1 /* Try to unroll loops, and split induction variables.
2 Copyright (C) 1992, 93, 94, 95, 97, 98, 1999 Free Software Foundation, Inc.
3 Contributed by James E. Wilson, Cygnus Support/UC Berkeley.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
22 /* Try to unroll a loop, and split induction variables.
24 Loops for which the number of iterations can be calculated exactly are
25 handled specially. If the number of iterations times the insn_count is
26 less than MAX_UNROLLED_INSNS, then the loop is unrolled completely.
27 Otherwise, we try to unroll the loop a number of times modulo the number
28 of iterations, so that only one exit test will be needed. It is unrolled
29 a number of times approximately equal to MAX_UNROLLED_INSNS divided by
32 Otherwise, if the number of iterations can be calculated exactly at
33 run time, and the loop is always entered at the top, then we try to
34 precondition the loop. That is, at run time, calculate how many times
35 the loop will execute, and then execute the loop body a few times so
36 that the remaining iterations will be some multiple of 4 (or 2 if the
37 loop is large). Then fall through to a loop unrolled 4 (or 2) times,
38 with only one exit test needed at the end of the loop.
40 Otherwise, if the number of iterations can not be calculated exactly,
41 not even at run time, then we still unroll the loop a number of times
42 approximately equal to MAX_UNROLLED_INSNS divided by the insn count,
43 but there must be an exit test after each copy of the loop body.
45 For each induction variable, which is dead outside the loop (replaceable)
46 or for which we can easily calculate the final value, if we can easily
47 calculate its value at each place where it is set as a function of the
48 current loop unroll count and the variable's value at loop entry, then
49 the induction variable is split into `N' different variables, one for
50 each copy of the loop body. One variable is live across the backward
51 branch, and the others are all calculated as a function of this variable.
52 This helps eliminate data dependencies, and leads to further opportunities
55 /* Possible improvements follow: */
57 /* ??? Add an extra pass somewhere to determine whether unrolling will
58 give any benefit. E.g. after generating all unrolled insns, compute the
59 cost of all insns and compare against cost of insns in rolled loop.
61 - On traditional architectures, unrolling a non-constant bound loop
62 is a win if there is a giv whose only use is in memory addresses, the
63 memory addresses can be split, and hence giv increments can be
65 - It is also a win if the loop is executed many times, and preconditioning
66 can be performed for the loop.
67 Add code to check for these and similar cases. */
69 /* ??? Improve control of which loops get unrolled. Could use profiling
70 info to only unroll the most commonly executed loops. Perhaps have
71 a user specifyable option to control the amount of code expansion,
72 or the percent of loops to consider for unrolling. Etc. */
74 /* ??? Look at the register copies inside the loop to see if they form a
75 simple permutation. If so, iterate the permutation until it gets back to
76 the start state. This is how many times we should unroll the loop, for
77 best results, because then all register copies can be eliminated.
78 For example, the lisp nreverse function should be unrolled 3 times
87 ??? The number of times to unroll the loop may also be based on data
88 references in the loop. For example, if we have a loop that references
89 x[i-1], x[i], and x[i+1], we should unroll it a multiple of 3 times. */
91 /* ??? Add some simple linear equation solving capability so that we can
92 determine the number of loop iterations for more complex loops.
93 For example, consider this loop from gdb
94 #define SWAP_TARGET_AND_HOST(buffer,len)
97 char *p = (char *) buffer;
98 char *q = ((char *) buffer) + len - 1;
99 int iterations = (len + 1) >> 1;
101 for (p; p < q; p++, q--;)
109 start value = p = &buffer + current_iteration
110 end value = q = &buffer + len - 1 - current_iteration
111 Given the loop exit test of "p < q", then there must be "q - p" iterations,
112 set equal to zero and solve for number of iterations:
113 q - p = len - 1 - 2*current_iteration = 0
114 current_iteration = (len - 1) / 2
115 Hence, there are (len - 1) / 2 (rounded up to the nearest integer)
116 iterations of this loop. */
118 /* ??? Currently, no labels are marked as loop invariant when doing loop
119 unrolling. This is because an insn inside the loop, that loads the address
120 of a label inside the loop into a register, could be moved outside the loop
121 by the invariant code motion pass if labels were invariant. If the loop
122 is subsequently unrolled, the code will be wrong because each unrolled
123 body of the loop will use the same address, whereas each actually needs a
124 different address. A case where this happens is when a loop containing
125 a switch statement is unrolled.
127 It would be better to let labels be considered invariant. When we
128 unroll loops here, check to see if any insns using a label local to the
129 loop were moved before the loop. If so, then correct the problem, by
130 moving the insn back into the loop, or perhaps replicate the insn before
131 the loop, one copy for each time the loop is unrolled. */
133 /* The prime factors looked for when trying to unroll a loop by some
134 number which is modulo the total number of iterations. Just checking
135 for these 4 prime factors will find at least one factor for 75% of
136 all numbers theoretically. Practically speaking, this will succeed
137 almost all of the time since loops are generally a multiple of 2
140 #define NUM_FACTORS 4
142 struct _factor { int factor, count; } factors[NUM_FACTORS]
143 = { {2, 0}, {3, 0}, {5, 0}, {7, 0}};
145 /* Describes the different types of loop unrolling performed. */
147 enum unroll_types { UNROLL_COMPLETELY, UNROLL_MODULO, UNROLL_NAIVE };
153 #include "insn-config.h"
154 #include "integrate.h"
158 #include "function.h"
163 /* This controls which loops are unrolled, and by how much we unroll
166 #ifndef MAX_UNROLLED_INSNS
167 #define MAX_UNROLLED_INSNS 100
170 /* Indexed by register number, if non-zero, then it contains a pointer
171 to a struct induction for a DEST_REG giv which has been combined with
172 one of more address givs. This is needed because whenever such a DEST_REG
173 giv is modified, we must modify the value of all split address givs
174 that were combined with this DEST_REG giv. */
176 static struct induction **addr_combined_regs;
178 /* Indexed by register number, if this is a splittable induction variable,
179 then this will hold the current value of the register, which depends on the
182 static rtx *splittable_regs;
184 /* Indexed by register number, if this is a splittable induction variable,
185 this indicates if it was made from a derived giv. */
186 static char *derived_regs;
188 /* Indexed by register number, if this is a splittable induction variable,
189 then this will hold the number of instructions in the loop that modify
190 the induction variable. Used to ensure that only the last insn modifying
191 a split iv will update the original iv of the dest. */
193 static int *splittable_regs_updates;
195 /* Forward declarations. */
197 static void init_reg_map PROTO((struct inline_remap *, int));
198 static rtx calculate_giv_inc PROTO((rtx, rtx, int));
199 static rtx initial_reg_note_copy PROTO((rtx, struct inline_remap *));
200 static void final_reg_note_copy PROTO((rtx, struct inline_remap *));
201 static void copy_loop_body PROTO((rtx, rtx, struct inline_remap *, rtx, int,
202 enum unroll_types, rtx, rtx, rtx, rtx));
203 static void iteration_info PROTO((rtx, rtx *, rtx *, rtx, rtx));
204 static int find_splittable_regs PROTO((enum unroll_types, rtx, rtx, rtx, int,
205 unsigned HOST_WIDE_INT));
206 static int find_splittable_givs PROTO((struct iv_class *, enum unroll_types,
207 rtx, rtx, rtx, int));
208 static int reg_dead_after_loop PROTO((rtx, rtx, rtx));
209 static rtx fold_rtx_mult_add PROTO((rtx, rtx, rtx, enum machine_mode));
210 static int verify_addresses PROTO((struct induction *, rtx, int));
211 static rtx remap_split_bivs PROTO((rtx));
212 static rtx find_common_reg_term PROTO((rtx, rtx));
213 static rtx subtract_reg_term PROTO((rtx, rtx));
214 static rtx loop_find_equiv_value PROTO((rtx, rtx));
216 /* Try to unroll one loop and split induction variables in the loop.
218 The loop is described by the arguments LOOP_END, INSN_COUNT, and
219 LOOP_START. END_INSERT_BEFORE indicates where insns should be added
220 which need to be executed when the loop falls through. STRENGTH_REDUCTION_P
221 indicates whether information generated in the strength reduction pass
224 This function is intended to be called from within `strength_reduce'
228 unroll_loop (loop_end, insn_count, loop_start, end_insert_before,
229 loop_info, strength_reduce_p)
233 rtx end_insert_before;
234 struct loop_info *loop_info;
235 int strength_reduce_p;
238 int unroll_number = 1;
239 rtx copy_start, copy_end;
240 rtx insn, sequence, pattern, tem;
241 int max_labelno, max_insnno;
243 struct inline_remap *map;
244 char *local_label = NULL;
246 int max_local_regnum;
251 int splitting_not_safe = 0;
252 enum unroll_types unroll_type;
253 int loop_preconditioned = 0;
255 /* This points to the last real insn in the loop, which should be either
256 a JUMP_INSN (for conditional jumps) or a BARRIER (for unconditional
260 /* Don't bother unrolling huge loops. Since the minimum factor is
261 two, loops greater than one half of MAX_UNROLLED_INSNS will never
263 if (insn_count > MAX_UNROLLED_INSNS / 2)
265 if (loop_dump_stream)
266 fprintf (loop_dump_stream, "Unrolling failure: Loop too big.\n");
270 /* When emitting debugger info, we can't unroll loops with unequal numbers
271 of block_beg and block_end notes, because that would unbalance the block
272 structure of the function. This can happen as a result of the
273 "if (foo) bar; else break;" optimization in jump.c. */
274 /* ??? Gcc has a general policy that -g is never supposed to change the code
275 that the compiler emits, so we must disable this optimization always,
276 even if debug info is not being output. This is rare, so this should
277 not be a significant performance problem. */
279 if (1 /* write_symbols != NO_DEBUG */)
281 int block_begins = 0;
284 for (insn = loop_start; insn != loop_end; insn = NEXT_INSN (insn))
286 if (GET_CODE (insn) == NOTE)
288 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG)
290 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END)
295 if (block_begins != block_ends)
297 if (loop_dump_stream)
298 fprintf (loop_dump_stream,
299 "Unrolling failure: Unbalanced block notes.\n");
304 /* Determine type of unroll to perform. Depends on the number of iterations
305 and the size of the loop. */
307 /* If there is no strength reduce info, then set
308 loop_info->n_iterations to zero. This can happen if
309 strength_reduce can't find any bivs in the loop. A value of zero
310 indicates that the number of iterations could not be calculated. */
312 if (! strength_reduce_p)
313 loop_info->n_iterations = 0;
315 if (loop_dump_stream && loop_info->n_iterations > 0)
317 fputs ("Loop unrolling: ", loop_dump_stream);
318 fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC,
319 loop_info->n_iterations);
320 fputs (" iterations.\n", loop_dump_stream);
323 /* Find and save a pointer to the last nonnote insn in the loop. */
325 last_loop_insn = prev_nonnote_insn (loop_end);
327 /* Calculate how many times to unroll the loop. Indicate whether or
328 not the loop is being completely unrolled. */
330 if (loop_info->n_iterations == 1)
332 /* If number of iterations is exactly 1, then eliminate the compare and
333 branch at the end of the loop since they will never be taken.
334 Then return, since no other action is needed here. */
336 /* If the last instruction is not a BARRIER or a JUMP_INSN, then
337 don't do anything. */
339 if (GET_CODE (last_loop_insn) == BARRIER)
341 /* Delete the jump insn. This will delete the barrier also. */
342 delete_insn (PREV_INSN (last_loop_insn));
344 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
347 rtx prev = PREV_INSN (last_loop_insn);
349 delete_insn (last_loop_insn);
351 /* The immediately preceding insn may be a compare which must be
353 if (sets_cc0_p (prev))
359 else if (loop_info->n_iterations > 0
360 && loop_info->n_iterations * insn_count < MAX_UNROLLED_INSNS)
362 unroll_number = loop_info->n_iterations;
363 unroll_type = UNROLL_COMPLETELY;
365 else if (loop_info->n_iterations > 0)
367 /* Try to factor the number of iterations. Don't bother with the
368 general case, only using 2, 3, 5, and 7 will get 75% of all
369 numbers theoretically, and almost all in practice. */
371 for (i = 0; i < NUM_FACTORS; i++)
372 factors[i].count = 0;
374 temp = loop_info->n_iterations;
375 for (i = NUM_FACTORS - 1; i >= 0; i--)
376 while (temp % factors[i].factor == 0)
379 temp = temp / factors[i].factor;
382 /* Start with the larger factors first so that we generally
383 get lots of unrolling. */
387 for (i = 3; i >= 0; i--)
388 while (factors[i].count--)
390 if (temp * factors[i].factor < MAX_UNROLLED_INSNS)
392 unroll_number *= factors[i].factor;
393 temp *= factors[i].factor;
399 /* If we couldn't find any factors, then unroll as in the normal
401 if (unroll_number == 1)
403 if (loop_dump_stream)
404 fprintf (loop_dump_stream,
405 "Loop unrolling: No factors found.\n");
408 unroll_type = UNROLL_MODULO;
412 /* Default case, calculate number of times to unroll loop based on its
414 if (unroll_number == 1)
416 if (8 * insn_count < MAX_UNROLLED_INSNS)
418 else if (4 * insn_count < MAX_UNROLLED_INSNS)
423 unroll_type = UNROLL_NAIVE;
426 /* Now we know how many times to unroll the loop. */
428 if (loop_dump_stream)
429 fprintf (loop_dump_stream,
430 "Unrolling loop %d times.\n", unroll_number);
433 if (unroll_type == UNROLL_COMPLETELY || unroll_type == UNROLL_MODULO)
435 /* Loops of these types can start with jump down to the exit condition
436 in rare circumstances.
438 Consider a pair of nested loops where the inner loop is part
439 of the exit code for the outer loop.
441 In this case jump.c will not duplicate the exit test for the outer
442 loop, so it will start with a jump to the exit code.
444 Then consider if the inner loop turns out to iterate once and
445 only once. We will end up deleting the jumps associated with
446 the inner loop. However, the loop notes are not removed from
447 the instruction stream.
449 And finally assume that we can compute the number of iterations
452 In this case unroll may want to unroll the outer loop even though
453 it starts with a jump to the outer loop's exit code.
455 We could try to optimize this case, but it hardly seems worth it.
456 Just return without unrolling the loop in such cases. */
459 while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
460 insn = NEXT_INSN (insn);
461 if (GET_CODE (insn) == JUMP_INSN)
465 if (unroll_type == UNROLL_COMPLETELY)
467 /* Completely unrolling the loop: Delete the compare and branch at
468 the end (the last two instructions). This delete must done at the
469 very end of loop unrolling, to avoid problems with calls to
470 back_branch_in_range_p, which is called by find_splittable_regs.
471 All increments of splittable bivs/givs are changed to load constant
474 copy_start = loop_start;
476 /* Set insert_before to the instruction immediately after the JUMP_INSN
477 (or BARRIER), so that any NOTEs between the JUMP_INSN and the end of
478 the loop will be correctly handled by copy_loop_body. */
479 insert_before = NEXT_INSN (last_loop_insn);
481 /* Set copy_end to the insn before the jump at the end of the loop. */
482 if (GET_CODE (last_loop_insn) == BARRIER)
483 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
484 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
486 copy_end = PREV_INSN (last_loop_insn);
488 /* The instruction immediately before the JUMP_INSN may be a compare
489 instruction which we do not want to copy. */
490 if (sets_cc0_p (PREV_INSN (copy_end)))
491 copy_end = PREV_INSN (copy_end);
496 /* We currently can't unroll a loop if it doesn't end with a
497 JUMP_INSN. There would need to be a mechanism that recognizes
498 this case, and then inserts a jump after each loop body, which
499 jumps to after the last loop body. */
500 if (loop_dump_stream)
501 fprintf (loop_dump_stream,
502 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
506 else if (unroll_type == UNROLL_MODULO)
508 /* Partially unrolling the loop: The compare and branch at the end
509 (the last two instructions) must remain. Don't copy the compare
510 and branch instructions at the end of the loop. Insert the unrolled
511 code immediately before the compare/branch at the end so that the
512 code will fall through to them as before. */
514 copy_start = loop_start;
516 /* Set insert_before to the jump insn at the end of the loop.
