLEL, check to see if it contains the CLOBBER
10902 we use to indicate that something didn't match. If we find such a
10903 thing, force rejection. */
10917 {
10920 else
10923 }
10925 /* If it isn't, there is the possibility that we previously had an insn
10926 that clobbered some register as a side effect, but the combined
10927 insn doesn't need to do that. So try once more without the clobbers
10928 unless this represents an ASM insn. */
10932 {
10937 {
10940 pos++;
10941 }
10951 {
10954 else
10957 }
10958 }
10965 /* Recognize all noop sets, these will be killed by followup pass. */
10969 /* If we had any clobbers to add, make a new pattern than contains
10970 them. Then check to make sure that all of them are dead. */
10972 {
10982 else
10989 {
10994 {
10998 }
10999 }
11001 }
11005 {
11012 /* Allow targets to reject combined insn. */
11014 {
11017 dump_file);
11019 /* Callers expect recog_for_combine to strip
11020 clobbers from the pattern on failure. */
11025 }
11030 }
11036 }
11038 /* Change every ZERO_EXTRACT and ZERO_EXTEND of a SUBREG that can be
11039 expressed as an AND and maybe an LSHIFTRT, to that formulation.
11040 Return whether anything was so changed. */
11042 static bool
11044 {
11049 {
11058 {
11066 }
11071 {
11074 }
11075 else
11080 mask--;
11086 }
11089 }
11091 /* Like recog, but we receive the address of a pointer to a new pattern.
11092 We try to match the rtx that the pointer points to.
11093 If that fails, we may try to modify or replace the pattern,
11094 storing the replacement into the same pointer object.
11096 Modifications include deletion or addition of CLOBBERs. If the
11097 instruction will still not match, we change ZERO_EXTEND and ZERO_EXTRACT
11098 to the equivalent AND and perhaps LSHIFTRT patterns, and try with that
11099 (and undo if that fails).
11101 PNOTES is a pointer to a location where any REG_UNUSED notes added for
11102 the CLOBBERs are placed.
11104 The value is the final insn code from the pattern ultimately matched,
11105 or -1. */
11107 static int
11109 {
11121 {
11124 {
11128 }
11129 }
11132 {
11137 }
11140 }
11141 \f
11142 /* Like gen_lowpart_general but for use by combine. In combine it
11143 is not possible to create any new pseudoregs. However, it is
11144 safe to create invalid memory addresses, because combine will
11145 try to recognize them and all they will do is make the combine
11146 attempt fail.
11148 If for some reason this cannot do its job, an rtx
11149 (clobber (const_int 0)) is returned.
11150 An insn containing that will not be recognized. */
11152 static rtx
11154 {
11158 rtx result;
11163 /* We can only support MODE being wider than a word if X is a
11164 constant integer or has a mode the same size. */
11169 /* X might be a paradoxical (subreg (mem)). In that case, gen_lowpart
11170 won't know what to do. So we will strip off the SUBREG here and
11171 process normally. */
11173 {
11176 /* For use in case we fall down into the address adjustments
11177 further below, we need to adjust the known mode and size of
11178 x; imode and isize, since we just adjusted x. */
11185 }
11193 {
11196 /* Refuse to work on a volatile memory ref or one with a mode-dependent
11197 address. */
11202 /* If we want to refer to something bigger than the original memref,
11203 generate a paradoxical subreg instead. That will force a reload
11204 of the original memref X. */
11211 /* Adjust the address so that the address-after-the-data is
11212 unchanged. */
11217 }
11219 /* If X is a comparison operator, rewrite it in a new mode. This
11220 probably won't match, but may allow further simplifications. */
11224 /* If we couldn't simplify X any other way, just enclose it in a
11225 SUBREG. Normally, this SUBREG won't match, but some patterns may
11226 include an explicit SUBREG or we may simplify it further in combine. */
11227 else
11228 {
11230 rtx res;
11234 {
11239 }
11243 }
11245 fail:
11247 }
11248 \f
11249 /* Try to simplify a comparison between OP0 and a constant OP1,
11250 where CODE is the comparison code that will be tested, into a
11251 (CODE OP0 const0_rtx) form.
11253 The result is a possibly different comparison code to use.
11254 *POP1 may be updated. */
11256 static enum rtx_code
11259 {
11263 /* Get the constant we are comparing against and turn off all bits
11264 not on in our mode. */
11268 /* If we are comparing against a constant power of two and the value
11269 being compared can only have that single bit nonzero (e.g., it was
11270 `and'ed with that bit), we can replace this with a comparison
11271 with zero. */
11279 {
11282 }
11284 /* Similarly, if we are comparing a value known to be either -1 or
11285 0 with -1, change it to the opposite comparison against zero. */
11290 {
11293 }
11295 /* Do some canonicalizations based on the comparison code. We prefer
11296 comparisons against zero and then prefer equality comparisons.
11297 If we can reduce the size of a constant, we will do that too. */
11299 {
11301 /* < C is equivalent to <= (C - 1) */
11303 {
11306 /* ... fall through to LE case below. */
11307 }
11308 else
11312 /* <= C is equivalent to < (C + 1); we do this for C < 0 */
11314 {
11317 }
11319 /* If we are doing a <= 0 comparison on a value known to have
11320 a zero sign bit, we can replace this with == 0. */
11330 /* >= C is equivalent to > (C - 1). */
11332 {
11335 /* ... fall through to GT below. */
11336 }
11337 else
11341 /* > C is equivalent to >= (C + 1); we do this for C < 0. */
11343 {
11346 }
11348 /* If we are doing a > 0 comparison on a value known to have
11349 a zero sign bit, we can replace this with != 0. */
11359 /* < C is equivalent to <= (C - 1). */
11361 {
11364 /* ... fall through ... */
11365 }
11366 /* (unsigned) < 0x80000000 is equivalent to >= 0. */
11370 {
11374 }
11375 else
11379 /* unsigned <= 0 is equivalent to == 0 */
11382 /* (unsigned) <= 0x7fffffff is equivalent to >= 0. */
11386 {
11389 }
11393 /* >= C is equivalent to > (C - 1). */
11395 {
11398 /* ... fall through ... */
11399 }
11401 /* (unsigned) >= 0x80000000 is equivalent to < 0. */
11405 {
11409 }
11410 else
11414 /* unsigned > 0 is equivalent to != 0 */
11417 /* (unsigned) > 0x7fffffff is equivalent to < 0. */
11421 {
11424 }
11429 }
11433 }
11434 \f
11435 /* Simplify a comparison between *POP0 and *POP1 where CODE is the
11436 comparison code that will be tested.
