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1 /* Optimize jump instructions, for GNU compiler.
2 Copyright (C) 1987, 1988, 1989, 1991, 1992 Free Software Foundation, Inc.
3
4 This file is part of GNU CC.
5
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.
10
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.
15
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
19
20
21 /* This is the jump-optimization pass of the compiler.
22 It is run two or three times: once before cse, sometimes once after cse,
23 and once after reload (before final).
24
25 jump_optimize deletes unreachable code and labels that are not used.
26 It also deletes jumps that jump to the following insn,
27 and simplifies jumps around unconditional jumps and jumps
28 to unconditional jumps.
29
30 Each CODE_LABEL has a count of the times it is used
31 stored in the LABEL_NUSES internal field, and each JUMP_INSN
32 has one label that it refers to stored in the
33 JUMP_LABEL internal field. With this we can detect labels that
34 become unused because of the deletion of all the jumps that
35 formerly used them. The JUMP_LABEL info is sometimes looked
36 at by later passes.
37
38 Optionally, cross-jumping can be done. Currently it is done
39 only the last time (when after reload and before final).
40 In fact, the code for cross-jumping now assumes that register
41 allocation has been done, since it uses `rtx_renumbered_equal_p'.
42
43 Jump optimization is done after cse when cse's constant-propagation
44 causes jumps to become unconditional or to be deleted.
45
46 Unreachable loops are not detected here, because the labels
47 have references and the insns appear reachable from the labels.
48 find_basic_blocks in flow.c finds and deletes such loops.
49
50 The subroutines delete_insn, redirect_jump, and invert_jump are used
51 from other passes as well. */
52
53 #include "config.h"
54 #include "rtl.h"
55 #include "flags.h"
56 #include "hard-reg-set.h"
57 #include "regs.h"
58 #include "expr.h"
59 #include "insn-config.h"
60 #include "insn-flags.h"
61 #include "real.h"
62
63 /* ??? Eventually must record somehow the labels used by jumps
64 from nested functions. */
65 /* Pre-record the next or previous real insn for each label?
66 No, this pass is very fast anyway. */
67 /* Condense consecutive labels?
68 This would make life analysis faster, maybe. */
69 /* Optimize jump y; x: ... y: jumpif... x?
70 Don't know if it is worth bothering with. */
71 /* Optimize two cases of conditional jump to conditional jump?
72 This can never delete any instruction or make anything dead,
73 or even change what is live at any point.
74 So perhaps let combiner do it. */
75
76 /* Vector indexed by uid.
77 For each CODE_LABEL, index by its uid to get first unconditional jump
78 that jumps to the label.
79 For each JUMP_INSN, index by its uid to get the next unconditional jump
80 that jumps to the same label.
81 Element 0 is the start of a chain of all return insns.
82 (It is safe to use element 0 because insn uid 0 is not used. */
83
84 static rtx *jump_chain;
85
86 /* List of labels referred to from initializers.
87 These can never be deleted. */
88 rtx forced_labels;
89
90 /* Maximum index in jump_chain. */
91
92 static int max_jump_chain;
93
94 /* Set nonzero by jump_optimize if control can fall through
95 to the end of the function. */
96 int can_reach_end;
97
98 /* Indicates whether death notes are significant in cross jump analysis.
99 Normally they are not significant, because of A and B jump to C,
100 and R dies in A, it must die in B. But this might not be true after
101 stack register conversion, and we must compare death notes in that
102 case. */
103
104 static int cross_jump_death_matters = 0;
105
106 static int duplicate_loop_exit_test ();
107 void redirect_tablejump ();
108 static int delete_labelref_insn ();
109 static void mark_jump_label ();
110 void delete_jump ();
111 void delete_computation ();
112 static void delete_from_jump_chain ();
113 static int tension_vector_labels ();
114 static void find_cross_jump ();
115 static void do_cross_jump ();
116 static int jump_back_p ();
117
118 extern rtx gen_jump ();
119 \f
120 /* Delete no-op jumps and optimize jumps to jumps
121 and jumps around jumps.
122 Delete unused labels and unreachable code.
123
124 If CROSS_JUMP is 1, detect matching code
125 before a jump and its destination and unify them.
126 If CROSS_JUMP is 2, do cross-jumping, but pay attention to death notes.
127
128 If NOOP_MOVES is nonzero, delete no-op move insns.
129
130 If AFTER_REGSCAN is nonzero, then this jump pass is being run immediately
131 after regscan, and it is safe to use regno_first_uid and regno_last_uid.
132
133 If `optimize' is zero, don't change any code,
134 just determine whether control drops off the end of the function.
135 This case occurs when we have -W and not -O.
136 It works because `delete_insn' checks the value of `optimize'
137 and refrains from actually deleting when that is 0. */
138
139 void
140 jump_optimize (f, cross_jump, noop_moves, after_regscan)
141 rtx f;
142 int cross_jump;
143 int noop_moves;
144 int after_regscan;
145 {
146 register rtx insn, next;
147 int changed;
148 int first = 1;
149 int max_uid = 0;
150 rtx last_insn;
151
152 cross_jump_death_matters = (cross_jump == 2);
153
154 /* Initialize LABEL_NUSES and JUMP_LABEL fields. */
155
156 for (insn = f; insn; insn = NEXT_INSN (insn))
157 {
158 if (GET_CODE (insn) == CODE_LABEL)
159 LABEL_NUSES (insn) = (LABEL_PRESERVE_P (insn) != 0);
160 else if (GET_CODE (insn) == JUMP_INSN)
161 JUMP_LABEL (insn) = 0;
162 if (INSN_UID (insn) > max_uid)
163 max_uid = INSN_UID (insn);
164 }
165
166 max_uid++;
167
168 /* Delete insns following barriers, up to next label. */
169
170 for (insn = f; insn;)
171 {
172 if (GET_CODE (insn) == BARRIER)
173 {
174 insn = NEXT_INSN (insn);
175 while (insn != 0 && GET_CODE (insn) != CODE_LABEL)
176 {
177 if (GET_CODE (insn) == NOTE
178 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_FUNCTION_END)
179 insn = NEXT_INSN (insn);
180 else
181 insn = delete_insn (insn);
182 }
183 /* INSN is now the code_label. */
184 }
185 else
186 insn = NEXT_INSN (insn);
187 }
188
189 /* Leave some extra room for labels and duplicate exit test insns
190 we make. */
191 max_jump_chain = max_uid * 14 / 10;
192 jump_chain = (rtx *) alloca (max_jump_chain * sizeof (rtx));
193 bzero (jump_chain, max_jump_chain * sizeof (rtx));
194
195 /* Mark the label each jump jumps to.
196 Combine consecutive labels, and count uses of labels.
197
198 For each label, make a chain (using `jump_chain')
199 of all the *unconditional* jumps that jump to it;
200 also make a chain of all returns. */
201
202 for (insn = f; insn; insn = NEXT_INSN (insn))
203 if ((GET_CODE (insn) == JUMP_INSN || GET_CODE (insn) == INSN
204 || GET_CODE (insn) == CALL_INSN)
205 && ! INSN_DELETED_P (insn))
206 {
207 mark_jump_label (PATTERN (insn), insn, cross_jump);
208 if (GET_CODE (insn) == JUMP_INSN)
209 {
210 if (JUMP_LABEL (insn) != 0 && simplejump_p (insn))
211 {
212 jump_chain[INSN_UID (insn)]
213 = jump_chain[INSN_UID (JUMP_LABEL (insn))];
214 jump_chain[INSN_UID (JUMP_LABEL (insn))] = insn;
215 }
216 if (GET_CODE (PATTERN (insn)) == RETURN)
217 {
218 jump_chain[INSN_UID (insn)] = jump_chain[0];
219 jump_chain[0] = insn;
220 }
221 }
222 }
223
224 /* Keep track of labels used from static data;
225 they cannot ever be deleted. */
226
227 for (insn = forced_labels; insn; insn = XEXP (insn, 1))
228 LABEL_NUSES (XEXP (insn, 0))++;
229
230 /* Delete all labels already not referenced.
231 Also find the last insn. */
232
233 last_insn = 0;
234 for (insn = f; insn; )
235 {
236 if (GET_CODE (insn) == CODE_LABEL && LABEL_NUSES (insn) == 0)
237 insn = delete_insn (insn);
238 else
239 {
240 last_insn = insn;
241 insn = NEXT_INSN (insn);
242 }
243 }
244
245 if (!optimize)
246 {
247 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
248 If so record that this function can drop off the end. */
249
250 insn = last_insn;
251 {
252 int n_labels = 1;
253 while (insn
254 /* One label can follow the end-note: the return label. */
255 && ((GET_CODE (insn) == CODE_LABEL && n_labels-- > 0)
256 /* Ordinary insns can follow it if returning a structure. */
257 || GET_CODE (insn) == INSN
258 /* If machine uses explicit RETURN insns, no epilogue,
259 then one of them follows the note. */
260 || (GET_CODE (insn) == JUMP_INSN
261 && GET_CODE (PATTERN (insn)) == RETURN)
262 /* Other kinds of notes can follow also. */
263 || (GET_CODE (insn) == NOTE
264 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_FUNCTION_END)))
265 insn = PREV_INSN (insn);
266 }
267
268 /* Report if control can fall through at the end of the function. */
269 if (insn && GET_CODE (insn) == NOTE
270 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_END
271 && ! INSN_DELETED_P (insn))
272 can_reach_end = 1;
273
274 /* Zero the "deleted" flag of all the "deleted" insns. */
275 for (insn = f; insn; insn = NEXT_INSN (insn))
276 INSN_DELETED_P (insn) = 0;
277 return;
278 }
279
280 #ifdef HAVE_return
281 if (HAVE_return)
282 {
283 /* If we fall through to the epilogue, see if we can insert a RETURN insn
284 in front of it. If the machine allows it at this point (we might be
285 after reload for a leaf routine), it will improve optimization for it
286 to be there. */
287 insn = get_last_insn ();
288 while (insn && GET_CODE (insn) == NOTE)
289 insn = PREV_INSN (insn);
290
291 if (insn && GET_CODE (insn) != BARRIER)
292 {
293 emit_jump_insn (gen_return ());
294 emit_barrier ();
295 }
296 }
297 #endif
298
299 if (noop_moves)
300 for (insn = f; insn; )
301 {
302 next = NEXT_INSN (insn);
303
304 if (GET_CODE (insn) == INSN)
305 {
306 register rtx body = PATTERN (insn);
307
308 /* Combine stack_adjusts with following push_insns. */
309 #ifdef PUSH_ROUNDING
310 if (GET_CODE (body) == SET
311 && SET_DEST (body) == stack_pointer_rtx
312 && GET_CODE (SET_SRC (body)) == PLUS
313 && XEXP (SET_SRC (body), 0) == stack_pointer_rtx
314 && GET_CODE (XEXP (SET_SRC (body), 1)) == CONST_INT
315 && INTVAL (XEXP (SET_SRC (body), 1)) > 0)
316 {
317 rtx p;
318 rtx stack_adjust_insn = insn;
319 int stack_adjust_amount = INTVAL (XEXP (SET_SRC (body), 1));
320 int total_pushed = 0;
321 int pushes = 0;
322
323 /* Find all successive push insns. */
324 p = insn;
325 /* Don't convert more than three pushes;
326 that starts adding too many displaced addresses
327 and the whole thing starts becoming a losing
328 proposition. */
329 while (pushes < 3)
330 {
331 rtx pbody, dest;
332 p = next_nonnote_insn (p);
333 if (p == 0 || GET_CODE (p) != INSN)
334 break;
335 pbody = PATTERN (p);
336 if (GET_CODE (pbody) != SET)
337 break;
338 dest = SET_DEST (pbody);
339 /* Allow a no-op move between the adjust and the push. */
340 if (GET_CODE (dest) == REG
341 && GET_CODE (SET_SRC (pbody)) == REG
342 && REGNO (dest) == REGNO (SET_SRC (pbody)))
343 continue;
344 if (! (GET_CODE (dest) == MEM
345 && GET_CODE (XEXP (dest, 0)) == POST_INC
346 && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx))
347 break;
348 pushes++;
349 if (total_pushed + GET_MODE_SIZE (SET_DEST (pbody))
350 > stack_adjust_amount)
351 break;
352 total_pushed += GET_MODE_SIZE (SET_DEST (pbody));
353 }
354
355 /* Discard the amount pushed from the stack adjust;
356 maybe eliminate it entirely. */
357 if (total_pushed >= stack_adjust_amount)
358 {
359 delete_insn (stack_adjust_insn);
360 total_pushed = stack_adjust_amount;
361 }
362 else
363 XEXP (SET_SRC (PATTERN (stack_adjust_insn)), 1)
364 = GEN_INT (stack_adjust_amount - total_pushed);
365
366 /* Change the appropriate push insns to ordinary stores. */
367 p = insn;
368 while (total_pushed > 0)
369 {
370 rtx pbody, dest;
371 p = next_nonnote_insn (p);
372 if (GET_CODE (p) != INSN)
373 break;
374 pbody = PATTERN (p);
375 if (GET_CODE (pbody) == SET)
376 break;
377 dest = SET_DEST (pbody);
378 if (! (GET_CODE (dest) == MEM
379 && GET_CODE (XEXP (dest, 0)) == POST_INC
380 && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx))
381 break;
382 total_pushed -= GET_MODE_SIZE (SET_DEST (pbody));
383 /* If this push doesn't fully fit in the space
384 of the stack adjust that we deleted,
385 make another stack adjust here for what we
386 didn't use up. There should be peepholes
387 to recognize the resulting sequence of insns. */
388 if (total_pushed < 0)
389 {
390 emit_insn_before (gen_add2_insn (stack_pointer_rtx,
391 GEN_INT (- total_pushed)),
392 p);
393 break;
394 }
395 XEXP (dest, 0)
396 = plus_constant (stack_pointer_rtx, total_pushed);
397 }
398 }
399 #endif
400
401 /* Detect and delete no-op move instructions
402 resulting from not allocating a parameter in a register. */
403
404 if (GET_CODE (body) == SET
405 && (SET_DEST (body) == SET_SRC (body)
406 || (GET_CODE (SET_DEST (body)) == MEM
407 && GET_CODE (SET_SRC (body)) == MEM
408 && rtx_equal_p (SET_SRC (body), SET_DEST (body))))
409 && ! (GET_CODE (SET_DEST (body)) == MEM
410 && MEM_VOLATILE_P (SET_DEST (body)))
411 && ! (GET_CODE (SET_SRC (body)) == MEM
412 && MEM_VOLATILE_P (SET_SRC (body))))
413 delete_insn (insn);
414
415 /* Detect and ignore no-op move instructions
416 resulting from smart or fortuitous register allocation. */
417
418 else if (GET_CODE (body) == SET)
419 {
420 int sreg = true_regnum (SET_SRC (body));
421 int dreg = true_regnum (SET_DEST (body));
422
423 if (sreg == dreg && sreg >= 0)
424 delete_insn (insn);
425 else if (sreg >= 0 && dreg >= 0)
426 {
427 rtx trial;
428 rtx tem = find_equiv_reg (NULL_RTX, insn, 0,
429 sreg, NULL_PTR, dreg,
430 GET_MODE (SET_SRC (body)));
431
432 #ifdef PRESERVE_DEATH_INFO_REGNO_P
433 /* Deleting insn could lose a death-note for SREG or DREG
434 so don't do it if final needs accurate death-notes. */
435 if (! PRESERVE_DEATH_INFO_REGNO_P (sreg)
436 && ! PRESERVE_DEATH_INFO_REGNO_P (dreg))
437 #endif
438 {
439 /* DREG may have been the target of a REG_DEAD note in
440 the insn which makes INSN redundant. If so, reorg
441 would still think it is dead. So search for such a
442 note and delete it if we find it. */
443 for (trial = prev_nonnote_insn (insn);
444 trial && GET_CODE (trial) != CODE_LABEL;
445 trial = prev_nonnote_insn (trial))
446 if (find_regno_note (trial, REG_DEAD, dreg))
447 {
448 remove_death (dreg, trial);
449 break;
450 }
451
452 if (tem != 0
453 && GET_MODE (tem) == GET_MODE (SET_DEST (body)))
454 delete_insn (insn);
455 }
456 }
457 else if (dreg >= 0 && CONSTANT_P (SET_SRC (body))
458 && find_equiv_reg (SET_SRC (body), insn, 0, dreg,
459 NULL_PTR, 0,
460 GET_MODE (SET_DEST (body))))
461 {
462 /* This handles the case where we have two consecutive
463 assignments of the same constant to pseudos that didn't
464 get a hard reg. Each SET from the constant will be
465 converted into a SET of the spill register and an
466 output reload will be made following it. This produces
467 two loads of the same constant into the same spill
468 register. */
469
470 rtx in_insn = insn;
471
472 /* Look back for a death note for the first reg.
473 If there is one, it is no longer accurate. */
474 while (in_insn && GET_CODE (in_insn) != CODE_LABEL)
475 {
476 if ((GET_CODE (in_insn) == INSN
477 || GET_CODE (in_insn) == JUMP_INSN)
478 && find_regno_note (in_insn, REG_DEAD, dreg))
479 {
480 remove_death (dreg, in_insn);
481 break;
482 }
483 in_insn = PREV_INSN (in_insn);
484 }
485
486 /* Delete the second load of the value. */
487 delete_insn (insn);
488 }
489 }
490 else if (GET_CODE (body) == PARALLEL)
491 {
492 /* If each part is a set between two identical registers or
493 a USE or CLOBBER, delete the insn. */
494 int i, sreg, dreg;
495 rtx tem;
496
497 for (i = XVECLEN (body, 0) - 1; i >= 0; i--)
498 {
499 tem = XVECEXP (body, 0, i);
500 if (GET_CODE (tem) == USE || GET_CODE (tem) == CLOBBER)
501 continue;
502
503 if (GET_CODE (tem) != SET
504 || (sreg = true_regnum (SET_SRC (tem))) < 0
505 || (dreg = true_regnum (SET_DEST (tem))) < 0
506 || dreg != sreg)
507 break;
508 }
509
510 if (i < 0)
511 delete_insn (insn);
512 }
513 #if !BYTES_BIG_ENDIAN /* Not worth the hair to detect this
514 in the big-endian case. */
515 /* Also delete insns to store bit fields if they are no-ops. */
516 else if (GET_CODE (body) == SET
517 && GET_CODE (SET_DEST (body)) == ZERO_EXTRACT
518 && XEXP (SET_DEST (body), 2) == const0_rtx
519 && XEXP (SET_DEST (body), 0) == SET_SRC (body)
520 && ! (GET_CODE (SET_SRC (body)) == MEM
521 && MEM_VOLATILE_P (SET_SRC (body))))
522 delete_insn (insn);
523 #endif /* not BYTES_BIG_ENDIAN */
524 }
525 insn = next;
526 }
527
528 /* If we haven't yet gotten to reload and we have just run regscan,
529 delete any insn that sets a register that isn't used elsewhere.
