| blob | 098e2d4dd7a475d405f561ebdb5b1a6f0775b1d3 |
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. */
70 /* ??? Eventually must record somehow the labels used by jumps
71 from nested functions. */
72 /* Pre-record the next or previous real insn for each label?
73 No, this pass is very fast anyway. */
74 /* Condense consecutive labels?
75 This would make life analysis faster, maybe. */
76 /* Optimize jump y; x: ... y: jumpif... x?
77 Don't know if it is worth bothering with. */
78 /* Optimize two cases of conditional jump to conditional jump?
79 This can never delete any instruction or make anything dead,
80 or even change what is live at any point.
81 So perhaps let combiner do it. */
83 /* Vector indexed by uid.
84 For each CODE_LABEL, index by its uid to get first unconditional jump
85 that jumps to the label.
86 For each JUMP_INSN, index by its uid to get the next unconditional jump
87 that jumps to the same label.
88 Element 0 is the start of a chain of all return insns.
89 (It is safe to use element 0 because insn uid 0 is not used. */
93 /* Maximum index in jump_chain. */
97 /* Set nonzero by jump_optimize if control can fall through
98 to the end of the function. */
101 /* Indicates whether death notes are significant in cross jump analysis.
102 Normally they are not significant, because of A and B jump to C,
103 and R dies in A, it must die in B. But this might not be true after
104 stack register conversion, and we must compare death notes in that
105 case. */
127 #ifndef HAVE_cc0
129 #endif
131 /* Main external entry point into the jump optimizer. See comments before
132 jump_optimize_1 for descriptions of the arguments. */
133 void
135 rtx f;
139 {
141 }
143 /* Alternate entry into the jump optimizer. This entry point only rebuilds
144 the JUMP_LABEL field in jumping insns and REG_LABEL notes in non-jumping
145 instructions. */
146 void
148 rtx f;
149 {
151 }
153 \f
154 /* Delete no-op jumps and optimize jumps to jumps
155 and jumps around jumps.
156 Delete unused labels and unreachable code.
158 If CROSS_JUMP is 1, detect matching code
159 before a jump and its destination and unify them.
160 If CROSS_JUMP is 2, do cross-jumping, but pay attention to death notes.
162 If NOOP_MOVES is nonzero, delete no-op move insns.
164 If AFTER_REGSCAN is nonzero, then this jump pass is being run immediately
165 after regscan, and it is safe to use regno_first_uid and regno_last_uid.
167 If MARK_LABELS_ONLY is nonzero, then we only rebuild the jump chain
168 and JUMP_LABEL field for jumping insns.
170 If `optimize' is zero, don't change any code,
171 just determine whether control drops off the end of the function.
172 This case occurs when we have -W and not -O.
173 It works because `delete_insn' checks the value of `optimize'
174 and refrains from actually deleting when that is 0. */
176 static void
178 rtx f;
183 {
189 rtx last_insn;
194 /* If we are performing cross jump optimizations, then initialize
195 tables mapping UIDs to EH regions to avoid incorrect movement
196 of insns from one EH region to another. */
202 /* Leave some extra room for labels and duplicate exit test insns
203 we make. */
210 /* Keep track of labels used from static data;
211 they cannot ever be deleted. */
218 /* Keep track of labels used for marking handlers for exception
219 regions; they cannot usually be deleted. */
224 /* Quit now if we just wanted to rebuild the JUMP_LABEL and REG_LABEL
225 notes and recompute LABEL_NUSES. */
234 {
235 /* CAN_REACH_END is persistent for each function. Once set it should
236 not be cleared. This is especially true for the case where we
237 delete the NOTE_FUNCTION_END note. CAN_REACH_END is cleared by
238 the front-end before compiling each function. */
242 /* Zero the "deleted" flag of all the "deleted" insns. */
246 /* Show that the jump chain is not valid. */
249 }
251 #ifdef HAVE_return
253 {
254 /* If we fall through to the epilogue, see if we can insert a RETURN insn
255 in front of it. If the machine allows it at this point (we might be
256 after reload for a leaf routine), it will improve optimization for it
257 to be there. */
263 {
266 }
267 }
268 #endif
273 /* If we haven't yet gotten to reload and we have just run regscan,
274 delete any insn that sets a register that isn't used elsewhere.
275 This helps some of the optimizations below by having less insns
276 being jumped around. */
280 {
288 /* We use regno_last_note_uid so as not to delete the setting
289 of a reg that's used in notes. A subsequent optimization
290 might arrange to use that reg for real. */
294 /* An ADDRESSOF expression can turn into a use of the internal arg
295 pointer, so do not delete the initialization of the internal
296 arg pointer yet. If it is truly dead, flow will delete the
297 initializing insn. */
300 }
302 /* Now iterate optimizing jumps until nothing changes over one pass. */
306 {
310 {
311 rtx reallabelprev;
313 rtx nlabel;
317 #if 0
318 /* If NOT the first iteration, if this is the last jump pass
319 (just before final), do the special peephole optimizations.
320 Avoiding the first iteration gives ordinary jump opts
321 a chance to work before peephole opts. */
326 #endif
328 /* That could have deleted some insns after INSN, so check now
329 what the following insn is. */
333 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
334 jump. Try to optimize by duplicating the loop exit test if so.
335 This is only safe immediately after regscan, because it uses
336 the values of regno_first_uid and regno_last_uid. */
341 {
344 {
348 }
349 }
358 /* Tension the labels in dispatch tables. */
365 /* If a dispatch table always goes to the same place,
366 get rid of it and replace the insn that uses it. */
370 {
385 /* Don't mess with a casesi insn. */
390 {
394 }
395 }
399 /* If a jump references the end of the function, try to turn
400 it into a RETURN insn, possibly a conditional one. */
407 /* Detect jump to following insn. */
409 {
414 }
416 /* If we have an unconditional jump preceded by a USE, try to put
417 the USE before the target and jump there. This simplifies many
418 of the optimizations below since we don't have to worry about
419 dealing with these USE insns. We only do this if the label
420 being branch to already has the identical USE or if code
421 never falls through to that label. */
430 /* Don't do this optimization if we have a loop containing only
431 the USE instruction, and the loop start label has a usage
432 count of 1. This is because we will redo this optimization
433 everytime through the outer loop, and jump opt will never
434 exit. */
438 {
440 {
443 }
449 }
451 /* Simplify if (...) x = a; else x = b; by converting it
452 to x = b; if (...) x = a;
453 if B is sufficiently simple, the test doesn't involve X,
454 and nothing in the test modifies B or X.
456 If we have small register classes, we also can't do this if X
457 is a hard register.
459 If the "x = b;" insn has any REG_NOTES, we don't do this because
460 of the possibility that we are running after CSE and there is a
461 REG_EQUAL note that is only valid if the branch has already been
462 taken. If we move the insn with the REG_EQUAL note, we may
463 fold the comparison to always be false in a later CSE pass.
464 (We could also delete the REG_NOTES when moving the insn, but it
465 seems simpler to not move it.) An exception is that we can move
466 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
467 value is the same as "b".
469 INSN is the branch over the `else' part.
471 We set:
473 TEMP to the jump insn preceding "x = a;"
474 TEMP1 to X
475 TEMP2 to the insn that sets "x = b;"
476 TEMP3 to the insn that sets "x = a;"
477 TEMP4 to the set of "x = b"; */
484 && (! SMALL_REGISTER_CLASSES
500 /* TEMP must skip over the "x = a;" insn */
503 /* There must be no other entries to the "x = b;" insn. */
505 /* INSN must either branch to the insn after TEMP2 or the insn
506 after TEMP2 must branch to the same place as INSN. */
511 {
512 /* The test expression, X, may be a complicated test with
513 multiple branches. See if we can find all the uses of
514 the label that TEMP branches to without hitting a CALL_INSN
515 or a jump to somewhere else. */
518 rtx p;
519 #ifdef HAVE_cc0
520 rtx q;
521 #endif
523 /* Set P to the first jump insn that goes around "x = a;". */
525 {
527 {
530 {
531 nuses--;
534 }
535 else
537 }
540 }
542 #ifdef HAVE_cc0
543 /* We cannot insert anything between a set of cc and its use
544 so if P uses cc0, we must back up to the previous insn. */
549 #endif
554 /* If we found all the uses and there was no data conflict, we
555 can move the assignment unless we can branch into the middle
556 from somewhere. */
563 /* Verify that registers used by the jump are not clobbered
564 by the instruction being moved. */
568 {
572 /* Set NEXT to an insn that we know won't go away. */
575 /* Delete the jump around the set. Note that we must do
576 this before we redirect the test jumps so that it won't
577 delete the code immediately following the assignment
578 we moved (which might be a jump). */
582 /* We either have two consecutive labels or a jump to
583 a jump, so adjust all the JUMP_INSNs to branch to where
584 INSN branches to. */
591 }
592 }
594 /* Simplify if (...) { x = a; goto l; } x = b; by converting it
595 to x = a; if (...) goto l; x = b;
596 if A is sufficiently simple, the test doesn't involve X,
597 and nothing in the test modifies A or X.
