| blob | 9cabf4145b7c8547157d4621b357642142163c31 |
1 /* Optimize jump instructions, for GNU compiler.
2 Copyright (C) 1987, 88, 89, 91-94, 1995 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, 675 Mass Ave, Cambridge, MA 02139, USA. */
21 /* This is the jump-optimization pass of the compiler.
22 It is run two or three times: once before cse, sometimes once after cse,
23 and once after reload (before final).
25 jump_optimize deletes unreachable code and labels that are not used.
26 It also deletes jumps that jump to the following insn,
27 and simplifies jumps around unconditional jumps and jumps
28 to unconditional jumps.
30 Each CODE_LABEL has a count of the times it is used
31 stored in the LABEL_NUSES internal field, and each JUMP_INSN
32 has one label that it refers to stored in the
33 JUMP_LABEL internal field. With this we can detect labels that
34 become unused because of the deletion of all the jumps that
35 formerly used them. The JUMP_LABEL info is sometimes looked
36 at by later passes.
38 Optionally, cross-jumping can be done. Currently it is done
39 only the last time (when after reload and before final).
40 In fact, the code for cross-jumping now assumes that register
41 allocation has been done, since it uses `rtx_renumbered_equal_p'.
43 Jump optimization is done after cse when cse's constant-propagation
44 causes jumps to become unconditional or to be deleted.
46 Unreachable loops are not detected here, because the labels
47 have references and the insns appear reachable from the labels.
48 find_basic_blocks in flow.c finds and deletes such loops.
50 The subroutines delete_insn, redirect_jump, and invert_jump are used
51 from other passes as well. */
63 /* ??? Eventually must record somehow the labels used by jumps
64 from nested functions. */
65 /* Pre-record the next or previous real insn for each label?
66 No, this pass is very fast anyway. */
67 /* Condense consecutive labels?
68 This would make life analysis faster, maybe. */
69 /* Optimize jump y; x: ... y: jumpif... x?
70 Don't know if it is worth bothering with. */
71 /* Optimize two cases of conditional jump to conditional jump?
72 This can never delete any instruction or make anything dead,
73 or even change what is live at any point.
74 So perhaps let combiner do it. */
76 /* Vector indexed by uid.
77 For each CODE_LABEL, index by its uid to get first unconditional jump
78 that jumps to the label.
79 For each JUMP_INSN, index by its uid to get the next unconditional jump
80 that jumps to the same label.
81 Element 0 is the start of a chain of all return insns.
82 (It is safe to use element 0 because insn uid 0 is not used. */
86 /* List of labels referred to from initializers.
87 These can never be deleted. */
88 rtx forced_labels;
90 /* Maximum index in jump_chain. */
94 /* Set nonzero by jump_optimize if control can fall through
95 to the end of the function. */
98 /* Indicates whether death notes are significant in cross jump analysis.
99 Normally they are not significant, because of A and B jump to C,
100 and R dies in A, it must die in B. But this might not be true after
101 stack register conversion, and we must compare death notes in that
102 case. */
116 \f
117 /* Delete no-op jumps and optimize jumps to jumps
118 and jumps around jumps.
119 Delete unused labels and unreachable code.
121 If CROSS_JUMP is 1, detect matching code
122 before a jump and its destination and unify them.
123 If CROSS_JUMP is 2, do cross-jumping, but pay attention to death notes.
125 If NOOP_MOVES is nonzero, delete no-op move insns.
127 If AFTER_REGSCAN is nonzero, then this jump pass is being run immediately
128 after regscan, and it is safe to use regno_first_uid and regno_last_uid.
130 If `optimize' is zero, don't change any code,
131 just determine whether control drops off the end of the function.
132 This case occurs when we have -W and not -O.
133 It works because `delete_insn' checks the value of `optimize'
134 and refrains from actually deleting when that is 0. */
136 void
138 rtx f;
142 {
147 rtx last_insn;
151 /* Initialize LABEL_NUSES and JUMP_LABEL fields. Delete any REG_LABEL
152 notes whose labels don't occur in the insn any more. */
155 {
162 {
167 }
171 }
173 max_uid++;
175 /* Delete insns following barriers, up to next label. */
178 {
180 {
183 {
187 else
189 }
190 /* INSN is now the code_label. */
191 }
192 else
194 }
196 /* Leave some extra room for labels and duplicate exit test insns
197 we make. */
202 /* Mark the label each jump jumps to.
203 Combine consecutive labels, and count uses of labels.
205 For each label, make a chain (using `jump_chain')
206 of all the *unconditional* jumps that jump to it;
207 also make a chain of all returns. */
212 {
215 {
217 {
221 }
223 {
226 }
227 }
228 }
230 /* Keep track of labels used from static data;
231 they cannot ever be deleted. */
236 /* Delete all labels already not referenced.
237 Also find the last insn. */
241 {
244 else
245 {
248 }
249 }
252 {
253 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
254 If so record that this function can drop off the end. */
257 {
260 /* One label can follow the end-note: the return label. */
262 /* Ordinary insns can follow it if returning a structure. */
264 /* If machine uses explicit RETURN insns, no epilogue,
265 then one of them follows the note. */
268 /* Other kinds of notes can follow also. */
272 }
274 /* Report if control can fall through at the end of the function. */
280 /* Zero the "deleted" flag of all the "deleted" insns. */
284 }
286 #ifdef HAVE_return
288 {
289 /* If we fall through to the epilogue, see if we can insert a RETURN insn
290 in front of it. If the machine allows it at this point (we might be
291 after reload for a leaf routine), it will improve optimization for it
292 to be there. */
298 {
301 }
302 }
303 #endif
307 {
311 {
314 /* Combine stack_adjusts with following push_insns. */
315 #ifdef PUSH_ROUNDING
322 {
323 rtx p;
329 /* Find all successive push insns. */
331 /* Don't convert more than three pushes;
332 that starts adding too many displaced addresses
333 and the whole thing starts becoming a losing
334 proposition. */
336 {
345 /* Allow a no-op move between the adjust and the push. */
354 pushes++;
359 }
361 /* Discard the amount pushed from the stack adjust;
362 maybe eliminate it entirely. */
364 {
367 }
368 else
372 /* Change the appropriate push insns to ordinary stores. */
375 {
389 /* If this push doesn't fully fit in the space
390 of the stack adjust that we deleted,
391 make another stack adjust here for what we
392 didn't use up. There should be peepholes
393 to recognize the resulting sequence of insns. */
395 {
398 p);
400 }
403 }
404 }
405 #endif
407 /* Detect and delete no-op move instructions
408 resulting from not allocating a parameter in a register. */
421 /* Detect and ignore no-op move instructions
422 resulting from smart or fortuitous register allocation. */
425 {
432 {
433 rtx trial;
438 #ifdef PRESERVE_DEATH_INFO_REGNO_P
439 /* Deleting insn could lose a death-note for SREG or DREG
440 so don't do it if final needs accurate death-notes. */
443 #endif
444 {
445 /* DREG may have been the target of a REG_DEAD note in
446 the insn which makes INSN redundant. If so, reorg
447 would still think it is dead. So search for such a
448 note and delete it if we find it. */
453 {
456 }
461 }
462 }
467 {
468 /* This handles the case where we have two consecutive
469 assignments of the same constant to pseudos that didn't
470 get a hard reg. Each SET from the constant will be
471 converted into a SET of the spill register and an
472 output reload will be made following it. This produces
473 two loads of the same constant into the same spill
474 register. */
478 /* Look back for a death note for the first reg.