530 This helps some of the optimizations below by having less insns
531 being jumped around. */
532
533 if (! reload_completed && after_regscan)
534 for (insn = f; insn; insn = next)
535 {
536 rtx set = single_set (insn);
537
538 next = NEXT_INSN (insn);
539
540 if (set && GET_CODE (SET_DEST (set)) == REG
541 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER
542 && regno_first_uid[REGNO (SET_DEST (set))] == INSN_UID (insn)
543 && regno_last_uid[REGNO (SET_DEST (set))] == INSN_UID (insn)
544 && ! side_effects_p (SET_SRC (set)))
545 delete_insn (insn);
546 }
547
548 /* Now iterate optimizing jumps until nothing changes over one pass. */
549 changed = 1;
550 while (changed)
551 {
552 changed = 0;
553
554 for (insn = f; insn; insn = next)
555 {
556 rtx reallabelprev;
557 rtx temp, temp1, temp2, temp3, temp4, temp5, temp6;
558 rtx nlabel;
559 int this_is_simplejump, this_is_condjump, reversep;
560 #if 0
561 /* If NOT the first iteration, if this is the last jump pass
562 (just before final), do the special peephole optimizations.
563 Avoiding the first iteration gives ordinary jump opts
564 a chance to work before peephole opts. */
565
566 if (reload_completed && !first && !flag_no_peephole)
567 if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
568 peephole (insn);
569 #endif
570
571 /* That could have deleted some insns after INSN, so check now
572 what the following insn is. */
573
574 next = NEXT_INSN (insn);
575
576 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
577 jump. Try to optimize by duplicating the loop exit test if so.
578 This is only safe immediately after regscan, because it uses
579 the values of regno_first_uid and regno_last_uid. */
580 if (after_regscan && GET_CODE (insn) == NOTE
581 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG
582 && (temp1 = next_nonnote_insn (insn)) != 0
583 && simplejump_p (temp1))
584 {
585 temp = PREV_INSN (insn);
586 if (duplicate_loop_exit_test (insn))
587 {
588 changed = 1;
589 next = NEXT_INSN (temp);
590 continue;
591 }
592 }
593
594 if (GET_CODE (insn) != JUMP_INSN)
595 continue;
596
597 this_is_simplejump = simplejump_p (insn);
598 this_is_condjump = condjump_p (insn);
599
600 /* Tension the labels in dispatch tables. */
601
602 if (GET_CODE (PATTERN (insn)) == ADDR_VEC)
603 changed |= tension_vector_labels (PATTERN (insn), 0);
604 if (GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
605 changed |= tension_vector_labels (PATTERN (insn), 1);
606
607 /* If a dispatch table always goes to the same place,
608 get rid of it and replace the insn that uses it. */
609
610 if (GET_CODE (PATTERN (insn)) == ADDR_VEC
611 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
612 {
613 int i;
614 rtx pat = PATTERN (insn);
615 int diff_vec_p = GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC;
616 int len = XVECLEN (pat, diff_vec_p);
617 rtx dispatch = prev_real_insn (insn);
618
619 for (i = 0; i < len; i++)
620 if (XEXP (XVECEXP (pat, diff_vec_p, i), 0)
621 != XEXP (XVECEXP (pat, diff_vec_p, 0), 0))
622 break;
623 if (i == len
624 && dispatch != 0
625 && GET_CODE (dispatch) == JUMP_INSN
626 && JUMP_LABEL (dispatch) != 0
627 /* Don't mess with a casesi insn. */
628 && !(GET_CODE (PATTERN (dispatch)) == SET
629 && (GET_CODE (SET_SRC (PATTERN (dispatch)))
630 == IF_THEN_ELSE))
631 && next_real_insn (JUMP_LABEL (dispatch)) == insn)
632 {
633 redirect_tablejump (dispatch,
634 XEXP (XVECEXP (pat, diff_vec_p, 0), 0));
635 changed = 1;
636 }
637 }
638
639 reallabelprev = prev_active_insn (JUMP_LABEL (insn));
640
641 /* If a jump references the end of the function, try to turn
642 it into a RETURN insn, possibly a conditional one. */
643 if (JUMP_LABEL (insn)
644 && next_active_insn (JUMP_LABEL (insn)) == 0)
645 changed |= redirect_jump (insn, NULL_RTX);
646
647 /* Detect jump to following insn. */
648 if (reallabelprev == insn && condjump_p (insn))
649 {
650 delete_jump (insn);
651 changed = 1;
652 continue;
653 }
654
655 /* If we have an unconditional jump preceded by a USE, try to put
656 the USE before the target and jump there. This simplifies many
657 of the optimizations below since we don't have to worry about
658 dealing with these USE insns. We only do this if the label
659 being branch to already has the identical USE or if code
660 never falls through to that label. */
661
662 if (this_is_simplejump
663 && (temp = prev_nonnote_insn (insn)) != 0
664 && GET_CODE (temp) == INSN && GET_CODE (PATTERN (temp)) == USE
665 && (temp1 = prev_nonnote_insn (JUMP_LABEL (insn))) != 0
666 && (GET_CODE (temp1) == BARRIER
667 || (GET_CODE (temp1) == INSN
668 && rtx_equal_p (PATTERN (temp), PATTERN (temp1)))))
669 {
670 if (GET_CODE (temp1) == BARRIER)
671 {
672 emit_insn_after (PATTERN (temp), temp1);
673 temp1 = NEXT_INSN (temp1);
674 }
675
676 delete_insn (temp);
677 redirect_jump (insn, get_label_before (temp1));
678 reallabelprev = prev_real_insn (temp1);
679 changed = 1;
680 }
681
682 /* Simplify if (...) x = a; else x = b; by converting it
683 to x = b; if (...) x = a;
684 if B is sufficiently simple, the test doesn't involve X,
685 and nothing in the test modifies B or X.
686
687 If we have small register classes, we also can't do this if X
688 is a hard register.
689
690 If the "x = b;" insn has any REG_NOTES, we don't do this because
691 of the possibility that we are running after CSE and there is a
692 REG_EQUAL note that is only valid if the branch has already been
693 taken. If we move the insn with the REG_EQUAL note, we may
694 fold the comparison to always be false in a later CSE pass.
695 (We could also delete the REG_NOTES when moving the insn, but it
696 seems simpler to not move it.) An exception is that we can move
697 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
698 value is the same as "b".
699
700 INSN is the branch over the `else' part.
701
702 We set:
703
704 TEMP to the jump insn preceding "x = a;"
705 TEMP1 to X
706 TEMP2 to the insn that sets "x = b;"
707 TEMP3 to the insn that sets "x = a;"
708 TEMP4 to the set of "x = b"; */
709
710 if (this_is_simplejump
711 && (temp3 = prev_active_insn (insn)) != 0
712 && GET_CODE (temp3) == INSN
713 && (temp4 = single_set (temp3)) != 0
714 && GET_CODE (temp1 = SET_DEST (temp4)) == REG
715 #ifdef SMALL_REGISTER_CLASSES
716 && REGNO (temp1) >= FIRST_PSEUDO_REGISTER
717 #endif
718 && (temp2 = next_active_insn (insn)) != 0
719 && GET_CODE (temp2) == INSN
720 && (temp4 = single_set (temp2)) != 0
721 && rtx_equal_p (SET_DEST (temp4), temp1)
722 && (GET_CODE (SET_SRC (temp4)) == REG
723 || GET_CODE (SET_SRC (temp4)) == SUBREG
724 || CONSTANT_P (SET_SRC (temp4)))
725 && (REG_NOTES (temp2) == 0
726 || ((REG_NOTE_KIND (REG_NOTES (temp2)) == REG_EQUAL
727 || REG_NOTE_KIND (REG_NOTES (temp2)) == REG_EQUIV)
728 && XEXP (REG_NOTES (temp2), 1) == 0
729 && rtx_equal_p (XEXP (REG_NOTES (temp2), 0),
730 SET_SRC (temp4))))
731 && (temp = prev_active_insn (temp3)) != 0
732 && condjump_p (temp) && ! simplejump_p (temp)
733 /* TEMP must skip over the "x = a;" insn */
734 && prev_real_insn (JUMP_LABEL (temp)) == insn
735 && no_labels_between_p (insn, JUMP_LABEL (temp))
736 /* There must be no other entries to the "x = b;" insn. */
737 && no_labels_between_p (JUMP_LABEL (temp), temp2)
738 /* INSN must either branch to the insn after TEMP2 or the insn
739 after TEMP2 must branch to the same place as INSN. */
740 && (reallabelprev == temp2
741 || ((temp5 = next_active_insn (temp2)) != 0
742 && simplejump_p (temp5)
743 && JUMP_LABEL (temp5) == JUMP_LABEL (insn))))
744 {
745 /* The test expression, X, may be a complicated test with
746 multiple branches. See if we can find all the uses of
747 the label that TEMP branches to without hitting a CALL_INSN
748 or a jump to somewhere else. */
749 rtx target = JUMP_LABEL (temp);
750 int nuses = LABEL_NUSES (target);
751 rtx p, q;
752
753 /* Set P to the first jump insn that goes around "x = a;". */
754 for (p = temp; nuses && p; p = prev_nonnote_insn (p))
755 {
756 if (GET_CODE (p) == JUMP_INSN)
757 {
758 if (condjump_p (p) && ! simplejump_p (p)
759 && JUMP_LABEL (p) == target)
760 {
761 nuses--;
762 if (nuses == 0)
763 break;
764 }
765 else
766 break;
767 }
768 else if (GET_CODE (p) == CALL_INSN)
769 break;
770 }
771
772 #ifdef HAVE_cc0
773 /* We cannot insert anything between a set of cc and its use
774 so if P uses cc0, we must back up to the previous insn. */
775 q = prev_nonnote_insn (p);
776 if (q && GET_RTX_CLASS (GET_CODE (q)) == 'i'
777 && sets_cc0_p (PATTERN (q)))
778 p = q;
779 #endif
780
781 if (p)
782 p = PREV_INSN (p);
783
784 /* If we found all the uses and there was no data conflict, we
785 can move the assignment unless we can branch into the middle
786 from somewhere. */
787 if (nuses == 0 && p
788 && no_labels_between_p (p, insn)
789 && ! reg_referenced_between_p (temp1, p, NEXT_INSN (temp3))
790 && ! reg_set_between_p (temp1, p, temp3)
791 && (GET_CODE (SET_SRC (temp4)) == CONST_INT
792 || ! reg_set_between_p (SET_SRC (temp4), p, temp2)))
793 {
794 emit_insn_after_with_line_notes (PATTERN (temp2), p, temp2);
795 delete_insn (temp2);
796
797 /* Set NEXT to an insn that we know won't go away. */
798 next = next_active_insn (insn);
799
800 /* Delete the jump around the set. Note that we must do
801 this before we redirect the test jumps so that it won't
802 delete the code immediately following the assignment
803 we moved (which might be a jump). */
804
805 delete_insn (insn);
806
807 /* We either have two consecutive labels or a jump to
808 a jump, so adjust all the JUMP_INSNs to branch to where
809 INSN branches to. */
810 for (p = NEXT_INSN (p); p != next; p = NEXT_INSN (p))
811 if (GET_CODE (p) == JUMP_INSN)
812 redirect_jump (p, target);
813
814 changed = 1;
815 continue;
816 }
817 }
818
819 #ifndef HAVE_cc0
820 /* If we have if (...) x = exp; and branches are expensive,
821 EXP is a single insn, does not have any side effects, cannot
822 trap, and is not too costly, convert this to
823 t = exp; if (...) x = t;
824
825 Don't do this when we have CC0 because it is unlikely to help
826 and we'd need to worry about where to place the new insn and
827 the potential for conflicts. We also can't do this when we have
828 notes on the insn for the same reason as above.
829
830 We set:
831
832 TEMP to the "x = exp;" insn.
833 TEMP1 to the single set in the "x = exp; insn.
834 TEMP2 to "x". */
835
836 if (! reload_completed
837 && this_is_condjump && ! this_is_simplejump
838 && BRANCH_COST >= 3
839 && (temp = next_nonnote_insn (insn)) != 0
840 && GET_CODE (temp) == INSN
841 && REG_NOTES (temp) == 0
842 && (reallabelprev == temp
843 || ((temp2 = next_active_insn (temp)) != 0
844 && simplejump_p (temp2)
845 && JUMP_LABEL (temp2) == JUMP_LABEL (insn)))
846 && (temp1 = single_set (temp)) != 0
847 && (temp2 = SET_DEST (temp1), GET_CODE (temp2) == REG)
848 && GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT
849 #ifdef SMALL_REGISTER_CLASSES
850 && REGNO (temp2) >= FIRST_PSEUDO_REGISTER
851 #endif
852 && GET_CODE (SET_SRC (temp1)) != REG
853 && GET_CODE (SET_SRC (temp1)) != SUBREG
854 && GET_CODE (SET_SRC (temp1)) != CONST_INT
855 && ! side_effects_p (SET_SRC (temp1))
856 && ! may_trap_p (SET_SRC (temp1))
857 && rtx_cost (SET_SRC (temp1)) < 10)
858 {
859 rtx new = gen_reg_rtx (GET_MODE (temp2));
860
861 if (validate_change (temp, &SET_DEST (temp1), new, 0))
862 {
863 next = emit_insn_after (gen_move_insn (temp2, new), insn);
864 emit_insn_after_with_line_notes (PATTERN (temp),
865 PREV_INSN (insn), temp);
866 delete_insn (temp);
867 }
868 }
869
870 /* Similarly, if it takes two insns to compute EXP but they
871 have the same destination. Here TEMP3 will be the second
872 insn and TEMP4 the SET from that insn. */
873
874 if (! reload_completed
875 && this_is_condjump && ! this_is_simplejump
876 && BRANCH_COST >= 4
877 && (temp = next_nonnote_insn (insn)) != 0
878 && GET_CODE (temp) == INSN
879 && REG_NOTES (temp) == 0
880 && (temp3 = next_nonnote_insn (temp)) != 0
881 && GET_CODE (temp3) == INSN
882 && REG_NOTES (temp3) == 0
883 && (reallabelprev == temp3
884 || ((temp2 = next_active_insn (temp3)) != 0
885 && simplejump_p (temp2)
886 && JUMP_LABEL (temp2) == JUMP_LABEL (insn)))
887 && (temp1 = single_set (temp)) != 0
888 && (temp2 = SET_DEST (temp1), GET_CODE (temp2) == REG)
889 && GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT
890 #ifdef SMALL_REGISTER_CLASSES
891 && REGNO (temp2) >= FIRST_PSEUDO_REGISTER
892 #endif
893 && ! side_effects_p (SET_SRC (temp1))
894 && ! may_trap_p (SET_SRC (temp1))
895 && rtx_cost (SET_SRC (temp1)) < 10
896 && (temp4 = single_set (temp3)) != 0
897 && rtx_equal_p (SET_DEST (temp4), temp2)
898 && ! side_effects_p (SET_SRC (temp4))
899 && ! may_trap_p (SET_SRC (temp4))
900 && rtx_cost (SET_SRC (temp4)) < 10)
901 {
902 rtx new = gen_reg_rtx (GET_MODE (temp2));
903
904 if (validate_change (temp, &SET_DEST (temp1), new, 0))
905 {
906 next = emit_insn_after (gen_move_insn (temp2, new), insn);
907 emit_insn_after_with_line_notes (PATTERN (temp),
908 PREV_INSN (insn), temp);
909 emit_insn_after_with_line_notes
910 (replace_rtx (PATTERN (temp3), temp2, new),
911 PREV_INSN (insn), temp3);
912 delete_insn (temp);
913 delete_insn (temp3);
914 }
915 }
916
917 /* Finally, handle the case where two insns are used to
918 compute EXP but a temporary register is used. Here we must
919 ensure that the temporary register is not used anywhere else. */
920
921 if (! reload_completed
922 && after_regscan
923 && this_is_condjump && ! this_is_simplejump
924 && BRANCH_COST >= 4
925 && (temp = next_nonnote_insn (insn)) != 0
926 && GET_CODE (temp) == INSN
927 && REG_NOTES (temp) == 0
928 && (temp3 = next_nonnote_insn (temp)) != 0
929 && GET_CODE (temp3) == INSN
930 && REG_NOTES (temp3) == 0
931 && (reallabelprev == temp3
932 || ((temp2 = next_active_insn (temp3)) != 0
933 && simplejump_p (temp2)
934 && JUMP_LABEL (temp2) == JUMP_LABEL (insn)))
935 && (temp1 = single_set (temp)) != 0
936 && (temp5 = SET_DEST (temp1), GET_CODE (temp5) == REG)
937 && REGNO (temp5) >= FIRST_PSEUDO_REGISTER
938 && regno_first_uid[REGNO (temp5)] == INSN_UID (temp)
939 && regno_last_uid[REGNO (temp5)] == INSN_UID (temp3)
940 && ! side_effects_p (SET_SRC (temp1))
941 && ! may_trap_p (SET_SRC (temp1))
942 && rtx_cost (SET_SRC (temp1)) < 10
943 && (temp4 = single_set (temp3)) != 0
944 && (temp2 = SET_DEST (temp4), GET_CODE (temp2) == REG)
945 && GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT
946 #ifdef SMALL_REGISTER_CLASSES
947 && REGNO (temp2) >= FIRST_PSEUDO_REGISTER
948 #endif
949 && rtx_equal_p (SET_DEST (temp4), temp2)
950 && ! side_effects_p (SET_SRC (temp4))
951 && ! may_trap_p (SET_SRC (temp4))
952 && rtx_cost (SET_SRC (temp4)) < 10)
953 {
954 rtx new = gen_reg_rtx (GET_MODE (temp2));
955
956 if (validate_change (temp3, &SET_DEST (temp4), new, 0))
957 {
958 next = emit_insn_after (gen_move_insn (temp2, new), insn);
959 emit_insn_after_with_line_notes (PATTERN (temp),
960 PREV_INSN (insn), temp);
961 emit_insn_after_with_line_notes (PATTERN (temp3),
962 PREV_INSN (insn), temp3);
963 delete_insn (temp);
964 delete_insn (temp3);
965 }
966 }
967 #endif /* HAVE_cc0 */
968
969 /* We deal with four cases:
970
971 1) x = a; if (...) x = b; and either A or B is zero,
972 2) if (...) x = 0; and jumps are expensive,
973 3) x = a; if (...) x = b; and A and B are constants where all the
974 set bits in A are also set in B and jumps are expensive, and
975 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
976 more expensive.
977 5) if (...) x = b; if jumps are even more expensive.
978
979 In each of these try to use a store-flag insn to avoid the jump.
980 (If the jump would be faster, the machine should not have
981 defined the scc insns!). These cases are often made by the
982 previous optimization.
983
984 INSN here is the jump around the store. We set:
985
986 TEMP to the "x = b;" insn.
987 TEMP1 to X.
988 TEMP2 to B (const0_rtx in the second case).
989 TEMP3 to A (X in the second case).
990 TEMP4 to the condition being tested.
991 TEMP5 to the earliest insn used to find the condition. */
992
993 if (/* We can't do this after reload has completed. */
994 ! reload_completed
995 && this_is_condjump && ! this_is_simplejump
996 /* Set TEMP to the "x = b;" insn. */
997 && (temp = next_nonnote_insn (insn)) != 0
998 && GET_CODE (temp) == INSN
999 && GET_CODE (PATTERN (temp)) == SET
1000 && GET_CODE (temp1 = SET_DEST (PATTERN (temp))) == REG
1001 #ifdef SMALL_REGISTER_CLASSES
1002 && REGNO (temp1) >= FIRST_PSEUDO_REGISTER
1003 #endif
1004 && GET_MODE_CLASS (GET_MODE (temp1)) == MODE_INT
1005 && (GET_CODE (temp2 = SET_SRC (PATTERN (temp))) == REG
1006 || GET_CODE (temp2) == SUBREG
1007 || GET_CODE (temp2) == CONST_INT)
1008 /* Allow either form, but prefer the former if both apply.
