| blob | 606fe2879989d65fcac0a84ca8cc58e39a0eafdb |
1 /* Optimize jump instructions, for GNU compiler.
2 Copyright (C) 1987, 88, 89, 91-97, 1998 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. */
67 /* ??? Eventually must record somehow the labels used by jumps
68 from nested functions. */
69 /* Pre-record the next or previous real insn for each label?
70 No, this pass is very fast anyway. */
71 /* Condense consecutive labels?
72 This would make life analysis faster, maybe. */
73 /* Optimize jump y; x: ... y: jumpif... x?
74 Don't know if it is worth bothering with. */
75 /* Optimize two cases of conditional jump to conditional jump?
76 This can never delete any instruction or make anything dead,
77 or even change what is live at any point.
78 So perhaps let combiner do it. */
80 /* Vector indexed by uid.
81 For each CODE_LABEL, index by its uid to get first unconditional jump
82 that jumps to the label.
83 For each JUMP_INSN, index by its uid to get the next unconditional jump
84 that jumps to the same label.
85 Element 0 is the start of a chain of all return insns.
86 (It is safe to use element 0 because insn uid 0 is not used. */
90 /* List of labels referred to from initializers.
91 These can never be deleted. */
92 rtx forced_labels;
94 /* Maximum index in jump_chain. */
98 /* Set nonzero by jump_optimize if control can fall through
99 to the end of the function. */
102 /* Indicates whether death notes are significant in cross jump analysis.
103 Normally they are not significant, because of A and B jump to C,
104 and R dies in A, it must die in B. But this might not be true after
105 stack register conversion, and we must compare death notes in that
106 case. */
121 #ifndef HAVE_cc0
123 #endif
125 \f
126 /* Delete no-op jumps and optimize jumps to jumps
127 and jumps around jumps.
128 Delete unused labels and unreachable code.
130 If CROSS_JUMP is 1, detect matching code
131 before a jump and its destination and unify them.
132 If CROSS_JUMP is 2, do cross-jumping, but pay attention to death notes.
134 If NOOP_MOVES is nonzero, delete no-op move insns.
136 If AFTER_REGSCAN is nonzero, then this jump pass is being run immediately
137 after regscan, and it is safe to use regno_first_uid and regno_last_uid.
139 If `optimize' is zero, don't change any code,
140 just determine whether control drops off the end of the function.
141 This case occurs when we have -W and not -O.
142 It works because `delete_insn' checks the value of `optimize'
143 and refrains from actually deleting when that is 0. */
145 void
147 rtx f;
151 {
156 rtx last_insn;
160 /* Initialize LABEL_NUSES and JUMP_LABEL fields. Delete any REG_LABEL
161 notes whose labels don't occur in the insn any more. */
164 {
171 {
176 }
180 }
182 max_uid++;
184 /* Delete insns following barriers, up to next label. */
187 {
189 {
192 {
196 else
198 }
199 /* INSN is now the code_label. */
200 }
201 else
203 }
205 /* Leave some extra room for labels and duplicate exit test insns
206 we make. */
211 /* Mark the label each jump jumps to.
212 Combine consecutive labels, and count uses of labels.
214 For each label, make a chain (using `jump_chain')
215 of all the *unconditional* jumps that jump to it;
216 also make a chain of all returns. */
220 {
223 {
225 {
229 }
231 {
234 }
235 }
236 }
238 /* Keep track of labels used from static data;
239 they cannot ever be deleted. */
246 /* Keep track of labels used for marking handlers for exception
247 regions; they cannot usually be deleted. */
254 /* Delete all labels already not referenced.
255 Also find the last insn. */
259 {
262 else
263 {
266 }
267 }
270 {
271 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
272 If so record that this function can drop off the end. */
275 {
278 /* One label can follow the end-note: the return label. */
280 /* Ordinary insns can follow it if returning a structure. */
282 /* If machine uses explicit RETURN insns, no epilogue,
283 then one of them follows the note. */
286 /* A barrier can follow the return insn. */
288 /* Other kinds of notes can follow also. */
292 }
294 /* Report if control can fall through at the end of the function. */
300 /* Zero the "deleted" flag of all the "deleted" insns. */
304 }
306 #ifdef HAVE_return
308 {
309 /* If we fall through to the epilogue, see if we can insert a RETURN insn
310 in front of it. If the machine allows it at this point (we might be
311 after reload for a leaf routine), it will improve optimization for it
312 to be there. */
318 {
321 }
322 }
323 #endif
327 {
331 {
334 /* Combine stack_adjusts with following push_insns. */
335 #ifdef PUSH_ROUNDING
342 {
343 rtx p;
349 /* Find all successive push insns. */
351 /* Don't convert more than three pushes;
352 that starts adding too many displaced addresses
353 and the whole thing starts becoming a losing
354 proposition. */
356 {
365 /* Allow a no-op move between the adjust and the push. */
374 pushes++;
379 }
381 /* Discard the amount pushed from the stack adjust;
382 maybe eliminate it entirely. */
384 {
387 }
388 else
392 /* Change the appropriate push insns to ordinary stores. */
395 {
409 /* If this push doesn't fully fit in the space
410 of the stack adjust that we deleted,
411 make another stack adjust here for what we
412 didn't use up. There should be peepholes
413 to recognize the resulting sequence of insns. */
415 {
418 p);
420 }
423 }
424 }
425 #endif
427 /* Detect and delete no-op move instructions
428 resulting from not allocating a parameter in a register. */
441 /* Detect and ignore no-op move instructions
442 resulting from smart or fortuitous register allocation. */
445 {
452 {
453 rtx trial;
460 {
461 /* DREG may have been the target of a REG_DEAD note in
462 the insn which makes INSN redundant. If so, reorg
463 would still think it is dead. So search for such a
464 note and delete it if we find it. */
470 {
473 }
474 #ifdef PRESERVE_DEATH_INFO_REGNO_P
475 /* Deleting insn could lose a death-note for SREG
476 so don't do it if final needs accurate
477 death-notes. */
480 {
481 /* Change this into a USE so that we won't emit
482 code for it, but still can keep the note. */
486 /* Remove all reg notes but the REG_DEAD one. */
489 }
490 else
491 #endif
493 }
494 }
499 {
500 /* This handles the case where we have two consecutive
501 assignments of the same constant to pseudos that didn't
502 get a hard reg. Each SET from the constant will be
503 converted into a SET of the spill register and an
504 output reload will be made following it. This produces
505 two loads of the same constant into the same spill
506 register. */
510 /* Look back for a death note for the first reg.
511 If there is one, it is no longer accurate. */
513 {
517 {
520 }
522 }
524 /* Delete the second load of the value. */
526 }
527 }
529 {
530 /* If each part is a set between two identical registers or
531 a USE or CLOBBER, delete the insn. */
533 rtx tem;
536 {
546 }
550 }
551 /* Also delete insns to store bit fields if they are no-ops. */
552 /* Not worth the hair to detect this in the big-endian case. */
561 }
563 }
565 /* If we haven't yet gotten to reload and we have just run regscan,
566 delete any insn that sets a register that isn't used elsewhere.
567 This helps some of the optimizations below by having less insns
568 being jumped around. */
572 {
580 /* We use regno_last_note_uid so as not to delete the setting
581 of a reg that's used in notes. A subsequent optimization
582 might arrange to use that reg for real. */
587 }
589 /* Now iterate optimizing jumps until nothing changes over one pass. */
592 {
596 {
597 rtx reallabelprev;
599 rtx nlabel;
602 #if 0
603 /* If NOT the first iteration, if this is the last jump pass
604 (just before final), do the special peephole optimizations.
605 Avoiding the first iteration gives ordinary jump opts
606 a chance to work before peephole opts. */
611 #endif
613 /* That could have deleted some insns after INSN, so check now
614 what the following insn is. */
618 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
619 jump. Try to optimize by duplicating the loop exit test if so.
