1 /* Try to unroll loops, and split induction variables.
2 Copyright (C) 1992, 93-95, 97-99, 2000 Free Software Foundation, Inc.
3 Contributed by James E. Wilson, Cygnus Support/UC Berkeley.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
22 /* Try to unroll a loop, and split induction variables.
24 Loops for which the number of iterations can be calculated exactly are
25 handled specially. If the number of iterations times the insn_count is
26 less than MAX_UNROLLED_INSNS, then the loop is unrolled completely.
27 Otherwise, we try to unroll the loop a number of times modulo the number
28 of iterations, so that only one exit test will be needed. It is unrolled
29 a number of times approximately equal to MAX_UNROLLED_INSNS divided by
32 Otherwise, if the number of iterations can be calculated exactly at
33 run time, and the loop is always entered at the top, then we try to
34 precondition the loop. That is, at run time, calculate how many times
35 the loop will execute, and then execute the loop body a few times so
36 that the remaining iterations will be some multiple of 4 (or 2 if the
37 loop is large). Then fall through to a loop unrolled 4 (or 2) times,
38 with only one exit test needed at the end of the loop.
40 Otherwise, if the number of iterations can not be calculated exactly,
41 not even at run time, then we still unroll the loop a number of times
42 approximately equal to MAX_UNROLLED_INSNS divided by the insn count,
43 but there must be an exit test after each copy of the loop body.
45 For each induction variable, which is dead outside the loop (replaceable)
46 or for which we can easily calculate the final value, if we can easily
47 calculate its value at each place where it is set as a function of the
48 current loop unroll count and the variable's value at loop entry, then
49 the induction variable is split into `N' different variables, one for
50 each copy of the loop body. One variable is live across the backward
51 branch, and the others are all calculated as a function of this variable.
52 This helps eliminate data dependencies, and leads to further opportunities
55 /* Possible improvements follow: */
57 /* ??? Add an extra pass somewhere to determine whether unrolling will
58 give any benefit. E.g. after generating all unrolled insns, compute the
59 cost of all insns and compare against cost of insns in rolled loop.
61 - On traditional architectures, unrolling a non-constant bound loop
62 is a win if there is a giv whose only use is in memory addresses, the
63 memory addresses can be split, and hence giv increments can be
65 - It is also a win if the loop is executed many times, and preconditioning
66 can be performed for the loop.
67 Add code to check for these and similar cases. */
69 /* ??? Improve control of which loops get unrolled. Could use profiling
70 info to only unroll the most commonly executed loops. Perhaps have
71 a user specifyable option to control the amount of code expansion,
72 or the percent of loops to consider for unrolling. Etc. */
74 /* ??? Look at the register copies inside the loop to see if they form a
75 simple permutation. If so, iterate the permutation until it gets back to
76 the start state. This is how many times we should unroll the loop, for
77 best results, because then all register copies can be eliminated.
78 For example, the lisp nreverse function should be unrolled 3 times
87 ??? The number of times to unroll the loop may also be based on data
88 references in the loop. For example, if we have a loop that references
89 x[i-1], x[i], and x[i+1], we should unroll it a multiple of 3 times. */
91 /* ??? Add some simple linear equation solving capability so that we can
92 determine the number of loop iterations for more complex loops.
93 For example, consider this loop from gdb
94 #define SWAP_TARGET_AND_HOST(buffer,len)
97 char *p = (char *) buffer;
98 char *q = ((char *) buffer) + len - 1;
99 int iterations = (len + 1) >> 1;
101 for (p; p < q; p++, q--;)
109 start value = p = &buffer + current_iteration
110 end value = q = &buffer + len - 1 - current_iteration
111 Given the loop exit test of "p < q", then there must be "q - p" iterations,
112 set equal to zero and solve for number of iterations:
113 q - p = len - 1 - 2*current_iteration = 0
114 current_iteration = (len - 1) / 2
115 Hence, there are (len - 1) / 2 (rounded up to the nearest integer)
116 iterations of this loop. */
118 /* ??? Currently, no labels are marked as loop invariant when doing loop
119 unrolling. This is because an insn inside the loop, that loads the address
120 of a label inside the loop into a register, could be moved outside the loop
121 by the invariant code motion pass if labels were invariant. If the loop
122 is subsequently unrolled, the code will be wrong because each unrolled
123 body of the loop will use the same address, whereas each actually needs a
124 different address. A case where this happens is when a loop containing
125 a switch statement is unrolled.
127 It would be better to let labels be considered invariant. When we
128 unroll loops here, check to see if any insns using a label local to the
129 loop were moved before the loop. If so, then correct the problem, by
130 moving the insn back into the loop, or perhaps replicate the insn before
131 the loop, one copy for each time the loop is unrolled. */
133 /* The prime factors looked for when trying to unroll a loop by some
134 number which is modulo the total number of iterations. Just checking
135 for these 4 prime factors will find at least one factor for 75% of
136 all numbers theoretically. Practically speaking, this will succeed
137 almost all of the time since loops are generally a multiple of 2
140 #define NUM_FACTORS 4
142 struct _factor { int factor, count; } factors[NUM_FACTORS]
143 = { {2, 0}, {3, 0}, {5, 0}, {7, 0}};
145 /* Describes the different types of loop unrolling performed. */
147 enum unroll_types { UNROLL_COMPLETELY, UNROLL_MODULO, UNROLL_NAIVE };
153 #include "insn-config.h"
154 #include "integrate.h"
158 #include "function.h"
163 /* This controls which loops are unrolled, and by how much we unroll
166 #ifndef MAX_UNROLLED_INSNS
167 #define MAX_UNROLLED_INSNS 100
170 /* Indexed by register number, if non-zero, then it contains a pointer
171 to a struct induction for a DEST_REG giv which has been combined with
172 one of more address givs. This is needed because whenever such a DEST_REG
173 giv is modified, we must modify the value of all split address givs
174 that were combined with this DEST_REG giv. */
176 static struct induction **addr_combined_regs;
178 /* Indexed by register number, if this is a splittable induction variable,
179 then this will hold the current value of the register, which depends on the
182 static rtx *splittable_regs;
184 /* Indexed by register number, if this is a splittable induction variable,
185 this indicates if it was made from a derived giv. */
186 static char *derived_regs;
188 /* Indexed by register number, if this is a splittable induction variable,
189 then this will hold the number of instructions in the loop that modify
190 the induction variable. Used to ensure that only the last insn modifying
191 a split iv will update the original iv of the dest. */
193 static int *splittable_regs_updates;
195 /* Forward declarations. */
197 static void init_reg_map PARAMS ((struct inline_remap *, int));
198 static rtx calculate_giv_inc PARAMS ((rtx, rtx, int));
199 static rtx initial_reg_note_copy PARAMS ((rtx, struct inline_remap *));
200 static void final_reg_note_copy PARAMS ((rtx, struct inline_remap *));
201 static void copy_loop_body PARAMS ((rtx, rtx, struct inline_remap *, rtx, int,
202 enum unroll_types, rtx, rtx, rtx, rtx));
203 static void iteration_info PARAMS ((rtx, rtx *, rtx *, rtx, rtx));
204 static int find_splittable_regs PARAMS ((enum unroll_types, rtx, rtx, rtx, int,
205 unsigned HOST_WIDE_INT));
206 static int find_splittable_givs PARAMS ((struct iv_class *, enum unroll_types,
207 rtx, rtx, rtx, int));
208 static int reg_dead_after_loop PARAMS ((rtx, rtx, rtx));
209 static rtx fold_rtx_mult_add PARAMS ((rtx, rtx, rtx, enum machine_mode));
210 static int verify_addresses PARAMS ((struct induction *, rtx, int));
211 static rtx remap_split_bivs PARAMS ((rtx));
212 static rtx find_common_reg_term PARAMS ((rtx, rtx));
213 static rtx subtract_reg_term PARAMS ((rtx, rtx));
214 static rtx loop_find_equiv_value PARAMS ((rtx, rtx));
216 /* Try to unroll one loop and split induction variables in the loop.
218 The loop is described by the arguments LOOP_END, INSN_COUNT, and
219 LOOP_START. END_INSERT_BEFORE indicates where insns should be added
220 which need to be executed when the loop falls through. STRENGTH_REDUCTION_P
221 indicates whether information generated in the strength reduction pass
224 This function is intended to be called from within `strength_reduce'
228 unroll_loop (loop, insn_count, end_insert_before, strength_reduce_p)
231 rtx end_insert_before;
232 int strength_reduce_p;
235 unsigned HOST_WIDE_INT temp;
236 int unroll_number = 1;
237 rtx copy_start, copy_end;
238 rtx insn, sequence, pattern, tem;
239 int max_labelno, max_insnno;
241 struct inline_remap *map;
242 char *local_label = NULL;
244 int max_local_regnum;
249 int splitting_not_safe = 0;
250 enum unroll_types unroll_type;
251 int loop_preconditioned = 0;
253 /* This points to the last real insn in the loop, which should be either
254 a JUMP_INSN (for conditional jumps) or a BARRIER (for unconditional
257 rtx loop_start = loop->start;
258 rtx loop_end = loop->end;
259 struct loop_info *loop_info = loop->info;
261 /* Don't bother unrolling huge loops. Since the minimum factor is
262 two, loops greater than one half of MAX_UNROLLED_INSNS will never
264 if (insn_count > MAX_UNROLLED_INSNS / 2)
266 if (loop_dump_stream)
267 fprintf (loop_dump_stream, "Unrolling failure: Loop too big.\n");
271 /* When emitting debugger info, we can't unroll loops with unequal numbers
272 of block_beg and block_end notes, because that would unbalance the block
273 structure of the function. This can happen as a result of the
274 "if (foo) bar; else break;" optimization in jump.c. */
275 /* ??? Gcc has a general policy that -g is never supposed to change the code
276 that the compiler emits, so we must disable this optimization always,
277 even if debug info is not being output. This is rare, so this should
278 not be a significant performance problem. */
280 if (1 /* write_symbols != NO_DEBUG */)
282 int block_begins = 0;
285 for (insn = loop_start; insn != loop_end; insn = NEXT_INSN (insn))
287 if (GET_CODE (insn) == NOTE)
289 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG)
291 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END)
293 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG
294 || NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)
296 /* Note, would be nice to add code to unroll EH
297 regions, but until that time, we punt (don't
298 unroll). For the proper way of doing it, see
299 expand_inline_function. */
301 if (loop_dump_stream)
302 fprintf (loop_dump_stream,
303 "Unrolling failure: cannot unroll EH regions.\n");
309 if (block_begins != block_ends)
311 if (loop_dump_stream)
312 fprintf (loop_dump_stream,
313 "Unrolling failure: Unbalanced block notes.\n");
318 /* Determine type of unroll to perform. Depends on the number of iterations
319 and the size of the loop. */
321 /* If there is no strength reduce info, then set
322 loop_info->n_iterations to zero. This can happen if
323 strength_reduce can't find any bivs in the loop. A value of zero
324 indicates that the number of iterations could not be calculated. */
326 if (! strength_reduce_p)
327 loop_info->n_iterations = 0;
329 if (loop_dump_stream && loop_info->n_iterations > 0)
331 fputs ("Loop unrolling: ", loop_dump_stream);
332 fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC,
333 loop_info->n_iterations);
334 fputs (" iterations.\n", loop_dump_stream);
337 /* Find and save a pointer to the last nonnote insn in the loop. */
339 last_loop_insn = prev_nonnote_insn (loop_end);
341 /* Calculate how many times to unroll the loop. Indicate whether or
342 not the loop is being completely unrolled. */
344 if (loop_info->n_iterations == 1)
346 /* If number of iterations is exactly 1, then eliminate the compare and
347 branch at the end of the loop since they will never be taken.
348 Then return, since no other action is needed here. */
350 /* If the last instruction is not a BARRIER or a JUMP_INSN, then
351 don't do anything. */
353 if (GET_CODE (last_loop_insn) == BARRIER)
355 /* Delete the jump insn. This will delete the barrier also. */
356 delete_insn (PREV_INSN (last_loop_insn));
358 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
361 rtx prev = PREV_INSN (last_loop_insn);
363 delete_insn (last_loop_insn);
365 /* The immediately preceding insn may be a compare which must be
367 if (sets_cc0_p (prev))
372 /* Remove the loop notes since this is no longer a loop. */
374 delete_insn (loop->vtop);
376 delete_insn (loop->cont);
378 delete_insn (loop_start);
380 delete_insn (loop_end);
384 else if (loop_info->n_iterations > 0
385 && loop_info->n_iterations * insn_count < MAX_UNROLLED_INSNS)
387 unroll_number = loop_info->n_iterations;
388 unroll_type = UNROLL_COMPLETELY;
390 else if (loop_info->n_iterations > 0)
392 /* Try to factor the number of iterations. Don't bother with the
393 general case, only using 2, 3, 5, and 7 will get 75% of all
394 numbers theoretically, and almost all in practice. */
396 for (i = 0; i < NUM_FACTORS; i++)
397 factors[i].count = 0;
399 temp = loop_info->n_iterations;
400 for (i = NUM_FACTORS - 1; i >= 0; i--)
401 while (temp % factors[i].factor == 0)
404 temp = temp / factors[i].factor;
407 /* Start with the larger factors first so that we generally
408 get lots of unrolling. */
412 for (i = 3; i >= 0; i--)
413 while (factors[i].count--)
415 if (temp * factors[i].factor < MAX_UNROLLED_INSNS)
417 unroll_number *= factors[i].factor;
418 temp *= factors[i].factor;
424 /* If we couldn't find any factors, then unroll as in the normal
426 if (unroll_number == 1)
428 if (loop_dump_stream)
429 fprintf (loop_dump_stream,
430 "Loop unrolling: No factors found.\n");
433 unroll_type = UNROLL_MODULO;
437 /* Default case, calculate number of times to unroll loop based on its
439 if (unroll_number == 1)
441 if (8 * insn_count < MAX_UNROLLED_INSNS)
443 else if (4 * insn_count < MAX_UNROLLED_INSNS)
448 unroll_type = UNROLL_NAIVE;
451 /* Now we know how many times to unroll the loop. */
453 if (loop_dump_stream)
454 fprintf (loop_dump_stream,
455 "Unrolling loop %d times.\n", unroll_number);
458 if (unroll_type == UNROLL_COMPLETELY || unroll_type == UNROLL_MODULO)
460 /* Loops of these types can start with jump down to the exit condition
461 in rare circumstances.
