]> gcc.gnu.org Git - gcc.git/blob - gcc/jump.c
git://gcc.gnu.org / gcc.git / blob
? search:
summary | shortlog | log | commit | commitdiff | tree
blame | history | raw | HEAD
*** empty log message ***
[gcc.git] / gcc / jump.c
1 /* Optimize jump instructions, for GNU compiler.
2 Copyright (C) 1987, 1988, 1989, 1991 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 rtx delete_insn ();
108 int redirect_jump ();
109 static int redirect_exp ();
110 void redirect_tablejump ();
111 static int delete_labelref_insn ();
112 int invert_jump ();
113 static int invert_exp ();
114 int condjump_p ();
115 int simplejump_p ();
116
117 extern rtx gen_jump ();
118
119 static void mark_jump_label ();
120 void delete_jump ();
121 static void delete_from_jump_chain ();
122 static int tension_vector_labels ();
123 static void find_cross_jump ();
124 static void do_cross_jump ();
125 static int jump_back_p ();
126 \f
127 /* Delete no-op jumps and optimize jumps to jumps
128 and jumps around jumps.
129 Delete unused labels and unreachable code.
130
131 If CROSS_JUMP is 1, detect matching code
132 before a jump and its destination and unify them.
133 If CROSS_JUMP is 2, do cross-jumping, but pay attention to death notes.
134
135 If NOOP_MOVES is nonzero, delete no-op move insns.
136
137 If AFTER_REGSCAN is nonzero, then this jump pass is being run immediately
138 after regscan, and it is safe to use regno_first_uid and regno_last_uid.
139
140 If `optimize' is zero, don't change any code,
141 just determine whether control drops off the end of the function.
142 This case occurs when we have -W and not -O.
143 It works because `delete_insn' checks the value of `optimize'
144 and refrains from actually deleting when that is 0. */
145
146 void
147 jump_optimize (f, cross_jump, noop_moves, after_regscan)
148 rtx f;
149 int cross_jump;
150 int noop_moves;
151 int after_regscan;
152 {
153 register rtx insn;
154 int changed;
155 int first = 1;
156 int max_uid = 0;
157 rtx last_insn;
158
159 cross_jump_death_matters = (cross_jump == 2);
160
161 /* Initialize LABEL_NUSES and JUMP_LABEL fields. */
162
163 for (insn = f; insn; insn = NEXT_INSN (insn))
164 {
165 if (GET_CODE (insn) == CODE_LABEL)
166 LABEL_NUSES (insn) = (LABEL_PRESERVE_P (insn) != 0);
167 else if (GET_CODE (insn) == JUMP_INSN)
168 JUMP_LABEL (insn) = 0;
169 if (INSN_UID (insn) > max_uid)
170 max_uid = INSN_UID (insn);
171 }
172
173 max_uid++;
174
175 /* Delete insns following barriers, up to next label. */
176
177 for (insn = f; insn;)
178 {
179 if (GET_CODE (insn) == BARRIER)
180 {
181 insn = NEXT_INSN (insn);
182 while (insn != 0 && GET_CODE (insn) != CODE_LABEL)
183 {
184 if (GET_CODE (insn) == NOTE
185 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_FUNCTION_END)
186 insn = NEXT_INSN (insn);
187 else
188 insn = delete_insn (insn);
189 }
190 /* INSN is now the code_label. */
191 }
192 else
193 insn = NEXT_INSN (insn);
194 }
195
196 /* Leave some extra room for labels and duplicate exit test insns
197 we make. */
198 max_jump_chain = max_uid * 14 / 10;
199 jump_chain = (rtx *) alloca (max_jump_chain * sizeof (rtx));
200 bzero (jump_chain, max_jump_chain * sizeof (rtx));
201
202 /* Mark the label each jump jumps to.
203 Combine consecutive labels, and count uses of labels.
204
205 For each label, make a chain (using `jump_chain')
206 of all the *unconditional* jumps that jump to it;
207 also make a chain of all returns. */
208
209 for (insn = f; insn; insn = NEXT_INSN (insn))
210 if ((GET_CODE (insn) == JUMP_INSN || GET_CODE (insn) == INSN
211 || GET_CODE (insn) == CALL_INSN)
212 && ! INSN_DELETED_P (insn))
213 {
214 mark_jump_label (PATTERN (insn), insn, cross_jump);
215 if (GET_CODE (insn) == JUMP_INSN)
216 {
217 if (JUMP_LABEL (insn) != 0 && simplejump_p (insn))
218 {
219 jump_chain[INSN_UID (insn)]
220 = jump_chain[INSN_UID (JUMP_LABEL (insn))];
221 jump_chain[INSN_UID (JUMP_LABEL (insn))] = insn;
222 }
223 if (GET_CODE (PATTERN (insn)) == RETURN)
224 {
225 jump_chain[INSN_UID (insn)] = jump_chain[0];
226 jump_chain[0] = insn;
227 }
228 }
229 }
230
231 /* Keep track of labels used from static data;
232 they cannot ever be deleted. */
233
234 for (insn = forced_labels; insn; insn = XEXP (insn, 1))
235 LABEL_NUSES (XEXP (insn, 0))++;
236
237 /* Delete all labels already not referenced.
238 Also find the last insn. */
239
240 last_insn = 0;
241 for (insn = f; insn; )
242 {
243 if (GET_CODE (insn) == CODE_LABEL && LABEL_NUSES (insn) == 0)
244 insn = delete_insn (insn);
245 else
246 {
247 last_insn = insn;
248 insn = NEXT_INSN (insn);
249 }
250 }
251
252 if (!optimize)
253 {
254 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
255 If so record that this function can drop off the end. */
256
257 insn = last_insn;
258 {
259 int n_labels = 1;
260 while (insn
261 /* One label can follow the end-note: the return label. */
262 && ((GET_CODE (insn) == CODE_LABEL && n_labels-- > 0)
263 /* Ordinary insns can follow it if returning a structure. */
264 || GET_CODE (insn) == INSN
265 /* If machine uses explicit RETURN insns, no epilogue,
266 then one of them follows the note. */
267 || (GET_CODE (insn) == JUMP_INSN
268 && GET_CODE (PATTERN (insn)) == RETURN)
269 /* Other kinds of notes can follow also. */
270 || (GET_CODE (insn) == NOTE
271 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_FUNCTION_END)))
272 insn = PREV_INSN (insn);
273 }
274
275 /* Report if control can fall through at the end of the function. */
276 if (insn && GET_CODE (insn) == NOTE
277 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_END
278 && ! INSN_DELETED_P (insn))
279 can_reach_end = 1;
280
281 /* Zero the "deleted" flag of all the "deleted" insns. */
282 for (insn = f; insn; insn = NEXT_INSN (insn))
283 INSN_DELETED_P (insn) = 0;
284 return;
285 }
286
287 #ifdef HAVE_return
288 if (HAVE_return)
289 {
290 /* If we fall through to the epilogue, see if we can insert a RETURN insn
291 in front of it. If the machine allows it at this point (we might be
292 after reload for a leaf routine), it will improve optimization for it
293 to be there. */
294 insn = get_last_insn ();
295 while (insn && GET_CODE (insn) == NOTE)
296 insn = PREV_INSN (insn);
297
298 if (insn && GET_CODE (insn) != BARRIER)
299 {
300 emit_jump_insn (gen_return ());
301 emit_barrier ();
302 }
303 }
304 #endif
305
306 if (noop_moves)
307 for (insn = f; insn; )
308 {
309 register rtx next = NEXT_INSN (insn);
310
311 if (GET_CODE (insn) == INSN)
312 {
313 register rtx body = PATTERN (insn);
314
315 /* Combine stack_adjusts with following push_insns. */
316 #ifdef PUSH_ROUNDING
317 if (GET_CODE (body) == SET
318 && SET_DEST (body) == stack_pointer_rtx
319 && GET_CODE (SET_SRC (body)) == PLUS
320 && XEXP (SET_SRC (body), 0) == stack_pointer_rtx
321 && GET_CODE (XEXP (SET_SRC (body), 1)) == CONST_INT
322 && INTVAL (XEXP (SET_SRC (body), 1)) > 0)
323 {
324 rtx p;
325 rtx stack_adjust_insn = insn;
326 int stack_adjust_amount = INTVAL (XEXP (SET_SRC (body), 1));
327 int total_pushed = 0;
328 int pushes = 0;
329
330 /* Find all successive push insns. */
331 p = insn;
332 /* Don't convert more than three pushes;
333 that starts adding too many displaced addresses
334 and the whole thing starts becoming a losing
335 proposition. */
336 while (pushes < 3)
337 {
338 rtx pbody, dest;
339 p = next_nonnote_insn (p);
340 if (p == 0 || GET_CODE (p) != INSN)
341 break;
342 pbody = PATTERN (p);
343 if (GET_CODE (pbody) != SET)
344 break;
345 dest = SET_DEST (pbody);
346 /* Allow a no-op move between the adjust and the push. */
347 if (GET_CODE (dest) == REG
348 && GET_CODE (SET_SRC (pbody)) == REG
349 && REGNO (dest) == REGNO (SET_SRC (pbody)))
350 continue;
351 if (! (GET_CODE (dest) == MEM
352 && GET_CODE (XEXP (dest, 0)) == POST_INC
353 && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx))
354 break;
355 pushes++;
356 if (total_pushed + GET_MODE_SIZE (SET_DEST (pbody))
357 > stack_adjust_amount)
358 break;
359 total_pushed += GET_MODE_SIZE (SET_DEST (pbody));
360 }
361
362 /* Discard the amount pushed from the stack adjust;
363 maybe eliminate it entirely. */
364 if (total_pushed >= stack_adjust_amount)
365 {
366 delete_insn (stack_adjust_insn);
367 total_pushed = stack_adjust_amount;
368 }
369 else
370 XEXP (SET_SRC (PATTERN (stack_adjust_insn)), 1)
371 = gen_rtx (CONST_INT, VOIDmode,
372 stack_adjust_amount - total_pushed);
373
374 /* Change the appropriate push insns to ordinary stores. */
375 p = insn;
376 while (total_pushed > 0)
377 {
378 rtx pbody, dest;
379 p = next_nonnote_insn (p);
380 if (GET_CODE (p) != INSN)
381 break;
382 pbody = PATTERN (p);
383 if (GET_CODE (pbody) == SET)
384 break;
385 dest = SET_DEST (pbody);
386 if (! (GET_CODE (dest) == MEM
387 && GET_CODE (XEXP (dest, 0)) == POST_INC
388 && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx))
389 break;
390 total_pushed -= GET_MODE_SIZE (SET_DEST (pbody));
391 /* If this push doesn't fully fit in the space
392 of the stack adjust that we deleted,
393 make another stack adjust here for what we
394 didn't use up. There should be peepholes
395 to recognize the resulting sequence of insns. */
396 if (total_pushed < 0)
397 {
398 emit_insn_before (gen_add2_insn (stack_pointer_rtx,
399 gen_rtx (CONST_INT, VOIDmode, - total_pushed)),
400 p);
401 break;
402 }
403 XEXP (dest, 0)
404 = plus_constant (stack_pointer_rtx, total_pushed);
405 }
406 }
407 #endif
408
409 /* Detect and delete no-op move instructions
410 resulting from not allocating a parameter in a register. */
411
412 if (GET_CODE (body) == SET
413 && (SET_DEST (body) == SET_SRC (body)
414 || (GET_CODE (SET_DEST (body)) == MEM
415 && GET_CODE (SET_SRC (body)) == MEM
416 && rtx_equal_p (SET_SRC (body), SET_DEST (body))))
417 && ! (GET_CODE (SET_DEST (body)) == MEM
418 && MEM_VOLATILE_P (SET_DEST (body)))
419 && ! (GET_CODE (SET_SRC (body)) == MEM
420 && MEM_VOLATILE_P (SET_SRC (body))))
421 delete_insn (insn);
422
423 /* Detect and ignore no-op move instructions
424 resulting from smart or fortuitous register allocation. */
425
426 else if (GET_CODE (body) == SET)
427 {
428 int sreg = true_regnum (SET_SRC (body));
429 int dreg = true_regnum (SET_DEST (body));
430
431 if (sreg == dreg && sreg >= 0)
432 delete_insn (insn);
433 else if (sreg >= 0 && dreg >= 0)
434 {
435 rtx trial;
436 rtx tem = find_equiv_reg (0, insn, 0,
437 sreg, 0, dreg,
438 GET_MODE (SET_SRC (body)));
439
440 #ifdef PRESERVE_DEATH_INFO_REGNO_P
441 /* Deleting insn could lose a death-note for SREG or DREG
442 so don't do it if final needs accurate death-notes. */
443 if (! PRESERVE_DEATH_INFO_REGNO_P (sreg)
444 && ! PRESERVE_DEATH_INFO_REGNO_P (dreg))
445 #endif
446 {
447 /* DREG may have been the target of a REG_DEAD note in
448 the insn which makes INSN redundant. If so, reorg
449 would still think it is dead. So search for such a
450 note and delete it if we find it. */
451 for (trial = prev_nonnote_insn (insn);
452 trial && GET_CODE (trial) != CODE_LABEL;
453 trial = prev_nonnote_insn (trial))
454 if (find_regno_note (trial, REG_DEAD, dreg))
455 {
456 remove_death (dreg, trial);
457 break;
458 }
459
460 if (tem != 0
461 && GET_MODE (tem) == GET_MODE (SET_DEST (body)))
462 delete_insn (insn);
463 }
464 }
465 else if (dreg >= 0 && CONSTANT_P (SET_SRC (body))
466 && find_equiv_reg (SET_SRC (body), insn, 0, dreg, 0,
467 0, GET_MODE (SET_DEST (body))))
468 {
469 /* This handles the case where we have two consecutive
470 assignments of the same constant to pseudos that didn't
471 get a hard reg. Each SET from the constant will be
472 converted into a SET of the spill register and an
473 output reload will be made following it. This produces
474 two loads of the same constant into the same spill
475 register. */
476
477 rtx in_insn = insn;
478
479 /* Look back for a death note for the first reg.
480 If there is one, it is no longer accurate. */
481 while (in_insn && GET_CODE (in_insn) != CODE_LABEL)
482 {
483 if ((GET_CODE (in_insn) == INSN
484 || GET_CODE (in_insn) == JUMP_INSN)
485 && find_regno_note (in_insn, REG_DEAD, dreg))
486 {
487 remove_death (dreg, in_insn);
488 break;
489 }
490 in_insn = PREV_INSN (in_insn);
491 }
492
493 /* Delete the second load of the value. */
494 delete_insn (insn);
495 }
496 }
497 else if (GET_CODE (body) == PARALLEL)
498 {
499 /* If each part is a set between two identical registers or
500 a USE or CLOBBER, delete the insn. */
501 int i, sreg, dreg;
502 rtx tem;
503
504 for (i = XVECLEN (body, 0) - 1; i >= 0; i--)
505 {
506 tem = XVECEXP (body, 0, i);
507 if (GET_CODE (tem) == USE || GET_CODE (tem) == CLOBBER)
508 continue;
509
510 if (GET_CODE (tem) != SET
511 || (sreg = true_regnum (SET_SRC (tem))) < 0
512 || (dreg = true_regnum (SET_DEST (tem))) < 0
513 || dreg != sreg)
514 break;
515 }
516
517 if (i < 0)
518 delete_insn (insn);
519 }
520 #if !BYTES_BIG_ENDIAN /* Not worth the hair to detect this
521 in the big-endian case. */
522 /* Also delete insns to store bit fields if they are no-ops. */
523 else if (GET_CODE (body) == SET
524 && GET_CODE (SET_DEST (body)) == ZERO_EXTRACT
525 && XEXP (SET_DEST (body), 2) == const0_rtx
526 && XEXP (SET_DEST (body), 0) == SET_SRC (body)
527 && ! (GET_CODE (SET_SRC (body)) == MEM
528 && MEM_VOLATILE_P (SET_SRC (body))))
529 delete_insn (insn);
530 #endif /* not BYTES_BIG_ENDIAN */
531 }
532 insn = next;
533 }
534
535 /* Now iterate optimizing jumps until nothing changes over one pass. */
536 changed = 1;
537 while (changed)
538 {
539 register rtx next;
540 changed = 0;
541
542 for (insn = f; insn; insn = next)
543 {
544 rtx reallabelprev;
545 rtx temp, temp1, temp2, temp3, temp4, temp5;
546 rtx nlabel;
547 int this_is_simplejump, this_is_condjump;
548 #if 0
549 /* If NOT the first iteration, if this is the last jump pass
550 (just before final), do the special peephole optimizations.
551 Avoiding the first iteration gives ordinary jump opts
552 a chance to work before peephole opts. */
553
554 if (reload_completed && !first && !flag_no_peephole)
555 if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
556 peephole (insn);
557 #endif
558
559 /* That could have deleted some insns after INSN, so check now
560 what the following insn is. */
561
562 next = NEXT_INSN (insn);
563
564 /* See if this is a NOTE_INSN_LOOP_BEG followed by an unconditional
565 jump. Try to optimize by duplicating the loop exit test if so.