599 If we have small register classes, we also can't do this if X
600 is a hard register.
602 If the "x = a;" insn has any REG_NOTES, we don't do this because
603 of the possibility that we are running after CSE and there is a
604 REG_EQUAL note that is only valid if the branch has already been
605 taken. If we move the insn with the REG_EQUAL note, we may
606 fold the comparison to always be false in a later CSE pass.
607 (We could also delete the REG_NOTES when moving the insn, but it
608 seems simpler to not move it.) An exception is that we can move
609 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
610 value is the same as "a".
612 INSN is the goto.
614 We set:
616 TEMP to the jump insn preceding "x = a;"
617 TEMP1 to X
618 TEMP2 to the insn that sets "x = b;"
619 TEMP3 to the insn that sets "x = a;"
620 TEMP4 to the set of "x = a"; */
627 && (! SMALL_REGISTER_CLASSES
643 /* TEMP must skip over the "x = a;" insn */
646 {
650 #ifdef HAVE_cc0
651 /* We cannot insert anything between a set of cc and its use. */
655 #endif
665 /* Verify that registers used by the jump are not clobbered
666 by the instruction being moved. */
671 {
676 /* Set NEXT to an insn that we know won't go away. */
679 }
684 }
686 #ifndef HAVE_cc0
687 /* If we have if (...) x = exp; and branches are expensive,
688 EXP is a single insn, does not have any side effects, cannot
689 trap, and is not too costly, convert this to
690 t = exp; if (...) x = t;
692 Don't do this when we have CC0 because it is unlikely to help
693 and we'd need to worry about where to place the new insn and
694 the potential for conflicts. We also can't do this when we have
695 notes on the insn for the same reason as above.
697 We set:
699 TEMP to the "x = exp;" insn.
700 TEMP1 to the single set in the "x = exp;" insn.
701 TEMP2 to "x". */
715 && (! SMALL_REGISTER_CLASSES
723 {
728 {
736 {
739 }
740 }
741 }
743 /* Similarly, if it takes two insns to compute EXP but they
744 have the same destination. Here TEMP3 will be the second
745 insn and TEMP4 the SET from that insn. */
763 && (! SMALL_REGISTER_CLASSES
773 {
779 {
780 /* Use the earliest of temp5 and temp6. */
786 emit_insn_after_with_line_notes
794 {
797 }
798 }
799 }
801 /* Finally, handle the case where two insns are used to
802 compute EXP but a temporary register is used. Here we must
803 ensure that the temporary register is not used anywhere else. */
806 && after_regscan
834 && (! SMALL_REGISTER_CLASSES
840 {
846 {
847 /* Use the earliest of temp5 and temp6. */
860 {
863 }
864 }
865 }
868 /* Try to use a conditional move (if the target has them), or a
869 store-flag insn. The general case is:
871 1) x = a; if (...) x = b; and
872 2) if (...) x = b;
874 If the jump would be faster, the machine should not have defined
875 the movcc or scc insns!. These cases are often made by the
876 previous optimization.
878 The second case is treated as x = x; if (...) x = b;.
880 INSN here is the jump around the store. We set:
882 TEMP to the "x op= b;" insn.
883 TEMP1 to X.
884 TEMP2 to B.
885 TEMP3 to A (X in the second case).
886 TEMP4 to the condition being tested.
887 TEMP5 to the earliest insn used to find the condition.
888 TEMP6 to the SET of TEMP. */
891 ! reload_completed
893 /* Set TEMP to the "x = b;" insn. */
898 && (! SMALL_REGISTER_CLASSES
902 /* Allow either form, but prefer the former if both apply.
903 There is no point in using the old value of TEMP1 if
904 it is a register, since cse will alias them. It can
905 lose if the old value were a hard register since CSE
906 won't replace hard registers. Avoid using TEMP3 if
907 small register classes and it is a hard register. */
911 /* Make the latter case look like x = x; if (...) x = b; */
913 /* INSN must either branch to the insn after TEMP or the insn
914 after TEMP must branch to the same place as INSN. */
920 /* We must be comparing objects whose modes imply the size.
921 We could handle BLKmode if (1) emit_store_flag could
922 and (2) we could find the size reliably. */
924 /* Even if branches are cheap, the store_flag optimization
925 can win when the operation to be performed can be
926 expressed directly. */
927 #ifdef HAVE_cc0
928 /* If the previous insn sets CC0 and something else, we can't
929 do this since we are going to delete that insn. */
936 #endif
937 )
938 {
939 #ifdef HAVE_conditional_move
940 /* First try a conditional move. */
941 {
947 /* Copy the compared variables into cond0 and cond1, so that
948 any side effects performed in or after the old comparison,
949 will not affect our compare which will come later. */
950 /* ??? Is it possible to just use the comparison in the jump
951 insn? After all, we're going to delete it. We'd have
952 to modify emit_conditional_move to take a comparison rtx
953 instead or write a new function. */
955 /* We want the target to be able to simplify comparisons with
956 zero (and maybe other constants as well), so don't create
957 pseudos for them. There's no need to either. */
961 else
964 /* Careful about copying these values -- an IOR or what may
965 need to do other things, like clobber flags. */
966 /* ??? Assume for the moment that AVAL is ok. */
971 /* If we're not dealing with a register or the insn is more
972 complex than a simple SET, duplicate the computation and
973 replace the destination with a new temporary. */
977 else
978 {
984 }
993 {
997 /* Save the conditional move sequence but don't emit it
998 yet. On some machines, like the alpha, it is possible
999 that temp5 == insn, so next generate the sequence that
1000 saves the compared values and then emit both
1001 sequences ensuring seq1 occurs before seq2. */
1005 /* "Now that we can't fail..." Famous last words.
1006 Generate the copy insns that preserve the compared
1007 values. */
1015 /* Validate the sequence -- this may be some weird
1016 bit-extract-and-test instruction for which there
1017 exists no complimentary bit-extract insn. */
1021 {
1024 }
1027 {
1030 /* Insert conditional move after insn, to be sure
1031 that the jump and a possible compare won't be
1032 separated. */
1035 /* ??? We can also delete the insn that sets X to A.
1036 Flow will do it too though. */
1042 {
1044 old_max_reg);
1046 }
1050 }
1051 }
1052 else
1054 }
1055 #endif
1057 /* That didn't work, try a store-flag insn.
1059 We further divide the cases into:
1061 1) x = a; if (...) x = b; and either A or B is zero,
1062 2) if (...) x = 0; and jumps are expensive,
1063 3) x = a; if (...) x = b; and A and B are constants where all
1064 the set bits in A are also set in B and jumps are expensive,
1065 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
1066 more expensive, and
1067 5) if (...) x = b; if jumps are even more expensive. */
1071 /* Make the latter case look like
1072 x = x; if (...) x = 0; */
1077 /* If B is zero, OK; if A is zero, can only do (1) if we
1078 can reverse the condition. See if (3) applies possibly
1079 by reversing the condition. Prefer reversing to (4) when
1080 branches are very expensive. */
1084 /* Check that the mask is a power of two,
1085 so that it can probably be generated
1086 with a shift. */
1103 insn)))))
1105 )
1106 {
1110 rtx target;
1112 /* If necessary, reverse the condition. */
1115 else
1118 /* If CVAL is non-zero, normalize to -1. Otherwise, if UVAL
1119 is the constant 1, it is best to just compute the result
1120 directly. If UVAL is constant and STORE_FLAG_VALUE
1121 includes all of its bits, it is best to compute the flag
1122 value unnormalized and `and' it with UVAL. Otherwise,
1123 normalize to -1 and `and' with UVAL. */
1130 /* We will be putting the store-flag insn immediately in
1131 front of the comparison that was originally being done,
1132 so we know all the variables in TEMP4 will be valid.
1133 However, this might be in front of the assignment of
1134 A to VAR. If it is, it would clobber the store-flag
1135 we will be emitting.
1137 Therefore, emit into a temporary which will be copied to
1138 VAR immediately after TEMP. */
1143 VOIDmode,
1146 normalizep);
1148 {
1149 rtx seq;
1155 /* Put the store-flag insns in front of the first insn
1156 used to compute the condition to ensure that we
1157 use the same values of them as the current
1158 comparison. However, the remainder of the insns we
1159 generate will be placed directly in front of the
1160 jump insn, in case any of the pseudos we use
1161 are modified earlier. */
1167 /* Both CVAL and UVAL are non-zero. */
1169 {
1177 else
1178 {
1184 }
1186 /* If we usually make new pseudos, do so here. This
1187 turns out to help machines that have conditional
1188 move insns. */
1189 /* ??? Conditional moves have already been handled.