479 If there is one, it is no longer accurate. */
481 {
485 {
488 }
490 }
492 /* Delete the second load of the value. */
494 }
495 }
497 {
498 /* If each part is a set between two identical registers or
499 a USE or CLOBBER, delete the insn. */
501 rtx tem;
504 {
514 }
518 }
519 /* Also delete insns to store bit fields if they are no-ops. */
520 /* Not worth the hair to detect this in the big-endian case. */
529 }
531 }
533 /* If we haven't yet gotten to reload and we have just run regscan,
534 delete any insn that sets a register that isn't used elsewhere.
535 This helps some of the optimizations below by having less insns
536 being jumped around. */
540 {
548 /* We use regno_last_note_uid so as not to delete the setting
549 of a reg that's used in notes. A subsequent optimization
550 might arrange to use that reg for real. */
555 }
557 /* Now iterate optimizing jumps until nothing changes over one pass. */
560 {
564 {
565 rtx reallabelprev;
567 rtx nlabel;
570 #if 0
571 /* If NOT the first iteration, if this is the last jump pass
572 (just before final), do the special peephole optimizations.
573 Avoiding the first iteration gives ordinary jump opts
574 a chance to work before peephole opts. */
579 #endif
581 /* That could have deleted some insns after INSN, so check now
582 what the following insn is. */
586 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
587 jump. Try to optimize by duplicating the loop exit test if so.
588 This is only safe immediately after regscan, because it uses
589 the values of regno_first_uid and regno_last_uid. */
594 {
597 {
601 }
602 }
611 /* Tension the labels in dispatch tables. */
618 /* If a dispatch table always goes to the same place,
619 get rid of it and replace the insn that uses it. */
623 {
638 /* Don't mess with a casesi insn. */
643 {
647 }
648 }
652 /* If a jump references the end of the function, try to turn
653 it into a RETURN insn, possibly a conditional one. */
660 /* Detect jump to following insn. */
662 {
667 }
669 /* If we have an unconditional jump preceded by a USE, try to put
670 the USE before the target and jump there. This simplifies many
671 of the optimizations below since we don't have to worry about
672 dealing with these USE insns. We only do this if the label
673 being branch to already has the identical USE or if code
674 never falls through to that label. */
683 {
685 {
688 }
694 }
696 /* Simplify if (...) x = a; else x = b; by converting it
697 to x = b; if (...) x = a;
698 if B is sufficiently simple, the test doesn't involve X,
699 and nothing in the test modifies B or X.
701 If we have small register classes, we also can't do this if X
702 is a hard register.
704 If the "x = b;" insn has any REG_NOTES, we don't do this because
705 of the possibility that we are running after CSE and there is a
706 REG_EQUAL note that is only valid if the branch has already been
707 taken. If we move the insn with the REG_EQUAL note, we may
708 fold the comparison to always be false in a later CSE pass.
709 (We could also delete the REG_NOTES when moving the insn, but it
710 seems simpler to not move it.) An exception is that we can move
711 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
712 value is the same as "b".
714 INSN is the branch over the `else' part.
716 We set:
718 TEMP to the jump insn preceding "x = a;"
719 TEMP1 to X
720 TEMP2 to the insn that sets "x = b;"
721 TEMP3 to the insn that sets "x = a;"
722 TEMP4 to the set of "x = b"; */
729 #ifdef SMALL_REGISTER_CLASSES
731 #endif
747 /* TEMP must skip over the "x = a;" insn */
750 /* There must be no other entries to the "x = b;" insn. */
752 /* INSN must either branch to the insn after TEMP2 or the insn
753 after TEMP2 must branch to the same place as INSN. */
758 {
759 /* The test expression, X, may be a complicated test with
760 multiple branches. See if we can find all the uses of
761 the label that TEMP branches to without hitting a CALL_INSN
762 or a jump to somewhere else. */
767 /* Set P to the first jump insn that goes around "x = a;". */
769 {
771 {
774 {
775 nuses--;
778 }
779 else
781 }
784 }
786 #ifdef HAVE_cc0
787 /* We cannot insert anything between a set of cc and its use
788 so if P uses cc0, we must back up to the previous insn. */
793 #endif
798 /* If we found all the uses and there was no data conflict, we
799 can move the assignment unless we can branch into the middle
800 from somewhere. */
807 {
811 /* Set NEXT to an insn that we know won't go away. */
814 /* Delete the jump around the set. Note that we must do
815 this before we redirect the test jumps so that it won't
816 delete the code immediately following the assignment
817 we moved (which might be a jump). */
821 /* We either have two consecutive labels or a jump to
822 a jump, so adjust all the JUMP_INSNs to branch to where
823 INSN branches to. */
830 }
831 }
833 #ifndef HAVE_cc0
834 /* If we have if (...) x = exp; and branches are expensive,
835 EXP is a single insn, does not have any side effects, cannot
836 trap, and is not too costly, convert this to
837 t = exp; if (...) x = t;
839 Don't do this when we have CC0 because it is unlikely to help
840 and we'd need to worry about where to place the new insn and
841 the potential for conflicts. We also can't do this when we have
842 notes on the insn for the same reason as above.
844 We set:
846 TEMP to the "x = exp;" insn.
847 TEMP1 to the single set in the "x = exp; insn.
848 TEMP2 to "x". */
863 #ifdef SMALL_REGISTER_CLASSES
865 #endif
872 {
876 {
882 }
883 }
885 /* Similarly, if it takes two insns to compute EXP but they
886 have the same destination. Here TEMP3 will be the second
887 insn and TEMP4 the SET from that insn. */
905 #ifdef SMALL_REGISTER_CLASSES
907 #endif
916 {
920 {
924 emit_insn_after_with_line_notes
930 }
931 }
933 /* Finally, handle the case where two insns are used to
934 compute EXP but a temporary register is used. Here we must
935 ensure that the temporary register is not used anywhere else. */
938 && after_regscan
966 #ifdef SMALL_REGISTER_CLASSES
968 #endif
973 {
977 {
986 }
987 }
990 /* Try to use a conditional move (if the target has them), or a
991 store-flag insn. The general case is:
993 1) x = a; if (...) x = b; and
994 2) if (...) x = b;
996 If the jump would be faster, the machine should not have defined
997 the movcc or scc insns!. These cases are often made by the
998 previous optimization.
1000 The second case is treated as x = x; if (...) x = b;.
1002 INSN here is the jump around the store. We set:
1004 TEMP to the "x = b;" insn.
1005 TEMP1 to X.
1006 TEMP2 to B.
1007 TEMP3 to A (X in the second case).
1008 TEMP4 to the condition being tested.
1009 TEMP5 to the earliest insn used to find the condition. */
1012 ! reload_completed
1014 /* Set TEMP to the "x = b;" insn. */
1019 #ifdef SMALL_REGISTER_CLASSES
1021 #endif
1024 /* ??? How about floating point constants? */
1026 /* Allow either form, but prefer the former if both apply.
1027 There is no point in using the old value of TEMP1 if
1028 it is a register, since cse will alias them. It can
1029 lose if the old value were a hard register since CSE
1030 won't replace hard registers. */
1032 /* Make the latter case look like x = x; if (...) x = b; */
1034 /* INSN must either branch to the insn after TEMP or the insn
1035 after TEMP must branch to the same place as INSN. */
1041 /* We must be comparing objects whose modes imply the size.