566 This is only safe immediately after regscan, because it uses
567 the values of regno_first_uid and regno_last_uid. */
568 if (after_regscan && GET_CODE (insn) == NOTE
569 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG
570 && (temp1 = next_nonnote_insn (insn)) != 0
571 && simplejump_p (temp1))
572 {
573 temp = PREV_INSN (insn);
574 if (duplicate_loop_exit_test (insn))
575 {
576 changed = 1;
577 next = NEXT_INSN (temp);
578 continue;
579 }
580 }
581
582 if (GET_CODE (insn) != JUMP_INSN)
583 continue;
584
585 this_is_simplejump = simplejump_p (insn);
586 this_is_condjump = condjump_p (insn);
587
588 /* Tension the labels in dispatch tables. */
589
590 if (GET_CODE (PATTERN (insn)) == ADDR_VEC)
591 changed |= tension_vector_labels (PATTERN (insn), 0);
592 if (GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
593 changed |= tension_vector_labels (PATTERN (insn), 1);
594
595 /* If a dispatch table always goes to the same place,
596 get rid of it and replace the insn that uses it. */
597
598 if (GET_CODE (PATTERN (insn)) == ADDR_VEC
599 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
600 {
601 int i;
602 rtx pat = PATTERN (insn);
603 int diff_vec_p = GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC;
604 int len = XVECLEN (pat, diff_vec_p);
605 rtx dispatch = prev_real_insn (insn);
606
607 for (i = 0; i < len; i++)
608 if (XEXP (XVECEXP (pat, diff_vec_p, i), 0)
609 != XEXP (XVECEXP (pat, diff_vec_p, 0), 0))
610 break;
611 if (i == len
612 && GET_CODE (dispatch) == JUMP_INSN
613 && JUMP_LABEL (dispatch) != 0
614 /* Don't mess with a casesi insn. */
615 && !(GET_CODE (PATTERN (dispatch)) == SET
616 && (GET_CODE (SET_SRC (PATTERN (dispatch)))
617 == IF_THEN_ELSE))
618 && next_real_insn (JUMP_LABEL (dispatch)) == insn)
619 {
620 redirect_tablejump (dispatch,
621 XEXP (XVECEXP (pat, diff_vec_p, 0), 0));
622 changed = 1;
623 }
624 }
625
626 reallabelprev = prev_active_insn (JUMP_LABEL (insn));
627
628 /* If a jump references the end of the function, try to turn
629 it into a RETURN insn, possibly a conditional one. */
630 if (JUMP_LABEL (insn)
631 && next_active_insn (JUMP_LABEL (insn)) == 0)
632 changed |= redirect_jump (insn, 0);
633
634 /* Detect jump to following insn. */
635 if (reallabelprev == insn && condjump_p (insn))
636 {
637 delete_jump (insn);
638 changed = 1;
639 continue;
640 }
641
642 /* If we have an unconditional jump preceded by a USE, try to put
643 the USE before the target and jump there. This simplifies many
644 of the optimizations below since we don't have to worry about
645 dealing with these USE insns. We only do this if the label
646 being branch to already has the identical USE or if code
647 never falls through to that label. */
648
649 if (this_is_simplejump
650 && (temp = prev_nonnote_insn (insn)) != 0
651 && GET_CODE (temp) == INSN && GET_CODE (PATTERN (temp)) == USE
652 && (temp1 = prev_nonnote_insn (JUMP_LABEL (insn))) != 0
653 && (GET_CODE (temp1) == BARRIER
654 || (GET_CODE (temp1) == INSN
655 && rtx_equal_p (PATTERN (temp), PATTERN (temp1)))))
656 {
657 if (GET_CODE (temp1) == BARRIER)
658 {
659 reorder_insns (temp, temp, temp1);
660 temp1 = NEXT_INSN (temp1);
661 }
662 else
663 delete_insn (temp);
664
665 redirect_jump (insn, get_label_before (temp1));
666 reallabelprev = prev_real_insn (temp1);
667 changed = 1;
668 }
669
670 /* Simplify if (...) x = a; else x = b; by converting it
671 to x = b; if (...) x = a;
672 if B is sufficiently simple, the test doesn't involve X,
673 and nothing in the test modifies B or X.
674
675 If we have small register classes, we also can't do this if X
676 is a hard register.
677
678 If the "x = b;" insn has any REG_NOTES, we don't do this because
679 of the possibility that we are running after CSE and there is a
680 REG_EQUAL note that is only valid if the branch has already been
681 taken. If we move the insn with the REG_EQUAL note, we may
682 fold the comparison to always be false in a later CSE pass.
683 (We could also delete the REG_NOTES when moving the insn, but it
684 seems simpler to not move it.) An exception is that we can move
685 the insn if the only note is a REG_EQUAL or REG_EQUIV whose
686 value is the same as "b".
687
688 INSN is the branch over the `else' part.
689
690 We set:
691
692 TEMP to the jump insn preceding "x = a;"
693 TEMP1 to X
694 TEMP2 to the insn that sets "x = b;"
695 TEMP3 to the insn that sets "x = a;" */
696
697 if (this_is_simplejump
698 && (temp3 = prev_active_insn (insn)) != 0
699 && GET_CODE (temp3) == INSN
700 && GET_CODE (PATTERN (temp3)) == SET
701 && GET_CODE (temp1 = SET_DEST (PATTERN (temp3))) == REG
702 #ifdef SMALL_REGISTER_CLASSES
703 && REGNO (temp1) >= FIRST_PSEUDO_REGISTER
704 #endif
705 && (temp2 = next_active_insn (insn)) != 0
706 && GET_CODE (temp2) == INSN
707 && GET_CODE (PATTERN (temp2)) == SET
708 && rtx_equal_p (SET_DEST (PATTERN (temp2)), temp1)
709 && (GET_CODE (SET_SRC (PATTERN (temp2))) == REG
710 || CONSTANT_P (SET_SRC (PATTERN (temp2))))
711 && (REG_NOTES (temp2) == 0
712 || ((REG_NOTE_KIND (REG_NOTES (temp2)) == REG_EQUAL
713 || REG_NOTE_KIND (REG_NOTES (temp2)) == REG_EQUIV)
714 && XEXP (REG_NOTES (temp2), 1) == 0
715 && rtx_equal_p (XEXP (REG_NOTES (temp2), 0),
716 SET_SRC (PATTERN (temp2)))))
717 && (temp = prev_active_insn (temp3)) != 0
718 && condjump_p (temp) && ! simplejump_p (temp)
719 /* TEMP must skip over the "x = a;" insn */
720 && prev_real_insn (JUMP_LABEL (temp)) == insn
721 && no_labels_between_p (insn, JUMP_LABEL (temp))
722 /* There must be no other entries to the "x = b;" insn. */
723 && no_labels_between_p (JUMP_LABEL (temp), temp2)
724 /* INSN must either branch to the insn after TEMP2 or the insn
725 after TEMP2 must branch to the same place as INSN. */
726 && (reallabelprev == temp2
727 || ((temp4 = next_active_insn (temp2)) != 0
728 && simplejump_p (temp4)
729 && JUMP_LABEL (temp4) == JUMP_LABEL (insn))))
730 {
731 /* The test expression, X, may be a complicated test with
732 multiple branches. See if we can find all the uses of
733 the label that TEMP branches to without hitting a CALL_INSN
734 or a jump to somewhere else. */
735 rtx target = JUMP_LABEL (temp);
736 int nuses = LABEL_NUSES (target);
737 rtx p, q;
738
739 /* Set P to the first jump insn that goes around "x = a;". */
740 for (p = temp; nuses && p; p = prev_nonnote_insn (p))
741 {
742 if (GET_CODE (p) == JUMP_INSN)
743 {
744 if (condjump_p (p) && ! simplejump_p (p)
745 && JUMP_LABEL (p) == target)
746 {
747 nuses--;
748 if (nuses == 0)
749 break;
750 }
751 else
752 break;
753 }
754 else if (GET_CODE (p) == CALL_INSN)
755 break;
756 }
757
758 #ifdef HAVE_cc0
759 /* We cannot insert anything between a set of cc and its use
760 so if P uses cc0, we must back up to the previous insn. */
761 q = prev_nonnote_insn (p);
762 if (q && GET_RTX_CLASS (GET_CODE (q)) == 'i'
763 && sets_cc0_p (PATTERN (q)))
764 p = q;
765 #endif
766
767 if (p)
768 p = PREV_INSN (p);
769
770 /* If we found all the uses and there was no data conflict, we
771 can move the assignment unless we can branch into the middle
772 from somewhere. */
773 if (nuses == 0 && p
774 && no_labels_between_p (p, insn)
775 && ! reg_referenced_between_p (temp1, p, NEXT_INSN (temp3))
776 && ! reg_set_between_p (temp1, p, temp3)
777 && (GET_CODE (SET_SRC (PATTERN (temp2))) == CONST_INT
778 || ! reg_set_between_p (SET_SRC (PATTERN (temp2)),
779 p, temp2)))
780 {
781 reorder_insns_with_line_notes (temp2, temp2, p);
782
783 /* Set NEXT to an insn that we know won't go away. */
784 next = next_active_insn (insn);
785
786 /* Delete the jump around the set. Note that we must do
787 this before we redirect the test jumps so that it won't
788 delete the code immediately following the assignment
789 we moved (which might be a jump). */
790
791 delete_insn (insn);
792
793 /* We either have two consecutive labels or a jump to
794 a jump, so adjust all the JUMP_INSNs to branch to where
795 INSN branches to. */
796 for (p = NEXT_INSN (p); p != next; p = NEXT_INSN (p))
797 if (GET_CODE (p) == JUMP_INSN)
798 redirect_jump (p, target);
799
800 changed = 1;
801 continue;
802 }
803 }
804
805 /* If we have x = a; if (...) x = b;
806 and either A or B is zero, or if we have if (...) x = 0;
807 and jumps are expensive, try to use a store-flag insn to
808 avoid the jump. (If the jump would be faster, the machine
809 should not have defined the scc insns!). These cases are often
810 made by the previous optimization.
811
812 INSN here is the jump around the store. We set:
813
814 TEMP to the "x = b;" insn.
815 TEMP1 to X.
816 TEMP2 to B (const0_rtx in the second case).
817 TEMP3 to A (X in the second case).
818 TEMP4 to the condition being tested.
819 TEMP5 to the earliest insn used to find the condition. */
820
821 if (/* We can't do this after reload has completed. */
822 ! reload_completed
823 && this_is_condjump && ! this_is_simplejump
824 /* Set TEMP to the "x = b;" insn. */
825 && (temp = next_nonnote_insn (insn)) != 0
826 && GET_CODE (temp) == INSN
827 && GET_CODE (PATTERN (temp)) == SET
828 && GET_CODE (temp1 = SET_DEST (PATTERN (temp))) == REG
829 #ifdef SMALL_REGISTER_CLASSES
830 && REGNO (temp1) >= FIRST_PSEUDO_REGISTER
831 #endif
832 && GET_MODE_CLASS (GET_MODE (temp1)) == MODE_INT
833 && (GET_CODE (temp2 = SET_SRC (PATTERN (temp))) == REG
834 || GET_CODE (temp2) == CONST_INT)
835 /* Allow either form, but prefer the former if both apply. */
836 && (((temp3 = reg_set_last (temp1, insn)) != 0
837 && ((GET_CODE (temp3) == REG
838 #ifdef SMALL_REGISTER_CLASSES
839 && REGNO (temp3) >= FIRST_PSEUDO_REGISTER
840 #endif
841 )
842 || GET_CODE (temp3) == CONST_INT))
843 /* Make the latter case look like x = x; if (...) x = 0; */
844 || ((temp3 = temp1, BRANCH_COST > 1)
845 && temp2 == const0_rtx))
846 /* INSN must either branch to the insn after TEMP or the insn
847 after TEMP must branch to the same place as INSN. */
848 && (reallabelprev == temp
849 || ((temp4 = next_active_insn (temp)) != 0
850 && simplejump_p (temp4)
851 && JUMP_LABEL (temp4) == JUMP_LABEL (insn)))
852 && (temp4 = get_condition (insn, &temp5)) != 0
853
854 /* If B is zero, OK; if A is zero, can only do this if we
855 can reverse the condition. */
856 && (temp2 == const0_rtx
857 || (temp3 == const0_rtx
858 && (can_reverse_comparison_p (temp4, insn)))))
859 {
860 enum rtx_code code = GET_CODE (temp4);
861 rtx yes = temp3, var = temp1;
862 int normalizep;
863 rtx target;
864
865 /* If necessary, reverse the condition. */
866 if (temp3 == const0_rtx)
867 code = reverse_condition (code), yes = temp2;
868
869 /* See if we can do this with a store-flag insn. */
870 start_sequence ();
871
872 /* If YES is the constant 1, it is best to just compute
873 the result directly. If YES is constant and STORE_FLAG_VALUE
874 includes all of its bits, it is best to compute the flag
875 value unnormalized and `and' it with YES. Otherwise,
876 normalize to -1 and `and' with YES. */
877 normalizep = (yes == const1_rtx ? 1
878 : (GET_CODE (yes) == CONST_INT
879 && (INTVAL (yes) & ~ STORE_FLAG_VALUE) == 0) ? 0
880 : -1);
881
882 /* We will be putting the store-flag insn immediately in
883 front of the comparison that was originally being done,
884 so we know all the variables in TEMP4 will be valid.
885 However, this might be in front of the assignment of
886 A to VAR. If it is, it would clobber the store-flag
887 we will be emitting.
888
889 Therefore, emit into a temporary which will be copied to
890 VAR immediately after TEMP. */
891
892 target = emit_store_flag (gen_reg_rtx (GET_MODE (var)), code,
893 XEXP (temp4, 0), XEXP (temp4, 1),
894 VOIDmode,
895 (code == LTU || code == LEU
896 || code == GEU || code == GTU),
897 normalizep);
898 if (target)
899 {
900 rtx seq;
901
902 if (normalizep != 1)
903 target = expand_and (yes, target,
904 (GET_CODE (target) == REG
905 ? target : 0));
906 seq = gen_sequence ();
907 end_sequence ();
908 emit_insn_before (seq, temp5);
909 emit_insn_after (gen_move_insn (var, target), insn);
910 delete_insn (temp);
911 next = NEXT_INSN (insn);
912 #ifdef HAVE_cc0
913 delete_insn (prev_nonnote_insn (insn));
914 #endif
915 delete_insn (insn);
916 changed = 1;
917 continue;
918 }
919 else
920 end_sequence ();
921 }
922
923 /* If branches are expensive, convert
924 if (foo) bar++; to bar += (foo != 0);
925 and similarly for "bar--;"
926
927 INSN is the conditional branch around the arithmetic. We set:
928
929 TEMP is the arithmetic insn.
930 TEMP1 is the SET doing the arthmetic.
931 TEMP2 is the operand being incremented or decremented.
932 TEMP3 to the condition being tested.
933 TEMP4 to the earliest insn used to find the condition. */
934
935 if (BRANCH_COST >= 2
936 && ! reload_completed
937 && this_is_condjump && ! this_is_simplejump
938 && (temp = next_nonnote_insn (insn)) != 0
939 && (temp1 = single_set (temp)) != 0
940 && (temp2 = SET_DEST (temp1),
941 GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT)
942 && GET_CODE (SET_SRC (temp1)) == PLUS
943 && (XEXP (SET_SRC (temp1), 1) == const1_rtx
944 || XEXP (SET_SRC (temp1), 1) == constm1_rtx)
945 && rtx_equal_p (temp2, XEXP (SET_SRC (temp1), 0))
946 /* INSN must either branch to the insn after TEMP or the insn
947 after TEMP must branch to the same place as INSN. */
948 && (reallabelprev == temp
949 || ((temp3 = next_active_insn (temp)) != 0
950 && simplejump_p (temp3)
951 && JUMP_LABEL (temp3) == JUMP_LABEL (insn)))
952 && (temp3 = get_condition (insn, &temp4)) != 0
953 && can_reverse_comparison_p (temp3, insn))
954 {
955 rtx target, seq;
956 enum rtx_code code = reverse_condition (GET_CODE (temp3));
957
958 start_sequence ();
959
960 target = emit_store_flag (gen_reg_rtx (GET_MODE (temp2)), code,
961 XEXP (temp3, 0), XEXP (temp3, 1),
962 VOIDmode,
963 (code == LTU || code == LEU
964 || code == GTU || code == GEU), 1);
965
966 /* If we can do the store-flag, do the addition or
967 subtraction. */
968
969 if (target)
970 target = expand_binop (GET_MODE (temp2),
971 (XEXP (SET_SRC (temp1), 1) == const1_rtx
972 ? add_optab : sub_optab),
973 temp2, target, temp2, OPTAB_WIDEN);
974
975 if (target != 0)
976 {
977 /* Put the result back in temp2 in case it isn't already.
978 Then replace the jump, possible a CC0-setting insn in
979 front of the jump, and TEMP, with the sequence we have
980 made. */
981
982 if (target != temp2)
983 emit_move_insn (temp2, target);
984
985 seq = get_insns ();
986 end_sequence ();
987
988 emit_insns_before (seq, temp4);
989 delete_insn (temp);
990 next = NEXT_INSN (insn);
991 #ifdef HAVE_cc0
992 delete_insn (prev_nonnote_insn (insn));
993 #endif
994 delete_insn (insn);
995 changed = 1;
996 continue;
997 }
998 else
999 end_sequence ();
1000 }
1001
1002 /* Simplify if (...) x = 1; else {...} if (x) ...
1003 We recognize this case scanning backwards as well.
1004
1005 TEMP is the assignment to x;
1006 TEMP1 is the label at the head of the second if. */
1007 /* ?? This should call get_condition to find the values being
1008 compared, instead of looking for a COMPARE insn when HAVE_cc0
1009 is not defined. This would allow it to work on the m88k. */
1010 /* ?? This optimization is only safe before cse is run if HAVE_cc0
1011 is not defined and the condition is tested by a separate compare
1012 insn. This is because the code below assumes that the result
1013 of the compare dies in the following branch.
