| blob | 2328d8f069982a1095e16dc860a80521dee9cbcc |
1 /* Optimize jump instructions, for GNU compiler.
2 Copyright (C) 1987, 88, 89, 91-98, 1999 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
9 any later version.
11 GNU CC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
22 /* This is the jump-optimization pass of the compiler.
23 It is run two or three times: once before cse, sometimes once after cse,
24 and once after reload (before final).
26 jump_optimize deletes unreachable code and labels that are not used.
27 It also deletes jumps that jump to the following insn,
28 and simplifies jumps around unconditional jumps and jumps
29 to unconditional jumps.
31 Each CODE_LABEL has a count of the times it is used
32 stored in the LABEL_NUSES internal field, and each JUMP_INSN
33 has one label that it refers to stored in the
34 JUMP_LABEL internal field. With this we can detect labels that
35 become unused because of the deletion of all the jumps that
36 formerly used them. The JUMP_LABEL info is sometimes looked
37 at by later passes.
39 Optionally, cross-jumping can be done. Currently it is done
40 only the last time (when after reload and before final).
41 In fact, the code for cross-jumping now assumes that register
42 allocation has been done, since it uses `rtx_renumbered_equal_p'.
44 Jump optimization is done after cse when cse's constant-propagation
45 causes jumps to become unconditional or to be deleted.
47 Unreachable loops are not detected here, because the labels
48 have references and the insns appear reachable from the labels.
49 find_basic_blocks in flow.c finds and deletes such loops.
51 The subroutines delete_insn, redirect_jump, and invert_jump are used
52 from other passes as well. */
71 /* ??? Eventually must record somehow the labels used by jumps
72 from nested functions. */
73 /* Pre-record the next or previous real insn for each label?
74 No, this pass is very fast anyway. */
75 /* Condense consecutive labels?
76 This would make life analysis faster, maybe. */
77 /* Optimize jump y; x: ... y: jumpif... x?
78 Don't know if it is worth bothering with. */
79 /* Optimize two cases of conditional jump to conditional jump?
80 This can never delete any instruction or make anything dead,
81 or even change what is live at any point.
82 So perhaps let combiner do it. */
84 /* Vector indexed by uid.
85 For each CODE_LABEL, index by its uid to get first unconditional jump
86 that jumps to the label.
87 For each JUMP_INSN, index by its uid to get the next unconditional jump
88 that jumps to the same label.
89 Element 0 is the start of a chain of all return insns.
90 (It is safe to use element 0 because insn uid 0 is not used. */
94 /* Maximum index in jump_chain. */
98 /* Set nonzero by jump_optimize if control can fall through
99 to the end of the function. */
102 /* Indicates whether death notes are significant in cross jump analysis.
103 Normally they are not significant, because of A and B jump to C,
104 and R dies in A, it must die in B. But this might not be true after
105 stack register conversion, and we must compare death notes in that
106 case. */
128 #if ! defined(HAVE_cc0) && ! defined(HAVE_conditional_arithmetic)
130 #endif
134 /* Main external entry point into the jump optimizer. See comments before
135 jump_optimize_1 for descriptions of the arguments. */
136 void
138 rtx f;
142 {
144 }
146 /* Alternate entry into the jump optimizer. This entry point only rebuilds
147 the JUMP_LABEL field in jumping insns and REG_LABEL notes in non-jumping
148 instructions. */
149 void
151 rtx f;
152 {
154 }
156 \f
157 /* Delete no-op jumps and optimize jumps to jumps
158 and jumps around jumps.
159 Delete unused labels and unreachable code.
161 If CROSS_JUMP is 1, detect matching code
162 before a jump and its destination and unify them.
163 If CROSS_JUMP is 2, do cross-jumping, but pay attention to death notes.
165 If NOOP_MOVES is nonzero, delete no-op move insns.
167 If AFTER_REGSCAN is nonzero, then this jump pass is being run immediately
168 after regscan, and it is safe to use regno_first_uid and regno_last_uid.
170 If MARK_LABELS_ONLY is nonzero, then we only rebuild the jump chain
171 and JUMP_LABEL field for jumping insns.
173 If `optimize' is zero, don't change any code,
174 just determine whether control drops off the end of the function.
175 This case occurs when we have -W and not -O.
176 It works because `delete_insn' checks the value of `optimize'
177 and refrains from actually deleting when that is 0. */
179 static void
181 rtx f;
186 {
192 rtx last_insn;
197 /* If we are performing cross jump optimizations, then initialize
198 tables mapping UIDs to EH regions to avoid incorrect movement
199 of insns from one EH region to another. */
205 /* Leave some extra room for labels and duplicate exit test insns
206 we make. */
213 /* Keep track of labels used from static data;
214 they cannot ever be deleted. */
221 /* Keep track of labels used for marking handlers for exception
222 regions; they cannot usually be deleted. */
227 /* Quit now if we just wanted to rebuild the JUMP_LABEL and REG_LABEL
228 notes and recompute LABEL_NUSES. */
237 {
238 /* CAN_REACH_END is persistent for each function. Once set it should
239 not be cleared. This is especially true for the case where we
240 delete the NOTE_FUNCTION_END note. CAN_REACH_END is cleared by
241 the front-end before compiling each function. */
245 /* Zero the "deleted" flag of all the "deleted" insns. */
249 /* Show that the jump chain is not valid. */
252 }
254 #ifdef HAVE_return
256 {
257 /* If we fall through to the epilogue, see if we can insert a RETURN insn
258 in front of it. If the machine allows it at this point (we might be
259 after reload for a leaf routine), it will improve optimization for it
260 to be there. */
266 {
269 }
270 }
271 #endif
276 /* If we haven't yet gotten to reload and we have just run regscan,
277 delete any insn that sets a register that isn't used elsewhere.
278 This helps some of the optimizations below by having less insns
279 being jumped around. */
283 {
291 /* We use regno_last_note_uid so as not to delete the setting
292 of a reg that's used in notes. A subsequent optimization
293 might arrange to use that reg for real. */
297 /* An ADDRESSOF expression can turn into a use of the internal arg
298 pointer, so do not delete the initialization of the internal
299 arg pointer yet. If it is truly dead, flow will delete the
300 initializing insn. */
303 }
305 /* Now iterate optimizing jumps until nothing changes over one pass. */
309 {
313 {
314 rtx reallabelprev;
316 rtx nlabel;
322 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
323 jump. Try to optimize by duplicating the loop exit test if so.
324 This is only safe immediately after regscan, because it uses
325 the values of regno_first_uid and regno_last_uid. */
330 {
333 {
337 }
338 }
347 /* Tension the labels in dispatch tables. */
354 /* See if this jump goes to another jump and redirect if so. */
359 /* If a dispatch table always goes to the same place,
360 get rid of it and replace the insn that uses it. */
364 {
379 /* Don't mess with a casesi insn. */
384 {
388 }
389 }
391 /* If a jump references the end of the function, try to turn
392 it into a RETURN insn, possibly a conditional one. */
401 /* Detect jump to following insn. */
403 {
408 }
410 /* Detect a conditional jump going to the same place
411 as an immediately following unconditional jump. */
417 {
418 /* Don't mess up test coverage analysis. */
426 {
430 }
431 }
433 /* Detect a conditional jump jumping over an unconditional jump. */
436 && ! this_is_simplejump
442 {
443 /* When we invert the unconditional jump, we will be
444 decrementing the usage count of its old label.
445 Make sure that we don't delete it now because that
446 might cause the following code to be deleted. */
454 {
455 /* It is very likely that if there are USE insns before
456 this jump, they hold REG_DEAD notes. These REG_DEAD
457 notes are no longer valid due to this optimization,
458 and will cause the life-analysis that following passes
459 (notably delayed-branch scheduling) to think that
460 these registers are dead when they are not.
462 To prevent this trouble, we just remove the USE insns
463 from the insn chain. */
467 {
471 }
475 }
477 /* We can now safely delete the label if it is unreferenced
478 since the delete_insn above has deleted the BARRIER. */
483 }
485 /* If we have an unconditional jump preceded by a USE, try to put
486 the USE before the target and jump there. This simplifies many
487 of the optimizations below since we don't have to worry about
488 dealing with these USE insns. We only do this if the label
489 being branch to already has the identical USE or if code
490 never falls through to that label. */
500 /* Don't do this optimization if we have a loop containing
501 only the USE instruction, and the loop start label has
502 a usage count of 1. This is because we will redo this
503 optimization everytime through the outer loop, and jump
504 opt will never exit. */
508 {
510 {
513 }
520 }
522 /* Simplify if (...) x = a; else x = b; by converting it
523 to x = b; if (...) x = a;
524 if B is sufficiently simple, the test doesn't involve X,
525 and nothing in the test modifies B or X.
527 If we have small register classes, we also can't do this if X
528 is a hard register.
530 If the "x = b;" insn has any REG_NOTES, we don't do this because
531 of the possibility that we are running after CSE and there is a
532 REG_EQUAL note that is only valid if the branch has already been
533 taken. If we move the insn with the REG_EQUAL note, we may
534 fold the comparison to always be false in a later CSE pass.
535 (We could also delete the REG_NOTES when moving the insn, but it
536 seems simpler to not move it.) An exception is that we can move
537 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
538 value is the same as "b".