11438 The result is a possibly different comparison code to use. *POP0 and
11439 *POP1 may be updated.
11441 It is possible that we might detect that a comparison is either always
11442 true or always false. However, we do not perform general constant
11443 folding in combine, so this knowledge isn't useful. Such tautologies
11444 should have been detected earlier. Hence we ignore all such cases. */
11446 static enum rtx_code
11448 {
11455 /* Try a few ways of applying the same transformation to both operands. */
11457 {
11458 #ifndef WORD_REGISTER_OPERATIONS
11459 /* The test below this one won't handle SIGN_EXTENDs on these machines,
11460 so check specially. */
11475 - (GET_MODE_PRECISION
11477 {
11480 }
11481 #endif
11483 /* If both operands are the same constant shift, see if we can ignore the
11484 shift. We can if the shift is a rotate or if the bits shifted out of
11485 this shift are known to be zero for both inputs and if the type of
11486 comparison is compatible with the shift. */
11499 {
11512 else
11514 }
11516 /* If both operands are AND's of a paradoxical SUBREG by constant, the
11517 SUBREGs are of the same mode, and, in both cases, the AND would
11518 be redundant if the comparison was done in the narrower mode,
11519 do the comparison in the narrower mode (e.g., we are AND'ing with 1
11520 and the operand's possibly nonzero bits are 0xffffff01; in that case
11521 if we only care about QImode, we don't need the AND). This case
11522 occurs if the output mode of an scc insn is not SImode and
11523 STORE_FLAG_VALUE == 1 (e.g., the 386).
11525 Similarly, check for a case where the AND's are ZERO_EXTEND
11526 operations from some narrower mode even though a SUBREG is not
11527 present. */
11532 {
11549 {
11553 /* The resulting comparison is always unsigned since we masked
11554 off the original sign bit. */
11558 }
11565 {
11571 }
11575 }
11577 /* If both operands are NOT, we can strip off the outer operation
11578 and adjust the comparison code for swapped operands; similarly for
11579 NEG, except that this must be an equality comparison. */
11585 else
11587 }
11589 /* If the first operand is a constant, swap the operands and adjust the
11590 comparison code appropriately, but don't do this if the second operand
11591 is already a constant integer. */
11593 {
11596 }
11598 /* We now enter a loop during which we will try to simplify the comparison.
11599 For the most part, we only are concerned with comparisons with zero,
11600 but some things may really be comparisons with zero but not start
11601 out looking that way. */
11604 {
11611 HOST_WIDE_INT const_op;
11613 /* We only want to handle integral modes. This catches VOIDmode,
11614 CCmode, and the floating-point modes. An exception is that we
11615 can handle VOIDmode if OP0 is a COMPARE or a comparison
11616 operation. */
11623 /* Try to simplify the compare to constant, possibly changing the
11624 comparison op, and/or changing op1 to zero. */
11628 /* Compute some predicates to simplify code below. */
11635 /* If this is a sign bit comparison and we can do arithmetic in
11636 MODE, say that we will only be needing the sign bit of OP0. */
11643 /* Now try cases based on the opcode of OP0. If none of the cases
11644 does a "continue", we exit this loop immediately after the
11645 switch. */
11648 {
11650 /* If we are extracting a single bit from a variable position in
11651 a constant that has only a single bit set and are comparing it
11652 with zero, we can convert this into an equality comparison
11653 between the position and the location of the single bit. */
11654 /* Except we can't if SHIFT_COUNT_TRUNCATED is set, since we might
11655 have already reduced the shift count modulo the word size. */
11661 {
11669 /* Result is nonzero iff shift count is equal to I. */
11672 }
11674 /* ... fall through ... */
11679 {
11682 }
11686 /* If testing for equality, we can take the NOT of the constant. */
11689 {
11693 }
11695 /* If just looking at the sign bit, reverse the sense of the
11696 comparison. */
11698 {
11702 }
11706 /* If testing for equality, we can take the NEG of the constant. */
11709 {
11713 }
11715 /* The remaining cases only apply to comparisons with zero. */
11719 /* When X is ABS or is known positive,
11720 (neg X) is < 0 if and only if X != 0. */
11728 {
11732 }
11734 /* If we have NEG of something whose two high-order bits are the
11735 same, we know that "(-a) < 0" is equivalent to "a > 0". */
11737 {
11741 }
11745 /* If we are testing equality and our count is a constant, we
11746 can perform the inverse operation on our RHS. */
11750 {
11754 }
11756 /* If we are doing a < 0 or >= 0 comparison, it means we are testing
11757 a particular bit. Convert it to an AND of a constant of that
11758 bit. This will be converted into a ZERO_EXTRACT. */
11762 {
11769 }
11771 /* Fall through. */
11774 /* ABS is ignorable inside an equality comparison with zero. */
11776 {
11779 }
11783 /* Can simplify (compare (zero/sign_extend FOO) CONST) to
11784 (compare FOO CONST) if CONST fits in FOO's mode and we
11785 are either testing inequality or have an unsigned
11786 comparison with ZERO_EXTEND or a signed comparison with
11787 SIGN_EXTEND. But don't do it if we don't have a compare
11788 insn of the given mode, since we'd have to revert it
11789 later on, and then we wouldn't know whether to sign- or
11790 zero-extend. */
11793 && ! unsigned_comparison_p
11797 {
11800 }
11804 /* Check for the case where we are comparing A - C1 with C2, that is
11806 (subreg:MODE (plus (A) (-C1))) op (C2)
11808 with C1 a constant, and try to lift the SUBREG, i.e. to do the
11809 comparison in the wider mode. One of the following two conditions
11810 must be true in order for this to be valid:
11812 1. The mode extension results in the same bit pattern being added
11813 on both sides and the comparison is equality or unsigned. As
11814 C2 has been truncated to fit in MODE, the pattern can only be
11815 all 0s or all 1s.