517 Set copy_end to before the jump insn at the end of the loop. */
518 if (GET_CODE (last_loop_insn) == BARRIER)
520 insert_before = PREV_INSN (last_loop_insn);
521 copy_end = PREV_INSN (insert_before);
523 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
525 insert_before = last_loop_insn;
527 /* The instruction immediately before the JUMP_INSN may be a compare
528 instruction which we do not want to copy or delete. */
529 if (sets_cc0_p (PREV_INSN (insert_before)))
530 insert_before = PREV_INSN (insert_before);
532 copy_end = PREV_INSN (insert_before);
536 /* We currently can't unroll a loop if it doesn't end with a
537 JUMP_INSN. There would need to be a mechanism that recognizes
538 this case, and then inserts a jump after each loop body, which
539 jumps to after the last loop body. */
540 if (loop_dump_stream)
541 fprintf (loop_dump_stream,
542 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
548 /* Normal case: Must copy the compare and branch instructions at the
551 if (GET_CODE (last_loop_insn) == BARRIER)
553 /* Loop ends with an unconditional jump and a barrier.
554 Handle this like above, don't copy jump and barrier.
555 This is not strictly necessary, but doing so prevents generating
556 unconditional jumps to an immediately following label.
558 This will be corrected below if the target of this jump is
559 not the start_label. */
561 insert_before = PREV_INSN (last_loop_insn);
562 copy_end = PREV_INSN (insert_before);
564 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
566 /* Set insert_before to immediately after the JUMP_INSN, so that
567 NOTEs at the end of the loop will be correctly handled by
569 insert_before = NEXT_INSN (last_loop_insn);
570 copy_end = last_loop_insn;
574 /* We currently can't unroll a loop if it doesn't end with a
575 JUMP_INSN. There would need to be a mechanism that recognizes
576 this case, and then inserts a jump after each loop body, which
577 jumps to after the last loop body. */
578 if (loop_dump_stream)
579 fprintf (loop_dump_stream,
580 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
584 /* If copying exit test branches because they can not be eliminated,
585 then must convert the fall through case of the branch to a jump past
586 the end of the loop. Create a label to emit after the loop and save
587 it for later use. Do not use the label after the loop, if any, since
588 it might be used by insns outside the loop, or there might be insns
589 added before it later by final_[bg]iv_value which must be after
590 the real exit label. */
591 exit_label = gen_label_rtx ();
594 while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
595 insn = NEXT_INSN (insn);
597 if (GET_CODE (insn) == JUMP_INSN)
599 /* The loop starts with a jump down to the exit condition test.
600 Start copying the loop after the barrier following this
602 copy_start = NEXT_INSN (insn);
604 /* Splitting induction variables doesn't work when the loop is
605 entered via a jump to the bottom, because then we end up doing
606 a comparison against a new register for a split variable, but
607 we did not execute the set insn for the new register because
608 it was skipped over. */
609 splitting_not_safe = 1;
610 if (loop_dump_stream)
611 fprintf (loop_dump_stream,
612 "Splitting not safe, because loop not entered at top.\n");
615 copy_start = loop_start;
618 /* This should always be the first label in the loop. */
619 start_label = NEXT_INSN (copy_start);
620 /* There may be a line number note and/or a loop continue note here. */
621 while (GET_CODE (start_label) == NOTE)
622 start_label = NEXT_INSN (start_label);
623 if (GET_CODE (start_label) != CODE_LABEL)
625 /* This can happen as a result of jump threading. If the first insns in
626 the loop test the same condition as the loop's backward jump, or the
627 opposite condition, then the backward jump will be modified to point
628 to elsewhere, and the loop's start label is deleted.
630 This case currently can not be handled by the loop unrolling code. */
632 if (loop_dump_stream)
633 fprintf (loop_dump_stream,
634 "Unrolling failure: unknown insns between BEG note and loop label.\n");
637 if (LABEL_NAME (start_label))
639 /* The jump optimization pass must have combined the original start label
640 with a named label for a goto. We can't unroll this case because
641 jumps which go to the named label must be handled differently than
642 jumps to the loop start, and it is impossible to differentiate them
644 if (loop_dump_stream)
645 fprintf (loop_dump_stream,
646 "Unrolling failure: loop start label is gone\n");
650 if (unroll_type == UNROLL_NAIVE
651 && GET_CODE (last_loop_insn) == BARRIER
652 && start_label != JUMP_LABEL (PREV_INSN (last_loop_insn)))
654 /* In this case, we must copy the jump and barrier, because they will
655 not be converted to jumps to an immediately following label. */
657 insert_before = NEXT_INSN (last_loop_insn);
658 copy_end = last_loop_insn;
661 if (unroll_type == UNROLL_NAIVE
662 && GET_CODE (last_loop_insn) == JUMP_INSN
663 && start_label != JUMP_LABEL (last_loop_insn))
665 /* ??? The loop ends with a conditional branch that does not branch back
666 to the loop start label. In this case, we must emit an unconditional
667 branch to the loop exit after emitting the final branch.
668 copy_loop_body does not have support for this currently, so we
669 give up. It doesn't seem worthwhile to unroll anyways since
670 unrolling would increase the number of branch instructions
672 if (loop_dump_stream)
673 fprintf (loop_dump_stream,
674 "Unrolling failure: final conditional branch not to loop start\n");
678 /* Allocate a translation table for the labels and insn numbers.
679 They will be filled in as we copy the insns in the loop. */
681 max_labelno = max_label_num ();
682 max_insnno = get_max_uid ();
684 map = (struct inline_remap *) alloca (sizeof (struct inline_remap));
686 map->integrating = 0;
687 map->const_equiv_varray = 0;
689 /* Allocate the label map. */
693 map->label_map = (rtx *) alloca (max_labelno * sizeof (rtx));
695 local_label = (char *) alloca (max_labelno);
696 bzero (local_label, max_labelno);
701 /* Search the loop and mark all local labels, i.e. the ones which have to
702 be distinct labels when copied. For all labels which might be
703 non-local, set their label_map entries to point to themselves.
704 If they happen to be local their label_map entries will be overwritten
705 before the loop body is copied. The label_map entries for local labels
706 will be set to a different value each time the loop body is copied. */
708 for (insn = copy_start; insn != loop_end; insn = NEXT_INSN (insn))
712 if (GET_CODE (insn) == CODE_LABEL)
713 local_label[CODE_LABEL_NUMBER (insn)] = 1;
714 else if (GET_CODE (insn) == JUMP_INSN)
716 if (JUMP_LABEL (insn))
717 set_label_in_map (map,
718 CODE_LABEL_NUMBER (JUMP_LABEL (insn)),
720 else if (GET_CODE (PATTERN (insn)) == ADDR_VEC
721 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
723 rtx pat = PATTERN (insn);
724 int diff_vec_p = GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC;
725 int len = XVECLEN (pat, diff_vec_p);
728 for (i = 0; i < len; i++)
730 label = XEXP (XVECEXP (pat, diff_vec_p, i), 0);
731 set_label_in_map (map,
732 CODE_LABEL_NUMBER (label),
737 else if ((note = find_reg_note (insn, REG_LABEL, NULL_RTX)))
738 set_label_in_map (map, CODE_LABEL_NUMBER (XEXP (note, 0)),
742 /* Allocate space for the insn map. */
744 map->insn_map = (rtx *) alloca (max_insnno * sizeof (rtx));
746 /* Set this to zero, to indicate that we are doing loop unrolling,
747 not function inlining. */
748 map->inline_target = 0;
750 /* The register and constant maps depend on the number of registers
751 present, so the final maps can't be created until after
752 find_splittable_regs is called. However, they are needed for
753 preconditioning, so we create temporary maps when preconditioning
756 /* The preconditioning code may allocate two new pseudo registers. */
757 maxregnum = max_reg_num ();
759 /* local_regno is only valid for regnos < max_local_regnum. */
760 max_local_regnum = maxregnum;
762 /* Allocate and zero out the splittable_regs and addr_combined_regs
763 arrays. These must be zeroed here because they will be used if
764 loop preconditioning is performed, and must be zero for that case.
766 It is safe to do this here, since the extra registers created by the
767 preconditioning code and find_splittable_regs will never be used
768 to access the splittable_regs[] and addr_combined_regs[] arrays. */
770 splittable_regs = (rtx *) alloca (maxregnum * sizeof (rtx));
771 bzero ((char *) splittable_regs, maxregnum * sizeof (rtx));
772 derived_regs = alloca (maxregnum);
773 bzero (derived_regs, maxregnum);
774 splittable_regs_updates = (int *) alloca (maxregnum * sizeof (int));
775 bzero ((char *) splittable_regs_updates, maxregnum * sizeof (int));
777 = (struct induction **) alloca (maxregnum * sizeof (struct induction *));
778 bzero ((char *) addr_combined_regs, maxregnum * sizeof (struct induction *));
779 local_regno = (char *) alloca (maxregnum);
780 bzero (local_regno, maxregnum);
782 /* Mark all local registers, i.e. the ones which are referenced only
784 if (INSN_UID (copy_end) < max_uid_for_loop)
786 int copy_start_luid = INSN_LUID (copy_start);
787 int copy_end_luid = INSN_LUID (copy_end);
789 /* If a register is used in the jump insn, we must not duplicate it
790 since it will also be used outside the loop. */
791 if (GET_CODE (copy_end) == JUMP_INSN)
794 /* If we have a target that uses cc0, then we also must not duplicate
795 the insn that sets cc0 before the jump insn, if one is present. */
797 if (GET_CODE (copy_end) == JUMP_INSN && sets_cc0_p (PREV_INSN (copy_end)))
801 /* If copy_start points to the NOTE that starts the loop, then we must
802 use the next luid, because invariant pseudo-regs moved out of the loop
803 have their lifetimes modified to start here, but they are not safe
805 if (copy_start == loop_start)
808 /* If a pseudo's lifetime is entirely contained within this loop, then we
809 can use a different pseudo in each unrolled copy of the loop. This
810 results in better code. */
811 /* We must limit the generic test to max_reg_before_loop, because only
812 these pseudo registers have valid regno_first_uid info. */
813 for (j = FIRST_PSEUDO_REGISTER; j < max_reg_before_loop; ++j)
814 if (REGNO_FIRST_UID (j) > 0 && REGNO_FIRST_UID (j) <= max_uid_for_loop
815 && uid_luid[REGNO_FIRST_UID (j)] >= copy_start_luid
816 && REGNO_LAST_UID (j) > 0 && REGNO_LAST_UID (j) <= max_uid_for_loop
817 && uid_luid[REGNO_LAST_UID (j)] <= copy_end_luid)
819 /* However, we must also check for loop-carried dependencies.
820 If the value the pseudo has at the end of iteration X is
821 used by iteration X+1, then we can not use a different pseudo
822 for each unrolled copy of the loop. */
823 /* A pseudo is safe if regno_first_uid is a set, and this
824 set dominates all instructions from regno_first_uid to
826 /* ??? This check is simplistic. We would get better code if
827 this check was more sophisticated. */
828 if (set_dominates_use (j, REGNO_FIRST_UID (j), REGNO_LAST_UID (j),
829 copy_start, copy_end))
832 if (loop_dump_stream)
835 fprintf (loop_dump_stream, "Marked reg %d as local\n", j);
837 fprintf (loop_dump_stream, "Did not mark reg %d as local\n",
841 /* Givs that have been created from multiple biv increments always have
843 for (j = first_increment_giv; j <= last_increment_giv; j++)
846 if (loop_dump_stream)
847 fprintf (loop_dump_stream, "Marked reg %d as local\n", j);
851 /* If this loop requires exit tests when unrolled, check to see if we
852 can precondition the loop so as to make the exit tests unnecessary.
853 Just like variable splitting, this is not safe if the loop is entered
854 via a jump to the bottom. Also, can not do this if no strength
855 reduce info, because precondition_loop_p uses this info. */
857 /* Must copy the loop body for preconditioning before the following
858 find_splittable_regs call since that will emit insns which need to
859 be after the preconditioned loop copies, but immediately before the
860 unrolled loop copies. */
862 /* Also, it is not safe to split induction variables for the preconditioned
863 copies of the loop body. If we split induction variables, then the code
864 assumes that each induction variable can be represented as a function
865 of its initial value and the loop iteration number. This is not true
866 in this case, because the last preconditioned copy of the loop body
867 could be any iteration from the first up to the `unroll_number-1'th,
868 depending on the initial value of the iteration variable. Therefore
869 we can not split induction variables here, because we can not calculate
870 their value. Hence, this code must occur before find_splittable_regs
873 if (unroll_type == UNROLL_NAIVE && ! splitting_not_safe && strength_reduce_p)
875 rtx initial_value, final_value, increment;
876 enum machine_mode mode;
878 if (precondition_loop_p (loop_start, loop_info,
879 &initial_value, &final_value, &increment,
884 int abs_inc, neg_inc;
886 map->reg_map = (rtx *) alloca (maxregnum * sizeof (rtx));
888 VARRAY_CONST_EQUIV_INIT (map->const_equiv_varray, maxregnum,
890 global_const_equiv_varray = map->const_equiv_varray;
892 init_reg_map (map, maxregnum);
894 /* Limit loop unrolling to 4, since this will make 7 copies of
896 if (unroll_number > 4)
899 /* Save the absolute value of the increment, and also whether or
900 not it is negative. */
902 abs_inc = INTVAL (increment);
911 /* Calculate the difference between the final and initial values.
912 Final value may be a (plus (reg x) (const_int 1)) rtx.
913 Let the following cse pass simplify this if initial value is
916 We must copy the final and initial values here to avoid
917 improperly shared rtl. */
919 diff = expand_binop (mode, sub_optab, copy_rtx (final_value),
920 copy_rtx (initial_value), NULL_RTX, 0,
923 /* Now calculate (diff % (unroll * abs (increment))) by using an
925 diff = expand_binop (GET_MODE (diff), and_optab, diff,
926 GEN_INT (unroll_number * abs_inc - 1),
927 NULL_RTX, 0, OPTAB_LIB_WIDEN);
929 /* Now emit a sequence of branches to jump to the proper precond
932 labels = (rtx *) alloca (sizeof (rtx) * unroll_number);
933 for (i = 0; i < unroll_number; i++)
934 labels[i] = gen_label_rtx ();
936 /* Check for the case where the initial value is greater than or
937 equal to the final value. In that case, we want to execute
938 exactly one loop iteration. The code below will fail for this
939 case. This check does not apply if the loop has a NE
940 comparison at the end. */
942 if (loop_info->comparison_code != NE)
944 emit_cmp_and_jump_insns (initial_value, final_value,
946 NULL_RTX, mode, 0, 0, labels[1]);
947 JUMP_LABEL (get_last_insn ()) = labels[1];
948 LABEL_NUSES (labels[1])++;
951 /* Assuming the unroll_number is 4, and the increment is 2, then
952 for a negative increment: for a positive increment:
953 diff = 0,1 precond 0 diff = 0,7 precond 0
954 diff = 2,3 precond 3 diff = 1,2 precond 1
955 diff = 4,5 precond 2 diff = 3,4 precond 2
956 diff = 6,7 precond 1 diff = 5,6 precond 3 */
958 /* We only need to emit (unroll_number - 1) branches here, the
959 last case just falls through to the following code. */
961 /* ??? This would give better code if we emitted a tree of branches
962 instead of the current linear list of branches. */
964 for (i = 0; i < unroll_number - 1; i++)
967 enum rtx_code cmp_code;
969 /* For negative increments, must invert the constant compared
970 against, except when comparing against zero. */
978 cmp_const = unroll_number - i;
987 emit_cmp_and_jump_insns (diff, GEN_INT (abs_inc * cmp_const),
988 cmp_code, NULL_RTX, mode, 0, 0,
990 JUMP_LABEL (get_last_insn ()) = labels[i];
991 LABEL_NUSES (labels[i])++;
994 /* If the increment is greater than one, then we need another branch,
995 to handle other cases equivalent to 0. */
997 /* ??? This should be merged into the code above somehow to help
998 simplify the code here, and reduce the number of branches emitted.
