| blob | 9748fb230467e76b53327920050deca8b81e888d |
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. */
68 /* ??? Eventually must record somehow the labels used by jumps
69 from nested functions. */
70 /* Pre-record the next or previous real insn for each label?
71 No, this pass is very fast anyway. */
72 /* Condense consecutive labels?
73 This would make life analysis faster, maybe. */
74 /* Optimize jump y; x: ... y: jumpif... x?
75 Don't know if it is worth bothering with. */
76 /* Optimize two cases of conditional jump to conditional jump?
77 This can never delete any instruction or make anything dead,
78 or even change what is live at any point.
79 So perhaps let combiner do it. */
81 /* Vector indexed by uid.
82 For each CODE_LABEL, index by its uid to get first unconditional jump
83 that jumps to the label.
84 For each JUMP_INSN, index by its uid to get the next unconditional jump
85 that jumps to the same label.
86 Element 0 is the start of a chain of all return insns.
87 (It is safe to use element 0 because insn uid 0 is not used. */
91 /* List of labels referred to from initializers.
92 These can never be deleted. */
93 rtx forced_labels;
95 /* Maximum index in jump_chain. */
99 /* Set nonzero by jump_optimize if control can fall through
100 to the end of the function. */
103 /* Indicates whether death notes are significant in cross jump analysis.
104 Normally they are not significant, because of A and B jump to C,
105 and R dies in A, it must die in B. But this might not be true after
106 stack register conversion, and we must compare death notes in that
107 case. */
122 #ifndef HAVE_cc0
124 #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 {
157 rtx last_insn;
161 /* Initialize LABEL_NUSES and JUMP_LABEL fields. Delete any REG_LABEL
162 notes whose labels don't occur in the insn any more. */
165 {
172 {
177 }
181 }
183 max_uid++;
185 /* Delete insns following barriers, up to next label. */
188 {
190 {
193 {
197 else
199 }
200 /* INSN is now the code_label. */
201 }
202 else
204 }
206 /* Leave some extra room for labels and duplicate exit test insns
207 we make. */
212 /* Mark the label each jump jumps to.
213 Combine consecutive labels, and count uses of labels.
215 For each label, make a chain (using `jump_chain')
216 of all the *unconditional* jumps that jump to it;
217 also make a chain of all returns. */
221 {
224 {
226 {
230 }
232 {
235 }
236 }
237 }
239 /* Keep track of labels used from static data;
240 they cannot ever be deleted. */
247 /* Keep track of labels used for marking handlers for exception
248 regions; they cannot usually be deleted. */
255 /* Delete all labels already not referenced.
256 Also find the last insn. */
260 {
263 else
264 {
267 }
268 }
271 {
272 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
273 If so record that this function can drop off the end. */
276 {
279 /* One label can follow the end-note: the return label. */
281 /* Ordinary insns can follow it if returning a structure. */
283 /* If machine uses explicit RETURN insns, no epilogue,
284 then one of them follows the note. */
287 /* A barrier can follow the return insn. */
289 /* Other kinds of notes can follow also. */
293 }
295 /* Report if control can fall through at the end of the function. */
301 /* Zero the "deleted" flag of all the "deleted" insns. */
305 /* Show that the jump chain is not valid. */
308 }
310 #ifdef HAVE_return
312 {
313 /* If we fall through to the epilogue, see if we can insert a RETURN insn
314 in front of it. If the machine allows it at this point (we might be
315 after reload for a leaf routine), it will improve optimization for it
316 to be there. */
322 {
325 }
326 }
327 #endif
331 {
335 {
338 /* Combine stack_adjusts with following push_insns. */
339 #ifdef PUSH_ROUNDING
346 {
347 rtx p;
353 /* Find all successive push insns. */
355 /* Don't convert more than three pushes;
356 that starts adding too many displaced addresses
357 and the whole thing starts becoming a losing
358 proposition. */
360 {
369 /* Allow a no-op move between the adjust and the push. */
378 pushes++;
383 }
385 /* Discard the amount pushed from the stack adjust;
386 maybe eliminate it entirely. */
388 {
391 }
392 else
396 /* Change the appropriate push insns to ordinary stores. */
399 {
408 /* Allow a no-op move between the adjust and the push. */
418 /* If this push doesn't fully fit in the space
419 of the stack adjust that we deleted,
420 make another stack adjust here for what we
421 didn't use up. There should be peepholes
422 to recognize the resulting sequence of insns. */
424 {
427 p);
429 }
432 }
433 }
434 #endif
436 /* Detect and delete no-op move instructions
437 resulting from not allocating a parameter in a register. */
450 /* Detect and ignore no-op move instructions
451 resulting from smart or fortuitous register allocation. */
454 {
461 {
462 rtx trial;
469 {
470 /* DREG may have been the target of a REG_DEAD note in
471 the insn which makes INSN redundant. If so, reorg
472 would still think it is dead. So search for such a
473 note and delete it if we find it. */
479 {
482 }
484 /* Deleting insn could lose a death-note for SREG. */
486 {
487 /* Change this into a USE so that we won't emit
488 code for it, but still can keep the note. */
492 /* Remove all reg notes but the REG_DEAD one. */
495 }
496 else
498 }
499 }
504 {
505 /* This handles the case where we have two consecutive
506 assignments of the same constant to pseudos that didn't
507 get a hard reg. Each SET from the constant will be
508 converted into a SET of the spill register and an
509 output reload will be made following it. This produces
510 two loads of the same constant into the same spill
511 register. */
515 /* Look back for a death note for the first reg.
516 If there is one, it is no longer accurate. */
518 {
522 {
525 }
527 }
529 /* Delete the second load of the value. */
531 }
532 }
534 {
535 /* If each part is a set between two identical registers or
536 a USE or CLOBBER, delete the insn. */
538 rtx tem;
541 {
551 }
555 }
556 /* Also delete insns to store bit fields if they are no-ops. */
557 /* Not worth the hair to detect this in the big-endian case. */
566 }
568 }
570 /* If we haven't yet gotten to reload and we have just run regscan,
571 delete any insn that sets a register that isn't used elsewhere.
572 This helps some of the optimizations below by having less insns
573 being jumped around. */
577 {
585 /* We use regno_last_note_uid so as not to delete the setting
586 of a reg that's used in notes. A subsequent optimization
587 might arrange to use that reg for real. */
592 }
594 /* Now iterate optimizing jumps until nothing changes over one pass. */
598 {
602 {
603 rtx reallabelprev;
605 rtx nlabel;
609 #if 0
610 /* If NOT the first iteration, if this is the last jump pass
611 (just before final), do the special peephole optimizations.
612 Avoiding the first iteration gives ordinary jump opts
613 a chance to work before peephole opts. */
618 #endif
620 /* That could have deleted some insns after INSN, so check now
621 what the following insn is. */
625 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
626 jump. Try to optimize by duplicating the loop exit test if so.
627 This is only safe immediately after regscan, because it uses
628 the values of regno_first_uid and regno_last_uid. */
633 {
636 {
640 }
641 }
650 /* Tension the labels in dispatch tables. */
657 /* If a dispatch table always goes to the same place,
658 get rid of it and replace the insn that uses it. */
662 {
677 /* Don't mess with a casesi insn. */
682 {
686 }
687 }
691 /* If a jump references the end of the function, try to turn
692 it into a RETURN insn, possibly a conditional one. */
699 /* Detect jump to following insn. */
701 {
706 }
708 /* If we have an unconditional jump preceded by a USE, try to put
709 the USE before the target and jump there. This simplifies many
710 of the optimizations below since we don't have to worry about
711 dealing with these USE insns. We only do this if the label
712 being branch to already has the identical USE or if code
713 never falls through to that label. */
722 /* Don't do this optimization if we have a loop containing only
723 the USE instruction, and the loop start label has a usage
724 count of 1. This is because we will redo this optimization
725 everytime through the outer loop, and jump opt will never
726 exit. */
730 {
732 {
735 }
741 }
743 /* Simplify if (...) x = a; else x = b; by converting it
744 to x = b; if (...) x = a;
745 if B is sufficiently simple, the test doesn't involve X,
746 and nothing in the test modifies B or X.