1190 This may be obsolete. */
1198 }
1200 {
1201 /* We know that either CVAL or UVAL is zero. If
1202 UVAL is zero, negate TARGET and `and' with CVAL.
1203 Otherwise, `and' with UVAL. */
1205 {
1209 }
1215 }
1220 #ifdef HAVE_cc0
1221 /* If INSN uses CC0, we must not separate it from the
1222 insn that sets cc0. */
1225 #endif
1233 {
1236 }
1240 }
1241 else
1243 }
1244 }
1246 /* If branches are expensive, convert
1247 if (foo) bar++; to bar += (foo != 0);
1248 and similarly for "bar--;"
1250 INSN is the conditional branch around the arithmetic. We set:
1252 TEMP is the arithmetic insn.
1253 TEMP1 is the SET doing the arithmetic.
1254 TEMP2 is the operand being incremented or decremented.
1255 TEMP3 to the condition being tested.
1256 TEMP4 to the earliest insn used to find the condition. */
1259 #ifdef HAVE_incscc
1260 || HAVE_incscc
1261 #endif
1262 #ifdef HAVE_decscc
1263 || HAVE_decscc
1264 #endif
1265 )
1266 && ! reload_completed
1278 /* INSN must either branch to the insn after TEMP or the insn
1279 after TEMP must branch to the same place as INSN. */
1285 /* We must be comparing objects whose modes imply the size.
1286 We could handle BLKmode if (1) emit_store_flag could
1287 and (2) we could find the size reliably. */
1290 {
1296 /* It must be the case that TEMP2 is not modified in the range
1297 [TEMP4, INSN). The one exception we make is if the insn
1298 before INSN sets TEMP2 to something which is also unchanged
1299 in that range. In that case, we can move the initialization
1300 into our sequence. */
1310 {
1314 }
1320 VOIDmode,
1324 /* If we can do the store-flag, do the addition or
1325 subtraction. */
1334 {
1335 /* Put the result back in temp2 in case it isn't already.
1336 Then replace the jump, possible a CC0-setting insn in
1337 front of the jump, and TEMP, with the sequence we have
1338 made. */
1353 #ifdef HAVE_cc0
1355 #endif
1359 {
1362 }
1366 }
1367 else
1369 }
1371 /* Simplify if (...) x = 1; else {...} if (x) ...
1372 We recognize this case scanning backwards as well.
1374 TEMP is the assignment to x;
1375 TEMP1 is the label at the head of the second if. */
1376 /* ?? This should call get_condition to find the values being
1377 compared, instead of looking for a COMPARE insn when HAVE_cc0
1378 is not defined. This would allow it to work on the m88k. */
1379 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1380 is not defined and the condition is tested by a separate compare
1381 insn. This is because the code below assumes that the result
1382 of the compare dies in the following branch.
1384 Not only that, but there might be other insns between the
1385 compare and branch whose results are live. Those insns need
1386 to be executed.
1388 A way to fix this is to move the insns at JUMP_LABEL (insn)
1389 to before INSN. If we are running before flow, they will
1390 be deleted if they aren't needed. But this doesn't work
1391 well after flow.
1393 This is really a special-case of jump threading, anyway. The
1394 right thing to do is to replace this and jump threading with
1395 much simpler code in cse.
1397 This code has been turned off in the non-cc0 case in the
1398 meantime. */
1400 #ifdef HAVE_cc0
1402 /* Safe to skip USE and CLOBBER insns here
1403 since they will not be deleted. */
1411 /* If we find that the next value tested is `x'
1412 (TEMP1 is the insn where this happens), win. */
1415 #ifdef HAVE_cc0
1416 /* Does temp1 `tst' the value of x? */
1420 #else
1421 /* Does temp1 compare the value of x against zero? */
1428 #endif
1430 {
1431 /* Get the if_then_else from the condjump. */
1434 {
1437 rtx cond
1440 rtx ultimate;
1446 else
1456 }
1457 }
1458 #endif
1460 #if 0
1461 /* @@ This needs a bit of work before it will be right.
1463 Any type of comparison can be accepted for the first and
1464 second compare. When rewriting the first jump, we must
1465 compute the what conditions can reach label3, and use the
1466 appropriate code. We can not simply reverse/swap the code
1467 of the first jump. In some cases, the second jump must be
1468 rewritten also.
1470 For example,
1471 < == converts to > ==
1472 < != converts to == >
1473 etc.
1475 If the code is written to only accept an '==' test for the second
1476 compare, then all that needs to be done is to swap the condition
1477 of the first branch.
1479 It is questionable whether we want this optimization anyways,
1480 since if the user wrote code like this because he/she knew that
1481 the jump to label1 is taken most of the time, then rewriting
1482 this gives slower code. */
1483 /* @@ This should call get_condition to find the values being
1484 compared, instead of looking for a COMPARE insn when HAVE_cc0
1485 is not defined. This would allow it to work on the m88k. */
1486 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1487 is not defined and the condition is tested by a separate compare
1488 insn. This is because the code below assumes that the result
1489 of the compare dies in the following branch. */
1491 /* Simplify test a ~= b
1492 condjump label1;
1493 test a == b
1494 condjump label2;
1495 jump label3;
1496 label1:
1498 rewriting as
1499 test a ~~= b
1500 condjump label3
1501 test a == b
1502 condjump label2
1503 label1:
1505 where ~= is an inequality, e.g. >, and ~~= is the swapped
1506 inequality, e.g. <.
1508 We recognize this case scanning backwards.
1510 TEMP is the conditional jump to `label2';
1511 TEMP1 is the test for `a == b';
1512 TEMP2 is the conditional jump to `label1';
1513 TEMP3 is the test for `a ~= b'. */
1522 #ifdef HAVE_cc0
1524 #else
1528 #endif
1542 {
1547 {
1550 }
1554 }
1555 #endif
1556 /* Simplify if (...) {... x = 1;} if (x) ...
1558 We recognize this case backwards.
1560 TEMP is the test of `x';
1561 TEMP1 is the assignment to `x' at the end of the
1562 previous statement. */
1563 /* @@ This should call get_condition to find the values being
1564 compared, instead of looking for a COMPARE insn when HAVE_cc0
1565 is not defined. This would allow it to work on the m88k. */
1566 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1567 is not defined and the condition is tested by a separate compare
1568 insn. This is because the code below assumes that the result
1569 of the compare dies in the following branch. */
1571 /* ??? This has to be turned off. The problem is that the
1572 unconditional jump might indirectly end up branching to the
1573 label between TEMP1 and TEMP. We can't detect this, in general,
1574 since it may become a jump to there after further optimizations.
1575 If that jump is done, it will be deleted, so we will retry
1576 this optimization in the next pass, thus an infinite loop.
1578 The present code prevents this by putting the jump after the
1579 label, but this is not logically correct. */
1580 #if 0
1582 /* Safe to skip USE and CLOBBER insns here
1583 since they will not be deleted. */
1588 #ifdef HAVE_cc0
1591 #else
1592 /* Temp must be a compare insn, we can not accept a register
1593 to register move here, since it may not be simply a
1594 tst insn. */
1600 #endif
1601 /* May skip USE or CLOBBER insns here
1602 for checking for opportunity, since we
1603 take care of them later. */
1607 #ifdef HAVE_cc0
1609 #else
1612 #endif
1614 /* If this isn't true, cse will do the job. */
1616 {
1617 /* Get the if_then_else from the condjump. */
1622 {
1624 rtx last_insn;
1625 rtx ultimate;
1626 rtx p;
1628 /* Get the place that condjump will jump to
1629 if it is reached from here. */
1633 else
1635 /* Get it as a CODE_LABEL. */
1638 else
1639 /* Get the label out of the LABEL_REF. */
1642 /* Insert the jump immediately before TEMP, specifically
1643 after the label that is between TEMP1 and TEMP. */
1646 /* If we would be branching to the next insn, the jump
1647 would immediately be deleted and the re-inserted in
1648 a subsequent pass over the code. So don't do anything
1649 in that case. */
1652 {
1655 last_insn);
1660 {
1664 }
1667 }
1668 }
1669 }
1670 #endif
1671 /* Detect a conditional jump going to the same place
1672 as an immediately following unconditional jump. */
1678 {
1681 /* ??? Optional. Disables some optimizations, but makes
1682 gcov output more accurate with -O. */
1689 {
1693 }
1694 }
1695 #ifdef HAVE_trap
1696 /* Detect a conditional jump jumping over an unconditional trap. */
1707 {
1713 {
1719 }
1720 }
1721 /* Detect a jump jumping to an unconditional trap. */
1726 && (this_is_simplejump
1728 {
1733 {
1735 /* Replace an unconditional jump to a trap with a trap. */
1737 {
1742 }
1747 {
1752 }
1753 }
1754 /* If the trap condition and jump condition are mutually
1755 exclusive, redirect the jump to the following insn. */
1757 && ! this_is_simplejump
1762 {
1765 }
1766 }
1767 #endif
1769 /* Detect a conditional jump jumping over an unconditional jump. */
1772 && ! this_is_simplejump
1778 {
1779 /* When we invert the unconditional jump, we will be
1780 decrementing the usage count of its old label.