1009 There is no point in using the old value of TEMP1 if
1010 it is a register, since cse will alias them. It can
1011 lose if the old value were a hard register since CSE
1012 won't replace hard registers. */
1013 && (((temp3 = reg_set_last (temp1, insn)) != 0
1014 && GET_CODE (temp3) == CONST_INT)
1015 /* Make the latter case look like x = x; if (...) x = 0; */
1016 || (temp3 = temp1,
1017 ((BRANCH_COST >= 2
1018 && temp2 == const0_rtx)
1019 || BRANCH_COST >= 3)))
1020 /* INSN must either branch to the insn after TEMP or the insn
1021 after TEMP must branch to the same place as INSN. */
1022 && (reallabelprev == temp
1023 || ((temp4 = next_active_insn (temp)) != 0
1024 && simplejump_p (temp4)
1025 && JUMP_LABEL (temp4) == JUMP_LABEL (insn)))
1026 && (temp4 = get_condition (insn, &temp5)) != 0
1027 /* We must be comparing objects whose modes imply the size.
1028 We could handle BLKmode if (1) emit_store_flag could
1029 and (2) we could find the size reliably. */
1030 && GET_MODE (XEXP (temp4, 0)) != BLKmode
1031
1032 /* If B is zero, OK; if A is zero, can only do (1) if we
1033 can reverse the condition. See if (3) applies possibly
1034 by reversing the condition. Prefer reversing to (4) when
1035 branches are very expensive. */
1036 && ((reversep = 0, temp2 == const0_rtx)
1037 || (temp3 == const0_rtx
1038 && (reversep = can_reverse_comparison_p (temp4, insn)))
1039 || (BRANCH_COST >= 2
1040 && GET_CODE (temp2) == CONST_INT
1041 && GET_CODE (temp3) == CONST_INT
1042 && ((INTVAL (temp2) & INTVAL (temp3)) == INTVAL (temp2)
1043 || ((INTVAL (temp2) & INTVAL (temp3)) == INTVAL (temp3)
1044 && (reversep = can_reverse_comparison_p (temp4,
1045 insn)))))
1046 || BRANCH_COST >= 3)
1047 #ifdef HAVE_cc0
1048 /* If the previous insn sets CC0 and something else, we can't
1049 do this since we are going to delete that insn. */
1050
1051 && ! ((temp6 = prev_nonnote_insn (insn)) != 0
1052 && GET_CODE (temp6) == INSN
1053 && (sets_cc0_p (PATTERN (temp6)) == -1
1054 || (sets_cc0_p (PATTERN (temp6)) == 1
1055 && FIND_REG_INC_NOTE (temp6, NULL_RTX))))
1056 #endif
1057 )
1058 {
1059 enum rtx_code code = GET_CODE (temp4);
1060 rtx uval, cval, var = temp1;
1061 int normalizep;
1062 rtx target;
1063
1064 /* If necessary, reverse the condition. */
1065 if (reversep)
1066 code = reverse_condition (code), uval = temp2, cval = temp3;
1067 else
1068 uval = temp3, cval = temp2;
1069
1070 /* See if we can do this with a store-flag insn. */
1071 start_sequence ();
1072
1073 /* If CVAL is non-zero, normalize to -1. Otherwise,
1074 if UVAL is the constant 1, it is best to just compute
1075 the result directly. If UVAL is constant and STORE_FLAG_VALUE
1076 includes all of its bits, it is best to compute the flag
1077 value unnormalized and `and' it with UVAL. Otherwise,
1078 normalize to -1 and `and' with UVAL. */
1079 normalizep = (cval != const0_rtx ? -1
1080 : (uval == const1_rtx ? 1
1081 : (GET_CODE (uval) == CONST_INT
1082 && (INTVAL (uval) & ~STORE_FLAG_VALUE) == 0)
1083 ? 0 : -1));
1084
1085 /* We will be putting the store-flag insn immediately in
1086 front of the comparison that was originally being done,
1087 so we know all the variables in TEMP4 will be valid.
1088 However, this might be in front of the assignment of
1089 A to VAR. If it is, it would clobber the store-flag
1090 we will be emitting.
1091
1092 Therefore, emit into a temporary which will be copied to
1093 VAR immediately after TEMP. */
1094
1095 target = emit_store_flag (gen_reg_rtx (GET_MODE (var)), code,
1096 XEXP (temp4, 0), XEXP (temp4, 1),
1097 VOIDmode,
1098 (code == LTU || code == LEU
1099 || code == GEU || code == GTU),
1100 normalizep);
1101 if (target)
1102 {
1103 rtx before = insn;
1104 rtx seq;
1105
1106 /* Put the store-flag insns in front of the first insn
1107 used to compute the condition to ensure that we
1108 use the same values of them as the current
1109 comparison. However, the remainder of the insns we
1110 generate will be placed directly in front of the
1111 jump insn, in case any of the pseudos we use
1112 are modified earlier. */
1113
1114 seq = get_insns ();
1115 end_sequence ();
1116
1117 emit_insns_before (seq, temp5);
1118
1119 start_sequence ();
1120
1121 /* Both CVAL and UVAL are non-zero. */
1122 if (cval != const0_rtx && uval != const0_rtx)
1123 {
1124 rtx tem1, tem2;
1125
1126 tem1 = expand_and (uval, target, NULL_RTX);
1127 if (GET_CODE (cval) == CONST_INT
1128 && GET_CODE (uval) == CONST_INT
1129 && (INTVAL (cval) & INTVAL (uval)) == INTVAL (cval))
1130 tem2 = cval;
1131 else
1132 {
1133 tem2 = expand_unop (GET_MODE (var), one_cmpl_optab,
1134 target, NULL_RTX, 0);
1135 tem2 = expand_and (cval, tem2,
1136 (GET_CODE (tem2) == REG
1137 ? tem2 : 0));
1138 }
1139
1140 /* If we usually make new pseudos, do so here. This
1141 turns out to help machines that have conditional
1142 move insns. */
1143
1144 if (flag_expensive_optimizations)
1145 target = 0;
1146
1147 target = expand_binop (GET_MODE (var), ior_optab,
1148 tem1, tem2, target,
1149 1, OPTAB_WIDEN);
1150 }
1151 else if (normalizep != 1)
1152 target = expand_and (uval, target,
1153 (GET_CODE (target) == REG
1154 && ! preserve_subexpressions_p ()
1155 ? target : NULL_RTX));
1156
1157 emit_move_insn (var, target);
1158 seq = get_insns ();
1159 end_sequence ();
1160
1161 #ifdef HAVE_cc0
1162 /* If INSN uses CC0, we must not separate it from the
1163 insn that sets cc0. */
1164
1165 if (reg_mentioned_p (cc0_rtx, PATTERN (before)))
1166 before = prev_nonnote_insn (before);
1167 #endif
1168
1169 emit_insns_before (seq, before);
1170
1171 delete_insn (temp);
1172 next = NEXT_INSN (insn);
1173
1174 delete_jump (insn);
1175 changed = 1;
1176 continue;
1177 }
1178 else
1179 end_sequence ();
1180 }
1181
1182 /* If branches are expensive, convert
1183 if (foo) bar++; to bar += (foo != 0);
1184 and similarly for "bar--;"
1185
1186 INSN is the conditional branch around the arithmetic. We set:
1187
1188 TEMP is the arithmetic insn.
1189 TEMP1 is the SET doing the arithmetic.
1190 TEMP2 is the operand being incremented or decremented.
1191 TEMP3 to the condition being tested.
1192 TEMP4 to the earliest insn used to find the condition. */
1193
1194 if ((BRANCH_COST >= 2
1195 #ifdef HAVE_incscc
1196 || HAVE_incscc
1197 #endif
1198 )
1199 && ! reload_completed
1200 && this_is_condjump && ! this_is_simplejump
1201 && (temp = next_nonnote_insn (insn)) != 0
1202 && (temp1 = single_set (temp)) != 0
1203 && (temp2 = SET_DEST (temp1),
1204 GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT)
1205 && GET_CODE (SET_SRC (temp1)) == PLUS
1206 && (XEXP (SET_SRC (temp1), 1) == const1_rtx
1207 || XEXP (SET_SRC (temp1), 1) == constm1_rtx)
1208 && rtx_equal_p (temp2, XEXP (SET_SRC (temp1), 0))
1209 /* INSN must either branch to the insn after TEMP or the insn
1210 after TEMP must branch to the same place as INSN. */
1211 && (reallabelprev == temp
1212 || ((temp3 = next_active_insn (temp)) != 0
1213 && simplejump_p (temp3)
1214 && JUMP_LABEL (temp3) == JUMP_LABEL (insn)))
1215 && (temp3 = get_condition (insn, &temp4)) != 0
1216 /* We must be comparing objects whose modes imply the size.
1217 We could handle BLKmode if (1) emit_store_flag could
1218 and (2) we could find the size reliably. */
1219 && GET_MODE (XEXP (temp3, 0)) != BLKmode
1220 && can_reverse_comparison_p (temp3, insn))
1221 {
1222 rtx temp6, target = 0, seq, init_insn = 0, init = temp2;
1223 enum rtx_code code = reverse_condition (GET_CODE (temp3));
1224
1225 start_sequence ();
1226
1227 /* It must be the case that TEMP2 is not modified in the range
1228 [TEMP4, INSN). The one exception we make is if the insn
1229 before INSN sets TEMP2 to something which is also unchanged
1230 in that range. In that case, we can move the initialization
1231 into our sequence. */
1232
1233 if ((temp5 = prev_active_insn (insn)) != 0
1234 && GET_CODE (temp5) == INSN
1235 && (temp6 = single_set (temp5)) != 0
1236 && rtx_equal_p (temp2, SET_DEST (temp6))
1237 && (CONSTANT_P (SET_SRC (temp6))
1238 || GET_CODE (SET_SRC (temp6)) == REG
1239 || GET_CODE (SET_SRC (temp6)) == SUBREG))
1240 {
1241 emit_insn (PATTERN (temp5));
1242 init_insn = temp5;
1243 init = SET_SRC (temp6);
1244 }
1245
1246 if (CONSTANT_P (init)
1247 || ! reg_set_between_p (init, PREV_INSN (temp4), insn))
1248 target = emit_store_flag (gen_reg_rtx (GET_MODE (temp2)), code,
1249 XEXP (temp3, 0), XEXP (temp3, 1),
1250 VOIDmode,
1251 (code == LTU || code == LEU
1252 || code == GTU || code == GEU), 1);
1253
1254 /* If we can do the store-flag, do the addition or
1255 subtraction. */
1256
1257 if (target)
1258 target = expand_binop (GET_MODE (temp2),
1259 (XEXP (SET_SRC (temp1), 1) == const1_rtx
1260 ? add_optab : sub_optab),
1261 temp2, target, temp2, OPTAB_WIDEN);
1262
1263 if (target != 0)
1264 {
1265 /* Put the result back in temp2 in case it isn't already.
1266 Then replace the jump, possible a CC0-setting insn in
1267 front of the jump, and TEMP, with the sequence we have
1268 made. */
1269
1270 if (target != temp2)
1271 emit_move_insn (temp2, target);
1272
1273 seq = get_insns ();
1274 end_sequence ();
1275
1276 emit_insns_before (seq, temp4);
1277 delete_insn (temp);
1278
1279 if (init_insn)
1280 delete_insn (init_insn);
1281
1282 next = NEXT_INSN (insn);
1283 #ifdef HAVE_cc0
1284 delete_insn (prev_nonnote_insn (insn));
1285 #endif
1286 delete_insn (insn);
1287 changed = 1;
1288 continue;
1289 }
1290 else
1291 end_sequence ();
1292 }
1293
1294 /* Simplify if (...) x = 1; else {...} if (x) ...
1295 We recognize this case scanning backwards as well.
1296
1297 TEMP is the assignment to x;
1298 TEMP1 is the label at the head of the second if. */
1299 /* ?? This should call get_condition to find the values being
1300 compared, instead of looking for a COMPARE insn when HAVE_cc0
1301 is not defined. This would allow it to work on the m88k. */
1302 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1303 is not defined and the condition is tested by a separate compare
1304 insn. This is because the code below assumes that the result
1305 of the compare dies in the following branch.
1306
1307 Not only that, but there might be other insns between the
1308 compare and branch whose results are live. Those insns need
1309 to be executed.
1310
1311 A way to fix this is to move the insns at JUMP_LABEL (insn)
1312 to before INSN. If we are running before flow, they will
1313 be deleted if they aren't needed. But this doesn't work
1314 well after flow.
1315
1316 This is really a special-case of jump threading, anyway. The
1317 right thing to do is to replace this and jump threading with
1318 much simpler code in cse.
1319
1320 This code has been turned off in the non-cc0 case in the
1321 meantime. */
1322
1323 #ifdef HAVE_cc0
1324 else if (this_is_simplejump
1325 /* Safe to skip USE and CLOBBER insns here
1326 since they will not be deleted. */
1327 && (temp = prev_active_insn (insn))
1328 && no_labels_between_p (temp, insn)
1329 && GET_CODE (temp) == INSN
1330 && GET_CODE (PATTERN (temp)) == SET
1331 && GET_CODE (SET_DEST (PATTERN (temp))) == REG
1332 && CONSTANT_P (SET_SRC (PATTERN (temp)))
1333 && (temp1 = next_active_insn (JUMP_LABEL (insn)))
1334 /* If we find that the next value tested is `x'
1335 (TEMP1 is the insn where this happens), win. */
1336 && GET_CODE (temp1) == INSN
1337 && GET_CODE (PATTERN (temp1)) == SET
1338 #ifdef HAVE_cc0
1339 /* Does temp1 `tst' the value of x? */
1340 && SET_SRC (PATTERN (temp1)) == SET_DEST (PATTERN (temp))
1341 && SET_DEST (PATTERN (temp1)) == cc0_rtx
1342 && (temp1 = next_nonnote_insn (temp1))
1343 #else
1344 /* Does temp1 compare the value of x against zero? */
1345 && GET_CODE (SET_SRC (PATTERN (temp1))) == COMPARE
1346 && XEXP (SET_SRC (PATTERN (temp1)), 1) == const0_rtx
1347 && (XEXP (SET_SRC (PATTERN (temp1)), 0)
1348 == SET_DEST (PATTERN (temp)))
1349 && GET_CODE (SET_DEST (PATTERN (temp1))) == REG
1350 && (temp1 = find_next_ref (SET_DEST (PATTERN (temp1)), temp1))
1351 #endif
1352 && condjump_p (temp1))
1353 {
1354 /* Get the if_then_else from the condjump. */
1355 rtx choice = SET_SRC (PATTERN (temp1));
1356 if (GET_CODE (choice) == IF_THEN_ELSE)
1357 {
1358 enum rtx_code code = GET_CODE (XEXP (choice, 0));
1359 rtx val = SET_SRC (PATTERN (temp));
1360 rtx cond
1361 = simplify_relational_operation (code, GET_MODE (SET_DEST (PATTERN (temp))),
1362 val, const0_rtx);
1363 rtx ultimate;
1364
1365 if (cond == const_true_rtx)
1366 ultimate = XEXP (choice, 1);
1367 else if (cond == const0_rtx)
1368 ultimate = XEXP (choice, 2);
1369 else
1370 ultimate = 0;
1371
1372 if (ultimate == pc_rtx)
1373 ultimate = get_label_after (temp1);
1374 else if (ultimate && GET_CODE (ultimate) != RETURN)
1375 ultimate = XEXP (ultimate, 0);
1376
1377 if (ultimate)
1378 changed |= redirect_jump (insn, ultimate);
1379 }
1380 }
1381 #endif
1382
1383 #if 0
1384 /* @@ This needs a bit of work before it will be right.
1385
1386 Any type of comparison can be accepted for the first and
1387 second compare. When rewriting the first jump, we must
1388 compute the what conditions can reach label3, and use the
1389 appropriate code. We can not simply reverse/swap the code
1390 of the first jump. In some cases, the second jump must be
1391 rewritten also.
1392
1393 For example,
1394 < == converts to > ==
1395 < != converts to == >
1396 etc.
1397
1398 If the code is written to only accept an '==' test for the second
1399 compare, then all that needs to be done is to swap the condition
1400 of the first branch.
1401
1402 It is questionable whether we want this optimization anyways,
1403 since if the user wrote code like this because he/she knew that
1404 the jump to label1 is taken most of the time, then rewriting
1405 this gives slower code. */
1406 /* @@ This should call get_condition to find the values being
1407 compared, instead of looking for a COMPARE insn when HAVE_cc0
1408 is not defined. This would allow it to work on the m88k. */
1409 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1410 is not defined and the condition is tested by a separate compare
1411 insn. This is because the code below assumes that the result
1412 of the compare dies in the following branch. */
1413
1414 /* Simplify test a ~= b
1415 condjump label1;
1416 test a == b
1417 condjump label2;
1418 jump label3;
1419 label1:
1420
1421 rewriting as
1422 test a ~~= b
1423 condjump label3
1424 test a == b
1425 condjump label2
1426 label1:
1427
1428 where ~= is an inequality, e.g. >, and ~~= is the swapped
1429 inequality, e.g. <.
1430
1431 We recognize this case scanning backwards.
1432
1433 TEMP is the conditional jump to `label2';
1434 TEMP1 is the test for `a == b';
1435 TEMP2 is the conditional jump to `label1';
1436 TEMP3 is the test for `a ~= b'. */
1437 else if (this_is_simplejump
1438 && (temp = prev_active_insn (insn))
1439 && no_labels_between_p (temp, insn)
1440 && condjump_p (temp)
1441 && (temp1 = prev_active_insn (temp))
1442 && no_labels_between_p (temp1, temp)
1443 && GET_CODE (temp1) == INSN
1444 && GET_CODE (PATTERN (temp1)) == SET
1445 #ifdef HAVE_cc0
1446 && sets_cc0_p (PATTERN (temp1)) == 1
1447 #else
1448 && GET_CODE (SET_SRC (PATTERN (temp1))) == COMPARE
1449 && GET_CODE (SET_DEST (PATTERN (temp1))) == REG
1450 && (temp == find_next_ref (SET_DEST (PATTERN (temp1)), temp1))
1451 #endif
1452 && (temp2 = prev_active_insn (temp1))
1453 && no_labels_between_p (temp2, temp1)
1454 && condjump_p (temp2)
1455 && JUMP_LABEL (temp2) == next_nonnote_insn (NEXT_INSN (insn))
1456 && (temp3 = prev_active_insn (temp2))
1457 && no_labels_between_p (temp3, temp2)
1458 && GET_CODE (PATTERN (temp3)) == SET
1459 && rtx_equal_p (SET_DEST (PATTERN (temp3)),
1460 SET_DEST (PATTERN (temp1)))
1461 && rtx_equal_p (SET_SRC (PATTERN (temp1)),
1462 SET_SRC (PATTERN (temp3)))
1463 && ! inequality_comparisons_p (PATTERN (temp))
1464 && inequality_comparisons_p (PATTERN (temp2)))
1465 {
1466 rtx fallthrough_label = JUMP_LABEL (temp2);
1467
1468 ++LABEL_NUSES (fallthrough_label);
1469 if (swap_jump (temp2, JUMP_LABEL (insn)))
1470 {
1471 delete_insn (insn);
1472 changed = 1;
1473 }
1474
1475 if (--LABEL_NUSES (fallthrough_label) == 0)
1476 delete_insn (fallthrough_label);
1477 }
1478 #endif
1479 /* Simplify if (...) {... x = 1;} if (x) ...