11817 2. The mode extension results in the sign bit being copied on
11818 each side.
11820 The difficulty here is that we have predicates for A but not for
11821 (A - C1) so we need to check that C1 is within proper bounds so
11822 as to perturbate A as little as possible. */
11829 {
11838 /* (A - C1) zero-extends if it is positive and sign-extends
11839 if it is negative, C2 both zero- and sign-extends. */
11843 /* (A - C1) sign-extends if it is positive and 1-extends
11844 if it is negative, C2 both sign- and 1-extends. */
11851 /* (A - C1) always sign-extends, like C2. */
11855 {
11858 }
11859 }
11861 /* If the inner mode is narrower and we are extracting the low part,
11862 we can treat the SUBREG as if it were a ZERO_EXTEND. */
11866 else
11869 /* ... fall through ... */
11879 {
11882 }
11886 /* (eq (plus X A) B) -> (eq X (minus B A)). We can only do
11887 this for equality comparisons due to pathological cases involving
11888 overflows. */
11892 {
11896 }
11898 /* (plus (abs X) (const_int -1)) is < 0 if and only if X == 0. */
11901 {
11905 }
11909 /* We used to optimize signed comparisons against zero, but that
11910 was incorrect. Unsigned comparisons against zero (GTU, LEU)
11911 arrive here as equality comparisons, or (GEU, LTU) are
11912 optimized away. No need to special-case them. */
11914 /* (eq (minus A B) C) -> (eq A (plus B C)) or
11915 (eq B (minus A C)), whichever simplifies. We can only do
11916 this for equality comparisons due to pathological cases involving
11917 overflows. */
11921 {
11925 }
11930 {
11934 }
11936 /* The sign bit of (minus (ashiftrt X C) X), where C is the number
11937 of bits in X minus 1, is one iff X > 0. */
11942 {
11946 }
11950 /* (eq (xor A B) C) -> (eq A (xor B C)). This is a simplification
11951 if C is zero or B is a constant. */
11955 {
11959 }
11967 /* We can't do anything if OP0 is a condition code value, rather
11968 than an actual data value. */
11974 /* Get the two operands being compared. */
11977 else
11980 /* Check for the cases where we simply want the result of the
11981 earlier test or the opposite of that result. */
11985 {
11989 else
11993 {
11998 }
11999 }
12003 /* The sign bit of (ior (plus X (const_int -1)) X) is nonzero
12004 iff X <= 0. */
12008 {
12012 }
12016 /* Convert (and (xshift 1 X) Y) to (and (lshiftrt Y X) 1). This
12017 will be converted to a ZERO_EXTRACT later. */
12021 {
12026 }
12028 /* If we are comparing (and (lshiftrt X C1) C2) for equality with
12029 zero and X is a comparison and C1 and C2 describe only bits set
12030 in STORE_FLAG_VALUE, we can compare with X. */
12038 {
12045 {
12048 }
12049 }
12051 /* If we are doing an equality comparison of an AND of a bit equal
12052 to the sign bit, replace this with a LT or GE comparison of
12053 the underlying value. */
12060 {
12064 }
12066 /* If this AND operation is really a ZERO_EXTEND from a narrower
12067 mode, the constant fits within that mode, and this is either an
12068 equality or unsigned comparison, try to do this comparison in
12069 the narrower mode.
12071 Note that in:
12073 (ne:DI (and:DI (reg:DI 4) (const_int 0xffffffff)) (const_int 0))
12074 -> (ne:DI (reg:SI 4) (const_int 0))
12076 unless TRULY_NOOP_TRUNCATION allows it or the register is
12077 known to hold a value of the required mode the
12078 transformation is invalid. */
12089 {
12092 }
12094 /* If this is (and:M1 (subreg:M2 X 0) (const_int C1)) where C1
12095 fits in both M1 and M2 and the SUBREG is either paradoxical
12096 or represents the low part, permute the SUBREG and the AND
12097 and try again. */
12099 {
12102 /* Require an integral mode, to avoid creating something like
12103 (AND:SF ...). */
12105 /* It is unsafe to commute the AND into the SUBREG if the
12106 SUBREG is paradoxical and WORD_REGISTER_OPERATIONS is
12107 not defined. As originally written the upper bits
12108 have a defined value due to the AND operation.
12109 However, if we commute the AND inside the SUBREG then
12110 they no longer have defined values and the meaning of
12111 the code has been changed. */
12113 #ifdef WORD_REGISTER_OPERATIONS
12116 #endif
12126 {
12132 }
12133 }
12135 /* Convert (ne (and (not X) 1) 0) to (eq (and X 1) 0). */
12139 {
12144 }
12146 /* Convert (ne (and (lshiftrt (not X)) 1) 0) to
12147 (eq (and (lshiftrt X) 1) 0).
