| blob | 4ffeeff3f2186f16e12ab7e6fda0c967303603be |
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. */
69 /* ??? Eventually must record somehow the labels used by jumps
70 from nested functions. */
71 /* Pre-record the next or previous real insn for each label?
72 No, this pass is very fast anyway. */
73 /* Condense consecutive labels?
74 This would make life analysis faster, maybe. */
75 /* Optimize jump y; x: ... y: jumpif... x?
76 Don't know if it is worth bothering with. */
77 /* Optimize two cases of conditional jump to conditional jump?
78 This can never delete any instruction or make anything dead,
79 or even change what is live at any point.
80 So perhaps let combiner do it. */
82 /* Vector indexed by uid.
83 For each CODE_LABEL, index by its uid to get first unconditional jump
84 that jumps to the label.
85 For each JUMP_INSN, index by its uid to get the next unconditional jump
86 that jumps to the same label.
87 Element 0 is the start of a chain of all return insns.
88 (It is safe to use element 0 because insn uid 0 is not used. */
92 /* List of labels referred to from initializers.
93 These can never be deleted. */
94 rtx forced_labels;
96 /* Maximum index in jump_chain. */
100 /* Set nonzero by jump_optimize if control can fall through
101 to the end of the function. */
104 /* Indicates whether death notes are significant in cross jump analysis.
105 Normally they are not significant, because of A and B jump to C,
106 and R dies in A, it must die in B. But this might not be true after
107 stack register conversion, and we must compare death notes in that
108 case. */
129 #ifndef HAVE_cc0
131 #endif
132 \f
133 /* Delete no-op jumps and optimize jumps to jumps
134 and jumps around jumps.
135 Delete unused labels and unreachable code.
137 If CROSS_JUMP is 1, detect matching code
138 before a jump and its destination and unify them.
139 If CROSS_JUMP is 2, do cross-jumping, but pay attention to death notes.
141 If NOOP_MOVES is nonzero, delete no-op move insns.
143 If AFTER_REGSCAN is nonzero, then this jump pass is being run immediately
144 after regscan, and it is safe to use regno_first_uid and regno_last_uid.
146 If `optimize' is zero, don't change any code,
147 just determine whether control drops off the end of the function.
148 This case occurs when we have -W and not -O.
149 It works because `delete_insn' checks the value of `optimize'
150 and refrains from actually deleting when that is 0. */
152 void
154 rtx f;
158 {
164 rtx last_insn;
169 /* If we are performing cross jump optimizations, then initialize
170 tables mapping UIDs to EH regions to avoid incorrect movement
171 of insns from one EH region to another. */
177 /* Leave some extra room for labels and duplicate exit test insns
178 we make. */
185 /* Keep track of labels used from static data;
186 they cannot ever be deleted. */
193 /* Keep track of labels used for marking handlers for exception
194 regions; they cannot usually be deleted. */
204 {
207 /* Zero the "deleted" flag of all the "deleted" insns. */
211 /* Show that the jump chain is not valid. */
214 }
216 #ifdef HAVE_return
218 {
219 /* If we fall through to the epilogue, see if we can insert a RETURN insn
220 in front of it. If the machine allows it at this point (we might be
221 after reload for a leaf routine), it will improve optimization for it
222 to be there. */
228 {
231 }
232 }
233 #endif
238 /* If we haven't yet gotten to reload and we have just run regscan,
239 delete any insn that sets a register that isn't used elsewhere.
240 This helps some of the optimizations below by having less insns
241 being jumped around. */
245 {
253 /* We use regno_last_note_uid so as not to delete the setting
254 of a reg that's used in notes. A subsequent optimization
255 might arrange to use that reg for real. */
260 }
262 /* Now iterate optimizing jumps until nothing changes over one pass. */
266 {
270 {
271 rtx reallabelprev;
273 rtx nlabel;
277 #if 0
278 /* If NOT the first iteration, if this is the last jump pass
279 (just before final), do the special peephole optimizations.
280 Avoiding the first iteration gives ordinary jump opts
281 a chance to work before peephole opts. */
286 #endif
288 /* That could have deleted some insns after INSN, so check now
289 what the following insn is. */
293 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
294 jump. Try to optimize by duplicating the loop exit test if so.
295 This is only safe immediately after regscan, because it uses
296 the values of regno_first_uid and regno_last_uid. */
301 {
304 {
308 }
309 }
318 /* Tension the labels in dispatch tables. */
325 /* If a dispatch table always goes to the same place,
326 get rid of it and replace the insn that uses it. */
330 {
345 /* Don't mess with a casesi insn. */
350 {
354 }
355 }
359 /* If a jump references the end of the function, try to turn
360 it into a RETURN insn, possibly a conditional one. */
367 /* Detect jump to following insn. */
369 {
374 }
376 /* If we have an unconditional jump preceded by a USE, try to put
377 the USE before the target and jump there. This simplifies many
378 of the optimizations below since we don't have to worry about
379 dealing with these USE insns. We only do this if the label
380 being branch to already has the identical USE or if code
381 never falls through to that label. */
390 /* Don't do this optimization if we have a loop containing only
391 the USE instruction, and the loop start label has a usage
392 count of 1. This is because we will redo this optimization
393 everytime through the outer loop, and jump opt will never
394 exit. */
398 {
400 {
403 }
409 }
411 /* Simplify if (...) x = a; else x = b; by converting it
412 to x = b; if (...) x = a;
413 if B is sufficiently simple, the test doesn't involve X,
414 and nothing in the test modifies B or X.
416 If we have small register classes, we also can't do this if X
417 is a hard register.
419 If the "x = b;" insn has any REG_NOTES, we don't do this because
420 of the possibility that we are running after CSE and there is a
421 REG_EQUAL note that is only valid if the branch has already been
422 taken. If we move the insn with the REG_EQUAL note, we may
423 fold the comparison to always be false in a later CSE pass.
424 (We could also delete the REG_NOTES when moving the insn, but it
425 seems simpler to not move it.) An exception is that we can move
426 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
427 value is the same as "b".
429 INSN is the branch over the `else' part.
431 We set:
433 TEMP to the jump insn preceding "x = a;"
434 TEMP1 to X
435 TEMP2 to the insn that sets "x = b;"
436 TEMP3 to the insn that sets "x = a;"
437 TEMP4 to the set of "x = b"; */
444 && (! SMALL_REGISTER_CLASSES
460 /* TEMP must skip over the "x = a;" insn */
463 /* There must be no other entries to the "x = b;" insn. */
465 /* INSN must either branch to the insn after TEMP2 or the insn
466 after TEMP2 must branch to the same place as INSN. */
471 {
472 /* The test expression, X, may be a complicated test with
473 multiple branches. See if we can find all the uses of
474 the label that TEMP branches to without hitting a CALL_INSN
475 or a jump to somewhere else. */
478 rtx p;
479 #ifdef HAVE_cc0
480 rtx q;
481 #endif
483 /* Set P to the first jump insn that goes around "x = a;". */
485 {
487 {
490 {
491 nuses--;
494 }
495 else
497 }
500 }
502 #ifdef HAVE_cc0
503 /* We cannot insert anything between a set of cc and its use
504 so if P uses cc0, we must back up to the previous insn. */
509 #endif
514 /* If we found all the uses and there was no data conflict, we
515 can move the assignment unless we can branch into the middle
516 from somewhere. */
523 /* Verify that registers used by the jump are not clobbered
524 by the instruction being moved. */
528 {
532 /* Set NEXT to an insn that we know won't go away. */
535 /* Delete the jump around the set. Note that we must do
536 this before we redirect the test jumps so that it won't
537 delete the code immediately following the assignment
538 we moved (which might be a jump). */
542 /* We either have two consecutive labels or a jump to
543 a jump, so adjust all the JUMP_INSNs to branch to where
544 INSN branches to. */
551 }
552 }
554 /* Simplify if (...) { x = a; goto l; } x = b; by converting it
555 to x = a; if (...) goto l; x = b;
556 if A is sufficiently simple, the test doesn't involve X,
557 and nothing in the test modifies A or X.
559 If we have small register classes, we also can't do this if X
560 is a hard register.
