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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. */
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. */
236 {
237 /* CAN_REACH_END is persistent for each function. Once set it should
238 not be cleared. This is especially true for the case where we
239 delete the NOTE_FUNCTION_END note. CAN_REACH_END is cleared by
240 the front-end before compiling each function. */
244 /* Zero the "deleted" flag of all the "deleted" insns. */
249 }
251 #ifdef HAVE_return
253 {
254 /* If we fall through to the epilogue, see if we can insert a RETURN insn
255 in front of it. If the machine allows it at this point (we might be
256 after reload for a leaf routine), it will improve optimization for it
257 to be there. */
263 {
266 }
267 }
268 #endif
273 /* If we haven't yet gotten to reload and we have just run regscan,
274 delete any insn that sets a register that isn't used elsewhere.
275 This helps some of the optimizations below by having less insns
276 being jumped around. */
280 {
288 /* We use regno_last_note_uid so as not to delete the setting
289 of a reg that's used in notes. A subsequent optimization
290 might arrange to use that reg for real. */
294 /* An ADDRESSOF expression can turn into a use of the internal arg
295 pointer, so do not delete the initialization of the internal
296 arg pointer yet. If it is truly dead, flow will delete the
297 initializing insn. */
300 }
302 /* Now iterate optimizing jumps until nothing changes over one pass. */
306 {
310 {
311 rtx reallabelprev;
313 rtx nlabel;
319 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
320 jump. Try to optimize by duplicating the loop exit test if so.
321 This is only safe immediately after regscan, because it uses
322 the values of regno_first_uid and regno_last_uid. */
327 {
330 {
334 }
335 }
344 /* Tension the labels in dispatch tables. */
351 /* See if this jump goes to another jump and redirect if so. */
356 /* If a dispatch table always goes to the same place,
357 get rid of it and replace the insn that uses it. */
361 {
367 rtx set;
378 /* Don't mess with a casesi insn.
379 XXX according to the comment before computed_jump_p(),
380 all casesi insns should be a parallel of the jump
381 and a USE of a LABEL_REF. */
385 {
389 }
390 }
392 /* If a jump references the end of the function, try to turn
393 it into a RETURN insn, possibly a conditional one. */
402 /* Detect jump to following insn. */
404 {
409 }
411 /* Detect a conditional jump going to the same place
412 as an immediately following unconditional jump. */
418 {
419 /* Don't mess up test coverage analysis. */
427 {
431 }
432 }
434 /* Detect a conditional jump jumping over an unconditional jump. */
437 && ! this_is_simplejump
443 {
444 /* When we invert the unconditional jump, we will be
445 decrementing the usage count of its old label.
446 Make sure that we don't delete it now because that
447 might cause the following code to be deleted. */
455 {
456 /* It is very likely that if there are USE insns before
457 this jump, they hold REG_DEAD notes. These REG_DEAD
458 notes are no longer valid due to this optimization,
459 and will cause the life-analysis that following passes
460 (notably delayed-branch scheduling) to think that
461 these registers are dead when they are not.
463 To prevent this trouble, we just remove the USE insns
464 from the insn chain. */
468 {
472 }
476 }
478 /* We can now safely delete the label if it is unreferenced
479 since the delete_insn above has deleted the BARRIER. */
484 }
486 /* If we have an unconditional jump preceded by a USE, try to put
487 the USE before the target and jump there. This simplifies many
488 of the optimizations below since we don't have to worry about
489 dealing with these USE insns. We only do this if the label
490 being branch to already has the identical USE or if code
491 never falls through to that label. */
501 /* Don't do this optimization if we have a loop containing
502 only the USE instruction, and the loop start label has
503 a usage count of 1. This is because we will redo this
504 optimization everytime through the outer loop, and jump
505 opt will never exit. */
509 {
511 {
514 }
521 }
523 /* Simplify if (...) x = a; else x = b; by converting it
524 to x = b; if (...) x = a;
525 if B is sufficiently simple, the test doesn't involve X,
526 and nothing in the test modifies B or X.
528 If we have small register classes, we also can't do this if X
529 is a hard register.
531 If the "x = b;" insn has any REG_NOTES, we don't do this because
532 of the possibility that we are running after CSE and there is a
533 REG_EQUAL note that is only valid if the branch has already been
534 taken. If we move the insn with the REG_EQUAL note, we may
535 fold the comparison to always be false in a later CSE pass.
536 (We could also delete the REG_NOTES when moving the insn, but it
537 seems simpler to not move it.) An exception is that we can move
538 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
539 value is the same as "b".
541 INSN is the branch over the `else' part.
543 We set:
545 TEMP to the jump insn preceding "x = a;"
546 TEMP1 to X
547 TEMP2 to the insn that sets "x = b;"
548 TEMP3 to the insn that sets "x = a;"
549 TEMP4 to the set of "x = b"; */
556 && (! SMALL_REGISTER_CLASSES
572 /* TEMP must skip over the "x = a;" insn */
575 /* There must be no other entries to the "x = b;" insn. */
577 /* INSN must either branch to the insn after TEMP2 or the insn
578 after TEMP2 must branch to the same place as INSN. */
583 {
584 /* The test expression, X, may be a complicated test with
585 multiple branches. See if we can find all the uses of
586 the label that TEMP branches to without hitting a CALL_INSN
587 or a jump to somewhere else. */
590 rtx p;
591 #ifdef HAVE_cc0
592 rtx q;
593 #endif
595 /* Set P to the first jump insn that goes around "x = a;". */
597 {
599 {
602 {
603 nuses--;
606 }
607 else
609 }
612 }
614 #ifdef HAVE_cc0
615 /* We cannot insert anything between a set of cc and its use
616 so if P uses cc0, we must back up to the previous insn. */
621 #endif
626 /* If we found all the uses and there was no data conflict, we
627 can move the assignment unless we can branch into the middle
628 from somewhere. */
635 /* Verify that registers used by the jump are not clobbered
636 by the instruction being moved. */
640 {
644 /* Set NEXT to an insn that we know won't go away. */
647 /* Delete the jump around the set. Note that we must do
648 this before we redirect the test jumps so that it won't
649 delete the code immediately following the assignment
650 we moved (which might be a jump). */
654 /* We either have two consecutive labels or a jump to
655 a jump, so adjust all the JUMP_INSNs to branch to where
656 INSN branches to. */
664 }
665 }
667 /* Simplify if (...) { x = a; goto l; } x = b; by converting it
668 to x = a; if (...) goto l; x = b;
669 if A is sufficiently simple, the test doesn't involve X,
670 and nothing in the test modifies A or X.
672 If we have small register classes, we also can't do this if X
673 is a hard register.
675 If the "x = a;" insn has any REG_NOTES, we don't do this because
676 of the possibility that we are running after CSE and there is a
677 REG_EQUAL note that is only valid if the branch has already been
678 taken. If we move the insn with the REG_EQUAL note, we may
679 fold the comparison to always be false in a later CSE pass.
680 (We could also delete the REG_NOTES when moving the insn, but it
681 seems simpler to not move it.) An exception is that we can move
682 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
683 value is the same as "a".
685 INSN is the goto.
687 We set:
689 TEMP to the jump insn preceding "x = a;"
690 TEMP1 to X
691 TEMP2 to the insn that sets "x = b;"
692 TEMP3 to the insn that sets "x = a;"
693 TEMP4 to the set of "x = a"; */
700 && (! SMALL_REGISTER_CLASSES
716 /* TEMP must skip over the "x = a;" insn */
719 {
723 #ifdef HAVE_cc0
724 /* We cannot insert anything between a set of cc and its use. */
728 #endif
738 /* Verify that registers used by the jump are not clobbered
739 by the instruction being moved. */
744 {
749 /* Set NEXT to an insn that we know won't go away. */
752 }
757 }
759 #if !defined(HAVE_cc0) && !defined(HAVE_conditional_arithmetic)
761 /* If we have if (...) x = exp; and branches are expensive,
762 EXP is a single insn, does not have any side effects, cannot
763 trap, and is not too costly, convert this to
764 t = exp; if (...) x = t;
766 Don't do this when we have CC0 because it is unlikely to help
767 and we'd need to worry about where to place the new insn and
768 the potential for conflicts. We also can't do this when we have
769 notes on the insn for the same reason as above.
771 If we have conditional arithmetic, this will make this
772 harder to optimize later and isn't needed, so don't do it
773 in that case either.
