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1 /* Optimize jump instructions, for GNU compiler.
2 Copyright (C) 1987, 88, 89, 91, 92, 1993 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 (GET_MODE (SET_DEST (pbody)))
350 > stack_adjust_amount)
351 break;
352 total_pushed += GET_MODE_SIZE (GET_MODE (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 (GET_MODE (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 /* We use regno_last_note_uid so as not to delete the setting
544 of a reg that's used in notes. A subsequent optimization
545 might arrange to use that reg for real. */
546 && regno_last_note_uid[REGNO (SET_DEST (set))] == INSN_UID (insn)
547 && ! side_effects_p (SET_SRC (set)))
548 delete_insn (insn);
549 }
550
551 /* Now iterate optimizing jumps until nothing changes over one pass. */
552 changed = 1;
553 while (changed)
554 {
555 changed = 0;
556
557 for (insn = f; insn; insn = next)
558 {
559 rtx reallabelprev;
560 rtx temp, temp1, temp2, temp3, temp4, temp5, temp6;
561 rtx nlabel;
562 int this_is_simplejump, this_is_condjump, reversep;
563 #if 0
564 /* If NOT the first iteration, if this is the last jump pass
565 (just before final), do the special peephole optimizations.
566 Avoiding the first iteration gives ordinary jump opts
567 a chance to work before peephole opts. */
568
569 if (reload_completed && !first && !flag_no_peephole)
570 if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
571 peephole (insn);
572 #endif
573
574 /* That could have deleted some insns after INSN, so check now
575 what the following insn is. */
576
577 next = NEXT_INSN (insn);
578
579 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
580 jump. Try to optimize by duplicating the loop exit test if so.
581 This is only safe immediately after regscan, because it uses
582 the values of regno_first_uid and regno_last_uid. */
583 if (after_regscan && GET_CODE (insn) == NOTE
584 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG
585 && (temp1 = next_nonnote_insn (insn)) != 0
586 && simplejump_p (temp1))
587 {
588 temp = PREV_INSN (insn);
589 if (duplicate_loop_exit_test (insn))
590 {
591 changed = 1;
592 next = NEXT_INSN (temp);
593 continue;
594 }
595 }
596
597 if (GET_CODE (insn) != JUMP_INSN)
598 continue;
599
600 this_is_simplejump = simplejump_p (insn);
601 this_is_condjump = condjump_p (insn);
602
603 /* Tension the labels in dispatch tables. */
604
605 if (GET_CODE (PATTERN (insn)) == ADDR_VEC)
606 changed |= tension_vector_labels (PATTERN (insn), 0);
607 if (GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
608 changed |= tension_vector_labels (PATTERN (insn), 1);
609
610 /* If a dispatch table always goes to the same place,
611 get rid of it and replace the insn that uses it. */
612
613 if (GET_CODE (PATTERN (insn)) == ADDR_VEC
614 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
615 {
616 int i;
617 rtx pat = PATTERN (insn);
618 int diff_vec_p = GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC;
619 int len = XVECLEN (pat, diff_vec_p);
620 rtx dispatch = prev_real_insn (insn);
621
622 for (i = 0; i < len; i++)
623 if (XEXP (XVECEXP (pat, diff_vec_p, i), 0)
624 != XEXP (XVECEXP (pat, diff_vec_p, 0), 0))
625 break;
626 if (i == len
627 && dispatch != 0
628 && GET_CODE (dispatch) == JUMP_INSN
629 && JUMP_LABEL (dispatch) != 0
630 /* Don't mess with a casesi insn. */
631 && !(GET_CODE (PATTERN (dispatch)) == SET
632 && (GET_CODE (SET_SRC (PATTERN (dispatch)))
633 == IF_THEN_ELSE))
634 && next_real_insn (JUMP_LABEL (dispatch)) == insn)
635 {
636 redirect_tablejump (dispatch,
637 XEXP (XVECEXP (pat, diff_vec_p, 0), 0));
638 changed = 1;
639 }
640 }
641
642 reallabelprev = prev_active_insn (JUMP_LABEL (insn));
643
644 /* If a jump references the end of the function, try to turn
645 it into a RETURN insn, possibly a conditional one. */
646 if (JUMP_LABEL (insn)
647 && (next_active_insn (JUMP_LABEL (insn)) == 0
648 || GET_CODE (PATTERN (next_active_insn (JUMP_LABEL (insn))))
649 == RETURN))
650 changed |= redirect_jump (insn, NULL_RTX);
651
652 /* Detect jump to following insn. */
653 if (reallabelprev == insn && condjump_p (insn))
654 {
655 delete_jump (insn);
656 changed = 1;
657 continue;
658 }
659
660 /* If we have an unconditional jump preceded by a USE, try to put
661 the USE before the target and jump there. This simplifies many
662 of the optimizations below since we don't have to worry about
663 dealing with these USE insns. We only do this if the label
664 being branch to already has the identical USE or if code
665 never falls through to that label. */
666
667 if (this_is_simplejump
668 && (temp = prev_nonnote_insn (insn)) != 0
669 && GET_CODE (temp) == INSN && GET_CODE (PATTERN (temp)) == USE
670 && (temp1 = prev_nonnote_insn (JUMP_LABEL (insn))) != 0
671 && (GET_CODE (temp1) == BARRIER
672 || (GET_CODE (temp1) == INSN
673 && rtx_equal_p (PATTERN (temp), PATTERN (temp1)))))
674 {
675 if (GET_CODE (temp1) == BARRIER)
676 {
677 emit_insn_after (PATTERN (temp), temp1);
678 temp1 = NEXT_INSN (temp1);
679 }
680
681 delete_insn (temp);
682 redirect_jump (insn, get_label_before (temp1));
683 reallabelprev = prev_real_insn (temp1);
684 changed = 1;
685 }
686
687 /* Simplify if (...) x = a; else x = b; by converting it
688 to x = b; if (...) x = a;
689 if B is sufficiently simple, the test doesn't involve X,
690 and nothing in the test modifies B or X.
691
692 If we have small register classes, we also can't do this if X
693 is a hard register.
694
695 If the "x = b;" insn has any REG_NOTES, we don't do this because
696 of the possibility that we are running after CSE and there is a
697 REG_EQUAL note that is only valid if the branch has already been
698 taken. If we move the insn with the REG_EQUAL note, we may
699 fold the comparison to always be false in a later CSE pass.
700 (We could also delete the REG_NOTES when moving the insn, but it
701 seems simpler to not move it.) An exception is that we can move
702 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
703 value is the same as "b".
704
705 INSN is the branch over the `else' part.
706
707 We set:
708
709 TEMP to the jump insn preceding "x = a;"
710 TEMP1 to X
711 TEMP2 to the insn that sets "x = b;"
712 TEMP3 to the insn that sets "x = a;"
713 TEMP4 to the set of "x = b"; */
714
715 if (this_is_simplejump
716 && (temp3 = prev_active_insn (insn)) != 0
717 && GET_CODE (temp3) == INSN
718 && (temp4 = single_set (temp3)) != 0
719 && GET_CODE (temp1 = SET_DEST (temp4)) == REG
720 #ifdef SMALL_REGISTER_CLASSES
721 && REGNO (temp1) >= FIRST_PSEUDO_REGISTER
722 #endif
723 && (temp2 = next_active_insn (insn)) != 0
724 && GET_CODE (temp2) == INSN
725 && (temp4 = single_set (temp2)) != 0
726 && rtx_equal_p (SET_DEST (temp4), temp1)
727 && (GET_CODE (SET_SRC (temp4)) == REG
728 || GET_CODE (SET_SRC (temp4)) == SUBREG
729 || CONSTANT_P (SET_SRC (temp4)))
730 && (REG_NOTES (temp2) == 0
731 || ((REG_NOTE_KIND (REG_NOTES (temp2)) == REG_EQUAL
732 || REG_NOTE_KIND (REG_NOTES (temp2)) == REG_EQUIV)
733 && XEXP (REG_NOTES (temp2), 1) == 0
734 && rtx_equal_p (XEXP (REG_NOTES (temp2), 0),
735 SET_SRC (temp4))))
736 && (temp = prev_active_insn (temp3)) != 0
737 && condjump_p (temp) && ! simplejump_p (temp)
738 /* TEMP must skip over the "x = a;" insn */
739 && prev_real_insn (JUMP_LABEL (temp)) == insn
740 && no_labels_between_p (insn, JUMP_LABEL (temp))
741 /* There must be no other entries to the "x = b;" insn. */
742 && no_labels_between_p (JUMP_LABEL (temp), temp2)
743 /* INSN must either branch to the insn after TEMP2 or the insn
744 after TEMP2 must branch to the same place as INSN. */
745 && (reallabelprev == temp2
746 || ((temp5 = next_active_insn (temp2)) != 0
747 && simplejump_p (temp5)
748 && JUMP_LABEL (temp5) == JUMP_LABEL (insn))))
749 {
750 /* The test expression, X, may be a complicated test with
751 multiple branches. See if we can find all the uses of
752 the label that TEMP branches to without hitting a CALL_INSN
753 or a jump to somewhere else. */
754 rtx target = JUMP_LABEL (temp);
755 int nuses = LABEL_NUSES (target);
756 rtx p, q;
757
758 /* Set P to the first jump insn that goes around "x = a;". */
759 for (p = temp; nuses && p; p = prev_nonnote_insn (p))
760 {
761 if (GET_CODE (p) == JUMP_INSN)
762 {
763 if (condjump_p (p) && ! simplejump_p (p)
764 && JUMP_LABEL (p) == target)
765 {
766 nuses--;
767 if (nuses == 0)
768 break;
769 }
770 else
771 break;
772 }
773 else if (GET_CODE (p) == CALL_INSN)
774 break;
775 }
776
777 #ifdef HAVE_cc0
778 /* We cannot insert anything between a set of cc and its use
779 so if P uses cc0, we must back up to the previous insn. */
780 q = prev_nonnote_insn (p);
781 if (q && GET_RTX_CLASS (GET_CODE (q)) == 'i'
782 && sets_cc0_p (PATTERN (q)))
783 p = q;
784 #endif
785
786 if (p)
787 p = PREV_INSN (p);
788
789 /* If we found all the uses and there was no data conflict, we
790 can move the assignment unless we can branch into the middle
791 from somewhere. */
792 if (nuses == 0 && p
793 && no_labels_between_p (p, insn)
794 && ! reg_referenced_between_p (temp1, p, NEXT_INSN (temp3))
795 && ! reg_set_between_p (temp1, p, temp3)
796 && (GET_CODE (SET_SRC (temp4)) == CONST_INT
797 || ! reg_set_between_p (SET_SRC (temp4), p, temp2)))
798 {
799 emit_insn_after_with_line_notes (PATTERN (temp2), p, temp2);
800 delete_insn (temp2);
801
802 /* Set NEXT to an insn that we know won't go away. */
803 next = next_active_insn (insn);
804
805 /* Delete the jump around the set. Note that we must do
806 this before we redirect the test jumps so that it won't
807 delete the code immediately following the assignment
808 we moved (which might be a jump). */
809
810 delete_insn (insn);
811
812 /* We either have two consecutive labels or a jump to
813 a jump, so adjust all the JUMP_INSNs to branch to where
814 INSN branches to. */
815 for (p = NEXT_INSN (p); p != next; p = NEXT_INSN (p))
816 if (GET_CODE (p) == JUMP_INSN)
817 redirect_jump (p, target);
818
819 changed = 1;
820 continue;
821 }
822 }
823
824 #ifndef HAVE_cc0
825 /* If we have if (...) x = exp; and branches are expensive,
826 EXP is a single insn, does not have any side effects, cannot
827 trap, and is not too costly, convert this to
828 t = exp; if (...) x = t;
829
830 Don't do this when we have CC0 because it is unlikely to help
831 and we'd need to worry about where to place the new insn and
832 the potential for conflicts. We also can't do this when we have
833 notes on the insn for the same reason as above.
834
835 We set:
836
837 TEMP to the "x = exp;" insn.
838 TEMP1 to the single set in the "x = exp; insn.
839 TEMP2 to "x". */
840
841 if (! reload_completed
842 && this_is_condjump && ! this_is_simplejump
843 && BRANCH_COST >= 3
844 && (temp = next_nonnote_insn (insn)) != 0
845 && GET_CODE (temp) == INSN
846 && REG_NOTES (temp) == 0
847 && (reallabelprev == temp
848 || ((temp2 = next_active_insn (temp)) != 0
849 && simplejump_p (temp2)
850 && JUMP_LABEL (temp2) == JUMP_LABEL (insn)))
851 && (temp1 = single_set (temp)) != 0
852 && (temp2 = SET_DEST (temp1), GET_CODE (temp2) == REG)
853 && GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT
854 #ifdef SMALL_REGISTER_CLASSES
855 && REGNO (temp2) >= FIRST_PSEUDO_REGISTER
856 #endif
857 && GET_CODE (SET_SRC (temp1)) != REG
858 && GET_CODE (SET_SRC (temp1)) != SUBREG
859 && GET_CODE (SET_SRC (temp1)) != CONST_INT
860 && ! side_effects_p (SET_SRC (temp1))
861 && ! may_trap_p (SET_SRC (temp1))
862 && rtx_cost (SET_SRC (temp1)) < 10)
863 {
864 rtx new = gen_reg_rtx (GET_MODE (temp2));
865
866 if (validate_change (temp, &SET_DEST (temp1), new, 0))
867 {
868 next = emit_insn_after (gen_move_insn (temp2, new), insn);
869 emit_insn_after_with_line_notes (PATTERN (temp),
870 PREV_INSN (insn), temp);
871 delete_insn (temp);
872 reallabelprev = prev_active_insn (JUMP_LABEL (insn));
873 }
874 }
875
876 /* Similarly, if it takes two insns to compute EXP but they
877 have the same destination. Here TEMP3 will be the second
878 insn and TEMP4 the SET from that insn. */
879
880 if (! reload_completed
881 && this_is_condjump && ! this_is_simplejump
882 && BRANCH_COST >= 4
883 && (temp = next_nonnote_insn (insn)) != 0
884 && GET_CODE (temp) == INSN
885 && REG_NOTES (temp) == 0
886 && (temp3 = next_nonnote_insn (temp)) != 0
887 && GET_CODE (temp3) == INSN
888 && REG_NOTES (temp3) == 0
889 && (reallabelprev == temp3
890 || ((temp2 = next_active_insn (temp3)) != 0
891 && simplejump_p (temp2)
892 && JUMP_LABEL (temp2) == JUMP_LABEL (insn)))
893 && (temp1 = single_set (temp)) != 0
894 && (temp2 = SET_DEST (temp1), GET_CODE (temp2) == REG)
895 && GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT
896 #ifdef SMALL_REGISTER_CLASSES
897 && REGNO (temp2) >= FIRST_PSEUDO_REGISTER
898 #endif
899 && ! side_effects_p (SET_SRC (temp1))
900 && ! may_trap_p (SET_SRC (temp1))
901 && rtx_cost (SET_SRC (temp1)) < 10
902 && (temp4 = single_set (temp3)) != 0
903 && rtx_equal_p (SET_DEST (temp4), temp2)
904 && ! side_effects_p (SET_SRC (temp4))
905 && ! may_trap_p (SET_SRC (temp4))
906 && rtx_cost (SET_SRC (temp4)) < 10)
907 {
908 rtx new = gen_reg_rtx (GET_MODE (temp2));
909
910 if (validate_change (temp, &SET_DEST (temp1), new, 0))
911 {
912 next = emit_insn_after (gen_move_insn (temp2, new), insn);
913 emit_insn_after_with_line_notes (PATTERN (temp),
914 PREV_INSN (insn), temp);
915 emit_insn_after_with_line_notes
916 (replace_rtx (PATTERN (temp3), temp2, new),
917 PREV_INSN (insn), temp3);
918 delete_insn (temp);
919 delete_insn (temp3);
920 reallabelprev = prev_active_insn (JUMP_LABEL (insn));
921 }
922 }
923
924 /* Finally, handle the case where two insns are used to
925 compute EXP but a temporary register is used. Here we must
926 ensure that the temporary register is not used anywhere else. */
927
928 if (! reload_completed
929 && after_regscan
930 && this_is_condjump && ! this_is_simplejump
931 && BRANCH_COST >= 4
932 && (temp = next_nonnote_insn (insn)) != 0
933 && GET_CODE (temp) == INSN
934 && REG_NOTES (temp) == 0
935 && (temp3 = next_nonnote_insn (temp)) != 0
936 && GET_CODE (temp3) == INSN
937 && REG_NOTES (temp3) == 0
938 && (reallabelprev == temp3
939 || ((temp2 = next_active_insn (temp3)) != 0
940 && simplejump_p (temp2)
941 && JUMP_LABEL (temp2) == JUMP_LABEL (insn)))
942 && (temp1 = single_set (temp)) != 0
943 && (temp5 = SET_DEST (temp1), GET_CODE (temp5) == REG)
944 && REGNO (temp5) >= FIRST_PSEUDO_REGISTER
945 && regno_first_uid[REGNO (temp5)] == INSN_UID (temp)
946 && regno_last_uid[REGNO (temp5)] == INSN_UID (temp3)
947 && ! side_effects_p (SET_SRC (temp1))
948 && ! may_trap_p (SET_SRC (temp1))
949 && rtx_cost (SET_SRC (temp1)) < 10
950 && (temp4 = single_set (temp3)) != 0
951 && (temp2 = SET_DEST (temp4), GET_CODE (temp2) == REG)
952 && GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT
953 #ifdef SMALL_REGISTER_CLASSES
954 && REGNO (temp2) >= FIRST_PSEUDO_REGISTER
955 #endif
956 && rtx_equal_p (SET_DEST (temp4), temp2)
957 && ! side_effects_p (SET_SRC (temp4))
958 && ! may_trap_p (SET_SRC (temp4))
959 && rtx_cost (SET_SRC (temp4)) < 10)
960 {
961 rtx new = gen_reg_rtx (GET_MODE (temp2));
962
963 if (validate_change (temp3, &SET_DEST (temp4), new, 0))
964 {
965 next = emit_insn_after (gen_move_insn (temp2, new), insn);
966 emit_insn_after_with_line_notes (PATTERN (temp),
967 PREV_INSN (insn), temp);
968 emit_insn_after_with_line_notes (PATTERN (temp3),
969 PREV_INSN (insn), temp3);
970 delete_insn (temp);
971 delete_insn (temp3);
972 reallabelprev = prev_active_insn (JUMP_LABEL (insn));
973 }
974 }
975 #endif /* HAVE_cc0 */
976
977 /* We deal with four cases:
978
979 1) x = a; if (...) x = b; and either A or B is zero,
980 2) if (...) x = 0; and jumps are expensive,
981 3) x = a; if (...) x = b; and A and B are constants where all the
982 set bits in A are also set in B and jumps are expensive, and
983 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
984 more expensive.
