1 /* Try to unroll loops, and split induction variables.
2 Copyright (C) 1992, 1993, 1994, 1995 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 };
151 #include "insn-config.h"
152 #include "integrate.h"
159 /* This controls which loops are unrolled, and by how much we unroll
162 #ifndef MAX_UNROLLED_INSNS
163 #define MAX_UNROLLED_INSNS 100
166 /* Indexed by register number, if non-zero, then it contains a pointer
167 to a struct induction for a DEST_REG giv which has been combined with
168 one of more address givs. This is needed because whenever such a DEST_REG
169 giv is modified, we must modify the value of all split address givs
170 that were combined with this DEST_REG giv. */
172 static struct induction **addr_combined_regs;
174 /* Indexed by register number, if this is a splittable induction variable,
175 then this will hold the current value of the register, which depends on the
178 static rtx *splittable_regs;
180 /* Indexed by register number, if this is a splittable induction variable,
181 then this will hold the number of instructions in the loop that modify
182 the induction variable. Used to ensure that only the last insn modifying
183 a split iv will update the original iv of the dest. */
185 static int *splittable_regs_updates;
187 /* Values describing the current loop's iteration variable. These are set up
188 by loop_iterations, and used by precondition_loop_p. */
190 static rtx loop_iteration_var;
191 static rtx loop_initial_value;
192 static rtx loop_increment;
193 static rtx loop_final_value;
195 /* Forward declarations. */
197 static void init_reg_map PROTO((struct inline_remap *, int));
198 static int precondition_loop_p PROTO((rtx *, rtx *, rtx *, rtx, rtx));
199 static rtx calculate_giv_inc PROTO((rtx, rtx, int));
200 static rtx initial_reg_note_copy PROTO((rtx, struct inline_remap *));
201 static void final_reg_note_copy PROTO((rtx, struct inline_remap *));
202 static void copy_loop_body PROTO((rtx, rtx, struct inline_remap *, rtx, int,
203 enum unroll_types, rtx, rtx, rtx, rtx));
204 static void iteration_info PROTO((rtx, rtx *, rtx *, rtx, rtx));
205 static rtx approx_final_value PROTO((enum rtx_code, rtx, int *, int *));
206 static int find_splittable_regs PROTO((enum unroll_types, rtx, rtx, rtx, int));
207 static int find_splittable_givs PROTO((struct iv_class *,enum unroll_types,
208 rtx, rtx, rtx, int));
209 static int reg_dead_after_loop PROTO((rtx, rtx, rtx));
210 static rtx fold_rtx_mult_add PROTO((rtx, rtx, rtx, enum machine_mode));
211 static rtx remap_split_bivs PROTO((rtx));
213 /* Try to unroll one loop and split induction variables in the loop.
215 The loop is described by the arguments LOOP_END, INSN_COUNT, and
216 LOOP_START. END_INSERT_BEFORE indicates where insns should be added
217 which need to be executed when the loop falls through. STRENGTH_REDUCTION_P
218 indicates whether information generated in the strength reduction pass
221 This function is intended to be called from within `strength_reduce'
225 unroll_loop (loop_end, insn_count, loop_start, end_insert_before,
230 rtx end_insert_before;
231 int strength_reduce_p;
234 int unroll_number = 1;
235 rtx copy_start, copy_end;
236 rtx insn, copy, sequence, pattern, tem;
237 int max_labelno, max_insnno;
239 struct inline_remap *map;
247 int splitting_not_safe = 0;
248 enum unroll_types unroll_type;
249 int loop_preconditioned = 0;
251 /* This points to the last real insn in the loop, which should be either
252 a JUMP_INSN (for conditional jumps) or a BARRIER (for unconditional
256 /* Don't bother unrolling huge loops. Since the minimum factor is
257 two, loops greater than one half of MAX_UNROLLED_INSNS will never
259 if (insn_count > MAX_UNROLLED_INSNS / 2)
261 if (loop_dump_stream)
262 fprintf (loop_dump_stream, "Unrolling failure: Loop too big.\n");
266 /* When emitting debugger info, we can't unroll loops with unequal numbers
267 of block_beg and block_end notes, because that would unbalance the block
268 structure of the function. This can happen as a result of the
269 "if (foo) bar; else break;" optimization in jump.c. */
271 if (write_symbols != NO_DEBUG)
273 int block_begins = 0;
276 for (insn = loop_start; insn != loop_end; insn = NEXT_INSN (insn))
278 if (GET_CODE (insn) == NOTE)
280 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG)
282 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END)
287 if (block_begins != block_ends)
289 if (loop_dump_stream)
290 fprintf (loop_dump_stream,
291 "Unrolling failure: Unbalanced block notes.\n");
296 /* Determine type of unroll to perform. Depends on the number of iterations
297 and the size of the loop. */
299 /* If there is no strength reduce info, then set loop_n_iterations to zero.
300 This can happen if strength_reduce can't find any bivs in the loop.
301 A value of zero indicates that the number of iterations could not be
304 if (! strength_reduce_p)
305 loop_n_iterations = 0;
307 if (loop_dump_stream && loop_n_iterations > 0)
308 fprintf (loop_dump_stream,
309 "Loop unrolling: %d iterations.\n", loop_n_iterations);
311 /* Find and save a pointer to the last nonnote insn in the loop. */
313 last_loop_insn = prev_nonnote_insn (loop_end);
315 /* Calculate how many times to unroll the loop. Indicate whether or
316 not the loop is being completely unrolled. */
318 if (loop_n_iterations == 1)
320 /* If number of iterations is exactly 1, then eliminate the compare and
321 branch at the end of the loop since they will never be taken.
322 Then return, since no other action is needed here. */
324 /* If the last instruction is not a BARRIER or a JUMP_INSN, then
325 don't do anything. */
327 if (GET_CODE (last_loop_insn) == BARRIER)
329 /* Delete the jump insn. This will delete the barrier also. */
330 delete_insn (PREV_INSN (last_loop_insn));
332 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
335 /* The immediately preceding insn is a compare which must be
337 delete_insn (last_loop_insn);
338 delete_insn (PREV_INSN (last_loop_insn));
340 /* The immediately preceding insn may not be the compare, so don't
342 delete_insn (last_loop_insn);
347 else if (loop_n_iterations > 0
348 && loop_n_iterations * insn_count < MAX_UNROLLED_INSNS)
350 unroll_number = loop_n_iterations;
351 unroll_type = UNROLL_COMPLETELY;
353 else if (loop_n_iterations > 0)
355 /* Try to factor the number of iterations. Don't bother with the
356 general case, only using 2, 3, 5, and 7 will get 75% of all
357 numbers theoretically, and almost all in practice. */
359 for (i = 0; i < NUM_FACTORS; i++)
360 factors[i].count = 0;
362 temp = loop_n_iterations;
363 for (i = NUM_FACTORS - 1; i >= 0; i--)
364 while (temp % factors[i].factor == 0)
367 temp = temp / factors[i].factor;
370 /* Start with the larger factors first so that we generally
371 get lots of unrolling. */
375 for (i = 3; i >= 0; i--)
376 while (factors[i].count--)
378 if (temp * factors[i].factor < MAX_UNROLLED_INSNS)
380 unroll_number *= factors[i].factor;
381 temp *= factors[i].factor;
387 /* If we couldn't find any factors, then unroll as in the normal
389 if (unroll_number == 1)
391 if (loop_dump_stream)
392 fprintf (loop_dump_stream,
393 "Loop unrolling: No factors found.\n");
396 unroll_type = UNROLL_MODULO;
400 /* Default case, calculate number of times to unroll loop based on its
402 if (unroll_number == 1)
404 if (8 * insn_count < MAX_UNROLLED_INSNS)
406 else if (4 * insn_count < MAX_UNROLLED_INSNS)
411 unroll_type = UNROLL_NAIVE;
414 /* Now we know how many times to unroll the loop. */
416 if (loop_dump_stream)
417 fprintf (loop_dump_stream,
418 "Unrolling loop %d times.\n", unroll_number);
421 if (unroll_type == UNROLL_COMPLETELY || unroll_type == UNROLL_MODULO)
423 /* Loops of these types should never start with a jump down to
424 the exit condition test. For now, check for this case just to
425 be sure. UNROLL_NAIVE loops can be of this form, this case is
428 while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
429 insn = NEXT_INSN (insn);
430 if (GET_CODE (insn) == JUMP_INSN)
434 if (unroll_type == UNROLL_COMPLETELY)
436 /* Completely unrolling the loop: Delete the compare and branch at
437 the end (the last two instructions). This delete must done at the
438 very end of loop unrolling, to avoid problems with calls to
439 back_branch_in_range_p, which is called by find_splittable_regs.
440 All increments of splittable bivs/givs are changed to load constant
443 copy_start = loop_start;
445 /* Set insert_before to the instruction immediately after the JUMP_INSN
446 (or BARRIER), so that any NOTEs between the JUMP_INSN and the end of
447 the loop will be correctly handled by copy_loop_body. */
448 insert_before = NEXT_INSN (last_loop_insn);
450 /* Set copy_end to the insn before the jump at the end of the loop. */
451 if (GET_CODE (last_loop_insn) == BARRIER)
452 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
453 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
456 /* The instruction immediately before the JUMP_INSN is a compare
457 instruction which we do not want to copy. */
458 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
460 /* The instruction immediately before the JUMP_INSN may not be the
461 compare, so we must copy it. */
462 copy_end = PREV_INSN (last_loop_insn);
467 /* We currently can't unroll a loop if it doesn't end with a
468 JUMP_INSN. There would need to be a mechanism that recognizes
469 this case, and then inserts a jump after each loop body, which
470 jumps to after the last loop body. */
471 if (loop_dump_stream)
472 fprintf (loop_dump_stream,
473 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
477 else if (unroll_type == UNROLL_MODULO)
479 /* Partially unrolling the loop: The compare and branch at the end
480 (the last two instructions) must remain. Don't copy the compare
481 and branch instructions at the end of the loop. Insert the unrolled
482 code immediately before the compare/branch at the end so that the
483 code will fall through to them as before. */
485 copy_start = loop_start;
487 /* Set insert_before to the jump insn at the end of the loop.
488 Set copy_end to before the jump insn at the end of the loop. */
489 if (GET_CODE (last_loop_insn) == BARRIER)
491 insert_before = PREV_INSN (last_loop_insn);
492 copy_end = PREV_INSN (insert_before);
494 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
497 /* The instruction immediately before the JUMP_INSN is a compare
498 instruction which we do not want to copy or delete. */
499 insert_before = PREV_INSN (last_loop_insn);
500 copy_end = PREV_INSN (insert_before);
502 /* The instruction immediately before the JUMP_INSN may not be the
503 compare, so we must copy it. */
504 insert_before = last_loop_insn;
505 copy_end = PREV_INSN (last_loop_insn);
510 /* We currently can't unroll a loop if it doesn't end with a
511 JUMP_INSN. There would need to be a mechanism that recognizes
512 this case, and then inserts a jump after each loop body, which
513 jumps to after the last loop body. */
514 if (loop_dump_stream)
515 fprintf (loop_dump_stream,
516 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
522 /* Normal case: Must copy the compare and branch instructions at the
525 if (GET_CODE (last_loop_insn) == BARRIER)
527 /* Loop ends with an unconditional jump and a barrier.
528 Handle this like above, don't copy jump and barrier.
529 This is not strictly necessary, but doing so prevents generating
530 unconditional jumps to an immediately following label.
532 This will be corrected below if the target of this jump is
533 not the start_label. */
535 insert_before = PREV_INSN (last_loop_insn);
536 copy_end = PREV_INSN (insert_before);
538 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
540 /* Set insert_before to immediately after the JUMP_INSN, so that
541 NOTEs at the end of the loop will be correctly handled by
543 insert_before = NEXT_INSN (last_loop_insn);
544 copy_end = last_loop_insn;
548 /* We currently can't unroll a loop if it doesn't end with a
549 JUMP_INSN. There would need to be a mechanism that recognizes
550 this case, and then inserts a jump after each loop body, which
551 jumps to after the last loop body. */
552 if (loop_dump_stream)
553 fprintf (loop_dump_stream,
554 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
558 /* If copying exit test branches because they can not be eliminated,
559 then must convert the fall through case of the branch to a jump past
560 the end of the loop. Create a label to emit after the loop and save
561 it for later use. Do not use the label after the loop, if any, since
562 it might be used by insns outside the loop, or there might be insns
563 added before it later by final_[bg]iv_value which must be after
564 the real exit label. */
565 exit_label = gen_label_rtx ();
568 while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
569 insn = NEXT_INSN (insn);
571 if (GET_CODE (insn) == JUMP_INSN)
573 /* The loop starts with a jump down to the exit condition test.