620 This is only safe immediately after regscan, because it uses
621 the values of regno_first_uid and regno_last_uid. */
626 {
629 {
633 }
634 }
643 /* Tension the labels in dispatch tables. */
650 /* If a dispatch table always goes to the same place,
651 get rid of it and replace the insn that uses it. */
655 {
670 /* Don't mess with a casesi insn. */
675 {
679 }
680 }
684 /* If a jump references the end of the function, try to turn
685 it into a RETURN insn, possibly a conditional one. */
692 /* Detect jump to following insn. */
694 {
699 }
701 /* If we have an unconditional jump preceded by a USE, try to put
702 the USE before the target and jump there. This simplifies many
703 of the optimizations below since we don't have to worry about
704 dealing with these USE insns. We only do this if the label
705 being branch to already has the identical USE or if code
706 never falls through to that label. */
715 /* Don't do this optimization if we have a loop containing only
716 the USE instruction, and the loop start label has a usage
717 count of 1. This is because we will redo this optimization
718 everytime through the outer loop, and jump opt will never
719 exit. */
723 {
725 {
728 }
734 }
736 /* Simplify if (...) x = a; else x = b; by converting it
737 to x = b; if (...) x = a;
738 if B is sufficiently simple, the test doesn't involve X,
739 and nothing in the test modifies B or X.
741 If we have small register classes, we also can't do this if X
742 is a hard register.
744 If the "x = b;" insn has any REG_NOTES, we don't do this because
745 of the possibility that we are running after CSE and there is a
746 REG_EQUAL note that is only valid if the branch has already been
747 taken. If we move the insn with the REG_EQUAL note, we may
748 fold the comparison to always be false in a later CSE pass.
749 (We could also delete the REG_NOTES when moving the insn, but it
750 seems simpler to not move it.) An exception is that we can move
751 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
752 value is the same as "b".
754 INSN is the branch over the `else' part.
756 We set:
758 TEMP to the jump insn preceding "x = a;"
759 TEMP1 to X
760 TEMP2 to the insn that sets "x = b;"
761 TEMP3 to the insn that sets "x = a;"
762 TEMP4 to the set of "x = b"; */
769 && (! SMALL_REGISTER_CLASSES
784 /* TEMP must skip over the "x = a;" insn */
787 /* There must be no other entries to the "x = b;" insn. */
789 /* INSN must either branch to the insn after TEMP2 or the insn
790 after TEMP2 must branch to the same place as INSN. */
795 {
796 /* The test expression, X, may be a complicated test with
797 multiple branches. See if we can find all the uses of
798 the label that TEMP branches to without hitting a CALL_INSN
799 or a jump to somewhere else. */
802 rtx p;
803 #ifdef HAVE_cc0
804 rtx q;
805 #endif
807 /* Set P to the first jump insn that goes around "x = a;". */
809 {
811 {
814 {
815 nuses--;
818 }
819 else
821 }
824 }
826 #ifdef HAVE_cc0
827 /* We cannot insert anything between a set of cc and its use
828 so if P uses cc0, we must back up to the previous insn. */
833 #endif
838 /* If we found all the uses and there was no data conflict, we
839 can move the assignment unless we can branch into the middle
840 from somewhere. */
847 {
851 /* Set NEXT to an insn that we know won't go away. */
854 /* Delete the jump around the set. Note that we must do
855 this before we redirect the test jumps so that it won't
856 delete the code immediately following the assignment
857 we moved (which might be a jump). */
861 /* We either have two consecutive labels or a jump to
862 a jump, so adjust all the JUMP_INSNs to branch to where
863 INSN branches to. */
870 }
871 }
873 /* Simplify if (...) { x = a; goto l; } x = b; by converting it
874 to x = a; if (...) goto l; x = b;
875 if A is sufficiently simple, the test doesn't involve X,
876 and nothing in the test modifies A or X.
878 If we have small register classes, we also can't do this if X
879 is a hard register.
881 If the "x = a;" insn has any REG_NOTES, we don't do this because
882 of the possibility that we are running after CSE and there is a
883 REG_EQUAL note that is only valid if the branch has already been
884 taken. If we move the insn with the REG_EQUAL note, we may
885 fold the comparison to always be false in a later CSE pass.
886 (We could also delete the REG_NOTES when moving the insn, but it
887 seems simpler to not move it.) An exception is that we can move
888 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
889 value is the same as "a".
891 INSN is the goto.
893 We set:
895 TEMP to the jump insn preceding "x = a;"
896 TEMP1 to X
897 TEMP2 to the insn that sets "x = b;"
898 TEMP3 to the insn that sets "x = a;"
899 TEMP4 to the set of "x = a"; */
906 && (! SMALL_REGISTER_CLASSES
925 /* TEMP must skip over the "x = a;" insn */
928 {
932 #ifdef HAVE_cc0
933 /* We cannot insert anything between a set of cc and its use. */
937 #endif
950 {
955 /* Set NEXT to an insn that we know won't go away. */
958 }
963 }
965 #ifndef HAVE_cc0
966 /* If we have if (...) x = exp; and branches are expensive,
967 EXP is a single insn, does not have any side effects, cannot
968 trap, and is not too costly, convert this to
969 t = exp; if (...) x = t;
971 Don't do this when we have CC0 because it is unlikely to help
972 and we'd need to worry about where to place the new insn and
973 the potential for conflicts. We also can't do this when we have
974 notes on the insn for the same reason as above.
976 We set:
978 TEMP to the "x = exp;" insn.
979 TEMP1 to the single set in the "x = exp; insn.
980 TEMP2 to "x". */
995 && (! SMALL_REGISTER_CLASSES
1003 {
1008 {
1014 }
1015 }
1017 /* Similarly, if it takes two insns to compute EXP but they
1018 have the same destination. Here TEMP3 will be the second
1019 insn and TEMP4 the SET from that insn. */
1037 && (! SMALL_REGISTER_CLASSES
1047 {
1053 {
1054 /* Use the earliest of temp5 and temp6. */
1060 emit_insn_after_with_line_notes
1066 }
1067 }
1069 /* Finally, handle the case where two insns are used to
1070 compute EXP but a temporary register is used. Here we must
1071 ensure that the temporary register is not used anywhere else. */
1074 && after_regscan
1102 && (! SMALL_REGISTER_CLASSES
1108 {
1114 {
1115 /* Use the earliest of temp5 and temp6. */
1126 }
1127 }
1130 /* Try to use a conditional move (if the target has them), or a
1131 store-flag insn. The general case is:
1133 1) x = a; if (...) x = b; and
1134 2) if (...) x = b;
1136 If the jump would be faster, the machine should not have defined
1137 the movcc or scc insns!. These cases are often made by the
1138 previous optimization.
1140 The second case is treated as x = x; if (...) x = b;.
1142 INSN here is the jump around the store. We set:
1144 TEMP to the "x = b;" insn.
1145 TEMP1 to X.
1146 TEMP2 to B.
1147 TEMP3 to A (X in the second case).
1148 TEMP4 to the condition being tested.
1149 TEMP5 to the earliest insn used to find the condition. */
1152 ! reload_completed
1154 /* Set TEMP to the "x = b;" insn. */
1159 && (! SMALL_REGISTER_CLASSES
1162 /* Allow either form, but prefer the former if both apply.
1163 There is no point in using the old value of TEMP1 if
1164 it is a register, since cse will alias them. It can
1165 lose if the old value were a hard register since CSE
1166 won't replace hard registers. Avoid using TEMP3 if
1167 small register classes and it is a hard register. */
1171 /* Make the latter case look like x = x; if (...) x = b; */
1173 /* INSN must either branch to the insn after TEMP or the insn
1174 after TEMP must branch to the same place as INSN. */
1180 /* We must be comparing objects whose modes imply the size.