562 If the "x = a;" insn has any REG_NOTES, we don't do this because
563 of the possibility that we are running after CSE and there is a
564 REG_EQUAL note that is only valid if the branch has already been
565 taken. If we move the insn with the REG_EQUAL note, we may
566 fold the comparison to always be false in a later CSE pass.
567 (We could also delete the REG_NOTES when moving the insn, but it
568 seems simpler to not move it.) An exception is that we can move
569 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
570 value is the same as "a".
572 INSN is the goto.
574 We set:
576 TEMP to the jump insn preceding "x = a;"
577 TEMP1 to X
578 TEMP2 to the insn that sets "x = b;"
579 TEMP3 to the insn that sets "x = a;"
580 TEMP4 to the set of "x = a"; */
587 && (! SMALL_REGISTER_CLASSES
603 /* TEMP must skip over the "x = a;" insn */
606 {
610 #ifdef HAVE_cc0
611 /* We cannot insert anything between a set of cc and its use. */
615 #endif
625 /* Verify that registers used by the jump are not clobbered
626 by the instruction being moved. */
631 {
636 /* Set NEXT to an insn that we know won't go away. */
639 }
644 }
646 #ifndef HAVE_cc0
647 /* If we have if (...) x = exp; and branches are expensive,
648 EXP is a single insn, does not have any side effects, cannot
649 trap, and is not too costly, convert this to
650 t = exp; if (...) x = t;
652 Don't do this when we have CC0 because it is unlikely to help
653 and we'd need to worry about where to place the new insn and
654 the potential for conflicts. We also can't do this when we have
655 notes on the insn for the same reason as above.
657 We set:
659 TEMP to the "x = exp;" insn.
660 TEMP1 to the single set in the "x = exp;" insn.
661 TEMP2 to "x". */
675 && (! SMALL_REGISTER_CLASSES
683 {
688 {
696 {
699 }
700 }
701 }
703 /* Similarly, if it takes two insns to compute EXP but they
704 have the same destination. Here TEMP3 will be the second
705 insn and TEMP4 the SET from that insn. */
723 && (! SMALL_REGISTER_CLASSES
733 {
739 {
740 /* Use the earliest of temp5 and temp6. */
746 emit_insn_after_with_line_notes
754 {
757 }
758 }
759 }
761 /* Finally, handle the case where two insns are used to
762 compute EXP but a temporary register is used. Here we must
763 ensure that the temporary register is not used anywhere else. */
766 && after_regscan
794 && (! SMALL_REGISTER_CLASSES
800 {
806 {
807 /* Use the earliest of temp5 and temp6. */
820 {
823 }
824 }
825 }
828 /* Try to use a conditional move (if the target has them), or a
829 store-flag insn. The general case is:
831 1) x = a; if (...) x = b; and
832 2) if (...) x = b;
834 If the jump would be faster, the machine should not have defined
835 the movcc or scc insns!. These cases are often made by the
836 previous optimization.
838 The second case is treated as x = x; if (...) x = b;.
840 INSN here is the jump around the store. We set:
842 TEMP to the "x = b;" insn.
843 TEMP1 to X.
844 TEMP2 to B.
845 TEMP3 to A (X in the second case).
846 TEMP4 to the condition being tested.
847 TEMP5 to the earliest insn used to find the condition. */
850 ! reload_completed
852 /* Set TEMP to the "x = b;" insn. */
857 && (! SMALL_REGISTER_CLASSES
861 /* Allow either form, but prefer the former if both apply.
862 There is no point in using the old value of TEMP1 if
863 it is a register, since cse will alias them. It can
864 lose if the old value were a hard register since CSE
865 won't replace hard registers. Avoid using TEMP3 if
866 small register classes and it is a hard register. */
870 /* Make the latter case look like x = x; if (...) x = b; */
872 /* INSN must either branch to the insn after TEMP or the insn
873 after TEMP must branch to the same place as INSN. */
879 /* We must be comparing objects whose modes imply the size.
880 We could handle BLKmode if (1) emit_store_flag could
881 and (2) we could find the size reliably. */
883 /* Even if branches are cheap, the store_flag optimization
884 can win when the operation to be performed can be
885 expressed directly. */
886 #ifdef HAVE_cc0
887 /* If the previous insn sets CC0 and something else, we can't
888 do this since we are going to delete that insn. */
895 #endif
896 )
897 {
898 #ifdef HAVE_conditional_move
899 /* First try a conditional move. */
900 {
904 rtx target;
906 /* Copy the compared variables into cond0 and cond1, so that
907 any side effects performed in or after the old comparison,
908 will not affect our compare which will come later. */
909 /* ??? Is it possible to just use the comparison in the jump
910 insn? After all, we're going to delete it. We'd have
911 to modify emit_conditional_move to take a comparison rtx
912 instead or write a new function. */
914 /* We want the target to be able to simplify comparisons with
915 zero (and maybe other constants as well), so don't create
916 pseudos for them. There's no need to either. */
920 else
934 {
937 /* Save the conditional move sequence but don't emit it
938 yet. On some machines, like the alpha, it is possible
939 that temp5 == insn, so next generate the sequence that
940 saves the compared values and then emit both
941 sequences ensuring seq1 occurs before seq2. */
945 /* Now that we can't fail, generate the copy insns that
946 preserve the compared values. */
955 /* Insert conditional move after insn, to be sure that
956 the jump and a possible compare won't be separated */
959 /* ??? We can also delete the insn that sets X to A.
960 Flow will do it too though. */
966 {
969 }
973 }
974 else
976 }
977 #endif
979 /* That didn't work, try a store-flag insn.
981 We further divide the cases into:
983 1) x = a; if (...) x = b; and either A or B is zero,
984 2) if (...) x = 0; and jumps are expensive,
985 3) x = a; if (...) x = b; and A and B are constants where all
986 the set bits in A are also set in B and jumps are expensive,
987 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
988 more expensive, and
989 5) if (...) x = b; if jumps are even more expensive. */
993 /* Make the latter case look like
994 x = x; if (...) x = 0; */
999 /* If B is zero, OK; if A is zero, can only do (1) if we
1000 can reverse the condition. See if (3) applies possibly
1001 by reversing the condition. Prefer reversing to (4) when
1002 branches are very expensive. */
1006 /* Check that the mask is a power of two,
1007 so that it can probably be generated
1008 with a shift. */
1025 insn)))))
1027 )
1028 {
1032 rtx target;
1034 /* If necessary, reverse the condition. */
1037 else
1040 /* If CVAL is non-zero, normalize to -1. Otherwise, if UVAL
1041 is the constant 1, it is best to just compute the result
1042 directly. If UVAL is constant and STORE_FLAG_VALUE
1043 includes all of its bits, it is best to compute the flag
1044 value unnormalized and `and' it with UVAL. Otherwise,
1045 normalize to -1 and `and' with UVAL. */
1052 /* We will be putting the store-flag insn immediately in
1053 front of the comparison that was originally being done,
1054 so we know all the variables in TEMP4 will be valid.
1055 However, this might be in front of the assignment of
1056 A to VAR. If it is, it would clobber the store-flag
1057 we will be emitting.
1059 Therefore, emit into a temporary which will be copied to
1060 VAR immediately after TEMP. */
1065 VOIDmode,
1068 normalizep);
1070 {
1071 rtx seq;
1077 /* Put the store-flag insns in front of the first insn
1078 used to compute the condition to ensure that we
1079 use the same values of them as the current
1080 comparison. However, the remainder of the insns we
1081 generate will be placed directly in front of the
1082 jump insn, in case any of the pseudos we use
1083 are modified earlier. */
1089 /* Both CVAL and UVAL are non-zero. */
1091 {
1099 else
1100 {
1106 }
1108 /* If we usually make new pseudos, do so here. This
1109 turns out to help machines that have conditional
1110 move insns. */
1111 /* ??? Conditional moves have already been handled.