999 For the negative increment case, the branch here could easily
1000 be merged with the `0' case branch above. For the positive
1001 increment case, it is not clear how this can be simplified. */
1006 enum rtx_code cmp_code;
1010 cmp_const = abs_inc - 1;
1015 cmp_const = abs_inc * (unroll_number - 1) + 1;
1019 emit_cmp_and_jump_insns (diff, GEN_INT (cmp_const), cmp_code,
1020 NULL_RTX, mode, 0, 0, labels[0]);
1021 JUMP_LABEL (get_last_insn ()) = labels[0];
1022 LABEL_NUSES (labels[0])++;
1025 sequence = gen_sequence ();
1027 emit_insn_before (sequence, loop_start);
1029 /* Only the last copy of the loop body here needs the exit
1030 test, so set copy_end to exclude the compare/branch here,
1031 and then reset it inside the loop when get to the last
1034 if (GET_CODE (last_loop_insn) == BARRIER)
1035 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
1036 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
1038 copy_end = PREV_INSN (last_loop_insn);
1040 /* The immediately preceding insn may be a compare which we do not
1042 if (sets_cc0_p (PREV_INSN (copy_end)))
1043 copy_end = PREV_INSN (copy_end);
1049 for (i = 1; i < unroll_number; i++)
1051 emit_label_after (labels[unroll_number - i],
1052 PREV_INSN (loop_start));
1054 bzero ((char *) map->insn_map, max_insnno * sizeof (rtx));
1055 bzero ((char *) &VARRAY_CONST_EQUIV (map->const_equiv_varray, 0),
1056 (VARRAY_SIZE (map->const_equiv_varray)
1057 * sizeof (struct const_equiv_data)));
1060 for (j = 0; j < max_labelno; j++)
1062 set_label_in_map (map, j, gen_label_rtx ());
1064 for (j = FIRST_PSEUDO_REGISTER; j < max_local_regnum; j++)
1067 map->reg_map[j] = gen_reg_rtx (GET_MODE (regno_reg_rtx[j]));
1068 record_base_value (REGNO (map->reg_map[j]),
1069 regno_reg_rtx[j], 0);
1071 /* The last copy needs the compare/branch insns at the end,
1072 so reset copy_end here if the loop ends with a conditional
1075 if (i == unroll_number - 1)
1077 if (GET_CODE (last_loop_insn) == BARRIER)
1078 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
1080 copy_end = last_loop_insn;
1083 /* None of the copies are the `last_iteration', so just
1084 pass zero for that parameter. */
1085 copy_loop_body (copy_start, copy_end, map, exit_label, 0,
1086 unroll_type, start_label, loop_end,
1087 loop_start, copy_end);
1089 emit_label_after (labels[0], PREV_INSN (loop_start));
1091 if (GET_CODE (last_loop_insn) == BARRIER)
1093 insert_before = PREV_INSN (last_loop_insn);
1094 copy_end = PREV_INSN (insert_before);
1098 insert_before = last_loop_insn;
1100 /* The instruction immediately before the JUMP_INSN may be a compare
1101 instruction which we do not want to copy or delete. */
1102 if (sets_cc0_p (PREV_INSN (insert_before)))
1103 insert_before = PREV_INSN (insert_before);
1105 copy_end = PREV_INSN (insert_before);
1108 /* Set unroll type to MODULO now. */
1109 unroll_type = UNROLL_MODULO;
1110 loop_preconditioned = 1;
1114 /* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
1115 the loop unless all loops are being unrolled. */
1116 if (unroll_type == UNROLL_NAIVE && ! flag_unroll_all_loops)
1118 if (loop_dump_stream)
1119 fprintf (loop_dump_stream, "Unrolling failure: Naive unrolling not being done.\n");
1123 /* At this point, we are guaranteed to unroll the loop. */
1125 /* Keep track of the unroll factor for the loop. */
1126 loop_info->unroll_number = unroll_number;
1128 /* For each biv and giv, determine whether it can be safely split into
1129 a different variable for each unrolled copy of the loop body.
1130 We precalculate and save this info here, since computing it is
1133 Do this before deleting any instructions from the loop, so that
1134 back_branch_in_range_p will work correctly. */
1136 if (splitting_not_safe)
1139 temp = find_splittable_regs (unroll_type, loop_start, loop_end,
1140 end_insert_before, unroll_number,
1141 loop_info->n_iterations);
1143 /* find_splittable_regs may have created some new registers, so must
1144 reallocate the reg_map with the new larger size, and must realloc
1145 the constant maps also. */
1147 maxregnum = max_reg_num ();
1148 map->reg_map = (rtx *) alloca (maxregnum * sizeof (rtx));
1150 init_reg_map (map, maxregnum);
1152 if (map->const_equiv_varray == 0)
1153 VARRAY_CONST_EQUIV_INIT (map->const_equiv_varray,
1154 maxregnum + temp * unroll_number * 2,
1156 global_const_equiv_varray = map->const_equiv_varray;
1158 /* Search the list of bivs and givs to find ones which need to be remapped
1159 when split, and set their reg_map entry appropriately. */
1161 for (bl = loop_iv_list; bl; bl = bl->next)
1163 if (REGNO (bl->biv->src_reg) != bl->regno)
1164 map->reg_map[bl->regno] = bl->biv->src_reg;
1166 /* Currently, non-reduced/final-value givs are never split. */
1167 for (v = bl->giv; v; v = v->next_iv)
1168 if (REGNO (v->src_reg) != bl->regno)
1169 map->reg_map[REGNO (v->dest_reg)] = v->src_reg;
1173 /* Use our current register alignment and pointer flags. */
1174 map->regno_pointer_flag = current_function->emit->regno_pointer_flag;
1175 map->regno_pointer_align = current_function->emit->regno_pointer_align;
1177 /* If the loop is being partially unrolled, and the iteration variables
1178 are being split, and are being renamed for the split, then must fix up
1179 the compare/jump instruction at the end of the loop to refer to the new
1180 registers. This compare isn't copied, so the registers used in it
1181 will never be replaced if it isn't done here. */
1183 if (unroll_type == UNROLL_MODULO)
1185 insn = NEXT_INSN (copy_end);
1186 if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
1187 PATTERN (insn) = remap_split_bivs (PATTERN (insn));
1190 /* For unroll_number times, make a copy of each instruction
1191 between copy_start and copy_end, and insert these new instructions
1192 before the end of the loop. */
1194 for (i = 0; i < unroll_number; i++)
1196 bzero ((char *) map->insn_map, max_insnno * sizeof (rtx));
1197 bzero ((char *) &VARRAY_CONST_EQUIV (map->const_equiv_varray, 0),
1198 VARRAY_SIZE (map->const_equiv_varray) * sizeof (struct const_equiv_data));
1201 for (j = 0; j < max_labelno; j++)
1203 set_label_in_map (map, j, gen_label_rtx ());
1205 for (j = FIRST_PSEUDO_REGISTER; j < max_local_regnum; j++)
1208 map->reg_map[j] = gen_reg_rtx (GET_MODE (regno_reg_rtx[j]));
1209 record_base_value (REGNO (map->reg_map[j]),
1210 regno_reg_rtx[j], 0);
1213 /* If loop starts with a branch to the test, then fix it so that
1214 it points to the test of the first unrolled copy of the loop. */
1215 if (i == 0 && loop_start != copy_start)
1217 insn = PREV_INSN (copy_start);
1218 pattern = PATTERN (insn);
1220 tem = get_label_from_map (map,
1222 (XEXP (SET_SRC (pattern), 0)));
1223 SET_SRC (pattern) = gen_rtx_LABEL_REF (VOIDmode, tem);
1225 /* Set the jump label so that it can be used by later loop unrolling
1227 JUMP_LABEL (insn) = tem;
1228 LABEL_NUSES (tem)++;
1231 copy_loop_body (copy_start, copy_end, map, exit_label,
1232 i == unroll_number - 1, unroll_type, start_label,
1233 loop_end, insert_before, insert_before);
1236 /* Before deleting any insns, emit a CODE_LABEL immediately after the last
1237 insn to be deleted. This prevents any runaway delete_insn call from
1238 more insns that it should, as it always stops at a CODE_LABEL. */
1240 /* Delete the compare and branch at the end of the loop if completely
1241 unrolling the loop. Deleting the backward branch at the end also
1242 deletes the code label at the start of the loop. This is done at
1243 the very end to avoid problems with back_branch_in_range_p. */
1245 if (unroll_type == UNROLL_COMPLETELY)
1246 safety_label = emit_label_after (gen_label_rtx (), last_loop_insn);
1248 safety_label = emit_label_after (gen_label_rtx (), copy_end);
1250 /* Delete all of the original loop instructions. Don't delete the
1251 LOOP_BEG note, or the first code label in the loop. */
1253 insn = NEXT_INSN (copy_start);
1254 while (insn != safety_label)
1256 /* ??? Don't delete named code labels. They will be deleted when the
1257 jump that references them is deleted. Otherwise, we end up deleting
1258 them twice, which causes them to completely disappear instead of turn
1259 into NOTE_INSN_DELETED_LABEL notes. This in turn causes aborts in
1260 dwarfout.c/dwarf2out.c. We could perhaps fix the dwarf*out.c files
1261 to handle deleted labels instead. Or perhaps fix DECL_RTL of the
1262 associated LABEL_DECL to point to one of the new label instances. */
1263 /* ??? Likewise, we can't delete a NOTE_INSN_DELETED_LABEL note. */
1264 if (insn != start_label
1265 && ! (GET_CODE (insn) == CODE_LABEL && LABEL_NAME (insn))
1266 && ! (GET_CODE (insn) == NOTE
1267 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_DELETED_LABEL))
1268 insn = delete_insn (insn);
1270 insn = NEXT_INSN (insn);
1273 /* Can now delete the 'safety' label emitted to protect us from runaway
1274 delete_insn calls. */
1275 if (INSN_DELETED_P (safety_label))
1277 delete_insn (safety_label);
1279 /* If exit_label exists, emit it after the loop. Doing the emit here
1280 forces it to have a higher INSN_UID than any insn in the unrolled loop.
1281 This is needed so that mostly_true_jump in reorg.c will treat jumps
1282 to this loop end label correctly, i.e. predict that they are usually
1285 emit_label_after (exit_label, loop_end);
1288 if (map && map->const_equiv_varray)
1289 VARRAY_FREE (map->const_equiv_varray);
1292 /* Return true if the loop can be safely, and profitably, preconditioned
1293 so that the unrolled copies of the loop body don't need exit tests.
1295 This only works if final_value, initial_value and increment can be
1296 determined, and if increment is a constant power of 2.
1297 If increment is not a power of 2, then the preconditioning modulo
1298 operation would require a real modulo instead of a boolean AND, and this
1299 is not considered `profitable'. */
1301 /* ??? If the loop is known to be executed very many times, or the machine
1302 has a very cheap divide instruction, then preconditioning is a win even
1303 when the increment is not a power of 2. Use RTX_COST to compute
1304 whether divide is cheap.
1305 ??? A divide by constant doesn't actually need a divide, look at
1306 expand_divmod. The reduced cost of this optimized modulo is not
1307 reflected in RTX_COST. */
1310 precondition_loop_p (loop_start, loop_info,
1311 initial_value, final_value, increment, mode)
1313 struct loop_info *loop_info;
1314 rtx *initial_value, *final_value, *increment;
1315 enum machine_mode *mode;
1318 if (loop_info->n_iterations > 0)
1320 *initial_value = const0_rtx;
1321 *increment = const1_rtx;
1322 *final_value = GEN_INT (loop_info->n_iterations);
1325 if (loop_dump_stream)
1327 fputs ("Preconditioning: Success, number of iterations known, ",
1329 fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC,
1330 loop_info->n_iterations);
1331 fputs (".\n", loop_dump_stream);
1336 if (loop_info->initial_value == 0)
1338 if (loop_dump_stream)
1339 fprintf (loop_dump_stream,
1340 "Preconditioning: Could not find initial value.\n");
1343 else if (loop_info->increment == 0)
1345 if (loop_dump_stream)
1346 fprintf (loop_dump_stream,
1347 "Preconditioning: Could not find increment value.\n");
1350 else if (GET_CODE (loop_info->increment) != CONST_INT)
1352 if (loop_dump_stream)
1353 fprintf (loop_dump_stream,
1354 "Preconditioning: Increment not a constant.\n");
1357 else if ((exact_log2 (INTVAL (loop_info->increment)) < 0)
1358 && (exact_log2 (- INTVAL (loop_info->increment)) < 0))
1360 if (loop_dump_stream)
1361 fprintf (loop_dump_stream,
1362 "Preconditioning: Increment not a constant power of 2.\n");
1366 /* Unsigned_compare and compare_dir can be ignored here, since they do
1367 not matter for preconditioning. */
1369 if (loop_info->final_value == 0)
1371 if (loop_dump_stream)
1372 fprintf (loop_dump_stream,
1373 "Preconditioning: EQ comparison loop.\n");
1377 /* Must ensure that final_value is invariant, so call invariant_p to
1378 check. Before doing so, must check regno against max_reg_before_loop
1379 to make sure that the register is in the range covered by invariant_p.
1380 If it isn't, then it is most likely a biv/giv which by definition are
1382 if ((GET_CODE (loop_info->final_value) == REG
1383 && REGNO (loop_info->final_value) >= max_reg_before_loop)
1384 || (GET_CODE (loop_info->final_value) == PLUS
1385 && REGNO (XEXP (loop_info->final_value, 0)) >= max_reg_before_loop)
1386 || ! invariant_p (loop_info->final_value))
1388 if (loop_dump_stream)
1389 fprintf (loop_dump_stream,
1390 "Preconditioning: Final value not invariant.\n");
1394 /* Fail for floating point values, since the caller of this function
1395 does not have code to deal with them. */
1396 if (GET_MODE_CLASS (GET_MODE (loop_info->final_value)) == MODE_FLOAT
1397 || GET_MODE_CLASS (GET_MODE (loop_info->initial_value)) == MODE_FLOAT)
1399 if (loop_dump_stream)
1400 fprintf (loop_dump_stream,
1401 "Preconditioning: Floating point final or initial value.\n");
1405 /* Fail if loop_info->iteration_var is not live before loop_start,
1406 since we need to test its value in the preconditioning code. */
1408 if (uid_luid[REGNO_FIRST_UID (REGNO (loop_info->iteration_var))]
1409 > INSN_LUID (loop_start))
1411 if (loop_dump_stream)
1412 fprintf (loop_dump_stream,
1413 "Preconditioning: Iteration var not live before loop start.\n");
1417 /* Note that iteration_info biases the initial value for GIV iterators
1418 such as "while (i-- > 0)" so that we can calculate the number of
1419 iterations just like for BIV iterators.
1421 Also note that the absolute values of initial_value and
1422 final_value are unimportant as only their difference is used for
1423 calculating the number of loop iterations. */
1424 *initial_value = loop_info->initial_value;
1425 *increment = loop_info->increment;
1426 *final_value = loop_info->final_value;
1428 /* Decide what mode to do these calculations in. Choose the larger
1429 of final_value's mode and initial_value's mode, or a full-word if
1430 both are constants. */
1431 *mode = GET_MODE (*final_value);
1432 if (*mode == VOIDmode)
1434 *mode = GET_MODE (*initial_value);
1435 if (*mode == VOIDmode)
1438 else if (*mode != GET_MODE (*initial_value)
1439 && (GET_MODE_SIZE (*mode)
1440 < GET_MODE_SIZE (GET_MODE (*initial_value))))
1441 *mode = GET_MODE (*initial_value);
1444 if (loop_dump_stream)
1445 fprintf (loop_dump_stream, "Preconditioning: Successful.\n");
1450 /* All pseudo-registers must be mapped to themselves. Two hard registers
1451 must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
1452 REGNUM, to avoid function-inlining specific conversions of these
1453 registers. All other hard regs can not be mapped because they may be
1458 init_reg_map (map, maxregnum)
1459 struct inline_remap *map;
1464 for (i = maxregnum - 1; i > LAST_VIRTUAL_REGISTER; i--)
1465 map->reg_map[i] = regno_reg_rtx[i];
1466 /* Just clear the rest of the entries. */
1467 for (i = LAST_VIRTUAL_REGISTER; i >= 0; i--)
1468 map->reg_map[i] = 0;
1470 map->reg_map[VIRTUAL_STACK_VARS_REGNUM]
1471 = regno_reg_rtx[VIRTUAL_STACK_VARS_REGNUM];
1472 map->reg_map[VIRTUAL_INCOMING_ARGS_REGNUM]
1473 = regno_reg_rtx[VIRTUAL_INCOMING_ARGS_REGNUM];
1476 /* Strength-reduction will often emit code for optimized biv/givs which
1477 calculates their value in a temporary register, and then copies the result
1478 to the iv. This procedure reconstructs the pattern computing the iv;
1479 verifying that all operands are of the proper form.