1181 We could handle BLKmode if (1) emit_store_flag could
1182 and (2) we could find the size reliably. */
1184 /* Even if branches are cheap, the store_flag optimization
1185 can win when the operation to be performed can be
1186 expressed directly. */
1187 #ifdef HAVE_cc0
1188 /* If the previous insn sets CC0 and something else, we can't
1189 do this since we are going to delete that insn. */
1196 #endif
1197 )
1198 {
1199 #ifdef HAVE_conditional_move
1200 /* First try a conditional move. */
1201 {
1205 rtx target;
1207 /* Copy the compared variables into cond0 and cond1, so that
1208 any side effects performed in or after the old comparison,
1209 will not affect our compare which will come later. */
1210 /* ??? Is it possible to just use the comparison in the jump
1211 insn? After all, we're going to delete it. We'd have
1212 to modify emit_conditional_move to take a comparison rtx
1213 instead or write a new function. */
1215 /* We want the target to be able to simplify comparisons with
1216 zero (and maybe other constants as well), so don't create
1217 pseudos for them. There's no need to either. */
1221 else
1235 {
1238 /* Save the conditional move sequence but don't emit it
1239 yet. On some machines, like the alpha, it is possible
1240 that temp5 == insn, so next generate the sequence that
1241 saves the compared values and then emit both
1242 sequences ensuring seq1 occurs before seq2. */
1246 /* Now that we can't fail, generate the copy insns that
1247 preserve the compared values. */
1256 /* Insert conditional move after insn, to be sure that
1257 the jump and a possible compare won't be separated */
1260 /* ??? We can also delete the insn that sets X to A.
1261 Flow will do it too though. */
1267 }
1268 else
1270 }
1271 #endif
1273 /* That didn't work, try a store-flag insn.
1275 We further divide the cases into:
1277 1) x = a; if (...) x = b; and either A or B is zero,
1278 2) if (...) x = 0; and jumps are expensive,
1279 3) x = a; if (...) x = b; and A and B are constants where all
1280 the set bits in A are also set in B and jumps are expensive,
1281 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
1282 more expensive, and
1283 5) if (...) x = b; if jumps are even more expensive. */
1287 /* Make the latter case look like
1288 x = x; if (...) x = 0; */
1293 /* If B is zero, OK; if A is zero, can only do (1) if we
1294 can reverse the condition. See if (3) applies possibly
1295 by reversing the condition. Prefer reversing to (4) when
1296 branches are very expensive. */
1300 /* Check that the mask is a power of two,
1301 so that it can probably be generated
1302 with a shift. */
1317 insn)))))
1319 )
1320 {
1324 rtx target;
1326 /* If necessary, reverse the condition. */
1329 else
1332 /* If CVAL is non-zero, normalize to -1. Otherwise, if UVAL
1333 is the constant 1, it is best to just compute the result
1334 directly. If UVAL is constant and STORE_FLAG_VALUE
1335 includes all of its bits, it is best to compute the flag
1336 value unnormalized and `and' it with UVAL. Otherwise,
1337 normalize to -1 and `and' with UVAL. */
1344 /* We will be putting the store-flag insn immediately in
1345 front of the comparison that was originally being done,
1346 so we know all the variables in TEMP4 will be valid.
1347 However, this might be in front of the assignment of
1348 A to VAR. If it is, it would clobber the store-flag
1349 we will be emitting.
1351 Therefore, emit into a temporary which will be copied to
1352 VAR immediately after TEMP. */
1357 VOIDmode,
1360 normalizep);
1362 {
1363 rtx seq;
1369 /* Put the store-flag insns in front of the first insn
1370 used to compute the condition to ensure that we
1371 use the same values of them as the current
1372 comparison. However, the remainder of the insns we
1373 generate will be placed directly in front of the
1374 jump insn, in case any of the pseudos we use
1375 are modified earlier. */
1381 /* Both CVAL and UVAL are non-zero. */
1383 {
1391 else
1392 {
1398 }
1400 /* If we usually make new pseudos, do so here. This
1401 turns out to help machines that have conditional
1402 move insns. */
1403 /* ??? Conditional moves have already been handled.
1404 This may be obsolete. */
1412 }
1414 {
1415 /* We know that either CVAL or UVAL is zero. If
1416 UVAL is zero, negate TARGET and `and' with CVAL.
1417 Otherwise, `and' with UVAL. */
1419 {
1423 }
1429 }
1434 #ifdef HAVE_cc0
1435 /* If INSN uses CC0, we must not separate it from the
1436 insn that sets cc0. */
1439 #endif
1447 }
1448 else
1450 }
1451 }
1453 /* If branches are expensive, convert
1454 if (foo) bar++; to bar += (foo != 0);
1455 and similarly for "bar--;"
1457 INSN is the conditional branch around the arithmetic. We set:
1459 TEMP is the arithmetic insn.
1460 TEMP1 is the SET doing the arithmetic.
1461 TEMP2 is the operand being incremented or decremented.
1462 TEMP3 to the condition being tested.
1463 TEMP4 to the earliest insn used to find the condition. */
1466 #ifdef HAVE_incscc
1467 || HAVE_incscc
1468 #endif
1469 #ifdef HAVE_decscc
1470 || HAVE_decscc
1471 #endif
1472 )
1473 && ! reload_completed
1485 /* INSN must either branch to the insn after TEMP or the insn
1486 after TEMP must branch to the same place as INSN. */
1492 /* We must be comparing objects whose modes imply the size.
1493 We could handle BLKmode if (1) emit_store_flag could
1494 and (2) we could find the size reliably. */
1497 {
1503 /* It must be the case that TEMP2 is not modified in the range
1504 [TEMP4, INSN). The one exception we make is if the insn
1505 before INSN sets TEMP2 to something which is also unchanged
1506 in that range. In that case, we can move the initialization
1507 into our sequence. */
1517 {
1521 }
1527 VOIDmode,
1531 /* If we can do the store-flag, do the addition or
1532 subtraction. */
1541 {
1542 /* Put the result back in temp2 in case it isn't already.
1543 Then replace the jump, possible a CC0-setting insn in
1544 front of the jump, and TEMP, with the sequence we have
1545 made. */
1560 #ifdef HAVE_cc0
1562 #endif
1566 }
1567 else
1569 }
1571 /* Simplify if (...) x = 1; else {...} if (x) ...
1572 We recognize this case scanning backwards as well.
1574 TEMP is the assignment to x;
1575 TEMP1 is the label at the head of the second if. */
1576 /* ?? This should call get_condition to find the values being
1577 compared, instead of looking for a COMPARE insn when HAVE_cc0
1578 is not defined. This would allow it to work on the m88k. */
1579 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1580 is not defined and the condition is tested by a separate compare
1581 insn. This is because the code below assumes that the result
1582 of the compare dies in the following branch.
1584 Not only that, but there might be other insns between the
1585 compare and branch whose results are live. Those insns need
1586 to be executed.
1588 A way to fix this is to move the insns at JUMP_LABEL (insn)
1589 to before INSN. If we are running before flow, they will
1590 be deleted if they aren't needed. But this doesn't work
1591 well after flow.
1593 This is really a special-case of jump threading, anyway. The
1594 right thing to do is to replace this and jump threading with
1595 much simpler code in cse.
1597 This code has been turned off in the non-cc0 case in the
1598 meantime. */
1600 #ifdef HAVE_cc0
1602 /* Safe to skip USE and CLOBBER insns here
1603 since they will not be deleted. */
1611 /* If we find that the next value tested is `x'
1612 (TEMP1 is the insn where this happens), win. */
1615 #ifdef HAVE_cc0
1616 /* Does temp1 `tst' the value of x? */
1620 #else
1621 /* Does temp1 compare the value of x against zero? */
1628 #endif
1630 {
1631 /* Get the if_then_else from the condjump. */
1634 {
1637 rtx cond
1640 rtx ultimate;
1646 else
1656 }
1657 }
1658 #endif
1660 #if 0
1661 /* @@ This needs a bit of work before it will be right.