1112 This may be obsolete. */
1120 }
1122 {
1123 /* We know that either CVAL or UVAL is zero. If
1124 UVAL is zero, negate TARGET and `and' with CVAL.
1125 Otherwise, `and' with UVAL. */
1127 {
1131 }
1137 }
1142 #ifdef HAVE_cc0
1143 /* If INSN uses CC0, we must not separate it from the
1144 insn that sets cc0. */
1147 #endif
1155 {
1158 }
1162 }
1163 else
1165 }
1166 }
1168 /* If branches are expensive, convert
1169 if (foo) bar++; to bar += (foo != 0);
1170 and similarly for "bar--;"
1172 INSN is the conditional branch around the arithmetic. We set:
1174 TEMP is the arithmetic insn.
1175 TEMP1 is the SET doing the arithmetic.
1176 TEMP2 is the operand being incremented or decremented.
1177 TEMP3 to the condition being tested.
1178 TEMP4 to the earliest insn used to find the condition. */
1181 #ifdef HAVE_incscc
1182 || HAVE_incscc
1183 #endif
1184 #ifdef HAVE_decscc
1185 || HAVE_decscc
1186 #endif
1187 )
1188 && ! reload_completed
1200 /* INSN must either branch to the insn after TEMP or the insn
1201 after TEMP must branch to the same place as INSN. */
1207 /* We must be comparing objects whose modes imply the size.
1208 We could handle BLKmode if (1) emit_store_flag could
1209 and (2) we could find the size reliably. */
1212 {
1218 /* It must be the case that TEMP2 is not modified in the range
1219 [TEMP4, INSN). The one exception we make is if the insn
1220 before INSN sets TEMP2 to something which is also unchanged
1221 in that range. In that case, we can move the initialization
1222 into our sequence. */
1232 {
1236 }
1242 VOIDmode,
1246 /* If we can do the store-flag, do the addition or
1247 subtraction. */
1256 {
1257 /* Put the result back in temp2 in case it isn't already.
1258 Then replace the jump, possible a CC0-setting insn in
1259 front of the jump, and TEMP, with the sequence we have
1260 made. */
1275 #ifdef HAVE_cc0
1277 #endif
1281 {
1284 }
1288 }
1289 else
1291 }
1293 /* Simplify if (...) x = 1; else {...} if (x) ...
1294 We recognize this case scanning backwards as well.
1296 TEMP is the assignment to x;
1297 TEMP1 is the label at the head of the second if. */
1298 /* ?? This should call get_condition to find the values being
1299 compared, instead of looking for a COMPARE insn when HAVE_cc0
1300 is not defined. This would allow it to work on the m88k. */
1301 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1302 is not defined and the condition is tested by a separate compare
1303 insn. This is because the code below assumes that the result
1304 of the compare dies in the following branch.
1306 Not only that, but there might be other insns between the
1307 compare and branch whose results are live. Those insns need
1308 to be executed.
1310 A way to fix this is to move the insns at JUMP_LABEL (insn)
1311 to before INSN. If we are running before flow, they will
1312 be deleted if they aren't needed. But this doesn't work
1313 well after flow.
1315 This is really a special-case of jump threading, anyway. The
1316 right thing to do is to replace this and jump threading with
1317 much simpler code in cse.
1319 This code has been turned off in the non-cc0 case in the
1320 meantime. */
1322 #ifdef HAVE_cc0
1324 /* Safe to skip USE and CLOBBER insns here
1325 since they will not be deleted. */
1333 /* If we find that the next value tested is `x'
1334 (TEMP1 is the insn where this happens), win. */
1337 #ifdef HAVE_cc0
1338 /* Does temp1 `tst' the value of x? */
1342 #else
1343 /* Does temp1 compare the value of x against zero? */
1350 #endif
1352 {
1353 /* Get the if_then_else from the condjump. */
1356 {
1359 rtx cond
1362 rtx ultimate;
1368 else
1378 }
1379 }
1380 #endif
1382 #if 0
1383 /* @@ This needs a bit of work before it will be right.
1385 Any type of comparison can be accepted for the first and
1386 second compare. When rewriting the first jump, we must
1387 compute the what conditions can reach label3, and use the
1388 appropriate code. We can not simply reverse/swap the code
1389 of the first jump. In some cases, the second jump must be
1390 rewritten also.
1392 For example,
1393 < == converts to > ==
1394 < != converts to == >
1395 etc.
1397 If the code is written to only accept an '==' test for the second
1398 compare, then all that needs to be done is to swap the condition
1399 of the first branch.
1401 It is questionable whether we want this optimization anyways,
1402 since if the user wrote code like this because he/she knew that
1403 the jump to label1 is taken most of the time, then rewriting
1404 this gives slower code. */
1405 /* @@ This should call get_condition to find the values being
1406 compared, instead of looking for a COMPARE insn when HAVE_cc0
1407 is not defined. This would allow it to work on the m88k. */
1408 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1409 is not defined and the condition is tested by a separate compare
1410 insn. This is because the code below assumes that the result
1411 of the compare dies in the following branch. */
1413 /* Simplify test a ~= b
1414 condjump label1;
1415 test a == b
1416 condjump label2;
1417 jump label3;
1418 label1:
1420 rewriting as
1421 test a ~~= b
1422 condjump label3
1423 test a == b
1424 condjump label2
1425 label1:
1427 where ~= is an inequality, e.g. >, and ~~= is the swapped
1428 inequality, e.g. <.
1430 We recognize this case scanning backwards.
1432 TEMP is the conditional jump to `label2';
1433 TEMP1 is the test for `a == b';
1434 TEMP2 is the conditional jump to `label1';
1435 TEMP3 is the test for `a ~= b'. */
1444 #ifdef HAVE_cc0
1446 #else
1450 #endif
1464 {
1469 {
1472 }
1476 }
1477 #endif
1478 /* Simplify if (...) {... x = 1;} if (x) ...
1480 We recognize this case backwards.
1482 TEMP is the test of `x';
1483 TEMP1 is the assignment to `x' at the end of the
1484 previous statement. */
1485 /* @@ This should call get_condition to find the values being
1486 compared, instead of looking for a COMPARE insn when HAVE_cc0
1487 is not defined. This would allow it to work on the m88k. */
1488 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1489 is not defined and the condition is tested by a separate compare
1490 insn. This is because the code below assumes that the result
1491 of the compare dies in the following branch. */
1493 /* ??? This has to be turned off. The problem is that the
1494 unconditional jump might indirectly end up branching to the
1495 label between TEMP1 and TEMP. We can't detect this, in general,
1496 since it may become a jump to there after further optimizations.
1497 If that jump is done, it will be deleted, so we will retry
1498 this optimization in the next pass, thus an infinite loop.
1500 The present code prevents this by putting the jump after the
1501 label, but this is not logically correct. */
1502 #if 0
1504 /* Safe to skip USE and CLOBBER insns here
1505 since they will not be deleted. */
1510 #ifdef HAVE_cc0
1513 #else
1514 /* Temp must be a compare insn, we can not accept a register
1515 to register move here, since it may not be simply a
1516 tst insn. */
1522 #endif
1523 /* May skip USE or CLOBBER insns here
1524 for checking for opportunity, since we
1525 take care of them later. */
1529 #ifdef HAVE_cc0
1531 #else
1534 #endif
1536 /* If this isn't true, cse will do the job. */
1538 {
1539 /* Get the if_then_else from the condjump. */
1544 {
1546 rtx last_insn;
1547 rtx ultimate;
1548 rtx p;
1550 /* Get the place that condjump will jump to
1551 if it is reached from here. */
1555 else
1557 /* Get it as a CODE_LABEL. */
1560 else
1561 /* Get the label out of the LABEL_REF. */
1564 /* Insert the jump immediately before TEMP, specifically
1565 after the label that is between TEMP1 and TEMP. */
1568 /* If we would be branching to the next insn, the jump
1569 would immediately be deleted and the re-inserted in
1570 a subsequent pass over the code. So don't do anything
1571 in that case. */
1574 {
1577 last_insn);
1582 {
1586 }
1589 }
1590 }
1591 }
1592 #endif
1593 /* Detect a conditional jump going to the same place
1594 as an immediately following unconditional jump. */
1600 {
1603 /* ??? Optional. Disables some optimizations, but makes
1604 gcov output more accurate with -O. */
1611 {
1615 }
1616 }
1617 #ifdef HAVE_trap
1618 /* Detect a conditional jump jumping over an unconditional trap. */
1629 {
1635 {
1641 }
1642 }
1643 /* Detect a jump jumping to an unconditional trap. */
1648 && (this_is_simplejump
1650 {
1655 {
1657 /* Replace an unconditional jump to a trap with a trap. */
1659 {
1664 }
1669 {
1674 }
1675 }
1676 /* If the trap condition and jump condition are mutually
1677 exclusive, redirect the jump to the following insn. */
1679 && ! this_is_simplejump
1684 {
1687 }
1688 }
1689 #endif
1691 /* Detect a conditional jump jumping over an unconditional jump. */
1694 && ! this_is_simplejump
1700 {
1701 /* When we invert the unconditional jump, we will be
1702 decrementing the usage count of its old label.
