| blob | 1f740fd801281c253e1a7b25a234975f8ab467cb |
1 /* Optimize jump instructions, for GNU compiler.
2 Copyright (C) 1987, 88, 89, 91-99, 2000 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. */
212 /* Keep track of labels used from static data;
213 they cannot ever be deleted. */
220 /* Keep track of labels used for marking handlers for exception
221 regions; they cannot usually be deleted. */
226 /* Quit now if we just wanted to rebuild the JUMP_LABEL and REG_LABEL
227 notes and recompute LABEL_NUSES. */
235 #ifdef HAVE_return
237 {
238 /* If we fall through to the epilogue, see if we can insert a RETURN insn
239 in front of it. If the machine allows it at this point (we might be
240 after reload for a leaf routine), it will improve optimization for it
241 to be there. */
247 {
250 }
251 }
252 #endif
257 /* If we haven't yet gotten to reload and we have just run regscan,
258 delete any insn that sets a register that isn't used elsewhere.
259 This helps some of the optimizations below by having less insns
260 being jumped around. */
264 {
272 /* We use regno_last_note_uid so as not to delete the setting
273 of a reg that's used in notes. A subsequent optimization
274 might arrange to use that reg for real. */
278 /* An ADDRESSOF expression can turn into a use of the internal arg
279 pointer, so do not delete the initialization of the internal
280 arg pointer yet. If it is truly dead, flow will delete the
281 initializing insn. */
284 }
286 /* Now iterate optimizing jumps until nothing changes over one pass. */
290 {
294 {
295 rtx reallabelprev;
297 rtx nlabel;
303 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
304 jump. Try to optimize by duplicating the loop exit test if so.
305 This is only safe immediately after regscan, because it uses
306 the values of regno_first_uid and regno_last_uid. */
311 {
314 {
318 }
319 }
328 /* Tension the labels in dispatch tables. */
335 /* See if this jump goes to another jump and redirect if so. */
343 /* If a dispatch table always goes to the same place,
344 get rid of it and replace the insn that uses it. */
348 {
354 rtx set;
365 /* Don't mess with a casesi insn.
366 XXX according to the comment before computed_jump_p(),
367 all casesi insns should be a parallel of the jump
368 and a USE of a LABEL_REF. */
372 {
376 }
377 }
379 /* If a jump references the end of the function, try to turn
380 it into a RETURN insn, possibly a conditional one. */
389 /* Detect jump to following insn. */
391 {
396 }
398 /* Detect a conditional jump going to the same place
399 as an immediately following unconditional jump. */
405 {
406 /* Don't mess up test coverage analysis. */
414 {
418 }
419 }
421 /* Detect a conditional jump jumping over an unconditional jump. */
424 && ! this_is_simplejump
430 {
431 /* When we invert the unconditional jump, we will be
432 decrementing the usage count of its old label.
433 Make sure that we don't delete it now because that
434 might cause the following code to be deleted. */
442 {
443 /* It is very likely that if there are USE insns before
444 this jump, they hold REG_DEAD notes. These REG_DEAD
445 notes are no longer valid due to this optimization,
446 and will cause the life-analysis that following passes
447 (notably delayed-branch scheduling) to think that
448 these registers are dead when they are not.
450 To prevent this trouble, we just remove the USE insns
451 from the insn chain. */
455 {
459 }
463 }
465 /* We can now safely delete the label if it is unreferenced
466 since the delete_insn above has deleted the BARRIER. */
471 }
473 /* If we have an unconditional jump preceded by a USE, try to put
474 the USE before the target and jump there. This simplifies many
475 of the optimizations below since we don't have to worry about
476 dealing with these USE insns. We only do this if the label
477 being branch to already has the identical USE or if code
478 never falls through to that label. */
488 /* Don't do this optimization if we have a loop containing
489 only the USE instruction, and the loop start label has
490 a usage count of 1. This is because we will redo this
491 optimization everytime through the outer loop, and jump
492 opt will never exit. */
496 {
498 {
501 }
508 }
510 /* Simplify if (...) x = a; else x = b; by converting it
511 to x = b; if (...) x = a;
512 if B is sufficiently simple, the test doesn't involve X,
513 and nothing in the test modifies B or X.
515 If we have small register classes, we also can't do this if X
516 is a hard register.
518 If the "x = b;" insn has any REG_NOTES, we don't do this because
519 of the possibility that we are running after CSE and there is a
520 REG_EQUAL note that is only valid if the branch has already been
521 taken. If we move the insn with the REG_EQUAL note, we may
522 fold the comparison to always be false in a later CSE pass.
523 (We could also delete the REG_NOTES when moving the insn, but it
524 seems simpler to not move it.) An exception is that we can move
525 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
526 value is the same as "b".
528 INSN is the branch over the `else' part.
530 We set:
532 TEMP to the jump insn preceding "x = a;"
533 TEMP1 to X
534 TEMP2 to the insn that sets "x = b;"
535 TEMP3 to the insn that sets "x = a;"
536 TEMP4 to the set of "x = b"; */
543 && (! SMALL_REGISTER_CLASSES
559 /* TEMP must skip over the "x = a;" insn */
562 /* There must be no other entries to the "x = b;" insn. */
564 /* INSN must either branch to the insn after TEMP2 or the insn
565 after TEMP2 must branch to the same place as INSN. */
570 {
571 /* The test expression, X, may be a complicated test with
572 multiple branches. See if we can find all the uses of
573 the label that TEMP branches to without hitting a CALL_INSN
574 or a jump to somewhere else. */
577 rtx p;
578 #ifdef HAVE_cc0
579 rtx q;
580 #endif
582 /* Set P to the first jump insn that goes around "x = a;". */
584 {
586 {
589 {
590 nuses--;
593 }
594 else
596 }
599 }
601 #ifdef HAVE_cc0
602 /* We cannot insert anything between a set of cc and its use
603 so if P uses cc0, we must back up to the previous insn. */
608 #endif
613 /* If we found all the uses and there was no data conflict, we
614 can move the assignment unless we can branch into the middle
615 from somewhere. */
622 /* Verify that registers used by the jump are not clobbered
623 by the instruction being moved. */
627 {
631 /* Set NEXT to an insn that we know won't go away. */
634 /* Delete the jump around the set. Note that we must do
635 this before we redirect the test jumps so that it won't
636 delete the code immediately following the assignment
637 we moved (which might be a jump). */
641 /* We either have two consecutive labels or a jump to
642 a jump, so adjust all the JUMP_INSNs to branch to where
643 INSN branches to. */
651 }
652 }
654 /* Simplify if (...) { x = a; goto l; } x = b; by converting it
655 to x = a; if (...) goto l; x = b;
656 if A is sufficiently simple, the test doesn't involve X,
657 and nothing in the test modifies A or X.
659 If we have small register classes, we also can't do this if X
660 is a hard register.
662 If the "x = a;" insn has any REG_NOTES, we don't do this because
663 of the possibility that we are running after CSE and there is a
664 REG_EQUAL note that is only valid if the branch has already been
665 taken. If we move the insn with the REG_EQUAL note, we may
666 fold the comparison to always be false in a later CSE pass.
667 (We could also delete the REG_NOTES when moving the insn, but it
668 seems simpler to not move it.) An exception is that we can move
669 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
670 value is the same as "a".
672 INSN is the goto.
674 We set:
676 TEMP to the jump insn preceding "x = a;"
677 TEMP1 to X
678 TEMP2 to the insn that sets "x = b;"
679 TEMP3 to the insn that sets "x = a;"
680 TEMP4 to the set of "x = a"; */
687 && (! SMALL_REGISTER_CLASSES
703 /* TEMP must skip over the "x = a;" insn */
706 {
710 #ifdef HAVE_cc0
711 /* We cannot insert anything between a set of cc and its use. */
715 #endif
725 /* Verify that registers used by the jump are not clobbered
726 by the instruction being moved. */
731 {
736 /* Set NEXT to an insn that we know won't go away. */
739 }
744 }
746 #if !defined(HAVE_cc0) && !defined(HAVE_conditional_arithmetic)
748 /* If we have if (...) x = exp; and branches are expensive,
749 EXP is a single insn, does not have any side effects, cannot
750 trap, and is not too costly, convert this to
751 t = exp; if (...) x = t;
753 Don't do this when we have CC0 because it is unlikely to help
754 and we'd need to worry about where to place the new insn and
755 the potential for conflicts. We also can't do this when we have
756 notes on the insn for the same reason as above.
758 If we have conditional arithmetic, this will make this
759 harder to optimize later and isn't needed, so don't do it
760 in that case either.