1663 Any type of comparison can be accepted for the first and
1664 second compare. When rewriting the first jump, we must
1665 compute the what conditions can reach label3, and use the
1666 appropriate code. We can not simply reverse/swap the code
1667 of the first jump. In some cases, the second jump must be
1668 rewritten also.
1670 For example,
1671 < == converts to > ==
1672 < != converts to == >
1673 etc.
1675 If the code is written to only accept an '==' test for the second
1676 compare, then all that needs to be done is to swap the condition
1677 of the first branch.
1679 It is questionable whether we want this optimization anyways,
1680 since if the user wrote code like this because he/she knew that
1681 the jump to label1 is taken most of the time, then rewriting
1682 this gives slower code. */
1683 /* @@ This should call get_condition to find the values being
1684 compared, instead of looking for a COMPARE insn when HAVE_cc0
1685 is not defined. This would allow it to work on the m88k. */
1686 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1687 is not defined and the condition is tested by a separate compare
1688 insn. This is because the code below assumes that the result
1689 of the compare dies in the following branch. */
1691 /* Simplify test a ~= b
1692 condjump label1;
1693 test a == b
1694 condjump label2;
1695 jump label3;
1696 label1:
1698 rewriting as
1699 test a ~~= b
1700 condjump label3
1701 test a == b
1702 condjump label2
1703 label1:
1705 where ~= is an inequality, e.g. >, and ~~= is the swapped
1706 inequality, e.g. <.
1708 We recognize this case scanning backwards.
1710 TEMP is the conditional jump to `label2';
1711 TEMP1 is the test for `a == b';
1712 TEMP2 is the conditional jump to `label1';
1713 TEMP3 is the test for `a ~= b'. */
1722 #ifdef HAVE_cc0
1724 #else
1728 #endif
1742 {
1747 {
1750 }
1754 }
1755 #endif
1756 /* Simplify if (...) {... x = 1;} if (x) ...
1758 We recognize this case backwards.
1760 TEMP is the test of `x';
1761 TEMP1 is the assignment to `x' at the end of the
1762 previous statement. */
1763 /* @@ This should call get_condition to find the values being
1764 compared, instead of looking for a COMPARE insn when HAVE_cc0
1765 is not defined. This would allow it to work on the m88k. */
1766 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1767 is not defined and the condition is tested by a separate compare
1768 insn. This is because the code below assumes that the result
1769 of the compare dies in the following branch. */
1771 /* ??? This has to be turned off. The problem is that the
1772 unconditional jump might indirectly end up branching to the
1773 label between TEMP1 and TEMP. We can't detect this, in general,
1774 since it may become a jump to there after further optimizations.
1775 If that jump is done, it will be deleted, so we will retry
1776 this optimization in the next pass, thus an infinite loop.
1778 The present code prevents this by putting the jump after the
1779 label, but this is not logically correct. */
1780 #if 0
1782 /* Safe to skip USE and CLOBBER insns here
1783 since they will not be deleted. */
1788 #ifdef HAVE_cc0
1791 #else
1792 /* Temp must be a compare insn, we can not accept a register
1793 to register move here, since it may not be simply a
1794 tst insn. */
1800 #endif
1801 /* May skip USE or CLOBBER insns here
1802 for checking for opportunity, since we
1803 take care of them later. */
1807 #ifdef HAVE_cc0
1809 #else
1812 #endif
1814 /* If this isn't true, cse will do the job. */
1816 {
1817 /* Get the if_then_else from the condjump. */
1822 {
1824 rtx last_insn;
1825 rtx ultimate;
1826 rtx p;
1828 /* Get the place that condjump will jump to
1829 if it is reached from here. */
1833 else
1835 /* Get it as a CODE_LABEL. */
1838 else
1839 /* Get the label out of the LABEL_REF. */
1842 /* Insert the jump immediately before TEMP, specifically
1843 after the label that is between TEMP1 and TEMP. */
1846 /* If we would be branching to the next insn, the jump
1847 would immediately be deleted and the re-inserted in
1848 a subsequent pass over the code. So don't do anything
1849 in that case. */
1852 {
1855 last_insn);
1860 {
1864 }
1867 }
1868 }
1869 }
1870 #endif
1871 /* Detect a conditional jump going to the same place
1872 as an immediately following unconditional jump. */
1878 {
1881 /* ??? Optional. Disables some optimizations, but makes
1882 gcov output more accurate with -O. */
1889 {
1893 }
1894 }
1895 /* Detect a conditional jump jumping over an unconditional jump. */
1898 && ! this_is_simplejump
1904 {
1905 /* When we invert the unconditional jump, we will be
1906 decrementing the usage count of its old label.
1907 Make sure that we don't delete it now because that
1908 might cause the following code to be deleted. */
1916 {
1917 /* It is very likely that if there are USE insns before
1918 this jump, they hold REG_DEAD notes. These REG_DEAD
1919 notes are no longer valid due to this optimization,
1920 and will cause the life-analysis that following passes
1921 (notably delayed-branch scheduling) to think that
1922 these registers are dead when they are not.
1924 To prevent this trouble, we just remove the USE insns
1925 from the insn chain. */
1929 {
1933 }
1938 }
1940 /* We can now safely delete the label if it is unreferenced
1941 since the delete_insn above has deleted the BARRIER. */
1945 }
1946 else
1947 {
1948 /* Detect a jump to a jump. */
1953 {
1956 }
1958 /* Look for if (foo) bar; else break; */
1959 /* The insns look like this:
1960 insn = condjump label1;
1961 ...range1 (some insns)...
1962 jump label2;
1963 label1:
1964 ...range2 (some insns)...
1965 jump somewhere unconditionally
1966 label2: */
1967 {
1970 /* Don't do this optimization on the first round, so that
1971 jump-around-a-jump gets simplified before we ask here
1972 whether a jump is unconditional.
1974 Also don't do it when we are called after reload since
1975 it will confuse reorg. */
1978 /* Make sure INSN is something we can invert. */
1985 {
1992 /* Invert the jump condition, so we
1993 still execute the same insns in each case. */
1995 {
2000 rtx rangenext;
2002 /* Include in each range any notes before it, to be
2003 sure that we get the line number note if any, even
2004 if there are other notes here. */
2013 /* Don't move NOTEs for blocks or loops; shift them
2014 outside the ranges, where they'll stay put. */
2018 /* Get current surrounds of the 2 ranges. */
2024 /* Splice range2 where range1 was. */
2029 /* Splice range1 where range2 was. */
2035 /* Check for a loop end note between the end of
2036 range2, and the next code label. If there is one,
2037 then what we have really seen is
2038 if (foo) break; end_of_loop;
2039 and moved the break sequence outside the loop.