1481 PATTERN must be the result of single_set.
1482 The return value is the amount that the giv is incremented by. */
1485 calculate_giv_inc (pattern, src_insn, regno)
1486 rtx pattern, src_insn;
1490 rtx increment_total = 0;
1494 /* Verify that we have an increment insn here. First check for a plus
1495 as the set source. */
1496 if (GET_CODE (SET_SRC (pattern)) != PLUS)
1498 /* SR sometimes computes the new giv value in a temp, then copies it
1500 src_insn = PREV_INSN (src_insn);
1501 pattern = PATTERN (src_insn);
1502 if (GET_CODE (SET_SRC (pattern)) != PLUS)
1505 /* The last insn emitted is not needed, so delete it to avoid confusing
1506 the second cse pass. This insn sets the giv unnecessarily. */
1507 delete_insn (get_last_insn ());
1510 /* Verify that we have a constant as the second operand of the plus. */
1511 increment = XEXP (SET_SRC (pattern), 1);
1512 if (GET_CODE (increment) != CONST_INT)
1514 /* SR sometimes puts the constant in a register, especially if it is
1515 too big to be an add immed operand. */
1516 src_insn = PREV_INSN (src_insn);
1517 increment = SET_SRC (PATTERN (src_insn));
1519 /* SR may have used LO_SUM to compute the constant if it is too large
1520 for a load immed operand. In this case, the constant is in operand
1521 one of the LO_SUM rtx. */
1522 if (GET_CODE (increment) == LO_SUM)
1523 increment = XEXP (increment, 1);
1525 /* Some ports store large constants in memory and add a REG_EQUAL
1526 note to the store insn. */
1527 else if (GET_CODE (increment) == MEM)
1529 rtx note = find_reg_note (src_insn, REG_EQUAL, 0);
1531 increment = XEXP (note, 0);
1534 else if (GET_CODE (increment) == IOR
1535 || GET_CODE (increment) == ASHIFT
1536 || GET_CODE (increment) == PLUS)
1538 /* The rs6000 port loads some constants with IOR.
1539 The alpha port loads some constants with ASHIFT and PLUS. */
1540 rtx second_part = XEXP (increment, 1);
1541 enum rtx_code code = GET_CODE (increment);
1543 src_insn = PREV_INSN (src_insn);
1544 increment = SET_SRC (PATTERN (src_insn));
1545 /* Don't need the last insn anymore. */
1546 delete_insn (get_last_insn ());
1548 if (GET_CODE (second_part) != CONST_INT
1549 || GET_CODE (increment) != CONST_INT)
1553 increment = GEN_INT (INTVAL (increment) | INTVAL (second_part));
1554 else if (code == PLUS)
1555 increment = GEN_INT (INTVAL (increment) + INTVAL (second_part));
1557 increment = GEN_INT (INTVAL (increment) << INTVAL (second_part));
1560 if (GET_CODE (increment) != CONST_INT)
1563 /* The insn loading the constant into a register is no longer needed,
1565 delete_insn (get_last_insn ());
1568 if (increment_total)
1569 increment_total = GEN_INT (INTVAL (increment_total) + INTVAL (increment));
1571 increment_total = increment;
1573 /* Check that the source register is the same as the register we expected
1574 to see as the source. If not, something is seriously wrong. */
1575 if (GET_CODE (XEXP (SET_SRC (pattern), 0)) != REG
1576 || REGNO (XEXP (SET_SRC (pattern), 0)) != regno)
1578 /* Some machines (e.g. the romp), may emit two add instructions for
1579 certain constants, so lets try looking for another add immediately
1580 before this one if we have only seen one add insn so far. */
1586 src_insn = PREV_INSN (src_insn);
1587 pattern = PATTERN (src_insn);
1589 delete_insn (get_last_insn ());
1597 return increment_total;
1600 /* Copy REG_NOTES, except for insn references, because not all insn_map
1601 entries are valid yet. We do need to copy registers now though, because
1602 the reg_map entries can change during copying. */
1605 initial_reg_note_copy (notes, map)
1607 struct inline_remap *map;
1614 copy = rtx_alloc (GET_CODE (notes));
1615 PUT_MODE (copy, GET_MODE (notes));
1617 if (GET_CODE (notes) == EXPR_LIST)
1618 XEXP (copy, 0) = copy_rtx_and_substitute (XEXP (notes, 0), map);
1619 else if (GET_CODE (notes) == INSN_LIST)
1620 /* Don't substitute for these yet. */
1621 XEXP (copy, 0) = XEXP (notes, 0);
1625 XEXP (copy, 1) = initial_reg_note_copy (XEXP (notes, 1), map);
1630 /* Fixup insn references in copied REG_NOTES. */
1633 final_reg_note_copy (notes, map)
1635 struct inline_remap *map;
1639 for (note = notes; note; note = XEXP (note, 1))
1640 if (GET_CODE (note) == INSN_LIST)
1641 XEXP (note, 0) = map->insn_map[INSN_UID (XEXP (note, 0))];
1644 /* Copy each instruction in the loop, substituting from map as appropriate.
1645 This is very similar to a loop in expand_inline_function. */
1648 copy_loop_body (copy_start, copy_end, map, exit_label, last_iteration,
1649 unroll_type, start_label, loop_end, insert_before,
1651 rtx copy_start, copy_end;
1652 struct inline_remap *map;
1655 enum unroll_types unroll_type;
1656 rtx start_label, loop_end, insert_before, copy_notes_from;
1660 int dest_reg_was_split, i;
1664 rtx final_label = 0;
1665 rtx giv_inc, giv_dest_reg, giv_src_reg;
1667 /* If this isn't the last iteration, then map any references to the
1668 start_label to final_label. Final label will then be emitted immediately
1669 after the end of this loop body if it was ever used.
1671 If this is the last iteration, then map references to the start_label
1673 if (! last_iteration)
1675 final_label = gen_label_rtx ();
1676 set_label_in_map (map, CODE_LABEL_NUMBER (start_label),
1680 set_label_in_map (map, CODE_LABEL_NUMBER (start_label), start_label);
1684 /* Emit a NOTE_INSN_DELETED to force at least two insns onto the sequence.
1685 Else gen_sequence could return a raw pattern for a jump which we pass
1686 off to emit_insn_before (instead of emit_jump_insn_before) which causes
1687 a variety of losing behaviors later. */
1688 emit_note (0, NOTE_INSN_DELETED);
1693 insn = NEXT_INSN (insn);
1695 map->orig_asm_operands_vector = 0;
1697 switch (GET_CODE (insn))
1700 pattern = PATTERN (insn);
1704 /* Check to see if this is a giv that has been combined with
1705 some split address givs. (Combined in the sense that
1706 `combine_givs' in loop.c has put two givs in the same register.)
1707 In this case, we must search all givs based on the same biv to
1708 find the address givs. Then split the address givs.
1709 Do this before splitting the giv, since that may map the
1710 SET_DEST to a new register. */
1712 if ((set = single_set (insn))
1713 && GET_CODE (SET_DEST (set)) == REG
1714 && addr_combined_regs[REGNO (SET_DEST (set))])
1716 struct iv_class *bl;
1717 struct induction *v, *tv;
1718 int regno = REGNO (SET_DEST (set));
1720 v = addr_combined_regs[REGNO (SET_DEST (set))];
1721 bl = reg_biv_class[REGNO (v->src_reg)];
1723 /* Although the giv_inc amount is not needed here, we must call
1724 calculate_giv_inc here since it might try to delete the
1725 last insn emitted. If we wait until later to call it,
1726 we might accidentally delete insns generated immediately
1727 below by emit_unrolled_add. */
1729 if (! derived_regs[regno])
1730 giv_inc = calculate_giv_inc (set, insn, regno);
1732 /* Now find all address giv's that were combined with this
1734 for (tv = bl->giv; tv; tv = tv->next_iv)
1735 if (tv->giv_type == DEST_ADDR && tv->same == v)
1739 /* If this DEST_ADDR giv was not split, then ignore it. */
1740 if (*tv->location != tv->dest_reg)
1743 /* Scale this_giv_inc if the multiplicative factors of
1744 the two givs are different. */
1745 this_giv_inc = INTVAL (giv_inc);
1746 if (tv->mult_val != v->mult_val)
1747 this_giv_inc = (this_giv_inc / INTVAL (v->mult_val)
1748 * INTVAL (tv->mult_val));
1750 tv->dest_reg = plus_constant (tv->dest_reg, this_giv_inc);
1751 *tv->location = tv->dest_reg;
1753 if (last_iteration && unroll_type != UNROLL_COMPLETELY)
1755 /* Must emit an insn to increment the split address
1756 giv. Add in the const_adjust field in case there
1757 was a constant eliminated from the address. */
1758 rtx value, dest_reg;
1760 /* tv->dest_reg will be either a bare register,
1761 or else a register plus a constant. */
1762 if (GET_CODE (tv->dest_reg) == REG)
1763 dest_reg = tv->dest_reg;
1765 dest_reg = XEXP (tv->dest_reg, 0);
1767 /* Check for shared address givs, and avoid
1768 incrementing the shared pseudo reg more than
1770 if (! tv->same_insn && ! tv->shared)
1772 /* tv->dest_reg may actually be a (PLUS (REG)
1773 (CONST)) here, so we must call plus_constant
1774 to add the const_adjust amount before calling
1775 emit_unrolled_add below. */
1776 value = plus_constant (tv->dest_reg,
1779 /* The constant could be too large for an add
1780 immediate, so can't directly emit an insn
1782 emit_unrolled_add (dest_reg, XEXP (value, 0),
1786 /* Reset the giv to be just the register again, in case
1787 it is used after the set we have just emitted.
1788 We must subtract the const_adjust factor added in
1790 tv->dest_reg = plus_constant (dest_reg,
1791 - tv->const_adjust);
1792 *tv->location = tv->dest_reg;
1797 /* If this is a setting of a splittable variable, then determine
1798 how to split the variable, create a new set based on this split,
1799 and set up the reg_map so that later uses of the variable will
1800 use the new split variable. */
1802 dest_reg_was_split = 0;
1804 if ((set = single_set (insn))
1805 && GET_CODE (SET_DEST (set)) == REG
1806 && splittable_regs[REGNO (SET_DEST (set))])
1808 int regno = REGNO (SET_DEST (set));
1811 dest_reg_was_split = 1;
1813 giv_dest_reg = SET_DEST (set);
1814 if (derived_regs[regno])
1816 /* ??? This relies on SET_SRC (SET) to be of
1817 the form (plus (reg) (const_int)), and thus
1818 forces recombine_givs to restrict the kind
1819 of giv derivations it does before unrolling. */
1820 giv_src_reg = XEXP (SET_SRC (set), 0);
1821 giv_inc = XEXP (SET_SRC (set), 1);
1825 giv_src_reg = giv_dest_reg;
1826 /* Compute the increment value for the giv, if it wasn't
1827 already computed above. */
1829 giv_inc = calculate_giv_inc (set, insn, regno);
1831 src_regno = REGNO (giv_src_reg);
1833 if (unroll_type == UNROLL_COMPLETELY)
1835 /* Completely unrolling the loop. Set the induction
1836 variable to a known constant value. */
1838 /* The value in splittable_regs may be an invariant
1839 value, so we must use plus_constant here. */
1840 splittable_regs[regno]
1841 = plus_constant (splittable_regs[src_regno],
1844 if (GET_CODE (splittable_regs[regno]) == PLUS)
1846 giv_src_reg = XEXP (splittable_regs[regno], 0);
1847 giv_inc = XEXP (splittable_regs[regno], 1);
1851 /* The splittable_regs value must be a REG or a
1852 CONST_INT, so put the entire value in the giv_src_reg
1854 giv_src_reg = splittable_regs[regno];
1855 giv_inc = const0_rtx;
1860 /* Partially unrolling loop. Create a new pseudo
1861 register for the iteration variable, and set it to
1862 be a constant plus the original register. Except
1863 on the last iteration, when the result has to
1864 go back into the original iteration var register. */
1866 /* Handle bivs which must be mapped to a new register
1867 when split. This happens for bivs which need their
1868 final value set before loop entry. The new register
1869 for the biv was stored in the biv's first struct
1870 induction entry by find_splittable_regs. */
1872 if (regno < max_reg_before_loop
1873 && REG_IV_TYPE (regno) == BASIC_INDUCT)
1875 giv_src_reg = reg_biv_class[regno]->biv->src_reg;
1876 giv_dest_reg = giv_src_reg;
1880 /* If non-reduced/final-value givs were split, then
1881 this would have to remap those givs also. See
1882 find_splittable_regs. */
1885 splittable_regs[regno]
1886 = GEN_INT (INTVAL (giv_inc)
1887 + INTVAL (splittable_regs[src_regno]));
1888 giv_inc = splittable_regs[regno];
1890 /* Now split the induction variable by changing the dest
1891 of this insn to a new register, and setting its
1892 reg_map entry to point to this new register.
1894 If this is the last iteration, and this is the last insn
1895 that will update the iv, then reuse the original dest,
1896 to ensure that the iv will have the proper value when
1897 the loop exits or repeats.
1899 Using splittable_regs_updates here like this is safe,
1900 because it can only be greater than one if all
1901 instructions modifying the iv are always executed in
1904 if (! last_iteration
1905 || (splittable_regs_updates[regno]-- != 1))
1907 tem = gen_reg_rtx (GET_MODE (giv_src_reg));
1909 map->reg_map[regno] = tem;
1910 record_base_value (REGNO (tem),
1911 giv_inc == const0_rtx
1913 : gen_rtx_PLUS (GET_MODE (giv_src_reg),
1914 giv_src_reg, giv_inc),
1918 map->reg_map[regno] = giv_src_reg;
1921 /* The constant being added could be too large for an add
1922 immediate, so can't directly emit an insn here. */
1923 emit_unrolled_add (giv_dest_reg, giv_src_reg, giv_inc);
1924 copy = get_last_insn ();
1925 pattern = PATTERN (copy);
1929 pattern = copy_rtx_and_substitute (pattern, map);
1930 copy = emit_insn (pattern);
1932 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
1935 /* If this insn is setting CC0, it may need to look at
1936 the insn that uses CC0 to see what type of insn it is.
1937 In that case, the call to recog via validate_change will
1938 fail. So don't substitute constants here. Instead,
1939 do it when we emit the following insn.
1941 For example, see the pyr.md file. That machine has signed and
1942 unsigned compares. The compare patterns must check the
1943 following branch insn to see which what kind of compare to
1946 If the previous insn set CC0, substitute constants on it as
1948 if (sets_cc0_p (PATTERN (copy)) != 0)
1953 try_constants (cc0_insn, map);
1955 try_constants (copy, map);
1958 try_constants (copy, map);
1961 /* Make split induction variable constants `permanent' since we
1962 know there are no backward branches across iteration variable
1963 settings which would invalidate this. */
1964 if (dest_reg_was_split)
1966 int regno = REGNO (SET_DEST (pattern));
1968 if ((size_t) regno < VARRAY_SIZE (map->const_equiv_varray)
1969 && (VARRAY_CONST_EQUIV (map->const_equiv_varray, regno).age
1971 VARRAY_CONST_EQUIV (map->const_equiv_varray, regno).age = -1;
1976 pattern = copy_rtx_and_substitute (PATTERN (insn), map);
1977 copy = emit_jump_insn (pattern);
1978 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
1980 if (JUMP_LABEL (insn) == start_label && insn == copy_end
1981 && ! last_iteration)
1983 /* This is a branch to the beginning of the loop; this is the
1984 last insn being copied; and this is not the last iteration.
