1 /* Try to unroll loops, and split induction variables.
2 Copyright (C) 1992, 1993, 1994, 1995, 1997, 1998, 1999, 2000, 2001, 2002
3 Free Software Foundation, Inc.
4 Contributed by James E. Wilson, Cygnus Support/UC Berkeley.
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 2, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING. If not, write to the Free
20 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
23 /* Try to unroll a loop, and split induction variables.
25 Loops for which the number of iterations can be calculated exactly are
26 handled specially. If the number of iterations times the insn_count is
27 less than MAX_UNROLLED_INSNS, then the loop is unrolled completely.
28 Otherwise, we try to unroll the loop a number of times modulo the number
29 of iterations, so that only one exit test will be needed. It is unrolled
30 a number of times approximately equal to MAX_UNROLLED_INSNS divided by
33 Otherwise, if the number of iterations can be calculated exactly at
34 run time, and the loop is always entered at the top, then we try to
35 precondition the loop. That is, at run time, calculate how many times
36 the loop will execute, and then execute the loop body a few times so
37 that the remaining iterations will be some multiple of 4 (or 2 if the
38 loop is large). Then fall through to a loop unrolled 4 (or 2) times,
39 with only one exit test needed at the end of the loop.
41 Otherwise, if the number of iterations can not be calculated exactly,
42 not even at run time, then we still unroll the loop a number of times
43 approximately equal to MAX_UNROLLED_INSNS divided by the insn count,
44 but there must be an exit test after each copy of the loop body.
46 For each induction variable, which is dead outside the loop (replaceable)
47 or for which we can easily calculate the final value, if we can easily
48 calculate its value at each place where it is set as a function of the
49 current loop unroll count and the variable's value at loop entry, then
50 the induction variable is split into `N' different variables, one for
51 each copy of the loop body. One variable is live across the backward
52 branch, and the others are all calculated as a function of this variable.
53 This helps eliminate data dependencies, and leads to further opportunities
56 /* Possible improvements follow: */
58 /* ??? Add an extra pass somewhere to determine whether unrolling will
59 give any benefit. E.g. after generating all unrolled insns, compute the
60 cost of all insns and compare against cost of insns in rolled loop.
62 - On traditional architectures, unrolling a non-constant bound loop
63 is a win if there is a giv whose only use is in memory addresses, the
64 memory addresses can be split, and hence giv increments can be
66 - It is also a win if the loop is executed many times, and preconditioning
67 can be performed for the loop.
68 Add code to check for these and similar cases. */
70 /* ??? Improve control of which loops get unrolled. Could use profiling
71 info to only unroll the most commonly executed loops. Perhaps have
72 a user specifyable option to control the amount of code expansion,
73 or the percent of loops to consider for unrolling. Etc. */
75 /* ??? Look at the register copies inside the loop to see if they form a
76 simple permutation. If so, iterate the permutation until it gets back to
77 the start state. This is how many times we should unroll the loop, for
78 best results, because then all register copies can be eliminated.
79 For example, the lisp nreverse function should be unrolled 3 times
88 ??? The number of times to unroll the loop may also be based on data
89 references in the loop. For example, if we have a loop that references
90 x[i-1], x[i], and x[i+1], we should unroll it a multiple of 3 times. */
92 /* ??? Add some simple linear equation solving capability so that we can
93 determine the number of loop iterations for more complex loops.
94 For example, consider this loop from gdb
95 #define SWAP_TARGET_AND_HOST(buffer,len)
98 char *p = (char *) buffer;
99 char *q = ((char *) buffer) + len - 1;
100 int iterations = (len + 1) >> 1;
102 for (p; p < q; p++, q--;)
110 start value = p = &buffer + current_iteration
111 end value = q = &buffer + len - 1 - current_iteration
112 Given the loop exit test of "p < q", then there must be "q - p" iterations,
113 set equal to zero and solve for number of iterations:
114 q - p = len - 1 - 2*current_iteration = 0
115 current_iteration = (len - 1) / 2
116 Hence, there are (len - 1) / 2 (rounded up to the nearest integer)
117 iterations of this loop. */
119 /* ??? Currently, no labels are marked as loop invariant when doing loop
120 unrolling. This is because an insn inside the loop, that loads the address
121 of a label inside the loop into a register, could be moved outside the loop
122 by the invariant code motion pass if labels were invariant. If the loop
123 is subsequently unrolled, the code will be wrong because each unrolled
124 body of the loop will use the same address, whereas each actually needs a
125 different address. A case where this happens is when a loop containing
126 a switch statement is unrolled.
128 It would be better to let labels be considered invariant. When we
129 unroll loops here, check to see if any insns using a label local to the
130 loop were moved before the loop. If so, then correct the problem, by
131 moving the insn back into the loop, or perhaps replicate the insn before
132 the loop, one copy for each time the loop is unrolled. */
138 #include "insn-config.h"
139 #include "integrate.h"
143 #include "function.h"
147 #include "hard-reg-set.h"
148 #include "basic-block.h"
151 /* The prime factors looked for when trying to unroll a loop by some
152 number which is modulo the total number of iterations. Just checking
153 for these 4 prime factors will find at least one factor for 75% of
154 all numbers theoretically. Practically speaking, this will succeed
155 almost all of the time since loops are generally a multiple of 2
158 #define NUM_FACTORS 4
160 static struct _factor { const int factor; int count; }
161 factors[NUM_FACTORS] = { {2, 0}, {3, 0}, {5, 0}, {7, 0}};
163 /* Describes the different types of loop unrolling performed. */
172 /* This controls which loops are unrolled, and by how much we unroll
175 #ifndef MAX_UNROLLED_INSNS
176 #define MAX_UNROLLED_INSNS 100
179 /* Indexed by register number, if non-zero, then it contains a pointer
180 to a struct induction for a DEST_REG giv which has been combined with
181 one of more address givs. This is needed because whenever such a DEST_REG
182 giv is modified, we must modify the value of all split address givs
183 that were combined with this DEST_REG giv. */
185 static struct induction **addr_combined_regs;
187 /* Indexed by register number, if this is a splittable induction variable,
188 then this will hold the current value of the register, which depends on the
191 static rtx *splittable_regs;
193 /* Indexed by register number, if this is a splittable induction variable,
194 then this will hold the number of instructions in the loop that modify
195 the induction variable. Used to ensure that only the last insn modifying
196 a split iv will update the original iv of the dest. */
198 static int *splittable_regs_updates;
200 /* Forward declarations. */
202 static void init_reg_map PARAMS ((struct inline_remap *, int));
203 static rtx calculate_giv_inc PARAMS ((rtx, rtx, unsigned int));
204 static rtx initial_reg_note_copy PARAMS ((rtx, struct inline_remap *));
205 static void final_reg_note_copy PARAMS ((rtx *, struct inline_remap *));
206 static void copy_loop_body PARAMS ((struct loop *, rtx, rtx,
207 struct inline_remap *, rtx, int,
208 enum unroll_types, rtx, rtx, rtx, rtx));
209 static int find_splittable_regs PARAMS ((const struct loop *,
210 enum unroll_types, int));
211 static int find_splittable_givs PARAMS ((const struct loop *,
212 struct iv_class *, enum unroll_types,
214 static int reg_dead_after_loop PARAMS ((const struct loop *, rtx));
215 static rtx fold_rtx_mult_add PARAMS ((rtx, rtx, rtx, enum machine_mode));
216 static int verify_addresses PARAMS ((struct induction *, rtx, int));
217 static rtx remap_split_bivs PARAMS ((struct loop *, rtx));
218 static rtx find_common_reg_term PARAMS ((rtx, rtx));
219 static rtx subtract_reg_term PARAMS ((rtx, rtx));
220 static rtx loop_find_equiv_value PARAMS ((const struct loop *, rtx));
221 static rtx ujump_to_loop_cont PARAMS ((rtx, rtx));
223 /* Try to unroll one loop and split induction variables in the loop.
225 The loop is described by the arguments LOOP and INSN_COUNT.
226 STRENGTH_REDUCTION_P indicates whether information generated in the
227 strength reduction pass is available.
229 This function is intended to be called from within `strength_reduce'
233 unroll_loop (loop, insn_count, strength_reduce_p)
236 int strength_reduce_p;
238 struct loop_info *loop_info = LOOP_INFO (loop);
239 struct loop_ivs *ivs = LOOP_IVS (loop);
242 unsigned HOST_WIDE_INT temp;
243 int unroll_number = 1;
244 rtx copy_start, copy_end;
245 rtx insn, sequence, pattern, tem;
246 int max_labelno, max_insnno;
248 struct inline_remap *map;
249 char *local_label = NULL;
251 unsigned int max_local_regnum;
252 unsigned int maxregnum;
256 int splitting_not_safe = 0;
257 enum unroll_types unroll_type = UNROLL_NAIVE;
258 int loop_preconditioned = 0;
260 /* This points to the last real insn in the loop, which should be either
261 a JUMP_INSN (for conditional jumps) or a BARRIER (for unconditional
264 rtx loop_start = loop->start;
265 rtx loop_end = loop->end;
267 /* Don't bother unrolling huge loops. Since the minimum factor is
268 two, loops greater than one half of MAX_UNROLLED_INSNS will never
270 if (insn_count > MAX_UNROLLED_INSNS / 2)
272 if (loop_dump_stream)
273 fprintf (loop_dump_stream, "Unrolling failure: Loop too big.\n");
277 /* When emitting debugger info, we can't unroll loops with unequal numbers
278 of block_beg and block_end notes, because that would unbalance the block
279 structure of the function. This can happen as a result of the
280 "if (foo) bar; else break;" optimization in jump.c. */
281 /* ??? Gcc has a general policy that -g is never supposed to change the code
282 that the compiler emits, so we must disable this optimization always,
283 even if debug info is not being output. This is rare, so this should
284 not be a significant performance problem. */
286 if (1 /* write_symbols != NO_DEBUG */)
288 int block_begins = 0;
291 for (insn = loop_start; insn != loop_end; insn = NEXT_INSN (insn))
293 if (GET_CODE (insn) == NOTE)
295 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG)
297 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END)
299 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG
300 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)
302 /* Note, would be nice to add code to unroll EH
303 regions, but until that time, we punt (don't
304 unroll). For the proper way of doing it, see
305 expand_inline_function. */
307 if (loop_dump_stream)
308 fprintf (loop_dump_stream,
309 "Unrolling failure: cannot unroll EH regions.\n");
315 if (block_begins != block_ends)
317 if (loop_dump_stream)
318 fprintf (loop_dump_stream,
319 "Unrolling failure: Unbalanced block notes.\n");
324 /* Determine type of unroll to perform. Depends on the number of iterations
325 and the size of the loop. */
327 /* If there is no strength reduce info, then set
328 loop_info->n_iterations to zero. This can happen if
329 strength_reduce can't find any bivs in the loop. A value of zero
330 indicates that the number of iterations could not be calculated. */
332 if (! strength_reduce_p)
333 loop_info->n_iterations = 0;
335 if (loop_dump_stream && loop_info->n_iterations > 0)
337 fputs ("Loop unrolling: ", loop_dump_stream);
338 fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC,
339 loop_info->n_iterations);
340 fputs (" iterations.\n", loop_dump_stream);
343 /* Find and save a pointer to the last nonnote insn in the loop. */
345 last_loop_insn = prev_nonnote_insn (loop_end);
347 /* Calculate how many times to unroll the loop. Indicate whether or
348 not the loop is being completely unrolled. */
350 if (loop_info->n_iterations == 1)
352 /* Handle the case where the loop begins with an unconditional
353 jump to the loop condition. Make sure to delete the jump
354 insn, otherwise the loop body will never execute. */
356 rtx ujump = ujump_to_loop_cont (loop->start, loop->cont);
358 delete_related_insns (ujump);
360 /* If number of iterations is exactly 1, then eliminate the compare and
361 branch at the end of the loop since they will never be taken.
362 Then return, since no other action is needed here. */
364 /* If the last instruction is not a BARRIER or a JUMP_INSN, then
365 don't do anything. */
367 if (GET_CODE (last_loop_insn) == BARRIER)
369 /* Delete the jump insn. This will delete the barrier also. */
370 delete_related_insns (PREV_INSN (last_loop_insn));
372 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
375 rtx prev = PREV_INSN (last_loop_insn);
377 delete_related_insns (last_loop_insn);
379 /* The immediately preceding insn may be a compare which must be
381 if (only_sets_cc0_p (prev))
382 delete_related_insns (prev);
386 /* Remove the loop notes since this is no longer a loop. */
388 delete_related_insns (loop->vtop);
390 delete_related_insns (loop->cont);
392 delete_related_insns (loop_start);
394 delete_related_insns (loop_end);
398 else if (loop_info->n_iterations > 0
399 /* Avoid overflow in the next expression. */
400 && loop_info->n_iterations < MAX_UNROLLED_INSNS
401 && loop_info->n_iterations * insn_count < MAX_UNROLLED_INSNS)
403 unroll_number = loop_info->n_iterations;
404 unroll_type = UNROLL_COMPLETELY;
406 else if (loop_info->n_iterations > 0)
408 /* Try to factor the number of iterations. Don't bother with the
409 general case, only using 2, 3, 5, and 7 will get 75% of all
410 numbers theoretically, and almost all in practice. */
412 for (i = 0; i < NUM_FACTORS; i++)
413 factors[i].count = 0;
415 temp = loop_info->n_iterations;
416 for (i = NUM_FACTORS - 1; i >= 0; i--)
417 while (temp % factors[i].factor == 0)
420 temp = temp / factors[i].factor;
423 /* Start with the larger factors first so that we generally
424 get lots of unrolling. */
428 for (i = 3; i >= 0; i--)
429 while (factors[i].count--)
431 if (temp * factors[i].factor < MAX_UNROLLED_INSNS)
433 unroll_number *= factors[i].factor;
434 temp *= factors[i].factor;
440 /* If we couldn't find any factors, then unroll as in the normal
442 if (unroll_number == 1)
444 if (loop_dump_stream)
445 fprintf (loop_dump_stream, "Loop unrolling: No factors found.\n");
448 unroll_type = UNROLL_MODULO;
451 /* Default case, calculate number of times to unroll loop based on its
453 if (unroll_type == UNROLL_NAIVE)
455 if (8 * insn_count < MAX_UNROLLED_INSNS)
457 else if (4 * insn_count < MAX_UNROLLED_INSNS)
463 /* Now we know how many times to unroll the loop. */
465 if (loop_dump_stream)
466 fprintf (loop_dump_stream, "Unrolling loop %d times.\n", unroll_number);
468 if (unroll_type == UNROLL_COMPLETELY || unroll_type == UNROLL_MODULO)
470 /* Loops of these types can start with jump down to the exit condition
471 in rare circumstances.
473 Consider a pair of nested loops where the inner loop is part
474 of the exit code for the outer loop.
476 In this case jump.c will not duplicate the exit test for the outer
477 loop, so it will start with a jump to the exit code.
479 Then consider if the inner loop turns out to iterate once and
480 only once. We will end up deleting the jumps associated with
481 the inner loop. However, the loop notes are not removed from
482 the instruction stream.
484 And finally assume that we can compute the number of iterations
487 In this case unroll may want to unroll the outer loop even though
488 it starts with a jump to the outer loop's exit code.
490 We could try to optimize this case, but it hardly seems worth it.
491 Just return without unrolling the loop in such cases. */
494 while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
495 insn = NEXT_INSN (insn);
496 if (GET_CODE (insn) == JUMP_INSN)
500 if (unroll_type == UNROLL_COMPLETELY)
502 /* Completely unrolling the loop: Delete the compare and branch at
503 the end (the last two instructions). This delete must done at the
504 very end of loop unrolling, to avoid problems with calls to
505 back_branch_in_range_p, which is called by find_splittable_regs.
506 All increments of splittable bivs/givs are changed to load constant
509 copy_start = loop_start;
511 /* Set insert_before to the instruction immediately after the JUMP_INSN
512 (or BARRIER), so that any NOTEs between the JUMP_INSN and the end of
513 the loop will be correctly handled by copy_loop_body. */
514 insert_before = NEXT_INSN (last_loop_insn);
516 /* Set copy_end to the insn before the jump at the end of the loop. */
517 if (GET_CODE (last_loop_insn) == BARRIER)
518 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
519 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
521 copy_end = PREV_INSN (last_loop_insn);
523 /* The instruction immediately before the JUMP_INSN may be a compare
524 instruction which we do not want to copy. */
525 if (sets_cc0_p (PREV_INSN (copy_end)))
526 copy_end = PREV_INSN (copy_end);
531 /* We currently can't unroll a loop if it doesn't end with a
532 JUMP_INSN. There would need to be a mechanism that recognizes
533 this case, and then inserts a jump after each loop body, which
534 jumps to after the last loop body. */
535 if (loop_dump_stream)
536 fprintf (loop_dump_stream,
537 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
541 else if (unroll_type == UNROLL_MODULO)
543 /* Partially unrolling the loop: The compare and branch at the end
544 (the last two instructions) must remain. Don't copy the compare
545 and branch instructions at the end of the loop. Insert the unrolled
546 code immediately before the compare/branch at the end so that the
547 code will fall through to them as before. */
549 copy_start = loop_start;
551 /* Set insert_before to the jump insn at the end of the loop.