985 5) if (...) x = b; if jumps are even more expensive.
986
987 In each of these try to use a store-flag insn to avoid the jump.
988 (If the jump would be faster, the machine should not have
989 defined the scc insns!). These cases are often made by the
990 previous optimization.
991
992 INSN here is the jump around the store. We set:
993
994 TEMP to the "x = b;" insn.
995 TEMP1 to X.
996 TEMP2 to B (const0_rtx in the second case).
997 TEMP3 to A (X in the second case).
998 TEMP4 to the condition being tested.
999 TEMP5 to the earliest insn used to find the condition. */
1000
1001 if (/* We can't do this after reload has completed. */
1002 ! reload_completed
1003 && this_is_condjump && ! this_is_simplejump
1004 /* Set TEMP to the "x = b;" insn. */
1005 && (temp = next_nonnote_insn (insn)) != 0
1006 && GET_CODE (temp) == INSN
1007 && GET_CODE (PATTERN (temp)) == SET
1008 && GET_CODE (temp1 = SET_DEST (PATTERN (temp))) == REG
1009 #ifdef SMALL_REGISTER_CLASSES
1010 && REGNO (temp1) >= FIRST_PSEUDO_REGISTER
1011 #endif
1012 && GET_MODE_CLASS (GET_MODE (temp1)) == MODE_INT
1013 && (GET_CODE (temp2 = SET_SRC (PATTERN (temp))) == REG
1014 || GET_CODE (temp2) == SUBREG
1015 || GET_CODE (temp2) == CONST_INT)
1016 /* Allow either form, but prefer the former if both apply.
1017 There is no point in using the old value of TEMP1 if
1018 it is a register, since cse will alias them. It can
1019 lose if the old value were a hard register since CSE
1020 won't replace hard registers. */
1021 && (((temp3 = reg_set_last (temp1, insn)) != 0
1022 && GET_CODE (temp3) == CONST_INT)
1023 /* Make the latter case look like x = x; if (...) x = 0; */
1024 || (temp3 = temp1,
1025 ((BRANCH_COST >= 2
1026 && temp2 == const0_rtx)
1027 #ifdef HAVE_conditional_move
1028 || 1
1029 #endif
1030 || BRANCH_COST >= 3)))
1031 /* INSN must either branch to the insn after TEMP or the insn
1032 after TEMP must branch to the same place as INSN. */
1033 && (reallabelprev == temp
1034 || ((temp4 = next_active_insn (temp)) != 0
1035 && simplejump_p (temp4)
1036 && JUMP_LABEL (temp4) == JUMP_LABEL (insn)))
1037 && (temp4 = get_condition (insn, &temp5)) != 0
1038 /* We must be comparing objects whose modes imply the size.
1039 We could handle BLKmode if (1) emit_store_flag could
1040 and (2) we could find the size reliably. */
1041 && GET_MODE (XEXP (temp4, 0)) != BLKmode
1042
1043 /* If B is zero, OK; if A is zero, can only do (1) if we
1044 can reverse the condition. See if (3) applies possibly
1045 by reversing the condition. Prefer reversing to (4) when
1046 branches are very expensive. */
1047 && ((reversep = 0, temp2 == const0_rtx)
1048 || (temp3 == const0_rtx
1049 && (reversep = can_reverse_comparison_p (temp4, insn)))
1050 || (BRANCH_COST >= 2
1051 && GET_CODE (temp2) == CONST_INT
1052 && GET_CODE (temp3) == CONST_INT
1053 && ((INTVAL (temp2) & INTVAL (temp3)) == INTVAL (temp2)
1054 || ((INTVAL (temp2) & INTVAL (temp3)) == INTVAL (temp3)
1055 && (reversep = can_reverse_comparison_p (temp4,
1056 insn)))))
1057 #ifdef HAVE_conditional_move
1058 || 1
1059 #endif
1060 || BRANCH_COST >= 3)
1061 #ifdef HAVE_cc0
1062 /* If the previous insn sets CC0 and something else, we can't
1063 do this since we are going to delete that insn. */
1064
1065 && ! ((temp6 = prev_nonnote_insn (insn)) != 0
1066 && GET_CODE (temp6) == INSN
1067 && (sets_cc0_p (PATTERN (temp6)) == -1
1068 || (sets_cc0_p (PATTERN (temp6)) == 1
1069 && FIND_REG_INC_NOTE (temp6, NULL_RTX))))
1070 #endif
1071 )
1072 {
1073 enum rtx_code code = GET_CODE (temp4);
1074 rtx uval, cval, var = temp1;
1075 int normalizep;
1076 rtx target;
1077
1078 /* If necessary, reverse the condition. */
1079 if (reversep)
1080 code = reverse_condition (code), uval = temp2, cval = temp3;
1081 else
1082 uval = temp3, cval = temp2;
1083
1084 /* See if we can do this with a store-flag insn. */
1085 start_sequence ();
1086
1087 /* If CVAL is non-zero, normalize to -1. Otherwise,
1088 if UVAL is the constant 1, it is best to just compute
1089 the result directly. If UVAL is constant and STORE_FLAG_VALUE
1090 includes all of its bits, it is best to compute the flag
1091 value unnormalized and `and' it with UVAL. Otherwise,
1092 normalize to -1 and `and' with UVAL. */
1093 normalizep = (cval != const0_rtx ? -1
1094 : (uval == const1_rtx ? 1
1095 : (GET_CODE (uval) == CONST_INT
1096 && (INTVAL (uval) & ~STORE_FLAG_VALUE) == 0)
1097 ? 0 : -1));
1098
1099 /* We will be putting the store-flag insn immediately in
1100 front of the comparison that was originally being done,
1101 so we know all the variables in TEMP4 will be valid.
1102 However, this might be in front of the assignment of
1103 A to VAR. If it is, it would clobber the store-flag
1104 we will be emitting.
1105
1106 Therefore, emit into a temporary which will be copied to
1107 VAR immediately after TEMP. */
1108
1109 target = emit_store_flag (gen_reg_rtx (GET_MODE (var)), code,
1110 XEXP (temp4, 0), XEXP (temp4, 1),
1111 VOIDmode,
1112 (code == LTU || code == LEU
1113 || code == GEU || code == GTU),
1114 normalizep);
1115 if (target)
1116 {
1117 rtx before = insn;
1118 rtx seq;
1119
1120 /* Put the store-flag insns in front of the first insn
1121 used to compute the condition to ensure that we
1122 use the same values of them as the current
1123 comparison. However, the remainder of the insns we
1124 generate will be placed directly in front of the
1125 jump insn, in case any of the pseudos we use
1126 are modified earlier. */
1127
1128 seq = get_insns ();
1129 end_sequence ();
1130
1131 emit_insns_before (seq, temp5);
1132
1133 start_sequence ();
1134
1135 /* Both CVAL and UVAL are non-zero. */
1136 if (cval != const0_rtx && uval != const0_rtx)
1137 {
1138 rtx tem1, tem2;
1139
1140 tem1 = expand_and (uval, target, NULL_RTX);
1141 if (GET_CODE (cval) == CONST_INT
1142 && GET_CODE (uval) == CONST_INT
1143 && (INTVAL (cval) & INTVAL (uval)) == INTVAL (cval))
1144 tem2 = cval;
1145 else
1146 {
1147 tem2 = expand_unop (GET_MODE (var), one_cmpl_optab,
1148 target, NULL_RTX, 0);
1149 tem2 = expand_and (cval, tem2,
1150 (GET_CODE (tem2) == REG
1151 ? tem2 : 0));
1152 }
1153
1154 /* If we usually make new pseudos, do so here. This
1155 turns out to help machines that have conditional
1156 move insns. */
1157
1158 if (flag_expensive_optimizations)
1159 target = 0;
1160
1161 target = expand_binop (GET_MODE (var), ior_optab,
1162 tem1, tem2, target,
1163 1, OPTAB_WIDEN);
1164 }
1165 else if (normalizep != 1)
1166 {
1167 /* We know that either CVAL or UVAL is zero. If
1168 UVAL is zero, negate TARGET and `and' with CVAL.
1169 Otherwise, `and' with UVAL. */
1170 if (uval == const0_rtx)
1171 {
1172 target = expand_unop (GET_MODE (var), one_cmpl_optab,
1173 target, NULL_RTX, 0);
1174 uval = cval;
1175 }
1176
1177 target = expand_and (uval, target,
1178 (GET_CODE (target) == REG
1179 && ! preserve_subexpressions_p ()
1180 ? target : NULL_RTX));
1181 }
1182
1183 emit_move_insn (var, target);
1184 seq = get_insns ();
1185 end_sequence ();
1186
1187 #ifdef HAVE_cc0
1188 /* If INSN uses CC0, we must not separate it from the
1189 insn that sets cc0. */
1190
1191 if (reg_mentioned_p (cc0_rtx, PATTERN (before)))
1192 before = prev_nonnote_insn (before);
1193 #endif
1194
1195 emit_insns_before (seq, before);
1196
1197 delete_insn (temp);
1198 next = NEXT_INSN (insn);
1199
1200 delete_jump (insn);
1201 changed = 1;
1202 continue;
1203 }
1204 else
1205 end_sequence ();
1206 }
1207
1208 /* If branches are expensive, convert
1209 if (foo) bar++; to bar += (foo != 0);
1210 and similarly for "bar--;"
1211
1212 INSN is the conditional branch around the arithmetic. We set:
1213
1214 TEMP is the arithmetic insn.
1215 TEMP1 is the SET doing the arithmetic.
1216 TEMP2 is the operand being incremented or decremented.
1217 TEMP3 to the condition being tested.
1218 TEMP4 to the earliest insn used to find the condition. */
1219
1220 if ((BRANCH_COST >= 2
1221 #ifdef HAVE_incscc
1222 || HAVE_incscc
1223 #endif
1224 #ifdef HAVE_decscc
1225 || HAVE_decscc
1226 #endif
1227 )
1228 && ! reload_completed
1229 && this_is_condjump && ! this_is_simplejump
1230 && (temp = next_nonnote_insn (insn)) != 0
1231 && (temp1 = single_set (temp)) != 0
1232 && (temp2 = SET_DEST (temp1),
1233 GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT)
1234 && GET_CODE (SET_SRC (temp1)) == PLUS
1235 && (XEXP (SET_SRC (temp1), 1) == const1_rtx
1236 || XEXP (SET_SRC (temp1), 1) == constm1_rtx)
1237 && rtx_equal_p (temp2, XEXP (SET_SRC (temp1), 0))
1238 /* INSN must either branch to the insn after TEMP or the insn
1239 after TEMP must branch to the same place as INSN. */
1240 && (reallabelprev == temp
1241 || ((temp3 = next_active_insn (temp)) != 0
1242 && simplejump_p (temp3)
1243 && JUMP_LABEL (temp3) == JUMP_LABEL (insn)))
1244 && (temp3 = get_condition (insn, &temp4)) != 0
1245 /* We must be comparing objects whose modes imply the size.
1246 We could handle BLKmode if (1) emit_store_flag could
1247 and (2) we could find the size reliably. */
1248 && GET_MODE (XEXP (temp3, 0)) != BLKmode
1249 && can_reverse_comparison_p (temp3, insn))
1250 {
1251 rtx temp6, target = 0, seq, init_insn = 0, init = temp2;
1252 enum rtx_code code = reverse_condition (GET_CODE (temp3));
1253
1254 start_sequence ();
1255
1256 /* It must be the case that TEMP2 is not modified in the range
1257 [TEMP4, INSN). The one exception we make is if the insn
1258 before INSN sets TEMP2 to something which is also unchanged
1259 in that range. In that case, we can move the initialization
1260 into our sequence. */
1261
1262 if ((temp5 = prev_active_insn (insn)) != 0
1263 && GET_CODE (temp5) == INSN
1264 && (temp6 = single_set (temp5)) != 0
1265 && rtx_equal_p (temp2, SET_DEST (temp6))
1266 && (CONSTANT_P (SET_SRC (temp6))
1267 || GET_CODE (SET_SRC (temp6)) == REG
1268 || GET_CODE (SET_SRC (temp6)) == SUBREG))
1269 {
1270 emit_insn (PATTERN (temp5));
1271 init_insn = temp5;
1272 init = SET_SRC (temp6);
1273 }
1274
1275 if (CONSTANT_P (init)
1276 || ! reg_set_between_p (init, PREV_INSN (temp4), insn))
1277 target = emit_store_flag (gen_reg_rtx (GET_MODE (temp2)), code,
1278 XEXP (temp3, 0), XEXP (temp3, 1),
1279 VOIDmode,
1280 (code == LTU || code == LEU
1281 || code == GTU || code == GEU), 1);
1282
1283 /* If we can do the store-flag, do the addition or
1284 subtraction. */
1285
1286 if (target)
1287 target = expand_binop (GET_MODE (temp2),
1288 (XEXP (SET_SRC (temp1), 1) == const1_rtx
1289 ? add_optab : sub_optab),
1290 temp2, target, temp2, 0, OPTAB_WIDEN);
1291
1292 if (target != 0)
1293 {
1294 /* Put the result back in temp2 in case it isn't already.
1295 Then replace the jump, possible a CC0-setting insn in
1296 front of the jump, and TEMP, with the sequence we have
1297 made. */
1298
1299 if (target != temp2)
1300 emit_move_insn (temp2, target);
1301
1302 seq = get_insns ();
1303 end_sequence ();
1304
1305 emit_insns_before (seq, temp4);
1306 delete_insn (temp);
1307
1308 if (init_insn)
1309 delete_insn (init_insn);
1310
1311 next = NEXT_INSN (insn);
1312 #ifdef HAVE_cc0
1313 delete_insn (prev_nonnote_insn (insn));
1314 #endif
1315 delete_insn (insn);
1316 changed = 1;
1317 continue;
1318 }
1319 else
1320 end_sequence ();
1321 }
1322
1323 /* Simplify if (...) x = 1; else {...} if (x) ...
1324 We recognize this case scanning backwards as well.
1325
1326 TEMP is the assignment to x;
1327 TEMP1 is the label at the head of the second if. */
1328 /* ?? This should call get_condition to find the values being
1329 compared, instead of looking for a COMPARE insn when HAVE_cc0
1330 is not defined. This would allow it to work on the m88k. */
1331 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1332 is not defined and the condition is tested by a separate compare
1333 insn. This is because the code below assumes that the result
1334 of the compare dies in the following branch.
1335
1336 Not only that, but there might be other insns between the
1337 compare and branch whose results are live. Those insns need
1338 to be executed.
1339
1340 A way to fix this is to move the insns at JUMP_LABEL (insn)
1341 to before INSN. If we are running before flow, they will
1342 be deleted if they aren't needed. But this doesn't work
1343 well after flow.
1344
1345 This is really a special-case of jump threading, anyway. The
1346 right thing to do is to replace this and jump threading with
1347 much simpler code in cse.