1480
1481 We recognize this case backwards.
1482
1483 TEMP is the test of `x';
1484 TEMP1 is the assignment to `x' at the end of the
1485 previous statement. */
1486 /* @@ This should call get_condition to find the values being
1487 compared, instead of looking for a COMPARE insn when HAVE_cc0
1488 is not defined. This would allow it to work on the m88k. */
1489 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1490 is not defined and the condition is tested by a separate compare
1491 insn. This is because the code below assumes that the result
1492 of the compare dies in the following branch. */
1493
1494 /* ??? This has to be turned off. The problem is that the
1495 unconditional jump might indirectly end up branching to the
1496 label between TEMP1 and TEMP. We can't detect this, in general,
1497 since it may become a jump to there after further optimizations.
1498 If that jump is done, it will be deleted, so we will retry
1499 this optimization in the next pass, thus an infinite loop.
1500
1501 The present code prevents this by putting the jump after the
1502 label, but this is not logically correct. */
1503 #if 0
1504 else if (this_is_condjump
1505 /* Safe to skip USE and CLOBBER insns here
1506 since they will not be deleted. */
1507 && (temp = prev_active_insn (insn))
1508 && no_labels_between_p (temp, insn)
1509 && GET_CODE (temp) == INSN
1510 && GET_CODE (PATTERN (temp)) == SET
1511 #ifdef HAVE_cc0
1512 && sets_cc0_p (PATTERN (temp)) == 1
1513 && GET_CODE (SET_SRC (PATTERN (temp))) == REG
1514 #else
1515 /* Temp must be a compare insn, we can not accept a register
1516 to register move here, since it may not be simply a
1517 tst insn. */
1518 && GET_CODE (SET_SRC (PATTERN (temp))) == COMPARE
1519 && XEXP (SET_SRC (PATTERN (temp)), 1) == const0_rtx
1520 && GET_CODE (XEXP (SET_SRC (PATTERN (temp)), 0)) == REG
1521 && GET_CODE (SET_DEST (PATTERN (temp))) == REG
1522 && insn == find_next_ref (SET_DEST (PATTERN (temp)), temp)
1523 #endif
1524 /* May skip USE or CLOBBER insns here
1525 for checking for opportunity, since we
1526 take care of them later. */
1527 && (temp1 = prev_active_insn (temp))
1528 && GET_CODE (temp1) == INSN
1529 && GET_CODE (PATTERN (temp1)) == SET
1530 #ifdef HAVE_cc0
1531 && SET_SRC (PATTERN (temp)) == SET_DEST (PATTERN (temp1))
1532 #else
1533 && (XEXP (SET_SRC (PATTERN (temp)), 0)
1534 == SET_DEST (PATTERN (temp1)))
1535 #endif
1536 && CONSTANT_P (SET_SRC (PATTERN (temp1)))
1537 /* If this isn't true, cse will do the job. */
1538 && ! no_labels_between_p (temp1, temp))
1539 {
1540 /* Get the if_then_else from the condjump. */
1541 rtx choice = SET_SRC (PATTERN (insn));
1542 if (GET_CODE (choice) == IF_THEN_ELSE
1543 && (GET_CODE (XEXP (choice, 0)) == EQ
1544 || GET_CODE (XEXP (choice, 0)) == NE))
1545 {
1546 int want_nonzero = (GET_CODE (XEXP (choice, 0)) == NE);
1547 rtx last_insn;
1548 rtx ultimate;
1549 rtx p;
1550
1551 /* Get the place that condjump will jump to
1552 if it is reached from here. */
1553 if ((SET_SRC (PATTERN (temp1)) != const0_rtx)
1554 == want_nonzero)
1555 ultimate = XEXP (choice, 1);
1556 else
1557 ultimate = XEXP (choice, 2);
1558 /* Get it as a CODE_LABEL. */
1559 if (ultimate == pc_rtx)
1560 ultimate = get_label_after (insn);
1561 else
1562 /* Get the label out of the LABEL_REF. */
1563 ultimate = XEXP (ultimate, 0);
1564
1565 /* Insert the jump immediately before TEMP, specifically
1566 after the label that is between TEMP1 and TEMP. */
1567 last_insn = PREV_INSN (temp);
1568
1569 /* If we would be branching to the next insn, the jump
1570 would immediately be deleted and the re-inserted in
1571 a subsequent pass over the code. So don't do anything
1572 in that case. */
1573 if (next_active_insn (last_insn)
1574 != next_active_insn (ultimate))
1575 {
1576 emit_barrier_after (last_insn);
1577 p = emit_jump_insn_after (gen_jump (ultimate),
1578 last_insn);
1579 JUMP_LABEL (p) = ultimate;
1580 ++LABEL_NUSES (ultimate);
1581 if (INSN_UID (ultimate) < max_jump_chain
1582 && INSN_CODE (p) < max_jump_chain)
1583 {
1584 jump_chain[INSN_UID (p)]
1585 = jump_chain[INSN_UID (ultimate)];
1586 jump_chain[INSN_UID (ultimate)] = p;
1587 }
1588 changed = 1;
1589 continue;
1590 }
1591 }
1592 }
1593 #endif
1594 /* Detect a conditional jump going to the same place
1595 as an immediately following unconditional jump. */
1596 else if (this_is_condjump
1597 && (temp = next_active_insn (insn)) != 0
1598 && simplejump_p (temp)
1599 && (next_active_insn (JUMP_LABEL (insn))
1600 == next_active_insn (JUMP_LABEL (temp))))
1601 {
1602 delete_jump (insn);
1603 changed = 1;
1604 continue;
1605 }
1606 /* Detect a conditional jump jumping over an unconditional jump. */
1607
1608 else if (this_is_condjump && ! this_is_simplejump
1609 && reallabelprev != 0
1610 && GET_CODE (reallabelprev) == JUMP_INSN
1611 && prev_active_insn (reallabelprev) == insn
1612 && no_labels_between_p (insn, reallabelprev)
1613 && simplejump_p (reallabelprev))
1614 {
1615 /* When we invert the unconditional jump, we will be
1616 decrementing the usage count of its old label.
1617 Make sure that we don't delete it now because that
1618 might cause the following code to be deleted. */
1619 rtx prev_uses = prev_nonnote_insn (reallabelprev);
1620 rtx prev_label = JUMP_LABEL (insn);
1621
1622 ++LABEL_NUSES (prev_label);
1623
1624 if (invert_jump (insn, JUMP_LABEL (reallabelprev)))
1625 {
1626 /* It is very likely that if there are USE insns before
1627 this jump, they hold REG_DEAD notes. These REG_DEAD
1628 notes are no longer valid due to this optimization,
1629 and will cause the life-analysis that following passes
1630 (notably delayed-branch scheduling) to think that
1631 these registers are dead when they are not.
1632
1633 To prevent this trouble, we just remove the USE insns
1634 from the insn chain. */
1635
1636 while (prev_uses && GET_CODE (prev_uses) == INSN
1637 && GET_CODE (PATTERN (prev_uses)) == USE)
1638 {
1639 rtx useless = prev_uses;
1640 prev_uses = prev_nonnote_insn (prev_uses);
1641 delete_insn (useless);
1642 }
1643
1644 delete_insn (reallabelprev);
1645 next = insn;
1646 changed = 1;
1647 }
1648
1649 /* We can now safely delete the label if it is unreferenced
1650 since the delete_insn above has deleted the BARRIER. */
1651 if (--LABEL_NUSES (prev_label) == 0)
1652 delete_insn (prev_label);
1653 continue;
1654 }
1655 else
1656 {
1657 /* Detect a jump to a jump. */
1658
1659 nlabel = follow_jumps (JUMP_LABEL (insn));
1660 if (nlabel != JUMP_LABEL (insn)
1661 && redirect_jump (insn, nlabel))
1662 {
1663 changed = 1;
1664 next = insn;
1665 }
1666
1667 /* Look for if (foo) bar; else break; */
1668 /* The insns look like this:
1669 insn = condjump label1;
1670 ...range1 (some insns)...
1671 jump label2;
1672 label1:
1673 ...range2 (some insns)...
1674 jump somewhere unconditionally
1675 label2: */
1676 {
1677 rtx label1 = next_label (insn);
1678 rtx range1end = label1 ? prev_active_insn (label1) : 0;
1679 /* Don't do this optimization on the first round, so that
1680 jump-around-a-jump gets simplified before we ask here
1681 whether a jump is unconditional.
1682
1683 Also don't do it when we are called after reload since
1684 it will confuse reorg. */
1685 if (! first
1686 && (reload_completed ? ! flag_delayed_branch : 1)
1687 /* Make sure INSN is something we can invert. */
1688 && condjump_p (insn)
1689 && label1 != 0
1690 && JUMP_LABEL (insn) == label1
1691 && LABEL_NUSES (label1) == 1
1692 && GET_CODE (range1end) == JUMP_INSN
1693 && simplejump_p (range1end))
1694 {
1695 rtx label2 = next_label (label1);
1696 rtx range2end = label2 ? prev_active_insn (label2) : 0;
1697 if (range1end != range2end
1698 && JUMP_LABEL (range1end) == label2
1699 && GET_CODE (range2end) == JUMP_INSN
1700 && GET_CODE (NEXT_INSN (range2end)) == BARRIER
1701 /* Invert the jump condition, so we
1702 still execute the same insns in each case. */
1703 && invert_jump (insn, label1))
1704 {
1705 rtx range1beg = next_active_insn (insn);
1706 rtx range2beg = next_active_insn (label1);
1707 rtx range1after, range2after;
1708 rtx range1before, range2before;
1709
1710 /* Include in each range any line number before it. */
1711 while (PREV_INSN (range1beg)
1712 && GET_CODE (PREV_INSN (range1beg)) == NOTE
1713 && NOTE_LINE_NUMBER (PREV_INSN (range1beg)) > 0)
1714 range1beg = PREV_INSN (range1beg);
1715
1716 while (PREV_INSN (range2beg)
1717 && GET_CODE (PREV_INSN (range2beg)) == NOTE
1718 && NOTE_LINE_NUMBER (PREV_INSN (range2beg)) > 0)
1719 range2beg = PREV_INSN (range2beg);
1720
1721 /* Don't move NOTEs for blocks or loops; shift them
1722 outside the ranges, where they'll stay put. */
1723 range1beg = squeeze_notes (range1beg, range1end);
1724 range2beg = squeeze_notes (range2beg, range2end);
1725
1726 /* Get current surrounds of the 2 ranges. */
1727 range1before = PREV_INSN (range1beg);
1728 range2before = PREV_INSN (range2beg);
1729 range1after = NEXT_INSN (range1end);
1730 range2after = NEXT_INSN (range2end);
1731
1732 /* Splice range2 where range1 was. */
1733 NEXT_INSN (range1before) = range2beg;
1734 PREV_INSN (range2beg) = range1before;
1735 NEXT_INSN (range2end) = range1after;
1736 PREV_INSN (range1after) = range2end;
1737 /* Splice range1 where range2 was. */
1738 NEXT_INSN (range2before) = range1beg;
1739 PREV_INSN (range1beg) = range2before;
1740 NEXT_INSN (range1end) = range2after;
1741 PREV_INSN (range2after) = range1end;
1742 changed = 1;
1743 continue;
1744 }
1745 }
1746 }
1747
1748 /* Now that the jump has been tensioned,
1749 try cross jumping: check for identical code
1750 before the jump and before its target label. */
1751
1752 /* First, cross jumping of conditional jumps: */
1753
1754 if (cross_jump && condjump_p (insn))
1755 {
1756 rtx newjpos, newlpos;
1757 rtx x = prev_real_insn (JUMP_LABEL (insn));
1758
1759 /* A conditional jump may be crossjumped
1760 only if the place it jumps to follows
1761 an opposing jump that comes back here. */
1762
1763 if (x != 0 && ! jump_back_p (x, insn))
1764 /* We have no opposing jump;
1765 cannot cross jump this insn. */
1766 x = 0;
1767
1768 newjpos = 0;
1769 /* TARGET is nonzero if it is ok to cross jump
1770 to code before TARGET. If so, see if matches. */
1771 if (x != 0)
1772 find_cross_jump (insn, x, 2,
1773 &newjpos, &newlpos);
1774
1775 if (newjpos != 0)
1776 {
1777 do_cross_jump (insn, newjpos, newlpos);
1778 /* Make the old conditional jump
1779 into an unconditional one. */
1780 SET_SRC (PATTERN (insn))
1781 = gen_rtx (LABEL_REF, VOIDmode, JUMP_LABEL (insn));
1782 INSN_CODE (insn) = -1;
1783 emit_barrier_after (insn);
1784 /* Add to jump_chain unless this is a new label
1785 whose UID is too large. */
1786 if (INSN_UID (JUMP_LABEL (insn)) < max_jump_chain)
1787 {
1788 jump_chain[INSN_UID (insn)]
1789 = jump_chain[INSN_UID (JUMP_LABEL (insn))];
1790 jump_chain[INSN_UID (JUMP_LABEL (insn))] = insn;
1791 }
1792 changed = 1;
1793 next = insn;
1794 }
1795 }
1796
1797 /* Cross jumping of unconditional jumps:
1798 a few differences. */
1799
1800 if (cross_jump && simplejump_p (insn))
1801 {
1802 rtx newjpos, newlpos;
1803 rtx target;
1804
1805 newjpos = 0;
1806
1807 /* TARGET is nonzero if it is ok to cross jump
1808 to code before TARGET. If so, see if matches. */
1809 find_cross_jump (insn, JUMP_LABEL (insn), 1,
1810 &newjpos, &newlpos);
1811
1812 /* If cannot cross jump to code before the label,
1813 see if we can cross jump to another jump to
1814 the same label. */
1815 /* Try each other jump to this label. */
1816 if (INSN_UID (JUMP_LABEL (insn)) < max_uid)
1817 for (target = jump_chain[INSN_UID (JUMP_LABEL (insn))];
1818 target != 0 && newjpos == 0;
1819 target = jump_chain[INSN_UID (target)])
1820 if (target != insn
1821 && JUMP_LABEL (target) == JUMP_LABEL (insn)
1822 /* Ignore TARGET if it's deleted. */
1823 && ! INSN_DELETED_P (target))
1824 find_cross_jump (insn, target, 2,
1825 &newjpos, &newlpos);
1826
1827 if (newjpos != 0)
1828 {
1829 do_cross_jump (insn, newjpos, newlpos);
1830 changed = 1;
1831 next = insn;
1832 }
1833 }
1834
1835 /* This code was dead in the previous jump.c! */
1836 if (cross_jump && GET_CODE (PATTERN (insn)) == RETURN)
1837 {
1838 /* Return insns all "jump to the same place"
1839 so we can cross-jump between any two of them. */
1840
1841 rtx newjpos, newlpos, target;
1842
1843 newjpos = 0;
1844
1845 /* If cannot cross jump to code before the label,
1846 see if we can cross jump to another jump to
1847 the same label. */
1848 /* Try each other jump to this label. */
1849 for (target = jump_chain[0];
1850 target != 0 && newjpos == 0;
1851 target = jump_chain[INSN_UID (target)])
1852 if (target != insn
1853 && ! INSN_DELETED_P (target)
1854 && GET_CODE (PATTERN (target)) == RETURN)
1855 find_cross_jump (insn, target, 2,
1856 &newjpos, &newlpos);
1857
1858 if (newjpos != 0)
1859 {
1860 do_cross_jump (insn, newjpos, newlpos);
1861 changed = 1;
1862 next = insn;
1863 }
1864 }
1865 }
1866 }
1867
1868 first = 0;
1869 }
1870
1871 /* Delete extraneous line number notes.
1872 Note that two consecutive notes for different lines are not really
1873 extraneous. There should be some indication where that line belonged,
1874 even if it became empty. */
1875
1876 {
1877 rtx last_note = 0;
1878
1879 for (insn = f; insn; insn = NEXT_INSN (insn))
1880 if (GET_CODE (insn) == NOTE && NOTE_LINE_NUMBER (insn) >= 0)
1881 {
1882 /* Delete this note if it is identical to previous note. */
1883 if (last_note
1884 && NOTE_SOURCE_FILE (insn) == NOTE_SOURCE_FILE (last_note)
1885 && NOTE_LINE_NUMBER (insn) == NOTE_LINE_NUMBER (last_note))
1886 {
1887 delete_insn (insn);
1888 continue;
1889 }
1890
1891 last_note = insn;
1892 }
1893 }
1894
1895 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
1896 If so, delete it, and record that this function can drop off the end. */
1897
1898 insn = last_insn;
1899 {
1900 int n_labels = 1;
1901 while (insn
1902 /* One label can follow the end-note: the return label. */
1903 && ((GET_CODE (insn) == CODE_LABEL && n_labels-- > 0)
1904 /* Ordinary insns can follow it if returning a structure. */
1905 || GET_CODE (insn) == INSN
1906 /* If machine uses explicit RETURN insns, no epilogue,
1907 then one of them follows the note. */
1908 || (GET_CODE (insn) == JUMP_INSN
1909 && GET_CODE (PATTERN (insn)) == RETURN)
1910 /* Other kinds of notes can follow also. */
1911 || (GET_CODE (insn) == NOTE
1912 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_FUNCTION_END)))
1913 insn = PREV_INSN (insn);
1914 }
1915
1916 /* Report if control can fall through at the end of the function. */
1917 if (insn && GET_CODE (insn) == NOTE
1918 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_END)
1919 {
1920 can_reach_end = 1;
1921 delete_insn (insn);
1922 }
1923
1924 /* Show JUMP_CHAIN no longer valid. */
1925 jump_chain = 0;
1926 }
1927 \f
1928 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
1929 jump. Assume that this unconditional jump is to the exit test code. If
1930 the code is sufficiently simple, make a copy of it before INSN,
1931 followed by a jump to the exit of the loop. Then delete the unconditional
1932 jump after INSN.
1933
1934 Note that it is possible we can get confused here if the jump immediately
1935 after the loop start branches outside the loop but within an outer loop.
1936 If we are near the exit of that loop, we will copy its exit test. This
1937 will not generate incorrect code, but could suppress some optimizations.