552 Set copy_end to before the jump insn at the end of the loop. */
553 if (GET_CODE (last_loop_insn) == BARRIER)
555 insert_before = PREV_INSN (last_loop_insn);
556 copy_end = PREV_INSN (insert_before);
558 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
560 insert_before = last_loop_insn;
562 /* The instruction immediately before the JUMP_INSN may be a compare
563 instruction which we do not want to copy or delete. */
564 if (sets_cc0_p (PREV_INSN (insert_before)))
565 insert_before = PREV_INSN (insert_before);
567 copy_end = PREV_INSN (insert_before);
571 /* We currently can't unroll a loop if it doesn't end with a
572 JUMP_INSN. There would need to be a mechanism that recognizes
573 this case, and then inserts a jump after each loop body, which
574 jumps to after the last loop body. */
575 if (loop_dump_stream)
576 fprintf (loop_dump_stream,
577 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
583 /* Normal case: Must copy the compare and branch instructions at the
586 if (GET_CODE (last_loop_insn) == BARRIER)
588 /* Loop ends with an unconditional jump and a barrier.
589 Handle this like above, don't copy jump and barrier.
590 This is not strictly necessary, but doing so prevents generating
591 unconditional jumps to an immediately following label.
593 This will be corrected below if the target of this jump is
594 not the start_label. */
596 insert_before = PREV_INSN (last_loop_insn);
597 copy_end = PREV_INSN (insert_before);
599 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
601 /* Set insert_before to immediately after the JUMP_INSN, so that
602 NOTEs at the end of the loop will be correctly handled by
604 insert_before = NEXT_INSN (last_loop_insn);
605 copy_end = last_loop_insn;
609 /* We currently can't unroll a loop if it doesn't end with a
610 JUMP_INSN. There would need to be a mechanism that recognizes
611 this case, and then inserts a jump after each loop body, which
612 jumps to after the last loop body. */
613 if (loop_dump_stream)
614 fprintf (loop_dump_stream,
615 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
619 /* If copying exit test branches because they can not be eliminated,
620 then must convert the fall through case of the branch to a jump past
621 the end of the loop. Create a label to emit after the loop and save
622 it for later use. Do not use the label after the loop, if any, since
623 it might be used by insns outside the loop, or there might be insns
624 added before it later by final_[bg]iv_value which must be after
625 the real exit label. */
626 exit_label = gen_label_rtx ();
629 while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
630 insn = NEXT_INSN (insn);
632 if (GET_CODE (insn) == JUMP_INSN)
634 /* The loop starts with a jump down to the exit condition test.
635 Start copying the loop after the barrier following this
637 copy_start = NEXT_INSN (insn);
639 /* Splitting induction variables doesn't work when the loop is
640 entered via a jump to the bottom, because then we end up doing
641 a comparison against a new register for a split variable, but
642 we did not execute the set insn for the new register because
643 it was skipped over. */
644 splitting_not_safe = 1;
645 if (loop_dump_stream)
646 fprintf (loop_dump_stream,
647 "Splitting not safe, because loop not entered at top.\n");
650 copy_start = loop_start;
653 /* This should always be the first label in the loop. */
654 start_label = NEXT_INSN (copy_start);
655 /* There may be a line number note and/or a loop continue note here. */
656 while (GET_CODE (start_label) == NOTE)
657 start_label = NEXT_INSN (start_label);
658 if (GET_CODE (start_label) != CODE_LABEL)
660 /* This can happen as a result of jump threading. If the first insns in
661 the loop test the same condition as the loop's backward jump, or the
662 opposite condition, then the backward jump will be modified to point
663 to elsewhere, and the loop's start label is deleted.
665 This case currently can not be handled by the loop unrolling code. */
667 if (loop_dump_stream)
668 fprintf (loop_dump_stream,
669 "Unrolling failure: unknown insns between BEG note and loop label.\n");
672 if (LABEL_NAME (start_label))
674 /* The jump optimization pass must have combined the original start label
675 with a named label for a goto. We can't unroll this case because
676 jumps which go to the named label must be handled differently than
677 jumps to the loop start, and it is impossible to differentiate them
679 if (loop_dump_stream)
680 fprintf (loop_dump_stream,
681 "Unrolling failure: loop start label is gone\n");
685 if (unroll_type == UNROLL_NAIVE
686 && GET_CODE (last_loop_insn) == BARRIER
687 && GET_CODE (PREV_INSN (last_loop_insn)) == JUMP_INSN
688 && start_label != JUMP_LABEL (PREV_INSN (last_loop_insn)))
690 /* In this case, we must copy the jump and barrier, because they will
691 not be converted to jumps to an immediately following label. */
693 insert_before = NEXT_INSN (last_loop_insn);
694 copy_end = last_loop_insn;
697 if (unroll_type == UNROLL_NAIVE
698 && GET_CODE (last_loop_insn) == JUMP_INSN
699 && start_label != JUMP_LABEL (last_loop_insn))
701 /* ??? The loop ends with a conditional branch that does not branch back
702 to the loop start label. In this case, we must emit an unconditional
703 branch to the loop exit after emitting the final branch.
704 copy_loop_body does not have support for this currently, so we
705 give up. It doesn't seem worthwhile to unroll anyways since
706 unrolling would increase the number of branch instructions
708 if (loop_dump_stream)
709 fprintf (loop_dump_stream,
710 "Unrolling failure: final conditional branch not to loop start\n");
714 /* Allocate a translation table for the labels and insn numbers.
715 They will be filled in as we copy the insns in the loop. */
717 max_labelno = max_label_num ();
718 max_insnno = get_max_uid ();
720 /* Various paths through the unroll code may reach the "egress" label
721 without initializing fields within the map structure.
723 To be safe, we use xcalloc to zero the memory. */
724 map = (struct inline_remap *) xcalloc (1, sizeof (struct inline_remap));
726 /* Allocate the label map. */
730 map->label_map = (rtx *) xmalloc (max_labelno * sizeof (rtx));
732 local_label = (char *) xcalloc (max_labelno, sizeof (char));
735 /* Search the loop and mark all local labels, i.e. the ones which have to
736 be distinct labels when copied. For all labels which might be
737 non-local, set their label_map entries to point to themselves.
738 If they happen to be local their label_map entries will be overwritten
739 before the loop body is copied. The label_map entries for local labels
740 will be set to a different value each time the loop body is copied. */
742 for (insn = copy_start; insn != loop_end; insn = NEXT_INSN (insn))
746 if (GET_CODE (insn) == CODE_LABEL)
747 local_label[CODE_LABEL_NUMBER (insn)] = 1;
748 else if (GET_CODE (insn) == JUMP_INSN)
750 if (JUMP_LABEL (insn))
751 set_label_in_map (map,
752 CODE_LABEL_NUMBER (JUMP_LABEL (insn)),
754 else if (GET_CODE (PATTERN (insn)) == ADDR_VEC
755 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
757 rtx pat = PATTERN (insn);
758 int diff_vec_p = GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC;
759 int len = XVECLEN (pat, diff_vec_p);
762 for (i = 0; i < len; i++)
764 label = XEXP (XVECEXP (pat, diff_vec_p, i), 0);
765 set_label_in_map (map, CODE_LABEL_NUMBER (label), label);
769 if ((note = find_reg_note (insn, REG_LABEL, NULL_RTX)))
770 set_label_in_map (map, CODE_LABEL_NUMBER (XEXP (note, 0)),
774 /* Allocate space for the insn map. */
776 map->insn_map = (rtx *) xmalloc (max_insnno * sizeof (rtx));
778 /* Set this to zero, to indicate that we are doing loop unrolling,
779 not function inlining. */
780 map->inline_target = 0;
782 /* The register and constant maps depend on the number of registers
783 present, so the final maps can't be created until after
784 find_splittable_regs is called. However, they are needed for
785 preconditioning, so we create temporary maps when preconditioning
788 /* The preconditioning code may allocate two new pseudo registers. */
789 maxregnum = max_reg_num ();
791 /* local_regno is only valid for regnos < max_local_regnum. */
792 max_local_regnum = maxregnum;
794 /* Allocate and zero out the splittable_regs and addr_combined_regs
795 arrays. These must be zeroed here because they will be used if
796 loop preconditioning is performed, and must be zero for that case.
798 It is safe to do this here, since the extra registers created by the
799 preconditioning code and find_splittable_regs will never be used
800 to access the splittable_regs[] and addr_combined_regs[] arrays. */
802 splittable_regs = (rtx *) xcalloc (maxregnum, sizeof (rtx));
803 splittable_regs_updates = (int *) xcalloc (maxregnum, sizeof (int));
805 = (struct induction **) xcalloc (maxregnum, sizeof (struct induction *));
806 local_regno = (char *) xcalloc (maxregnum, sizeof (char));
808 /* Mark all local registers, i.e. the ones which are referenced only
810 if (INSN_UID (copy_end) < max_uid_for_loop)
812 int copy_start_luid = INSN_LUID (copy_start);
813 int copy_end_luid = INSN_LUID (copy_end);
815 /* If a register is used in the jump insn, we must not duplicate it
816 since it will also be used outside the loop. */
817 if (GET_CODE (copy_end) == JUMP_INSN)
820 /* If we have a target that uses cc0, then we also must not duplicate
821 the insn that sets cc0 before the jump insn, if one is present. */
823 if (GET_CODE (copy_end) == JUMP_INSN
824 && sets_cc0_p (PREV_INSN (copy_end)))
828 /* If copy_start points to the NOTE that starts the loop, then we must
829 use the next luid, because invariant pseudo-regs moved out of the loop
830 have their lifetimes modified to start here, but they are not safe
832 if (copy_start == loop_start)
835 /* If a pseudo's lifetime is entirely contained within this loop, then we
836 can use a different pseudo in each unrolled copy of the loop. This
837 results in better code. */
838 /* We must limit the generic test to max_reg_before_loop, because only
839 these pseudo registers have valid regno_first_uid info. */
840 for (r = FIRST_PSEUDO_REGISTER; r < max_reg_before_loop; ++r)
841 if (REGNO_FIRST_UID (r) > 0 && REGNO_FIRST_UID (r) <= max_uid_for_loop
842 && REGNO_FIRST_LUID (r) >= copy_start_luid
843 && REGNO_LAST_UID (r) > 0 && REGNO_LAST_UID (r) <= max_uid_for_loop
844 && REGNO_LAST_LUID (r) <= copy_end_luid)
846 /* However, we must also check for loop-carried dependencies.
847 If the value the pseudo has at the end of iteration X is
848 used by iteration X+1, then we can not use a different pseudo
849 for each unrolled copy of the loop. */
850 /* A pseudo is safe if regno_first_uid is a set, and this
851 set dominates all instructions from regno_first_uid to
853 /* ??? This check is simplistic. We would get better code if
854 this check was more sophisticated. */
855 if (set_dominates_use (r, REGNO_FIRST_UID (r), REGNO_LAST_UID (r),
856 copy_start, copy_end))
859 if (loop_dump_stream)
862 fprintf (loop_dump_stream, "Marked reg %d as local\n", r);
864 fprintf (loop_dump_stream, "Did not mark reg %d as local\n",
870 /* If this loop requires exit tests when unrolled, check to see if we
871 can precondition the loop so as to make the exit tests unnecessary.
872 Just like variable splitting, this is not safe if the loop is entered
873 via a jump to the bottom. Also, can not do this if no strength
874 reduce info, because precondition_loop_p uses this info. */
876 /* Must copy the loop body for preconditioning before the following
877 find_splittable_regs call since that will emit insns which need to
878 be after the preconditioned loop copies, but immediately before the
879 unrolled loop copies. */
881 /* Also, it is not safe to split induction variables for the preconditioned
882 copies of the loop body. If we split induction variables, then the code
883 assumes that each induction variable can be represented as a function
884 of its initial value and the loop iteration number. This is not true
885 in this case, because the last preconditioned copy of the loop body
886 could be any iteration from the first up to the `unroll_number-1'th,
887 depending on the initial value of the iteration variable. Therefore
888 we can not split induction variables here, because we can not calculate
889 their value. Hence, this code must occur before find_splittable_regs
892 if (unroll_type == UNROLL_NAIVE && ! splitting_not_safe && strength_reduce_p)
894 rtx initial_value, final_value, increment;
895 enum machine_mode mode;
897 if (precondition_loop_p (loop,
898 &initial_value, &final_value, &increment,
903 int abs_inc, neg_inc;
904 enum rtx_code cc = loop_info->comparison_code;
905 int less_p = (cc == LE || cc == LEU || cc == LT || cc == LTU);
906 int unsigned_p = (cc == LEU || cc == GEU || cc == LTU || cc == GTU);
908 map->reg_map = (rtx *) xmalloc (maxregnum * sizeof (rtx));
910 VARRAY_CONST_EQUIV_INIT (map->const_equiv_varray, maxregnum,
911 "unroll_loop_precondition");
912 global_const_equiv_varray = map->const_equiv_varray;
914 init_reg_map (map, maxregnum);
916 /* Limit loop unrolling to 4, since this will make 7 copies of
918 if (unroll_number > 4)
921 /* Save the absolute value of the increment, and also whether or
922 not it is negative. */
924 abs_inc = INTVAL (increment);
933 /* Calculate the difference between the final and initial values.
934 Final value may be a (plus (reg x) (const_int 1)) rtx.
935 Let the following cse pass simplify this if initial value is
938 We must copy the final and initial values here to avoid
939 improperly shared rtl.
941 We have to deal with for (i = 0; --i < 6;) type loops.
942 For such loops the real final value is the first time the
943 loop variable overflows, so the diff we calculate is the
944 distance from the overflow value. This is 0 or ~0 for
945 unsigned loops depending on the direction, or INT_MAX,
946 INT_MAX+1 for signed loops. We really do not need the
947 exact value, since we are only interested in the diff
948 modulo the increment, and the increment is a power of 2,
949 so we can pretend that the overflow value is 0/~0. */
951 if (cc == NE || less_p != neg_inc)
952 diff = expand_simple_binop (mode, MINUS, copy_rtx (final_value),
953 copy_rtx (initial_value), NULL_RTX, 0,
956 diff = expand_simple_unop (mode, neg_inc ? NOT : NEG,
957 copy_rtx (initial_value), NULL_RTX, 0);
959 /* Now calculate (diff % (unroll * abs (increment))) by using an
961 diff = expand_simple_binop (GET_MODE (diff), AND, diff,
962 GEN_INT (unroll_number * abs_inc - 1),
963 NULL_RTX, 0, OPTAB_LIB_WIDEN);
965 /* Now emit a sequence of branches to jump to the proper precond
968 labels = (rtx *) xmalloc (sizeof (rtx) * unroll_number);
969 for (i = 0; i < unroll_number; i++)
970 labels[i] = gen_label_rtx ();
972 /* Check for the case where the initial value is greater than or
973 equal to the final value. In that case, we want to execute
974 exactly one loop iteration. The code below will fail for this
975 case. This check does not apply if the loop has a NE
976 comparison at the end. */
980 rtx incremented_initval;
981 incremented_initval = expand_simple_binop (mode, PLUS,
986 emit_cmp_and_jump_insns (incremented_initval, final_value,
987 less_p ? GE : LE, NULL_RTX,
988 mode, unsigned_p, labels[1]);
989 predict_insn_def (get_last_insn (), PRED_LOOP_CONDITION,
991 JUMP_LABEL (get_last_insn ()) = labels[1];
992 LABEL_NUSES (labels[1])++;
995 /* Assuming the unroll_number is 4, and the increment is 2, then
996 for a negative increment: for a positive increment:
997 diff = 0,1 precond 0 diff = 0,7 precond 0
998 diff = 2,3 precond 3 diff = 1,2 precond 1
999 diff = 4,5 precond 2 diff = 3,4 precond 2
1000 diff = 6,7 precond 1 diff = 5,6 precond 3 */
1002 /* We only need to emit (unroll_number - 1) branches here, the
1003 last case just falls through to the following code. */
1005 /* ??? This would give better code if we emitted a tree of branches
1006 instead of the current linear list of branches. */
1008 for (i = 0; i < unroll_number - 1; i++)
1011 enum rtx_code cmp_code;
1013 /* For negative increments, must invert the constant compared
1014 against, except when comparing against zero. */
1022 cmp_const = unroll_number - i;
1031 emit_cmp_and_jump_insns (diff, GEN_INT (abs_inc * cmp_const),
1032 cmp_code, NULL_RTX, mode, 0, labels[i]);
1033 JUMP_LABEL (get_last_insn ()) = labels[i];
1034 LABEL_NUSES (labels[i])++;
1035 predict_insn (get_last_insn (), PRED_LOOP_PRECONDITIONING,
1036 REG_BR_PROB_BASE / (unroll_number - i));
1039 /* If the increment is greater than one, then we need another branch,
1040 to handle other cases equivalent to 0. */
1042 /* ??? This should be merged into the code above somehow to help
1043 simplify the code here, and reduce the number of branches emitted.