748 If we have small register classes, we also can't do this if X
749 is a hard register.
751 If the "x = b;" insn has any REG_NOTES, we don't do this because
752 of the possibility that we are running after CSE and there is a
753 REG_EQUAL note that is only valid if the branch has already been
754 taken. If we move the insn with the REG_EQUAL note, we may
755 fold the comparison to always be false in a later CSE pass.
756 (We could also delete the REG_NOTES when moving the insn, but it
757 seems simpler to not move it.) An exception is that we can move
758 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
759 value is the same as "b".
761 INSN is the branch over the `else' part.
763 We set:
765 TEMP to the jump insn preceding "x = a;"
766 TEMP1 to X
767 TEMP2 to the insn that sets "x = b;"
768 TEMP3 to the insn that sets "x = a;"
769 TEMP4 to the set of "x = b"; */
776 && (! SMALL_REGISTER_CLASSES
792 /* TEMP must skip over the "x = a;" insn */
795 /* There must be no other entries to the "x = b;" insn. */
797 /* INSN must either branch to the insn after TEMP2 or the insn
798 after TEMP2 must branch to the same place as INSN. */
803 {
804 /* The test expression, X, may be a complicated test with
805 multiple branches. See if we can find all the uses of
806 the label that TEMP branches to without hitting a CALL_INSN
807 or a jump to somewhere else. */
810 rtx p;
811 #ifdef HAVE_cc0
812 rtx q;
813 #endif
815 /* Set P to the first jump insn that goes around "x = a;". */
817 {
819 {
822 {
823 nuses--;
826 }
827 else
829 }
832 }
834 #ifdef HAVE_cc0
835 /* We cannot insert anything between a set of cc and its use
836 so if P uses cc0, we must back up to the previous insn. */
841 #endif
846 /* If we found all the uses and there was no data conflict, we
847 can move the assignment unless we can branch into the middle
848 from somewhere. */
855 /* Verify that registers used by the jump are not clobbered
856 by the instruction being moved. */
859 {
863 /* Set NEXT to an insn that we know won't go away. */
866 /* Delete the jump around the set. Note that we must do
867 this before we redirect the test jumps so that it won't
868 delete the code immediately following the assignment
869 we moved (which might be a jump). */
873 /* We either have two consecutive labels or a jump to
874 a jump, so adjust all the JUMP_INSNs to branch to where
875 INSN branches to. */
882 }
883 }
885 /* Simplify if (...) { x = a; goto l; } x = b; by converting it
886 to x = a; if (...) goto l; x = b;
887 if A is sufficiently simple, the test doesn't involve X,
888 and nothing in the test modifies A or X.
890 If we have small register classes, we also can't do this if X
891 is a hard register.
893 If the "x = a;" insn has any REG_NOTES, we don't do this because
894 of the possibility that we are running after CSE and there is a
895 REG_EQUAL note that is only valid if the branch has already been
896 taken. If we move the insn with the REG_EQUAL note, we may
897 fold the comparison to always be false in a later CSE pass.
898 (We could also delete the REG_NOTES when moving the insn, but it
899 seems simpler to not move it.) An exception is that we can move
900 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
901 value is the same as "a".
903 INSN is the goto.
905 We set:
907 TEMP to the jump insn preceding "x = a;"
908 TEMP1 to X
909 TEMP2 to the insn that sets "x = b;"
910 TEMP3 to the insn that sets "x = a;"
911 TEMP4 to the set of "x = a"; */
918 && (! SMALL_REGISTER_CLASSES
934 /* TEMP must skip over the "x = a;" insn */
937 {
941 #ifdef HAVE_cc0
942 /* We cannot insert anything between a set of cc and its use. */
946 #endif
956 /* Verify that registers used by the jump are not clobbered
957 by the instruction being moved. */
961 {
966 /* Set NEXT to an insn that we know won't go away. */
969 }
974 }
976 #ifndef HAVE_cc0
977 /* If we have if (...) x = exp; and branches are expensive,
978 EXP is a single insn, does not have any side effects, cannot
979 trap, and is not too costly, convert this to
980 t = exp; if (...) x = t;
982 Don't do this when we have CC0 because it is unlikely to help
983 and we'd need to worry about where to place the new insn and
984 the potential for conflicts. We also can't do this when we have
985 notes on the insn for the same reason as above.
987 We set:
989 TEMP to the "x = exp;" insn.
990 TEMP1 to the single set in the "x = exp;" insn.
991 TEMP2 to "x". */
1005 && (! SMALL_REGISTER_CLASSES
1013 {
1018 {
1026 {
1029 }
1030 }
1031 }
1033 /* Similarly, if it takes two insns to compute EXP but they
1034 have the same destination. Here TEMP3 will be the second
1035 insn and TEMP4 the SET from that insn. */
1053 && (! SMALL_REGISTER_CLASSES
1063 {
1069 {
1070 /* Use the earliest of temp5 and temp6. */
1076 emit_insn_after_with_line_notes
1084 {
1087 }
1088 }
1089 }
1091 /* Finally, handle the case where two insns are used to
1092 compute EXP but a temporary register is used. Here we must
1093 ensure that the temporary register is not used anywhere else. */
1096 && after_regscan
1124 && (! SMALL_REGISTER_CLASSES
1130 {
1136 {
1137 /* Use the earliest of temp5 and temp6. */
1150 {
1153 }
1154 }
1155 }
1158 /* Try to use a conditional move (if the target has them), or a
1159 store-flag insn. The general case is:
1161 1) x = a; if (...) x = b; and
1162 2) if (...) x = b;
1164 If the jump would be faster, the machine should not have defined
1165 the movcc or scc insns!. These cases are often made by the
1166 previous optimization.
1168 The second case is treated as x = x; if (...) x = b;.
1170 INSN here is the jump around the store. We set:
1172 TEMP to the "x = b;" insn.
1173 TEMP1 to X.
1174 TEMP2 to B.
1175 TEMP3 to A (X in the second case).
1176 TEMP4 to the condition being tested.
1177 TEMP5 to the earliest insn used to find the condition. */
1180 ! reload_completed
1182 /* Set TEMP to the "x = b;" insn. */
1187 && (! SMALL_REGISTER_CLASSES
1191 /* Allow either form, but prefer the former if both apply.
1192 There is no point in using the old value of TEMP1 if
1193 it is a register, since cse will alias them. It can
1194 lose if the old value were a hard register since CSE
1195 won't replace hard registers. Avoid using TEMP3 if
1196 small register classes and it is a hard register. */
1200 /* Make the latter case look like x = x; if (...) x = b; */
1202 /* INSN must either branch to the insn after TEMP or the insn
1203 after TEMP must branch to the same place as INSN. */
1209 /* We must be comparing objects whose modes imply the size.
1210 We could handle BLKmode if (1) emit_store_flag could
1211 and (2) we could find the size reliably. */
1213 /* Even if branches are cheap, the store_flag optimization
1214 can win when the operation to be performed can be
1215 expressed directly. */
1216 #ifdef HAVE_cc0
1217 /* If the previous insn sets CC0 and something else, we can't
1218 do this since we are going to delete that insn. */
1225 #endif
1226 )
1227 {
1228 #ifdef HAVE_conditional_move
1229 /* First try a conditional move. */
1230 {
1234 rtx target;
1236 /* Copy the compared variables into cond0 and cond1, so that
1237 any side effects performed in or after the old comparison,
1238 will not affect our compare which will come later. */
1239 /* ??? Is it possible to just use the comparison in the jump
1240 insn? After all, we're going to delete it. We'd have
1241 to modify emit_conditional_move to take a comparison rtx
1242 instead or write a new function. */
1244 /* We want the target to be able to simplify comparisons with
1245 zero (and maybe other constants as well), so don't create
1246 pseudos for them. There's no need to either. */
1250 else
1264 {
1267 /* Save the conditional move sequence but don't emit it
1268 yet. On some machines, like the alpha, it is possible
1269 that temp5 == insn, so next generate the sequence that
1270 saves the compared values and then emit both
1271 sequences ensuring seq1 occurs before seq2. */
1275 /* Now that we can't fail, generate the copy insns that
1276 preserve the compared values. */
1285 /* Insert conditional move after insn, to be sure that
1286 the jump and a possible compare won't be separated */
1289 /* ??? We can also delete the insn that sets X to A.