1938 However, such cases are degenerate loops anyway.
1939
1940 Return 1 if we made the change, else 0.
1941
1942 This is only safe immediately after a regscan pass because it uses the
1943 values of regno_first_uid and regno_last_uid. */
1944
1945 static int
1946 duplicate_loop_exit_test (loop_start)
1947 rtx loop_start;
1948 {
1949 rtx insn, set, p;
1950 rtx copy, link;
1951 int num_insns = 0;
1952 rtx exitcode = NEXT_INSN (JUMP_LABEL (next_nonnote_insn (loop_start)));
1953 rtx lastexit;
1954 int max_reg = max_reg_num ();
1955 rtx *reg_map = 0;
1956
1957 /* Scan the exit code. We do not perform this optimization if any insn:
1958
1959 is a CALL_INSN
1960 is a CODE_LABEL
1961 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
1962 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
1963 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
1964 are not valid
1965
1966 Also, don't do this if the exit code is more than 20 insns. */
1967
1968 for (insn = exitcode;
1969 insn
1970 && ! (GET_CODE (insn) == NOTE
1971 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END);
1972 insn = NEXT_INSN (insn))
1973 {
1974 switch (GET_CODE (insn))
1975 {
1976 case CODE_LABEL:
1977 case CALL_INSN:
1978 return 0;
1979 case NOTE:
1980 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG
1981 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG
1982 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END)
1983 return 0;
1984 break;
1985 case JUMP_INSN:
1986 case INSN:
1987 if (++num_insns > 20
1988 || find_reg_note (insn, REG_RETVAL, NULL_RTX)
1989 || find_reg_note (insn, REG_LIBCALL, NULL_RTX))
1990 return 0;
1991 break;
1992 }
1993 }
1994
1995 /* Unless INSN is zero, we can do the optimization. */
1996 if (insn == 0)
1997 return 0;
1998
1999 lastexit = insn;
2000
2001 /* See if any insn sets a register only used in the loop exit code and
2002 not a user variable. If so, replace it with a new register. */
2003 for (insn = exitcode; insn != lastexit; insn = NEXT_INSN (insn))
2004 if (GET_CODE (insn) == INSN
2005 && (set = single_set (insn)) != 0
2006 && GET_CODE (SET_DEST (set)) == REG
2007 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER
2008 && regno_first_uid[REGNO (SET_DEST (set))] == INSN_UID (insn))
2009 {
2010 for (p = NEXT_INSN (insn); p != lastexit; p = NEXT_INSN (p))
2011 if (regno_last_uid[REGNO (SET_DEST (set))] == INSN_UID (p))
2012 break;
2013
2014 if (p != lastexit)
2015 {
2016 /* We can do the replacement. Allocate reg_map if this is the
2017 first replacement we found. */
2018 if (reg_map == 0)
2019 {
2020 reg_map = (rtx *) alloca (max_reg * sizeof (rtx));
2021 bzero (reg_map, max_reg * sizeof (rtx));
2022 }
2023
2024 REG_LOOP_TEST_P (SET_DEST (set)) = 1;
2025
2026 reg_map[REGNO (SET_DEST (set))]
2027 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
2028 }
2029 }
2030
2031 /* Now copy each insn. */
2032 for (insn = exitcode; insn != lastexit; insn = NEXT_INSN (insn))
2033 switch (GET_CODE (insn))
2034 {
2035 case BARRIER:
2036 copy = emit_barrier_before (loop_start);
2037 break;
2038 case NOTE:
2039 /* Only copy line-number notes. */
2040 if (NOTE_LINE_NUMBER (insn) >= 0)
2041 {
2042 copy = emit_note_before (NOTE_LINE_NUMBER (insn), loop_start);
2043 NOTE_SOURCE_FILE (copy) = NOTE_SOURCE_FILE (insn);
2044 }
2045 break;
2046
2047 case INSN:
2048 copy = emit_insn_before (copy_rtx (PATTERN (insn)), loop_start);
2049 if (reg_map)
2050 replace_regs (PATTERN (copy), reg_map, max_reg, 1);
2051
2052 mark_jump_label (PATTERN (copy), copy, 0);
2053
2054 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
2055 make them. */
2056 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
2057 if (REG_NOTE_KIND (link) != REG_LABEL)
2058 REG_NOTES (copy)
2059 = copy_rtx (gen_rtx (EXPR_LIST, REG_NOTE_KIND (link),
2060 XEXP (link, 0), REG_NOTES (copy)));
2061 if (reg_map && REG_NOTES (copy))
2062 replace_regs (REG_NOTES (copy), reg_map, max_reg, 1);
2063 break;
2064
2065 case JUMP_INSN:
2066 copy = emit_jump_insn_before (copy_rtx (PATTERN (insn)), loop_start);
2067 if (reg_map)
2068 replace_regs (PATTERN (copy), reg_map, max_reg, 1);
2069 mark_jump_label (PATTERN (copy), copy, 0);
2070 if (REG_NOTES (insn))
2071 {
2072 REG_NOTES (copy) = copy_rtx (REG_NOTES (insn));
2073 if (reg_map)
2074 replace_regs (REG_NOTES (copy), reg_map, max_reg, 1);
2075 }
2076
2077 /* If this is a simple jump, add it to the jump chain. */
2078
2079 if (INSN_UID (copy) < max_jump_chain && JUMP_LABEL (copy)
2080 && simplejump_p (copy))
2081 {
2082 jump_chain[INSN_UID (copy)]
2083 = jump_chain[INSN_UID (JUMP_LABEL (copy))];
2084 jump_chain[INSN_UID (JUMP_LABEL (copy))] = copy;
2085 }
2086 break;
2087
2088 default:
2089 abort ();
2090 }
2091
2092 /* Now clean up by emitting a jump to the end label and deleting the jump
2093 at the start of the loop. */
2094 if (GET_CODE (copy) != BARRIER)
2095 {
2096 copy = emit_jump_insn_before (gen_jump (get_label_after (insn)),
2097 loop_start);
2098 mark_jump_label (PATTERN (copy), copy, 0);
2099 if (INSN_UID (copy) < max_jump_chain
2100 && INSN_UID (JUMP_LABEL (copy)) < max_jump_chain)
2101 {
2102 jump_chain[INSN_UID (copy)]
2103 = jump_chain[INSN_UID (JUMP_LABEL (copy))];
2104 jump_chain[INSN_UID (JUMP_LABEL (copy))] = copy;
2105 }
2106 emit_barrier_before (loop_start);
2107 }
2108
2109 delete_insn (next_nonnote_insn (loop_start));
2110
2111 /* Mark the exit code as the virtual top of the converted loop. */
2112 emit_note_before (NOTE_INSN_LOOP_VTOP, exitcode);
2113
2114 return 1;
2115 }
2116 \f
2117 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
2118 loop-end notes between START and END out before START. Assume that
2119 END is not such a note. START may be such a note. Returns the value
2120 of the new starting insn, which may be different if the original start
2121 was such a note. */
2122
2123 rtx
2124 squeeze_notes (start, end)
2125 rtx start, end;
2126 {
2127 rtx insn;
2128 rtx next;
2129
2130 for (insn = start; insn != end; insn = next)
2131 {
2132 next = NEXT_INSN (insn);
2133 if (GET_CODE (insn) == NOTE
2134 && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END
2135 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG
2136 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG
2137 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END
2138 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_CONT
2139 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_VTOP))
2140 {
2141 if (insn == start)
2142 start = next;
2143 else
2144 {
2145 rtx prev = PREV_INSN (insn);
2146 PREV_INSN (insn) = PREV_INSN (start);
2147 NEXT_INSN (insn) = start;
2148 NEXT_INSN (PREV_INSN (insn)) = insn;
2149 PREV_INSN (NEXT_INSN (insn)) = insn;
2150 NEXT_INSN (prev) = next;
2151 PREV_INSN (next) = prev;
2152 }
2153 }
2154 }
2155
2156 return start;
2157 }
2158 \f
2159 /* Compare the instructions before insn E1 with those before E2
2160 to find an opportunity for cross jumping.
2161 (This means detecting identical sequences of insns followed by
2162 jumps to the same place, or followed by a label and a jump
2163 to that label, and replacing one with a jump to the other.)
2164
2165 Assume E1 is a jump that jumps to label E2
2166 (that is not always true but it might as well be).
2167 Find the longest possible equivalent sequences
2168 and store the first insns of those sequences into *F1 and *F2.
2169 Store zero there if no equivalent preceding instructions are found.
2170
2171 We give up if we find a label in stream 1.
2172 Actually we could transfer that label into stream 2. */
2173
2174 static void
2175 find_cross_jump (e1, e2, minimum, f1, f2)
2176 rtx e1, e2;
2177 int minimum;
2178 rtx *f1, *f2;
2179 {
2180 register rtx i1 = e1, i2 = e2;
2181 register rtx p1, p2;
2182 int lose = 0;
2183
2184 rtx last1 = 0, last2 = 0;
2185 rtx afterlast1 = 0, afterlast2 = 0;
2186 rtx prev1;
2187
2188 *f1 = 0;
2189 *f2 = 0;
2190
2191 while (1)
2192 {
2193 i1 = prev_nonnote_insn (i1);
2194
2195 i2 = PREV_INSN (i2);
2196 while (i2 && (GET_CODE (i2) == NOTE || GET_CODE (i2) == CODE_LABEL))
2197 i2 = PREV_INSN (i2);
2198
2199 if (i1 == 0)
2200 break;
2201
2202 /* Don't allow the range of insns preceding E1 or E2
2203 to include the other (E2 or E1). */
2204 if (i2 == e1 || i1 == e2)
2205 break;
2206
2207 /* If we will get to this code by jumping, those jumps will be
2208 tensioned to go directly to the new label (before I2),
2209 so this cross-jumping won't cost extra. So reduce the minimum. */
2210 if (GET_CODE (i1) == CODE_LABEL)
2211 {
2212 --minimum;
2213 break;
2214 }
2215
2216 if (i2 == 0 || GET_CODE (i1) != GET_CODE (i2))
2217 break;
2218
2219 p1 = PATTERN (i1);
2220 p2 = PATTERN (i2);
2221
2222 #ifdef STACK_REGS
2223 /* If cross_jump_death_matters is not 0, the insn's mode
2224 indicates whether or not the insn contains any stack-like
2225 regs. */
2226
2227 if (cross_jump_death_matters && GET_MODE (i1) == QImode)
2228 {
2229 /* If register stack conversion has already been done, then
2230 death notes must also be compared before it is certain that
2231 the two instruction streams match. */
2232
2233 rtx note;
2234 HARD_REG_SET i1_regset, i2_regset;
2235
2236 CLEAR_HARD_REG_SET (i1_regset);
2237 CLEAR_HARD_REG_SET (i2_regset);
2238
2239 for (note = REG_NOTES (i1); note; note = XEXP (note, 1))
2240 if (REG_NOTE_KIND (note) == REG_DEAD
2241 && STACK_REG_P (XEXP (note, 0)))
2242 SET_HARD_REG_BIT (i1_regset, REGNO (XEXP (note, 0)));
2243
2244 for (note = REG_NOTES (i2); note; note = XEXP (note, 1))
2245 if (REG_NOTE_KIND (note) == REG_DEAD
2246 && STACK_REG_P (XEXP (note, 0)))
2247 SET_HARD_REG_BIT (i2_regset, REGNO (XEXP (note, 0)));
2248
2249 GO_IF_HARD_REG_EQUAL (i1_regset, i2_regset, done);
2250
2251 lose = 1;
2252
2253 done:
2254 ;
2255 }
2256 #endif
2257
2258 if (lose || GET_CODE (p1) != GET_CODE (p2)
2259 || ! rtx_renumbered_equal_p (p1, p2))
2260 {
2261 /* The following code helps take care of G++ cleanups. */
2262 rtx equiv1;
2263 rtx equiv2;
2264
2265 if (!lose && GET_CODE (p1) == GET_CODE (p2)
2266 && ((equiv1 = find_reg_note (i1, REG_EQUAL, NULL_RTX)) != 0
2267 || (equiv1 = find_reg_note (i1, REG_EQUIV, NULL_RTX)) != 0)
2268 && ((equiv2 = find_reg_note (i2, REG_EQUAL, NULL_RTX)) != 0
2269 || (equiv2 = find_reg_note (i2, REG_EQUIV, NULL_RTX)) != 0)
2270 /* If the equivalences are not to a constant, they may
2271 reference pseudos that no longer exist, so we can't
2272 use them. */
2273 && CONSTANT_P (XEXP (equiv1, 0))
2274 && rtx_equal_p (XEXP (equiv1, 0), XEXP (equiv2, 0)))
2275 {
2276 rtx s1 = single_set (i1);
2277 rtx s2 = single_set (i2);
2278 if (s1 != 0 && s2 != 0
2279 && rtx_renumbered_equal_p (SET_DEST (s1), SET_DEST (s2)))
2280 {
2281 validate_change (i1, &SET_SRC (s1), XEXP (equiv1, 0), 1);
2282 validate_change (i2, &SET_SRC (s2), XEXP (equiv2, 0), 1);
2283 if (! rtx_renumbered_equal_p (p1, p2))
2284 cancel_changes (0);
2285 else if (apply_change_group ())
2286 goto win;
2287 }
2288 }
2289
2290 /* Insns fail to match; cross jumping is limited to the following
2291 insns. */
2292
2293 #ifdef HAVE_cc0
2294 /* Don't allow the insn after a compare to be shared by
2295 cross-jumping unless the compare is also shared.
2296 Here, if either of these non-matching insns is a compare,
2297 exclude the following insn from possible cross-jumping. */
2298 if (sets_cc0_p (p1) || sets_cc0_p (p2))
2299 last1 = afterlast1, last2 = afterlast2, ++minimum;
2300 #endif
2301
2302 /* If cross-jumping here will feed a jump-around-jump
2303 optimization, this jump won't cost extra, so reduce
2304 the minimum. */
2305 if (GET_CODE (i1) == JUMP_INSN
2306 && JUMP_LABEL (i1)
2307 && prev_real_insn (JUMP_LABEL (i1)) == e1)
2308 --minimum;
2309 break;
2310 }
2311
2312 win:
2313 if (GET_CODE (p1) != USE && GET_CODE (p1) != CLOBBER)
2314 {
2315 /* Ok, this insn is potentially includable in a cross-jump here. */
2316 afterlast1 = last1, afterlast2 = last2;
2317 last1 = i1, last2 = i2, --minimum;
2318 }
2319 }
2320
2321 /* We have to be careful that we do not cross-jump into the middle of
2322 USE-CALL_INSN-CLOBBER sequence. This sequence is used instead of
2323 putting the USE and CLOBBERs inside the CALL_INSN. The delay slot
2324 scheduler needs to know what registers are used and modified by the
2325 CALL_INSN and needs the adjacent USE and CLOBBERs to do so.
2326
2327 ??? At some point we should probably change this so that these are
2328 part of the CALL_INSN. The way we are doing it now is a kludge that
2329 is now causing trouble. */
2330
2331 if (last1 != 0 && GET_CODE (last1) == CALL_INSN
2332 && (prev1 = prev_nonnote_insn (last1))
2333 && GET_CODE (prev1) == INSN
2334 && GET_CODE (PATTERN (prev1)) == USE)
2335 {
2336 /* Remove this CALL_INSN from the range we can cross-jump. */
2337 last1 = next_real_insn (last1);
2338 last2 = next_real_insn (last2);
2339
2340 minimum++;
2341 }
2342
2343 /* Skip past CLOBBERS since they may be right after a CALL_INSN. It
2344 isn't worth checking for the CALL_INSN. */
2345 while (last1 != 0 && GET_CODE (PATTERN (last1)) == CLOBBER)
2346 last1 = next_real_insn (last1), last2 = next_real_insn (last2);
2347
2348 if (minimum <= 0 && last1 != 0 && last1 != e1)
2349 *f1 = last1, *f2 = last2;
2350 }
2351
2352 static void
2353 do_cross_jump (insn, newjpos, newlpos)
2354 rtx insn, newjpos, newlpos;
2355 {
2356 /* Find an existing label at this point
2357 or make a new one if there is none. */
2358 register rtx label = get_label_before (newlpos);
2359
2360 /* Make the same jump insn jump to the new point. */
2361 if (GET_CODE (PATTERN (insn)) == RETURN)
2362 {
2363 /* Remove from jump chain of returns. */
2364 delete_from_jump_chain (insn);
2365 /* Change the insn. */
2366 PATTERN (insn) = gen_jump (label);
2367 INSN_CODE (insn) = -1;
2368 JUMP_LABEL (insn) = label;
2369 LABEL_NUSES (label)++;
2370 /* Add to new the jump chain. */
2371 if (INSN_UID (label) < max_jump_chain
2372 && INSN_UID (insn) < max_jump_chain)
2373 {
2374 jump_chain[INSN_UID (insn)] = jump_chain[INSN_UID (label)];
2375 jump_chain[INSN_UID (label)] = insn;
2376 }
2377 }
2378 else
2379 redirect_jump (insn, label);
2380
2381 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
2382 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
2383 the NEWJPOS stream. */
2384
2385 while (newjpos != insn)
2386 {
2387 rtx lnote;
2388
2389 for (lnote = REG_NOTES (newlpos); lnote; lnote = XEXP (lnote, 1))
2390 if ((REG_NOTE_KIND (lnote) == REG_EQUAL
2391 || REG_NOTE_KIND (lnote) == REG_EQUIV)
2392 && ! find_reg_note (newjpos, REG_EQUAL, XEXP (lnote, 0))
2393 && ! find_reg_note (newjpos, REG_EQUIV, XEXP (lnote, 0)))
2394 remove_note (newlpos, lnote);
2395
2396 delete_insn (newjpos);
2397 newjpos = next_real_insn (newjpos);
2398 newlpos = next_real_insn (newlpos);
2399 }
2400 }
2401 \f
2402 /* Return the label before INSN, or put a new label there. */
2403
2404 rtx
2405 get_label_before (insn)
2406 rtx insn;
2407 {
2408 rtx label;
2409
2410 /* Find an existing label at this point
2411 or make a new one if there is none. */
2412 label = prev_nonnote_insn (insn);
2413
2414 if (label == 0 || GET_CODE (label) != CODE_LABEL)
2415 {
2416 rtx prev = PREV_INSN (insn);
2417
2418 /* Don't put a label between a CALL_INSN and USE insns that precede
2419 it. */
2420
2421 if (GET_CODE (insn) == CALL_INSN
2422 || (GET_CODE (insn) == INSN && GET_CODE (PATTERN (insn)) == SEQUENCE
2423 && GET_CODE (XVECEXP (PATTERN (insn), 0, 0)) == CALL_INSN))
2424 while (GET_CODE (prev) == INSN && GET_CODE (PATTERN (prev)) == USE)
2425 prev = PREV_INSN (prev);
2426
2427 label = gen_label_rtx ();
2428 emit_label_after (label, prev);
2429 LABEL_NUSES (label) = 0;
2430 }
2431 return label;
2432 }
2433
2434 /* Return the label after INSN, or put a new label there. */
2435
2436 rtx
2437 get_label_after (insn)
2438 rtx insn;
2439 {
2440 rtx label;
2441
2442 /* Find an existing label at this point
2443 or make a new one if there is none. */
2444 label = next_nonnote_insn (insn);
2445
2446 if (label == 0 || GET_CODE (label) != CODE_LABEL)
2447 {
2448 /* Don't put a label between a CALL_INSN and CLOBBER insns
2449 following it. */
2450
2451 if (GET_CODE (insn) == CALL_INSN
2452 || (GET_CODE (insn) == INSN && GET_CODE (PATTERN (insn)) == SEQUENCE
2453 && GET_CODE (XVECEXP (PATTERN (insn), 0, 0)) == CALL_INSN))
2454 while (GET_CODE (NEXT_INSN (insn)) == INSN
2455 && GET_CODE (PATTERN (NEXT_INSN (insn))) == CLOBBER)
2456 insn = NEXT_INSN (insn);
2457
2458 label = gen_label_rtx ();
2459 emit_label_after (label, insn);
2460 LABEL_NUSES (label) = 0;
2461 }
2462 return label;
2463 }
2464 \f
2465 /* Return 1 if INSN is a jump that jumps to right after TARGET
2466 only on the condition that TARGET itself would drop through.