1014
1015 Not only that, but there might be other insns between the
1016 compare and branch whose results are live. Those insns need
1017 to be executed.
1018
1019 A way to fix this is to move the insns at JUMP_LABEL (insn)
1020 to before INSN. If we are running before flow, they will
1021 be deleted if they aren't needed. But this doesn't work
1022 well after flow.
1023
1024 This is really a special-case of jump threading, anyway. The
1025 right thing to do is to replace this and jump threading with
1026 much simpler code in cse.
1027
1028 This code has been turned off in the non-cc0 case in the
1029 meantime. */
1030
1031 #ifdef HAVE_cc0
1032 else if (this_is_simplejump
1033 /* Safe to skip USE and CLOBBER insns here
1034 since they will not be deleted. */
1035 && (temp = prev_active_insn (insn))
1036 && no_labels_between_p (temp, insn)
1037 && GET_CODE (temp) == INSN
1038 && GET_CODE (PATTERN (temp)) == SET
1039 && GET_CODE (SET_DEST (PATTERN (temp))) == REG
1040 && CONSTANT_P (SET_SRC (PATTERN (temp)))
1041 && (temp1 = next_active_insn (JUMP_LABEL (insn)))
1042 /* If we find that the next value tested is `x'
1043 (TEMP1 is the insn where this happens), win. */
1044 && GET_CODE (temp1) == INSN
1045 && GET_CODE (PATTERN (temp1)) == SET
1046 #ifdef HAVE_cc0
1047 /* Does temp1 `tst' the value of x? */
1048 && SET_SRC (PATTERN (temp1)) == SET_DEST (PATTERN (temp))
1049 && SET_DEST (PATTERN (temp1)) == cc0_rtx
1050 && (temp1 = next_nonnote_insn (temp1))
1051 #else
1052 /* Does temp1 compare the value of x against zero? */
1053 && GET_CODE (SET_SRC (PATTERN (temp1))) == COMPARE
1054 && XEXP (SET_SRC (PATTERN (temp1)), 1) == const0_rtx
1055 && (XEXP (SET_SRC (PATTERN (temp1)), 0)
1056 == SET_DEST (PATTERN (temp)))
1057 && GET_CODE (SET_DEST (PATTERN (temp1))) == REG
1058 && (temp1 = find_next_ref (SET_DEST (PATTERN (temp1)), temp1))
1059 #endif
1060 && condjump_p (temp1))
1061 {
1062 /* Get the if_then_else from the condjump. */
1063 rtx choice = SET_SRC (PATTERN (temp1));
1064 if (GET_CODE (choice) == IF_THEN_ELSE)
1065 {
1066 enum rtx_code code = GET_CODE (XEXP (choice, 0));
1067 rtx val = SET_SRC (PATTERN (temp));
1068 rtx cond
1069 = simplify_relational_operation (code, GET_MODE (SET_DEST (PATTERN (temp))),
1070 val, const0_rtx);
1071 rtx ultimate;
1072
1073 if (cond == const_true_rtx)
1074 ultimate = XEXP (choice, 1);
1075 else if (cond == const0_rtx)
1076 ultimate = XEXP (choice, 2);
1077 else
1078 ultimate = 0;
1079
1080 if (ultimate == pc_rtx)
1081 ultimate = get_label_after (temp1);
1082 else if (ultimate && GET_CODE (ultimate) != RETURN)
1083 ultimate = XEXP (ultimate, 0);
1084
1085 if (ultimate)
1086 changed |= redirect_jump (insn, ultimate);
1087 }
1088 }
1089 #endif
1090
1091 #if 0
1092 /* @@ This needs a bit of work before it will be right.
1093
1094 Any type of comparison can be accepted for the first and
1095 second compare. When rewriting the first jump, we must
1096 compute the what conditions can reach label3, and use the
1097 appropriate code. We can not simply reverse/swap the code
1098 of the first jump. In some cases, the second jump must be
1099 rewritten also.
1100
1101 For example,
1102 < == converts to > ==
1103 < != converts to == >
1104 etc.
1105
1106 If the code is written to only accept an '==' test for the second
1107 compare, then all that needs to be done is to swap the condition
1108 of the first branch.
1109
1110 It is questionable whether we want this optimization anyways,
1111 since if the user wrote code like this because he/she knew that
1112 the jump to label1 is taken most of the time, then rewritting
1113 this gives slower code. */
1114 /* @@ This should call get_condition to find the values being
1115 compared, instead of looking for a COMPARE insn when HAVE_cc0
1116 is not defined. This would allow it to work on the m88k. */
1117 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1118 is not defined and the condition is tested by a separate compare
1119 insn. This is because the code below assumes that the result
1120 of the compare dies in the following branch. */
1121
1122 /* Simplify test a ~= b
1123 condjump label1;
1124 test a == b
1125 condjump label2;
1126 jump label3;
1127 label1:
1128
1129 rewriting as
1130 test a ~~= b
1131 condjump label3
1132 test a == b
1133 condjump label2
1134 label1:
1135
1136 where ~= is an inequality, e.g. >, and ~~= is the swapped
1137 inequality, e.g. <.
1138
1139 We recognize this case scanning backwards.
1140
1141 TEMP is the conditional jump to `label2';
1142 TEMP1 is the test for `a == b';
1143 TEMP2 is the conditional jump to `label1';
1144 TEMP3 is the test for `a ~= b'. */
1145 else if (this_is_simplejump
1146 && (temp = prev_active_insn (insn))
1147 && no_labels_between_p (temp, insn)
1148 && condjump_p (temp)
1149 && (temp1 = prev_active_insn (temp))
1150 && no_labels_between_p (temp1, temp)
1151 && GET_CODE (temp1) == INSN
1152 && GET_CODE (PATTERN (temp1)) == SET
1153 #ifdef HAVE_cc0
1154 && sets_cc0_p (PATTERN (temp1)) == 1
1155 #else
1156 && GET_CODE (SET_SRC (PATTERN (temp1))) == COMPARE
1157 && GET_CODE (SET_DEST (PATTERN (temp1))) == REG
1158 && (temp == find_next_ref (SET_DEST (PATTERN (temp1)), temp1))
1159 #endif
1160 && (temp2 = prev_active_insn (temp1))
1161 && no_labels_between_p (temp2, temp1)
1162 && condjump_p (temp2)
1163 && JUMP_LABEL (temp2) == next_nonnote_insn (NEXT_INSN (insn))
1164 && (temp3 = prev_active_insn (temp2))
1165 && no_labels_between_p (temp3, temp2)
1166 && GET_CODE (PATTERN (temp3)) == SET
1167 && rtx_equal_p (SET_DEST (PATTERN (temp3)),
1168 SET_DEST (PATTERN (temp1)))
1169 && rtx_equal_p (SET_SRC (PATTERN (temp1)),
1170 SET_SRC (PATTERN (temp3)))
1171 && ! inequality_comparisons_p (PATTERN (temp))
1172 && inequality_comparisons_p (PATTERN (temp2)))
1173 {
1174 rtx fallthrough_label = JUMP_LABEL (temp2);
1175
1176 ++LABEL_NUSES (fallthrough_label);
1177 if (swap_jump (temp2, JUMP_LABEL (insn)))
1178 {
1179 delete_insn (insn);
1180 changed = 1;
1181 }
1182
1183 if (--LABEL_NUSES (fallthrough_label) == 0)
1184 delete_insn (fallthrough_label);
1185 }
1186 #endif
1187 /* Simplify if (...) {... x = 1;} if (x) ...
1188
1189 We recognize this case backwards.
1190
1191 TEMP is the test of `x';
1192 TEMP1 is the assignment to `x' at the end of the
1193 previous statement. */
1194 /* @@ This should call get_condition to find the values being
1195 compared, instead of looking for a COMPARE insn when HAVE_cc0
1196 is not defined. This would allow it to work on the m88k. */
1197 /* @@ This optimization is only safe before cse is run if HAVE_cc0
1198 is not defined and the condition is tested by a separate compare
1199 insn. This is because the code below assumes that the result
1200 of the compare dies in the following branch. */
1201
1202 /* ??? This has to be turned off. The problem is that the
1203 unconditional jump might indirectly end up branching to the
1204 label between TEMP1 and TEMP. We can't detect this, in general,
1205 since it may become a jump to there after further optimizations.
1206 If that jump is done, it will be deleted, so we will retry
1207 this optimization in the next pass, thus an infinite loop.
1208
1209 The present code prevents this by putting the jump after the
1210 label, but this is not logically correct. */
1211 #if 0
1212 else if (this_is_condjump
1213 /* Safe to skip USE and CLOBBER insns here
1214 since they will not be deleted. */
1215 && (temp = prev_active_insn (insn))
1216 && no_labels_between_p (temp, insn)
1217 && GET_CODE (temp) == INSN
1218 && GET_CODE (PATTERN (temp)) == SET
1219 #ifdef HAVE_cc0
1220 && sets_cc0_p (PATTERN (temp)) == 1
1221 && GET_CODE (SET_SRC (PATTERN (temp))) == REG
1222 #else
1223 /* Temp must be a compare insn, we can not accept a register
1224 to register move here, since it may not be simply a
1225 tst insn. */
1226 && GET_CODE (SET_SRC (PATTERN (temp))) == COMPARE
1227 && XEXP (SET_SRC (PATTERN (temp)), 1) == const0_rtx
1228 && GET_CODE (XEXP (SET_SRC (PATTERN (temp)), 0)) == REG
1229 && GET_CODE (SET_DEST (PATTERN (temp))) == REG
1230 && insn == find_next_ref (SET_DEST (PATTERN (temp)), temp)
1231 #endif
1232 /* May skip USE or CLOBBER insns here
1233 for checking for opportunity, since we
1234 take care of them later. */
1235 && (temp1 = prev_active_insn (temp))
1236 && GET_CODE (temp1) == INSN
1237 && GET_CODE (PATTERN (temp1)) == SET
1238 #ifdef HAVE_cc0
1239 && SET_SRC (PATTERN (temp)) == SET_DEST (PATTERN (temp1))
1240 #else
1241 && (XEXP (SET_SRC (PATTERN (temp)), 0)
1242 == SET_DEST (PATTERN (temp1)))
1243 #endif
1244 && CONSTANT_P (SET_SRC (PATTERN (temp1)))
1245 /* If this isn't true, cse will do the job. */
1246 && ! no_labels_between_p (temp1, temp))
1247 {
1248 /* Get the if_then_else from the condjump. */
1249 rtx choice = SET_SRC (PATTERN (insn));
1250 if (GET_CODE (choice) == IF_THEN_ELSE
1251 && (GET_CODE (XEXP (choice, 0)) == EQ
1252 || GET_CODE (XEXP (choice, 0)) == NE))
1253 {
1254 int want_nonzero = (GET_CODE (XEXP (choice, 0)) == NE);
1255 rtx last_insn;
1256 rtx ultimate;
1257 rtx p;
1258
1259 /* Get the place that condjump will jump to
1260 if it is reached from here. */
1261 if ((SET_SRC (PATTERN (temp1)) != const0_rtx)
1262 == want_nonzero)
1263 ultimate = XEXP (choice, 1);
1264 else
1265 ultimate = XEXP (choice, 2);
1266 /* Get it as a CODE_LABEL. */
1267 if (ultimate == pc_rtx)
1268 ultimate = get_label_after (insn);
1269 else
1270 /* Get the label out of the LABEL_REF. */
1271 ultimate = XEXP (ultimate, 0);
1272
1273 /* Insert the jump immediately before TEMP, specifically
1274 after the label that is between TEMP1 and TEMP. */
1275 last_insn = PREV_INSN (temp);
1276
1277 /* If we would be branching to the next insn, the jump
1278 would immediately be deleted and the re-inserted in
1279 a subsequent pass over the code. So don't do anything
1280 in that case. */
1281 if (next_active_insn (last_insn)
1282 != next_active_insn (ultimate))
1283 {
1284 emit_barrier_after (last_insn);
1285 p = emit_jump_insn_after (gen_jump (ultimate),
1286 last_insn);
1287 JUMP_LABEL (p) = ultimate;
1288 ++LABEL_NUSES (ultimate);
1289 if (INSN_UID (ultimate) < max_jump_chain
1290 && INSN_CODE (p) < max_jump_chain)
1291 {
1292 jump_chain[INSN_UID (p)]
1293 = jump_chain[INSN_UID (ultimate)];
1294 jump_chain[INSN_UID (ultimate)] = p;
1295 }
1296 changed = 1;
1297 continue;
1298 }
1299 }
1300 }
1301 #endif
1302 /* Detect a conditional jump going to the same place
1303 as an immediately following unconditional jump. */
1304 else if (this_is_condjump
1305 && (temp = next_active_insn (insn)) != 0
1306 && simplejump_p (temp)
1307 && (next_active_insn (JUMP_LABEL (insn))
1308 == next_active_insn (JUMP_LABEL (temp))))
1309 {
1310 delete_jump (insn);
1311 changed = 1;
1312 continue;
1313 }
1314 /* Detect a conditional jump jumping over an unconditional jump. */
1315
1316 else if (this_is_condjump && ! this_is_simplejump
1317 && reallabelprev != 0
1318 && GET_CODE (reallabelprev) == JUMP_INSN
1319 && prev_active_insn (reallabelprev) == insn
1320 && no_labels_between_p (insn, reallabelprev)
1321 && simplejump_p (reallabelprev))
1322 {
1323 /* When we invert the unconditional jump, we will be
1324 decrementing the usage count of its old label.
1325 Make sure that we don't delete it now because that
1326 might cause the following code to be deleted. */
1327 rtx prev_uses = prev_nonnote_insn (reallabelprev);
1328 rtx prev_label = JUMP_LABEL (insn);
1329
1330 ++LABEL_NUSES (prev_label);
1331
1332 if (invert_jump (insn, JUMP_LABEL (reallabelprev)))
1333 {
1334 /* It is very likely that if there are USE insns before
1335 this jump, they hold REG_DEAD notes. These REG_DEAD
1336 notes are no longer valid due to this optimization,
1337 and will cause the life-analysis that following passes
1338 (notably delayed-branch scheduling) to think that
1339 these registers are dead when they are not.
1340
1341 To prevent this trouble, we just remove the USE insns
1342 from the insn chain. */
1343
1344 while (prev_uses && GET_CODE (prev_uses) == INSN
1345 && GET_CODE (PATTERN (prev_uses)) == USE)
1346 {
1347 rtx useless = prev_uses;
1348 prev_uses = prev_nonnote_insn (prev_uses);
1349 delete_insn (useless);
1350 }
1351
1352 delete_insn (reallabelprev);
1353 next = insn;
1354 changed = 1;
1355 }
1356
1357 /* We can now safely delete the label if it is unreferenced
1358 since the delete_insn above has deleted the BARRIER. */
1359 if (--LABEL_NUSES (prev_label) == 0)
1360 delete_insn (prev_label);
1361 continue;
1362 }
1363 else
1364 {
1365 /* Detect a jump to a jump. */
1366
1367 nlabel = follow_jumps (JUMP_LABEL (insn));
1368 if (nlabel != JUMP_LABEL (insn)
1369 && redirect_jump (insn, nlabel))
1370 {
1371 changed = 1;
1372 next = insn;
1373 }
1374
1375 /* Look for if (foo) bar; else break; */
1376 /* The insns look like this:
1377 insn = condjump label1;
1378 ...range1 (some insns)...
1379 jump label2;
1380 label1:
1381 ...range2 (some insns)...
1382 jump somewhere unconditionally
1383 label2: */
1384 {
1385 rtx label1 = next_label (insn);
1386 rtx range1end = label1 ? prev_active_insn (label1) : 0;
1387 /* Don't do this optimization on the first round, so that
1388 jump-around-a-jump gets simplified before we ask here
1389 whether a jump is unconditional.