1781 Make sure that we don't delete it now because that
1782 might cause the following code to be deleted. */
1790 {
1791 /* It is very likely that if there are USE insns before
1792 this jump, they hold REG_DEAD notes. These REG_DEAD
1793 notes are no longer valid due to this optimization,
1794 and will cause the life-analysis that following passes
1795 (notably delayed-branch scheduling) to think that
1796 these registers are dead when they are not.
1798 To prevent this trouble, we just remove the USE insns
1799 from the insn chain. */
1803 {
1807 }
1812 }
1814 /* We can now safely delete the label if it is unreferenced
1815 since the delete_insn above has deleted the BARRIER. */
1819 }
1820 else
1821 {
1822 /* Detect a jump to a jump. */
1827 {
1830 }
1832 /* Look for if (foo) bar; else break; */
1833 /* The insns look like this:
1834 insn = condjump label1;
1835 ...range1 (some insns)...
1836 jump label2;
1837 label1:
1838 ...range2 (some insns)...
1839 jump somewhere unconditionally
1840 label2: */
1841 {
1844 /* Don't do this optimization on the first round, so that
1845 jump-around-a-jump gets simplified before we ask here
1846 whether a jump is unconditional.
1848 Also don't do it when we are called after reload since
1849 it will confuse reorg. */
1852 /* Make sure INSN is something we can invert. */
1859 {
1866 /* Invert the jump condition, so we
1867 still execute the same insns in each case. */
1869 {
1874 rtx rangenext;
1876 /* Include in each range any notes before it, to be
1877 sure that we get the line number note if any, even
1878 if there are other notes here. */
1887 /* Don't move NOTEs for blocks or loops; shift them
1888 outside the ranges, where they'll stay put. */
1892 /* Get current surrounds of the 2 ranges. */
1898 /* Splice range2 where range1 was. */
1903 /* Splice range1 where range2 was. */
1909 /* Check for a loop end note between the end of
1910 range2, and the next code label. If there is one,
1911 then what we have really seen is
1912 if (foo) break; end_of_loop;
1913 and moved the break sequence outside the loop.
1914 We must move the LOOP_END note to where the
1915 loop really ends now, or we will confuse loop
1916 optimization. Stop if we find a LOOP_BEG note
1917 first, since we don't want to move the LOOP_END
1918 note in that case. */
1920 {
1923 {
1926 {
1937 }
1941 }
1942 }
1945 }
1946 }
1947 }
1949 /* Now that the jump has been tensioned,
1950 try cross jumping: check for identical code
1951 before the jump and before its target label. */
1953 /* First, cross jumping of conditional jumps: */
1956 {
1960 /* A conditional jump may be crossjumped
1961 only if the place it jumps to follows
1962 an opposing jump that comes back here. */
1965 /* We have no opposing jump;
1966 cannot cross jump this insn. */
1970 /* TARGET is nonzero if it is ok to cross jump
1971 to code before TARGET. If so, see if matches. */
1977 {
1979 /* Make the old conditional jump
1980 into an unconditional one. */
1985 /* Add to jump_chain unless this is a new label
1986 whose UID is too large. */
1988 {
1992 }
1995 }
1996 }
1998 /* Cross jumping of unconditional jumps:
1999 a few differences. */
2002 {
2004 rtx target;
2008 /* TARGET is nonzero if it is ok to cross jump
2009 to code before TARGET. If so, see if matches. */
2013 /* If cannot cross jump to code before the label,
2014 see if we can cross jump to another jump to
2015 the same label. */
2016 /* Try each other jump to this label. */
2023 /* Ignore TARGET if it's deleted. */
2029 {
2033 }
2034 }
2036 /* This code was dead in the previous jump.c! */
2038 {
2039 /* Return insns all "jump to the same place"
2040 so we can cross-jump between any two of them. */
2046 /* If cannot cross jump to code before the label,
2047 see if we can cross jump to another jump to
2048 the same label. */
2049 /* Try each other jump to this label. */
2060 {
2064 }
2065 }
2066 }
2067 }
2070 }
2072 /* Delete extraneous line number notes.
2073 Note that two consecutive notes for different lines are not really
2074 extraneous. There should be some indication where that line belonged,
2075 even if it became empty. */
2077 {
2082 {
2083 /* Delete this note if it is identical to previous note. */
2087 {
2090 }
2093 }
2094 }
2096 #ifdef HAVE_return
2098 {
2099 /* If we fall through to the epilogue, see if we can insert a RETURN insn
2100 in front of it. If the machine allows it at this point (we might be
2101 after reload for a leaf routine), it will improve optimization for it
2102 to be there. We do this both here and at the start of this pass since
2103 the RETURN might have been deleted by some of our optimizations. */
2109 {
2112 }
2113 }
2114 #endif
2116 /* CAN_REACH_END is persistent for each function. Once set it should
2117 not be cleared. This is especially true for the case where we
2118 delete the NOTE_FUNCTION_END note. CAN_REACH_END is cleared by
2119 the front-end before compiling each function. */
2123 /* Show JUMP_CHAIN no longer valid. */
2125 }
2126 \f
2127 /* Initialize LABEL_NUSES and JUMP_LABEL fields. Delete any REG_LABEL
2128 notes whose labels don't occur in the insn any more. Returns the
2129 largest INSN_UID found. */
2130 static int
2132 rtx f;
2133 {
2135 rtx insn;
2138 {
2144 {
2148 {
2153 }
2154 }
2157 }
2160 }
2162 /* Delete insns following barriers, up to next label.
2164 Also delete no-op jumps created by gcse. */
2165 static void
2167 rtx f;
2168 {
2169 rtx insn;
2172 {
2174 {
2180 {
2184 else
2186 }
2187 /* INSN is now the code_label. */
2188 }
2189 /* Also remove (set (pc) (pc)) insns which can be created by
2190 gcse. We eliminate such insns now to avoid having them
2191 cause problems later. */
2198 else
2200 }
2201 }
2203 /* Mark the label each jump jumps to.
2204 Combine consecutive labels, and count uses of labels.
2206 For each label, make a chain (using `jump_chain')
2207 of all the *unconditional* jumps that jump to it;
2208 also make a chain of all returns.
2210 CROSS_JUMP indicates whether we are doing cross jumping
2211 and if we are whether we will be paying attention to
2212 death notes or not. */
2214 static void
2216 rtx f;
2218 {
2219 rtx insn;
2223 {
2226 {
2228 {
2232 }
2234 {
2237 }
2238 }
2239 }
2240 }
2242 /* Delete all labels already not referenced.
2243 Also find and return the last insn. */
2245 static rtx
2247 rtx f;
2248 {
2250 rtx insn;
2253 {
2256 else
2257 {
2260 }
2261 }
2264 }
2266 /* Delete various simple forms of moves which have no necessary
2267 side effect. */
2269 static void
2271 rtx f;
2272 {
2276 {
2280 {
2283 /* Combine stack_adjusts with following push_insns. */
2284 #ifdef PUSH_ROUNDING
2291 {
2292 rtx p;
2298 /* Find all successive push insns. */
2300 /* Don't convert more than three pushes;
2301 that starts adding too many displaced addresses
2302 and the whole thing starts becoming a losing
2303 proposition. */
2305 {
2314 /* Allow a no-op move between the adjust and the push. */
2323 pushes++;
2328 }
2330 /* Discard the amount pushed from the stack adjust;
2331 maybe eliminate it entirely. */
2333 {
2336 }
2337 else
2341 /* Change the appropriate push insns to ordinary stores. */
2344 {
2353 /* Allow a no-op move between the adjust and the push. */
2363 /* If this push doesn't fully fit in the space
2364 of the stack adjust that we deleted,
2365 make another stack adjust here for what we
2366 didn't use up. There should be peepholes
2367 to recognize the resulting sequence of insns. */
2369 {
2372 p);
2374 }
2377 }
2378 }
2379 #endif
2381 /* Detect and delete no-op move instructions
2382 resulting from not allocating a parameter in a register. */
2395 /* Detect and ignore no-op move instructions
2396 resulting from smart or fortuitous register allocation. */
2399 {
2406 {
2407 rtx trial;
2414 {
2415 /* DREG may have been the target of a REG_DEAD note in
2416 the insn which makes INSN redundant. If so, reorg
2417 would still think it is dead. So search for such a
2418 note and delete it if we find it. */
2424 {
2427 }
2429 /* Deleting insn could lose a death-note for SREG. */
2431 {
2432 /* Change this into a USE so that we won't emit
2433 code for it, but still can keep the note. */
2437 /* Remove all reg notes but the REG_DEAD one. */
2440 }
2441 else
2443 }
2444 }
2449 {
2450 /* This handles the case where we have two consecutive
2451 assignments of the same constant to pseudos that didn't
2452 get a hard reg. Each SET from the constant will be
2453 converted into a SET of the spill register and an
2454 output reload will be made following it. This produces
2455 two loads of the same constant into the same spill
2456 register. */
2460 /* Look back for a death note for the first reg.