574 Start copying the loop after the barrier following this
576 copy_start = NEXT_INSN (insn);
578 /* Splitting induction variables doesn't work when the loop is
579 entered via a jump to the bottom, because then we end up doing
580 a comparison against a new register for a split variable, but
581 we did not execute the set insn for the new register because
582 it was skipped over. */
583 splitting_not_safe = 1;
584 if (loop_dump_stream)
585 fprintf (loop_dump_stream,
586 "Splitting not safe, because loop not entered at top.\n");
589 copy_start = loop_start;
592 /* This should always be the first label in the loop. */
593 start_label = NEXT_INSN (copy_start);
594 /* There may be a line number note and/or a loop continue note here. */
595 while (GET_CODE (start_label) == NOTE)
596 start_label = NEXT_INSN (start_label);
597 if (GET_CODE (start_label) != CODE_LABEL)
599 /* This can happen as a result of jump threading. If the first insns in
600 the loop test the same condition as the loop's backward jump, or the
601 opposite condition, then the backward jump will be modified to point
602 to elsewhere, and the loop's start label is deleted.
604 This case currently can not be handled by the loop unrolling code. */
606 if (loop_dump_stream)
607 fprintf (loop_dump_stream,
608 "Unrolling failure: unknown insns between BEG note and loop label.\n");
611 if (LABEL_NAME (start_label))
613 /* The jump optimization pass must have combined the original start label
614 with a named label for a goto. We can't unroll this case because
615 jumps which go to the named label must be handled differently than
616 jumps to the loop start, and it is impossible to differentiate them
618 if (loop_dump_stream)
619 fprintf (loop_dump_stream,
620 "Unrolling failure: loop start label is gone\n");
624 if (unroll_type == UNROLL_NAIVE
625 && GET_CODE (last_loop_insn) == BARRIER
626 && start_label != JUMP_LABEL (PREV_INSN (last_loop_insn)))
628 /* In this case, we must copy the jump and barrier, because they will
629 not be converted to jumps to an immediately following label. */
631 insert_before = NEXT_INSN (last_loop_insn);
632 copy_end = last_loop_insn;
635 /* Allocate a translation table for the labels and insn numbers.
636 They will be filled in as we copy the insns in the loop. */
638 max_labelno = max_label_num ();
639 max_insnno = get_max_uid ();
641 map = (struct inline_remap *) alloca (sizeof (struct inline_remap));
643 map->integrating = 0;
645 /* Allocate the label map. */
649 map->label_map = (rtx *) alloca (max_labelno * sizeof (rtx));
651 local_label = (char *) alloca (max_labelno);
652 bzero (local_label, max_labelno);
657 /* Search the loop and mark all local labels, i.e. the ones which have to
658 be distinct labels when copied. For all labels which might be
659 non-local, set their label_map entries to point to themselves.
660 If they happen to be local their label_map entries will be overwritten
661 before the loop body is copied. The label_map entries for local labels
662 will be set to a different value each time the loop body is copied. */
664 for (insn = copy_start; insn != loop_end; insn = NEXT_INSN (insn))
666 if (GET_CODE (insn) == CODE_LABEL)
667 local_label[CODE_LABEL_NUMBER (insn)] = 1;
668 else if (GET_CODE (insn) == JUMP_INSN)
670 if (JUMP_LABEL (insn))
671 map->label_map[CODE_LABEL_NUMBER (JUMP_LABEL (insn))]
673 else if (GET_CODE (PATTERN (insn)) == ADDR_VEC
674 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
676 rtx pat = PATTERN (insn);
677 int diff_vec_p = GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC;
678 int len = XVECLEN (pat, diff_vec_p);
681 for (i = 0; i < len; i++)
683 label = XEXP (XVECEXP (pat, diff_vec_p, i), 0);
684 map->label_map[CODE_LABEL_NUMBER (label)] = label;
690 /* Allocate space for the insn map. */
692 map->insn_map = (rtx *) alloca (max_insnno * sizeof (rtx));
694 /* Set this to zero, to indicate that we are doing loop unrolling,
695 not function inlining. */
696 map->inline_target = 0;
698 /* The register and constant maps depend on the number of registers
699 present, so the final maps can't be created until after
700 find_splittable_regs is called. However, they are needed for
701 preconditioning, so we create temporary maps when preconditioning
704 /* The preconditioning code may allocate two new pseudo registers. */
705 maxregnum = max_reg_num ();
707 /* Allocate and zero out the splittable_regs and addr_combined_regs
708 arrays. These must be zeroed here because they will be used if
709 loop preconditioning is performed, and must be zero for that case.
711 It is safe to do this here, since the extra registers created by the
712 preconditioning code and find_splittable_regs will never be used
713 to access the splittable_regs[] and addr_combined_regs[] arrays. */
715 splittable_regs = (rtx *) alloca (maxregnum * sizeof (rtx));
716 bzero ((char *) splittable_regs, maxregnum * sizeof (rtx));
717 splittable_regs_updates = (int *) alloca (maxregnum * sizeof (int));
718 bzero ((char *) splittable_regs_updates, maxregnum * sizeof (int));
720 = (struct induction **) alloca (maxregnum * sizeof (struct induction *));
721 bzero ((char *) addr_combined_regs, maxregnum * sizeof (struct induction *));
722 /* We must limit it to max_reg_before_loop, because only these pseudo
723 registers have valid regno_first_uid info. Any register created after
724 that is unlikely to be local to the loop anyways. */
725 local_regno = (char *) alloca (max_reg_before_loop);
726 bzero (local_regno, max_reg_before_loop);
728 /* Mark all local registers, i.e. the ones which are referenced only
730 if (INSN_UID (copy_end) < max_uid_for_loop)
732 int copy_start_luid = INSN_LUID (copy_start);
733 int copy_end_luid = INSN_LUID (copy_end);
735 /* If a register is used in the jump insn, we must not duplicate it
736 since it will also be used outside the loop. */
737 if (GET_CODE (copy_end) == JUMP_INSN)
739 /* If copy_start points to the NOTE that starts the loop, then we must
740 use the next luid, because invariant pseudo-regs moved out of the loop
741 have their lifetimes modified to start here, but they are not safe
743 if (copy_start == loop_start)
746 for (j = FIRST_PSEUDO_REGISTER; j < max_reg_before_loop; ++j)
747 if (regno_first_uid[j] > 0 && regno_first_uid[j] <= max_uid_for_loop
748 && uid_luid[regno_first_uid[j]] >= copy_start_luid
749 && regno_last_uid[j] > 0 && regno_last_uid[j] <= max_uid_for_loop
750 && uid_luid[regno_last_uid[j]] <= copy_end_luid)
754 /* If this loop requires exit tests when unrolled, check to see if we
755 can precondition the loop so as to make the exit tests unnecessary.
756 Just like variable splitting, this is not safe if the loop is entered
757 via a jump to the bottom. Also, can not do this if no strength
758 reduce info, because precondition_loop_p uses this info. */
760 /* Must copy the loop body for preconditioning before the following
761 find_splittable_regs call since that will emit insns which need to
762 be after the preconditioned loop copies, but immediately before the
763 unrolled loop copies. */
765 /* Also, it is not safe to split induction variables for the preconditioned
766 copies of the loop body. If we split induction variables, then the code
767 assumes that each induction variable can be represented as a function
768 of its initial value and the loop iteration number. This is not true
769 in this case, because the last preconditioned copy of the loop body
770 could be any iteration from the first up to the `unroll_number-1'th,
771 depending on the initial value of the iteration variable. Therefore
772 we can not split induction variables here, because we can not calculate
773 their value. Hence, this code must occur before find_splittable_regs
776 if (unroll_type == UNROLL_NAIVE && ! splitting_not_safe && strength_reduce_p)
778 rtx initial_value, final_value, increment;
780 if (precondition_loop_p (&initial_value, &final_value, &increment,
781 loop_start, loop_end))
783 register rtx diff, temp;
784 enum machine_mode mode;
786 int abs_inc, neg_inc;
788 map->reg_map = (rtx *) alloca (maxregnum * sizeof (rtx));
790 map->const_equiv_map = (rtx *) alloca (maxregnum * sizeof (rtx));
791 map->const_age_map = (unsigned *) alloca (maxregnum
792 * sizeof (unsigned));
793 map->const_equiv_map_size = maxregnum;
794 global_const_equiv_map = map->const_equiv_map;
795 global_const_equiv_map_size = maxregnum;
797 init_reg_map (map, maxregnum);
799 /* Limit loop unrolling to 4, since this will make 7 copies of
801 if (unroll_number > 4)
804 /* Save the absolute value of the increment, and also whether or
805 not it is negative. */
807 abs_inc = INTVAL (increment);
816 /* Decide what mode to do these calculations in. Choose the larger
817 of final_value's mode and initial_value's mode, or a full-word if
818 both are constants. */
819 mode = GET_MODE (final_value);
820 if (mode == VOIDmode)
822 mode = GET_MODE (initial_value);
823 if (mode == VOIDmode)
826 else if (mode != GET_MODE (initial_value)
827 && (GET_MODE_SIZE (mode)
828 < GET_MODE_SIZE (GET_MODE (initial_value))))
829 mode = GET_MODE (initial_value);
831 /* Calculate the difference between the final and initial values.
832 Final value may be a (plus (reg x) (const_int 1)) rtx.
833 Let the following cse pass simplify this if initial value is
836 We must copy the final and initial values here to avoid
837 improperly shared rtl. */
839 diff = expand_binop (mode, sub_optab, copy_rtx (final_value),
840 copy_rtx (initial_value), NULL_RTX, 0,
843 /* Now calculate (diff % (unroll * abs (increment))) by using an
845 diff = expand_binop (GET_MODE (diff), and_optab, diff,
846 GEN_INT (unroll_number * abs_inc - 1),
847 NULL_RTX, 0, OPTAB_LIB_WIDEN);
849 /* Now emit a sequence of branches to jump to the proper precond
852 labels = (rtx *) alloca (sizeof (rtx) * unroll_number);
853 for (i = 0; i < unroll_number; i++)
854 labels[i] = gen_label_rtx ();
856 /* Check for the case where the initial value is greater than or equal
857 to the final value. In that case, we want to execute exactly
858 one loop iteration. The code below will fail for this case. */
860 emit_cmp_insn (initial_value, final_value, neg_inc ? LE : GE,
861 NULL_RTX, mode, 0, 0);
863 emit_jump_insn (gen_ble (labels[1]));
865 emit_jump_insn (gen_bge (labels[1]));
866 JUMP_LABEL (get_last_insn ()) = labels[1];
867 LABEL_NUSES (labels[1])++;
869 /* Assuming the unroll_number is 4, and the increment is 2, then
870 for a negative increment: for a positive increment:
871 diff = 0,1 precond 0 diff = 0,7 precond 0
872 diff = 2,3 precond 3 diff = 1,2 precond 1
873 diff = 4,5 precond 2 diff = 3,4 precond 2
874 diff = 6,7 precond 1 diff = 5,6 precond 3 */
876 /* We only need to emit (unroll_number - 1) branches here, the
877 last case just falls through to the following code. */
879 /* ??? This would give better code if we emitted a tree of branches
880 instead of the current linear list of branches. */
882 for (i = 0; i < unroll_number - 1; i++)
885 enum rtx_code cmp_code;
887 /* For negative increments, must invert the constant compared
888 against, except when comparing against zero. */
896 cmp_const = unroll_number - i;
905 emit_cmp_insn (diff, GEN_INT (abs_inc * cmp_const),
906 cmp_code, NULL_RTX, mode, 0, 0);
909 emit_jump_insn (gen_beq (labels[i]));
911 emit_jump_insn (gen_bge (labels[i]));
913 emit_jump_insn (gen_ble (labels[i]));
914 JUMP_LABEL (get_last_insn ()) = labels[i];
915 LABEL_NUSES (labels[i])++;
918 /* If the increment is greater than one, then we need another branch,
919 to handle other cases equivalent to 0. */
921 /* ??? This should be merged into the code above somehow to help
922 simplify the code here, and reduce the number of branches emitted.