1042 We could handle BLKmode if (1) emit_store_flag could
1043 and (2) we could find the size reliably. */
1045 /* No point in doing any of this if branches are cheap or we
1046 don't have conditional moves. */
1048 #ifdef HAVE_conditional_move
1050 #endif
1051 )
1052 #ifdef HAVE_cc0
1053 /* If the previous insn sets CC0 and something else, we can't
1054 do this since we are going to delete that insn. */
1061 #endif
1062 )
1063 {
1064 #ifdef HAVE_conditional_move
1065 /* First try a conditional move. */
1066 {
1070 rtx target;
1072 /* Copy the compared variables into cond0 and cond1, so that
1073 any side effects performed in or after the old comparison,
1074 will not affect our compare which will come later. */
1075 /* ??? Is it possible to just use the comparison in the jump
1076 insn? After all, we're going to delete it. We'd have
1077 to modify emit_conditional_move to take a comparison rtx
1078 instead or write a new function. */
1080 /* We want the target to be able to simplify comparisons with
1081 zero (and maybe other constants as well), so don't create
1082 pseudos for them. There's no need to either. */
1086 else
1100 {
1103 /* Save the conditional move sequence but don't emit it
1104 yet. On some machines, like the alpha, it is possible
1105 that temp5 == insn, so next generate the sequence that
1106 saves the compared values and then emit both
1107 sequences ensuring seq1 occurs before seq2. */
1111 /* Now that we can't fail, generate the copy insns that
1112 preserve the compared values. */
1123 /* ??? We can also delete the insn that sets X to A.
1124 Flow will do it too though. */
1130 }
1131 else
1133 }
1134 #endif
1136 /* That didn't work, try a store-flag insn.
1138 We further divide the cases into:
1140 1) x = a; if (...) x = b; and either A or B is zero,
1141 2) if (...) x = 0; and jumps are expensive,
1142 3) x = a; if (...) x = b; and A and B are constants where all
1143 the set bits in A are also set in B and jumps are expensive,
1144 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
1145 more expensive, and
1146 5) if (...) x = b; if jumps are even more expensive. */
1150 /* Make the latter case look like
1151 x = x; if (...) x = 0; */
1156 /* If B is zero, OK; if A is zero, can only do (1) if we
1157 can reverse the condition. See if (3) applies possibly
1158 by reversing the condition. Prefer reversing to (4) when
1159 branches are very expensive. */
1169 insn)))))
1171 )
1172 {
1176 rtx target;
1178 /* If necessary, reverse the condition. */
1181 else
1184 /* If CVAL is non-zero, normalize to -1. Otherwise, if UVAL
1185 is the constant 1, it is best to just compute the result
1186 directly. If UVAL is constant and STORE_FLAG_VALUE
1187 includes all of its bits, it is best to compute the flag
1188 value unnormalized and `and' it with UVAL. Otherwise,
1189 normalize to -1 and `and' with UVAL. */
1196 /* We will be putting the store-flag insn immediately in
1197 front of the comparison that was originally being done,
1198 so we know all the variables in TEMP4 will be valid.
1199 However, this might be in front of the assignment of
1200 A to VAR. If it is, it would clobber the store-flag
1201 we will be emitting.
1203 Therefore, emit into a temporary which will be copied to
1204 VAR immediately after TEMP. */
1209 VOIDmode,
1212 normalizep);
1214 {
1215 rtx seq;
1221 /* Put the store-flag insns in front of the first insn
1222 used to compute the condition to ensure that we
1223 use the same values of them as the current
1224 comparison. However, the remainder of the insns we
1225 generate will be placed directly in front of the
1226 jump insn, in case any of the pseudos we use
1227 are modified earlier. */
1233 /* Both CVAL and UVAL are non-zero. */
1235 {
1243 else
1244 {
1250 }
1252 /* If we usually make new pseudos, do so here. This
1253 turns out to help machines that have conditional
1254 move insns. */
1255 /* ??? Conditional moves have already been handled.
1256 This may be obsolete. */
1264 }
1266 {
1267 /* We know that either CVAL or UVAL is zero. If
1268 UVAL is zero, negate TARGET and `and' with CVAL.
1269 Otherwise, `and' with UVAL. */
1271 {
1275 }
1281 }
1286 #ifdef HAVE_cc0
1287 /* If INSN uses CC0, we must not separate it from the
1288 insn that sets cc0. */
1291 #endif
1299 }
1300 else
1302 }
1303 }
1305 /* If branches are expensive, convert
1306 if (foo) bar++; to bar += (foo != 0);
1307 and similarly for "bar--;"
1309 INSN is the conditional branch around the arithmetic. We set:
1311 TEMP is the arithmetic insn.
1312 TEMP1 is the SET doing the arithmetic.
1313 TEMP2 is the operand being incremented or decremented.
1314 TEMP3 to the condition being tested.
1315 TEMP4 to the earliest insn used to find the condition. */
1318 #ifdef HAVE_incscc
1319 || HAVE_incscc
1320 #endif
1321 #ifdef HAVE_decscc
1322 || HAVE_decscc
1323 #endif
1324 )
1325 && ! reload_completed
1337 /* INSN must either branch to the insn after TEMP or the insn
1338 after TEMP must branch to the same place as INSN. */
1344 /* We must be comparing objects whose modes imply the size.
1345 We could handle BLKmode if (1) emit_store_flag could
1346 and (2) we could find the size reliably. */
1349 {
1355 /* It must be the case that TEMP2 is not modified in the range
1356 [TEMP4, INSN). The one exception we make is if the insn
1357 before INSN sets TEMP2 to something which is also unchanged
1358 in that range. In that case, we can move the initialization
1359 into our sequence. */
1368 {
1372 }
1378 VOIDmode,
1382 /* If we can do the store-flag, do the addition or
1383 subtraction. */
1392 {
1393 /* Put the result back in temp2 in case it isn't already.
1394 Then replace the jump, possible a CC0-setting insn in
1395 front of the jump, and TEMP, with the sequence we have
1396 made. */
1411 #ifdef HAVE_cc0
1413 #endif
1417 }
1418 else
1420 }
1422 /* Simplify if (...) x = 1; else {...} if (x) ...
1423 We recognize this case scanning backwards as well.
1425 TEMP is the assignment to x;
1426 TEMP1 is the label at the head of the second if. */
1427 /* ?? This should call get_condition to find the values being
1428 compared, instead of looking for a COMPARE insn when HAVE_cc0
1429 is not defined. This would allow it to work on the m88k. */
1430 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1431 is not defined and the condition is tested by a separate compare
1432 insn. This is because the code below assumes that the result
1433 of the compare dies in the following branch.
1435 Not only that, but there might be other insns between the
1436 compare and branch whose results are live. Those insns need
1437 to be executed.
1439 A way to fix this is to move the insns at JUMP_LABEL (insn)
1440 to before INSN. If we are running before flow, they will
1441 be deleted if they aren't needed. But this doesn't work
1442 well after flow.
1444 This is really a special-case of jump threading, anyway. The
1445 right thing to do is to replace this and jump threading with
1446 much simpler code in cse.