775 We set:
777 TEMP to the "x = exp;" insn.
778 TEMP1 to the single set in the "x = exp;" insn.
779 TEMP2 to "x". */
793 && (! SMALL_REGISTER_CLASSES
801 {
806 {
814 {
817 }
818 }
819 }
821 /* Similarly, if it takes two insns to compute EXP but they
822 have the same destination. Here TEMP3 will be the second
823 insn and TEMP4 the SET from that insn. */
841 && (! SMALL_REGISTER_CLASSES
851 {
857 {
858 /* Use the earliest of temp5 and temp6. */
864 emit_insn_after_with_line_notes
872 {
875 }
876 }
877 }
879 /* Finally, handle the case where two insns are used to
880 compute EXP but a temporary register is used. Here we must
881 ensure that the temporary register is not used anywhere else. */
884 && after_regscan
912 && (! SMALL_REGISTER_CLASSES
918 {
924 {
925 /* Use the earliest of temp5 and temp6. */
938 {
941 }
942 }
943 }
946 #ifdef HAVE_conditional_arithmetic
947 /* ??? This is disabled in genconfig, as this simple-minded
948 transformation can incredibly lengthen register lifetimes.
950 Consider this example from cexp.c's yyparse:
952 234 (set (pc)
953 (if_then_else (ne (reg:DI 149) (const_int 0 [0x0]))
954 (label_ref 248) (pc)))
955 237 (set (reg/i:DI 0 $0) (const_int 1 [0x1]))
956 239 (set (pc) (label_ref 2382))
957 248 (code_label ("yybackup"))
959 This will be transformed to:
961 237 (set (reg/i:DI 0 $0)
962 (if_then_else:DI (eq (reg:DI 149) (const_int 0 [0x0]))
963 (const_int 1 [0x1]) (reg/i:DI 0 $0)))
964 239 (set (pc)
965 (if_then_else (eq (reg:DI 149) (const_int 0 [0x0]))
966 (label_ref 2382) (pc)))
968 which, from this narrow viewpoint looks fine. Except that
969 between this and 3 other ocurrences of the same pattern, $0
970 is now live for basically the entire function, and we'll
971 get an abort in caller_save.
973 Any replacement for this code should recall that a set of
974 a register that is not live need not, and indeed should not,
975 be conditionalized. Either that, or delay the transformation
976 until after register allocation. */
978 /* See if this is a conditional jump around a small number of
979 instructions that we can conditionalize. Don't do this before
980 the initial CSE pass or after reload.
982 We reject any insns that have side effects or may trap.
983 Strictly speaking, this is not needed since the machine may
984 support conditionalizing these too, but we won't deal with that
985 now. Specifically, this means that we can't conditionalize a
986 CALL_INSN, which some machines, such as the ARC, can do, but
987 this is a very minor optimization. */
992 insn))
993 {
1004 /* Scan forward BRANCH_COST real insns looking for the JUMP_LABEL
1005 of this insn. We see if we think we can conditionalize the
1006 insns we pass. For now, we only deal with insns that have
1007 one SET. We stop after an insn that modifies anything in
1008 OURCOND, if we have too many insns, or if we have an insn
1009 with a side effect or that may trip. Note that we will
1010 be modifying any unconditional jumps we encounter to be
1011 conditional; this will have the effect of also doing this
1012 optimization on the "else" the next time around. */
1017 {
1018 /* Ignore everything but an active insn. */
1024 /* If this was an unconditional jump, record it since we'll
1025 need to remove the BARRIER if we succeed. We can only
1026 have one such jump since there must be a label after
1027 the BARRIER and it's either ours, in which case it's the
1028 only one or some other, in which case we'd fail.
1029 Likewise if it's a CALL_INSN followed by a BARRIER. */
1035 {
1038 else
1039 changed_jump
1041 }
1043 /* See if we are allowed another insn and if this insn
1044 if one we think we may be able to handle. */
1046 || last_insn
1054 gen_rtx_IF_THEN_ELSE
1059 else
1060 {
1061 /* This is a CALL_INSN that doesn't have a SET. */
1068 gen_rtx_IF_THEN_ELSE
1072 }
1077 }
1079 /* If we've reached our jump label, haven't failed, and all
1080 the changes above are valid, we can delete this jump
1081 insn. Also remove a BARRIER after any jump that used
1082 to be unconditional and remove any REG_EQUAL or REG_EQUIV
1083 that might have previously been present on insns we
1084 made conditional. */
1087 {
1098 {
1100 {
1103 }
1106 }
1111 }
1112 else
1113 {
1116 }
1117 }
1118 #endif
1119 /* If branches are expensive, convert
1120 if (foo) bar++; to bar += (foo != 0);
1121 and similarly for "bar--;"
1123 INSN is the conditional branch around the arithmetic. We set:
1125 TEMP is the arithmetic insn.
1126 TEMP1 is the SET doing the arithmetic.
1127 TEMP2 is the operand being incremented or decremented.
1128 TEMP3 to the condition being tested.
1129 TEMP4 to the earliest insn used to find the condition. */
1132 #ifdef HAVE_incscc
1133 || HAVE_incscc
1134 #endif
1135 #ifdef HAVE_decscc
1136 || HAVE_decscc
1137 #endif
1138 )
1139 && ! reload_completed
1151 /* INSN must either branch to the insn after TEMP or the insn
1152 after TEMP must branch to the same place as INSN. */
1158 /* We must be comparing objects whose modes imply the size.
1159 We could handle BLKmode if (1) emit_store_flag could
1160 and (2) we could find the size reliably. */
1163 {
1169 /* It must be the case that TEMP2 is not modified in the range
1170 [TEMP4, INSN). The one exception we make is if the insn
1171 before INSN sets TEMP2 to something which is also unchanged
1172 in that range. In that case, we can move the initialization
1173 into our sequence. */
1183 {
1187 }
1193 VOIDmode,
1197 /* If we can do the store-flag, do the addition or
1198 subtraction. */
1207 {
1208 /* Put the result back in temp2 in case it isn't already.
1209 Then replace the jump, possible a CC0-setting insn in
1210 front of the jump, and TEMP, with the sequence we have
1211 made. */
1226 #ifdef HAVE_cc0
1228 #endif
1232 {
1235 }
1239 }
1240 else
1242 }
1244 /* Try to use a conditional move (if the target has them), or a
1245 store-flag insn. If the target has conditional arithmetic as
1246 well as conditional move, the above code will have done something.
1247 Note that we prefer the above code since it is more general: the
1248 code below can make changes that require work to undo.
1250 The general case here is:
1252 1) x = a; if (...) x = b; and
1253 2) if (...) x = b;
1255 If the jump would be faster, the machine should not have defined
1256 the movcc or scc insns!. These cases are often made by the
1257 previous optimization.
1259 The second case is treated as x = x; if (...) x = b;.
1261 INSN here is the jump around the store. We set:
1263 TEMP to the "x op= b;" insn.
1264 TEMP1 to X.
1265 TEMP2 to B.
1266 TEMP3 to A (X in the second case).
1267 TEMP4 to the condition being tested.
1268 TEMP5 to the earliest insn used to find the condition.
1269 TEMP6 to the SET of TEMP. */
1272 ! reload_completed
1273 #ifdef HAVE_conditional_arithmetic
1274 /* Defer this until after CSE so the above code gets the
1275 first crack at it. */
1276 && cse_not_expected
1277 #endif
1279 /* Set TEMP to the "x = b;" insn. */
1284 && (! SMALL_REGISTER_CLASSES
1288 /* Allow either form, but prefer the former if both apply.
1289 There is no point in using the old value of TEMP1 if
1290 it is a register, since cse will alias them. It can
1291 lose if the old value were a hard register since CSE
1292 won't replace hard registers. Avoid using TEMP3 if
1293 small register classes and it is a hard register. */
1297 /* Make the latter case look like x = x; if (...) x = b; */
1299 /* INSN must either branch to the insn after TEMP or the insn
1300 after TEMP must branch to the same place as INSN. */
1306 /* We must be comparing objects whose modes imply the size.
1307 We could handle BLKmode if (1) emit_store_flag could
1308 and (2) we could find the size reliably. */
1310 /* Even if branches are cheap, the store_flag optimization
1311 can win when the operation to be performed can be
1312 expressed directly. */
1313 #ifdef HAVE_cc0
1314 /* If the previous insn sets CC0 and something else, we can't
1315 do this since we are going to delete that insn. */
1322 #endif
1323 )
1324 {
1325 #ifdef HAVE_conditional_move
1326 /* First try a conditional move. */
1327 {
1333 /* Copy the compared variables into cond0 and cond1, so that
1334 any side effects performed in or after the old comparison,
1335 will not affect our compare which will come later. */
1336 /* ??? Is it possible to just use the comparison in the jump
1337 insn? After all, we're going to delete it. We'd have
1338 to modify emit_conditional_move to take a comparison rtx
1339 instead or write a new function. */
1341 /* We want the target to be able to simplify comparisons with
1342 zero (and maybe other constants as well), so don't create
1343 pseudos for them. There's no need to either. */
1347 else
1350 /* Careful about copying these values -- an IOR or what may
1351 need to do other things, like clobber flags. */
1352 /* ??? Assume for the moment that AVAL is ok. */
1357 /* We're dealing with a single_set insn with no side effects
1358 on SET_SRC. We do need to be reasonably certain that if
1359 we need to force BVAL into a register that we won't
1360 clobber the flags -- general_operand should suffice. */
1363 else
1364 {
1370 }
1379 {
1383 /* Save the conditional move sequence but don't emit it
1384 yet. On some machines, like the alpha, it is possible
1385 that temp5 == insn, so next generate the sequence that
1386 saves the compared values and then emit both
1387 sequences ensuring seq1 occurs before seq2. */
1391 /* "Now that we can't fail..." Famous last words.