2467 Assumes that TARGET is a conditional jump. */
2468
2469 static int
2470 jump_back_p (insn, target)
2471 rtx insn, target;
2472 {
2473 rtx cinsn, ctarget;
2474 enum rtx_code codei, codet;
2475
2476 if (simplejump_p (insn) || ! condjump_p (insn)
2477 || simplejump_p (target)
2478 || target != prev_real_insn (JUMP_LABEL (insn)))
2479 return 0;
2480
2481 cinsn = XEXP (SET_SRC (PATTERN (insn)), 0);
2482 ctarget = XEXP (SET_SRC (PATTERN (target)), 0);
2483
2484 codei = GET_CODE (cinsn);
2485 codet = GET_CODE (ctarget);
2486
2487 if (XEXP (SET_SRC (PATTERN (insn)), 1) == pc_rtx)
2488 {
2489 if (! can_reverse_comparison_p (cinsn, insn))
2490 return 0;
2491 codei = reverse_condition (codei);
2492 }
2493
2494 if (XEXP (SET_SRC (PATTERN (target)), 2) == pc_rtx)
2495 {
2496 if (! can_reverse_comparison_p (ctarget, target))
2497 return 0;
2498 codet = reverse_condition (codet);
2499 }
2500
2501 return (codei == codet
2502 && rtx_renumbered_equal_p (XEXP (cinsn, 0), XEXP (ctarget, 0))
2503 && rtx_renumbered_equal_p (XEXP (cinsn, 1), XEXP (ctarget, 1)));
2504 }
2505 \f
2506 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
2507 return non-zero if it is safe to reverse this comparison. It is if our
2508 floating-point is not IEEE, if this is an NE or EQ comparison, or if
2509 this is known to be an integer comparison. */
2510
2511 int
2512 can_reverse_comparison_p (comparison, insn)
2513 rtx comparison;
2514 rtx insn;
2515 {
2516 rtx arg0;
2517
2518 /* If this is not actually a comparison, we can't reverse it. */
2519 if (GET_RTX_CLASS (GET_CODE (comparison)) != '<')
2520 return 0;
2521
2522 if (TARGET_FLOAT_FORMAT != IEEE_FLOAT_FORMAT
2523 /* If this is an NE comparison, it is safe to reverse it to an EQ
2524 comparison and vice versa, even for floating point. If no operands
2525 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
2526 always false and NE is always true, so the reversal is also valid. */
2527 || GET_CODE (comparison) == NE
2528 || GET_CODE (comparison) == EQ)
2529 return 1;
2530
2531 arg0 = XEXP (comparison, 0);
2532
2533 /* Make sure ARG0 is one of the actual objects being compared. If we
2534 can't do this, we can't be sure the comparison can be reversed.
2535
2536 Handle cc0 and a MODE_CC register. */
2537 if ((GET_CODE (arg0) == REG && GET_MODE_CLASS (GET_MODE (arg0)) == MODE_CC)
2538 #ifdef HAVE_cc0
2539 || arg0 == cc0_rtx
2540 #endif
2541 )
2542 {
2543 rtx prev = prev_nonnote_insn (insn);
2544 rtx set = single_set (prev);
2545
2546 if (set == 0 || SET_DEST (set) != arg0)
2547 return 0;
2548
2549 arg0 = SET_SRC (set);
2550
2551 if (GET_CODE (arg0) == COMPARE)
2552 arg0 = XEXP (arg0, 0);
2553 }
2554
2555 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
2556 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
2557 return (GET_CODE (arg0) == CONST_INT
2558 || (GET_MODE (arg0) != VOIDmode
2559 && GET_MODE_CLASS (GET_MODE (arg0)) != MODE_CC
2560 && GET_MODE_CLASS (GET_MODE (arg0)) != MODE_FLOAT));
2561 }
2562
2563 /* Given an rtx-code for a comparison, return the code
2564 for the negated comparison.
2565 WATCH OUT! reverse_condition is not safe to use on a jump
2566 that might be acting on the results of an IEEE floating point comparison,
2567 because of the special treatment of non-signaling nans in comparisons.
2568 Use can_reverse_comparison_p to be sure. */
2569
2570 enum rtx_code
2571 reverse_condition (code)
2572 enum rtx_code code;
2573 {
2574 switch (code)
2575 {
2576 case EQ:
2577 return NE;
2578
2579 case NE:
2580 return EQ;
2581
2582 case GT:
2583 return LE;
2584
2585 case GE:
2586 return LT;
2587
2588 case LT:
2589 return GE;
2590
2591 case LE:
2592 return GT;
2593
2594 case GTU:
2595 return LEU;
2596
2597 case GEU:
2598 return LTU;
2599
2600 case LTU:
2601 return GEU;
2602
2603 case LEU:
2604 return GTU;
2605
2606 default:
2607 abort ();
2608 return UNKNOWN;
2609 }
2610 }
2611
2612 /* Similar, but return the code when two operands of a comparison are swapped.
2613 This IS safe for IEEE floating-point. */
2614
2615 enum rtx_code
2616 swap_condition (code)
2617 enum rtx_code code;
2618 {
2619 switch (code)
2620 {
2621 case EQ:
2622 case NE:
2623 return code;
2624
2625 case GT:
2626 return LT;
2627
2628 case GE:
2629 return LE;
2630
2631 case LT:
2632 return GT;
2633
2634 case LE:
2635 return GE;
2636
2637 case GTU:
2638 return LTU;
2639
2640 case GEU:
2641 return LEU;
2642
2643 case LTU:
2644 return GTU;
2645
2646 case LEU:
2647 return GEU;
2648
2649 default:
2650 abort ();
2651 return UNKNOWN;
2652 }
2653 }
2654
2655 /* Given a comparison CODE, return the corresponding unsigned comparison.
2656 If CODE is an equality comparison or already an unsigned comparison,
2657 CODE is returned. */
2658
2659 enum rtx_code
2660 unsigned_condition (code)
2661 enum rtx_code code;
2662 {
2663 switch (code)
2664 {
2665 case EQ:
2666 case NE:
2667 case GTU:
2668 case GEU:
2669 case LTU:
2670 case LEU:
2671 return code;
2672
2673 case GT:
2674 return GTU;
2675
2676 case GE:
2677 return GEU;
2678
2679 case LT:
2680 return LTU;
2681
2682 case LE:
2683 return LEU;
2684
2685 default:
2686 abort ();
2687 }
2688 }
2689
2690 /* Similarly, return the signed version of a comparison. */
2691
2692 enum rtx_code
2693 signed_condition (code)
2694 enum rtx_code code;
2695 {
2696 switch (code)
2697 {
2698 case EQ:
2699 case NE:
2700 case GT:
2701 case GE:
2702 case LT:
2703 case LE:
2704 return code;
2705
2706 case GTU:
2707 return GT;
2708
2709 case GEU:
2710 return GE;
2711
2712 case LTU:
2713 return LT;
2714
2715 case LEU:
2716 return LE;
2717
2718 default:
2719 abort ();
2720 }
2721 }
2722 \f
2723 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
2724 truth of CODE1 implies the truth of CODE2. */
2725
2726 int
2727 comparison_dominates_p (code1, code2)
2728 enum rtx_code code1, code2;
2729 {
2730 if (code1 == code2)
2731 return 1;
2732
2733 switch (code1)
2734 {
2735 case EQ:
2736 if (code2 == LE || code2 == LEU || code2 == GE || code2 == GEU)
2737 return 1;
2738 break;
2739
2740 case LT:
2741 if (code2 == LE)
2742 return 1;
2743 break;
2744
2745 case GT:
2746 if (code2 == GE)
2747 return 1;
2748 break;
2749
2750 case LTU:
2751 if (code2 == LEU)
2752 return 1;
2753 break;
2754
2755 case GTU:
2756 if (code2 == GEU)
2757 return 1;
2758 break;
2759 }
2760
2761 return 0;
2762 }
2763 \f
2764 /* Return 1 if INSN is an unconditional jump and nothing else. */
2765
2766 int
2767 simplejump_p (insn)
2768 rtx insn;
2769 {
2770 return (GET_CODE (insn) == JUMP_INSN
2771 && GET_CODE (PATTERN (insn)) == SET
2772 && GET_CODE (SET_DEST (PATTERN (insn))) == PC
2773 && GET_CODE (SET_SRC (PATTERN (insn))) == LABEL_REF);
2774 }
2775
2776 /* Return nonzero if INSN is a (possibly) conditional jump
2777 and nothing more. */
2778
2779 int
2780 condjump_p (insn)
2781 rtx insn;
2782 {
2783 register rtx x = PATTERN (insn);
2784 if (GET_CODE (x) != SET)
2785 return 0;
2786 if (GET_CODE (SET_DEST (x)) != PC)
2787 return 0;
2788 if (GET_CODE (SET_SRC (x)) == LABEL_REF)
2789 return 1;
2790 if (GET_CODE (SET_SRC (x)) != IF_THEN_ELSE)
2791 return 0;
2792 if (XEXP (SET_SRC (x), 2) == pc_rtx
2793 && (GET_CODE (XEXP (SET_SRC (x), 1)) == LABEL_REF
2794 || GET_CODE (XEXP (SET_SRC (x), 1)) == RETURN))
2795 return 1;
2796 if (XEXP (SET_SRC (x), 1) == pc_rtx
2797 && (GET_CODE (XEXP (SET_SRC (x), 2)) == LABEL_REF
2798 || GET_CODE (XEXP (SET_SRC (x), 2)) == RETURN))
2799 return 1;
2800 return 0;
2801 }
2802
2803 /* Return 1 if X is an RTX that does nothing but set the condition codes
2804 and CLOBBER or USE registers.
2805 Return -1 if X does explicitly set the condition codes,
2806 but also does other things. */
2807
2808 int
2809 sets_cc0_p (x)
2810 rtx x;
2811 {
2812 #ifdef HAVE_cc0
2813 if (GET_CODE (x) == SET && SET_DEST (x) == cc0_rtx)
2814 return 1;
2815 if (GET_CODE (x) == PARALLEL)
2816 {
2817 int i;
2818 int sets_cc0 = 0;
2819 int other_things = 0;
2820 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
2821 {
2822 if (GET_CODE (XVECEXP (x, 0, i)) == SET
2823 && SET_DEST (XVECEXP (x, 0, i)) == cc0_rtx)
2824 sets_cc0 = 1;
2825 else if (GET_CODE (XVECEXP (x, 0, i)) == SET)
2826 other_things = 1;
2827 }
2828 return ! sets_cc0 ? 0 : other_things ? -1 : 1;
2829 }
2830 return 0;
2831 #else
2832 abort ();
2833 #endif
2834 }
2835 \f
2836 /* Follow any unconditional jump at LABEL;
2837 return the ultimate label reached by any such chain of jumps.
2838 If LABEL is not followed by a jump, return LABEL.
2839 If the chain loops or we can't find end, return LABEL,
2840 since that tells caller to avoid changing the insn.
2841
2842 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
2843 a USE or CLOBBER. */
2844
2845 rtx
2846 follow_jumps (label)
2847 rtx label;
2848 {
2849 register rtx insn;
2850 register rtx next;
2851 register rtx value = label;
2852 register int depth;
2853
2854 for (depth = 0;
2855 (depth < 10
2856 && (insn = next_active_insn (value)) != 0
2857 && GET_CODE (insn) == JUMP_INSN
2858 && (JUMP_LABEL (insn) != 0 || GET_CODE (PATTERN (insn)) == RETURN)
2859 && (next = NEXT_INSN (insn))
2860 && GET_CODE (next) == BARRIER);
2861 depth++)
2862 {
2863 /* Don't chain through the insn that jumps into a loop
2864 from outside the loop,
2865 since that would create multiple loop entry jumps
2866 and prevent loop optimization. */
2867 rtx tem;
2868 if (!reload_completed)
2869 for (tem = value; tem != insn; tem = NEXT_INSN (tem))
2870 if (GET_CODE (tem) == NOTE
2871 && NOTE_LINE_NUMBER (tem) == NOTE_INSN_LOOP_BEG)
2872 return value;
2873
2874 /* If we have found a cycle, make the insn jump to itself. */
2875 if (JUMP_LABEL (insn) == label)
2876 return label;
2877 value = JUMP_LABEL (insn);
2878 }
2879 if (depth == 10)
2880 return label;
2881 return value;
2882 }
2883
2884 /* Assuming that field IDX of X is a vector of label_refs,
2885 replace each of them by the ultimate label reached by it.
2886 Return nonzero if a change is made.
2887 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
2888
2889 static int
2890 tension_vector_labels (x, idx)
2891 register rtx x;
2892 register int idx;
2893 {
2894 int changed = 0;
2895 register int i;
2896 for (i = XVECLEN (x, idx) - 1; i >= 0; i--)
2897 {
2898 register rtx olabel = XEXP (XVECEXP (x, idx, i), 0);
2899 register rtx nlabel = follow_jumps (olabel);
2900 if (nlabel && nlabel != olabel)
2901 {
2902 XEXP (XVECEXP (x, idx, i), 0) = nlabel;
2903 ++LABEL_NUSES (nlabel);
2904 if (--LABEL_NUSES (olabel) == 0)
2905 delete_insn (olabel);
2906 changed = 1;
2907 }
2908 }
2909 return changed;
2910 }
2911 \f
2912 /* Find all CODE_LABELs referred to in X, and increment their use counts.
2913 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
2914 in INSN, then store one of them in JUMP_LABEL (INSN).
2915 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
2916 referenced in INSN, add a REG_LABEL note containing that label to INSN.
2917 Also, when there are consecutive labels, canonicalize on the last of them.
2918
2919 Note that two labels separated by a loop-beginning note
2920 must be kept distinct if we have not yet done loop-optimization,
2921 because the gap between them is where loop-optimize
2922 will want to move invariant code to. CROSS_JUMP tells us
2923 that loop-optimization is done with.
2924
2925 Once reload has completed (CROSS_JUMP non-zero), we need not consider
2926 two labels distinct if they are separated by only USE or CLOBBER insns. */
2927
2928 static void
2929 mark_jump_label (x, insn, cross_jump)
2930 register rtx x;
2931 rtx insn;
2932 int cross_jump;
2933 {
2934 register RTX_CODE code = GET_CODE (x);
2935 register int i;
2936 register char *fmt;
2937
2938 switch (code)
2939 {
2940 case PC:
2941 case CC0:
2942 case REG:
2943 case SUBREG:
2944 case CONST_INT:
2945 case SYMBOL_REF:
2946 case CONST_DOUBLE:
2947 case CLOBBER:
2948 case CALL:
2949 return;
2950
2951 case MEM:
2952 /* If this is a constant-pool reference, see if it is a label. */
2953 if (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
2954 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))
2955 mark_jump_label (get_pool_constant (XEXP (x, 0)), insn, cross_jump);
2956 break;
2957
2958 case LABEL_REF:
2959 {
2960 register rtx label = XEXP (x, 0);
2961 register rtx next;
2962 if (GET_CODE (label) != CODE_LABEL)
2963 abort ();
2964 /* Ignore references to labels of containing functions. */
2965 if (LABEL_REF_NONLOCAL_P (x))
2966 break;
2967 /* If there are other labels following this one,
2968 replace it with the last of the consecutive labels. */
2969 for (next = NEXT_INSN (label); next; next = NEXT_INSN (next))
2970 {
2971 if (GET_CODE (next) == CODE_LABEL)
2972 label = next;
2973 else if (cross_jump && GET_CODE (next) == INSN
2974 && (GET_CODE (PATTERN (next)) == USE
2975 || GET_CODE (PATTERN (next)) == CLOBBER))
2976 continue;
2977 else if (GET_CODE (next) != NOTE)
2978 break;
2979 else if (! cross_jump
2980 && (NOTE_LINE_NUMBER (next) == NOTE_INSN_LOOP_BEG
2981 || NOTE_LINE_NUMBER (next) == NOTE_INSN_FUNCTION_END))
2982 break;
2983 }
2984 XEXP (x, 0) = label;
2985 ++LABEL_NUSES (label);
2986 if (insn)
2987 {
2988 if (GET_CODE (insn) == JUMP_INSN)
2989 JUMP_LABEL (insn) = label;
2990 else if (! find_reg_note (insn, REG_LABEL, label))
2991 {
2992 rtx next = next_real_insn (label);
2993 /* Don't record labels that refer to dispatch tables.
2994 This is not necessary, since the tablejump
2995 references the same label.
2996 And if we did record them, flow.c would make worse code. */
2997 if (next == 0
2998 || ! (GET_CODE (next) == JUMP_INSN
2999 && (GET_CODE (PATTERN (next)) == ADDR_VEC
3000 || GET_CODE (PATTERN (next)) == ADDR_DIFF_VEC)))
3001 {
3002 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_LABEL, label,
3003 REG_NOTES (insn));
3004 /* Record in the note whether label is nonlocal. */
3005 LABEL_REF_NONLOCAL_P (REG_NOTES (insn))
3006 = LABEL_REF_NONLOCAL_P (x);
3007 }
3008 }
3009 }
3010 return;
3011 }
3012
3013 /* Do walk the labels in a vector, but not the first operand of an
3014 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
3015 case ADDR_VEC:
3016 case ADDR_DIFF_VEC:
3017 {
3018 int eltnum = code == ADDR_DIFF_VEC ? 1 : 0;
3019
3020 for (i = 0; i < XVECLEN (x, eltnum); i++)
3021 mark_jump_label (XVECEXP (x, eltnum, i), NULL_RTX, cross_jump);
3022 return;
3023 }
3024 }
3025
3026 fmt = GET_RTX_FORMAT (code);
3027 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3028 {
3029 if (fmt[i] == 'e')
3030 mark_jump_label (XEXP (x, i), insn, cross_jump);
3031 else if (fmt[i] == 'E')
3032 {
3033 register int j;
3034 for (j = 0; j < XVECLEN (x, i); j++)
3035 mark_jump_label (XVECEXP (x, i, j), insn, cross_jump);
3036 }
3037 }
3038 }
3039
3040 /* If all INSN does is set the pc, delete it,
3041 and delete the insn that set the condition codes for it
3042 if that's what the previous thing was. */
3043
3044 void
3045 delete_jump (insn)
3046 rtx insn;
3047 {
3048 register rtx set = single_set (insn);
3049
3050 if (set && GET_CODE (SET_DEST (set)) == PC)
3051 delete_computation (insn);
3052 }
3053
3054 /* Delete INSN and recursively delete insns that compute values used only
3055 by INSN. This uses the REG_DEAD notes computed during flow analysis.
3056 If we are running before flow.c, we need do nothing since flow.c will
3057 delete dead code. We also can't know if the registers being used are
3058 dead or not at this point.
3059
3060 Otherwise, look at all our REG_DEAD notes. If a previous insn does
3061 nothing other than set a register that dies in this insn, we can delete
3062 that insn as well.