1348
1349 This code has been turned off in the non-cc0 case in the
1350 meantime. */
1351
1352 #ifdef HAVE_cc0
1353 else if (this_is_simplejump
1354 /* Safe to skip USE and CLOBBER insns here
1355 since they will not be deleted. */
1356 && (temp = prev_active_insn (insn))
1357 && no_labels_between_p (temp, insn)
1358 && GET_CODE (temp) == INSN
1359 && GET_CODE (PATTERN (temp)) == SET
1360 && GET_CODE (SET_DEST (PATTERN (temp))) == REG
1361 && CONSTANT_P (SET_SRC (PATTERN (temp)))
1362 && (temp1 = next_active_insn (JUMP_LABEL (insn)))
1363 /* If we find that the next value tested is `x'
1364 (TEMP1 is the insn where this happens), win. */
1365 && GET_CODE (temp1) == INSN
1366 && GET_CODE (PATTERN (temp1)) == SET
1367 #ifdef HAVE_cc0
1368 /* Does temp1 `tst' the value of x? */
1369 && SET_SRC (PATTERN (temp1)) == SET_DEST (PATTERN (temp))
1370 && SET_DEST (PATTERN (temp1)) == cc0_rtx
1371 && (temp1 = next_nonnote_insn (temp1))
1372 #else
1373 /* Does temp1 compare the value of x against zero? */
1374 && GET_CODE (SET_SRC (PATTERN (temp1))) == COMPARE
1375 && XEXP (SET_SRC (PATTERN (temp1)), 1) == const0_rtx
1376 && (XEXP (SET_SRC (PATTERN (temp1)), 0)
1377 == SET_DEST (PATTERN (temp)))
1378 && GET_CODE (SET_DEST (PATTERN (temp1))) == REG
1379 && (temp1 = find_next_ref (SET_DEST (PATTERN (temp1)), temp1))
1380 #endif
1381 && condjump_p (temp1))
1382 {
1383 /* Get the if_then_else from the condjump. */
1384 rtx choice = SET_SRC (PATTERN (temp1));
1385 if (GET_CODE (choice) == IF_THEN_ELSE)
1386 {
1387 enum rtx_code code = GET_CODE (XEXP (choice, 0));
1388 rtx val = SET_SRC (PATTERN (temp));
1389 rtx cond
1390 = simplify_relational_operation (code, GET_MODE (SET_DEST (PATTERN (temp))),
1391 val, const0_rtx);
1392 rtx ultimate;
1393
1394 if (cond == const_true_rtx)
1395 ultimate = XEXP (choice, 1);
1396 else if (cond == const0_rtx)
1397 ultimate = XEXP (choice, 2);
1398 else
1399 ultimate = 0;
1400
1401 if (ultimate == pc_rtx)
1402 ultimate = get_label_after (temp1);
1403 else if (ultimate && GET_CODE (ultimate) != RETURN)
1404 ultimate = XEXP (ultimate, 0);
1405
1406 if (ultimate)
1407 changed |= redirect_jump (insn, ultimate);
1408 }
1409 }
1410 #endif
1411
1412 #if 0
1413 /* @@ This needs a bit of work before it will be right.
1414
1415 Any type of comparison can be accepted for the first and
1416 second compare. When rewriting the first jump, we must
1417 compute the what conditions can reach label3, and use the
1418 appropriate code. We can not simply reverse/swap the code
1419 of the first jump. In some cases, the second jump must be
1420 rewritten also.
1421
1422 For example,
1423 < == converts to > ==
1424 < != converts to == >
1425 etc.
1426
1427 If the code is written to only accept an '==' test for the second
1428 compare, then all that needs to be done is to swap the condition
1429 of the first branch.
1430
1431 It is questionable whether we want this optimization anyways,
1432 since if the user wrote code like this because he/she knew that
1433 the jump to label1 is taken most of the time, then rewriting
1434 this gives slower code. */
1435 /* @@ This should call get_condition to find the values being
1436 compared, instead of looking for a COMPARE insn when HAVE_cc0
1437 is not defined. This would allow it to work on the m88k. */
1438 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1439 is not defined and the condition is tested by a separate compare
1440 insn. This is because the code below assumes that the result
1441 of the compare dies in the following branch. */
1442
1443 /* Simplify test a ~= b
1444 condjump label1;
1445 test a == b
1446 condjump label2;
1447 jump label3;
1448 label1:
1449
1450 rewriting as
1451 test a ~~= b
1452 condjump label3
1453 test a == b
1454 condjump label2
1455 label1:
1456
1457 where ~= is an inequality, e.g. >, and ~~= is the swapped
1458 inequality, e.g. <.
1459
1460 We recognize this case scanning backwards.
1461
1462 TEMP is the conditional jump to `label2';
1463 TEMP1 is the test for `a == b';
1464 TEMP2 is the conditional jump to `label1';
1465 TEMP3 is the test for `a ~= b'. */
1466 else if (this_is_simplejump
1467 && (temp = prev_active_insn (insn))
1468 && no_labels_between_p (temp, insn)
1469 && condjump_p (temp)
1470 && (temp1 = prev_active_insn (temp))
1471 && no_labels_between_p (temp1, temp)
1472 && GET_CODE (temp1) == INSN
1473 && GET_CODE (PATTERN (temp1)) == SET
1474 #ifdef HAVE_cc0
1475 && sets_cc0_p (PATTERN (temp1)) == 1
1476 #else
1477 && GET_CODE (SET_SRC (PATTERN (temp1))) == COMPARE
1478 && GET_CODE (SET_DEST (PATTERN (temp1))) == REG
1479 && (temp == find_next_ref (SET_DEST (PATTERN (temp1)), temp1))
1480 #endif
1481 && (temp2 = prev_active_insn (temp1))
1482 && no_labels_between_p (temp2, temp1)
1483 && condjump_p (temp2)
1484 && JUMP_LABEL (temp2) == next_nonnote_insn (NEXT_INSN (insn))
1485 && (temp3 = prev_active_insn (temp2))
1486 && no_labels_between_p (temp3, temp2)
1487 && GET_CODE (PATTERN (temp3)) == SET
1488 && rtx_equal_p (SET_DEST (PATTERN (temp3)),
1489 SET_DEST (PATTERN (temp1)))
1490 && rtx_equal_p (SET_SRC (PATTERN (temp1)),
1491 SET_SRC (PATTERN (temp3)))
1492 && ! inequality_comparisons_p (PATTERN (temp))
1493 && inequality_comparisons_p (PATTERN (temp2)))
1494 {
1495 rtx fallthrough_label = JUMP_LABEL (temp2);
1496
1497 ++LABEL_NUSES (fallthrough_label);
1498 if (swap_jump (temp2, JUMP_LABEL (insn)))
1499 {
1500 delete_insn (insn);
1501 changed = 1;
1502 }
1503
1504 if (--LABEL_NUSES (fallthrough_label) == 0)
1505 delete_insn (fallthrough_label);
1506 }
1507 #endif
1508 /* Simplify if (...) {... x = 1;} if (x) ...
1509
1510 We recognize this case backwards.
1511
1512 TEMP is the test of `x';
1513 TEMP1 is the assignment to `x' at the end of the
1514 previous statement. */
1515 /* @@ This should call get_condition to find the values being
1516 compared, instead of looking for a COMPARE insn when HAVE_cc0
1517 is not defined. This would allow it to work on the m88k. */
1518 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1519 is not defined and the condition is tested by a separate compare
1520 insn. This is because the code below assumes that the result
1521 of the compare dies in the following branch. */
1522
1523 /* ??? This has to be turned off. The problem is that the
1524 unconditional jump might indirectly end up branching to the
1525 label between TEMP1 and TEMP. We can't detect this, in general,
1526 since it may become a jump to there after further optimizations.
1527 If that jump is done, it will be deleted, so we will retry
1528 this optimization in the next pass, thus an infinite loop.
1529
1530 The present code prevents this by putting the jump after the
1531 label, but this is not logically correct. */
1532 #if 0
1533 else if (this_is_condjump
1534 /* Safe to skip USE and CLOBBER insns here
1535 since they will not be deleted. */
1536 && (temp = prev_active_insn (insn))
1537 && no_labels_between_p (temp, insn)
1538 && GET_CODE (temp) == INSN
1539 && GET_CODE (PATTERN (temp)) == SET
1540 #ifdef HAVE_cc0
1541 && sets_cc0_p (PATTERN (temp)) == 1
1542 && GET_CODE (SET_SRC (PATTERN (temp))) == REG
1543 #else
1544 /* Temp must be a compare insn, we can not accept a register
1545 to register move here, since it may not be simply a
1546 tst insn. */
1547 && GET_CODE (SET_SRC (PATTERN (temp))) == COMPARE
1548 && XEXP (SET_SRC (PATTERN (temp)), 1) == const0_rtx
1549 && GET_CODE (XEXP (SET_SRC (PATTERN (temp)), 0)) == REG
1550 && GET_CODE (SET_DEST (PATTERN (temp))) == REG
1551 && insn == find_next_ref (SET_DEST (PATTERN (temp)), temp)
1552 #endif
1553 /* May skip USE or CLOBBER insns here
1554 for checking for opportunity, since we
1555 take care of them later. */
1556 && (temp1 = prev_active_insn (temp))
1557 && GET_CODE (temp1) == INSN
1558 && GET_CODE (PATTERN (temp1)) == SET
1559 #ifdef HAVE_cc0
1560 && SET_SRC (PATTERN (temp)) == SET_DEST (PATTERN (temp1))
1561 #else
1562 && (XEXP (SET_SRC (PATTERN (temp)), 0)
1563 == SET_DEST (PATTERN (temp1)))
1564 #endif
1565 && CONSTANT_P (SET_SRC (PATTERN (temp1)))
1566 /* If this isn't true, cse will do the job. */
1567 && ! no_labels_between_p (temp1, temp))
1568 {
1569 /* Get the if_then_else from the condjump. */
1570 rtx choice = SET_SRC (PATTERN (insn));
1571 if (GET_CODE (choice) == IF_THEN_ELSE
1572 && (GET_CODE (XEXP (choice, 0)) == EQ
1573 || GET_CODE (XEXP (choice, 0)) == NE))
1574 {
1575 int want_nonzero = (GET_CODE (XEXP (choice, 0)) == NE);
1576 rtx last_insn;
1577 rtx ultimate;
1578 rtx p;
1579
1580 /* Get the place that condjump will jump to
1581 if it is reached from here. */
1582 if ((SET_SRC (PATTERN (temp1)) != const0_rtx)
1583 == want_nonzero)
1584 ultimate = XEXP (choice, 1);
1585 else
1586 ultimate = XEXP (choice, 2);
1587 /* Get it as a CODE_LABEL. */
1588 if (ultimate == pc_rtx)
1589 ultimate = get_label_after (insn);
1590 else
1591 /* Get the label out of the LABEL_REF. */
1592 ultimate = XEXP (ultimate, 0);
1593
1594 /* Insert the jump immediately before TEMP, specifically
1595 after the label that is between TEMP1 and TEMP. */
1596 last_insn = PREV_INSN (temp);
1597
1598 /* If we would be branching to the next insn, the jump
1599 would immediately be deleted and the re-inserted in
1600 a subsequent pass over the code. So don't do anything
1601 in that case. */
1602 if (next_active_insn (last_insn)
1603 != next_active_insn (ultimate))
1604 {
1605 emit_barrier_after (last_insn);
1606 p = emit_jump_insn_after (gen_jump (ultimate),
1607 last_insn);
1608 JUMP_LABEL (p) = ultimate;
1609 ++LABEL_NUSES (ultimate);
1610 if (INSN_UID (ultimate) < max_jump_chain
1611 && INSN_CODE (p) < max_jump_chain)
1612 {
1613 jump_chain[INSN_UID (p)]
1614 = jump_chain[INSN_UID (ultimate)];
1615 jump_chain[INSN_UID (ultimate)] = p;
1616 }
1617 changed = 1;
1618 continue;
1619 }
1620 }
1621 }
1622 #endif
1623 /* Detect a conditional jump going to the same place
1624 as an immediately following unconditional jump. */
1625 else if (this_is_condjump
1626 && (temp = next_active_insn (insn)) != 0
1627 && simplejump_p (temp)
1628 && (next_active_insn (JUMP_LABEL (insn))
1629 == next_active_insn (JUMP_LABEL (temp))))
1630 {
1631 delete_jump (insn);
1632 changed = 1;
1633 continue;
1634 }
1635 /* Detect a conditional jump jumping over an unconditional jump. */
1636
1637 else if (this_is_condjump && ! this_is_simplejump
1638 && reallabelprev != 0
1639 && GET_CODE (reallabelprev) == JUMP_INSN
1640 && prev_active_insn (reallabelprev) == insn
1641 && no_labels_between_p (insn, reallabelprev)
1642 && simplejump_p (reallabelprev))
1643 {
1644 /* When we invert the unconditional jump, we will be
1645 decrementing the usage count of its old label.
1646 Make sure that we don't delete it now because that
1647 might cause the following code to be deleted. */
1648 rtx prev_uses = prev_nonnote_insn (reallabelprev);
1649 rtx prev_label = JUMP_LABEL (insn);
1650
1651 if (prev_label)
1652 ++LABEL_NUSES (prev_label);
1653
1654 if (invert_jump (insn, JUMP_LABEL (reallabelprev)))
1655 {
1656 /* It is very likely that if there are USE insns before
1657 this jump, they hold REG_DEAD notes. These REG_DEAD
1658 notes are no longer valid due to this optimization,
1659 and will cause the life-analysis that following passes
1660 (notably delayed-branch scheduling) to think that
1661 these registers are dead when they are not.
1662
1663 To prevent this trouble, we just remove the USE insns
1664 from the insn chain. */
1665
1666 while (prev_uses && GET_CODE (prev_uses) == INSN
1667 && GET_CODE (PATTERN (prev_uses)) == USE)
1668 {
1669 rtx useless = prev_uses;
1670 prev_uses = prev_nonnote_insn (prev_uses);
1671 delete_insn (useless);
1672 }
1673
1674 delete_insn (reallabelprev);
1675 next = insn;
1676 changed = 1;
1677 }
1678
1679 /* We can now safely delete the label if it is unreferenced
1680 since the delete_insn above has deleted the BARRIER. */
1681 if (prev_label && --LABEL_NUSES (prev_label) == 0)
1682 delete_insn (prev_label);
1683 continue;
1684 }
1685 else
1686 {
1687 /* Detect a jump to a jump. */
1688
1689 nlabel = follow_jumps (JUMP_LABEL (insn));
1690 if (nlabel != JUMP_LABEL (insn)
1691 && redirect_jump (insn, nlabel))
1692 {
1693 changed = 1;
1694 next = insn;
1695 }
1696
1697 /* Look for if (foo) bar; else break; */
1698 /* The insns look like this:
1699 insn = condjump label1;
1700 ...range1 (some insns)...
1701 jump label2;
1702 label1:
1703 ...range2 (some insns)...
1704 jump somewhere unconditionally
1705 label2: */
1706 {
1707 rtx label1 = next_label (insn);
1708 rtx range1end = label1 ? prev_active_insn (label1) : 0;
1709 /* Don't do this optimization on the first round, so that
1710 jump-around-a-jump gets simplified before we ask here
1711 whether a jump is unconditional.