1290 Flow will do it too though. */
1296 {
1299 }
1303 }
1304 else
1306 }
1307 #endif
1309 /* That didn't work, try a store-flag insn.
1311 We further divide the cases into:
1313 1) x = a; if (...) x = b; and either A or B is zero,
1314 2) if (...) x = 0; and jumps are expensive,
1315 3) x = a; if (...) x = b; and A and B are constants where all
1316 the set bits in A are also set in B and jumps are expensive,
1317 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
1318 more expensive, and
1319 5) if (...) x = b; if jumps are even more expensive. */
1323 /* Make the latter case look like
1324 x = x; if (...) x = 0; */
1329 /* If B is zero, OK; if A is zero, can only do (1) if we
1330 can reverse the condition. See if (3) applies possibly
1331 by reversing the condition. Prefer reversing to (4) when
1332 branches are very expensive. */
1336 /* Check that the mask is a power of two,
1337 so that it can probably be generated
1338 with a shift. */
1355 insn)))))
1357 )
1358 {
1362 rtx target;
1364 /* If necessary, reverse the condition. */
1367 else
1370 /* If CVAL is non-zero, normalize to -1. Otherwise, if UVAL
1371 is the constant 1, it is best to just compute the result
1372 directly. If UVAL is constant and STORE_FLAG_VALUE
1373 includes all of its bits, it is best to compute the flag
1374 value unnormalized and `and' it with UVAL. Otherwise,
1375 normalize to -1 and `and' with UVAL. */
1382 /* We will be putting the store-flag insn immediately in
1383 front of the comparison that was originally being done,
1384 so we know all the variables in TEMP4 will be valid.
1385 However, this might be in front of the assignment of
1386 A to VAR. If it is, it would clobber the store-flag
1387 we will be emitting.
1389 Therefore, emit into a temporary which will be copied to
1390 VAR immediately after TEMP. */
1395 VOIDmode,
1398 normalizep);
1400 {
1401 rtx seq;
1407 /* Put the store-flag insns in front of the first insn
1408 used to compute the condition to ensure that we
1409 use the same values of them as the current
1410 comparison. However, the remainder of the insns we
1411 generate will be placed directly in front of the
1412 jump insn, in case any of the pseudos we use
1413 are modified earlier. */
1419 /* Both CVAL and UVAL are non-zero. */
1421 {
1429 else
1430 {
1436 }
1438 /* If we usually make new pseudos, do so here. This
1439 turns out to help machines that have conditional
1440 move insns. */
1441 /* ??? Conditional moves have already been handled.
1442 This may be obsolete. */
1450 }
1452 {
1453 /* We know that either CVAL or UVAL is zero. If
1454 UVAL is zero, negate TARGET and `and' with CVAL.
1455 Otherwise, `and' with UVAL. */
1457 {
1461 }
1467 }
1472 #ifdef HAVE_cc0
1473 /* If INSN uses CC0, we must not separate it from the
1474 insn that sets cc0. */
1477 #endif
1485 {
1488 }
1492 }
1493 else
1495 }
1496 }
1498 /* If branches are expensive, convert
1499 if (foo) bar++; to bar += (foo != 0);
1500 and similarly for "bar--;"
1502 INSN is the conditional branch around the arithmetic. We set:
1504 TEMP is the arithmetic insn.
1505 TEMP1 is the SET doing the arithmetic.
1506 TEMP2 is the operand being incremented or decremented.
1507 TEMP3 to the condition being tested.
1508 TEMP4 to the earliest insn used to find the condition. */
1511 #ifdef HAVE_incscc
1512 || HAVE_incscc
1513 #endif
1514 #ifdef HAVE_decscc
1515 || HAVE_decscc
1516 #endif
1517 )
1518 && ! reload_completed
1530 /* INSN must either branch to the insn after TEMP or the insn
1531 after TEMP must branch to the same place as INSN. */
1537 /* We must be comparing objects whose modes imply the size.
1538 We could handle BLKmode if (1) emit_store_flag could
1539 and (2) we could find the size reliably. */
1542 {
1548 /* It must be the case that TEMP2 is not modified in the range
1549 [TEMP4, INSN). The one exception we make is if the insn
1550 before INSN sets TEMP2 to something which is also unchanged
1551 in that range. In that case, we can move the initialization
1552 into our sequence. */
1562 {
1566 }
1572 VOIDmode,
1576 /* If we can do the store-flag, do the addition or
1577 subtraction. */
1586 {
1587 /* Put the result back in temp2 in case it isn't already.
1588 Then replace the jump, possible a CC0-setting insn in
1589 front of the jump, and TEMP, with the sequence we have
1590 made. */
1605 #ifdef HAVE_cc0
1607 #endif
1611 {
1614 }
1618 }
1619 else
1621 }
1623 /* Simplify if (...) x = 1; else {...} if (x) ...
1624 We recognize this case scanning backwards as well.
1626 TEMP is the assignment to x;
1627 TEMP1 is the label at the head of the second if. */
1628 /* ?? This should call get_condition to find the values being
1629 compared, instead of looking for a COMPARE insn when HAVE_cc0
1630 is not defined. This would allow it to work on the m88k. */
1631 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1632 is not defined and the condition is tested by a separate compare
1633 insn. This is because the code below assumes that the result
1634 of the compare dies in the following branch.
1636 Not only that, but there might be other insns between the
1637 compare and branch whose results are live. Those insns need
1638 to be executed.
1640 A way to fix this is to move the insns at JUMP_LABEL (insn)
1641 to before INSN. If we are running before flow, they will
1642 be deleted if they aren't needed. But this doesn't work
1643 well after flow.
1645 This is really a special-case of jump threading, anyway. The
1646 right thing to do is to replace this and jump threading with
1647 much simpler code in cse.
1649 This code has been turned off in the non-cc0 case in the
1650 meantime. */
1652 #ifdef HAVE_cc0
1654 /* Safe to skip USE and CLOBBER insns here
1655 since they will not be deleted. */
1663 /* If we find that the next value tested is `x'
1664 (TEMP1 is the insn where this happens), win. */
1667 #ifdef HAVE_cc0
1668 /* Does temp1 `tst' the value of x? */
1672 #else
1673 /* Does temp1 compare the value of x against zero? */
1680 #endif
1682 {
1683 /* Get the if_then_else from the condjump. */
1686 {
1689 rtx cond
1692 rtx ultimate;
1698 else
1708 }
1709 }
1710 #endif
1712 #if 0
1713 /* @@ This needs a bit of work before it will be right.
1715 Any type of comparison can be accepted for the first and
1716 second compare. When rewriting the first jump, we must
1717 compute the what conditions can reach label3, and use the
1718 appropriate code. We can not simply reverse/swap the code
1719 of the first jump. In some cases, the second jump must be
1720 rewritten also.
1722 For example,
1723 < == converts to > ==
1724 < != converts to == >
1725 etc.
1727 If the code is written to only accept an '==' test for the second
1728 compare, then all that needs to be done is to swap the condition
1729 of the first branch.