762 We set:
764 TEMP to the "x = exp;" insn.
765 TEMP1 to the single set in the "x = exp;" insn.
766 TEMP2 to "x". */
780 && (! SMALL_REGISTER_CLASSES
788 {
793 {
801 {
804 }
805 }
806 }
808 /* Similarly, if it takes two insns to compute EXP but they
809 have the same destination. Here TEMP3 will be the second
810 insn and TEMP4 the SET from that insn. */
828 && (! SMALL_REGISTER_CLASSES
838 {
844 {
845 /* Use the earliest of temp5 and temp6. */
851 emit_insn_after_with_line_notes
859 {
862 }
863 }
864 }
866 /* Finally, handle the case where two insns are used to
867 compute EXP but a temporary register is used. Here we must
868 ensure that the temporary register is not used anywhere else. */
871 && after_regscan
899 && (! SMALL_REGISTER_CLASSES
905 {
911 {
912 /* Use the earliest of temp5 and temp6. */
925 {
928 }
929 }
930 }
933 #ifdef HAVE_conditional_arithmetic
934 /* ??? This is disabled in genconfig, as this simple-minded
935 transformation can incredibly lengthen register lifetimes.
937 Consider this example from cexp.c's yyparse:
939 234 (set (pc)
940 (if_then_else (ne (reg:DI 149) (const_int 0 [0x0]))
941 (label_ref 248) (pc)))
942 237 (set (reg/i:DI 0 $0) (const_int 1 [0x1]))
943 239 (set (pc) (label_ref 2382))
944 248 (code_label ("yybackup"))
946 This will be transformed to:
948 237 (set (reg/i:DI 0 $0)
949 (if_then_else:DI (eq (reg:DI 149) (const_int 0 [0x0]))
950 (const_int 1 [0x1]) (reg/i:DI 0 $0)))
951 239 (set (pc)
952 (if_then_else (eq (reg:DI 149) (const_int 0 [0x0]))
953 (label_ref 2382) (pc)))
955 which, from this narrow viewpoint looks fine. Except that
956 between this and 3 other ocurrences of the same pattern, $0
957 is now live for basically the entire function, and we'll
958 get an abort in caller_save.
960 Any replacement for this code should recall that a set of
961 a register that is not live need not, and indeed should not,
962 be conditionalized. Either that, or delay the transformation
963 until after register allocation. */
965 /* See if this is a conditional jump around a small number of
966 instructions that we can conditionalize. Don't do this before
967 the initial CSE pass or after reload.
969 We reject any insns that have side effects or may trap.
970 Strictly speaking, this is not needed since the machine may
971 support conditionalizing these too, but we won't deal with that
972 now. Specifically, this means that we can't conditionalize a
973 CALL_INSN, which some machines, such as the ARC, can do, but
974 this is a very minor optimization. */
979 insn))
980 {
991 /* Scan forward BRANCH_COST real insns looking for the JUMP_LABEL
992 of this insn. We see if we think we can conditionalize the
993 insns we pass. For now, we only deal with insns that have
994 one SET. We stop after an insn that modifies anything in
995 OURCOND, if we have too many insns, or if we have an insn
996 with a side effect or that may trip. Note that we will
997 be modifying any unconditional jumps we encounter to be
998 conditional; this will have the effect of also doing this
999 optimization on the "else" the next time around. */
1004 {
1005 /* Ignore everything but an active insn. */
1011 /* If this was an unconditional jump, record it since we'll
1012 need to remove the BARRIER if we succeed. We can only
1013 have one such jump since there must be a label after
1014 the BARRIER and it's either ours, in which case it's the
1015 only one or some other, in which case we'd fail.
1016 Likewise if it's a CALL_INSN followed by a BARRIER. */
1022 {
1025 else
1026 changed_jump
1028 }
1030 /* See if we are allowed another insn and if this insn
1031 if one we think we may be able to handle. */
1033 || last_insn
1041 gen_rtx_IF_THEN_ELSE
1046 else
1047 {
1048 /* This is a CALL_INSN that doesn't have a SET. */
1055 gen_rtx_IF_THEN_ELSE
1059 }
1064 }
1066 /* If we've reached our jump label, haven't failed, and all
1067 the changes above are valid, we can delete this jump
1068 insn. Also remove a BARRIER after any jump that used
1069 to be unconditional and remove any REG_EQUAL or REG_EQUIV
1070 that might have previously been present on insns we
1071 made conditional. */
1074 {
1085 {
1087 {
1090 }
1093 }
1098 }
1099 else
1100 {
1103 }
1104 }
1105 #endif
1106 /* If branches are expensive, convert
1107 if (foo) bar++; to bar += (foo != 0);
1108 and similarly for "bar--;"
1110 INSN is the conditional branch around the arithmetic. We set:
1112 TEMP is the arithmetic insn.
1113 TEMP1 is the SET doing the arithmetic.
1114 TEMP2 is the operand being incremented or decremented.
1115 TEMP3 to the condition being tested.
1116 TEMP4 to the earliest insn used to find the condition. */
1119 #ifdef HAVE_incscc
1120 || HAVE_incscc
1121 #endif
1122 #ifdef HAVE_decscc
1123 || HAVE_decscc
1124 #endif
1125 )
1126 && ! reload_completed
1138 /* INSN must either branch to the insn after TEMP or the insn
1139 after TEMP must branch to the same place as INSN. */
1145 /* We must be comparing objects whose modes imply the size.
1146 We could handle BLKmode if (1) emit_store_flag could
1147 and (2) we could find the size reliably. */
1150 {
1156 /* It must be the case that TEMP2 is not modified in the range
1157 [TEMP4, INSN). The one exception we make is if the insn
1158 before INSN sets TEMP2 to something which is also unchanged
1159 in that range. In that case, we can move the initialization
1160 into our sequence. */
1170 {
1174 }
1180 VOIDmode,
1184 /* If we can do the store-flag, do the addition or
1185 subtraction. */
1194 {
1195 /* Put the result back in temp2 in case it isn't already.
1196 Then replace the jump, possible a CC0-setting insn in
1197 front of the jump, and TEMP, with the sequence we have
1198 made. */
1213 #ifdef HAVE_cc0
1215 #endif
1219 {
1222 }
1226 }
1227 else
1229 }
1231 /* Try to use a conditional move (if the target has them), or a
1232 store-flag insn. If the target has conditional arithmetic as
1233 well as conditional move, the above code will have done something.
1234 Note that we prefer the above code since it is more general: the
1235 code below can make changes that require work to undo.
1237 The general case here is:
1239 1) x = a; if (...) x = b; and
1240 2) if (...) x = b;
1242 If the jump would be faster, the machine should not have defined
1243 the movcc or scc insns!. These cases are often made by the
1244 previous optimization.
1246 The second case is treated as x = x; if (...) x = b;.
1248 INSN here is the jump around the store. We set:
1250 TEMP to the "x op= b;" insn.
1251 TEMP1 to X.
1252 TEMP2 to B.
1253 TEMP3 to A (X in the second case).
1254 TEMP4 to the condition being tested.
1255 TEMP5 to the earliest insn used to find the condition.
1256 TEMP6 to the SET of TEMP. */
1259 ! reload_completed
1260 #ifdef HAVE_conditional_arithmetic
1261 /* Defer this until after CSE so the above code gets the
1262 first crack at it. */
1263 && cse_not_expected
1264 #endif
1266 /* Set TEMP to the "x = b;" insn. */
1271 && (! SMALL_REGISTER_CLASSES
1275 /* Allow either form, but prefer the former if both apply.
1276 There is no point in using the old value of TEMP1 if
1277 it is a register, since cse will alias them. It can
1278 lose if the old value were a hard register since CSE
1279 won't replace hard registers. Avoid using TEMP3 if
1280 small register classes and it is a hard register. */
1284 /* Make the latter case look like x = x; if (...) x = b; */
1286 /* INSN must either branch to the insn after TEMP or the insn
1287 after TEMP must branch to the same place as INSN. */
1293 /* We must be comparing objects whose modes imply the size.