1703 Make sure that we don't delete it now because that
1704 might cause the following code to be deleted. */
1712 {
1713 /* It is very likely that if there are USE insns before
1714 this jump, they hold REG_DEAD notes. These REG_DEAD
1715 notes are no longer valid due to this optimization,
1716 and will cause the life-analysis that following passes
1717 (notably delayed-branch scheduling) to think that
1718 these registers are dead when they are not.
1720 To prevent this trouble, we just remove the USE insns
1721 from the insn chain. */
1725 {
1729 }
1734 }
1736 /* We can now safely delete the label if it is unreferenced
1737 since the delete_insn above has deleted the BARRIER. */
1741 }
1742 else
1743 {
1744 /* Detect a jump to a jump. */
1749 {
1752 }
1754 /* Look for if (foo) bar; else break; */
1755 /* The insns look like this:
1756 insn = condjump label1;
1757 ...range1 (some insns)...
1758 jump label2;
1759 label1:
1760 ...range2 (some insns)...
1761 jump somewhere unconditionally
1762 label2: */
1763 {
1766 /* Don't do this optimization on the first round, so that
1767 jump-around-a-jump gets simplified before we ask here
1768 whether a jump is unconditional.
1770 Also don't do it when we are called after reload since
1771 it will confuse reorg. */
1774 /* Make sure INSN is something we can invert. */
1781 {
1788 /* Invert the jump condition, so we
1789 still execute the same insns in each case. */
1791 {
1796 rtx rangenext;
1798 /* Include in each range any notes before it, to be
1799 sure that we get the line number note if any, even
1800 if there are other notes here. */
1809 /* Don't move NOTEs for blocks or loops; shift them
1810 outside the ranges, where they'll stay put. */
1814 /* Get current surrounds of the 2 ranges. */
1820 /* Splice range2 where range1 was. */
1825 /* Splice range1 where range2 was. */
1831 /* Check for a loop end note between the end of
1832 range2, and the next code label. If there is one,
1833 then what we have really seen is
1834 if (foo) break; end_of_loop;
1835 and moved the break sequence outside the loop.
1836 We must move the LOOP_END note to where the
1837 loop really ends now, or we will confuse loop
1838 optimization. Stop if we find a LOOP_BEG note
1839 first, since we don't want to move the LOOP_END
1840 note in that case. */
1842 {
1845 {
1848 {
1859 }
1863 }
1864 }
1867 }
1868 }
1869 }
1871 /* Now that the jump has been tensioned,
1872 try cross jumping: check for identical code
1873 before the jump and before its target label. */
1875 /* First, cross jumping of conditional jumps: */
1878 {
1882 /* A conditional jump may be crossjumped
1883 only if the place it jumps to follows
1884 an opposing jump that comes back here. */
1887 /* We have no opposing jump;
1888 cannot cross jump this insn. */
1892 /* TARGET is nonzero if it is ok to cross jump
1893 to code before TARGET. If so, see if matches. */
1899 {
1901 /* Make the old conditional jump
1902 into an unconditional one. */
1907 /* Add to jump_chain unless this is a new label
1908 whose UID is too large. */
1910 {
1914 }
1917 }
1918 }
1920 /* Cross jumping of unconditional jumps:
1921 a few differences. */
1924 {
1926 rtx target;
1930 /* TARGET is nonzero if it is ok to cross jump
1931 to code before TARGET. If so, see if matches. */
1935 /* If cannot cross jump to code before the label,
1936 see if we can cross jump to another jump to
1937 the same label. */
1938 /* Try each other jump to this label. */
1945 /* Ignore TARGET if it's deleted. */
1951 {
1955 }
1956 }
1958 /* This code was dead in the previous jump.c! */
1960 {
1961 /* Return insns all "jump to the same place"
1962 so we can cross-jump between any two of them. */
1968 /* If cannot cross jump to code before the label,
1969 see if we can cross jump to another jump to
1970 the same label. */
1971 /* Try each other jump to this label. */
1982 {
1986 }
1987 }
1988 }
1989 }
1992 }
1994 /* Delete extraneous line number notes.
1995 Note that two consecutive notes for different lines are not really
1996 extraneous. There should be some indication where that line belonged,
1997 even if it became empty. */
1999 {
2004 {
2005 /* Delete this note if it is identical to previous note. */
2009 {
2012 }
2015 }
2016 }
2018 #ifdef HAVE_return
2020 {
2021 /* If we fall through to the epilogue, see if we can insert a RETURN insn
2022 in front of it. If the machine allows it at this point (we might be
2023 after reload for a leaf routine), it will improve optimization for it
2024 to be there. We do this both here and at the start of this pass since
2025 the RETURN might have been deleted by some of our optimizations. */
2031 {
2034 }
2035 }
2036 #endif
2040 /* Show JUMP_CHAIN no longer valid. */
2042 }
2043 \f
2044 /* Initialize LABEL_NUSES and JUMP_LABEL fields. Delete any REG_LABEL
2045 notes whose labels don't occur in the insn any more. Returns the
2046 largest INSN_UID found. */
2047 static int
2049 rtx f;
2050 {
2052 rtx insn;
2055 {
2061 {
2065 {
2070 }
2071 }
2074 }
2077 }
2079 /* Delete insns following barriers, up to next label.
2081 Also delete no-op jumps created by gcse. */
2082 static void
2084 rtx f;
2085 {
2086 rtx insn;
2089 {
2091 {
2094 {
2098 else
2100 }
2101 /* INSN is now the code_label. */
2102 }
2103 /* Also remove (set (pc) (pc)) insns which can be created by
2104 gcse. We eliminate such insns now to avoid having them
2105 cause problems later. */
2111 else
2113 }
2114 }
2116 /* Mark the label each jump jumps to.
2117 Combine consecutive labels, and count uses of labels.
2119 For each label, make a chain (using `jump_chain')
2120 of all the *unconditional* jumps that jump to it;
2121 also make a chain of all returns.
2123 CROSS_JUMP indicates whether we are doing cross jumping
2124 and if we are whether we will be paying attention to
2125 death notes or not. */
2127 static void
2129 rtx f;
2131 {
2132 rtx insn;
2136 {
2139 {
2141 {
2145 }
2147 {
2150 }
2151 }
2152 }
2153 }
2155 /* Delete all labels already not referenced.
2156 Also find and return the last insn. */
2158 static rtx
2160 rtx f;
2161 {
2163 rtx insn;
2166 {
2169 else
2170 {
2173 }
2174 }
2177 }
2179 /* Delete various simple forms of moves which have no necessary
2180 side effect. */
2182 static void
2184 rtx f;
2185 {
2189 {
2193 {
2196 /* Combine stack_adjusts with following push_insns. */
2197 #ifdef PUSH_ROUNDING
2204 {
2205 rtx p;
2211 /* Find all successive push insns. */
2213 /* Don't convert more than three pushes;
2214 that starts adding too many displaced addresses
2215 and the whole thing starts becoming a losing
2216 proposition. */
2218 {
2227 /* Allow a no-op move between the adjust and the push. */
2236 pushes++;
2241 }
2243 /* Discard the amount pushed from the stack adjust;
2244 maybe eliminate it entirely. */
2246 {
2249 }
2250 else
2254 /* Change the appropriate push insns to ordinary stores. */
2257 {
2266 /* Allow a no-op move between the adjust and the push. */
2276 /* If this push doesn't fully fit in the space
2277 of the stack adjust that we deleted,
2278 make another stack adjust here for what we
2279 didn't use up. There should be peepholes
2280 to recognize the resulting sequence of insns. */
2282 {
2285 p);
2287 }
2290 }
2291 }
2292 #endif
2294 /* Detect and delete no-op move instructions
2295 resulting from not allocating a parameter in a register. */
2308 /* Detect and ignore no-op move instructions
2309 resulting from smart or fortuitous register allocation. */
2312 {
2319 {
2320 rtx trial;
2327 {
2328 /* DREG may have been the target of a REG_DEAD note in
2329 the insn which makes INSN redundant. If so, reorg
2330 would still think it is dead. So search for such a
2331 note and delete it if we find it. */
2337 {
2340 }
2342 /* Deleting insn could lose a death-note for SREG. */
2344 {
2345 /* Change this into a USE so that we won't emit
2346 code for it, but still can keep the note. */
2350 /* Remove all reg notes but the REG_DEAD one. */
2353 }
2354 else
2356 }
2357 }
2362 {
2363 /* This handles the case where we have two consecutive
2364 assignments of the same constant to pseudos that didn't
2365 get a hard reg. Each SET from the constant will be
2366 converted into a SET of the spill register and an
2367 output reload will be made following it. This produces
2368 two loads of the same constant into the same spill
2369 register. */
2373 /* Look back for a death note for the first reg.