1731 It is questionable whether we want this optimization anyways,
1732 since if the user wrote code like this because he/she knew that
1733 the jump to label1 is taken most of the time, then rewriting
1734 this gives slower code. */
1735 /* @@ This should call get_condition to find the values being
1736 compared, instead of looking for a COMPARE insn when HAVE_cc0
1737 is not defined. This would allow it to work on the m88k. */
1738 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1739 is not defined and the condition is tested by a separate compare
1740 insn. This is because the code below assumes that the result
1741 of the compare dies in the following branch. */
1743 /* Simplify test a ~= b
1744 condjump label1;
1745 test a == b
1746 condjump label2;
1747 jump label3;
1748 label1:
1750 rewriting as
1751 test a ~~= b
1752 condjump label3
1753 test a == b
1754 condjump label2
1755 label1:
1757 where ~= is an inequality, e.g. >, and ~~= is the swapped
1758 inequality, e.g. <.
1760 We recognize this case scanning backwards.
1762 TEMP is the conditional jump to `label2';
1763 TEMP1 is the test for `a == b';
1764 TEMP2 is the conditional jump to `label1';
1765 TEMP3 is the test for `a ~= b'. */
1774 #ifdef HAVE_cc0
1776 #else
1780 #endif
1794 {
1799 {
1802 }
1806 }
1807 #endif
1808 /* Simplify if (...) {... x = 1;} if (x) ...
1810 We recognize this case backwards.
1812 TEMP is the test of `x';
1813 TEMP1 is the assignment to `x' at the end of the
1814 previous statement. */
1815 /* @@ This should call get_condition to find the values being
1816 compared, instead of looking for a COMPARE insn when HAVE_cc0
1817 is not defined. This would allow it to work on the m88k. */
1818 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1819 is not defined and the condition is tested by a separate compare
1820 insn. This is because the code below assumes that the result
1821 of the compare dies in the following branch. */
1823 /* ??? This has to be turned off. The problem is that the
1824 unconditional jump might indirectly end up branching to the
1825 label between TEMP1 and TEMP. We can't detect this, in general,
1826 since it may become a jump to there after further optimizations.
1827 If that jump is done, it will be deleted, so we will retry
1828 this optimization in the next pass, thus an infinite loop.
1830 The present code prevents this by putting the jump after the
1831 label, but this is not logically correct. */
1832 #if 0
1834 /* Safe to skip USE and CLOBBER insns here
1835 since they will not be deleted. */
1840 #ifdef HAVE_cc0
1843 #else
1844 /* Temp must be a compare insn, we can not accept a register
1845 to register move here, since it may not be simply a
1846 tst insn. */
1852 #endif
1853 /* May skip USE or CLOBBER insns here
1854 for checking for opportunity, since we
1855 take care of them later. */
1859 #ifdef HAVE_cc0
1861 #else
1864 #endif
1866 /* If this isn't true, cse will do the job. */
1868 {
1869 /* Get the if_then_else from the condjump. */
1874 {
1876 rtx last_insn;
1877 rtx ultimate;
1878 rtx p;
1880 /* Get the place that condjump will jump to
1881 if it is reached from here. */
1885 else
1887 /* Get it as a CODE_LABEL. */
1890 else
1891 /* Get the label out of the LABEL_REF. */
1894 /* Insert the jump immediately before TEMP, specifically
1895 after the label that is between TEMP1 and TEMP. */
1898 /* If we would be branching to the next insn, the jump
1899 would immediately be deleted and the re-inserted in
1900 a subsequent pass over the code. So don't do anything
1901 in that case. */
1904 {
1907 last_insn);
1912 {
1916 }
1919 }
1920 }
1921 }
1922 #endif
1923 /* Detect a conditional jump going to the same place
1924 as an immediately following unconditional jump. */
1930 {
1933 /* ??? Optional. Disables some optimizations, but makes
1934 gcov output more accurate with -O. */
1941 {
1945 }
1946 }
1947 #ifdef HAVE_trap
1948 /* Detect a conditional jump jumping over an unconditional trap. */
1959 {
1965 {
1971 }
1972 }
1973 /* Detect a jump jumping to an unconditional trap. */
1978 && (this_is_simplejump
1980 {
1985 {
1987 /* Replace an unconditional jump to a trap with a trap. */
1989 {
1994 }
1999 {
2004 }
2005 }
2006 /* If the trap condition and jump condition are mutually
2007 exclusive, redirect the jump to the following insn. */
2009 && ! this_is_simplejump
2014 {
2017 }
2018 }
2019 #endif
2021 /* Detect a conditional jump jumping over an unconditional jump. */
2024 && ! this_is_simplejump
2030 {
2031 /* When we invert the unconditional jump, we will be
2032 decrementing the usage count of its old label.
2033 Make sure that we don't delete it now because that
2034 might cause the following code to be deleted. */
2042 {
2043 /* It is very likely that if there are USE insns before
2044 this jump, they hold REG_DEAD notes. These REG_DEAD
2045 notes are no longer valid due to this optimization,
2046 and will cause the life-analysis that following passes
2047 (notably delayed-branch scheduling) to think that
2048 these registers are dead when they are not.
2050 To prevent this trouble, we just remove the USE insns
2051 from the insn chain. */
2055 {
2059 }
2064 }
2066 /* We can now safely delete the label if it is unreferenced
2067 since the delete_insn above has deleted the BARRIER. */
2071 }
2072 else
2073 {
2074 /* Detect a jump to a jump. */
2079 {
2082 }
2084 /* Look for if (foo) bar; else break; */
2085 /* The insns look like this:
2086 insn = condjump label1;
2087 ...range1 (some insns)...
2088 jump label2;
2089 label1:
2090 ...range2 (some insns)...
2091 jump somewhere unconditionally
2092 label2: */
2093 {
2096 /* Don't do this optimization on the first round, so that
2097 jump-around-a-jump gets simplified before we ask here
2098 whether a jump is unconditional.
2100 Also don't do it when we are called after reload since
2101 it will confuse reorg. */
2104 /* Make sure INSN is something we can invert. */
2111 {
2118 /* Invert the jump condition, so we
2119 still execute the same insns in each case. */
2121 {
2126 rtx rangenext;
2128 /* Include in each range any notes before it, to be
2129 sure that we get the line number note if any, even
2130 if there are other notes here. */
2139 /* Don't move NOTEs for blocks or loops; shift them
2140 outside the ranges, where they'll stay put. */
2144 /* Get current surrounds of the 2 ranges. */
2150 /* Splice range2 where range1 was. */
2155 /* Splice range1 where range2 was. */
2161 /* Check for a loop end note between the end of
2162 range2, and the next code label. If there is one,
2163 then what we have really seen is
2164 if (foo) break; end_of_loop;
2165 and moved the break sequence outside the loop.
2166 We must move the LOOP_END note to where the
2167 loop really ends now, or we will confuse loop
2168 optimization. Stop if we find a LOOP_BEG note
2169 first, since we don't want to move the LOOP_END
2170 note in that case. */
2172 {
2175 {
2178 {
2189 }
2193 }
2194 }
2197 }
2198 }
2199 }
2201 /* Now that the jump has been tensioned,
2202 try cross jumping: check for identical code
2203 before the jump and before its target label. */
2205 /* First, cross jumping of conditional jumps: */
2208 {
2212 /* A conditional jump may be crossjumped
2213 only if the place it jumps to follows
2214 an opposing jump that comes back here. */
2217 /* We have no opposing jump;
2218 cannot cross jump this insn. */
2222 /* TARGET is nonzero if it is ok to cross jump
2223 to code before TARGET. If so, see if matches. */
2229 {
2231 /* Make the old conditional jump
2232 into an unconditional one. */
2237 /* Add to jump_chain unless this is a new label
2238 whose UID is too large. */
2240 {
2244 }
2247 }
2248 }
2250 /* Cross jumping of unconditional jumps:
2251 a few differences. */
2254 {
2256 rtx target;
2260 /* TARGET is nonzero if it is ok to cross jump
2261 to code before TARGET. If so, see if matches. */
2265 /* If cannot cross jump to code before the label,
2266 see if we can cross jump to another jump to
2267 the same label. */
2268 /* Try each other jump to this label. */
2275 /* Ignore TARGET if it's deleted. */
2281 {
2285 }
2286 }
2288 /* This code was dead in the previous jump.c! */
2290 {
2291 /* Return insns all "jump to the same place"
2292 so we can cross-jump between any two of them. */
2298 /* If cannot cross jump to code before the label,
2299 see if we can cross jump to another jump to
2300 the same label. */
2301 /* Try each other jump to this label. */
2312 {
2316 }
2317 }
2318 }
2319 }
2322 }
2324 /* Delete extraneous line number notes.