1392 Generate the copy insns that preserve the compared
1393 values. */
1401 /* Validate the sequence -- this may be some weird
1402 bit-extract-and-test instruction for which there
1403 exists no complimentary bit-extract insn. */
1407 {
1410 }
1413 {
1416 /* Insert conditional move after insn, to be sure
1417 that the jump and a possible compare won't be
1418 separated. */
1421 /* ??? We can also delete the insn that sets X to A.
1422 Flow will do it too though. */
1428 {
1430 old_max_reg);
1432 }
1436 }
1437 }
1438 else
1440 }
1441 #endif
1443 /* That didn't work, try a store-flag insn.
1445 We further divide the cases into:
1447 1) x = a; if (...) x = b; and either A or B is zero,
1448 2) if (...) x = 0; and jumps are expensive,
1449 3) x = a; if (...) x = b; and A and B are constants where all
1450 the set bits in A are also set in B and jumps are expensive,
1451 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
1452 more expensive, and
1453 5) if (...) x = b; if jumps are even more expensive. */
1456 /* We will be passing this as operand into expand_and. No
1457 good if it's not valid as an operand. */
1460 /* Make the latter case look like
1461 x = x; if (...) x = 0; */
1466 /* If B is zero, OK; if A is zero, can only do (1) if we
1467 can reverse the condition. See if (3) applies possibly
1468 by reversing the condition. Prefer reversing to (4) when
1469 branches are very expensive. */
1473 /* Check that the mask is a power of two,
1474 so that it can probably be generated
1475 with a shift. */
1492 insn)))))
1494 )
1495 {
1499 rtx target;
1501 /* If necessary, reverse the condition. */
1504 else
1507 /* If CVAL is non-zero, normalize to -1. Otherwise, if UVAL
1508 is the constant 1, it is best to just compute the result
1509 directly. If UVAL is constant and STORE_FLAG_VALUE
1510 includes all of its bits, it is best to compute the flag
1511 value unnormalized and `and' it with UVAL. Otherwise,
1512 normalize to -1 and `and' with UVAL. */
1519 /* We will be putting the store-flag insn immediately in
1520 front of the comparison that was originally being done,
1521 so we know all the variables in TEMP4 will be valid.
1522 However, this might be in front of the assignment of
1523 A to VAR. If it is, it would clobber the store-flag
1524 we will be emitting.
1526 Therefore, emit into a temporary which will be copied to
1527 VAR immediately after TEMP. */
1532 VOIDmode,
1535 normalizep);
1537 {
1538 rtx seq;
1544 /* Put the store-flag insns in front of the first insn
1545 used to compute the condition to ensure that we
1546 use the same values of them as the current
1547 comparison. However, the remainder of the insns we
1548 generate will be placed directly in front of the
1549 jump insn, in case any of the pseudos we use
1550 are modified earlier. */
1556 /* Both CVAL and UVAL are non-zero. */
1558 {
1566 else
1567 {
1573 }
1575 /* If we usually make new pseudos, do so here. This
1576 turns out to help machines that have conditional
1577 move insns. */
1578 /* ??? Conditional moves have already been handled.
1579 This may be obsolete. */
1587 }
1589 {
1590 /* We know that either CVAL or UVAL is zero. If
1591 UVAL is zero, negate TARGET and `and' with CVAL.
1592 Otherwise, `and' with UVAL. */
1594 {
1598 }
1604 }
1609 #ifdef HAVE_cc0
1610 /* If INSN uses CC0, we must not separate it from the
1611 insn that sets cc0. */
1614 #endif
1622 {
1625 }
1629 }
1630 else
1632 }
1633 }
1636 /* Simplify if (...) x = 1; else {...} if (x) ...
1637 We recognize this case scanning backwards as well.
1639 TEMP is the assignment to x;
1640 TEMP1 is the label at the head of the second if. */
1641 /* ?? This should call get_condition to find the values being
1642 compared, instead of looking for a COMPARE insn when HAVE_cc0
1643 is not defined. This would allow it to work on the m88k. */
1644 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1645 is not defined and the condition is tested by a separate compare
1646 insn. This is because the code below assumes that the result
1647 of the compare dies in the following branch.
1649 Not only that, but there might be other insns between the
1650 compare and branch whose results are live. Those insns need
1651 to be executed.
1653 A way to fix this is to move the insns at JUMP_LABEL (insn)
1654 to before INSN. If we are running before flow, they will
1655 be deleted if they aren't needed. But this doesn't work
1656 well after flow.
1658 This is really a special-case of jump threading, anyway. The
1659 right thing to do is to replace this and jump threading with
1660 much simpler code in cse.
1662 This code has been turned off in the non-cc0 case in the
1663 meantime. */
1665 #ifdef HAVE_cc0
1667 /* Safe to skip USE and CLOBBER insns here
1668 since they will not be deleted. */
1676 /* If we find that the next value tested is `x'
1677 (TEMP1 is the insn where this happens), win. */
1680 #ifdef HAVE_cc0
1681 /* Does temp1 `tst' the value of x? */
1685 #else
1686 /* Does temp1 compare the value of x against zero? */
1693 #endif
1695 {
1696 /* Get the if_then_else from the condjump. */
1699 {
1702 rtx cond
1705 rtx ultimate;
1711 else
1721 }
1722 }
1723 #endif
1725 #if 0
1726 /* @@ This needs a bit of work before it will be right.
1728 Any type of comparison can be accepted for the first and
1729 second compare. When rewriting the first jump, we must
1730 compute the what conditions can reach label3, and use the
1731 appropriate code. We can not simply reverse/swap the code
1732 of the first jump. In some cases, the second jump must be
1733 rewritten also.
1735 For example,
1736 < == converts to > ==
1737 < != converts to == >
1738 etc.
1740 If the code is written to only accept an '==' test for the second
1741 compare, then all that needs to be done is to swap the condition
1742 of the first branch.
1744 It is questionable whether we want this optimization anyways,
1745 since if the user wrote code like this because he/she knew that
1746 the jump to label1 is taken most of the time, then rewriting
1747 this gives slower code. */
1748 /* @@ This should call get_condition to find the values being
1749 compared, instead of looking for a COMPARE insn when HAVE_cc0
1750 is not defined. This would allow it to work on the m88k. */
1751 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1752 is not defined and the condition is tested by a separate compare
1753 insn. This is because the code below assumes that the result
1754 of the compare dies in the following branch. */
1756 /* Simplify test a ~= b
1757 condjump label1;
1758 test a == b
1759 condjump label2;
1760 jump label3;
1761 label1:
1763 rewriting as
1764 test a ~~= b
1765 condjump label3
1766 test a == b
1767 condjump label2
1768 label1:
1770 where ~= is an inequality, e.g. >, and ~~= is the swapped
1771 inequality, e.g. <.
1773 We recognize this case scanning backwards.
1775 TEMP is the conditional jump to `label2';
1776 TEMP1 is the test for `a == b';
1777 TEMP2 is the conditional jump to `label1';
1778 TEMP3 is the test for `a ~= b'. */
1787 #ifdef HAVE_cc0
1789 #else
1793 #endif
1807 {
1812 {
1815 }
1819 }
1820 #endif
1821 /* Simplify if (...) {... x = 1;} if (x) ...
1823 We recognize this case backwards.
1825 TEMP is the test of `x';
1826 TEMP1 is the assignment to `x' at the end of the
1827 previous statement. */
1828 /* @@ This should call get_condition to find the values being
1829 compared, instead of looking for a COMPARE insn when HAVE_cc0
1830 is not defined. This would allow it to work on the m88k. */
1831 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1832 is not defined and the condition is tested by a separate compare
1833 insn. This is because the code below assumes that the result
1834 of the compare dies in the following branch. */
1836 /* ??? This has to be turned off. The problem is that the
1837 unconditional jump might indirectly end up branching to the
1838 label between TEMP1 and TEMP. We can't detect this, in general,
1839 since it may become a jump to there after further optimizations.
1840 If that jump is done, it will be deleted, so we will retry
1841 this optimization in the next pass, thus an infinite loop.