2040 We must move the LOOP_END note to where the
2041 loop really ends now, or we will confuse loop
2042 optimization. Stop if we find a LOOP_BEG note
2043 first, since we don't want to move the LOOP_END
2044 note in that case. */
2046 {
2049 {
2052 {
2063 }
2067 }
2068 }
2071 }
2072 }
2073 }
2075 /* Now that the jump has been tensioned,
2076 try cross jumping: check for identical code
2077 before the jump and before its target label. */
2079 /* First, cross jumping of conditional jumps: */
2082 {
2086 /* A conditional jump may be crossjumped
2087 only if the place it jumps to follows
2088 an opposing jump that comes back here. */
2091 /* We have no opposing jump;
2092 cannot cross jump this insn. */
2096 /* TARGET is nonzero if it is ok to cross jump
2097 to code before TARGET. If so, see if matches. */
2103 {
2105 /* Make the old conditional jump
2106 into an unconditional one. */
2111 /* Add to jump_chain unless this is a new label
2112 whose UID is too large. */
2114 {
2118 }
2121 }
2122 }
2124 /* Cross jumping of unconditional jumps:
2125 a few differences. */
2128 {
2130 rtx target;
2134 /* TARGET is nonzero if it is ok to cross jump
2135 to code before TARGET. If so, see if matches. */
2139 /* If cannot cross jump to code before the label,
2140 see if we can cross jump to another jump to
2141 the same label. */
2142 /* Try each other jump to this label. */
2149 /* Ignore TARGET if it's deleted. */
2155 {
2159 }
2160 }
2162 /* This code was dead in the previous jump.c! */
2164 {
2165 /* Return insns all "jump to the same place"
2166 so we can cross-jump between any two of them. */
2172 /* If cannot cross jump to code before the label,
2173 see if we can cross jump to another jump to
2174 the same label. */
2175 /* Try each other jump to this label. */
2186 {
2190 }
2191 }
2192 }
2193 }
2196 }
2198 /* Delete extraneous line number notes.
2199 Note that two consecutive notes for different lines are not really
2200 extraneous. There should be some indication where that line belonged,
2201 even if it became empty. */
2203 {
2208 {
2209 /* Delete this note if it is identical to previous note. */
2213 {
2216 }
2219 }
2220 }
2222 #ifdef HAVE_return
2224 {
2225 /* If we fall through to the epilogue, see if we can insert a RETURN insn
2226 in front of it. If the machine allows it at this point (we might be
2227 after reload for a leaf routine), it will improve optimization for it
2228 to be there. We do this both here and at the start of this pass since
2229 the RETURN might have been deleted by some of our optimizations. */
2235 {
2238 }
2239 }
2240 #endif
2242 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
2243 If so, delete it, and record that this function can drop off the end. */
2246 {
2249 /* One label can follow the end-note: the return label. */
2251 /* Ordinary insns can follow it if returning a structure. */
2253 /* If machine uses explicit RETURN insns, no epilogue,
2254 then one of them follows the note. */
2257 /* A barrier can follow the return insn. */
2259 /* Other kinds of notes can follow also. */
2263 }
2265 /* Report if control can fall through at the end of the function. */
2268 {
2271 }
2273 /* Show JUMP_CHAIN no longer valid. */
2275 }
2276 \f
2277 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
2278 jump. Assume that this unconditional jump is to the exit test code. If
2279 the code is sufficiently simple, make a copy of it before INSN,
2280 followed by a jump to the exit of the loop. Then delete the unconditional
2281 jump after INSN.
2283 Return 1 if we made the change, else 0.
2285 This is only safe immediately after a regscan pass because it uses the
2286 values of regno_first_uid and regno_last_uid. */
2288 static int
2290 rtx loop_start;
2291 {
2296 rtx lastexit;
2300 /* Scan the exit code. We do not perform this optimization if any insn:
2302 is a CALL_INSN
2303 is a CODE_LABEL
2304 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
2305 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
2306 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
2307 are not valid
2309 Also, don't do this if the exit code is more than 20 insns. */
2312 insn
2316 {
2318 {
2323 /* We could be in front of the wrong NOTE_INSN_LOOP_END if there is
2324 a jump immediately after the loop start that branches outside
2325 the loop but within an outer loop, near the exit test.
2326 If we copied this exit test and created a phony
2327 NOTE_INSN_LOOP_VTOP, this could make instructions immediately
2328 before the exit test look like these could be safely moved
2329 out of the loop even if they actually may be never executed.
2330 This can be avoided by checking here for NOTE_INSN_LOOP_CONT. */
2347 }
2348 }
2350 /* Unless INSN is zero, we can do the optimization. */
2356 /* See if any insn sets a register only used in the loop exit code and
2357 not a user variable. If so, replace it with a new register. */
2366 {
2372 {
2373 /* We can do the replacement. Allocate reg_map if this is the
2374 first replacement we found. */
2376 {
2379 }
2384 }
2385 }
2387 /* Now copy each insn. */
2390 {
2395 /* Only copy line-number notes. */
2397 {
2400 }
2410 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
2411 make them. */
2428 {
2432 }
2434 /* If this is a simple jump, add it to the jump chain. */
2438 {
2442 }
2447 }
2449 /* Now clean up by emitting a jump to the end label and deleting the jump
2450 at the start of the loop. */
2452 {
2454 loop_start);
2458 {
2462 }
2464 }
2466 /* Mark the exit code as the virtual top of the converted loop. */
2472 }
2473 \f
2474 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
2475 loop-end notes between START and END out before START. Assume that
2476 END is not such a note. START may be such a note. Returns the value
2477 of the new starting insn, which may be different if the original start
2478 was such a note. */
2480 rtx
2483 {
2484 rtx insn;
2485 rtx next;
2488 {
2497 {
2500 else
2501 {
2509 }
2510 }
2511 }
2514 }
2515 \f
2516 /* Compare the instructions before insn E1 with those before E2
2517 to find an opportunity for cross jumping.
2518 (This means detecting identical sequences of insns followed by
2519 jumps to the same place, or followed by a label and a jump
2520 to that label, and replacing one with a jump to the other.)
2522 Assume E1 is a jump that jumps to label E2
2523 (that is not always true but it might as well be).
2524 Find the longest possible equivalent sequences
2525 and store the first insns of those sequences into *F1 and *F2.
2526 Store zero there if no equivalent preceding instructions are found.
2528 We give up if we find a label in stream 1.
2529 Actually we could transfer that label into stream 2. */
2531 static void
2536 {
2548 {
2558 /* Don't allow the range of insns preceding E1 or E2
2559 to include the other (E2 or E1). */
2563 /* If we will get to this code by jumping, those jumps will be
2564 tensioned to go directly to the new label (before I2),
2565 so this cross-jumping won't cost extra. So reduce the minimum. */
2567 {
2570 }
2578 /* If this is a CALL_INSN, compare register usage information.
2579 If we don't check this on stack register machines, the two
2580 CALL_INSNs might be merged leaving reg-stack.c with mismatching
2581 numbers of stack registers in the same basic block.
2582 If we don't check this on machines with delay slots, a delay slot may
2583 be filled that clobbers a parameter expected by the subroutine.
2585 ??? We take the simple route for now and assume that if they're
2586 equal, they were constructed identically. */
2593 #ifdef STACK_REGS
2594 /* If cross_jump_death_matters is not 0, the insn's mode
2595 indicates whether or not the insn contains any stack-like
2596 regs. */
2599 {
2600 /* If register stack conversion has already been done, then
2601 death notes must also be compared before it is certain that
2602 the two instruction streams match. */
2604 rtx note;
2624 done:
2625 ;
2626 }
2627 #endif
2629 /* Don't allow old-style asm or volatile extended asms to be accepted
2630 for cross jumping purposes. It is conceptually correct to allow
2631 them, since cross-jumping preserves the dynamic instruction order
2632 even though it is changing the static instruction order. However,
2633 if an asm is being used to emit an assembler pseudo-op, such as
2634 the MIPS `.set reorder' pseudo-op, then the static instruction order
2635 matters and it must be preserved. */
2643 {
2644 /* The following code helps take care of G++ cleanups. */
2645 rtx equiv1;
2646 rtx equiv2;
2653 /* If the equivalences are not to a constant, they may
2654 reference pseudos that no longer exist, so we can't
2655 use them. */
2658 {
2663 {
2670 }
2671 }
2673 /* Insns fail to match; cross jumping is limited to the following
2674 insns. */
2676 #ifdef HAVE_cc0
2677 /* Don't allow the insn after a compare to be shared by
2678 cross-jumping unless the compare is also shared.