1712
1713 Also don't do it when we are called after reload since
1714 it will confuse reorg. */
1715 if (! first
1716 && (reload_completed ? ! flag_delayed_branch : 1)
1717 /* Make sure INSN is something we can invert. */
1718 && condjump_p (insn)
1719 && label1 != 0
1720 && JUMP_LABEL (insn) == label1
1721 && LABEL_NUSES (label1) == 1
1722 && GET_CODE (range1end) == JUMP_INSN
1723 && simplejump_p (range1end))
1724 {
1725 rtx label2 = next_label (label1);
1726 rtx range2end = label2 ? prev_active_insn (label2) : 0;
1727 if (range1end != range2end
1728 && JUMP_LABEL (range1end) == label2
1729 && GET_CODE (range2end) == JUMP_INSN
1730 && GET_CODE (NEXT_INSN (range2end)) == BARRIER
1731 /* Invert the jump condition, so we
1732 still execute the same insns in each case. */
1733 && invert_jump (insn, label1))
1734 {
1735 rtx range1beg = next_active_insn (insn);
1736 rtx range2beg = next_active_insn (label1);
1737 rtx range1after, range2after;
1738 rtx range1before, range2before;
1739
1740 /* Include in each range any notes before it, to be
1741 sure that we get the line number note if any, even
1742 if there are other notes here. */
1743 while (PREV_INSN (range1beg)
1744 && GET_CODE (PREV_INSN (range1beg)) == NOTE)
1745 range1beg = PREV_INSN (range1beg);
1746
1747 while (PREV_INSN (range2beg)
1748 && GET_CODE (PREV_INSN (range2beg)) == NOTE)
1749 range2beg = PREV_INSN (range2beg);
1750
1751 /* Don't move NOTEs for blocks or loops; shift them
1752 outside the ranges, where they'll stay put. */
1753 range1beg = squeeze_notes (range1beg, range1end);
1754 range2beg = squeeze_notes (range2beg, range2end);
1755
1756 /* Get current surrounds of the 2 ranges. */
1757 range1before = PREV_INSN (range1beg);
1758 range2before = PREV_INSN (range2beg);
1759 range1after = NEXT_INSN (range1end);
1760 range2after = NEXT_INSN (range2end);
1761
1762 /* Splice range2 where range1 was. */
1763 NEXT_INSN (range1before) = range2beg;
1764 PREV_INSN (range2beg) = range1before;
1765 NEXT_INSN (range2end) = range1after;
1766 PREV_INSN (range1after) = range2end;
1767 /* Splice range1 where range2 was. */
1768 NEXT_INSN (range2before) = range1beg;
1769 PREV_INSN (range1beg) = range2before;
1770 NEXT_INSN (range1end) = range2after;
1771 PREV_INSN (range2after) = range1end;
1772 changed = 1;
1773 continue;
1774 }
1775 }
1776 }
1777
1778 /* Now that the jump has been tensioned,
1779 try cross jumping: check for identical code
1780 before the jump and before its target label. */
1781
1782 /* First, cross jumping of conditional jumps: */
1783
1784 if (cross_jump && condjump_p (insn))
1785 {
1786 rtx newjpos, newlpos;
1787 rtx x = prev_real_insn (JUMP_LABEL (insn));
1788
1789 /* A conditional jump may be crossjumped
1790 only if the place it jumps to follows
1791 an opposing jump that comes back here. */
1792
1793 if (x != 0 && ! jump_back_p (x, insn))
1794 /* We have no opposing jump;
1795 cannot cross jump this insn. */
1796 x = 0;
1797
1798 newjpos = 0;
1799 /* TARGET is nonzero if it is ok to cross jump
1800 to code before TARGET. If so, see if matches. */
1801 if (x != 0)
1802 find_cross_jump (insn, x, 2,
1803 &newjpos, &newlpos);
1804
1805 if (newjpos != 0)
1806 {
1807 do_cross_jump (insn, newjpos, newlpos);
1808 /* Make the old conditional jump
1809 into an unconditional one. */
1810 SET_SRC (PATTERN (insn))
1811 = gen_rtx (LABEL_REF, VOIDmode, JUMP_LABEL (insn));
1812 INSN_CODE (insn) = -1;
1813 emit_barrier_after (insn);
1814 /* Add to jump_chain unless this is a new label
1815 whose UID is too large. */
1816 if (INSN_UID (JUMP_LABEL (insn)) < max_jump_chain)
1817 {
1818 jump_chain[INSN_UID (insn)]
1819 = jump_chain[INSN_UID (JUMP_LABEL (insn))];
1820 jump_chain[INSN_UID (JUMP_LABEL (insn))] = insn;
1821 }
1822 changed = 1;
1823 next = insn;
1824 }
1825 }
1826
1827 /* Cross jumping of unconditional jumps:
1828 a few differences. */
1829
1830 if (cross_jump && simplejump_p (insn))
1831 {
1832 rtx newjpos, newlpos;
1833 rtx target;
1834
1835 newjpos = 0;
1836
1837 /* TARGET is nonzero if it is ok to cross jump
1838 to code before TARGET. If so, see if matches. */
1839 find_cross_jump (insn, JUMP_LABEL (insn), 1,
1840 &newjpos, &newlpos);
1841
1842 /* If cannot cross jump to code before the label,
1843 see if we can cross jump to another jump to
1844 the same label. */
1845 /* Try each other jump to this label. */
1846 if (INSN_UID (JUMP_LABEL (insn)) < max_uid)
1847 for (target = jump_chain[INSN_UID (JUMP_LABEL (insn))];
1848 target != 0 && newjpos == 0;
1849 target = jump_chain[INSN_UID (target)])
1850 if (target != insn
1851 && JUMP_LABEL (target) == JUMP_LABEL (insn)
1852 /* Ignore TARGET if it's deleted. */
1853 && ! INSN_DELETED_P (target))
1854 find_cross_jump (insn, target, 2,
1855 &newjpos, &newlpos);
1856
1857 if (newjpos != 0)
1858 {
1859 do_cross_jump (insn, newjpos, newlpos);
1860 changed = 1;
1861 next = insn;
1862 }
1863 }
1864
1865 /* This code was dead in the previous jump.c! */
1866 if (cross_jump && GET_CODE (PATTERN (insn)) == RETURN)
1867 {
1868 /* Return insns all "jump to the same place"
1869 so we can cross-jump between any two of them. */
1870
1871 rtx newjpos, newlpos, target;
1872
1873 newjpos = 0;
1874
1875 /* If cannot cross jump to code before the label,
1876 see if we can cross jump to another jump to
1877 the same label. */
1878 /* Try each other jump to this label. */
1879 for (target = jump_chain[0];
1880 target != 0 && newjpos == 0;
1881 target = jump_chain[INSN_UID (target)])
1882 if (target != insn
1883 && ! INSN_DELETED_P (target)
1884 && GET_CODE (PATTERN (target)) == RETURN)
1885 find_cross_jump (insn, target, 2,
1886 &newjpos, &newlpos);
1887
1888 if (newjpos != 0)
1889 {
1890 do_cross_jump (insn, newjpos, newlpos);
1891 changed = 1;
1892 next = insn;
1893 }
1894 }
1895 }
1896 }
1897
1898 first = 0;
1899 }
1900
1901 /* Delete extraneous line number notes.
1902 Note that two consecutive notes for different lines are not really
1903 extraneous. There should be some indication where that line belonged,
1904 even if it became empty. */
1905
1906 {
1907 rtx last_note = 0;
1908
1909 for (insn = f; insn; insn = NEXT_INSN (insn))
1910 if (GET_CODE (insn) == NOTE && NOTE_LINE_NUMBER (insn) >= 0)
1911 {
1912 /* Delete this note if it is identical to previous note. */
1913 if (last_note
1914 && NOTE_SOURCE_FILE (insn) == NOTE_SOURCE_FILE (last_note)
1915 && NOTE_LINE_NUMBER (insn) == NOTE_LINE_NUMBER (last_note))
1916 {
1917 delete_insn (insn);
1918 continue;
1919 }
1920
1921 last_note = insn;
1922 }
1923 }
1924
1925 #ifdef HAVE_return
1926 if (HAVE_return)
1927 {
1928 /* If we fall through to the epilogue, see if we can insert a RETURN insn
1929 in front of it. If the machine allows it at this point (we might be
1930 after reload for a leaf routine), it will improve optimization for it
1931 to be there. We do this both here and at the start of this pass since
1932 the RETURN might have been deleted by some of our optimizations. */
1933 insn = get_last_insn ();
1934 while (insn && GET_CODE (insn) == NOTE)
1935 insn = PREV_INSN (insn);
1936
1937 if (insn && GET_CODE (insn) != BARRIER)
1938 {
1939 emit_jump_insn (gen_return ());
1940 emit_barrier ();
1941 }
1942 }
1943 #endif
1944
1945 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
1946 If so, delete it, and record that this function can drop off the end. */
1947
1948 insn = last_insn;
1949 {
1950 int n_labels = 1;
1951 while (insn
1952 /* One label can follow the end-note: the return label. */
1953 && ((GET_CODE (insn) == CODE_LABEL && n_labels-- > 0)
1954 /* Ordinary insns can follow it if returning a structure. */
1955 || GET_CODE (insn) == INSN
1956 /* If machine uses explicit RETURN insns, no epilogue,
1957 then one of them follows the note. */
1958 || (GET_CODE (insn) == JUMP_INSN
1959 && GET_CODE (PATTERN (insn)) == RETURN)
1960 /* Other kinds of notes can follow also. */
1961 || (GET_CODE (insn) == NOTE
1962 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_FUNCTION_END)))
1963 insn = PREV_INSN (insn);
1964 }
1965
1966 /* Report if control can fall through at the end of the function. */
1967 if (insn && GET_CODE (insn) == NOTE
1968 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_END)
1969 {
1970 can_reach_end = 1;
1971 delete_insn (insn);
1972 }
1973
1974 /* Show JUMP_CHAIN no longer valid. */
1975 jump_chain = 0;
1976 }
1977 \f
1978 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
1979 jump. Assume that this unconditional jump is to the exit test code. If
1980 the code is sufficiently simple, make a copy of it before INSN,
1981 followed by a jump to the exit of the loop. Then delete the unconditional
1982 jump after INSN.
1983
1984 Note that it is possible we can get confused here if the jump immediately
1985 after the loop start branches outside the loop but within an outer loop.
1986 If we are near the exit of that loop, we will copy its exit test. This
1987 will not generate incorrect code, but could suppress some optimizations.
1988 However, such cases are degenerate loops anyway.
1989
1990 Return 1 if we made the change, else 0.
1991
1992 This is only safe immediately after a regscan pass because it uses the
1993 values of regno_first_uid and regno_last_uid. */
1994
1995 static int
1996 duplicate_loop_exit_test (loop_start)
1997 rtx loop_start;
1998 {
1999 rtx insn, set, p;
2000 rtx copy, link;
2001 int num_insns = 0;
2002 rtx exitcode = NEXT_INSN (JUMP_LABEL (next_nonnote_insn (loop_start)));
2003 rtx lastexit;
2004 int max_reg = max_reg_num ();
2005 rtx *reg_map = 0;
2006
2007 /* Scan the exit code. We do not perform this optimization if any insn:
2008
2009 is a CALL_INSN
2010 is a CODE_LABEL
2011 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
2012 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
2013 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
2014 are not valid
2015
2016 Also, don't do this if the exit code is more than 20 insns. */
2017
2018 for (insn = exitcode;
2019 insn
2020 && ! (GET_CODE (insn) == NOTE
2021 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END);
2022 insn = NEXT_INSN (insn))
2023 {
2024 switch (GET_CODE (insn))
2025 {
2026 case CODE_LABEL:
2027 case CALL_INSN:
2028 return 0;
2029 case NOTE:
2030 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG
2031 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG
2032 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END)
2033 return 0;
2034 break;
2035 case JUMP_INSN:
2036 case INSN:
2037 if (++num_insns > 20
2038 || find_reg_note (insn, REG_RETVAL, NULL_RTX)
2039 || find_reg_note (insn, REG_LIBCALL, NULL_RTX))
2040 return 0;
2041 break;
2042 }
2043 }
2044
2045 /* Unless INSN is zero, we can do the optimization. */
2046 if (insn == 0)
2047 return 0;
2048
2049 lastexit = insn;
2050
2051 /* See if any insn sets a register only used in the loop exit code and
2052 not a user variable. If so, replace it with a new register. */
2053 for (insn = exitcode; insn != lastexit; insn = NEXT_INSN (insn))
2054 if (GET_CODE (insn) == INSN
2055 && (set = single_set (insn)) != 0
2056 && GET_CODE (SET_DEST (set)) == REG
2057 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER
2058 && regno_first_uid[REGNO (SET_DEST (set))] == INSN_UID (insn))
2059 {
2060 for (p = NEXT_INSN (insn); p != lastexit; p = NEXT_INSN (p))
2061 if (regno_last_uid[REGNO (SET_DEST (set))] == INSN_UID (p))
2062 break;
2063
2064 if (p != lastexit)
2065 {
2066 /* We can do the replacement. Allocate reg_map if this is the
2067 first replacement we found. */
2068 if (reg_map == 0)
2069 {
2070 reg_map = (rtx *) alloca (max_reg * sizeof (rtx));
2071 bzero (reg_map, max_reg * sizeof (rtx));
2072 }
2073
2074 REG_LOOP_TEST_P (SET_DEST (set)) = 1;
2075
2076 reg_map[REGNO (SET_DEST (set))]
2077 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
2078 }
2079 }
2080
2081 /* Now copy each insn. */
2082 for (insn = exitcode; insn != lastexit; insn = NEXT_INSN (insn))
2083 switch (GET_CODE (insn))
2084 {
2085 case BARRIER:
2086 copy = emit_barrier_before (loop_start);
2087 break;
2088 case NOTE:
2089 /* Only copy line-number notes. */
2090 if (NOTE_LINE_NUMBER (insn) >= 0)
2091 {
2092 copy = emit_note_before (NOTE_LINE_NUMBER (insn), loop_start);
2093 NOTE_SOURCE_FILE (copy) = NOTE_SOURCE_FILE (insn);
2094 }
2095 break;
2096
2097 case INSN:
2098 copy = emit_insn_before (copy_rtx (PATTERN (insn)), loop_start);
2099 if (reg_map)
2100 replace_regs (PATTERN (copy), reg_map, max_reg, 1);
2101
2102 mark_jump_label (PATTERN (copy), copy, 0);
2103
2104 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
2105 make them. */
2106 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
2107 if (REG_NOTE_KIND (link) != REG_LABEL)
2108 REG_NOTES (copy)
2109 = copy_rtx (gen_rtx (EXPR_LIST, REG_NOTE_KIND (link),
2110 XEXP (link, 0), REG_NOTES (copy)));
2111 if (reg_map && REG_NOTES (copy))
2112 replace_regs (REG_NOTES (copy), reg_map, max_reg, 1);
2113 break;
2114
2115 case JUMP_INSN:
2116 copy = emit_jump_insn_before (copy_rtx (PATTERN (insn)), loop_start);
2117 if (reg_map)
2118 replace_regs (PATTERN (copy), reg_map, max_reg, 1);
2119 mark_jump_label (PATTERN (copy), copy, 0);
2120 if (REG_NOTES (insn))
2121 {
2122 REG_NOTES (copy) = copy_rtx (REG_NOTES (insn));
2123 if (reg_map)
2124 replace_regs (REG_NOTES (copy), reg_map, max_reg, 1);
2125 }
2126
2127 /* If this is a simple jump, add it to the jump chain. */
2128
2129 if (INSN_UID (copy) < max_jump_chain && JUMP_LABEL (copy)
2130 && simplejump_p (copy))
2131 {
2132 jump_chain[INSN_UID (copy)]
2133 = jump_chain[INSN_UID (JUMP_LABEL (copy))];
2134 jump_chain[INSN_UID (JUMP_LABEL (copy))] = copy;
2135 }
2136 break;
2137
2138 default:
2139 abort ();
2140 }
2141
2142 /* Now clean up by emitting a jump to the end label and deleting the jump
2143 at the start of the loop. */
2144 if (GET_CODE (copy) != BARRIER)
2145 {
2146 copy = emit_jump_insn_before (gen_jump (get_label_after (insn)),
2147 loop_start);
2148 mark_jump_label (PATTERN (copy), copy, 0);
2149 if (INSN_UID (copy) < max_jump_chain
2150 && INSN_UID (JUMP_LABEL (copy)) < max_jump_chain)
2151 {
2152 jump_chain[INSN_UID (copy)]
2153 = jump_chain[INSN_UID (JUMP_LABEL (copy))];
2154 jump_chain[INSN_UID (JUMP_LABEL (copy))] = copy;
2155 }
2156 emit_barrier_before (loop_start);
2157 }
2158
2159 delete_insn (next_nonnote_insn (loop_start));
2160
2161 /* Mark the exit code as the virtual top of the converted loop. */
2162 emit_note_before (NOTE_INSN_LOOP_VTOP, exitcode);
2163
2164 return 1;
2165 }
2166 \f
2167 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
2168 loop-end notes between START and END out before START. Assume that
2169 END is not such a note. START may be such a note. Returns the value
2170 of the new starting insn, which may be different if the original start
2171 was such a note. */
2172
2173 rtx
2174 squeeze_notes (start, end)
2175 rtx start, end;
2176 {
2177 rtx insn;
2178 rtx next;
2179
2180 for (insn = start; insn != end; insn = next)
2181 {
2182 next = NEXT_INSN (insn);
2183 if (GET_CODE (insn) == NOTE
2184 && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END
2185 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG
2186 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG
2187 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END
2188 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_CONT
2189 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_VTOP))
2190 {
2191 if (insn == start)
2192 start = next;
2193 else
2194 {
2195 rtx prev = PREV_INSN (insn);
2196 PREV_INSN (insn) = PREV_INSN (start);
2197 NEXT_INSN (insn) = start;
2198 NEXT_INSN (PREV_INSN (insn)) = insn;
2199 PREV_INSN (NEXT_INSN (insn)) = insn;
2200 NEXT_INSN (prev) = next;
2201 PREV_INSN (next) = prev;
2202 }
2203 }
2204 }
2205
2206 return start;
2207 }
2208 \f
2209 /* Compare the instructions before insn E1 with those before E2
2210 to find an opportunity for cross jumping.
2211 (This means detecting identical sequences of insns followed by
2212 jumps to the same place, or followed by a label and a jump
2213 to that label, and replacing one with a jump to the other.)
2214
2215 Assume E1 is a jump that jumps to label E2
2216 (that is not always true but it might as well be).
2217 Find the longest possible equivalent sequences
2218 and store the first insns of those sequences into *F1 and *F2.