2461 If there is one, it is no longer accurate. */
2463 {
2467 {
2470 }
2472 }
2474 /* Delete the second load of the value. */
2476 }
2477 }
2479 {
2480 /* If each part is a set between two identical registers or
2481 a USE or CLOBBER, delete the insn. */
2483 rtx tem;
2486 {
2496 }
2500 }
2501 /* Also delete insns to store bit fields if they are no-ops. */
2502 /* Not worth the hair to detect this in the big-endian case. */
2511 }
2513 }
2514 }
2516 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
2517 If so indicate that this function can drop off the end by returning
2518 1, else return 0.
2520 CHECK_DELETED indicates whether we must check if the note being
2521 searched for has the deleted flag set.
2523 DELETE_FINAL_NOTE indicates whether we should delete the note
2524 if we find it. */
2526 static int
2528 rtx last;
2531 {
2536 {
2539 /* One label can follow the end-note: the return label. */
2542 /* Ordinary insns can follow it if returning a structure. */
2545 /* If machine uses explicit RETURN insns, no epilogue,
2546 then one of them follows the note. */
2550 /* A barrier can follow the return insn. */
2553 /* Other kinds of notes can follow also. */
2562 }
2564 /* See if we backed up to the appropriate type of note. */
2570 {
2574 }
2577 }
2579 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
2580 jump. Assume that this unconditional jump is to the exit test code. If
2581 the code is sufficiently simple, make a copy of it before INSN,
2582 followed by a jump to the exit of the loop. Then delete the unconditional
2583 jump after INSN.
2585 Return 1 if we made the change, else 0.
2587 This is only safe immediately after a regscan pass because it uses the
2588 values of regno_first_uid and regno_last_uid. */
2590 static int
2592 rtx loop_start;
2593 {
2598 rtx lastexit;
2602 /* Scan the exit code. We do not perform this optimization if any insn:
2604 is a CALL_INSN
2605 is a CODE_LABEL
2606 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
2607 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
2608 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
2609 is not valid.
2611 We also do not do this if we find an insn with ASM_OPERANDS. While
2612 this restriction should not be necessary, copying an insn with
2613 ASM_OPERANDS can confuse asm_noperands in some cases.
2615 Also, don't do this if the exit code is more than 20 insns. */
2618 insn
2622 {
2624 {
2629 /* We could be in front of the wrong NOTE_INSN_LOOP_END if there is
2630 a jump immediately after the loop start that branches outside
2631 the loop but within an outer loop, near the exit test.
2632 If we copied this exit test and created a phony
2633 NOTE_INSN_LOOP_VTOP, this could make instructions immediately
2634 before the exit test look like these could be safely moved
2635 out of the loop even if they actually may be never executed.
2636 This can be avoided by checking here for NOTE_INSN_LOOP_CONT. */
2645 /* If we were to duplicate this code, we would not move
2646 the BLOCK notes, and so debugging the moved code would
2647 be difficult. Thus, we only move the code with -O2 or
2648 higher. */
2654 /* The code below would grossly mishandle REG_WAS_0 notes,
2655 so get rid of them here. */
2666 }
2667 }
2669 /* Unless INSN is zero, we can do the optimization. */
2675 /* See if any insn sets a register only used in the loop exit code and
2676 not a user variable. If so, replace it with a new register. */
2685 {
2691 {
2692 /* We can do the replacement. Allocate reg_map if this is the
2693 first replacement we found. */
2695 {
2698 }
2703 }
2704 }
2706 /* Now copy each insn. */
2708 {
2710 {
2715 /* Only copy line-number notes. */
2717 {
2720 }
2730 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
2731 make them. */
2748 {
2752 }
2754 /* If this is a simple jump, add it to the jump chain. */
2758 {
2762 }
2767 }
2769 /* Record the first insn we copied. We need it so that we can
2770 scan the copied insns for new pseudo registers. */
2773 }
2775 /* Now clean up by emitting a jump to the end label and deleting the jump
2776 at the start of the loop. */
2778 {
2780 loop_start);
2782 /* Record the first insn we copied. We need it so that we can
2783 scan the copied insns for new pseudo registers. This may not
2784 be strictly necessary since we should have copied at least one
2785 insn above. But I am going to be safe. */
2792 {
2796 }
2798 }
2800 /* Now scan from the first insn we copied to the last insn we copied
2801 (copy) for new pseudo registers. Do this after the code to jump to
2802 the end label since that might create a new pseudo too. */
2805 /* Mark the exit code as the virtual top of the converted loop. */
2811 }
2812 \f
2813 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
2814 loop-end notes between START and END out before START. Assume that
2815 END is not such a note. START may be such a note. Returns the value
2816 of the new starting insn, which may be different if the original start
2817 was such a note. */
2819 rtx
2822 {
2823 rtx insn;
2824 rtx next;
2827 {
2836 {
2839 else
2840 {
2848 }
2849 }
2850 }
2853 }
2854 \f
2855 /* Compare the instructions before insn E1 with those before E2
2856 to find an opportunity for cross jumping.
2857 (This means detecting identical sequences of insns followed by
2858 jumps to the same place, or followed by a label and a jump
2859 to that label, and replacing one with a jump to the other.)
2861 Assume E1 is a jump that jumps to label E2
2862 (that is not always true but it might as well be).
2863 Find the longest possible equivalent sequences
2864 and store the first insns of those sequences into *F1 and *F2.
2865 Store zero there if no equivalent preceding instructions are found.
2867 We give up if we find a label in stream 1.
2868 Actually we could transfer that label into stream 2. */
2870 static void
2875 {
2887 {
2897 /* Don't allow the range of insns preceding E1 or E2
2898 to include the other (E2 or E1). */
2902 /* If we will get to this code by jumping, those jumps will be
2903 tensioned to go directly to the new label (before I2),
2904 so this cross-jumping won't cost extra. So reduce the minimum. */
2906 {
2909 }
2914 /* Avoid moving insns across EH regions if either of the insns
2915 can throw. */
2924 /* If this is a CALL_INSN, compare register usage information.
2925 If we don't check this on stack register machines, the two
2926 CALL_INSNs might be merged leaving reg-stack.c with mismatching
2927 numbers of stack registers in the same basic block.
2928 If we don't check this on machines with delay slots, a delay slot may
2929 be filled that clobbers a parameter expected by the subroutine.
2931 ??? We take the simple route for now and assume that if they're
2932 equal, they were constructed identically. */
2939 #ifdef STACK_REGS
2940 /* If cross_jump_death_matters is not 0, the insn's mode
2941 indicates whether or not the insn contains any stack-like
2942 regs. */
2945 {
2946 /* If register stack conversion has already been done, then
2947 death notes must also be compared before it is certain that
2948 the two instruction streams match. */
2950 rtx note;
2970 done:
2971 ;
2972 }
2973 #endif
2975 /* Don't allow old-style asm or volatile extended asms to be accepted
2976 for cross jumping purposes. It is conceptually correct to allow
2977 them, since cross-jumping preserves the dynamic instruction order
2978 even though it is changing the static instruction order. However,
2979 if an asm is being used to emit an assembler pseudo-op, such as
2980 the MIPS `.set reorder' pseudo-op, then the static instruction order
2981 matters and it must be preserved. */
2989 {
2990 /* The following code helps take care of G++ cleanups. */
2991 rtx equiv1;
2992 rtx equiv2;
2999 /* If the equivalences are not to a constant, they may
3000 reference pseudos that no longer exist, so we can't
3001 use them. */
3004 {
3009 {
3016 }
3017 }
3019 /* Insns fail to match; cross jumping is limited to the following
3020 insns. */
3022 #ifdef HAVE_cc0
3023 /* Don't allow the insn after a compare to be shared by
3024 cross-jumping unless the compare is also shared.