923 For the negative increment case, the branch here could easily
924 be merged with the `0' case branch above. For the positive
925 increment case, it is not clear how this can be simplified. */
930 enum rtx_code cmp_code;
934 cmp_const = abs_inc - 1;
939 cmp_const = abs_inc * (unroll_number - 1) + 1;
943 emit_cmp_insn (diff, GEN_INT (cmp_const), cmp_code, NULL_RTX,
947 emit_jump_insn (gen_ble (labels[0]));
949 emit_jump_insn (gen_bge (labels[0]));
950 JUMP_LABEL (get_last_insn ()) = labels[0];
951 LABEL_NUSES (labels[0])++;
954 sequence = gen_sequence ();
956 emit_insn_before (sequence, loop_start);
958 /* Only the last copy of the loop body here needs the exit
959 test, so set copy_end to exclude the compare/branch here,
960 and then reset it inside the loop when get to the last
963 if (GET_CODE (last_loop_insn) == BARRIER)
964 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
965 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
968 /* The immediately preceding insn is a compare which we do not
970 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
972 /* The immediately preceding insn may not be a compare, so we
974 copy_end = PREV_INSN (last_loop_insn);
980 for (i = 1; i < unroll_number; i++)
982 emit_label_after (labels[unroll_number - i],
983 PREV_INSN (loop_start));
985 bzero ((char *) map->insn_map, max_insnno * sizeof (rtx));
986 bzero ((char *) map->const_equiv_map, maxregnum * sizeof (rtx));
987 bzero ((char *) map->const_age_map,
988 maxregnum * sizeof (unsigned));
991 for (j = 0; j < max_labelno; j++)
993 map->label_map[j] = gen_label_rtx ();
995 for (j = FIRST_PSEUDO_REGISTER; j < max_reg_before_loop; j++)
997 map->reg_map[j] = gen_reg_rtx (GET_MODE (regno_reg_rtx[j]));
999 /* The last copy needs the compare/branch insns at the end,
1000 so reset copy_end here if the loop ends with a conditional
1003 if (i == unroll_number - 1)
1005 if (GET_CODE (last_loop_insn) == BARRIER)
1006 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
1008 copy_end = last_loop_insn;
1011 /* None of the copies are the `last_iteration', so just
1012 pass zero for that parameter. */
1013 copy_loop_body (copy_start, copy_end, map, exit_label, 0,
1014 unroll_type, start_label, loop_end,
1015 loop_start, copy_end);
1017 emit_label_after (labels[0], PREV_INSN (loop_start));
1019 if (GET_CODE (last_loop_insn) == BARRIER)
1021 insert_before = PREV_INSN (last_loop_insn);
1022 copy_end = PREV_INSN (insert_before);
1027 /* The immediately preceding insn is a compare which we do not
1029 insert_before = PREV_INSN (last_loop_insn);
1030 copy_end = PREV_INSN (insert_before);
1032 /* The immediately preceding insn may not be a compare, so we
1034 insert_before = last_loop_insn;
1035 copy_end = PREV_INSN (last_loop_insn);
1039 /* Set unroll type to MODULO now. */
1040 unroll_type = UNROLL_MODULO;
1041 loop_preconditioned = 1;
1045 /* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
1046 the loop unless all loops are being unrolled. */
1047 if (unroll_type == UNROLL_NAIVE && ! flag_unroll_all_loops)
1049 if (loop_dump_stream)
1050 fprintf (loop_dump_stream, "Unrolling failure: Naive unrolling not being done.\n");
1054 /* At this point, we are guaranteed to unroll the loop. */
1056 /* For each biv and giv, determine whether it can be safely split into
1057 a different variable for each unrolled copy of the loop body.
1058 We precalculate and save this info here, since computing it is
1061 Do this before deleting any instructions from the loop, so that
1062 back_branch_in_range_p will work correctly. */
1064 if (splitting_not_safe)
1067 temp = find_splittable_regs (unroll_type, loop_start, loop_end,
1068 end_insert_before, unroll_number);
1070 /* find_splittable_regs may have created some new registers, so must
1071 reallocate the reg_map with the new larger size, and must realloc
1072 the constant maps also. */
1074 maxregnum = max_reg_num ();
1075 map->reg_map = (rtx *) alloca (maxregnum * sizeof (rtx));
1077 init_reg_map (map, maxregnum);
1079 /* Space is needed in some of the map for new registers, so new_maxregnum
1080 is an (over)estimate of how many registers will exist at the end. */
1081 new_maxregnum = maxregnum + (temp * unroll_number * 2);
1083 /* Must realloc space for the constant maps, because the number of registers
1084 may have changed. */
1086 map->const_equiv_map = (rtx *) alloca (new_maxregnum * sizeof (rtx));
1087 map->const_age_map = (unsigned *) alloca (new_maxregnum * sizeof (unsigned));
1089 map->const_equiv_map_size = new_maxregnum;
1090 global_const_equiv_map = map->const_equiv_map;
1091 global_const_equiv_map_size = new_maxregnum;
1093 /* Search the list of bivs and givs to find ones which need to be remapped
1094 when split, and set their reg_map entry appropriately. */
1096 for (bl = loop_iv_list; bl; bl = bl->next)
1098 if (REGNO (bl->biv->src_reg) != bl->regno)
1099 map->reg_map[bl->regno] = bl->biv->src_reg;
1101 /* Currently, non-reduced/final-value givs are never split. */
1102 for (v = bl->giv; v; v = v->next_iv)
1103 if (REGNO (v->src_reg) != bl->regno)
1104 map->reg_map[REGNO (v->dest_reg)] = v->src_reg;
1108 /* If the loop is being partially unrolled, and the iteration variables
1109 are being split, and are being renamed for the split, then must fix up
1110 the compare/jump instruction at the end of the loop to refer to the new
1111 registers. This compare isn't copied, so the registers used in it
1112 will never be replaced if it isn't done here. */
1114 if (unroll_type == UNROLL_MODULO)
1116 insn = NEXT_INSN (copy_end);
1117 if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
1118 PATTERN (insn) = remap_split_bivs (PATTERN (insn));
1121 /* For unroll_number - 1 times, make a copy of each instruction
1122 between copy_start and copy_end, and insert these new instructions
1123 before the end of the loop. */
1125 for (i = 0; i < unroll_number; i++)
1127 bzero ((char *) map->insn_map, max_insnno * sizeof (rtx));
1128 bzero ((char *) map->const_equiv_map, new_maxregnum * sizeof (rtx));
1129 bzero ((char *) map->const_age_map, new_maxregnum * sizeof (unsigned));
1132 for (j = 0; j < max_labelno; j++)
1134 map->label_map[j] = gen_label_rtx ();
1136 for (j = FIRST_PSEUDO_REGISTER; j < max_reg_before_loop; j++)
1138 map->reg_map[j] = gen_reg_rtx (GET_MODE (regno_reg_rtx[j]));
1140 /* If loop starts with a branch to the test, then fix it so that
1141 it points to the test of the first unrolled copy of the loop. */
1142 if (i == 0 && loop_start != copy_start)
1144 insn = PREV_INSN (copy_start);
1145 pattern = PATTERN (insn);
1147 tem = map->label_map[CODE_LABEL_NUMBER
1148 (XEXP (SET_SRC (pattern), 0))];
1149 SET_SRC (pattern) = gen_rtx (LABEL_REF, VOIDmode, tem);
1151 /* Set the jump label so that it can be used by later loop unrolling
1153 JUMP_LABEL (insn) = tem;
1154 LABEL_NUSES (tem)++;
1157 copy_loop_body (copy_start, copy_end, map, exit_label,
1158 i == unroll_number - 1, unroll_type, start_label,
1159 loop_end, insert_before, insert_before);
1162 /* Before deleting any insns, emit a CODE_LABEL immediately after the last
1163 insn to be deleted. This prevents any runaway delete_insn call from
1164 more insns that it should, as it always stops at a CODE_LABEL. */
1166 /* Delete the compare and branch at the end of the loop if completely
1167 unrolling the loop. Deleting the backward branch at the end also
1168 deletes the code label at the start of the loop. This is done at
1169 the very end to avoid problems with back_branch_in_range_p. */
1171 if (unroll_type == UNROLL_COMPLETELY)
1172 safety_label = emit_label_after (gen_label_rtx (), last_loop_insn);
1174 safety_label = emit_label_after (gen_label_rtx (), copy_end);
1176 /* Delete all of the original loop instructions. Don't delete the
1177 LOOP_BEG note, or the first code label in the loop. */
1179 insn = NEXT_INSN (copy_start);
1180 while (insn != safety_label)
1182 if (insn != start_label)
1183 insn = delete_insn (insn);
1185 insn = NEXT_INSN (insn);
1188 /* Can now delete the 'safety' label emitted to protect us from runaway
1189 delete_insn calls. */
1190 if (INSN_DELETED_P (safety_label))
1192 delete_insn (safety_label);
1194 /* If exit_label exists, emit it after the loop. Doing the emit here
1195 forces it to have a higher INSN_UID than any insn in the unrolled loop.
1196 This is needed so that mostly_true_jump in reorg.c will treat jumps
1197 to this loop end label correctly, i.e. predict that they are usually
1200 emit_label_after (exit_label, loop_end);
1203 /* Return true if the loop can be safely, and profitably, preconditioned
1204 so that the unrolled copies of the loop body don't need exit tests.
1206 This only works if final_value, initial_value and increment can be
1207 determined, and if increment is a constant power of 2.
1208 If increment is not a power of 2, then the preconditioning modulo
1209 operation would require a real modulo instead of a boolean AND, and this
1210 is not considered `profitable'. */
1212 /* ??? If the loop is known to be executed very many times, or the machine
1213 has a very cheap divide instruction, then preconditioning is a win even
1214 when the increment is not a power of 2. Use RTX_COST to compute
1215 whether divide is cheap. */
1218 precondition_loop_p (initial_value, final_value, increment, loop_start,
1220 rtx *initial_value, *final_value, *increment;
1221 rtx loop_start, loop_end;
1224 if (loop_n_iterations > 0)
1226 *initial_value = const0_rtx;
1227 *increment = const1_rtx;
1228 *final_value = GEN_INT (loop_n_iterations);
1230 if (loop_dump_stream)
1231 fprintf (loop_dump_stream,
1232 "Preconditioning: Success, number of iterations known, %d.\n",
1237 if (loop_initial_value == 0)
1239 if (loop_dump_stream)
1240 fprintf (loop_dump_stream,
1241 "Preconditioning: Could not find initial value.\n");
1244 else if (loop_increment == 0)
1246 if (loop_dump_stream)
1247 fprintf (loop_dump_stream,
1248 "Preconditioning: Could not find increment value.\n");
1251 else if (GET_CODE (loop_increment) != CONST_INT)
1253 if (loop_dump_stream)
1254 fprintf (loop_dump_stream,
1255 "Preconditioning: Increment not a constant.\n");
1258 else if ((exact_log2 (INTVAL (loop_increment)) < 0)
1259 && (exact_log2 (- INTVAL (loop_increment)) < 0))
1261 if (loop_dump_stream)
1262 fprintf (loop_dump_stream,
1263 "Preconditioning: Increment not a constant power of 2.\n");
1267 /* Unsigned_compare and compare_dir can be ignored here, since they do
1268 not matter for preconditioning. */
1270 if (loop_final_value == 0)
1272 if (loop_dump_stream)
1273 fprintf (loop_dump_stream,
1274 "Preconditioning: EQ comparison loop.\n");
1278 /* Must ensure that final_value is invariant, so call invariant_p to
1279 check. Before doing so, must check regno against max_reg_before_loop
1280 to make sure that the register is in the range covered by invariant_p.
1281 If it isn't, then it is most likely a biv/giv which by definition are
1283 if ((GET_CODE (loop_final_value) == REG
1284 && REGNO (loop_final_value) >= max_reg_before_loop)
1285 || (GET_CODE (loop_final_value) == PLUS
1286 && REGNO (XEXP (loop_final_value, 0)) >= max_reg_before_loop)
1287 || ! invariant_p (loop_final_value))
1289 if (loop_dump_stream)
1290 fprintf (loop_dump_stream,
1291 "Preconditioning: Final value not invariant.\n");
1295 /* Fail for floating point values, since the caller of this function
1296 does not have code to deal with them. */
1297 if (GET_MODE_CLASS (GET_MODE (loop_final_value)) == MODE_FLOAT
1298 || GET_MODE_CLASS (GET_MODE (loop_initial_value)) == MODE_FLOAT)
1300 if (loop_dump_stream)
1301 fprintf (loop_dump_stream,
1302 "Preconditioning: Floating point final or initial value.\n");
1306 /* Now set initial_value to be the iteration_var, since that may be a
1307 simpler expression, and is guaranteed to be correct if all of the
1308 above tests succeed.
1310 We can not use the initial_value as calculated, because it will be
1311 one too small for loops of the form "while (i-- > 0)". We can not
1312 emit code before the loop_skip_over insns to fix this problem as this
1313 will then give a number one too large for loops of the form
1316 Note that all loops that reach here are entered at the top, because
1317 this function is not called if the loop starts with a jump. */
1319 /* Fail if loop_iteration_var is not live before loop_start, since we need
1320 to test its value in the preconditioning code. */
1322 if (uid_luid[regno_first_uid[REGNO (loop_iteration_var)]]
1323 > INSN_LUID (loop_start))
1325 if (loop_dump_stream)
1326 fprintf (loop_dump_stream,
1327 "Preconditioning: Iteration var not live before loop start.\n");
1331 *initial_value = loop_iteration_var;
1332 *increment = loop_increment;
1333 *final_value = loop_final_value;
1336 if (loop_dump_stream)
1337 fprintf (loop_dump_stream, "Preconditioning: Successful.\n");
1342 /* All pseudo-registers must be mapped to themselves. Two hard registers
1343 must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
1344 REGNUM, to avoid function-inlining specific conversions of these
1345 registers. All other hard regs can not be mapped because they may be
1350 init_reg_map (map, maxregnum)
1351 struct inline_remap *map;
1356 for (i = maxregnum - 1; i > LAST_VIRTUAL_REGISTER; i--)
1357 map->reg_map[i] = regno_reg_rtx[i];
1358 /* Just clear the rest of the entries. */
1359 for (i = LAST_VIRTUAL_REGISTER; i >= 0; i--)
1360 map->reg_map[i] = 0;
1362 map->reg_map[VIRTUAL_STACK_VARS_REGNUM]
1363 = regno_reg_rtx[VIRTUAL_STACK_VARS_REGNUM];
1364 map->reg_map[VIRTUAL_INCOMING_ARGS_REGNUM]
1365 = regno_reg_rtx[VIRTUAL_INCOMING_ARGS_REGNUM];
1368 /* Strength-reduction will often emit code for optimized biv/givs which
1369 calculates their value in a temporary register, and then copies the result
1370 to the iv. This procedure reconstructs the pattern computing the iv;
1371 verifying that all operands are of the proper form.