1044 For the negative increment case, the branch here could easily
1045 be merged with the `0' case branch above. For the positive
1046 increment case, it is not clear how this can be simplified. */
1051 enum rtx_code cmp_code;
1055 cmp_const = abs_inc - 1;
1060 cmp_const = abs_inc * (unroll_number - 1) + 1;
1064 emit_cmp_and_jump_insns (diff, GEN_INT (cmp_const), cmp_code,
1065 NULL_RTX, mode, 0, labels[0]);
1066 JUMP_LABEL (get_last_insn ()) = labels[0];
1067 LABEL_NUSES (labels[0])++;
1070 sequence = gen_sequence ();
1072 loop_insn_hoist (loop, sequence);
1074 /* Only the last copy of the loop body here needs the exit
1075 test, so set copy_end to exclude the compare/branch here,
1076 and then reset it inside the loop when get to the last
1079 if (GET_CODE (last_loop_insn) == BARRIER)
1080 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
1081 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
1083 copy_end = PREV_INSN (last_loop_insn);
1085 /* The immediately preceding insn may be a compare which
1086 we do not want to copy. */
1087 if (sets_cc0_p (PREV_INSN (copy_end)))
1088 copy_end = PREV_INSN (copy_end);
1094 for (i = 1; i < unroll_number; i++)
1096 emit_label_after (labels[unroll_number - i],
1097 PREV_INSN (loop_start));
1099 memset ((char *) map->insn_map, 0, max_insnno * sizeof (rtx));
1100 memset ((char *) &VARRAY_CONST_EQUIV (map->const_equiv_varray, 0),
1101 0, (VARRAY_SIZE (map->const_equiv_varray)
1102 * sizeof (struct const_equiv_data)));
1105 for (j = 0; j < max_labelno; j++)
1107 set_label_in_map (map, j, gen_label_rtx ());
1109 for (r = FIRST_PSEUDO_REGISTER; r < max_local_regnum; r++)
1113 = gen_reg_rtx (GET_MODE (regno_reg_rtx[r]));
1114 record_base_value (REGNO (map->reg_map[r]),
1115 regno_reg_rtx[r], 0);
1117 /* The last copy needs the compare/branch insns at the end,
1118 so reset copy_end here if the loop ends with a conditional
1121 if (i == unroll_number - 1)
1123 if (GET_CODE (last_loop_insn) == BARRIER)
1124 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
1126 copy_end = last_loop_insn;
1129 /* None of the copies are the `last_iteration', so just
1130 pass zero for that parameter. */
1131 copy_loop_body (loop, copy_start, copy_end, map, exit_label, 0,
1132 unroll_type, start_label, loop_end,
1133 loop_start, copy_end);
1135 emit_label_after (labels[0], PREV_INSN (loop_start));
1137 if (GET_CODE (last_loop_insn) == BARRIER)
1139 insert_before = PREV_INSN (last_loop_insn);
1140 copy_end = PREV_INSN (insert_before);
1144 insert_before = last_loop_insn;
1146 /* The instruction immediately before the JUMP_INSN may
1147 be a compare instruction which we do not want to copy
1149 if (sets_cc0_p (PREV_INSN (insert_before)))
1150 insert_before = PREV_INSN (insert_before);
1152 copy_end = PREV_INSN (insert_before);
1155 /* Set unroll type to MODULO now. */
1156 unroll_type = UNROLL_MODULO;
1157 loop_preconditioned = 1;
1164 /* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
1165 the loop unless all loops are being unrolled. */
1166 if (unroll_type == UNROLL_NAIVE && ! flag_unroll_all_loops)
1168 if (loop_dump_stream)
1169 fprintf (loop_dump_stream,
1170 "Unrolling failure: Naive unrolling not being done.\n");
1174 /* At this point, we are guaranteed to unroll the loop. */
1176 /* Keep track of the unroll factor for the loop. */
1177 loop_info->unroll_number = unroll_number;
1179 /* For each biv and giv, determine whether it can be safely split into
1180 a different variable for each unrolled copy of the loop body.
1181 We precalculate and save this info here, since computing it is
1184 Do this before deleting any instructions from the loop, so that
1185 back_branch_in_range_p will work correctly. */
1187 if (splitting_not_safe)
1190 temp = find_splittable_regs (loop, unroll_type, unroll_number);
1192 /* find_splittable_regs may have created some new registers, so must
1193 reallocate the reg_map with the new larger size, and must realloc
1194 the constant maps also. */
1196 maxregnum = max_reg_num ();
1197 map->reg_map = (rtx *) xmalloc (maxregnum * sizeof (rtx));
1199 init_reg_map (map, maxregnum);
1201 if (map->const_equiv_varray == 0)
1202 VARRAY_CONST_EQUIV_INIT (map->const_equiv_varray,
1203 maxregnum + temp * unroll_number * 2,
1205 global_const_equiv_varray = map->const_equiv_varray;
1207 /* Search the list of bivs and givs to find ones which need to be remapped
1208 when split, and set their reg_map entry appropriately. */
1210 for (bl = ivs->list; bl; bl = bl->next)
1212 if (REGNO (bl->biv->src_reg) != bl->regno)
1213 map->reg_map[bl->regno] = bl->biv->src_reg;
1215 /* Currently, non-reduced/final-value givs are never split. */
1216 for (v = bl->giv; v; v = v->next_iv)
1217 if (REGNO (v->src_reg) != bl->regno)
1218 map->reg_map[REGNO (v->dest_reg)] = v->src_reg;
1222 /* Use our current register alignment and pointer flags. */
1223 map->regno_pointer_align = cfun->emit->regno_pointer_align;
1224 map->x_regno_reg_rtx = cfun->emit->x_regno_reg_rtx;
1226 /* If the loop is being partially unrolled, and the iteration variables
1227 are being split, and are being renamed for the split, then must fix up
1228 the compare/jump instruction at the end of the loop to refer to the new
1229 registers. This compare isn't copied, so the registers used in it
1230 will never be replaced if it isn't done here. */
1232 if (unroll_type == UNROLL_MODULO)
1234 insn = NEXT_INSN (copy_end);
1235 if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
1236 PATTERN (insn) = remap_split_bivs (loop, PATTERN (insn));
1239 /* For unroll_number times, make a copy of each instruction
1240 between copy_start and copy_end, and insert these new instructions
1241 before the end of the loop. */
1243 for (i = 0; i < unroll_number; i++)
1245 memset ((char *) map->insn_map, 0, max_insnno * sizeof (rtx));
1246 memset ((char *) &VARRAY_CONST_EQUIV (map->const_equiv_varray, 0), 0,
1247 VARRAY_SIZE (map->const_equiv_varray) * sizeof (struct const_equiv_data));
1250 for (j = 0; j < max_labelno; j++)
1252 set_label_in_map (map, j, gen_label_rtx ());
1254 for (r = FIRST_PSEUDO_REGISTER; r < max_local_regnum; r++)
1257 map->reg_map[r] = gen_reg_rtx (GET_MODE (regno_reg_rtx[r]));
1258 record_base_value (REGNO (map->reg_map[r]),
1259 regno_reg_rtx[r], 0);
1262 /* If loop starts with a branch to the test, then fix it so that
1263 it points to the test of the first unrolled copy of the loop. */
1264 if (i == 0 && loop_start != copy_start)
1266 insn = PREV_INSN (copy_start);
1267 pattern = PATTERN (insn);
1269 tem = get_label_from_map (map,
1271 (XEXP (SET_SRC (pattern), 0)));
1272 SET_SRC (pattern) = gen_rtx_LABEL_REF (VOIDmode, tem);
1274 /* Set the jump label so that it can be used by later loop unrolling
1276 JUMP_LABEL (insn) = tem;
1277 LABEL_NUSES (tem)++;
1280 copy_loop_body (loop, copy_start, copy_end, map, exit_label,
1281 i == unroll_number - 1, unroll_type, start_label,
1282 loop_end, insert_before, insert_before);
1285 /* Before deleting any insns, emit a CODE_LABEL immediately after the last
1286 insn to be deleted. This prevents any runaway delete_insn call from
1287 more insns that it should, as it always stops at a CODE_LABEL. */
1289 /* Delete the compare and branch at the end of the loop if completely
1290 unrolling the loop. Deleting the backward branch at the end also
1291 deletes the code label at the start of the loop. This is done at
1292 the very end to avoid problems with back_branch_in_range_p. */
1294 if (unroll_type == UNROLL_COMPLETELY)
1295 safety_label = emit_label_after (gen_label_rtx (), last_loop_insn);
1297 safety_label = emit_label_after (gen_label_rtx (), copy_end);
1299 /* Delete all of the original loop instructions. Don't delete the
1300 LOOP_BEG note, or the first code label in the loop. */
1302 insn = NEXT_INSN (copy_start);
1303 while (insn != safety_label)
1305 /* ??? Don't delete named code labels. They will be deleted when the
1306 jump that references them is deleted. Otherwise, we end up deleting
1307 them twice, which causes them to completely disappear instead of turn
1308 into NOTE_INSN_DELETED_LABEL notes. This in turn causes aborts in
1309 dwarfout.c/dwarf2out.c. We could perhaps fix the dwarf*out.c files
1310 to handle deleted labels instead. Or perhaps fix DECL_RTL of the
1311 associated LABEL_DECL to point to one of the new label instances. */
1312 /* ??? Likewise, we can't delete a NOTE_INSN_DELETED_LABEL note. */
1313 if (insn != start_label
1314 && ! (GET_CODE (insn) == CODE_LABEL && LABEL_NAME (insn))
1315 && ! (GET_CODE (insn) == NOTE
1316 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_DELETED_LABEL))
1317 insn = delete_related_insns (insn);
1319 insn = NEXT_INSN (insn);
1322 /* Can now delete the 'safety' label emitted to protect us from runaway
1323 delete_related_insns calls. */
1324 if (INSN_DELETED_P (safety_label))
1326 delete_related_insns (safety_label);
1328 /* If exit_label exists, emit it after the loop. Doing the emit here
1329 forces it to have a higher INSN_UID than any insn in the unrolled loop.
1330 This is needed so that mostly_true_jump in reorg.c will treat jumps
1331 to this loop end label correctly, i.e. predict that they are usually
1334 emit_label_after (exit_label, loop_end);
1337 if (unroll_type == UNROLL_COMPLETELY)
1339 /* Remove the loop notes since this is no longer a loop. */
1341 delete_related_insns (loop->vtop);
1343 delete_related_insns (loop->cont);
1345 delete_related_insns (loop_start);
1347 delete_related_insns (loop_end);
1350 if (map->const_equiv_varray)
1351 VARRAY_FREE (map->const_equiv_varray);
1354 free (map->label_map);
1357 free (map->insn_map);
1358 free (splittable_regs);
1359 free (splittable_regs_updates);
1360 free (addr_combined_regs);
1363 free (map->reg_map);
1367 /* Return true if the loop can be safely, and profitably, preconditioned
1368 so that the unrolled copies of the loop body don't need exit tests.
1370 This only works if final_value, initial_value and increment can be
1371 determined, and if increment is a constant power of 2.
1372 If increment is not a power of 2, then the preconditioning modulo
1373 operation would require a real modulo instead of a boolean AND, and this
1374 is not considered `profitable'. */
1376 /* ??? If the loop is known to be executed very many times, or the machine
1377 has a very cheap divide instruction, then preconditioning is a win even
1378 when the increment is not a power of 2. Use RTX_COST to compute
1379 whether divide is cheap.
1380 ??? A divide by constant doesn't actually need a divide, look at
1381 expand_divmod. The reduced cost of this optimized modulo is not
1382 reflected in RTX_COST. */
1385 precondition_loop_p (loop, initial_value, final_value, increment, mode)
1386 const struct loop *loop;
1387 rtx *initial_value, *final_value, *increment;
1388 enum machine_mode *mode;
1390 rtx loop_start = loop->start;
1391 struct loop_info *loop_info = LOOP_INFO (loop);
1393 if (loop_info->n_iterations > 0)
1395 *initial_value = const0_rtx;
1396 *increment = const1_rtx;
1397 *final_value = GEN_INT (loop_info->n_iterations);
1400 if (loop_dump_stream)
1402 fputs ("Preconditioning: Success, number of iterations known, ",
1404 fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC,
1405 loop_info->n_iterations);
1406 fputs (".\n", loop_dump_stream);
1411 if (loop_info->iteration_var == 0)
1413 if (loop_dump_stream)
1414 fprintf (loop_dump_stream,
1415 "Preconditioning: Could not find iteration variable.\n");
1418 else if (loop_info->initial_value == 0)
1420 if (loop_dump_stream)
1421 fprintf (loop_dump_stream,
1422 "Preconditioning: Could not find initial value.\n");
1425 else if (loop_info->increment == 0)
1427 if (loop_dump_stream)
1428 fprintf (loop_dump_stream,
1429 "Preconditioning: Could not find increment value.\n");
1432 else if (GET_CODE (loop_info->increment) != CONST_INT)
1434 if (loop_dump_stream)
1435 fprintf (loop_dump_stream,
1436 "Preconditioning: Increment not a constant.\n");
1439 else if ((exact_log2 (INTVAL (loop_info->increment)) < 0)
1440 && (exact_log2 (-INTVAL (loop_info->increment)) < 0))
1442 if (loop_dump_stream)
1443 fprintf (loop_dump_stream,
1444 "Preconditioning: Increment not a constant power of 2.\n");
1448 /* Unsigned_compare and compare_dir can be ignored here, since they do
1449 not matter for preconditioning. */
1451 if (loop_info->final_value == 0)
1453 if (loop_dump_stream)
1454 fprintf (loop_dump_stream,
1455 "Preconditioning: EQ comparison loop.\n");
1459 /* Must ensure that final_value is invariant, so call
1460 loop_invariant_p to check. Before doing so, must check regno
1461 against max_reg_before_loop to make sure that the register is in
1462 the range covered by loop_invariant_p. If it isn't, then it is
1463 most likely a biv/giv which by definition are not invariant. */
1464 if ((GET_CODE (loop_info->final_value) == REG
1465 && REGNO (loop_info->final_value) >= max_reg_before_loop)
1466 || (GET_CODE (loop_info->final_value) == PLUS
1467 && REGNO (XEXP (loop_info->final_value, 0)) >= max_reg_before_loop)
1468 || ! loop_invariant_p (loop, loop_info->final_value))
1470 if (loop_dump_stream)
1471 fprintf (loop_dump_stream,
1472 "Preconditioning: Final value not invariant.\n");
1476 /* Fail for floating point values, since the caller of this function
1477 does not have code to deal with them. */
1478 if (GET_MODE_CLASS (GET_MODE (loop_info->final_value)) == MODE_FLOAT
1479 || GET_MODE_CLASS (GET_MODE (loop_info->initial_value)) == MODE_FLOAT)
1481 if (loop_dump_stream)
1482 fprintf (loop_dump_stream,
1483 "Preconditioning: Floating point final or initial value.\n");
1487 /* Fail if loop_info->iteration_var is not live before loop_start,
1488 since we need to test its value in the preconditioning code. */
1490 if (REGNO_FIRST_LUID (REGNO (loop_info->iteration_var))
1491 > INSN_LUID (loop_start))
1493 if (loop_dump_stream)
1494 fprintf (loop_dump_stream,
1495 "Preconditioning: Iteration var not live before loop start.\n");
1499 /* Note that loop_iterations biases the initial value for GIV iterators
1500 such as "while (i-- > 0)" so that we can calculate the number of
1501 iterations just like for BIV iterators.