540 INSN is the branch over the `else' part.
542 We set:
544 TEMP to the jump insn preceding "x = a;"
545 TEMP1 to X
546 TEMP2 to the insn that sets "x = b;"
547 TEMP3 to the insn that sets "x = a;"
548 TEMP4 to the set of "x = b"; */
555 && (! SMALL_REGISTER_CLASSES
571 /* TEMP must skip over the "x = a;" insn */
574 /* There must be no other entries to the "x = b;" insn. */
576 /* INSN must either branch to the insn after TEMP2 or the insn
577 after TEMP2 must branch to the same place as INSN. */
582 {
583 /* The test expression, X, may be a complicated test with
584 multiple branches. See if we can find all the uses of
585 the label that TEMP branches to without hitting a CALL_INSN
586 or a jump to somewhere else. */
589 rtx p;
590 #ifdef HAVE_cc0
591 rtx q;
592 #endif
594 /* Set P to the first jump insn that goes around "x = a;". */
596 {
598 {
601 {
602 nuses--;
605 }
606 else
608 }
611 }
613 #ifdef HAVE_cc0
614 /* We cannot insert anything between a set of cc and its use
615 so if P uses cc0, we must back up to the previous insn. */
620 #endif
625 /* If we found all the uses and there was no data conflict, we
626 can move the assignment unless we can branch into the middle
627 from somewhere. */
634 /* Verify that registers used by the jump are not clobbered
635 by the instruction being moved. */
639 {
643 /* Set NEXT to an insn that we know won't go away. */
646 /* Delete the jump around the set. Note that we must do
647 this before we redirect the test jumps so that it won't
648 delete the code immediately following the assignment
649 we moved (which might be a jump). */
653 /* We either have two consecutive labels or a jump to
654 a jump, so adjust all the JUMP_INSNs to branch to where
655 INSN branches to. */
663 }
664 }
666 /* Simplify if (...) { x = a; goto l; } x = b; by converting it
667 to x = a; if (...) goto l; x = b;
668 if A is sufficiently simple, the test doesn't involve X,
669 and nothing in the test modifies A or X.
671 If we have small register classes, we also can't do this if X
672 is a hard register.
674 If the "x = a;" insn has any REG_NOTES, we don't do this because
675 of the possibility that we are running after CSE and there is a
676 REG_EQUAL note that is only valid if the branch has already been
677 taken. If we move the insn with the REG_EQUAL note, we may
678 fold the comparison to always be false in a later CSE pass.
679 (We could also delete the REG_NOTES when moving the insn, but it
680 seems simpler to not move it.) An exception is that we can move
681 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
682 value is the same as "a".
684 INSN is the goto.
686 We set:
688 TEMP to the jump insn preceding "x = a;"
689 TEMP1 to X
690 TEMP2 to the insn that sets "x = b;"
691 TEMP3 to the insn that sets "x = a;"
692 TEMP4 to the set of "x = a"; */
699 && (! SMALL_REGISTER_CLASSES
715 /* TEMP must skip over the "x = a;" insn */
718 {
722 #ifdef HAVE_cc0
723 /* We cannot insert anything between a set of cc and its use. */
727 #endif
737 /* Verify that registers used by the jump are not clobbered
738 by the instruction being moved. */
743 {
748 /* Set NEXT to an insn that we know won't go away. */
751 }
756 }
758 #if !defined(HAVE_cc0) && !defined(HAVE_conditional_arithmetic)
760 /* If we have if (...) x = exp; and branches are expensive,
761 EXP is a single insn, does not have any side effects, cannot
762 trap, and is not too costly, convert this to
763 t = exp; if (...) x = t;
765 Don't do this when we have CC0 because it is unlikely to help
766 and we'd need to worry about where to place the new insn and
767 the potential for conflicts. We also can't do this when we have
768 notes on the insn for the same reason as above.
770 If we have conditional arithmetic, this will make this
771 harder to optimize later and isn't needed, so don't do it
772 in that case either.
774 We set:
776 TEMP to the "x = exp;" insn.
777 TEMP1 to the single set in the "x = exp;" insn.
778 TEMP2 to "x". */
792 && (! SMALL_REGISTER_CLASSES
800 {
805 {
813 {
816 }
817 }
818 }
820 /* Similarly, if it takes two insns to compute EXP but they
821 have the same destination. Here TEMP3 will be the second
822 insn and TEMP4 the SET from that insn. */
840 && (! SMALL_REGISTER_CLASSES
850 {
856 {
857 /* Use the earliest of temp5 and temp6. */
863 emit_insn_after_with_line_notes
871 {
874 }
875 }
876 }
878 /* Finally, handle the case where two insns are used to
879 compute EXP but a temporary register is used. Here we must
880 ensure that the temporary register is not used anywhere else. */
883 && after_regscan
911 && (! SMALL_REGISTER_CLASSES
917 {
923 {
924 /* Use the earliest of temp5 and temp6. */
937 {
940 }
941 }
942 }
945 #ifdef HAVE_conditional_arithmetic
946 /* ??? This is disabled in genconfig, as this simple-minded
947 transformation can incredibly lengthen register lifetimes.
949 Consider this example from cexp.c's yyparse:
951 234 (set (pc)
952 (if_then_else (ne (reg:DI 149) (const_int 0 [0x0]))
953 (label_ref 248) (pc)))
954 237 (set (reg/i:DI 0 $0) (const_int 1 [0x1]))
955 239 (set (pc) (label_ref 2382))
956 248 (code_label ("yybackup"))
958 This will be transformed to:
960 237 (set (reg/i:DI 0 $0)
961 (if_then_else:DI (eq (reg:DI 149) (const_int 0 [0x0]))
962 (const_int 1 [0x1]) (reg/i:DI 0 $0)))
963 239 (set (pc)
964 (if_then_else (eq (reg:DI 149) (const_int 0 [0x0]))
965 (label_ref 2382) (pc)))
967 which, from this narrow viewpoint looks fine. Except that
968 between this and 3 other ocurrences of the same pattern, $0
969 is now live for basically the entire function, and we'll
970 get an abort in caller_save.
972 Any replacement for this code should recall that a set of
973 a register that is not live need not, and indeed should not,
974 be conditionalized. Either that, or delay the transformation
975 until after register allocation. */
977 /* See if this is a conditional jump around a small number of
978 instructions that we can conditionalize. Don't do this before
979 the initial CSE pass or after reload.
981 We reject any insns that have side effects or may trap.
982 Strictly speaking, this is not needed since the machine may
983 support conditionalizing these too, but we won't deal with that
984 now. Specifically, this means that we can't conditionalize a
985 CALL_INSN, which some machines, such as the ARC, can do, but
986 this is a very minor optimization. */
991 insn))
992 {
1003 /* Scan forward BRANCH_COST real insns looking for the JUMP_LABEL
1004 of this insn. We see if we think we can conditionalize the
1005 insns we pass. For now, we only deal with insns that have
1006 one SET. We stop after an insn that modifies anything in
1007 OURCOND, if we have too many insns, or if we have an insn
1008 with a side effect or that may trip. Note that we will
1009 be modifying any unconditional jumps we encounter to be
1010 conditional; this will have the effect of also doing this
1011 optimization on the "else" the next time around. */
1016 {
1017 /* Ignore everything but an active insn. */
1023 /* If this was an unconditional jump, record it since we'll
1024 need to remove the BARRIER if we succeed. We can only
1025 have one such jump since there must be a label after
1026 the BARRIER and it's either ours, in which case it's the
1027 only one or some other, in which case we'd fail. */
1032 /* See if we are allowed another insn and if this insn
1033 if one we think we may be able to handle. */
1035 || last_insn
1040 else
1042 gen_rtx_IF_THEN_ELSE
1050 }
1052 /* If we've reached our jump label, haven't failed, and all
1053 the changes above are valid, we can delete this jump
1054 insn. Also remove a BARRIER after any jump that used
1055 to be unconditional and remove any REG_EQUAL or REG_EQUIV
1056 that might have previously been present on insns we
1057 made conditional. */
1060 {
1071 {
1076 }
1081 }
1082 else
1083 {
1086 }
1087 }
1088 #endif
1090 /* Try to use a conditional move (if the target has them), or a
1091 store-flag insn. If the target has conditional arithmetic as
1092 well as conditional move, the above code will have done something.
1093 Note that we prefer the above code since it is more general: the
1094 code below can make changes that require work to undo.
1096 The general case here is:
1098 1) x = a; if (...) x = b; and
1099 2) if (...) x = b;
1101 If the jump would be faster, the machine should not have defined
1102 the movcc or scc insns!. These cases are often made by the
1103 previous optimization.
1105 The second case is treated as x = x; if (...) x = b;.
1107 INSN here is the jump around the store. We set:
1109 TEMP to the "x op= b;" insn.
1110 TEMP1 to X.
1111 TEMP2 to B.
1112 TEMP3 to A (X in the second case).
1113 TEMP4 to the condition being tested.
1114 TEMP5 to the earliest insn used to find the condition.
1115 TEMP6 to the SET of TEMP. */
1118 ! reload_completed
1119 #ifdef HAVE_conditional_arithmetic
1120 /* Defer this until after CSE so the above code gets the
1121 first crack at it. */
1122 && cse_not_expected
1123 #endif
1125 /* Set TEMP to the "x = b;" insn. */
1130 && (! SMALL_REGISTER_CLASSES
1134 /* Allow either form, but prefer the former if both apply.