2219 Store zero there if no equivalent preceding instructions are found.
2220
2221 We give up if we find a label in stream 1.
2222 Actually we could transfer that label into stream 2. */
2223
2224 static void
2225 find_cross_jump (e1, e2, minimum, f1, f2)
2226 rtx e1, e2;
2227 int minimum;
2228 rtx *f1, *f2;
2229 {
2230 register rtx i1 = e1, i2 = e2;
2231 register rtx p1, p2;
2232 int lose = 0;
2233
2234 rtx last1 = 0, last2 = 0;
2235 rtx afterlast1 = 0, afterlast2 = 0;
2236 rtx prev1;
2237
2238 *f1 = 0;
2239 *f2 = 0;
2240
2241 while (1)
2242 {
2243 i1 = prev_nonnote_insn (i1);
2244
2245 i2 = PREV_INSN (i2);
2246 while (i2 && (GET_CODE (i2) == NOTE || GET_CODE (i2) == CODE_LABEL))
2247 i2 = PREV_INSN (i2);
2248
2249 if (i1 == 0)
2250 break;
2251
2252 /* Don't allow the range of insns preceding E1 or E2
2253 to include the other (E2 or E1). */
2254 if (i2 == e1 || i1 == e2)
2255 break;
2256
2257 /* If we will get to this code by jumping, those jumps will be
2258 tensioned to go directly to the new label (before I2),
2259 so this cross-jumping won't cost extra. So reduce the minimum. */
2260 if (GET_CODE (i1) == CODE_LABEL)
2261 {
2262 --minimum;
2263 break;
2264 }
2265
2266 if (i2 == 0 || GET_CODE (i1) != GET_CODE (i2))
2267 break;
2268
2269 p1 = PATTERN (i1);
2270 p2 = PATTERN (i2);
2271
2272 #ifdef STACK_REGS
2273 /* If cross_jump_death_matters is not 0, the insn's mode
2274 indicates whether or not the insn contains any stack-like
2275 regs. */
2276
2277 if (cross_jump_death_matters && GET_MODE (i1) == QImode)
2278 {
2279 /* If register stack conversion has already been done, then
2280 death notes must also be compared before it is certain that
2281 the two instruction streams match. */
2282
2283 rtx note;
2284 HARD_REG_SET i1_regset, i2_regset;
2285
2286 CLEAR_HARD_REG_SET (i1_regset);
2287 CLEAR_HARD_REG_SET (i2_regset);
2288
2289 for (note = REG_NOTES (i1); note; note = XEXP (note, 1))
2290 if (REG_NOTE_KIND (note) == REG_DEAD
2291 && STACK_REG_P (XEXP (note, 0)))
2292 SET_HARD_REG_BIT (i1_regset, REGNO (XEXP (note, 0)));
2293
2294 for (note = REG_NOTES (i2); note; note = XEXP (note, 1))
2295 if (REG_NOTE_KIND (note) == REG_DEAD
2296 && STACK_REG_P (XEXP (note, 0)))
2297 SET_HARD_REG_BIT (i2_regset, REGNO (XEXP (note, 0)));
2298
2299 GO_IF_HARD_REG_EQUAL (i1_regset, i2_regset, done);
2300
2301 lose = 1;
2302
2303 done:
2304 ;
2305 }
2306 #endif
2307
2308 if (lose || GET_CODE (p1) != GET_CODE (p2)
2309 || ! rtx_renumbered_equal_p (p1, p2))
2310 {
2311 /* The following code helps take care of G++ cleanups. */
2312 rtx equiv1;
2313 rtx equiv2;
2314
2315 if (!lose && GET_CODE (p1) == GET_CODE (p2)
2316 && ((equiv1 = find_reg_note (i1, REG_EQUAL, NULL_RTX)) != 0
2317 || (equiv1 = find_reg_note (i1, REG_EQUIV, NULL_RTX)) != 0)
2318 && ((equiv2 = find_reg_note (i2, REG_EQUAL, NULL_RTX)) != 0
2319 || (equiv2 = find_reg_note (i2, REG_EQUIV, NULL_RTX)) != 0)
2320 /* If the equivalences are not to a constant, they may
2321 reference pseudos that no longer exist, so we can't
2322 use them. */
2323 && CONSTANT_P (XEXP (equiv1, 0))
2324 && rtx_equal_p (XEXP (equiv1, 0), XEXP (equiv2, 0)))
2325 {
2326 rtx s1 = single_set (i1);
2327 rtx s2 = single_set (i2);
2328 if (s1 != 0 && s2 != 0
2329 && rtx_renumbered_equal_p (SET_DEST (s1), SET_DEST (s2)))
2330 {
2331 validate_change (i1, &SET_SRC (s1), XEXP (equiv1, 0), 1);
2332 validate_change (i2, &SET_SRC (s2), XEXP (equiv2, 0), 1);
2333 if (! rtx_renumbered_equal_p (p1, p2))
2334 cancel_changes (0);
2335 else if (apply_change_group ())
2336 goto win;
2337 }
2338 }
2339
2340 /* Insns fail to match; cross jumping is limited to the following
2341 insns. */
2342
2343 #ifdef HAVE_cc0
2344 /* Don't allow the insn after a compare to be shared by
2345 cross-jumping unless the compare is also shared.
2346 Here, if either of these non-matching insns is a compare,
2347 exclude the following insn from possible cross-jumping. */
2348 if (sets_cc0_p (p1) || sets_cc0_p (p2))
2349 last1 = afterlast1, last2 = afterlast2, ++minimum;
2350 #endif
2351
2352 /* If cross-jumping here will feed a jump-around-jump
2353 optimization, this jump won't cost extra, so reduce
2354 the minimum. */
2355 if (GET_CODE (i1) == JUMP_INSN
2356 && JUMP_LABEL (i1)
2357 && prev_real_insn (JUMP_LABEL (i1)) == e1)
2358 --minimum;
2359 break;
2360 }
2361
2362 win:
2363 if (GET_CODE (p1) != USE && GET_CODE (p1) != CLOBBER)
2364 {
2365 /* Ok, this insn is potentially includable in a cross-jump here. */
2366 afterlast1 = last1, afterlast2 = last2;
2367 last1 = i1, last2 = i2, --minimum;
2368 }
2369 }
2370
2371 /* We have to be careful that we do not cross-jump into the middle of
2372 USE-CALL_INSN-CLOBBER sequence. This sequence is used instead of
2373 putting the USE and CLOBBERs inside the CALL_INSN. The delay slot
2374 scheduler needs to know what registers are used and modified by the
2375 CALL_INSN and needs the adjacent USE and CLOBBERs to do so.
2376
2377 ??? At some point we should probably change this so that these are
2378 part of the CALL_INSN. The way we are doing it now is a kludge that
2379 is now causing trouble. */
2380
2381 if (last1 != 0 && GET_CODE (last1) == CALL_INSN
2382 && (prev1 = prev_nonnote_insn (last1))
2383 && GET_CODE (prev1) == INSN
2384 && GET_CODE (PATTERN (prev1)) == USE)
2385 {
2386 /* Remove this CALL_INSN from the range we can cross-jump. */
2387 last1 = next_real_insn (last1);
2388 last2 = next_real_insn (last2);
2389
2390 minimum++;
2391 }
2392
2393 /* Skip past CLOBBERS since they may be right after a CALL_INSN. It
2394 isn't worth checking for the CALL_INSN. */
2395 while (last1 != 0 && GET_CODE (PATTERN (last1)) == CLOBBER)
2396 last1 = next_real_insn (last1), last2 = next_real_insn (last2);
2397
2398 if (minimum <= 0 && last1 != 0 && last1 != e1)
2399 *f1 = last1, *f2 = last2;
2400 }
2401
2402 static void
2403 do_cross_jump (insn, newjpos, newlpos)
2404 rtx insn, newjpos, newlpos;
2405 {
2406 /* Find an existing label at this point
2407 or make a new one if there is none. */
2408 register rtx label = get_label_before (newlpos);
2409
2410 /* Make the same jump insn jump to the new point. */
2411 if (GET_CODE (PATTERN (insn)) == RETURN)
2412 {
2413 /* Remove from jump chain of returns. */
2414 delete_from_jump_chain (insn);
2415 /* Change the insn. */
2416 PATTERN (insn) = gen_jump (label);
2417 INSN_CODE (insn) = -1;
2418 JUMP_LABEL (insn) = label;
2419 LABEL_NUSES (label)++;
2420 /* Add to new the jump chain. */
2421 if (INSN_UID (label) < max_jump_chain
2422 && INSN_UID (insn) < max_jump_chain)
2423 {
2424 jump_chain[INSN_UID (insn)] = jump_chain[INSN_UID (label)];
2425 jump_chain[INSN_UID (label)] = insn;
2426 }
2427 }
2428 else
2429 redirect_jump (insn, label);
2430
2431 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
2432 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
2433 the NEWJPOS stream. */
2434
2435 while (newjpos != insn)
2436 {
2437 rtx lnote;
2438
2439 for (lnote = REG_NOTES (newlpos); lnote; lnote = XEXP (lnote, 1))
2440 if ((REG_NOTE_KIND (lnote) == REG_EQUAL
2441 || REG_NOTE_KIND (lnote) == REG_EQUIV)
2442 && ! find_reg_note (newjpos, REG_EQUAL, XEXP (lnote, 0))
2443 && ! find_reg_note (newjpos, REG_EQUIV, XEXP (lnote, 0)))
2444 remove_note (newlpos, lnote);
2445
2446 delete_insn (newjpos);
2447 newjpos = next_real_insn (newjpos);
2448 newlpos = next_real_insn (newlpos);
2449 }
2450 }
2451 \f
2452 /* Return the label before INSN, or put a new label there. */
2453
2454 rtx
2455 get_label_before (insn)
2456 rtx insn;
2457 {
2458 rtx label;
2459
2460 /* Find an existing label at this point
2461 or make a new one if there is none. */
2462 label = prev_nonnote_insn (insn);
2463
2464 if (label == 0 || GET_CODE (label) != CODE_LABEL)
2465 {
2466 rtx prev = PREV_INSN (insn);
2467
2468 /* Don't put a label between a CALL_INSN and USE insns that precede
2469 it. */
2470
2471 if (GET_CODE (insn) == CALL_INSN
2472 || (GET_CODE (insn) == INSN && GET_CODE (PATTERN (insn)) == SEQUENCE
2473 && GET_CODE (XVECEXP (PATTERN (insn), 0, 0)) == CALL_INSN))
2474 while (GET_CODE (prev) == INSN && GET_CODE (PATTERN (prev)) == USE)
2475 prev = PREV_INSN (prev);
2476
2477 label = gen_label_rtx ();
2478 emit_label_after (label, prev);
2479 LABEL_NUSES (label) = 0;
2480 }
2481 return label;
2482 }
2483
2484 /* Return the label after INSN, or put a new label there. */
2485
2486 rtx
2487 get_label_after (insn)
2488 rtx insn;
2489 {
2490 rtx label;
2491
2492 /* Find an existing label at this point
2493 or make a new one if there is none. */
2494 label = next_nonnote_insn (insn);
2495
2496 if (label == 0 || GET_CODE (label) != CODE_LABEL)
2497 {
2498 /* Don't put a label between a CALL_INSN and CLOBBER insns
2499 following it. */
2500
2501 if (GET_CODE (insn) == CALL_INSN
2502 || (GET_CODE (insn) == INSN && GET_CODE (PATTERN (insn)) == SEQUENCE
2503 && GET_CODE (XVECEXP (PATTERN (insn), 0, 0)) == CALL_INSN))
2504 while (GET_CODE (NEXT_INSN (insn)) == INSN
2505 && GET_CODE (PATTERN (NEXT_INSN (insn))) == CLOBBER)
2506 insn = NEXT_INSN (insn);
2507
2508 label = gen_label_rtx ();
2509 emit_label_after (label, insn);
2510 LABEL_NUSES (label) = 0;
2511 }
2512 return label;
2513 }
2514 \f
2515 /* Return 1 if INSN is a jump that jumps to right after TARGET
2516 only on the condition that TARGET itself would drop through.
2517 Assumes that TARGET is a conditional jump. */
2518
2519 static int
2520 jump_back_p (insn, target)
2521 rtx insn, target;
2522 {
2523 rtx cinsn, ctarget;
2524 enum rtx_code codei, codet;
2525
2526 if (simplejump_p (insn) || ! condjump_p (insn)
2527 || simplejump_p (target)
2528 || target != prev_real_insn (JUMP_LABEL (insn)))
2529 return 0;
2530
2531 cinsn = XEXP (SET_SRC (PATTERN (insn)), 0);
2532 ctarget = XEXP (SET_SRC (PATTERN (target)), 0);
2533
2534 codei = GET_CODE (cinsn);
2535 codet = GET_CODE (ctarget);
2536
2537 if (XEXP (SET_SRC (PATTERN (insn)), 1) == pc_rtx)
2538 {
2539 if (! can_reverse_comparison_p (cinsn, insn))
2540 return 0;
2541 codei = reverse_condition (codei);
2542 }
2543
2544 if (XEXP (SET_SRC (PATTERN (target)), 2) == pc_rtx)
2545 {
2546 if (! can_reverse_comparison_p (ctarget, target))
2547 return 0;
2548 codet = reverse_condition (codet);
2549 }
2550
2551 return (codei == codet
2552 && rtx_renumbered_equal_p (XEXP (cinsn, 0), XEXP (ctarget, 0))
2553 && rtx_renumbered_equal_p (XEXP (cinsn, 1), XEXP (ctarget, 1)));
2554 }
2555 \f
2556 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
2557 return non-zero if it is safe to reverse this comparison. It is if our
2558 floating-point is not IEEE, if this is an NE or EQ comparison, or if
2559 this is known to be an integer comparison. */
2560
2561 int
2562 can_reverse_comparison_p (comparison, insn)
2563 rtx comparison;
2564 rtx insn;
2565 {
2566 rtx arg0;
2567
2568 /* If this is not actually a comparison, we can't reverse it. */
2569 if (GET_RTX_CLASS (GET_CODE (comparison)) != '<')
2570 return 0;
2571
2572 if (TARGET_FLOAT_FORMAT != IEEE_FLOAT_FORMAT
2573 /* If this is an NE comparison, it is safe to reverse it to an EQ
2574 comparison and vice versa, even for floating point. If no operands
2575 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
2576 always false and NE is always true, so the reversal is also valid. */
2577 || flag_fast_math
2578 || GET_CODE (comparison) == NE
2579 || GET_CODE (comparison) == EQ)
2580 return 1;
2581
2582 arg0 = XEXP (comparison, 0);
2583
2584 /* Make sure ARG0 is one of the actual objects being compared. If we
2585 can't do this, we can't be sure the comparison can be reversed.
2586
2587 Handle cc0 and a MODE_CC register. */
2588 if ((GET_CODE (arg0) == REG && GET_MODE_CLASS (GET_MODE (arg0)) == MODE_CC)
2589 #ifdef HAVE_cc0
2590 || arg0 == cc0_rtx
2591 #endif
2592 )
2593 {
2594 rtx prev = prev_nonnote_insn (insn);
2595 rtx set = single_set (prev);
2596
2597 if (set == 0 || SET_DEST (set) != arg0)
2598 return 0;
2599
2600 arg0 = SET_SRC (set);
2601
2602 if (GET_CODE (arg0) == COMPARE)
2603 arg0 = XEXP (arg0, 0);
2604 }
2605
2606 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
2607 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
2608 return (GET_CODE (arg0) == CONST_INT
2609 || (GET_MODE (arg0) != VOIDmode
2610 && GET_MODE_CLASS (GET_MODE (arg0)) != MODE_CC
2611 && GET_MODE_CLASS (GET_MODE (arg0)) != MODE_FLOAT));
2612 }
2613
2614 /* Given an rtx-code for a comparison, return the code
2615 for the negated comparison.
2616 WATCH OUT! reverse_condition is not safe to use on a jump
2617 that might be acting on the results of an IEEE floating point comparison,
2618 because of the special treatment of non-signaling nans in comparisons.
2619 Use can_reverse_comparison_p to be sure. */
2620
2621 enum rtx_code
2622 reverse_condition (code)
2623 enum rtx_code code;
2624 {
2625 switch (code)
2626 {
2627 case EQ:
2628 return NE;
2629
2630 case NE:
2631 return EQ;
2632
2633 case GT:
2634 return LE;
2635
2636 case GE:
2637 return LT;
2638
2639 case LT:
2640 return GE;
2641
2642 case LE:
2643 return GT;
2644
2645 case GTU:
2646 return LEU;
2647
2648 case GEU:
2649 return LTU;
2650
2651 case LTU:
2652 return GEU;
2653
2654 case LEU:
2655 return GTU;
2656
2657 default:
2658 abort ();
2659 return UNKNOWN;
2660 }
2661 }
2662
2663 /* Similar, but return the code when two operands of a comparison are swapped.
2664 This IS safe for IEEE floating-point. */
2665
2666 enum rtx_code
2667 swap_condition (code)
2668 enum rtx_code code;
2669 {
2670 switch (code)
2671 {
2672 case EQ:
2673 case NE:
2674 return code;
2675
2676 case GT:
2677 return LT;
2678
2679 case GE:
2680 return LE;
2681
2682 case LT:
2683 return GT;
2684
2685 case LE:
2686 return GE;
2687
2688 case GTU:
2689 return LTU;
2690
2691 case GEU:
2692 return LEU;
2693
2694 case LTU:
2695 return GTU;
2696
2697 case LEU:
2698 return GEU;
2699
2700 default:
2701 abort ();
2702 return UNKNOWN;
2703 }
2704 }
2705
2706 /* Given a comparison CODE, return the corresponding unsigned comparison.