1985 In this case, we want to change the original fall through
1986 case to be a branch past the end of the loop, and the
1987 original jump label case to fall_through. */
1989 if (invert_exp (pattern, copy))
1991 if (! redirect_exp (&pattern,
1992 get_label_from_map (map,
1994 (JUMP_LABEL (insn))),
2001 rtx lab = gen_label_rtx ();
2002 /* Can't do it by reversing the jump (probably because we
2003 couldn't reverse the conditions), so emit a new
2004 jump_insn after COPY, and redirect the jump around
2006 jmp = emit_jump_insn_after (gen_jump (exit_label), copy);
2007 jmp = emit_barrier_after (jmp);
2008 emit_label_after (lab, jmp);
2009 LABEL_NUSES (lab) = 0;
2010 if (! redirect_exp (&pattern,
2011 get_label_from_map (map,
2013 (JUMP_LABEL (insn))),
2021 try_constants (cc0_insn, map);
2024 try_constants (copy, map);
2026 /* Set the jump label of COPY correctly to avoid problems with
2027 later passes of unroll_loop, if INSN had jump label set. */
2028 if (JUMP_LABEL (insn))
2032 /* Can't use the label_map for every insn, since this may be
2033 the backward branch, and hence the label was not mapped. */
2034 if ((set = single_set (copy)))
2036 tem = SET_SRC (set);
2037 if (GET_CODE (tem) == LABEL_REF)
2038 label = XEXP (tem, 0);
2039 else if (GET_CODE (tem) == IF_THEN_ELSE)
2041 if (XEXP (tem, 1) != pc_rtx)
2042 label = XEXP (XEXP (tem, 1), 0);
2044 label = XEXP (XEXP (tem, 2), 0);
2048 if (label && GET_CODE (label) == CODE_LABEL)
2049 JUMP_LABEL (copy) = label;
2052 /* An unrecognizable jump insn, probably the entry jump
2053 for a switch statement. This label must have been mapped,
2054 so just use the label_map to get the new jump label. */
2056 = get_label_from_map (map,
2057 CODE_LABEL_NUMBER (JUMP_LABEL (insn)));
2060 /* If this is a non-local jump, then must increase the label
2061 use count so that the label will not be deleted when the
2062 original jump is deleted. */
2063 LABEL_NUSES (JUMP_LABEL (copy))++;
2065 else if (GET_CODE (PATTERN (copy)) == ADDR_VEC
2066 || GET_CODE (PATTERN (copy)) == ADDR_DIFF_VEC)
2068 rtx pat = PATTERN (copy);
2069 int diff_vec_p = GET_CODE (pat) == ADDR_DIFF_VEC;
2070 int len = XVECLEN (pat, diff_vec_p);
2073 for (i = 0; i < len; i++)
2074 LABEL_NUSES (XEXP (XVECEXP (pat, diff_vec_p, i), 0))++;
2077 /* If this used to be a conditional jump insn but whose branch
2078 direction is now known, we must do something special. */
2079 if (condjump_p (insn) && !simplejump_p (insn) && map->last_pc_value)
2082 /* If the previous insn set cc0 for us, delete it. */
2083 if (sets_cc0_p (PREV_INSN (copy)))
2084 delete_insn (PREV_INSN (copy));
2087 /* If this is now a no-op, delete it. */
2088 if (map->last_pc_value == pc_rtx)
2090 /* Don't let delete_insn delete the label referenced here,
2091 because we might possibly need it later for some other
2092 instruction in the loop. */
2093 if (JUMP_LABEL (copy))
2094 LABEL_NUSES (JUMP_LABEL (copy))++;
2096 if (JUMP_LABEL (copy))
2097 LABEL_NUSES (JUMP_LABEL (copy))--;
2101 /* Otherwise, this is unconditional jump so we must put a
2102 BARRIER after it. We could do some dead code elimination
2103 here, but jump.c will do it just as well. */
2109 pattern = copy_rtx_and_substitute (PATTERN (insn), map);
2110 copy = emit_call_insn (pattern);
2111 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
2113 /* Because the USAGE information potentially contains objects other
2114 than hard registers, we need to copy it. */
2115 CALL_INSN_FUNCTION_USAGE (copy)
2116 = copy_rtx_and_substitute (CALL_INSN_FUNCTION_USAGE (insn), map);
2120 try_constants (cc0_insn, map);
2123 try_constants (copy, map);
2125 /* Be lazy and assume CALL_INSNs clobber all hard registers. */
2126 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2127 VARRAY_CONST_EQUIV (map->const_equiv_varray, i).rtx = 0;
2131 /* If this is the loop start label, then we don't need to emit a
2132 copy of this label since no one will use it. */
2134 if (insn != start_label)
2136 copy = emit_label (get_label_from_map (map,
2137 CODE_LABEL_NUMBER (insn)));
2143 copy = emit_barrier ();
2147 /* VTOP and CONT notes are valid only before the loop exit test.
2148 If placed anywhere else, loop may generate bad code. */
2149 /* BASIC_BLOCK notes exist to stabilize basic block structures with
2150 the associated rtl. We do not want to share the structure in
2153 if (NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
2154 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
2155 && ((NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP
2156 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_CONT)
2157 || (last_iteration && unroll_type != UNROLL_COMPLETELY)))
2158 copy = emit_note (NOTE_SOURCE_FILE (insn),
2159 NOTE_LINE_NUMBER (insn));
2168 map->insn_map[INSN_UID (insn)] = copy;
2170 while (insn != copy_end);
2172 /* Now finish coping the REG_NOTES. */
2176 insn = NEXT_INSN (insn);
2177 if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN
2178 || GET_CODE (insn) == CALL_INSN)
2179 && map->insn_map[INSN_UID (insn)])
2180 final_reg_note_copy (REG_NOTES (map->insn_map[INSN_UID (insn)]), map);
2182 while (insn != copy_end);
2184 /* There may be notes between copy_notes_from and loop_end. Emit a copy of
2185 each of these notes here, since there may be some important ones, such as
2186 NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
2187 iteration, because the original notes won't be deleted.
2189 We can't use insert_before here, because when from preconditioning,
2190 insert_before points before the loop. We can't use copy_end, because
2191 there may be insns already inserted after it (which we don't want to
2192 copy) when not from preconditioning code. */
2194 if (! last_iteration)
2196 for (insn = copy_notes_from; insn != loop_end; insn = NEXT_INSN (insn))
2198 /* VTOP notes are valid only before the loop exit test.
2199 If placed anywhere else, loop may generate bad code.
2200 There is no need to test for NOTE_INSN_LOOP_CONT notes
2201 here, since COPY_NOTES_FROM will be at most one or two (for cc0)
2202 instructions before the last insn in the loop, and if the
2203 end test is that short, there will be a VTOP note between
2204 the CONT note and the test. */
2205 if (GET_CODE (insn) == NOTE
2206 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
2207 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
2208 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP)
2209 emit_note (NOTE_SOURCE_FILE (insn), NOTE_LINE_NUMBER (insn));
2213 if (final_label && LABEL_NUSES (final_label) > 0)
2214 emit_label (final_label);
2216 tem = gen_sequence ();
2218 emit_insn_before (tem, insert_before);
2221 /* Emit an insn, using the expand_binop to ensure that a valid insn is
2222 emitted. This will correctly handle the case where the increment value
2223 won't fit in the immediate field of a PLUS insns. */
2226 emit_unrolled_add (dest_reg, src_reg, increment)
2227 rtx dest_reg, src_reg, increment;
2231 result = expand_binop (GET_MODE (dest_reg), add_optab, src_reg, increment,
2232 dest_reg, 0, OPTAB_LIB_WIDEN);
2234 if (dest_reg != result)
2235 emit_move_insn (dest_reg, result);
2238 /* Searches the insns between INSN and LOOP_END. Returns 1 if there
2239 is a backward branch in that range that branches to somewhere between
2240 LOOP_START and INSN. Returns 0 otherwise. */
2242 /* ??? This is quadratic algorithm. Could be rewritten to be linear.
2243 In practice, this is not a problem, because this function is seldom called,
2244 and uses a negligible amount of CPU time on average. */
2247 back_branch_in_range_p (insn, loop_start, loop_end)
2249 rtx loop_start, loop_end;
2251 rtx p, q, target_insn;
2252 rtx orig_loop_end = loop_end;
2254 /* Stop before we get to the backward branch at the end of the loop. */
2255 loop_end = prev_nonnote_insn (loop_end);
2256 if (GET_CODE (loop_end) == BARRIER)
2257 loop_end = PREV_INSN (loop_end);
2259 /* Check in case insn has been deleted, search forward for first non
2260 deleted insn following it. */
2261 while (INSN_DELETED_P (insn))
2262 insn = NEXT_INSN (insn);
2264 /* Check for the case where insn is the last insn in the loop. Deal
2265 with the case where INSN was a deleted loop test insn, in which case
2266 it will now be the NOTE_LOOP_END. */
2267 if (insn == loop_end || insn == orig_loop_end)
2270 for (p = NEXT_INSN (insn); p != loop_end; p = NEXT_INSN (p))
2272 if (GET_CODE (p) == JUMP_INSN)
2274 target_insn = JUMP_LABEL (p);
2276 /* Search from loop_start to insn, to see if one of them is
2277 the target_insn. We can't use INSN_LUID comparisons here,
2278 since insn may not have an LUID entry. */
2279 for (q = loop_start; q != insn; q = NEXT_INSN (q))
2280 if (q == target_insn)
2288 /* Try to generate the simplest rtx for the expression
2289 (PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
2293 fold_rtx_mult_add (mult1, mult2, add1, mode)
2294 rtx mult1, mult2, add1;
2295 enum machine_mode mode;
2300 /* The modes must all be the same. This should always be true. For now,
2301 check to make sure. */
2302 if ((GET_MODE (mult1) != mode && GET_MODE (mult1) != VOIDmode)
2303 || (GET_MODE (mult2) != mode && GET_MODE (mult2) != VOIDmode)
2304 || (GET_MODE (add1) != mode && GET_MODE (add1) != VOIDmode))
2307 /* Ensure that if at least one of mult1/mult2 are constant, then mult2
2308 will be a constant. */
2309 if (GET_CODE (mult1) == CONST_INT)
2316 mult_res = simplify_binary_operation (MULT, mode, mult1, mult2);
2318 mult_res = gen_rtx_MULT (mode, mult1, mult2);
2320 /* Again, put the constant second. */
2321 if (GET_CODE (add1) == CONST_INT)
2328 result = simplify_binary_operation (PLUS, mode, add1, mult_res);
2330 result = gen_rtx_PLUS (mode, add1, mult_res);
2335 /* Searches the list of induction struct's for the biv BL, to try to calculate
2336 the total increment value for one iteration of the loop as a constant.
2338 Returns the increment value as an rtx, simplified as much as possible,
2339 if it can be calculated. Otherwise, returns 0. */
2342 biv_total_increment (bl, loop_start, loop_end)
2343 struct iv_class *bl;
2344 rtx loop_start, loop_end;
2346 struct induction *v;
2349 /* For increment, must check every instruction that sets it. Each
2350 instruction must be executed only once each time through the loop.
2351 To verify this, we check that the insn is always executed, and that
2352 there are no backward branches after the insn that branch to before it.
2353 Also, the insn must have a mult_val of one (to make sure it really is
2356 result = const0_rtx;
2357 for (v = bl->biv; v; v = v->next_iv)
2359 if (v->always_computable && v->mult_val == const1_rtx
2360 && ! v->maybe_multiple)
2361 result = fold_rtx_mult_add (result, const1_rtx, v->add_val, v->mode);
2369 /* Determine the initial value of the iteration variable, and the amount
2370 that it is incremented each loop. Use the tables constructed by
2371 the strength reduction pass to calculate these values.
2373 Initial_value and/or increment are set to zero if their values could not
2377 iteration_info (iteration_var, initial_value, increment, loop_start, loop_end)
2378 rtx iteration_var, *initial_value, *increment;
2379 rtx loop_start, loop_end;
2381 struct iv_class *bl;
2383 struct induction *v;
2386 /* Clear the result values, in case no answer can be found. */
2390 /* The iteration variable can be either a giv or a biv. Check to see
2391 which it is, and compute the variable's initial value, and increment
2392 value if possible. */
2394 /* If this is a new register, can't handle it since we don't have any
2395 reg_iv_type entry for it. */
2396 if ((unsigned) REGNO (iteration_var) >= reg_iv_type->num_elements)
2398 if (loop_dump_stream)
2399 fprintf (loop_dump_stream,
2400 "Loop unrolling: No reg_iv_type entry for iteration var.\n");
2404 /* Reject iteration variables larger than the host wide int size, since they
2405 could result in a number of iterations greater than the range of our
2406 `unsigned HOST_WIDE_INT' variable loop_info->n_iterations. */
2407 else if ((GET_MODE_BITSIZE (GET_MODE (iteration_var))
2408 > HOST_BITS_PER_WIDE_INT))
2410 if (loop_dump_stream)
2411 fprintf (loop_dump_stream,
2412 "Loop unrolling: Iteration var rejected because mode too large.\n");
2415 else if (GET_MODE_CLASS (GET_MODE (iteration_var)) != MODE_INT)
2417 if (loop_dump_stream)
2418 fprintf (loop_dump_stream,
2419 "Loop unrolling: Iteration var not an integer.\n");
2422 else if (REG_IV_TYPE (REGNO (iteration_var)) == BASIC_INDUCT)
2424 /* When reg_iv_type / reg_iv_info is resized for biv increments
2425 that are turned into givs, reg_biv_class is not resized.
2426 So check here that we don't make an out-of-bounds access. */
2427 if (REGNO (iteration_var) >= max_reg_before_loop)
2430 /* Grab initial value, only useful if it is a constant. */
2431 bl = reg_biv_class[REGNO (iteration_var)];
2432 *initial_value = bl->initial_value;
2434 *increment = biv_total_increment (bl, loop_start, loop_end);
2436 else if (REG_IV_TYPE (REGNO (iteration_var)) == GENERAL_INDUCT)
2438 HOST_WIDE_INT offset = 0;
2439 struct induction *v = REG_IV_INFO (REGNO (iteration_var));
2441 if (REGNO (v->src_reg) >= max_reg_before_loop)
2444 bl = reg_biv_class[REGNO (v->src_reg)];
2446 /* Increment value is mult_val times the increment value of the biv. */
2448 *increment = biv_total_increment (bl, loop_start, loop_end);
2451 struct induction *biv_inc;
2454 = fold_rtx_mult_add (v->mult_val, *increment, const0_rtx, v->mode);
2455 /* The caller assumes that one full increment has occured at the
2456 first loop test. But that's not true when the biv is incremented
2457 after the giv is set (which is the usual case), e.g.:
2458 i = 6; do {;} while (i++ < 9) .
2459 Therefore, we bias the initial value by subtracting the amount of
2460 the increment that occurs between the giv set and the giv test. */
2461 for (biv_inc = bl->biv; biv_inc; biv_inc = biv_inc->next_iv)
2463 if (loop_insn_first_p (v->insn, biv_inc->insn))
2464 offset -= INTVAL (biv_inc->add_val);
2466 offset *= INTVAL (v->mult_val);
2468 if (loop_dump_stream)
2469 fprintf (loop_dump_stream,
2470 "Loop unrolling: Giv iterator, initial value bias %ld.\n",
2472 /* Initial value is mult_val times the biv's initial value plus
2473 add_val. Only useful if it is a constant. */
2475 = fold_rtx_mult_add (v->mult_val,
2476 plus_constant (bl->initial_value, offset),
2477 v->add_val, v->mode);
2481 if (loop_dump_stream)
2482 fprintf (loop_dump_stream,
2483 "Loop unrolling: Not basic or general induction var.\n");
2489 /* For each biv and giv, determine whether it can be safely split into
2490 a different variable for each unrolled copy of the loop body. If it
2491 is safe to split, then indicate that by saving some useful info
2492 in the splittable_regs array.
2494 If the loop is being completely unrolled, then splittable_regs will hold
2495 the current value of the induction variable while the loop is unrolled.
2496 It must be set to the initial value of the induction variable here.
2497 Otherwise, splittable_regs will hold the difference between the current
2498 value of the induction variable and the value the induction variable had
2499 at the top of the loop. It must be set to the value 0 here.