3063
3064 On machines with CC0, if CC0 is used in this insn, we may be able to
3065 delete the insn that set it. */
3066
3067 void
3068 delete_computation (insn)
3069 rtx insn;
3070 {
3071 rtx note, next;
3072
3073 #ifdef HAVE_cc0
3074 if (reg_referenced_p (cc0_rtx, PATTERN (insn)))
3075 {
3076 rtx prev = prev_nonnote_insn (insn);
3077 /* We assume that at this stage
3078 CC's are always set explicitly
3079 and always immediately before the jump that
3080 will use them. So if the previous insn
3081 exists to set the CC's, delete it
3082 (unless it performs auto-increments, etc.). */
3083 if (prev && GET_CODE (prev) == INSN
3084 && sets_cc0_p (PATTERN (prev)))
3085 {
3086 if (sets_cc0_p (PATTERN (prev)) > 0
3087 && !FIND_REG_INC_NOTE (prev, NULL_RTX))
3088 delete_computation (prev);
3089 else
3090 /* Otherwise, show that cc0 won't be used. */
3091 REG_NOTES (prev) = gen_rtx (EXPR_LIST, REG_UNUSED,
3092 cc0_rtx, REG_NOTES (prev));
3093 }
3094 }
3095 #endif
3096
3097 for (note = REG_NOTES (insn); note; note = next)
3098 {
3099 rtx our_prev;
3100
3101 next = XEXP (note, 1);
3102
3103 if (REG_NOTE_KIND (note) != REG_DEAD
3104 /* Verify that the REG_NOTE is legitimate. */
3105 || GET_CODE (XEXP (note, 0)) != REG)
3106 continue;
3107
3108 for (our_prev = prev_nonnote_insn (insn);
3109 our_prev && GET_CODE (our_prev) == INSN;
3110 our_prev = prev_nonnote_insn (our_prev))
3111 {
3112 /* If we reach a SEQUENCE, it is too complex to try to
3113 do anything with it, so give up. */
3114 if (GET_CODE (PATTERN (our_prev)) == SEQUENCE)
3115 break;
3116
3117 if (GET_CODE (PATTERN (our_prev)) == USE
3118 && GET_CODE (XEXP (PATTERN (our_prev), 0)) == INSN)
3119 /* reorg creates USEs that look like this. We leave them
3120 alone because reorg needs them for its own purposes. */
3121 break;
3122
3123 if (reg_set_p (XEXP (note, 0), PATTERN (our_prev)))
3124 {
3125 if (FIND_REG_INC_NOTE (our_prev, NULL_RTX))
3126 break;
3127
3128 if (GET_CODE (PATTERN (our_prev)) == PARALLEL)
3129 {
3130 /* If we find a SET of something else, we can't
3131 delete the insn. */
3132
3133 int i;
3134
3135 for (i = 0; i < XVECLEN (PATTERN (our_prev), 0); i++)
3136 {
3137 rtx part = XVECEXP (PATTERN (our_prev), 0, i);
3138
3139 if (GET_CODE (part) == SET
3140 && SET_DEST (part) != XEXP (note, 0))
3141 break;
3142 }
3143
3144 if (i == XVECLEN (PATTERN (our_prev), 0))
3145 delete_computation (our_prev);
3146 }
3147 else if (GET_CODE (PATTERN (our_prev)) == SET
3148 && SET_DEST (PATTERN (our_prev)) == XEXP (note, 0))
3149 delete_computation (our_prev);
3150
3151 break;
3152 }
3153
3154 /* If OUR_PREV references the register that dies here, it is an
3155 additional use. Hence any prior SET isn't dead. However, this
3156 insn becomes the new place for the REG_DEAD note. */
3157 if (reg_overlap_mentioned_p (XEXP (note, 0),
3158 PATTERN (our_prev)))
3159 {
3160 XEXP (note, 1) = REG_NOTES (our_prev);
3161 REG_NOTES (our_prev) = note;
3162 break;
3163 }
3164 }
3165 }
3166
3167 delete_insn (insn);
3168 }
3169 \f
3170 /* Delete insn INSN from the chain of insns and update label ref counts.
3171 May delete some following insns as a consequence; may even delete
3172 a label elsewhere and insns that follow it.
3173
3174 Returns the first insn after INSN that was not deleted. */
3175
3176 rtx
3177 delete_insn (insn)
3178 register rtx insn;
3179 {
3180 register rtx next = NEXT_INSN (insn);
3181 register rtx prev = PREV_INSN (insn);
3182 register int was_code_label = (GET_CODE (insn) == CODE_LABEL);
3183 register int dont_really_delete = 0;
3184
3185 while (next && INSN_DELETED_P (next))
3186 next = NEXT_INSN (next);
3187
3188 /* This insn is already deleted => return first following nondeleted. */
3189 if (INSN_DELETED_P (insn))
3190 return next;
3191
3192 /* Don't delete user-declared labels. Convert them to special NOTEs
3193 instead. */
3194 if (was_code_label && LABEL_NAME (insn) != 0
3195 && optimize && ! dont_really_delete)
3196 {
3197 PUT_CODE (insn, NOTE);
3198 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED_LABEL;
3199 NOTE_SOURCE_FILE (insn) = 0;
3200 dont_really_delete = 1;
3201 }
3202 else
3203 /* Mark this insn as deleted. */
3204 INSN_DELETED_P (insn) = 1;
3205
3206 /* If this is an unconditional jump, delete it from the jump chain. */
3207 if (simplejump_p (insn))
3208 delete_from_jump_chain (insn);
3209
3210 /* If instruction is followed by a barrier,
3211 delete the barrier too. */
3212
3213 if (next != 0 && GET_CODE (next) == BARRIER)
3214 {
3215 INSN_DELETED_P (next) = 1;
3216 next = NEXT_INSN (next);
3217 }
3218
3219 /* Patch out INSN (and the barrier if any) */
3220
3221 if (optimize && ! dont_really_delete)
3222 {
3223 if (prev)
3224 {
3225 NEXT_INSN (prev) = next;
3226 if (GET_CODE (prev) == INSN && GET_CODE (PATTERN (prev)) == SEQUENCE)
3227 NEXT_INSN (XVECEXP (PATTERN (prev), 0,
3228 XVECLEN (PATTERN (prev), 0) - 1)) = next;
3229 }
3230
3231 if (next)
3232 {
3233 PREV_INSN (next) = prev;
3234 if (GET_CODE (next) == INSN && GET_CODE (PATTERN (next)) == SEQUENCE)
3235 PREV_INSN (XVECEXP (PATTERN (next), 0, 0)) = prev;
3236 }
3237
3238 if (prev && NEXT_INSN (prev) == 0)
3239 set_last_insn (prev);
3240 }
3241
3242 /* If deleting a jump, decrement the count of the label,
3243 and delete the label if it is now unused. */
3244
3245 if (GET_CODE (insn) == JUMP_INSN && JUMP_LABEL (insn))
3246 if (--LABEL_NUSES (JUMP_LABEL (insn)) == 0)
3247 {
3248 /* This can delete NEXT or PREV,
3249 either directly if NEXT is JUMP_LABEL (INSN),
3250 or indirectly through more levels of jumps. */
3251 delete_insn (JUMP_LABEL (insn));
3252 /* I feel a little doubtful about this loop,
3253 but I see no clean and sure alternative way
3254 to find the first insn after INSN that is not now deleted.
3255 I hope this works. */
3256 while (next && INSN_DELETED_P (next))
3257 next = NEXT_INSN (next);
3258 return next;
3259 }
3260
3261 while (prev && (INSN_DELETED_P (prev) || GET_CODE (prev) == NOTE))
3262 prev = PREV_INSN (prev);
3263
3264 /* If INSN was a label and a dispatch table follows it,
3265 delete the dispatch table. The tablejump must have gone already.
3266 It isn't useful to fall through into a table. */
3267
3268 if (was_code_label
3269 && NEXT_INSN (insn) != 0
3270 && GET_CODE (NEXT_INSN (insn)) == JUMP_INSN
3271 && (GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_VEC
3272 || GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_DIFF_VEC))
3273 next = delete_insn (NEXT_INSN (insn));
3274
3275 /* If INSN was a label, delete insns following it if now unreachable. */
3276
3277 if (was_code_label && prev && GET_CODE (prev) == BARRIER)
3278 {
3279 register RTX_CODE code;
3280 while (next != 0
3281 && ((code = GET_CODE (next)) == INSN
3282 || code == JUMP_INSN || code == CALL_INSN
3283 || code == NOTE
3284 || (code == CODE_LABEL && INSN_DELETED_P (next))))
3285 {
3286 if (code == NOTE
3287 && NOTE_LINE_NUMBER (next) != NOTE_INSN_FUNCTION_END)
3288 next = NEXT_INSN (next);
3289 /* Keep going past other deleted labels to delete what follows. */
3290 else if (code == CODE_LABEL && INSN_DELETED_P (next))
3291 next = NEXT_INSN (next);
3292 else
3293 /* Note: if this deletes a jump, it can cause more
3294 deletion of unreachable code, after a different label.
3295 As long as the value from this recursive call is correct,
3296 this invocation functions correctly. */
3297 next = delete_insn (next);
3298 }
3299 }
3300
3301 return next;
3302 }
3303
3304 /* Advance from INSN till reaching something not deleted
3305 then return that. May return INSN itself. */
3306
3307 rtx
3308 next_nondeleted_insn (insn)
3309 rtx insn;
3310 {
3311 while (INSN_DELETED_P (insn))
3312 insn = NEXT_INSN (insn);
3313 return insn;
3314 }
3315 \f
3316 /* Delete a range of insns from FROM to TO, inclusive.
3317 This is for the sake of peephole optimization, so assume
3318 that whatever these insns do will still be done by a new
3319 peephole insn that will replace them. */
3320
3321 void
3322 delete_for_peephole (from, to)
3323 register rtx from, to;
3324 {
3325 register rtx insn = from;
3326
3327 while (1)
3328 {
3329 register rtx next = NEXT_INSN (insn);
3330 register rtx prev = PREV_INSN (insn);
3331
3332 if (GET_CODE (insn) != NOTE)
3333 {
3334 INSN_DELETED_P (insn) = 1;
3335
3336 /* Patch this insn out of the chain. */
3337 /* We don't do this all at once, because we
3338 must preserve all NOTEs. */
3339 if (prev)
3340 NEXT_INSN (prev) = next;
3341
3342 if (next)
3343 PREV_INSN (next) = prev;
3344 }
3345
3346 if (insn == to)
3347 break;
3348 insn = next;
3349 }
3350
3351 /* Note that if TO is an unconditional jump
3352 we *do not* delete the BARRIER that follows,
3353 since the peephole that replaces this sequence
3354 is also an unconditional jump in that case. */
3355 }
3356 \f
3357 /* Invert the condition of the jump JUMP, and make it jump
3358 to label NLABEL instead of where it jumps now. */
3359
3360 int
3361 invert_jump (jump, nlabel)
3362 rtx jump, nlabel;
3363 {
3364 register rtx olabel = JUMP_LABEL (jump);
3365
3366 /* We have to either invert the condition and change the label or
3367 do neither. Either operation could fail. We first try to invert
3368 the jump. If that succeeds, we try changing the label. If that fails,
3369 we invert the jump back to what it was. */
3370
3371 if (! invert_exp (PATTERN (jump), jump))
3372 return 0;
3373
3374 if (redirect_jump (jump, nlabel))
3375 return 1;
3376
3377 if (! invert_exp (PATTERN (jump), jump))
3378 /* This should just be putting it back the way it was. */
3379 abort ();
3380
3381 return 0;
3382 }
3383
3384 /* Invert the jump condition of rtx X contained in jump insn, INSN.
3385
3386 Return 1 if we can do so, 0 if we cannot find a way to do so that
3387 matches a pattern. */
3388
3389 int
3390 invert_exp (x, insn)
3391 rtx x;
3392 rtx insn;
3393 {
3394 register RTX_CODE code;
3395 register int i;
3396 register char *fmt;
3397
3398 code = GET_CODE (x);
3399
3400 if (code == IF_THEN_ELSE)
3401 {
3402 register rtx comp = XEXP (x, 0);
3403 register rtx tem;
3404
3405 /* We can do this in two ways: The preferable way, which can only
3406 be done if this is not an integer comparison, is to reverse
3407 the comparison code. Otherwise, swap the THEN-part and ELSE-part
3408 of the IF_THEN_ELSE. If we can't do either, fail. */
3409
3410 if (can_reverse_comparison_p (comp, insn)
3411 && validate_change (insn, &XEXP (x, 0),
3412 gen_rtx (reverse_condition (GET_CODE (comp)),
3413 GET_MODE (comp), XEXP (comp, 0),
3414 XEXP (comp, 1)), 0))
3415 return 1;
3416
3417 tem = XEXP (x, 1);
3418 validate_change (insn, &XEXP (x, 1), XEXP (x, 2), 1);
3419 validate_change (insn, &XEXP (x, 2), tem, 1);
3420 return apply_change_group ();
3421 }
3422
3423 fmt = GET_RTX_FORMAT (code);
3424 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3425 {
3426 if (fmt[i] == 'e')
3427 if (! invert_exp (XEXP (x, i), insn))
3428 return 0;
3429 if (fmt[i] == 'E')
3430 {
3431 register int j;
3432 for (j = 0; j < XVECLEN (x, i); j++)
3433 if (!invert_exp (XVECEXP (x, i, j), insn))
3434 return 0;
3435 }
3436 }
3437
3438 return 1;
3439 }
3440 \f
3441 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
3442 If the old jump target label is unused as a result,
3443 it and the code following it may be deleted.
3444
3445 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
3446 RETURN insn.
3447
3448 The return value will be 1 if the change was made, 0 if it wasn't (this
3449 can only occur for NLABEL == 0). */
3450
3451 int
3452 redirect_jump (jump, nlabel)
3453 rtx jump, nlabel;
3454 {
3455 register rtx olabel = JUMP_LABEL (jump);
3456
3457 if (nlabel == olabel)
3458 return 1;
3459
3460 if (! redirect_exp (&PATTERN (jump), olabel, nlabel, jump))
3461 return 0;
3462
3463 /* If this is an unconditional branch, delete it from the jump_chain of
3464 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
3465 have UID's in range and JUMP_CHAIN is valid). */
3466 if (jump_chain && (simplejump_p (jump)
3467 || GET_CODE (PATTERN (jump)) == RETURN))
3468 {
3469 int label_index = nlabel ? INSN_UID (nlabel) : 0;
3470
3471 delete_from_jump_chain (jump);
3472 if (label_index < max_jump_chain
3473 && INSN_UID (jump) < max_jump_chain)
3474 {
3475 jump_chain[INSN_UID (jump)] = jump_chain[label_index];
3476 jump_chain[label_index] = jump;
3477 }
3478 }
3479
3480 JUMP_LABEL (jump) = nlabel;
3481 if (nlabel)
3482 ++LABEL_NUSES (nlabel);
3483
3484 if (olabel && --LABEL_NUSES (olabel) == 0)
3485 delete_insn (olabel);
3486
3487 return 1;
3488 }
3489
3490 /* Delete the instruction JUMP from any jump chain it might be on. */
3491
3492 static void
3493 delete_from_jump_chain (jump)
3494 rtx jump;
3495 {
3496 int index;
3497 rtx olabel = JUMP_LABEL (jump);
3498
3499 /* Handle unconditional jumps. */
3500 if (jump_chain && olabel != 0
3501 && INSN_UID (olabel) < max_jump_chain
3502 && simplejump_p (jump))
3503 index = INSN_UID (olabel);
3504 /* Handle return insns. */
3505 else if (jump_chain && GET_CODE (PATTERN (jump)) == RETURN)
3506 index = 0;
3507 else return;
3508
3509 if (jump_chain[index] == jump)
3510 jump_chain[index] = jump_chain[INSN_UID (jump)];
3511 else
3512 {
3513 rtx insn;
3514
3515 for (insn = jump_chain[index];
3516 insn != 0;
3517 insn = jump_chain[INSN_UID (insn)])
3518 if (jump_chain[INSN_UID (insn)] == jump)
3519 {
3520 jump_chain[INSN_UID (insn)] = jump_chain[INSN_UID (jump)];
3521 break;
3522 }
3523 }
3524 }
3525
3526 /* If NLABEL is nonzero, throughout the rtx at LOC,
3527 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
3528 zero, alter (RETURN) to (LABEL_REF NLABEL).
3529
3530 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
3531 validity with validate_change. Convert (set (pc) (label_ref olabel))
3532 to (return).