2707 If CODE is an equality comparison or already an unsigned comparison,
2708 CODE is returned. */
2709
2710 enum rtx_code
2711 unsigned_condition (code)
2712 enum rtx_code code;
2713 {
2714 switch (code)
2715 {
2716 case EQ:
2717 case NE:
2718 case GTU:
2719 case GEU:
2720 case LTU:
2721 case LEU:
2722 return code;
2723
2724 case GT:
2725 return GTU;
2726
2727 case GE:
2728 return GEU;
2729
2730 case LT:
2731 return LTU;
2732
2733 case LE:
2734 return LEU;
2735
2736 default:
2737 abort ();
2738 }
2739 }
2740
2741 /* Similarly, return the signed version of a comparison. */
2742
2743 enum rtx_code
2744 signed_condition (code)
2745 enum rtx_code code;
2746 {
2747 switch (code)
2748 {
2749 case EQ:
2750 case NE:
2751 case GT:
2752 case GE:
2753 case LT:
2754 case LE:
2755 return code;
2756
2757 case GTU:
2758 return GT;
2759
2760 case GEU:
2761 return GE;
2762
2763 case LTU:
2764 return LT;
2765
2766 case LEU:
2767 return LE;
2768
2769 default:
2770 abort ();
2771 }
2772 }
2773 \f
2774 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
2775 truth of CODE1 implies the truth of CODE2. */
2776
2777 int
2778 comparison_dominates_p (code1, code2)
2779 enum rtx_code code1, code2;
2780 {
2781 if (code1 == code2)
2782 return 1;
2783
2784 switch (code1)
2785 {
2786 case EQ:
2787 if (code2 == LE || code2 == LEU || code2 == GE || code2 == GEU)
2788 return 1;
2789 break;
2790
2791 case LT:
2792 if (code2 == LE)
2793 return 1;
2794 break;
2795
2796 case GT:
2797 if (code2 == GE)
2798 return 1;
2799 break;
2800
2801 case LTU:
2802 if (code2 == LEU)
2803 return 1;
2804 break;
2805
2806 case GTU:
2807 if (code2 == GEU)
2808 return 1;
2809 break;
2810 }
2811
2812 return 0;
2813 }
2814 \f
2815 /* Return 1 if INSN is an unconditional jump and nothing else. */
2816
2817 int
2818 simplejump_p (insn)
2819 rtx insn;
2820 {
2821 return (GET_CODE (insn) == JUMP_INSN
2822 && GET_CODE (PATTERN (insn)) == SET
2823 && GET_CODE (SET_DEST (PATTERN (insn))) == PC
2824 && GET_CODE (SET_SRC (PATTERN (insn))) == LABEL_REF);
2825 }
2826
2827 /* Return nonzero if INSN is a (possibly) conditional jump
2828 and nothing more. */
2829
2830 int
2831 condjump_p (insn)
2832 rtx insn;
2833 {
2834 register rtx x = PATTERN (insn);
2835 if (GET_CODE (x) != SET)
2836 return 0;
2837 if (GET_CODE (SET_DEST (x)) != PC)
2838 return 0;
2839 if (GET_CODE (SET_SRC (x)) == LABEL_REF)
2840 return 1;
2841 if (GET_CODE (SET_SRC (x)) != IF_THEN_ELSE)
2842 return 0;
2843 if (XEXP (SET_SRC (x), 2) == pc_rtx
2844 && (GET_CODE (XEXP (SET_SRC (x), 1)) == LABEL_REF
2845 || GET_CODE (XEXP (SET_SRC (x), 1)) == RETURN))
2846 return 1;
2847 if (XEXP (SET_SRC (x), 1) == pc_rtx
2848 && (GET_CODE (XEXP (SET_SRC (x), 2)) == LABEL_REF
2849 || GET_CODE (XEXP (SET_SRC (x), 2)) == RETURN))
2850 return 1;
2851 return 0;
2852 }
2853
2854 /* Return 1 if X is an RTX that does nothing but set the condition codes
2855 and CLOBBER or USE registers.
2856 Return -1 if X does explicitly set the condition codes,
2857 but also does other things. */
2858
2859 int
2860 sets_cc0_p (x)
2861 rtx x;
2862 {
2863 #ifdef HAVE_cc0
2864 if (GET_CODE (x) == SET && SET_DEST (x) == cc0_rtx)
2865 return 1;
2866 if (GET_CODE (x) == PARALLEL)
2867 {
2868 int i;
2869 int sets_cc0 = 0;
2870 int other_things = 0;
2871 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
2872 {
2873 if (GET_CODE (XVECEXP (x, 0, i)) == SET
2874 && SET_DEST (XVECEXP (x, 0, i)) == cc0_rtx)
2875 sets_cc0 = 1;
2876 else if (GET_CODE (XVECEXP (x, 0, i)) == SET)
2877 other_things = 1;
2878 }
2879 return ! sets_cc0 ? 0 : other_things ? -1 : 1;
2880 }
2881 return 0;
2882 #else
2883 abort ();
2884 #endif
2885 }
2886 \f
2887 /* Follow any unconditional jump at LABEL;
2888 return the ultimate label reached by any such chain of jumps.
2889 If LABEL is not followed by a jump, return LABEL.
2890 If the chain loops or we can't find end, return LABEL,
2891 since that tells caller to avoid changing the insn.
2892
2893 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
2894 a USE or CLOBBER. */
2895
2896 rtx
2897 follow_jumps (label)
2898 rtx label;
2899 {
2900 register rtx insn;
2901 register rtx next;
2902 register rtx value = label;
2903 register int depth;
2904
2905 for (depth = 0;
2906 (depth < 10
2907 && (insn = next_active_insn (value)) != 0
2908 && GET_CODE (insn) == JUMP_INSN
2909 && (JUMP_LABEL (insn) != 0 || GET_CODE (PATTERN (insn)) == RETURN)
2910 && (next = NEXT_INSN (insn))
2911 && GET_CODE (next) == BARRIER);
2912 depth++)
2913 {
2914 /* Don't chain through the insn that jumps into a loop
2915 from outside the loop,
2916 since that would create multiple loop entry jumps
2917 and prevent loop optimization. */
2918 rtx tem;
2919 if (!reload_completed)
2920 for (tem = value; tem != insn; tem = NEXT_INSN (tem))
2921 if (GET_CODE (tem) == NOTE
2922 && NOTE_LINE_NUMBER (tem) == NOTE_INSN_LOOP_BEG)
2923 return value;
2924
2925 /* If we have found a cycle, make the insn jump to itself. */
2926 if (JUMP_LABEL (insn) == label)
2927 return label;
2928
2929 tem = next_active_insn (JUMP_LABEL (insn));
2930 if (tem && (GET_CODE (PATTERN (tem)) == ADDR_VEC
2931 || GET_CODE (PATTERN (tem)) == ADDR_DIFF_VEC))
2932 break;
2933
2934 value = JUMP_LABEL (insn);
2935 }
2936 if (depth == 10)
2937 return label;
2938 return value;
2939 }
2940
2941 /* Assuming that field IDX of X is a vector of label_refs,
2942 replace each of them by the ultimate label reached by it.
2943 Return nonzero if a change is made.
2944 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
2945
2946 static int
2947 tension_vector_labels (x, idx)
2948 register rtx x;
2949 register int idx;
2950 {
2951 int changed = 0;
2952 register int i;
2953 for (i = XVECLEN (x, idx) - 1; i >= 0; i--)
2954 {
2955 register rtx olabel = XEXP (XVECEXP (x, idx, i), 0);
2956 register rtx nlabel = follow_jumps (olabel);
2957 if (nlabel && nlabel != olabel)
2958 {
2959 XEXP (XVECEXP (x, idx, i), 0) = nlabel;
2960 ++LABEL_NUSES (nlabel);
2961 if (--LABEL_NUSES (olabel) == 0)
2962 delete_insn (olabel);
2963 changed = 1;
2964 }
2965 }
2966 return changed;
2967 }
2968 \f
2969 /* Find all CODE_LABELs referred to in X, and increment their use counts.
2970 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
2971 in INSN, then store one of them in JUMP_LABEL (INSN).
2972 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
2973 referenced in INSN, add a REG_LABEL note containing that label to INSN.
2974 Also, when there are consecutive labels, canonicalize on the last of them.
2975
2976 Note that two labels separated by a loop-beginning note
2977 must be kept distinct if we have not yet done loop-optimization,
2978 because the gap between them is where loop-optimize
2979 will want to move invariant code to. CROSS_JUMP tells us
2980 that loop-optimization is done with.
2981
2982 Once reload has completed (CROSS_JUMP non-zero), we need not consider
2983 two labels distinct if they are separated by only USE or CLOBBER insns. */
2984
2985 static void
2986 mark_jump_label (x, insn, cross_jump)
2987 register rtx x;
2988 rtx insn;
2989 int cross_jump;
2990 {
2991 register RTX_CODE code = GET_CODE (x);
2992 register int i;
2993 register char *fmt;
2994
2995 switch (code)
2996 {
2997 case PC:
2998 case CC0:
2999 case REG:
3000 case SUBREG:
3001 case CONST_INT:
3002 case SYMBOL_REF:
3003 case CONST_DOUBLE:
3004 case CLOBBER:
3005 case CALL:
3006 return;
3007
3008 case MEM:
3009 /* If this is a constant-pool reference, see if it is a label. */
3010 if (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
3011 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))
3012 mark_jump_label (get_pool_constant (XEXP (x, 0)), insn, cross_jump);
3013 break;
3014
3015 case LABEL_REF:
3016 {
3017 register rtx label = XEXP (x, 0);
3018 register rtx next;
3019 if (GET_CODE (label) != CODE_LABEL)
3020 abort ();
3021 /* Ignore references to labels of containing functions. */
3022 if (LABEL_REF_NONLOCAL_P (x))
3023 break;
3024 /* If there are other labels following this one,
3025 replace it with the last of the consecutive labels. */
3026 for (next = NEXT_INSN (label); next; next = NEXT_INSN (next))
3027 {
3028 if (GET_CODE (next) == CODE_LABEL)
3029 label = next;
3030 else if (cross_jump && GET_CODE (next) == INSN
3031 && (GET_CODE (PATTERN (next)) == USE
3032 || GET_CODE (PATTERN (next)) == CLOBBER))
3033 continue;
3034 else if (GET_CODE (next) != NOTE)
3035 break;
3036 else if (! cross_jump
3037 && (NOTE_LINE_NUMBER (next) == NOTE_INSN_LOOP_BEG
3038 || NOTE_LINE_NUMBER (next) == NOTE_INSN_FUNCTION_END))
3039 break;
3040 }
3041 XEXP (x, 0) = label;
3042 ++LABEL_NUSES (label);
3043 if (insn)
3044 {
3045 if (GET_CODE (insn) == JUMP_INSN)
3046 JUMP_LABEL (insn) = label;
3047 else if (! find_reg_note (insn, REG_LABEL, label))
3048 {
3049 rtx next = next_real_insn (label);
3050 /* Don't record labels that refer to dispatch tables.
3051 This is not necessary, since the tablejump
3052 references the same label.
3053 And if we did record them, flow.c would make worse code. */
3054 if (next == 0
3055 || ! (GET_CODE (next) == JUMP_INSN
3056 && (GET_CODE (PATTERN (next)) == ADDR_VEC
3057 || GET_CODE (PATTERN (next)) == ADDR_DIFF_VEC)))
3058 {
3059 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_LABEL, label,
3060 REG_NOTES (insn));
3061 /* Record in the note whether label is nonlocal. */
3062 LABEL_REF_NONLOCAL_P (REG_NOTES (insn))
3063 = LABEL_REF_NONLOCAL_P (x);
3064 }
3065 }
3066 }
3067 return;
3068 }
3069
3070 /* Do walk the labels in a vector, but not the first operand of an
3071 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
3072 case ADDR_VEC:
3073 case ADDR_DIFF_VEC:
3074 {
3075 int eltnum = code == ADDR_DIFF_VEC ? 1 : 0;
3076
3077 for (i = 0; i < XVECLEN (x, eltnum); i++)
3078 mark_jump_label (XVECEXP (x, eltnum, i), NULL_RTX, cross_jump);
3079 return;
3080 }
3081 }
3082
3083 fmt = GET_RTX_FORMAT (code);
3084 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3085 {
3086 if (fmt[i] == 'e')
3087 mark_jump_label (XEXP (x, i), insn, cross_jump);
3088 else if (fmt[i] == 'E')
3089 {
3090 register int j;
3091 for (j = 0; j < XVECLEN (x, i); j++)
3092 mark_jump_label (XVECEXP (x, i, j), insn, cross_jump);
3093 }
3094 }
3095 }
3096
3097 /* If all INSN does is set the pc, delete it,
3098 and delete the insn that set the condition codes for it
3099 if that's what the previous thing was. */
3100
3101 void
3102 delete_jump (insn)
3103 rtx insn;
3104 {
3105 register rtx set = single_set (insn);
3106
3107 if (set && GET_CODE (SET_DEST (set)) == PC)
3108 delete_computation (insn);
3109 }
3110
3111 /* Delete INSN and recursively delete insns that compute values used only
3112 by INSN. This uses the REG_DEAD notes computed during flow analysis.
3113 If we are running before flow.c, we need do nothing since flow.c will
3114 delete dead code. We also can't know if the registers being used are
3115 dead or not at this point.
3116
3117 Otherwise, look at all our REG_DEAD notes. If a previous insn does
3118 nothing other than set a register that dies in this insn, we can delete
3119 that insn as well.
3120
3121 On machines with CC0, if CC0 is used in this insn, we may be able to
3122 delete the insn that set it. */
3123
3124 void
3125 delete_computation (insn)
3126 rtx insn;
3127 {
3128 rtx note, next;
3129
3130 #ifdef HAVE_cc0
3131 if (reg_referenced_p (cc0_rtx, PATTERN (insn)))
3132 {
3133 rtx prev = prev_nonnote_insn (insn);
3134 /* We assume that at this stage
3135 CC's are always set explicitly
3136 and always immediately before the jump that
3137 will use them. So if the previous insn
3138 exists to set the CC's, delete it
3139 (unless it performs auto-increments, etc.). */
3140 if (prev && GET_CODE (prev) == INSN
3141 && sets_cc0_p (PATTERN (prev)))
3142 {
3143 if (sets_cc0_p (PATTERN (prev)) > 0
3144 && !FIND_REG_INC_NOTE (prev, NULL_RTX))
3145 delete_computation (prev);
3146 else
3147 /* Otherwise, show that cc0 won't be used. */
3148 REG_NOTES (prev) = gen_rtx (EXPR_LIST, REG_UNUSED,
3149 cc0_rtx, REG_NOTES (prev));
3150 }
3151 }
3152 #endif
3153
3154 for (note = REG_NOTES (insn); note; note = next)
3155 {
3156 rtx our_prev;
3157
3158 next = XEXP (note, 1);
3159
3160 if (REG_NOTE_KIND (note) != REG_DEAD
3161 /* Verify that the REG_NOTE is legitimate. */
3162 || GET_CODE (XEXP (note, 0)) != REG)
3163 continue;
3164
3165 for (our_prev = prev_nonnote_insn (insn);
3166 our_prev && GET_CODE (our_prev) == INSN;
3167 our_prev = prev_nonnote_insn (our_prev))
3168 {
3169 /* If we reach a SEQUENCE, it is too complex to try to
3170 do anything with it, so give up. */
3171 if (GET_CODE (PATTERN (our_prev)) == SEQUENCE)
3172 break;
3173
3174 if (GET_CODE (PATTERN (our_prev)) == USE
3175 && GET_CODE (XEXP (PATTERN (our_prev), 0)) == INSN)
3176 /* reorg creates USEs that look like this. We leave them
3177 alone because reorg needs them for its own purposes. */
3178 break;
3179
3180 if (reg_set_p (XEXP (note, 0), PATTERN (our_prev)))
3181 {
3182 if (FIND_REG_INC_NOTE (our_prev, NULL_RTX))
3183 break;
3184
3185 if (GET_CODE (PATTERN (our_prev)) == PARALLEL)
3186 {
3187 /* If we find a SET of something else, we can't
3188 delete the insn. */
3189
3190 int i;
3191
3192 for (i = 0; i < XVECLEN (PATTERN (our_prev), 0); i++)
3193 {
3194 rtx part = XVECEXP (PATTERN (our_prev), 0, i);
3195
3196 if (GET_CODE (part) == SET
3197 && SET_DEST (part) != XEXP (note, 0))
3198 break;
3199 }
3200
3201 if (i == XVECLEN (PATTERN (our_prev), 0))
3202 delete_computation (our_prev);
3203 }
3204 else if (GET_CODE (PATTERN (our_prev)) == SET
3205 && SET_DEST (PATTERN (our_prev)) == XEXP (note, 0))
3206 delete_computation (our_prev);
3207
3208 break;
3209 }
3210
3211 /* If OUR_PREV references the register that dies here, it is an
3212 additional use. Hence any prior SET isn't dead. However, this
3213 insn becomes the new place for the REG_DEAD note. */
3214 if (reg_overlap_mentioned_p (XEXP (note, 0),
3215 PATTERN (our_prev)))
3216 {
3217 XEXP (note, 1) = REG_NOTES (our_prev);
3218 REG_NOTES (our_prev) = note;
3219 break;
3220 }
3221 }
3222 }
3223
3224 delete_insn (insn);
3225 }
3226 \f
3227 /* Delete insn INSN from the chain of insns and update label ref counts.
3228 May delete some following insns as a consequence; may even delete
3229 a label elsewhere and insns that follow it.