12148 Also handle the case where (not X) is expressed using xor. */
12152 {
12164 {
12165 op0
12170 }
12171 }
12175 /* If we have (compare (ashift FOO N) (const_int C)) and
12176 the high order N bits of FOO (N+1 if an inequality comparison)
12177 are known to be zero, we can do this by comparing FOO with C
12178 shifted right N bits so long as the low-order N bits of C are
12179 zero. */
12191 {
12192 /* We must perform a logical shift, not an arithmetic one,
12193 as we want the top N bits of C to be zero. */
12200 }
12202 /* If we are doing a sign bit comparison, it means we are testing
12203 a particular bit. Convert it to the appropriate AND. */
12206 {
12213 }
12215 /* If this an equality comparison with zero and we are shifting
12216 the low bit to the sign bit, we can convert this to an AND of the
12217 low-order bit. */
12221 {
12224 }
12228 /* If this is an equality comparison with zero, we can do this
12229 as a logical shift, which might be much simpler. */
12232 {
12237 }
12239 /* If OP0 is a sign extension and CODE is not an unsigned comparison,
12240 do the comparison in a narrower mode. */
12250 {
12253 }
12255 /* Likewise if OP0 is a PLUS of a sign extension with a
12256 constant, which is usually represented with the PLUS
12257 between the shifts. */
12269 {
12277 new_const);
12279 }
12281 /* ... fall through ... */
12283 /* If we have (compare (xshiftrt FOO N) (const_int C)) and
12284 the low order N bits of FOO are known to be zero, we can do this
12285 by comparing FOO with C shifted left N bits so long as no
12286 overflow occurs. Even if the low order N bits of FOO aren't known
12287 to be zero, if the comparison is >= or < we can use the same
12288 optimization and for > or <= by setting all the low
12289 order N bits in the comparison constant. */
12300 {
12301 unsigned HOST_WIDE_INT low_bits
12306 {
12307 /* If the shift was logical, then we must make the condition
12308 unsigned. */
12316 const_op
12321 }
12322 }
12324 /* If we are using this shift to extract just the sign bit, we
12325 can replace this with an LT or GE comparison. */
12330 {
12334 }
12339 }
12342 }
12344 /* Now make any compound operations involved in this comparison. Then,
12345 check for an outmost SUBREG on OP0 that is not doing anything or is
12346 paradoxical. The latter transformation must only be performed when
12347 it is known that the "extra" bits will be the same in op0 and op1 or
12348 that they don't matter. There are three cases to consider:
12350 1. SUBREG_REG (op0) is a register. In this case the bits are don't
12351 care bits and we can assume they have any convenient value. So
12352 making the transformation is safe.
12354 2. SUBREG_REG (op0) is a memory and LOAD_EXTEND_OP is not defined.
12355 In this case the upper bits of op0 are undefined. We should not make
12356 the simplification in that case as we do not know the contents of
12357 those bits.
12359 3. SUBREG_REG (op0) is a memory and LOAD_EXTEND_OP is defined and not
12360 UNKNOWN. In that case we know those bits are zeros or ones. We must
12361 also be sure that they are the same as the upper bits of op1.
12363 We can never remove a SUBREG for a non-equality comparison because
12364 the sign bit is in a different place in the underlying object. */
12373 {
12375 {
12376 /* For paradoxical subregs, allow case 1 as above. Case 3 isn't
12377 implemented. */
12379 {
12382 }
12383 }
12389 {
12395 }
12396 }
12398 /* We now do the opposite procedure: Some machines don't have compare
12399 insns in all modes. If OP0's mode is an integer mode smaller than a
12400 word and we can't do a compare in that mode, see if there is a larger
12401 mode for which we can do the compare. There are a number of cases in
12402 which we can use the wider mode. */
12412 {
12415 /* If this is a test for negative, we can make an explicit
12416 test of the sign bit. Test this first so we can use
12417 a paradoxical subreg to extend OP0. */
12421 {
12422 unsigned HOST_WIDE_INT sign
12429 }
12431 /* If the only nonzero bits in OP0 and OP1 are those in the
12432 narrower mode and this is an equality or unsigned comparison,
12433 we can use the wider mode. Similarly for sign-extended
12434 values, in which case it is true for all comparisons. */
12451 {
12452 /* If OP0 is an AND and we don't have an AND in MODE either,
12453 make a new AND in the proper mode. */
12461 else
12462 {
12464 {
12467 }
12468 else
12469 {
12472 }
12474 }
12475 }
12476 }
12478 /* We may have changed the comparison operands. Re-canonicalize. */
12480 {
12483 }
12485 /* If this machine only supports a subset of valid comparisons, see if we
12486 can convert an unsupported one into a supported one. */
12493 }
12494 \f
12495 /* Utility function for record_value_for_reg. Count number of
12496 rtxs in X. */
12497 static int
12499 {
12506 {
12526 }
12537 }
12538 \f
12539 /* Utility function for following routine. Called when X is part of a value
12540 being stored into last_set_value. Sets last_set_table_tick
12541 for each register mentioned. Similar to mention_regs in cse.c */
12543 static void
12545 {
12551 {
12557 {
12560 }
12563 }
12567 {
12568 /* Check for identical subexpressions. If x contains
12569 identical subexpression we only have to traverse one of
12570 them. */
12572 {
12573 /* Note that at this point x1 has already been
12574 processed. */
12578 /* If x0 and x1 are identical then there is no need to
12579 process x0. */
12583 /* If x0 is identical to a subexpression of x1 then while
12584 processing x1, x0 has already been processed. Thus we
12585 are done with x. */
12590 /* If x1 is identical to a subexpression of x0 then we
12591 still have to process the rest of x0. */
12594 {
12597 }
12598 }
12601 }
12605 }
12607 /* Record that REG is set to VALUE in insn INSN. If VALUE is zero, we
12608 are saying that the register is clobbered and we no longer know its
12609 value. If INSN is zero, don't update reg_stat[].last_set; this is
12610 only permitted with VALUE also zero and is used to invalidate the
12611 register. */
12613 static void
12615 {
12621 /* If VALUE contains REG and we have a previous value for REG, substitute
12622 the previous value. */
12624 {
12625 rtx tem;
12627 /* Set things up so get_last_value is allowed to see anything set up to
12628 our insn. */
12632 /* If TEM is simply a binary operation with two CLOBBERs as operands,
12633 it isn't going to be useful and will take a lot of time to process,
12634 so just use the CLOBBER. */
12637 {
12643 {
12644 /* If there are two or more occurrences of REG in VALUE,
12645 prevent the value from growing too much. */
12648 }
12651 }
12652 }
12654 /* For each register modified, show we don't know its value, that
12655 we don't know about its bitwise content, that its value has been
12656 updated, and that we don't know the location of the death of the
12657 register. */
12659 {
12671 }
12673 /* Mark registers that are being referenced in this value. */
12677 /* Now update the status of each register being set.