1503 Also note that the absolute values of initial_value and
1504 final_value are unimportant as only their difference is used for
1505 calculating the number of loop iterations. */
1506 *initial_value = loop_info->initial_value;
1507 *increment = loop_info->increment;
1508 *final_value = loop_info->final_value;
1510 /* Decide what mode to do these calculations in. Choose the larger
1511 of final_value's mode and initial_value's mode, or a full-word if
1512 both are constants. */
1513 *mode = GET_MODE (*final_value);
1514 if (*mode == VOIDmode)
1516 *mode = GET_MODE (*initial_value);
1517 if (*mode == VOIDmode)
1520 else if (*mode != GET_MODE (*initial_value)
1521 && (GET_MODE_SIZE (*mode)
1522 < GET_MODE_SIZE (GET_MODE (*initial_value))))
1523 *mode = GET_MODE (*initial_value);
1526 if (loop_dump_stream)
1527 fprintf (loop_dump_stream, "Preconditioning: Successful.\n");
1531 /* All pseudo-registers must be mapped to themselves. Two hard registers
1532 must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
1533 REGNUM, to avoid function-inlining specific conversions of these
1534 registers. All other hard regs can not be mapped because they may be
1539 init_reg_map (map, maxregnum)
1540 struct inline_remap *map;
1545 for (i = maxregnum - 1; i > LAST_VIRTUAL_REGISTER; i--)
1546 map->reg_map[i] = regno_reg_rtx[i];
1547 /* Just clear the rest of the entries. */
1548 for (i = LAST_VIRTUAL_REGISTER; i >= 0; i--)
1549 map->reg_map[i] = 0;
1551 map->reg_map[VIRTUAL_STACK_VARS_REGNUM]
1552 = regno_reg_rtx[VIRTUAL_STACK_VARS_REGNUM];
1553 map->reg_map[VIRTUAL_INCOMING_ARGS_REGNUM]
1554 = regno_reg_rtx[VIRTUAL_INCOMING_ARGS_REGNUM];
1557 /* Strength-reduction will often emit code for optimized biv/givs which
1558 calculates their value in a temporary register, and then copies the result
1559 to the iv. This procedure reconstructs the pattern computing the iv;
1560 verifying that all operands are of the proper form.
1562 PATTERN must be the result of single_set.
1563 The return value is the amount that the giv is incremented by. */
1566 calculate_giv_inc (pattern, src_insn, regno)
1567 rtx pattern, src_insn;
1571 rtx increment_total = 0;
1575 /* Verify that we have an increment insn here. First check for a plus
1576 as the set source. */
1577 if (GET_CODE (SET_SRC (pattern)) != PLUS)
1579 /* SR sometimes computes the new giv value in a temp, then copies it
1581 src_insn = PREV_INSN (src_insn);
1582 pattern = single_set (src_insn);
1583 if (GET_CODE (SET_SRC (pattern)) != PLUS)
1586 /* The last insn emitted is not needed, so delete it to avoid confusing
1587 the second cse pass. This insn sets the giv unnecessarily. */
1588 delete_related_insns (get_last_insn ());
1591 /* Verify that we have a constant as the second operand of the plus. */
1592 increment = XEXP (SET_SRC (pattern), 1);
1593 if (GET_CODE (increment) != CONST_INT)
1595 /* SR sometimes puts the constant in a register, especially if it is
1596 too big to be an add immed operand. */
1597 increment = find_last_value (increment, &src_insn, NULL_RTX, 0);
1599 /* SR may have used LO_SUM to compute the constant if it is too large
1600 for a load immed operand. In this case, the constant is in operand
1601 one of the LO_SUM rtx. */
1602 if (GET_CODE (increment) == LO_SUM)
1603 increment = XEXP (increment, 1);
1605 /* Some ports store large constants in memory and add a REG_EQUAL
1606 note to the store insn. */
1607 else if (GET_CODE (increment) == MEM)
1609 rtx note = find_reg_note (src_insn, REG_EQUAL, 0);
1611 increment = XEXP (note, 0);
1614 else if (GET_CODE (increment) == IOR
1615 || GET_CODE (increment) == ASHIFT
1616 || GET_CODE (increment) == PLUS)
1618 /* The rs6000 port loads some constants with IOR.
1619 The alpha port loads some constants with ASHIFT and PLUS. */
1620 rtx second_part = XEXP (increment, 1);
1621 enum rtx_code code = GET_CODE (increment);
1623 increment = find_last_value (XEXP (increment, 0),
1624 &src_insn, NULL_RTX, 0);
1625 /* Don't need the last insn anymore. */
1626 delete_related_insns (get_last_insn ());
1628 if (GET_CODE (second_part) != CONST_INT
1629 || GET_CODE (increment) != CONST_INT)
1633 increment = GEN_INT (INTVAL (increment) | INTVAL (second_part));
1634 else if (code == PLUS)
1635 increment = GEN_INT (INTVAL (increment) + INTVAL (second_part));
1637 increment = GEN_INT (INTVAL (increment) << INTVAL (second_part));
1640 if (GET_CODE (increment) != CONST_INT)
1643 /* The insn loading the constant into a register is no longer needed,
1645 delete_related_insns (get_last_insn ());
1648 if (increment_total)
1649 increment_total = GEN_INT (INTVAL (increment_total) + INTVAL (increment));
1651 increment_total = increment;
1653 /* Check that the source register is the same as the register we expected
1654 to see as the source. If not, something is seriously wrong. */
1655 if (GET_CODE (XEXP (SET_SRC (pattern), 0)) != REG
1656 || REGNO (XEXP (SET_SRC (pattern), 0)) != regno)
1658 /* Some machines (e.g. the romp), may emit two add instructions for
1659 certain constants, so lets try looking for another add immediately
1660 before this one if we have only seen one add insn so far. */
1666 src_insn = PREV_INSN (src_insn);
1667 pattern = single_set (src_insn);
1669 delete_related_insns (get_last_insn ());
1677 return increment_total;
1680 /* Copy REG_NOTES, except for insn references, because not all insn_map
1681 entries are valid yet. We do need to copy registers now though, because
1682 the reg_map entries can change during copying. */
1685 initial_reg_note_copy (notes, map)
1687 struct inline_remap *map;
1694 copy = rtx_alloc (GET_CODE (notes));
1695 PUT_REG_NOTE_KIND (copy, REG_NOTE_KIND (notes));
1697 if (GET_CODE (notes) == EXPR_LIST)
1698 XEXP (copy, 0) = copy_rtx_and_substitute (XEXP (notes, 0), map, 0);
1699 else if (GET_CODE (notes) == INSN_LIST)
1700 /* Don't substitute for these yet. */
1701 XEXP (copy, 0) = copy_rtx (XEXP (notes, 0));
1705 XEXP (copy, 1) = initial_reg_note_copy (XEXP (notes, 1), map);
1710 /* Fixup insn references in copied REG_NOTES. */
1713 final_reg_note_copy (notesp, map)
1715 struct inline_remap *map;
1721 if (GET_CODE (note) == INSN_LIST)
1723 /* Sometimes, we have a REG_WAS_0 note that points to a
1724 deleted instruction. In that case, we can just delete the
1726 if (REG_NOTE_KIND (note) == REG_WAS_0)
1728 *notesp = XEXP (note, 1);
1733 rtx insn = map->insn_map[INSN_UID (XEXP (note, 0))];
1735 /* If we failed to remap the note, something is awry. */
1739 XEXP (note, 0) = insn;
1743 notesp = &XEXP (note, 1);
1747 /* Copy each instruction in the loop, substituting from map as appropriate.
1748 This is very similar to a loop in expand_inline_function. */
1751 copy_loop_body (loop, copy_start, copy_end, map, exit_label, last_iteration,
1752 unroll_type, start_label, loop_end, insert_before,
1755 rtx copy_start, copy_end;
1756 struct inline_remap *map;
1759 enum unroll_types unroll_type;
1760 rtx start_label, loop_end, insert_before, copy_notes_from;
1762 struct loop_ivs *ivs = LOOP_IVS (loop);
1764 rtx set, tem, copy = NULL_RTX;
1765 int dest_reg_was_split, i;
1769 rtx final_label = 0;
1770 rtx giv_inc, giv_dest_reg, giv_src_reg;
1772 /* If this isn't the last iteration, then map any references to the
1773 start_label to final_label. Final label will then be emitted immediately
1774 after the end of this loop body if it was ever used.
1776 If this is the last iteration, then map references to the start_label
1778 if (! last_iteration)
1780 final_label = gen_label_rtx ();
1781 set_label_in_map (map, CODE_LABEL_NUMBER (start_label), final_label);
1784 set_label_in_map (map, CODE_LABEL_NUMBER (start_label), start_label);
1788 /* Emit a NOTE_INSN_DELETED to force at least two insns onto the sequence.
1789 Else gen_sequence could return a raw pattern for a jump which we pass
1790 off to emit_insn_before (instead of emit_jump_insn_before) which causes
1791 a variety of losing behaviors later. */
1792 emit_note (0, NOTE_INSN_DELETED);
1797 insn = NEXT_INSN (insn);
1799 map->orig_asm_operands_vector = 0;
1801 switch (GET_CODE (insn))
1804 pattern = PATTERN (insn);
1808 /* Check to see if this is a giv that has been combined with
1809 some split address givs. (Combined in the sense that
1810 `combine_givs' in loop.c has put two givs in the same register.)
1811 In this case, we must search all givs based on the same biv to
1812 find the address givs. Then split the address givs.
1813 Do this before splitting the giv, since that may map the
1814 SET_DEST to a new register. */
1816 if ((set = single_set (insn))
1817 && GET_CODE (SET_DEST (set)) == REG
1818 && addr_combined_regs[REGNO (SET_DEST (set))])
1820 struct iv_class *bl;
1821 struct induction *v, *tv;
1822 unsigned int regno = REGNO (SET_DEST (set));
1824 v = addr_combined_regs[REGNO (SET_DEST (set))];
1825 bl = REG_IV_CLASS (ivs, REGNO (v->src_reg));
1827 /* Although the giv_inc amount is not needed here, we must call
1828 calculate_giv_inc here since it might try to delete the
1829 last insn emitted. If we wait until later to call it,
1830 we might accidentally delete insns generated immediately
1831 below by emit_unrolled_add. */
1833 giv_inc = calculate_giv_inc (set, insn, regno);
1835 /* Now find all address giv's that were combined with this
1837 for (tv = bl->giv; tv; tv = tv->next_iv)
1838 if (tv->giv_type == DEST_ADDR && tv->same == v)
1842 /* If this DEST_ADDR giv was not split, then ignore it. */
1843 if (*tv->location != tv->dest_reg)
1846 /* Scale this_giv_inc if the multiplicative factors of
1847 the two givs are different. */
1848 this_giv_inc = INTVAL (giv_inc);
1849 if (tv->mult_val != v->mult_val)
1850 this_giv_inc = (this_giv_inc / INTVAL (v->mult_val)
1851 * INTVAL (tv->mult_val));
1853 tv->dest_reg = plus_constant (tv->dest_reg, this_giv_inc);
1854 *tv->location = tv->dest_reg;
1856 if (last_iteration && unroll_type != UNROLL_COMPLETELY)
1858 /* Must emit an insn to increment the split address
1859 giv. Add in the const_adjust field in case there
1860 was a constant eliminated from the address. */
1861 rtx value, dest_reg;
1863 /* tv->dest_reg will be either a bare register,
1864 or else a register plus a constant. */
1865 if (GET_CODE (tv->dest_reg) == REG)
1866 dest_reg = tv->dest_reg;
1868 dest_reg = XEXP (tv->dest_reg, 0);
1870 /* Check for shared address givs, and avoid
1871 incrementing the shared pseudo reg more than
1873 if (! tv->same_insn && ! tv->shared)
1875 /* tv->dest_reg may actually be a (PLUS (REG)
1876 (CONST)) here, so we must call plus_constant
1877 to add the const_adjust amount before calling
1878 emit_unrolled_add below. */
1879 value = plus_constant (tv->dest_reg,
1882 if (GET_CODE (value) == PLUS)
1884 /* The constant could be too large for an add
1885 immediate, so can't directly emit an insn
1887 emit_unrolled_add (dest_reg, XEXP (value, 0),
1892 /* Reset the giv to be just the register again, in case
1893 it is used after the set we have just emitted.
1894 We must subtract the const_adjust factor added in
1896 tv->dest_reg = plus_constant (dest_reg,
1898 *tv->location = tv->dest_reg;
1903 /* If this is a setting of a splittable variable, then determine
1904 how to split the variable, create a new set based on this split,
1905 and set up the reg_map so that later uses of the variable will
1906 use the new split variable. */
1908 dest_reg_was_split = 0;
1910 if ((set = single_set (insn))
1911 && GET_CODE (SET_DEST (set)) == REG
1912 && splittable_regs[REGNO (SET_DEST (set))])
1914 unsigned int regno = REGNO (SET_DEST (set));
1915 unsigned int src_regno;
1917 dest_reg_was_split = 1;
1919 giv_dest_reg = SET_DEST (set);
1920 giv_src_reg = giv_dest_reg;
1921 /* Compute the increment value for the giv, if it wasn't
1922 already computed above. */
1924 giv_inc = calculate_giv_inc (set, insn, regno);
1926 src_regno = REGNO (giv_src_reg);
1928 if (unroll_type == UNROLL_COMPLETELY)
1930 /* Completely unrolling the loop. Set the induction
1931 variable to a known constant value. */
1933 /* The value in splittable_regs may be an invariant
1934 value, so we must use plus_constant here. */
1935 splittable_regs[regno]
1936 = plus_constant (splittable_regs[src_regno],
1939 if (GET_CODE (splittable_regs[regno]) == PLUS)
1941 giv_src_reg = XEXP (splittable_regs[regno], 0);
1942 giv_inc = XEXP (splittable_regs[regno], 1);
1946 /* The splittable_regs value must be a REG or a
1947 CONST_INT, so put the entire value in the giv_src_reg
1949 giv_src_reg = splittable_regs[regno];
1950 giv_inc = const0_rtx;
1955 /* Partially unrolling loop. Create a new pseudo
1956 register for the iteration variable, and set it to
1957 be a constant plus the original register. Except
1958 on the last iteration, when the result has to
1959 go back into the original iteration var register. */
1961 /* Handle bivs which must be mapped to a new register
1962 when split. This happens for bivs which need their
1963 final value set before loop entry. The new register
1964 for the biv was stored in the biv's first struct
1965 induction entry by find_splittable_regs. */
1967 if (regno < ivs->n_regs
1968 && REG_IV_TYPE (ivs, regno) == BASIC_INDUCT)
1970 giv_src_reg = REG_IV_CLASS (ivs, regno)->biv->src_reg;
1971 giv_dest_reg = giv_src_reg;
1975 /* If non-reduced/final-value givs were split, then
1976 this would have to remap those givs also. See
1977 find_splittable_regs. */
1980 splittable_regs[regno]
1981 = simplify_gen_binary (PLUS, GET_MODE (giv_src_reg),
1983 splittable_regs[src_regno]);
1984 giv_inc = splittable_regs[regno];
1986 /* Now split the induction variable by changing the dest
1987 of this insn to a new register, and setting its
1988 reg_map entry to point to this new register.
1990 If this is the last iteration, and this is the last insn
1991 that will update the iv, then reuse the original dest,
1992 to ensure that the iv will have the proper value when
1993 the loop exits or repeats.
1995 Using splittable_regs_updates here like this is safe,
1996 because it can only be greater than one if all
1997 instructions modifying the iv are always executed in
2000 if (! last_iteration
2001 || (splittable_regs_updates[regno]-- != 1))
2003 tem = gen_reg_rtx (GET_MODE (giv_src_reg));
2005 map->reg_map[regno] = tem;
2006 record_base_value (REGNO (tem),
2007 giv_inc == const0_rtx
2009 : gen_rtx_PLUS (GET_MODE (giv_src_reg),
2010 giv_src_reg, giv_inc),
2014 map->reg_map[regno] = giv_src_reg;
2017 /* The constant being added could be too large for an add
2018 immediate, so can't directly emit an insn here. */
2019 emit_unrolled_add (giv_dest_reg, giv_src_reg, giv_inc);
2020 copy = get_last_insn ();
2021 pattern = PATTERN (copy);
2025 pattern = copy_rtx_and_substitute (pattern, map, 0);
2026 copy = emit_insn (pattern);
2028 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
2031 /* If this insn is setting CC0, it may need to look at
2032 the insn that uses CC0 to see what type of insn it is.
2033 In that case, the call to recog via validate_change will
2034 fail. So don't substitute constants here. Instead,
2035 do it when we emit the following insn.
2037 For example, see the pyr.md file. That machine has signed and
2038 unsigned compares. The compare patterns must check the
2039 following branch insn to see which what kind of compare to
2042 If the previous insn set CC0, substitute constants on it as
2044 if (sets_cc0_p (PATTERN (copy)) != 0)
2049 try_constants (cc0_insn, map);
2051 try_constants (copy, map);
2054 try_constants (copy, map);
2057 /* Make split induction variable constants `permanent' since we
2058 know there are no backward branches across iteration variable
2059 settings which would invalidate this. */
2060 if (dest_reg_was_split)
2062 int regno = REGNO (SET_DEST (set));
2064 if ((size_t) regno < VARRAY_SIZE (map->const_equiv_varray)
2065 && (VARRAY_CONST_EQUIV (map->const_equiv_varray, regno).age
2067 VARRAY_CONST_EQUIV (map->const_equiv_varray, regno).age = -1;
2072 pattern = copy_rtx_and_substitute (PATTERN (insn), map, 0);
2073 copy = emit_jump_insn (pattern);
2074 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
2076 if (JUMP_LABEL (insn))
2078 JUMP_LABEL (copy) = get_label_from_map (map,
2080 (JUMP_LABEL (insn)));
2081 LABEL_NUSES (JUMP_LABEL (copy))++;
2083 if (JUMP_LABEL (insn) == start_label && insn == copy_end
2084 && ! last_iteration)
2087 /* This is a branch to the beginning of the loop; this is the
2088 last insn being copied; and this is not the last iteration.