1843 The present code prevents this by putting the jump after the
1844 label, but this is not logically correct. */
1845 #if 0
1847 /* Safe to skip USE and CLOBBER insns here
1848 since they will not be deleted. */
1853 #ifdef HAVE_cc0
1856 #else
1857 /* Temp must be a compare insn, we can not accept a register
1858 to register move here, since it may not be simply a
1859 tst insn. */
1865 #endif
1866 /* May skip USE or CLOBBER insns here
1867 for checking for opportunity, since we
1868 take care of them later. */
1872 #ifdef HAVE_cc0
1874 #else
1877 #endif
1879 /* If this isn't true, cse will do the job. */
1881 {
1882 /* Get the if_then_else from the condjump. */
1887 {
1889 rtx last_insn;
1890 rtx ultimate;
1891 rtx p;
1893 /* Get the place that condjump will jump to
1894 if it is reached from here. */
1898 else
1900 /* Get it as a CODE_LABEL. */
1903 else
1904 /* Get the label out of the LABEL_REF. */
1907 /* Insert the jump immediately before TEMP, specifically
1908 after the label that is between TEMP1 and TEMP. */
1911 /* If we would be branching to the next insn, the jump
1912 would immediately be deleted and the re-inserted in
1913 a subsequent pass over the code. So don't do anything
1914 in that case. */
1917 {
1920 last_insn);
1925 {
1929 }
1932 }
1933 }
1934 }
1935 #endif
1936 #ifdef HAVE_trap
1937 /* Detect a conditional jump jumping over an unconditional trap. */
1948 {
1954 {
1960 }
1961 }
1962 /* Detect a jump jumping to an unconditional trap. */
1967 && (this_is_simplejump
1969 {
1974 {
1976 /* Replace an unconditional jump to a trap with a trap. */
1978 {
1983 }
1988 {
1993 }
1994 }
1995 /* If the trap condition and jump condition are mutually
1996 exclusive, redirect the jump to the following insn. */
1998 && ! this_is_simplejump
2003 {
2006 }
2007 }
2008 #endif
2009 else
2010 {
2011 /* Detect a jump to a jump. */
2013 /* Look for if (foo) bar; else break; */
2014 /* The insns look like this:
2015 insn = condjump label1;
2016 ...range1 (some insns)...
2017 jump label2;
2018 label1:
2019 ...range2 (some insns)...
2020 jump somewhere unconditionally
2021 label2: */
2022 {
2025 /* Don't do this optimization on the first round, so that
2026 jump-around-a-jump gets simplified before we ask here
2027 whether a jump is unconditional.
2029 Also don't do it when we are called after reload since
2030 it will confuse reorg. */
2033 /* Make sure INSN is something we can invert. */
2040 {
2047 /* Invert the jump condition, so we
2048 still execute the same insns in each case. */
2050 {
2055 rtx rangenext;
2057 /* Include in each range any notes before it, to be
2058 sure that we get the line number note if any, even
2059 if there are other notes here. */
2068 /* Don't move NOTEs for blocks or loops; shift them
2069 outside the ranges, where they'll stay put. */
2073 /* Get current surrounds of the 2 ranges. */
2079 /* Splice range2 where range1 was. */
2084 /* Splice range1 where range2 was. */
2090 /* Check for loop notes between the end of
2091 range2, and the next code label. If there is one,
2092 then what we have really seen is
2093 if (foo) break; end_of_loop;
2094 and moved the break sequence outside the loop.
2095 We must move LOOP_END, LOOP_VTOP and LOOP_CONT
2096 notes (in order) to where the loop really ends now,
2097 or we will confuse loop optimization. Stop if we
2098 find a LOOP_BEG note first, since we don't want to
2099 move the notes in that case. */
2101 {
2104 {
2109 {
2120 }
2124 }
2125 }
2128 }
2129 }
2130 }
2132 /* Now that the jump has been tensioned,
2133 try cross jumping: check for identical code
2134 before the jump and before its target label. */
2136 /* First, cross jumping of conditional jumps: */
2139 {
2143 /* A conditional jump may be crossjumped
2144 only if the place it jumps to follows
2145 an opposing jump that comes back here. */
2148 /* We have no opposing jump;
2149 cannot cross jump this insn. */
2153 /* TARGET is nonzero if it is ok to cross jump
2154 to code before TARGET. If so, see if matches. */
2160 {
2162 /* Make the old conditional jump
2163 into an unconditional one. */
2168 /* Add to jump_chain unless this is a new label
2169 whose UID is too large. */
2171 {
2175 }
2178 }
2179 }
2181 /* Cross jumping of unconditional jumps:
2182 a few differences. */
2185 {
2187 rtx target;
2191 /* TARGET is nonzero if it is ok to cross jump
2192 to code before TARGET. If so, see if matches. */
2196 /* If cannot cross jump to code before the label,
2197 see if we can cross jump to another jump to
2198 the same label. */
2199 /* Try each other jump to this label. */
2206 /* Ignore TARGET if it's deleted. */
2212 {
2216 }
2217 }
2219 /* This code was dead in the previous jump.c! */
2221 {
2222 /* Return insns all "jump to the same place"
2223 so we can cross-jump between any two of them. */
2229 /* If cannot cross jump to code before the label,
2230 see if we can cross jump to another jump to
2231 the same label. */
2232 /* Try each other jump to this label. */
2243 {
2247 }
2248 }
2249 }
2250 }
2253 }
2255 /* Delete extraneous line number notes.
2256 Note that two consecutive notes for different lines are not really
2257 extraneous. There should be some indication where that line belonged,
2258 even if it became empty. */
2260 {
2265 {
2266 /* Delete this note if it is identical to previous note. */
2270 {
2273 }
2276 }
2277 }
2279 #ifdef HAVE_return
2281 {
2282 /* If we fall through to the epilogue, see if we can insert a RETURN insn
2283 in front of it. If the machine allows it at this point (we might be
2284 after reload for a leaf routine), it will improve optimization for it
2285 to be there. We do this both here and at the start of this pass since
2286 the RETURN might have been deleted by some of our optimizations. */
2292 {
2295 }
2296 }
2297 #endif
2299 /* CAN_REACH_END is persistent for each function. Once set it should
2300 not be cleared. This is especially true for the case where we
2301 delete the NOTE_FUNCTION_END note. CAN_REACH_END is cleared by
2302 the front-end before compiling each function. */
2306 end:
2307 /* Clean up. */
2310 }
2311 \f
2312 /* Initialize LABEL_NUSES and JUMP_LABEL fields. Delete any REG_LABEL
2313 notes whose labels don't occur in the insn any more. Returns the
2314 largest INSN_UID found. */
2315 static int
2317 rtx f;
2318 {
2320 rtx insn;
2323 {
2329 {
2333 {
2338 }
2339 }
2342 }
2345 }
2347 /* Delete insns following barriers, up to next label.
2349 Also delete no-op jumps created by gcse. */
2350 static void
2352 rtx f;
2353 {
2354 rtx insn;
2357 {
2359 {
2365 {
2369 else
2371 }
2372 /* INSN is now the code_label. */
2373 }
2374 /* Also remove (set (pc) (pc)) insns which can be created by
2375 gcse. We eliminate such insns now to avoid having them
2376 cause problems later. */
2383 else
2385 }
2386 }
2388 /* Mark the label each jump jumps to.
2389 Combine consecutive labels, and count uses of labels.
2391 For each label, make a chain (using `jump_chain')
2392 of all the *unconditional* jumps that jump to it;
2393 also make a chain of all returns.
2395 CROSS_JUMP indicates whether we are doing cross jumping
2396 and if we are whether we will be paying attention to
2397 death notes or not. */
2399 static void
2401 rtx f;
2403 {
2404 rtx insn;
2408 {
2411 {
2413 {
2417 }
2419 {
2422 }
2423 }
2424 }
2425 }
2427 /* Delete all labels already not referenced.
2428 Also find and return the last insn. */
2430 static rtx
2432 rtx f;
2433 {
2435 rtx insn;
2438 {
2443 else
2444 {
2447 }
2448 }
2451 }
2453 /* Delete various simple forms of moves which have no necessary
2454 side effect. */
2456 static void
2458 rtx f;
2459 {
2463 {
2467 {
2470 /* Combine stack_adjusts with following push_insns. */
2471 #ifdef PUSH_ROUNDING
2478 {
2479 rtx p;
2485 /* Find all successive push insns. */
2487 /* Don't convert more than three pushes;
2488 that starts adding too many displaced addresses
2489 and the whole thing starts becoming a losing
2490 proposition. */
2492 {
2501 /* Allow a no-op move between the adjust and the push. */
2510 pushes++;
2515 }
2517 /* Discard the amount pushed from the stack adjust;
2518 maybe eliminate it entirely. */
2520 {
2523 }
2524 else
2528 /* Change the appropriate push insns to ordinary stores. */
2531 {
2540 /* Allow a no-op move between the adjust and the push. */
2550 /* If this push doesn't fully fit in the space
2551 of the stack adjust that we deleted,
2552 make another stack adjust here for what we
2553 didn't use up. There should be peepholes
2554 to recognize the resulting sequence of insns. */
2556 {
2559 p);
2561 }
2564 }
2565 }
2566 #endif
2568 /* Detect and delete no-op move instructions
2569 resulting from not allocating a parameter in a register. */
2582 /* Detect and ignore no-op move instructions
2583 resulting from smart or fortuitous register allocation. */
2586 {
2593 {
2594 rtx trial;
2601 {
2602 /* DREG may have been the target of a REG_DEAD note in
2603 the insn which makes INSN redundant. If so, reorg
2604 would still think it is dead. So search for such a
2605 note and delete it if we find it. */
2611 {
2614 }
2616 /* Deleting insn could lose a death-note for SREG. */
2618 {
2619 /* Change this into a USE so that we won't emit
2620 code for it, but still can keep the note. */
2624 /* Remove all reg notes but the REG_DEAD one. */
2627 }
2628 else
2630 }
2631 }
2636 {
2637 /* This handles the case where we have two consecutive
2638 assignments of the same constant to pseudos that didn't
2639 get a hard reg. Each SET from the constant will be
2640 converted into a SET of the spill register and an
2641 output reload will be made following it. This produces
2642 two loads of the same constant into the same spill
2643 register. */
2647 /* Look back for a death note for the first reg.