2325 Note that two consecutive notes for different lines are not really
2326 extraneous. There should be some indication where that line belonged,
2327 even if it became empty. */
2329 {
2334 {
2335 /* Delete this note if it is identical to previous note. */
2339 {
2342 }
2345 }
2346 }
2348 #ifdef HAVE_return
2350 {
2351 /* If we fall through to the epilogue, see if we can insert a RETURN insn
2352 in front of it. If the machine allows it at this point (we might be
2353 after reload for a leaf routine), it will improve optimization for it
2354 to be there. We do this both here and at the start of this pass since
2355 the RETURN might have been deleted by some of our optimizations. */
2361 {
2364 }
2365 }
2366 #endif
2368 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
2369 If so, delete it, and record that this function can drop off the end. */
2372 {
2375 /* One label can follow the end-note: the return label. */
2377 /* Ordinary insns can follow it if returning a structure. */
2379 /* If machine uses explicit RETURN insns, no epilogue,
2380 then one of them follows the note. */
2383 /* A barrier can follow the return insn. */
2385 /* Other kinds of notes can follow also. */
2389 }
2391 /* Report if control can fall through at the end of the function. */
2394 {
2397 }
2399 /* Show JUMP_CHAIN no longer valid. */
2401 }
2402 \f
2403 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
2404 jump. Assume that this unconditional jump is to the exit test code. If
2405 the code is sufficiently simple, make a copy of it before INSN,
2406 followed by a jump to the exit of the loop. Then delete the unconditional
2407 jump after INSN.
2409 Return 1 if we made the change, else 0.
2411 This is only safe immediately after a regscan pass because it uses the
2412 values of regno_first_uid and regno_last_uid. */
2414 static int
2416 rtx loop_start;
2417 {
2422 rtx lastexit;
2426 /* Scan the exit code. We do not perform this optimization if any insn:
2428 is a CALL_INSN
2429 is a CODE_LABEL
2430 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
2431 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
2432 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
2433 is not valid.
2435 We also do not do this if we find an insn with ASM_OPERANDS. While
2436 this restriction should not be necessary, copying an insn with
2437 ASM_OPERANDS can confuse asm_noperands in some cases.
2439 Also, don't do this if the exit code is more than 20 insns. */
2442 insn
2446 {
2448 {
2453 /* We could be in front of the wrong NOTE_INSN_LOOP_END if there is
2454 a jump immediately after the loop start that branches outside
2455 the loop but within an outer loop, near the exit test.
2456 If we copied this exit test and created a phony
2457 NOTE_INSN_LOOP_VTOP, this could make instructions immediately
2458 before the exit test look like these could be safely moved
2459 out of the loop even if they actually may be never executed.
2460 This can be avoided by checking here for NOTE_INSN_LOOP_CONT. */
2469 /* If we were to duplicate this code, we would not move
2470 the BLOCK notes, and so debugging the moved code would
2471 be difficult. Thus, we only move the code with -O2 or
2472 higher. */
2478 /* The code below would grossly mishandle REG_WAS_0 notes,
2479 so get rid of them here. */
2490 }
2491 }
2493 /* Unless INSN is zero, we can do the optimization. */
2499 /* See if any insn sets a register only used in the loop exit code and
2500 not a user variable. If so, replace it with a new register. */
2509 {
2515 {
2516 /* We can do the replacement. Allocate reg_map if this is the
2517 first replacement we found. */
2519 {
2522 }
2527 }
2528 }
2530 /* Now copy each insn. */
2533 {
2538 /* Only copy line-number notes. */
2540 {
2543 }
2553 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
2554 make them. */
2571 {
2575 }
2577 /* If this is a simple jump, add it to the jump chain. */
2581 {
2585 }
2590 }
2592 /* Now clean up by emitting a jump to the end label and deleting the jump
2593 at the start of the loop. */
2595 {
2597 loop_start);
2601 {
2605 }
2607 }
2609 /* Mark the exit code as the virtual top of the converted loop. */
2615 }
2616 \f
2617 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
2618 loop-end notes between START and END out before START. Assume that
2619 END is not such a note. START may be such a note. Returns the value
2620 of the new starting insn, which may be different if the original start
2621 was such a note. */
2623 rtx
2626 {
2627 rtx insn;
2628 rtx next;
2631 {
2640 {
2643 else
2644 {
2652 }
2653 }
2654 }
2657 }
2658 \f
2659 /* Compare the instructions before insn E1 with those before E2
2660 to find an opportunity for cross jumping.
2661 (This means detecting identical sequences of insns followed by
2662 jumps to the same place, or followed by a label and a jump
2663 to that label, and replacing one with a jump to the other.)
2665 Assume E1 is a jump that jumps to label E2
2666 (that is not always true but it might as well be).
2667 Find the longest possible equivalent sequences
2668 and store the first insns of those sequences into *F1 and *F2.
2669 Store zero there if no equivalent preceding instructions are found.
2671 We give up if we find a label in stream 1.
2672 Actually we could transfer that label into stream 2. */
2674 static void
2679 {
2691 {
2701 /* Don't allow the range of insns preceding E1 or E2
2702 to include the other (E2 or E1). */
2706 /* If we will get to this code by jumping, those jumps will be
2707 tensioned to go directly to the new label (before I2),
2708 so this cross-jumping won't cost extra. So reduce the minimum. */
2710 {
2713 }
2721 /* If this is a CALL_INSN, compare register usage information.
2722 If we don't check this on stack register machines, the two
2723 CALL_INSNs might be merged leaving reg-stack.c with mismatching
2724 numbers of stack registers in the same basic block.
2725 If we don't check this on machines with delay slots, a delay slot may
2726 be filled that clobbers a parameter expected by the subroutine.
2728 ??? We take the simple route for now and assume that if they're
2729 equal, they were constructed identically. */
2736 #ifdef STACK_REGS
2737 /* If cross_jump_death_matters is not 0, the insn's mode
2738 indicates whether or not the insn contains any stack-like
2739 regs. */
2742 {
2743 /* If register stack conversion has already been done, then
2744 death notes must also be compared before it is certain that
2745 the two instruction streams match. */
2747 rtx note;
2767 done:
2768 ;
2769 }
2770 #endif
2772 /* Don't allow old-style asm or volatile extended asms to be accepted
2773 for cross jumping purposes. It is conceptually correct to allow
2774 them, since cross-jumping preserves the dynamic instruction order
2775 even though it is changing the static instruction order. However,
2776 if an asm is being used to emit an assembler pseudo-op, such as
2777 the MIPS `.set reorder' pseudo-op, then the static instruction order
2778 matters and it must be preserved. */
2786 {
2787 /* The following code helps take care of G++ cleanups. */
2788 rtx equiv1;
2789 rtx equiv2;
2796 /* If the equivalences are not to a constant, they may
2797 reference pseudos that no longer exist, so we can't
2798 use them. */
2801 {
2806 {
2813 }
2814 }
2816 /* Insns fail to match; cross jumping is limited to the following
2817 insns. */
2819 #ifdef HAVE_cc0
2820 /* Don't allow the insn after a compare to be shared by
2821 cross-jumping unless the compare is also shared.