1294 We could handle BLKmode if (1) emit_store_flag could
1295 and (2) we could find the size reliably. */
1297 /* Even if branches are cheap, the store_flag optimization
1298 can win when the operation to be performed can be
1299 expressed directly. */
1300 #ifdef HAVE_cc0
1301 /* If the previous insn sets CC0 and something else, we can't
1302 do this since we are going to delete that insn. */
1309 #endif
1310 )
1311 {
1312 #ifdef HAVE_conditional_move
1313 /* First try a conditional move. */
1314 {
1320 /* Copy the compared variables into cond0 and cond1, so that
1321 any side effects performed in or after the old comparison,
1322 will not affect our compare which will come later. */
1323 /* ??? Is it possible to just use the comparison in the jump
1324 insn? After all, we're going to delete it. We'd have
1325 to modify emit_conditional_move to take a comparison rtx
1326 instead or write a new function. */
1328 /* We want the target to be able to simplify comparisons with
1329 zero (and maybe other constants as well), so don't create
1330 pseudos for them. There's no need to either. */
1334 else
1337 /* Careful about copying these values -- an IOR or what may
1338 need to do other things, like clobber flags. */
1339 /* ??? Assume for the moment that AVAL is ok. */
1344 /* We're dealing with a single_set insn with no side effects
1345 on SET_SRC. We do need to be reasonably certain that if
1346 we need to force BVAL into a register that we won't
1347 clobber the flags -- general_operand should suffice. */
1350 else
1351 {
1357 }
1366 {
1370 /* Save the conditional move sequence but don't emit it
1371 yet. On some machines, like the alpha, it is possible
1372 that temp5 == insn, so next generate the sequence that
1373 saves the compared values and then emit both
1374 sequences ensuring seq1 occurs before seq2. */
1378 /* "Now that we can't fail..." Famous last words.
1379 Generate the copy insns that preserve the compared
1380 values. */
1388 /* Validate the sequence -- this may be some weird
1389 bit-extract-and-test instruction for which there
1390 exists no complimentary bit-extract insn. */
1394 {
1397 }
1400 {
1403 /* Insert conditional move after insn, to be sure
1404 that the jump and a possible compare won't be
1405 separated. */
1408 /* ??? We can also delete the insn that sets X to A.
1409 Flow will do it too though. */
1415 {
1417 old_max_reg);
1419 }
1423 }
1424 }
1425 else
1427 }
1428 #endif
1430 /* That didn't work, try a store-flag insn.
1432 We further divide the cases into:
1434 1) x = a; if (...) x = b; and either A or B is zero,
1435 2) if (...) x = 0; and jumps are expensive,
1436 3) x = a; if (...) x = b; and A and B are constants where all
1437 the set bits in A are also set in B and jumps are expensive,
1438 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
1439 more expensive, and
1440 5) if (...) x = b; if jumps are even more expensive. */
1443 /* We will be passing this as operand into expand_and. No
1444 good if it's not valid as an operand. */
1447 /* Make the latter case look like
1448 x = x; if (...) x = 0; */
1453 /* If B is zero, OK; if A is zero, can only do (1) if we
1454 can reverse the condition. See if (3) applies possibly
1455 by reversing the condition. Prefer reversing to (4) when
1456 branches are very expensive. */
1460 /* Check that the mask is a power of two,
1461 so that it can probably be generated
1462 with a shift. */
1479 insn)))))
1481 )
1482 {
1486 rtx target;
1488 /* If necessary, reverse the condition. */
1491 else
1494 /* If CVAL is non-zero, normalize to -1. Otherwise, if UVAL
1495 is the constant 1, it is best to just compute the result
1496 directly. If UVAL is constant and STORE_FLAG_VALUE
1497 includes all of its bits, it is best to compute the flag
1498 value unnormalized and `and' it with UVAL. Otherwise,
1499 normalize to -1 and `and' with UVAL. */
1506 /* We will be putting the store-flag insn immediately in
1507 front of the comparison that was originally being done,
1508 so we know all the variables in TEMP4 will be valid.
1509 However, this might be in front of the assignment of
1510 A to VAR. If it is, it would clobber the store-flag
1511 we will be emitting.
1513 Therefore, emit into a temporary which will be copied to
1514 VAR immediately after TEMP. */
1519 VOIDmode,
1522 normalizep);
1524 {
1525 rtx seq;
1531 /* Put the store-flag insns in front of the first insn
1532 used to compute the condition to ensure that we
1533 use the same values of them as the current
1534 comparison. However, the remainder of the insns we
1535 generate will be placed directly in front of the
1536 jump insn, in case any of the pseudos we use
1537 are modified earlier. */
1543 /* Both CVAL and UVAL are non-zero. */
1545 {
1553 else
1554 {
1560 }
1562 /* If we usually make new pseudos, do so here. This
1563 turns out to help machines that have conditional
1564 move insns. */
1565 /* ??? Conditional moves have already been handled.
1566 This may be obsolete. */
1574 }
1576 {
1577 /* We know that either CVAL or UVAL is zero. If
1578 UVAL is zero, negate TARGET and `and' with CVAL.
1579 Otherwise, `and' with UVAL. */
1581 {
1585 }
1591 }
1596 #ifdef HAVE_cc0
1597 /* If INSN uses CC0, we must not separate it from the
1598 insn that sets cc0. */
1601 #endif
1609 {
1612 }
1616 }
1617 else
1619 }
1620 }
1623 /* Simplify if (...) x = 1; else {...} if (x) ...
1624 We recognize this case scanning backwards as well.
1626 TEMP is the assignment to x;
1627 TEMP1 is the label at the head of the second if. */
1628 /* ?? This should call get_condition to find the values being
1629 compared, instead of looking for a COMPARE insn when HAVE_cc0
1630 is not defined. This would allow it to work on the m88k. */
1631 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1632 is not defined and the condition is tested by a separate compare
1633 insn. This is because the code below assumes that the result
1634 of the compare dies in the following branch.
1636 Not only that, but there might be other insns between the
1637 compare and branch whose results are live. Those insns need
1638 to be executed.
1640 A way to fix this is to move the insns at JUMP_LABEL (insn)
1641 to before INSN. If we are running before flow, they will
1642 be deleted if they aren't needed. But this doesn't work
1643 well after flow.
1645 This is really a special-case of jump threading, anyway. The
1646 right thing to do is to replace this and jump threading with
1647 much simpler code in cse.
1649 This code has been turned off in the non-cc0 case in the
1650 meantime. */
1652 #ifdef HAVE_cc0
1654 /* Safe to skip USE and CLOBBER insns here
1655 since they will not be deleted. */
1663 /* If we find that the next value tested is `x'
1664 (TEMP1 is the insn where this happens), win. */
1667 #ifdef HAVE_cc0
1668 /* Does temp1 `tst' the value of x? */
1672 #else
1673 /* Does temp1 compare the value of x against zero? */
1680 #endif
1682 {
1683 /* Get the if_then_else from the condjump. */
1686 {
1689 rtx cond
1692 rtx ultimate;
1698 else
1708 }
1709 }
1710 #endif
1712 #if 0
1713 /* @@ This needs a bit of work before it will be right.
1715 Any type of comparison can be accepted for the first and
1716 second compare. When rewriting the first jump, we must
1717 compute the what conditions can reach label3, and use the
1718 appropriate code. We can not simply reverse/swap the code
1719 of the first jump. In some cases, the second jump must be
1720 rewritten also.
1722 For example,
1723 < == converts to > ==
1724 < != converts to == >
1725 etc.
1727 If the code is written to only accept an '==' test for the second
1728 compare, then all that needs to be done is to swap the condition
1729 of the first branch.
1731 It is questionable whether we want this optimization anyways,
1732 since if the user wrote code like this because he/she knew that
1733 the jump to label1 is taken most of the time, then rewriting
1734 this gives slower code. */
1735 /* @@ This should call get_condition to find the values being
1736 compared, instead of looking for a COMPARE insn when HAVE_cc0
1737 is not defined. This would allow it to work on the m88k. */
1738 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1739 is not defined and the condition is tested by a separate compare
1740 insn. This is because the code below assumes that the result
1741 of the compare dies in the following branch. */
1743 /* Simplify test a ~= b
1744 condjump label1;
1745 test a == b
1746 condjump label2;
1747 jump label3;
1748 label1:
1750 rewriting as
1751 test a ~~= b
1752 condjump label3
1753 test a == b
1754 condjump label2
1755 label1:
1757 where ~= is an inequality, e.g. >, and ~~= is the swapped
1758 inequality, e.g. <.
1760 We recognize this case scanning backwards.
1762 TEMP is the conditional jump to `label2';
1763 TEMP1 is the test for `a == b';
1764 TEMP2 is the conditional jump to `label1';
1765 TEMP3 is the test for `a ~= b'. */
1774 #ifdef HAVE_cc0
1776 #else
1780 #endif
1794 {
1799 {
1802 }
1806 }
1807 #endif
1808 /* Simplify if (...) {... x = 1;} if (x) ...