2648 If there is one, it is no longer accurate. */
2650 {
2654 {
2657 }
2659 }
2661 /* Delete the second load of the value. */
2663 }
2664 }
2666 {
2667 /* If each part is a set between two identical registers or
2668 a USE or CLOBBER, delete the insn. */
2670 rtx tem;
2673 {
2683 }
2687 }
2688 /* Also delete insns to store bit fields if they are no-ops. */
2689 /* Not worth the hair to detect this in the big-endian case. */
2698 }
2700 }
2701 }
2703 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
2704 If so indicate that this function can drop off the end by returning
2705 1, else return 0.
2707 CHECK_DELETED indicates whether we must check if the note being
2708 searched for has the deleted flag set.
2710 DELETE_FINAL_NOTE indicates whether we should delete the note
2711 if we find it. */
2713 static int
2715 rtx last;
2718 {
2723 {
2726 /* One label can follow the end-note: the return label. */
2729 /* Ordinary insns can follow it if returning a structure. */
2732 /* If machine uses explicit RETURN insns, no epilogue,
2733 then one of them follows the note. */
2737 /* A barrier can follow the return insn. */
2740 /* Other kinds of notes can follow also. */
2749 }
2751 /* See if we backed up to the appropriate type of note. */
2757 {
2761 }
2764 }
2766 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
2767 jump. Assume that this unconditional jump is to the exit test code. If
2768 the code is sufficiently simple, make a copy of it before INSN,
2769 followed by a jump to the exit of the loop. Then delete the unconditional
2770 jump after INSN.
2772 Return 1 if we made the change, else 0.
2774 This is only safe immediately after a regscan pass because it uses the
2775 values of regno_first_uid and regno_last_uid. */
2777 static int
2779 rtx loop_start;
2780 {
2785 rtx lastexit;
2789 /* Scan the exit code. We do not perform this optimization if any insn:
2791 is a CALL_INSN
2792 is a CODE_LABEL
2793 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
2794 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
2795 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
2796 is not valid.
2798 We also do not do this if we find an insn with ASM_OPERANDS. While
2799 this restriction should not be necessary, copying an insn with
2800 ASM_OPERANDS can confuse asm_noperands in some cases.
2802 Also, don't do this if the exit code is more than 20 insns. */
2805 insn
2809 {
2811 {
2816 /* We could be in front of the wrong NOTE_INSN_LOOP_END if there is
2817 a jump immediately after the loop start that branches outside
2818 the loop but within an outer loop, near the exit test.
2819 If we copied this exit test and created a phony
2820 NOTE_INSN_LOOP_VTOP, this could make instructions immediately
2821 before the exit test look like these could be safely moved
2822 out of the loop even if they actually may be never executed.
2823 This can be avoided by checking here for NOTE_INSN_LOOP_CONT. */
2832 /* If we were to duplicate this code, we would not move
2833 the BLOCK notes, and so debugging the moved code would
2834 be difficult. Thus, we only move the code with -O2 or
2835 higher. */
2841 /* The code below would grossly mishandle REG_WAS_0 notes,
2842 so get rid of them here. */
2852 }
2853 }
2855 /* Unless INSN is zero, we can do the optimization. */
2861 /* See if any insn sets a register only used in the loop exit code and
2862 not a user variable. If so, replace it with a new register. */
2871 {
2877 {
2878 /* We can do the replacement. Allocate reg_map if this is the
2879 first replacement we found. */
2886 }
2887 }
2889 /* Now copy each insn. */
2891 {
2893 {
2898 /* Only copy line-number notes. */
2900 {
2903 }
2913 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
2914 make them. */
2931 {
2935 }
2937 /* If this is a simple jump, add it to the jump chain. */
2941 {
2945 }
2950 }
2952 /* Record the first insn we copied. We need it so that we can
2953 scan the copied insns for new pseudo registers. */
2956 }
2958 /* Now clean up by emitting a jump to the end label and deleting the jump
2959 at the start of the loop. */
2961 {
2963 loop_start);
2965 /* Record the first insn we copied. We need it so that we can
2966 scan the copied insns for new pseudo registers. This may not
2967 be strictly necessary since we should have copied at least one
2968 insn above. But I am going to be safe. */
2975 {
2979 }
2981 }
2983 /* Now scan from the first insn we copied to the last insn we copied
2984 (copy) for new pseudo registers. Do this after the code to jump to
2985 the end label since that might create a new pseudo too. */
2988 /* Mark the exit code as the virtual top of the converted loop. */
2993 /* Clean up. */
2998 }
2999 \f
3000 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
3001 loop-end notes between START and END out before START. Assume that
3002 END is not such a note. START may be such a note. Returns the value
3003 of the new starting insn, which may be different if the original start
3004 was such a note. */
3006 rtx
3009 {
3010 rtx insn;
3011 rtx next;
3014 {
3023 {
3026 else
3027 {
3035 }
3036 }
3037 }
3040 }
3041 \f
3042 /* Compare the instructions before insn E1 with those before E2
3043 to find an opportunity for cross jumping.
3044 (This means detecting identical sequences of insns followed by
3045 jumps to the same place, or followed by a label and a jump
3046 to that label, and replacing one with a jump to the other.)
3048 Assume E1 is a jump that jumps to label E2
3049 (that is not always true but it might as well be).
3050 Find the longest possible equivalent sequences
3051 and store the first insns of those sequences into *F1 and *F2.
3052 Store zero there if no equivalent preceding instructions are found.
3054 We give up if we find a label in stream 1.
3055 Actually we could transfer that label into stream 2. */
3057 static void
3062 {
3074 {
3084 /* Don't allow the range of insns preceding E1 or E2
3085 to include the other (E2 or E1). */
3089 /* If we will get to this code by jumping, those jumps will be
3090 tensioned to go directly to the new label (before I2),
3091 so this cross-jumping won't cost extra. So reduce the minimum. */
3093 {
3096 }
3101 /* Avoid moving insns across EH regions if either of the insns
3102 can throw. */
3111 /* If this is a CALL_INSN, compare register usage information.
3112 If we don't check this on stack register machines, the two
3113 CALL_INSNs might be merged leaving reg-stack.c with mismatching
3114 numbers of stack registers in the same basic block.
3115 If we don't check this on machines with delay slots, a delay slot may
3116 be filled that clobbers a parameter expected by the subroutine.
3118 ??? We take the simple route for now and assume that if they're
3119 equal, they were constructed identically. */
3126 #ifdef STACK_REGS
3127 /* If cross_jump_death_matters is not 0, the insn's mode
3128 indicates whether or not the insn contains any stack-like
3129 regs. */
3132 {
3133 /* If register stack conversion has already been done, then
3134 death notes must also be compared before it is certain that
3135 the two instruction streams match. */
3137 rtx note;
3157 done:
3158 ;
3159 }
3160 #endif
3162 /* Don't allow old-style asm or volatile extended asms to be accepted
3163 for cross jumping purposes. It is conceptually correct to allow
3164 them, since cross-jumping preserves the dynamic instruction order
3165 even though it is changing the static instruction order. However,
3166 if an asm is being used to emit an assembler pseudo-op, such as
3167 the MIPS `.set reorder' pseudo-op, then the static instruction order
3168 matters and it must be preserved. */
3176 {
3177 /* The following code helps take care of G++ cleanups. */
3178 rtx equiv1;
3179 rtx equiv2;
3186 /* If the equivalences are not to a constant, they may
3187 reference pseudos that no longer exist, so we can't
3188 use them. */
3191 {
3196 {
3203 }
3204 }
3206 /* Insns fail to match; cross jumping is limited to the following
3207 insns. */
3209 #ifdef HAVE_cc0
3210 /* Don't allow the insn after a compare to be shared by
3211 cross-jumping unless the compare is also shared.