1135 There is no point in using the old value of TEMP1 if
1136 it is a register, since cse will alias them. It can
1137 lose if the old value were a hard register since CSE
1138 won't replace hard registers. Avoid using TEMP3 if
1139 small register classes and it is a hard register. */
1143 /* Make the latter case look like x = x; if (...) x = b; */
1145 /* INSN must either branch to the insn after TEMP or the insn
1146 after TEMP must branch to the same place as INSN. */
1152 /* We must be comparing objects whose modes imply the size.
1153 We could handle BLKmode if (1) emit_store_flag could
1154 and (2) we could find the size reliably. */
1156 /* Even if branches are cheap, the store_flag optimization
1157 can win when the operation to be performed can be
1158 expressed directly. */
1159 #ifdef HAVE_cc0
1160 /* If the previous insn sets CC0 and something else, we can't
1161 do this since we are going to delete that insn. */
1168 #endif
1169 )
1170 {
1171 #ifdef HAVE_conditional_move
1172 /* First try a conditional move. */
1173 {
1179 /* Copy the compared variables into cond0 and cond1, so that
1180 any side effects performed in or after the old comparison,
1181 will not affect our compare which will come later. */
1182 /* ??? Is it possible to just use the comparison in the jump
1183 insn? After all, we're going to delete it. We'd have
1184 to modify emit_conditional_move to take a comparison rtx
1185 instead or write a new function. */
1187 /* We want the target to be able to simplify comparisons with
1188 zero (and maybe other constants as well), so don't create
1189 pseudos for them. There's no need to either. */
1193 else
1196 /* Careful about copying these values -- an IOR or what may
1197 need to do other things, like clobber flags. */
1198 /* ??? Assume for the moment that AVAL is ok. */
1203 /* We're dealing with a single_set insn with no side effects
1204 on SET_SRC. We do need to be reasonably certain that if
1205 we need to force BVAL into a register that we won't
1206 clobber the flags -- general_operand should suffice. */
1209 else
1210 {
1216 }
1225 {
1229 /* Save the conditional move sequence but don't emit it
1230 yet. On some machines, like the alpha, it is possible
1231 that temp5 == insn, so next generate the sequence that
1232 saves the compared values and then emit both
1233 sequences ensuring seq1 occurs before seq2. */
1237 /* "Now that we can't fail..." Famous last words.
1238 Generate the copy insns that preserve the compared
1239 values. */
1247 /* Validate the sequence -- this may be some weird
1248 bit-extract-and-test instruction for which there
1249 exists no complimentary bit-extract insn. */
1253 {
1256 }
1259 {
1262 /* Insert conditional move after insn, to be sure
1263 that the jump and a possible compare won't be
1264 separated. */
1267 /* ??? We can also delete the insn that sets X to A.
1268 Flow will do it too though. */
1274 {
1276 old_max_reg);
1278 }
1282 }
1283 }
1284 else
1286 }
1287 #endif
1289 /* That didn't work, try a store-flag insn.
1291 We further divide the cases into:
1293 1) x = a; if (...) x = b; and either A or B is zero,
1294 2) if (...) x = 0; and jumps are expensive,
1295 3) x = a; if (...) x = b; and A and B are constants where all
1296 the set bits in A are also set in B and jumps are expensive,
1297 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
1298 more expensive, and
1299 5) if (...) x = b; if jumps are even more expensive. */
1303 /* Make the latter case look like
1304 x = x; if (...) x = 0; */
1309 /* If B is zero, OK; if A is zero, can only do (1) if we
1310 can reverse the condition. See if (3) applies possibly
1311 by reversing the condition. Prefer reversing to (4) when
1312 branches are very expensive. */
1316 /* Check that the mask is a power of two,
1317 so that it can probably be generated
1318 with a shift. */
1335 insn)))))
1337 )
1338 {
1342 rtx target;
1344 /* If necessary, reverse the condition. */
1347 else
1350 /* If CVAL is non-zero, normalize to -1. Otherwise, if UVAL
1351 is the constant 1, it is best to just compute the result
1352 directly. If UVAL is constant and STORE_FLAG_VALUE
1353 includes all of its bits, it is best to compute the flag
1354 value unnormalized and `and' it with UVAL. Otherwise,
1355 normalize to -1 and `and' with UVAL. */
1362 /* We will be putting the store-flag insn immediately in
1363 front of the comparison that was originally being done,
1364 so we know all the variables in TEMP4 will be valid.
1365 However, this might be in front of the assignment of
1366 A to VAR. If it is, it would clobber the store-flag
1367 we will be emitting.
1369 Therefore, emit into a temporary which will be copied to
1370 VAR immediately after TEMP. */
1375 VOIDmode,
1378 normalizep);
1380 {
1381 rtx seq;
1387 /* Put the store-flag insns in front of the first insn
1388 used to compute the condition to ensure that we
1389 use the same values of them as the current
1390 comparison. However, the remainder of the insns we
1391 generate will be placed directly in front of the
1392 jump insn, in case any of the pseudos we use
1393 are modified earlier. */
1399 /* Both CVAL and UVAL are non-zero. */
1401 {
1409 else
1410 {
1416 }
1418 /* If we usually make new pseudos, do so here. This
1419 turns out to help machines that have conditional
1420 move insns. */
1421 /* ??? Conditional moves have already been handled.
1422 This may be obsolete. */
1430 }
1432 {
1433 /* We know that either CVAL or UVAL is zero. If
1434 UVAL is zero, negate TARGET and `and' with CVAL.
1435 Otherwise, `and' with UVAL. */
1437 {
1441 }
1447 }
1452 #ifdef HAVE_cc0
1453 /* If INSN uses CC0, we must not separate it from the
1454 insn that sets cc0. */
1457 #endif
1465 {
1468 }
1472 }
1473 else
1475 }
1476 }
1478 /* If branches are expensive, convert
1479 if (foo) bar++; to bar += (foo != 0);
1480 and similarly for "bar--;"
1482 INSN is the conditional branch around the arithmetic. We set:
1484 TEMP is the arithmetic insn.
1485 TEMP1 is the SET doing the arithmetic.
1486 TEMP2 is the operand being incremented or decremented.
1487 TEMP3 to the condition being tested.
1488 TEMP4 to the earliest insn used to find the condition. */
1491 #ifdef HAVE_incscc
1492 || HAVE_incscc
1493 #endif
1494 #ifdef HAVE_decscc
1495 || HAVE_decscc
1496 #endif
1497 )
1498 && ! reload_completed
1510 /* INSN must either branch to the insn after TEMP or the insn
1511 after TEMP must branch to the same place as INSN. */
1517 /* We must be comparing objects whose modes imply the size.
1518 We could handle BLKmode if (1) emit_store_flag could
1519 and (2) we could find the size reliably. */
1522 {
1528 /* It must be the case that TEMP2 is not modified in the range
1529 [TEMP4, INSN). The one exception we make is if the insn
1530 before INSN sets TEMP2 to something which is also unchanged
1531 in that range. In that case, we can move the initialization
1532 into our sequence. */
1542 {
1546 }
1552 VOIDmode,
1556 /* If we can do the store-flag, do the addition or
1557 subtraction. */
1566 {
1567 /* Put the result back in temp2 in case it isn't already.
1568 Then replace the jump, possible a CC0-setting insn in
1569 front of the jump, and TEMP, with the sequence we have
1570 made. */
1585 #ifdef HAVE_cc0
1587 #endif
1591 {
1594 }
1598 }
1599 else
1601 }
1603 /* Simplify if (...) x = 1; else {...} if (x) ...
1604 We recognize this case scanning backwards as well.
1606 TEMP is the assignment to x;
1607 TEMP1 is the label at the head of the second if. */
1608 /* ?? This should call get_condition to find the values being
1609 compared, instead of looking for a COMPARE insn when HAVE_cc0
1610 is not defined. This would allow it to work on the m88k. */
1611 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1612 is not defined and the condition is tested by a separate compare
1613 insn. This is because the code below assumes that the result
1614 of the compare dies in the following branch.
1616 Not only that, but there might be other insns between the
1617 compare and branch whose results are live. Those insns need
1618 to be executed.
1620 A way to fix this is to move the insns at JUMP_LABEL (insn)
1621 to before INSN. If we are running before flow, they will
1622 be deleted if they aren't needed. But this doesn't work
1623 well after flow.
1625 This is really a special-case of jump threading, anyway. The
1626 right thing to do is to replace this and jump threading with
1627 much simpler code in cse.
1629 This code has been turned off in the non-cc0 case in the
1630 meantime. */
1632 #ifdef HAVE_cc0
1634 /* Safe to skip USE and CLOBBER insns here
1635 since they will not be deleted. */
1643 /* If we find that the next value tested is `x'
1644 (TEMP1 is the insn where this happens), win. */
1647 #ifdef HAVE_cc0
1648 /* Does temp1 `tst' the value of x? */
1652 #else
1653 /* Does temp1 compare the value of x against zero? */
1660 #endif
1662 {
1663 /* Get the if_then_else from the condjump. */
1666 {
1669 rtx cond
1672 rtx ultimate;
1678 else
1688 }
1689 }
1690 #endif
1692 #if 0
1693 /* @@ This needs a bit of work before it will be right.
1695 Any type of comparison can be accepted for the first and
1696 second compare. When rewriting the first jump, we must
1697 compute the what conditions can reach label3, and use the
1698 appropriate code. We can not simply reverse/swap the code
1699 of the first jump. In some cases, the second jump must be
1700 rewritten also.