1810 We recognize this case backwards.
1812 TEMP is the test of `x';
1813 TEMP1 is the assignment to `x' at the end of the
1814 previous statement. */
1815 /* @@ This should call get_condition to find the values being
1816 compared, instead of looking for a COMPARE insn when HAVE_cc0
1817 is not defined. This would allow it to work on the m88k. */
1818 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1819 is not defined and the condition is tested by a separate compare
1820 insn. This is because the code below assumes that the result
1821 of the compare dies in the following branch. */
1823 /* ??? This has to be turned off. The problem is that the
1824 unconditional jump might indirectly end up branching to the
1825 label between TEMP1 and TEMP. We can't detect this, in general,
1826 since it may become a jump to there after further optimizations.
1827 If that jump is done, it will be deleted, so we will retry
1828 this optimization in the next pass, thus an infinite loop.
1830 The present code prevents this by putting the jump after the
1831 label, but this is not logically correct. */
1832 #if 0
1834 /* Safe to skip USE and CLOBBER insns here
1835 since they will not be deleted. */
1840 #ifdef HAVE_cc0
1843 #else
1844 /* Temp must be a compare insn, we can not accept a register
1845 to register move here, since it may not be simply a
1846 tst insn. */
1852 #endif
1853 /* May skip USE or CLOBBER insns here
1854 for checking for opportunity, since we
1855 take care of them later. */
1859 #ifdef HAVE_cc0
1861 #else
1864 #endif
1866 /* If this isn't true, cse will do the job. */
1868 {
1869 /* Get the if_then_else from the condjump. */
1874 {
1876 rtx last_insn;
1877 rtx ultimate;
1878 rtx p;
1880 /* Get the place that condjump will jump to
1881 if it is reached from here. */
1885 else
1887 /* Get it as a CODE_LABEL. */
1890 else
1891 /* Get the label out of the LABEL_REF. */
1894 /* Insert the jump immediately before TEMP, specifically
1895 after the label that is between TEMP1 and TEMP. */
1898 /* If we would be branching to the next insn, the jump
1899 would immediately be deleted and the re-inserted in
1900 a subsequent pass over the code. So don't do anything
1901 in that case. */
1904 {
1907 last_insn);
1912 {
1916 }
1919 }
1920 }
1921 }
1922 #endif
1923 #ifdef HAVE_trap
1924 /* Detect a conditional jump jumping over an unconditional trap. */
1935 {
1941 {
1947 }
1948 }
1949 /* Detect a jump jumping to an unconditional trap. */
1954 && (this_is_simplejump
1956 {
1961 {
1963 /* Replace an unconditional jump to a trap with a trap. */
1965 {
1970 }
1975 {
1980 }
1981 }
1982 /* If the trap condition and jump condition are mutually
1983 exclusive, redirect the jump to the following insn. */
1985 && ! this_is_simplejump
1990 {
1993 }
1994 }
1995 #endif
1996 else
1997 {
1998 /* Now that the jump has been tensioned,
1999 try cross jumping: check for identical code
2000 before the jump and before its target label. */
2002 /* First, cross jumping of conditional jumps: */
2005 {
2009 /* A conditional jump may be crossjumped
2010 only if the place it jumps to follows
2011 an opposing jump that comes back here. */
2014 /* We have no opposing jump;
2015 cannot cross jump this insn. */
2019 /* TARGET is nonzero if it is ok to cross jump
2020 to code before TARGET. If so, see if matches. */
2026 {
2028 /* Make the old conditional jump
2029 into an unconditional one. */
2034 /* Add to jump_chain unless this is a new label
2035 whose UID is too large. */
2037 {
2041 }
2044 }
2045 }
2047 /* Cross jumping of unconditional jumps:
2048 a few differences. */
2051 {
2053 rtx target;
2057 /* TARGET is nonzero if it is ok to cross jump
2058 to code before TARGET. If so, see if matches. */
2062 /* If cannot cross jump to code before the label,
2063 see if we can cross jump to another jump to
2064 the same label. */
2065 /* Try each other jump to this label. */
2072 /* Ignore TARGET if it's deleted. */
2078 {
2082 }
2083 }
2085 /* This code was dead in the previous jump.c! */
2087 {
2088 /* Return insns all "jump to the same place"
2089 so we can cross-jump between any two of them. */
2095 /* If cannot cross jump to code before the label,
2096 see if we can cross jump to another jump to
2097 the same label. */
2098 /* Try each other jump to this label. */
2109 {
2113 }
2114 }
2115 }
2116 }
2119 }
2121 /* Delete extraneous line number notes.
2122 Note that two consecutive notes for different lines are not really
2123 extraneous. There should be some indication where that line belonged,
2124 even if it became empty. */
2126 {
2131 {
2132 /* Delete this note if it is identical to previous note. */
2136 {
2139 }
2142 }
2143 }
2145 #ifdef HAVE_return
2147 {
2148 /* If we fall through to the epilogue, see if we can insert a RETURN insn
2149 in front of it. If the machine allows it at this point (we might be
2150 after reload for a leaf routine), it will improve optimization for it
2151 to be there. We do this both here and at the start of this pass since
2152 the RETURN might have been deleted by some of our optimizations. */
2158 {
2161 }
2162 }
2163 #endif
2165 /* CAN_REACH_END is persistent for each function. Once set it should
2166 not be cleared. This is especially true for the case where we
2167 delete the NOTE_FUNCTION_END note. CAN_REACH_END is cleared by
2168 the front-end before compiling each function. */
2172 end:
2173 /* Clean up. */
2176 }
2177 \f
2178 /* Initialize LABEL_NUSES and JUMP_LABEL fields. Delete any REG_LABEL
2179 notes whose labels don't occur in the insn any more. Returns the
2180 largest INSN_UID found. */
2181 static int
2183 rtx f;
2184 {
2186 rtx insn;
2189 {
2195 {
2199 {
2204 }
2205 }
2208 }
2211 }
2213 /* Delete insns following barriers, up to next label.
2215 Also delete no-op jumps created by gcse. */
2216 static void
2218 rtx f;
2219 {
2220 rtx insn;
2223 {
2225 {
2231 {
2235 else
2237 }
2238 /* INSN is now the code_label. */
2239 }
2240 /* Also remove (set (pc) (pc)) insns which can be created by
2241 gcse. We eliminate such insns now to avoid having them
2242 cause problems later. */
2249 else
2251 }
2252 }
2254 /* Mark the label each jump jumps to.
2255 Combine consecutive labels, and count uses of labels.
2257 For each label, make a chain (using `jump_chain')
2258 of all the *unconditional* jumps that jump to it;
2259 also make a chain of all returns.
2261 CROSS_JUMP indicates whether we are doing cross jumping
2262 and if we are whether we will be paying attention to
2263 death notes or not. */
2265 static void
2267 rtx f;
2269 {
2270 rtx insn;
2274 {
2277 {
2279 {
2283 }
2285 {
2288 }
2289 }
2290 }
2291 }
2293 /* Delete all labels already not referenced.
2294 Also find and return the last insn. */
2296 static rtx
2298 rtx f;
2299 {
2301 rtx insn;
2304 {
2309 else
2310 {
2313 }
2314 }
2317 }
2319 /* Delete various simple forms of moves which have no necessary
2320 side effect. */
2322 static void
2324 rtx f;
2325 {
2329 {
2333 {
2336 /* Combine stack_adjusts with following push_insns. */
2337 #ifdef PUSH_ROUNDING
2344 {
2345 rtx p;
2351 /* Find all successive push insns. */
2353 /* Don't convert more than three pushes;
2354 that starts adding too many displaced addresses
2355 and the whole thing starts becoming a losing
2356 proposition. */
2358 {
2367 /* Allow a no-op move between the adjust and the push. */
2376 pushes++;
2381 }
2383 /* Discard the amount pushed from the stack adjust;
2384 maybe eliminate it entirely. */
2386 {
2389 }
2390 else
2394 /* Change the appropriate push insns to ordinary stores. */
2397 {
2406 /* Allow a no-op move between the adjust and the push. */
2416 /* If this push doesn't fully fit in the space
2417 of the stack adjust that we deleted,
2418 make another stack adjust here for what we
2419 didn't use up. There should be peepholes
2420 to recognize the resulting sequence of insns. */
2422 {
2425 p);
2427 }
2430 }
2431 }
2432 #endif
2434 /* Detect and delete no-op move instructions
2435 resulting from not allocating a parameter in a register. */
2448 /* Detect and ignore no-op move instructions
2449 resulting from smart or fortuitous register allocation. */
2452 {
2459 {
2460 rtx trial;
2467 {
2468 /* DREG may have been the target of a REG_DEAD note in
2469 the insn which makes INSN redundant. If so, reorg
2470 would still think it is dead. So search for such a
2471 note and delete it if we find it. */
2477 {
2480 }
2482 /* Deleting insn could lose a death-note for SREG. */
2484 {
2485 /* Change this into a USE so that we won't emit
2486 code for it, but still can keep the note. */
2490 /* Remove all reg notes but the REG_DEAD one. */
2493 }
2494 else
2496 }
2497 }
2502 {
2503 /* This handles the case where we have two consecutive
2504 assignments of the same constant to pseudos that didn't
2505 get a hard reg. Each SET from the constant will be
2506 converted into a SET of the spill register and an
2507 output reload will be made following it. This produces
2508 two loads of the same constant into the same spill
2509 register. */
2513 /* Look back for a death note for the first reg.