463 Consider a pair of nested loops where the inner loop is part
464 of the exit code for the outer loop.
466 In this case jump.c will not duplicate the exit test for the outer
467 loop, so it will start with a jump to the exit code.
469 Then consider if the inner loop turns out to iterate once and
470 only once. We will end up deleting the jumps associated with
471 the inner loop. However, the loop notes are not removed from
472 the instruction stream.
474 And finally assume that we can compute the number of iterations
477 In this case unroll may want to unroll the outer loop even though
478 it starts with a jump to the outer loop's exit code.
480 We could try to optimize this case, but it hardly seems worth it.
481 Just return without unrolling the loop in such cases. */
484 while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
485 insn = NEXT_INSN (insn);
486 if (GET_CODE (insn) == JUMP_INSN)
490 if (unroll_type == UNROLL_COMPLETELY)
492 /* Completely unrolling the loop: Delete the compare and branch at
493 the end (the last two instructions). This delete must done at the
494 very end of loop unrolling, to avoid problems with calls to
495 back_branch_in_range_p, which is called by find_splittable_regs.
496 All increments of splittable bivs/givs are changed to load constant
499 copy_start = loop_start;
501 /* Set insert_before to the instruction immediately after the JUMP_INSN
502 (or BARRIER), so that any NOTEs between the JUMP_INSN and the end of
503 the loop will be correctly handled by copy_loop_body. */
504 insert_before = NEXT_INSN (last_loop_insn);
506 /* Set copy_end to the insn before the jump at the end of the loop. */
507 if (GET_CODE (last_loop_insn) == BARRIER)
508 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
509 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
511 copy_end = PREV_INSN (last_loop_insn);
513 /* The instruction immediately before the JUMP_INSN may be a compare
514 instruction which we do not want to copy. */
515 if (sets_cc0_p (PREV_INSN (copy_end)))
516 copy_end = PREV_INSN (copy_end);
521 /* We currently can't unroll a loop if it doesn't end with a
522 JUMP_INSN. There would need to be a mechanism that recognizes
523 this case, and then inserts a jump after each loop body, which
524 jumps to after the last loop body. */
525 if (loop_dump_stream)
526 fprintf (loop_dump_stream,
527 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
531 else if (unroll_type == UNROLL_MODULO)
533 /* Partially unrolling the loop: The compare and branch at the end
534 (the last two instructions) must remain. Don't copy the compare
535 and branch instructions at the end of the loop. Insert the unrolled
536 code immediately before the compare/branch at the end so that the
537 code will fall through to them as before. */
539 copy_start = loop_start;
541 /* Set insert_before to the jump insn at the end of the loop.
542 Set copy_end to before the jump insn at the end of the loop. */
543 if (GET_CODE (last_loop_insn) == BARRIER)
545 insert_before = PREV_INSN (last_loop_insn);
546 copy_end = PREV_INSN (insert_before);
548 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
550 insert_before = last_loop_insn;
552 /* The instruction immediately before the JUMP_INSN may be a compare
553 instruction which we do not want to copy or delete. */
554 if (sets_cc0_p (PREV_INSN (insert_before)))
555 insert_before = PREV_INSN (insert_before);
557 copy_end = PREV_INSN (insert_before);
561 /* We currently can't unroll a loop if it doesn't end with a
562 JUMP_INSN. There would need to be a mechanism that recognizes
563 this case, and then inserts a jump after each loop body, which
564 jumps to after the last loop body. */
565 if (loop_dump_stream)
566 fprintf (loop_dump_stream,
567 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
573 /* Normal case: Must copy the compare and branch instructions at the
576 if (GET_CODE (last_loop_insn) == BARRIER)
578 /* Loop ends with an unconditional jump and a barrier.
579 Handle this like above, don't copy jump and barrier.
580 This is not strictly necessary, but doing so prevents generating
581 unconditional jumps to an immediately following label.
583 This will be corrected below if the target of this jump is
584 not the start_label. */
586 insert_before = PREV_INSN (last_loop_insn);
587 copy_end = PREV_INSN (insert_before);
589 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
591 /* Set insert_before to immediately after the JUMP_INSN, so that
592 NOTEs at the end of the loop will be correctly handled by
594 insert_before = NEXT_INSN (last_loop_insn);
595 copy_end = last_loop_insn;
599 /* We currently can't unroll a loop if it doesn't end with a
600 JUMP_INSN. There would need to be a mechanism that recognizes
601 this case, and then inserts a jump after each loop body, which
602 jumps to after the last loop body. */
603 if (loop_dump_stream)
604 fprintf (loop_dump_stream,
605 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
609 /* If copying exit test branches because they can not be eliminated,
610 then must convert the fall through case of the branch to a jump past
611 the end of the loop. Create a label to emit after the loop and save
612 it for later use. Do not use the label after the loop, if any, since
613 it might be used by insns outside the loop, or there might be insns
614 added before it later by final_[bg]iv_value which must be after
615 the real exit label. */
616 exit_label = gen_label_rtx ();
619 while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
620 insn = NEXT_INSN (insn);
622 if (GET_CODE (insn) == JUMP_INSN)
624 /* The loop starts with a jump down to the exit condition test.
625 Start copying the loop after the barrier following this
627 copy_start = NEXT_INSN (insn);
629 /* Splitting induction variables doesn't work when the loop is
630 entered via a jump to the bottom, because then we end up doing
631 a comparison against a new register for a split variable, but
632 we did not execute the set insn for the new register because
633 it was skipped over. */
634 splitting_not_safe = 1;
635 if (loop_dump_stream)
636 fprintf (loop_dump_stream,
637 "Splitting not safe, because loop not entered at top.\n");
640 copy_start = loop_start;
643 /* This should always be the first label in the loop. */
644 start_label = NEXT_INSN (copy_start);
645 /* There may be a line number note and/or a loop continue note here. */
646 while (GET_CODE (start_label) == NOTE)
647 start_label = NEXT_INSN (start_label);
648 if (GET_CODE (start_label) != CODE_LABEL)
650 /* This can happen as a result of jump threading. If the first insns in
651 the loop test the same condition as the loop's backward jump, or the
652 opposite condition, then the backward jump will be modified to point
653 to elsewhere, and the loop's start label is deleted.
655 This case currently can not be handled by the loop unrolling code. */
657 if (loop_dump_stream)
658 fprintf (loop_dump_stream,
659 "Unrolling failure: unknown insns between BEG note and loop label.\n");
662 if (LABEL_NAME (start_label))
664 /* The jump optimization pass must have combined the original start label
665 with a named label for a goto. We can't unroll this case because
666 jumps which go to the named label must be handled differently than
667 jumps to the loop start, and it is impossible to differentiate them
669 if (loop_dump_stream)
670 fprintf (loop_dump_stream,
671 "Unrolling failure: loop start label is gone\n");
675 if (unroll_type == UNROLL_NAIVE
676 && GET_CODE (last_loop_insn) == BARRIER
677 && GET_CODE (PREV_INSN (last_loop_insn)) == JUMP_INSN
678 && start_label != JUMP_LABEL (PREV_INSN (last_loop_insn)))
680 /* In this case, we must copy the jump and barrier, because they will
681 not be converted to jumps to an immediately following label. */
683 insert_before = NEXT_INSN (last_loop_insn);
684 copy_end = last_loop_insn;
687 if (unroll_type == UNROLL_NAIVE
688 && GET_CODE (last_loop_insn) == JUMP_INSN
689 && start_label != JUMP_LABEL (last_loop_insn))
691 /* ??? The loop ends with a conditional branch that does not branch back
692 to the loop start label. In this case, we must emit an unconditional
693 branch to the loop exit after emitting the final branch.
694 copy_loop_body does not have support for this currently, so we
695 give up. It doesn't seem worthwhile to unroll anyways since
696 unrolling would increase the number of branch instructions
698 if (loop_dump_stream)
699 fprintf (loop_dump_stream,
700 "Unrolling failure: final conditional branch not to loop start\n");
704 /* Allocate a translation table for the labels and insn numbers.
705 They will be filled in as we copy the insns in the loop. */
707 max_labelno = max_label_num ();
708 max_insnno = get_max_uid ();
710 /* Various paths through the unroll code may reach the "egress" label
711 without initializing fields within the map structure.
713 To be safe, we use xcalloc to zero the memory. */
714 map = (struct inline_remap *) xcalloc (1, sizeof (struct inline_remap));
716 /* Allocate the label map. */
720 map->label_map = (rtx *) xmalloc (max_labelno * sizeof (rtx));
722 local_label = (char *) xcalloc (max_labelno, sizeof (char));
725 /* Search the loop and mark all local labels, i.e. the ones which have to
726 be distinct labels when copied. For all labels which might be
727 non-local, set their label_map entries to point to themselves.
728 If they happen to be local their label_map entries will be overwritten
729 before the loop body is copied. The label_map entries for local labels
730 will be set to a different value each time the loop body is copied. */
732 for (insn = copy_start; insn != loop_end; insn = NEXT_INSN (insn))
736 if (GET_CODE (insn) == CODE_LABEL)
737 local_label[CODE_LABEL_NUMBER (insn)] = 1;
738 else if (GET_CODE (insn) == JUMP_INSN)
740 if (JUMP_LABEL (insn))
741 set_label_in_map (map,
742 CODE_LABEL_NUMBER (JUMP_LABEL (insn)),
744 else if (GET_CODE (PATTERN (insn)) == ADDR_VEC
745 || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
747 rtx pat = PATTERN (insn);
748 int diff_vec_p = GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC;
749 int len = XVECLEN (pat, diff_vec_p);
752 for (i = 0; i < len; i++)
754 label = XEXP (XVECEXP (pat, diff_vec_p, i), 0);
755 set_label_in_map (map,
756 CODE_LABEL_NUMBER (label),
761 else if ((note = find_reg_note (insn, REG_LABEL, NULL_RTX)))
762 set_label_in_map (map, CODE_LABEL_NUMBER (XEXP (note, 0)),
766 /* Allocate space for the insn map. */
768 map->insn_map = (rtx *) xmalloc (max_insnno * sizeof (rtx));
770 /* Set this to zero, to indicate that we are doing loop unrolling,
771 not function inlining. */
772 map->inline_target = 0;
774 /* The register and constant maps depend on the number of registers
775 present, so the final maps can't be created until after
776 find_splittable_regs is called. However, they are needed for
777 preconditioning, so we create temporary maps when preconditioning
780 /* The preconditioning code may allocate two new pseudo registers. */
781 maxregnum = max_reg_num ();
783 /* local_regno is only valid for regnos < max_local_regnum. */
784 max_local_regnum = maxregnum;
786 /* Allocate and zero out the splittable_regs and addr_combined_regs
787 arrays. These must be zeroed here because they will be used if
788 loop preconditioning is performed, and must be zero for that case.
790 It is safe to do this here, since the extra registers created by the
791 preconditioning code and find_splittable_regs will never be used
792 to access the splittable_regs[] and addr_combined_regs[] arrays. */
794 splittable_regs = (rtx *) xcalloc (maxregnum, sizeof (rtx));
795 derived_regs = (char *) xcalloc (maxregnum, sizeof (char));
796 splittable_regs_updates = (int *) xcalloc (maxregnum, sizeof (int));
798 = (struct induction **) xcalloc (maxregnum, sizeof (struct induction *));
799 local_regno = (char *) xcalloc (maxregnum, sizeof (char));
801 /* Mark all local registers, i.e. the ones which are referenced only
803 if (INSN_UID (copy_end) < max_uid_for_loop)
805 int copy_start_luid = INSN_LUID (copy_start);
806 int copy_end_luid = INSN_LUID (copy_end);
808 /* If a register is used in the jump insn, we must not duplicate it
809 since it will also be used outside the loop. */
810 if (GET_CODE (copy_end) == JUMP_INSN)
813 /* If we have a target that uses cc0, then we also must not duplicate
814 the insn that sets cc0 before the jump insn, if one is present. */
816 if (GET_CODE (copy_end) == JUMP_INSN && sets_cc0_p (PREV_INSN (copy_end)))
820 /* If copy_start points to the NOTE that starts the loop, then we must
821 use the next luid, because invariant pseudo-regs moved out of the loop
822 have their lifetimes modified to start here, but they are not safe
824 if (copy_start == loop_start)
827 /* If a pseudo's lifetime is entirely contained within this loop, then we
828 can use a different pseudo in each unrolled copy of the loop. This
829 results in better code. */
830 /* We must limit the generic test to max_reg_before_loop, because only
831 these pseudo registers have valid regno_first_uid info. */
832 for (j = FIRST_PSEUDO_REGISTER; j < max_reg_before_loop; ++j)
833 if (REGNO_FIRST_UID (j) > 0 && REGNO_FIRST_UID (j) <= max_uid_for_loop
834 && uid_luid[REGNO_FIRST_UID (j)] >= copy_start_luid
835 && REGNO_LAST_UID (j) > 0 && REGNO_LAST_UID (j) <= max_uid_for_loop
836 && uid_luid[REGNO_LAST_UID (j)] <= copy_end_luid)
838 /* However, we must also check for loop-carried dependencies.