1702 For example,
1703 < == converts to > ==
1704 < != converts to == >
1705 etc.
1707 If the code is written to only accept an '==' test for the second
1708 compare, then all that needs to be done is to swap the condition
1709 of the first branch.
1711 It is questionable whether we want this optimization anyways,
1712 since if the user wrote code like this because he/she knew that
1713 the jump to label1 is taken most of the time, then rewriting
1714 this gives slower code. */
1715 /* @@ This should call get_condition to find the values being
1716 compared, instead of looking for a COMPARE insn when HAVE_cc0
1717 is not defined. This would allow it to work on the m88k. */
1718 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1719 is not defined and the condition is tested by a separate compare
1720 insn. This is because the code below assumes that the result
1721 of the compare dies in the following branch. */
1723 /* Simplify test a ~= b
1724 condjump label1;
1725 test a == b
1726 condjump label2;
1727 jump label3;
1728 label1:
1730 rewriting as
1731 test a ~~= b
1732 condjump label3
1733 test a == b
1734 condjump label2
1735 label1:
1737 where ~= is an inequality, e.g. >, and ~~= is the swapped
1738 inequality, e.g. <.
1740 We recognize this case scanning backwards.
1742 TEMP is the conditional jump to `label2';
1743 TEMP1 is the test for `a == b';
1744 TEMP2 is the conditional jump to `label1';
1745 TEMP3 is the test for `a ~= b'. */
1754 #ifdef HAVE_cc0
1756 #else
1760 #endif
1774 {
1779 {
1782 }
1786 }
1787 #endif
1788 /* Simplify if (...) {... x = 1;} if (x) ...
1790 We recognize this case backwards.
1792 TEMP is the test of `x';
1793 TEMP1 is the assignment to `x' at the end of the
1794 previous statement. */
1795 /* @@ This should call get_condition to find the values being
1796 compared, instead of looking for a COMPARE insn when HAVE_cc0
1797 is not defined. This would allow it to work on the m88k. */
1798 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1799 is not defined and the condition is tested by a separate compare
1800 insn. This is because the code below assumes that the result
1801 of the compare dies in the following branch. */
1803 /* ??? This has to be turned off. The problem is that the
1804 unconditional jump might indirectly end up branching to the
1805 label between TEMP1 and TEMP. We can't detect this, in general,
1806 since it may become a jump to there after further optimizations.
1807 If that jump is done, it will be deleted, so we will retry
1808 this optimization in the next pass, thus an infinite loop.
1810 The present code prevents this by putting the jump after the
1811 label, but this is not logically correct. */
1812 #if 0
1814 /* Safe to skip USE and CLOBBER insns here
1815 since they will not be deleted. */
1820 #ifdef HAVE_cc0
1823 #else
1824 /* Temp must be a compare insn, we can not accept a register
1825 to register move here, since it may not be simply a
1826 tst insn. */
1832 #endif
1833 /* May skip USE or CLOBBER insns here
1834 for checking for opportunity, since we
1835 take care of them later. */
1839 #ifdef HAVE_cc0
1841 #else
1844 #endif
1846 /* If this isn't true, cse will do the job. */
1848 {
1849 /* Get the if_then_else from the condjump. */
1854 {
1856 rtx last_insn;
1857 rtx ultimate;
1858 rtx p;
1860 /* Get the place that condjump will jump to
1861 if it is reached from here. */
1865 else
1867 /* Get it as a CODE_LABEL. */
1870 else
1871 /* Get the label out of the LABEL_REF. */
1874 /* Insert the jump immediately before TEMP, specifically
1875 after the label that is between TEMP1 and TEMP. */
1878 /* If we would be branching to the next insn, the jump
1879 would immediately be deleted and the re-inserted in
1880 a subsequent pass over the code. So don't do anything
1881 in that case. */
1884 {
1887 last_insn);
1892 {
1896 }
1899 }
1900 }
1901 }
1902 #endif
1903 #ifdef HAVE_trap
1904 /* Detect a conditional jump jumping over an unconditional trap. */
1915 {
1921 {
1927 }
1928 }
1929 /* Detect a jump jumping to an unconditional trap. */
1934 && (this_is_simplejump
1936 {
1941 {
1943 /* Replace an unconditional jump to a trap with a trap. */
1945 {
1950 }
1955 {
1960 }
1961 }
1962 /* If the trap condition and jump condition are mutually
1963 exclusive, redirect the jump to the following insn. */
1965 && ! this_is_simplejump
1970 {
1973 }
1974 }
1975 #endif
1976 else
1977 {
1978 /* Detect a jump to a jump. */
1980 /* Look for if (foo) bar; else break; */
1981 /* The insns look like this:
1982 insn = condjump label1;
1983 ...range1 (some insns)...
1984 jump label2;
1985 label1:
1986 ...range2 (some insns)...
1987 jump somewhere unconditionally
1988 label2: */
1989 {
1992 /* Don't do this optimization on the first round, so that
1993 jump-around-a-jump gets simplified before we ask here
1994 whether a jump is unconditional.
1996 Also don't do it when we are called after reload since
1997 it will confuse reorg. */
2000 /* Make sure INSN is something we can invert. */
2007 {
2014 /* Invert the jump condition, so we
2015 still execute the same insns in each case. */
2017 {
2022 rtx rangenext;
2024 /* Include in each range any notes before it, to be
2025 sure that we get the line number note if any, even
2026 if there are other notes here. */
2035 /* Don't move NOTEs for blocks or loops; shift them
2036 outside the ranges, where they'll stay put. */
2040 /* Get current surrounds of the 2 ranges. */
2046 /* Splice range2 where range1 was. */
2051 /* Splice range1 where range2 was. */
2057 /* Check for a loop end note between the end of
2058 range2, and the next code label. If there is one,
2059 then what we have really seen is
2060 if (foo) break; end_of_loop;
2061 and moved the break sequence outside the loop.
2062 We must move the LOOP_END note to where the
2063 loop really ends now, or we will confuse loop
2064 optimization. Stop if we find a LOOP_BEG note
2065 first, since we don't want to move the LOOP_END
2066 note in that case. */
2068 {
2071 {
2074 {
2085 }
2089 }
2090 }
2093 }
2094 }
2095 }
2097 /* Now that the jump has been tensioned,
2098 try cross jumping: check for identical code
2099 before the jump and before its target label. */
2101 /* First, cross jumping of conditional jumps: */
2104 {
2108 /* A conditional jump may be crossjumped
2109 only if the place it jumps to follows
2110 an opposing jump that comes back here. */
2113 /* We have no opposing jump;
2114 cannot cross jump this insn. */
2118 /* TARGET is nonzero if it is ok to cross jump
2119 to code before TARGET. If so, see if matches. */
2125 {
2127 /* Make the old conditional jump
2128 into an unconditional one. */
2133 /* Add to jump_chain unless this is a new label
2134 whose UID is too large. */
2136 {
2140 }
2143 }
2144 }
2146 /* Cross jumping of unconditional jumps:
2147 a few differences. */
2150 {
2152 rtx target;
2156 /* TARGET is nonzero if it is ok to cross jump
2157 to code before TARGET. If so, see if matches. */
2161 /* If cannot cross jump to code before the label,
2162 see if we can cross jump to another jump to
2163 the same label. */
2164 /* Try each other jump to this label. */
2171 /* Ignore TARGET if it's deleted. */
2177 {
2181 }
2182 }
2184 /* This code was dead in the previous jump.c! */
2186 {
2187 /* Return insns all "jump to the same place"
2188 so we can cross-jump between any two of them. */
2194 /* If cannot cross jump to code before the label,
2195 see if we can cross jump to another jump to
2196 the same label. */
2197 /* Try each other jump to this label. */
2208 {
2212 }
2213 }
2214 }
2215 }
2218 }
2220 /* Delete extraneous line number notes.
2221 Note that two consecutive notes for different lines are not really
2222 extraneous. There should be some indication where that line belonged,
2223 even if it became empty. */
2225 {
2230 {
2231 /* Delete this note if it is identical to previous note. */
2235 {
2238 }
2241 }
2242 }
2244 #ifdef HAVE_return
2246 {
2247 /* If we fall through to the epilogue, see if we can insert a RETURN insn
2248 in front of it. If the machine allows it at this point (we might be
2249 after reload for a leaf routine), it will improve optimization for it
2250 to be there. We do this both here and at the start of this pass since
2251 the RETURN might have been deleted by some of our optimizations. */
2257 {
2260 }
2261 }
2262 #endif
2264 /* CAN_REACH_END is persistent for each function. Once set it should
2265 not be cleared. This is especially true for the case where we
2266 delete the NOTE_FUNCTION_END note. CAN_REACH_END is cleared by
2267 the front-end before compiling each function. */
2271 /* Show JUMP_CHAIN no longer valid. */
2273 }
2274 \f
2275 /* Initialize LABEL_NUSES and JUMP_LABEL fields. Delete any REG_LABEL
2276 notes whose labels don't occur in the insn any more. Returns the
2277 largest INSN_UID found. */
2278 static int
2280 rtx f;
2281 {
2283 rtx insn;
2286 {
2292 {
2296 {
2301 }
2302 }
2305 }
2308 }
2310 /* Delete insns following barriers, up to next label.