1373 The return value is the amount that the giv is incremented by. */
1376 calculate_giv_inc (pattern, src_insn, regno)
1377 rtx pattern, src_insn;
1381 rtx increment_total = 0;
1385 /* Verify that we have an increment insn here. First check for a plus
1386 as the set source. */
1387 if (GET_CODE (SET_SRC (pattern)) != PLUS)
1389 /* SR sometimes computes the new giv value in a temp, then copies it
1391 src_insn = PREV_INSN (src_insn);
1392 pattern = PATTERN (src_insn);
1393 if (GET_CODE (SET_SRC (pattern)) != PLUS)
1396 /* The last insn emitted is not needed, so delete it to avoid confusing
1397 the second cse pass. This insn sets the giv unnecessarily. */
1398 delete_insn (get_last_insn ());
1401 /* Verify that we have a constant as the second operand of the plus. */
1402 increment = XEXP (SET_SRC (pattern), 1);
1403 if (GET_CODE (increment) != CONST_INT)
1405 /* SR sometimes puts the constant in a register, especially if it is
1406 too big to be an add immed operand. */
1407 src_insn = PREV_INSN (src_insn);
1408 increment = SET_SRC (PATTERN (src_insn));
1410 /* SR may have used LO_SUM to compute the constant if it is too large
1411 for a load immed operand. In this case, the constant is in operand
1412 one of the LO_SUM rtx. */
1413 if (GET_CODE (increment) == LO_SUM)
1414 increment = XEXP (increment, 1);
1415 else if (GET_CODE (increment) == IOR
1416 || GET_CODE (increment) == ASHIFT)
1418 /* The rs6000 port loads some constants with IOR.
1419 The alpha port loads some constants with ASHIFT. */
1420 rtx second_part = XEXP (increment, 1);
1421 enum rtx_code code = GET_CODE (increment);
1423 src_insn = PREV_INSN (src_insn);
1424 increment = SET_SRC (PATTERN (src_insn));
1425 /* Don't need the last insn anymore. */
1426 delete_insn (get_last_insn ());
1428 if (GET_CODE (second_part) != CONST_INT
1429 || GET_CODE (increment) != CONST_INT)
1433 increment = GEN_INT (INTVAL (increment) | INTVAL (second_part));
1435 increment = GEN_INT (INTVAL (increment) << INTVAL (second_part));
1438 if (GET_CODE (increment) != CONST_INT)
1441 /* The insn loading the constant into a register is no longer needed,
1443 delete_insn (get_last_insn ());
1446 if (increment_total)
1447 increment_total = GEN_INT (INTVAL (increment_total) + INTVAL (increment));
1449 increment_total = increment;
1451 /* Check that the source register is the same as the register we expected
1452 to see as the source. If not, something is seriously wrong. */
1453 if (GET_CODE (XEXP (SET_SRC (pattern), 0)) != REG
1454 || REGNO (XEXP (SET_SRC (pattern), 0)) != regno)
1456 /* Some machines (e.g. the romp), may emit two add instructions for
1457 certain constants, so lets try looking for another add immediately
1458 before this one if we have only seen one add insn so far. */
1464 src_insn = PREV_INSN (src_insn);
1465 pattern = PATTERN (src_insn);
1467 delete_insn (get_last_insn ());
1475 return increment_total;
1478 /* Copy REG_NOTES, except for insn references, because not all insn_map
1479 entries are valid yet. We do need to copy registers now though, because
1480 the reg_map entries can change during copying. */
1483 initial_reg_note_copy (notes, map)
1485 struct inline_remap *map;
1492 copy = rtx_alloc (GET_CODE (notes));
1493 PUT_MODE (copy, GET_MODE (notes));
1495 if (GET_CODE (notes) == EXPR_LIST)
1496 XEXP (copy, 0) = copy_rtx_and_substitute (XEXP (notes, 0), map);
1497 else if (GET_CODE (notes) == INSN_LIST)
1498 /* Don't substitute for these yet. */
1499 XEXP (copy, 0) = XEXP (notes, 0);
1503 XEXP (copy, 1) = initial_reg_note_copy (XEXP (notes, 1), map);
1508 /* Fixup insn references in copied REG_NOTES. */
1511 final_reg_note_copy (notes, map)
1513 struct inline_remap *map;
1517 for (note = notes; note; note = XEXP (note, 1))
1518 if (GET_CODE (note) == INSN_LIST)
1519 XEXP (note, 0) = map->insn_map[INSN_UID (XEXP (note, 0))];
1522 /* Copy each instruction in the loop, substituting from map as appropriate.
1523 This is very similar to a loop in expand_inline_function. */
1526 copy_loop_body (copy_start, copy_end, map, exit_label, last_iteration,
1527 unroll_type, start_label, loop_end, insert_before,
1529 rtx copy_start, copy_end;
1530 struct inline_remap *map;
1533 enum unroll_types unroll_type;
1534 rtx start_label, loop_end, insert_before, copy_notes_from;
1538 int dest_reg_was_split, i;
1540 rtx final_label = 0;
1541 rtx giv_inc, giv_dest_reg, giv_src_reg;
1543 /* If this isn't the last iteration, then map any references to the
1544 start_label to final_label. Final label will then be emitted immediately
1545 after the end of this loop body if it was ever used.
1547 If this is the last iteration, then map references to the start_label
1549 if (! last_iteration)
1551 final_label = gen_label_rtx ();
1552 map->label_map[CODE_LABEL_NUMBER (start_label)] = final_label;
1555 map->label_map[CODE_LABEL_NUMBER (start_label)] = start_label;
1562 insn = NEXT_INSN (insn);
1564 map->orig_asm_operands_vector = 0;
1566 switch (GET_CODE (insn))
1569 pattern = PATTERN (insn);
1573 /* Check to see if this is a giv that has been combined with
1574 some split address givs. (Combined in the sense that
1575 `combine_givs' in loop.c has put two givs in the same register.)
1576 In this case, we must search all givs based on the same biv to
1577 find the address givs. Then split the address givs.
1578 Do this before splitting the giv, since that may map the
1579 SET_DEST to a new register. */
1581 if (GET_CODE (pattern) == SET
1582 && GET_CODE (SET_DEST (pattern)) == REG
1583 && addr_combined_regs[REGNO (SET_DEST (pattern))])
1585 struct iv_class *bl;
1586 struct induction *v, *tv;
1587 int regno = REGNO (SET_DEST (pattern));
1589 v = addr_combined_regs[REGNO (SET_DEST (pattern))];
1590 bl = reg_biv_class[REGNO (v->src_reg)];
1592 /* Although the giv_inc amount is not needed here, we must call
1593 calculate_giv_inc here since it might try to delete the
1594 last insn emitted. If we wait until later to call it,
1595 we might accidentally delete insns generated immediately
1596 below by emit_unrolled_add. */
1598 giv_inc = calculate_giv_inc (pattern, insn, regno);
1600 /* Now find all address giv's that were combined with this
1602 for (tv = bl->giv; tv; tv = tv->next_iv)
1603 if (tv->giv_type == DEST_ADDR && tv->same == v)
1605 int this_giv_inc = INTVAL (giv_inc);
1607 /* Scale this_giv_inc if the multiplicative factors of
1608 the two givs are different. */
1609 if (tv->mult_val != v->mult_val)
1610 this_giv_inc = (this_giv_inc / INTVAL (v->mult_val)
1611 * INTVAL (tv->mult_val));
1613 tv->dest_reg = plus_constant (tv->dest_reg, this_giv_inc);
1614 *tv->location = tv->dest_reg;
1616 if (last_iteration && unroll_type != UNROLL_COMPLETELY)
1618 /* Must emit an insn to increment the split address
1619 giv. Add in the const_adjust field in case there
1620 was a constant eliminated from the address. */
1621 rtx value, dest_reg;
1623 /* tv->dest_reg will be either a bare register,
1624 or else a register plus a constant. */
1625 if (GET_CODE (tv->dest_reg) == REG)
1626 dest_reg = tv->dest_reg;
1628 dest_reg = XEXP (tv->dest_reg, 0);
1630 /* Check for shared address givs, and avoid
1631 incrementing the shared pseudo reg more than
1633 if (! tv->same_insn)
1635 /* tv->dest_reg may actually be a (PLUS (REG)
1636 (CONST)) here, so we must call plus_constant
1637 to add the const_adjust amount before calling
1638 emit_unrolled_add below. */
1639 value = plus_constant (tv->dest_reg,
1642 /* The constant could be too large for an add
1643 immediate, so can't directly emit an insn
1645 emit_unrolled_add (dest_reg, XEXP (value, 0),
1649 /* Reset the giv to be just the register again, in case
1650 it is used after the set we have just emitted.
1651 We must subtract the const_adjust factor added in
1653 tv->dest_reg = plus_constant (dest_reg,
1654 - tv->const_adjust);
1655 *tv->location = tv->dest_reg;
1660 /* If this is a setting of a splittable variable, then determine
1661 how to split the variable, create a new set based on this split,
1662 and set up the reg_map so that later uses of the variable will
1663 use the new split variable. */
1665 dest_reg_was_split = 0;
1667 if (GET_CODE (pattern) == SET
1668 && GET_CODE (SET_DEST (pattern)) == REG
1669 && splittable_regs[REGNO (SET_DEST (pattern))])
1671 int regno = REGNO (SET_DEST (pattern));
1673 dest_reg_was_split = 1;
1675 /* Compute the increment value for the giv, if it wasn't
1676 already computed above. */
1679 giv_inc = calculate_giv_inc (pattern, insn, regno);
1680 giv_dest_reg = SET_DEST (pattern);
1681 giv_src_reg = SET_DEST (pattern);
1683 if (unroll_type == UNROLL_COMPLETELY)
1685 /* Completely unrolling the loop. Set the induction
1686 variable to a known constant value. */
1688 /* The value in splittable_regs may be an invariant
1689 value, so we must use plus_constant here. */
1690 splittable_regs[regno]
1691 = plus_constant (splittable_regs[regno], INTVAL (giv_inc));
1693 if (GET_CODE (splittable_regs[regno]) == PLUS)
1695 giv_src_reg = XEXP (splittable_regs[regno], 0);
1696 giv_inc = XEXP (splittable_regs[regno], 1);
1700 /* The splittable_regs value must be a REG or a
1701 CONST_INT, so put the entire value in the giv_src_reg
1703 giv_src_reg = splittable_regs[regno];
1704 giv_inc = const0_rtx;
1709 /* Partially unrolling loop. Create a new pseudo
1710 register for the iteration variable, and set it to
1711 be a constant plus the original register. Except
1712 on the last iteration, when the result has to
1713 go back into the original iteration var register. */
1715 /* Handle bivs which must be mapped to a new register
1716 when split. This happens for bivs which need their
1717 final value set before loop entry. The new register
1718 for the biv was stored in the biv's first struct
1719 induction entry by find_splittable_regs. */
1721 if (regno < max_reg_before_loop
1722 && reg_iv_type[regno] == BASIC_INDUCT)
1724 giv_src_reg = reg_biv_class[regno]->biv->src_reg;
1725 giv_dest_reg = giv_src_reg;
1729 /* If non-reduced/final-value givs were split, then
1730 this would have to remap those givs also. See
1731 find_splittable_regs. */
1734 splittable_regs[regno]
1735 = GEN_INT (INTVAL (giv_inc)
1736 + INTVAL (splittable_regs[regno]));
1737 giv_inc = splittable_regs[regno];
1739 /* Now split the induction variable by changing the dest
1740 of this insn to a new register, and setting its
1741 reg_map entry to point to this new register.
1743 If this is the last iteration, and this is the last insn
1744 that will update the iv, then reuse the original dest,
1745 to ensure that the iv will have the proper value when
1746 the loop exits or repeats.
1748 Using splittable_regs_updates here like this is safe,
1749 because it can only be greater than one if all
1750 instructions modifying the iv are always executed in
1753 if (! last_iteration
1754 || (splittable_regs_updates[regno]-- != 1))
1756 tem = gen_reg_rtx (GET_MODE (giv_src_reg));
1758 map->reg_map[regno] = tem;
1761 map->reg_map[regno] = giv_src_reg;
1764 /* The constant being added could be too large for an add
1765 immediate, so can't directly emit an insn here. */
1766 emit_unrolled_add (giv_dest_reg, giv_src_reg, giv_inc);
1767 copy = get_last_insn ();
1768 pattern = PATTERN (copy);
1772 pattern = copy_rtx_and_substitute (pattern, map);
1773 copy = emit_insn (pattern);
1775 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
1778 /* If this insn is setting CC0, it may need to look at
1779 the insn that uses CC0 to see what type of insn it is.
1780 In that case, the call to recog via validate_change will
1781 fail. So don't substitute constants here. Instead,
1782 do it when we emit the following insn.