2822 Here, if either of these non-matching insns is a compare,
2823 exclude the following insn from possible cross-jumping. */
2826 #endif
2828 /* If cross-jumping here will feed a jump-around-jump
2829 optimization, this jump won't cost extra, so reduce
2830 the minimum. */
2836 }
2838 win:
2840 {
2841 /* Ok, this insn is potentially includable in a cross-jump here. */
2844 }
2845 }
2849 }
2851 static void
2854 {
2855 /* Find an existing label at this point
2856 or make a new one if there is none. */
2859 /* Make the same jump insn jump to the new point. */
2861 {
2862 /* Remove from jump chain of returns. */
2864 /* Change the insn. */
2869 /* Add to new the jump chain. */
2872 {
2875 }
2876 }
2877 else
2880 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
2881 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
2882 the NEWJPOS stream. */
2885 {
2886 rtx lnote;
2898 }
2899 }
2900 \f
2901 /* Return the label before INSN, or put a new label there. */
2903 rtx
2905 rtx insn;
2906 {
2907 rtx label;
2909 /* Find an existing label at this point
2910 or make a new one if there is none. */
2914 {
2920 }
2922 }
2924 /* Return the label after INSN, or put a new label there. */
2926 rtx
2928 rtx insn;
2929 {
2930 rtx label;
2932 /* Find an existing label at this point
2933 or make a new one if there is none. */
2937 {
2941 }
2943 }
2944 \f
2945 /* Return 1 if INSN is a jump that jumps to right after TARGET
2946 only on the condition that TARGET itself would drop through.
2947 Assumes that TARGET is a conditional jump. */
2949 static int
2952 {
2968 {
2972 }
2975 {
2979 }
2984 }
2985 \f
2986 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
2987 return non-zero if it is safe to reverse this comparison. It is if our
2988 floating-point is not IEEE, if this is an NE or EQ comparison, or if
2989 this is known to be an integer comparison. */
2991 int
2993 rtx comparison;
2994 rtx insn;
2995 {
2996 rtx arg0;
2998 /* If this is not actually a comparison, we can't reverse it. */
3003 /* If this is an NE comparison, it is safe to reverse it to an EQ
3004 comparison and vice versa, even for floating point. If no operands
3005 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
3006 always false and NE is always true, so the reversal is also valid. */
3007 || flag_fast_math
3014 /* Make sure ARG0 is one of the actual objects being compared. If we
3015 can't do this, we can't be sure the comparison can be reversed.
3017 Handle cc0 and a MODE_CC register. */
3019 #ifdef HAVE_cc0
3021 #endif
3022 )
3023 {
3034 }
3036 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
3037 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
3042 }
3044 /* Given an rtx-code for a comparison, return the code
3045 for the negated comparison.
3046 WATCH OUT! reverse_condition is not safe to use on a jump
3047 that might be acting on the results of an IEEE floating point comparison,
3048 because of the special treatment of non-signaling nans in comparisons.
3049 Use can_reverse_comparison_p to be sure. */
3051 enum rtx_code
3054 {
3056 {
3090 }
3091 }
3093 /* Similar, but return the code when two operands of a comparison are swapped.
3094 This IS safe for IEEE floating-point. */
3096 enum rtx_code
3099 {
3101 {
3133 }
3134 }
3136 /* Given a comparison CODE, return the corresponding unsigned comparison.
3137 If CODE is an equality comparison or already an unsigned comparison,
3138 CODE is returned. */
3140 enum rtx_code
3143 {
3145 {
3168 }
3169 }
3171 /* Similarly, return the signed version of a comparison. */
3173 enum rtx_code
3176 {
3178 {
3201 }
3202 }
3203 \f
3204 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
3205 truth of CODE1 implies the truth of CODE2. */
3207 int
3210 {
3215 {
3243 }
3246 }
3247 \f
3248 /* Return 1 if INSN is an unconditional jump and nothing else. */
3250 int
3252 rtx insn;
3253 {
3258 }
3260 /* Return nonzero if INSN is a (possibly) conditional jump
3261 and nothing more. */
3263 int
3265 rtx insn;
3266 {
3285 }
3287 /* Return nonzero if INSN is a (possibly) conditional jump
3288 and nothing more. */
3290 int
3292 rtx insn;
3293 {
3298 else
3318 }
3320 #ifdef HAVE_cc0
3322 /* Return 1 if X is an RTX that does nothing but set the condition codes
3323 and CLOBBER or USE registers.
3324 Return -1 if X does explicitly set the condition codes,
3325 but also does other things. */
3327 int
3329 rtx x ATTRIBUTE_UNUSED;
3330 {
3334 {
3339 {
3345 }
3347 }
3349 }
3350 #endif
3351 \f
3352 /* Follow any unconditional jump at LABEL;
3353 return the ultimate label reached by any such chain of jumps.
3354 If LABEL is not followed by a jump, return LABEL.
3355 If the chain loops or we can't find end, return LABEL,
3356 since that tells caller to avoid changing the insn.
3358 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
3359 a USE or CLOBBER. */
3361 rtx
3363 rtx label;
3364 {
3378 depth++)
3379 {
3380 /* Don't chain through the insn that jumps into a loop
3381 from outside the loop,
3382 since that would create multiple loop entry jumps
3383 and prevent loop optimization. */
3384 rtx tem;
3389 /* ??? Optional. Disables some optimizations, but makes
3390 gcov output more accurate with -O. */
3394 /* If we have found a cycle, make the insn jump to itself. */
3404 }
3408 }
3410 /* Assuming that field IDX of X is a vector of label_refs,
3411 replace each of them by the ultimate label reached by it.
3412 Return nonzero if a change is made.
3413 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
3415 static int
3419 {
3423 {
3427 {
3433 }
3434 }
3436 }
3437 \f
3438 /* Find all CODE_LABELs referred to in X, and increment their use counts.
3439 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
3440 in INSN, then store one of them in JUMP_LABEL (INSN).
3441 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
3442 referenced in INSN, add a REG_LABEL note containing that label to INSN.
3443 Also, when there are consecutive labels, canonicalize on the last of them.
3445 Note that two labels separated by a loop-beginning note
3446 must be kept distinct if we have not yet done loop-optimization,
3447 because the gap between them is where loop-optimize
3448 will want to move invariant code to. CROSS_JUMP tells us
3449 that loop-optimization is done with.
3451 Once reload has completed (CROSS_JUMP non-zero), we need not consider
3452 two labels distinct if they are separated by only USE or CLOBBER insns. */
3454 static void
3457 rtx insn;
3459 {
3465 {
3478 /* If this is a constant-pool reference, see if it is a label. */
3485 {
3488 rtx note;
3489 rtx next;
3494 /* Ignore references to labels of containing functions. */
3498 /* If there are other labels following this one,
3499 replace it with the last of the consecutive labels. */
3501 {
3513 /* ??? Optional. Disables some optimizations, but
3514 makes gcov output more accurate with -O. */
3517 }
3524 {
3528 /* If we've changed OLABEL and we had a REG_LABEL note
3529 for it, update it as well. */
3534 /* Otherwise, add a REG_LABEL note for LABEL unless there already
3535 is one. */
3537 {
3538 /* This code used to ignore labels which refered to dispatch
3539 tables to avoid flow.c generating worse code.
3541 However, in the presense of global optimizations like
3542 gcse which call find_basic_blocks without calling
3543 life_analysis, not recording such labels will lead
3544 to compiler aborts because of inconsistencies in the
3545 flow graph. So we go ahead and record the label.
3547 It may also be the case that the optimization argument
3548 is no longer valid because of the more accurate cfg
3549 we build in find_basic_blocks -- it no longer pessimizes
3550 code when it finds a REG_LABEL note. */
3553 }
3554 }
3556 }
3558 /* Do walk the labels in a vector, but not the first operand of an
3559 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
3563 {
3568 }
3573 }
3577 {
3581 {
3585 }
3586 }
3587 }
3589 /* If all INSN does is set the pc, delete it,
3590 and delete the insn that set the condition codes for it
3591 if that's what the previous thing was. */
3593 void
3595 rtx insn;
3596 {
3601 }
3603 /* Delete INSN and recursively delete insns that compute values used only
3604 by INSN. This uses the REG_DEAD notes computed during flow analysis.