2312 Also delete no-op jumps created by gcse. */
2313 static void
2315 rtx f;
2316 {
2317 rtx insn;
2320 {
2322 {
2328 {
2332 else
2334 }
2335 /* INSN is now the code_label. */
2336 }
2337 /* Also remove (set (pc) (pc)) insns which can be created by
2338 gcse. We eliminate such insns now to avoid having them
2339 cause problems later. */
2346 else
2348 }
2349 }
2351 /* Mark the label each jump jumps to.
2352 Combine consecutive labels, and count uses of labels.
2354 For each label, make a chain (using `jump_chain')
2355 of all the *unconditional* jumps that jump to it;
2356 also make a chain of all returns.
2358 CROSS_JUMP indicates whether we are doing cross jumping
2359 and if we are whether we will be paying attention to
2360 death notes or not. */
2362 static void
2364 rtx f;
2366 {
2367 rtx insn;
2371 {
2374 {
2376 {
2380 }
2382 {
2385 }
2386 }
2387 }
2388 }
2390 /* Delete all labels already not referenced.
2391 Also find and return the last insn. */
2393 static rtx
2395 rtx f;
2396 {
2398 rtx insn;
2401 {
2404 else
2405 {
2408 }
2409 }
2412 }
2414 /* Delete various simple forms of moves which have no necessary
2415 side effect. */
2417 static void
2419 rtx f;
2420 {
2424 {
2428 {
2431 /* Combine stack_adjusts with following push_insns. */
2432 #ifdef PUSH_ROUNDING
2439 {
2440 rtx p;
2446 /* Find all successive push insns. */
2448 /* Don't convert more than three pushes;
2449 that starts adding too many displaced addresses
2450 and the whole thing starts becoming a losing
2451 proposition. */
2453 {
2462 /* Allow a no-op move between the adjust and the push. */
2471 pushes++;
2476 }
2478 /* Discard the amount pushed from the stack adjust;
2479 maybe eliminate it entirely. */
2481 {
2484 }
2485 else
2489 /* Change the appropriate push insns to ordinary stores. */
2492 {
2501 /* Allow a no-op move between the adjust and the push. */
2511 /* If this push doesn't fully fit in the space
2512 of the stack adjust that we deleted,
2513 make another stack adjust here for what we
2514 didn't use up. There should be peepholes
2515 to recognize the resulting sequence of insns. */
2517 {
2520 p);
2522 }
2525 }
2526 }
2527 #endif
2529 /* Detect and delete no-op move instructions
2530 resulting from not allocating a parameter in a register. */
2543 /* Detect and ignore no-op move instructions
2544 resulting from smart or fortuitous register allocation. */
2547 {
2554 {
2555 rtx trial;
2562 {
2563 /* DREG may have been the target of a REG_DEAD note in
2564 the insn which makes INSN redundant. If so, reorg
2565 would still think it is dead. So search for such a
2566 note and delete it if we find it. */
2572 {
2575 }
2577 /* Deleting insn could lose a death-note for SREG. */
2579 {
2580 /* Change this into a USE so that we won't emit
2581 code for it, but still can keep the note. */
2585 /* Remove all reg notes but the REG_DEAD one. */
2588 }
2589 else
2591 }
2592 }
2597 {
2598 /* This handles the case where we have two consecutive
2599 assignments of the same constant to pseudos that didn't
2600 get a hard reg. Each SET from the constant will be
2601 converted into a SET of the spill register and an
2602 output reload will be made following it. This produces
2603 two loads of the same constant into the same spill
2604 register. */
2608 /* Look back for a death note for the first reg.
2609 If there is one, it is no longer accurate. */
2611 {
2615 {
2618 }
2620 }
2622 /* Delete the second load of the value. */
2624 }
2625 }
2627 {
2628 /* If each part is a set between two identical registers or
2629 a USE or CLOBBER, delete the insn. */
2631 rtx tem;
2634 {
2644 }
2648 }
2649 /* Also delete insns to store bit fields if they are no-ops. */
2650 /* Not worth the hair to detect this in the big-endian case. */
2659 }
2661 }
2662 }
2664 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
2665 If so indicate that this function can drop off the end by returning
2666 1, else return 0.
2668 CHECK_DELETED indicates whether we must check if the note being
2669 searched for has the deleted flag set.
2671 DELETE_FINAL_NOTE indicates whether we should delete the note
2672 if we find it. */
2674 static int
2676 rtx last;
2679 {
2684 {
2687 /* One label can follow the end-note: the return label. */
2690 /* Ordinary insns can follow it if returning a structure. */
2693 /* If machine uses explicit RETURN insns, no epilogue,
2694 then one of them follows the note. */
2698 /* A barrier can follow the return insn. */
2701 /* Other kinds of notes can follow also. */
2710 }
2712 /* See if we backed up to the appropriate type of note. */
2718 {
2722 }
2725 }
2727 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
2728 jump. Assume that this unconditional jump is to the exit test code. If
2729 the code is sufficiently simple, make a copy of it before INSN,
2730 followed by a jump to the exit of the loop. Then delete the unconditional
2731 jump after INSN.
2733 Return 1 if we made the change, else 0.
2735 This is only safe immediately after a regscan pass because it uses the
2736 values of regno_first_uid and regno_last_uid. */
2738 static int
2740 rtx loop_start;
2741 {
2746 rtx lastexit;
2750 /* Scan the exit code. We do not perform this optimization if any insn:
2752 is a CALL_INSN
2753 is a CODE_LABEL
2754 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
2755 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
2756 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
2757 is not valid.
2759 We also do not do this if we find an insn with ASM_OPERANDS. While
2760 this restriction should not be necessary, copying an insn with
2761 ASM_OPERANDS can confuse asm_noperands in some cases.
2763 Also, don't do this if the exit code is more than 20 insns. */
2766 insn
2770 {
2772 {
2777 /* We could be in front of the wrong NOTE_INSN_LOOP_END if there is
2778 a jump immediately after the loop start that branches outside
2779 the loop but within an outer loop, near the exit test.
2780 If we copied this exit test and created a phony
2781 NOTE_INSN_LOOP_VTOP, this could make instructions immediately
2782 before the exit test look like these could be safely moved
2783 out of the loop even if they actually may be never executed.
2784 This can be avoided by checking here for NOTE_INSN_LOOP_CONT. */
2793 /* If we were to duplicate this code, we would not move
2794 the BLOCK notes, and so debugging the moved code would
2795 be difficult. Thus, we only move the code with -O2 or
2796 higher. */
2802 /* The code below would grossly mishandle REG_WAS_0 notes,
2803 so get rid of them here. */
2813 }
2814 }
2816 /* Unless INSN is zero, we can do the optimization. */
2822 /* See if any insn sets a register only used in the loop exit code and
2823 not a user variable. If so, replace it with a new register. */
2832 {
2838 {
2839 /* We can do the replacement. Allocate reg_map if this is the
2840 first replacement we found. */
2842 {
2845 }
2850 }
2851 }
2853 /* Now copy each insn. */
2855 {
2857 {
2862 /* Only copy line-number notes. */
2864 {
2867 }
2877 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
2878 make them. */
2895 {
2899 }
2901 /* If this is a simple jump, add it to the jump chain. */
2905 {
2909 }
2914 }
2916 /* Record the first insn we copied. We need it so that we can
2917 scan the copied insns for new pseudo registers. */
2920 }
2922 /* Now clean up by emitting a jump to the end label and deleting the jump
2923 at the start of the loop. */
2925 {
2927 loop_start);
2929 /* Record the first insn we copied. We need it so that we can
2930 scan the copied insns for new pseudo registers. This may not
2931 be strictly necessary since we should have copied at least one
2932 insn above. But I am going to be safe. */
2939 {
2943 }
2945 }
2947 /* Now scan from the first insn we copied to the last insn we copied
2948 (copy) for new pseudo registers. Do this after the code to jump to
2949 the end label since that might create a new pseudo too. */
2952 /* Mark the exit code as the virtual top of the converted loop. */
2958 }
2959 \f
2960 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
2961 loop-end notes between START and END out before START. Assume that
2962 END is not such a note. START may be such a note. Returns the value
2963 of the new starting insn, which may be different if the original start
2964 was such a note. */
2966 rtx
2969 {
2970 rtx insn;
2971 rtx next;
2974 {
2983 {
2986 else
2987 {
2995 }
2996 }
2997 }
3000 }
3001 \f
3002 /* Compare the instructions before insn E1 with those before E2
3003 to find an opportunity for cross jumping.
3004 (This means detecting identical sequences of insns followed by
3005 jumps to the same place, or followed by a label and a jump
3006 to that label, and replacing one with a jump to the other.)
3008 Assume E1 is a jump that jumps to label E2
3009 (that is not always true but it might as well be).
3010 Find the longest possible equivalent sequences
3011 and store the first insns of those sequences into *F1 and *F2.
3012 Store zero there if no equivalent preceding instructions are found.
3014 We give up if we find a label in stream 1.
3015 Actually we could transfer that label into stream 2. */
3017 static void
3022 {
3034 {
3044 /* Don't allow the range of insns preceding E1 or E2
3045 to include the other (E2 or E1). */
3049 /* If we will get to this code by jumping, those jumps will be
3050 tensioned to go directly to the new label (before I2),
3051 so this cross-jumping won't cost extra. So reduce the minimum. */
3053 {
3056 }
3061 /* Avoid moving insns across EH regions if either of the insns
3062 can throw. */
3071 /* If this is a CALL_INSN, compare register usage information.
3072 If we don't check this on stack register machines, the two
3073 CALL_INSNs might be merged leaving reg-stack.c with mismatching
3074 numbers of stack registers in the same basic block.