1448 This code has been turned off in the non-cc0 case in the
1449 meantime. */
1451 #ifdef HAVE_cc0
1453 /* Safe to skip USE and CLOBBER insns here
1454 since they will not be deleted. */
1462 /* If we find that the next value tested is `x'
1463 (TEMP1 is the insn where this happens), win. */
1466 #ifdef HAVE_cc0
1467 /* Does temp1 `tst' the value of x? */
1471 #else
1472 /* Does temp1 compare the value of x against zero? */
1479 #endif
1481 {
1482 /* Get the if_then_else from the condjump. */
1485 {
1488 rtx cond
1491 rtx ultimate;
1497 else
1507 }
1508 }
1509 #endif
1511 #if 0
1512 /* @@ This needs a bit of work before it will be right.
1514 Any type of comparison can be accepted for the first and
1515 second compare. When rewriting the first jump, we must
1516 compute the what conditions can reach label3, and use the
1517 appropriate code. We can not simply reverse/swap the code
1518 of the first jump. In some cases, the second jump must be
1519 rewritten also.
1521 For example,
1522 < == converts to > ==
1523 < != converts to == >
1524 etc.
1526 If the code is written to only accept an '==' test for the second
1527 compare, then all that needs to be done is to swap the condition
1528 of the first branch.
1530 It is questionable whether we want this optimization anyways,
1531 since if the user wrote code like this because he/she knew that
1532 the jump to label1 is taken most of the time, then rewriting
1533 this gives slower code. */
1534 /* @@ This should call get_condition to find the values being
1535 compared, instead of looking for a COMPARE insn when HAVE_cc0
1536 is not defined. This would allow it to work on the m88k. */
1537 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1538 is not defined and the condition is tested by a separate compare
1539 insn. This is because the code below assumes that the result
1540 of the compare dies in the following branch. */
1542 /* Simplify test a ~= b
1543 condjump label1;
1544 test a == b
1545 condjump label2;
1546 jump label3;
1547 label1:
1549 rewriting as
1550 test a ~~= b
1551 condjump label3
1552 test a == b
1553 condjump label2
1554 label1:
1556 where ~= is an inequality, e.g. >, and ~~= is the swapped
1557 inequality, e.g. <.
1559 We recognize this case scanning backwards.
1561 TEMP is the conditional jump to `label2';
1562 TEMP1 is the test for `a == b';
1563 TEMP2 is the conditional jump to `label1';
1564 TEMP3 is the test for `a ~= b'. */
1573 #ifdef HAVE_cc0
1575 #else
1579 #endif
1593 {
1598 {
1601 }
1605 }
1606 #endif
1607 /* Simplify if (...) {... x = 1;} if (x) ...
1609 We recognize this case backwards.
1611 TEMP is the test of `x';
1612 TEMP1 is the assignment to `x' at the end of the
1613 previous statement. */
1614 /* @@ This should call get_condition to find the values being
1615 compared, instead of looking for a COMPARE insn when HAVE_cc0
1616 is not defined. This would allow it to work on the m88k. */
1617 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1618 is not defined and the condition is tested by a separate compare
1619 insn. This is because the code below assumes that the result
1620 of the compare dies in the following branch. */
1622 /* ??? This has to be turned off. The problem is that the
1623 unconditional jump might indirectly end up branching to the
1624 label between TEMP1 and TEMP. We can't detect this, in general,
1625 since it may become a jump to there after further optimizations.
1626 If that jump is done, it will be deleted, so we will retry
1627 this optimization in the next pass, thus an infinite loop.
1629 The present code prevents this by putting the jump after the
1630 label, but this is not logically correct. */
1631 #if 0
1633 /* Safe to skip USE and CLOBBER insns here
1634 since they will not be deleted. */
1639 #ifdef HAVE_cc0
1642 #else
1643 /* Temp must be a compare insn, we can not accept a register
1644 to register move here, since it may not be simply a
1645 tst insn. */
1651 #endif
1652 /* May skip USE or CLOBBER insns here
1653 for checking for opportunity, since we
1654 take care of them later. */
1658 #ifdef HAVE_cc0
1660 #else
1663 #endif
1665 /* If this isn't true, cse will do the job. */
1667 {
1668 /* Get the if_then_else from the condjump. */
1673 {
1675 rtx last_insn;
1676 rtx ultimate;
1677 rtx p;
1679 /* Get the place that condjump will jump to
1680 if it is reached from here. */
1684 else
1686 /* Get it as a CODE_LABEL. */
1689 else
1690 /* Get the label out of the LABEL_REF. */
1693 /* Insert the jump immediately before TEMP, specifically
1694 after the label that is between TEMP1 and TEMP. */
1697 /* If we would be branching to the next insn, the jump
1698 would immediately be deleted and the re-inserted in
1699 a subsequent pass over the code. So don't do anything
1700 in that case. */
1703 {
1706 last_insn);
1711 {
1715 }
1718 }
1719 }
1720 }
1721 #endif
1722 /* Detect a conditional jump going to the same place
1723 as an immediately following unconditional jump. */
1729 {
1733 }
1734 /* Detect a conditional jump jumping over an unconditional jump. */
1737 && ! this_is_simplejump
1743 {
1744 /* When we invert the unconditional jump, we will be
1745 decrementing the usage count of its old label.
1746 Make sure that we don't delete it now because that
1747 might cause the following code to be deleted. */
1755 {
1756 /* It is very likely that if there are USE insns before
1757 this jump, they hold REG_DEAD notes. These REG_DEAD
1758 notes are no longer valid due to this optimization,
1759 and will cause the life-analysis that following passes
1760 (notably delayed-branch scheduling) to think that
1761 these registers are dead when they are not.
1763 To prevent this trouble, we just remove the USE insns
1764 from the insn chain. */
1768 {
1772 }
1777 }
1779 /* We can now safely delete the label if it is unreferenced
1780 since the delete_insn above has deleted the BARRIER. */
1784 }
1785 else
1786 {
1787 /* Detect a jump to a jump. */
1792 {
1795 }
1797 /* Look for if (foo) bar; else break; */
1798 /* The insns look like this:
1799 insn = condjump label1;
1800 ...range1 (some insns)...
1801 jump label2;
1802 label1:
1803 ...range2 (some insns)...
1804 jump somewhere unconditionally
1805 label2: */
1806 {
1809 /* Don't do this optimization on the first round, so that
1810 jump-around-a-jump gets simplified before we ask here
1811 whether a jump is unconditional.
1813 Also don't do it when we are called after reload since
1814 it will confuse reorg. */
1817 /* Make sure INSN is something we can invert. */
1824 {
1831 /* Invert the jump condition, so we
1832 still execute the same insns in each case. */
1834 {
1839 rtx rangenext;
1841 /* Include in each range any notes before it, to be
1842 sure that we get the line number note if any, even
1843 if there are other notes here. */
1852 /* Don't move NOTEs for blocks or loops; shift them
1853 outside the ranges, where they'll stay put. */
1857 /* Get current surrounds of the 2 ranges. */
1863 /* Splice range2 where range1 was. */
1868 /* Splice range1 where range2 was. */
1874 /* Check for a loop end note between the end of
1875 range2, and the next code label. If there is one,
1876 then what we have really seen is
1877 if (foo) break; end_of_loop;
1878 and moved the break sequence outside the loop.