839 If the value the pseudo has at the end of iteration X is
840 used by iteration X+1, then we can not use a different pseudo
841 for each unrolled copy of the loop. */
842 /* A pseudo is safe if regno_first_uid is a set, and this
843 set dominates all instructions from regno_first_uid to
845 /* ??? This check is simplistic. We would get better code if
846 this check was more sophisticated. */
847 if (set_dominates_use (j, REGNO_FIRST_UID (j), REGNO_LAST_UID (j),
848 copy_start, copy_end))
851 if (loop_dump_stream)
854 fprintf (loop_dump_stream, "Marked reg %d as local\n", j);
856 fprintf (loop_dump_stream, "Did not mark reg %d as local\n",
860 /* Givs that have been created from multiple biv increments always have
862 for (j = first_increment_giv; j <= last_increment_giv; j++)
865 if (loop_dump_stream)
866 fprintf (loop_dump_stream, "Marked reg %d as local\n", j);
870 /* If this loop requires exit tests when unrolled, check to see if we
871 can precondition the loop so as to make the exit tests unnecessary.
872 Just like variable splitting, this is not safe if the loop is entered
873 via a jump to the bottom. Also, can not do this if no strength
874 reduce info, because precondition_loop_p uses this info. */
876 /* Must copy the loop body for preconditioning before the following
877 find_splittable_regs call since that will emit insns which need to
878 be after the preconditioned loop copies, but immediately before the
879 unrolled loop copies. */
881 /* Also, it is not safe to split induction variables for the preconditioned
882 copies of the loop body. If we split induction variables, then the code
883 assumes that each induction variable can be represented as a function
884 of its initial value and the loop iteration number. This is not true
885 in this case, because the last preconditioned copy of the loop body
886 could be any iteration from the first up to the `unroll_number-1'th,
887 depending on the initial value of the iteration variable. Therefore
888 we can not split induction variables here, because we can not calculate
889 their value. Hence, this code must occur before find_splittable_regs
892 if (unroll_type == UNROLL_NAIVE && ! splitting_not_safe && strength_reduce_p)
894 rtx initial_value, final_value, increment;
895 enum machine_mode mode;
897 if (precondition_loop_p (loop_start, loop_info,
898 &initial_value, &final_value, &increment,
903 int abs_inc, neg_inc;
905 map->reg_map = (rtx *) xmalloc (maxregnum * sizeof (rtx));
907 VARRAY_CONST_EQUIV_INIT (map->const_equiv_varray, maxregnum,
909 global_const_equiv_varray = map->const_equiv_varray;
911 init_reg_map (map, maxregnum);
913 /* Limit loop unrolling to 4, since this will make 7 copies of
915 if (unroll_number > 4)
918 /* Save the absolute value of the increment, and also whether or
919 not it is negative. */
921 abs_inc = INTVAL (increment);
930 /* Calculate the difference between the final and initial values.
931 Final value may be a (plus (reg x) (const_int 1)) rtx.
932 Let the following cse pass simplify this if initial value is
935 We must copy the final and initial values here to avoid
936 improperly shared rtl. */
938 diff = expand_binop (mode, sub_optab, copy_rtx (final_value),
939 copy_rtx (initial_value), NULL_RTX, 0,
942 /* Now calculate (diff % (unroll * abs (increment))) by using an
944 diff = expand_binop (GET_MODE (diff), and_optab, diff,
945 GEN_INT (unroll_number * abs_inc - 1),
946 NULL_RTX, 0, OPTAB_LIB_WIDEN);
948 /* Now emit a sequence of branches to jump to the proper precond
951 labels = (rtx *) xmalloc (sizeof (rtx) * unroll_number);
952 for (i = 0; i < unroll_number; i++)
953 labels[i] = gen_label_rtx ();
955 /* Check for the case where the initial value is greater than or
956 equal to the final value. In that case, we want to execute
957 exactly one loop iteration. The code below will fail for this
958 case. This check does not apply if the loop has a NE
959 comparison at the end. */
961 if (loop_info->comparison_code != NE)
963 emit_cmp_and_jump_insns (initial_value, final_value,
965 NULL_RTX, mode, 0, 0, labels[1]);
966 JUMP_LABEL (get_last_insn ()) = labels[1];
967 LABEL_NUSES (labels[1])++;
970 /* Assuming the unroll_number is 4, and the increment is 2, then
971 for a negative increment: for a positive increment:
972 diff = 0,1 precond 0 diff = 0,7 precond 0
973 diff = 2,3 precond 3 diff = 1,2 precond 1
974 diff = 4,5 precond 2 diff = 3,4 precond 2
975 diff = 6,7 precond 1 diff = 5,6 precond 3 */
977 /* We only need to emit (unroll_number - 1) branches here, the
978 last case just falls through to the following code. */
980 /* ??? This would give better code if we emitted a tree of branches
981 instead of the current linear list of branches. */
983 for (i = 0; i < unroll_number - 1; i++)
986 enum rtx_code cmp_code;
988 /* For negative increments, must invert the constant compared
989 against, except when comparing against zero. */
997 cmp_const = unroll_number - i;
1006 emit_cmp_and_jump_insns (diff, GEN_INT (abs_inc * cmp_const),
1007 cmp_code, NULL_RTX, mode, 0, 0,
1009 JUMP_LABEL (get_last_insn ()) = labels[i];
1010 LABEL_NUSES (labels[i])++;
1013 /* If the increment is greater than one, then we need another branch,
1014 to handle other cases equivalent to 0. */
1016 /* ??? This should be merged into the code above somehow to help
1017 simplify the code here, and reduce the number of branches emitted.
1018 For the negative increment case, the branch here could easily
1019 be merged with the `0' case branch above. For the positive
1020 increment case, it is not clear how this can be simplified. */
1025 enum rtx_code cmp_code;
1029 cmp_const = abs_inc - 1;
1034 cmp_const = abs_inc * (unroll_number - 1) + 1;
1038 emit_cmp_and_jump_insns (diff, GEN_INT (cmp_const), cmp_code,
1039 NULL_RTX, mode, 0, 0, labels[0]);
1040 JUMP_LABEL (get_last_insn ()) = labels[0];
1041 LABEL_NUSES (labels[0])++;
1044 sequence = gen_sequence ();
1046 emit_insn_before (sequence, loop_start);
1048 /* Only the last copy of the loop body here needs the exit
1049 test, so set copy_end to exclude the compare/branch here,
1050 and then reset it inside the loop when get to the last
1053 if (GET_CODE (last_loop_insn) == BARRIER)
1054 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
1055 else if (GET_CODE (last_loop_insn) == JUMP_INSN)
1057 copy_end = PREV_INSN (last_loop_insn);
1059 /* The immediately preceding insn may be a compare which we do not
1061 if (sets_cc0_p (PREV_INSN (copy_end)))
1062 copy_end = PREV_INSN (copy_end);
1068 for (i = 1; i < unroll_number; i++)
1070 emit_label_after (labels[unroll_number - i],
1071 PREV_INSN (loop_start));
1073 bzero ((char *) map->insn_map, max_insnno * sizeof (rtx));
1074 bzero ((char *) &VARRAY_CONST_EQUIV (map->const_equiv_varray, 0),
1075 (VARRAY_SIZE (map->const_equiv_varray)
1076 * sizeof (struct const_equiv_data)));
1079 for (j = 0; j < max_labelno; j++)
1081 set_label_in_map (map, j, gen_label_rtx ());
1083 for (j = FIRST_PSEUDO_REGISTER; j < max_local_regnum; j++)
1086 map->reg_map[j] = gen_reg_rtx (GET_MODE (regno_reg_rtx[j]));
1087 record_base_value (REGNO (map->reg_map[j]),
1088 regno_reg_rtx[j], 0);
1090 /* The last copy needs the compare/branch insns at the end,
1091 so reset copy_end here if the loop ends with a conditional
1094 if (i == unroll_number - 1)
1096 if (GET_CODE (last_loop_insn) == BARRIER)
1097 copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
1099 copy_end = last_loop_insn;
1102 /* None of the copies are the `last_iteration', so just
1103 pass zero for that parameter. */
1104 copy_loop_body (copy_start, copy_end, map, exit_label, 0,
1105 unroll_type, start_label, loop_end,
1106 loop_start, copy_end);
1108 emit_label_after (labels[0], PREV_INSN (loop_start));
1110 if (GET_CODE (last_loop_insn) == BARRIER)
1112 insert_before = PREV_INSN (last_loop_insn);
1113 copy_end = PREV_INSN (insert_before);
1117 insert_before = last_loop_insn;
1119 /* The instruction immediately before the JUMP_INSN may be a compare
1120 instruction which we do not want to copy or delete. */
1121 if (sets_cc0_p (PREV_INSN (insert_before)))
1122 insert_before = PREV_INSN (insert_before);
1124 copy_end = PREV_INSN (insert_before);
1127 /* Set unroll type to MODULO now. */
1128 unroll_type = UNROLL_MODULO;
1129 loop_preconditioned = 1;
1136 /* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
1137 the loop unless all loops are being unrolled. */
1138 if (unroll_type == UNROLL_NAIVE && ! flag_unroll_all_loops)
1140 if (loop_dump_stream)
1141 fprintf (loop_dump_stream, "Unrolling failure: Naive unrolling not being done.\n");
1145 /* At this point, we are guaranteed to unroll the loop. */
1147 /* Keep track of the unroll factor for the loop. */
1148 loop_info->unroll_number = unroll_number;
1150 /* For each biv and giv, determine whether it can be safely split into
1151 a different variable for each unrolled copy of the loop body.
1152 We precalculate and save this info here, since computing it is
1155 Do this before deleting any instructions from the loop, so that
1156 back_branch_in_range_p will work correctly. */
1158 if (splitting_not_safe)
1161 temp = find_splittable_regs (unroll_type, loop_start, loop_end,
1162 end_insert_before, unroll_number,
1163 loop_info->n_iterations);
1165 /* find_splittable_regs may have created some new registers, so must
1166 reallocate the reg_map with the new larger size, and must realloc
1167 the constant maps also. */
1169 maxregnum = max_reg_num ();
1170 map->reg_map = (rtx *) xmalloc (maxregnum * sizeof (rtx));
1172 init_reg_map (map, maxregnum);
1174 if (map->const_equiv_varray == 0)
1175 VARRAY_CONST_EQUIV_INIT (map->const_equiv_varray,
1176 maxregnum + temp * unroll_number * 2,
1178 global_const_equiv_varray = map->const_equiv_varray;
1180 /* Search the list of bivs and givs to find ones which need to be remapped
1181 when split, and set their reg_map entry appropriately. */
1183 for (bl = loop_iv_list; bl; bl = bl->next)
1185 if (REGNO (bl->biv->src_reg) != bl->regno)
1186 map->reg_map[bl->regno] = bl->biv->src_reg;
1188 /* Currently, non-reduced/final-value givs are never split. */
1189 for (v = bl->giv; v; v = v->next_iv)
1190 if (REGNO (v->src_reg) != bl->regno)
1191 map->reg_map[REGNO (v->dest_reg)] = v->src_reg;
1195 /* Use our current register alignment and pointer flags. */
1196 map->regno_pointer_flag = cfun->emit->regno_pointer_flag;
1197 map->regno_pointer_align = cfun->emit->regno_pointer_align;
1199 /* If the loop is being partially unrolled, and the iteration variables
1200 are being split, and are being renamed for the split, then must fix up
1201 the compare/jump instruction at the end of the loop to refer to the new
1202 registers. This compare isn't copied, so the registers used in it
1203 will never be replaced if it isn't done here. */
1205 if (unroll_type == UNROLL_MODULO)
1207 insn = NEXT_INSN (copy_end);
1208 if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
1209 PATTERN (insn) = remap_split_bivs (PATTERN (insn));
1212 /* For unroll_number times, make a copy of each instruction
1213 between copy_start and copy_end, and insert these new instructions
1214 before the end of the loop. */
1216 for (i = 0; i < unroll_number; i++)
1218 bzero ((char *) map->insn_map, max_insnno * sizeof (rtx));
1219 bzero ((char *) &VARRAY_CONST_EQUIV (map->const_equiv_varray, 0),
1220 VARRAY_SIZE (map->const_equiv_varray) * sizeof (struct const_equiv_data));
1223 for (j = 0; j < max_labelno; j++)
1225 set_label_in_map (map, j, gen_label_rtx ());
1227 for (j = FIRST_PSEUDO_REGISTER; j < max_local_regnum; j++)
1230 map->reg_map[j] = gen_reg_rtx (GET_MODE (regno_reg_rtx[j]));
1231 record_base_value (REGNO (map->reg_map[j]),
1232 regno_reg_rtx[j], 0);
1235 /* If loop starts with a branch to the test, then fix it so that
1236 it points to the test of the first unrolled copy of the loop. */
1237 if (i == 0 && loop_start != copy_start)
1239 insn = PREV_INSN (copy_start);
1240 pattern = PATTERN (insn);
1242 tem = get_label_from_map (map,
1244 (XEXP (SET_SRC (pattern), 0)));
1245 SET_SRC (pattern) = gen_rtx_LABEL_REF (VOIDmode, tem);
1247 /* Set the jump label so that it can be used by later loop unrolling
1249 JUMP_LABEL (insn) = tem;
1250 LABEL_NUSES (tem)++;
1253 copy_loop_body (copy_start, copy_end, map, exit_label,
1254 i == unroll_number - 1, unroll_type, start_label,
1255 loop_end, insert_before, insert_before);
1258 /* Before deleting any insns, emit a CODE_LABEL immediately after the last
1259 insn to be deleted. This prevents any runaway delete_insn call from
1260 more insns that it should, as it always stops at a CODE_LABEL. */
1262 /* Delete the compare and branch at the end of the loop if completely
1263 unrolling the loop. Deleting the backward branch at the end also
1264 deletes the code label at the start of the loop. This is done at
1265 the very end to avoid problems with back_branch_in_range_p. */
1267 if (unroll_type == UNROLL_COMPLETELY)
1268 safety_label = emit_label_after (gen_label_rtx (), last_loop_insn);
1270 safety_label = emit_label_after (gen_label_rtx (), copy_end);
1272 /* Delete all of the original loop instructions. Don't delete the
1273 LOOP_BEG note, or the first code label in the loop. */
1275 insn = NEXT_INSN (copy_start);
1276 while (insn != safety_label)
1278 /* ??? Don't delete named code labels. They will be deleted when the
1279 jump that references them is deleted. Otherwise, we end up deleting
1280 them twice, which causes them to completely disappear instead of turn
1281 into NOTE_INSN_DELETED_LABEL notes. This in turn causes aborts in
1282 dwarfout.c/dwarf2out.c. We could perhaps fix the dwarf*out.c files
1283 to handle deleted labels instead. Or perhaps fix DECL_RTL of the
1284 associated LABEL_DECL to point to one of the new label instances. */
1285 /* ??? Likewise, we can't delete a NOTE_INSN_DELETED_LABEL note. */
1286 if (insn != start_label
1287 && ! (GET_CODE (insn) == CODE_LABEL && LABEL_NAME (insn))
1288 && ! (GET_CODE (insn) == NOTE
1289 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_DELETED_LABEL))
1290 insn = delete_insn (insn);
1292 insn = NEXT_INSN (insn);
1295 /* Can now delete the 'safety' label emitted to protect us from runaway
1296 delete_insn calls. */
1297 if (INSN_DELETED_P (safety_label))
1299 delete_insn (safety_label);
1301 /* If exit_label exists, emit it after the loop. Doing the emit here
1302 forces it to have a higher INSN_UID than any insn in the unrolled loop.