3212 Here, if either of these non-matching insns is a compare,
3213 exclude the following insn from possible cross-jumping. */
3216 #endif
3218 /* If cross-jumping here will feed a jump-around-jump
3219 optimization, this jump won't cost extra, so reduce
3220 the minimum. */
3226 }
3228 win:
3230 {
3231 /* Ok, this insn is potentially includable in a cross-jump here. */
3234 }
3235 }
3239 }
3241 static void
3244 {
3245 /* Find an existing label at this point
3246 or make a new one if there is none. */
3249 /* Make the same jump insn jump to the new point. */
3251 {
3252 /* Remove from jump chain of returns. */
3254 /* Change the insn. */
3259 /* Add to new the jump chain. */
3262 {
3265 }
3266 }
3267 else
3270 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
3271 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
3272 the NEWJPOS stream. */
3275 {
3276 rtx lnote;
3288 }
3289 }
3290 \f
3291 /* Return the label before INSN, or put a new label there. */
3293 rtx
3295 rtx insn;
3296 {
3297 rtx label;
3299 /* Find an existing label at this point
3300 or make a new one if there is none. */
3304 {
3310 }
3312 }
3314 /* Return the label after INSN, or put a new label there. */
3316 rtx
3318 rtx insn;
3319 {
3320 rtx label;
3322 /* Find an existing label at this point
3323 or make a new one if there is none. */
3327 {
3331 }
3333 }
3334 \f
3335 /* Return 1 if INSN is a jump that jumps to right after TARGET
3336 only on the condition that TARGET itself would drop through.
3337 Assumes that TARGET is a conditional jump. */
3339 static int
3342 {
3358 {
3362 }
3365 {
3369 }
3374 }
3375 \f
3376 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
3377 return non-zero if it is safe to reverse this comparison. It is if our
3378 floating-point is not IEEE, if this is an NE or EQ comparison, or if
3379 this is known to be an integer comparison. */
3381 int
3383 rtx comparison;
3384 rtx insn;
3385 {
3386 rtx arg0;
3388 /* If this is not actually a comparison, we can't reverse it. */
3393 /* If this is an NE comparison, it is safe to reverse it to an EQ
3394 comparison and vice versa, even for floating point. If no operands
3395 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
3396 always false and NE is always true, so the reversal is also valid. */
3397 || flag_fast_math
3404 /* Make sure ARG0 is one of the actual objects being compared. If we
3405 can't do this, we can't be sure the comparison can be reversed.
3407 Handle cc0 and a MODE_CC register. */
3409 #ifdef HAVE_cc0
3411 #endif
3412 )
3413 {
3415 rtx set;
3417 /* First see if the condition code mode alone if enough to say we can
3418 reverse the condition. If not, then search backwards for a set of
3419 ARG0. We do not need to check for an insn clobbering it since valid
3420 code will contain set a set with no intervening clobber. But
3421 stop when we reach a label. */
3422 #ifdef REVERSIBLE_CC_MODE
3426 #endif
3433 {
3439 }
3440 }
3442 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
3443 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
3448 }
3450 /* Given an rtx-code for a comparison, return the code
3451 for the negated comparison.
3452 WATCH OUT! reverse_condition is not safe to use on a jump
3453 that might be acting on the results of an IEEE floating point comparison,
3454 because of the special treatment of non-signaling nans in comparisons.
3455 Use can_reverse_comparison_p to be sure. */
3457 enum rtx_code
3460 {
3462 {
3496 }
3497 }
3499 /* Similar, but return the code when two operands of a comparison are swapped.
3500 This IS safe for IEEE floating-point. */
3502 enum rtx_code
3505 {
3507 {
3539 }
3540 }
3542 /* Given a comparison CODE, return the corresponding unsigned comparison.
3543 If CODE is an equality comparison or already an unsigned comparison,
3544 CODE is returned. */
3546 enum rtx_code
3549 {
3551 {
3574 }
3575 }
3577 /* Similarly, return the signed version of a comparison. */
3579 enum rtx_code
3582 {
3584 {
3607 }
3608 }
3609 \f
3610 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
3611 truth of CODE1 implies the truth of CODE2. */
3613 int
3616 {
3621 {
3649 }
3652 }
3653 \f
3654 /* Return 1 if INSN is an unconditional jump and nothing else. */
3656 int
3658 rtx insn;
3659 {
3664 }
3666 /* Return nonzero if INSN is a (possibly) conditional jump
3667 and nothing more. */
3669 int
3671 rtx insn;
3672 {
3691 }
3693 /* Return nonzero if INSN is a (possibly) conditional jump inside a
3694 PARALLEL. */
3696 int
3698 rtx insn;
3699 {
3704 else
3724 }
3726 /* Return the label of a conditional jump. */
3728 rtx
3730 rtx insn;
3731 {
3750 }
3752 /* Return true if INSN is a (possibly conditional) return insn. */
3754 static int
3758 {
3761 }
3763 int
3765 rtx insn;
3766 {
3768 }
3770 /* Return true if INSN is a jump that only transfers control and
3771 nothing more. */
3773 int
3775 rtx insn;
3776 {
3777 rtx set;
3791 }
3793 #ifdef HAVE_cc0
3795 /* Return 1 if X is an RTX that does nothing but set the condition codes
3796 and CLOBBER or USE registers.
3797 Return -1 if X does explicitly set the condition codes,
3798 but also does other things. */
3800 int
3802 rtx x ATTRIBUTE_UNUSED;
3803 {
3807 {
3812 {
3818 }
3820 }
3822 }
3823 #endif
3824 \f
3825 /* Follow any unconditional jump at LABEL;
3826 return the ultimate label reached by any such chain of jumps.
3827 If LABEL is not followed by a jump, return LABEL.
3828 If the chain loops or we can't find end, return LABEL,
3829 since that tells caller to avoid changing the insn.
3831 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
3832 a USE or CLOBBER. */
3834 rtx
3836 rtx label;
3837 {
3851 depth++)
3852 {
3853 /* Don't chain through the insn that jumps into a loop
3854 from outside the loop,
3855 since that would create multiple loop entry jumps
3856 and prevent loop optimization. */
3857 rtx tem;
3862 /* ??? Optional. Disables some optimizations, but makes
3863 gcov output more accurate with -O. */
3867 /* If we have found a cycle, make the insn jump to itself. */
3877 }
3881 }
3883 /* Assuming that field IDX of X is a vector of label_refs,
3884 replace each of them by the ultimate label reached by it.
3885 Return nonzero if a change is made.
3886 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
3888 static int
3892 {
3896 {
3900 {
3906 }
3907 }
3909 }
3910 \f
3911 /* Find all CODE_LABELs referred to in X, and increment their use counts.
3912 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
3913 in INSN, then store one of them in JUMP_LABEL (INSN).
3914 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
3915 referenced in INSN, add a REG_LABEL note containing that label to INSN.
3916 Also, when there are consecutive labels, canonicalize on the last of them.
3918 Note that two labels separated by a loop-beginning note
3919 must be kept distinct if we have not yet done loop-optimization,
3920 because the gap between them is where loop-optimize
3921 will want to move invariant code to. CROSS_JUMP tells us
3922 that loop-optimization is done with.
3924 Once reload has completed (CROSS_JUMP non-zero), we need not consider
3925 two labels distinct if they are separated by only USE or CLOBBER insns. */
3927 static void
3930 rtx insn;
3932 {
3938 {
3951 /* If this is a constant-pool reference, see if it is a label. */
3958 {
3961 rtx note;
3962 rtx next;
3967 /* Ignore references to labels of containing functions. */
3971 /* If there are other labels following this one,
3972 replace it with the last of the consecutive labels. */
3974 {
3986 /* ??? Optional. Disables some optimizations, but
3987 makes gcov output more accurate with -O. */
3990 }
3997 {
4001 /* If we've changed OLABEL and we had a REG_LABEL note
4002 for it, update it as well. */
4007 /* Otherwise, add a REG_LABEL note for LABEL unless there already
4008 is one. */
4010 {
4011 /* This code used to ignore labels which refered to dispatch
4012 tables to avoid flow.c generating worse code.
4014 However, in the presense of global optimizations like
4015 gcse which call find_basic_blocks without calling
4016 life_analysis, not recording such labels will lead
4017 to compiler aborts because of inconsistencies in the
4018 flow graph. So we go ahead and record the label.