1879 We must move the LOOP_END note to where the
1880 loop really ends now, or we will confuse loop
1881 optimization. */
1883 {
1888 {
1899 }
1900 }
1903 }
1904 }
1905 }
1907 /* Now that the jump has been tensioned,
1908 try cross jumping: check for identical code
1909 before the jump and before its target label. */
1911 /* First, cross jumping of conditional jumps: */
1914 {
1918 /* A conditional jump may be crossjumped
1919 only if the place it jumps to follows
1920 an opposing jump that comes back here. */
1923 /* We have no opposing jump;
1924 cannot cross jump this insn. */
1928 /* TARGET is nonzero if it is ok to cross jump
1929 to code before TARGET. If so, see if matches. */
1935 {
1937 /* Make the old conditional jump
1938 into an unconditional one. */
1943 /* Add to jump_chain unless this is a new label
1944 whose UID is too large. */
1946 {
1950 }
1953 }
1954 }
1956 /* Cross jumping of unconditional jumps:
1957 a few differences. */
1960 {
1962 rtx target;
1966 /* TARGET is nonzero if it is ok to cross jump
1967 to code before TARGET. If so, see if matches. */
1971 /* If cannot cross jump to code before the label,
1972 see if we can cross jump to another jump to
1973 the same label. */
1974 /* Try each other jump to this label. */
1981 /* Ignore TARGET if it's deleted. */
1987 {
1991 }
1992 }
1994 /* This code was dead in the previous jump.c! */
1996 {
1997 /* Return insns all "jump to the same place"
1998 so we can cross-jump between any two of them. */
2004 /* If cannot cross jump to code before the label,
2005 see if we can cross jump to another jump to
2006 the same label. */
2007 /* Try each other jump to this label. */
2018 {
2022 }
2023 }
2024 }
2025 }
2028 }
2030 /* Delete extraneous line number notes.
2031 Note that two consecutive notes for different lines are not really
2032 extraneous. There should be some indication where that line belonged,
2033 even if it became empty. */
2035 {
2040 {
2041 /* Delete this note if it is identical to previous note. */
2045 {
2048 }
2051 }
2052 }
2054 #ifdef HAVE_return
2056 {
2057 /* If we fall through to the epilogue, see if we can insert a RETURN insn
2058 in front of it. If the machine allows it at this point (we might be
2059 after reload for a leaf routine), it will improve optimization for it
2060 to be there. We do this both here and at the start of this pass since
2061 the RETURN might have been deleted by some of our optimizations. */
2067 {
2070 }
2071 }
2072 #endif
2074 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
2075 If so, delete it, and record that this function can drop off the end. */
2078 {
2081 /* One label can follow the end-note: the return label. */
2083 /* Ordinary insns can follow it if returning a structure. */
2085 /* If machine uses explicit RETURN insns, no epilogue,
2086 then one of them follows the note. */
2089 /* Other kinds of notes can follow also. */
2093 }
2095 /* Report if control can fall through at the end of the function. */
2098 {
2101 }
2103 /* Show JUMP_CHAIN no longer valid. */
2105 }
2106 \f
2107 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
2108 jump. Assume that this unconditional jump is to the exit test code. If
2109 the code is sufficiently simple, make a copy of it before INSN,
2110 followed by a jump to the exit of the loop. Then delete the unconditional
2111 jump after INSN.
2113 Note that it is possible we can get confused here if the jump immediately
2114 after the loop start branches outside the loop but within an outer loop.
2115 If we are near the exit of that loop, we will copy its exit test. This
2116 will not generate incorrect code, but could suppress some optimizations.
2117 However, such cases are degenerate loops anyway.
2119 Return 1 if we made the change, else 0.
2121 This is only safe immediately after a regscan pass because it uses the
2122 values of regno_first_uid and regno_last_uid. */
2124 static int
2126 rtx loop_start;
2127 {
2132 rtx lastexit;
2136 /* Scan the exit code. We do not perform this optimization if any insn:
2138 is a CALL_INSN
2139 is a CODE_LABEL
2140 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
2141 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
2142 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
2143 are not valid
2145 Also, don't do this if the exit code is more than 20 insns. */
2148 insn
2152 {
2154 {
2171 }
2172 }
2174 /* Unless INSN is zero, we can do the optimization. */
2180 /* See if any insn sets a register only used in the loop exit code and
2181 not a user variable. If so, replace it with a new register. */
2190 {
2196 {
2197 /* We can do the replacement. Allocate reg_map if this is the
2198 first replacement we found. */
2200 {
2203 }
2208 }
2209 }
2211 /* Now copy each insn. */
2214 {
2219 /* Only copy line-number notes. */
2221 {
2224 }
2234 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
2235 make them. */
2251 {
2255 }
2257 /* If this is a simple jump, add it to the jump chain. */
2261 {
2265 }
2270 }
2272 /* Now clean up by emitting a jump to the end label and deleting the jump
2273 at the start of the loop. */
2275 {
2277 loop_start);
2281 {
2285 }
2287 }
2289 /* Mark the exit code as the virtual top of the converted loop. */
2295 }
2296 \f
2297 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
2298 loop-end notes between START and END out before START. Assume that
2299 END is not such a note. START may be such a note. Returns the value
2300 of the new starting insn, which may be different if the original start
2301 was such a note. */
2303 rtx
2306 {
2307 rtx insn;
2308 rtx next;
2311 {
2320 {
2323 else
2324 {
2332 }
2333 }
2334 }
2337 }
2338 \f
2339 /* Compare the instructions before insn E1 with those before E2
2340 to find an opportunity for cross jumping.
2341 (This means detecting identical sequences of insns followed by
2342 jumps to the same place, or followed by a label and a jump
2343 to that label, and replacing one with a jump to the other.)
2345 Assume E1 is a jump that jumps to label E2
2346 (that is not always true but it might as well be).
2347 Find the longest possible equivalent sequences
2348 and store the first insns of those sequences into *F1 and *F2.
2349 Store zero there if no equivalent preceding instructions are found.
2351 We give up if we find a label in stream 1.
2352 Actually we could transfer that label into stream 2. */
2354 static void
2359 {
2366 rtx prev1;
2372 {
2382 /* Don't allow the range of insns preceding E1 or E2
2383 to include the other (E2 or E1). */
2387 /* If we will get to this code by jumping, those jumps will be
2388 tensioned to go directly to the new label (before I2),
2389 so this cross-jumping won't cost extra. So reduce the minimum. */
2391 {
2394 }
2402 /* If this is a CALL_INSN, compare register usage information.
2403 If we don't check this on stack register machines, the two
2404 CALL_INSNs might be merged leaving reg-stack.c with mismatching
2405 numbers of stack registers in the same basic block.
2406 If we don't check this on machines with delay slots, a delay slot may
2407 be filled that clobbers a parameter expected by the subroutine.
2409 ??? We take the simple route for now and assume that if they're
2410 equal, they were constructed identically. */
2417 #ifdef STACK_REGS
2418 /* If cross_jump_death_matters is not 0, the insn's mode
2419 indicates whether or not the insn contains any stack-like
2420 regs. */
2423 {
2424 /* If register stack conversion has already been done, then
2425 death notes must also be compared before it is certain that
2426 the two instruction streams match. */
2428 rtx note;
2448 done:
2449 ;
2450 }
2451 #endif
2455 {
2456 /* The following code helps take care of G++ cleanups. */
2457 rtx equiv1;
2458 rtx equiv2;
2465 /* If the equivalences are not to a constant, they may
2466 reference pseudos that no longer exist, so we can't
2467 use them. */
2470 {
2475 {
2482 }
2483 }
2485 /* Insns fail to match; cross jumping is limited to the following
2486 insns. */
2488 #ifdef HAVE_cc0
2489 /* Don't allow the insn after a compare to be shared by
2490 cross-jumping unless the compare is also shared.