1303 This is needed so that mostly_true_jump in reorg.c will treat jumps
1304 to this loop end label correctly, i.e. predict that they are usually
1307 emit_label_after (exit_label, loop_end);
1310 if (unroll_type == UNROLL_COMPLETELY)
1312 /* Remove the loop notes since this is no longer a loop. */
1314 delete_insn (loop->vtop);
1316 delete_insn (loop->cont);
1318 delete_insn (loop_start);
1320 delete_insn (loop_end);
1323 if (map->const_equiv_varray)
1324 VARRAY_FREE (map->const_equiv_varray);
1327 free (map->label_map);
1330 free (map->insn_map);
1331 free (splittable_regs);
1332 free (derived_regs);
1333 free (splittable_regs_updates);
1334 free (addr_combined_regs);
1337 free (map->reg_map);
1341 /* Return true if the loop can be safely, and profitably, preconditioned
1342 so that the unrolled copies of the loop body don't need exit tests.
1344 This only works if final_value, initial_value and increment can be
1345 determined, and if increment is a constant power of 2.
1346 If increment is not a power of 2, then the preconditioning modulo
1347 operation would require a real modulo instead of a boolean AND, and this
1348 is not considered `profitable'. */
1350 /* ??? If the loop is known to be executed very many times, or the machine
1351 has a very cheap divide instruction, then preconditioning is a win even
1352 when the increment is not a power of 2. Use RTX_COST to compute
1353 whether divide is cheap.
1354 ??? A divide by constant doesn't actually need a divide, look at
1355 expand_divmod. The reduced cost of this optimized modulo is not
1356 reflected in RTX_COST. */
1359 precondition_loop_p (loop_start, loop_info,
1360 initial_value, final_value, increment, mode)
1362 struct loop_info *loop_info;
1363 rtx *initial_value, *final_value, *increment;
1364 enum machine_mode *mode;
1367 if (loop_info->n_iterations > 0)
1369 *initial_value = const0_rtx;
1370 *increment = const1_rtx;
1371 *final_value = GEN_INT (loop_info->n_iterations);
1374 if (loop_dump_stream)
1376 fputs ("Preconditioning: Success, number of iterations known, ",
1378 fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC,
1379 loop_info->n_iterations);
1380 fputs (".\n", loop_dump_stream);
1385 if (loop_info->initial_value == 0)
1387 if (loop_dump_stream)
1388 fprintf (loop_dump_stream,
1389 "Preconditioning: Could not find initial value.\n");
1392 else if (loop_info->increment == 0)
1394 if (loop_dump_stream)
1395 fprintf (loop_dump_stream,
1396 "Preconditioning: Could not find increment value.\n");
1399 else if (GET_CODE (loop_info->increment) != CONST_INT)
1401 if (loop_dump_stream)
1402 fprintf (loop_dump_stream,
1403 "Preconditioning: Increment not a constant.\n");
1406 else if ((exact_log2 (INTVAL (loop_info->increment)) < 0)
1407 && (exact_log2 (- INTVAL (loop_info->increment)) < 0))
1409 if (loop_dump_stream)
1410 fprintf (loop_dump_stream,
1411 "Preconditioning: Increment not a constant power of 2.\n");
1415 /* Unsigned_compare and compare_dir can be ignored here, since they do
1416 not matter for preconditioning. */
1418 if (loop_info->final_value == 0)
1420 if (loop_dump_stream)
1421 fprintf (loop_dump_stream,
1422 "Preconditioning: EQ comparison loop.\n");
1426 /* Must ensure that final_value is invariant, so call invariant_p to
1427 check. Before doing so, must check regno against max_reg_before_loop
1428 to make sure that the register is in the range covered by invariant_p.
1429 If it isn't, then it is most likely a biv/giv which by definition are
1431 if ((GET_CODE (loop_info->final_value) == REG
1432 && REGNO (loop_info->final_value) >= max_reg_before_loop)
1433 || (GET_CODE (loop_info->final_value) == PLUS
1434 && REGNO (XEXP (loop_info->final_value, 0)) >= max_reg_before_loop)
1435 || ! invariant_p (loop_info->final_value))
1437 if (loop_dump_stream)
1438 fprintf (loop_dump_stream,
1439 "Preconditioning: Final value not invariant.\n");
1443 /* Fail for floating point values, since the caller of this function
1444 does not have code to deal with them. */
1445 if (GET_MODE_CLASS (GET_MODE (loop_info->final_value)) == MODE_FLOAT
1446 || GET_MODE_CLASS (GET_MODE (loop_info->initial_value)) == MODE_FLOAT)
1448 if (loop_dump_stream)
1449 fprintf (loop_dump_stream,
1450 "Preconditioning: Floating point final or initial value.\n");
1454 /* Fail if loop_info->iteration_var is not live before loop_start,
1455 since we need to test its value in the preconditioning code. */
1457 if (uid_luid[REGNO_FIRST_UID (REGNO (loop_info->iteration_var))]
1458 > INSN_LUID (loop_start))
1460 if (loop_dump_stream)
1461 fprintf (loop_dump_stream,
1462 "Preconditioning: Iteration var not live before loop start.\n");
1466 /* Note that iteration_info biases the initial value for GIV iterators
1467 such as "while (i-- > 0)" so that we can calculate the number of
1468 iterations just like for BIV iterators.
1470 Also note that the absolute values of initial_value and
1471 final_value are unimportant as only their difference is used for
1472 calculating the number of loop iterations. */
1473 *initial_value = loop_info->initial_value;
1474 *increment = loop_info->increment;
1475 *final_value = loop_info->final_value;
1477 /* Decide what mode to do these calculations in. Choose the larger
1478 of final_value's mode and initial_value's mode, or a full-word if
1479 both are constants. */
1480 *mode = GET_MODE (*final_value);
1481 if (*mode == VOIDmode)
1483 *mode = GET_MODE (*initial_value);
1484 if (*mode == VOIDmode)
1487 else if (*mode != GET_MODE (*initial_value)
1488 && (GET_MODE_SIZE (*mode)
1489 < GET_MODE_SIZE (GET_MODE (*initial_value))))
1490 *mode = GET_MODE (*initial_value);
1493 if (loop_dump_stream)
1494 fprintf (loop_dump_stream, "Preconditioning: Successful.\n");
1499 /* All pseudo-registers must be mapped to themselves. Two hard registers
1500 must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
1501 REGNUM, to avoid function-inlining specific conversions of these
1502 registers. All other hard regs can not be mapped because they may be
1507 init_reg_map (map, maxregnum)
1508 struct inline_remap *map;
1513 for (i = maxregnum - 1; i > LAST_VIRTUAL_REGISTER; i--)
1514 map->reg_map[i] = regno_reg_rtx[i];
1515 /* Just clear the rest of the entries. */
1516 for (i = LAST_VIRTUAL_REGISTER; i >= 0; i--)
1517 map->reg_map[i] = 0;
1519 map->reg_map[VIRTUAL_STACK_VARS_REGNUM]
1520 = regno_reg_rtx[VIRTUAL_STACK_VARS_REGNUM];
1521 map->reg_map[VIRTUAL_INCOMING_ARGS_REGNUM]
1522 = regno_reg_rtx[VIRTUAL_INCOMING_ARGS_REGNUM];
1525 /* Strength-reduction will often emit code for optimized biv/givs which
1526 calculates their value in a temporary register, and then copies the result
1527 to the iv. This procedure reconstructs the pattern computing the iv;
1528 verifying that all operands are of the proper form.
1530 PATTERN must be the result of single_set.
1531 The return value is the amount that the giv is incremented by. */
1534 calculate_giv_inc (pattern, src_insn, regno)
1535 rtx pattern, src_insn;
1539 rtx increment_total = 0;
1543 /* Verify that we have an increment insn here. First check for a plus
1544 as the set source. */
1545 if (GET_CODE (SET_SRC (pattern)) != PLUS)
1547 /* SR sometimes computes the new giv value in a temp, then copies it
1549 src_insn = PREV_INSN (src_insn);
1550 pattern = PATTERN (src_insn);
1551 if (GET_CODE (SET_SRC (pattern)) != PLUS)
1554 /* The last insn emitted is not needed, so delete it to avoid confusing
1555 the second cse pass. This insn sets the giv unnecessarily. */
1556 delete_insn (get_last_insn ());
1559 /* Verify that we have a constant as the second operand of the plus. */
1560 increment = XEXP (SET_SRC (pattern), 1);
1561 if (GET_CODE (increment) != CONST_INT)
1563 /* SR sometimes puts the constant in a register, especially if it is
1564 too big to be an add immed operand. */
1565 src_insn = PREV_INSN (src_insn);
1566 increment = SET_SRC (PATTERN (src_insn));
1568 /* SR may have used LO_SUM to compute the constant if it is too large
1569 for a load immed operand. In this case, the constant is in operand
1570 one of the LO_SUM rtx. */
1571 if (GET_CODE (increment) == LO_SUM)
1572 increment = XEXP (increment, 1);
1574 /* Some ports store large constants in memory and add a REG_EQUAL
1575 note to the store insn. */
1576 else if (GET_CODE (increment) == MEM)
1578 rtx note = find_reg_note (src_insn, REG_EQUAL, 0);
1580 increment = XEXP (note, 0);
1583 else if (GET_CODE (increment) == IOR
1584 || GET_CODE (increment) == ASHIFT
1585 || GET_CODE (increment) == PLUS)
1587 /* The rs6000 port loads some constants with IOR.
1588 The alpha port loads some constants with ASHIFT and PLUS. */
1589 rtx second_part = XEXP (increment, 1);
1590 enum rtx_code code = GET_CODE (increment);
1592 src_insn = PREV_INSN (src_insn);
1593 increment = SET_SRC (PATTERN (src_insn));
1594 /* Don't need the last insn anymore. */
1595 delete_insn (get_last_insn ());
1597 if (GET_CODE (second_part) != CONST_INT
1598 || GET_CODE (increment) != CONST_INT)
1602 increment = GEN_INT (INTVAL (increment) | INTVAL (second_part));
1603 else if (code == PLUS)
1604 increment = GEN_INT (INTVAL (increment) + INTVAL (second_part));
1606 increment = GEN_INT (INTVAL (increment) << INTVAL (second_part));
1609 if (GET_CODE (increment) != CONST_INT)
1612 /* The insn loading the constant into a register is no longer needed,
1614 delete_insn (get_last_insn ());
1617 if (increment_total)
1618 increment_total = GEN_INT (INTVAL (increment_total) + INTVAL (increment));
1620 increment_total = increment;
1622 /* Check that the source register is the same as the register we expected
1623 to see as the source. If not, something is seriously wrong. */
1624 if (GET_CODE (XEXP (SET_SRC (pattern), 0)) != REG
1625 || REGNO (XEXP (SET_SRC (pattern), 0)) != regno)
1627 /* Some machines (e.g. the romp), may emit two add instructions for
1628 certain constants, so lets try looking for another add immediately
1629 before this one if we have only seen one add insn so far. */
1635 src_insn = PREV_INSN (src_insn);
1636 pattern = PATTERN (src_insn);
1638 delete_insn (get_last_insn ());
1646 return increment_total;
1649 /* Copy REG_NOTES, except for insn references, because not all insn_map
1650 entries are valid yet. We do need to copy registers now though, because
1651 the reg_map entries can change during copying. */
1654 initial_reg_note_copy (notes, map)
1656 struct inline_remap *map;
1663 copy = rtx_alloc (GET_CODE (notes));
1664 PUT_MODE (copy, GET_MODE (notes));
1666 if (GET_CODE (notes) == EXPR_LIST)
1667 XEXP (copy, 0) = copy_rtx_and_substitute (XEXP (notes, 0), map, 0);
1668 else if (GET_CODE (notes) == INSN_LIST)
1669 /* Don't substitute for these yet. */
1670 XEXP (copy, 0) = XEXP (notes, 0);
1674 XEXP (copy, 1) = initial_reg_note_copy (XEXP (notes, 1), map);
1679 /* Fixup insn references in copied REG_NOTES. */
1682 final_reg_note_copy (notes, map)
1684 struct inline_remap *map;
1688 for (note = notes; note; note = XEXP (note, 1))
1689 if (GET_CODE (note) == INSN_LIST)
1690 XEXP (note, 0) = map->insn_map[INSN_UID (XEXP (note, 0))];
1693 /* Copy each instruction in the loop, substituting from map as appropriate.