2514 If there is one, it is no longer accurate. */
2516 {
2520 {
2523 }
2525 }
2527 /* Delete the second load of the value. */
2529 }
2530 }
2532 {
2533 /* If each part is a set between two identical registers or
2534 a USE or CLOBBER, delete the insn. */
2536 rtx tem;
2539 {
2549 }
2553 }
2554 /* Also delete insns to store bit fields if they are no-ops. */
2555 /* Not worth the hair to detect this in the big-endian case. */
2564 }
2566 }
2567 }
2569 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
2570 If so indicate that this function can drop off the end by returning
2571 1, else return 0.
2573 CHECK_DELETED indicates whether we must check if the note being
2574 searched for has the deleted flag set.
2576 DELETE_FINAL_NOTE indicates whether we should delete the note
2577 if we find it. */
2579 static int
2581 rtx last;
2583 {
2588 {
2591 /* One label can follow the end-note: the return label. */
2594 /* Ordinary insns can follow it if returning a structure. */
2597 /* If machine uses explicit RETURN insns, no epilogue,
2598 then one of them follows the note. */
2602 /* A barrier can follow the return insn. */
2605 /* Other kinds of notes can follow also. */
2614 }
2616 /* See if we backed up to the appropriate type of note. */
2620 {
2624 }
2627 }
2629 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
2630 jump. Assume that this unconditional jump is to the exit test code. If
2631 the code is sufficiently simple, make a copy of it before INSN,
2632 followed by a jump to the exit of the loop. Then delete the unconditional
2633 jump after INSN.
2635 Return 1 if we made the change, else 0.
2637 This is only safe immediately after a regscan pass because it uses the
2638 values of regno_first_uid and regno_last_uid. */
2640 static int
2642 rtx loop_start;
2643 {
2648 rtx lastexit;
2652 /* Scan the exit code. We do not perform this optimization if any insn:
2654 is a CALL_INSN
2655 is a CODE_LABEL
2656 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
2657 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
2658 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
2659 is not valid.
2661 We also do not do this if we find an insn with ASM_OPERANDS. While
2662 this restriction should not be necessary, copying an insn with
2663 ASM_OPERANDS can confuse asm_noperands in some cases.
2665 Also, don't do this if the exit code is more than 20 insns. */
2668 insn
2672 {
2674 {
2679 /* We could be in front of the wrong NOTE_INSN_LOOP_END if there is
2680 a jump immediately after the loop start that branches outside
2681 the loop but within an outer loop, near the exit test.
2682 If we copied this exit test and created a phony
2683 NOTE_INSN_LOOP_VTOP, this could make instructions immediately
2684 before the exit test look like these could be safely moved
2685 out of the loop even if they actually may be never executed.
2686 This can be avoided by checking here for NOTE_INSN_LOOP_CONT. */
2695 /* If we were to duplicate this code, we would not move
2696 the BLOCK notes, and so debugging the moved code would
2697 be difficult. Thus, we only move the code with -O2 or
2698 higher. */
2704 /* The code below would grossly mishandle REG_WAS_0 notes,
2705 so get rid of them here. */
2715 }
2716 }
2718 /* Unless INSN is zero, we can do the optimization. */
2724 /* See if any insn sets a register only used in the loop exit code and
2725 not a user variable. If so, replace it with a new register. */
2734 {
2740 {
2741 /* We can do the replacement. Allocate reg_map if this is the
2742 first replacement we found. */
2749 }
2750 }
2752 /* Now copy each insn. */
2754 {
2756 {
2761 /* Only copy line-number notes. */
2763 {
2766 }
2776 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
2777 make them. */
2794 {
2798 }
2800 /* If this is a simple jump, add it to the jump chain. */
2804 {
2808 }
2813 }
2815 /* Record the first insn we copied. We need it so that we can
2816 scan the copied insns for new pseudo registers. */
2819 }
2821 /* Now clean up by emitting a jump to the end label and deleting the jump
2822 at the start of the loop. */
2824 {
2826 loop_start);
2828 /* Record the first insn we copied. We need it so that we can
2829 scan the copied insns for new pseudo registers. This may not
2830 be strictly necessary since we should have copied at least one
2831 insn above. But I am going to be safe. */
2838 {
2842 }
2844 }
2846 /* Now scan from the first insn we copied to the last insn we copied
2847 (copy) for new pseudo registers. Do this after the code to jump to
2848 the end label since that might create a new pseudo too. */
2851 /* Mark the exit code as the virtual top of the converted loop. */
2856 /* Clean up. */
2861 }
2862 \f
2863 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
2864 loop-end notes between START and END out before START. Assume that
2865 END is not such a note. START may be such a note. Returns the value
2866 of the new starting insn, which may be different if the original start
2867 was such a note. */
2869 rtx
2872 {
2873 rtx insn;
2874 rtx next;
2877 {
2886 {
2889 else
2890 {
2898 }
2899 }
2900 }
2903 }
2904 \f
2905 /* Compare the instructions before insn E1 with those before E2
2906 to find an opportunity for cross jumping.
2907 (This means detecting identical sequences of insns followed by
2908 jumps to the same place, or followed by a label and a jump
2909 to that label, and replacing one with a jump to the other.)
2911 Assume E1 is a jump that jumps to label E2
2912 (that is not always true but it might as well be).
2913 Find the longest possible equivalent sequences
2914 and store the first insns of those sequences into *F1 and *F2.
2915 Store zero there if no equivalent preceding instructions are found.
2917 We give up if we find a label in stream 1.
2918 Actually we could transfer that label into stream 2. */
2920 static void
2925 {
2937 {
2947 /* Don't allow the range of insns preceding E1 or E2
2948 to include the other (E2 or E1). */
2952 /* If we will get to this code by jumping, those jumps will be
2953 tensioned to go directly to the new label (before I2),
2954 so this cross-jumping won't cost extra. So reduce the minimum. */
2956 {
2959 }
2964 /* Avoid moving insns across EH regions if either of the insns
2965 can throw. */
2974 /* If this is a CALL_INSN, compare register usage information.
2975 If we don't check this on stack register machines, the two
2976 CALL_INSNs might be merged leaving reg-stack.c with mismatching
2977 numbers of stack registers in the same basic block.
2978 If we don't check this on machines with delay slots, a delay slot may
2979 be filled that clobbers a parameter expected by the subroutine.
2981 ??? We take the simple route for now and assume that if they're
2982 equal, they were constructed identically. */
2989 #ifdef STACK_REGS
2990 /* If cross_jump_death_matters is not 0, the insn's mode
2991 indicates whether or not the insn contains any stack-like
2992 regs. */
2995 {
2996 /* If register stack conversion has already been done, then
2997 death notes must also be compared before it is certain that
2998 the two instruction streams match. */
3000 rtx note;
3020 done:
3021 ;
3022 }
3023 #endif
3025 /* Don't allow old-style asm or volatile extended asms to be accepted
3026 for cross jumping purposes. It is conceptually correct to allow
3027 them, since cross-jumping preserves the dynamic instruction order
3028 even though it is changing the static instruction order. However,
3029 if an asm is being used to emit an assembler pseudo-op, such as
3030 the MIPS `.set reorder' pseudo-op, then the static instruction order
3031 matters and it must be preserved. */
3039 {
3040 /* The following code helps take care of G++ cleanups. */
3041 rtx equiv1;
3042 rtx equiv2;
3049 /* If the equivalences are not to a constant, they may
3050 reference pseudos that no longer exist, so we can't
3051 use them. */
3054 {
3059 {
3066 }
3067 }
3069 /* Insns fail to match; cross jumping is limited to the following
3070 insns. */
3072 #ifdef HAVE_cc0
3073 /* Don't allow the insn after a compare to be shared by
3074 cross-jumping unless the compare is also shared.