1784 For example, see the pyr.md file. That machine has signed and
1785 unsigned compares. The compare patterns must check the
1786 following branch insn to see which what kind of compare to
1789 If the previous insn set CC0, substitute constants on it as
1791 if (sets_cc0_p (PATTERN (copy)) != 0)
1796 try_constants (cc0_insn, map);
1798 try_constants (copy, map);
1801 try_constants (copy, map);
1804 /* Make split induction variable constants `permanent' since we
1805 know there are no backward branches across iteration variable
1806 settings which would invalidate this. */
1807 if (dest_reg_was_split)
1809 int regno = REGNO (SET_DEST (pattern));
1811 if (regno < map->const_equiv_map_size
1812 && map->const_age_map[regno] == map->const_age)
1813 map->const_age_map[regno] = -1;
1818 pattern = copy_rtx_and_substitute (PATTERN (insn), map);
1819 copy = emit_jump_insn (pattern);
1820 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
1822 if (JUMP_LABEL (insn) == start_label && insn == copy_end
1823 && ! last_iteration)
1825 /* This is a branch to the beginning of the loop; this is the
1826 last insn being copied; and this is not the last iteration.
1827 In this case, we want to change the original fall through
1828 case to be a branch past the end of the loop, and the
1829 original jump label case to fall_through. */
1831 if (invert_exp (pattern, copy))
1833 if (! redirect_exp (&pattern,
1834 map->label_map[CODE_LABEL_NUMBER
1835 (JUMP_LABEL (insn))],
1842 rtx lab = gen_label_rtx ();
1843 /* Can't do it by reversing the jump (probably because we
1844 couldn't reverse the conditions), so emit a new
1845 jump_insn after COPY, and redirect the jump around
1847 jmp = emit_jump_insn_after (gen_jump (exit_label), copy);
1848 jmp = emit_barrier_after (jmp);
1849 emit_label_after (lab, jmp);
1850 LABEL_NUSES (lab) = 0;
1851 if (! redirect_exp (&pattern,
1852 map->label_map[CODE_LABEL_NUMBER
1853 (JUMP_LABEL (insn))],
1861 try_constants (cc0_insn, map);
1864 try_constants (copy, map);
1866 /* Set the jump label of COPY correctly to avoid problems with
1867 later passes of unroll_loop, if INSN had jump label set. */
1868 if (JUMP_LABEL (insn))
1872 /* Can't use the label_map for every insn, since this may be
1873 the backward branch, and hence the label was not mapped. */
1874 if (GET_CODE (pattern) == SET)
1876 tem = SET_SRC (pattern);
1877 if (GET_CODE (tem) == LABEL_REF)
1878 label = XEXP (tem, 0);
1879 else if (GET_CODE (tem) == IF_THEN_ELSE)
1881 if (XEXP (tem, 1) != pc_rtx)
1882 label = XEXP (XEXP (tem, 1), 0);
1884 label = XEXP (XEXP (tem, 2), 0);
1888 if (label && GET_CODE (label) == CODE_LABEL)
1889 JUMP_LABEL (copy) = label;
1892 /* An unrecognizable jump insn, probably the entry jump
1893 for a switch statement. This label must have been mapped,
1894 so just use the label_map to get the new jump label. */
1896 = map->label_map[CODE_LABEL_NUMBER (JUMP_LABEL (insn))];
1899 /* If this is a non-local jump, then must increase the label
1900 use count so that the label will not be deleted when the
1901 original jump is deleted. */
1902 LABEL_NUSES (JUMP_LABEL (copy))++;
1904 else if (GET_CODE (PATTERN (copy)) == ADDR_VEC
1905 || GET_CODE (PATTERN (copy)) == ADDR_DIFF_VEC)
1907 rtx pat = PATTERN (copy);
1908 int diff_vec_p = GET_CODE (pat) == ADDR_DIFF_VEC;
1909 int len = XVECLEN (pat, diff_vec_p);
1912 for (i = 0; i < len; i++)
1913 LABEL_NUSES (XEXP (XVECEXP (pat, diff_vec_p, i), 0))++;
1916 /* If this used to be a conditional jump insn but whose branch
1917 direction is now known, we must do something special. */
1918 if (condjump_p (insn) && !simplejump_p (insn) && map->last_pc_value)
1921 /* The previous insn set cc0 for us. So delete it. */
1922 delete_insn (PREV_INSN (copy));
1925 /* If this is now a no-op, delete it. */
1926 if (map->last_pc_value == pc_rtx)
1928 /* Don't let delete_insn delete the label referenced here,
1929 because we might possibly need it later for some other
1930 instruction in the loop. */
1931 if (JUMP_LABEL (copy))
1932 LABEL_NUSES (JUMP_LABEL (copy))++;
1934 if (JUMP_LABEL (copy))
1935 LABEL_NUSES (JUMP_LABEL (copy))--;
1939 /* Otherwise, this is unconditional jump so we must put a
1940 BARRIER after it. We could do some dead code elimination
1941 here, but jump.c will do it just as well. */
1947 pattern = copy_rtx_and_substitute (PATTERN (insn), map);
1948 copy = emit_call_insn (pattern);
1949 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
1951 /* Because the USAGE information potentially contains objects other
1952 than hard registers, we need to copy it. */
1953 CALL_INSN_FUNCTION_USAGE (copy) =
1954 copy_rtx_and_substitute (CALL_INSN_FUNCTION_USAGE (insn), map);
1958 try_constants (cc0_insn, map);
1961 try_constants (copy, map);
1963 /* Be lazy and assume CALL_INSNs clobber all hard registers. */
1964 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1965 map->const_equiv_map[i] = 0;
1969 /* If this is the loop start label, then we don't need to emit a
1970 copy of this label since no one will use it. */
1972 if (insn != start_label)
1974 copy = emit_label (map->label_map[CODE_LABEL_NUMBER (insn)]);
1980 copy = emit_barrier ();
1984 /* VTOP notes are valid only before the loop exit test. If placed
1985 anywhere else, loop may generate bad code. */
1987 if (NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
1988 && (NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP
1989 || (last_iteration && unroll_type != UNROLL_COMPLETELY)))
1990 copy = emit_note (NOTE_SOURCE_FILE (insn),
1991 NOTE_LINE_NUMBER (insn));
2001 map->insn_map[INSN_UID (insn)] = copy;
2003 while (insn != copy_end);
2005 /* Now finish coping the REG_NOTES. */
2009 insn = NEXT_INSN (insn);
2010 if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN
2011 || GET_CODE (insn) == CALL_INSN)
2012 && map->insn_map[INSN_UID (insn)])
2013 final_reg_note_copy (REG_NOTES (map->insn_map[INSN_UID (insn)]), map);
2015 while (insn != copy_end);
2017 /* There may be notes between copy_notes_from and loop_end. Emit a copy of
2018 each of these notes here, since there may be some important ones, such as
2019 NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
2020 iteration, because the original notes won't be deleted.
2022 We can't use insert_before here, because when from preconditioning,
2023 insert_before points before the loop. We can't use copy_end, because
2024 there may be insns already inserted after it (which we don't want to
2025 copy) when not from preconditioning code. */
2027 if (! last_iteration)
2029 for (insn = copy_notes_from; insn != loop_end; insn = NEXT_INSN (insn))
2031 if (GET_CODE (insn) == NOTE
2032 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED)
2033 emit_note (NOTE_SOURCE_FILE (insn), NOTE_LINE_NUMBER (insn));
2037 if (final_label && LABEL_NUSES (final_label) > 0)
2038 emit_label (final_label);
2040 tem = gen_sequence ();
2042 emit_insn_before (tem, insert_before);
2045 /* Emit an insn, using the expand_binop to ensure that a valid insn is
2046 emitted. This will correctly handle the case where the increment value
2047 won't fit in the immediate field of a PLUS insns. */
2050 emit_unrolled_add (dest_reg, src_reg, increment)
2051 rtx dest_reg, src_reg, increment;
2055 result = expand_binop (GET_MODE (dest_reg), add_optab, src_reg, increment,
2056 dest_reg, 0, OPTAB_LIB_WIDEN);
2058 if (dest_reg != result)
2059 emit_move_insn (dest_reg, result);
2062 /* Searches the insns between INSN and LOOP_END. Returns 1 if there
2063 is a backward branch in that range that branches to somewhere between
2064 LOOP_START and INSN. Returns 0 otherwise. */
2066 /* ??? This is quadratic algorithm. Could be rewritten to be linear.
2067 In practice, this is not a problem, because this function is seldom called,
2068 and uses a negligible amount of CPU time on average. */
2071 back_branch_in_range_p (insn, loop_start, loop_end)
2073 rtx loop_start, loop_end;
2075 rtx p, q, target_insn;
2077 /* Stop before we get to the backward branch at the end of the loop. */
2078 loop_end = prev_nonnote_insn (loop_end);
2079 if (GET_CODE (loop_end) == BARRIER)
2080 loop_end = PREV_INSN (loop_end);
2082 /* Check in case insn has been deleted, search forward for first non
2083 deleted insn following it. */
2084 while (INSN_DELETED_P (insn))
2085 insn = NEXT_INSN (insn);
2087 /* Check for the case where insn is the last insn in the loop. */
2088 if (insn == loop_end)
2091 for (p = NEXT_INSN (insn); p != loop_end; p = NEXT_INSN (p))
2093 if (GET_CODE (p) == JUMP_INSN)
2095 target_insn = JUMP_LABEL (p);
2097 /* Search from loop_start to insn, to see if one of them is
2098 the target_insn. We can't use INSN_LUID comparisons here,
2099 since insn may not have an LUID entry. */
2100 for (q = loop_start; q != insn; q = NEXT_INSN (q))
2101 if (q == target_insn)
2109 /* Try to generate the simplest rtx for the expression
2110 (PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
2114 fold_rtx_mult_add (mult1, mult2, add1, mode)
2115 rtx mult1, mult2, add1;
2116 enum machine_mode mode;
2121 /* The modes must all be the same. This should always be true. For now,
2122 check to make sure. */
2123 if ((GET_MODE (mult1) != mode && GET_MODE (mult1) != VOIDmode)
2124 || (GET_MODE (mult2) != mode && GET_MODE (mult2) != VOIDmode)
2125 || (GET_MODE (add1) != mode && GET_MODE (add1) != VOIDmode))
2128 /* Ensure that if at least one of mult1/mult2 are constant, then mult2
2129 will be a constant. */
2130 if (GET_CODE (mult1) == CONST_INT)
2137 mult_res = simplify_binary_operation (MULT, mode, mult1, mult2);
2139 mult_res = gen_rtx (MULT, mode, mult1, mult2);
2141 /* Again, put the constant second. */
2142 if (GET_CODE (add1) == CONST_INT)
2149 result = simplify_binary_operation (PLUS, mode, add1, mult_res);
2151 result = gen_rtx (PLUS, mode, add1, mult_res);
2156 /* Searches the list of induction struct's for the biv BL, to try to calculate
2157 the total increment value for one iteration of the loop as a constant.
2159 Returns the increment value as an rtx, simplified as much as possible,
2160 if it can be calculated. Otherwise, returns 0. */
2163 biv_total_increment (bl, loop_start, loop_end)
2164 struct iv_class *bl;
2165 rtx loop_start, loop_end;
2167 struct induction *v;
2170 /* For increment, must check every instruction that sets it. Each
2171 instruction must be executed only once each time through the loop.
2172 To verify this, we check that the the insn is always executed, and that
2173 there are no backward branches after the insn that branch to before it.
2174 Also, the insn must have a mult_val of one (to make sure it really is
2177 result = const0_rtx;
2178 for (v = bl->biv; v; v = v->next_iv)
2180 if (v->always_computable && v->mult_val == const1_rtx
2181 && ! back_branch_in_range_p (v->insn, loop_start, loop_end))
2182 result = fold_rtx_mult_add (result, const1_rtx, v->add_val, v->mode);
2190 /* Determine the initial value of the iteration variable, and the amount
2191 that it is incremented each loop. Use the tables constructed by
2192 the strength reduction pass to calculate these values.