1694 This is very similar to a loop in expand_inline_function. */
1697 copy_loop_body (copy_start, copy_end, map, exit_label, last_iteration,
1698 unroll_type, start_label, loop_end, insert_before,
1700 rtx copy_start, copy_end;
1701 struct inline_remap *map;
1704 enum unroll_types unroll_type;
1705 rtx start_label, loop_end, insert_before, copy_notes_from;
1708 rtx set, tem, copy = NULL_RTX;
1709 int dest_reg_was_split, i;
1713 rtx final_label = 0;
1714 rtx giv_inc, giv_dest_reg, giv_src_reg;
1716 /* If this isn't the last iteration, then map any references to the
1717 start_label to final_label. Final label will then be emitted immediately
1718 after the end of this loop body if it was ever used.
1720 If this is the last iteration, then map references to the start_label
1722 if (! last_iteration)
1724 final_label = gen_label_rtx ();
1725 set_label_in_map (map, CODE_LABEL_NUMBER (start_label),
1729 set_label_in_map (map, CODE_LABEL_NUMBER (start_label), start_label);
1733 /* Emit a NOTE_INSN_DELETED to force at least two insns onto the sequence.
1734 Else gen_sequence could return a raw pattern for a jump which we pass
1735 off to emit_insn_before (instead of emit_jump_insn_before) which causes
1736 a variety of losing behaviors later. */
1737 emit_note (0, NOTE_INSN_DELETED);
1742 insn = NEXT_INSN (insn);
1744 map->orig_asm_operands_vector = 0;
1746 switch (GET_CODE (insn))
1749 pattern = PATTERN (insn);
1753 /* Check to see if this is a giv that has been combined with
1754 some split address givs. (Combined in the sense that
1755 `combine_givs' in loop.c has put two givs in the same register.)
1756 In this case, we must search all givs based on the same biv to
1757 find the address givs. Then split the address givs.
1758 Do this before splitting the giv, since that may map the
1759 SET_DEST to a new register. */
1761 if ((set = single_set (insn))
1762 && GET_CODE (SET_DEST (set)) == REG
1763 && addr_combined_regs[REGNO (SET_DEST (set))])
1765 struct iv_class *bl;
1766 struct induction *v, *tv;
1767 int regno = REGNO (SET_DEST (set));
1769 v = addr_combined_regs[REGNO (SET_DEST (set))];
1770 bl = reg_biv_class[REGNO (v->src_reg)];
1772 /* Although the giv_inc amount is not needed here, we must call
1773 calculate_giv_inc here since it might try to delete the
1774 last insn emitted. If we wait until later to call it,
1775 we might accidentally delete insns generated immediately
1776 below by emit_unrolled_add. */
1778 if (! derived_regs[regno])
1779 giv_inc = calculate_giv_inc (set, insn, regno);
1781 /* Now find all address giv's that were combined with this
1783 for (tv = bl->giv; tv; tv = tv->next_iv)
1784 if (tv->giv_type == DEST_ADDR && tv->same == v)
1788 /* If this DEST_ADDR giv was not split, then ignore it. */
1789 if (*tv->location != tv->dest_reg)
1792 /* Scale this_giv_inc if the multiplicative factors of
1793 the two givs are different. */
1794 this_giv_inc = INTVAL (giv_inc);
1795 if (tv->mult_val != v->mult_val)
1796 this_giv_inc = (this_giv_inc / INTVAL (v->mult_val)
1797 * INTVAL (tv->mult_val));
1799 tv->dest_reg = plus_constant (tv->dest_reg, this_giv_inc);
1800 *tv->location = tv->dest_reg;
1802 if (last_iteration && unroll_type != UNROLL_COMPLETELY)
1804 /* Must emit an insn to increment the split address
1805 giv. Add in the const_adjust field in case there
1806 was a constant eliminated from the address. */
1807 rtx value, dest_reg;
1809 /* tv->dest_reg will be either a bare register,
1810 or else a register plus a constant. */
1811 if (GET_CODE (tv->dest_reg) == REG)
1812 dest_reg = tv->dest_reg;
1814 dest_reg = XEXP (tv->dest_reg, 0);
1816 /* Check for shared address givs, and avoid
1817 incrementing the shared pseudo reg more than
1819 if (! tv->same_insn && ! tv->shared)
1821 /* tv->dest_reg may actually be a (PLUS (REG)
1822 (CONST)) here, so we must call plus_constant
1823 to add the const_adjust amount before calling
1824 emit_unrolled_add below. */
1825 value = plus_constant (tv->dest_reg,
1828 if (GET_CODE (value) == PLUS)
1830 /* The constant could be too large for an add
1831 immediate, so can't directly emit an insn
1833 emit_unrolled_add (dest_reg, XEXP (value, 0),
1838 /* Reset the giv to be just the register again, in case
1839 it is used after the set we have just emitted.
1840 We must subtract the const_adjust factor added in
1842 tv->dest_reg = plus_constant (dest_reg,
1843 - tv->const_adjust);
1844 *tv->location = tv->dest_reg;
1849 /* If this is a setting of a splittable variable, then determine
1850 how to split the variable, create a new set based on this split,
1851 and set up the reg_map so that later uses of the variable will
1852 use the new split variable. */
1854 dest_reg_was_split = 0;
1856 if ((set = single_set (insn))
1857 && GET_CODE (SET_DEST (set)) == REG
1858 && splittable_regs[REGNO (SET_DEST (set))])
1860 int regno = REGNO (SET_DEST (set));
1863 dest_reg_was_split = 1;
1865 giv_dest_reg = SET_DEST (set);
1866 if (derived_regs[regno])
1868 /* ??? This relies on SET_SRC (SET) to be of
1869 the form (plus (reg) (const_int)), and thus
1870 forces recombine_givs to restrict the kind
1871 of giv derivations it does before unrolling. */
1872 giv_src_reg = XEXP (SET_SRC (set), 0);
1873 giv_inc = XEXP (SET_SRC (set), 1);
1877 giv_src_reg = giv_dest_reg;
1878 /* Compute the increment value for the giv, if it wasn't
1879 already computed above. */
1881 giv_inc = calculate_giv_inc (set, insn, regno);
1883 src_regno = REGNO (giv_src_reg);
1885 if (unroll_type == UNROLL_COMPLETELY)
1887 /* Completely unrolling the loop. Set the induction
1888 variable to a known constant value. */
1890 /* The value in splittable_regs may be an invariant
1891 value, so we must use plus_constant here. */
1892 splittable_regs[regno]
1893 = plus_constant (splittable_regs[src_regno],
1896 if (GET_CODE (splittable_regs[regno]) == PLUS)
1898 giv_src_reg = XEXP (splittable_regs[regno], 0);
1899 giv_inc = XEXP (splittable_regs[regno], 1);
1903 /* The splittable_regs value must be a REG or a
1904 CONST_INT, so put the entire value in the giv_src_reg
1906 giv_src_reg = splittable_regs[regno];
1907 giv_inc = const0_rtx;
1912 /* Partially unrolling loop. Create a new pseudo
1913 register for the iteration variable, and set it to
1914 be a constant plus the original register. Except
1915 on the last iteration, when the result has to
1916 go back into the original iteration var register. */
1918 /* Handle bivs which must be mapped to a new register
1919 when split. This happens for bivs which need their
1920 final value set before loop entry. The new register
1921 for the biv was stored in the biv's first struct
1922 induction entry by find_splittable_regs. */
1924 if (regno < max_reg_before_loop
1925 && REG_IV_TYPE (regno) == BASIC_INDUCT)
1927 giv_src_reg = reg_biv_class[regno]->biv->src_reg;
1928 giv_dest_reg = giv_src_reg;
1932 /* If non-reduced/final-value givs were split, then
1933 this would have to remap those givs also. See
1934 find_splittable_regs. */
1937 splittable_regs[regno]
1938 = GEN_INT (INTVAL (giv_inc)
1939 + INTVAL (splittable_regs[src_regno]));
1940 giv_inc = splittable_regs[regno];
1942 /* Now split the induction variable by changing the dest
1943 of this insn to a new register, and setting its
1944 reg_map entry to point to this new register.
1946 If this is the last iteration, and this is the last insn
1947 that will update the iv, then reuse the original dest,
1948 to ensure that the iv will have the proper value when
1949 the loop exits or repeats.
1951 Using splittable_regs_updates here like this is safe,
1952 because it can only be greater than one if all
1953 instructions modifying the iv are always executed in
1956 if (! last_iteration
1957 || (splittable_regs_updates[regno]-- != 1))
1959 tem = gen_reg_rtx (GET_MODE (giv_src_reg));
1961 map->reg_map[regno] = tem;
1962 record_base_value (REGNO (tem),
1963 giv_inc == const0_rtx
1965 : gen_rtx_PLUS (GET_MODE (giv_src_reg),
1966 giv_src_reg, giv_inc),
1970 map->reg_map[regno] = giv_src_reg;
1973 /* The constant being added could be too large for an add
1974 immediate, so can't directly emit an insn here. */
1975 emit_unrolled_add (giv_dest_reg, giv_src_reg, giv_inc);
1976 copy = get_last_insn ();
1977 pattern = PATTERN (copy);
1981 pattern = copy_rtx_and_substitute (pattern, map, 0);
1982 copy = emit_insn (pattern);
1984 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
1987 /* If this insn is setting CC0, it may need to look at
1988 the insn that uses CC0 to see what type of insn it is.
1989 In that case, the call to recog via validate_change will
1990 fail. So don't substitute constants here. Instead,
1991 do it when we emit the following insn.
1993 For example, see the pyr.md file. That machine has signed and
1994 unsigned compares. The compare patterns must check the
1995 following branch insn to see which what kind of compare to
1998 If the previous insn set CC0, substitute constants on it as
2000 if (sets_cc0_p (PATTERN (copy)) != 0)
2005 try_constants (cc0_insn, map);
2007 try_constants (copy, map);
2010 try_constants (copy, map);
2013 /* Make split induction variable constants `permanent' since we
2014 know there are no backward branches across iteration variable
2015 settings which would invalidate this. */
2016 if (dest_reg_was_split)
2018 int regno = REGNO (SET_DEST (set));
2020 if ((size_t) regno < VARRAY_SIZE (map->const_equiv_varray)
2021 && (VARRAY_CONST_EQUIV (map->const_equiv_varray, regno).age
2023 VARRAY_CONST_EQUIV (map->const_equiv_varray, regno).age = -1;
2028 pattern = copy_rtx_and_substitute (PATTERN (insn), map, 0);
2029 copy = emit_jump_insn (pattern);
2030 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
2032 if (JUMP_LABEL (insn) == start_label && insn == copy_end
2033 && ! last_iteration)
2035 /* This is a branch to the beginning of the loop; this is the
2036 last insn being copied; and this is not the last iteration.