3075 Here, if either of these non-matching insns is a compare,
3076 exclude the following insn from possible cross-jumping. */
3079 #endif
3081 /* If cross-jumping here will feed a jump-around-jump
3082 optimization, this jump won't cost extra, so reduce
3083 the minimum. */
3089 }
3091 win:
3093 {
3094 /* Ok, this insn is potentially includable in a cross-jump here. */
3097 }
3098 }
3102 }
3104 static void
3107 {
3108 /* Find an existing label at this point
3109 or make a new one if there is none. */
3112 /* Make the same jump insn jump to the new point. */
3114 {
3115 /* Remove from jump chain of returns. */
3117 /* Change the insn. */
3122 /* Add to new the jump chain. */
3125 {
3128 }
3129 }
3130 else
3133 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
3134 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
3135 the NEWJPOS stream. */
3138 {
3139 rtx lnote;
3151 }
3152 }
3153 \f
3154 /* Return the label before INSN, or put a new label there. */
3156 rtx
3158 rtx insn;
3159 {
3160 rtx label;
3162 /* Find an existing label at this point
3163 or make a new one if there is none. */
3167 {
3173 }
3175 }
3177 /* Return the label after INSN, or put a new label there. */
3179 rtx
3181 rtx insn;
3182 {
3183 rtx label;
3185 /* Find an existing label at this point
3186 or make a new one if there is none. */
3190 {
3194 }
3196 }
3197 \f
3198 /* Return 1 if INSN is a jump that jumps to right after TARGET
3199 only on the condition that TARGET itself would drop through.
3200 Assumes that TARGET is a conditional jump. */
3202 static int
3205 {
3221 {
3225 }
3228 {
3232 }
3237 }
3238 \f
3239 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
3240 return non-zero if it is safe to reverse this comparison. It is if our
3241 floating-point is not IEEE, if this is an NE or EQ comparison, or if
3242 this is known to be an integer comparison. */
3244 int
3246 rtx comparison;
3247 rtx insn;
3248 {
3249 rtx arg0;
3251 /* If this is not actually a comparison, we can't reverse it. */
3256 /* If this is an NE comparison, it is safe to reverse it to an EQ
3257 comparison and vice versa, even for floating point. If no operands
3258 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
3259 always false and NE is always true, so the reversal is also valid. */
3260 || flag_fast_math
3267 /* Make sure ARG0 is one of the actual objects being compared. If we
3268 can't do this, we can't be sure the comparison can be reversed.
3270 Handle cc0 and a MODE_CC register. */
3272 #ifdef HAVE_cc0
3274 #endif
3275 )
3276 {
3278 rtx set;
3280 /* First see if the condition code mode alone if enough to say we can
3281 reverse the condition. If not, then search backwards for a set of
3282 ARG0. We do not need to check for an insn clobbering it since valid
3283 code will contain set a set with no intervening clobber. But
3284 stop when we reach a label. */
3285 #ifdef REVERSIBLE_CC_MODE
3289 #endif
3296 {
3302 }
3303 }
3305 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
3306 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
3311 }
3313 /* Given an rtx-code for a comparison, return the code for the negated
3314 comparison. If no such code exists, return UNKNOWN.
3316 WATCH OUT! reverse_condition is not safe to use on a jump that might
3317 be acting on the results of an IEEE floating point comparison, because
3318 of the special treatment of non-signaling nans in comparisons.
3319 Use can_reverse_comparison_p to be sure. */
3321 enum rtx_code
3324 {
3326 {
3362 }
3363 }
3365 /* Similar, but we're allowed to generate unordered comparisons, which
3366 makes it safe for IEEE floating-point. Of course, we have to recognize
3367 that the target will support them too... */
3369 enum rtx_code
3372 {
3373 /* Non-IEEE formats don't have unordered conditions. */
3378 {
3418 }
3419 }
3421 /* Similar, but return the code when two operands of a comparison are swapped.
3422 This IS safe for IEEE floating-point. */
3424 enum rtx_code
3427 {
3429 {
3465 }
3466 }
3468 /* Given a comparison CODE, return the corresponding unsigned comparison.
3469 If CODE is an equality comparison or already an unsigned comparison,
3470 CODE is returned. */
3472 enum rtx_code
3475 {
3477 {
3497 }
3498 }
3500 /* Similarly, return the signed version of a comparison. */
3502 enum rtx_code
3505 {
3507 {
3527 }
3528 }
3529 \f
3530 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
3531 truth of CODE1 implies the truth of CODE2. */
3533 int
3536 {
3541 {
3586 }
3589 }
3590 \f
3591 /* Return 1 if INSN is an unconditional jump and nothing else. */
3593 int
3595 rtx insn;
3596 {
3601 }
3603 /* Return nonzero if INSN is a (possibly) conditional jump
3604 and nothing more. */
3606 int
3608 rtx insn;
3609 {
3628 }
3630 /* Return nonzero if INSN is a (possibly) conditional jump inside a
3631 PARALLEL. */
3633 int
3635 rtx insn;
3636 {
3641 else
3661 }
3663 /* Return the label of a conditional jump. */
3665 rtx
3667 rtx insn;
3668 {
3687 }
3689 /* Return true if INSN is a (possibly conditional) return insn. */
3691 static int
3695 {
3698 }
3700 int
3702 rtx insn;
3703 {
3705 }
3707 /* Return true if INSN is a jump that only transfers control and
3708 nothing more. */
3710 int
3712 rtx insn;
3713 {
3714 rtx set;
3728 }
3730 #ifdef HAVE_cc0
3732 /* Return 1 if X is an RTX that does nothing but set the condition codes
3733 and CLOBBER or USE registers.
3734 Return -1 if X does explicitly set the condition codes,
3735 but also does other things. */
3737 int
3739 rtx x ATTRIBUTE_UNUSED;
3740 {
3744 {
3749 {
3755 }
3757 }
3759 }
3760 #endif
3761 \f
3762 /* Follow any unconditional jump at LABEL;
3763 return the ultimate label reached by any such chain of jumps.
3764 If LABEL is not followed by a jump, return LABEL.
3765 If the chain loops or we can't find end, return LABEL,
3766 since that tells caller to avoid changing the insn.
3768 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
3769 a USE or CLOBBER. */
3771 rtx
3773 rtx label;
3774 {
3788 depth++)
3789 {
3790 /* Don't chain through the insn that jumps into a loop
3791 from outside the loop,
3792 since that would create multiple loop entry jumps
3793 and prevent loop optimization. */
3794 rtx tem;
3799 /* ??? Optional. Disables some optimizations, but makes
3800 gcov output more accurate with -O. */
3804 /* If we have found a cycle, make the insn jump to itself. */
3814 }
3818 }
3820 /* Assuming that field IDX of X is a vector of label_refs,
3821 replace each of them by the ultimate label reached by it.
3822 Return nonzero if a change is made.
3823 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
3825 static int
3829 {
3833 {
3837 {
3843 }
3844 }
3846 }
3847 \f
3848 /* Find all CODE_LABELs referred to in X, and increment their use counts.
3849 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
3850 in INSN, then store one of them in JUMP_LABEL (INSN).
3851 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
3852 referenced in INSN, add a REG_LABEL note containing that label to INSN.
3853 Also, when there are consecutive labels, canonicalize on the last of them.
3855 Note that two labels separated by a loop-beginning note
3856 must be kept distinct if we have not yet done loop-optimization,
3857 because the gap between them is where loop-optimize
3858 will want to move invariant code to. CROSS_JUMP tells us
3859 that loop-optimization is done with.
3861 Once reload has completed (CROSS_JUMP non-zero), we need not consider
3862 two labels distinct if they are separated by only USE or CLOBBER insns. */
3864 static void
3867 rtx insn;
3869 {
3875 {
3888 /* If this is a constant-pool reference, see if it is a label. */
3895 {
3898 rtx note;
3899 rtx next;
3904 /* Ignore references to labels of containing functions. */
3908 /* If there are other labels following this one,
3909 replace it with the last of the consecutive labels. */
3911 {
3923 /* ??? Optional. Disables some optimizations, but
3924 makes gcov output more accurate with -O. */
3927 }
3934 {
3938 /* If we've changed OLABEL and we had a REG_LABEL note
3939 for it, update it as well. */
3944 /* Otherwise, add a REG_LABEL note for LABEL unless there already
3945 is one. */
3947 {
3948 /* This code used to ignore labels which refered to dispatch
3949 tables to avoid flow.c generating worse code.
3951 However, in the presense of global optimizations like
3952 gcse which call find_basic_blocks without calling
3953 life_analysis, not recording such labels will lead
3954 to compiler aborts because of inconsistencies in the
3955 flow graph. So we go ahead and record the label.