12678 If someone is using this register in this block, set this register
12679 to invalid since we will get confused between the two lives in this
12680 basic block. This makes using this register always invalid. In cse, we
12681 scan the table to invalidate all entries using this register, but this
12682 is too much work for us. */
12685 {
12691 else
12693 }
12695 /* The value being assigned might refer to X (like in "x++;"). In that
12696 case, we must replace it with (clobber (const_int 0)) to prevent
12697 infinite loops. */
12700 {
12704 }
12706 /* For the main register being modified, update the value, the mode, the
12707 nonzero bits, and the number of sign bit copies. */
12712 {
12720 rsp->last_set_sign_bit_copies
12722 }
12723 }
12725 /* Called via note_stores from record_dead_and_set_regs to handle one
12726 SET or CLOBBER in an insn. DATA is the instruction in which the
12727 set is occurring. */
12729 static void
12731 {
12738 {
12742 }
12745 {
12746 /* If we are setting the whole register, we know its value. Otherwise
12747 show that we don't know the value. We can handle SUBREG in
12748 some cases. */
12759 else
12761 }
12763 /* Ignore pushes, they clobber nothing. */
12766 }
12768 /* Update the records of when each REG was most recently set or killed
12769 for the things done by INSN. This is the last thing done in processing
12770 INSN in the combiner loop.
12772 We update reg_stat[], in particular fields last_set, last_set_value,
12773 last_set_mode, last_set_nonzero_bits, last_set_sign_bit_copies,
12774 last_death, and also the similar information mem_last_set (which insn
12775 most recently modified memory) and last_call_luid (which insn was the
12776 most recent subroutine call). */
12778 static void
12780 {
12781 rtx link;
12785 {
12788 {
12793 {
12798 }
12799 }
12802 }
12805 {
12806 hard_reg_set_iterator hrsi;
12808 {
12820 }
12824 /* We can't combine into a call pattern. Remember, though, that
12825 the return value register is set at this LUID. We could
12826 still replace a register with the return value from the
12827 wrong subroutine call! */
12829 }
12830 else
12832 }
12834 /* If a SUBREG has the promoted bit set, it is in fact a property of the
12835 register present in the SUBREG, so for each such SUBREG go back and
12836 adjust nonzero and sign bit information of the registers that are
12837 known to have some zero/sign bits set.
12839 This is needed because when combine blows the SUBREGs away, the
12840 information on zero/sign bits is lost and further combines can be
12841 missed because of that. */
12843 static void
12845 {
12847 rtx set;
12855 {
12864 {
12867 }
12871 {
12874 }
12877 {
12880 }
12881 else
12883 }
12884 }
12886 /* Check if X, a register, is known to contain a value already
12887 truncated to MODE. In this case we can use a subreg to refer to
12888 the truncated value even though in the generic case we would need
12889 an explicit truncation. */
12891 static bool
12893 {
12905 }
12907 /* If X is a hard reg or a subreg record the mode that the register is
12908 accessed in. For non-TRULY_NOOP_TRUNCATION targets we might be able
12909 to turn a truncate into a subreg using this information. Return true
12910 if traversing X is complete. */
12912 static bool
12914 {
12915 machine_mode truncated_mode;
12919 {
12930 }
12931 /* ??? For hard-regs we now record everything. We might be able to
12932 optimize this using last_set_mode. */
12935 else
12943 {
12946 }
12949 }
12951 /* Callback for note_uses. Find hardregs and subregs of pseudos and
12952 the modes they are used in. This can help truning TRUNCATEs into
12953 SUBREGs. */
12955 static void
12957 {
12962 }
12964 /* Scan X for promoted SUBREGs. For each one found,
12965 note what it implies to the registers used in it. */
12967 static void
12969 {
12974 else
12975 {
12981 {
12991 }
12992 }
12993 }
12994 \f
12995 /* Verify that all the registers and memory references mentioned in *LOC are
12996 still valid. *LOC was part of a value set in INSN when label_tick was
12997 equal to TICK. Return 0 if some are not. If REPLACE is nonzero, replace
12998 the invalid references with (clobber (const_int 0)) and return 1. This
12999 replacement is useful because we often can get useful information about
13000 the form of a value (e.g., if it was produced by a shift that always
13001 produces -1 or 0) even though we don't know exactly what registers it
13002 was produced from. */
13004 static int
13006 {
13013 {
13019 {
13022 /* If this is a pseudo-register that was only set once and not
13023 live at the beginning of the function, it is always valid. */
13027 && (!REGNO_REG_SET_P
13029 regno)))
13031 {
13035 }
13036 }
13039 }
13040 /* If this is a memory reference, make sure that there were no stores after
13041 it that might have clobbered the value. We don't have alias info, so we
13042 assume any store invalidates it. Moreover, we only have local UIDs, so
13043 we also assume that there were stores in the intervening basic blocks. */
13046 {
13050 }
13053 {
13055 {
13056 /* Check for identical subexpressions. If x contains
13057 identical subexpression we only have to traverse one of
13058 them. */
13060 {
13061 /* Note that at this point x0 has already been checked
13062 and found valid. */
13066 /* If x0 and x1 are identical then x is also valid. */
13070 /* If x1 is identical to a subexpression of x0 then
13071 while checking x0, x1 has already been checked. Thus
13072 it is valid and so as x. */
13077 /* If x0 is identical to a subexpression of x1 then x is
13078 valid iff the rest of x1 is valid. */
13081 return
13085 }
13090 }
13096 }
13098 /* If we haven't found a reason for it to be invalid, it is valid. */
13100 }
13102 /* Get the last value assigned to X, if known. Some registers
13103 in the value may be replaced with (clobber (const_int 0)) if their value
13104 is known longer known reliably. */
13106 static rtx
13108 {
13110 rtx value;
13113 /* If this is a non-paradoxical SUBREG, get the value of its operand and
13114 then convert it to the desired mode. If this is a paradoxical SUBREG,
13115 we cannot predict what values the "extra" bits might have. */
13129 /* If we don't have a value, or if it isn't for this basic block and
13130 it's either a hard register, set more than once, or it's a live
13131 at the beginning of the function, return 0.