3605 If we are running before flow.c, we need do nothing since flow.c will
3606 delete dead code. We also can't know if the registers being used are
3607 dead or not at this point.
3609 Otherwise, look at all our REG_DEAD notes. If a previous insn does
3610 nothing other than set a register that dies in this insn, we can delete
3611 that insn as well.
3613 On machines with CC0, if CC0 is used in this insn, we may be able to
3614 delete the insn that set it. */
3616 static void
3618 rtx insn;
3619 {
3622 #ifdef HAVE_cc0
3624 {
3626 /* We assume that at this stage
3627 CC's are always set explicitly
3628 and always immediately before the jump that
3629 will use them. So if the previous insn
3630 exists to set the CC's, delete it
3631 (unless it performs auto-increments, etc.). */
3634 {
3638 else
3639 /* Otherwise, show that cc0 won't be used. */
3642 }
3643 }
3644 #endif
3647 {
3648 rtx our_prev;
3653 /* Verify that the REG_NOTE is legitimate. */
3660 {
3661 /* If we reach a SEQUENCE, it is too complex to try to
3662 do anything with it, so give up. */
3668 /* reorg creates USEs that look like this. We leave them
3669 alone because reorg needs them for its own purposes. */
3673 {
3678 {
3679 /* If we find a SET of something else, we can't
3680 delete the insn. */
3685 {
3691 }
3695 }
3701 }
3703 /* If OUR_PREV references the register that dies here, it is an
3704 additional use. Hence any prior SET isn't dead. However, this
3705 insn becomes the new place for the REG_DEAD note. */
3708 {
3712 }
3713 }
3714 }
3717 }
3718 \f
3719 /* Delete insn INSN from the chain of insns and update label ref counts.
3720 May delete some following insns as a consequence; may even delete
3721 a label elsewhere and insns that follow it.
3723 Returns the first insn after INSN that was not deleted. */
3725 rtx
3728 {
3737 /* This insn is already deleted => return first following nondeleted. */
3741 /* Don't delete user-declared labels. Convert them to special NOTEs
3742 instead. */
3745 {
3750 }
3751 else
3752 /* Mark this insn as deleted. */
3755 /* If this is an unconditional jump, delete it from the jump chain. */
3759 /* If instruction is followed by a barrier,
3760 delete the barrier too. */
3763 {
3766 }
3768 /* Patch out INSN (and the barrier if any) */
3771 {
3773 {
3778 }
3781 {
3785 }
3789 }
3791 /* If deleting a jump, decrement the count of the label,
3792 and delete the label if it is now unused. */
3796 {
3797 /* This can delete NEXT or PREV,
3798 either directly if NEXT is JUMP_LABEL (INSN),
3799 or indirectly through more levels of jumps. */
3801 /* I feel a little doubtful about this loop,
3802 but I see no clean and sure alternative way
3803 to find the first insn after INSN that is not now deleted.
3804 I hope this works. */
3808 }
3810 /* Likewise if we're deleting a dispatch table. */
3815 {
3826 }
3831 /* If INSN was a label and a dispatch table follows it,
3832 delete the dispatch table. The tablejump must have gone already.
3833 It isn't useful to fall through into a table. */
3842 /* If INSN was a label, delete insns following it if now unreachable. */
3845 {
3851 {
3855 /* Keep going past other deleted labels to delete what follows. */
3858 else
3859 /* Note: if this deletes a jump, it can cause more
3860 deletion of unreachable code, after a different label.
3861 As long as the value from this recursive call is correct,
3862 this invocation functions correctly. */
3864 }
3865 }
3868 }
3870 /* Advance from INSN till reaching something not deleted
3871 then return that. May return INSN itself. */
3873 rtx
3875 rtx insn;
3876 {
3880 }
3881 \f
3882 /* Delete a range of insns from FROM to TO, inclusive.
3883 This is for the sake of peephole optimization, so assume
3884 that whatever these insns do will still be done by a new
3885 peephole insn that will replace them. */
3887 void
3890 {
3894 {
3899 {
3902 /* Patch this insn out of the chain. */
3903 /* We don't do this all at once, because we
3904 must preserve all NOTEs. */
3910 }
3915 }
3917 /* Note that if TO is an unconditional jump
3918 we *do not* delete the BARRIER that follows,
3919 since the peephole that replaces this sequence
3920 is also an unconditional jump in that case. */
3921 }
3922 \f
3923 /* Invert the condition of the jump JUMP, and make it jump
3924 to label NLABEL instead of where it jumps now. */
3926 int
3929 {
3930 /* We have to either invert the condition and change the label or
3931 do neither. Either operation could fail. We first try to invert
3932 the jump. If that succeeds, we try changing the label. If that fails,
3933 we invert the jump back to what it was. */
3939 {
3941 {
3944 /* An inverted jump means that a probability taken becomes a
3945 probability not taken. Subtract the branch probability from the
3946 probability base to convert it back to a taken probability.
3947 (We don't flip the probability on a branch that's never taken. */
3950 }
3953 }
3956 /* This should just be putting it back the way it was. */
3960 }
3962 /* Invert the jump condition of rtx X contained in jump insn, INSN.
3964 Return 1 if we can do so, 0 if we cannot find a way to do so that
3965 matches a pattern. */
3967 int
3969 rtx x;
3970 rtx insn;
3971 {
3979 {
3983 /* We can do this in two ways: The preferable way, which can only
3984 be done if this is not an integer comparison, is to reverse
3985 the comparison code. Otherwise, swap the THEN-part and ELSE-part
3986 of the IF_THEN_ELSE. If we can't do either, fail. */
3999 }
4003 {
4008 {
4013 }
4014 }
4017 }
4018 \f
4019 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
4020 If the old jump target label is unused as a result,
4021 it and the code following it may be deleted.
4023 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
4024 RETURN insn.
4026 The return value will be 1 if the change was made, 0 if it wasn't (this
4027 can only occur for NLABEL == 0). */
4029 int
4032 {
4041 /* If this is an unconditional branch, delete it from the jump_chain of
4042 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
4043 have UID's in range and JUMP_CHAIN is valid). */
4046 {
4052 {
4055 }
4056 }
4066 }
4068 /* Delete the instruction JUMP from any jump chain it might be on. */
4070 static void
4072 rtx jump;
4073 {
4077 /* Handle unconditional jumps. */
4082 /* Handle return insns. */
4089 else
4090 {
4091 rtx insn;
4097 {
4100 }
4101 }
4102 }
4104 /* If NLABEL is nonzero, throughout the rtx at LOC,
4105 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
4106 zero, alter (RETURN) to (LABEL_REF NLABEL).
4108 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
4109 validity with validate_change. Convert (set (pc) (label_ref olabel))
4110 to (return).
4112 Return 0 if we found a change we would like to make but it is invalid.
4113 Otherwise, return 1. */
4115 int
4119 rtx insn;
4120 {
4127 {
4129 {
4132 else
4135 }
4136 }
4138 {
4143 }
4152 {
4157 {
4162 }
4163 }
4166 }
4167 \f
4168 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
4170 If the old jump target label (before the dispatch table) becomes unused,
4171 it and the dispatch table may be deleted. In that case, find the insn
4172 before the jump references that label and delete it and logical successors
4173 too. */
4175 static void
4178 {
4181 /* Add this jump to the jump_chain of NLABEL. */
4184 {
4187 }
4195 {
4198 }
4199 }
4201 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
4202 If we found one, delete it and then delete this insn if DELETE_THIS is
4203 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
4205 static int
4209 {
4211 rtx link;
4215 {
4217 {
4220 }
4221 else
4223 }
4227 {
4229 {
4232 }
4233 else
4235 }
4238 }
4239 \f
4240 /* Like rtx_equal_p except that it considers two REGs as equal
4241 if they renumber to the same value and considers two commutative
4242 operations to be the same if the order of the operands has been
4243 reversed.