3957 It may also be the case that the optimization argument
3958 is no longer valid because of the more accurate cfg
3959 we build in find_basic_blocks -- it no longer pessimizes
3960 code when it finds a REG_LABEL note. */
3963 }
3964 }
3966 }
3968 /* Do walk the labels in a vector, but not the first operand of an
3969 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
3973 {
3978 }
3983 }
3987 {
3991 {
3995 }
3996 }
3997 }
3999 /* If all INSN does is set the pc, delete it,
4000 and delete the insn that set the condition codes for it
4001 if that's what the previous thing was. */
4003 void
4005 rtx insn;
4006 {
4011 }
4013 /* Verify INSN is a BARRIER and delete it. */
4015 void
4017 rtx insn;
4018 {
4023 }
4025 /* Recursively delete prior insns that compute the value (used only by INSN
4026 which the caller is deleting) stored in the register mentioned by NOTE
4027 which is a REG_DEAD note associated with INSN. */
4029 static void
4031 rtx note;
4032 rtx insn;
4033 {
4034 rtx our_prev;
4041 {
4044 /* If we reach a CALL which is not calling a const function
4045 or the callee pops the arguments, then give up. */
4051 /* If we reach a SEQUENCE, it is too complex to try to
4052 do anything with it, so give up. */
4058 /* reorg creates USEs that look like this. We leave them
4059 alone because reorg needs them for its own purposes. */
4063 {
4068 {
4069 /* If we find a SET of something else, we can't
4070 delete the insn. */
4075 {
4081 }
4085 }
4088 {
4090 int dest_endregno
4102 /* We may have a multi-word hard register and some, but not
4103 all, of the words of the register are needed in subsequent
4104 insns. Write REG_UNUSED notes for those parts that were not
4105 needed. */
4108 {
4120 }
4121 }
4124 }
4126 /* If PAT references the register that dies here, it is an
4127 additional use. Hence any prior SET isn't dead. However, this
4128 insn becomes the new place for the REG_DEAD note. */
4130 {
4134 }
4135 }
4136 }
4138 /* Delete INSN and recursively delete insns that compute values used only
4139 by INSN. This uses the REG_DEAD notes computed during flow analysis.
4140 If we are running before flow.c, we need do nothing since flow.c will
4141 delete dead code. We also can't know if the registers being used are
4142 dead or not at this point.
4144 Otherwise, look at all our REG_DEAD notes. If a previous insn does
4145 nothing other than set a register that dies in this insn, we can delete
4146 that insn as well.
4148 On machines with CC0, if CC0 is used in this insn, we may be able to
4149 delete the insn that set it. */
4151 static void
4153 rtx insn;
4154 {
4156 rtx set;
4158 #ifdef HAVE_cc0
4160 {
4162 /* We assume that at this stage
4163 CC's are always set explicitly
4164 and always immediately before the jump that
4165 will use them. So if the previous insn
4166 exists to set the CC's, delete it
4167 (unless it performs auto-increments, etc.). */
4170 {
4174 else
4175 /* Otherwise, show that cc0 won't be used. */
4178 }
4179 }
4180 #endif
4182 #ifdef INSN_SCHEDULING
4183 /* ?!? The schedulers do not keep REG_DEAD notes accurate after
4184 reload has completed. The schedulers need to be fixed. Until
4185 they are, we must not rely on the death notes here. */
4187 {
4190 }
4191 #endif
4193 /* The REG_DEAD note may have been omitted for a register
4194 which is both set and used by the insn. */
4197 {
4199 int dest_endregno
4206 {
4215 }
4216 }
4219 {
4223 /* Verify that the REG_NOTE is legitimate. */
4228 }
4231 }
4232 \f
4233 /* Delete insn INSN from the chain of insns and update label ref counts.
4234 May delete some following insns as a consequence; may even delete
4235 a label elsewhere and insns that follow it.
4237 Returns the first insn after INSN that was not deleted. */
4239 rtx
4242 {
4251 /* This insn is already deleted => return first following nondeleted. */
4258 /* Don't delete user-declared labels. Convert them to special NOTEs
4259 instead. */
4261 {
4266 }
4267 else
4268 /* Mark this insn as deleted. */
4271 /* If this is an unconditional jump, delete it from the jump chain. */
4275 /* If instruction is followed by a barrier,
4276 delete the barrier too. */
4279 {
4282 }
4284 /* Patch out INSN (and the barrier if any) */
4287 {
4289 {
4294 }
4297 {
4301 }
4305 }
4307 /* If deleting a jump, decrement the count of the label,
4308 and delete the label if it is now unused. */
4311 {
4315 {
4316 /* This can delete NEXT or PREV,
4317 either directly if NEXT is JUMP_LABEL (INSN),
4318 or indirectly through more levels of jumps. */
4321 /* I feel a little doubtful about this loop,
4322 but I see no clean and sure alternative way
4323 to find the first insn after INSN that is not now deleted.
4324 I hope this works. */
4328 }
4333 {
4334 /* If we're deleting the tablejump, delete the dispatch table.
4335 We may not be able to kill the label immediately preceeding
4336 just yet, as it might be referenced in code leading up to
4337 the tablejump. */
4339 }
4340 }
4342 /* Likewise if we're deleting a dispatch table. */
4347 {
4358 }
4363 /* If INSN was a label and a dispatch table follows it,
4364 delete the dispatch table. The tablejump must have gone already.
4365 It isn't useful to fall through into a table. */
4374 /* If INSN was a label, delete insns following it if now unreachable. */
4377 {
4383 {
4387 /* Keep going past other deleted labels to delete what follows. */
4390 else
4391 /* Note: if this deletes a jump, it can cause more
4392 deletion of unreachable code, after a different label.
4393 As long as the value from this recursive call is correct,
4394 this invocation functions correctly. */
4396 }
4397 }
4400 }
4402 /* Advance from INSN till reaching something not deleted
4403 then return that. May return INSN itself. */
4405 rtx
4407 rtx insn;
4408 {
4412 }
4413 \f
4414 /* Delete a range of insns from FROM to TO, inclusive.
4415 This is for the sake of peephole optimization, so assume
4416 that whatever these insns do will still be done by a new
4417 peephole insn that will replace them. */
4419 void
4422 {
4426 {
4431 {
4434 /* Patch this insn out of the chain. */
4435 /* We don't do this all at once, because we
4436 must preserve all NOTEs. */
4442 }
4447 }
4449 /* Note that if TO is an unconditional jump
4450 we *do not* delete the BARRIER that follows,
4451 since the peephole that replaces this sequence
4452 is also an unconditional jump in that case. */
4453 }
4454 \f
4455 /* We have determined that INSN is never reached, and are about to
4456 delete it. Print a warning if the user asked for one.
4458 To try to make this warning more useful, this should only be called
4459 once per basic block not reached, and it only warns when the basic
4460 block contains more than one line from the current function, and
4461 contains at least one operation. CSE and inlining can duplicate insns,
4462 so it's possible to get spurious warnings from this. */
4464 void
4466 rtx avoided_insn;
4467 {
4468 rtx insn;
4476 /* Scan forwards, looking at LINE_NUMBER notes, until
4477 we hit a LABEL or we run out of insns. */
4480 {
4485 {
4488 else
4491 }
4494 }
4499 }
4500 \f
4501 /* Invert the condition of the jump JUMP, and make it jump
4502 to label NLABEL instead of where it jumps now. */
4504 int
4507 {
4508 /* We have to either invert the condition and change the label or
4509 do neither. Either operation could fail. We first try to invert
4510 the jump. If that succeeds, we try changing the label. If that fails,
4511 we invert the jump back to what it was. */
4517 {
4519 {
4522 /* An inverted jump means that a probability taken becomes a
4523 probability not taken. Subtract the branch probability from the
4524 probability base to convert it back to a taken probability.
4525 (We don't flip the probability on a branch that's never taken. */
4528 }
4531 }
4534 /* This should just be putting it back the way it was. */
4538 }
4540 /* Invert the jump condition of rtx X contained in jump insn, INSN.
4542 Return 1 if we can do so, 0 if we cannot find a way to do so that
4543 matches a pattern. */
4545 int
4547 rtx x;
4548 rtx insn;
4549 {
4557 {
4561 /* We can do this in two ways: The preferable way, which can only
4562 be done if this is not an integer comparison, is to reverse
4563 the comparison code. Otherwise, swap the THEN-part and ELSE-part
4564 of the IF_THEN_ELSE. If we can't do either, fail. */
4577 }
4581 {
4583 {
4586 }
4588 {
4593 }
4594 }
4597 }
4598 \f
4599 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
4600 If the old jump target label is unused as a result,
4601 it and the code following it may be deleted.