13133 Because if it's not live at the beginning of the function then the reg
13134 is always set before being used (is never used without being set).
13135 And, if it's set only once, and it's always set before use, then all
13136 uses must have the same last value, even if it's not from this basic
13137 block. */
13144 || REGNO_REG_SET_P
13148 /* If the value was set in a later insn than the ones we are processing,
13149 we can't use it even if the register was only set once. */
13154 /* If the value has all its registers valid, return it. */
13158 /* Otherwise, make a copy and replace any invalid register with
13159 (clobber (const_int 0)). If that fails for some reason, return 0. */
13166 }
13167 \f
13168 /* Return nonzero if expression X refers to a REG or to memory
13169 that is set in an instruction more recent than FROM_LUID. */
13171 static int
13173 {
13179 {
13183 #ifdef PUSH_ROUNDING
13184 /* Don't allow uses of the stack pointer to be moved,
13185 because we don't know whether the move crosses a push insn. */
13188 #endif
13190 {
13196 }
13198 }
13206 {
13208 {
13213 }
13217 }
13219 }
13220 \f
13221 /* Define three variables used for communication between the following
13222 routines. */
13227 /* Function called via note_stores from reg_dead_at_p.
13229 If DEST is within [reg_dead_regno, reg_dead_endregno), set
13230 reg_dead_flag to 1 if X is a CLOBBER and to -1 it is a SET. */
13232 static void
13234 {
13244 }
13246 /* Return nonzero if REG is known to be dead at INSN.
13248 We scan backwards from INSN. If we hit a REG_DEAD note or a CLOBBER
13249 referencing REG, it is dead. If we hit a SET referencing REG, it is
13250 live. Otherwise, see if it is live or dead at the start of the basic
13251 block we are in. Hard regs marked as being live in NEWPAT_USED_REGS
13252 must be assumed to be always live. */
13254 static int
13256 {
13257 basic_block block;
13260 /* Set variables for reg_dead_at_p_1. */
13266 /* Check that reg isn't mentioned in NEWPAT_USED_REGS. For fixed registers
13267 we allow the machine description to decide whether use-and-clobber
13268 patterns are OK. */
13270 {
13274 }
13276 /* Scan backwards until we find a REG_DEAD note, SET, CLOBBER, or
13277 beginning of basic block. */
13280 {
13282 {
13292 }
13298 }
13300 /* Look at live-in sets for the basic block that we were in. */
13306 }
13307 \f
13308 /* Note hard registers in X that are used. */
13310 static void
13312 {
13318 {
13322 CASE_CONST_ANY:
13327 /* CC0 must die in the insn after it is set, so we don't need to take
13328 special note of it here. */
13333 /* If we are clobbering a MEM, mark any hard registers inside the
13334 address as used. */
13341 /* A hard reg in a wide mode may really be multiple registers.
13342 If so, mark all of them just like the first. */
13344 {
13345 /* None of this applies to the stack, frame or arg pointers. */
13347 #if !HARD_FRAME_POINTER_IS_FRAME_POINTER
13349 #endif
13356 }
13360 {
13361 /* If setting a MEM, or a SUBREG of a MEM, then note any hard regs in
13362 the address. */
13374 }
13379 }
13381 /* Recursively scan the operands of this expression. */
13383 {
13387 {
13391 {
13396 }
13397 }
13398 }
13399 }
13400 \f
13401 /* Remove register number REGNO from the dead registers list of INSN.
13403 Return the note used to record the death, if there was one. */
13405 rtx
13407 {
13414 }
13416 /* For each register (hardware or pseudo) used within expression X, if its
13417 death is in an instruction with luid between FROM_LUID (inclusive) and
13418 TO_INSN (exclusive), put a REG_DEAD note for that register in the
13419 list headed by PNOTES.
13421 That said, don't move registers killed by maybe_kill_insn.
13423 This is done when X is being merged by combination into TO_INSN. These
13424 notes will then be distributed as needed. */
13426 static void
13429 {
13435 {
13439 /* Don't move the register if it gets killed in between from and to. */
13448 {
13451 /* It is possible for the call above to return 0. This can occur
13452 when last_death points to I2 or I1 that we combined with.