2501 Returns the total number of instructions that set registers that are
2504 /* ?? If the loop is only unrolled twice, then most of the restrictions to
2505 constant values are unnecessary, since we can easily calculate increment
2506 values in this case even if nothing is constant. The increment value
2507 should not involve a multiply however. */
2509 /* ?? Even if the biv/giv increment values aren't constant, it may still
2510 be beneficial to split the variable if the loop is only unrolled a few
2511 times, since multiplies by small integers (1,2,3,4) are very cheap. */
2514 find_splittable_regs (unroll_type, loop_start, loop_end, end_insert_before,
2515 unroll_number, n_iterations)
2516 enum unroll_types unroll_type;
2517 rtx loop_start, loop_end;
2518 rtx end_insert_before;
2520 unsigned HOST_WIDE_INT n_iterations;
2522 struct iv_class *bl;
2523 struct induction *v;
2525 rtx biv_final_value;
2529 for (bl = loop_iv_list; bl; bl = bl->next)
2531 /* Biv_total_increment must return a constant value,
2532 otherwise we can not calculate the split values. */
2534 increment = biv_total_increment (bl, loop_start, loop_end);
2535 if (! increment || GET_CODE (increment) != CONST_INT)
2538 /* The loop must be unrolled completely, or else have a known number
2539 of iterations and only one exit, or else the biv must be dead
2540 outside the loop, or else the final value must be known. Otherwise,
2541 it is unsafe to split the biv since it may not have the proper
2542 value on loop exit. */
2544 /* loop_number_exit_count is non-zero if the loop has an exit other than
2545 a fall through at the end. */
2548 biv_final_value = 0;
2549 if (unroll_type != UNROLL_COMPLETELY
2550 && (loop_number_exit_count[uid_loop_num[INSN_UID (loop_start)]]
2551 || unroll_type == UNROLL_NAIVE)
2552 && (uid_luid[REGNO_LAST_UID (bl->regno)] >= INSN_LUID (loop_end)
2554 || INSN_UID (bl->init_insn) >= max_uid_for_loop
2555 || (uid_luid[REGNO_FIRST_UID (bl->regno)]
2556 < INSN_LUID (bl->init_insn))
2557 || reg_mentioned_p (bl->biv->dest_reg, SET_SRC (bl->init_set)))
2558 && ! (biv_final_value = final_biv_value (bl, loop_start, loop_end,
2562 /* If any of the insns setting the BIV don't do so with a simple
2563 PLUS, we don't know how to split it. */
2564 for (v = bl->biv; biv_splittable && v; v = v->next_iv)
2565 if ((tem = single_set (v->insn)) == 0
2566 || GET_CODE (SET_DEST (tem)) != REG
2567 || REGNO (SET_DEST (tem)) != bl->regno
2568 || GET_CODE (SET_SRC (tem)) != PLUS)
2571 /* If final value is non-zero, then must emit an instruction which sets
2572 the value of the biv to the proper value. This is done after
2573 handling all of the givs, since some of them may need to use the
2574 biv's value in their initialization code. */
2576 /* This biv is splittable. If completely unrolling the loop, save
2577 the biv's initial value. Otherwise, save the constant zero. */
2579 if (biv_splittable == 1)
2581 if (unroll_type == UNROLL_COMPLETELY)
2583 /* If the initial value of the biv is itself (i.e. it is too
2584 complicated for strength_reduce to compute), or is a hard
2585 register, or it isn't invariant, then we must create a new
2586 pseudo reg to hold the initial value of the biv. */
2588 if (GET_CODE (bl->initial_value) == REG
2589 && (REGNO (bl->initial_value) == bl->regno
2590 || REGNO (bl->initial_value) < FIRST_PSEUDO_REGISTER
2591 || ! invariant_p (bl->initial_value)))
2593 rtx tem = gen_reg_rtx (bl->biv->mode);
2595 record_base_value (REGNO (tem), bl->biv->add_val, 0);
2596 emit_insn_before (gen_move_insn (tem, bl->biv->src_reg),
2599 if (loop_dump_stream)
2600 fprintf (loop_dump_stream, "Biv %d initial value remapped to %d.\n",
2601 bl->regno, REGNO (tem));
2603 splittable_regs[bl->regno] = tem;
2606 splittable_regs[bl->regno] = bl->initial_value;
2609 splittable_regs[bl->regno] = const0_rtx;
2611 /* Save the number of instructions that modify the biv, so that
2612 we can treat the last one specially. */
2614 splittable_regs_updates[bl->regno] = bl->biv_count;
2615 result += bl->biv_count;
2617 if (loop_dump_stream)
2618 fprintf (loop_dump_stream,
2619 "Biv %d safe to split.\n", bl->regno);
2622 /* Check every giv that depends on this biv to see whether it is
2623 splittable also. Even if the biv isn't splittable, givs which
2624 depend on it may be splittable if the biv is live outside the
2625 loop, and the givs aren't. */
2627 result += find_splittable_givs (bl, unroll_type, loop_start, loop_end,
2628 increment, unroll_number);
2630 /* If final value is non-zero, then must emit an instruction which sets
2631 the value of the biv to the proper value. This is done after
2632 handling all of the givs, since some of them may need to use the
2633 biv's value in their initialization code. */
2634 if (biv_final_value)
2636 /* If the loop has multiple exits, emit the insns before the
2637 loop to ensure that it will always be executed no matter
2638 how the loop exits. Otherwise emit the insn after the loop,
2639 since this is slightly more efficient. */
2640 if (! loop_number_exit_count[uid_loop_num[INSN_UID (loop_start)]])
2641 emit_insn_before (gen_move_insn (bl->biv->src_reg,
2646 /* Create a new register to hold the value of the biv, and then
2647 set the biv to its final value before the loop start. The biv
2648 is set to its final value before loop start to ensure that
2649 this insn will always be executed, no matter how the loop
2651 rtx tem = gen_reg_rtx (bl->biv->mode);
2652 record_base_value (REGNO (tem), bl->biv->add_val, 0);
2654 emit_insn_before (gen_move_insn (tem, bl->biv->src_reg),
2656 emit_insn_before (gen_move_insn (bl->biv->src_reg,
2660 if (loop_dump_stream)
2661 fprintf (loop_dump_stream, "Biv %d mapped to %d for split.\n",
2662 REGNO (bl->biv->src_reg), REGNO (tem));
2664 /* Set up the mapping from the original biv register to the new
2666 bl->biv->src_reg = tem;
2673 /* Return 1 if the first and last unrolled copy of the address giv V is valid
2674 for the instruction that is using it. Do not make any changes to that
2678 verify_addresses (v, giv_inc, unroll_number)
2679 struct induction *v;
2684 rtx orig_addr = *v->location;
2685 rtx last_addr = plus_constant (v->dest_reg,
2686 INTVAL (giv_inc) * (unroll_number - 1));
2688 /* First check to see if either address would fail. Handle the fact
2689 that we have may have a match_dup. */
2690 if (! validate_replace_rtx (*v->location, v->dest_reg, v->insn)
2691 || ! validate_replace_rtx (*v->location, last_addr, v->insn))
2694 /* Now put things back the way they were before. This should always
2696 if (! validate_replace_rtx (*v->location, orig_addr, v->insn))
2702 /* For every giv based on the biv BL, check to determine whether it is
2703 splittable. This is a subroutine to find_splittable_regs ().
2705 Return the number of instructions that set splittable registers. */
2708 find_splittable_givs (bl, unroll_type, loop_start, loop_end, increment,
2710 struct iv_class *bl;
2711 enum unroll_types unroll_type;
2712 rtx loop_start, loop_end;
2716 struct induction *v, *v2;
2721 /* Scan the list of givs, and set the same_insn field when there are
2722 multiple identical givs in the same insn. */
2723 for (v = bl->giv; v; v = v->next_iv)
2724 for (v2 = v->next_iv; v2; v2 = v2->next_iv)
2725 if (v->insn == v2->insn && rtx_equal_p (v->new_reg, v2->new_reg)
2729 for (v = bl->giv; v; v = v->next_iv)
2733 /* Only split the giv if it has already been reduced, or if the loop is
2734 being completely unrolled. */
2735 if (unroll_type != UNROLL_COMPLETELY && v->ignore)
2738 /* The giv can be split if the insn that sets the giv is executed once
2739 and only once on every iteration of the loop. */
2740 /* An address giv can always be split. v->insn is just a use not a set,
2741 and hence it does not matter whether it is always executed. All that
2742 matters is that all the biv increments are always executed, and we
2743 won't reach here if they aren't. */
2744 if (v->giv_type != DEST_ADDR
2745 && (! v->always_computable
2746 || back_branch_in_range_p (v->insn, loop_start, loop_end)))
2749 /* The giv increment value must be a constant. */
2750 giv_inc = fold_rtx_mult_add (v->mult_val, increment, const0_rtx,
2752 if (! giv_inc || GET_CODE (giv_inc) != CONST_INT)
2755 /* The loop must be unrolled completely, or else have a known number of
2756 iterations and only one exit, or else the giv must be dead outside
2757 the loop, or else the final value of the giv must be known.
2758 Otherwise, it is not safe to split the giv since it may not have the
2759 proper value on loop exit. */
2761 /* The used outside loop test will fail for DEST_ADDR givs. They are
2762 never used outside the loop anyways, so it is always safe to split a
2766 if (unroll_type != UNROLL_COMPLETELY
2767 && (loop_number_exit_count[uid_loop_num[INSN_UID (loop_start)]]
2768 || unroll_type == UNROLL_NAIVE)
2769 && v->giv_type != DEST_ADDR
2770 /* The next part is true if the pseudo is used outside the loop.
2771 We assume that this is true for any pseudo created after loop
2772 starts, because we don't have a reg_n_info entry for them. */
2773 && (REGNO (v->dest_reg) >= max_reg_before_loop
2774 || (REGNO_FIRST_UID (REGNO (v->dest_reg)) != INSN_UID (v->insn)
2775 /* Check for the case where the pseudo is set by a shift/add
2776 sequence, in which case the first insn setting the pseudo
2777 is the first insn of the shift/add sequence. */
2778 && (! (tem = find_reg_note (v->insn, REG_RETVAL, NULL_RTX))
2779 || (REGNO_FIRST_UID (REGNO (v->dest_reg))
2780 != INSN_UID (XEXP (tem, 0)))))
2781 /* Line above always fails if INSN was moved by loop opt. */
2782 || (uid_luid[REGNO_LAST_UID (REGNO (v->dest_reg))]
2783 >= INSN_LUID (loop_end)))
2784 /* Givs made from biv increments are missed by the above test, so
2785 test explicitly for them. */
2786 && (REGNO (v->dest_reg) < first_increment_giv
2787 || REGNO (v->dest_reg) > last_increment_giv)
2788 && ! (final_value = v->final_value))
2792 /* Currently, non-reduced/final-value givs are never split. */
2793 /* Should emit insns after the loop if possible, as the biv final value
2796 /* If the final value is non-zero, and the giv has not been reduced,
2797 then must emit an instruction to set the final value. */
2798 if (final_value && !v->new_reg)
2800 /* Create a new register to hold the value of the giv, and then set
2801 the giv to its final value before the loop start. The giv is set
2802 to its final value before loop start to ensure that this insn
2803 will always be executed, no matter how we exit. */
2804 tem = gen_reg_rtx (v->mode);
2805 emit_insn_before (gen_move_insn (tem, v->dest_reg), loop_start);
2806 emit_insn_before (gen_move_insn (v->dest_reg, final_value),
2809 if (loop_dump_stream)
2810 fprintf (loop_dump_stream, "Giv %d mapped to %d for split.\n",
2811 REGNO (v->dest_reg), REGNO (tem));
2817 /* This giv is splittable. If completely unrolling the loop, save the
2818 giv's initial value. Otherwise, save the constant zero for it. */
2820 if (unroll_type == UNROLL_COMPLETELY)
2822 /* It is not safe to use bl->initial_value here, because it may not
2823 be invariant. It is safe to use the initial value stored in
2824 the splittable_regs array if it is set. In rare cases, it won't
2825 be set, so then we do exactly the same thing as
2826 find_splittable_regs does to get a safe value. */
2827 rtx biv_initial_value;
2829 if (splittable_regs[bl->regno])
2830 biv_initial_value = splittable_regs[bl->regno];
2831 else if (GET_CODE (bl->initial_value) != REG
2832 || (REGNO (bl->initial_value) != bl->regno
2833 && REGNO (bl->initial_value) >= FIRST_PSEUDO_REGISTER))
2834 biv_initial_value = bl->initial_value;
2837 rtx tem = gen_reg_rtx (bl->biv->mode);
2839 record_base_value (REGNO (tem), bl->biv->add_val, 0);
2840 emit_insn_before (gen_move_insn (tem, bl->biv->src_reg),
2842 biv_initial_value = tem;
2844 value = fold_rtx_mult_add (v->mult_val, biv_initial_value,
2845 v->add_val, v->mode);
2852 /* If a giv was combined with another giv, then we can only split
2853 this giv if the giv it was combined with was reduced. This
2854 is because the value of v->new_reg is meaningless in this
2856 if (v->same && ! v->same->new_reg)
2858 if (loop_dump_stream)
2859 fprintf (loop_dump_stream,
2860 "giv combined with unreduced giv not split.\n");
2863 /* If the giv is an address destination, it could be something other
2864 than a simple register, these have to be treated differently. */
2865 else if (v->giv_type == DEST_REG)
2867 /* If value is not a constant, register, or register plus
2868 constant, then compute its value into a register before
2869 loop start. This prevents invalid rtx sharing, and should
2870 generate better code. We can use bl->initial_value here
2871 instead of splittable_regs[bl->regno] because this code
2872 is going before the loop start. */
2873 if (unroll_type == UNROLL_COMPLETELY
2874 && GET_CODE (value) != CONST_INT
2875 && GET_CODE (value) != REG
2876 && (GET_CODE (value) != PLUS
2877 || GET_CODE (XEXP (value, 0)) != REG
2878 || GET_CODE (XEXP (value, 1)) != CONST_INT))
2880 rtx tem = gen_reg_rtx (v->mode);
2881 record_base_value (REGNO (tem), v->add_val, 0);
2882 emit_iv_add_mult (bl->initial_value, v->mult_val,
2883 v->add_val, tem, loop_start);
2887 splittable_regs[REGNO (v->new_reg)] = value;
2888 derived_regs[REGNO (v->new_reg)] = v->derived_from != 0;
2892 /* Splitting address givs is useful since it will often allow us
2893 to eliminate some increment insns for the base giv as
2896 /* If the addr giv is combined with a dest_reg giv, then all
2897 references to that dest reg will be remapped, which is NOT
2898 what we want for split addr regs. We always create a new
2899 register for the split addr giv, just to be safe. */
2901 /* If we have multiple identical address givs within a
2902 single instruction, then use a single pseudo reg for
2903 both. This is necessary in case one is a match_dup
2906 v->const_adjust = 0;
2910 v->dest_reg = v->same_insn->dest_reg;
2911 if (loop_dump_stream)
2912 fprintf (loop_dump_stream,
2913 "Sharing address givs in insn %d\n",
2914 INSN_UID (v->insn));
2916 /* If multiple address GIVs have been combined with the
2917 same dest_reg GIV, do not create a new register for
2919 else if (unroll_type != UNROLL_COMPLETELY
2920 && v->giv_type == DEST_ADDR
2921 && v->same && v->same->giv_type == DEST_ADDR
2922 && v->same->unrolled
2923 /* combine_givs_p may return true for some cases
2924 where the add and mult values are not equal.
2925 To share a register here, the values must be
2927 && rtx_equal_p (v->same->mult_val, v->mult_val)
2928 && rtx_equal_p (v->same->add_val, v->add_val)
2929 /* If the memory references have different modes,
2930 then the address may not be valid and we must
2931 not share registers. */
2932 && verify_addresses (v, giv_inc, unroll_number))
2934 v->dest_reg = v->same->dest_reg;
2937 else if (unroll_type != UNROLL_COMPLETELY)
2939 /* If not completely unrolling the loop, then create a new
2940 register to hold the split value of the DEST_ADDR giv.
2941 Emit insn to initialize its value before loop start. */
2943 rtx tem = gen_reg_rtx (v->mode);
2944 struct induction *same = v->same;
2945 rtx new_reg = v->new_reg;
2946 record_base_value (REGNO (tem), v->add_val, 0);
2948 if (same && same->derived_from)
2950 /* calculate_giv_inc doesn't work for derived givs.
2951 copy_loop_body works around the problem for the
2952 DEST_REG givs themselves, but it can't handle
2953 DEST_ADDR givs that have been combined with
2954 a derived DEST_REG giv.
2955 So Handle V as if the giv from which V->SAME has
2956 been derived has been combined with V.
2957 recombine_givs only derives givs from givs that
2958 are reduced the ordinary, so we need not worry
2959 about same->derived_from being in turn derived. */
2961 same = same->derived_from;
2962 new_reg = express_from (same, v);
2963 new_reg = replace_rtx (new_reg, same->dest_reg,
2967 /* If the address giv has a constant in its new_reg value,
2968 then this constant can be pulled out and put in value,
2969 instead of being part of the initialization code. */
2971 if (GET_CODE (new_reg) == PLUS
2972 && GET_CODE (XEXP (new_reg, 1)) == CONST_INT)
2975 = plus_constant (tem, INTVAL (XEXP (new_reg, 1)));
2977 /* Only succeed if this will give valid addresses.