3075 If we don't check this on machines with delay slots, a delay slot may
3076 be filled that clobbers a parameter expected by the subroutine.
3078 ??? We take the simple route for now and assume that if they're
3079 equal, they were constructed identically. */
3086 #ifdef STACK_REGS
3087 /* If cross_jump_death_matters is not 0, the insn's mode
3088 indicates whether or not the insn contains any stack-like
3089 regs. */
3092 {
3093 /* If register stack conversion has already been done, then
3094 death notes must also be compared before it is certain that
3095 the two instruction streams match. */
3097 rtx note;
3117 done:
3118 ;
3119 }
3120 #endif
3122 /* Don't allow old-style asm or volatile extended asms to be accepted
3123 for cross jumping purposes. It is conceptually correct to allow
3124 them, since cross-jumping preserves the dynamic instruction order
3125 even though it is changing the static instruction order. However,
3126 if an asm is being used to emit an assembler pseudo-op, such as
3127 the MIPS `.set reorder' pseudo-op, then the static instruction order
3128 matters and it must be preserved. */
3136 {
3137 /* The following code helps take care of G++ cleanups. */
3138 rtx equiv1;
3139 rtx equiv2;
3146 /* If the equivalences are not to a constant, they may
3147 reference pseudos that no longer exist, so we can't
3148 use them. */
3151 {
3156 {
3163 }
3164 }
3166 /* Insns fail to match; cross jumping is limited to the following
3167 insns. */
3169 #ifdef HAVE_cc0
3170 /* Don't allow the insn after a compare to be shared by
3171 cross-jumping unless the compare is also shared.
3172 Here, if either of these non-matching insns is a compare,
3173 exclude the following insn from possible cross-jumping. */
3176 #endif
3178 /* If cross-jumping here will feed a jump-around-jump
3179 optimization, this jump won't cost extra, so reduce
3180 the minimum. */
3186 }
3188 win:
3190 {
3191 /* Ok, this insn is potentially includable in a cross-jump here. */
3194 }
3195 }
3199 }
3201 static void
3204 {
3205 /* Find an existing label at this point
3206 or make a new one if there is none. */
3209 /* Make the same jump insn jump to the new point. */
3211 {
3212 /* Remove from jump chain of returns. */
3214 /* Change the insn. */
3219 /* Add to new the jump chain. */
3222 {
3225 }
3226 }
3227 else
3230 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
3231 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
3232 the NEWJPOS stream. */
3235 {
3236 rtx lnote;
3248 }
3249 }
3250 \f
3251 /* Return the label before INSN, or put a new label there. */
3253 rtx
3255 rtx insn;
3256 {
3257 rtx label;
3259 /* Find an existing label at this point
3260 or make a new one if there is none. */
3264 {
3270 }
3272 }
3274 /* Return the label after INSN, or put a new label there. */
3276 rtx
3278 rtx insn;
3279 {
3280 rtx label;
3282 /* Find an existing label at this point
3283 or make a new one if there is none. */
3287 {
3291 }
3293 }
3294 \f
3295 /* Return 1 if INSN is a jump that jumps to right after TARGET
3296 only on the condition that TARGET itself would drop through.
3297 Assumes that TARGET is a conditional jump. */
3299 static int
3302 {
3318 {
3322 }
3325 {
3329 }
3334 }
3335 \f
3336 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
3337 return non-zero if it is safe to reverse this comparison. It is if our
3338 floating-point is not IEEE, if this is an NE or EQ comparison, or if
3339 this is known to be an integer comparison. */
3341 int
3343 rtx comparison;
3344 rtx insn;
3345 {
3346 rtx arg0;
3348 /* If this is not actually a comparison, we can't reverse it. */
3353 /* If this is an NE comparison, it is safe to reverse it to an EQ
3354 comparison and vice versa, even for floating point. If no operands
3355 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
3356 always false and NE is always true, so the reversal is also valid. */
3357 || flag_fast_math
3364 /* Make sure ARG0 is one of the actual objects being compared. If we
3365 can't do this, we can't be sure the comparison can be reversed.
3367 Handle cc0 and a MODE_CC register. */
3369 #ifdef HAVE_cc0
3371 #endif
3372 )
3373 {
3375 rtx set;
3377 /* First see if the condition code mode alone if enough to say we can
3378 reverse the condition. If not, then search backwards for a set of
3379 ARG0. We do not need to check for an insn clobbering it since valid
3380 code will contain set a set with no intervening clobber. But
3381 stop when we reach a label. */
3382 #ifdef REVERSIBLE_CC_MODE
3386 #endif
3393 {
3399 }
3400 }
3402 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
3403 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
3408 }
3410 /* Given an rtx-code for a comparison, return the code
3411 for the negated comparison.
3412 WATCH OUT! reverse_condition is not safe to use on a jump
3413 that might be acting on the results of an IEEE floating point comparison,
3414 because of the special treatment of non-signaling nans in comparisons.
3415 Use can_reverse_comparison_p to be sure. */
3417 enum rtx_code
3420 {
3422 {
3456 }
3457 }
3459 /* Similar, but return the code when two operands of a comparison are swapped.
3460 This IS safe for IEEE floating-point. */
3462 enum rtx_code
3465 {
3467 {
3499 }
3500 }
3502 /* Given a comparison CODE, return the corresponding unsigned comparison.
3503 If CODE is an equality comparison or already an unsigned comparison,
3504 CODE is returned. */
3506 enum rtx_code
3509 {
3511 {
3534 }
3535 }
3537 /* Similarly, return the signed version of a comparison. */
3539 enum rtx_code
3542 {
3544 {
3567 }
3568 }
3569 \f
3570 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
3571 truth of CODE1 implies the truth of CODE2. */
3573 int
3576 {
3581 {
3609 }
3612 }
3613 \f
3614 /* Return 1 if INSN is an unconditional jump and nothing else. */
3616 int
3618 rtx insn;
3619 {
3624 }
3626 /* Return nonzero if INSN is a (possibly) conditional jump
3627 and nothing more. */
3629 int
3631 rtx insn;
3632 {
3651 }
3653 /* Return nonzero if INSN is a (possibly) conditional jump inside a
3654 PARALLEL. */
3656 int
3658 rtx insn;
3659 {
3664 else
3684 }
3686 /* Return the label of a conditional jump. */
3688 rtx
3690 rtx insn;
3691 {
3710 }
3712 /* Return true if INSN is a (possibly conditional) return insn. */
3714 static int
3718 {
3721 }
3723 int
3725 rtx insn;
3726 {
3728 }
3730 /* Return true if INSN is a jump that only transfers control and
3731 nothing more. */
3733 int
3735 rtx insn;
3736 {
3737 rtx set;
3751 }
3753 #ifdef HAVE_cc0
3755 /* Return 1 if X is an RTX that does nothing but set the condition codes
3756 and CLOBBER or USE registers.
3757 Return -1 if X does explicitly set the condition codes,
3758 but also does other things. */
3760 int
3762 rtx x ATTRIBUTE_UNUSED;
3763 {
3767 {
3772 {
3778 }
3780 }
3782 }
3783 #endif
3784 \f
3785 /* Follow any unconditional jump at LABEL;
3786 return the ultimate label reached by any such chain of jumps.
3787 If LABEL is not followed by a jump, return LABEL.
3788 If the chain loops or we can't find end, return LABEL,
3789 since that tells caller to avoid changing the insn.
3791 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
3792 a USE or CLOBBER. */
3794 rtx
3796 rtx label;
3797 {
3811 depth++)
3812 {
3813 /* Don't chain through the insn that jumps into a loop
3814 from outside the loop,
3815 since that would create multiple loop entry jumps
3816 and prevent loop optimization. */
3817 rtx tem;
3822 /* ??? Optional. Disables some optimizations, but makes
3823 gcov output more accurate with -O. */
3827 /* If we have found a cycle, make the insn jump to itself. */
3837 }
3841 }
3843 /* Assuming that field IDX of X is a vector of label_refs,
3844 replace each of them by the ultimate label reached by it.
3845 Return nonzero if a change is made.
3846 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
3848 static int
3852 {
3856 {
3860 {
3866 }
3867 }
3869 }
3870 \f
3871 /* Find all CODE_LABELs referred to in X, and increment their use counts.
3872 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
3873 in INSN, then store one of them in JUMP_LABEL (INSN).
3874 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
3875 referenced in INSN, add a REG_LABEL note containing that label to INSN.
3876 Also, when there are consecutive labels, canonicalize on the last of them.
3878 Note that two labels separated by a loop-beginning note
3879 must be kept distinct if we have not yet done loop-optimization,
3880 because the gap between them is where loop-optimize
3881 will want to move invariant code to. CROSS_JUMP tells us
3882 that loop-optimization is done with.
3884 Once reload has completed (CROSS_JUMP non-zero), we need not consider
3885 two labels distinct if they are separated by only USE or CLOBBER insns. */
3887 static void
3890 rtx insn;
3892 {
3898 {
3911 /* If this is a constant-pool reference, see if it is a label. */
3918 {
3921 rtx note;
3922 rtx next;
3927 /* Ignore references to labels of containing functions. */
3931 /* If there are other labels following this one,
3932 replace it with the last of the consecutive labels. */
3934 {
3946 /* ??? Optional. Disables some optimizations, but
3947 makes gcov output more accurate with -O. */
3950 }
3957 {
3961 /* If we've changed OLABEL and we had a REG_LABEL note
3962 for it, update it as well. */
3967 /* Otherwise, add a REG_LABEL note for LABEL unless there already
3968 is one. */
3970 {
3971 /* This code used to ignore labels which refered to dispatch
3972 tables to avoid flow.c generating worse code.