3533
3534 Return 0 if we found a change we would like to make but it is invalid.
3535 Otherwise, return 1. */
3536
3537 int
3538 redirect_exp (loc, olabel, nlabel, insn)
3539 rtx *loc;
3540 rtx olabel, nlabel;
3541 rtx insn;
3542 {
3543 register rtx x = *loc;
3544 register RTX_CODE code = GET_CODE (x);
3545 register int i;
3546 register char *fmt;
3547
3548 if (code == LABEL_REF)
3549 {
3550 if (XEXP (x, 0) == olabel)
3551 {
3552 if (nlabel)
3553 XEXP (x, 0) = nlabel;
3554 else
3555 return validate_change (insn, loc, gen_rtx (RETURN, VOIDmode), 0);
3556 return 1;
3557 }
3558 }
3559 else if (code == RETURN && olabel == 0)
3560 {
3561 x = gen_rtx (LABEL_REF, VOIDmode, nlabel);
3562 if (loc == &PATTERN (insn))
3563 x = gen_rtx (SET, VOIDmode, pc_rtx, x);
3564 return validate_change (insn, loc, x, 0);
3565 }
3566
3567 if (code == SET && nlabel == 0 && SET_DEST (x) == pc_rtx
3568 && GET_CODE (SET_SRC (x)) == LABEL_REF
3569 && XEXP (SET_SRC (x), 0) == olabel)
3570 return validate_change (insn, loc, gen_rtx (RETURN, VOIDmode), 0);
3571
3572 fmt = GET_RTX_FORMAT (code);
3573 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3574 {
3575 if (fmt[i] == 'e')
3576 if (! redirect_exp (&XEXP (x, i), olabel, nlabel, insn))
3577 return 0;
3578 if (fmt[i] == 'E')
3579 {
3580 register int j;
3581 for (j = 0; j < XVECLEN (x, i); j++)
3582 if (! redirect_exp (&XVECEXP (x, i, j), olabel, nlabel, insn))
3583 return 0;
3584 }
3585 }
3586
3587 return 1;
3588 }
3589 \f
3590 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
3591
3592 If the old jump target label (before the dispatch table) becomes unused,
3593 it and the dispatch table may be deleted. In that case, find the insn
3594 before the jump references that label and delete it and logical successors
3595 too. */
3596
3597 void
3598 redirect_tablejump (jump, nlabel)
3599 rtx jump, nlabel;
3600 {
3601 register rtx olabel = JUMP_LABEL (jump);
3602
3603 /* Add this jump to the jump_chain of NLABEL. */
3604 if (jump_chain && INSN_UID (nlabel) < max_jump_chain
3605 && INSN_UID (jump) < max_jump_chain)
3606 {
3607 jump_chain[INSN_UID (jump)] = jump_chain[INSN_UID (nlabel)];
3608 jump_chain[INSN_UID (nlabel)] = jump;
3609 }
3610
3611 PATTERN (jump) = gen_jump (nlabel);
3612 JUMP_LABEL (jump) = nlabel;
3613 ++LABEL_NUSES (nlabel);
3614 INSN_CODE (jump) = -1;
3615
3616 if (--LABEL_NUSES (olabel) == 0)
3617 {
3618 delete_labelref_insn (jump, olabel, 0);
3619 delete_insn (olabel);
3620 }
3621 }
3622
3623 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
3624 If we found one, delete it and then delete this insn if DELETE_THIS is
3625 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
3626
3627 static int
3628 delete_labelref_insn (insn, label, delete_this)
3629 rtx insn, label;
3630 int delete_this;
3631 {
3632 int deleted = 0;
3633 rtx link;
3634
3635 if (GET_CODE (insn) != NOTE
3636 && reg_mentioned_p (label, PATTERN (insn)))
3637 {
3638 if (delete_this)
3639 {
3640 delete_insn (insn);
3641 deleted = 1;
3642 }
3643 else
3644 return 1;
3645 }
3646
3647 for (link = LOG_LINKS (insn); link; link = XEXP (link, 1))
3648 if (delete_labelref_insn (XEXP (link, 0), label, 1))
3649 {
3650 if (delete_this)
3651 {
3652 delete_insn (insn);
3653 deleted = 1;
3654 }
3655 else
3656 return 1;
3657 }
3658
3659 return deleted;
3660 }
3661 \f
3662 /* Like rtx_equal_p except that it considers two REGs as equal
3663 if they renumber to the same value. */
3664
3665 int
3666 rtx_renumbered_equal_p (x, y)
3667 rtx x, y;
3668 {
3669 register int i;
3670 register RTX_CODE code = GET_CODE (x);
3671 register char *fmt;
3672
3673 if (x == y)
3674 return 1;
3675 if ((code == REG || (code == SUBREG && GET_CODE (SUBREG_REG (x)) == REG))
3676 && (GET_CODE (y) == REG || (GET_CODE (y) == SUBREG
3677 && GET_CODE (SUBREG_REG (y)) == REG)))
3678 {
3679 register int j;
3680
3681 if (GET_MODE (x) != GET_MODE (y))
3682 return 0;
3683
3684 /* If we haven't done any renumbering, don't
3685 make any assumptions. */
3686 if (reg_renumber == 0)
3687 return rtx_equal_p (x, y);
3688
3689 if (code == SUBREG)
3690 {
3691 i = REGNO (SUBREG_REG (x));
3692 if (reg_renumber[i] >= 0)
3693 i = reg_renumber[i];
3694 i += SUBREG_WORD (x);
3695 }
3696 else
3697 {
3698 i = REGNO (x);
3699 if (reg_renumber[i] >= 0)
3700 i = reg_renumber[i];
3701 }
3702 if (GET_CODE (y) == SUBREG)
3703 {
3704 j = REGNO (SUBREG_REG (y));
3705 if (reg_renumber[j] >= 0)
3706 j = reg_renumber[j];
3707 j += SUBREG_WORD (y);
3708 }
3709 else
3710 {
3711 j = REGNO (y);
3712 if (reg_renumber[j] >= 0)
3713 j = reg_renumber[j];
3714 }
3715 return i == j;
3716 }
3717 /* Now we have disposed of all the cases
3718 in which different rtx codes can match. */
3719 if (code != GET_CODE (y))
3720 return 0;
3721 switch (code)
3722 {
3723 case PC:
3724 case CC0:
3725 case ADDR_VEC:
3726 case ADDR_DIFF_VEC:
3727 return 0;
3728
3729 case CONST_INT:
3730 return XINT (x, 0) == XINT (y, 0);
3731
3732 case LABEL_REF:
3733 /* We can't assume nonlocal labels have their following insns yet. */
3734 if (LABEL_REF_NONLOCAL_P (x) || LABEL_REF_NONLOCAL_P (y))
3735 return XEXP (x, 0) == XEXP (y, 0);
3736 /* Two label-refs are equivalent if they point at labels
3737 in the same position in the instruction stream. */
3738 return (next_real_insn (XEXP (x, 0))
3739 == next_real_insn (XEXP (y, 0)));
3740
3741 case SYMBOL_REF:
3742 return XSTR (x, 0) == XSTR (y, 0);
3743 }
3744
3745 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
3746
3747 if (GET_MODE (x) != GET_MODE (y))
3748 return 0;
3749
3750 /* Compare the elements. If any pair of corresponding elements
3751 fail to match, return 0 for the whole things. */
3752
3753 fmt = GET_RTX_FORMAT (code);
3754 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3755 {
3756 register int j;
3757 switch (fmt[i])
3758 {
3759 case 'w':
3760 if (XWINT (x, i) != XWINT (y, i))
3761 return 0;
3762 break;
3763
3764 case 'i':
3765 if (XINT (x, i) != XINT (y, i))
3766 return 0;
3767 break;
3768
3769 case 's':
3770 if (strcmp (XSTR (x, i), XSTR (y, i)))
3771 return 0;
3772 break;
3773
3774 case 'e':
3775 if (! rtx_renumbered_equal_p (XEXP (x, i), XEXP (y, i)))
3776 return 0;
3777 break;
3778
3779 case 'u':
3780 if (XEXP (x, i) != XEXP (y, i))
3781 return 0;
3782 /* fall through. */
3783 case '0':
3784 break;
3785
3786 case 'E':
3787 if (XVECLEN (x, i) != XVECLEN (y, i))
3788 return 0;
3789 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
3790 if (!rtx_renumbered_equal_p (XVECEXP (x, i, j), XVECEXP (y, i, j)))
3791 return 0;
3792 break;
3793
3794 default:
3795 abort ();
3796 }
3797 }
3798 return 1;
3799 }
3800 \f
3801 /* If X is a hard register or equivalent to one or a subregister of one,
3802 return the hard register number. If X is a pseudo register that was not
3803 assigned a hard register, return the pseudo register number. Otherwise,
3804 return -1. Any rtx is valid for X. */
3805
3806 int
3807 true_regnum (x)
3808 rtx x;
3809 {
3810 if (GET_CODE (x) == REG)
3811 {
3812 if (REGNO (x) >= FIRST_PSEUDO_REGISTER && reg_renumber[REGNO (x)] >= 0)
3813 return reg_renumber[REGNO (x)];
3814 return REGNO (x);
3815 }
3816 if (GET_CODE (x) == SUBREG)
3817 {
3818 int base = true_regnum (SUBREG_REG (x));
3819 if (base >= 0 && base < FIRST_PSEUDO_REGISTER)
3820 return SUBREG_WORD (x) + base;
3821 }
3822 return -1;
3823 }
3824 \f
3825 /* Optimize code of the form:
3826
3827 for (x = a[i]; x; ...)
3828 ...
3829 for (x = a[i]; x; ...)
3830 ...
3831 foo:
3832
3833 Loop optimize will change the above code into
3834
3835 if (x = a[i])
3836 for (;;)
3837 { ...; if (! (x = ...)) break; }
3838 if (x = a[i])
3839 for (;;)
3840 { ...; if (! (x = ...)) break; }
3841 foo:
3842
3843 In general, if the first test fails, the program can branch
3844 directly to `foo' and skip the second try which is doomed to fail.
3845 We run this after loop optimization and before flow analysis. */
3846
3847 /* When comparing the insn patterns, we track the fact that different
3848 pseudo-register numbers may have been used in each computation.
3849 The following array stores an equivalence -- same_regs[I] == J means
3850 that pseudo register I was used in the first set of tests in a context
3851 where J was used in the second set. We also count the number of such
3852 pending equivalences. If nonzero, the expressions really aren't the
3853 same. */
3854
3855 static short *same_regs;
3856
3857 static int num_same_regs;
3858
3859 /* Track any registers modified between the target of the first jump and
3860 the second jump. They never compare equal. */
3861
3862 static char *modified_regs;
3863
3864 /* Record if memory was modified. */
3865
3866 static int modified_mem;
3867
3868 /* Called via note_stores on each insn between the target of the first
3869 branch and the second branch. It marks any changed registers. */
3870
3871 static void
3872 mark_modified_reg (dest, x)
3873 rtx dest;
3874 rtx x;
3875 {
3876 int regno, i;
3877
3878 if (GET_CODE (dest) == SUBREG)
3879 dest = SUBREG_REG (dest);
3880
3881 if (GET_CODE (dest) == MEM)
3882 modified_mem = 1;
3883
3884 if (GET_CODE (dest) != REG)
3885 return;
3886
3887 regno = REGNO (dest);
3888 if (regno >= FIRST_PSEUDO_REGISTER)
3889 modified_regs[regno] = 1;
3890 else
3891 for (i = 0; i < HARD_REGNO_NREGS (regno, GET_MODE (dest)); i++)
3892 modified_regs[regno + i] = 1;
3893 }
3894
3895 /* F is the first insn in the chain of insns. */
3896
3897 void
3898 thread_jumps (f, max_reg, verbose)
3899 rtx f;
3900 int max_reg;
3901 int verbose;
3902 {
3903 /* Basic algorithm is to find a conditional branch,
3904 the label it may branch to, and the branch after
3905 that label. If the two branches test the same condition,
3906 walk back from both branch paths until the insn patterns
3907 differ, or code labels are hit. If we make it back to
3908 the target of the first branch, then we know that the first branch
3909 will either always succeed or always fail depending on the relative
3910 senses of the two branches. So adjust the first branch accordingly
3911 in this case. */
3912
3913 rtx label, b1, b2, t1, t2;
3914 enum rtx_code code1, code2;
3915 rtx b1op0, b1op1, b2op0, b2op1;
3916 int changed = 1;
3917 int i;
3918 short *all_reset;
3919
3920 /* Allocate register tables and quick-reset table. */
3921 modified_regs = (char *) alloca (max_reg * sizeof (char));
3922 same_regs = (short *) alloca (max_reg * sizeof (short));
3923 all_reset = (short *) alloca (max_reg * sizeof (short));
3924 for (i = 0; i < max_reg; i++)
3925 all_reset[i] = -1;
3926
3927 while (changed)
3928 {
3929 changed = 0;
3930
3931 for (b1 = f; b1; b1 = NEXT_INSN (b1))
3932 {
3933 /* Get to a candidate branch insn. */
3934 if (GET_CODE (b1) != JUMP_INSN
3935 || ! condjump_p (b1) || simplejump_p (b1)
3936 || JUMP_LABEL (b1) == 0)
3937 continue;
3938
3939 bzero (modified_regs, max_reg * sizeof (char));
3940 modified_mem = 0;
3941
3942 bcopy (all_reset, same_regs, max_reg * sizeof (short));
3943 num_same_regs = 0;
3944
3945 label = JUMP_LABEL (b1);
3946
3947 /* Look for a branch after the target. Record any registers and
3948 memory modified between the target and the branch. Stop when we
3949 get to a label since we can't know what was changed there. */
3950 for (b2 = NEXT_INSN (label); b2; b2 = NEXT_INSN (b2))
3951 {
3952 if (GET_CODE (b2) == CODE_LABEL)
3953 break;
3954
3955 else if (GET_CODE (b2) == JUMP_INSN)
3956 {
3957 /* If this is an unconditional jump and is the only use of
3958 its target label, we can follow it. */
3959 if (simplejump_p (b2)
3960 && JUMP_LABEL (b2) != 0
3961 && LABEL_NUSES (JUMP_LABEL (b2)) == 1)
3962 {
3963 b2 = JUMP_LABEL (b2);
3964 continue;
3965 }
3966 else
3967 break;
3968 }
3969
3970 if (GET_CODE (b2) != CALL_INSN && GET_CODE (b2) != INSN)
3971 continue;
3972
3973 if (GET_CODE (b2) == CALL_INSN)
3974 {
3975 modified_mem = 1;
3976 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
3977 if (call_used_regs[i] && ! fixed_regs[i]
3978 && i != STACK_POINTER_REGNUM
3979 && i != FRAME_POINTER_REGNUM
3980 && i != ARG_POINTER_REGNUM)
3981 modified_regs[i] = 1;
3982 }
3983
3984 note_stores (PATTERN (b2), mark_modified_reg);
3985 }
3986
3987 /* Check the next candidate branch insn from the label
3988 of the first. */
3989 if (b2 == 0
3990 || GET_CODE (b2) != JUMP_INSN
3991 || b2 == b1
3992 || ! condjump_p (b2)
3993 || simplejump_p (b2))
3994 continue;
3995
3996 /* Get the comparison codes and operands, reversing the
3997 codes if appropriate. If we don't have comparison codes,
3998 we can't do anything. */
3999 b1op0 = XEXP (XEXP (SET_SRC (PATTERN (b1)), 0), 0);
4000 b1op1 = XEXP (XEXP (SET_SRC (PATTERN (b1)), 0), 1);
4001 code1 = GET_CODE (XEXP (SET_SRC (PATTERN (b1)), 0));
4002 if (XEXP (SET_SRC (PATTERN (b1)), 1) == pc_rtx)
4003 code1 = reverse_condition (code1);
4004
4005 b2op0 = XEXP (XEXP (SET_SRC (PATTERN (b2)), 0), 0);
4006 b2op1 = XEXP (XEXP (SET_SRC (PATTERN (b2)), 0), 1);
4007 code2 = GET_CODE (XEXP (SET_SRC (PATTERN (b2)), 0));
4008 if (XEXP (SET_SRC (PATTERN (b2)), 1) == pc_rtx)
4009 code2 = reverse_condition (code2);
4010
4011 /* If they test the same things and knowing that B1 branches
4012 tells us whether or not B2 branches, check if we
4013 can thread the branch. */
4014 if (rtx_equal_for_thread_p (b1op0, b2op0, b2)
4015 && rtx_equal_for_thread_p (b1op1, b2op1, b2)
4016 && (comparison_dominates_p (code1, code2)
4017 || comparison_dominates_p (code1, reverse_condition (code2))))
4018 {
4019 t1 = prev_nonnote_insn (b1);
4020 t2 = prev_nonnote_insn (b2);
4021
4022 while (t1 != 0 && t2 != 0)
4023 {
4024 if (t1 == 0 || t2 == 0)
4025 break;
4026
4027 if (t2 == label)
4028 {
4029 /* We have reached the target of the first branch.
4030 If there are no pending register equivalents,
4031 we know that this branch will either always
4032 succeed (if the senses of the two branches are
4033 the same) or always fail (if not). */
4034 rtx new_label;
4035
4036 if (num_same_regs != 0)
4037 break;
4038
4039 if (comparison_dominates_p (code1, code2))
4040 new_label = JUMP_LABEL (b2);
4041 else
4042 new_label = get_label_after (b2);
4043
4044 if (JUMP_LABEL (b1) != new_label
4045 && redirect_jump (b1, new_label))
4046 changed = 1;
4047 break;
4048 }
4049
4050 /* If either of these is not a normal insn (it might be
4051 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
4052 have already been skipped above.) Similarly, fail
4053 if the insns are different. */
4054 if (GET_CODE (t1) != INSN || GET_CODE (t2) != INSN
4055 || recog_memoized (t1) != recog_memoized (t2)
4056 || ! rtx_equal_for_thread_p (PATTERN (t1),
4057 PATTERN (t2), t2))
4058 break;
4059
4060 t1 = prev_nonnote_insn (t1);
4061 t2 = prev_nonnote_insn (t2);
4062 }
4063 }
4064 }
4065 }
4066 }
4067 \f
4068 /* This is like RTX_EQUAL_P except that it knows about our handling of
4069 possibly equivalent registers and knows to consider volatile and
4070 modified objects as not equal.
4071
4072 YINSN is the insn containing Y. */
4073
4074 int
4075 rtx_equal_for_thread_p (x, y, yinsn)
4076 rtx x, y;
4077 rtx yinsn;
4078 {
4079 register int i;
4080 register int j;
4081 register enum rtx_code code;
4082 register char *fmt;
4083
4084 code = GET_CODE (x);
4085 /* Rtx's of different codes cannot be equal. */
4086 if (code != GET_CODE (y))
4087 return 0;
4088
4089 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
4090 (REG:SI x) and (REG:HI x) are NOT equivalent. */
4091
4092 if (GET_MODE (x) != GET_MODE (y))
4093 return 0;
4094
4095 /* Handle special-cases first. */
4096 switch (code)
4097 {
4098 case REG:
4099 if (REGNO (x) == REGNO (y) && ! modified_regs[REGNO (x)])
4100 return 1;
4101
4102 /* If neither is user variable or hard register, check for possible
4103 equivalence. */
4104 if (REG_USERVAR_P (x) || REG_USERVAR_P (y)
4105 || REGNO (x) < FIRST_PSEUDO_REGISTER
4106 || REGNO (y) < FIRST_PSEUDO_REGISTER)
4107 return 0;
4108
4109 if (same_regs[REGNO (x)] == -1)
4110 {
4111 same_regs[REGNO (x)] = REGNO (y);
4112 num_same_regs++;
4113
4114 /* If this is the first time we are seeing a register on the `Y'
4115 side, see if it is the last use. If not, we can't thread the
4116 jump, so mark it as not equivalent. */
4117 if (regno_last_uid[REGNO (y)] != INSN_UID (yinsn))
4118 return 0;
4119
4120 return 1;
4121 }
4122 else
4123 return (same_regs[REGNO (x)] == REGNO (y));
4124
4125 break;
4126
4127 case MEM:
4128 /* If memory modified or either volatile, not equivalent.
4129 Else, check address. */
4130 if (modified_mem || MEM_VOLATILE_P (x) || MEM_VOLATILE_P (y))
4131 return 0;
4132
4133 return rtx_equal_for_thread_p (XEXP (x, 0), XEXP (y, 0), yinsn);
4134
4135 case ASM_INPUT:
4136 if (MEM_VOLATILE_P (x) || MEM_VOLATILE_P (y))
4137 return 0;
4138
4139 break;
4140
4141 case SET:
4142 /* Cancel a pending `same_regs' if setting equivalenced registers.
4143 Then process source. */
4144 if (GET_CODE (SET_DEST (x)) == REG
4145 && GET_CODE (SET_DEST (y)) == REG)
4146 {
4147 if (same_regs[REGNO (SET_DEST (x))] == REGNO (SET_DEST (y)))
4148 {
4149 same_regs[REGNO (SET_DEST (x))] = -1;
4150 num_same_regs--;
4151 }
4152 else if (REGNO (SET_DEST (x)) != REGNO (SET_DEST (y)))
4153 return 0;
4154 }
4155 else
4156 if (rtx_equal_for_thread_p (SET_DEST (x), SET_DEST (y), yinsn) == 0)
4157 return 0;
4158
4159 return rtx_equal_for_thread_p (SET_SRC (x), SET_SRC (y), yinsn);
4160
4161 case LABEL_REF:
4162 return XEXP (x, 0) == XEXP (y, 0);
4163
4164 case SYMBOL_REF:
4165 return XSTR (x, 0) == XSTR (y, 0);
4166 }
4167
4168 if (x == y)
4169 return 1;
4170
4171 fmt = GET_RTX_FORMAT (code);
4172 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
4173 {
4174 switch (fmt[i])
4175 {
4176 case 'w':
4177 if (XWINT (x, i) != XWINT (y, i))
4178 return 0;
4179 break;
4180
4181 case 'n':
4182 case 'i':
4183 if (XINT (x, i) != XINT (y, i))
4184 return 0;
4185 break;
4186
4187 case 'V':
4188 case 'E':
4189 /* Two vectors must have the same length. */
4190 if (XVECLEN (x, i) != XVECLEN (y, i))
4191 return 0;
4192
4193 /* And the corresponding elements must match. */
4194 for (j = 0; j < XVECLEN (x, i); j++)
4195 if (rtx_equal_for_thread_p (XVECEXP (x, i, j),
4196 XVECEXP (y, i, j), yinsn) == 0)
4197 return 0;
4198 break;
4199
4200 case 'e':
4201 if (rtx_equal_for_thread_p (XEXP (x, i), XEXP (y, i), yinsn) == 0)
4202 return 0;
4203 break;
4204
4205 case 'S':
4206 case 's':
4207 if (strcmp (XSTR (x, i), XSTR (y, i)))
4208 return 0;
4209 break;
4210
4211 case 'u':
4212 /* These are just backpointers, so they don't matter. */
4213 break;
4214
4215 case '0':
4216 break;
4217
4218 /* It is believed that rtx's at this level will never
4219 contain anything but integers and other rtx's,
4220 except for within LABEL_REFs and SYMBOL_REFs. */
4221 default:
4222 abort ();
4223 }
4224 }
4225 return 1;
4226 }
GNU Compiler Collection
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