2089 In this case, we want to change the original fall through
2090 case to be a branch past the end of the loop, and the
2091 original jump label case to fall_through. */
2093 if (!invert_jump (copy, exit_label, 0))
2096 rtx lab = gen_label_rtx ();
2097 /* Can't do it by reversing the jump (probably because we
2098 couldn't reverse the conditions), so emit a new
2099 jump_insn after COPY, and redirect the jump around
2101 jmp = emit_jump_insn_after (gen_jump (exit_label), copy);
2102 JUMP_LABEL (jmp) = exit_label;
2103 LABEL_NUSES (exit_label)++;
2104 jmp = emit_barrier_after (jmp);
2105 emit_label_after (lab, jmp);
2106 LABEL_NUSES (lab) = 0;
2107 if (!redirect_jump (copy, lab, 0))
2114 try_constants (cc0_insn, map);
2117 try_constants (copy, map);
2119 /* Set the jump label of COPY correctly to avoid problems with
2120 later passes of unroll_loop, if INSN had jump label set. */
2121 if (JUMP_LABEL (insn))
2125 /* Can't use the label_map for every insn, since this may be
2126 the backward branch, and hence the label was not mapped. */
2127 if ((set = single_set (copy)))
2129 tem = SET_SRC (set);
2130 if (GET_CODE (tem) == LABEL_REF)
2131 label = XEXP (tem, 0);
2132 else if (GET_CODE (tem) == IF_THEN_ELSE)
2134 if (XEXP (tem, 1) != pc_rtx)
2135 label = XEXP (XEXP (tem, 1), 0);
2137 label = XEXP (XEXP (tem, 2), 0);
2141 if (label && GET_CODE (label) == CODE_LABEL)
2142 JUMP_LABEL (copy) = label;
2145 /* An unrecognizable jump insn, probably the entry jump
2146 for a switch statement. This label must have been mapped,
2147 so just use the label_map to get the new jump label. */
2149 = get_label_from_map (map,
2150 CODE_LABEL_NUMBER (JUMP_LABEL (insn)));
2153 /* If this is a non-local jump, then must increase the label
2154 use count so that the label will not be deleted when the
2155 original jump is deleted. */
2156 LABEL_NUSES (JUMP_LABEL (copy))++;
2158 else if (GET_CODE (PATTERN (copy)) == ADDR_VEC
2159 || GET_CODE (PATTERN (copy)) == ADDR_DIFF_VEC)
2161 rtx pat = PATTERN (copy);
2162 int diff_vec_p = GET_CODE (pat) == ADDR_DIFF_VEC;
2163 int len = XVECLEN (pat, diff_vec_p);
2166 for (i = 0; i < len; i++)
2167 LABEL_NUSES (XEXP (XVECEXP (pat, diff_vec_p, i), 0))++;
2170 /* If this used to be a conditional jump insn but whose branch
2171 direction is now known, we must do something special. */
2172 if (any_condjump_p (insn) && onlyjump_p (insn) && map->last_pc_value)
2175 /* If the previous insn set cc0 for us, delete it. */
2176 if (only_sets_cc0_p (PREV_INSN (copy)))
2177 delete_related_insns (PREV_INSN (copy));
2180 /* If this is now a no-op, delete it. */
2181 if (map->last_pc_value == pc_rtx)
2187 /* Otherwise, this is unconditional jump so we must put a
2188 BARRIER after it. We could do some dead code elimination
2189 here, but jump.c will do it just as well. */
2195 pattern = copy_rtx_and_substitute (PATTERN (insn), map, 0);
2196 copy = emit_call_insn (pattern);
2197 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
2199 /* Because the USAGE information potentially contains objects other
2200 than hard registers, we need to copy it. */
2201 CALL_INSN_FUNCTION_USAGE (copy)
2202 = copy_rtx_and_substitute (CALL_INSN_FUNCTION_USAGE (insn),
2207 try_constants (cc0_insn, map);
2210 try_constants (copy, map);
2212 /* Be lazy and assume CALL_INSNs clobber all hard registers. */
2213 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2214 VARRAY_CONST_EQUIV (map->const_equiv_varray, i).rtx = 0;
2218 /* If this is the loop start label, then we don't need to emit a
2219 copy of this label since no one will use it. */
2221 if (insn != start_label)
2223 copy = emit_label (get_label_from_map (map,
2224 CODE_LABEL_NUMBER (insn)));
2230 copy = emit_barrier ();
2234 /* VTOP and CONT notes are valid only before the loop exit test.
2235 If placed anywhere else, loop may generate bad code. */
2236 /* BASIC_BLOCK notes exist to stabilize basic block structures with
2237 the associated rtl. We do not want to share the structure in
2240 if (NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
2241 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED_LABEL
2242 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
2243 && ((NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP
2244 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_CONT)
2245 || (last_iteration && unroll_type != UNROLL_COMPLETELY)))
2246 copy = emit_note (NOTE_SOURCE_FILE (insn),
2247 NOTE_LINE_NUMBER (insn));
2256 map->insn_map[INSN_UID (insn)] = copy;
2258 while (insn != copy_end);
2260 /* Now finish coping the REG_NOTES. */
2264 insn = NEXT_INSN (insn);
2265 if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN
2266 || GET_CODE (insn) == CALL_INSN)
2267 && map->insn_map[INSN_UID (insn)])
2268 final_reg_note_copy (®_NOTES (map->insn_map[INSN_UID (insn)]), map);
2270 while (insn != copy_end);
2272 /* There may be notes between copy_notes_from and loop_end. Emit a copy of
2273 each of these notes here, since there may be some important ones, such as
2274 NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
2275 iteration, because the original notes won't be deleted.
2277 We can't use insert_before here, because when from preconditioning,
2278 insert_before points before the loop. We can't use copy_end, because
2279 there may be insns already inserted after it (which we don't want to
2280 copy) when not from preconditioning code. */
2282 if (! last_iteration)
2284 for (insn = copy_notes_from; insn != loop_end; insn = NEXT_INSN (insn))
2286 /* VTOP notes are valid only before the loop exit test.
2287 If placed anywhere else, loop may generate bad code.
2288 There is no need to test for NOTE_INSN_LOOP_CONT notes
2289 here, since COPY_NOTES_FROM will be at most one or two (for cc0)
2290 instructions before the last insn in the loop, and if the
2291 end test is that short, there will be a VTOP note between
2292 the CONT note and the test. */
2293 if (GET_CODE (insn) == NOTE
2294 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
2295 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
2296 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP)
2297 emit_note (NOTE_SOURCE_FILE (insn), NOTE_LINE_NUMBER (insn));
2301 if (final_label && LABEL_NUSES (final_label) > 0)
2302 emit_label (final_label);
2304 tem = gen_sequence ();
2306 loop_insn_emit_before (loop, 0, insert_before, tem);
2309 /* Emit an insn, using the expand_binop to ensure that a valid insn is
2310 emitted. This will correctly handle the case where the increment value
2311 won't fit in the immediate field of a PLUS insns. */
2314 emit_unrolled_add (dest_reg, src_reg, increment)
2315 rtx dest_reg, src_reg, increment;
2319 result = expand_simple_binop (GET_MODE (dest_reg), PLUS, src_reg, increment,
2320 dest_reg, 0, OPTAB_LIB_WIDEN);
2322 if (dest_reg != result)
2323 emit_move_insn (dest_reg, result);
2326 /* Searches the insns between INSN and LOOP->END. Returns 1 if there
2327 is a backward branch in that range that branches to somewhere between
2328 LOOP->START and INSN. Returns 0 otherwise. */
2330 /* ??? This is quadratic algorithm. Could be rewritten to be linear.
2331 In practice, this is not a problem, because this function is seldom called,
2332 and uses a negligible amount of CPU time on average. */
2335 back_branch_in_range_p (loop, insn)
2336 const struct loop *loop;
2339 rtx p, q, target_insn;
2340 rtx loop_start = loop->start;
2341 rtx loop_end = loop->end;
2342 rtx orig_loop_end = loop->end;
2344 /* Stop before we get to the backward branch at the end of the loop. */
2345 loop_end = prev_nonnote_insn (loop_end);
2346 if (GET_CODE (loop_end) == BARRIER)
2347 loop_end = PREV_INSN (loop_end);
2349 /* Check in case insn has been deleted, search forward for first non
2350 deleted insn following it. */
2351 while (INSN_DELETED_P (insn))
2352 insn = NEXT_INSN (insn);
2354 /* Check for the case where insn is the last insn in the loop. Deal
2355 with the case where INSN was a deleted loop test insn, in which case
2356 it will now be the NOTE_LOOP_END. */
2357 if (insn == loop_end || insn == orig_loop_end)
2360 for (p = NEXT_INSN (insn); p != loop_end; p = NEXT_INSN (p))
2362 if (GET_CODE (p) == JUMP_INSN)
2364 target_insn = JUMP_LABEL (p);
2366 /* Search from loop_start to insn, to see if one of them is
2367 the target_insn. We can't use INSN_LUID comparisons here,
2368 since insn may not have an LUID entry. */
2369 for (q = loop_start; q != insn; q = NEXT_INSN (q))
2370 if (q == target_insn)
2378 /* Try to generate the simplest rtx for the expression
2379 (PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
2383 fold_rtx_mult_add (mult1, mult2, add1, mode)
2384 rtx mult1, mult2, add1;
2385 enum machine_mode mode;
2390 /* The modes must all be the same. This should always be true. For now,
2391 check to make sure. */
2392 if ((GET_MODE (mult1) != mode && GET_MODE (mult1) != VOIDmode)
2393 || (GET_MODE (mult2) != mode && GET_MODE (mult2) != VOIDmode)
2394 || (GET_MODE (add1) != mode && GET_MODE (add1) != VOIDmode))
2397 /* Ensure that if at least one of mult1/mult2 are constant, then mult2
2398 will be a constant. */
2399 if (GET_CODE (mult1) == CONST_INT)
2406 mult_res = simplify_binary_operation (MULT, mode, mult1, mult2);
2408 mult_res = gen_rtx_MULT (mode, mult1, mult2);
2410 /* Again, put the constant second. */
2411 if (GET_CODE (add1) == CONST_INT)
2418 result = simplify_binary_operation (PLUS, mode, add1, mult_res);
2420 result = gen_rtx_PLUS (mode, add1, mult_res);
2425 /* Searches the list of induction struct's for the biv BL, to try to calculate
2426 the total increment value for one iteration of the loop as a constant.
2428 Returns the increment value as an rtx, simplified as much as possible,
2429 if it can be calculated. Otherwise, returns 0. */
2432 biv_total_increment (bl)
2433 const struct iv_class *bl;
2435 struct induction *v;
2438 /* For increment, must check every instruction that sets it. Each
2439 instruction must be executed only once each time through the loop.
2440 To verify this, we check that the insn is always executed, and that
2441 there are no backward branches after the insn that branch to before it.
2442 Also, the insn must have a mult_val of one (to make sure it really is
2445 result = const0_rtx;
2446 for (v = bl->biv; v; v = v->next_iv)
2448 if (v->always_computable && v->mult_val == const1_rtx
2449 && ! v->maybe_multiple)
2450 result = fold_rtx_mult_add (result, const1_rtx, v->add_val, v->mode);
2458 /* For each biv and giv, determine whether it can be safely split into
2459 a different variable for each unrolled copy of the loop body. If it
2460 is safe to split, then indicate that by saving some useful info
2461 in the splittable_regs array.
2463 If the loop is being completely unrolled, then splittable_regs will hold
2464 the current value of the induction variable while the loop is unrolled.
2465 It must be set to the initial value of the induction variable here.
2466 Otherwise, splittable_regs will hold the difference between the current
2467 value of the induction variable and the value the induction variable had
2468 at the top of the loop. It must be set to the value 0 here.
2470 Returns the total number of instructions that set registers that are
2473 /* ?? If the loop is only unrolled twice, then most of the restrictions to
2474 constant values are unnecessary, since we can easily calculate increment
2475 values in this case even if nothing is constant. The increment value
2476 should not involve a multiply however. */
2478 /* ?? Even if the biv/giv increment values aren't constant, it may still
2479 be beneficial to split the variable if the loop is only unrolled a few
2480 times, since multiplies by small integers (1,2,3,4) are very cheap. */
2483 find_splittable_regs (loop, unroll_type, unroll_number)
2484 const struct loop *loop;
2485 enum unroll_types unroll_type;
2488 struct loop_ivs *ivs = LOOP_IVS (loop);
2489 struct iv_class *bl;
2490 struct induction *v;
2492 rtx biv_final_value;
2496 for (bl = ivs->list; bl; bl = bl->next)
2498 /* Biv_total_increment must return a constant value,
2499 otherwise we can not calculate the split values. */
2501 increment = biv_total_increment (bl);
2502 if (! increment || GET_CODE (increment) != CONST_INT)
2505 /* The loop must be unrolled completely, or else have a known number
2506 of iterations and only one exit, or else the biv must be dead
2507 outside the loop, or else the final value must be known. Otherwise,
2508 it is unsafe to split the biv since it may not have the proper
2509 value on loop exit. */
2511 /* loop_number_exit_count is non-zero if the loop has an exit other than
2512 a fall through at the end. */
2515 biv_final_value = 0;
2516 if (unroll_type != UNROLL_COMPLETELY
2517 && (loop->exit_count || unroll_type == UNROLL_NAIVE)
2518 && (REGNO_LAST_LUID (bl->regno) >= INSN_LUID (loop->end)
2520 || INSN_UID (bl->init_insn) >= max_uid_for_loop
2521 || (REGNO_FIRST_LUID (bl->regno)
2522 < INSN_LUID (bl->init_insn))
2523 || reg_mentioned_p (bl->biv->dest_reg, SET_SRC (bl->init_set)))
2524 && ! (biv_final_value = final_biv_value (loop, bl)))
2527 /* If any of the insns setting the BIV don't do so with a simple
2528 PLUS, we don't know how to split it. */
2529 for (v = bl->biv; biv_splittable && v; v = v->next_iv)
2530 if ((tem = single_set (v->insn)) == 0
2531 || GET_CODE (SET_DEST (tem)) != REG
2532 || REGNO (SET_DEST (tem)) != bl->regno
2533 || GET_CODE (SET_SRC (tem)) != PLUS)
2536 /* If final value is non-zero, then must emit an instruction which sets
2537 the value of the biv to the proper value. This is done after
2538 handling all of the givs, since some of them may need to use the
2539 biv's value in their initialization code. */
2541 /* This biv is splittable. If completely unrolling the loop, save
2542 the biv's initial value. Otherwise, save the constant zero. */
2544 if (biv_splittable == 1)
2546 if (unroll_type == UNROLL_COMPLETELY)
2548 /* If the initial value of the biv is itself (i.e. it is too
2549 complicated for strength_reduce to compute), or is a hard
2550 register, or it isn't invariant, then we must create a new
2551 pseudo reg to hold the initial value of the biv. */
2553 if (GET_CODE (bl->initial_value) == REG
2554 && (REGNO (bl->initial_value) == bl->regno
2555 || REGNO (bl->initial_value) < FIRST_PSEUDO_REGISTER
2556 || ! loop_invariant_p (loop, bl->initial_value)))
2558 rtx tem = gen_reg_rtx (bl->biv->mode);
2560 record_base_value (REGNO (tem), bl->biv->add_val, 0);
2561 loop_insn_hoist (loop,
2562 gen_move_insn (tem, bl->biv->src_reg));
2564 if (loop_dump_stream)
2565 fprintf (loop_dump_stream,
2566 "Biv %d initial value remapped to %d.\n",
2567 bl->regno, REGNO (tem));
2569 splittable_regs[bl->regno] = tem;
2572 splittable_regs[bl->regno] = bl->initial_value;
2575 splittable_regs[bl->regno] = const0_rtx;
2577 /* Save the number of instructions that modify the biv, so that
2578 we can treat the last one specially. */
2580 splittable_regs_updates[bl->regno] = bl->biv_count;
2581 result += bl->biv_count;
2583 if (loop_dump_stream)
2584 fprintf (loop_dump_stream,
2585 "Biv %d safe to split.\n", bl->regno);
2588 /* Check every giv that depends on this biv to see whether it is
2589 splittable also. Even if the biv isn't splittable, givs which
2590 depend on it may be splittable if the biv is live outside the
2591 loop, and the givs aren't. */
2593 result += find_splittable_givs (loop, bl, unroll_type, increment,
2596 /* If final value is non-zero, then must emit an instruction which sets
2597 the value of the biv to the proper value. This is done after
2598 handling all of the givs, since some of them may need to use the
2599 biv's value in their initialization code. */
2600 if (biv_final_value)
2602 /* If the loop has multiple exits, emit the insns before the
2603 loop to ensure that it will always be executed no matter
2604 how the loop exits. Otherwise emit the insn after the loop,
2605 since this is slightly more efficient. */
2606 if (! loop->exit_count)
2607 loop_insn_sink (loop, gen_move_insn (bl->biv->src_reg,
2611 /* Create a new register to hold the value of the biv, and then
2612 set the biv to its final value before the loop start. The biv
2613 is set to its final value before loop start to ensure that
2614 this insn will always be executed, no matter how the loop
2616 rtx tem = gen_reg_rtx (bl->biv->mode);
2617 record_base_value (REGNO (tem), bl->biv->add_val, 0);
2619 loop_insn_hoist (loop, gen_move_insn (tem, bl->biv->src_reg));
2620 loop_insn_hoist (loop, gen_move_insn (bl->biv->src_reg,
2623 if (loop_dump_stream)
2624 fprintf (loop_dump_stream, "Biv %d mapped to %d for split.\n",
2625 REGNO (bl->biv->src_reg), REGNO (tem));
2627 /* Set up the mapping from the original biv register to the new
2629 bl->biv->src_reg = tem;
2636 /* Return 1 if the first and last unrolled copy of the address giv V is valid
2637 for the instruction that is using it. Do not make any changes to that
2641 verify_addresses (v, giv_inc, unroll_number)
2642 struct induction *v;
2647 rtx orig_addr = *v->location;
2648 rtx last_addr = plus_constant (v->dest_reg,
2649 INTVAL (giv_inc) * (unroll_number - 1));
2651 /* First check to see if either address would fail. Handle the fact
2652 that we have may have a match_dup. */
2653 if (! validate_replace_rtx (*v->location, v->dest_reg, v->insn)
2654 || ! validate_replace_rtx (*v->location, last_addr, v->insn))
2657 /* Now put things back the way they were before. This should always
2659 if (! validate_replace_rtx (*v->location, orig_addr, v->insn))
2665 /* For every giv based on the biv BL, check to determine whether it is
2666 splittable. This is a subroutine to find_splittable_regs ().