3025 Here, if either of these non-matching insns is a compare,
3026 exclude the following insn from possible cross-jumping. */
3029 #endif
3031 /* If cross-jumping here will feed a jump-around-jump
3032 optimization, this jump won't cost extra, so reduce
3033 the minimum. */
3039 }
3041 win:
3043 {
3044 /* Ok, this insn is potentially includable in a cross-jump here. */
3047 }
3048 }
3052 }
3054 static void
3057 {
3058 /* Find an existing label at this point
3059 or make a new one if there is none. */
3062 /* Make the same jump insn jump to the new point. */
3064 {
3065 /* Remove from jump chain of returns. */
3067 /* Change the insn. */
3072 /* Add to new the jump chain. */
3075 {
3078 }
3079 }
3080 else
3083 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
3084 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
3085 the NEWJPOS stream. */
3088 {
3089 rtx lnote;
3101 }
3102 }
3103 \f
3104 /* Return the label before INSN, or put a new label there. */
3106 rtx
3108 rtx insn;
3109 {
3110 rtx label;
3112 /* Find an existing label at this point
3113 or make a new one if there is none. */
3117 {
3123 }
3125 }
3127 /* Return the label after INSN, or put a new label there. */
3129 rtx
3131 rtx insn;
3132 {
3133 rtx label;
3135 /* Find an existing label at this point
3136 or make a new one if there is none. */
3140 {
3144 }
3146 }
3147 \f
3148 /* Return 1 if INSN is a jump that jumps to right after TARGET
3149 only on the condition that TARGET itself would drop through.
3150 Assumes that TARGET is a conditional jump. */
3152 static int
3155 {
3171 {
3175 }
3178 {
3182 }
3187 }
3188 \f
3189 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
3190 return non-zero if it is safe to reverse this comparison. It is if our
3191 floating-point is not IEEE, if this is an NE or EQ comparison, or if
3192 this is known to be an integer comparison. */
3194 int
3196 rtx comparison;
3197 rtx insn;
3198 {
3199 rtx arg0;
3201 /* If this is not actually a comparison, we can't reverse it. */
3206 /* If this is an NE comparison, it is safe to reverse it to an EQ
3207 comparison and vice versa, even for floating point. If no operands
3208 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
3209 always false and NE is always true, so the reversal is also valid. */
3210 || flag_fast_math
3217 /* Make sure ARG0 is one of the actual objects being compared. If we
3218 can't do this, we can't be sure the comparison can be reversed.
3220 Handle cc0 and a MODE_CC register. */
3222 #ifdef HAVE_cc0
3224 #endif
3225 )
3226 {
3228 rtx set;
3230 /* If the comparison itself was a loop invariant, it could have been
3231 hoisted out of the loop. If we proceed to unroll such a loop, then
3232 we may not be able to find the comparison when copying the loop.
3234 Returning zero in that case is the safe thing to do. */
3246 }
3248 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
3249 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
3254 }
3256 /* Given an rtx-code for a comparison, return the code
3257 for the negated comparison.
3258 WATCH OUT! reverse_condition is not safe to use on a jump
3259 that might be acting on the results of an IEEE floating point comparison,
3260 because of the special treatment of non-signaling nans in comparisons.
3261 Use can_reverse_comparison_p to be sure. */
3263 enum rtx_code
3266 {
3268 {
3302 }
3303 }
3305 /* Similar, but return the code when two operands of a comparison are swapped.
3306 This IS safe for IEEE floating-point. */
3308 enum rtx_code
3311 {
3313 {
3345 }
3346 }
3348 /* Given a comparison CODE, return the corresponding unsigned comparison.
3349 If CODE is an equality comparison or already an unsigned comparison,
3350 CODE is returned. */
3352 enum rtx_code
3355 {
3357 {
3380 }
3381 }
3383 /* Similarly, return the signed version of a comparison. */
3385 enum rtx_code
3388 {
3390 {
3413 }
3414 }
3415 \f
3416 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
3417 truth of CODE1 implies the truth of CODE2. */
3419 int
3422 {
3427 {
3455 }
3458 }
3459 \f
3460 /* Return 1 if INSN is an unconditional jump and nothing else. */
3462 int
3464 rtx insn;
3465 {
3470 }
3472 /* Return nonzero if INSN is a (possibly) conditional jump
3473 and nothing more. */
3475 int
3477 rtx insn;
3478 {
3497 }
3499 /* Return nonzero if INSN is a (possibly) conditional jump
3500 and nothing more. */
3502 int
3504 rtx insn;
3505 {
3510 else
3530 }
3532 /* Return the label of a conditional jump. */
3534 rtx
3536 rtx insn;
3537 {
3556 }
3558 /* Return true if INSN is a (possibly conditional) return insn. */
3560 static int
3564 {
3567 }
3569 int
3571 rtx insn;
3572 {
3574 }
3576 /* Return true if INSN is a jump that only transfers control and
3577 nothing more. */
3579 int
3581 rtx insn;
3582 {
3583 rtx set;
3597 }
3599 #ifdef HAVE_cc0
3601 /* Return 1 if X is an RTX that does nothing but set the condition codes
3602 and CLOBBER or USE registers.
3603 Return -1 if X does explicitly set the condition codes,
3604 but also does other things. */
3606 int
3608 rtx x ATTRIBUTE_UNUSED;
3609 {
3613 {
3618 {
3624 }
3626 }
3628 }
3629 #endif
3630 \f
3631 /* Follow any unconditional jump at LABEL;
3632 return the ultimate label reached by any such chain of jumps.
3633 If LABEL is not followed by a jump, return LABEL.
3634 If the chain loops or we can't find end, return LABEL,
3635 since that tells caller to avoid changing the insn.
3637 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
3638 a USE or CLOBBER. */
3640 rtx
3642 rtx label;
3643 {
3657 depth++)
3658 {
3659 /* Don't chain through the insn that jumps into a loop
3660 from outside the loop,
3661 since that would create multiple loop entry jumps
3662 and prevent loop optimization. */
3663 rtx tem;
3668 /* ??? Optional. Disables some optimizations, but makes
3669 gcov output more accurate with -O. */
3673 /* If we have found a cycle, make the insn jump to itself. */
3683 }
3687 }
3689 /* Assuming that field IDX of X is a vector of label_refs,
3690 replace each of them by the ultimate label reached by it.
3691 Return nonzero if a change is made.
3692 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
3694 static int
3698 {
3702 {
3706 {
3712 }
3713 }
3715 }
3716 \f
3717 /* Find all CODE_LABELs referred to in X, and increment their use counts.
3718 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
3719 in INSN, then store one of them in JUMP_LABEL (INSN).
3720 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
3721 referenced in INSN, add a REG_LABEL note containing that label to INSN.
3722 Also, when there are consecutive labels, canonicalize on the last of them.
3724 Note that two labels separated by a loop-beginning note
3725 must be kept distinct if we have not yet done loop-optimization,
3726 because the gap between them is where loop-optimize
3727 will want to move invariant code to. CROSS_JUMP tells us
3728 that loop-optimization is done with.
3730 Once reload has completed (CROSS_JUMP non-zero), we need not consider
3731 two labels distinct if they are separated by only USE or CLOBBER insns. */
3733 static void
3736 rtx insn;
3738 {
3744 {
3757 /* If this is a constant-pool reference, see if it is a label. */
3764 {
3767 rtx note;
3768 rtx next;
3773 /* Ignore references to labels of containing functions. */
3777 /* If there are other labels following this one,
3778 replace it with the last of the consecutive labels. */
3780 {
3792 /* ??? Optional. Disables some optimizations, but
3793 makes gcov output more accurate with -O. */
3796 }
3803 {
3807 /* If we've changed OLABEL and we had a REG_LABEL note
3808 for it, update it as well. */
3813 /* Otherwise, add a REG_LABEL note for LABEL unless there already
3814 is one. */
3816 {
3817 /* This code used to ignore labels which refered to dispatch
3818 tables to avoid flow.c generating worse code.
3820 However, in the presense of global optimizations like
3821 gcse which call find_basic_blocks without calling
3822 life_analysis, not recording such labels will lead
3823 to compiler aborts because of inconsistencies in the
3824 flow graph. So we go ahead and record the label.