4603 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
4604 RETURN insn.
4606 The return value will be 1 if the change was made, 0 if it wasn't (this
4607 can only occur for NLABEL == 0). */
4609 int
4612 {
4621 /* If this is an unconditional branch, delete it from the jump_chain of
4622 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
4623 have UID's in range and JUMP_CHAIN is valid). */
4626 {
4632 {
4635 }
4636 }
4642 /* If we're eliding the jump over exception cleanups at the end of a
4643 function, move the function end note so that -Wreturn-type works. */
4653 }
4655 /* Delete the instruction JUMP from any jump chain it might be on. */
4657 static void
4659 rtx jump;
4660 {
4664 /* Handle unconditional jumps. */
4669 /* Handle return insns. */
4676 else
4677 {
4678 rtx insn;
4684 {
4687 }
4688 }
4689 }
4691 /* If NLABEL is nonzero, throughout the rtx at LOC,
4692 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
4693 zero, alter (RETURN) to (LABEL_REF NLABEL).
4695 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
4696 validity with validate_change. Convert (set (pc) (label_ref olabel))
4697 to (return).
4699 Return 0 if we found a change we would like to make but it is invalid.
4700 Otherwise, return 1. */
4702 int
4706 rtx insn;
4707 {
4714 {
4716 {
4719 else
4722 }
4723 }
4725 {
4730 }
4739 {
4741 {
4744 }
4746 {
4751 }
4752 }
4755 }
4756 \f
4757 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
4759 If the old jump target label (before the dispatch table) becomes unused,
4760 it and the dispatch table may be deleted. In that case, find the insn
4761 before the jump references that label and delete it and logical successors
4762 too. */
4764 static void
4767 {
4770 /* Add this jump to the jump_chain of NLABEL. */
4773 {
4776 }
4784 {
4787 }
4788 }
4790 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
4791 If we found one, delete it and then delete this insn if DELETE_THIS is
4792 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
4794 static int
4798 {
4800 rtx link;
4804 {
4806 {
4809 }
4810 else
4812 }
4816 {
4818 {
4821 }
4822 else
4824 }
4827 }
4828 \f
4829 /* Like rtx_equal_p except that it considers two REGs as equal
4830 if they renumber to the same value and considers two commutative
4831 operations to be the same if the order of the operands has been
4832 reversed.
4834 ??? Addition is not commutative on the PA due to the weird implicit
4835 space register selection rules for memory addresses. Therefore, we
4836 don't consider a + b == b + a.
4838 We could/should make this test a little tighter. Possibly only
4839 disabling it on the PA via some backend macro or only disabling this
4840 case when the PLUS is inside a MEM. */
4842 int
4845 {
4856 {
4863 /* If we haven't done any renumbering, don't
4864 make any assumptions. */
4869 {
4874 {
4877 }
4878 }
4880 else
4881 {
4885 }
4888 {
4893 {
4896 }
4897 }
4899 else
4900 {
4904 }
4907 }
4909 /* Now we have disposed of all the cases
4910 in which different rtx codes can match. */
4915 {
4926 /* We can't assume nonlocal labels have their following insns yet. */
4930 /* Two label-refs are equivalent if they point at labels
4931 in the same position in the instruction stream. */
4939 /* If we didn't match EQ equality above, they aren't the same. */
4944 }
4946 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
4951 /* For commutative operations, the RTX match if the operand match in any
4952 order. Also handle the simple binary and unary cases without a loop.
4954 ??? Don't consider PLUS a commutative operator; see comments above. */
4967 /* Compare the elements. If any pair of corresponding elements
4968 fail to match, return 0 for the whole things. */
4972 {
4975 {
4999 /* fall through. */
5013 }
5014 }
5016 }
5017 \f
5018 /* If X is a hard register or equivalent to one or a subregister of one,
5019 return the hard register number. If X is a pseudo register that was not
5020 assigned a hard register, return the pseudo register number. Otherwise,
5021 return -1. Any rtx is valid for X. */
5023 int
5025 rtx x;
5026 {
5028 {
5032 }
5034 {
5038 }
5040 }
5041 \f
5042 /* Optimize code of the form:
5044 for (x = a[i]; x; ...)
5045 ...
5046 for (x = a[i]; x; ...)
5047 ...
5048 foo:
5050 Loop optimize will change the above code into
5052 if (x = a[i])
5053 for (;;)
5054 { ...; if (! (x = ...)) break; }
5055 if (x = a[i])
5056 for (;;)
5057 { ...; if (! (x = ...)) break; }
5058 foo:
5060 In general, if the first test fails, the program can branch
5061 directly to `foo' and skip the second try which is doomed to fail.
5062 We run this after loop optimization and before flow analysis. */
5064 /* When comparing the insn patterns, we track the fact that different
5065 pseudo-register numbers may have been used in each computation.
5066 The following array stores an equivalence -- same_regs[I] == J means
5067 that pseudo register I was used in the first set of tests in a context
5068 where J was used in the second set. We also count the number of such
5069 pending equivalences. If nonzero, the expressions really aren't the
5070 same. */
5076 /* Track any registers modified between the target of the first jump and
5077 the second jump. They never compare equal. */
5081 /* Record if memory was modified. */
5085 /* Called via note_stores on each insn between the target of the first
5086 branch and the second branch. It marks any changed registers. */
5088 static void
5090 rtx dest;
5091 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. */
5239 b1)
5242 {
5247 {
5249 {
5250 /* We have reached the target of the first branch.
5251 If there are no pending register equivalents,
5252 we know that this branch will either always
5253 succeed (if the senses of the two branches are
5254 the same) or always fail (if not). */
5255 rtx new_label;
5262 else
5266 {
5272 {
5273 /* Don't thread to the loop label. If a loop
5274 label is reused, loop optimization will
5275 be disabled for that loop. */
5278 }
5280 }
5282 }
5284 /* If either of these is not a normal insn (it might be
5285 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
5286 have already been skipped above.) Similarly, fail
5287 if the insns are different. */
5296 }
5297 }
5298 }
5299 }
5301 /* Clean up. */
5305 }
5306 \f
5307 /* This is like RTX_EQUAL_P except that it knows about our handling of
5308 possibly equivalent registers and knows to consider volatile and
5309 modified objects as not equal.
5311 YINSN is the insn containing Y. */
5313 int
5316 rtx yinsn;
5317 {
5324 /* Rtx's of different codes cannot be equal. */
5328 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
5329 (REG:SI x) and (REG:HI x) are NOT equivalent. */
5334 /* For floating-point, consider everything unequal. This is a bit
5335 pessimistic, but this pass would only rarely do anything for FP
5336 anyway. */
5341 /* For commutative operations, the RTX match if the operand match in any
5342 order. Also handle the simple binary and unary cases without a loop. */
5354 /* Handle special-cases first. */
5356 {
5361 /* If neither is user variable or hard register, check for possible
5362 equivalence. */
5369 {
5371 num_same_regs++;
5373 /* If this is the first time we are seeing a register on the `Y'
5374 side, see if it is the last use. If not, we can't thread the
5375 jump, so mark it as not equivalent. */
5380 }
5381 else
5387 /* If memory modified or either volatile, not equivalent.
5388 Else, check address. */
5401 /* Cancel a pending `same_regs' if setting equivalenced registers.
5402 Then process source. */
5405 {
5407 {
5409 num_same_regs--;
5410 }
5413 }
5414 else
5428 }
5435 {
5437 {
5451 /* Two vectors must have the same length. */
5455 /* And the corresponding elements must match. */
5474 /* These are just backpointers, so they don't matter. */
5481 /* It is believed that rtx's at this level will never
5482 contain anything but integers and other rtx's,
5483 except for within LABEL_REFs and SYMBOL_REFs. */
5486 }
5487 }
5489 }
5490 \f
5492 #if !defined(HAVE_cc0) && !defined(HAVE_conditional_arithmetic)
5493 /* Return the insn that NEW can be safely inserted in front of starting at
5494 the jump insn INSN. Return 0 if it is not safe to do this jump
5495 optimization. Note that NEW must contain a single set. */
5497 static rtx
5499 rtx insn;
5501 {
5503 rtx prev;
5505 /* If NEW does not clobber, it is safe to insert NEW before INSN. */
5512 insn))
5518 /* There is a good chance that the previous insn PREV sets the thing
5519 being clobbered (often the CC in a hard reg). If PREV does not
5520 use what NEW sets, we can insert NEW before PREV. */
5526 insn)
5528 prev))
5532 }