2374 If there is one, it is no longer accurate. */
2376 {
2380 {
2383 }
2385 }
2387 /* Delete the second load of the value. */
2389 }
2390 }
2392 {
2393 /* If each part is a set between two identical registers or
2394 a USE or CLOBBER, delete the insn. */
2396 rtx tem;
2399 {
2409 }
2413 }
2414 /* Also delete insns to store bit fields if they are no-ops. */
2415 /* Not worth the hair to detect this in the big-endian case. */
2424 }
2426 }
2427 }
2429 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
2430 If so indicate that this function can drop off the end by returning
2431 1, else return 0.
2433 CHECK_DELETED indicates whether we must check if the note being
2434 searched for has the deleted flag set.
2436 DELETE_FINAL_NOTE indicates whether we should delete the note
2437 if we find it. */
2439 static int
2441 rtx last;
2444 {
2449 {
2452 /* One label can follow the end-note: the return label. */
2455 /* Ordinary insns can follow it if returning a structure. */
2458 /* If machine uses explicit RETURN insns, no epilogue,
2459 then one of them follows the note. */
2463 /* A barrier can follow the return insn. */
2466 /* Other kinds of notes can follow also. */
2475 }
2477 /* See if we backed up to the appropriate type of note. */
2483 {
2487 }
2490 }
2492 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
2493 jump. Assume that this unconditional jump is to the exit test code. If
2494 the code is sufficiently simple, make a copy of it before INSN,
2495 followed by a jump to the exit of the loop. Then delete the unconditional
2496 jump after INSN.
2498 Return 1 if we made the change, else 0.
2500 This is only safe immediately after a regscan pass because it uses the
2501 values of regno_first_uid and regno_last_uid. */
2503 static int
2505 rtx loop_start;
2506 {
2511 rtx lastexit;
2515 /* Scan the exit code. We do not perform this optimization if any insn:
2517 is a CALL_INSN
2518 is a CODE_LABEL
2519 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
2520 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
2521 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
2522 is not valid.
2524 We also do not do this if we find an insn with ASM_OPERANDS. While
2525 this restriction should not be necessary, copying an insn with
2526 ASM_OPERANDS can confuse asm_noperands in some cases.
2528 Also, don't do this if the exit code is more than 20 insns. */
2531 insn
2535 {
2537 {
2542 /* We could be in front of the wrong NOTE_INSN_LOOP_END if there is
2543 a jump immediately after the loop start that branches outside
2544 the loop but within an outer loop, near the exit test.
2545 If we copied this exit test and created a phony
2546 NOTE_INSN_LOOP_VTOP, this could make instructions immediately
2547 before the exit test look like these could be safely moved
2548 out of the loop even if they actually may be never executed.
2549 This can be avoided by checking here for NOTE_INSN_LOOP_CONT. */
2558 /* If we were to duplicate this code, we would not move
2559 the BLOCK notes, and so debugging the moved code would
2560 be difficult. Thus, we only move the code with -O2 or
2561 higher. */
2567 /* The code below would grossly mishandle REG_WAS_0 notes,
2568 so get rid of them here. */
2579 }
2580 }
2582 /* Unless INSN is zero, we can do the optimization. */
2588 /* See if any insn sets a register only used in the loop exit code and
2589 not a user variable. If so, replace it with a new register. */
2598 {
2604 {
2605 /* We can do the replacement. Allocate reg_map if this is the
2606 first replacement we found. */
2608 {
2611 }
2616 }
2617 }
2619 /* Now copy each insn. */
2622 {
2627 /* Only copy line-number notes. */
2629 {
2632 }
2642 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
2643 make them. */
2660 {
2664 }
2666 /* If this is a simple jump, add it to the jump chain. */
2670 {
2674 }
2679 }
2681 /* Now clean up by emitting a jump to the end label and deleting the jump
2682 at the start of the loop. */
2684 {
2686 loop_start);
2690 {
2694 }
2696 }
2698 /* Mark the exit code as the virtual top of the converted loop. */
2704 }
2705 \f
2706 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
2707 loop-end notes between START and END out before START. Assume that
2708 END is not such a note. START may be such a note. Returns the value
2709 of the new starting insn, which may be different if the original start
2710 was such a note. */
2712 rtx
2715 {
2716 rtx insn;
2717 rtx next;
2720 {
2729 {
2732 else
2733 {
2741 }
2742 }
2743 }
2746 }
2747 \f
2748 /* Compare the instructions before insn E1 with those before E2
2749 to find an opportunity for cross jumping.
2750 (This means detecting identical sequences of insns followed by
2751 jumps to the same place, or followed by a label and a jump
2752 to that label, and replacing one with a jump to the other.)
2754 Assume E1 is a jump that jumps to label E2
2755 (that is not always true but it might as well be).
2756 Find the longest possible equivalent sequences
2757 and store the first insns of those sequences into *F1 and *F2.
2758 Store zero there if no equivalent preceding instructions are found.
2760 We give up if we find a label in stream 1.
2761 Actually we could transfer that label into stream 2. */
2763 static void
2768 {
2780 {
2790 /* Don't allow the range of insns preceding E1 or E2
2791 to include the other (E2 or E1). */
2795 /* If we will get to this code by jumping, those jumps will be
2796 tensioned to go directly to the new label (before I2),
2797 so this cross-jumping won't cost extra. So reduce the minimum. */
2799 {
2802 }
2807 /* Avoid moving insns across EH regions if either of the insns
2808 can throw. */
2817 /* If this is a CALL_INSN, compare register usage information.
2818 If we don't check this on stack register machines, the two
2819 CALL_INSNs might be merged leaving reg-stack.c with mismatching
2820 numbers of stack registers in the same basic block.
2821 If we don't check this on machines with delay slots, a delay slot may
2822 be filled that clobbers a parameter expected by the subroutine.
2824 ??? We take the simple route for now and assume that if they're
2825 equal, they were constructed identically. */
2832 #ifdef STACK_REGS
2833 /* If cross_jump_death_matters is not 0, the insn's mode
2834 indicates whether or not the insn contains any stack-like
2835 regs. */
2838 {
2839 /* If register stack conversion has already been done, then
2840 death notes must also be compared before it is certain that
2841 the two instruction streams match. */
2843 rtx note;
2863 done:
2864 ;
2865 }
2866 #endif
2868 /* Don't allow old-style asm or volatile extended asms to be accepted
2869 for cross jumping purposes. It is conceptually correct to allow
2870 them, since cross-jumping preserves the dynamic instruction order
2871 even though it is changing the static instruction order. However,
2872 if an asm is being used to emit an assembler pseudo-op, such as
2873 the MIPS `.set reorder' pseudo-op, then the static instruction order
2874 matters and it must be preserved. */
2882 {
2883 /* The following code helps take care of G++ cleanups. */
2884 rtx equiv1;
2885 rtx equiv2;
2892 /* If the equivalences are not to a constant, they may
2893 reference pseudos that no longer exist, so we can't
2894 use them. */
2897 {
2902 {
2909 }
2910 }
2912 /* Insns fail to match; cross jumping is limited to the following
2913 insns. */
2915 #ifdef HAVE_cc0
2916 /* Don't allow the insn after a compare to be shared by
2917 cross-jumping unless the compare is also shared.