2668 Return the number of instructions that set splittable registers. */
2671 find_splittable_givs (loop, bl, unroll_type, increment, unroll_number)
2672 const struct loop *loop;
2673 struct iv_class *bl;
2674 enum unroll_types unroll_type;
2678 struct loop_ivs *ivs = LOOP_IVS (loop);
2679 struct induction *v, *v2;
2684 /* Scan the list of givs, and set the same_insn field when there are
2685 multiple identical givs in the same insn. */
2686 for (v = bl->giv; v; v = v->next_iv)
2687 for (v2 = v->next_iv; v2; v2 = v2->next_iv)
2688 if (v->insn == v2->insn && rtx_equal_p (v->new_reg, v2->new_reg)
2692 for (v = bl->giv; v; v = v->next_iv)
2696 /* Only split the giv if it has already been reduced, or if the loop is
2697 being completely unrolled. */
2698 if (unroll_type != UNROLL_COMPLETELY && v->ignore)
2701 /* The giv can be split if the insn that sets the giv is executed once
2702 and only once on every iteration of the loop. */
2703 /* An address giv can always be split. v->insn is just a use not a set,
2704 and hence it does not matter whether it is always executed. All that
2705 matters is that all the biv increments are always executed, and we
2706 won't reach here if they aren't. */
2707 if (v->giv_type != DEST_ADDR
2708 && (! v->always_computable
2709 || back_branch_in_range_p (loop, v->insn)))
2712 /* The giv increment value must be a constant. */
2713 giv_inc = fold_rtx_mult_add (v->mult_val, increment, const0_rtx,
2715 if (! giv_inc || GET_CODE (giv_inc) != CONST_INT)
2718 /* The loop must be unrolled completely, or else have a known number of
2719 iterations and only one exit, or else the giv must be dead outside
2720 the loop, or else the final value of the giv must be known.
2721 Otherwise, it is not safe to split the giv since it may not have the
2722 proper value on loop exit. */
2724 /* The used outside loop test will fail for DEST_ADDR givs. They are
2725 never used outside the loop anyways, so it is always safe to split a
2729 if (unroll_type != UNROLL_COMPLETELY
2730 && (loop->exit_count || unroll_type == UNROLL_NAIVE)
2731 && v->giv_type != DEST_ADDR
2732 /* The next part is true if the pseudo is used outside the loop.
2733 We assume that this is true for any pseudo created after loop
2734 starts, because we don't have a reg_n_info entry for them. */
2735 && (REGNO (v->dest_reg) >= max_reg_before_loop
2736 || (REGNO_FIRST_UID (REGNO (v->dest_reg)) != INSN_UID (v->insn)
2737 /* Check for the case where the pseudo is set by a shift/add
2738 sequence, in which case the first insn setting the pseudo
2739 is the first insn of the shift/add sequence. */
2740 && (! (tem = find_reg_note (v->insn, REG_RETVAL, NULL_RTX))
2741 || (REGNO_FIRST_UID (REGNO (v->dest_reg))
2742 != INSN_UID (XEXP (tem, 0)))))
2743 /* Line above always fails if INSN was moved by loop opt. */
2744 || (REGNO_LAST_LUID (REGNO (v->dest_reg))
2745 >= INSN_LUID (loop->end)))
2746 && ! (final_value = v->final_value))
2750 /* Currently, non-reduced/final-value givs are never split. */
2751 /* Should emit insns after the loop if possible, as the biv final value
2754 /* If the final value is non-zero, and the giv has not been reduced,
2755 then must emit an instruction to set the final value. */
2756 if (final_value && !v->new_reg)
2758 /* Create a new register to hold the value of the giv, and then set
2759 the giv to its final value before the loop start. The giv is set
2760 to its final value before loop start to ensure that this insn
2761 will always be executed, no matter how we exit. */
2762 tem = gen_reg_rtx (v->mode);
2763 loop_insn_hoist (loop, gen_move_insn (tem, v->dest_reg));
2764 loop_insn_hoist (loop, gen_move_insn (v->dest_reg, final_value));
2766 if (loop_dump_stream)
2767 fprintf (loop_dump_stream, "Giv %d mapped to %d for split.\n",
2768 REGNO (v->dest_reg), REGNO (tem));
2774 /* This giv is splittable. If completely unrolling the loop, save the
2775 giv's initial value. Otherwise, save the constant zero for it. */
2777 if (unroll_type == UNROLL_COMPLETELY)
2779 /* It is not safe to use bl->initial_value here, because it may not
2780 be invariant. It is safe to use the initial value stored in
2781 the splittable_regs array if it is set. In rare cases, it won't
2782 be set, so then we do exactly the same thing as
2783 find_splittable_regs does to get a safe value. */
2784 rtx biv_initial_value;
2786 if (splittable_regs[bl->regno])
2787 biv_initial_value = splittable_regs[bl->regno];
2788 else if (GET_CODE (bl->initial_value) != REG
2789 || (REGNO (bl->initial_value) != bl->regno
2790 && REGNO (bl->initial_value) >= FIRST_PSEUDO_REGISTER))
2791 biv_initial_value = bl->initial_value;
2794 rtx tem = gen_reg_rtx (bl->biv->mode);
2796 record_base_value (REGNO (tem), bl->biv->add_val, 0);
2797 loop_insn_hoist (loop, gen_move_insn (tem, bl->biv->src_reg));
2798 biv_initial_value = tem;
2800 biv_initial_value = extend_value_for_giv (v, biv_initial_value);
2801 value = fold_rtx_mult_add (v->mult_val, biv_initial_value,
2802 v->add_val, v->mode);
2809 /* If a giv was combined with another giv, then we can only split
2810 this giv if the giv it was combined with was reduced. This
2811 is because the value of v->new_reg is meaningless in this
2813 if (v->same && ! v->same->new_reg)
2815 if (loop_dump_stream)
2816 fprintf (loop_dump_stream,
2817 "giv combined with unreduced giv not split.\n");
2820 /* If the giv is an address destination, it could be something other
2821 than a simple register, these have to be treated differently. */
2822 else if (v->giv_type == DEST_REG)
2824 /* If value is not a constant, register, or register plus
2825 constant, then compute its value into a register before
2826 loop start. This prevents invalid rtx sharing, and should
2827 generate better code. We can use bl->initial_value here
2828 instead of splittable_regs[bl->regno] because this code
2829 is going before the loop start. */
2830 if (unroll_type == UNROLL_COMPLETELY
2831 && GET_CODE (value) != CONST_INT
2832 && GET_CODE (value) != REG
2833 && (GET_CODE (value) != PLUS
2834 || GET_CODE (XEXP (value, 0)) != REG
2835 || GET_CODE (XEXP (value, 1)) != CONST_INT))
2837 rtx tem = gen_reg_rtx (v->mode);
2838 record_base_value (REGNO (tem), v->add_val, 0);
2839 loop_iv_add_mult_hoist (loop, bl->initial_value, v->mult_val,
2844 splittable_regs[REGNO (v->new_reg)] = value;
2848 /* Splitting address givs is useful since it will often allow us
2849 to eliminate some increment insns for the base giv as
2852 /* If the addr giv is combined with a dest_reg giv, then all
2853 references to that dest reg will be remapped, which is NOT
2854 what we want for split addr regs. We always create a new
2855 register for the split addr giv, just to be safe. */
2857 /* If we have multiple identical address givs within a
2858 single instruction, then use a single pseudo reg for
2859 both. This is necessary in case one is a match_dup
2862 v->const_adjust = 0;
2866 v->dest_reg = v->same_insn->dest_reg;
2867 if (loop_dump_stream)
2868 fprintf (loop_dump_stream,
2869 "Sharing address givs in insn %d\n",
2870 INSN_UID (v->insn));
2872 /* If multiple address GIVs have been combined with the
2873 same dest_reg GIV, do not create a new register for
2875 else if (unroll_type != UNROLL_COMPLETELY
2876 && v->giv_type == DEST_ADDR
2877 && v->same && v->same->giv_type == DEST_ADDR
2878 && v->same->unrolled
2879 /* combine_givs_p may return true for some cases
2880 where the add and mult values are not equal.
2881 To share a register here, the values must be
2883 && rtx_equal_p (v->same->mult_val, v->mult_val)
2884 && rtx_equal_p (v->same->add_val, v->add_val)
2885 /* If the memory references have different modes,
2886 then the address may not be valid and we must
2887 not share registers. */
2888 && verify_addresses (v, giv_inc, unroll_number))
2890 v->dest_reg = v->same->dest_reg;
2893 else if (unroll_type != UNROLL_COMPLETELY)
2895 /* If not completely unrolling the loop, then create a new
2896 register to hold the split value of the DEST_ADDR giv.
2897 Emit insn to initialize its value before loop start. */
2899 rtx tem = gen_reg_rtx (v->mode);
2900 struct induction *same = v->same;
2901 rtx new_reg = v->new_reg;
2902 record_base_value (REGNO (tem), v->add_val, 0);
2904 /* If the address giv has a constant in its new_reg value,
2905 then this constant can be pulled out and put in value,
2906 instead of being part of the initialization code. */
2908 if (GET_CODE (new_reg) == PLUS
2909 && GET_CODE (XEXP (new_reg, 1)) == CONST_INT)
2912 = plus_constant (tem, INTVAL (XEXP (new_reg, 1)));
2914 /* Only succeed if this will give valid addresses.
2915 Try to validate both the first and the last
2916 address resulting from loop unrolling, if
2917 one fails, then can't do const elim here. */
2918 if (verify_addresses (v, giv_inc, unroll_number))
2920 /* Save the negative of the eliminated const, so
2921 that we can calculate the dest_reg's increment
2923 v->const_adjust = -INTVAL (XEXP (new_reg, 1));
2925 new_reg = XEXP (new_reg, 0);
2926 if (loop_dump_stream)
2927 fprintf (loop_dump_stream,
2928 "Eliminating constant from giv %d\n",
2937 /* If the address hasn't been checked for validity yet, do so
2938 now, and fail completely if either the first or the last
2939 unrolled copy of the address is not a valid address
2940 for the instruction that uses it. */
2941 if (v->dest_reg == tem
2942 && ! verify_addresses (v, giv_inc, unroll_number))
2944 for (v2 = v->next_iv; v2; v2 = v2->next_iv)
2945 if (v2->same_insn == v)
2948 if (loop_dump_stream)
2949 fprintf (loop_dump_stream,
2950 "Invalid address for giv at insn %d\n",
2951 INSN_UID (v->insn));
2955 v->new_reg = new_reg;
2958 /* We set this after the address check, to guarantee that
2959 the register will be initialized. */
2962 /* To initialize the new register, just move the value of
2963 new_reg into it. This is not guaranteed to give a valid
2964 instruction on machines with complex addressing modes.
2965 If we can't recognize it, then delete it and emit insns
2966 to calculate the value from scratch. */
2967 loop_insn_hoist (loop, gen_rtx_SET (VOIDmode, tem,
2968 copy_rtx (v->new_reg)));
2969 if (recog_memoized (PREV_INSN (loop->start)) < 0)
2973 /* We can't use bl->initial_value to compute the initial
2974 value, because the loop may have been preconditioned.
2975 We must calculate it from NEW_REG. */
2976 delete_related_insns (PREV_INSN (loop->start));
2979 ret = force_operand (v->new_reg, tem);
2981 emit_move_insn (tem, ret);
2982 sequence = gen_sequence ();
2984 loop_insn_hoist (loop, sequence);
2986 if (loop_dump_stream)
2987 fprintf (loop_dump_stream,
2988 "Invalid init insn, rewritten.\n");
2993 v->dest_reg = value;
2995 /* Check the resulting address for validity, and fail
2996 if the resulting address would be invalid. */
2997 if (! verify_addresses (v, giv_inc, unroll_number))
2999 for (v2 = v->next_iv; v2; v2 = v2->next_iv)
3000 if (v2->same_insn == v)
3003 if (loop_dump_stream)
3004 fprintf (loop_dump_stream,
3005 "Invalid address for giv at insn %d\n",
3006 INSN_UID (v->insn));
3011 /* Store the value of dest_reg into the insn. This sharing
3012 will not be a problem as this insn will always be copied
3015 *v->location = v->dest_reg;
3017 /* If this address giv is combined with a dest reg giv, then
3018 save the base giv's induction pointer so that we will be
3019 able to handle this address giv properly. The base giv
3020 itself does not have to be splittable. */
3022 if (v->same && v->same->giv_type == DEST_REG)
3023 addr_combined_regs[REGNO (v->same->new_reg)] = v->same;
3025 if (GET_CODE (v->new_reg) == REG)
3027 /* This giv maybe hasn't been combined with any others.