2037 In this case, we want to change the original fall through
2038 case to be a branch past the end of the loop, and the
2039 original jump label case to fall_through. */
2041 if (invert_exp (pattern, copy))
2043 if (! redirect_exp (&pattern,
2044 get_label_from_map (map,
2046 (JUMP_LABEL (insn))),
2053 rtx lab = gen_label_rtx ();
2054 /* Can't do it by reversing the jump (probably because we
2055 couldn't reverse the conditions), so emit a new
2056 jump_insn after COPY, and redirect the jump around
2058 jmp = emit_jump_insn_after (gen_jump (exit_label), copy);
2059 jmp = emit_barrier_after (jmp);
2060 emit_label_after (lab, jmp);
2061 LABEL_NUSES (lab) = 0;
2062 if (! redirect_exp (&pattern,
2063 get_label_from_map (map,
2065 (JUMP_LABEL (insn))),
2073 try_constants (cc0_insn, map);
2076 try_constants (copy, map);
2078 /* Set the jump label of COPY correctly to avoid problems with
2079 later passes of unroll_loop, if INSN had jump label set. */
2080 if (JUMP_LABEL (insn))
2084 /* Can't use the label_map for every insn, since this may be
2085 the backward branch, and hence the label was not mapped. */
2086 if ((set = single_set (copy)))
2088 tem = SET_SRC (set);
2089 if (GET_CODE (tem) == LABEL_REF)
2090 label = XEXP (tem, 0);
2091 else if (GET_CODE (tem) == IF_THEN_ELSE)
2093 if (XEXP (tem, 1) != pc_rtx)
2094 label = XEXP (XEXP (tem, 1), 0);
2096 label = XEXP (XEXP (tem, 2), 0);
2100 if (label && GET_CODE (label) == CODE_LABEL)
2101 JUMP_LABEL (copy) = label;
2104 /* An unrecognizable jump insn, probably the entry jump
2105 for a switch statement. This label must have been mapped,
2106 so just use the label_map to get the new jump label. */
2108 = get_label_from_map (map,
2109 CODE_LABEL_NUMBER (JUMP_LABEL (insn)));
2112 /* If this is a non-local jump, then must increase the label
2113 use count so that the label will not be deleted when the
2114 original jump is deleted. */
2115 LABEL_NUSES (JUMP_LABEL (copy))++;
2117 else if (GET_CODE (PATTERN (copy)) == ADDR_VEC
2118 || GET_CODE (PATTERN (copy)) == ADDR_DIFF_VEC)
2120 rtx pat = PATTERN (copy);
2121 int diff_vec_p = GET_CODE (pat) == ADDR_DIFF_VEC;
2122 int len = XVECLEN (pat, diff_vec_p);
2125 for (i = 0; i < len; i++)
2126 LABEL_NUSES (XEXP (XVECEXP (pat, diff_vec_p, i), 0))++;
2129 /* If this used to be a conditional jump insn but whose branch
2130 direction is now known, we must do something special. */
2131 if (condjump_p (insn) && !simplejump_p (insn) && map->last_pc_value)
2134 /* If the previous insn set cc0 for us, delete it. */
2135 if (sets_cc0_p (PREV_INSN (copy)))
2136 delete_insn (PREV_INSN (copy));
2139 /* If this is now a no-op, delete it. */
2140 if (map->last_pc_value == pc_rtx)
2142 /* Don't let delete_insn delete the label referenced here,
2143 because we might possibly need it later for some other
2144 instruction in the loop. */
2145 if (JUMP_LABEL (copy))
2146 LABEL_NUSES (JUMP_LABEL (copy))++;
2148 if (JUMP_LABEL (copy))
2149 LABEL_NUSES (JUMP_LABEL (copy))--;
2153 /* Otherwise, this is unconditional jump so we must put a
2154 BARRIER after it. We could do some dead code elimination
2155 here, but jump.c will do it just as well. */
2161 pattern = copy_rtx_and_substitute (PATTERN (insn), map, 0);
2162 copy = emit_call_insn (pattern);
2163 REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
2165 /* Because the USAGE information potentially contains objects other
2166 than hard registers, we need to copy it. */
2167 CALL_INSN_FUNCTION_USAGE (copy)
2168 = copy_rtx_and_substitute (CALL_INSN_FUNCTION_USAGE (insn),
2173 try_constants (cc0_insn, map);
2176 try_constants (copy, map);
2178 /* Be lazy and assume CALL_INSNs clobber all hard registers. */
2179 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2180 VARRAY_CONST_EQUIV (map->const_equiv_varray, i).rtx = 0;
2184 /* If this is the loop start label, then we don't need to emit a
2185 copy of this label since no one will use it. */
2187 if (insn != start_label)
2189 copy = emit_label (get_label_from_map (map,
2190 CODE_LABEL_NUMBER (insn)));
2196 copy = emit_barrier ();
2200 /* VTOP and CONT notes are valid only before the loop exit test.
2201 If placed anywhere else, loop may generate bad code. */
2202 /* BASIC_BLOCK notes exist to stabilize basic block structures with
2203 the associated rtl. We do not want to share the structure in
2206 if (NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
2207 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
2208 && ((NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP
2209 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_CONT)
2210 || (last_iteration && unroll_type != UNROLL_COMPLETELY)))
2211 copy = emit_note (NOTE_SOURCE_FILE (insn),
2212 NOTE_LINE_NUMBER (insn));
2221 map->insn_map[INSN_UID (insn)] = copy;
2223 while (insn != copy_end);
2225 /* Now finish coping the REG_NOTES. */
2229 insn = NEXT_INSN (insn);
2230 if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN
2231 || GET_CODE (insn) == CALL_INSN)
2232 && map->insn_map[INSN_UID (insn)])
2233 final_reg_note_copy (REG_NOTES (map->insn_map[INSN_UID (insn)]), map);
2235 while (insn != copy_end);
2237 /* There may be notes between copy_notes_from and loop_end. Emit a copy of
2238 each of these notes here, since there may be some important ones, such as
2239 NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
2240 iteration, because the original notes won't be deleted.
2242 We can't use insert_before here, because when from preconditioning,
2243 insert_before points before the loop. We can't use copy_end, because
2244 there may be insns already inserted after it (which we don't want to
2245 copy) when not from preconditioning code. */
2247 if (! last_iteration)
2249 for (insn = copy_notes_from; insn != loop_end; insn = NEXT_INSN (insn))
2251 /* VTOP notes are valid only before the loop exit test.
2252 If placed anywhere else, loop may generate bad code.
2253 There is no need to test for NOTE_INSN_LOOP_CONT notes
2254 here, since COPY_NOTES_FROM will be at most one or two (for cc0)
2255 instructions before the last insn in the loop, and if the
2256 end test is that short, there will be a VTOP note between
2257 the CONT note and the test. */
2258 if (GET_CODE (insn) == NOTE
2259 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
2260 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
2261 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP)
2262 emit_note (NOTE_SOURCE_FILE (insn), NOTE_LINE_NUMBER (insn));
2266 if (final_label && LABEL_NUSES (final_label) > 0)
2267 emit_label (final_label);
2269 tem = gen_sequence ();
2271 emit_insn_before (tem, insert_before);
2274 /* Emit an insn, using the expand_binop to ensure that a valid insn is
2275 emitted. This will correctly handle the case where the increment value
2276 won't fit in the immediate field of a PLUS insns. */
2279 emit_unrolled_add (dest_reg, src_reg, increment)
2280 rtx dest_reg, src_reg, increment;
2284 result = expand_binop (GET_MODE (dest_reg), add_optab, src_reg, increment,
2285 dest_reg, 0, OPTAB_LIB_WIDEN);
2287 if (dest_reg != result)
2288 emit_move_insn (dest_reg, result);
2291 /* Searches the insns between INSN and LOOP_END. Returns 1 if there
2292 is a backward branch in that range that branches to somewhere between
2293 LOOP_START and INSN. Returns 0 otherwise. */
2295 /* ??? This is quadratic algorithm. Could be rewritten to be linear.
2296 In practice, this is not a problem, because this function is seldom called,
2297 and uses a negligible amount of CPU time on average. */
2300 back_branch_in_range_p (insn, loop_start, loop_end)
2302 rtx loop_start, loop_end;
2304 rtx p, q, target_insn;
2305 rtx orig_loop_end = loop_end;
2307 /* Stop before we get to the backward branch at the end of the loop. */
2308 loop_end = prev_nonnote_insn (loop_end);
2309 if (GET_CODE (loop_end) == BARRIER)
2310 loop_end = PREV_INSN (loop_end);
2312 /* Check in case insn has been deleted, search forward for first non
2313 deleted insn following it. */
2314 while (INSN_DELETED_P (insn))
2315 insn = NEXT_INSN (insn);
2317 /* Check for the case where insn is the last insn in the loop. Deal
2318 with the case where INSN was a deleted loop test insn, in which case
2319 it will now be the NOTE_LOOP_END. */
2320 if (insn == loop_end || insn == orig_loop_end)
2323 for (p = NEXT_INSN (insn); p != loop_end; p = NEXT_INSN (p))
2325 if (GET_CODE (p) == JUMP_INSN)
2327 target_insn = JUMP_LABEL (p);
2329 /* Search from loop_start to insn, to see if one of them is
2330 the target_insn. We can't use INSN_LUID comparisons here,
2331 since insn may not have an LUID entry. */
2332 for (q = loop_start; q != insn; q = NEXT_INSN (q))
2333 if (q == target_insn)
2341 /* Try to generate the simplest rtx for the expression
2342 (PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
2346 fold_rtx_mult_add (mult1, mult2, add1, mode)
2347 rtx mult1, mult2, add1;
2348 enum machine_mode mode;
2353 /* The modes must all be the same. This should always be true. For now,
2354 check to make sure. */
2355 if ((GET_MODE (mult1) != mode && GET_MODE (mult1) != VOIDmode)
2356 || (GET_MODE (mult2) != mode && GET_MODE (mult2) != VOIDmode)
2357 || (GET_MODE (add1) != mode && GET_MODE (add1) != VOIDmode))
2360 /* Ensure that if at least one of mult1/mult2 are constant, then mult2
2361 will be a constant. */
2362 if (GET_CODE (mult1) == CONST_INT)
2369 mult_res = simplify_binary_operation (MULT, mode, mult1, mult2);
2371 mult_res = gen_rtx_MULT (mode, mult1, mult2);
2373 /* Again, put the constant second. */
2374 if (GET_CODE (add1) == CONST_INT)
2381 result = simplify_binary_operation (PLUS, mode, add1, mult_res);
2383 result = gen_rtx_PLUS (mode, add1, mult_res);
2388 /* Searches the list of induction struct's for the biv BL, to try to calculate
2389 the total increment value for one iteration of the loop as a constant.
2391 Returns the increment value as an rtx, simplified as much as possible,
2392 if it can be calculated. Otherwise, returns 0. */
2395 biv_total_increment (bl, loop_start, loop_end)
2396 struct iv_class *bl;
2397 rtx loop_start ATTRIBUTE_UNUSED, loop_end ATTRIBUTE_UNUSED;
2399 struct induction *v;
2402 /* For increment, must check every instruction that sets it. Each
2403 instruction must be executed only once each time through the loop.
2404 To verify this, we check that the insn is always executed, and that
2405 there are no backward branches after the insn that branch to before it.
2406 Also, the insn must have a mult_val of one (to make sure it really is
2409 result = const0_rtx;
2410 for (v = bl->biv; v; v = v->next_iv)
2412 if (v->always_computable && v->mult_val == const1_rtx
2413 && ! v->maybe_multiple)
2414 result = fold_rtx_mult_add (result, const1_rtx, v->add_val, v->mode);
2422 /* Determine the initial value of the iteration variable, and the amount
2423 that it is incremented each loop. Use the tables constructed by
2424 the strength reduction pass to calculate these values.
2426 Initial_value and/or increment are set to zero if their values could not
2430 iteration_info (iteration_var, initial_value, increment, loop_start, loop_end)
2431 rtx iteration_var, *initial_value, *increment;
2432 rtx loop_start, loop_end;
2434 struct iv_class *bl;
2436 struct induction *v;
2439 /* Clear the result values, in case no answer can be found. */
2443 /* The iteration variable can be either a giv or a biv. Check to see
2444 which it is, and compute the variable's initial value, and increment
2445 value if possible. */
2447 /* If this is a new register, can't handle it since we don't have any
2448 reg_iv_type entry for it. */
2449 if ((unsigned) REGNO (iteration_var) >= reg_iv_type->num_elements)
2451 if (loop_dump_stream)
2452 fprintf (loop_dump_stream,
2453 "Loop unrolling: No reg_iv_type entry for iteration var.\n");
2457 /* Reject iteration variables larger than the host wide int size, since they
2458 could result in a number of iterations greater than the range of our
2459 `unsigned HOST_WIDE_INT' variable loop_info->n_iterations. */
2460 else if ((GET_MODE_BITSIZE (GET_MODE (iteration_var))
2461 > HOST_BITS_PER_WIDE_INT))
2463 if (loop_dump_stream)
2464 fprintf (loop_dump_stream,
2465 "Loop unrolling: Iteration var rejected because mode too large.\n");
2468 else if (GET_MODE_CLASS (GET_MODE (iteration_var)) != MODE_INT)
2470 if (loop_dump_stream)
2471 fprintf (loop_dump_stream,
2472 "Loop unrolling: Iteration var not an integer.\n");
2475 else if (REG_IV_TYPE (REGNO (iteration_var)) == BASIC_INDUCT)
2477 /* When reg_iv_type / reg_iv_info is resized for biv increments
2478 that are turned into givs, reg_biv_class is not resized.
2479 So check here that we don't make an out-of-bounds access. */
2480 if (REGNO (iteration_var) >= max_reg_before_loop)
2483 /* Grab initial value, only useful if it is a constant. */
2484 bl = reg_biv_class[REGNO (iteration_var)];
2485 *initial_value = bl->initial_value;
2487 *increment = biv_total_increment (bl, loop_start, loop_end);
2489 else if (REG_IV_TYPE (REGNO (iteration_var)) == GENERAL_INDUCT)
2491 HOST_WIDE_INT offset = 0;
2492 struct induction *v = REG_IV_INFO (REGNO (iteration_var));
2494 if (REGNO (v->src_reg) >= max_reg_before_loop)
2497 bl = reg_biv_class[REGNO (v->src_reg)];
2499 /* Increment value is mult_val times the increment value of the biv. */
2501 *increment = biv_total_increment (bl, loop_start, loop_end);
2504 struct induction *biv_inc;
2507 = fold_rtx_mult_add (v->mult_val, *increment, const0_rtx, v->mode);
2508 /* The caller assumes that one full increment has occured at the
2509 first loop test. But that's not true when the biv is incremented
2510 after the giv is set (which is the usual case), e.g.:
2511 i = 6; do {;} while (i++ < 9) .
2512 Therefore, we bias the initial value by subtracting the amount of
2513 the increment that occurs between the giv set and the giv test. */
2514 for (biv_inc = bl->biv; biv_inc; biv_inc = biv_inc->next_iv)
2516 if (loop_insn_first_p (v->insn, biv_inc->insn))
2517 offset -= INTVAL (biv_inc->add_val);
2519 offset *= INTVAL (v->mult_val);
2521 if (loop_dump_stream)
2522 fprintf (loop_dump_stream,
2523 "Loop unrolling: Giv iterator, initial value bias %ld.\n",
2525 /* Initial value is mult_val times the biv's initial value plus
2526 add_val. Only useful if it is a constant. */
2528 = fold_rtx_mult_add (v->mult_val,
2529 plus_constant (bl->initial_value, offset),
2530 v->add_val, v->mode);
2534 if (loop_dump_stream)
2535 fprintf (loop_dump_stream,
2536 "Loop unrolling: Not basic or general induction var.\n");
2542 /* For each biv and giv, determine whether it can be safely split into
2543 a different variable for each unrolled copy of the loop body. If it
2544 is safe to split, then indicate that by saving some useful info
2545 in the splittable_regs array.