2978 Try to validate both the first and the last
2979 address resulting from loop unrolling, if
2980 one fails, then can't do const elim here. */
2981 if (verify_addresses (v, giv_inc, unroll_number))
2983 /* Save the negative of the eliminated const, so
2984 that we can calculate the dest_reg's increment
2986 v->const_adjust = - INTVAL (XEXP (new_reg, 1));
2988 new_reg = XEXP (new_reg, 0);
2989 if (loop_dump_stream)
2990 fprintf (loop_dump_stream,
2991 "Eliminating constant from giv %d\n",
3000 /* If the address hasn't been checked for validity yet, do so
3001 now, and fail completely if either the first or the last
3002 unrolled copy of the address is not a valid address
3003 for the instruction that uses it. */
3004 if (v->dest_reg == tem
3005 && ! verify_addresses (v, giv_inc, unroll_number))
3007 for (v2 = v->next_iv; v2; v2 = v2->next_iv)
3008 if (v2->same_insn == v)
3011 if (loop_dump_stream)
3012 fprintf (loop_dump_stream,
3013 "Invalid address for giv at insn %d\n",
3014 INSN_UID (v->insn));
3018 v->new_reg = new_reg;
3021 /* We set this after the address check, to guarantee that
3022 the register will be initialized. */
3025 /* To initialize the new register, just move the value of
3026 new_reg into it. This is not guaranteed to give a valid
3027 instruction on machines with complex addressing modes.
3028 If we can't recognize it, then delete it and emit insns
3029 to calculate the value from scratch. */
3030 emit_insn_before (gen_rtx_SET (VOIDmode, tem,
3031 copy_rtx (v->new_reg)),
3033 if (recog_memoized (PREV_INSN (loop_start)) < 0)
3037 /* We can't use bl->initial_value to compute the initial
3038 value, because the loop may have been preconditioned.
3039 We must calculate it from NEW_REG. Try using
3040 force_operand instead of emit_iv_add_mult. */
3041 delete_insn (PREV_INSN (loop_start));
3044 ret = force_operand (v->new_reg, tem);
3046 emit_move_insn (tem, ret);
3047 sequence = gen_sequence ();
3049 emit_insn_before (sequence, loop_start);
3051 if (loop_dump_stream)
3052 fprintf (loop_dump_stream,
3053 "Invalid init insn, rewritten.\n");
3058 v->dest_reg = value;
3060 /* Check the resulting address for validity, and fail
3061 if the resulting address would be invalid. */
3062 if (! verify_addresses (v, giv_inc, unroll_number))
3064 for (v2 = v->next_iv; v2; v2 = v2->next_iv)
3065 if (v2->same_insn == v)
3068 if (loop_dump_stream)
3069 fprintf (loop_dump_stream,
3070 "Invalid address for giv at insn %d\n",
3071 INSN_UID (v->insn));
3074 if (v->same && v->same->derived_from)
3076 /* Handle V as if the giv from which V->SAME has
3077 been derived has been combined with V. */
3079 v->same = v->same->derived_from;
3080 v->new_reg = express_from (v->same, v);
3081 v->new_reg = replace_rtx (v->new_reg, v->same->dest_reg,
3087 /* Store the value of dest_reg into the insn. This sharing
3088 will not be a problem as this insn will always be copied
3091 *v->location = v->dest_reg;
3093 /* If this address giv is combined with a dest reg giv, then
3094 save the base giv's induction pointer so that we will be
3095 able to handle this address giv properly. The base giv
3096 itself does not have to be splittable. */
3098 if (v->same && v->same->giv_type == DEST_REG)
3099 addr_combined_regs[REGNO (v->same->new_reg)] = v->same;
3101 if (GET_CODE (v->new_reg) == REG)
3103 /* This giv maybe hasn't been combined with any others.
3104 Make sure that it's giv is marked as splittable here. */
3106 splittable_regs[REGNO (v->new_reg)] = value;
3107 derived_regs[REGNO (v->new_reg)] = v->derived_from != 0;
3109 /* Make it appear to depend upon itself, so that the
3110 giv will be properly split in the main loop above. */
3114 addr_combined_regs[REGNO (v->new_reg)] = v;
3118 if (loop_dump_stream)
3119 fprintf (loop_dump_stream, "DEST_ADDR giv being split.\n");
3125 /* Currently, unreduced giv's can't be split. This is not too much
3126 of a problem since unreduced giv's are not live across loop
3127 iterations anyways. When unrolling a loop completely though,
3128 it makes sense to reduce&split givs when possible, as this will
3129 result in simpler instructions, and will not require that a reg
3130 be live across loop iterations. */
3132 splittable_regs[REGNO (v->dest_reg)] = value;
3133 fprintf (stderr, "Giv %d at insn %d not reduced\n",
3134 REGNO (v->dest_reg), INSN_UID (v->insn));
3140 /* Unreduced givs are only updated once by definition. Reduced givs
3141 are updated as many times as their biv is. Mark it so if this is
3142 a splittable register. Don't need to do anything for address givs
3143 where this may not be a register. */
3145 if (GET_CODE (v->new_reg) == REG)
3149 count = reg_biv_class[REGNO (v->src_reg)]->biv_count;
3151 if (count > 1 && v->derived_from)
3152 /* In this case, there is one set where the giv insn was and one
3153 set each after each biv increment. (Most are likely dead.) */
3156 splittable_regs_updates[REGNO (v->new_reg)] = count;
3161 if (loop_dump_stream)
3165 if (GET_CODE (v->dest_reg) == CONST_INT)
3167 else if (GET_CODE (v->dest_reg) != REG)
3168 regnum = REGNO (XEXP (v->dest_reg, 0));
3170 regnum = REGNO (v->dest_reg);
3171 fprintf (loop_dump_stream, "Giv %d at insn %d safe to split.\n",
3172 regnum, INSN_UID (v->insn));
3179 /* Try to prove that the register is dead after the loop exits. Trace every
3180 loop exit looking for an insn that will always be executed, which sets
3181 the register to some value, and appears before the first use of the register
3182 is found. If successful, then return 1, otherwise return 0. */
3184 /* ?? Could be made more intelligent in the handling of jumps, so that
3185 it can search past if statements and other similar structures. */
3188 reg_dead_after_loop (reg, loop_start, loop_end)
3189 rtx reg, loop_start, loop_end;
3194 int label_count = 0;
3195 int this_loop_num = uid_loop_num[INSN_UID (loop_start)];
3197 /* In addition to checking all exits of this loop, we must also check
3198 all exits of inner nested loops that would exit this loop. We don't
3199 have any way to identify those, so we just give up if there are any
3200 such inner loop exits. */
3202 for (label = loop_number_exit_labels[this_loop_num]; label;
3203 label = LABEL_NEXTREF (label))
3206 if (label_count != loop_number_exit_count[this_loop_num])
3209 /* HACK: Must also search the loop fall through exit, create a label_ref
3210 here which points to the loop_end, and append the loop_number_exit_labels
3212 label = gen_rtx_LABEL_REF (VOIDmode, loop_end);
3213 LABEL_NEXTREF (label) = loop_number_exit_labels[this_loop_num];
3215 for ( ; label; label = LABEL_NEXTREF (label))
3217 /* Succeed if find an insn which sets the biv or if reach end of
3218 function. Fail if find an insn that uses the biv, or if come to
3219 a conditional jump. */
3221 insn = NEXT_INSN (XEXP (label, 0));
3224 code = GET_CODE (insn);
3225 if (GET_RTX_CLASS (code) == 'i')
3229 if (reg_referenced_p (reg, PATTERN (insn)))
3232 set = single_set (insn);
3233 if (set && rtx_equal_p (SET_DEST (set), reg))
3237 if (code == JUMP_INSN)
3239 if (GET_CODE (PATTERN (insn)) == RETURN)
3241 else if (! simplejump_p (insn)
3242 /* Prevent infinite loop following infinite loops. */
3243 || jump_count++ > 20)
3246 insn = JUMP_LABEL (insn);
3249 insn = NEXT_INSN (insn);
3253 /* Success, the register is dead on all loop exits. */
3257 /* Try to calculate the final value of the biv, the value it will have at
3258 the end of the loop. If we can do it, return that value. */
3261 final_biv_value (bl, loop_start, loop_end, n_iterations)
3262 struct iv_class *bl;
3263 rtx loop_start, loop_end;
3264 unsigned HOST_WIDE_INT n_iterations;
3268 /* ??? This only works for MODE_INT biv's. Reject all others for now. */
3270 if (GET_MODE_CLASS (bl->biv->mode) != MODE_INT)
3273 /* The final value for reversed bivs must be calculated differently than
3274 for ordinary bivs. In this case, there is already an insn after the
3275 loop which sets this biv's final value (if necessary), and there are
3276 no other loop exits, so we can return any value. */
3279 if (loop_dump_stream)
3280 fprintf (loop_dump_stream,
3281 "Final biv value for %d, reversed biv.\n", bl->regno);
3286 /* Try to calculate the final value as initial value + (number of iterations
3287 * increment). For this to work, increment must be invariant, the only
3288 exit from the loop must be the fall through at the bottom (otherwise
3289 it may not have its final value when the loop exits), and the initial
3290 value of the biv must be invariant. */
3292 if (n_iterations != 0
3293 && ! loop_number_exit_count[uid_loop_num[INSN_UID (loop_start)]]
3294 && invariant_p (bl->initial_value))
3296 increment = biv_total_increment (bl, loop_start, loop_end);
3298 if (increment && invariant_p (increment))
3300 /* Can calculate the loop exit value, emit insns after loop
3301 end to calculate this value into a temporary register in
3302 case it is needed later. */
3304 tem = gen_reg_rtx (bl->biv->mode);
3305 record_base_value (REGNO (tem), bl->biv->add_val, 0);
3306 /* Make sure loop_end is not the last insn. */
3307 if (NEXT_INSN (loop_end) == 0)
3308 emit_note_after (NOTE_INSN_DELETED, loop_end);
3309 emit_iv_add_mult (increment, GEN_INT (n_iterations),
3310 bl->initial_value, tem, NEXT_INSN (loop_end));
3312 if (loop_dump_stream)
3313 fprintf (loop_dump_stream,
3314 "Final biv value for %d, calculated.\n", bl->regno);
3320 /* Check to see if the biv is dead at all loop exits. */
3321 if (reg_dead_after_loop (bl->biv->src_reg, loop_start, loop_end))
3323 if (loop_dump_stream)
3324 fprintf (loop_dump_stream,
3325 "Final biv value for %d, biv dead after loop exit.\n",
3334 /* Try to calculate the final value of the giv, the value it will have at
3335 the end of the loop. If we can do it, return that value. */
3338 final_giv_value (v, loop_start, loop_end, n_iterations)
3339 struct induction *v;
3340 rtx loop_start, loop_end;
3341 unsigned HOST_WIDE_INT n_iterations;
3343 struct iv_class *bl;
3346 rtx insert_before, seq;
3348 bl = reg_biv_class[REGNO (v->src_reg)];
3350 /* The final value for givs which depend on reversed bivs must be calculated
3351 differently than for ordinary givs. In this case, there is already an
3352 insn after the loop which sets this giv's final value (if necessary),
3353 and there are no other loop exits, so we can return any value. */
3356 if (loop_dump_stream)
3357 fprintf (loop_dump_stream,
3358 "Final giv value for %d, depends on reversed biv\n",
3359 REGNO (v->dest_reg));
3363 /* Try to calculate the final value as a function of the biv it depends
3364 upon. The only exit from the loop must be the fall through at the bottom
3365 (otherwise it may not have its final value when the loop exits). */
3367 /* ??? Can calculate the final giv value by subtracting off the
3368 extra biv increments times the giv's mult_val. The loop must have
3369 only one exit for this to work, but the loop iterations does not need
3372 if (n_iterations != 0
3373 && ! loop_number_exit_count[uid_loop_num[INSN_UID (loop_start)]])
3375 /* ?? It is tempting to use the biv's value here since these insns will
3376 be put after the loop, and hence the biv will have its final value
3377 then. However, this fails if the biv is subsequently eliminated.
3378 Perhaps determine whether biv's are eliminable before trying to
3379 determine whether giv's are replaceable so that we can use the
3380 biv value here if it is not eliminable. */
3382 /* We are emitting code after the end of the loop, so we must make
3383 sure that bl->initial_value is still valid then. It will still
3384 be valid if it is invariant. */
3386 increment = biv_total_increment (bl, loop_start, loop_end);
3388 if (increment && invariant_p (increment)
3389 && invariant_p (bl->initial_value))
3391 /* Can calculate the loop exit value of its biv as
3392 (n_iterations * increment) + initial_value */
3394 /* The loop exit value of the giv is then
3395 (final_biv_value - extra increments) * mult_val + add_val.
3396 The extra increments are any increments to the biv which
3397 occur in the loop after the giv's value is calculated.
3398 We must search from the insn that sets the giv to the end
3399 of the loop to calculate this value. */
3401 insert_before = NEXT_INSN (loop_end);
3403 /* Put the final biv value in tem. */
3404 tem = gen_reg_rtx (bl->biv->mode);
3405 record_base_value (REGNO (tem), bl->biv->add_val, 0);
3406 emit_iv_add_mult (increment, GEN_INT (n_iterations),
3407 bl->initial_value, tem, insert_before);
3409 /* Subtract off extra increments as we find them. */
3410 for (insn = NEXT_INSN (v->insn); insn != loop_end;
3411 insn = NEXT_INSN (insn))
3413 struct induction *biv;
3415 for (biv = bl->biv; biv; biv = biv->next_iv)
3416 if (biv->insn == insn)
3419 tem = expand_binop (GET_MODE (tem), sub_optab, tem,
3420 biv->add_val, NULL_RTX, 0,
3422 seq = gen_sequence ();
3424 emit_insn_before (seq, insert_before);
3428 /* Now calculate the giv's final value. */
3429 emit_iv_add_mult (tem, v->mult_val, v->add_val, tem,
3432 if (loop_dump_stream)
3433 fprintf (loop_dump_stream,
3434 "Final giv value for %d, calc from biv's value.\n",
3435 REGNO (v->dest_reg));
3441 /* Replaceable giv's should never reach here. */
3445 /* Check to see if the biv is dead at all loop exits. */
3446 if (reg_dead_after_loop (v->dest_reg, loop_start, loop_end))
3448 if (loop_dump_stream)
3449 fprintf (loop_dump_stream,
3450 "Final giv value for %d, giv dead after loop exit.\n",
3451 REGNO (v->dest_reg));
3460 /* Look back before LOOP_START for then insn that sets REG and return
3461 the equivalent constant if there is a REG_EQUAL note otherwise just
3462 the SET_SRC of REG. */
3465 loop_find_equiv_value (loop_start, reg)
3473 for (insn = PREV_INSN (loop_start); insn ; insn = PREV_INSN (insn))
3475 if (GET_CODE (insn) == CODE_LABEL)
3478 else if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
3479 && reg_set_p (reg, insn))
3481 /* We found the last insn before the loop that sets the register.
3482 If it sets the entire register, and has a REG_EQUAL note,
3483 then use the value of the REG_EQUAL note. */
3484 if ((set = single_set (insn))
3485 && (SET_DEST (set) == reg))
3487 rtx note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
3489 /* Only use the REG_EQUAL note if it is a constant.
3490 Other things, divide in particular, will cause
3491 problems later if we use them. */
3492 if (note && GET_CODE (XEXP (note, 0)) != EXPR_LIST
3493 && CONSTANT_P (XEXP (note, 0)))
3494 ret = XEXP (note, 0);
3496 ret = SET_SRC (set);
3504 /* Return a simplified rtx for the expression OP - REG.