4020 It may also be the case that the optimization argument
4021 is no longer valid because of the more accurate cfg
4022 we build in find_basic_blocks -- it no longer pessimizes
4023 code when it finds a REG_LABEL note. */
4026 }
4027 }
4029 }
4031 /* Do walk the labels in a vector, but not the first operand of an
4032 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
4036 {
4041 }
4046 }
4050 {
4054 {
4058 }
4059 }
4060 }
4062 /* If all INSN does is set the pc, delete it,
4063 and delete the insn that set the condition codes for it
4064 if that's what the previous thing was. */
4066 void
4068 rtx insn;
4069 {
4074 }
4076 /* Verify INSN is a BARRIER and delete it. */
4078 void
4080 rtx insn;
4081 {
4086 }
4088 /* Recursively delete prior insns that compute the value (used only by INSN
4089 which the caller is deleting) stored in the register mentioned by NOTE
4090 which is a REG_DEAD note associated with INSN. */
4092 static void
4094 rtx note;
4095 rtx insn;
4096 {
4097 rtx our_prev;
4104 {
4107 /* If we reach a CALL which is not calling a const function
4108 or the callee pops the arguments, then give up. */
4114 /* If we reach a SEQUENCE, it is too complex to try to
4115 do anything with it, so give up. */
4121 /* reorg creates USEs that look like this. We leave them
4122 alone because reorg needs them for its own purposes. */
4126 {
4131 {
4132 /* If we find a SET of something else, we can't
4133 delete the insn. */
4138 {
4144 }
4148 }
4151 {
4153 int dest_endregno
4165 /* We may have a multi-word hard register and some, but not
4166 all, of the words of the register are needed in subsequent
4167 insns. Write REG_UNUSED notes for those parts that were not
4168 needed. */
4171 {
4183 }
4184 }
4187 }
4189 /* If PAT references the register that dies here, it is an
4190 additional use. Hence any prior SET isn't dead. However, this
4191 insn becomes the new place for the REG_DEAD note. */
4193 {
4197 }
4198 }
4199 }
4201 /* Delete INSN and recursively delete insns that compute values used only
4202 by INSN. This uses the REG_DEAD notes computed during flow analysis.
4203 If we are running before flow.c, we need do nothing since flow.c will
4204 delete dead code. We also can't know if the registers being used are
4205 dead or not at this point.
4207 Otherwise, look at all our REG_DEAD notes. If a previous insn does
4208 nothing other than set a register that dies in this insn, we can delete
4209 that insn as well.
4211 On machines with CC0, if CC0 is used in this insn, we may be able to
4212 delete the insn that set it. */
4214 static void
4216 rtx insn;
4217 {
4219 rtx set;
4221 #ifdef HAVE_cc0
4223 {
4225 /* We assume that at this stage
4226 CC's are always set explicitly
4227 and always immediately before the jump that
4228 will use them. So if the previous insn
4229 exists to set the CC's, delete it
4230 (unless it performs auto-increments, etc.). */
4233 {
4237 else
4238 /* Otherwise, show that cc0 won't be used. */
4241 }
4242 }
4243 #endif
4245 #ifdef INSN_SCHEDULING
4246 /* ?!? The schedulers do not keep REG_DEAD notes accurate after
4247 reload has completed. The schedulers need to be fixed. Until
4248 they are, we must not rely on the death notes here. */
4250 {
4253 }
4254 #endif
4256 /* The REG_DEAD note may have been omitted for a register
4257 which is both set and used by the insn. */
4260 {
4262 int dest_endregno
4269 {
4278 }
4279 }
4282 {
4286 /* Verify that the REG_NOTE is legitimate. */
4291 }
4294 }
4295 \f
4296 /* Delete insn INSN from the chain of insns and update label ref counts.
4297 May delete some following insns as a consequence; may even delete
4298 a label elsewhere and insns that follow it.
4300 Returns the first insn after INSN that was not deleted. */
4302 rtx
4305 {
4314 /* This insn is already deleted => return first following nondeleted. */
4321 /* Don't delete user-declared labels. Convert them to special NOTEs
4322 instead. */
4325 {
4330 }
4331 else
4332 /* Mark this insn as deleted. */
4335 /* If this is an unconditional jump, delete it from the jump chain. */
4339 /* If instruction is followed by a barrier,
4340 delete the barrier too. */
4343 {
4346 }
4348 /* Patch out INSN (and the barrier if any) */
4351 {
4353 {
4358 }
4361 {
4365 }
4369 }
4371 /* If deleting a jump, decrement the count of the label,
4372 and delete the label if it is now unused. */
4375 {
4379 {
4380 /* This can delete NEXT or PREV,
4381 either directly if NEXT is JUMP_LABEL (INSN),
4382 or indirectly through more levels of jumps. */
4385 /* I feel a little doubtful about this loop,
4386 but I see no clean and sure alternative way
4387 to find the first insn after INSN that is not now deleted.
4388 I hope this works. */
4392 }
4397 {
4398 /* If we're deleting the tablejump, delete the dispatch table.
4399 We may not be able to kill the label immediately preceeding
4400 just yet, as it might be referenced in code leading up to
4401 the tablejump. */
4403 }
4404 }
4406 /* Likewise if we're deleting a dispatch table. */
4411 {
4422 }
4427 /* If INSN was a label and a dispatch table follows it,
4428 delete the dispatch table. The tablejump must have gone already.
4429 It isn't useful to fall through into a table. */
4438 /* If INSN was a label, delete insns following it if now unreachable. */
4441 {
4447 {
4451 /* Keep going past other deleted labels to delete what follows. */
4454 else
4455 /* Note: if this deletes a jump, it can cause more
4456 deletion of unreachable code, after a different label.
4457 As long as the value from this recursive call is correct,
4458 this invocation functions correctly. */
4460 }
4461 }
4464 }
4466 /* Advance from INSN till reaching something not deleted
4467 then return that. May return INSN itself. */
4469 rtx
4471 rtx insn;
4472 {
4476 }
4477 \f
4478 /* Delete a range of insns from FROM to TO, inclusive.
4479 This is for the sake of peephole optimization, so assume
4480 that whatever these insns do will still be done by a new
4481 peephole insn that will replace them. */
4483 void
4486 {
4490 {
4495 {
4498 /* Patch this insn out of the chain. */
4499 /* We don't do this all at once, because we
4500 must preserve all NOTEs. */
4506 }
4511 }
4513 /* Note that if TO is an unconditional jump
4514 we *do not* delete the BARRIER that follows,
4515 since the peephole that replaces this sequence
4516 is also an unconditional jump in that case. */
4517 }
4518 \f
4519 /* We have determined that INSN is never reached, and are about to
4520 delete it. Print a warning if the user asked for one.
4522 To try to make this warning more useful, this should only be called
4523 once per basic block not reached, and it only warns when the basic
4524 block contains more than one line from the current function, and
4525 contains at least one operation. CSE and inlining can duplicate insns,
4526 so it's possible to get spurious warnings from this. */
4528 void
4530 rtx avoided_insn;
4531 {
4532 rtx insn;
4540 /* Scan forwards, looking at LINE_NUMBER notes, until
4541 we hit a LABEL or we run out of insns. */
4544 {
4549 {
4552 else
4555 }
4558 }
4563 }
4564 \f
4565 /* Invert the condition of the jump JUMP, and make it jump
4566 to label NLABEL instead of where it jumps now. */
4568 int
4571 {
4572 /* We have to either invert the condition and change the label or
4573 do neither. Either operation could fail. We first try to invert
4574 the jump. If that succeeds, we try changing the label. If that fails,
4575 we invert the jump back to what it was. */
4581 {
4583 {
4586 /* An inverted jump means that a probability taken becomes a
4587 probability not taken. Subtract the branch probability from the
4588 probability base to convert it back to a taken probability.
4589 (We don't flip the probability on a branch that's never taken. */
4592 }
4595 }
4598 /* This should just be putting it back the way it was. */
4602 }
4604 /* Invert the jump condition of rtx X contained in jump insn, INSN.
4606 Return 1 if we can do so, 0 if we cannot find a way to do so that
4607 matches a pattern. */
4609 int
4611 rtx x;
4612 rtx insn;
4613 {
4621 {
4625 /* We can do this in two ways: The preferable way, which can only
4626 be done if this is not an integer comparison, is to reverse
4627 the comparison code. Otherwise, swap the THEN-part and ELSE-part
4628 of the IF_THEN_ELSE. If we can't do either, fail. */
4641 }
4645 {
4650 {
4655 }
4656 }
4659 }
4660 \f
4661 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
4662 If the old jump target label is unused as a result,
4663 it and the code following it may be deleted.
4665 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
4666 RETURN insn.
4668 The return value will be 1 if the change was made, 0 if it wasn't (this
4669 can only occur for NLABEL == 0). */
4671 int
4674 {
4683 /* If this is an unconditional branch, delete it from the jump_chain of
4684 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
4685 have UID's in range and JUMP_CHAIN is valid). */
4688 {
4694 {
4697 }
4698 }
4708 }
4710 /* Delete the instruction JUMP from any jump chain it might be on. */
4712 static void
4714 rtx jump;
4715 {
4719 /* Handle unconditional jumps. */
4724 /* Handle return insns. */
4731 else
4732 {
4733 rtx insn;
4739 {
4742 }
4743 }
4744 }
4746 /* If NLABEL is nonzero, throughout the rtx at LOC,
4747 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
4748 zero, alter (RETURN) to (LABEL_REF NLABEL).