1390
1391 Also don't do it when we are called after reload since
1392 it will confuse reorg. */
1393 if (! first
1394 && (reload_completed ? ! flag_delayed_branch : 1)
1395 /* Make sure INSN is something we can invert. */
1396 && condjump_p (insn)
1397 && label1 != 0
1398 && JUMP_LABEL (insn) == label1
1399 && LABEL_NUSES (label1) == 1
1400 && GET_CODE (range1end) == JUMP_INSN
1401 && simplejump_p (range1end))
1402 {
1403 rtx label2 = next_label (label1);
1404 rtx range2end = label2 ? prev_active_insn (label2) : 0;
1405 if (range1end != range2end
1406 && JUMP_LABEL (range1end) == label2
1407 && GET_CODE (range2end) == JUMP_INSN
1408 && GET_CODE (NEXT_INSN (range2end)) == BARRIER
1409 /* Invert the jump condition, so we
1410 still execute the same insns in each case. */
1411 && invert_jump (insn, label1))
1412 {
1413 rtx range1beg = next_active_insn (insn);
1414 rtx range2beg = next_active_insn (label1);
1415 rtx range1after, range2after;
1416 rtx range1before, range2before;
1417
1418 /* Include in each range any line number before it. */
1419 while (PREV_INSN (range1beg)
1420 && GET_CODE (PREV_INSN (range1beg)) == NOTE
1421 && NOTE_LINE_NUMBER (PREV_INSN (range1beg)) > 0)
1422 range1beg = PREV_INSN (range1beg);
1423
1424 while (PREV_INSN (range2beg)
1425 && GET_CODE (PREV_INSN (range2beg)) == NOTE
1426 && NOTE_LINE_NUMBER (PREV_INSN (range2beg)) > 0)
1427 range2beg = PREV_INSN (range2beg);
1428
1429 /* Don't move NOTEs for blocks or loops; shift them
1430 outside the ranges, where they'll stay put. */
1431 range1beg = squeeze_notes (range1beg, range1end);
1432 range2beg = squeeze_notes (range2beg, range2end);
1433
1434 /* Get current surrounds of the 2 ranges. */
1435 range1before = PREV_INSN (range1beg);
1436 range2before = PREV_INSN (range2beg);
1437 range1after = NEXT_INSN (range1end);
1438 range2after = NEXT_INSN (range2end);
1439
1440 /* Splice range2 where range1 was. */
1441 NEXT_INSN (range1before) = range2beg;
1442 PREV_INSN (range2beg) = range1before;
1443 NEXT_INSN (range2end) = range1after;
1444 PREV_INSN (range1after) = range2end;
1445 /* Splice range1 where range2 was. */
1446 NEXT_INSN (range2before) = range1beg;
1447 PREV_INSN (range1beg) = range2before;
1448 NEXT_INSN (range1end) = range2after;
1449 PREV_INSN (range2after) = range1end;
1450 changed = 1;
1451 continue;
1452 }
1453 }
1454 }
1455
1456 /* Now that the jump has been tensioned,
1457 try cross jumping: check for identical code
1458 before the jump and before its target label. */
1459
1460 /* First, cross jumping of conditional jumps: */
1461
1462 if (cross_jump && condjump_p (insn))
1463 {
1464 rtx newjpos, newlpos;
1465 rtx x = prev_real_insn (JUMP_LABEL (insn));
1466
1467 /* A conditional jump may be crossjumped
1468 only if the place it jumps to follows
1469 an opposing jump that comes back here. */
1470
1471 if (x != 0 && ! jump_back_p (x, insn))
1472 /* We have no opposing jump;
1473 cannot cross jump this insn. */
1474 x = 0;
1475
1476 newjpos = 0;
1477 /* TARGET is nonzero if it is ok to cross jump
1478 to code before TARGET. If so, see if matches. */
1479 if (x != 0)
1480 find_cross_jump (insn, x, 2,
1481 &newjpos, &newlpos);
1482
1483 if (newjpos != 0)
1484 {
1485 do_cross_jump (insn, newjpos, newlpos);
1486 /* Make the old conditional jump
1487 into an unconditional one. */
1488 SET_SRC (PATTERN (insn))
1489 = gen_rtx (LABEL_REF, VOIDmode, JUMP_LABEL (insn));
1490 INSN_CODE (insn) = -1;
1491 emit_barrier_after (insn);
1492 /* Add to jump_chain unless this is a new label
1493 whose UID is too large. */
1494 if (INSN_UID (JUMP_LABEL (insn)) < max_jump_chain)
1495 {
1496 jump_chain[INSN_UID (insn)]
1497 = jump_chain[INSN_UID (JUMP_LABEL (insn))];
1498 jump_chain[INSN_UID (JUMP_LABEL (insn))] = insn;
1499 }
1500 changed = 1;
1501 next = insn;
1502 }
1503 }
1504
1505 /* Cross jumping of unconditional jumps:
1506 a few differences. */
1507
1508 if (cross_jump && simplejump_p (insn))
1509 {
1510 rtx newjpos, newlpos;
1511 rtx target;
1512
1513 newjpos = 0;
1514
1515 /* TARGET is nonzero if it is ok to cross jump
1516 to code before TARGET. If so, see if matches. */
1517 find_cross_jump (insn, JUMP_LABEL (insn), 1,
1518 &newjpos, &newlpos);
1519
1520 /* If cannot cross jump to code before the label,
1521 see if we can cross jump to another jump to
1522 the same label. */
1523 /* Try each other jump to this label. */
1524 if (INSN_UID (JUMP_LABEL (insn)) < max_uid)
1525 for (target = jump_chain[INSN_UID (JUMP_LABEL (insn))];
1526 target != 0 && newjpos == 0;
1527 target = jump_chain[INSN_UID (target)])
1528 if (target != insn
1529 && JUMP_LABEL (target) == JUMP_LABEL (insn)
1530 /* Ignore TARGET if it's deleted. */
1531 && ! INSN_DELETED_P (target))
1532 find_cross_jump (insn, target, 2,
1533 &newjpos, &newlpos);
1534
1535 if (newjpos != 0)
1536 {
1537 do_cross_jump (insn, newjpos, newlpos);
1538 changed = 1;
1539 next = insn;
1540 }
1541 }
1542
1543 /* This code was dead in the previous jump.c! */
1544 if (cross_jump && GET_CODE (PATTERN (insn)) == RETURN)
1545 {
1546 /* Return insns all "jump to the same place"
1547 so we can cross-jump between any two of them. */
1548
1549 rtx newjpos, newlpos, target;
1550
1551 newjpos = 0;
1552
1553 /* If cannot cross jump to code before the label,
1554 see if we can cross jump to another jump to
1555 the same label. */
1556 /* Try each other jump to this label. */
1557 for (target = jump_chain[0];
1558 target != 0 && newjpos == 0;
1559 target = jump_chain[INSN_UID (target)])
1560 if (target != insn
1561 && ! INSN_DELETED_P (target)
1562 && GET_CODE (PATTERN (target)) == RETURN)
1563 find_cross_jump (insn, target, 2,
1564 &newjpos, &newlpos);
1565
1566 if (newjpos != 0)
1567 {
1568 do_cross_jump (insn, newjpos, newlpos);
1569 changed = 1;
1570 next = insn;
1571 }
1572 }
1573 }
1574 }
1575
1576 first = 0;
1577 }
1578
1579 /* Delete extraneous line number notes.
1580 Note that two consecutive notes for different lines are not really
1581 extraneous. There should be some indication where that line belonged,
1582 even if it became empty. */
1583
1584 {
1585 rtx last_note = 0;
1586
1587 for (insn = f; insn; insn = NEXT_INSN (insn))
1588 if (GET_CODE (insn) == NOTE && NOTE_LINE_NUMBER (insn) >= 0)
1589 {
1590 /* Delete this note if it is identical to previous note. */
1591 if (last_note
1592 && NOTE_SOURCE_FILE (insn) == NOTE_SOURCE_FILE (last_note)
1593 && NOTE_LINE_NUMBER (insn) == NOTE_LINE_NUMBER (last_note))
1594 {
1595 delete_insn (insn);
1596 continue;
1597 }
1598
1599 last_note = insn;
1600 }
1601 }
1602
1603 /* See if there is still a NOTE_INSN_FUNCTION_END in this function.
1604 If so, delete it, and record that this function can drop off the end. */
1605
1606 insn = last_insn;
1607 {
1608 int n_labels = 1;
1609 while (insn
1610 /* One label can follow the end-note: the return label. */
1611 && ((GET_CODE (insn) == CODE_LABEL && n_labels-- > 0)
1612 /* Ordinary insns can follow it if returning a structure. */
1613 || GET_CODE (insn) == INSN
1614 /* If machine uses explicit RETURN insns, no epilogue,
1615 then one of them follows the note. */
1616 || (GET_CODE (insn) == JUMP_INSN
1617 && GET_CODE (PATTERN (insn)) == RETURN)
1618 /* Other kinds of notes can follow also. */
1619 || (GET_CODE (insn) == NOTE
1620 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_FUNCTION_END)))
1621 insn = PREV_INSN (insn);
1622 }
1623
1624 /* Report if control can fall through at the end of the function. */
1625 if (insn && GET_CODE (insn) == NOTE
1626 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_END)
1627 {
1628 can_reach_end = 1;
1629 delete_insn (insn);
1630 }
1631
1632 /* Show JUMP_CHAIN no longer valid. */
1633 jump_chain = 0;
1634 }
1635 \f
1636 /* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
1637 jump. Assume that this unconditional jump is to the exit test code. If
1638 the code is sufficiently simple, make a copy of it before INSN,
1639 followed by a jump to the exit of the loop. Then delete the unconditional
1640 jump after INSN.
1641
1642 Note that it is possible we can get confused here if the jump immediately
1643 after the loop start branches outside the loop but within an outer loop.
1644 If we are near the exit of that loop, we will copy its exit test. This
1645 will not generate incorrect code, but could suppress some optimizations.
1646 However, such cases are degenerate loops anyway.
1647
1648 Return 1 if we made the change, else 0.
1649
1650 This is only safe immediately after a regscan pass because it uses the
1651 values of regno_first_uid and regno_last_uid. */
1652
1653 static int
1654 duplicate_loop_exit_test (loop_start)
1655 rtx loop_start;
1656 {
1657 rtx insn, set, p;
1658 rtx copy, link;
1659 int num_insns = 0;
1660 rtx exitcode = NEXT_INSN (JUMP_LABEL (next_nonnote_insn (loop_start)));
1661 rtx lastexit;
1662 int max_reg = max_reg_num ();
1663 rtx *reg_map = 0;
1664
1665 /* Scan the exit code. We do not perform this optimization if any insn:
1666
1667 is a CALL_INSN
1668 is a CODE_LABEL
1669 has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
1670 is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
1671 is a NOTE_INSN_BLOCK_{BEG,END} because duplicating these notes
1672 are not valid
1673
1674 Also, don't do this if the exit code is more than 20 insns. */
1675
1676 for (insn = exitcode;
1677 insn
1678 && ! (GET_CODE (insn) == NOTE
1679 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END);
1680 insn = NEXT_INSN (insn))
1681 {
1682 switch (GET_CODE (insn))
1683 {
1684 case CODE_LABEL:
1685 case CALL_INSN:
1686 return 0;
1687 case NOTE:
1688 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG
1689 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG
1690 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END)
1691 return 0;
1692 break;
1693 case JUMP_INSN:
1694 case INSN:
1695 if (++num_insns > 20
1696 || find_reg_note (insn, REG_RETVAL, 0)
1697 || find_reg_note (insn, REG_LIBCALL, 0))
1698 return 0;
1699 break;
1700 }
1701 }
1702
1703 /* Unless INSN is zero, we can do the optimization. */
1704 if (insn == 0)
1705 return 0;
1706
1707 lastexit = insn;
1708
1709 /* See if any insn sets a register only used in the loop exit code and
1710 not a user variable. If so, replace it with a new register. */
1711 for (insn = exitcode; insn != lastexit; insn = NEXT_INSN (insn))
1712 if (GET_CODE (insn) == INSN
1713 && (set = single_set (insn)) != 0
1714 && GET_CODE (SET_DEST (set)) == REG
1715 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER
1716 && regno_first_uid[REGNO (SET_DEST (set))] == INSN_UID (insn))
1717 {
1718 for (p = NEXT_INSN (insn); p != lastexit; p = NEXT_INSN (p))
1719 if (regno_last_uid[REGNO (SET_DEST (set))] == INSN_UID (p))
1720 break;
1721
1722 if (p != lastexit)
1723 {
1724 /* We can do the replacement. Allocate reg_map if this is the
1725 first replacement we found. */
1726 if (reg_map == 0)
1727 {
1728 reg_map = (rtx *) alloca (max_reg * sizeof (rtx));
1729 bzero (reg_map, max_reg * sizeof (rtx));
1730 }
1731
1732 REG_LOOP_TEST_P (SET_DEST (set)) = 1;
1733
1734 reg_map[REGNO (SET_DEST (set))]
1735 = gen_reg_rtx (GET_MODE (SET_DEST (set)));
1736 }
1737 }
1738
1739 /* Now copy each insn. */
1740 for (insn = exitcode; insn != lastexit; insn = NEXT_INSN (insn))
1741 switch (GET_CODE (insn))
1742 {
1743 case BARRIER:
1744 copy = emit_barrier_before (loop_start);
1745 break;
1746 case NOTE:
1747 /* Only copy line-number notes. */
1748 if (NOTE_LINE_NUMBER (insn) >= 0)
1749 {
1750 copy = emit_note_before (NOTE_LINE_NUMBER (insn), loop_start);
1751 NOTE_SOURCE_FILE (copy) = NOTE_SOURCE_FILE (insn);
1752 }
1753 break;
1754
1755 case INSN:
1756 copy = emit_insn_before (copy_rtx (PATTERN (insn)), loop_start);
1757 if (reg_map)
1758 replace_regs (PATTERN (copy), reg_map, max_reg, 1);
1759
1760 mark_jump_label (PATTERN (copy), copy, 0);
1761
1762 /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
1763 make them. */
1764 for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
1765 if (REG_NOTE_KIND (link) != REG_LABEL)
1766 REG_NOTES (copy)
1767 = copy_rtx (gen_rtx (EXPR_LIST, REG_NOTE_KIND (link),
1768 XEXP (link, 0), REG_NOTES (copy)));
1769 if (reg_map && REG_NOTES (copy))
1770 replace_regs (REG_NOTES (copy), reg_map, max_reg, 1);
1771 break;
1772
1773 case JUMP_INSN:
1774 copy = emit_jump_insn_before (copy_rtx (PATTERN (insn)), loop_start);
1775 if (reg_map)
1776 replace_regs (PATTERN (copy), reg_map, max_reg, 1);
1777 mark_jump_label (PATTERN (copy), copy, 0);
1778 if (REG_NOTES (insn))
1779 {
1780 REG_NOTES (copy) = copy_rtx (REG_NOTES (insn));
1781 if (reg_map)
1782 replace_regs (REG_NOTES (copy), reg_map, max_reg, 1);
1783 }
1784
1785 /* If this is a simple jump, add it to the jump chain. */
1786
1787 if (INSN_UID (copy) < max_jump_chain && JUMP_LABEL (copy)
1788 && simplejump_p (copy))
1789 {
1790 jump_chain[INSN_UID (copy)]
1791 = jump_chain[INSN_UID (JUMP_LABEL (copy))];
1792 jump_chain[INSN_UID (JUMP_LABEL (copy))] = copy;
1793 }
1794 break;
1795
1796 default:
1797 abort ();
1798 }
1799
1800 /* Now clean up by emitting a jump to the end label and deleting the jump
1801 at the start of the loop. */
1802 if (GET_CODE (copy) != BARRIER)
1803 {
1804 copy = emit_jump_insn_before (gen_jump (get_label_after (insn)),
1805 loop_start);
1806 mark_jump_label (PATTERN (copy), copy, 0);
1807 if (INSN_UID (copy) < max_jump_chain
1808 && INSN_UID (JUMP_LABEL (copy)) < max_jump_chain)
1809 {
1810 jump_chain[INSN_UID (copy)]
1811 = jump_chain[INSN_UID (JUMP_LABEL (copy))];
1812 jump_chain[INSN_UID (JUMP_LABEL (copy))] = copy;
1813 }
1814 emit_barrier_before (loop_start);
1815 }
1816
1817 delete_insn (next_nonnote_insn (loop_start));
1818
1819 /* Mark the exit code as the virtual top of the converted loop. */
1820 emit_note_before (NOTE_INSN_LOOP_VTOP, exitcode);
1821
1822 return 1;
1823 }
1824 \f
1825 /* Move all block-beg, block-end, loop-beg, loop-cont, loop-vtop, and
1826 loop-end notes between START and END out before START. Assume that
1827 END is not such a note. START may be such a note. Returns the value
1828 of the new starting insn, which may be different if the original start
1829 was such a note. */
1830
1831 rtx
1832 squeeze_notes (start, end)
1833 rtx start, end;
1834 {
1835 rtx insn;
1836 rtx next;
1837
1838 for (insn = start; insn != end; insn = next)
1839 {
1840 next = NEXT_INSN (insn);
1841 if (GET_CODE (insn) == NOTE
1842 && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END
1843 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG
1844 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG
1845 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END
1846 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_CONT
1847 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_VTOP))
1848 {
1849 if (insn == start)
1850 start = next;
1851 else
1852 {
1853 rtx prev = PREV_INSN (insn);
1854 PREV_INSN (insn) = PREV_INSN (start);
1855 NEXT_INSN (insn) = start;
1856 NEXT_INSN (PREV_INSN (insn)) = insn;
1857 PREV_INSN (NEXT_INSN (insn)) = insn;
1858 NEXT_INSN (prev) = next;
1859 PREV_INSN (next) = prev;
1860 }
1861 }
1862 }
1863
1864 return start;
1865 }
1866 \f
1867 /* Compare the instructions before insn E1 with those before E2
1868 to find an opportunity for cross jumping.
1869 (This means detecting identical sequences of insns followed by
1870 jumps to the same place, or followed by a label and a jump
1871 to that label, and replacing one with a jump to the other.)
1872
1873 Assume E1 is a jump that jumps to label E2
1874 (that is not always true but it might as well be).
1875 Find the longest possible equivalent sequences
1876 and store the first insns of those sequences into *F1 and *F2.