3974 However, in the presense of global optimizations like
3975 gcse which call find_basic_blocks without calling
3976 life_analysis, not recording such labels will lead
3977 to compiler aborts because of inconsistencies in the
3978 flow graph. So we go ahead and record the label.
3980 It may also be the case that the optimization argument
3981 is no longer valid because of the more accurate cfg
3982 we build in find_basic_blocks -- it no longer pessimizes
3983 code when it finds a REG_LABEL note. */
3986 }
3987 }
3989 }
3991 /* Do walk the labels in a vector, but not the first operand of an
3992 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
3996 {
4001 }
4006 }
4010 {
4014 {
4018 }
4019 }
4020 }
4022 /* If all INSN does is set the pc, delete it,
4023 and delete the insn that set the condition codes for it
4024 if that's what the previous thing was. */
4026 void
4028 rtx insn;
4029 {
4034 }
4036 /* Recursively delete prior insns that compute the value (used only by INSN
4037 which the caller is deleting) stored in the register mentioned by NOTE
4038 which is a REG_DEAD note associated with INSN. */
4040 static void
4042 rtx note;
4043 rtx insn;
4044 {
4045 rtx our_prev;
4052 {
4055 /* If we reach a CALL which is not calling a const function
4056 or the callee pops the arguments, then give up. */
4062 /* If we reach a SEQUENCE, it is too complex to try to
4063 do anything with it, so give up. */
4069 /* reorg creates USEs that look like this. We leave them
4070 alone because reorg needs them for its own purposes. */
4074 {
4079 {
4080 /* If we find a SET of something else, we can't
4081 delete the insn. */
4086 {
4092 }
4096 }
4099 {
4101 int dest_endregno
4113 /* We may have a multi-word hard register and some, but not
4114 all, of the words of the register are needed in subsequent
4115 insns. Write REG_UNUSED notes for those parts that were not
4116 needed. */
4119 {
4131 }
4132 }
4135 }
4137 /* If PAT references the register that dies here, it is an
4138 additional use. Hence any prior SET isn't dead. However, this
4139 insn becomes the new place for the REG_DEAD note. */
4141 {
4145 }
4146 }
4147 }
4149 /* Delete INSN and recursively delete insns that compute values used only
4150 by INSN. This uses the REG_DEAD notes computed during flow analysis.
4151 If we are running before flow.c, we need do nothing since flow.c will
4152 delete dead code. We also can't know if the registers being used are
4153 dead or not at this point.
4155 Otherwise, look at all our REG_DEAD notes. If a previous insn does
4156 nothing other than set a register that dies in this insn, we can delete
4157 that insn as well.
4159 On machines with CC0, if CC0 is used in this insn, we may be able to
4160 delete the insn that set it. */
4162 static void
4164 rtx insn;
4165 {
4167 rtx set;
4169 #ifdef HAVE_cc0
4171 {
4173 /* We assume that at this stage
4174 CC's are always set explicitly
4175 and always immediately before the jump that
4176 will use them. So if the previous insn
4177 exists to set the CC's, delete it
4178 (unless it performs auto-increments, etc.). */
4181 {
4185 else
4186 /* Otherwise, show that cc0 won't be used. */
4189 }
4190 }
4191 #endif
4193 #ifdef INSN_SCHEDULING
4194 /* ?!? The schedulers do not keep REG_DEAD notes accurate after
4195 reload has completed. The schedulers need to be fixed. Until
4196 they are, we must not rely on the death notes here. */
4198 {
4201 }
4202 #endif
4204 /* The REG_DEAD note may have been omitted for a register
4205 which is both set and used by the insn. */
4208 {
4210 int dest_endregno
4217 {
4226 }
4227 }
4230 {
4234 /* Verify that the REG_NOTE is legitimate. */
4239 }
4242 }
4243 \f
4244 /* Delete insn INSN from the chain of insns and update label ref counts.
4245 May delete some following insns as a consequence; may even delete
4246 a label elsewhere and insns that follow it.
4248 Returns the first insn after INSN that was not deleted. */
4250 rtx
4253 {
4262 /* This insn is already deleted => return first following nondeleted. */
4269 /* Don't delete user-declared labels. Convert them to special NOTEs
4270 instead. */
4273 {
4278 }
4279 else
4280 /* Mark this insn as deleted. */
4283 /* If this is an unconditional jump, delete it from the jump chain. */
4287 /* If instruction is followed by a barrier,
4288 delete the barrier too. */
4291 {
4294 }
4296 /* Patch out INSN (and the barrier if any) */
4299 {
4301 {
4306 }
4309 {
4313 }
4317 }
4319 /* If deleting a jump, decrement the count of the label,
4320 and delete the label if it is now unused. */
4323 {
4327 {
4328 /* This can delete NEXT or PREV,
4329 either directly if NEXT is JUMP_LABEL (INSN),
4330 or indirectly through more levels of jumps. */
4333 /* I feel a little doubtful about this loop,
4334 but I see no clean and sure alternative way
4335 to find the first insn after INSN that is not now deleted.
4336 I hope this works. */
4340 }
4345 {
4346 /* If we're deleting the tablejump, delete the dispatch table.
4347 We may not be able to kill the label immediately preceeding
4348 just yet, as it might be referenced in code leading up to
4349 the tablejump. */
4351 }
4352 }
4354 /* Likewise if we're deleting a dispatch table. */
4359 {
4370 }
4375 /* If INSN was a label and a dispatch table follows it,
4376 delete the dispatch table. The tablejump must have gone already.
4377 It isn't useful to fall through into a table. */
4386 /* If INSN was a label, delete insns following it if now unreachable. */
4389 {
4395 {
4399 /* Keep going past other deleted labels to delete what follows. */
4402 else
4403 /* Note: if this deletes a jump, it can cause more
4404 deletion of unreachable code, after a different label.
4405 As long as the value from this recursive call is correct,
4406 this invocation functions correctly. */
4408 }
4409 }
4412 }
4414 /* Advance from INSN till reaching something not deleted
4415 then return that. May return INSN itself. */
4417 rtx
4419 rtx insn;
4420 {
4424 }
4425 \f
4426 /* Delete a range of insns from FROM to TO, inclusive.
4427 This is for the sake of peephole optimization, so assume
4428 that whatever these insns do will still be done by a new
4429 peephole insn that will replace them. */
4431 void
4434 {
4438 {
4443 {
4446 /* Patch this insn out of the chain. */
4447 /* We don't do this all at once, because we
4448 must preserve all NOTEs. */
4454 }
4459 }
4461 /* Note that if TO is an unconditional jump
4462 we *do not* delete the BARRIER that follows,
4463 since the peephole that replaces this sequence
4464 is also an unconditional jump in that case. */
4465 }
4466 \f
4467 /* We have determined that INSN is never reached, and are about to
4468 delete it. Print a warning if the user asked for one.
4470 To try to make this warning more useful, this should only be called
4471 once per basic block not reached, and it only warns when the basic
4472 block contains more than one line from the current function, and
4473 contains at least one operation. CSE and inlining can duplicate insns,
4474 so it's possible to get spurious warnings from this. */
4476 void
4478 rtx avoided_insn;
4479 {
4480 rtx insn;
4488 /* Scan forwards, looking at LINE_NUMBER notes, until
4489 we hit a LABEL or we run out of insns. */
4492 {
4497 {
4500 else
4503 }
4506 }
4511 }
4512 \f
4513 /* Invert the condition of the jump JUMP, and make it jump
4514 to label NLABEL instead of where it jumps now. */
4516 int
4519 {
4520 /* We have to either invert the condition and change the label or
4521 do neither. Either operation could fail. We first try to invert
4522 the jump. If that succeeds, we try changing the label. If that fails,
4523 we invert the jump back to what it was. */
4529 {
4531 {
4534 /* An inverted jump means that a probability taken becomes a
4535 probability not taken. Subtract the branch probability from the
4536 probability base to convert it back to a taken probability.
4537 (We don't flip the probability on a branch that's never taken. */
4540 }
4543 }
4546 /* This should just be putting it back the way it was. */
4550 }
4552 /* Invert the jump condition of rtx X contained in jump insn, INSN.
4554 Return 1 if we can do so, 0 if we cannot find a way to do so that
4555 matches a pattern. */
4557 int
4559 rtx x;
4560 rtx insn;
4561 {
4569 {
4573 /* We can do this in two ways: The preferable way, which can only
4574 be done if this is not an integer comparison, is to reverse
4575 the comparison code. Otherwise, swap the THEN-part and ELSE-part
4576 of the IF_THEN_ELSE. If we can't do either, fail. */
4589 }
4593 {
4598 {
4603 }
4604 }
4607 }
4608 \f
4609 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
4610 If the old jump target label is unused as a result,
4611 it and the code following it may be deleted.