13453 In that case make a new note.
13455 We must also check for the case where X is a hard register
13456 and NOTE is a death note for a range of hard registers
13457 including X. In that case, we must put REG_DEAD notes for
13458 the remaining registers in place of NOTE. */
13463 {
13472 }
13474 /* If we didn't find any note, or if we found a REG_DEAD note that
13475 covers only part of the given reg, and we have a multi-reg hard
13476 register, then to be safe we must check for REG_DEAD notes
13477 for each register other than the first. They could have
13478 their own REG_DEAD notes lying around. */
13485 {
13492 else
13498 }
13501 {
13504 }
13505 else
13507 }
13510 }
13513 {
13518 /* In the case of a ZERO_EXTRACT, a STRICT_LOW_PART, or a SUBREG
13519 that accesses one word of a multi-word item, some
13520 piece of everything register in the expression is used by
13521 this insn, so remove any old death. */
13522 /* ??? So why do we test for equality of the sizes? */
13531 {
13534 }
13536 /* If this is some other SUBREG, we know it replaces the entire
13537 value, so use that as the destination. */
13541 /* If this is a MEM, adjust deaths of anything used in the address.
13542 For a REG (the only other possibility), the entire value is
13543 being replaced so the old value is not used in this insn. */
13549 }
13558 {
13560 {
13565 }
13568 }
13569 }
13570 \f
13571 /* Return 1 if X is the target of a bit-field assignment in BODY, the
13572 pattern of an insn. X must be a REG. */
13574 static int
13576 {
13580 {
13582 rtx target;
13589 else
13606 }
13614 }
13615 \f
13616 /* Given a chain of REG_NOTES originally from FROM_INSN, try to place them
13617 as appropriate. I3 and I2 are the insns resulting from the combination
13618 insns including FROM (I2 may be zero).
13620 ELIM_I2 and ELIM_I1 are either zero or registers that we know will
13621 not need REG_DEAD notes because they are being substituted for. This
13622 saves searching in the most common cases.
13624 Each note in the list is either ignored or placed on some insns, depending
13625 on the type of note. */
13627 static void
13630 {
13632 rtx tem_note;
13636 {
13641 {
13644 /* Doesn't matter much where we put this, as long as it's somewhere.
13645 It is preferable to keep these notes on branches, which is most
13646 likely to be i3. */
13653 else
13654 {
13657 }
13661 /* These notes must remain with the call or trapping instruction. */
13666 else
13667 {
13673 /* ??? Otherwise assume we've combined things such that we
13674 can now prove that the instructions can't trap. Drop the
13675 note in this case. */
13676 }
13680 /* ??? How to distribute between i3-i1. Assume i3 contains the
13681 entire adjustment. Assert i3 contains at least some adjust. */
13683 {
13685 /* fixup_args_size_notes looks at REG_NORETURN note,
13686 so ensure the note is placed there first. */
13688 {
13692 {
13698 }
13699 }
13701 /* emit_call_1 adds for !ACCUMULATE_OUTGOING_ARGS
13702 REG_ARGS_SIZE note to all noreturn calls, allow that here. */
13705 && !ACCUMULATE_OUTGOING_ARGS
13707 }
13714 /* These notes must remain with the call. It should not be
13715 possible for both I2 and I3 to be a call. */
13718 else
13719 {
13722 }
13726 /* Any clobbers for i3 may still exist, and so we must process
13727 REG_UNUSED notes from that insn.
13729 Any clobbers from i2 or i1 can only exist if they were added by
13730 recog_for_combine. In that case, recog_for_combine created the
13731 necessary REG_UNUSED notes. Trying to keep any original
13732 REG_UNUSED notes from these insns can cause incorrect output
13733 if it is for the same register as the original i3 dest.
13734 In that case, we will notice that the register is set in i3,
13735 and then add a REG_UNUSED note for the destination of i3, which
13736 is wrong. However, it is possible to have REG_UNUSED notes from
13737 i2 or i1 for register which were both used and clobbered, so
13738 we keep notes from i2 or i1 if they will turn into REG_DEAD
13739 notes. */
13741 /* If this register is set or clobbered in I3, put the note there
13742 unless there is one already. */
13744 {
13752 }
13753 /* Otherwise, if this register is used by I3, then this register
13754 now dies here, so we must put a REG_DEAD note here unless there
13755 is one already. */
13761 {
13764 }
13770 /* These notes say something about results of an insn. We can
13771 only support them if they used to be on I3 in which case they
13772 remain on I3. Otherwise they are ignored.
13774 If the note refers to an expression that is not a constant, we
13775 must also ignore the note since we cannot tell whether the
13776 equivalence is still true. It might be possible to do
13777 slightly better than this (we only have a problem if I2DEST
13778 or I1DEST is present in the expression), but it doesn't
13779 seem worth the trouble. */
13787 /* These notes say something about how a register is used. They must
13788 be present on any use of the register in I2 or I3. */
13793 {
13796 else
13798 }
13803 /* This can show up in several ways -- either directly in the
13804 pattern, or hidden off in the constant pool with (or without?)
13805 a REG_EQUAL note. */
13806 /* ??? Ignore the without-reg_equal-note problem for now. */
13818 {
13821 else
13823 }
13825 /* For REG_LABEL_TARGET on a JUMP_P, we prefer to put the note
13826 as a JUMP_LABEL or decrement LABEL_NUSES if it's already
13827 there. */
13832 {
13839 }
13845 {
13853 }
13857 /* This note says something about the value of a register prior
13858 to the execution of an insn. It is too much trouble to see
13859 if the note is still correct in all situations. It is better
13860 to simply delete it. */
13864 /* If we replaced the right hand side of FROM_INSN with a
13865 REG_EQUAL note, the original use of the dying register
13866 will not have been combined into I3 and I2. In such cases,
13867 FROM_INSN is guaranteed to be the first of the combined
13868 instructions, so we simply need to search back before
13869 FROM_INSN for the previous use or set of this register,
13870 then alter the notes there appropriately.
13872 If the register is used as an input in I3, it dies there.
13873 Similarly for I2, if it is nonzero and adjacent to I3.
13875 If the register is not used as an input in either I3 or I2
13876 and it is not one of the registers we were supposed to eliminate,
13877 there are two possibilities. We might have a non-adjacent I2
13878 or we might have somehow eliminated an additional register
13879 from a computation. For example, we might have had A & B where
13880 we discover that B will always be zero. In this case we will
13881 eliminate the reference to A.