2679 Here, if either of these non-matching insns is a compare,
2680 exclude the following insn from possible cross-jumping. */
2683 #endif
2685 /* If cross-jumping here will feed a jump-around-jump
2686 optimization, this jump won't cost extra, so reduce
2687 the minimum. */
2693 }
2695 win:
2697 {
2698 /* Ok, this insn is potentially includable in a cross-jump here. */
2701 }
2702 }
2706 }
2708 static void
2711 {
2712 /* Find an existing label at this point
2713 or make a new one if there is none. */
2716 /* Make the same jump insn jump to the new point. */
2718 {
2719 /* Remove from jump chain of returns. */
2721 /* Change the insn. */
2726 /* Add to new the jump chain. */
2729 {
2732 }
2733 }
2734 else
2737 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
2738 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
2739 the NEWJPOS stream. */
2742 {
2743 rtx lnote;
2755 }
2756 }
2757 \f
2758 /* Return the label before INSN, or put a new label there. */
2760 rtx
2762 rtx insn;
2763 {
2764 rtx label;
2766 /* Find an existing label at this point
2767 or make a new one if there is none. */
2771 {
2777 }
2779 }
2781 /* Return the label after INSN, or put a new label there. */
2783 rtx
2785 rtx insn;
2786 {
2787 rtx label;
2789 /* Find an existing label at this point
2790 or make a new one if there is none. */
2794 {
2798 }
2800 }
2801 \f
2802 /* Return 1 if INSN is a jump that jumps to right after TARGET
2803 only on the condition that TARGET itself would drop through.
2804 Assumes that TARGET is a conditional jump. */
2806 static int
2809 {
2825 {
2829 }
2832 {
2836 }
2841 }
2842 \f
2843 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
2844 return non-zero if it is safe to reverse this comparison. It is if our
2845 floating-point is not IEEE, if this is an NE or EQ comparison, or if
2846 this is known to be an integer comparison. */
2848 int
2850 rtx comparison;
2851 rtx insn;
2852 {
2853 rtx arg0;
2855 /* If this is not actually a comparison, we can't reverse it. */
2860 /* If this is an NE comparison, it is safe to reverse it to an EQ
2861 comparison and vice versa, even for floating point. If no operands
2862 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
2863 always false and NE is always true, so the reversal is also valid. */
2864 || flag_fast_math
2871 /* Make sure ARG0 is one of the actual objects being compared. If we
2872 can't do this, we can't be sure the comparison can be reversed.
2874 Handle cc0 and a MODE_CC register. */
2876 #ifdef HAVE_cc0
2878 #endif
2879 )
2880 {
2891 }
2893 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
2894 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
2899 }
2901 /* Given an rtx-code for a comparison, return the code
2902 for the negated comparison.
2903 WATCH OUT! reverse_condition is not safe to use on a jump
2904 that might be acting on the results of an IEEE floating point comparison,
2905 because of the special treatment of non-signaling nans in comparisons.
2906 Use can_reverse_comparison_p to be sure. */
2908 enum rtx_code
2911 {
2913 {
2947 }
2948 }
2950 /* Similar, but return the code when two operands of a comparison are swapped.
2951 This IS safe for IEEE floating-point. */
2953 enum rtx_code
2956 {
2958 {
2990 }
2991 }
2993 /* Given a comparison CODE, return the corresponding unsigned comparison.
2994 If CODE is an equality comparison or already an unsigned comparison,
2995 CODE is returned. */
2997 enum rtx_code
3000 {
3002 {
3025 }
3026 }
3028 /* Similarly, return the signed version of a comparison. */
3030 enum rtx_code
3033 {
3035 {
3058 }
3059 }
3060 \f
3061 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
3062 truth of CODE1 implies the truth of CODE2. */
3064 int
3067 {
3072 {
3100 }
3103 }
3104 \f
3105 /* Return 1 if INSN is an unconditional jump and nothing else. */
3107 int
3109 rtx insn;
3110 {
3115 }
3117 /* Return nonzero if INSN is a (possibly) conditional jump
3118 and nothing more. */
3120 int
3122 rtx insn;
3123 {
3142 }
3144 /* Return nonzero if INSN is a (possibly) conditional jump
3145 and nothing more. */
3147 int
3149 rtx insn;
3150 {
3155 else
3175 }
3177 /* Return 1 if X is an RTX that does nothing but set the condition codes
3178 and CLOBBER or USE registers.
3179 Return -1 if X does explicitly set the condition codes,
3180 but also does other things. */
3182 int
3184 rtx x;
3185 {
3186 #ifdef HAVE_cc0
3190 {
3195 {
3201 }
3203 }
3205 #else
3207 #endif
3208 }
3209 \f
3210 /* Follow any unconditional jump at LABEL;
3211 return the ultimate label reached by any such chain of jumps.
3212 If LABEL is not followed by a jump, return LABEL.
3213 If the chain loops or we can't find end, return LABEL,
3214 since that tells caller to avoid changing the insn.
3216 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
3217 a USE or CLOBBER. */
3219 rtx
3221 rtx label;
3222 {
3236 depth++)
3237 {
3238 /* Don't chain through the insn that jumps into a loop
3239 from outside the loop,
3240 since that would create multiple loop entry jumps
3241 and prevent loop optimization. */
3242 rtx tem;
3247 /* ??? Optional. Disables some optimizations, but makes
3248 gcov output more accurate with -O. */
3252 /* If we have found a cycle, make the insn jump to itself. */
3262 }
3266 }
3268 /* Assuming that field IDX of X is a vector of label_refs,
3269 replace each of them by the ultimate label reached by it.
3270 Return nonzero if a change is made.
3271 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
3273 static int
3277 {
3281 {
3285 {
3291 }
3292 }
3294 }
3295 \f
3296 /* Find all CODE_LABELs referred to in X, and increment their use counts.
3297 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
3298 in INSN, then store one of them in JUMP_LABEL (INSN).
3299 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
3300 referenced in INSN, add a REG_LABEL note containing that label to INSN.
3301 Also, when there are consecutive labels, canonicalize on the last of them.
3303 Note that two labels separated by a loop-beginning note
3304 must be kept distinct if we have not yet done loop-optimization,
3305 because the gap between them is where loop-optimize
3306 will want to move invariant code to. CROSS_JUMP tells us
3307 that loop-optimization is done with.
3309 Once reload has completed (CROSS_JUMP non-zero), we need not consider
3310 two labels distinct if they are separated by only USE or CLOBBER insns. */
3312 static void
3315 rtx insn;
3317 {
3323 {
3336 /* If this is a constant-pool reference, see if it is a label. */
3343 {
3346 rtx note;
3347 rtx next;
3352 /* Ignore references to labels of containing functions. */
3356 /* If there are other labels following this one,
3357 replace it with the last of the consecutive labels. */
3359 {
3371 /* ??? Optional. Disables some optimizations, but
3372 makes gcov output more accurate with -O. */
3375 }
3382 {
3386 /* If we've changed OLABEL and we had a REG_LABEL note
3387 for it, update it as well. */
3392 /* Otherwise, add a REG_LABEL note for LABEL unless there already
3393 is one. */
3395 {
3396 /* This code used to ignore labels which refered to dispatch
3397 tables to avoid flow.c generating worse code.
3399 However, in the presense of global optimizations like
3400 gcse which call find_basic_blocks without calling
3401 life_analysis, not recording such labels will lead
3402 to compiler aborts because of inconsistencies in the
3403 flow graph. So we go ahead and record the label.
3405 It may also be the case that the optimization argument
3406 is no longer valid because of the more accurate cfg
3407 we build in find_basic_blocks -- it no longer pessimizes
3408 code when it finds a REG_LABEL note. */
3411 }
3412 }
3414 }
3416 /* Do walk the labels in a vector, but not the first operand of an
3417 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
3421 {
3426 }
3431 }
3435 {
3439 {
3443 }
3444 }
3445 }
3447 /* If all INSN does is set the pc, delete it,
3448 and delete the insn that set the condition codes for it
3449 if that's what the previous thing was. */
3451 void
3453 rtx insn;
3454 {
3459 }
3461 /* Delete INSN and recursively delete insns that compute values used only
3462 by INSN. This uses the REG_DEAD notes computed during flow analysis.