2194 Initial_value and/or increment are set to zero if their values could not
2198 iteration_info (iteration_var, initial_value, increment, loop_start, loop_end)
2199 rtx iteration_var, *initial_value, *increment;
2200 rtx loop_start, loop_end;
2202 struct iv_class *bl;
2203 struct induction *v, *b;
2205 /* Clear the result values, in case no answer can be found. */
2209 /* The iteration variable can be either a giv or a biv. Check to see
2210 which it is, and compute the variable's initial value, and increment
2211 value if possible. */
2213 /* If this is a new register, can't handle it since we don't have any
2214 reg_iv_type entry for it. */
2215 if (REGNO (iteration_var) >= max_reg_before_loop)
2217 if (loop_dump_stream)
2218 fprintf (loop_dump_stream,
2219 "Loop unrolling: No reg_iv_type entry for iteration var.\n");
2222 /* Reject iteration variables larger than the host long size, since they
2223 could result in a number of iterations greater than the range of our
2224 `unsigned long' variable loop_n_iterations. */
2225 else if (GET_MODE_BITSIZE (GET_MODE (iteration_var)) > HOST_BITS_PER_LONG)
2227 if (loop_dump_stream)
2228 fprintf (loop_dump_stream,
2229 "Loop unrolling: Iteration var rejected because mode larger than host long.\n");
2232 else if (GET_MODE_CLASS (GET_MODE (iteration_var)) != MODE_INT)
2234 if (loop_dump_stream)
2235 fprintf (loop_dump_stream,
2236 "Loop unrolling: Iteration var not an integer.\n");
2239 else if (reg_iv_type[REGNO (iteration_var)] == BASIC_INDUCT)
2241 /* Grab initial value, only useful if it is a constant. */
2242 bl = reg_biv_class[REGNO (iteration_var)];
2243 *initial_value = bl->initial_value;
2245 *increment = biv_total_increment (bl, loop_start, loop_end);
2247 else if (reg_iv_type[REGNO (iteration_var)] == GENERAL_INDUCT)
2250 /* ??? The code below does not work because the incorrect number of
2251 iterations is calculated when the biv is incremented after the giv
2252 is set (which is the usual case). This can probably be accounted
2253 for by biasing the initial_value by subtracting the amount of the
2254 increment that occurs between the giv set and the giv test. However,
2255 a giv as an iterator is very rare, so it does not seem worthwhile
2257 /* ??? An example failure is: i = 6; do {;} while (i++ < 9). */
2258 if (loop_dump_stream)
2259 fprintf (loop_dump_stream,
2260 "Loop unrolling: Giv iterators are not handled.\n");
2263 /* Initial value is mult_val times the biv's initial value plus
2264 add_val. Only useful if it is a constant. */
2265 v = reg_iv_info[REGNO (iteration_var)];
2266 bl = reg_biv_class[REGNO (v->src_reg)];
2267 *initial_value = fold_rtx_mult_add (v->mult_val, bl->initial_value,
2268 v->add_val, v->mode);
2270 /* Increment value is mult_val times the increment value of the biv. */
2272 *increment = biv_total_increment (bl, loop_start, loop_end);
2274 *increment = fold_rtx_mult_add (v->mult_val, *increment, const0_rtx,
2280 if (loop_dump_stream)
2281 fprintf (loop_dump_stream,
2282 "Loop unrolling: Not basic or general induction var.\n");
2287 /* Calculate the approximate final value of the iteration variable
2288 which has an loop exit test with code COMPARISON_CODE and comparison value
2289 of COMPARISON_VALUE. Also returns an indication of whether the comparison
2290 was signed or unsigned, and the direction of the comparison. This info is
2291 needed to calculate the number of loop iterations. */
2294 approx_final_value (comparison_code, comparison_value, unsigned_p, compare_dir)
2295 enum rtx_code comparison_code;
2296 rtx comparison_value;
2300 /* Calculate the final value of the induction variable.
2301 The exact final value depends on the branch operator, and increment sign.
2302 This is only an approximate value. It will be wrong if the iteration
2303 variable is not incremented by one each time through the loop, and
2304 approx final value - start value % increment != 0. */
2307 switch (comparison_code)
2313 return plus_constant (comparison_value, 1);
2318 return plus_constant (comparison_value, -1);
2320 /* Can not calculate a final value for this case. */
2327 return comparison_value;
2333 return comparison_value;
2336 return comparison_value;
2342 /* For each biv and giv, determine whether it can be safely split into
2343 a different variable for each unrolled copy of the loop body. If it
2344 is safe to split, then indicate that by saving some useful info
2345 in the splittable_regs array.
2347 If the loop is being completely unrolled, then splittable_regs will hold
2348 the current value of the induction variable while the loop is unrolled.
2349 It must be set to the initial value of the induction variable here.
2350 Otherwise, splittable_regs will hold the difference between the current
2351 value of the induction variable and the value the induction variable had
2352 at the top of the loop. It must be set to the value 0 here.
2354 Returns the total number of instructions that set registers that are
2357 /* ?? If the loop is only unrolled twice, then most of the restrictions to
2358 constant values are unnecessary, since we can easily calculate increment
2359 values in this case even if nothing is constant. The increment value
2360 should not involve a multiply however. */
2362 /* ?? Even if the biv/giv increment values aren't constant, it may still
2363 be beneficial to split the variable if the loop is only unrolled a few
2364 times, since multiplies by small integers (1,2,3,4) are very cheap. */
2367 find_splittable_regs (unroll_type, loop_start, loop_end, end_insert_before,
2369 enum unroll_types unroll_type;
2370 rtx loop_start, loop_end;
2371 rtx end_insert_before;
2374 struct iv_class *bl;
2375 struct induction *v;
2377 rtx biv_final_value;
2381 for (bl = loop_iv_list; bl; bl = bl->next)
2383 /* Biv_total_increment must return a constant value,
2384 otherwise we can not calculate the split values. */
2386 increment = biv_total_increment (bl, loop_start, loop_end);
2387 if (! increment || GET_CODE (increment) != CONST_INT)
2390 /* The loop must be unrolled completely, or else have a known number
2391 of iterations and only one exit, or else the biv must be dead
2392 outside the loop, or else the final value must be known. Otherwise,
2393 it is unsafe to split the biv since it may not have the proper
2394 value on loop exit. */
2396 /* loop_number_exit_count is non-zero if the loop has an exit other than
2397 a fall through at the end. */
2400 biv_final_value = 0;
2401 if (unroll_type != UNROLL_COMPLETELY
2402 && (loop_number_exit_count[uid_loop_num[INSN_UID (loop_start)]]
2403 || unroll_type == UNROLL_NAIVE)
2404 && (uid_luid[regno_last_uid[bl->regno]] >= INSN_LUID (loop_end)
2406 || INSN_UID (bl->init_insn) >= max_uid_for_loop
2407 || (uid_luid[regno_first_uid[bl->regno]]
2408 < INSN_LUID (bl->init_insn))
2409 || reg_mentioned_p (bl->biv->dest_reg, SET_SRC (bl->init_set)))
2410 && ! (biv_final_value = final_biv_value (bl, loop_start, loop_end)))
2413 /* If any of the insns setting the BIV don't do so with a simple
2414 PLUS, we don't know how to split it. */
2415 for (v = bl->biv; biv_splittable && v; v = v->next_iv)
2416 if ((tem = single_set (v->insn)) == 0
2417 || GET_CODE (SET_DEST (tem)) != REG
2418 || REGNO (SET_DEST (tem)) != bl->regno
2419 || GET_CODE (SET_SRC (tem)) != PLUS)
2422 /* If final value is non-zero, then must emit an instruction which sets
2423 the value of the biv to the proper value. This is done after
2424 handling all of the givs, since some of them may need to use the
2425 biv's value in their initialization code. */
2427 /* This biv is splittable. If completely unrolling the loop, save
2428 the biv's initial value. Otherwise, save the constant zero. */
2430 if (biv_splittable == 1)
2432 if (unroll_type == UNROLL_COMPLETELY)
2434 /* If the initial value of the biv is itself (i.e. it is too
2435 complicated for strength_reduce to compute), or is a hard
2436 register, or it isn't invariant, then we must create a new
2437 pseudo reg to hold the initial value of the biv. */
2439 if (GET_CODE (bl->initial_value) == REG
2440 && (REGNO (bl->initial_value) == bl->regno
2441 || REGNO (bl->initial_value) < FIRST_PSEUDO_REGISTER
2442 || ! invariant_p (bl->initial_value)))
2444 rtx tem = gen_reg_rtx (bl->biv->mode);
2446 emit_insn_before (gen_move_insn (tem, bl->biv->src_reg),
2449 if (loop_dump_stream)
2450 fprintf (loop_dump_stream, "Biv %d initial value remapped to %d.\n",
2451 bl->regno, REGNO (tem));
2453 splittable_regs[bl->regno] = tem;
2456 splittable_regs[bl->regno] = bl->initial_value;
2459 splittable_regs[bl->regno] = const0_rtx;
2461 /* Save the number of instructions that modify the biv, so that
2462 we can treat the last one specially. */
2464 splittable_regs_updates[bl->regno] = bl->biv_count;
2465 result += bl->biv_count;
2467 if (loop_dump_stream)
2468 fprintf (loop_dump_stream,
2469 "Biv %d safe to split.\n", bl->regno);
2472 /* Check every giv that depends on this biv to see whether it is
2473 splittable also. Even if the biv isn't splittable, givs which
2474 depend on it may be splittable if the biv is live outside the
2475 loop, and the givs aren't. */
2477 result += find_splittable_givs (bl, unroll_type, loop_start, loop_end,
2478 increment, unroll_number);
2480 /* If final value is non-zero, then must emit an instruction which sets
2481 the value of the biv to the proper value. This is done after
2482 handling all of the givs, since some of them may need to use the
2483 biv's value in their initialization code. */
2484 if (biv_final_value)
2486 /* If the loop has multiple exits, emit the insns before the
2487 loop to ensure that it will always be executed no matter
2488 how the loop exits. Otherwise emit the insn after the loop,
2489 since this is slightly more efficient. */
2490 if (! loop_number_exit_count[uid_loop_num[INSN_UID (loop_start)]])
2491 emit_insn_before (gen_move_insn (bl->biv->src_reg,
2496 /* Create a new register to hold the value of the biv, and then
2497 set the biv to its final value before the loop start. The biv
2498 is set to its final value before loop start to ensure that
2499 this insn will always be executed, no matter how the loop
2501 rtx tem = gen_reg_rtx (bl->biv->mode);
2502 emit_insn_before (gen_move_insn (tem, bl->biv->src_reg),
2504 emit_insn_before (gen_move_insn (bl->biv->src_reg,
2508 if (loop_dump_stream)
2509 fprintf (loop_dump_stream, "Biv %d mapped to %d for split.\n",
2510 REGNO (bl->biv->src_reg), REGNO (tem));
2512 /* Set up the mapping from the original biv register to the new
2514 bl->biv->src_reg = tem;
2521 /* Return 1 if the first and last unrolled copy of the address giv V is valid
2522 for the instruction that is using it. Do not make any changes to that
2526 verify_addresses (v, giv_inc, unroll_number)
2527 struct induction *v;
2532 rtx orig_addr = *v->location;
2533 rtx last_addr = plus_constant (v->dest_reg,
2534 INTVAL (giv_inc) * (unroll_number - 1));
2536 /* First check to see if either address would fail. */
2537 if (! validate_change (v->insn, v->location, v->dest_reg, 0)
2538 || ! validate_change (v->insn, v->location, last_addr, 0))
2541 /* Now put things back the way they were before. This will always
2543 validate_change (v->insn, v->location, orig_addr, 0);
2548 /* For every giv based on the biv BL, check to determine whether it is
2549 splittable. This is a subroutine to find_splittable_regs ().
2551 Return the number of instructions that set splittable registers. */
2554 find_splittable_givs (bl, unroll_type, loop_start, loop_end, increment,
2556 struct iv_class *bl;
2557 enum unroll_types unroll_type;
2558 rtx loop_start, loop_end;
2562 struct induction *v, *v2;
2567 /* Scan the list of givs, and set the same_insn field when there are
2568 multiple identical givs in the same insn. */
2569 for (v = bl->giv; v; v = v->next_iv)
2570 for (v2 = v->next_iv; v2; v2 = v2->next_iv)
2571 if (v->insn == v2->insn && rtx_equal_p (v->new_reg, v2->new_reg)
2575 for (v = bl->giv; v; v = v->next_iv)
2579 /* Only split the giv if it has already been reduced, or if the loop is
2580 being completely unrolled. */
2581 if (unroll_type != UNROLL_COMPLETELY && v->ignore)
2584 /* The giv can be split if the insn that sets the giv is executed once
2585 and only once on every iteration of the loop. */
2586 /* An address giv can always be split. v->insn is just a use not a set,
2587 and hence it does not matter whether it is always executed. All that
2588 matters is that all the biv increments are always executed, and we
2589 won't reach here if they aren't. */
2590 if (v->giv_type != DEST_ADDR
2591 && (! v->always_computable
2592 || back_branch_in_range_p (v->insn, loop_start, loop_end)))
2595 /* The giv increment value must be a constant. */
2596 giv_inc = fold_rtx_mult_add (v->mult_val, increment, const0_rtx,
2598 if (! giv_inc || GET_CODE (giv_inc) != CONST_INT)
2601 /* The loop must be unrolled completely, or else have a known number of
2602 iterations and only one exit, or else the giv must be dead outside
2603 the loop, or else the final value of the giv must be known.