1877 Store zero there if no equivalent preceding instructions are found.
1878
1879 We give up if we find a label in stream 1.
1880 Actually we could transfer that label into stream 2. */
1881
1882 static void
1883 find_cross_jump (e1, e2, minimum, f1, f2)
1884 rtx e1, e2;
1885 int minimum;
1886 rtx *f1, *f2;
1887 {
1888 register rtx i1 = e1, i2 = e2;
1889 register rtx p1, p2;
1890 int lose = 0;
1891
1892 rtx last1 = 0, last2 = 0;
1893 rtx afterlast1 = 0, afterlast2 = 0;
1894 rtx prev1;
1895
1896 *f1 = 0;
1897 *f2 = 0;
1898
1899 while (1)
1900 {
1901 i1 = prev_nonnote_insn (i1);
1902
1903 i2 = PREV_INSN (i2);
1904 while (i2 && (GET_CODE (i2) == NOTE || GET_CODE (i2) == CODE_LABEL))
1905 i2 = PREV_INSN (i2);
1906
1907 if (i1 == 0)
1908 break;
1909
1910 /* Don't allow the range of insns preceding E1 or E2
1911 to include the other (E2 or E1). */
1912 if (i2 == e1 || i1 == e2)
1913 break;
1914
1915 /* If we will get to this code by jumping, those jumps will be
1916 tensioned to go directly to the new label (before I2),
1917 so this cross-jumping won't cost extra. So reduce the minimum. */
1918 if (GET_CODE (i1) == CODE_LABEL)
1919 {
1920 --minimum;
1921 break;
1922 }
1923
1924 if (i2 == 0 || GET_CODE (i1) != GET_CODE (i2))
1925 break;
1926
1927 p1 = PATTERN (i1);
1928 p2 = PATTERN (i2);
1929
1930 #ifdef STACK_REGS
1931 /* If cross_jump_death_matters is not 0, the insn's mode
1932 indicates whether or not the insn contains any stack-like
1933 regs. */
1934
1935 if (cross_jump_death_matters && GET_MODE (i1) == QImode)
1936 {
1937 /* If register stack conversion has already been done, then
1938 death notes must also be compared before it is certain that
1939 the two instruction streams match. */
1940
1941 rtx note;
1942 HARD_REG_SET i1_regset, i2_regset;
1943
1944 CLEAR_HARD_REG_SET (i1_regset);
1945 CLEAR_HARD_REG_SET (i2_regset);
1946
1947 for (note = REG_NOTES (i1); note; note = XEXP (note, 1))
1948 if (REG_NOTE_KIND (note) == REG_DEAD
1949 && STACK_REG_P (XEXP (note, 0)))
1950 SET_HARD_REG_BIT (i1_regset, REGNO (XEXP (note, 0)));
1951
1952 for (note = REG_NOTES (i2); note; note = XEXP (note, 1))
1953 if (REG_NOTE_KIND (note) == REG_DEAD
1954 && STACK_REG_P (XEXP (note, 0)))
1955 SET_HARD_REG_BIT (i2_regset, REGNO (XEXP (note, 0)));
1956
1957 GO_IF_HARD_REG_EQUAL (i1_regset, i2_regset, done);
1958
1959 lose = 1;
1960
1961 done:
1962 ;
1963 }
1964 #endif
1965
1966 if (lose || GET_CODE (p1) != GET_CODE (p2)
1967 || ! rtx_renumbered_equal_p (p1, p2))
1968 {
1969 /* The following code helps take care of G++ cleanups. */
1970 rtx equiv1;
1971 rtx equiv2;
1972
1973 if (!lose && GET_CODE (p1) == GET_CODE (p2)
1974 && ((equiv1 = find_reg_note (i1, REG_EQUAL, 0)) != 0
1975 || (equiv1 = find_reg_note (i1, REG_EQUIV, 0)) != 0)
1976 && ((equiv2 = find_reg_note (i2, REG_EQUAL, 0)) != 0
1977 || (equiv2 = find_reg_note (i2, REG_EQUIV, 0)) != 0)
1978 /* If the equivalences are not to a constant, they may
1979 reference pseudos that no longer exist, so we can't
1980 use them. */
1981 && CONSTANT_P (XEXP (equiv1, 0))
1982 && rtx_equal_p (XEXP (equiv1, 0), XEXP (equiv2, 0)))
1983 {
1984 rtx s1 = single_set (i1);
1985 rtx s2 = single_set (i2);
1986 if (s1 != 0 && s2 != 0
1987 && rtx_renumbered_equal_p (SET_DEST (s1), SET_DEST (s2)))
1988 {
1989 validate_change (i1, &SET_SRC (s1), XEXP (equiv1, 0), 1);
1990 validate_change (i2, &SET_SRC (s2), XEXP (equiv2, 0), 1);
1991 if (! rtx_renumbered_equal_p (p1, p2))
1992 cancel_changes (0);
1993 else if (apply_change_group ())
1994 goto win;
1995 }
1996 }
1997
1998 /* Insns fail to match; cross jumping is limited to the following
1999 insns. */
2000
2001 #ifdef HAVE_cc0
2002 /* Don't allow the insn after a compare to be shared by
2003 cross-jumping unless the compare is also shared.
2004 Here, if either of these non-matching insns is a compare,
2005 exclude the following insn from possible cross-jumping. */
2006 if (sets_cc0_p (p1) || sets_cc0_p (p2))
2007 last1 = afterlast1, last2 = afterlast2, ++minimum;
2008 #endif
2009
2010 /* If cross-jumping here will feed a jump-around-jump
2011 optimization, this jump won't cost extra, so reduce
2012 the minimum. */
2013 if (GET_CODE (i1) == JUMP_INSN
2014 && JUMP_LABEL (i1)
2015 && prev_real_insn (JUMP_LABEL (i1)) == e1)
2016 --minimum;
2017 break;
2018 }
2019
2020 win:
2021 if (GET_CODE (p1) != USE && GET_CODE (p1) != CLOBBER)
2022 {
2023 /* Ok, this insn is potentially includable in a cross-jump here. */
2024 afterlast1 = last1, afterlast2 = last2;
2025 last1 = i1, last2 = i2, --minimum;
2026 }
2027 }
2028
2029 /* We have to be careful that we do not cross-jump into the middle of
2030 USE-CALL_INSN-CLOBBER sequence. This sequence is used instead of
2031 putting the USE and CLOBBERs inside the CALL_INSN. The delay slot
2032 scheduler needs to know what registers are used and modified by the
2033 CALL_INSN and needs the adjacent USE and CLOBBERs to do so.
2034
2035 ??? At some point we should probably change this so that these are
2036 part of the CALL_INSN. The way we are doing it now is a kludge that
2037 is now causing trouble. */
2038
2039 if (last1 != 0 && GET_CODE (last1) == CALL_INSN
2040 && (prev1 = prev_nonnote_insn (last1))
2041 && GET_CODE (prev1) == INSN
2042 && GET_CODE (PATTERN (prev1)) == USE)
2043 {
2044 /* Remove this CALL_INSN from the range we can cross-jump. */
2045 last1 = next_real_insn (last1);
2046 last2 = next_real_insn (last2);
2047
2048 minimum++;
2049 }
2050
2051 /* Skip past CLOBBERS since they may be right after a CALL_INSN. It
2052 isn't worth checking for the CALL_INSN. */
2053 while (last1 != 0 && GET_CODE (PATTERN (last1)) == CLOBBER)
2054 last1 = next_real_insn (last1), last2 = next_real_insn (last2);
2055
2056 if (minimum <= 0 && last1 != 0 && last1 != e1)
2057 *f1 = last1, *f2 = last2;
2058 }
2059
2060 static void
2061 do_cross_jump (insn, newjpos, newlpos)
2062 rtx insn, newjpos, newlpos;
2063 {
2064 /* Find an existing label at this point
2065 or make a new one if there is none. */
2066 register rtx label = get_label_before (newlpos);
2067
2068 /* Make the same jump insn jump to the new point. */
2069 if (GET_CODE (PATTERN (insn)) == RETURN)
2070 {
2071 /* Remove from jump chain of returns. */
2072 delete_from_jump_chain (insn);
2073 /* Change the insn. */
2074 PATTERN (insn) = gen_jump (label);
2075 INSN_CODE (insn) = -1;
2076 JUMP_LABEL (insn) = label;
2077 LABEL_NUSES (label)++;
2078 /* Add to new the jump chain. */
2079 if (INSN_UID (label) < max_jump_chain
2080 && INSN_UID (insn) < max_jump_chain)
2081 {
2082 jump_chain[INSN_UID (insn)] = jump_chain[INSN_UID (label)];
2083 jump_chain[INSN_UID (label)] = insn;
2084 }
2085 }
2086 else
2087 redirect_jump (insn, label);
2088
2089 /* Delete the matching insns before the jump. Also, remove any REG_EQUAL
2090 or REG_EQUIV note in the NEWLPOS stream that isn't also present in
2091 the NEWJPOS stream. */
2092
2093 while (newjpos != insn)
2094 {
2095 rtx lnote;
2096
2097 for (lnote = REG_NOTES (newlpos); lnote; lnote = XEXP (lnote, 1))
2098 if ((REG_NOTE_KIND (lnote) == REG_EQUAL
2099 || REG_NOTE_KIND (lnote) == REG_EQUIV)
2100 && ! find_reg_note (newjpos, REG_EQUAL, XEXP (lnote, 0))
2101 && ! find_reg_note (newjpos, REG_EQUIV, XEXP (lnote, 0)))
2102 remove_note (newlpos, lnote);
2103
2104 delete_insn (newjpos);
2105 newjpos = next_real_insn (newjpos);
2106 newlpos = next_real_insn (newlpos);
2107 }
2108 }
2109 \f
2110 /* Return the label before INSN, or put a new label there. */
2111
2112 rtx
2113 get_label_before (insn)
2114 rtx insn;
2115 {
2116 rtx label;
2117
2118 /* Find an existing label at this point
2119 or make a new one if there is none. */
2120 label = prev_nonnote_insn (insn);
2121
2122 if (label == 0 || GET_CODE (label) != CODE_LABEL)
2123 {
2124 rtx prev = PREV_INSN (insn);
2125
2126 /* Don't put a label between a CALL_INSN and USE insns that preceed
2127 it. */
2128
2129 if (GET_CODE (insn) == CALL_INSN
2130 || (GET_CODE (insn) == INSN && GET_CODE (PATTERN (insn)) == SEQUENCE
2131 && GET_CODE (XVECEXP (PATTERN (insn), 0, 0)) == CALL_INSN))
2132 while (GET_CODE (prev) == INSN && GET_CODE (PATTERN (prev)) == USE)
2133 prev = PREV_INSN (prev);
2134
2135 label = gen_label_rtx ();
2136 emit_label_after (label, prev);
2137 LABEL_NUSES (label) = 0;
2138 }
2139 return label;
2140 }
2141
2142 /* Return the label after INSN, or put a new label there. */
2143
2144 rtx
2145 get_label_after (insn)
2146 rtx insn;
2147 {
2148 rtx label;
2149
2150 /* Find an existing label at this point
2151 or make a new one if there is none. */
2152 label = next_nonnote_insn (insn);
2153
2154 if (label == 0 || GET_CODE (label) != CODE_LABEL)
2155 {
2156 /* Don't put a label between a CALL_INSN and CLOBBER insns
2157 following it. */
2158
2159 if (GET_CODE (insn) == CALL_INSN
2160 || (GET_CODE (insn) == INSN && GET_CODE (PATTERN (insn)) == SEQUENCE
2161 && GET_CODE (XVECEXP (PATTERN (insn), 0, 0)) == CALL_INSN))
2162 while (GET_CODE (NEXT_INSN (insn)) == INSN
2163 && GET_CODE (PATTERN (NEXT_INSN (insn))) == CLOBBER)
2164 insn = NEXT_INSN (insn);
2165
2166 label = gen_label_rtx ();
2167 emit_label_after (label, insn);
2168 LABEL_NUSES (label) = 0;
2169 }
2170 return label;
2171 }
2172 \f
2173 /* Return 1 if INSN is a jump that jumps to right after TARGET
2174 only on the condition that TARGET itself would drop through.
2175 Assumes that TARGET is a conditional jump. */
2176
2177 static int
2178 jump_back_p (insn, target)
2179 rtx insn, target;
2180 {
2181 rtx cinsn, ctarget;
2182 enum rtx_code codei, codet;
2183
2184 if (simplejump_p (insn) || ! condjump_p (insn)
2185 || simplejump_p (target)
2186 || target != prev_real_insn (JUMP_LABEL (insn)))
2187 return 0;
2188
2189 cinsn = XEXP (SET_SRC (PATTERN (insn)), 0);
2190 ctarget = XEXP (SET_SRC (PATTERN (target)), 0);
2191
2192 codei = GET_CODE (cinsn);
2193 codet = GET_CODE (ctarget);
2194
2195 if (XEXP (SET_SRC (PATTERN (insn)), 1) == pc_rtx)
2196 {
2197 if (! can_reverse_comparison_p (cinsn, insn))
2198 return 0;
2199 codei = reverse_condition (codei);
2200 }
2201
2202 if (XEXP (SET_SRC (PATTERN (target)), 2) == pc_rtx)
2203 {
2204 if (! can_reverse_comparison_p (ctarget, target))
2205 return 0;
2206 codet = reverse_condition (codet);
2207 }
2208
2209 return (codei == codet
2210 && rtx_renumbered_equal_p (XEXP (cinsn, 0), XEXP (ctarget, 0))
2211 && rtx_renumbered_equal_p (XEXP (cinsn, 1), XEXP (ctarget, 1)));
2212 }
2213 \f
2214 /* Given a comparison, COMPARISON, inside a conditional jump insn, INSN,
2215 return non-zero if it is safe to reverse this comparison. It is if our
2216 floating-point is not IEEE, if this is an NE or EQ comparison, or if
2217 this is known to be an integer comparison. */
2218
2219 int
2220 can_reverse_comparison_p (comparison, insn)
2221 rtx comparison;
2222 rtx insn;
2223 {
2224 rtx arg0;
2225
2226 /* If this is not actually a comparison, we can't reverse it. */
2227 if (GET_RTX_CLASS (GET_CODE (comparison)) != '<')
2228 return 0;
2229
2230 if (TARGET_FLOAT_FORMAT != IEEE_FLOAT_FORMAT
2231 /* If this is an NE comparison, it is safe to reverse it to an EQ
2232 comparison and vice versa, even for floating point. If no operands
2233 are NaNs, the reversal is valid. If some operand is a NaN, EQ is
2234 always false and NE is always true, so the reversal is also valid. */
2235 || GET_CODE (comparison) == NE
2236 || GET_CODE (comparison) == EQ)
2237 return 1;
2238
2239 arg0 = XEXP (comparison, 0);
2240
2241 /* Make sure ARG0 is one of the actual objects being compared. If we
2242 can't do this, we can't be sure the comparison can be reversed.
2243
2244 Handle cc0 and a MODE_CC register. */
2245 if ((GET_CODE (arg0) == REG && GET_MODE_CLASS (GET_MODE (arg0)) == MODE_CC)
2246 #ifdef HAVE_cc0
2247 || arg0 == cc0_rtx
2248 #endif
2249 )
2250 {
2251 rtx prev = prev_nonnote_insn (insn);
2252 rtx set = single_set (prev);
2253
2254 if (set == 0 || SET_DEST (set) != arg0)
2255 return 0;
2256
2257 arg0 = SET_SRC (set);
2258
2259 if (GET_CODE (arg0) == COMPARE)
2260 arg0 = XEXP (arg0, 0);
2261 }
2262
2263 /* We can reverse this if ARG0 is a CONST_INT or if its mode is
2264 not VOIDmode and neither a MODE_CC nor MODE_FLOAT type. */
2265 return (GET_CODE (arg0) == CONST_INT
2266 || (GET_MODE (arg0) != VOIDmode
2267 && GET_MODE_CLASS (GET_MODE (arg0)) != MODE_CC
2268 && GET_MODE_CLASS (GET_MODE (arg0)) != MODE_FLOAT));
2269 }
2270
2271 /* Given an rtx-code for a comparison, return the code
2272 for the negated comparison.
2273 WATCH OUT! reverse_condition is not safe to use on a jump
2274 that might be acting on the results of an IEEE floating point comparison,
2275 because of the special treatment of non-signaling nans in comparisons.
2276 Use can_reverse_comparison_p to be sure. */
2277
2278 enum rtx_code
2279 reverse_condition (code)
2280 enum rtx_code code;
2281 {
2282 switch (code)
2283 {
2284 case EQ:
2285 return NE;
2286
2287 case NE:
2288 return EQ;
2289
2290 case GT:
2291 return LE;
2292
2293 case GE:
2294 return LT;
2295
2296 case LT:
2297 return GE;
2298
2299 case LE:
2300 return GT;
2301
2302 case GTU:
2303 return LEU;
2304
2305 case GEU:
2306 return LTU;
2307
2308 case LTU:
2309 return GEU;
2310
2311 case LEU:
2312 return GTU;
2313
2314 default:
2315 abort ();
2316 return UNKNOWN;
2317 }
2318 }
2319
2320 /* Similar, but return the code when two operands of a comparison are swapped.
2321 This IS safe for IEEE floating-point. */
2322
2323 enum rtx_code
2324 swap_condition (code)
2325 enum rtx_code code;
2326 {
2327 switch (code)
2328 {
2329 case EQ:
2330 case NE:
2331 return code;
2332
2333 case GT:
2334 return LT;
2335
2336 case GE:
2337 return LE;
2338
2339 case LT:
2340 return GT;
2341
2342 case LE:
2343 return GE;
2344
2345 case GTU:
2346 return LTU;
2347
2348 case GEU:
2349 return LEU;
2350
2351 case LTU:
2352 return GTU;
2353
2354 case LEU:
2355 return GEU;
2356
2357 default:
2358 abort ();
2359 return UNKNOWN;
2360 }
2361 }
2362
2363 /* Given a comparison CODE, return the corresponding unsigned comparison.