4750 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
4751 validity with validate_change. Convert (set (pc) (label_ref olabel))
4752 to (return).
4754 Return 0 if we found a change we would like to make but it is invalid.
4755 Otherwise, return 1. */
4757 int
4761 rtx insn;
4762 {
4769 {
4771 {
4774 else
4777 }
4778 }
4780 {
4785 }
4794 {
4799 {
4804 }
4805 }
4808 }
4809 \f
4810 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
4812 If the old jump target label (before the dispatch table) becomes unused,
4813 it and the dispatch table may be deleted. In that case, find the insn
4814 before the jump references that label and delete it and logical successors
4815 too. */
4817 static void
4820 {
4823 /* Add this jump to the jump_chain of NLABEL. */
4826 {
4829 }
4837 {
4840 }
4841 }
4843 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
4844 If we found one, delete it and then delete this insn if DELETE_THIS is
4845 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
4847 static int
4851 {
4853 rtx link;
4857 {
4859 {
4862 }
4863 else
4865 }
4869 {
4871 {
4874 }
4875 else
4877 }
4880 }
4881 \f
4882 /* Like rtx_equal_p except that it considers two REGs as equal
4883 if they renumber to the same value and considers two commutative
4884 operations to be the same if the order of the operands has been
4885 reversed.
4887 ??? Addition is not commutative on the PA due to the weird implicit
4888 space register selection rules for memory addresses. Therefore, we
4889 don't consider a + b == b + a.
4891 We could/should make this test a little tighter. Possibly only
4892 disabling it on the PA via some backend macro or only disabling this
4893 case when the PLUS is inside a MEM. */
4895 int
4898 {
4909 {
4916 /* If we haven't done any renumbering, don't
4917 make any assumptions. */
4922 {
4927 {
4930 }
4931 }
4933 else
4934 {
4938 }
4941 {
4946 {
4949 }
4950 }
4952 else
4953 {
4957 }
4960 }
4962 /* Now we have disposed of all the cases
4963 in which different rtx codes can match. */
4968 {
4979 /* We can't assume nonlocal labels have their following insns yet. */
4983 /* Two label-refs are equivalent if they point at labels
4984 in the same position in the instruction stream. */
4992 /* If we didn't match EQ equality above, they aren't the same. */
4997 }
4999 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
5004 /* For commutative operations, the RTX match if the operand match in any
5005 order. Also handle the simple binary and unary cases without a loop.
5007 ??? Don't consider PLUS a commutative operator; see comments above. */
5020 /* Compare the elements. If any pair of corresponding elements
5021 fail to match, return 0 for the whole things. */
5025 {
5028 {
5052 /* fall through. */
5066 }
5067 }
5069 }
5070 \f
5071 /* If X is a hard register or equivalent to one or a subregister of one,
5072 return the hard register number. If X is a pseudo register that was not
5073 assigned a hard register, return the pseudo register number. Otherwise,
5074 return -1. Any rtx is valid for X. */
5076 int
5078 rtx x;
5079 {
5081 {
5085 }
5087 {
5091 }
5093 }
5094 \f
5095 /* Optimize code of the form:
5097 for (x = a[i]; x; ...)
5098 ...
5099 for (x = a[i]; x; ...)
5100 ...
5101 foo:
5103 Loop optimize will change the above code into
5105 if (x = a[i])
5106 for (;;)
5107 { ...; if (! (x = ...)) break; }
5108 if (x = a[i])
5109 for (;;)
5110 { ...; if (! (x = ...)) break; }
5111 foo:
5113 In general, if the first test fails, the program can branch
5114 directly to `foo' and skip the second try which is doomed to fail.
5115 We run this after loop optimization and before flow analysis. */
5117 /* When comparing the insn patterns, we track the fact that different
5118 pseudo-register numbers may have been used in each computation.
5119 The following array stores an equivalence -- same_regs[I] == J means
5120 that pseudo register I was used in the first set of tests in a context
5121 where J was used in the second set. We also count the number of such
5122 pending equivalences. If nonzero, the expressions really aren't the
5123 same. */
5129 /* Track any registers modified between the target of the first jump and
5130 the second jump. They never compare equal. */
5134 /* Record if memory was modified. */
5138 /* Called via note_stores on each insn between the target of the first
5139 branch and the second branch. It marks any changed registers. */
5141 static void
5143 rtx dest;
5144 rtx x ATTRIBUTE_UNUSED;
5146 {
5161 else
5164 }
5166 /* F is the first insn in the chain of insns. */
5168 void
5170 rtx f;
5173 {
5174 /* Basic algorithm is to find a conditional branch,
5175 the label it may branch to, and the branch after
5176 that label. If the two branches test the same condition,
5177 walk back from both branch paths until the insn patterns
5178 differ, or code labels are hit. If we make it back to
5179 the target of the first branch, then we know that the first branch
5180 will either always succeed or always fail depending on the relative
5181 senses of the two branches. So adjust the first branch accordingly
5182 in this case. */
5191 /* Allocate register tables and quick-reset table. */
5199 {
5203 {
5204 /* Get to a candidate branch insn. */
5219 /* Look for a branch after the target. Record any registers and
5220 memory modified between the target and the branch. Stop when we
5221 get to a label since we can't know what was changed there. */
5223 {
5228 {
5229 /* If this is an unconditional jump and is the only use of
5230 its target label, we can follow it. */
5234 {
5237 }
5238 else
5240 }
5246 {
5255 }
5258 }
5260 /* Check the next candidate branch insn from the label
5261 of the first. */
5269 /* Get the comparison codes and operands, reversing the
5270 codes if appropriate. If we don't have comparison codes,
5271 we can't do anything. */
5284 /* If they test the same things and knowing that B1 branches
5285 tells us whether or not B2 branches, check if we
5286 can thread the branch. */
5293 b1))))
5294 {
5299 {
5301 {
5302 /* We have reached the target of the first branch.
5303 If there are no pending register equivalents,
5304 we know that this branch will either always
5305 succeed (if the senses of the two branches are
5306 the same) or always fail (if not). */
5307 rtx new_label;
5314 else
5318 {
5324 {
5325 /* Don't thread to the loop label. If a loop
5326 label is reused, loop optimization will
5327 be disabled for that loop. */
5330 }
5332 }
5334 }
5336 /* If either of these is not a normal insn (it might be
5337 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
5338 have already been skipped above.) Similarly, fail
5339 if the insns are different. */
5348 }
5349 }
5350 }
5351 }
5353 /* Clean up. */
5357 }
5358 \f
5359 /* This is like RTX_EQUAL_P except that it knows about our handling of
5360 possibly equivalent registers and knows to consider volatile and
5361 modified objects as not equal.
5363 YINSN is the insn containing Y. */
5365 int
5368 rtx yinsn;
5369 {
5376 /* Rtx's of different codes cannot be equal. */
5380 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
5381 (REG:SI x) and (REG:HI x) are NOT equivalent. */
5386 /* For floating-point, consider everything unequal. This is a bit
5387 pessimistic, but this pass would only rarely do anything for FP
5388 anyway. */
5393 /* For commutative operations, the RTX match if the operand match in any
5394 order. Also handle the simple binary and unary cases without a loop. */
5406 /* Handle special-cases first. */
5408 {
5413 /* If neither is user variable or hard register, check for possible
5414 equivalence. */
5421 {
5423 num_same_regs++;
5425 /* If this is the first time we are seeing a register on the `Y'
5426 side, see if it is the last use. If not, we can't thread the
5427 jump, so mark it as not equivalent. */
5432 }
5433 else
5439 /* If memory modified or either volatile, not equivalent.
5440 Else, check address. */
5453 /* Cancel a pending `same_regs' if setting equivalenced registers.
5454 Then process source. */
5457 {
5459 {
5461 num_same_regs--;
5462 }
5465 }
5466 else
5480 }
5487 {
5489 {
5503 /* Two vectors must have the same length. */
5507 /* And the corresponding elements must match. */
5526 /* These are just backpointers, so they don't matter. */
5533 /* It is believed that rtx's at this level will never
5534 contain anything but integers and other rtx's,
5535 except for within LABEL_REFs and SYMBOL_REFs. */
5538 }
5539 }
5541 }
5542 \f
5544 #if !defined(HAVE_cc0) && !defined(HAVE_conditional_arithmetic)
5545 /* Return the insn that NEW can be safely inserted in front of starting at
5546 the jump insn INSN. Return 0 if it is not safe to do this jump
5547 optimization. Note that NEW must contain a single set. */
5549 static rtx
5551 rtx insn;
5553 {
5555 rtx prev;
5557 /* If NEW does not clobber, it is safe to insert NEW before INSN. */
5564 insn))
5570 /* There is a good chance that the previous insn PREV sets the thing
5571 being clobbered (often the CC in a hard reg). If PREV does not
5572 use what NEW sets, we can insert NEW before PREV. */
5578 insn)
5580 prev))
5584 }