2918 Here, if either of these non-matching insns is a compare,
2919 exclude the following insn from possible cross-jumping. */
2922 #endif
2924 /* If cross-jumping here will feed a jump-around-jump
2925 optimization, this jump won't cost extra, so reduce
2926 the minimum. */
2932 }
2934 win:
2936 {
2937 /* Ok, this insn is potentially includable in a cross-jump here. */
2940 }
2941 }
2945 }
2947 static void
2950 {
2951 /* Find an existing label at this point
2952 or make a new one if there is none. */
2955 /* Make the same jump insn jump to the new point. */
2957 {
2958 /* Remove from jump chain of returns. */
2960 /* Change the insn. */
2965 /* Add to new the jump chain. */
2968 {
2971 }
2972 }
2973 else
2976 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
2977 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
2978 the NEWJPOS stream. */
2981 {
2982 rtx lnote;
2994 }
2995 }
2996 \f
2997 /* Return the label before INSN, or put a new label there. */
2999 rtx
3001 rtx insn;
3002 {
3003 rtx label;
3005 /* Find an existing label at this point
3006 or make a new one if there is none. */
3010 {
3016 }
3018 }
3020 /* Return the label after INSN, or put a new label there. */
3022 rtx
3024 rtx insn;
3025 {
3026 rtx label;
3028 /* Find an existing label at this point
3029 or make a new one if there is none. */
3033 {
3037 }
3039 }
3040 \f
3041 /* Return 1 if INSN is a jump that jumps to right after TARGET
3042 only on the condition that TARGET itself would drop through.
3043 Assumes that TARGET is a conditional jump. */
3045 static int
3048 {
3064 {
3068 }
3071 {
3075 }
3080 }
3081 \f
3082 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
3083 return non-zero if it is safe to reverse this comparison. It is if our
3084 floating-point is not IEEE, if this is an NE or EQ comparison, or if
3085 this is known to be an integer comparison. */
3087 int
3089 rtx comparison;
3090 rtx insn;
3091 {
3092 rtx arg0;
3094 /* If this is not actually a comparison, we can't reverse it. */
3099 /* If this is an NE comparison, it is safe to reverse it to an EQ
3100 comparison and vice versa, even for floating point. If no operands
3101 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
3102 always false and NE is always true, so the reversal is also valid. */
3103 || flag_fast_math
3110 /* Make sure ARG0 is one of the actual objects being compared. If we
3111 can't do this, we can't be sure the comparison can be reversed.
3113 Handle cc0 and a MODE_CC register. */
3115 #ifdef HAVE_cc0
3117 #endif
3118 )
3119 {
3130 }
3132 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
3133 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
3138 }
3140 /* Given an rtx-code for a comparison, return the code
3141 for the negated comparison.
3142 WATCH OUT! reverse_condition is not safe to use on a jump
3143 that might be acting on the results of an IEEE floating point comparison,
3144 because of the special treatment of non-signaling nans in comparisons.
3145 Use can_reverse_comparison_p to be sure. */
3147 enum rtx_code
3150 {
3152 {
3186 }
3187 }
3189 /* Similar, but return the code when two operands of a comparison are swapped.
3190 This IS safe for IEEE floating-point. */
3192 enum rtx_code
3195 {
3197 {
3229 }
3230 }
3232 /* Given a comparison CODE, return the corresponding unsigned comparison.
3233 If CODE is an equality comparison or already an unsigned comparison,
3234 CODE is returned. */
3236 enum rtx_code
3239 {
3241 {
3264 }
3265 }
3267 /* Similarly, return the signed version of a comparison. */
3269 enum rtx_code
3272 {
3274 {
3297 }
3298 }
3299 \f
3300 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
3301 truth of CODE1 implies the truth of CODE2. */
3303 int
3306 {
3311 {
3339 }
3342 }
3343 \f
3344 /* Return 1 if INSN is an unconditional jump and nothing else. */
3346 int
3348 rtx insn;
3349 {
3354 }
3356 /* Return nonzero if INSN is a (possibly) conditional jump
3357 and nothing more. */
3359 int
3361 rtx insn;
3362 {
3381 }
3383 /* Return nonzero if INSN is a (possibly) conditional jump
3384 and nothing more. */
3386 int
3388 rtx insn;
3389 {
3394 else
3414 }
3416 /* Return the label of a conditional jump. */
3418 rtx
3420 rtx insn;
3421 {
3440 }
3442 /* Return true if INSN is a (possibly conditional) return insn. */
3444 static int
3448 {
3451 }
3453 int
3455 rtx insn;
3456 {
3458 }
3460 #ifdef HAVE_cc0
3462 /* Return 1 if X is an RTX that does nothing but set the condition codes
3463 and CLOBBER or USE registers.
3464 Return -1 if X does explicitly set the condition codes,
3465 but also does other things. */
3467 int
3469 rtx x ATTRIBUTE_UNUSED;
3470 {
3474 {
3479 {
3485 }
3487 }
3489 }
3490 #endif
3491 \f
3492 /* Follow any unconditional jump at LABEL;
3493 return the ultimate label reached by any such chain of jumps.
3494 If LABEL is not followed by a jump, return LABEL.
3495 If the chain loops or we can't find end, return LABEL,
3496 since that tells caller to avoid changing the insn.
3498 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
3499 a USE or CLOBBER. */
3501 rtx
3503 rtx label;
3504 {
3518 depth++)
3519 {
3520 /* Don't chain through the insn that jumps into a loop
3521 from outside the loop,
3522 since that would create multiple loop entry jumps
3523 and prevent loop optimization. */
3524 rtx tem;
3529 /* ??? Optional. Disables some optimizations, but makes
3530 gcov output more accurate with -O. */
3534 /* If we have found a cycle, make the insn jump to itself. */
3544 }
3548 }
3550 /* Assuming that field IDX of X is a vector of label_refs,
3551 replace each of them by the ultimate label reached by it.
3552 Return nonzero if a change is made.
3553 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
3555 static int
3559 {
3563 {
3567 {
3573 }
3574 }
3576 }
3577 \f
3578 /* Find all CODE_LABELs referred to in X, and increment their use counts.
3579 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
3580 in INSN, then store one of them in JUMP_LABEL (INSN).
3581 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
3582 referenced in INSN, add a REG_LABEL note containing that label to INSN.
3583 Also, when there are consecutive labels, canonicalize on the last of them.
3585 Note that two labels separated by a loop-beginning note
3586 must be kept distinct if we have not yet done loop-optimization,
3587 because the gap between them is where loop-optimize
3588 will want to move invariant code to. CROSS_JUMP tells us
3589 that loop-optimization is done with.
3591 Once reload has completed (CROSS_JUMP non-zero), we need not consider
3592 two labels distinct if they are separated by only USE or CLOBBER insns. */
3594 static void
3597 rtx insn;
3599 {
3605 {
3618 /* If this is a constant-pool reference, see if it is a label. */
3625 {
3628 rtx note;
3629 rtx next;
3634 /* Ignore references to labels of containing functions. */
3638 /* If there are other labels following this one,
3639 replace it with the last of the consecutive labels. */
3641 {
3653 /* ??? Optional. Disables some optimizations, but
3654 makes gcov output more accurate with -O. */
3657 }
3664 {
3668 /* If we've changed OLABEL and we had a REG_LABEL note
3669 for it, update it as well. */
3674 /* Otherwise, add a REG_LABEL note for LABEL unless there already
3675 is one. */
3677 {
3678 /* This code used to ignore labels which refered to dispatch
3679 tables to avoid flow.c generating worse code.
3681 However, in the presense of global optimizations like
3682 gcse which call find_basic_blocks without calling
3683 life_analysis, not recording such labels will lead
3684 to compiler aborts because of inconsistencies in the
3685 flow graph. So we go ahead and record the label.