2491 Here, if either of these non-matching insns is a compare,
2492 exclude the following insn from possible cross-jumping. */
2495 #endif
2497 /* If cross-jumping here will feed a jump-around-jump
2498 optimization, this jump won't cost extra, so reduce
2499 the minimum. */
2505 }
2507 win:
2509 {
2510 /* Ok, this insn is potentially includable in a cross-jump here. */
2513 }
2514 }
2518 }
2520 static void
2523 {
2524 /* Find an existing label at this point
2525 or make a new one if there is none. */
2528 /* Make the same jump insn jump to the new point. */
2530 {
2531 /* Remove from jump chain of returns. */
2533 /* Change the insn. */
2538 /* Add to new the jump chain. */
2541 {
2544 }
2545 }
2546 else
2549 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
2550 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
2551 the NEWJPOS stream. */
2554 {
2555 rtx lnote;
2567 }
2568 }
2569 \f
2570 /* Return the label before INSN, or put a new label there. */
2572 rtx
2574 rtx insn;
2575 {
2576 rtx label;
2578 /* Find an existing label at this point
2579 or make a new one if there is none. */
2583 {
2589 }
2591 }
2593 /* Return the label after INSN, or put a new label there. */
2595 rtx
2597 rtx insn;
2598 {
2599 rtx label;
2601 /* Find an existing label at this point
2602 or make a new one if there is none. */
2606 {
2610 }
2612 }
2613 \f
2614 /* Return 1 if INSN is a jump that jumps to right after TARGET
2615 only on the condition that TARGET itself would drop through.
2616 Assumes that TARGET is a conditional jump. */
2618 static int
2621 {
2637 {
2641 }
2644 {
2648 }
2653 }
2654 \f
2655 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
2656 return non-zero if it is safe to reverse this comparison. It is if our
2657 floating-point is not IEEE, if this is an NE or EQ comparison, or if
2658 this is known to be an integer comparison. */
2660 int
2662 rtx comparison;
2663 rtx insn;
2664 {
2665 rtx arg0;
2667 /* If this is not actually a comparison, we can't reverse it. */
2672 /* If this is an NE comparison, it is safe to reverse it to an EQ
2673 comparison and vice versa, even for floating point. If no operands
2674 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
2675 always false and NE is always true, so the reversal is also valid. */
2676 || flag_fast_math
2683 /* Make sure ARG0 is one of the actual objects being compared. If we
2684 can't do this, we can't be sure the comparison can be reversed.
2686 Handle cc0 and a MODE_CC register. */
2688 #ifdef HAVE_cc0
2690 #endif
2691 )
2692 {
2703 }
2705 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
2706 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
2711 }
2713 /* Given an rtx-code for a comparison, return the code
2714 for the negated comparison.
2715 WATCH OUT! reverse_condition is not safe to use on a jump
2716 that might be acting on the results of an IEEE floating point comparison,
2717 because of the special treatment of non-signaling nans in comparisons.
2718 Use can_reverse_comparison_p to be sure. */
2720 enum rtx_code
2723 {
2725 {
2759 }
2760 }
2762 /* Similar, but return the code when two operands of a comparison are swapped.
2763 This IS safe for IEEE floating-point. */
2765 enum rtx_code
2768 {
2770 {
2802 }
2803 }
2805 /* Given a comparison CODE, return the corresponding unsigned comparison.
2806 If CODE is an equality comparison or already an unsigned comparison,
2807 CODE is returned. */
2809 enum rtx_code
2812 {
2814 {
2837 }
2838 }
2840 /* Similarly, return the signed version of a comparison. */
2842 enum rtx_code
2845 {
2847 {
2870 }
2871 }
2872 \f
2873 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
2874 truth of CODE1 implies the truth of CODE2. */
2876 int
2879 {
2884 {
2909 }
2912 }
2913 \f
2914 /* Return 1 if INSN is an unconditional jump and nothing else. */
2916 int
2918 rtx insn;
2919 {
2924 }
2926 /* Return nonzero if INSN is a (possibly) conditional jump
2927 and nothing more. */
2929 int
2931 rtx insn;
2932 {
2951 }
2953 /* Return nonzero if INSN is a (possibly) conditional jump
2954 and nothing more. */
2956 int
2958 rtx insn;
2959 {
2964 else
2984 }
2986 /* Return 1 if X is an RTX that does nothing but set the condition codes
2987 and CLOBBER or USE registers.
2988 Return -1 if X does explicitly set the condition codes,
2989 but also does other things. */
2991 int
2993 rtx x;
2994 {
2995 #ifdef HAVE_cc0
2999 {
3004 {
3010 }
3012 }
3014 #else
3016 #endif
3017 }
3018 \f
3019 /* Follow any unconditional jump at LABEL;
3020 return the ultimate label reached by any such chain of jumps.
3021 If LABEL is not followed by a jump, return LABEL.
3022 If the chain loops or we can't find end, return LABEL,
3023 since that tells caller to avoid changing the insn.
3025 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
3026 a USE or CLOBBER. */
3028 rtx
3030 rtx label;
3031 {
3044 depth++)
3045 {
3046 /* Don't chain through the insn that jumps into a loop
3047 from outside the loop,
3048 since that would create multiple loop entry jumps
3049 and prevent loop optimization. */
3050 rtx tem;
3057 /* If we have found a cycle, make the insn jump to itself. */
3067 }
3071 }
3073 /* Assuming that field IDX of X is a vector of label_refs,
3074 replace each of them by the ultimate label reached by it.
3075 Return nonzero if a change is made.
3076 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
3078 static int
3082 {
3086 {
3090 {
3096 }
3097 }
3099 }
3100 \f
3101 /* Find all CODE_LABELs referred to in X, and increment their use counts.
3102 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
3103 in INSN, then store one of them in JUMP_LABEL (INSN).
3104 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
3105 referenced in INSN, add a REG_LABEL note containing that label to INSN.
3106 Also, when there are consecutive labels, canonicalize on the last of them.
3108 Note that two labels separated by a loop-beginning note
3109 must be kept distinct if we have not yet done loop-optimization,
3110 because the gap between them is where loop-optimize
3111 will want to move invariant code to. CROSS_JUMP tells us
3112 that loop-optimization is done with.
3114 Once reload has completed (CROSS_JUMP non-zero), we need not consider
3115 two labels distinct if they are separated by only USE or CLOBBER insns. */
3117 static void
3120 rtx insn;
3122 {
3128 {
3141 /* If this is a constant-pool reference, see if it is a label. */
3148 {
3151 rtx note;
3152 rtx next;
3157 /* Ignore references to labels of containing functions. */
3161 /* If there are other labels following this one,
3162 replace it with the last of the consecutive labels. */
3164 {
3177 }
3183 {
3187 /* If we've changed OLABEL and we had a REG_LABEL note
3188 for it, update it as well. */
3193 /* Otherwise, add a REG_LABEL note for LABEL unless there already
3194 is one. */
3196 {
3198 /* Don't record labels that refer to dispatch tables.