3230
3231 Returns the first insn after INSN that was not deleted. */
3232
3233 rtx
3234 delete_insn (insn)
3235 register rtx insn;
3236 {
3237 register rtx next = NEXT_INSN (insn);
3238 register rtx prev = PREV_INSN (insn);
3239 register int was_code_label = (GET_CODE (insn) == CODE_LABEL);
3240 register int dont_really_delete = 0;
3241
3242 while (next && INSN_DELETED_P (next))
3243 next = NEXT_INSN (next);
3244
3245 /* This insn is already deleted => return first following nondeleted. */
3246 if (INSN_DELETED_P (insn))
3247 return next;
3248
3249 /* Don't delete user-declared labels. Convert them to special NOTEs
3250 instead. */
3251 if (was_code_label && LABEL_NAME (insn) != 0
3252 && optimize && ! dont_really_delete)
3253 {
3254 PUT_CODE (insn, NOTE);
3255 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED_LABEL;
3256 NOTE_SOURCE_FILE (insn) = 0;
3257 dont_really_delete = 1;
3258 }
3259 else
3260 /* Mark this insn as deleted. */
3261 INSN_DELETED_P (insn) = 1;
3262
3263 /* If this is an unconditional jump, delete it from the jump chain. */
3264 if (simplejump_p (insn))
3265 delete_from_jump_chain (insn);
3266
3267 /* If instruction is followed by a barrier,
3268 delete the barrier too. */
3269
3270 if (next != 0 && GET_CODE (next) == BARRIER)
3271 {
3272 INSN_DELETED_P (next) = 1;
3273 next = NEXT_INSN (next);
3274 }
3275
3276 /* Patch out INSN (and the barrier if any) */
3277
3278 if (optimize && ! dont_really_delete)
3279 {
3280 if (prev)
3281 {
3282 NEXT_INSN (prev) = next;
3283 if (GET_CODE (prev) == INSN && GET_CODE (PATTERN (prev)) == SEQUENCE)
3284 NEXT_INSN (XVECEXP (PATTERN (prev), 0,
3285 XVECLEN (PATTERN (prev), 0) - 1)) = next;
3286 }
3287
3288 if (next)
3289 {
3290 PREV_INSN (next) = prev;
3291 if (GET_CODE (next) == INSN && GET_CODE (PATTERN (next)) == SEQUENCE)
3292 PREV_INSN (XVECEXP (PATTERN (next), 0, 0)) = prev;
3293 }
3294
3295 if (prev && NEXT_INSN (prev) == 0)
3296 set_last_insn (prev);
3297 }
3298
3299 /* If deleting a jump, decrement the count of the label,
3300 and delete the label if it is now unused. */
3301
3302 if (GET_CODE (insn) == JUMP_INSN && JUMP_LABEL (insn))
3303 if (--LABEL_NUSES (JUMP_LABEL (insn)) == 0)
3304 {
3305 /* This can delete NEXT or PREV,
3306 either directly if NEXT is JUMP_LABEL (INSN),
3307 or indirectly through more levels of jumps. */
3308 delete_insn (JUMP_LABEL (insn));
3309 /* I feel a little doubtful about this loop,
3310 but I see no clean and sure alternative way
3311 to find the first insn after INSN that is not now deleted.
3312 I hope this works. */
3313 while (next && INSN_DELETED_P (next))
3314 next = NEXT_INSN (next);
3315 return next;
3316 }
3317
3318 while (prev && (INSN_DELETED_P (prev) || GET_CODE (prev) == NOTE))
3319 prev = PREV_INSN (prev);
3320
3321 /* If INSN was a label and a dispatch table follows it,
3322 delete the dispatch table. The tablejump must have gone already.
3323 It isn't useful to fall through into a table. */
3324
3325 if (was_code_label
3326 && NEXT_INSN (insn) != 0
3327 && GET_CODE (NEXT_INSN (insn)) == JUMP_INSN
3328 && (GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_VEC
3329 || GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_DIFF_VEC))
3330 next = delete_insn (NEXT_INSN (insn));
3331
3332 /* If INSN was a label, delete insns following it if now unreachable. */
3333
3334 if (was_code_label && prev && GET_CODE (prev) == BARRIER)
3335 {
3336 register RTX_CODE code;
3337 while (next != 0
3338 && ((code = GET_CODE (next)) == INSN
3339 || code == JUMP_INSN || code == CALL_INSN
3340 || code == NOTE
3341 || (code == CODE_LABEL && INSN_DELETED_P (next))))
3342 {
3343 if (code == NOTE
3344 && NOTE_LINE_NUMBER (next) != NOTE_INSN_FUNCTION_END)
3345 next = NEXT_INSN (next);
3346 /* Keep going past other deleted labels to delete what follows. */
3347 else if (code == CODE_LABEL && INSN_DELETED_P (next))
3348 next = NEXT_INSN (next);
3349 else
3350 /* Note: if this deletes a jump, it can cause more
3351 deletion of unreachable code, after a different label.
3352 As long as the value from this recursive call is correct,
3353 this invocation functions correctly. */
3354 next = delete_insn (next);
3355 }
3356 }
3357
3358 return next;
3359 }
3360
3361 /* Advance from INSN till reaching something not deleted
3362 then return that. May return INSN itself. */
3363
3364 rtx
3365 next_nondeleted_insn (insn)
3366 rtx insn;
3367 {
3368 while (INSN_DELETED_P (insn))
3369 insn = NEXT_INSN (insn);
3370 return insn;
3371 }
3372 \f
3373 /* Delete a range of insns from FROM to TO, inclusive.
3374 This is for the sake of peephole optimization, so assume
3375 that whatever these insns do will still be done by a new
3376 peephole insn that will replace them. */
3377
3378 void
3379 delete_for_peephole (from, to)
3380 register rtx from, to;
3381 {
3382 register rtx insn = from;
3383
3384 while (1)
3385 {
3386 register rtx next = NEXT_INSN (insn);
3387 register rtx prev = PREV_INSN (insn);
3388
3389 if (GET_CODE (insn) != NOTE)
3390 {
3391 INSN_DELETED_P (insn) = 1;
3392
3393 /* Patch this insn out of the chain. */
3394 /* We don't do this all at once, because we
3395 must preserve all NOTEs. */
3396 if (prev)
3397 NEXT_INSN (prev) = next;
3398
3399 if (next)
3400 PREV_INSN (next) = prev;
3401 }
3402
3403 if (insn == to)
3404 break;
3405 insn = next;
3406 }
3407
3408 /* Note that if TO is an unconditional jump
3409 we *do not* delete the BARRIER that follows,
3410 since the peephole that replaces this sequence
3411 is also an unconditional jump in that case. */
3412 }
3413 \f
3414 /* Invert the condition of the jump JUMP, and make it jump
3415 to label NLABEL instead of where it jumps now. */
3416
3417 int
3418 invert_jump (jump, nlabel)
3419 rtx jump, nlabel;
3420 {
3421 register rtx olabel = JUMP_LABEL (jump);
3422
3423 /* We have to either invert the condition and change the label or
3424 do neither. Either operation could fail. We first try to invert
3425 the jump. If that succeeds, we try changing the label. If that fails,
3426 we invert the jump back to what it was. */
3427
3428 if (! invert_exp (PATTERN (jump), jump))
3429 return 0;
3430
3431 if (redirect_jump (jump, nlabel))
3432 return 1;
3433
3434 if (! invert_exp (PATTERN (jump), jump))
3435 /* This should just be putting it back the way it was. */
3436 abort ();
3437
3438 return 0;
3439 }
3440
3441 /* Invert the jump condition of rtx X contained in jump insn, INSN.
3442
3443 Return 1 if we can do so, 0 if we cannot find a way to do so that
3444 matches a pattern. */
3445
3446 int
3447 invert_exp (x, insn)
3448 rtx x;
3449 rtx insn;
3450 {
3451 register RTX_CODE code;
3452 register int i;
3453 register char *fmt;
3454
3455 code = GET_CODE (x);
3456
3457 if (code == IF_THEN_ELSE)
3458 {
3459 register rtx comp = XEXP (x, 0);
3460 register rtx tem;
3461
3462 /* We can do this in two ways: The preferable way, which can only
3463 be done if this is not an integer comparison, is to reverse
3464 the comparison code. Otherwise, swap the THEN-part and ELSE-part
3465 of the IF_THEN_ELSE. If we can't do either, fail. */
3466
3467 if (can_reverse_comparison_p (comp, insn)
3468 && validate_change (insn, &XEXP (x, 0),
3469 gen_rtx (reverse_condition (GET_CODE (comp)),
3470 GET_MODE (comp), XEXP (comp, 0),
3471 XEXP (comp, 1)), 0))
3472 return 1;
3473
3474 tem = XEXP (x, 1);
3475 validate_change (insn, &XEXP (x, 1), XEXP (x, 2), 1);
3476 validate_change (insn, &XEXP (x, 2), tem, 1);
3477 return apply_change_group ();
3478 }
3479
3480 fmt = GET_RTX_FORMAT (code);
3481 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3482 {
3483 if (fmt[i] == 'e')
3484 if (! invert_exp (XEXP (x, i), insn))
3485 return 0;
3486 if (fmt[i] == 'E')
3487 {
3488 register int j;
3489 for (j = 0; j < XVECLEN (x, i); j++)
3490 if (!invert_exp (XVECEXP (x, i, j), insn))
3491 return 0;
3492 }
3493 }
3494
3495 return 1;
3496 }
3497 \f
3498 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
3499 If the old jump target label is unused as a result,
3500 it and the code following it may be deleted.
3501
3502 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
3503 RETURN insn.
3504
3505 The return value will be 1 if the change was made, 0 if it wasn't (this
3506 can only occur for NLABEL == 0). */
3507
3508 int
3509 redirect_jump (jump, nlabel)
3510 rtx jump, nlabel;
3511 {
3512 register rtx olabel = JUMP_LABEL (jump);
3513
3514 if (nlabel == olabel)
3515 return 1;
3516
3517 if (! redirect_exp (&PATTERN (jump), olabel, nlabel, jump))
3518 return 0;
3519
3520 /* If this is an unconditional branch, delete it from the jump_chain of
3521 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
3522 have UID's in range and JUMP_CHAIN is valid). */
3523 if (jump_chain && (simplejump_p (jump)
3524 || GET_CODE (PATTERN (jump)) == RETURN))
3525 {
3526 int label_index = nlabel ? INSN_UID (nlabel) : 0;
3527
3528 delete_from_jump_chain (jump);
3529 if (label_index < max_jump_chain
3530 && INSN_UID (jump) < max_jump_chain)
3531 {
3532 jump_chain[INSN_UID (jump)] = jump_chain[label_index];
3533 jump_chain[label_index] = jump;
3534 }
3535 }
3536
3537 JUMP_LABEL (jump) = nlabel;
3538 if (nlabel)
3539 ++LABEL_NUSES (nlabel);
3540
3541 if (olabel && --LABEL_NUSES (olabel) == 0)
3542 delete_insn (olabel);
3543
3544 return 1;
3545 }
3546
3547 /* Delete the instruction JUMP from any jump chain it might be on. */
3548
3549 static void
3550 delete_from_jump_chain (jump)
3551 rtx jump;
3552 {
3553 int index;
3554 rtx olabel = JUMP_LABEL (jump);
3555
3556 /* Handle unconditional jumps. */
3557 if (jump_chain && olabel != 0
3558 && INSN_UID (olabel) < max_jump_chain
3559 && simplejump_p (jump))
3560 index = INSN_UID (olabel);
3561 /* Handle return insns. */
3562 else if (jump_chain && GET_CODE (PATTERN (jump)) == RETURN)
3563 index = 0;
3564 else return;
3565
3566 if (jump_chain[index] == jump)
3567 jump_chain[index] = jump_chain[INSN_UID (jump)];
3568 else
3569 {
3570 rtx insn;
3571
3572 for (insn = jump_chain[index];
3573 insn != 0;
3574 insn = jump_chain[INSN_UID (insn)])
3575 if (jump_chain[INSN_UID (insn)] == jump)
3576 {
3577 jump_chain[INSN_UID (insn)] = jump_chain[INSN_UID (jump)];
3578 break;
3579 }
3580 }
3581 }
3582
3583 /* If NLABEL is nonzero, throughout the rtx at LOC,
3584 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
3585 zero, alter (RETURN) to (LABEL_REF NLABEL).
3586
3587 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
3588 validity with validate_change. Convert (set (pc) (label_ref olabel))
3589 to (return).
3590
3591 Return 0 if we found a change we would like to make but it is invalid.
3592 Otherwise, return 1. */
3593
3594 int
3595 redirect_exp (loc, olabel, nlabel, insn)
3596 rtx *loc;
3597 rtx olabel, nlabel;
3598 rtx insn;
3599 {
3600 register rtx x = *loc;
3601 register RTX_CODE code = GET_CODE (x);
3602 register int i;
3603 register char *fmt;
3604
3605 if (code == LABEL_REF)
3606 {
3607 if (XEXP (x, 0) == olabel)
3608 {
3609 if (nlabel)
3610 XEXP (x, 0) = nlabel;
3611 else
3612 return validate_change (insn, loc, gen_rtx (RETURN, VOIDmode), 0);
3613 return 1;
3614 }
3615 }
3616 else if (code == RETURN && olabel == 0)
3617 {
3618 x = gen_rtx (LABEL_REF, VOIDmode, nlabel);
3619 if (loc == &PATTERN (insn))
3620 x = gen_rtx (SET, VOIDmode, pc_rtx, x);
3621 return validate_change (insn, loc, x, 0);
3622 }
3623
3624 if (code == SET && nlabel == 0 && SET_DEST (x) == pc_rtx
3625 && GET_CODE (SET_SRC (x)) == LABEL_REF
3626 && XEXP (SET_SRC (x), 0) == olabel)
3627 return validate_change (insn, loc, gen_rtx (RETURN, VOIDmode), 0);
3628
3629 fmt = GET_RTX_FORMAT (code);
3630 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3631 {
3632 if (fmt[i] == 'e')
3633 if (! redirect_exp (&XEXP (x, i), olabel, nlabel, insn))
3634 return 0;
3635 if (fmt[i] == 'E')
3636 {
3637 register int j;
3638 for (j = 0; j < XVECLEN (x, i); j++)
3639 if (! redirect_exp (&XVECEXP (x, i, j), olabel, nlabel, insn))
3640 return 0;
3641 }
3642 }
3643
3644 return 1;
3645 }
3646 \f
3647 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
3648
3649 If the old jump target label (before the dispatch table) becomes unused,
3650 it and the dispatch table may be deleted. In that case, find the insn
3651 before the jump references that label and delete it and logical successors
3652 too. */
3653
3654 void
3655 redirect_tablejump (jump, nlabel)
3656 rtx jump, nlabel;
3657 {
3658 register rtx olabel = JUMP_LABEL (jump);
3659
3660 /* Add this jump to the jump_chain of NLABEL. */
3661 if (jump_chain && INSN_UID (nlabel) < max_jump_chain
3662 && INSN_UID (jump) < max_jump_chain)
3663 {
3664 jump_chain[INSN_UID (jump)] = jump_chain[INSN_UID (nlabel)];
3665 jump_chain[INSN_UID (nlabel)] = jump;
3666 }
3667
3668 PATTERN (jump) = gen_jump (nlabel);
3669 JUMP_LABEL (jump) = nlabel;
3670 ++LABEL_NUSES (nlabel);
3671 INSN_CODE (jump) = -1;
3672
3673 if (--LABEL_NUSES (olabel) == 0)
3674 {
3675 delete_labelref_insn (jump, olabel, 0);
3676 delete_insn (olabel);
3677 }
3678 }
3679
3680 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
3681 If we found one, delete it and then delete this insn if DELETE_THIS is
3682 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
3683
3684 static int
3685 delete_labelref_insn (insn, label, delete_this)
3686 rtx insn, label;
3687 int delete_this;
3688 {
3689 int deleted = 0;
3690 rtx link;
3691
3692 if (GET_CODE (insn) != NOTE
3693 && reg_mentioned_p (label, PATTERN (insn)))
3694 {
3695 if (delete_this)
3696 {
3697 delete_insn (insn);
3698 deleted = 1;
3699 }
3700 else
3701 return 1;
3702 }
3703
3704 for (link = LOG_LINKS (insn); link; link = XEXP (link, 1))
3705 if (delete_labelref_insn (XEXP (link, 0), label, 1))
3706 {
3707 if (delete_this)
3708 {
3709 delete_insn (insn);
3710 deleted = 1;
3711 }
3712 else
3713 return 1;
3714 }
3715
3716 return deleted;
3717 }
3718 \f
3719 /* Like rtx_equal_p except that it considers two REGs as equal
3720 if they renumber to the same value. */
3721
3722 int
3723 rtx_renumbered_equal_p (x, y)
3724 rtx x, y;
3725 {
3726 register int i;
3727 register RTX_CODE code = GET_CODE (x);
3728 register char *fmt;
3729
3730 if (x == y)
3731 return 1;
3732 if ((code == REG || (code == SUBREG && GET_CODE (SUBREG_REG (x)) == REG))
3733 && (GET_CODE (y) == REG || (GET_CODE (y) == SUBREG
3734 && GET_CODE (SUBREG_REG (y)) == REG)))
3735 {
3736 register int j;
3737
3738 if (GET_MODE (x) != GET_MODE (y))
3739 return 0;
3740
3741 /* If we haven't done any renumbering, don't
3742 make any assumptions. */
3743 if (reg_renumber == 0)
3744 return rtx_equal_p (x, y);
3745
3746 if (code == SUBREG)
3747 {
3748 i = REGNO (SUBREG_REG (x));
3749 if (reg_renumber[i] >= 0)
3750 i = reg_renumber[i];
3751 i += SUBREG_WORD (x);
3752 }
3753 else
3754 {
3755 i = REGNO (x);
3756 if (reg_renumber[i] >= 0)
3757 i = reg_renumber[i];
3758 }
3759 if (GET_CODE (y) == SUBREG)
3760 {
3761 j = REGNO (SUBREG_REG (y));
3762 if (reg_renumber[j] >= 0)
3763 j = reg_renumber[j];
3764 j += SUBREG_WORD (y);
3765 }
3766 else
3767 {
3768 j = REGNO (y);
3769 if (reg_renumber[j] >= 0)
3770 j = reg_renumber[j];
3771 }
3772 return i == j;
3773 }
3774 /* Now we have disposed of all the cases
3775 in which different rtx codes can match. */
3776 if (code != GET_CODE (y))
3777 return 0;
3778 switch (code)
3779 {
3780 case PC:
3781 case CC0:
3782 case ADDR_VEC:
3783 case ADDR_DIFF_VEC:
3784 return 0;
3785
3786 case CONST_INT:
3787 return INTVAL (x) == INTVAL (y);
3788
3789 case LABEL_REF:
3790 /* We can't assume nonlocal labels have their following insns yet. */
3791 if (LABEL_REF_NONLOCAL_P (x) || LABEL_REF_NONLOCAL_P (y))
3792 return XEXP (x, 0) == XEXP (y, 0);
3793 /* Two label-refs are equivalent if they point at labels
3794 in the same position in the instruction stream. */
3795 return (next_real_insn (XEXP (x, 0))
3796 == next_real_insn (XEXP (y, 0)));
3797
3798 case SYMBOL_REF:
3799 return XSTR (x, 0) == XSTR (y, 0);
3800 }
3801
3802 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
3803
3804 if (GET_MODE (x) != GET_MODE (y))
3805 return 0;
3806
3807 /* Compare the elements. If any pair of corresponding elements
3808 fail to match, return 0 for the whole things. */
3809
3810 fmt = GET_RTX_FORMAT (code);
3811 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3812 {
3813 register int j;
3814 switch (fmt[i])
3815 {
3816 case 'w':
3817 if (XWINT (x, i) != XWINT (y, i))
3818 return 0;
3819 break;
3820
3821 case 'i':
3822 if (XINT (x, i) != XINT (y, i))
3823 return 0;
3824 break;
3825
3826 case 's':
3827 if (strcmp (XSTR (x, i), XSTR (y, i)))
3828 return 0;
3829 break;
3830
3831 case 'e':
3832 if (! rtx_renumbered_equal_p (XEXP (x, i), XEXP (y, i)))
3833 return 0;
3834 break;
3835
3836 case 'u':
3837 if (XEXP (x, i) != XEXP (y, i))
3838 return 0;
3839 /* fall through. */
3840 case '0':
3841 break;
3842
3843 case 'E':
3844 if (XVECLEN (x, i) != XVECLEN (y, i))
3845 return 0;
3846 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
3847 if (!rtx_renumbered_equal_p (XVECEXP (x, i, j), XVECEXP (y, i, j)))
3848 return 0;
3849 break;
3850
3851 default:
3852 abort ();
3853 }
3854 }
3855 return 1;
3856 }
3857 \f
3858 /* If X is a hard register or equivalent to one or a subregister of one,
3859 return the hard register number. If X is a pseudo register that was not
3860 assigned a hard register, return the pseudo register number. Otherwise,
3861 return -1. Any rtx is valid for X. */
3862
3863 int
3864 true_regnum (x)
3865 rtx x;
3866 {
3867 if (GET_CODE (x) == REG)
3868 {
3869 if (REGNO (x) >= FIRST_PSEUDO_REGISTER && reg_renumber[REGNO (x)] >= 0)
3870 return reg_renumber[REGNO (x)];
3871 return REGNO (x);
3872 }
3873 if (GET_CODE (x) == SUBREG)
3874 {
3875 int base = true_regnum (SUBREG_REG (x));
3876 if (base >= 0 && base < FIRST_PSEUDO_REGISTER)
3877 return SUBREG_WORD (x) + base;
3878 }
3879 return -1;
3880 }
3881 \f
3882 /* Optimize code of the form:
3883
3884 for (x = a[i]; x; ...)