2547 If the loop is being completely unrolled, then splittable_regs will hold
2548 the current value of the induction variable while the loop is unrolled.
2549 It must be set to the initial value of the induction variable here.
2550 Otherwise, splittable_regs will hold the difference between the current
2551 value of the induction variable and the value the induction variable had
2552 at the top of the loop. It must be set to the value 0 here.
2554 Returns the total number of instructions that set registers that are
2557 /* ?? If the loop is only unrolled twice, then most of the restrictions to
2558 constant values are unnecessary, since we can easily calculate increment
2559 values in this case even if nothing is constant. The increment value
2560 should not involve a multiply however. */
2562 /* ?? Even if the biv/giv increment values aren't constant, it may still
2563 be beneficial to split the variable if the loop is only unrolled a few
2564 times, since multiplies by small integers (1,2,3,4) are very cheap. */
2567 find_splittable_regs (unroll_type, loop_start, loop_end, end_insert_before,
2568 unroll_number, n_iterations)
2569 enum unroll_types unroll_type;
2570 rtx loop_start, loop_end;
2571 rtx end_insert_before;
2573 unsigned HOST_WIDE_INT n_iterations;
2575 struct iv_class *bl;
2576 struct induction *v;
2578 rtx biv_final_value;
2582 for (bl = loop_iv_list; bl; bl = bl->next)
2584 /* Biv_total_increment must return a constant value,
2585 otherwise we can not calculate the split values. */
2587 increment = biv_total_increment (bl, loop_start, loop_end);
2588 if (! increment || GET_CODE (increment) != CONST_INT)
2591 /* The loop must be unrolled completely, or else have a known number
2592 of iterations and only one exit, or else the biv must be dead
2593 outside the loop, or else the final value must be known. Otherwise,
2594 it is unsafe to split the biv since it may not have the proper
2595 value on loop exit. */
2597 /* loop_number_exit_count is non-zero if the loop has an exit other than
2598 a fall through at the end. */
2601 biv_final_value = 0;
2602 if (unroll_type != UNROLL_COMPLETELY
2603 && (uid_loop[INSN_UID (loop_start)]->exit_count
2604 || unroll_type == UNROLL_NAIVE)
2605 && (uid_luid[REGNO_LAST_UID (bl->regno)] >= INSN_LUID (loop_end)
2607 || INSN_UID (bl->init_insn) >= max_uid_for_loop
2608 || (uid_luid[REGNO_FIRST_UID (bl->regno)]
2609 < INSN_LUID (bl->init_insn))
2610 || reg_mentioned_p (bl->biv->dest_reg, SET_SRC (bl->init_set)))
2611 && ! (biv_final_value = final_biv_value (bl, loop_start, loop_end,
2615 /* If any of the insns setting the BIV don't do so with a simple
2616 PLUS, we don't know how to split it. */
2617 for (v = bl->biv; biv_splittable && v; v = v->next_iv)
2618 if ((tem = single_set (v->insn)) == 0
2619 || GET_CODE (SET_DEST (tem)) != REG
2620 || REGNO (SET_DEST (tem)) != bl->regno
2621 || GET_CODE (SET_SRC (tem)) != PLUS)
2624 /* If final value is non-zero, then must emit an instruction which sets
2625 the value of the biv to the proper value. This is done after
2626 handling all of the givs, since some of them may need to use the
2627 biv's value in their initialization code. */
2629 /* This biv is splittable. If completely unrolling the loop, save
2630 the biv's initial value. Otherwise, save the constant zero. */
2632 if (biv_splittable == 1)
2634 if (unroll_type == UNROLL_COMPLETELY)
2636 /* If the initial value of the biv is itself (i.e. it is too
2637 complicated for strength_reduce to compute), or is a hard
2638 register, or it isn't invariant, then we must create a new
2639 pseudo reg to hold the initial value of the biv. */
2641 if (GET_CODE (bl->initial_value) == REG
2642 && (REGNO (bl->initial_value) == bl->regno
2643 || REGNO (bl->initial_value) < FIRST_PSEUDO_REGISTER
2644 || ! invariant_p (bl->initial_value)))
2646 rtx tem = gen_reg_rtx (bl->biv->mode);
2648 record_base_value (REGNO (tem), bl->biv->add_val, 0);
2649 emit_insn_before (gen_move_insn (tem, bl->biv->src_reg),
2652 if (loop_dump_stream)
2653 fprintf (loop_dump_stream, "Biv %d initial value remapped to %d.\n",
2654 bl->regno, REGNO (tem));
2656 splittable_regs[bl->regno] = tem;
2659 splittable_regs[bl->regno] = bl->initial_value;
2662 splittable_regs[bl->regno] = const0_rtx;
2664 /* Save the number of instructions that modify the biv, so that
2665 we can treat the last one specially. */
2667 splittable_regs_updates[bl->regno] = bl->biv_count;
2668 result += bl->biv_count;
2670 if (loop_dump_stream)
2671 fprintf (loop_dump_stream,
2672 "Biv %d safe to split.\n", bl->regno);
2675 /* Check every giv that depends on this biv to see whether it is
2676 splittable also. Even if the biv isn't splittable, givs which
2677 depend on it may be splittable if the biv is live outside the
2678 loop, and the givs aren't. */
2680 result += find_splittable_givs (bl, unroll_type, loop_start, loop_end,
2681 increment, unroll_number);
2683 /* If final value is non-zero, then must emit an instruction which sets
2684 the value of the biv to the proper value. This is done after
2685 handling all of the givs, since some of them may need to use the
2686 biv's value in their initialization code. */
2687 if (biv_final_value)
2689 /* If the loop has multiple exits, emit the insns before the
2690 loop to ensure that it will always be executed no matter
2691 how the loop exits. Otherwise emit the insn after the loop,
2692 since this is slightly more efficient. */
2693 if (! uid_loop[INSN_UID (loop_start)]->exit_count)
2694 emit_insn_before (gen_move_insn (bl->biv->src_reg,
2699 /* Create a new register to hold the value of the biv, and then
2700 set the biv to its final value before the loop start. The biv
2701 is set to its final value before loop start to ensure that
2702 this insn will always be executed, no matter how the loop
2704 rtx tem = gen_reg_rtx (bl->biv->mode);
2705 record_base_value (REGNO (tem), bl->biv->add_val, 0);
2707 emit_insn_before (gen_move_insn (tem, bl->biv->src_reg),
2709 emit_insn_before (gen_move_insn (bl->biv->src_reg,
2713 if (loop_dump_stream)
2714 fprintf (loop_dump_stream, "Biv %d mapped to %d for split.\n",
2715 REGNO (bl->biv->src_reg), REGNO (tem));
2717 /* Set up the mapping from the original biv register to the new
2719 bl->biv->src_reg = tem;
2726 /* Return 1 if the first and last unrolled copy of the address giv V is valid
2727 for the instruction that is using it. Do not make any changes to that
2731 verify_addresses (v, giv_inc, unroll_number)
2732 struct induction *v;
2737 rtx orig_addr = *v->location;
2738 rtx last_addr = plus_constant (v->dest_reg,
2739 INTVAL (giv_inc) * (unroll_number - 1));
2741 /* First check to see if either address would fail. Handle the fact
2742 that we have may have a match_dup. */
2743 if (! validate_replace_rtx (*v->location, v->dest_reg, v->insn)
2744 || ! validate_replace_rtx (*v->location, last_addr, v->insn))
2747 /* Now put things back the way they were before. This should always
2749 if (! validate_replace_rtx (*v->location, orig_addr, v->insn))
2755 /* For every giv based on the biv BL, check to determine whether it is
2756 splittable. This is a subroutine to find_splittable_regs ().
2758 Return the number of instructions that set splittable registers. */
2761 find_splittable_givs (bl, unroll_type, loop_start, loop_end, increment,
2763 struct iv_class *bl;
2764 enum unroll_types unroll_type;
2765 rtx loop_start, loop_end;
2769 struct induction *v, *v2;
2774 /* Scan the list of givs, and set the same_insn field when there are
2775 multiple identical givs in the same insn. */
2776 for (v = bl->giv; v; v = v->next_iv)
2777 for (v2 = v->next_iv; v2; v2 = v2->next_iv)
2778 if (v->insn == v2->insn && rtx_equal_p (v->new_reg, v2->new_reg)
2782 for (v = bl->giv; v; v = v->next_iv)
2786 /* Only split the giv if it has already been reduced, or if the loop is
2787 being completely unrolled. */
2788 if (unroll_type != UNROLL_COMPLETELY && v->ignore)
2791 /* The giv can be split if the insn that sets the giv is executed once
2792 and only once on every iteration of the loop. */
2793 /* An address giv can always be split. v->insn is just a use not a set,
2794 and hence it does not matter whether it is always executed. All that
2795 matters is that all the biv increments are always executed, and we
2796 won't reach here if they aren't. */
2797 if (v->giv_type != DEST_ADDR
2798 && (! v->always_computable
2799 || back_branch_in_range_p (v->insn, loop_start, loop_end)))
2802 /* The giv increment value must be a constant. */
2803 giv_inc = fold_rtx_mult_add (v->mult_val, increment, const0_rtx,
2805 if (! giv_inc || GET_CODE (giv_inc) != CONST_INT)
2808 /* The loop must be unrolled completely, or else have a known number of
2809 iterations and only one exit, or else the giv must be dead outside
2810 the loop, or else the final value of the giv must be known.
2811 Otherwise, it is not safe to split the giv since it may not have the
2812 proper value on loop exit. */
2814 /* The used outside loop test will fail for DEST_ADDR givs. They are
2815 never used outside the loop anyways, so it is always safe to split a
2819 if (unroll_type != UNROLL_COMPLETELY
2820 && (uid_loop[INSN_UID (loop_start)]->exit_count
2821 || unroll_type == UNROLL_NAIVE)
2822 && v->giv_type != DEST_ADDR
2823 /* The next part is true if the pseudo is used outside the loop.
2824 We assume that this is true for any pseudo created after loop
2825 starts, because we don't have a reg_n_info entry for them. */
2826 && (REGNO (v->dest_reg) >= max_reg_before_loop
2827 || (REGNO_FIRST_UID (REGNO (v->dest_reg)) != INSN_UID (v->insn)
2828 /* Check for the case where the pseudo is set by a shift/add
2829 sequence, in which case the first insn setting the pseudo
2830 is the first insn of the shift/add sequence. */
2831 && (! (tem = find_reg_note (v->insn, REG_RETVAL, NULL_RTX))
2832 || (REGNO_FIRST_UID (REGNO (v->dest_reg))
2833 != INSN_UID (XEXP (tem, 0)))))
2834 /* Line above always fails if INSN was moved by loop opt. */
2835 || (uid_luid[REGNO_LAST_UID (REGNO (v->dest_reg))]
2836 >= INSN_LUID (loop_end)))
2837 /* Givs made from biv increments are missed by the above test, so
2838 test explicitly for them. */
2839 && (REGNO (v->dest_reg) < first_increment_giv
2840 || REGNO (v->dest_reg) > last_increment_giv)
2841 && ! (final_value = v->final_value))
2845 /* Currently, non-reduced/final-value givs are never split. */
2846 /* Should emit insns after the loop if possible, as the biv final value
2849 /* If the final value is non-zero, and the giv has not been reduced,
2850 then must emit an instruction to set the final value. */
2851 if (final_value && !v->new_reg)
2853 /* Create a new register to hold the value of the giv, and then set
2854 the giv to its final value before the loop start. The giv is set
2855 to its final value before loop start to ensure that this insn
2856 will always be executed, no matter how we exit. */
2857 tem = gen_reg_rtx (v->mode);
2858 emit_insn_before (gen_move_insn (tem, v->dest_reg), loop_start);
2859 emit_insn_before (gen_move_insn (v->dest_reg, final_value),
2862 if (loop_dump_stream)
2863 fprintf (loop_dump_stream, "Giv %d mapped to %d for split.\n",
2864 REGNO (v->dest_reg), REGNO (tem));
2870 /* This giv is splittable. If completely unrolling the loop, save the
2871 giv's initial value. Otherwise, save the constant zero for it. */
2873 if (unroll_type == UNROLL_COMPLETELY)
2875 /* It is not safe to use bl->initial_value here, because it may not
2876 be invariant. It is safe to use the initial value stored in
2877 the splittable_regs array if it is set. In rare cases, it won't
2878 be set, so then we do exactly the same thing as
2879 find_splittable_regs does to get a safe value. */
2880 rtx biv_initial_value;
2882 if (splittable_regs[bl->regno])
2883 biv_initial_value = splittable_regs[bl->regno];
2884 else if (GET_CODE (bl->initial_value) != REG
2885 || (REGNO (bl->initial_value) != bl->regno
2886 && REGNO (bl->initial_value) >= FIRST_PSEUDO_REGISTER))
2887 biv_initial_value = bl->initial_value;
2890 rtx tem = gen_reg_rtx (bl->biv->mode);
2892 record_base_value (REGNO (tem), bl->biv->add_val, 0);
2893 emit_insn_before (gen_move_insn (tem, bl->biv->src_reg),
2895 biv_initial_value = tem;
2897 value = fold_rtx_mult_add (v->mult_val, biv_initial_value,
2898 v->add_val, v->mode);
2905 /* If a giv was combined with another giv, then we can only split
2906 this giv if the giv it was combined with was reduced. This
2907 is because the value of v->new_reg is meaningless in this
2909 if (v->same && ! v->same->new_reg)
2911 if (loop_dump_stream)
2912 fprintf (loop_dump_stream,
2913 "giv combined with unreduced giv not split.\n");
2916 /* If the giv is an address destination, it could be something other
2917 than a simple register, these have to be treated differently. */
2918 else if (v->giv_type == DEST_REG)
2920 /* If value is not a constant, register, or register plus
2921 constant, then compute its value into a register before
2922 loop start. This prevents invalid rtx sharing, and should
2923 generate better code. We can use bl->initial_value here
2924 instead of splittable_regs[bl->regno] because this code
2925 is going before the loop start. */
2926 if (unroll_type == UNROLL_COMPLETELY
2927 && GET_CODE (value) != CONST_INT
2928 && GET_CODE (value) != REG
2929 && (GET_CODE (value) != PLUS
2930 || GET_CODE (XEXP (value, 0)) != REG
2931 || GET_CODE (XEXP (value, 1)) != CONST_INT))
2933 rtx tem = gen_reg_rtx (v->mode);
2934 record_base_value (REGNO (tem), v->add_val, 0);
2935 emit_iv_add_mult (bl->initial_value, v->mult_val,
2936 v->add_val, tem, loop_start);
2940 splittable_regs[REGNO (v->new_reg)] = value;
2941 derived_regs[REGNO (v->new_reg)] = v->derived_from != 0;
2945 /* Splitting address givs is useful since it will often allow us
2946 to eliminate some increment insns for the base giv as
2949 /* If the addr giv is combined with a dest_reg giv, then all
2950 references to that dest reg will be remapped, which is NOT
2951 what we want for split addr regs. We always create a new
2952 register for the split addr giv, just to be safe. */
2954 /* If we have multiple identical address givs within a
2955 single instruction, then use a single pseudo reg for
2956 both. This is necessary in case one is a match_dup
2959 v->const_adjust = 0;
2963 v->dest_reg = v->same_insn->dest_reg;
2964 if (loop_dump_stream)
2965 fprintf (loop_dump_stream,
2966 "Sharing address givs in insn %d\n",
2967 INSN_UID (v->insn));
2969 /* If multiple address GIVs have been combined with the
2970 same dest_reg GIV, do not create a new register for
2972 else if (unroll_type != UNROLL_COMPLETELY
2973 && v->giv_type == DEST_ADDR
2974 && v->same && v->same->giv_type == DEST_ADDR
2975 && v->same->unrolled
2976 /* combine_givs_p may return true for some cases
2977 where the add and mult values are not equal.