3687 It may also be the case that the optimization argument
3688 is no longer valid because of the more accurate cfg
3689 we build in find_basic_blocks -- it no longer pessimizes
3690 code when it finds a REG_LABEL note. */
3693 }
3694 }
3696 }
3698 /* Do walk the labels in a vector, but not the first operand of an
3699 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
3703 {
3708 }
3713 }
3717 {
3721 {
3725 }
3726 }
3727 }
3729 /* If all INSN does is set the pc, delete it,
3730 and delete the insn that set the condition codes for it
3731 if that's what the previous thing was. */
3733 void
3735 rtx insn;
3736 {
3741 }
3743 /* Delete INSN and recursively delete insns that compute values used only
3744 by INSN. This uses the REG_DEAD notes computed during flow analysis.
3745 If we are running before flow.c, we need do nothing since flow.c will
3746 delete dead code. We also can't know if the registers being used are
3747 dead or not at this point.
3749 Otherwise, look at all our REG_DEAD notes. If a previous insn does
3750 nothing other than set a register that dies in this insn, we can delete
3751 that insn as well.
3753 On machines with CC0, if CC0 is used in this insn, we may be able to
3754 delete the insn that set it. */
3756 static void
3758 rtx insn;
3759 {
3762 #ifdef HAVE_cc0
3764 {
3766 /* We assume that at this stage
3767 CC's are always set explicitly
3768 and always immediately before the jump that
3769 will use them. So if the previous insn
3770 exists to set the CC's, delete it
3771 (unless it performs auto-increments, etc.). */
3774 {
3778 else
3779 /* Otherwise, show that cc0 won't be used. */
3782 }
3783 }
3784 #endif
3786 #ifdef INSN_SCHEDULING
3787 /* ?!? The schedulers do not keep REG_DEAD notes accurate after
3788 reload has completed. The schedulers need to be fixed. Until
3789 they are, we must not rely on the death notes here. */
3791 {
3794 }
3795 #endif
3798 {
3799 rtx our_prev;
3804 /* Verify that the REG_NOTE is legitimate. */
3811 {
3812 /* If we reach a SEQUENCE, it is too complex to try to
3813 do anything with it, so give up. */
3819 /* reorg creates USEs that look like this. We leave them
3820 alone because reorg needs them for its own purposes. */
3824 {
3829 {
3830 /* If we find a SET of something else, we can't
3831 delete the insn. */
3836 {
3842 }
3846 }
3852 }
3854 /* If OUR_PREV references the register that dies here, it is an
3855 additional use. Hence any prior SET isn't dead. However, this
3856 insn becomes the new place for the REG_DEAD note. */
3859 {
3863 }
3864 }
3865 }
3868 }
3869 \f
3870 /* Delete insn INSN from the chain of insns and update label ref counts.
3871 May delete some following insns as a consequence; may even delete
3872 a label elsewhere and insns that follow it.
3874 Returns the first insn after INSN that was not deleted. */
3876 rtx
3879 {
3888 /* This insn is already deleted => return first following nondeleted. */
3892 /* Don't delete user-declared labels. Convert them to special NOTEs
3893 instead. */
3896 {
3901 }
3902 else
3903 /* Mark this insn as deleted. */
3906 /* If this is an unconditional jump, delete it from the jump chain. */
3910 /* If instruction is followed by a barrier,
3911 delete the barrier too. */
3914 {
3917 }
3919 /* Patch out INSN (and the barrier if any) */
3922 {
3924 {
3929 }
3932 {
3936 }
3940 }
3942 /* If deleting a jump, decrement the count of the label,
3943 and delete the label if it is now unused. */
3947 {
3948 /* This can delete NEXT or PREV,
3949 either directly if NEXT is JUMP_LABEL (INSN),
3950 or indirectly through more levels of jumps. */
3952 /* I feel a little doubtful about this loop,
3953 but I see no clean and sure alternative way
3954 to find the first insn after INSN that is not now deleted.
3955 I hope this works. */
3959 }
3961 /* Likewise if we're deleting a dispatch table. */
3966 {
3977 }
3982 /* If INSN was a label and a dispatch table follows it,
3983 delete the dispatch table. The tablejump must have gone already.
3984 It isn't useful to fall through into a table. */
3993 /* If INSN was a label, delete insns following it if now unreachable. */
3996 {
4002 {
4006 /* Keep going past other deleted labels to delete what follows. */
4009 else
4010 /* Note: if this deletes a jump, it can cause more
4011 deletion of unreachable code, after a different label.
4012 As long as the value from this recursive call is correct,
4013 this invocation functions correctly. */
4015 }
4016 }
4019 }
4021 /* Advance from INSN till reaching something not deleted
4022 then return that. May return INSN itself. */
4024 rtx
4026 rtx insn;
4027 {
4031 }
4032 \f
4033 /* Delete a range of insns from FROM to TO, inclusive.
4034 This is for the sake of peephole optimization, so assume
4035 that whatever these insns do will still be done by a new
4036 peephole insn that will replace them. */
4038 void
4041 {
4045 {
4050 {
4053 /* Patch this insn out of the chain. */
4054 /* We don't do this all at once, because we
4055 must preserve all NOTEs. */
4061 }
4066 }
4068 /* Note that if TO is an unconditional jump
4069 we *do not* delete the BARRIER that follows,
4070 since the peephole that replaces this sequence
4071 is also an unconditional jump in that case. */
4072 }
4073 \f
4074 /* Invert the condition of the jump JUMP, and make it jump
4075 to label NLABEL instead of where it jumps now. */
4077 int
4080 {
4081 /* We have to either invert the condition and change the label or
4082 do neither. Either operation could fail. We first try to invert
4083 the jump. If that succeeds, we try changing the label. If that fails,
4084 we invert the jump back to what it was. */
4090 {
4092 {
4095 /* An inverted jump means that a probability taken becomes a
4096 probability not taken. Subtract the branch probability from the
4097 probability base to convert it back to a taken probability.
4098 (We don't flip the probability on a branch that's never taken. */
4101 }
4104 }
4107 /* This should just be putting it back the way it was. */
4111 }
4113 /* Invert the jump condition of rtx X contained in jump insn, INSN.
4115 Return 1 if we can do so, 0 if we cannot find a way to do so that
4116 matches a pattern. */
4118 int
4120 rtx x;
4121 rtx insn;
4122 {
4130 {
4134 /* We can do this in two ways: The preferable way, which can only
4135 be done if this is not an integer comparison, is to reverse
4136 the comparison code. Otherwise, swap the THEN-part and ELSE-part
4137 of the IF_THEN_ELSE. If we can't do either, fail. */
4150 }
4154 {
4159 {
4164 }
4165 }
4168 }
4169 \f
4170 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
4171 If the old jump target label is unused as a result,
4172 it and the code following it may be deleted.
4174 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
4175 RETURN insn.
4177 The return value will be 1 if the change was made, 0 if it wasn't (this
4178 can only occur for NLABEL == 0). */
4180 int
4183 {
4192 /* If this is an unconditional branch, delete it from the jump_chain of
4193 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
4194 have UID's in range and JUMP_CHAIN is valid). */
4197 {
4203 {
4206 }
4207 }
4217 }
4219 /* Delete the instruction JUMP from any jump chain it might be on. */
4221 static void
4223 rtx jump;
4224 {
4228 /* Handle unconditional jumps. */
4233 /* Handle return insns. */
4240 else
4241 {
4242 rtx insn;
4248 {
4251 }
4252 }
4253 }
4255 /* If NLABEL is nonzero, throughout the rtx at LOC,
4256 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
4257 zero, alter (RETURN) to (LABEL_REF NLABEL).
4259 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
4260 validity with validate_change. Convert (set (pc) (label_ref olabel))
4261 to (return).