3028 Make sure that it's giv is marked as splittable here. */
3030 splittable_regs[REGNO (v->new_reg)] = value;
3032 /* Make it appear to depend upon itself, so that the
3033 giv will be properly split in the main loop above. */
3037 addr_combined_regs[REGNO (v->new_reg)] = v;
3041 if (loop_dump_stream)
3042 fprintf (loop_dump_stream, "DEST_ADDR giv being split.\n");
3048 /* Currently, unreduced giv's can't be split. This is not too much
3049 of a problem since unreduced giv's are not live across loop
3050 iterations anyways. When unrolling a loop completely though,
3051 it makes sense to reduce&split givs when possible, as this will
3052 result in simpler instructions, and will not require that a reg
3053 be live across loop iterations. */
3055 splittable_regs[REGNO (v->dest_reg)] = value;
3056 fprintf (stderr, "Giv %d at insn %d not reduced\n",
3057 REGNO (v->dest_reg), INSN_UID (v->insn));
3063 /* Unreduced givs are only updated once by definition. Reduced givs
3064 are updated as many times as their biv is. Mark it so if this is
3065 a splittable register. Don't need to do anything for address givs
3066 where this may not be a register. */
3068 if (GET_CODE (v->new_reg) == REG)
3072 count = REG_IV_CLASS (ivs, REGNO (v->src_reg))->biv_count;
3074 splittable_regs_updates[REGNO (v->new_reg)] = count;
3079 if (loop_dump_stream)
3083 if (GET_CODE (v->dest_reg) == CONST_INT)
3085 else if (GET_CODE (v->dest_reg) != REG)
3086 regnum = REGNO (XEXP (v->dest_reg, 0));
3088 regnum = REGNO (v->dest_reg);
3089 fprintf (loop_dump_stream, "Giv %d at insn %d safe to split.\n",
3090 regnum, INSN_UID (v->insn));
3097 /* Try to prove that the register is dead after the loop exits. Trace every
3098 loop exit looking for an insn that will always be executed, which sets
3099 the register to some value, and appears before the first use of the register
3100 is found. If successful, then return 1, otherwise return 0. */
3102 /* ?? Could be made more intelligent in the handling of jumps, so that
3103 it can search past if statements and other similar structures. */
3106 reg_dead_after_loop (loop, reg)
3107 const struct loop *loop;
3113 int label_count = 0;
3115 /* In addition to checking all exits of this loop, we must also check
3116 all exits of inner nested loops that would exit this loop. We don't
3117 have any way to identify those, so we just give up if there are any
3118 such inner loop exits. */
3120 for (label = loop->exit_labels; label; label = LABEL_NEXTREF (label))
3123 if (label_count != loop->exit_count)
3126 /* HACK: Must also search the loop fall through exit, create a label_ref
3127 here which points to the loop->end, and append the loop_number_exit_labels
3129 label = gen_rtx_LABEL_REF (VOIDmode, loop->end);
3130 LABEL_NEXTREF (label) = loop->exit_labels;
3132 for (; label; label = LABEL_NEXTREF (label))
3134 /* Succeed if find an insn which sets the biv or if reach end of
3135 function. Fail if find an insn that uses the biv, or if come to
3136 a conditional jump. */
3138 insn = NEXT_INSN (XEXP (label, 0));
3141 code = GET_CODE (insn);
3142 if (GET_RTX_CLASS (code) == 'i')
3146 if (reg_referenced_p (reg, PATTERN (insn)))
3149 set = single_set (insn);
3150 if (set && rtx_equal_p (SET_DEST (set), reg))
3154 if (code == JUMP_INSN)
3156 if (GET_CODE (PATTERN (insn)) == RETURN)
3158 else if (!any_uncondjump_p (insn)
3159 /* Prevent infinite loop following infinite loops. */
3160 || jump_count++ > 20)
3163 insn = JUMP_LABEL (insn);
3166 insn = NEXT_INSN (insn);
3170 /* Success, the register is dead on all loop exits. */
3174 /* Try to calculate the final value of the biv, the value it will have at
3175 the end of the loop. If we can do it, return that value. */
3178 final_biv_value (loop, bl)
3179 const struct loop *loop;
3180 struct iv_class *bl;
3182 unsigned HOST_WIDE_INT n_iterations = LOOP_INFO (loop)->n_iterations;
3185 /* ??? This only works for MODE_INT biv's. Reject all others for now. */
3187 if (GET_MODE_CLASS (bl->biv->mode) != MODE_INT)
3190 /* The final value for reversed bivs must be calculated differently than
3191 for ordinary bivs. In this case, there is already an insn after the
3192 loop which sets this biv's final value (if necessary), and there are
3193 no other loop exits, so we can return any value. */
3196 if (loop_dump_stream)
3197 fprintf (loop_dump_stream,
3198 "Final biv value for %d, reversed biv.\n", bl->regno);
3203 /* Try to calculate the final value as initial value + (number of iterations
3204 * increment). For this to work, increment must be invariant, the only
3205 exit from the loop must be the fall through at the bottom (otherwise
3206 it may not have its final value when the loop exits), and the initial
3207 value of the biv must be invariant. */
3209 if (n_iterations != 0
3210 && ! loop->exit_count
3211 && loop_invariant_p (loop, bl->initial_value))
3213 increment = biv_total_increment (bl);
3215 if (increment && loop_invariant_p (loop, increment))
3217 /* Can calculate the loop exit value, emit insns after loop
3218 end to calculate this value into a temporary register in
3219 case it is needed later. */
3221 tem = gen_reg_rtx (bl->biv->mode);
3222 record_base_value (REGNO (tem), bl->biv->add_val, 0);
3223 loop_iv_add_mult_sink (loop, increment, GEN_INT (n_iterations),
3224 bl->initial_value, tem);
3226 if (loop_dump_stream)
3227 fprintf (loop_dump_stream,
3228 "Final biv value for %d, calculated.\n", bl->regno);
3234 /* Check to see if the biv is dead at all loop exits. */
3235 if (reg_dead_after_loop (loop, bl->biv->src_reg))
3237 if (loop_dump_stream)
3238 fprintf (loop_dump_stream,
3239 "Final biv value for %d, biv dead after loop exit.\n",
3248 /* Try to calculate the final value of the giv, the value it will have at
3249 the end of the loop. If we can do it, return that value. */
3252 final_giv_value (loop, v)
3253 const struct loop *loop;
3254 struct induction *v;
3256 struct loop_ivs *ivs = LOOP_IVS (loop);
3257 struct iv_class *bl;
3261 rtx loop_end = loop->end;
3262 unsigned HOST_WIDE_INT n_iterations = LOOP_INFO (loop)->n_iterations;
3264 bl = REG_IV_CLASS (ivs, REGNO (v->src_reg));
3266 /* The final value for givs which depend on reversed bivs must be calculated
3267 differently than for ordinary givs. In this case, there is already an
3268 insn after the loop which sets this giv's final value (if necessary),
3269 and there are no other loop exits, so we can return any value. */
3272 if (loop_dump_stream)
3273 fprintf (loop_dump_stream,
3274 "Final giv value for %d, depends on reversed biv\n",
3275 REGNO (v->dest_reg));
3279 /* Try to calculate the final value as a function of the biv it depends
3280 upon. The only exit from the loop must be the fall through at the bottom
3281 (otherwise it may not have its final value when the loop exits). */
3283 /* ??? Can calculate the final giv value by subtracting off the
3284 extra biv increments times the giv's mult_val. The loop must have
3285 only one exit for this to work, but the loop iterations does not need
3288 if (n_iterations != 0
3289 && ! loop->exit_count)
3291 /* ?? It is tempting to use the biv's value here since these insns will
3292 be put after the loop, and hence the biv will have its final value
3293 then. However, this fails if the biv is subsequently eliminated.
3294 Perhaps determine whether biv's are eliminable before trying to
3295 determine whether giv's are replaceable so that we can use the
3296 biv value here if it is not eliminable. */
3298 /* We are emitting code after the end of the loop, so we must make
3299 sure that bl->initial_value is still valid then. It will still
3300 be valid if it is invariant. */
3302 increment = biv_total_increment (bl);
3304 if (increment && loop_invariant_p (loop, increment)
3305 && loop_invariant_p (loop, bl->initial_value))
3307 /* Can calculate the loop exit value of its biv as
3308 (n_iterations * increment) + initial_value */
3310 /* The loop exit value of the giv is then
3311 (final_biv_value - extra increments) * mult_val + add_val.
3312 The extra increments are any increments to the biv which
3313 occur in the loop after the giv's value is calculated.
3314 We must search from the insn that sets the giv to the end
3315 of the loop to calculate this value. */
3317 /* Put the final biv value in tem. */
3318 tem = gen_reg_rtx (v->mode);
3319 record_base_value (REGNO (tem), bl->biv->add_val, 0);
3320 loop_iv_add_mult_sink (loop, extend_value_for_giv (v, increment),
3321 GEN_INT (n_iterations),
3322 extend_value_for_giv (v, bl->initial_value),
3325 /* Subtract off extra increments as we find them. */
3326 for (insn = NEXT_INSN (v->insn); insn != loop_end;
3327 insn = NEXT_INSN (insn))
3329 struct induction *biv;
3331 for (biv = bl->biv; biv; biv = biv->next_iv)
3332 if (biv->insn == insn)
3335 tem = expand_simple_binop (GET_MODE (tem), MINUS, tem,
3336 biv->add_val, NULL_RTX, 0,
3338 seq = gen_sequence ();
3340 loop_insn_sink (loop, seq);
3344 /* Now calculate the giv's final value. */
3345 loop_iv_add_mult_sink (loop, tem, v->mult_val, v->add_val, tem);
3347 if (loop_dump_stream)
3348 fprintf (loop_dump_stream,
3349 "Final giv value for %d, calc from biv's value.\n",
3350 REGNO (v->dest_reg));
3356 /* Replaceable giv's should never reach here. */
3360 /* Check to see if the biv is dead at all loop exits. */
3361 if (reg_dead_after_loop (loop, v->dest_reg))
3363 if (loop_dump_stream)
3364 fprintf (loop_dump_stream,
3365 "Final giv value for %d, giv dead after loop exit.\n",
3366 REGNO (v->dest_reg));
3374 /* Look back before LOOP->START for the insn that sets REG and return
3375 the equivalent constant if there is a REG_EQUAL note otherwise just
3376 the SET_SRC of REG. */
3379 loop_find_equiv_value (loop, reg)
3380 const struct loop *loop;
3383 rtx loop_start = loop->start;
3388 for (insn = PREV_INSN (loop_start); insn; insn = PREV_INSN (insn))
3390 if (GET_CODE (insn) == CODE_LABEL)
3393 else if (INSN_P (insn) && reg_set_p (reg, insn))
3395 /* We found the last insn before the loop that sets the register.
3396 If it sets the entire register, and has a REG_EQUAL note,
3397 then use the value of the REG_EQUAL note. */
3398 if ((set = single_set (insn))
3399 && (SET_DEST (set) == reg))
3401 rtx note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
3403 /* Only use the REG_EQUAL note if it is a constant.
3404 Other things, divide in particular, will cause
3405 problems later if we use them. */
3406 if (note && GET_CODE (XEXP (note, 0)) != EXPR_LIST
3407 && CONSTANT_P (XEXP (note, 0)))
3408 ret = XEXP (note, 0);
3410 ret = SET_SRC (set);
3412 /* We cannot do this if it changes between the
3413 assignment and loop start though. */
3414 if (modified_between_p (ret, insn, loop_start))
3423 /* Return a simplified rtx for the expression OP - REG.
3425 REG must appear in OP, and OP must be a register or the sum of a register
3428 Thus, the return value must be const0_rtx or the second term.
3430 The caller is responsible for verifying that REG appears in OP and OP has
3434 subtract_reg_term (op, reg)
3439 if (GET_CODE (op) == PLUS)
3441 if (XEXP (op, 0) == reg)
3442 return XEXP (op, 1);
3443 else if (XEXP (op, 1) == reg)
3444 return XEXP (op, 0);
3446 /* OP does not contain REG as a term. */
3450 /* Find and return register term common to both expressions OP0 and
3451 OP1 or NULL_RTX if no such term exists. Each expression must be a
3452 REG or a PLUS of a REG. */
3455 find_common_reg_term (op0, op1)
3458 if ((GET_CODE (op0) == REG || GET_CODE (op0) == PLUS)
3459 && (GET_CODE (op1) == REG || GET_CODE (op1) == PLUS))
3466 if (GET_CODE (op0) == PLUS)
3467 op01 = XEXP (op0, 1), op00 = XEXP (op0, 0);
3469 op01 = const0_rtx, op00 = op0;
3471 if (GET_CODE (op1) == PLUS)
3472 op11 = XEXP (op1, 1), op10 = XEXP (op1, 0);
3474 op11 = const0_rtx, op10 = op1;
3476 /* Find and return common register term if present. */
3477 if (REG_P (op00) && (op00 == op10 || op00 == op11))
3479 else if (REG_P (op01) && (op01 == op10 || op01 == op11))
3483 /* No common register term found. */
3487 /* Determine the loop iterator and calculate the number of loop
3488 iterations. Returns the exact number of loop iterations if it can
3489 be calculated, otherwise returns zero. */
3491 unsigned HOST_WIDE_INT
3492 loop_iterations (loop)
3495 struct loop_info *loop_info = LOOP_INFO (loop);
3496 struct loop_ivs *ivs = LOOP_IVS (loop);
3497 rtx comparison, comparison_value;
3498 rtx iteration_var, initial_value, increment, final_value;
3499 enum rtx_code comparison_code;
3501 unsigned HOST_WIDE_INT abs_inc;
3502 unsigned HOST_WIDE_INT abs_diff;
3505 int unsigned_p, compare_dir, final_larger;
3508 struct iv_class *bl;
3510 loop_info->n_iterations = 0;
3511 loop_info->initial_value = 0;
3512 loop_info->initial_equiv_value = 0;
3513 loop_info->comparison_value = 0;
3514 loop_info->final_value = 0;
3515 loop_info->final_equiv_value = 0;
3516 loop_info->increment = 0;
3517 loop_info->iteration_var = 0;
3518 loop_info->unroll_number = 1;
3521 /* We used to use prev_nonnote_insn here, but that fails because it might
3522 accidentally get the branch for a contained loop if the branch for this
3523 loop was deleted. We can only trust branches immediately before the
3525 last_loop_insn = PREV_INSN (loop->end);
3527 /* ??? We should probably try harder to find the jump insn
3528 at the end of the loop. The following code assumes that
3529 the last loop insn is a jump to the top of the loop. */
3530 if (GET_CODE (last_loop_insn) != JUMP_INSN)
3532 if (loop_dump_stream)
3533 fprintf (loop_dump_stream,
3534 "Loop iterations: No final conditional branch found.\n");
3538 /* If there is a more than a single jump to the top of the loop
3539 we cannot (easily) determine the iteration count. */
3540 if (LABEL_NUSES (JUMP_LABEL (last_loop_insn)) > 1)
3542 if (loop_dump_stream)
3543 fprintf (loop_dump_stream,
3544 "Loop iterations: Loop has multiple back edges.\n");
3548 /* If there are multiple conditionalized loop exit tests, they may jump
3549 back to differing CODE_LABELs. */
3550 if (loop->top && loop->cont)
3552 rtx temp = PREV_INSN (last_loop_insn);
3556 if (GET_CODE (temp) == JUMP_INSN)
3558 /* There are some kinds of jumps we can't deal with easily. */
3559 if (JUMP_LABEL (temp) == 0)
3561 if (loop_dump_stream)
3564 "Loop iterations: Jump insn has null JUMP_LABEL.\n");
3568 if (/* Previous unrolling may have generated new insns not
3569 covered by the uid_luid array. */
3570 INSN_UID (JUMP_LABEL (temp)) < max_uid_for_loop
3571 /* Check if we jump back into the loop body. */
3572 && INSN_LUID (JUMP_LABEL (temp)) > INSN_LUID (loop->top)
3573 && INSN_LUID (JUMP_LABEL (temp)) < INSN_LUID (loop->cont))
3575 if (loop_dump_stream)
3578 "Loop iterations: Loop has multiple back edges.\n");
3583 while ((temp = PREV_INSN (temp)) != loop->cont);
3586 /* Find the iteration variable. If the last insn is a conditional
3587 branch, and the insn before tests a register value, make that the
3588 iteration variable. */
3590 comparison = get_condition_for_loop (loop, last_loop_insn);
3591 if (comparison == 0)
3593 if (loop_dump_stream)
3594 fprintf (loop_dump_stream,
3595 "Loop iterations: No final comparison found.\n");
3599 /* ??? Get_condition may switch position of induction variable and
3600 invariant register when it canonicalizes the comparison. */
3602 comparison_code = GET_CODE (comparison);
3603 iteration_var = XEXP (comparison, 0);
3604 comparison_value = XEXP (comparison, 1);
3606 if (GET_CODE (iteration_var) != REG)
3608 if (loop_dump_stream)
3609 fprintf (loop_dump_stream,
3610 "Loop iterations: Comparison not against register.\n");
3614 /* The only new registers that are created before loop iterations
3615 are givs made from biv increments or registers created by
3616 load_mems. In the latter case, it is possible that try_copy_prop
3617 will propagate a new pseudo into the old iteration register but
3618 this will be marked by having the REG_USERVAR_P bit set. */
3620 if ((unsigned) REGNO (iteration_var) >= ivs->n_regs
3621 && ! REG_USERVAR_P (iteration_var))
3624 /* Determine the initial value of the iteration variable, and the amount
3625 that it is incremented each loop. Use the tables constructed by
3626 the strength reduction pass to calculate these values. */
3628 /* Clear the result values, in case no answer can be found. */
3632 /* The iteration variable can be either a giv or a biv. Check to see
3633 which it is, and compute the variable's initial value, and increment
3634 value if possible. */
3636 /* If this is a new register, can't handle it since we don't have any
3637 reg_iv_type entry for it. */
3638 if ((unsigned) REGNO (iteration_var) >= ivs->n_regs)
3640 if (loop_dump_stream)
3641 fprintf (loop_dump_stream,
3642 "Loop iterations: No reg_iv_type entry for iteration var.\n");
3646 /* Reject iteration variables larger than the host wide int size, since they
3647 could result in a number of iterations greater than the range of our
3648 `unsigned HOST_WIDE_INT' variable loop_info->n_iterations. */
3649 else if ((GET_MODE_BITSIZE (GET_MODE (iteration_var))
3650 > HOST_BITS_PER_WIDE_INT))
3652 if (loop_dump_stream)
3653 fprintf (loop_dump_stream,
3654 "Loop iterations: Iteration var rejected because mode too large.\n");
3657 else if (GET_MODE_CLASS (GET_MODE (iteration_var)) != MODE_INT)
3659 if (loop_dump_stream)
3660 fprintf (loop_dump_stream,
3661 "Loop iterations: Iteration var not an integer.\n");
3664 else if (REG_IV_TYPE (ivs, REGNO (iteration_var)) == BASIC_INDUCT)
3666 if (REGNO (iteration_var) >= ivs->n_regs)
3669 /* Grab initial value, only useful if it is a constant. */
3670 bl = REG_IV_CLASS (ivs, REGNO (iteration_var));
3671 initial_value = bl->initial_value;
3672 if (!bl->biv->always_executed || bl->biv->maybe_multiple)
3674 if (loop_dump_stream)
3675 fprintf (loop_dump_stream,
3676 "Loop iterations: Basic induction var not set once in each iteration.\n");
3680 increment = biv_total_increment (bl);
3682 else if (REG_IV_TYPE (ivs, REGNO (iteration_var)) == GENERAL_INDUCT)
3684 HOST_WIDE_INT offset = 0;
3685 struct induction *v = REG_IV_INFO (ivs, REGNO (iteration_var));
3686 rtx biv_initial_value;
3688 if (REGNO (v->src_reg) >= ivs->n_regs)
3691 if (!v->always_executed || v->maybe_multiple)
3693 if (loop_dump_stream)
3694 fprintf (loop_dump_stream,
3695 "Loop iterations: General induction var not set once in each iteration.\n");
3699 bl = REG_IV_CLASS (ivs, REGNO (v->src_reg));
3701 /* Increment value is mult_val times the increment value of the biv. */
3703 increment = biv_total_increment (bl);
3706 struct induction *biv_inc;
3708 increment = fold_rtx_mult_add (v->mult_val,
3709 extend_value_for_giv (v, increment),
3710 const0_rtx, v->mode);
3711 /* The caller assumes that one full increment has occurred at the
3712 first loop test. But that's not true when the biv is incremented
3713 after the giv is set (which is the usual case), e.g.:
3714 i = 6; do {;} while (i++ < 9) .