13883 In both cases, we must search to see if we can find a previous
13884 use of A and put the death note there. */
13890 else
13891 {
13902 && !(i2mod
13904 i2mod_old_rhs)))
13909 /* If the new I2 sets the same register that is marked dead
13910 in the note, the note now should not be put on I2, as the
13911 note refers to a previous incarnation of the reg. */
13914 }
13917 {
13921 {
13923 {
13927 }
13929 /* If the register is being set at TEM_INSN, see if that is all
13930 TEM_INSN is doing. If so, delete TEM_INSN. Otherwise, make this
13931 into a REG_UNUSED note instead. Don't delete sets to
13932 global register vars. */
13936 {
13947 ;
13949 /* Verify that it was the set, and not a clobber that
13950 modified the register.
13952 CC0 targets must be careful to maintain setter/user
13953 pairs. If we cannot delete the setter due to side
13954 effects, mark the user with an UNUSED note instead
13955 of deleting it. */
13959 #if HAVE_cc0
13963 #endif
13964 )
13965 {
13966 /* Move the notes and links of TEM_INSN elsewhere.
13967 This might delete other dead insns recursively.
13968 First set the pattern to something that won't use
13969 any register. */
13983 /* Delete the setter too. */
13985 {
13998 }
13999 }
14000 else
14001 {
14004 /* If there isn't already a REG_UNUSED note, put one
14005 here. Do not place a REG_DEAD note, even if
14006 the register is also used here; that would not
14007 match the algorithm used in lifetime analysis
14008 and can cause the consistency check in the
14009 scheduler to fail. */
14014 }
14015 }
14019 {
14022 /* If we are doing a 3->2 combination, and we have a
14023 register which formerly died in i3 and was not used
14024 by i2, which now no longer dies in i3 and is used in
14025 i2 but does not die in i2, and place is between i2
14026 and i3, then we may need to move a link from place to
14027 i2. */
14029 && from_insn
14032 {
14036 }
14038 }
14042 }
14044 }
14046 /* If the register is set or already dead at PLACE, we needn't do
14047 anything with this note if it is still a REG_DEAD note.
14048 We check here if it is set at all, not if is it totally replaced,
14049 which is what `dead_or_set_p' checks, so also check for it being
14050 set partially. */
14053 {
14059 {
14060 /* Unless the register previously died in PLACE, clear
14061 last_death. [I no longer understand why this is
14062 being done.] */
14066 }
14067 else
14070 /* If this is a death note for a hard reg that is occupying
14071 multiple registers, ensure that we are still using all
14072 parts of the object. If we find a piece of the object
14073 that is unused, we must arrange for an appropriate REG_DEAD
14074 note to be added for it. However, we can't just emit a USE
14075 and tag the note to it, since the register might actually
14076 be dead; so we recourse, and the recursive call then finds
14077 the previous insn that used this register. */
14080 {
14089 {
14092 }
14095 {
14096 /* Put only REG_DEAD notes for pieces that are
14097 not already dead or set. */
14101 {
14108 {
14110 NULL_RTX);
14114 NULL_RTX);
14115 }
14120 {
14122 {
14126 }
14130 {
14133 }
14134 }
14135 }
14138 }
14139 }
14140 }
14144 /* Any other notes should not be present at this point in the
14145 compilation. */
14147 }
14150 {
14153 }
14157 }
14158 }
14159 \f
14160 /* Similarly to above, distribute the LOG_LINKS that used to be present on
14161 I3, I2, and I1 to new locations. This is also called to add a link
14162 pointing at I3 when I3's destination is changed. */
14164 static void
14166 {
14170 {
14177 /* If the insn that this link points to is a NOTE, ignore it. */
14186 {
14189 {
14205 }
14208 }
14209 else
14219 /* A LOG_LINK is defined as being placed on the first insn that uses
14220 a register and points to the insn that sets the register. Start
14221 searching at the next insn after the target of the link and stop
14222 when we reach a set of the register or the end of the basic block.
14224 Note that this correctly handles the link that used to point from
14225 I3 to I2. Also note that not much searching is typically done here
14226 since most links don't point very far away. */
14235 {
14239 }
14242 {
14245 }
14249 /* If we found a place to put the link, place it there unless there
14250 is already a link to the same insn as LINK at that point. */
14253 {
14261 {
14265 /* Set added_links_insn to the earliest insn we added a
14266 link to. */
14270 }
14271 }
14272 }
14273 }
14274 \f
14275 /* Check for any register or memory mentioned in EQUIV that is not
14276 mentioned in EXPR. This is used to restrict EQUIV to "specializations"
14277 of EXPR where some registers may have been replaced by constants. */
14279 static bool
14281 {
14284 {
14289 }
14291 }
14292 \f
14293 DEBUG_FUNCTION void
14295 {
14296 fprintf
14298 ";; Combiner statistics: %d attempts, %d substitutions (%d requiring new space),\n;; %d successes.\n\n",
14300 }
14302 void
14304 {
14305 fprintf
14307 "\n;; Combiner totals: %d attempts, %d substitutions (%d requiring new space),\n;; %d successes.\n",
14309 }
14310 \f
14311 /* Try combining insns through substitution. */
14312 static unsigned int
14314 {
14324 rebuild_jump_labels_after_combine
14327 /* Combining insns may have turned an indirect jump into a
14328 direct jump. Rebuild the JUMP_LABEL fields of jumping
14329 instructions. */
14331 {
14336 }
14340 }
14345 {
14355 };
14358 {
14362 {}
14364 /* opt_pass methods: */
14367 {
14369 }
14375 rtl_opt_pass *
14377 {
14379 }