4613 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
4614 RETURN insn.
4616 The return value will be 1 if the change was made, 0 if it wasn't (this
4617 can only occur for NLABEL == 0). */
4619 int
4622 {
4631 /* If this is an unconditional branch, delete it from the jump_chain of
4632 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
4633 have UID's in range and JUMP_CHAIN is valid). */
4636 {
4642 {
4645 }
4646 }
4656 }
4658 /* Delete the instruction JUMP from any jump chain it might be on. */
4660 static void
4662 rtx jump;
4663 {
4667 /* Handle unconditional jumps. */
4672 /* Handle return insns. */
4679 else
4680 {
4681 rtx insn;
4687 {
4690 }
4691 }
4692 }
4694 /* If NLABEL is nonzero, throughout the rtx at LOC,
4695 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
4696 zero, alter (RETURN) to (LABEL_REF NLABEL).
4698 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
4699 validity with validate_change. Convert (set (pc) (label_ref olabel))
4700 to (return).
4702 Return 0 if we found a change we would like to make but it is invalid.
4703 Otherwise, return 1. */
4705 int
4709 rtx insn;
4710 {
4717 {
4719 {
4722 else
4725 }
4726 }
4728 {
4733 }
4742 {
4747 {
4752 }
4753 }
4756 }
4757 \f
4758 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
4760 If the old jump target label (before the dispatch table) becomes unused,
4761 it and the dispatch table may be deleted. In that case, find the insn
4762 before the jump references that label and delete it and logical successors
4763 too. */
4765 static void
4768 {
4771 /* Add this jump to the jump_chain of NLABEL. */
4774 {
4777 }
4785 {
4788 }
4789 }
4791 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
4792 If we found one, delete it and then delete this insn if DELETE_THIS is
4793 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
4795 static int
4799 {
4801 rtx link;
4805 {
4807 {
4810 }
4811 else
4813 }
4817 {
4819 {
4822 }
4823 else
4825 }
4828 }
4829 \f
4830 /* Like rtx_equal_p except that it considers two REGs as equal
4831 if they renumber to the same value and considers two commutative
4832 operations to be the same if the order of the operands has been
4833 reversed.
4835 ??? Addition is not commutative on the PA due to the weird implicit
4836 space register selection rules for memory addresses. Therefore, we
4837 don't consider a + b == b + a.
4839 We could/should make this test a little tighter. Possibly only
4840 disabling it on the PA via some backend macro or only disabling this
4841 case when the PLUS is inside a MEM. */
4843 int
4846 {
4857 {
4864 /* If we haven't done any renumbering, don't
4865 make any assumptions. */
4870 {
4875 {
4878 }
4879 }
4881 else
4882 {
4886 }
4889 {
4894 {
4897 }
4898 }
4900 else
4901 {
4905 }
4908 }
4910 /* Now we have disposed of all the cases
4911 in which different rtx codes can match. */
4916 {
4927 /* We can't assume nonlocal labels have their following insns yet. */
4931 /* Two label-refs are equivalent if they point at labels
4932 in the same position in the instruction stream. */
4940 /* If we didn't match EQ equality above, they aren't the same. */
4945 }
4947 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
4952 /* For commutative operations, the RTX match if the operand match in any
4953 order. Also handle the simple binary and unary cases without a loop.
4955 ??? Don't consider PLUS a commutative operator; see comments above. */
4968 /* Compare the elements. If any pair of corresponding elements
4969 fail to match, return 0 for the whole things. */
4973 {
4976 {
5000 /* fall through. */
5014 }
5015 }
5017 }
5018 \f
5019 /* If X is a hard register or equivalent to one or a subregister of one,
5020 return the hard register number. If X is a pseudo register that was not
5021 assigned a hard register, return the pseudo register number. Otherwise,
5022 return -1. Any rtx is valid for X. */
5024 int
5026 rtx x;
5027 {
5029 {
5033 }
5035 {
5039 }
5041 }
5042 \f
5043 /* Optimize code of the form:
5045 for (x = a[i]; x; ...)
5046 ...
5047 for (x = a[i]; x; ...)
5048 ...
5049 foo:
5051 Loop optimize will change the above code into
5053 if (x = a[i])
5054 for (;;)
5055 { ...; if (! (x = ...)) break; }
5056 if (x = a[i])
5057 for (;;)
5058 { ...; if (! (x = ...)) break; }
5059 foo:
5061 In general, if the first test fails, the program can branch
5062 directly to `foo' and skip the second try which is doomed to fail.
5063 We run this after loop optimization and before flow analysis. */
5065 /* When comparing the insn patterns, we track the fact that different
5066 pseudo-register numbers may have been used in each computation.
5067 The following array stores an equivalence -- same_regs[I] == J means
5068 that pseudo register I was used in the first set of tests in a context
5069 where J was used in the second set. We also count the number of such
5070 pending equivalences. If nonzero, the expressions really aren't the
5071 same. */
5077 /* Track any registers modified between the target of the first jump and
5078 the second jump. They never compare equal. */
5082 /* Record if memory was modified. */
5086 /* Called via note_stores on each insn between the target of the first
5087 branch and the second branch. It marks any changed registers. */
5089 static void
5091 rtx dest;
5092 rtx x ATTRIBUTE_UNUSED;
5093 {
5108 else
5111 }
5113 /* F is the first insn in the chain of insns. */
5115 void
5117 rtx f;
5120 {
5121 /* Basic algorithm is to find a conditional branch,
5122 the label it may branch to, and the branch after
5123 that label. If the two branches test the same condition,
5124 walk back from both branch paths until the insn patterns
5125 differ, or code labels are hit. If we make it back to
5126 the target of the first branch, then we know that the first branch
5127 will either always succeed or always fail depending on the relative
5128 senses of the two branches. So adjust the first branch accordingly
5129 in this case. */
5138 /* Allocate register tables and quick-reset table. */
5146 {
5150 {
5151 /* Get to a candidate branch insn. */
5166 /* Look for a branch after the target. Record any registers and
5167 memory modified between the target and the branch. Stop when we
5168 get to a label since we can't know what was changed there. */
5170 {
5175 {
5176 /* If this is an unconditional jump and is the only use of
5177 its target label, we can follow it. */
5181 {
5184 }
5185 else
5187 }
5193 {
5202 }
5205 }
5207 /* Check the next candidate branch insn from the label
5208 of the first. */
5216 /* Get the comparison codes and operands, reversing the
5217 codes if appropriate. If we don't have comparison codes,
5218 we can't do anything. */
5231 /* If they test the same things and knowing that B1 branches
5232 tells us whether or not B2 branches, check if we
5233 can thread the branch. */
5240 b1))))
5241 {
5246 {
5248 {
5249 /* We have reached the target of the first branch.
5250 If there are no pending register equivalents,
5251 we know that this branch will either always
5252 succeed (if the senses of the two branches are
5253 the same) or always fail (if not). */
5254 rtx new_label;
5261 else
5265 {
5271 {
5272 /* Don't thread to the loop label. If a loop
5273 label is reused, loop optimization will
5274 be disabled for that loop. */
5277 }
5279 }
5281 }
5283 /* If either of these is not a normal insn (it might be
5284 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
5285 have already been skipped above.) Similarly, fail
5286 if the insns are different. */
5295 }
5296 }
5297 }
5298 }
5299 }
5300 \f
5301 /* This is like RTX_EQUAL_P except that it knows about our handling of
5302 possibly equivalent registers and knows to consider volatile and
5303 modified objects as not equal.
5305 YINSN is the insn containing Y. */
5307 int
5310 rtx yinsn;
5311 {
5318 /* Rtx's of different codes cannot be equal. */
5322 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
5323 (REG:SI x) and (REG:HI x) are NOT equivalent. */
5328 /* For floating-point, consider everything unequal. This is a bit
5329 pessimistic, but this pass would only rarely do anything for FP
5330 anyway. */
5335 /* For commutative operations, the RTX match if the operand match in any
5336 order. Also handle the simple binary and unary cases without a loop. */
5348 /* Handle special-cases first. */
5350 {
5355 /* If neither is user variable or hard register, check for possible
5356 equivalence. */
5363 {
5365 num_same_regs++;
5367 /* If this is the first time we are seeing a register on the `Y'
5368 side, see if it is the last use. If not, we can't thread the
5369 jump, so mark it as not equivalent. */
5374 }
5375 else
5381 /* If memory modified or either volatile, not equivalent.
5382 Else, check address. */
5395 /* Cancel a pending `same_regs' if setting equivalenced registers.
5396 Then process source. */
5399 {
5401 {
5403 num_same_regs--;
5404 }
5407 }
5408 else
5422 }
5429 {
5431 {
5445 /* Two vectors must have the same length. */
5449 /* And the corresponding elements must match. */
5468 /* These are just backpointers, so they don't matter. */
5475 /* It is believed that rtx's at this level will never
5476 contain anything but integers and other rtx's,
5477 except for within LABEL_REFs and SYMBOL_REFs. */
5480 }
5481 }
5483 }
5484 \f
5486 #if !defined(HAVE_cc0) && !defined(HAVE_conditional_arithmetic)
5487 /* Return the insn that NEW can be safely inserted in front of starting at
5488 the jump insn INSN. Return 0 if it is not safe to do this jump
5489 optimization. Note that NEW must contain a single set. */
5491 static rtx
5493 rtx insn;
5495 {
5497 rtx prev;
5499 /* If NEW does not clobber, it is safe to insert NEW before INSN. */
5506 insn))
5512 /* There is a good chance that the previous insn PREV sets the thing
5513 being clobbered (often the CC in a hard reg). If PREV does not
5514 use what NEW sets, we can insert NEW before PREV. */
5520 insn)
5522 prev))
5526 }