3885 ...
3886 for (x = a[i]; x; ...)
3887 ...
3888 foo:
3889
3890 Loop optimize will change the above code into
3891
3892 if (x = a[i])
3893 for (;;)
3894 { ...; if (! (x = ...)) break; }
3895 if (x = a[i])
3896 for (;;)
3897 { ...; if (! (x = ...)) break; }
3898 foo:
3899
3900 In general, if the first test fails, the program can branch
3901 directly to `foo' and skip the second try which is doomed to fail.
3902 We run this after loop optimization and before flow analysis. */
3903
3904 /* When comparing the insn patterns, we track the fact that different
3905 pseudo-register numbers may have been used in each computation.
3906 The following array stores an equivalence -- same_regs[I] == J means
3907 that pseudo register I was used in the first set of tests in a context
3908 where J was used in the second set. We also count the number of such
3909 pending equivalences. If nonzero, the expressions really aren't the
3910 same. */
3911
3912 static int *same_regs;
3913
3914 static int num_same_regs;
3915
3916 /* Track any registers modified between the target of the first jump and
3917 the second jump. They never compare equal. */
3918
3919 static char *modified_regs;
3920
3921 /* Record if memory was modified. */
3922
3923 static int modified_mem;
3924
3925 /* Called via note_stores on each insn between the target of the first
3926 branch and the second branch. It marks any changed registers. */
3927
3928 static void
3929 mark_modified_reg (dest, x)
3930 rtx dest;
3931 rtx x;
3932 {
3933 int regno, i;
3934
3935 if (GET_CODE (dest) == SUBREG)
3936 dest = SUBREG_REG (dest);
3937
3938 if (GET_CODE (dest) == MEM)
3939 modified_mem = 1;
3940
3941 if (GET_CODE (dest) != REG)
3942 return;
3943
3944 regno = REGNO (dest);
3945 if (regno >= FIRST_PSEUDO_REGISTER)
3946 modified_regs[regno] = 1;
3947 else
3948 for (i = 0; i < HARD_REGNO_NREGS (regno, GET_MODE (dest)); i++)
3949 modified_regs[regno + i] = 1;
3950 }
3951
3952 /* F is the first insn in the chain of insns. */
3953
3954 void
3955 thread_jumps (f, max_reg, flag_before_loop)
3956 rtx f;
3957 int max_reg;
3958 int flag_before_loop;
3959 {
3960 /* Basic algorithm is to find a conditional branch,
3961 the label it may branch to, and the branch after
3962 that label. If the two branches test the same condition,
3963 walk back from both branch paths until the insn patterns
3964 differ, or code labels are hit. If we make it back to
3965 the target of the first branch, then we know that the first branch
3966 will either always succeed or always fail depending on the relative
3967 senses of the two branches. So adjust the first branch accordingly
3968 in this case. */
3969
3970 rtx label, b1, b2, t1, t2;
3971 enum rtx_code code1, code2;
3972 rtx b1op0, b1op1, b2op0, b2op1;
3973 int changed = 1;
3974 int i;
3975 int *all_reset;
3976
3977 /* Allocate register tables and quick-reset table. */
3978 modified_regs = (char *) alloca (max_reg * sizeof (char));
3979 same_regs = (int *) alloca (max_reg * sizeof (int));
3980 all_reset = (int *) alloca (max_reg * sizeof (int));
3981 for (i = 0; i < max_reg; i++)
3982 all_reset[i] = -1;
3983
3984 while (changed)
3985 {
3986 changed = 0;
3987
3988 for (b1 = f; b1; b1 = NEXT_INSN (b1))
3989 {
3990 /* Get to a candidate branch insn. */
3991 if (GET_CODE (b1) != JUMP_INSN
3992 || ! condjump_p (b1) || simplejump_p (b1)
3993 || JUMP_LABEL (b1) == 0)
3994 continue;
3995
3996 bzero (modified_regs, max_reg * sizeof (char));
3997 modified_mem = 0;
3998
3999 bcopy (all_reset, same_regs, max_reg * sizeof (int));
4000 num_same_regs = 0;
4001
4002 label = JUMP_LABEL (b1);
4003
4004 /* Look for a branch after the target. Record any registers and
4005 memory modified between the target and the branch. Stop when we
4006 get to a label since we can't know what was changed there. */
4007 for (b2 = NEXT_INSN (label); b2; b2 = NEXT_INSN (b2))
4008 {
4009 if (GET_CODE (b2) == CODE_LABEL)
4010 break;
4011
4012 else if (GET_CODE (b2) == JUMP_INSN)
4013 {
4014 /* If this is an unconditional jump and is the only use of
4015 its target label, we can follow it. */
4016 if (simplejump_p (b2)
4017 && JUMP_LABEL (b2) != 0
4018 && LABEL_NUSES (JUMP_LABEL (b2)) == 1)
4019 {
4020 b2 = JUMP_LABEL (b2);
4021 continue;
4022 }
4023 else
4024 break;
4025 }
4026
4027 if (GET_CODE (b2) != CALL_INSN && GET_CODE (b2) != INSN)
4028 continue;
4029
4030 if (GET_CODE (b2) == CALL_INSN)
4031 {
4032 modified_mem = 1;
4033 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
4034 if (call_used_regs[i] && ! fixed_regs[i]
4035 && i != STACK_POINTER_REGNUM
4036 && i != FRAME_POINTER_REGNUM
4037 && i != HARD_FRAME_POINTER_REGNUM
4038 && i != ARG_POINTER_REGNUM)
4039 modified_regs[i] = 1;
4040 }
4041
4042 note_stores (PATTERN (b2), mark_modified_reg);
4043 }
4044
4045 /* Check the next candidate branch insn from the label
4046 of the first. */
4047 if (b2 == 0
4048 || GET_CODE (b2) != JUMP_INSN
4049 || b2 == b1
4050 || ! condjump_p (b2)
4051 || simplejump_p (b2))
4052 continue;
4053
4054 /* Get the comparison codes and operands, reversing the
4055 codes if appropriate. If we don't have comparison codes,
4056 we can't do anything. */
4057 b1op0 = XEXP (XEXP (SET_SRC (PATTERN (b1)), 0), 0);
4058 b1op1 = XEXP (XEXP (SET_SRC (PATTERN (b1)), 0), 1);
4059 code1 = GET_CODE (XEXP (SET_SRC (PATTERN (b1)), 0));
4060 if (XEXP (SET_SRC (PATTERN (b1)), 1) == pc_rtx)
4061 code1 = reverse_condition (code1);
4062
4063 b2op0 = XEXP (XEXP (SET_SRC (PATTERN (b2)), 0), 0);
4064 b2op1 = XEXP (XEXP (SET_SRC (PATTERN (b2)), 0), 1);
4065 code2 = GET_CODE (XEXP (SET_SRC (PATTERN (b2)), 0));
4066 if (XEXP (SET_SRC (PATTERN (b2)), 1) == pc_rtx)
4067 code2 = reverse_condition (code2);
4068
4069 /* If they test the same things and knowing that B1 branches
4070 tells us whether or not B2 branches, check if we
4071 can thread the branch. */
4072 if (rtx_equal_for_thread_p (b1op0, b2op0, b2)
4073 && rtx_equal_for_thread_p (b1op1, b2op1, b2)
4074 && (comparison_dominates_p (code1, code2)
4075 || comparison_dominates_p (code1, reverse_condition (code2))))
4076 {
4077 t1 = prev_nonnote_insn (b1);
4078 t2 = prev_nonnote_insn (b2);
4079
4080 while (t1 != 0 && t2 != 0)
4081 {
4082 if (t2 == label)
4083 {
4084 /* We have reached the target of the first branch.
4085 If there are no pending register equivalents,
4086 we know that this branch will either always
4087 succeed (if the senses of the two branches are
4088 the same) or always fail (if not). */
4089 rtx new_label;
4090
4091 if (num_same_regs != 0)
4092 break;
4093
4094 if (comparison_dominates_p (code1, code2))
4095 new_label = JUMP_LABEL (b2);
4096 else
4097 new_label = get_label_after (b2);
4098
4099 if (JUMP_LABEL (b1) != new_label)
4100 {
4101 rtx prev = PREV_INSN (new_label);
4102
4103 if (flag_before_loop
4104 && NOTE_LINE_NUMBER (prev) == NOTE_INSN_LOOP_BEG)
4105 {
4106 /* Don't thread to the loop label. If a loop
4107 label is reused, loop optimization will
4108 be disabled for that loop. */
4109 new_label = gen_label_rtx ();
4110 emit_label_after (new_label, PREV_INSN (prev));
4111 }
4112 changed |= redirect_jump (b1, new_label);
4113 }
4114 break;
4115 }
4116
4117 /* If either of these is not a normal insn (it might be
4118 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
4119 have already been skipped above.) Similarly, fail
4120 if the insns are different. */
4121 if (GET_CODE (t1) != INSN || GET_CODE (t2) != INSN
4122 || recog_memoized (t1) != recog_memoized (t2)
4123 || ! rtx_equal_for_thread_p (PATTERN (t1),
4124 PATTERN (t2), t2))
4125 break;
4126
4127 t1 = prev_nonnote_insn (t1);
4128 t2 = prev_nonnote_insn (t2);
4129 }
4130 }
4131 }
4132 }
4133 }
4134 \f
4135 /* This is like RTX_EQUAL_P except that it knows about our handling of
4136 possibly equivalent registers and knows to consider volatile and
4137 modified objects as not equal.
4138
4139 YINSN is the insn containing Y. */
4140
4141 int
4142 rtx_equal_for_thread_p (x, y, yinsn)
4143 rtx x, y;
4144 rtx yinsn;
4145 {
4146 register int i;
4147 register int j;
4148 register enum rtx_code code;
4149 register char *fmt;
4150
4151 code = GET_CODE (x);
4152 /* Rtx's of different codes cannot be equal. */
4153 if (code != GET_CODE (y))
4154 return 0;
4155
4156 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
4157 (REG:SI x) and (REG:HI x) are NOT equivalent. */
4158
4159 if (GET_MODE (x) != GET_MODE (y))
4160 return 0;
4161
4162 /* Handle special-cases first. */
4163 switch (code)
4164 {
4165 case REG:
4166 if (REGNO (x) == REGNO (y) && ! modified_regs[REGNO (x)])
4167 return 1;
4168
4169 /* If neither is user variable or hard register, check for possible
4170 equivalence. */
4171 if (REG_USERVAR_P (x) || REG_USERVAR_P (y)
4172 || REGNO (x) < FIRST_PSEUDO_REGISTER
4173 || REGNO (y) < FIRST_PSEUDO_REGISTER)
4174 return 0;
4175
4176 if (same_regs[REGNO (x)] == -1)
4177 {
4178 same_regs[REGNO (x)] = REGNO (y);
4179 num_same_regs++;
4180
4181 /* If this is the first time we are seeing a register on the `Y'
4182 side, see if it is the last use. If not, we can't thread the
4183 jump, so mark it as not equivalent. */
4184 if (regno_last_uid[REGNO (y)] != INSN_UID (yinsn))
4185 return 0;
4186
4187 return 1;
4188 }
4189 else
4190 return (same_regs[REGNO (x)] == REGNO (y));
4191
4192 break;
4193
4194 case MEM:
4195 /* If memory modified or either volatile, not equivalent.
4196 Else, check address. */
4197 if (modified_mem || MEM_VOLATILE_P (x) || MEM_VOLATILE_P (y))
4198 return 0;
4199
4200 return rtx_equal_for_thread_p (XEXP (x, 0), XEXP (y, 0), yinsn);
4201
4202 case ASM_INPUT:
4203 if (MEM_VOLATILE_P (x) || MEM_VOLATILE_P (y))
4204 return 0;
4205
4206 break;
4207
4208 case SET:
4209 /* Cancel a pending `same_regs' if setting equivalenced registers.
4210 Then process source. */
4211 if (GET_CODE (SET_DEST (x)) == REG
4212 && GET_CODE (SET_DEST (y)) == REG)
4213 {
4214 if (same_regs[REGNO (SET_DEST (x))] == REGNO (SET_DEST (y)))
4215 {
4216 same_regs[REGNO (SET_DEST (x))] = -1;
4217 num_same_regs--;
4218 }
4219 else if (REGNO (SET_DEST (x)) != REGNO (SET_DEST (y)))
4220 return 0;
4221 }
4222 else
4223 if (rtx_equal_for_thread_p (SET_DEST (x), SET_DEST (y), yinsn) == 0)
4224 return 0;
4225
4226 return rtx_equal_for_thread_p (SET_SRC (x), SET_SRC (y), yinsn);
4227
4228 case LABEL_REF:
4229 return XEXP (x, 0) == XEXP (y, 0);
4230
4231 case SYMBOL_REF:
4232 return XSTR (x, 0) == XSTR (y, 0);
4233 }
4234
4235 if (x == y)
4236 return 1;
4237
4238 fmt = GET_RTX_FORMAT (code);
4239 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
4240 {
4241 switch (fmt[i])
4242 {
4243 case 'w':
4244 if (XWINT (x, i) != XWINT (y, i))
4245 return 0;
4246 break;
4247
4248 case 'n':
4249 case 'i':
4250 if (XINT (x, i) != XINT (y, i))
4251 return 0;
4252 break;
4253
4254 case 'V':
4255 case 'E':
4256 /* Two vectors must have the same length. */
4257 if (XVECLEN (x, i) != XVECLEN (y, i))
4258 return 0;
4259
4260 /* And the corresponding elements must match. */
4261 for (j = 0; j < XVECLEN (x, i); j++)
4262 if (rtx_equal_for_thread_p (XVECEXP (x, i, j),
4263 XVECEXP (y, i, j), yinsn) == 0)
4264 return 0;
4265 break;
4266
4267 case 'e':
4268 if (rtx_equal_for_thread_p (XEXP (x, i), XEXP (y, i), yinsn) == 0)
4269 return 0;
4270 break;
4271
4272 case 'S':
4273 case 's':
4274 if (strcmp (XSTR (x, i), XSTR (y, i)))
4275 return 0;
4276 break;
4277
4278 case 'u':
4279 /* These are just backpointers, so they don't matter. */
4280 break;
4281
4282 case '0':
4283 break;
4284
4285 /* It is believed that rtx's at this level will never
4286 contain anything but integers and other rtx's,
4287 except for within LABEL_REFs and SYMBOL_REFs. */
4288 default:
4289 abort ();
4290 }
4291 }
4292 return 1;
4293 }
GNU Compiler Collection
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