2364 If CODE is an equality comparison or already an unsigned comparison,
2365 CODE is returned. */
2366
2367 enum rtx_code
2368 unsigned_condition (code)
2369 enum rtx_code code;
2370 {
2371 switch (code)
2372 {
2373 case EQ:
2374 case NE:
2375 case GTU:
2376 case GEU:
2377 case LTU:
2378 case LEU:
2379 return code;
2380
2381 case GT:
2382 return GTU;
2383
2384 case GE:
2385 return GEU;
2386
2387 case LT:
2388 return LTU;
2389
2390 case LE:
2391 return LEU;
2392
2393 default:
2394 abort ();
2395 }
2396 }
2397
2398 /* Similarly, return the signed version of a comparison. */
2399
2400 enum rtx_code
2401 signed_condition (code)
2402 enum rtx_code code;
2403 {
2404 switch (code)
2405 {
2406 case EQ:
2407 case NE:
2408 case GT:
2409 case GE:
2410 case LT:
2411 case LE:
2412 return code;
2413
2414 case GTU:
2415 return GT;
2416
2417 case GEU:
2418 return GE;
2419
2420 case LTU:
2421 return LT;
2422
2423 case LEU:
2424 return LE;
2425
2426 default:
2427 abort ();
2428 }
2429 }
2430 \f
2431 /* Return non-zero if CODE1 is more strict than CODE2, i.e., if the
2432 truth of CODE1 implies the truth of CODE2. */
2433
2434 int
2435 comparison_dominates_p (code1, code2)
2436 enum rtx_code code1, code2;
2437 {
2438 if (code1 == code2)
2439 return 1;
2440
2441 switch (code1)
2442 {
2443 case EQ:
2444 if (code2 == LE || code2 == LEU || code2 == GE || code2 == GEU)
2445 return 1;
2446 break;
2447
2448 case LT:
2449 if (code2 == LE)
2450 return 1;
2451 break;
2452
2453 case GT:
2454 if (code2 == GE)
2455 return 1;
2456 break;
2457
2458 case LTU:
2459 if (code2 == LEU)
2460 return 1;
2461 break;
2462
2463 case GTU:
2464 if (code2 == GEU)
2465 return 1;
2466 break;
2467 }
2468
2469 return 0;
2470 }
2471 \f
2472 /* Return 1 if INSN is an unconditional jump and nothing else. */
2473
2474 int
2475 simplejump_p (insn)
2476 rtx insn;
2477 {
2478 return (GET_CODE (insn) == JUMP_INSN
2479 && GET_CODE (PATTERN (insn)) == SET
2480 && GET_CODE (SET_DEST (PATTERN (insn))) == PC
2481 && GET_CODE (SET_SRC (PATTERN (insn))) == LABEL_REF);
2482 }
2483
2484 /* Return nonzero if INSN is a (possibly) conditional jump
2485 and nothing more. */
2486
2487 int
2488 condjump_p (insn)
2489 rtx insn;
2490 {
2491 register rtx x = PATTERN (insn);
2492 if (GET_CODE (x) != SET)
2493 return 0;
2494 if (GET_CODE (SET_DEST (x)) != PC)
2495 return 0;
2496 if (GET_CODE (SET_SRC (x)) == LABEL_REF)
2497 return 1;
2498 if (GET_CODE (SET_SRC (x)) != IF_THEN_ELSE)
2499 return 0;
2500 if (XEXP (SET_SRC (x), 2) == pc_rtx
2501 && (GET_CODE (XEXP (SET_SRC (x), 1)) == LABEL_REF
2502 || GET_CODE (XEXP (SET_SRC (x), 1)) == RETURN))
2503 return 1;
2504 if (XEXP (SET_SRC (x), 1) == pc_rtx
2505 && (GET_CODE (XEXP (SET_SRC (x), 2)) == LABEL_REF
2506 || GET_CODE (XEXP (SET_SRC (x), 2)) == RETURN))
2507 return 1;
2508 return 0;
2509 }
2510
2511 /* Return 1 if X is an RTX that does nothing but set the condition codes
2512 and CLOBBER or USE registers.
2513 Return -1 if X does explicitly set the condition codes,
2514 but also does other things. */
2515
2516 int
2517 sets_cc0_p (x)
2518 rtx x;
2519 {
2520 #ifdef HAVE_cc0
2521 if (GET_CODE (x) == SET && SET_DEST (x) == cc0_rtx)
2522 return 1;
2523 if (GET_CODE (x) == PARALLEL)
2524 {
2525 int i;
2526 int sets_cc0 = 0;
2527 int other_things = 0;
2528 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
2529 {
2530 if (GET_CODE (XVECEXP (x, 0, i)) == SET
2531 && SET_DEST (XVECEXP (x, 0, i)) == cc0_rtx)
2532 sets_cc0 = 1;
2533 else if (GET_CODE (XVECEXP (x, 0, i)) == SET)
2534 other_things = 1;
2535 }
2536 return ! sets_cc0 ? 0 : other_things ? -1 : 1;
2537 }
2538 return 0;
2539 #else
2540 abort ();
2541 #endif
2542 }
2543 \f
2544 /* Follow any unconditional jump at LABEL;
2545 return the ultimate label reached by any such chain of jumps.
2546 If LABEL is not followed by a jump, return LABEL.
2547 If the chain loops or we can't find end, return LABEL,
2548 since that tells caller to avoid changing the insn.
2549
2550 If RELOAD_COMPLETED is 0, we do not chain across a NOTE_INSN_LOOP_BEG or
2551 a USE or CLOBBER. */
2552
2553 rtx
2554 follow_jumps (label)
2555 rtx label;
2556 {
2557 register rtx insn;
2558 register rtx next;
2559 register rtx value = label;
2560 register int depth;
2561
2562 for (depth = 0;
2563 (depth < 10
2564 && (insn = next_active_insn (value)) != 0
2565 && GET_CODE (insn) == JUMP_INSN
2566 && (JUMP_LABEL (insn) != 0 || GET_CODE (PATTERN (insn)) == RETURN)
2567 && (next = NEXT_INSN (insn))
2568 && GET_CODE (next) == BARRIER);
2569 depth++)
2570 {
2571 /* Don't chain through the insn that jumps into a loop
2572 from outside the loop,
2573 since that would create multiple loop entry jumps
2574 and prevent loop optimization. */
2575 rtx tem;
2576 if (!reload_completed)
2577 for (tem = value; tem != insn; tem = NEXT_INSN (tem))
2578 if (GET_CODE (tem) == NOTE
2579 && NOTE_LINE_NUMBER (tem) == NOTE_INSN_LOOP_BEG)
2580 return value;
2581
2582 /* If we have found a cycle, make the insn jump to itself. */
2583 if (JUMP_LABEL (insn) == label)
2584 return label;
2585 value = JUMP_LABEL (insn);
2586 }
2587 if (depth == 10)
2588 return label;
2589 return value;
2590 }
2591
2592 /* Assuming that field IDX of X is a vector of label_refs,
2593 replace each of them by the ultimate label reached by it.
2594 Return nonzero if a change is made.
2595 If IGNORE_LOOPS is 0, we do not chain across a NOTE_INSN_LOOP_BEG. */
2596
2597 static int
2598 tension_vector_labels (x, idx)
2599 register rtx x;
2600 register int idx;
2601 {
2602 int changed = 0;
2603 register int i;
2604 for (i = XVECLEN (x, idx) - 1; i >= 0; i--)
2605 {
2606 register rtx olabel = XEXP (XVECEXP (x, idx, i), 0);
2607 register rtx nlabel = follow_jumps (olabel);
2608 if (nlabel && nlabel != olabel)
2609 {
2610 XEXP (XVECEXP (x, idx, i), 0) = nlabel;
2611 ++LABEL_NUSES (nlabel);
2612 if (--LABEL_NUSES (olabel) == 0)
2613 delete_insn (olabel);
2614 changed = 1;
2615 }
2616 }
2617 return changed;
2618 }
2619 \f
2620 /* Find all CODE_LABELs referred to in X, and increment their use counts.
2621 If INSN is a JUMP_INSN and there is at least one CODE_LABEL referenced
2622 in INSN, then store one of them in JUMP_LABEL (INSN).
2623 If INSN is an INSN or a CALL_INSN and there is at least one CODE_LABEL
2624 referenced in INSN, add a REG_LABEL note containing that label to INSN.
2625 Also, when there are consecutive labels, canonicalize on the last of them.
2626
2627 Note that two labels separated by a loop-beginning note
2628 must be kept distinct if we have not yet done loop-optimization,
2629 because the gap between them is where loop-optimize
2630 will want to move invariant code to. CROSS_JUMP tells us
2631 that loop-optimization is done with.
2632
2633 Once reload has completed (CROSS_JUMP non-zero), we need not consider
2634 two labels distinct if they are separated by only USE or CLOBBER insns. */
2635
2636 static void
2637 mark_jump_label (x, insn, cross_jump)
2638 register rtx x;
2639 rtx insn;
2640 int cross_jump;
2641 {
2642 register RTX_CODE code = GET_CODE (x);
2643 register int i;
2644 register char *fmt;
2645
2646 switch (code)
2647 {
2648 case PC:
2649 case CC0:
2650 case REG:
2651 case SUBREG:
2652 case CONST_INT:
2653 case SYMBOL_REF:
2654 case CONST_DOUBLE:
2655 case CLOBBER:
2656 case CALL:
2657 return;
2658
2659 case MEM:
2660 /* If this is a constant-pool reference, see if it is a label. */
2661 if (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
2662 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))
2663 mark_jump_label (get_pool_constant (XEXP (x, 0)), insn, cross_jump);
2664 break;
2665
2666 case LABEL_REF:
2667 {
2668 register rtx label = XEXP (x, 0);
2669 register rtx next;
2670 if (GET_CODE (label) != CODE_LABEL)
2671 abort ();
2672 /* If there are other labels following this one,
2673 replace it with the last of the consecutive labels. */
2674 for (next = NEXT_INSN (label); next; next = NEXT_INSN (next))
2675 {
2676 if (GET_CODE (next) == CODE_LABEL)
2677 label = next;
2678 else if (cross_jump && GET_CODE (next) == INSN
2679 && (GET_CODE (PATTERN (next)) == USE
2680 || GET_CODE (PATTERN (next)) == CLOBBER))
2681 continue;
2682 else if (GET_CODE (next) != NOTE)
2683 break;
2684 else if (! cross_jump
2685 && (NOTE_LINE_NUMBER (next) == NOTE_INSN_LOOP_BEG
2686 || NOTE_LINE_NUMBER (next) == NOTE_INSN_FUNCTION_END))
2687 break;
2688 }
2689 XEXP (x, 0) = label;
2690 ++LABEL_NUSES (label);
2691 if (insn)
2692 {
2693 if (GET_CODE (insn) == JUMP_INSN)
2694 JUMP_LABEL (insn) = label;
2695 else if (! find_reg_note (insn, REG_LABEL, label))
2696 {
2697 rtx next = next_real_insn (label);
2698 /* Don't record labels that refer to dispatch tables.
2699 This is not necessary, since the tablejump
2700 references the same label.
2701 And if we did record them, flow.c would make worse code. */
2702 if (next == 0
2703 || ! (GET_CODE (next) == JUMP_INSN
2704 && (GET_CODE (PATTERN (next)) == ADDR_VEC
2705 || GET_CODE (PATTERN (next)) == ADDR_DIFF_VEC)))
2706 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_LABEL, label,
2707 REG_NOTES (insn));
2708 }
2709 }
2710 return;
2711 }
2712
2713 /* Do walk the labels in a vector, but not the first operand of an
2714 ADDR_DIFF_VEC. Don't set the JUMP_LABEL of a vector. */
2715 case ADDR_VEC:
2716 case ADDR_DIFF_VEC:
2717 {
2718 int eltnum = code == ADDR_DIFF_VEC ? 1 : 0;
2719
2720 for (i = 0; i < XVECLEN (x, eltnum); i++)
2721 mark_jump_label (XVECEXP (x, eltnum, i), 0, cross_jump);
2722 return;
2723 }
2724 }
2725
2726 fmt = GET_RTX_FORMAT (code);
2727 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2728 {
2729 if (fmt[i] == 'e')
2730 mark_jump_label (XEXP (x, i), insn, cross_jump);
2731 else if (fmt[i] == 'E')
2732 {
2733 register int j;
2734 for (j = 0; j < XVECLEN (x, i); j++)
2735 mark_jump_label (XVECEXP (x, i, j), insn, cross_jump);
2736 }
2737 }
2738 }
2739
2740 /* If all INSN does is set the pc, delete it,
2741 and delete the insn that set the condition codes for it
2742 if that's what the previous thing was. */
2743
2744 void
2745 delete_jump (insn)
2746 rtx insn;
2747 {
2748 register rtx x = PATTERN (insn);
2749 register rtx prev;
2750
2751 if (GET_CODE (x) == SET
2752 && GET_CODE (SET_DEST (x)) == PC)
2753 {
2754 prev = prev_nonnote_insn (insn);
2755 #ifdef HAVE_cc0
2756 /* We assume that at this stage
2757 CC's are always set explicitly
2758 and always immediately before the jump that
2759 will use them. So if the previous insn
2760 exists to set the CC's, delete it
2761 (unless it performs auto-increments, etc.). */
2762 if (prev && GET_CODE (prev) == INSN
2763 && sets_cc0_p (PATTERN (prev)))
2764 {
2765 if (sets_cc0_p (PATTERN (prev)) > 0
2766 && !FIND_REG_INC_NOTE (prev, 0))
2767 delete_insn (prev);
2768 else
2769 /* Otherwise, show that cc0 won't be used. */
2770 REG_NOTES (prev) = gen_rtx (EXPR_LIST, REG_UNUSED,
2771 cc0_rtx, REG_NOTES (prev));
2772 }
2773 #else
2774 {
2775 rtx note;
2776
2777 /* If we are running before flow.c, we need do nothing since flow.c
2778 will delete the set of the condition code if it is dead. We also
2779 can't know if the register being used as the condition code is
2780 dead or not at this point.
2781
2782 Otherwise, look at all our REG_DEAD notes. If a previous insn
2783 does nothing other than set a register that dies in this jump,
2784 we can delete the insn. */
2785
2786 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
2787 {
2788 rtx our_prev;
2789
2790 if (REG_NOTE_KIND (note) != REG_DEAD
2791 /* Verify that the REG_NOTE has a legal value. */
2792 || GET_CODE (XEXP (note, 0)) != REG)
2793 continue;
2794
2795 for (our_prev = prev_nonnote_insn (insn);
2796 our_prev && GET_CODE (our_prev) == INSN;
2797 our_prev = prev_nonnote_insn (our_prev))
2798 {
2799 /* If we reach a SEQUENCE, it is too complex to try to
2800 do anything with it, so give up. */
2801 if (GET_CODE (PATTERN (our_prev)) == SEQUENCE)
2802 break;
2803
2804 if (GET_CODE (PATTERN (our_prev)) == USE
2805 && GET_CODE (XEXP (PATTERN (our_prev), 0)) == INSN)
2806 /* reorg creates USEs that look like this. We leave them
2807 alone because reorg needs them for its own purposes. */
2808 break;
2809
2810 if (reg_set_p (XEXP (note, 0), PATTERN (our_prev)))
2811 {
2812 if (FIND_REG_INC_NOTE (our_prev, 0))
2813 break;
2814
2815 if (GET_CODE (PATTERN (our_prev)) == PARALLEL)
2816 {
2817 /* If we find a SET of something else, we can't
2818 delete the insn. */
2819
2820 int i;
2821
2822 for (i = 0; i < XVECLEN (PATTERN (our_prev), 0); i++)
2823 {
2824 rtx part = XVECEXP (PATTERN (our_prev), 0, i);
2825
2826 if (GET_CODE (part) == SET
2827 && SET_DEST (part) != XEXP (note, 0))
2828 break;
2829 }
2830
2831 if (i == XVECLEN (PATTERN (our_prev), 0))
2832 delete_insn (our_prev);
2833 }
2834 else if (GET_CODE (PATTERN (our_prev)) == SET
2835 && SET_DEST (PATTERN (our_prev)) == XEXP (note, 0))
2836 delete_insn (our_prev);
2837
2838 break;
2839 }
2840
2841 /* If OUR_PREV references the register that dies here,
2842 it is an additional use. Hence any prior SET isn't
2843 dead. */
2844 if (reg_overlap_mentioned_p (XEXP (note, 0),
2845 PATTERN (our_prev)))
2846 break;
2847 }
2848 }
2849 }
2850 #endif
2851 /* Now delete the jump insn itself. */
2852 delete_insn (insn);
2853 }
2854 }
2855 \f
2856 /* Delete insn INSN from the chain of insns and update label ref counts.
2857 May delete some following insns as a consequence; may even delete
2858 a label elsewhere and insns that follow it.