2604 Otherwise, it is not safe to split the giv since it may not have the
2605 proper value on loop exit. */
2607 /* The used outside loop test will fail for DEST_ADDR givs. They are
2608 never used outside the loop anyways, so it is always safe to split a
2612 if (unroll_type != UNROLL_COMPLETELY
2613 && (loop_number_exit_count[uid_loop_num[INSN_UID (loop_start)]]
2614 || unroll_type == UNROLL_NAIVE)
2615 && v->giv_type != DEST_ADDR
2616 && ((regno_first_uid[REGNO (v->dest_reg)] != INSN_UID (v->insn)
2617 /* Check for the case where the pseudo is set by a shift/add
2618 sequence, in which case the first insn setting the pseudo
2619 is the first insn of the shift/add sequence. */
2620 && (! (tem = find_reg_note (v->insn, REG_RETVAL, NULL_RTX))
2621 || (regno_first_uid[REGNO (v->dest_reg)]
2622 != INSN_UID (XEXP (tem, 0)))))
2623 /* Line above always fails if INSN was moved by loop opt. */
2624 || (uid_luid[regno_last_uid[REGNO (v->dest_reg)]]
2625 >= INSN_LUID (loop_end)))
2626 && ! (final_value = v->final_value))
2630 /* Currently, non-reduced/final-value givs are never split. */
2631 /* Should emit insns after the loop if possible, as the biv final value
2634 /* If the final value is non-zero, and the giv has not been reduced,
2635 then must emit an instruction to set the final value. */
2636 if (final_value && !v->new_reg)
2638 /* Create a new register to hold the value of the giv, and then set
2639 the giv to its final value before the loop start. The giv is set
2640 to its final value before loop start to ensure that this insn
2641 will always be executed, no matter how we exit. */
2642 tem = gen_reg_rtx (v->mode);
2643 emit_insn_before (gen_move_insn (tem, v->dest_reg), loop_start);
2644 emit_insn_before (gen_move_insn (v->dest_reg, final_value),
2647 if (loop_dump_stream)
2648 fprintf (loop_dump_stream, "Giv %d mapped to %d for split.\n",
2649 REGNO (v->dest_reg), REGNO (tem));
2655 /* This giv is splittable. If completely unrolling the loop, save the
2656 giv's initial value. Otherwise, save the constant zero for it. */
2658 if (unroll_type == UNROLL_COMPLETELY)
2660 /* It is not safe to use bl->initial_value here, because it may not
2661 be invariant. It is safe to use the initial value stored in
2662 the splittable_regs array if it is set. In rare cases, it won't
2663 be set, so then we do exactly the same thing as
2664 find_splittable_regs does to get a safe value. */
2665 rtx biv_initial_value;
2667 if (splittable_regs[bl->regno])
2668 biv_initial_value = splittable_regs[bl->regno];
2669 else if (GET_CODE (bl->initial_value) != REG
2670 || (REGNO (bl->initial_value) != bl->regno
2671 && REGNO (bl->initial_value) >= FIRST_PSEUDO_REGISTER))
2672 biv_initial_value = bl->initial_value;
2675 rtx tem = gen_reg_rtx (bl->biv->mode);
2677 emit_insn_before (gen_move_insn (tem, bl->biv->src_reg),
2679 biv_initial_value = tem;
2681 value = fold_rtx_mult_add (v->mult_val, biv_initial_value,
2682 v->add_val, v->mode);
2689 /* If a giv was combined with another giv, then we can only split
2690 this giv if the giv it was combined with was reduced. This
2691 is because the value of v->new_reg is meaningless in this
2693 if (v->same && ! v->same->new_reg)
2695 if (loop_dump_stream)
2696 fprintf (loop_dump_stream,
2697 "giv combined with unreduced giv not split.\n");
2700 /* If the giv is an address destination, it could be something other
2701 than a simple register, these have to be treated differently. */
2702 else if (v->giv_type == DEST_REG)
2704 /* If value is not a constant, register, or register plus
2705 constant, then compute its value into a register before
2706 loop start. This prevents invalid rtx sharing, and should
2707 generate better code. We can use bl->initial_value here
2708 instead of splittable_regs[bl->regno] because this code
2709 is going before the loop start. */
2710 if (unroll_type == UNROLL_COMPLETELY
2711 && GET_CODE (value) != CONST_INT
2712 && GET_CODE (value) != REG
2713 && (GET_CODE (value) != PLUS
2714 || GET_CODE (XEXP (value, 0)) != REG
2715 || GET_CODE (XEXP (value, 1)) != CONST_INT))
2717 rtx tem = gen_reg_rtx (v->mode);
2718 emit_iv_add_mult (bl->initial_value, v->mult_val,
2719 v->add_val, tem, loop_start);
2723 splittable_regs[REGNO (v->new_reg)] = value;
2727 /* Splitting address givs is useful since it will often allow us
2728 to eliminate some increment insns for the base giv as
2731 /* If the addr giv is combined with a dest_reg giv, then all
2732 references to that dest reg will be remapped, which is NOT
2733 what we want for split addr regs. We always create a new
2734 register for the split addr giv, just to be safe. */
2736 /* ??? If there are multiple address givs which have been
2737 combined with the same dest_reg giv, then we may only need
2738 one new register for them. Pulling out constants below will
2739 catch some of the common cases of this. Currently, I leave
2740 the work of simplifying multiple address givs to the
2741 following cse pass. */
2743 /* As a special case, if we have multiple identical address givs
2744 within a single instruction, then we do use a single pseudo
2745 reg for both. This is necessary in case one is a match_dup
2748 v->const_adjust = 0;
2752 v->dest_reg = v->same_insn->dest_reg;
2753 if (loop_dump_stream)
2754 fprintf (loop_dump_stream,
2755 "Sharing address givs in insn %d\n",
2756 INSN_UID (v->insn));
2758 else if (unroll_type != UNROLL_COMPLETELY)
2760 /* If not completely unrolling the loop, then create a new
2761 register to hold the split value of the DEST_ADDR giv.
2762 Emit insn to initialize its value before loop start. */
2763 tem = gen_reg_rtx (v->mode);
2765 /* If the address giv has a constant in its new_reg value,
2766 then this constant can be pulled out and put in value,
2767 instead of being part of the initialization code. */
2769 if (GET_CODE (v->new_reg) == PLUS
2770 && GET_CODE (XEXP (v->new_reg, 1)) == CONST_INT)
2773 = plus_constant (tem, INTVAL (XEXP (v->new_reg,1)));
2775 /* Only succeed if this will give valid addresses.
2776 Try to validate both the first and the last
2777 address resulting from loop unrolling, if
2778 one fails, then can't do const elim here. */
2779 if (! verify_addresses (v, giv_inc, unroll_number))
2781 /* Save the negative of the eliminated const, so
2782 that we can calculate the dest_reg's increment
2784 v->const_adjust = - INTVAL (XEXP (v->new_reg, 1));
2786 v->new_reg = XEXP (v->new_reg, 0);
2787 if (loop_dump_stream)
2788 fprintf (loop_dump_stream,
2789 "Eliminating constant from giv %d\n",
2798 /* If the address hasn't been checked for validity yet, do so
2799 now, and fail completely if either the first or the last
2800 unrolled copy of the address is not a valid address
2801 for the instruction that uses it. */
2802 if (v->dest_reg == tem
2803 && ! verify_addresses (v, giv_inc, unroll_number))
2805 if (loop_dump_stream)
2806 fprintf (loop_dump_stream,
2807 "Invalid address for giv at insn %d\n",
2808 INSN_UID (v->insn));
2812 /* To initialize the new register, just move the value of
2813 new_reg into it. This is not guaranteed to give a valid
2814 instruction on machines with complex addressing modes.
2815 If we can't recognize it, then delete it and emit insns
2816 to calculate the value from scratch. */
2817 emit_insn_before (gen_rtx (SET, VOIDmode, tem,
2818 copy_rtx (v->new_reg)),
2820 if (recog_memoized (PREV_INSN (loop_start)) < 0)
2824 /* We can't use bl->initial_value to compute the initial
2825 value, because the loop may have been preconditioned.
2826 We must calculate it from NEW_REG. Try using
2827 force_operand instead of emit_iv_add_mult. */
2828 delete_insn (PREV_INSN (loop_start));
2831 ret = force_operand (v->new_reg, tem);
2833 emit_move_insn (tem, ret);
2834 sequence = gen_sequence ();
2836 emit_insn_before (sequence, loop_start);
2838 if (loop_dump_stream)
2839 fprintf (loop_dump_stream,
2840 "Invalid init insn, rewritten.\n");
2845 v->dest_reg = value;
2847 /* Check the resulting address for validity, and fail
2848 if the resulting address would be invalid. */
2849 if (! verify_addresses (v, giv_inc, unroll_number))
2851 if (loop_dump_stream)
2852 fprintf (loop_dump_stream,
2853 "Invalid address for giv at insn %d\n",
2854 INSN_UID (v->insn));
2859 /* Store the value of dest_reg into the insn. This sharing
2860 will not be a problem as this insn will always be copied
2863 *v->location = v->dest_reg;
2865 /* If this address giv is combined with a dest reg giv, then
2866 save the base giv's induction pointer so that we will be
2867 able to handle this address giv properly. The base giv
2868 itself does not have to be splittable. */
2870 if (v->same && v->same->giv_type == DEST_REG)
2871 addr_combined_regs[REGNO (v->same->new_reg)] = v->same;
2873 if (GET_CODE (v->new_reg) == REG)
2875 /* This giv maybe hasn't been combined with any others.
2876 Make sure that it's giv is marked as splittable here. */
2878 splittable_regs[REGNO (v->new_reg)] = value;
2880 /* Make it appear to depend upon itself, so that the
2881 giv will be properly split in the main loop above. */
2885 addr_combined_regs[REGNO (v->new_reg)] = v;
2889 if (loop_dump_stream)
2890 fprintf (loop_dump_stream, "DEST_ADDR giv being split.\n");
2896 /* Currently, unreduced giv's can't be split. This is not too much
2897 of a problem since unreduced giv's are not live across loop
2898 iterations anyways. When unrolling a loop completely though,
2899 it makes sense to reduce&split givs when possible, as this will
2900 result in simpler instructions, and will not require that a reg
2901 be live across loop iterations. */
2903 splittable_regs[REGNO (v->dest_reg)] = value;
2904 fprintf (stderr, "Giv %d at insn %d not reduced\n",
2905 REGNO (v->dest_reg), INSN_UID (v->insn));
2911 /* Givs are only updated once by definition. Mark it so if this is
2912 a splittable register. Don't need to do anything for address givs
2913 where this may not be a register. */
2915 if (GET_CODE (v->new_reg) == REG)
2916 splittable_regs_updates[REGNO (v->new_reg)] = 1;
2920 if (loop_dump_stream)
2924 if (GET_CODE (v->dest_reg) == CONST_INT)
2926 else if (GET_CODE (v->dest_reg) != REG)
2927 regnum = REGNO (XEXP (v->dest_reg, 0));
2929 regnum = REGNO (v->dest_reg);
2930 fprintf (loop_dump_stream, "Giv %d at insn %d safe to split.\n",
2931 regnum, INSN_UID (v->insn));
2938 /* Try to prove that the register is dead after the loop exits. Trace every
2939 loop exit looking for an insn that will always be executed, which sets
2940 the register to some value, and appears before the first use of the register
2941 is found. If successful, then return 1, otherwise return 0. */
2943 /* ?? Could be made more intelligent in the handling of jumps, so that
2944 it can search past if statements and other similar structures. */
2947 reg_dead_after_loop (reg, loop_start, loop_end)
2948 rtx reg, loop_start, loop_end;
2953 int label_count = 0;
2954 int this_loop_num = uid_loop_num[INSN_UID (loop_start)];
2956 /* In addition to checking all exits of this loop, we must also check
2957 all exits of inner nested loops that would exit this loop. We don't
2958 have any way to identify those, so we just give up if there are any
2959 such inner loop exits. */
2961 for (label = loop_number_exit_labels[this_loop_num]; label;
2962 label = LABEL_NEXTREF (label))
2965 if (label_count != loop_number_exit_count[this_loop_num])
2968 /* HACK: Must also search the loop fall through exit, create a label_ref
2969 here which points to the loop_end, and append the loop_number_exit_labels
2971 label = gen_rtx (LABEL_REF, VOIDmode, loop_end);
2972 LABEL_NEXTREF (label) = loop_number_exit_labels[this_loop_num];
2974 for ( ; label; label = LABEL_NEXTREF (label))
2976 /* Succeed if find an insn which sets the biv or if reach end of
2977 function. Fail if find an insn that uses the biv, or if come to
2978 a conditional jump. */
2980 insn = NEXT_INSN (XEXP (label, 0));
2983 code = GET_CODE (insn);
2984 if (GET_RTX_CLASS (code) == 'i')
2988 if (reg_referenced_p (reg, PATTERN (insn)))
2991 set = single_set (insn);
2992 if (set && rtx_equal_p (SET_DEST (set), reg))
2996 if (code == JUMP_INSN)
2998 if (GET_CODE (PATTERN (insn)) == RETURN)
3000 else if (! simplejump_p (insn)
3001 /* Prevent infinite loop following infinite loops. */
3002 || jump_count++ > 20)
3005 insn = JUMP_LABEL (insn);
3008 insn = NEXT_INSN (insn);
3012 /* Success, the register is dead on all loop exits. */
3016 /* Try to calculate the final value of the biv, the value it will have at
3017 the end of the loop. If we can do it, return that value. */
3020 final_biv_value (bl, loop_start, loop_end)
3021 struct iv_class *bl;
3022 rtx loop_start, loop_end;
3026 /* ??? This only works for MODE_INT biv's. Reject all others for now. */
3028 if (GET_MODE_CLASS (bl->biv->mode) != MODE_INT)
3031 /* The final value for reversed bivs must be calculated differently than
3032 for ordinary bivs. In this case, there is already an insn after the
3033 loop which sets this biv's final value (if necessary), and there are
3034 no other loop exits, so we can return any value. */
3037 if (loop_dump_stream)
3038 fprintf (loop_dump_stream,
3039 "Final biv value for %d, reversed biv.\n", bl->regno);
3044 /* Try to calculate the final value as initial value + (number of iterations
3045 * increment). For this to work, increment must be invariant, the only
3046 exit from the loop must be the fall through at the bottom (otherwise
3047 it may not have its final value when the loop exits), and the initial
3048 value of the biv must be invariant. */
3050 if (loop_n_iterations != 0
3051 && ! loop_number_exit_count[uid_loop_num[INSN_UID (loop_start)]]
3052 && invariant_p (bl->initial_value))
3054 increment = biv_total_increment (bl, loop_start, loop_end);
3056 if (increment && invariant_p (increment))
3058 /* Can calculate the loop exit value, emit insns after loop
3059 end to calculate this value into a temporary register in
3060 case it is needed later. */
3062 tem = gen_reg_rtx (bl->biv->mode);
3063 /* Make sure loop_end is not the last insn. */
3064 if (NEXT_INSN (loop_end) == 0)
3065 emit_note_after (NOTE_INSN_DELETED, loop_end);
3066 emit_iv_add_mult (increment, GEN_INT (loop_n_iterations),
3067 bl->initial_value, tem, NEXT_INSN (loop_end));
3069 if (loop_dump_stream)
3070 fprintf (loop_dump_stream,
3071 "Final biv value for %d, calculated.\n", bl->regno);
3077 /* Check to see if the biv is dead at all loop exits. */
3078 if (reg_dead_after_loop (bl->biv->src_reg, loop_start, loop_end))
3080 if (loop_dump_stream)
3081 fprintf (loop_dump_stream,
3082 "Final biv value for %d, biv dead after loop exit.\n",
3091 /* Try to calculate the final value of the giv, the value it will have at
3092 the end of the loop. If we can do it, return that value. */
3095 final_giv_value (v, loop_start, loop_end)
3096 struct induction *v;
3097 rtx loop_start, loop_end;
3099 struct iv_class *bl;
3102 rtx insert_before, seq;
3104 bl = reg_biv_class[REGNO (v->src_reg)];
3106 /* The final value for givs which depend on reversed bivs must be calculated
3107 differently than for ordinary givs. In this case, there is already an
3108 insn after the loop which sets this giv's final value (if necessary),
3109 and there are no other loop exits, so we can return any value. */
3112 if (loop_dump_stream)
3113 fprintf (loop_dump_stream,
3114 "Final giv value for %d, depends on reversed biv\n",
3115 REGNO (v->dest_reg));
3119 /* Try to calculate the final value as a function of the biv it depends
3120 upon. The only exit from the loop must be the fall through at the bottom
3121 (otherwise it may not have its final value when the loop exits). */
3123 /* ??? Can calculate the final giv value by subtracting off the
3124 extra biv increments times the giv's mult_val. The loop must have
3125 only one exit for this to work, but the loop iterations does not need
3128 if (loop_n_iterations != 0
3129 && ! loop_number_exit_count[uid_loop_num[INSN_UID (loop_start)]])
3131 /* ?? It is tempting to use the biv's value here since these insns will
3132 be put after the loop, and hence the biv will have its final value
3133 then. However, this fails if the biv is subsequently eliminated.