4263 Return 0 if we found a change we would like to make but it is invalid.
4264 Otherwise, return 1. */
4266 int
4270 rtx insn;
4271 {
4278 {
4280 {
4283 else
4286 }
4287 }
4289 {
4294 }
4303 {
4308 {
4313 }
4314 }
4317 }
4318 \f
4319 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
4321 If the old jump target label (before the dispatch table) becomes unused,
4322 it and the dispatch table may be deleted. In that case, find the insn
4323 before the jump references that label and delete it and logical successors
4324 too. */
4326 static void
4329 {
4332 /* Add this jump to the jump_chain of NLABEL. */
4335 {
4338 }
4346 {
4349 }
4350 }
4352 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
4353 If we found one, delete it and then delete this insn if DELETE_THIS is
4354 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
4356 static int
4360 {
4362 rtx link;
4366 {
4368 {
4371 }
4372 else
4374 }
4378 {
4380 {
4383 }
4384 else
4386 }
4389 }
4390 \f
4391 /* Like rtx_equal_p except that it considers two REGs as equal
4392 if they renumber to the same value and considers two commutative
4393 operations to be the same if the order of the operands has been
4394 reversed.
4396 ??? Addition is not commutative on the PA due to the weird implicit
4397 space register selection rules for memory addresses. Therefore, we
4398 don't consider a + b == b + a.
4400 We could/should make this test a little tighter. Possibly only
4401 disabling it on the PA via some backend macro or only disabling this
4402 case when the PLUS is inside a MEM. */
4404 int
4407 {
4418 {
4425 /* If we haven't done any renumbering, don't
4426 make any assumptions. */
4431 {
4436 {
4439 }
4440 }
4442 else
4443 {
4447 }
4450 {
4455 {
4458 }
4459 }
4461 else
4462 {
4466 }
4469 }
4471 /* Now we have disposed of all the cases
4472 in which different rtx codes can match. */
4477 {
4488 /* We can't assume nonlocal labels have their following insns yet. */
4492 /* Two label-refs are equivalent if they point at labels
4493 in the same position in the instruction stream. */
4501 /* If we didn't match EQ equality above, they aren't the same. */
4506 }
4508 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
4513 /* For commutative operations, the RTX match if the operand match in any
4514 order. Also handle the simple binary and unary cases without a loop.
4516 ??? Don't consider PLUS a commutative operator; see comments above. */
4529 /* Compare the elements. If any pair of corresponding elements
4530 fail to match, return 0 for the whole things. */
4534 {
4537 {
4561 /* fall through. */
4575 }
4576 }
4578 }
4579 \f
4580 /* If X is a hard register or equivalent to one or a subregister of one,
4581 return the hard register number. If X is a pseudo register that was not
4582 assigned a hard register, return the pseudo register number. Otherwise,
4583 return -1. Any rtx is valid for X. */
4585 int
4587 rtx x;
4588 {
4590 {
4594 }
4596 {
4600 }
4602 }
4603 \f
4604 /* Optimize code of the form:
4606 for (x = a[i]; x; ...)
4607 ...
4608 for (x = a[i]; x; ...)
4609 ...
4610 foo:
4612 Loop optimize will change the above code into
4614 if (x = a[i])
4615 for (;;)
4616 { ...; if (! (x = ...)) break; }
4617 if (x = a[i])
4618 for (;;)
4619 { ...; if (! (x = ...)) break; }
4620 foo:
4622 In general, if the first test fails, the program can branch
4623 directly to `foo' and skip the second try which is doomed to fail.
4624 We run this after loop optimization and before flow analysis. */
4626 /* When comparing the insn patterns, we track the fact that different
4627 pseudo-register numbers may have been used in each computation.
4628 The following array stores an equivalence -- same_regs[I] == J means
4629 that pseudo register I was used in the first set of tests in a context
4630 where J was used in the second set. We also count the number of such
4631 pending equivalences. If nonzero, the expressions really aren't the
4632 same. */
4638 /* Track any registers modified between the target of the first jump and
4639 the second jump. They never compare equal. */
4643 /* Record if memory was modified. */
4647 /* Called via note_stores on each insn between the target of the first
4648 branch and the second branch. It marks any changed registers. */
4650 static void
4652 rtx dest;
4653 rtx x ATTRIBUTE_UNUSED;
4654 {
4669 else
4672 }
4674 /* F is the first insn in the chain of insns. */
4676 void
4678 rtx f;
4681 {
4682 /* Basic algorithm is to find a conditional branch,
4683 the label it may branch to, and the branch after
4684 that label. If the two branches test the same condition,
4685 walk back from both branch paths until the insn patterns
4686 differ, or code labels are hit. If we make it back to
4687 the target of the first branch, then we know that the first branch
4688 will either always succeed or always fail depending on the relative
4689 senses of the two branches. So adjust the first branch accordingly
4690 in this case. */
4699 /* Allocate register tables and quick-reset table. */
4707 {
4711 {
4712 /* Get to a candidate branch insn. */
4727 /* Look for a branch after the target. Record any registers and
4728 memory modified between the target and the branch. Stop when we
4729 get to a label since we can't know what was changed there. */
4731 {
4736 {
4737 /* If this is an unconditional jump and is the only use of
4738 its target label, we can follow it. */
4742 {
4745 }
4746 else
4748 }
4754 {
4763 }
4766 }
4768 /* Check the next candidate branch insn from the label
4769 of the first. */
4777 /* Get the comparison codes and operands, reversing the
4778 codes if appropriate. If we don't have comparison codes,
4779 we can't do anything. */
4792 /* If they test the same things and knowing that B1 branches
4793 tells us whether or not B2 branches, check if we
4794 can thread the branch. */
4801 b1))))
4802 {
4807 {
4809 {
4810 /* We have reached the target of the first branch.
4811 If there are no pending register equivalents,
4812 we know that this branch will either always
4813 succeed (if the senses of the two branches are
4814 the same) or always fail (if not). */
4815 rtx new_label;
4822 else
4826 {
4832 {
4833 /* Don't thread to the loop label. If a loop
4834 label is reused, loop optimization will
4835 be disabled for that loop. */
4838 }
4840 }
4842 }
4844 /* If either of these is not a normal insn (it might be
4845 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
4846 have already been skipped above.) Similarly, fail
4847 if the insns are different. */
4856 }
4857 }
4858 }
4859 }
4860 }
4861 \f
4862 /* This is like RTX_EQUAL_P except that it knows about our handling of
4863 possibly equivalent registers and knows to consider volatile and
4864 modified objects as not equal.
4866 YINSN is the insn containing Y. */
4868 int
4871 rtx yinsn;
4872 {
4879 /* Rtx's of different codes cannot be equal. */
4883 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
4884 (REG:SI x) and (REG:HI x) are NOT equivalent. */
4889 /* For floating-point, consider everything unequal. This is a bit
4890 pessimistic, but this pass would only rarely do anything for FP
4891 anyway. */
4896 /* For commutative operations, the RTX match if the operand match in any
4897 order. Also handle the simple binary and unary cases without a loop. */
4909 /* Handle special-cases first. */
4911 {
4916 /* If neither is user variable or hard register, check for possible
4917 equivalence. */
4924 {
4926 num_same_regs++;
4928 /* If this is the first time we are seeing a register on the `Y'
4929 side, see if it is the last use. If not, we can't thread the
4930 jump, so mark it as not equivalent. */
4935 }
4936 else
4942 /* If memory modified or either volatile, not equivalent.
4943 Else, check address. */
4956 /* Cancel a pending `same_regs' if setting equivalenced registers.
4957 Then process source. */
4960 {
4962 {
4964 num_same_regs--;
4965 }
4968 }
4969 else
4983 }
4990 {
4992 {
5006 /* Two vectors must have the same length. */
5010 /* And the corresponding elements must match. */
5029 /* These are just backpointers, so they don't matter. */
5035 /* It is believed that rtx's at this level will never
5036 contain anything but integers and other rtx's,
5037 except for within LABEL_REFs and SYMBOL_REFs. */
5040 }
5041 }
5043 }
5044 \f
5046 #ifndef HAVE_cc0
5047 /* Return the insn that NEW can be safely inserted in front of starting at
5048 the jump insn INSN. Return 0 if it is not safe to do this jump
5049 optimization. Note that NEW must contain a single set. */
5051 static rtx
5053 rtx insn;
5055 {
5057 rtx prev;
5059 /* If NEW does not clobber, it is safe to insert NEW before INSN. */
5066 insn))
5072 /* There is a good chance that the previous insn PREV sets the thing
5073 being clobbered (often the CC in a hard reg). If PREV does not
5074 use what NEW sets, we can insert NEW before PREV. */
5080 insn)
5082 prev))
5086 }