3199 This is not necessary, since the tablejump
3200 references the same label.
3201 And if we did record them, flow.c would make worse code. */
3208 }
3209 }
3211 }
3213 /* Do walk the labels in a vector, but not the first operand of an
3214 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
3217 {
3223 }
3224 }
3228 {
3232 {
3236 }
3237 }
3238 }
3240 /* If all INSN does is set the pc, delete it,
3241 and delete the insn that set the condition codes for it
3242 if that's what the previous thing was. */
3244 void
3246 rtx insn;
3247 {
3252 }
3254 /* Delete INSN and recursively delete insns that compute values used only
3255 by INSN. This uses the REG_DEAD notes computed during flow analysis.
3256 If we are running before flow.c, we need do nothing since flow.c will
3257 delete dead code. We also can't know if the registers being used are
3258 dead or not at this point.
3260 Otherwise, look at all our REG_DEAD notes. If a previous insn does
3261 nothing other than set a register that dies in this insn, we can delete
3262 that insn as well.
3264 On machines with CC0, if CC0 is used in this insn, we may be able to
3265 delete the insn that set it. */
3267 static void
3269 rtx insn;
3270 {
3273 #ifdef HAVE_cc0
3275 {
3277 /* We assume that at this stage
3278 CC's are always set explicitly
3279 and always immediately before the jump that
3280 will use them. So if the previous insn
3281 exists to set the CC's, delete it
3282 (unless it performs auto-increments, etc.). */
3285 {
3289 else
3290 /* Otherwise, show that cc0 won't be used. */
3293 }
3294 }
3295 #endif
3298 {
3299 rtx our_prev;
3304 /* Verify that the REG_NOTE is legitimate. */
3311 {
3312 /* If we reach a SEQUENCE, it is too complex to try to
3313 do anything with it, so give up. */
3319 /* reorg creates USEs that look like this. We leave them
3320 alone because reorg needs them for its own purposes. */
3324 {
3329 {
3330 /* If we find a SET of something else, we can't
3331 delete the insn. */
3336 {
3342 }
3346 }
3352 }
3354 /* If OUR_PREV references the register that dies here, it is an
3355 additional use. Hence any prior SET isn't dead. However, this
3356 insn becomes the new place for the REG_DEAD note. */
3359 {
3363 }
3364 }
3365 }
3368 }
3369 \f
3370 /* Delete insn INSN from the chain of insns and update label ref counts.
3371 May delete some following insns as a consequence; may even delete
3372 a label elsewhere and insns that follow it.
3374 Returns the first insn after INSN that was not deleted. */
3376 rtx
3379 {
3388 /* This insn is already deleted => return first following nondeleted. */
3392 /* Don't delete user-declared labels. Convert them to special NOTEs
3393 instead. */
3396 {
3401 }
3402 else
3403 /* Mark this insn as deleted. */
3406 /* If this is an unconditional jump, delete it from the jump chain. */
3410 /* If instruction is followed by a barrier,
3411 delete the barrier too. */
3414 {
3417 }
3419 /* Patch out INSN (and the barrier if any) */
3422 {
3424 {
3429 }
3432 {
3436 }
3440 }
3442 /* If deleting a jump, decrement the count of the label,
3443 and delete the label if it is now unused. */
3447 {
3448 /* This can delete NEXT or PREV,
3449 either directly if NEXT is JUMP_LABEL (INSN),
3450 or indirectly through more levels of jumps. */
3452 /* I feel a little doubtful about this loop,
3453 but I see no clean and sure alternative way
3454 to find the first insn after INSN that is not now deleted.
3455 I hope this works. */
3459 }
3461 /* Likewise if we're deleting a dispatch table. */
3466 {
3477 }
3482 /* If INSN was a label and a dispatch table follows it,
3483 delete the dispatch table. The tablejump must have gone already.
3484 It isn't useful to fall through into a table. */
3493 /* If INSN was a label, delete insns following it if now unreachable. */
3496 {
3502 {
3506 /* Keep going past other deleted labels to delete what follows. */
3509 else
3510 /* Note: if this deletes a jump, it can cause more
3511 deletion of unreachable code, after a different label.
3512 As long as the value from this recursive call is correct,
3513 this invocation functions correctly. */
3515 }
3516 }
3519 }
3521 /* Advance from INSN till reaching something not deleted
3522 then return that. May return INSN itself. */
3524 rtx
3526 rtx insn;
3527 {
3531 }
3532 \f
3533 /* Delete a range of insns from FROM to TO, inclusive.
3534 This is for the sake of peephole optimization, so assume
3535 that whatever these insns do will still be done by a new
3536 peephole insn that will replace them. */
3538 void
3541 {
3545 {
3550 {
3553 /* Patch this insn out of the chain. */
3554 /* We don't do this all at once, because we
3555 must preserve all NOTEs. */
3561 }
3566 }
3568 /* Note that if TO is an unconditional jump
3569 we *do not* delete the BARRIER that follows,
3570 since the peephole that replaces this sequence
3571 is also an unconditional jump in that case. */
3572 }
3573 \f
3574 /* Invert the condition of the jump JUMP, and make it jump
3575 to label NLABEL instead of where it jumps now. */
3577 int
3580 {
3581 /* We have to either invert the condition and change the label or
3582 do neither. Either operation could fail. We first try to invert
3583 the jump. If that succeeds, we try changing the label. If that fails,
3584 we invert the jump back to what it was. */
3593 /* This should just be putting it back the way it was. */
3597 }
3599 /* Invert the jump condition of rtx X contained in jump insn, INSN.
3601 Return 1 if we can do so, 0 if we cannot find a way to do so that
3602 matches a pattern. */
3604 int
3606 rtx x;
3607 rtx insn;
3608 {
3616 {
3620 /* We can do this in two ways: The preferable way, which can only
3621 be done if this is not an integer comparison, is to reverse
3622 the comparison code. Otherwise, swap the THEN-part and ELSE-part
3623 of the IF_THEN_ELSE. If we can't do either, fail. */
3636 }
3640 {
3645 {
3650 }
3651 }
3654 }
3655 \f
3656 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
3657 If the old jump target label is unused as a result,
3658 it and the code following it may be deleted.
3660 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
3661 RETURN insn.
3663 The return value will be 1 if the change was made, 0 if it wasn't (this
3664 can only occur for NLABEL == 0). */
3666 int
3669 {
3678 /* If this is an unconditional branch, delete it from the jump_chain of
3679 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
3680 have UID's in range and JUMP_CHAIN is valid). */
3683 {
3689 {
3692 }
3693 }
3703 }
3705 /* Delete the instruction JUMP from any jump chain it might be on. */
3707 static void
3709 rtx jump;
3710 {
3714 /* Handle unconditional jumps. */
3719 /* Handle return insns. */
3726 else
3727 {
3728 rtx insn;
3734 {
3737 }
3738 }
3739 }
3741 /* If NLABEL is nonzero, throughout the rtx at LOC,
3742 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
3743 zero, alter (RETURN) to (LABEL_REF NLABEL).
3745 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
3746 validity with validate_change. Convert (set (pc) (label_ref olabel))
3747 to (return).