2859
2860 Returns the first insn after INSN that was not deleted. */
2861
2862 rtx
2863 delete_insn (insn)
2864 register rtx insn;
2865 {
2866 register rtx next = NEXT_INSN (insn);
2867 register rtx prev = PREV_INSN (insn);
2868
2869 while (next && INSN_DELETED_P (next))
2870 next = NEXT_INSN (next);
2871
2872 /* This insn is already deleted => return first following nondeleted. */
2873 if (INSN_DELETED_P (insn))
2874 return next;
2875
2876 /* Mark this insn as deleted. */
2877
2878 INSN_DELETED_P (insn) = 1;
2879
2880 /* If this is an unconditional jump, delete it from the jump chain. */
2881 if (simplejump_p (insn))
2882 delete_from_jump_chain (insn);
2883
2884 /* If instruction is followed by a barrier,
2885 delete the barrier too. */
2886
2887 if (next != 0 && GET_CODE (next) == BARRIER)
2888 {
2889 INSN_DELETED_P (next) = 1;
2890 next = NEXT_INSN (next);
2891 }
2892
2893 /* Patch out INSN (and the barrier if any) */
2894
2895 if (optimize)
2896 {
2897 if (prev)
2898 {
2899 NEXT_INSN (prev) = next;
2900 if (GET_CODE (prev) == INSN && GET_CODE (PATTERN (prev)) == SEQUENCE)
2901 NEXT_INSN (XVECEXP (PATTERN (prev), 0,
2902 XVECLEN (PATTERN (prev), 0) - 1)) = next;
2903 }
2904
2905 if (next)
2906 {
2907 PREV_INSN (next) = prev;
2908 if (GET_CODE (next) == INSN && GET_CODE (PATTERN (next)) == SEQUENCE)
2909 PREV_INSN (XVECEXP (PATTERN (next), 0, 0)) = prev;
2910 }
2911
2912 if (prev && NEXT_INSN (prev) == 0)
2913 set_last_insn (prev);
2914 }
2915
2916 /* If deleting a jump, decrement the count of the label,
2917 and delete the label if it is now unused. */
2918
2919 if (GET_CODE (insn) == JUMP_INSN && JUMP_LABEL (insn))
2920 if (--LABEL_NUSES (JUMP_LABEL (insn)) == 0)
2921 {
2922 /* This can delete NEXT or PREV,
2923 either directly if NEXT is JUMP_LABEL (INSN),
2924 or indirectly through more levels of jumps. */
2925 delete_insn (JUMP_LABEL (insn));
2926 /* I feel a little doubtful about this loop,
2927 but I see no clean and sure alternative way
2928 to find the first insn after INSN that is not now deleted.
2929 I hope this works. */
2930 while (next && INSN_DELETED_P (next))
2931 next = NEXT_INSN (next);
2932 return next;
2933 }
2934
2935 while (prev && (INSN_DELETED_P (prev) || GET_CODE (prev) == NOTE))
2936 prev = PREV_INSN (prev);
2937
2938 /* If INSN was a label and a dispatch table follows it,
2939 delete the dispatch table. The tablejump must have gone already.
2940 It isn't useful to fall through into a table. */
2941
2942 if (GET_CODE (insn) == CODE_LABEL
2943 && NEXT_INSN (insn) != 0
2944 && GET_CODE (NEXT_INSN (insn)) == JUMP_INSN
2945 && (GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_VEC
2946 || GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_DIFF_VEC))
2947 next = delete_insn (NEXT_INSN (insn));
2948
2949 /* If INSN was a label, delete insns following it if now unreachable. */
2950
2951 if (GET_CODE (insn) == CODE_LABEL && prev
2952 && GET_CODE (prev) == BARRIER)
2953 {
2954 register RTX_CODE code;
2955 while (next != 0
2956 && ((code = GET_CODE (next)) == INSN
2957 || code == JUMP_INSN || code == CALL_INSN
2958 || code == NOTE
2959 || (code == CODE_LABEL && INSN_DELETED_P (next))))
2960 {
2961 if (code == NOTE
2962 && NOTE_LINE_NUMBER (next) != NOTE_INSN_FUNCTION_END)
2963 next = NEXT_INSN (next);
2964 /* Keep going past other deleted labels to delete what follows. */
2965 else if (code == CODE_LABEL && INSN_DELETED_P (next))
2966 next = NEXT_INSN (next);
2967 else
2968 /* Note: if this deletes a jump, it can cause more
2969 deletion of unreachable code, after a different label.
2970 As long as the value from this recursive call is correct,
2971 this invocation functions correctly. */
2972 next = delete_insn (next);
2973 }
2974 }
2975
2976 return next;
2977 }
2978
2979 /* Advance from INSN till reaching something not deleted
2980 then return that. May return INSN itself. */
2981
2982 rtx
2983 next_nondeleted_insn (insn)
2984 rtx insn;
2985 {
2986 while (INSN_DELETED_P (insn))
2987 insn = NEXT_INSN (insn);
2988 return insn;
2989 }
2990 \f
2991 /* Delete a range of insns from FROM to TO, inclusive.
2992 This is for the sake of peephole optimization, so assume
2993 that whatever these insns do will still be done by a new
2994 peephole insn that will replace them. */
2995
2996 void
2997 delete_for_peephole (from, to)
2998 register rtx from, to;
2999 {
3000 register rtx insn = from;
3001
3002 while (1)
3003 {
3004 register rtx next = NEXT_INSN (insn);
3005 register rtx prev = PREV_INSN (insn);
3006
3007 if (GET_CODE (insn) != NOTE)
3008 {
3009 INSN_DELETED_P (insn) = 1;
3010
3011 /* Patch this insn out of the chain. */
3012 /* We don't do this all at once, because we
3013 must preserve all NOTEs. */
3014 if (prev)
3015 NEXT_INSN (prev) = next;
3016
3017 if (next)
3018 PREV_INSN (next) = prev;
3019 }
3020
3021 if (insn == to)
3022 break;
3023 insn = next;
3024 }
3025
3026 /* Note that if TO is an unconditional jump
3027 we *do not* delete the BARRIER that follows,
3028 since the peephole that replaces this sequence
3029 is also an unconditional jump in that case. */
3030 }
3031 \f
3032 /* Invert the condition of the jump JUMP, and make it jump
3033 to label NLABEL instead of where it jumps now. */
3034
3035 int
3036 invert_jump (jump, nlabel)
3037 rtx jump, nlabel;
3038 {
3039 register rtx olabel = JUMP_LABEL (jump);
3040
3041 /* We have to either invert the condition and change the label or
3042 do neither. Either operation could fail. We first try to invert
3043 the jump. If that succeeds, we try changing the label. If that fails,
3044 we invert the jump back to what it was. */
3045
3046 if (! invert_exp (PATTERN (jump), jump))
3047 return 0;
3048
3049 if (redirect_jump (jump, nlabel))
3050 return 1;
3051
3052 if (! invert_exp (PATTERN (jump), jump))
3053 /* This should just be putting it back the way it was. */
3054 abort ();
3055
3056 return 0;
3057 }
3058
3059 /* Invert the jump condition of rtx X contained in jump insn, INSN.
3060
3061 Return 1 if we can do so, 0 if we cannot find a way to do so that
3062 matches a pattern. */
3063
3064 static int
3065 invert_exp (x, insn)
3066 rtx x;
3067 rtx insn;
3068 {
3069 register RTX_CODE code;
3070 register int i;
3071 register char *fmt;
3072
3073 code = GET_CODE (x);
3074
3075 if (code == IF_THEN_ELSE)
3076 {
3077 register rtx comp = XEXP (x, 0);
3078 register rtx tem;
3079
3080 /* We can do this in two ways: The preferable way, which can only
3081 be done if this is not an integer comparison, is to reverse
3082 the comparison code. Otherwise, swap the THEN-part and ELSE-part
3083 of the IF_THEN_ELSE. If we can't do either, fail. */
3084
3085 if (can_reverse_comparison_p (comp, insn)
3086 && validate_change (insn, &XEXP (x, 0),
3087 gen_rtx (reverse_condition (GET_CODE (comp)),
3088 GET_MODE (comp), XEXP (comp, 0),
3089 XEXP (comp, 1)), 0))
3090 return 1;
3091
3092 tem = XEXP (x, 1);
3093 validate_change (insn, &XEXP (x, 1), XEXP (x, 2), 1);
3094 validate_change (insn, &XEXP (x, 2), tem, 1);
3095 return apply_change_group ();
3096 }
3097
3098 fmt = GET_RTX_FORMAT (code);
3099 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3100 {
3101 if (fmt[i] == 'e')
3102 if (! invert_exp (XEXP (x, i), insn))
3103 return 0;
3104 if (fmt[i] == 'E')
3105 {
3106 register int j;
3107 for (j = 0; j < XVECLEN (x, i); j++)
3108 if (!invert_exp (XVECEXP (x, i, j), insn))
3109 return 0;
3110 }
3111 }
3112
3113 return 1;
3114 }
3115 \f
3116 /* Make jump JUMP jump to label NLABEL instead of where it jumps now.
3117 If the old jump target label is unused as a result,
3118 it and the code following it may be deleted.
3119
3120 If NLABEL is zero, we are to turn the jump into a (possibly conditional)
3121 RETURN insn.
3122
3123 The return value will be 1 if the change was made, 0 if it wasn't (this
3124 can only occur for NLABEL == 0). */
3125
3126 int
3127 redirect_jump (jump, nlabel)
3128 rtx jump, nlabel;
3129 {
3130 register rtx olabel = JUMP_LABEL (jump);
3131
3132 if (nlabel == olabel)
3133 return 1;
3134
3135 if (! redirect_exp (&PATTERN (jump), olabel, nlabel, jump))
3136 return 0;
3137
3138 /* If this is an unconditional branch, delete it from the jump_chain of
3139 OLABEL and add it to the jump_chain of NLABEL (assuming both labels
3140 have UID's in range and JUMP_CHAIN is valid). */
3141 if (jump_chain && (simplejump_p (jump)
3142 || GET_CODE (PATTERN (jump)) == RETURN))
3143 {
3144 int label_index = nlabel ? INSN_UID (nlabel) : 0;
3145
3146 delete_from_jump_chain (jump);
3147 if (label_index < max_jump_chain
3148 && INSN_UID (jump) < max_jump_chain)
3149 {
3150 jump_chain[INSN_UID (jump)] = jump_chain[label_index];
3151 jump_chain[label_index] = jump;
3152 }
3153 }
3154
3155 JUMP_LABEL (jump) = nlabel;
3156 if (nlabel)
3157 ++LABEL_NUSES (nlabel);
3158
3159 if (olabel && --LABEL_NUSES (olabel) == 0)
3160 delete_insn (olabel);
3161
3162 return 1;
3163 }
3164
3165 /* Delete the instruction JUMP from any jump chain it might be on. */
3166
3167 static void
3168 delete_from_jump_chain (jump)
3169 rtx jump;
3170 {
3171 int index;
3172 rtx olabel = JUMP_LABEL (jump);
3173
3174 /* Handle unconditional jumps. */
3175 if (jump_chain && olabel != 0
3176 && INSN_UID (olabel) < max_jump_chain
3177 && simplejump_p (jump))
3178 index = INSN_UID (olabel);
3179 /* Handle return insns. */
3180 else if (jump_chain && GET_CODE (PATTERN (jump)) == RETURN)
3181 index = 0;
3182 else return;
3183
3184 if (jump_chain[index] == jump)
3185 jump_chain[index] = jump_chain[INSN_UID (jump)];
3186 else
3187 {
3188 rtx insn;
3189
3190 for (insn = jump_chain[index];
3191 insn != 0;
3192 insn = jump_chain[INSN_UID (insn)])
3193 if (jump_chain[INSN_UID (insn)] == jump)
3194 {
3195 jump_chain[INSN_UID (insn)] = jump_chain[INSN_UID (jump)];
3196 break;
3197 }
3198 }
3199 }
3200
3201 /* If NLABEL is nonzero, throughout the rtx at LOC,
3202 alter (LABEL_REF OLABEL) to (LABEL_REF NLABEL). If OLABEL is
3203 zero, alter (RETURN) to (LABEL_REF NLABEL).
3204
3205 If NLABEL is zero, alter (LABEL_REF OLABEL) to (RETURN) and check
3206 validity with validate_change. Convert (set (pc) (label_ref olabel))
3207 to (return).
3208
3209 Return 0 if we found a change we would like to make but it is invalid.
3210 Otherwise, return 1. */
3211
3212 static int
3213 redirect_exp (loc, olabel, nlabel, insn)
3214 rtx *loc;
3215 rtx olabel, nlabel;
3216 rtx insn;
3217 {
3218 register rtx x = *loc;
3219 register RTX_CODE code = GET_CODE (x);
3220 register int i;
3221 register char *fmt;
3222
3223 if (code == LABEL_REF)
3224 {
3225 if (XEXP (x, 0) == olabel)
3226 {
3227 if (nlabel)
3228 XEXP (x, 0) = nlabel;
3229 else
3230 return validate_change (insn, loc, gen_rtx (RETURN, VOIDmode), 0);
3231 return 1;
3232 }
3233 }
3234 else if (code == RETURN && olabel == 0)
3235 {
3236 x = gen_rtx (LABEL_REF, VOIDmode, nlabel);
3237 if (loc == &PATTERN (insn))
3238 x = gen_rtx (SET, VOIDmode, pc_rtx, x);
3239 return validate_change (insn, loc, x, 0);
3240 }
3241
3242 if (code == SET && nlabel == 0 && SET_DEST (x) == pc_rtx
3243 && GET_CODE (SET_SRC (x)) == LABEL_REF
3244 && XEXP (SET_SRC (x), 0) == olabel)
3245 return validate_change (insn, loc, gen_rtx (RETURN, VOIDmode), 0);
3246
3247 fmt = GET_RTX_FORMAT (code);
3248 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3249 {
3250 if (fmt[i] == 'e')
3251 if (! redirect_exp (&XEXP (x, i), olabel, nlabel, insn))
3252 return 0;
3253 if (fmt[i] == 'E')
3254 {
3255 register int j;
3256 for (j = 0; j < XVECLEN (x, i); j++)
3257 if (! redirect_exp (&XVECEXP (x, i, j), olabel, nlabel, insn))
3258 return 0;
3259 }
3260 }
3261
3262 return 1;
3263 }
3264 \f
3265 /* Make jump JUMP jump to label NLABEL, assuming it used to be a tablejump.
3266
3267 If the old jump target label (before the dispatch table) becomes unused,
3268 it and the dispatch table may be deleted. In that case, find the insn
3269 before the jump references that label and delete it and logical sucessors
3270 too. */
3271
3272 void
3273 redirect_tablejump (jump, nlabel)
3274 rtx jump, nlabel;
3275 {
3276 register rtx olabel = JUMP_LABEL (jump);
3277
3278 /* Add this jump to the jump_chain of NLABEL. */
3279 if (jump_chain && INSN_UID (nlabel) < max_jump_chain
3280 && INSN_UID (jump) < max_jump_chain)
3281 {
3282 jump_chain[INSN_UID (jump)] = jump_chain[INSN_UID (nlabel)];
3283 jump_chain[INSN_UID (nlabel)] = jump;
3284 }
3285
3286 PATTERN (jump) = gen_jump (nlabel);
3287 JUMP_LABEL (jump) = nlabel;
3288 ++LABEL_NUSES (nlabel);
3289 INSN_CODE (jump) = -1;
3290
3291 if (--LABEL_NUSES (olabel) == 0)
3292 {
3293 delete_labelref_insn (jump, olabel, 0);
3294 delete_insn (olabel);
3295 }
3296 }
3297
3298 /* Find the insn referencing LABEL that is a logical predecessor of INSN.