3715 Therefore, we bias the initial value by subtracting the amount of
3716 the increment that occurs between the giv set and the giv test. */
3717 for (biv_inc = bl->biv; biv_inc; biv_inc = biv_inc->next_iv)
3719 if (loop_insn_first_p (v->insn, biv_inc->insn))
3720 offset -= INTVAL (biv_inc->add_val);
3723 if (loop_dump_stream)
3724 fprintf (loop_dump_stream,
3725 "Loop iterations: Giv iterator, initial value bias %ld.\n",
3728 /* Initial value is mult_val times the biv's initial value plus
3729 add_val. Only useful if it is a constant. */
3730 biv_initial_value = extend_value_for_giv (v, bl->initial_value);
3732 = fold_rtx_mult_add (v->mult_val,
3733 plus_constant (biv_initial_value, offset),
3734 v->add_val, v->mode);
3738 if (loop_dump_stream)
3739 fprintf (loop_dump_stream,
3740 "Loop iterations: Not basic or general induction var.\n");
3744 if (initial_value == 0)
3749 switch (comparison_code)
3764 /* Cannot determine loop iterations with this case. */
3783 /* If the comparison value is an invariant register, then try to find
3784 its value from the insns before the start of the loop. */
3786 final_value = comparison_value;
3787 if (GET_CODE (comparison_value) == REG
3788 && loop_invariant_p (loop, comparison_value))
3790 final_value = loop_find_equiv_value (loop, comparison_value);
3792 /* If we don't get an invariant final value, we are better
3793 off with the original register. */
3794 if (! loop_invariant_p (loop, final_value))
3795 final_value = comparison_value;
3798 /* Calculate the approximate final value of the induction variable
3799 (on the last successful iteration). The exact final value
3800 depends on the branch operator, and increment sign. It will be
3801 wrong if the iteration variable is not incremented by one each
3802 time through the loop and (comparison_value + off_by_one -
3803 initial_value) % increment != 0.
3804 ??? Note that the final_value may overflow and thus final_larger
3805 will be bogus. A potentially infinite loop will be classified
3806 as immediate, e.g. for (i = 0x7ffffff0; i <= 0x7fffffff; i++) */
3808 final_value = plus_constant (final_value, off_by_one);
3810 /* Save the calculated values describing this loop's bounds, in case
3811 precondition_loop_p will need them later. These values can not be
3812 recalculated inside precondition_loop_p because strength reduction
3813 optimizations may obscure the loop's structure.
3815 These values are only required by precondition_loop_p and insert_bct
3816 whenever the number of iterations cannot be computed at compile time.
3817 Only the difference between final_value and initial_value is
3818 important. Note that final_value is only approximate. */
3819 loop_info->initial_value = initial_value;
3820 loop_info->comparison_value = comparison_value;
3821 loop_info->final_value = plus_constant (comparison_value, off_by_one);
3822 loop_info->increment = increment;
3823 loop_info->iteration_var = iteration_var;
3824 loop_info->comparison_code = comparison_code;
3827 /* Try to determine the iteration count for loops such
3828 as (for i = init; i < init + const; i++). When running the
3829 loop optimization twice, the first pass often converts simple
3830 loops into this form. */
3832 if (REG_P (initial_value))
3838 reg1 = initial_value;
3839 if (GET_CODE (final_value) == PLUS)
3840 reg2 = XEXP (final_value, 0), const2 = XEXP (final_value, 1);
3842 reg2 = final_value, const2 = const0_rtx;
3844 /* Check for initial_value = reg1, final_value = reg2 + const2,
3845 where reg1 != reg2. */
3846 if (REG_P (reg2) && reg2 != reg1)
3850 /* Find what reg1 is equivalent to. Hopefully it will
3851 either be reg2 or reg2 plus a constant. */
3852 temp = loop_find_equiv_value (loop, reg1);
3854 if (find_common_reg_term (temp, reg2))
3855 initial_value = temp;
3858 /* Find what reg2 is equivalent to. Hopefully it will
3859 either be reg1 or reg1 plus a constant. Let's ignore
3860 the latter case for now since it is not so common. */
3861 temp = loop_find_equiv_value (loop, reg2);
3863 if (temp == loop_info->iteration_var)
3864 temp = initial_value;
3866 final_value = (const2 == const0_rtx)
3867 ? reg1 : gen_rtx_PLUS (GET_MODE (reg1), reg1, const2);
3870 else if (loop->vtop && GET_CODE (reg2) == CONST_INT)
3874 /* When running the loop optimizer twice, check_dbra_loop
3875 further obfuscates reversible loops of the form:
3876 for (i = init; i < init + const; i++). We often end up with
3877 final_value = 0, initial_value = temp, temp = temp2 - init,
3878 where temp2 = init + const. If the loop has a vtop we
3879 can replace initial_value with const. */
3881 temp = loop_find_equiv_value (loop, reg1);
3883 if (GET_CODE (temp) == MINUS && REG_P (XEXP (temp, 0)))
3885 rtx temp2 = loop_find_equiv_value (loop, XEXP (temp, 0));
3887 if (GET_CODE (temp2) == PLUS
3888 && XEXP (temp2, 0) == XEXP (temp, 1))
3889 initial_value = XEXP (temp2, 1);
3894 /* If have initial_value = reg + const1 and final_value = reg +
3895 const2, then replace initial_value with const1 and final_value
3896 with const2. This should be safe since we are protected by the
3897 initial comparison before entering the loop if we have a vtop.
3898 For example, a + b < a + c is not equivalent to b < c for all a
3899 when using modulo arithmetic.
3901 ??? Without a vtop we could still perform the optimization if we check
3902 the initial and final values carefully. */
3904 && (reg_term = find_common_reg_term (initial_value, final_value)))
3906 initial_value = subtract_reg_term (initial_value, reg_term);
3907 final_value = subtract_reg_term (final_value, reg_term);
3910 loop_info->initial_equiv_value = initial_value;
3911 loop_info->final_equiv_value = final_value;
3913 /* For EQ comparison loops, we don't have a valid final value.
3914 Check this now so that we won't leave an invalid value if we
3915 return early for any other reason. */
3916 if (comparison_code == EQ)
3917 loop_info->final_equiv_value = loop_info->final_value = 0;
3921 if (loop_dump_stream)
3922 fprintf (loop_dump_stream,
3923 "Loop iterations: Increment value can't be calculated.\n");
3927 if (GET_CODE (increment) != CONST_INT)
3929 /* If we have a REG, check to see if REG holds a constant value. */
3930 /* ??? Other RTL, such as (neg (reg)) is possible here, but it isn't
3931 clear if it is worthwhile to try to handle such RTL. */
3932 if (GET_CODE (increment) == REG || GET_CODE (increment) == SUBREG)
3933 increment = loop_find_equiv_value (loop, increment);
3935 if (GET_CODE (increment) != CONST_INT)
3937 if (loop_dump_stream)
3939 fprintf (loop_dump_stream,
3940 "Loop iterations: Increment value not constant ");
3941 print_simple_rtl (loop_dump_stream, increment);
3942 fprintf (loop_dump_stream, ".\n");
3946 loop_info->increment = increment;
3949 if (GET_CODE (initial_value) != CONST_INT)
3951 if (loop_dump_stream)
3953 fprintf (loop_dump_stream,
3954 "Loop iterations: Initial value not constant ");
3955 print_simple_rtl (loop_dump_stream, initial_value);
3956 fprintf (loop_dump_stream, ".\n");
3960 else if (comparison_code == EQ)
3962 if (loop_dump_stream)
3963 fprintf (loop_dump_stream, "Loop iterations: EQ comparison loop.\n");
3966 else if (GET_CODE (final_value) != CONST_INT)
3968 if (loop_dump_stream)
3970 fprintf (loop_dump_stream,
3971 "Loop iterations: Final value not constant ");
3972 print_simple_rtl (loop_dump_stream, final_value);
3973 fprintf (loop_dump_stream, ".\n");
3978 /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
3981 = ((unsigned HOST_WIDE_INT) INTVAL (final_value)
3982 > (unsigned HOST_WIDE_INT) INTVAL (initial_value))
3983 - ((unsigned HOST_WIDE_INT) INTVAL (final_value)
3984 < (unsigned HOST_WIDE_INT) INTVAL (initial_value));
3986 final_larger = (INTVAL (final_value) > INTVAL (initial_value))
3987 - (INTVAL (final_value) < INTVAL (initial_value));
3989 if (INTVAL (increment) > 0)
3991 else if (INTVAL (increment) == 0)
3996 /* There are 27 different cases: compare_dir = -1, 0, 1;
3997 final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
3998 There are 4 normal cases, 4 reverse cases (where the iteration variable
3999 will overflow before the loop exits), 4 infinite loop cases, and 15
4000 immediate exit (0 or 1 iteration depending on loop type) cases.
4001 Only try to optimize the normal cases. */
4003 /* (compare_dir/final_larger/increment_dir)
4004 Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
4005 Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
4006 Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
4007 Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
4009 /* ?? If the meaning of reverse loops (where the iteration variable
4010 will overflow before the loop exits) is undefined, then could
4011 eliminate all of these special checks, and just always assume
4012 the loops are normal/immediate/infinite. Note that this means
4013 the sign of increment_dir does not have to be known. Also,
4014 since it does not really hurt if immediate exit loops or infinite loops
4015 are optimized, then that case could be ignored also, and hence all
4016 loops can be optimized.
4018 According to ANSI Spec, the reverse loop case result is undefined,
4019 because the action on overflow is undefined.
4021 See also the special test for NE loops below. */
4023 if (final_larger == increment_dir && final_larger != 0
4024 && (final_larger == compare_dir || compare_dir == 0))
4029 if (loop_dump_stream)
4030 fprintf (loop_dump_stream, "Loop iterations: Not normal loop.\n");
4034 /* Calculate the number of iterations, final_value is only an approximation,
4035 so correct for that. Note that abs_diff and n_iterations are
4036 unsigned, because they can be as large as 2^n - 1. */
4038 inc = INTVAL (increment);
4041 abs_diff = INTVAL (final_value) - INTVAL (initial_value);
4046 abs_diff = INTVAL (initial_value) - INTVAL (final_value);
4052 /* Given that iteration_var is going to iterate over its own mode,
4053 not HOST_WIDE_INT, disregard higher bits that might have come
4054 into the picture due to sign extension of initial and final
4056 abs_diff &= ((unsigned HOST_WIDE_INT) 1
4057 << (GET_MODE_BITSIZE (GET_MODE (iteration_var)) - 1)
4060 /* For NE tests, make sure that the iteration variable won't miss
4061 the final value. If abs_diff mod abs_incr is not zero, then the
4062 iteration variable will overflow before the loop exits, and we
4063 can not calculate the number of iterations. */
4064 if (compare_dir == 0 && (abs_diff % abs_inc) != 0)
4067 /* Note that the number of iterations could be calculated using
4068 (abs_diff + abs_inc - 1) / abs_inc, provided care was taken to
4069 handle potential overflow of the summation. */
4070 loop_info->n_iterations = abs_diff / abs_inc + ((abs_diff % abs_inc) != 0);
4071 return loop_info->n_iterations;
4074 /* Replace uses of split bivs with their split pseudo register. This is
4075 for original instructions which remain after loop unrolling without
4079 remap_split_bivs (loop, x)
4083 struct loop_ivs *ivs = LOOP_IVS (loop);
4091 code = GET_CODE (x);
4106 /* If non-reduced/final-value givs were split, then this would also
4107 have to remap those givs also. */
4109 if (REGNO (x) < ivs->n_regs
4110 && REG_IV_TYPE (ivs, REGNO (x)) == BASIC_INDUCT)
4111 return REG_IV_CLASS (ivs, REGNO (x))->biv->src_reg;
4118 fmt = GET_RTX_FORMAT (code);
4119 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
4122 XEXP (x, i) = remap_split_bivs (loop, XEXP (x, i));
4123 else if (fmt[i] == 'E')
4126 for (j = 0; j < XVECLEN (x, i); j++)
4127 XVECEXP (x, i, j) = remap_split_bivs (loop, XVECEXP (x, i, j));
4133 /* If FIRST_UID is a set of REGNO, and FIRST_UID dominates LAST_UID (e.g.
4134 FIST_UID is always executed if LAST_UID is), then return 1. Otherwise
4135 return 0. COPY_START is where we can start looking for the insns
4136 FIRST_UID and LAST_UID. COPY_END is where we stop looking for these
4139 If there is no JUMP_INSN between LOOP_START and FIRST_UID, then FIRST_UID
4140 must dominate LAST_UID.
4142 If there is a CODE_LABEL between FIRST_UID and LAST_UID, then FIRST_UID
4143 may not dominate LAST_UID.
4145 If there is no CODE_LABEL between FIRST_UID and LAST_UID, then FIRST_UID
4146 must dominate LAST_UID. */
4149 set_dominates_use (regno, first_uid, last_uid, copy_start, copy_end)
4156 int passed_jump = 0;
4157 rtx p = NEXT_INSN (copy_start);
4159 while (INSN_UID (p) != first_uid)
4161 if (GET_CODE (p) == JUMP_INSN)
4163 /* Could not find FIRST_UID. */
4169 /* Verify that FIRST_UID is an insn that entirely sets REGNO. */
4170 if (! INSN_P (p) || ! dead_or_set_regno_p (p, regno))
4173 /* FIRST_UID is always executed. */
4174 if (passed_jump == 0)
4177 while (INSN_UID (p) != last_uid)
4179 /* If we see a CODE_LABEL between FIRST_UID and LAST_UID, then we
4180 can not be sure that FIRST_UID dominates LAST_UID. */
4181 if (GET_CODE (p) == CODE_LABEL)
4183 /* Could not find LAST_UID, but we reached the end of the loop, so
4185 else if (p == copy_end)
4190 /* FIRST_UID is always executed if LAST_UID is executed. */
4194 /* This routine is called when the number of iterations for the unrolled
4195 loop is one. The goal is to identify a loop that begins with an
4196 unconditional branch to the loop continuation note (or a label just after).
4197 In this case, the unconditional branch that starts the loop needs to be
4198 deleted so that we execute the single iteration. */
4201 ujump_to_loop_cont (loop_start, loop_cont)
4205 rtx x, label, label_ref;
4207 /* See if loop start, or the next insn is an unconditional jump. */
4208 loop_start = next_nonnote_insn (loop_start);
4210 x = pc_set (loop_start);
4214 label_ref = SET_SRC (x);
4218 /* Examine insn after loop continuation note. Return if not a label. */
4219 label = next_nonnote_insn (loop_cont);
4220 if (label == 0 || GET_CODE (label) != CODE_LABEL)
4223 /* Return the loop start if the branch label matches the code label. */
4224 if (CODE_LABEL_NUMBER (label) == CODE_LABEL_NUMBER (XEXP (label_ref, 0)))