3826 It may also be the case that the optimization argument
3827 is no longer valid because of the more accurate cfg
3828 we build in find_basic_blocks -- it no longer pessimizes
3829 code when it finds a REG_LABEL note. */
3832 }
3833 }
3835 }
3837 /* Do walk the labels in a vector, but not the first operand of an
3838 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
3842 {
3847 }
3852 }
3856 {
3860 {
3864 }
3865 }
3866 }
3868 /* If all INSN does is set the pc, delete it,
3869 and delete the insn that set the condition codes for it
3870 if that's what the previous thing was. */
3872 void
3874 rtx insn;
3875 {
3880 }
3882 /* Recursively delete prior insns that compute the value (used only by INSN
3883 which the caller is deleting) stored in the register mentioned by NOTE
3884 which is a REG_DEAD note associated with INSN. */
3886 static void
3888 rtx note;
3889 rtx insn;
3890 {
3891 rtx our_prev;
3898 {
3901 /* If we reach a CALL which is not calling a const function
3902 or the callee pops the arguments, then give up. */
3908 /* If we reach a SEQUENCE, it is too complex to try to
3909 do anything with it, so give up. */
3915 /* reorg creates USEs that look like this. We leave them
3916 alone because reorg needs them for its own purposes. */
3920 {
3925 {
3926 /* If we find a SET of something else, we can't
3927 delete the insn. */
3932 {
3938 }
3942 }
3945 {
3947 int dest_endregno
3959 /* We may have a multi-word hard register and some, but not
3960 all, of the words of the register are needed in subsequent
3961 insns. Write REG_UNUSED notes for those parts that were not
3962 needed. */
3965 {
3977 }
3978 }
3981 }
3983 /* If PAT references the register that dies here, it is an
3984 additional use. Hence any prior SET isn't dead. However, this
3985 insn becomes the new place for the REG_DEAD note. */
3987 {
3991 }
3992 }
3993 }
3995 /* Delete INSN and recursively delete insns that compute values used only
3996 by INSN. This uses the REG_DEAD notes computed during flow analysis.
3997 If we are running before flow.c, we need do nothing since flow.c will
3998 delete dead code. We also can't know if the registers being used are
3999 dead or not at this point.
4001 Otherwise, look at all our REG_DEAD notes. If a previous insn does
4002 nothing other than set a register that dies in this insn, we can delete
4003 that insn as well.
4005 On machines with CC0, if CC0 is used in this insn, we may be able to
4006 delete the insn that set it. */
4008 static void
4010 rtx insn;
4011 {
4013 rtx set;
4015 #ifdef HAVE_cc0
4017 {
4019 /* We assume that at this stage
4020 CC's are always set explicitly
4021 and always immediately before the jump that
4022 will use them. So if the previous insn
4023 exists to set the CC's, delete it
4024 (unless it performs auto-increments, etc.). */
4027 {
4031 else
4032 /* Otherwise, show that cc0 won't be used. */
4035 }
4036 }
4037 #endif
4039 #ifdef INSN_SCHEDULING
4040 /* ?!? The schedulers do not keep REG_DEAD notes accurate after
4041 reload has completed. The schedulers need to be fixed. Until
4042 they are, we must not rely on the death notes here. */
4044 {
4047 }
4048 #endif
4050 /* The REG_DEAD note may have been omitted for a register
4051 which is both set and used by the insn. */
4054 {
4056 int dest_endregno
4063 {
4072 }
4073 }
4076 {
4080 /* Verify that the REG_NOTE is legitimate. */
4085 }
4088 }
4089 \f
4090 /* Delete insn INSN from the chain of insns and update label ref counts.
4091 May delete some following insns as a consequence; may even delete
4092 a label elsewhere and insns that follow it.
4094 Returns the first insn after INSN that was not deleted. */
4096 rtx
4099 {
4108 /* This insn is already deleted => return first following nondeleted. */
4115 /* Don't delete user-declared labels. Convert them to special NOTEs
4116 instead. */
4119 {
4124 }
4125 else
4126 /* Mark this insn as deleted. */
4129 /* If this is an unconditional jump, delete it from the jump chain. */
4133 /* If instruction is followed by a barrier,
4134 delete the barrier too. */
4137 {
4140 }
4142 /* Patch out INSN (and the barrier if any) */
4145 {
4147 {
4152 }
4155 {
4159 }
4163 }
4165 /* If deleting a jump, decrement the count of the label,
4166 and delete the label if it is now unused. */
4169 {
4173 {
4174 /* This can delete NEXT or PREV,
4175 either directly if NEXT is JUMP_LABEL (INSN),
4176 or indirectly through more levels of jumps. */
4179 /* I feel a little doubtful about this loop,
4180 but I see no clean and sure alternative way
4181 to find the first insn after INSN that is not now deleted.
4182 I hope this works. */
4186 }
4191 {
4192 /* If we're deleting the tablejump, delete the dispatch table.
4193 We may not be able to kill the label immediately preceeding
4194 just yet, as it might be referenced in code leading up to
4195 the tablejump. */
4197 }
4198 }
4200 /* Likewise if we're deleting a dispatch table. */
4205 {
4216 }
4221 /* If INSN was a label and a dispatch table follows it,
4222 delete the dispatch table. The tablejump must have gone already.
4223 It isn't useful to fall through into a table. */
4232 /* If INSN was a label, delete insns following it if now unreachable. */
4235 {
4241 {
4245 /* Keep going past other deleted labels to delete what follows. */
4248 else
4249 /* Note: if this deletes a jump, it can cause more
4250 deletion of unreachable code, after a different label.
4251 As long as the value from this recursive call is correct,
4252 this invocation functions correctly. */
4254 }
4255 }
4258 }
4260 /* Advance from INSN till reaching something not deleted
4261 then return that. May return INSN itself. */
4263 rtx
4265 rtx insn;
4266 {
4270 }
4271 \f
4272 /* Delete a range of insns from FROM to TO, inclusive.
4273 This is for the sake of peephole optimization, so assume
4274 that whatever these insns do will still be done by a new
4275 peephole insn that will replace them. */
4277 void
4280 {
4284 {
4289 {
4292 /* Patch this insn out of the chain. */
4293 /* We don't do this all at once, because we
4294 must preserve all NOTEs. */
4300 }
4305 }
4307 /* Note that if TO is an unconditional jump
4308 we *do not* delete the BARRIER that follows,
4309 since the peephole that replaces this sequence
4310 is also an unconditional jump in that case. */
4311 }
4312 \f
4313 /* We have determined that INSN is never reached, and are about to
4314 delete it. Print a warning if the user asked for one.
4316 To try to make this warning more useful, this should only be called
4317 once per basic block not reached, and it only warns when the basic
4318 block contains more than one line from the current function, and
4319 contains at least one operation. CSE and inlining can duplicate insns,
4320 so it's possible to get spurious warnings from this. */
4322 void
4324 rtx avoided_insn;
4325 {
4326 rtx insn;
4334 /* Scan forwards, looking at LINE_NUMBER notes, until
4335 we hit a LABEL or we run out of insns. */
4338 {
4343 {
4346 else
4349 }
4352 }
4357 }
4358 \f
4359 /* Invert the condition of the jump JUMP, and make it jump
4360 to label NLABEL instead of where it jumps now. */
4362 int
4365 {
4366 /* We have to either invert the condition and change the label or
4367 do neither. Either operation could fail. We first try to invert
4368 the jump. If that succeeds, we try changing the label. If that fails,
4369 we invert the jump back to what it was. */
4375 {
4377 {
4380 /* An inverted jump means that a probability taken becomes a
4381 probability not taken. Subtract the branch probability from the
4382 probability base to convert it back to a taken probability.
4383 (We don't flip the probability on a branch that's never taken. */
4386 }
4389 }
4392 /* This should just be putting it back the way it was. */
4396 }
4398 /* Invert the jump condition of rtx X contained in jump insn, INSN.
4400 Return 1 if we can do so, 0 if we cannot find a way to do so that
4401 matches a pattern. */
4403 int
4405 rtx x;
4406 rtx insn;
4407 {
4415 {
4419 /* We can do this in two ways: The preferable way, which can only
4420 be done if this is not an integer comparison, is to reverse
4421 the comparison code. Otherwise, swap the THEN-part and ELSE-part
4422 of the IF_THEN_ELSE. If we can't do either, fail. */
4435 }
4439 {
4444 {
4449 }
4450 }
4453 }
4454 \f
4455 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
4456 If the old jump target label is unused as a result,
4457 it and the code following it may be deleted.
4459 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
4460 RETURN insn.
4462 The return value will be 1 if the change was made, 0 if it wasn't (this
4463 can only occur for NLABEL == 0). */
4465 int
4468 {
4477 /* If this is an unconditional branch, delete it from the jump_chain of
4478 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
4479 have UID's in range and JUMP_CHAIN is valid). */
4482 {
4488 {
4491 }
4492 }
4502 }
4504 /* Delete the instruction JUMP from any jump chain it might be on. */
4506 static void
4508 rtx jump;
4509 {
4513 /* Handle unconditional jumps. */
4518 /* Handle return insns. */
4525 else
4526 {
4527 rtx insn;
4533 {
4536 }
4537 }
4538 }
4540 /* If NLABEL is nonzero, throughout the rtx at LOC,
4541 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
4542 zero, alter (RETURN) to (LABEL_REF NLABEL).
4544 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
4545 validity with validate_change. Convert (set (pc) (label_ref olabel))
4546 to (return).