3506 REG must appear in OP, and OP must be a register or the sum of a register
3509 Thus, the return value must be const0_rtx or the second term.
3511 The caller is responsible for verifying that REG appears in OP and OP has
3515 subtract_reg_term (op, reg)
3520 if (GET_CODE (op) == PLUS)
3522 if (XEXP (op, 0) == reg)
3523 return XEXP (op, 1);
3524 else if (XEXP (op, 1) == reg)
3525 return XEXP (op, 0);
3527 /* OP does not contain REG as a term. */
3532 /* Find and return register term common to both expressions OP0 and
3533 OP1 or NULL_RTX if no such term exists. Each expression must be a
3534 REG or a PLUS of a REG. */
3537 find_common_reg_term (op0, op1)
3540 if ((GET_CODE (op0) == REG || GET_CODE (op0) == PLUS)
3541 && (GET_CODE (op1) == REG || GET_CODE (op1) == PLUS))
3548 if (GET_CODE (op0) == PLUS)
3549 op01 = XEXP (op0, 1), op00 = XEXP (op0, 0);
3551 op01 = const0_rtx, op00 = op0;
3553 if (GET_CODE (op1) == PLUS)
3554 op11 = XEXP (op1, 1), op10 = XEXP (op1, 0);
3556 op11 = const0_rtx, op10 = op1;
3558 /* Find and return common register term if present. */
3559 if (REG_P (op00) && (op00 == op10 || op00 == op11))
3561 else if (REG_P (op01) && (op01 == op10 || op01 == op11))
3565 /* No common register term found. */
3569 /* Calculate the number of loop iterations. Returns the exact number of loop
3570 iterations if it can be calculated, otherwise returns zero. */
3572 unsigned HOST_WIDE_INT
3573 loop_iterations (loop_start, loop_end, loop_info)
3574 rtx loop_start, loop_end;
3575 struct loop_info *loop_info;
3577 rtx comparison, comparison_value;
3578 rtx iteration_var, initial_value, increment, final_value;
3579 enum rtx_code comparison_code;
3580 HOST_WIDE_INT abs_inc;
3581 unsigned HOST_WIDE_INT abs_diff;
3584 int unsigned_p, compare_dir, final_larger;
3588 loop_info->n_iterations = 0;
3589 loop_info->initial_value = 0;
3590 loop_info->initial_equiv_value = 0;
3591 loop_info->comparison_value = 0;
3592 loop_info->final_value = 0;
3593 loop_info->final_equiv_value = 0;
3594 loop_info->increment = 0;
3595 loop_info->iteration_var = 0;
3596 loop_info->unroll_number = 1;
3598 /* We used to use prev_nonnote_insn here, but that fails because it might
3599 accidentally get the branch for a contained loop if the branch for this
3600 loop was deleted. We can only trust branches immediately before the
3602 last_loop_insn = PREV_INSN (loop_end);
3604 /* ??? We should probably try harder to find the jump insn
3605 at the end of the loop. The following code assumes that
3606 the last loop insn is a jump to the top of the loop. */
3607 if (GET_CODE (last_loop_insn) != JUMP_INSN)
3609 if (loop_dump_stream)
3610 fprintf (loop_dump_stream,
3611 "Loop iterations: No final conditional branch found.\n");
3615 /* If there is a more than a single jump to the top of the loop
3616 we cannot (easily) determine the iteration count. */
3617 if (LABEL_NUSES (JUMP_LABEL (last_loop_insn)) > 1)
3619 if (loop_dump_stream)
3620 fprintf (loop_dump_stream,
3621 "Loop iterations: Loop has multiple back edges.\n");
3625 /* Find the iteration variable. If the last insn is a conditional
3626 branch, and the insn before tests a register value, make that the
3627 iteration variable. */
3629 comparison = get_condition_for_loop (last_loop_insn);
3630 if (comparison == 0)
3632 if (loop_dump_stream)
3633 fprintf (loop_dump_stream,
3634 "Loop iterations: No final comparison found.\n");
3638 /* ??? Get_condition may switch position of induction variable and
3639 invariant register when it canonicalizes the comparison. */
3641 comparison_code = GET_CODE (comparison);
3642 iteration_var = XEXP (comparison, 0);
3643 comparison_value = XEXP (comparison, 1);
3645 if (GET_CODE (iteration_var) != REG)
3647 if (loop_dump_stream)
3648 fprintf (loop_dump_stream,
3649 "Loop iterations: Comparison not against register.\n");
3653 /* The only new registers that care created before loop iterations are
3654 givs made from biv increments, so this should never occur. */
3656 if ((unsigned) REGNO (iteration_var) >= reg_iv_type->num_elements)
3659 iteration_info (iteration_var, &initial_value, &increment,
3660 loop_start, loop_end);
3661 if (initial_value == 0)
3662 /* iteration_info already printed a message. */
3667 switch (comparison_code)
3682 /* Cannot determine loop iterations with this case. */
3701 /* If the comparison value is an invariant register, then try to find
3702 its value from the insns before the start of the loop. */
3704 final_value = comparison_value;
3705 if (GET_CODE (comparison_value) == REG && invariant_p (comparison_value))
3707 final_value = loop_find_equiv_value (loop_start, comparison_value);
3708 /* If we don't get an invariant final value, we are better
3709 off with the original register. */
3710 if (!invariant_p (final_value))
3711 final_value = comparison_value;
3714 /* Calculate the approximate final value of the induction variable
3715 (on the last successful iteration). The exact final value
3716 depends on the branch operator, and increment sign. It will be
3717 wrong if the iteration variable is not incremented by one each
3718 time through the loop and (comparison_value + off_by_one -
3719 initial_value) % increment != 0.
3720 ??? Note that the final_value may overflow and thus final_larger
3721 will be bogus. A potentially infinite loop will be classified
3722 as immediate, e.g. for (i = 0x7ffffff0; i <= 0x7fffffff; i++) */
3724 final_value = plus_constant (final_value, off_by_one);
3726 /* Save the calculated values describing this loop's bounds, in case
3727 precondition_loop_p will need them later. These values can not be
3728 recalculated inside precondition_loop_p because strength reduction
3729 optimizations may obscure the loop's structure.
3731 These values are only required by precondition_loop_p and insert_bct
3732 whenever the number of iterations cannot be computed at compile time.
3733 Only the difference between final_value and initial_value is
3734 important. Note that final_value is only approximate. */
3735 loop_info->initial_value = initial_value;
3736 loop_info->comparison_value = comparison_value;
3737 loop_info->final_value = plus_constant (comparison_value, off_by_one);
3738 loop_info->increment = increment;
3739 loop_info->iteration_var = iteration_var;
3740 loop_info->comparison_code = comparison_code;
3742 /* Try to determine the iteration count for loops such
3743 as (for i = init; i < init + const; i++). When running the
3744 loop optimization twice, the first pass often converts simple
3745 loops into this form. */
3747 if (REG_P (initial_value))
3753 reg1 = initial_value;
3754 if (GET_CODE (final_value) == PLUS)
3755 reg2 = XEXP (final_value, 0), const2 = XEXP (final_value, 1);
3757 reg2 = final_value, const2 = const0_rtx;
3759 /* Check for initial_value = reg1, final_value = reg2 + const2,
3760 where reg1 != reg2. */
3761 if (REG_P (reg2) && reg2 != reg1)
3765 /* Find what reg1 is equivalent to. Hopefully it will
3766 either be reg2 or reg2 plus a constant. */
3767 temp = loop_find_equiv_value (loop_start, reg1);
3768 if (find_common_reg_term (temp, reg2))
3769 initial_value = temp;
3772 /* Find what reg2 is equivalent to. Hopefully it will
3773 either be reg1 or reg1 plus a constant. Let's ignore
3774 the latter case for now since it is not so common. */
3775 temp = loop_find_equiv_value (loop_start, reg2);
3776 if (temp == loop_info->iteration_var)
3777 temp = initial_value;
3779 final_value = (const2 == const0_rtx)
3780 ? reg1 : gen_rtx_PLUS (GET_MODE (reg1), reg1, const2);
3783 else if (loop_info->vtop && GET_CODE (reg2) == CONST_INT)
3787 /* When running the loop optimizer twice, check_dbra_loop
3788 further obfuscates reversible loops of the form:
3789 for (i = init; i < init + const; i++). We often end up with
3790 final_value = 0, initial_value = temp, temp = temp2 - init,
3791 where temp2 = init + const. If the loop has a vtop we
3792 can replace initial_value with const. */
3794 temp = loop_find_equiv_value (loop_start, reg1);
3795 if (GET_CODE (temp) == MINUS && REG_P (XEXP (temp, 0)))
3797 rtx temp2 = loop_find_equiv_value (loop_start, XEXP (temp, 0));
3798 if (GET_CODE (temp2) == PLUS
3799 && XEXP (temp2, 0) == XEXP (temp, 1))
3800 initial_value = XEXP (temp2, 1);
3805 /* If have initial_value = reg + const1 and final_value = reg +
3806 const2, then replace initial_value with const1 and final_value
3807 with const2. This should be safe since we are protected by the
3808 initial comparison before entering the loop if we have a vtop.
3809 For example, a + b < a + c is not equivalent to b < c for all a
3810 when using modulo arithmetic.
3812 ??? Without a vtop we could still perform the optimization if we check
3813 the initial and final values carefully. */
3815 && (reg_term = find_common_reg_term (initial_value, final_value)))
3817 initial_value = subtract_reg_term (initial_value, reg_term);
3818 final_value = subtract_reg_term (final_value, reg_term);
3821 loop_info->initial_equiv_value = initial_value;
3822 loop_info->final_equiv_value = final_value;
3824 /* For EQ comparison loops, we don't have a valid final value.
3825 Check this now so that we won't leave an invalid value if we
3826 return early for any other reason. */
3827 if (comparison_code == EQ)
3828 loop_info->final_equiv_value = loop_info->final_value = 0;
3832 if (loop_dump_stream)
3833 fprintf (loop_dump_stream,
3834 "Loop iterations: Increment value can't be calculated.\n");
3838 if (GET_CODE (increment) != CONST_INT)
3840 /* If we have a REG, check to see if REG holds a constant value. */
3841 /* ??? Other RTL, such as (neg (reg)) is possible here, but it isn't
3842 clear if it is worthwhile to try to handle such RTL. */
3843 if (GET_CODE (increment) == REG || GET_CODE (increment) == SUBREG)
3844 increment = loop_find_equiv_value (loop_start, increment);
3846 if (GET_CODE (increment) != CONST_INT)
3848 if (loop_dump_stream)
3850 fprintf (loop_dump_stream,
3851 "Loop iterations: Increment value not constant ");
3852 print_rtl (loop_dump_stream, increment);
3853 fprintf (loop_dump_stream, ".\n");
3857 loop_info->increment = increment;
3860 if (GET_CODE (initial_value) != CONST_INT)
3862 if (loop_dump_stream)
3864 fprintf (loop_dump_stream,
3865 "Loop iterations: Initial value not constant ");
3866 print_rtl (loop_dump_stream, initial_value);
3867 fprintf (loop_dump_stream, ".\n");
3871 else if (comparison_code == EQ)
3873 if (loop_dump_stream)
3874 fprintf (loop_dump_stream,
3875 "Loop iterations: EQ comparison loop.\n");
3878 else if (GET_CODE (final_value) != CONST_INT)
3880 if (loop_dump_stream)
3882 fprintf (loop_dump_stream,
3883 "Loop iterations: Final value not constant ");
3884 print_rtl (loop_dump_stream, final_value);
3885 fprintf (loop_dump_stream, ".\n");
3890 /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
3893 = ((unsigned HOST_WIDE_INT) INTVAL (final_value)
3894 > (unsigned HOST_WIDE_INT) INTVAL (initial_value))
3895 - ((unsigned HOST_WIDE_INT) INTVAL (final_value)
3896 < (unsigned HOST_WIDE_INT) INTVAL (initial_value));
3898 final_larger = (INTVAL (final_value) > INTVAL (initial_value))
3899 - (INTVAL (final_value) < INTVAL (initial_value));
3901 if (INTVAL (increment) > 0)
3903 else if (INTVAL (increment) == 0)
3908 /* There are 27 different cases: compare_dir = -1, 0, 1;
3909 final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
3910 There are 4 normal cases, 4 reverse cases (where the iteration variable
3911 will overflow before the loop exits), 4 infinite loop cases, and 15
3912 immediate exit (0 or 1 iteration depending on loop type) cases.
3913 Only try to optimize the normal cases. */
3915 /* (compare_dir/final_larger/increment_dir)
3916 Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
3917 Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
3918 Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
3919 Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
3921 /* ?? If the meaning of reverse loops (where the iteration variable
3922 will overflow before the loop exits) is undefined, then could
3923 eliminate all of these special checks, and just always assume
3924 the loops are normal/immediate/infinite. Note that this means
3925 the sign of increment_dir does not have to be known. Also,
3926 since it does not really hurt if immediate exit loops or infinite loops
3927 are optimized, then that case could be ignored also, and hence all
3928 loops can be optimized.
3930 According to ANSI Spec, the reverse loop case result is undefined,
3931 because the action on overflow is undefined.
3933 See also the special test for NE loops below. */
3935 if (final_larger == increment_dir && final_larger != 0
3936 && (final_larger == compare_dir || compare_dir == 0))
3941 if (loop_dump_stream)
3942 fprintf (loop_dump_stream,
3943 "Loop iterations: Not normal loop.\n");
3947 /* Calculate the number of iterations, final_value is only an approximation,
3948 so correct for that. Note that abs_diff and n_iterations are
3949 unsigned, because they can be as large as 2^n - 1. */
3951 abs_inc = INTVAL (increment);
3953 abs_diff = INTVAL (final_value) - INTVAL (initial_value);
3954 else if (abs_inc < 0)
3956 abs_diff = INTVAL (initial_value) - INTVAL (final_value);
3962 /* For NE tests, make sure that the iteration variable won't miss
3963 the final value. If abs_diff mod abs_incr is not zero, then the
3964 iteration variable will overflow before the loop exits, and we
3965 can not calculate the number of iterations. */
3966 if (compare_dir == 0 && (abs_diff % abs_inc) != 0)
3969 /* Note that the number of iterations could be calculated using
3970 (abs_diff + abs_inc - 1) / abs_inc, provided care was taken to
3971 handle potential overflow of the summation. */
3972 loop_info->n_iterations = abs_diff / abs_inc + ((abs_diff % abs_inc) != 0);
3973 return loop_info->n_iterations;
3977 /* Replace uses of split bivs with their split pseudo register. This is
3978 for original instructions which remain after loop unrolling without
3982 remap_split_bivs (x)
3985 register enum rtx_code code;
3987 register const char *fmt;
3992 code = GET_CODE (x);
4007 /* If non-reduced/final-value givs were split, then this would also
4008 have to remap those givs also. */
4010 if (REGNO (x) < max_reg_before_loop
4011 && REG_IV_TYPE (REGNO (x)) == BASIC_INDUCT)
4012 return reg_biv_class[REGNO (x)]->biv->src_reg;
4019 fmt = GET_RTX_FORMAT (code);
4020 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
4023 XEXP (x, i) = remap_split_bivs (XEXP (x, i));
4027 for (j = 0; j < XVECLEN (x, i); j++)
4028 XVECEXP (x, i, j) = remap_split_bivs (XVECEXP (x, i, j));
4034 /* If FIRST_UID is a set of REGNO, and FIRST_UID dominates LAST_UID (e.g.
4035 FIST_UID is always executed if LAST_UID is), then return 1. Otherwise
4036 return 0. COPY_START is where we can start looking for the insns
4037 FIRST_UID and LAST_UID. COPY_END is where we stop looking for these
4040 If there is no JUMP_INSN between LOOP_START and FIRST_UID, then FIRST_UID
4041 must dominate LAST_UID.
4043 If there is a CODE_LABEL between FIRST_UID and LAST_UID, then FIRST_UID
4044 may not dominate LAST_UID.
4046 If there is no CODE_LABEL between FIRST_UID and LAST_UID, then FIRST_UID
4047 must dominate LAST_UID. */
4050 set_dominates_use (regno, first_uid, last_uid, copy_start, copy_end)
4057 int passed_jump = 0;
4058 rtx p = NEXT_INSN (copy_start);
4060 while (INSN_UID (p) != first_uid)
4062 if (GET_CODE (p) == JUMP_INSN)
4064 /* Could not find FIRST_UID. */
4070 /* Verify that FIRST_UID is an insn that entirely sets REGNO. */
4071 if (GET_RTX_CLASS (GET_CODE (p)) != 'i'
4072 || ! dead_or_set_regno_p (p, regno))
4075 /* FIRST_UID is always executed. */
4076 if (passed_jump == 0)
4079 while (INSN_UID (p) != last_uid)
4081 /* If we see a CODE_LABEL between FIRST_UID and LAST_UID, then we
4082 can not be sure that FIRST_UID dominates LAST_UID. */
4083 if (GET_CODE (p) == CODE_LABEL)
4085 /* Could not find LAST_UID, but we reached the end of the loop, so
4087 else if (p == copy_end)
4092 /* FIRST_UID is always executed if LAST_UID is executed. */