3299 If we found one, delete it and then delete this insn if DELETE_THIS is
3300 non-zero. Return non-zero if INSN or a predecessor references LABEL. */
3301
3302 static int
3303 delete_labelref_insn (insn, label, delete_this)
3304 rtx insn, label;
3305 int delete_this;
3306 {
3307 int deleted = 0;
3308 rtx link;
3309
3310 if (GET_CODE (insn) != NOTE
3311 && reg_mentioned_p (label, PATTERN (insn)))
3312 {
3313 if (delete_this)
3314 {
3315 delete_insn (insn);
3316 deleted = 1;
3317 }
3318 else
3319 return 1;
3320 }
3321
3322 for (link = LOG_LINKS (insn); link; link = XEXP (link, 1))
3323 if (delete_labelref_insn (XEXP (link, 0), label, 1))
3324 {
3325 if (delete_this)
3326 {
3327 delete_insn (insn);
3328 deleted = 1;
3329 }
3330 else
3331 return 1;
3332 }
3333
3334 return deleted;
3335 }
3336 \f
3337 /* Like rtx_equal_p except that it considers two REGs as equal
3338 if they renumber to the same value. */
3339
3340 int
3341 rtx_renumbered_equal_p (x, y)
3342 rtx x, y;
3343 {
3344 register int i;
3345 register RTX_CODE code = GET_CODE (x);
3346 register char *fmt;
3347
3348 if (x == y)
3349 return 1;
3350 if ((code == REG || (code == SUBREG && GET_CODE (SUBREG_REG (x)) == REG))
3351 && (GET_CODE (y) == REG || (GET_CODE (y) == SUBREG
3352 && GET_CODE (SUBREG_REG (y)) == REG)))
3353 {
3354 register int j;
3355
3356 if (GET_MODE (x) != GET_MODE (y))
3357 return 0;
3358
3359 /* If we haven't done any renumbering, don't
3360 make any assumptions. */
3361 if (reg_renumber == 0)
3362 return rtx_equal_p (x, y);
3363
3364 if (code == SUBREG)
3365 {
3366 i = REGNO (SUBREG_REG (x));
3367 if (reg_renumber[i] >= 0)
3368 i = reg_renumber[i];
3369 i += SUBREG_WORD (x);
3370 }
3371 else
3372 {
3373 i = REGNO (x);
3374 if (reg_renumber[i] >= 0)
3375 i = reg_renumber[i];
3376 }
3377 if (GET_CODE (y) == SUBREG)
3378 {
3379 j = REGNO (SUBREG_REG (y));
3380 if (reg_renumber[j] >= 0)
3381 j = reg_renumber[j];
3382 j += SUBREG_WORD (y);
3383 }
3384 else
3385 {
3386 j = REGNO (y);
3387 if (reg_renumber[j] >= 0)
3388 j = reg_renumber[j];
3389 }
3390 return i == j;
3391 }
3392 /* Now we have disposed of all the cases
3393 in which different rtx codes can match. */
3394 if (code != GET_CODE (y))
3395 return 0;
3396 switch (code)
3397 {
3398 case PC:
3399 case CC0:
3400 case ADDR_VEC:
3401 case ADDR_DIFF_VEC:
3402 return 0;
3403
3404 case CONST_INT:
3405 return XINT (x, 0) == XINT (y, 0);
3406
3407 case LABEL_REF:
3408 /* Two label-refs are equivalent if they point at labels
3409 in the same position in the instruction stream. */
3410 return (next_real_insn (XEXP (x, 0))
3411 == next_real_insn (XEXP (y, 0)));
3412
3413 case SYMBOL_REF:
3414 return XSTR (x, 0) == XSTR (y, 0);
3415 }
3416
3417 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
3418
3419 if (GET_MODE (x) != GET_MODE (y))
3420 return 0;
3421
3422 /* Compare the elements. If any pair of corresponding elements
3423 fail to match, return 0 for the whole things. */
3424
3425 fmt = GET_RTX_FORMAT (code);
3426 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3427 {
3428 register int j;
3429 switch (fmt[i])
3430 {
3431 case 'i':
3432 if (XINT (x, i) != XINT (y, i))
3433 return 0;
3434 break;
3435
3436 case 's':
3437 if (strcmp (XSTR (x, i), XSTR (y, i)))
3438 return 0;
3439 break;
3440
3441 case 'e':
3442 if (! rtx_renumbered_equal_p (XEXP (x, i), XEXP (y, i)))
3443 return 0;
3444 break;
3445
3446 case 'u':
3447 if (XEXP (x, i) != XEXP (y, i))
3448 return 0;
3449 /* fall through. */
3450 case '0':
3451 break;
3452
3453 case 'E':
3454 if (XVECLEN (x, i) != XVECLEN (y, i))
3455 return 0;
3456 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
3457 if (!rtx_renumbered_equal_p (XVECEXP (x, i, j), XVECEXP (y, i, j)))
3458 return 0;
3459 break;
3460
3461 default:
3462 abort ();
3463 }
3464 }
3465 return 1;
3466 }
3467 \f
3468 /* If X is a hard register or equivalent to one or a subregister of one,
3469 return the hard register number. If X is a pseudo register that was not
3470 assigned a hard register, return the pseudo register number. Otherwise,
3471 return -1. Any rtx is valid for X. */
3472
3473 int
3474 true_regnum (x)
3475 rtx x;
3476 {
3477 if (GET_CODE (x) == REG)
3478 {
3479 if (REGNO (x) >= FIRST_PSEUDO_REGISTER && reg_renumber[REGNO (x)] >= 0)
3480 return reg_renumber[REGNO (x)];
3481 return REGNO (x);
3482 }
3483 if (GET_CODE (x) == SUBREG)
3484 {
3485 int base = true_regnum (SUBREG_REG (x));
3486 if (base >= 0 && base < FIRST_PSEUDO_REGISTER)
3487 return SUBREG_WORD (x) + base;
3488 }
3489 return -1;
3490 }
3491 \f
3492 /* Optimize code of the form:
3493
3494 for (x = a[i]; x; ...)
3495 ...
3496 for (x = a[i]; x; ...)
3497 ...
3498 foo:
3499
3500 Loop optimize will change the above code into
3501
3502 if (x = a[i])
3503 for (;;)
3504 { ...; if (! (x = ...)) break; }
3505 if (x = a[i])
3506 for (;;)
3507 { ...; if (! (x = ...)) break; }
3508 foo:
3509
3510 In general, if the first test fails, the program can branch
3511 directly to `foo' and skip the second try which is doomed to fail.
3512 We run this after loop optimization and before flow analysis. */
3513
3514 /* When comparing the insn patterns, we track the fact that different
3515 pseudo-register numbers may have been used in each computation.
3516 The following array stores an equivalence -- same_regs[I] == J means
3517 that pseudo register I was used in the first set of tests in a context
3518 where J was used in the second set. We also count the number of such
3519 pending equivalences. If nonzero, the expressions really aren't the
3520 same. */
3521
3522 static short *same_regs;
3523
3524 static int num_same_regs;
3525
3526 /* Track any registers modified between the target of the first jump and
3527 the second jump. They never compare equal. */
3528
3529 static char *modified_regs;
3530
3531 /* Record if memory was modified. */
3532
3533 static int modified_mem;
3534
3535 /* Called via note_stores on each insn between the target of the first
3536 branch and the second branch. It marks any changed registers. */
3537
3538 static void
3539 mark_modified_reg (dest, x)
3540 rtx dest;
3541 rtx x;
3542 {
3543 int regno, i;
3544
3545 if (GET_CODE (dest) == SUBREG)
3546 dest = SUBREG_REG (dest);
3547
3548 if (GET_CODE (dest) == MEM)
3549 modified_mem = 1;
3550
3551 if (GET_CODE (dest) != REG)
3552 return;
3553
3554 regno = REGNO (dest);
3555 if (regno >= FIRST_PSEUDO_REGISTER)
3556 modified_regs[regno] = 1;
3557 else
3558 for (i = 0; i < HARD_REGNO_NREGS (regno, GET_MODE (dest)); i++)
3559 modified_regs[regno + i] = 1;
3560 }
3561
3562 /* F is the first insn in the chain of insns. */
3563
3564 void
3565 thread_jumps (f, max_reg, verbose)
3566 rtx f;
3567 int max_reg;
3568 int verbose;
3569 {
3570 /* Basic algorithm is to find a conditional branch,
3571 the label it may branch to, and the branch after
3572 that label. If the two branches test the same condition,
3573 walk back from both branch paths until the insn patterns
3574 differ, or code labels are hit. If we make it back to
3575 the target of the first branch, then we know that the first branch
3576 will either always succeed or always fail depending on the relative
3577 senses of the two branches. So adjust the first branch accordingly
3578 in this case. */
3579
3580 rtx label, b1, b2, t1, t2;
3581 enum rtx_code code1, code2;
3582 rtx b1op0, b1op1, b2op0, b2op1;
3583 int changed = 1;
3584 int i;
3585 short *all_reset;
3586
3587 /* Allocate register tables and quick-reset table. */
3588 modified_regs = (char *) alloca (max_reg * sizeof (char));
3589 same_regs = (short *) alloca (max_reg * sizeof (short));
3590 all_reset = (short *) alloca (max_reg * sizeof (short));
3591 for (i = 0; i < max_reg; i++)
3592 all_reset[i] = -1;
3593
3594 while (changed)
3595 {
3596 changed = 0;
3597
3598 for (b1 = f; b1; b1 = NEXT_INSN (b1))
3599 {
3600 /* Get to a candidate branch insn. */
3601 if (GET_CODE (b1) != JUMP_INSN
3602 || ! condjump_p (b1) || simplejump_p (b1)
3603 || JUMP_LABEL (b1) == 0)
3604 continue;
3605
3606 bzero (modified_regs, max_reg * sizeof (char));
3607 modified_mem = 0;
3608
3609 bcopy (all_reset, same_regs, max_reg * sizeof (short));
3610 num_same_regs = 0;
3611
3612 label = JUMP_LABEL (b1);
3613
3614 /* Look for a branch after the target. Record any registers and
3615 memory modified between the target and the branch. Stop when we
3616 get to a label since we can't know what was changed there. */
3617 for (b2 = NEXT_INSN (label); b2; b2 = NEXT_INSN (b2))
3618 {
3619 if (GET_CODE (b2) == CODE_LABEL)
3620 break;
3621
3622 else if (GET_CODE (b2) == JUMP_INSN)
3623 {
3624 /* If this is an unconditional jump and is the only use of
3625 its target label, we can follow it. */
3626 if (simplejump_p (b2)
3627 && JUMP_LABEL (b2) != 0
3628 && LABEL_NUSES (JUMP_LABEL (b2)) == 1)
3629 {
3630 b2 = JUMP_LABEL (b2);
3631 continue;
3632 }
3633 else
3634 break;
3635 }
3636
3637 if (GET_CODE (b2) != CALL_INSN && GET_CODE (b2) != INSN)
3638 continue;
3639
3640 if (GET_CODE (b2) == CALL_INSN)
3641 {
3642 modified_mem = 1;
3643 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
3644 if (call_used_regs[i] && ! fixed_regs[i]
3645 && i != STACK_POINTER_REGNUM
3646 && i != FRAME_POINTER_REGNUM
3647 && i != ARG_POINTER_REGNUM)
3648 modified_regs[i] = 1;
3649 }
3650
3651 note_stores (PATTERN (b2), mark_modified_reg);
3652 }
3653
3654 /* Check the next candidate branch insn from the label
3655 of the first. */
3656 if (b2 == 0
3657 || GET_CODE (b2) != JUMP_INSN
3658 || b2 == b1
3659 || ! condjump_p (b2)
3660 || simplejump_p (b2))
3661 continue;
3662
3663 /* Get the comparison codes and operands, reversing the
3664 codes if appropriate. If we don't have comparison codes,
3665 we can't do anything. */
3666 b1op0 = XEXP (XEXP (SET_SRC (PATTERN (b1)), 0), 0);
3667 b1op1 = XEXP (XEXP (SET_SRC (PATTERN (b1)), 0), 1);
3668 code1 = GET_CODE (XEXP (SET_SRC (PATTERN (b1)), 0));
3669 if (XEXP (SET_SRC (PATTERN (b1)), 1) == pc_rtx)
3670 code1 = reverse_condition (code1);
3671
3672 b2op0 = XEXP (XEXP (SET_SRC (PATTERN (b2)), 0), 0);
3673 b2op1 = XEXP (XEXP (SET_SRC (PATTERN (b2)), 0), 1);
3674 code2 = GET_CODE (XEXP (SET_SRC (PATTERN (b2)), 0));
3675 if (XEXP (SET_SRC (PATTERN (b2)), 1) == pc_rtx)
3676 code2 = reverse_condition (code2);
3677
3678 /* If they test the same things and knowing that B1 branches
3679 tells us whether or not B2 branches, check if we
3680 can thread the branch. */
3681 if (rtx_equal_for_thread_p (b1op0, b2op0, b2)
3682 && rtx_equal_for_thread_p (b1op1, b2op1, b2)
3683 && (comparison_dominates_p (code1, code2)
3684 || comparison_dominates_p (code1, reverse_condition (code2))))
3685 {
3686 t1 = prev_nonnote_insn (b1);
3687 t2 = prev_nonnote_insn (b2);
3688
3689 while (t1 != 0 && t2 != 0)
3690 {
3691 if (t1 == 0 || t2 == 0)
3692 break;
3693
3694 if (t2 == label)
3695 {
3696 /* We have reached the target of the first branch.
3697 If there are no pending register equivalents,
3698 we know that this branch will either always
3699 succeed (if the senses of the two branches are
3700 the same) or always fail (if not). */
3701 rtx new_label;
3702
3703 if (num_same_regs != 0)
3704 break;
3705
3706 if (comparison_dominates_p (code1, code2))
3707 new_label = JUMP_LABEL (b2);
3708 else
3709 new_label = get_label_after (b2);
3710
3711 if (JUMP_LABEL (b1) != new_label
3712 && redirect_jump (b1, new_label))
3713 changed = 1;
3714 break;
3715 }
3716
3717 /* If either of these is not a normal insn (it might be
3718 a JUMP_INSN, CALL_INSN, or CODE_LABEL) we fail. (NOTEs
3719 have already been skipped above.) Similarly, fail
3720 if the insns are different. */
3721 if (GET_CODE (t1) != INSN || GET_CODE (t2) != INSN
3722 || recog_memoized (t1) != recog_memoized (t2)
3723 || ! rtx_equal_for_thread_p (PATTERN (t1),
3724 PATTERN (t2), t2))
3725 break;
3726
3727 t1 = prev_nonnote_insn (t1);
3728 t2 = prev_nonnote_insn (t2);
3729 }
3730 }
3731 }
3732 }
3733 }
3734 \f
3735 /* This is like RTX_EQUAL_P except that it knows about our handling of
3736 possibly equivalent registers and knows to consider volatile and
3737 modified objects as not equal.
3738
3739 YINSN is the insn containing Y. */
3740
3741 int
3742 rtx_equal_for_thread_p (x, y, yinsn)
3743 rtx x, y;
3744 rtx yinsn;
3745 {
3746 register int i;
3747 register int j;
3748 register enum rtx_code code;
3749 register char *fmt;
3750
3751 code = GET_CODE (x);
3752 /* Rtx's of different codes cannot be equal. */
3753 if (code != GET_CODE (y))
3754 return 0;
3755
3756 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
3757 (REG:SI x) and (REG:HI x) are NOT equivalent. */
3758
3759 if (GET_MODE (x) != GET_MODE (y))
3760 return 0;
3761
3762 /* Handle special-cases first. */
3763 switch (code)
3764 {
3765 case REG:
3766 if (REGNO (x) == REGNO (y) && ! modified_regs[REGNO (x)])
3767 return 1;
3768
3769 /* If neither is user variable or hard register, check for possible
3770 equivalence. */
3771 if (REG_USERVAR_P (x) || REG_USERVAR_P (y)
3772 || REGNO (x) < FIRST_PSEUDO_REGISTER
3773 || REGNO (y) < FIRST_PSEUDO_REGISTER)
3774 return 0;
3775
3776 if (same_regs[REGNO (x)] == -1)
3777 {
3778 same_regs[REGNO (x)] = REGNO (y);
3779 num_same_regs++;
3780
3781 /* If this is the first time we are seeing a register on the `Y'
3782 side, see if it is the last use. If not, we can't thread the
3783 jump, so mark it as not equivalent. */
3784 if (regno_last_uid[REGNO (y)] != INSN_UID (yinsn))
3785 return 0;
3786
3787 return 1;
3788 }
3789 else
3790 return (same_regs[REGNO (x)] == REGNO (y));
3791
3792 break;
3793
3794 case MEM:
3795 /* If memory modified or either volatile, not eqivalent.
3796 Else, check address. */
3797 if (modified_mem || MEM_VOLATILE_P (x) || MEM_VOLATILE_P (y))
3798 return 0;
3799
3800 return rtx_equal_for_thread_p (XEXP (x, 0), XEXP (y, 0), yinsn);
3801
3802 case ASM_INPUT:
3803 if (MEM_VOLATILE_P (x) || MEM_VOLATILE_P (y))
3804 return 0;
3805
3806 break;
3807
3808 case SET:
3809 /* Cancel a pending `same_regs' if setting equivalenced registers.
3810 Then process source. */
3811 if (GET_CODE (SET_DEST (x)) == REG
3812 && GET_CODE (SET_DEST (y)) == REG)
3813 {
3814 if (same_regs[REGNO (SET_DEST (x))] == REGNO (SET_DEST (y)))
3815 {
3816 same_regs[REGNO (SET_DEST (x))] = -1;
3817 num_same_regs--;
3818 }
3819 else if (REGNO (SET_DEST (x)) != REGNO (SET_DEST (y)))
3820 return 0;
3821 }
3822 else
3823 if (rtx_equal_for_thread_p (SET_DEST (x), SET_DEST (y), yinsn) == 0)
3824 return 0;
3825
3826 return rtx_equal_for_thread_p (SET_SRC (x), SET_SRC (y), yinsn);
3827
3828 case LABEL_REF:
3829 return XEXP (x, 0) == XEXP (y, 0);
3830
3831 case SYMBOL_REF:
3832 return XSTR (x, 0) == XSTR (y, 0);
3833 }
3834
3835 if (x == y)
3836 return 1;
3837
3838 fmt = GET_RTX_FORMAT (code);
3839 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3840 {
3841 switch (fmt[i])
3842 {
3843 case 'n':
3844 case 'i':
3845 if (XINT (x, i) != XINT (y, i))
3846 return 0;
3847 break;
3848
3849 case 'V':
3850 case 'E':
3851 /* Two vectors must have the same length. */
3852 if (XVECLEN (x, i) != XVECLEN (y, i))
3853 return 0;
3854
3855 /* And the corresponding elements must match. */
3856 for (j = 0; j < XVECLEN (x, i); j++)
3857 if (rtx_equal_for_thread_p (XVECEXP (x, i, j),
3858 XVECEXP (y, i, j), yinsn) == 0)
3859 return 0;
3860 break;
3861
3862 case 'e':
3863 if (rtx_equal_for_thread_p (XEXP (x, i), XEXP (y, i), yinsn) == 0)
3864 return 0;
3865 break;
3866
3867 case 'S':
3868 case 's':
3869 if (strcmp (XSTR (x, i), XSTR (y, i)))
3870 return 0;
3871 break;
3872
3873 case 'u':
3874 /* These are just backpointers, so they don't matter. */
3875 break;
3876
3877 case '0':
3878 break;
3879
3880 /* It is believed that rtx's at this level will never
3881 contain anything but integers and other rtx's,
3882 except for within LABEL_REFs and SYMBOL_REFs. */
3883 default:
3884 abort ();
3885 }
3886 }
3887 return 1;
3888 }
GNU Compiler Collection
This page took 0.214205 seconds and 6 git commands to generate.