4245 ??? Addition is not commutative on the PA due to the weird implicit
4246 space register selection rules for memory addresses. Therefore, we
4247 don't consider a + b == b + a.
4249 We could/should make this test a little tighter. Possibly only
4250 disabling it on the PA via some backend macro or only disabling this
4251 case when the PLUS is inside a MEM. */
4253 int
4256 {
4267 {
4274 /* If we haven't done any renumbering, don't
4275 make any assumptions. */
4280 {
4285 {
4288 }
4289 }
4291 else
4292 {
4296 }
4299 {
4304 {
4307 }
4308 }
4310 else
4311 {
4315 }
4318 }
4320 /* Now we have disposed of all the cases
4321 in which different rtx codes can match. */
4326 {
4337 /* We can't assume nonlocal labels have their following insns yet. */
4341 /* Two label-refs are equivalent if they point at labels
4342 in the same position in the instruction stream. */
4351 }
4353 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
4358 /* For commutative operations, the RTX match if the operand match in any
4359 order. Also handle the simple binary and unary cases without a loop.
4361 ??? Don't consider PLUS a commutative operator; see comments above. */
4374 /* Compare the elements. If any pair of corresponding elements
4375 fail to match, return 0 for the whole things. */
4379 {
4382 {
4406 /* fall through. */
4420 }
4421 }
4423 }
4424 \f
4425 /* If X is a hard register or equivalent to one or a subregister of one,
4426 return the hard register number. If X is a pseudo register that was not
4427 assigned a hard register, return the pseudo register number. Otherwise,
4428 return -1. Any rtx is valid for X. */
4430 int
4432 rtx x;
4433 {
4435 {
4439 }
4441 {
4445 }
4447 }
4448 \f
4449 /* Optimize code of the form:
4451 for (x = a[i]; x; ...)
4452 ...
4453 for (x = a[i]; x; ...)
4454 ...
4455 foo:
4457 Loop optimize will change the above code into
4459 if (x = a[i])
4460 for (;;)
4461 { ...; if (! (x = ...)) break; }
4462 if (x = a[i])
4463 for (;;)
4464 { ...; if (! (x = ...)) break; }
4465 foo:
4467 In general, if the first test fails, the program can branch
4468 directly to `foo' and skip the second try which is doomed to fail.
4469 We run this after loop optimization and before flow analysis. */
4471 /* When comparing the insn patterns, we track the fact that different
4472 pseudo-register numbers may have been used in each computation.
4473 The following array stores an equivalence -- same_regs[I] == J means
4474 that pseudo register I was used in the first set of tests in a context
4475 where J was used in the second set. We also count the number of such
4476 pending equivalences. If nonzero, the expressions really aren't the
4477 same. */
4483 /* Track any registers modified between the target of the first jump and
4484 the second jump. They never compare equal. */
4488 /* Record if memory was modified. */
4492 /* Called via note_stores on each insn between the target of the first
4493 branch and the second branch. It marks any changed registers. */
4495 static void
4497 rtx dest;
4498 rtx x ATTRIBUTE_UNUSED;
4499 {
4514 else
4517 }
4519 /* F is the first insn in the chain of insns. */
4521 void
4523 rtx f;
4526 {
4527 /* Basic algorithm is to find a conditional branch,
4528 the label it may branch to, and the branch after
4529 that label. If the two branches test the same condition,
4530 walk back from both branch paths until the insn patterns
4531 differ, or code labels are hit. If we make it back to
4532 the target of the first branch, then we know that the first branch
4533 will either always succeed or always fail depending on the relative
4534 senses of the two branches. So adjust the first branch accordingly
4535 in this case. */
4544 /* Allocate register tables and quick-reset table. */
4552 {
4556 {
4557 /* Get to a candidate branch insn. */
4572 /* Look for a branch after the target. Record any registers and
4573 memory modified between the target and the branch. Stop when we
4574 get to a label since we can't know what was changed there. */
4576 {
4581 {
4582 /* If this is an unconditional jump and is the only use of
4583 its target label, we can follow it. */
4587 {
4590 }
4591 else
4593 }
4599 {
4608 }
4611 }
4613 /* Check the next candidate branch insn from the label
4614 of the first. */
4622 /* Get the comparison codes and operands, reversing the
4623 codes if appropriate. If we don't have comparison codes,
4624 we can't do anything. */
4637 /* If they test the same things and knowing that B1 branches
4638 tells us whether or not B2 branches, check if we
4639 can thread the branch. */
4646 b1))))
4647 {
4652 {
4654 {
4655 /* We have reached the target of the first branch.
4656 If there are no pending register equivalents,
4657 we know that this branch will either always
4658 succeed (if the senses of the two branches are
4659 the same) or always fail (if not). */
4660 rtx new_label;
4667 else
4671 {
4677 {
4678 /* Don't thread to the loop label. If a loop
4679 label is reused, loop optimization will
4680 be disabled for that loop. */
4683 }
4685 }
4687 }
4689 /* If either of these is not a normal insn (it might be
4690 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
4691 have already been skipped above.) Similarly, fail
4692 if the insns are different. */
4701 }
4702 }
4703 }
4704 }
4705 }
4706 \f
4707 /* This is like RTX_EQUAL_P except that it knows about our handling of
4708 possibly equivalent registers and knows to consider volatile and
4709 modified objects as not equal.
4711 YINSN is the insn containing Y. */
4713 int
4716 rtx yinsn;
4717 {
4724 /* Rtx's of different codes cannot be equal. */
4728 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
4729 (REG:SI x) and (REG:HI x) are NOT equivalent. */
4734 /* For floating-point, consider everything unequal. This is a bit
4735 pessimistic, but this pass would only rarely do anything for FP
4736 anyway. */
4741 /* For commutative operations, the RTX match if the operand match in any
4742 order. Also handle the simple binary and unary cases without a loop. */
4754 /* Handle special-cases first. */
4756 {
4761 /* If neither is user variable or hard register, check for possible
4762 equivalence. */
4769 {
4771 num_same_regs++;
4773 /* If this is the first time we are seeing a register on the `Y'
4774 side, see if it is the last use. If not, we can't thread the
4775 jump, so mark it as not equivalent. */
4780 }
4781 else
4787 /* If memory modified or either volatile, not equivalent.
4788 Else, check address. */
4801 /* Cancel a pending `same_regs' if setting equivalenced registers.
4802 Then process source. */
4805 {
4807 {
4809 num_same_regs--;
4810 }
4813 }
4814 else
4828 }
4835 {
4837 {
4851 /* Two vectors must have the same length. */
4855 /* And the corresponding elements must match. */
4874 /* These are just backpointers, so they don't matter. */
4880 /* It is believed that rtx's at this level will never
4881 contain anything but integers and other rtx's,
4882 except for within LABEL_REFs and SYMBOL_REFs. */
4885 }
4886 }
4888 }
4889 \f
4891 #ifndef HAVE_cc0
4892 /* Return the insn that NEW can be safely inserted in front of starting at
4893 the jump insn INSN. Return 0 if it is not safe to do this jump
4894 optimization. Note that NEW must contain a single set. */
4896 static rtx
4898 rtx insn;
4900 {
4902 rtx prev;
4904 /* If NEW does not clobber, it is safe to insert NEW before INSN. */
4911 insn))
4917 /* There is a good chance that the previous insn PREV sets the thing
4918 being clobbered (often the CC in a hard reg). If PREV does not
4919 use what NEW sets, we can insert NEW before PREV. */
4925 insn)
4927 prev))
4931 }