3463 If we are running before flow.c, we need do nothing since flow.c will
3464 delete dead code. We also can't know if the registers being used are
3465 dead or not at this point.
3467 Otherwise, look at all our REG_DEAD notes. If a previous insn does
3468 nothing other than set a register that dies in this insn, we can delete
3469 that insn as well.
3471 On machines with CC0, if CC0 is used in this insn, we may be able to
3472 delete the insn that set it. */
3474 static void
3476 rtx insn;
3477 {
3480 #ifdef HAVE_cc0
3482 {
3484 /* We assume that at this stage
3485 CC's are always set explicitly
3486 and always immediately before the jump that
3487 will use them. So if the previous insn
3488 exists to set the CC's, delete it
3489 (unless it performs auto-increments, etc.). */
3492 {
3496 else
3497 /* Otherwise, show that cc0 won't be used. */
3500 }
3501 }
3502 #endif
3505 {
3506 rtx our_prev;
3511 /* Verify that the REG_NOTE is legitimate. */
3518 {
3519 /* If we reach a SEQUENCE, it is too complex to try to
3520 do anything with it, so give up. */
3526 /* reorg creates USEs that look like this. We leave them
3527 alone because reorg needs them for its own purposes. */
3531 {
3536 {
3537 /* If we find a SET of something else, we can't
3538 delete the insn. */
3543 {
3549 }
3553 }
3559 }
3561 /* If OUR_PREV references the register that dies here, it is an
3562 additional use. Hence any prior SET isn't dead. However, this
3563 insn becomes the new place for the REG_DEAD note. */
3566 {
3570 }
3571 }
3572 }
3575 }
3576 \f
3577 /* Delete insn INSN from the chain of insns and update label ref counts.
3578 May delete some following insns as a consequence; may even delete
3579 a label elsewhere and insns that follow it.
3581 Returns the first insn after INSN that was not deleted. */
3583 rtx
3586 {
3595 /* This insn is already deleted => return first following nondeleted. */
3599 /* Don't delete user-declared labels. Convert them to special NOTEs
3600 instead. */
3603 {
3608 }
3609 else
3610 /* Mark this insn as deleted. */
3613 /* If this is an unconditional jump, delete it from the jump chain. */
3617 /* If instruction is followed by a barrier,
3618 delete the barrier too. */
3621 {
3624 }
3626 /* Patch out INSN (and the barrier if any) */
3629 {
3631 {
3636 }
3639 {
3643 }
3647 }
3649 /* If deleting a jump, decrement the count of the label,
3650 and delete the label if it is now unused. */
3654 {
3655 /* This can delete NEXT or PREV,
3656 either directly if NEXT is JUMP_LABEL (INSN),
3657 or indirectly through more levels of jumps. */
3659 /* I feel a little doubtful about this loop,
3660 but I see no clean and sure alternative way
3661 to find the first insn after INSN that is not now deleted.
3662 I hope this works. */
3666 }
3668 /* Likewise if we're deleting a dispatch table. */
3673 {
3684 }
3689 /* If INSN was a label and a dispatch table follows it,
3690 delete the dispatch table. The tablejump must have gone already.
3691 It isn't useful to fall through into a table. */
3700 /* If INSN was a label, delete insns following it if now unreachable. */
3703 {
3709 {
3713 /* Keep going past other deleted labels to delete what follows. */
3716 else
3717 /* Note: if this deletes a jump, it can cause more
3718 deletion of unreachable code, after a different label.
3719 As long as the value from this recursive call is correct,
3720 this invocation functions correctly. */
3722 }
3723 }
3726 }
3728 /* Advance from INSN till reaching something not deleted
3729 then return that. May return INSN itself. */
3731 rtx
3733 rtx insn;
3734 {
3738 }
3739 \f
3740 /* Delete a range of insns from FROM to TO, inclusive.
3741 This is for the sake of peephole optimization, so assume
3742 that whatever these insns do will still be done by a new
3743 peephole insn that will replace them. */
3745 void
3748 {
3752 {
3757 {
3760 /* Patch this insn out of the chain. */
3761 /* We don't do this all at once, because we
3762 must preserve all NOTEs. */
3768 }
3773 }
3775 /* Note that if TO is an unconditional jump
3776 we *do not* delete the BARRIER that follows,
3777 since the peephole that replaces this sequence
3778 is also an unconditional jump in that case. */
3779 }
3780 \f
3781 /* Invert the condition of the jump JUMP, and make it jump
3782 to label NLABEL instead of where it jumps now. */
3784 int
3787 {
3788 /* We have to either invert the condition and change the label or
3789 do neither. Either operation could fail. We first try to invert
3790 the jump. If that succeeds, we try changing the label. If that fails,
3791 we invert the jump back to what it was. */
3797 {
3799 {
3802 /* An inverted jump means that a probability taken becomes a
3803 probability not taken. Subtract the branch probability from the
3804 probability base to convert it back to a taken probability.
3805 (We don't flip the probability on a branch that's never taken. */
3808 }
3811 }
3814 /* This should just be putting it back the way it was. */
3818 }
3820 /* Invert the jump condition of rtx X contained in jump insn, INSN.
3822 Return 1 if we can do so, 0 if we cannot find a way to do so that
3823 matches a pattern. */
3825 int
3827 rtx x;
3828 rtx insn;
3829 {
3837 {
3841 /* We can do this in two ways: The preferable way, which can only
3842 be done if this is not an integer comparison, is to reverse
3843 the comparison code. Otherwise, swap the THEN-part and ELSE-part
3844 of the IF_THEN_ELSE. If we can't do either, fail. */
3857 }
3861 {
3866 {
3871 }
3872 }
3875 }
3876 \f
3877 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
3878 If the old jump target label is unused as a result,
3879 it and the code following it may be deleted.
3881 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
3882 RETURN insn.
3884 The return value will be 1 if the change was made, 0 if it wasn't (this
3885 can only occur for NLABEL == 0). */
3887 int
3890 {
3899 /* If this is an unconditional branch, delete it from the jump_chain of
3900 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
3901 have UID's in range and JUMP_CHAIN is valid). */
3904 {
3910 {
3913 }
3914 }
3924 }
3926 /* Delete the instruction JUMP from any jump chain it might be on. */
3928 static void
3930 rtx jump;
3931 {
3935 /* Handle unconditional jumps. */
3940 /* Handle return insns. */
3947 else
3948 {
3949 rtx insn;
3955 {
3958 }
3959 }
3960 }
3962 /* If NLABEL is nonzero, throughout the rtx at LOC,
3963 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
3964 zero, alter (RETURN) to (LABEL_REF NLABEL).
3966 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
3967 validity with validate_change. Convert (set (pc) (label_ref olabel))
3968 to (return).