3134 Perhaps determine whether biv's are eliminable before trying to
3135 determine whether giv's are replaceable so that we can use the
3136 biv value here if it is not eliminable. */
3138 increment = biv_total_increment (bl, loop_start, loop_end);
3140 if (increment && invariant_p (increment))
3142 /* Can calculate the loop exit value of its biv as
3143 (loop_n_iterations * increment) + initial_value */
3145 /* The loop exit value of the giv is then
3146 (final_biv_value - extra increments) * mult_val + add_val.
3147 The extra increments are any increments to the biv which
3148 occur in the loop after the giv's value is calculated.
3149 We must search from the insn that sets the giv to the end
3150 of the loop to calculate this value. */
3152 insert_before = NEXT_INSN (loop_end);
3154 /* Put the final biv value in tem. */
3155 tem = gen_reg_rtx (bl->biv->mode);
3156 emit_iv_add_mult (increment, GEN_INT (loop_n_iterations),
3157 bl->initial_value, tem, insert_before);
3159 /* Subtract off extra increments as we find them. */
3160 for (insn = NEXT_INSN (v->insn); insn != loop_end;
3161 insn = NEXT_INSN (insn))
3163 struct induction *biv;
3165 for (biv = bl->biv; biv; biv = biv->next_iv)
3166 if (biv->insn == insn)
3169 tem = expand_binop (GET_MODE (tem), sub_optab, tem,
3170 biv->add_val, NULL_RTX, 0,
3172 seq = gen_sequence ();
3174 emit_insn_before (seq, insert_before);
3178 /* Now calculate the giv's final value. */
3179 emit_iv_add_mult (tem, v->mult_val, v->add_val, tem,
3182 if (loop_dump_stream)
3183 fprintf (loop_dump_stream,
3184 "Final giv value for %d, calc from biv's value.\n",
3185 REGNO (v->dest_reg));
3191 /* Replaceable giv's should never reach here. */
3195 /* Check to see if the biv is dead at all loop exits. */
3196 if (reg_dead_after_loop (v->dest_reg, loop_start, loop_end))
3198 if (loop_dump_stream)
3199 fprintf (loop_dump_stream,
3200 "Final giv value for %d, giv dead after loop exit.\n",
3201 REGNO (v->dest_reg));
3210 /* Calculate the number of loop iterations. Returns the exact number of loop
3211 iterations if it can be calculated, otherwise returns zero. */
3213 unsigned HOST_WIDE_INT
3214 loop_iterations (loop_start, loop_end)
3215 rtx loop_start, loop_end;
3217 rtx comparison, comparison_value;
3218 rtx iteration_var, initial_value, increment, final_value;
3219 enum rtx_code comparison_code;
3222 int unsigned_compare, compare_dir, final_larger;
3223 unsigned long tempu;
3226 /* First find the iteration variable. If the last insn is a conditional
3227 branch, and the insn before tests a register value, make that the
3228 iteration variable. */
3230 loop_initial_value = 0;
3232 loop_final_value = 0;
3233 loop_iteration_var = 0;
3235 /* We used to use pren_nonnote_insn here, but that fails because it might
3236 accidentally get the branch for a contained loop if the branch for this
3237 loop was deleted. We can only trust branches immediately before the
3239 last_loop_insn = PREV_INSN (loop_end);
3241 comparison = get_condition_for_loop (last_loop_insn);
3242 if (comparison == 0)
3244 if (loop_dump_stream)
3245 fprintf (loop_dump_stream,
3246 "Loop unrolling: No final conditional branch found.\n");
3250 /* ??? Get_condition may switch position of induction variable and
3251 invariant register when it canonicalizes the comparison. */
3253 comparison_code = GET_CODE (comparison);
3254 iteration_var = XEXP (comparison, 0);
3255 comparison_value = XEXP (comparison, 1);
3257 if (GET_CODE (iteration_var) != REG)
3259 if (loop_dump_stream)
3260 fprintf (loop_dump_stream,
3261 "Loop unrolling: Comparison not against register.\n");
3265 /* Loop iterations is always called before any new registers are created
3266 now, so this should never occur. */
3268 if (REGNO (iteration_var) >= max_reg_before_loop)
3271 iteration_info (iteration_var, &initial_value, &increment,
3272 loop_start, loop_end);
3273 if (initial_value == 0)
3274 /* iteration_info already printed a message. */
3277 /* If the comparison value is an invariant register, then try to find
3278 its value from the insns before the start of the loop. */
3280 if (GET_CODE (comparison_value) == REG && invariant_p (comparison_value))
3284 for (insn = PREV_INSN (loop_start); insn ; insn = PREV_INSN (insn))
3286 if (GET_CODE (insn) == CODE_LABEL)
3289 else if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
3290 && reg_set_p (comparison_value, insn))
3292 /* We found the last insn before the loop that sets the register.
3293 If it sets the entire register, and has a REG_EQUAL note,
3294 then use the value of the REG_EQUAL note. */
3295 if ((set = single_set (insn))
3296 && (SET_DEST (set) == comparison_value))
3298 rtx note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
3300 /* Only use the REG_EQUAL note if it is a constant.
3301 Other things, divide in particular, will cause
3302 problems later if we use them. */
3303 if (note && GET_CODE (XEXP (note, 0)) != EXPR_LIST
3304 && CONSTANT_P (XEXP (note, 0)))
3305 comparison_value = XEXP (note, 0);
3312 final_value = approx_final_value (comparison_code, comparison_value,
3313 &unsigned_compare, &compare_dir);
3315 /* Save the calculated values describing this loop's bounds, in case
3316 precondition_loop_p will need them later. These values can not be
3317 recalculated inside precondition_loop_p because strength reduction
3318 optimizations may obscure the loop's structure. */
3320 loop_iteration_var = iteration_var;
3321 loop_initial_value = initial_value;
3322 loop_increment = increment;
3323 loop_final_value = final_value;
3327 if (loop_dump_stream)
3328 fprintf (loop_dump_stream,
3329 "Loop unrolling: Increment value can't be calculated.\n");
3332 else if (GET_CODE (increment) != CONST_INT)
3334 if (loop_dump_stream)
3335 fprintf (loop_dump_stream,
3336 "Loop unrolling: Increment value not constant.\n");
3339 else if (GET_CODE (initial_value) != CONST_INT)
3341 if (loop_dump_stream)
3342 fprintf (loop_dump_stream,
3343 "Loop unrolling: Initial value not constant.\n");
3346 else if (final_value == 0)
3348 if (loop_dump_stream)
3349 fprintf (loop_dump_stream,
3350 "Loop unrolling: EQ comparison loop.\n");
3353 else if (GET_CODE (final_value) != CONST_INT)
3355 if (loop_dump_stream)
3356 fprintf (loop_dump_stream,
3357 "Loop unrolling: Final value not constant.\n");
3361 /* ?? Final value and initial value do not have to be constants.
3362 Only their difference has to be constant. When the iteration variable
3363 is an array address, the final value and initial value might both
3364 be addresses with the same base but different constant offsets.
3365 Final value must be invariant for this to work.
3367 To do this, need some way to find the values of registers which are
3370 /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
3371 if (unsigned_compare)
3373 = ((unsigned HOST_WIDE_INT) INTVAL (final_value)
3374 > (unsigned HOST_WIDE_INT) INTVAL (initial_value))
3375 - ((unsigned HOST_WIDE_INT) INTVAL (final_value)
3376 < (unsigned HOST_WIDE_INT) INTVAL (initial_value));
3378 final_larger = (INTVAL (final_value) > INTVAL (initial_value))
3379 - (INTVAL (final_value) < INTVAL (initial_value));
3381 if (INTVAL (increment) > 0)
3383 else if (INTVAL (increment) == 0)
3388 /* There are 27 different cases: compare_dir = -1, 0, 1;
3389 final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
3390 There are 4 normal cases, 4 reverse cases (where the iteration variable
3391 will overflow before the loop exits), 4 infinite loop cases, and 15
3392 immediate exit (0 or 1 iteration depending on loop type) cases.
3393 Only try to optimize the normal cases. */
3395 /* (compare_dir/final_larger/increment_dir)
3396 Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
3397 Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
3398 Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
3399 Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
3401 /* ?? If the meaning of reverse loops (where the iteration variable
3402 will overflow before the loop exits) is undefined, then could
3403 eliminate all of these special checks, and just always assume
3404 the loops are normal/immediate/infinite. Note that this means
3405 the sign of increment_dir does not have to be known. Also,
3406 since it does not really hurt if immediate exit loops or infinite loops
3407 are optimized, then that case could be ignored also, and hence all
3408 loops can be optimized.
3410 According to ANSI Spec, the reverse loop case result is undefined,
3411 because the action on overflow is undefined.
3413 See also the special test for NE loops below. */
3415 if (final_larger == increment_dir && final_larger != 0
3416 && (final_larger == compare_dir || compare_dir == 0))
3421 if (loop_dump_stream)
3422 fprintf (loop_dump_stream,
3423 "Loop unrolling: Not normal loop.\n");
3427 /* Calculate the number of iterations, final_value is only an approximation,
3428 so correct for that. Note that tempu and loop_n_iterations are
3429 unsigned, because they can be as large as 2^n - 1. */
3431 i = INTVAL (increment);
3433 tempu = INTVAL (final_value) - INTVAL (initial_value);
3436 tempu = INTVAL (initial_value) - INTVAL (final_value);
3442 /* For NE tests, make sure that the iteration variable won't miss the
3443 final value. If tempu mod i is not zero, then the iteration variable
3444 will overflow before the loop exits, and we can not calculate the
3445 number of iterations. */
3446 if (compare_dir == 0 && (tempu % i) != 0)
3449 return tempu / i + ((tempu % i) != 0);
3452 /* Replace uses of split bivs with their split pseudo register. This is
3453 for original instructions which remain after loop unrolling without
3457 remap_split_bivs (x)
3460 register enum rtx_code code;
3467 code = GET_CODE (x);
3482 /* If non-reduced/final-value givs were split, then this would also
3483 have to remap those givs also. */
3485 if (REGNO (x) < max_reg_before_loop
3486 && reg_iv_type[REGNO (x)] == BASIC_INDUCT)
3487 return reg_biv_class[REGNO (x)]->biv->src_reg;
3490 fmt = GET_RTX_FORMAT (code);
3491 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
3494 XEXP (x, i) = remap_split_bivs (XEXP (x, i));
3498 for (j = 0; j < XVECLEN (x, i); j++)
3499 XVECEXP (x, i, j) = remap_split_bivs (XVECEXP (x, i, j));