4548 Return 0 if we found a change we would like to make but it is invalid.
4549 Otherwise, return 1. */
4551 int
4555 rtx insn;
4556 {
4563 {
4565 {
4568 else
4571 }
4572 }
4574 {
4579 }
4588 {
4593 {
4598 }
4599 }
4602 }
4603 \f
4604 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
4606 If the old jump target label (before the dispatch table) becomes unused,
4607 it and the dispatch table may be deleted. In that case, find the insn
4608 before the jump references that label and delete it and logical successors
4609 too. */
4611 static void
4614 {
4617 /* Add this jump to the jump_chain of NLABEL. */
4620 {
4623 }
4631 {
4634 }
4635 }
4637 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
4638 If we found one, delete it and then delete this insn if DELETE_THIS is
4639 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
4641 static int
4645 {
4647 rtx link;
4651 {
4653 {
4656 }
4657 else
4659 }
4663 {
4665 {
4668 }
4669 else
4671 }
4674 }
4675 \f
4676 /* Like rtx_equal_p except that it considers two REGs as equal
4677 if they renumber to the same value and considers two commutative
4678 operations to be the same if the order of the operands has been
4679 reversed.
4681 ??? Addition is not commutative on the PA due to the weird implicit
4682 space register selection rules for memory addresses. Therefore, we
4683 don't consider a + b == b + a.
4685 We could/should make this test a little tighter. Possibly only
4686 disabling it on the PA via some backend macro or only disabling this
4687 case when the PLUS is inside a MEM. */
4689 int
4692 {
4703 {
4710 /* If we haven't done any renumbering, don't
4711 make any assumptions. */
4716 {
4721 {
4724 }
4725 }
4727 else
4728 {
4732 }
4735 {
4740 {
4743 }
4744 }
4746 else
4747 {
4751 }
4754 }
4756 /* Now we have disposed of all the cases
4757 in which different rtx codes can match. */
4762 {
4773 /* We can't assume nonlocal labels have their following insns yet. */
4777 /* Two label-refs are equivalent if they point at labels
4778 in the same position in the instruction stream. */
4786 /* If we didn't match EQ equality above, they aren't the same. */
4791 }
4793 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
4798 /* For commutative operations, the RTX match if the operand match in any
4799 order. Also handle the simple binary and unary cases without a loop.
4801 ??? Don't consider PLUS a commutative operator; see comments above. */
4814 /* Compare the elements. If any pair of corresponding elements
4815 fail to match, return 0 for the whole things. */
4819 {
4822 {
4846 /* fall through. */
4860 }
4861 }
4863 }
4864 \f
4865 /* If X is a hard register or equivalent to one or a subregister of one,
4866 return the hard register number. If X is a pseudo register that was not
4867 assigned a hard register, return the pseudo register number. Otherwise,
4868 return -1. Any rtx is valid for X. */
4870 int
4872 rtx x;
4873 {
4875 {
4879 }
4881 {
4885 }
4887 }
4888 \f
4889 /* Optimize code of the form:
4891 for (x = a[i]; x; ...)
4892 ...
4893 for (x = a[i]; x; ...)
4894 ...
4895 foo:
4897 Loop optimize will change the above code into
4899 if (x = a[i])
4900 for (;;)
4901 { ...; if (! (x = ...)) break; }
4902 if (x = a[i])
4903 for (;;)
4904 { ...; if (! (x = ...)) break; }
4905 foo:
4907 In general, if the first test fails, the program can branch
4908 directly to `foo' and skip the second try which is doomed to fail.
4909 We run this after loop optimization and before flow analysis. */
4911 /* When comparing the insn patterns, we track the fact that different
4912 pseudo-register numbers may have been used in each computation.
4913 The following array stores an equivalence -- same_regs[I] == J means
4914 that pseudo register I was used in the first set of tests in a context
4915 where J was used in the second set. We also count the number of such
4916 pending equivalences. If nonzero, the expressions really aren't the
4917 same. */
4923 /* Track any registers modified between the target of the first jump and
4924 the second jump. They never compare equal. */
4928 /* Record if memory was modified. */
4932 /* Called via note_stores on each insn between the target of the first
4933 branch and the second branch. It marks any changed registers. */
4935 static void
4937 rtx dest;
4938 rtx x ATTRIBUTE_UNUSED;
4939 {
4954 else
4957 }
4959 /* F is the first insn in the chain of insns. */
4961 void
4963 rtx f;
4966 {
4967 /* Basic algorithm is to find a conditional branch,
4968 the label it may branch to, and the branch after
4969 that label. If the two branches test the same condition,
4970 walk back from both branch paths until the insn patterns
4971 differ, or code labels are hit. If we make it back to
4972 the target of the first branch, then we know that the first branch
4973 will either always succeed or always fail depending on the relative
4974 senses of the two branches. So adjust the first branch accordingly
4975 in this case. */
4984 /* Allocate register tables and quick-reset table. */
4992 {
4996 {
4997 /* Get to a candidate branch insn. */
5012 /* Look for a branch after the target. Record any registers and
5013 memory modified between the target and the branch. Stop when we
5014 get to a label since we can't know what was changed there. */
5016 {
5021 {
5022 /* If this is an unconditional jump and is the only use of
5023 its target label, we can follow it. */
5027 {
5030 }
5031 else
5033 }
5039 {
5048 }
5051 }
5053 /* Check the next candidate branch insn from the label
5054 of the first. */
5062 /* Get the comparison codes and operands, reversing the
5063 codes if appropriate. If we don't have comparison codes,
5064 we can't do anything. */
5077 /* If they test the same things and knowing that B1 branches
5078 tells us whether or not B2 branches, check if we
5079 can thread the branch. */
5086 b1))))
5087 {
5092 {
5094 {
5095 /* We have reached the target of the first branch.
5096 If there are no pending register equivalents,
5097 we know that this branch will either always
5098 succeed (if the senses of the two branches are
5099 the same) or always fail (if not). */
5100 rtx new_label;
5107 else
5111 {
5117 {
5118 /* Don't thread to the loop label. If a loop
5119 label is reused, loop optimization will
5120 be disabled for that loop. */
5123 }
5125 }
5127 }
5129 /* If either of these is not a normal insn (it might be
5130 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
5131 have already been skipped above.) Similarly, fail
5132 if the insns are different. */
5141 }
5142 }
5143 }
5144 }
5145 }
5146 \f
5147 /* This is like RTX_EQUAL_P except that it knows about our handling of
5148 possibly equivalent registers and knows to consider volatile and
5149 modified objects as not equal.
5151 YINSN is the insn containing Y. */
5153 int
5156 rtx yinsn;
5157 {
5164 /* Rtx's of different codes cannot be equal. */
5168 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
5169 (REG:SI x) and (REG:HI x) are NOT equivalent. */
5174 /* For floating-point, consider everything unequal. This is a bit
5175 pessimistic, but this pass would only rarely do anything for FP
5176 anyway. */
5181 /* For commutative operations, the RTX match if the operand match in any
5182 order. Also handle the simple binary and unary cases without a loop. */
5194 /* Handle special-cases first. */
5196 {
5201 /* If neither is user variable or hard register, check for possible
5202 equivalence. */
5209 {
5211 num_same_regs++;
5213 /* If this is the first time we are seeing a register on the `Y'
5214 side, see if it is the last use. If not, we can't thread the
5215 jump, so mark it as not equivalent. */
5220 }
5221 else
5227 /* If memory modified or either volatile, not equivalent.
5228 Else, check address. */
5241 /* Cancel a pending `same_regs' if setting equivalenced registers.
5242 Then process source. */
5245 {
5247 {
5249 num_same_regs--;
5250 }
5253 }
5254 else
5268 }
5275 {
5277 {
5291 /* Two vectors must have the same length. */
5295 /* And the corresponding elements must match. */
5314 /* These are just backpointers, so they don't matter. */
5321 /* It is believed that rtx's at this level will never
5322 contain anything but integers and other rtx's,
5323 except for within LABEL_REFs and SYMBOL_REFs. */
5326 }
5327 }
5329 }
5330 \f
5332 #ifndef HAVE_cc0
5333 /* Return the insn that NEW can be safely inserted in front of starting at
5334 the jump insn INSN. Return 0 if it is not safe to do this jump
5335 optimization. Note that NEW must contain a single set. */
5337 static rtx
5339 rtx insn;
5341 {
5343 rtx prev;
5345 /* If NEW does not clobber, it is safe to insert NEW before INSN. */
5352 insn))
5358 /* There is a good chance that the previous insn PREV sets the thing
5359 being clobbered (often the CC in a hard reg). If PREV does not
5360 use what NEW sets, we can insert NEW before PREV. */
5366 insn)
5368 prev))
5372 }