3970 Return 0 if we found a change we would like to make but it is invalid.
3971 Otherwise, return 1. */
3973 int
3977 rtx insn;
3978 {
3985 {
3987 {
3990 else
3993 }
3994 }
3996 {
4001 }
4010 {
4015 {
4020 }
4021 }
4024 }
4025 \f
4026 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
4028 If the old jump target label (before the dispatch table) becomes unused,
4029 it and the dispatch table may be deleted. In that case, find the insn
4030 before the jump references that label and delete it and logical successors
4031 too. */
4033 static void
4036 {
4039 /* Add this jump to the jump_chain of NLABEL. */
4042 {
4045 }
4053 {
4056 }
4057 }
4059 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
4060 If we found one, delete it and then delete this insn if DELETE_THIS is
4061 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
4063 static int
4067 {
4069 rtx link;
4073 {
4075 {
4078 }
4079 else
4081 }
4085 {
4087 {
4090 }
4091 else
4093 }
4096 }
4097 \f
4098 /* Like rtx_equal_p except that it considers two REGs as equal
4099 if they renumber to the same value and considers two commutative
4100 operations to be the same if the order of the operands has been
4101 reversed. */
4103 int
4106 {
4117 {
4124 /* If we haven't done any renumbering, don't
4125 make any assumptions. */
4130 {
4135 {
4138 }
4139 }
4141 else
4142 {
4146 }
4149 {
4154 {
4157 }
4158 }
4160 else
4161 {
4165 }
4168 }
4170 /* Now we have disposed of all the cases
4171 in which different rtx codes can match. */
4176 {
4187 /* We can't assume nonlocal labels have their following insns yet. */
4191 /* Two label-refs are equivalent if they point at labels
4192 in the same position in the instruction stream. */
4201 }
4203 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
4208 /* For commutative operations, the RTX match if the operand match in any
4209 order. Also handle the simple binary and unary cases without a loop. */
4221 /* Compare the elements. If any pair of corresponding elements
4222 fail to match, return 0 for the whole things. */
4226 {
4229 {
4253 /* fall through. */
4267 }
4268 }
4270 }
4271 \f
4272 /* If X is a hard register or equivalent to one or a subregister of one,
4273 return the hard register number. If X is a pseudo register that was not
4274 assigned a hard register, return the pseudo register number. Otherwise,
4275 return -1. Any rtx is valid for X. */
4277 int
4279 rtx x;
4280 {
4282 {
4286 }
4288 {
4292 }
4294 }
4295 \f
4296 /* Optimize code of the form:
4298 for (x = a[i]; x; ...)
4299 ...
4300 for (x = a[i]; x; ...)
4301 ...
4302 foo:
4304 Loop optimize will change the above code into
4306 if (x = a[i])
4307 for (;;)
4308 { ...; if (! (x = ...)) break; }
4309 if (x = a[i])
4310 for (;;)
4311 { ...; if (! (x = ...)) break; }
4312 foo:
4314 In general, if the first test fails, the program can branch
4315 directly to `foo' and skip the second try which is doomed to fail.
4316 We run this after loop optimization and before flow analysis. */
4318 /* When comparing the insn patterns, we track the fact that different
4319 pseudo-register numbers may have been used in each computation.
4320 The following array stores an equivalence -- same_regs[I] == J means
4321 that pseudo register I was used in the first set of tests in a context
4322 where J was used in the second set. We also count the number of such
4323 pending equivalences. If nonzero, the expressions really aren't the
4324 same. */
4330 /* Track any registers modified between the target of the first jump and
4331 the second jump. They never compare equal. */
4335 /* Record if memory was modified. */
4339 /* Called via note_stores on each insn between the target of the first
4340 branch and the second branch. It marks any changed registers. */
4342 static void
4344 rtx dest;
4345 rtx x ATTRIBUTE_UNUSED;
4346 {
4361 else
4364 }
4366 /* F is the first insn in the chain of insns. */
4368 void
4370 rtx f;
4373 {
4374 /* Basic algorithm is to find a conditional branch,
4375 the label it may branch to, and the branch after
4376 that label. If the two branches test the same condition,
4377 walk back from both branch paths until the insn patterns
4378 differ, or code labels are hit. If we make it back to
4379 the target of the first branch, then we know that the first branch
4380 will either always succeed or always fail depending on the relative
4381 senses of the two branches. So adjust the first branch accordingly
4382 in this case. */
4391 /* Allocate register tables and quick-reset table. */
4399 {
4403 {
4404 /* Get to a candidate branch insn. */
4419 /* Look for a branch after the target. Record any registers and
4420 memory modified between the target and the branch. Stop when we
4421 get to a label since we can't know what was changed there. */
4423 {
4428 {
4429 /* If this is an unconditional jump and is the only use of
4430 its target label, we can follow it. */
4434 {
4437 }
4438 else
4440 }
4446 {
4455 }
4458 }
4460 /* Check the next candidate branch insn from the label
4461 of the first. */
4469 /* Get the comparison codes and operands, reversing the
4470 codes if appropriate. If we don't have comparison codes,
4471 we can't do anything. */
4484 /* If they test the same things and knowing that B1 branches
4485 tells us whether or not B2 branches, check if we
4486 can thread the branch. */
4493 b1))))
4494 {
4499 {
4501 {
4502 /* We have reached the target of the first branch.
4503 If there are no pending register equivalents,
4504 we know that this branch will either always
4505 succeed (if the senses of the two branches are
4506 the same) or always fail (if not). */
4507 rtx new_label;
4514 else
4518 {
4524 {
4525 /* Don't thread to the loop label. If a loop
4526 label is reused, loop optimization will
4527 be disabled for that loop. */
4530 }
4532 }
4534 }
4536 /* If either of these is not a normal insn (it might be
4537 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
4538 have already been skipped above.) Similarly, fail
4539 if the insns are different. */
4548 }
4549 }
4550 }
4551 }
4552 }
4553 \f
4554 /* This is like RTX_EQUAL_P except that it knows about our handling of
4555 possibly equivalent registers and knows to consider volatile and
4556 modified objects as not equal.
4558 YINSN is the insn containing Y. */
4560 int
4563 rtx yinsn;
4564 {
4571 /* Rtx's of different codes cannot be equal. */
4575 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
4576 (REG:SI x) and (REG:HI x) are NOT equivalent. */
4581 /* For floating-point, consider everything unequal. This is a bit
4582 pessimistic, but this pass would only rarely do anything for FP
4583 anyway. */
4588 /* For commutative operations, the RTX match if the operand match in any
4589 order. Also handle the simple binary and unary cases without a loop. */
4601 /* Handle special-cases first. */
4603 {
4608 /* If neither is user variable or hard register, check for possible
4609 equivalence. */
4616 {
4618 num_same_regs++;
4620 /* If this is the first time we are seeing a register on the `Y'
4621 side, see if it is the last use. If not, we can't thread the
4622 jump, so mark it as not equivalent. */
4627 }
4628 else
4634 /* If memory modified or either volatile, not equivalent.
4635 Else, check address. */
4648 /* Cancel a pending `same_regs' if setting equivalenced registers.
4649 Then process source. */
4652 {
4654 {
4656 num_same_regs--;
4657 }
4660 }
4661 else
4675 }
4682 {
4684 {
4698 /* Two vectors must have the same length. */
4702 /* And the corresponding elements must match. */
4721 /* These are just backpointers, so they don't matter. */
4727 /* It is believed that rtx's at this level will never
4728 contain anything but integers and other rtx's,
4729 except for within LABEL_REFs and SYMBOL_REFs. */
4732 }
4733 }
4735 }
4736 \f
4738 #ifndef HAVE_cc0
4739 /* Return the insn that NEW can be safely inserted in front of starting at
4740 the jump insn INSN. Return 0 if it is not safe to do this jump
4741 optimization. Note that NEW must contain a single set. */
4743 static rtx
4745 rtx insn;
4747 {
4749 rtx prev;
4751 /* If NEW does not clobber, it is safe to insert NEW before INSN. */
4758 insn))
4764 /* There is a good chance that the previous insn PREV sets the thing
4765 being clobbered (often the CC in a hard reg). If PREV does not
4766 use what NEW sets, we can insert NEW before PREV. */
4772 insn)
4774 prev))
4778 }
4781 /* Return 1 if the value of X is unsafe to arbitrarily evaluate, i.e.
4782 might fault on some arguments. This is used in connection with
4783 conditional move optimization. */
4785 static int
4787 rtx x;
4788 {
4794 {
4821 && !flag_fast_math
4826 {
4837 }
4839 }
4848 }