3749 Return 0 if we found a change we would like to make but it is invalid.
3750 Otherwise, return 1. */
3752 int
3756 rtx insn;
3757 {
3764 {
3766 {
3769 else
3772 }
3773 }
3775 {
3780 }
3789 {
3794 {
3799 }
3800 }
3803 }
3804 \f
3805 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
3807 If the old jump target label (before the dispatch table) becomes unused,
3808 it and the dispatch table may be deleted. In that case, find the insn
3809 before the jump references that label and delete it and logical successors
3810 too. */
3812 static void
3815 {
3818 /* Add this jump to the jump_chain of NLABEL. */
3821 {
3824 }
3832 {
3835 }
3836 }
3838 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
3839 If we found one, delete it and then delete this insn if DELETE_THIS is
3840 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
3842 static int
3846 {
3848 rtx link;
3852 {
3854 {
3857 }
3858 else
3860 }
3864 {
3866 {
3869 }
3870 else
3872 }
3875 }
3876 \f
3877 /* Like rtx_equal_p except that it considers two REGs as equal
3878 if they renumber to the same value and considers two commutative
3879 operations to be the same if the order of the operands has been
3880 reversed. */
3882 int
3885 {
3896 {
3903 /* If we haven't done any renumbering, don't
3904 make any assumptions. */
3909 {
3914 {
3917 }
3918 }
3920 else
3921 {
3925 }
3928 {
3933 {
3936 }
3937 }
3939 else
3940 {
3944 }
3947 }
3949 /* Now we have disposed of all the cases
3950 in which different rtx codes can match. */
3955 {
3966 /* We can't assume nonlocal labels have their following insns yet. */
3970 /* Two label-refs are equivalent if they point at labels
3971 in the same position in the instruction stream. */
3977 }
3979 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
3984 /* For commutative operations, the RTX match if the operand match in any
3985 order. Also handle the simple binary and unary cases without a loop. */
3997 /* Compare the elements. If any pair of corresponding elements
3998 fail to match, return 0 for the whole things. */
4002 {
4005 {
4029 /* fall through. */
4043 }
4044 }
4046 }
4047 \f
4048 /* If X is a hard register or equivalent to one or a subregister of one,
4049 return the hard register number. If X is a pseudo register that was not
4050 assigned a hard register, return the pseudo register number. Otherwise,
4051 return -1. Any rtx is valid for X. */
4053 int
4055 rtx x;
4056 {
4058 {
4062 }
4064 {
4068 }
4070 }
4071 \f
4072 /* Optimize code of the form:
4074 for (x = a[i]; x; ...)
4075 ...
4076 for (x = a[i]; x; ...)
4077 ...
4078 foo:
4080 Loop optimize will change the above code into
4082 if (x = a[i])
4083 for (;;)
4084 { ...; if (! (x = ...)) break; }
4085 if (x = a[i])
4086 for (;;)
4087 { ...; if (! (x = ...)) break; }
4088 foo:
4090 In general, if the first test fails, the program can branch
4091 directly to `foo' and skip the second try which is doomed to fail.
4092 We run this after loop optimization and before flow analysis. */
4094 /* When comparing the insn patterns, we track the fact that different
4095 pseudo-register numbers may have been used in each computation.
4096 The following array stores an equivalence -- same_regs[I] == J means
4097 that pseudo register I was used in the first set of tests in a context
4098 where J was used in the second set. We also count the number of such
4099 pending equivalences. If nonzero, the expressions really aren't the
4100 same. */
4106 /* Track any registers modified between the target of the first jump and
4107 the second jump. They never compare equal. */
4111 /* Record if memory was modified. */
4115 /* Called via note_stores on each insn between the target of the first
4116 branch and the second branch. It marks any changed registers. */
4118 static void
4120 rtx dest;
4121 rtx x;
4122 {
4137 else
4140 }
4142 /* F is the first insn in the chain of insns. */
4144 void
4146 rtx f;
4149 {
4150 /* Basic algorithm is to find a conditional branch,
4151 the label it may branch to, and the branch after
4152 that label. If the two branches test the same condition,
4153 walk back from both branch paths until the insn patterns
4154 differ, or code labels are hit. If we make it back to
4155 the target of the first branch, then we know that the first branch
4156 will either always succeed or always fail depending on the relative
4157 senses of the two branches. So adjust the first branch accordingly
4158 in this case. */
4167 /* Allocate register tables and quick-reset table. */
4175 {
4179 {
4180 /* Get to a candidate branch insn. */
4195 /* Look for a branch after the target. Record any registers and
4196 memory modified between the target and the branch. Stop when we
4197 get to a label since we can't know what was changed there. */
4199 {
4204 {
4205 /* If this is an unconditional jump and is the only use of
4206 its target label, we can follow it. */
4210 {
4213 }
4214 else
4216 }
4222 {
4231 }
4234 }
4236 /* Check the next candidate branch insn from the label
4237 of the first. */
4245 /* Get the comparison codes and operands, reversing the
4246 codes if appropriate. If we don't have comparison codes,
4247 we can't do anything. */
4260 /* If they test the same things and knowing that B1 branches
4261 tells us whether or not B2 branches, check if we
4262 can thread the branch. */
4267 {
4272 {
4274 {
4275 /* We have reached the target of the first branch.
4276 If there are no pending register equivalents,
4277 we know that this branch will either always
4278 succeed (if the senses of the two branches are
4279 the same) or always fail (if not). */
4280 rtx new_label;
4287 else
4291 {
4296 {
4297 /* Don't thread to the loop label. If a loop
4298 label is reused, loop optimization will
4299 be disabled for that loop. */
4302 }
4304 }
4306 }
4308 /* If either of these is not a normal insn (it might be
4309 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
4310 have already been skipped above.) Similarly, fail
4311 if the insns are different. */
4320 }
4321 }
4322 }
4323 }
4324 }
4325 \f
4326 /* This is like RTX_EQUAL_P except that it knows about our handling of
4327 possibly equivalent registers and knows to consider volatile and
4328 modified objects as not equal.
4330 YINSN is the insn containing Y. */
4332 int
4335 rtx yinsn;
4336 {
4343 /* Rtx's of different codes cannot be equal. */
4347 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
4348 (REG:SI x) and (REG:HI x) are NOT equivalent. */
4353 /* For commutative operations, the RTX match if the operand match in any
4354 order. Also handle the simple binary and unary cases without a loop. */
4366 /* Handle special-cases first. */
4368 {
4373 /* If neither is user variable or hard register, check for possible
4374 equivalence. */
4381 {
4383 num_same_regs++;
4385 /* If this is the first time we are seeing a register on the `Y'
4386 side, see if it is the last use. If not, we can't thread the
4387 jump, so mark it as not equivalent. */
4392 }
4393 else
4399 /* If memory modified or either volatile, not equivalent.
4400 Else, check address. */
4413 /* Cancel a pending `same_regs' if setting equivalenced registers.
4414 Then process source. */
4417 {
4419 {
4421 num_same_regs--;
4422 }
4425 }
4426 else
4437 }
4444 {
4446 {
4460 /* Two vectors must have the same length. */
4464 /* And the corresponding elements must match. */
4483 /* These are just backpointers, so they don't matter. */
4489 /* It is believed that rtx's at this level will never
4490 contain anything but integers and other rtx's,
4491 except for within LABEL_REFs and SYMBOL_REFs. */
4494 }
4495 }
4497 }