2978 To share a register here, the values must be
2980 && rtx_equal_p (v->same->mult_val, v->mult_val)
2981 && rtx_equal_p (v->same->add_val, v->add_val)
2982 /* If the memory references have different modes,
2983 then the address may not be valid and we must
2984 not share registers. */
2985 && verify_addresses (v, giv_inc, unroll_number))
2987 v->dest_reg = v->same->dest_reg;
2990 else if (unroll_type != UNROLL_COMPLETELY)
2992 /* If not completely unrolling the loop, then create a new
2993 register to hold the split value of the DEST_ADDR giv.
2994 Emit insn to initialize its value before loop start. */
2996 rtx tem = gen_reg_rtx (v->mode);
2997 struct induction *same = v->same;
2998 rtx new_reg = v->new_reg;
2999 record_base_value (REGNO (tem), v->add_val, 0);
3001 if (same && same->derived_from)
3003 /* calculate_giv_inc doesn't work for derived givs.
3004 copy_loop_body works around the problem for the
3005 DEST_REG givs themselves, but it can't handle
3006 DEST_ADDR givs that have been combined with
3007 a derived DEST_REG giv.
3008 So Handle V as if the giv from which V->SAME has
3009 been derived has been combined with V.
3010 recombine_givs only derives givs from givs that
3011 are reduced the ordinary, so we need not worry
3012 about same->derived_from being in turn derived. */
3014 same = same->derived_from;
3015 new_reg = express_from (same, v);
3016 new_reg = replace_rtx (new_reg, same->dest_reg,
3020 /* If the address giv has a constant in its new_reg value,
3021 then this constant can be pulled out and put in value,
3022 instead of being part of the initialization code. */
3024 if (GET_CODE (new_reg) == PLUS
3025 && GET_CODE (XEXP (new_reg, 1)) == CONST_INT)
3028 = plus_constant (tem, INTVAL (XEXP (new_reg, 1)));
3030 /* Only succeed if this will give valid addresses.
3031 Try to validate both the first and the last
3032 address resulting from loop unrolling, if
3033 one fails, then can't do const elim here. */
3034 if (verify_addresses (v, giv_inc, unroll_number))
3036 /* Save the negative of the eliminated const, so
3037 that we can calculate the dest_reg's increment
3039 v->const_adjust = - INTVAL (XEXP (new_reg, 1));
3041 new_reg = XEXP (new_reg, 0);
3042 if (loop_dump_stream)
3043 fprintf (loop_dump_stream,
3044 "Eliminating constant from giv %d\n",
3053 /* If the address hasn't been checked for validity yet, do so
3054 now, and fail completely if either the first or the last
3055 unrolled copy of the address is not a valid address
3056 for the instruction that uses it. */
3057 if (v->dest_reg == tem
3058 && ! verify_addresses (v, giv_inc, unroll_number))
3060 for (v2 = v->next_iv; v2; v2 = v2->next_iv)
3061 if (v2->same_insn == v)
3064 if (loop_dump_stream)
3065 fprintf (loop_dump_stream,
3066 "Invalid address for giv at insn %d\n",
3067 INSN_UID (v->insn));
3071 v->new_reg = new_reg;
3074 /* We set this after the address check, to guarantee that
3075 the register will be initialized. */
3078 /* To initialize the new register, just move the value of
3079 new_reg into it. This is not guaranteed to give a valid
3080 instruction on machines with complex addressing modes.
3081 If we can't recognize it, then delete it and emit insns
3082 to calculate the value from scratch. */
3083 emit_insn_before (gen_rtx_SET (VOIDmode, tem,
3084 copy_rtx (v->new_reg)),
3086 if (recog_memoized (PREV_INSN (loop_start)) < 0)
3090 /* We can't use bl->initial_value to compute the initial
3091 value, because the loop may have been preconditioned.
3092 We must calculate it from NEW_REG. Try using
3093 force_operand instead of emit_iv_add_mult. */
3094 delete_insn (PREV_INSN (loop_start));
3097 ret = force_operand (v->new_reg, tem);
3099 emit_move_insn (tem, ret);
3100 sequence = gen_sequence ();
3102 emit_insn_before (sequence, loop_start);
3104 if (loop_dump_stream)
3105 fprintf (loop_dump_stream,
3106 "Invalid init insn, rewritten.\n");
3111 v->dest_reg = value;
3113 /* Check the resulting address for validity, and fail
3114 if the resulting address would be invalid. */
3115 if (! verify_addresses (v, giv_inc, unroll_number))
3117 for (v2 = v->next_iv; v2; v2 = v2->next_iv)
3118 if (v2->same_insn == v)
3121 if (loop_dump_stream)
3122 fprintf (loop_dump_stream,
3123 "Invalid address for giv at insn %d\n",
3124 INSN_UID (v->insn));
3127 if (v->same && v->same->derived_from)
3129 /* Handle V as if the giv from which V->SAME has
3130 been derived has been combined with V. */
3132 v->same = v->same->derived_from;
3133 v->new_reg = express_from (v->same, v);
3134 v->new_reg = replace_rtx (v->new_reg, v->same->dest_reg,
3140 /* Store the value of dest_reg into the insn. This sharing
3141 will not be a problem as this insn will always be copied
3144 *v->location = v->dest_reg;
3146 /* If this address giv is combined with a dest reg giv, then
3147 save the base giv's induction pointer so that we will be
3148 able to handle this address giv properly. The base giv
3149 itself does not have to be splittable. */
3151 if (v->same && v->same->giv_type == DEST_REG)
3152 addr_combined_regs[REGNO (v->same->new_reg)] = v->same;
3154 if (GET_CODE (v->new_reg) == REG)
3156 /* This giv maybe hasn't been combined with any others.
3157 Make sure that it's giv is marked as splittable here. */
3159 splittable_regs[REGNO (v->new_reg)] = value;
3160 derived_regs[REGNO (v->new_reg)] = v->derived_from != 0;
3162 /* Make it appear to depend upon itself, so that the
3163 giv will be properly split in the main loop above. */
3167 addr_combined_regs[REGNO (v->new_reg)] = v;
3171 if (loop_dump_stream)
3172 fprintf (loop_dump_stream, "DEST_ADDR giv being split.\n");
3178 /* Currently, unreduced giv's can't be split. This is not too much
3179 of a problem since unreduced giv's are not live across loop
3180 iterations anyways. When unrolling a loop completely though,
3181 it makes sense to reduce&split givs when possible, as this will
3182 result in simpler instructions, and will not require that a reg
3183 be live across loop iterations. */
3185 splittable_regs[REGNO (v->dest_reg)] = value;
3186 fprintf (stderr, "Giv %d at insn %d not reduced\n",
3187 REGNO (v->dest_reg), INSN_UID (v->insn));
3193 /* Unreduced givs are only updated once by definition. Reduced givs
3194 are updated as many times as their biv is. Mark it so if this is
3195 a splittable register. Don't need to do anything for address givs
3196 where this may not be a register. */
3198 if (GET_CODE (v->new_reg) == REG)
3202 count = reg_biv_class[REGNO (v->src_reg)]->biv_count;
3204 if (count > 1 && v->derived_from)
3205 /* In this case, there is one set where the giv insn was and one
3206 set each after each biv increment. (Most are likely dead.) */
3209 splittable_regs_updates[REGNO (v->new_reg)] = count;
3214 if (loop_dump_stream)
3218 if (GET_CODE (v->dest_reg) == CONST_INT)
3220 else if (GET_CODE (v->dest_reg) != REG)
3221 regnum = REGNO (XEXP (v->dest_reg, 0));
3223 regnum = REGNO (v->dest_reg);
3224 fprintf (loop_dump_stream, "Giv %d at insn %d safe to split.\n",
3225 regnum, INSN_UID (v->insn));
3232 /* Try to prove that the register is dead after the loop exits. Trace every
3233 loop exit looking for an insn that will always be executed, which sets
3234 the register to some value, and appears before the first use of the register
3235 is found. If successful, then return 1, otherwise return 0. */
3237 /* ?? Could be made more intelligent in the handling of jumps, so that
3238 it can search past if statements and other similar structures. */
3241 reg_dead_after_loop (reg, loop_start, loop_end)
3242 rtx reg, loop_start, loop_end;
3247 int label_count = 0;
3248 struct loop *loop = uid_loop[INSN_UID (loop_start)];
3250 /* In addition to checking all exits of this loop, we must also check
3251 all exits of inner nested loops that would exit this loop. We don't
3252 have any way to identify those, so we just give up if there are any
3253 such inner loop exits. */
3255 for (label = loop->exit_labels; label; label = LABEL_NEXTREF (label))
3258 if (label_count != loop->exit_count)
3261 /* HACK: Must also search the loop fall through exit, create a label_ref
3262 here which points to the loop_end, and append the loop_number_exit_labels
3264 label = gen_rtx_LABEL_REF (VOIDmode, loop_end);
3265 LABEL_NEXTREF (label) = loop->exit_labels;
3267 for ( ; label; label = LABEL_NEXTREF (label))
3269 /* Succeed if find an insn which sets the biv or if reach end of
3270 function. Fail if find an insn that uses the biv, or if come to
3271 a conditional jump. */
3273 insn = NEXT_INSN (XEXP (label, 0));
3276 code = GET_CODE (insn);
3277 if (GET_RTX_CLASS (code) == 'i')
3281 if (reg_referenced_p (reg, PATTERN (insn)))
3284 set = single_set (insn);
3285 if (set && rtx_equal_p (SET_DEST (set), reg))
3289 if (code == JUMP_INSN)
3291 if (GET_CODE (PATTERN (insn)) == RETURN)
3293 else if (! simplejump_p (insn)
3294 /* Prevent infinite loop following infinite loops. */
3295 || jump_count++ > 20)
3298 insn = JUMP_LABEL (insn);
3301 insn = NEXT_INSN (insn);
3305 /* Success, the register is dead on all loop exits. */
3309 /* Try to calculate the final value of the biv, the value it will have at
3310 the end of the loop. If we can do it, return that value. */
3313 final_biv_value (bl, loop_start, loop_end, n_iterations)
3314 struct iv_class *bl;
3315 rtx loop_start, loop_end;
3316 unsigned HOST_WIDE_INT n_iterations;
3320 /* ??? This only works for MODE_INT biv's. Reject all others for now. */
3322 if (GET_MODE_CLASS (bl->biv->mode) != MODE_INT)
3325 /* The final value for reversed bivs must be calculated differently than
3326 for ordinary bivs. In this case, there is already an insn after the
3327 loop which sets this biv's final value (if necessary), and there are
3328 no other loop exits, so we can return any value. */
3331 if (loop_dump_stream)
3332 fprintf (loop_dump_stream,
3333 "Final biv value for %d, reversed biv.\n", bl->regno);
3338 /* Try to calculate the final value as initial value + (number of iterations
3339 * increment). For this to work, increment must be invariant, the only
3340 exit from the loop must be the fall through at the bottom (otherwise
3341 it may not have its final value when the loop exits), and the initial
3342 value of the biv must be invariant. */
3344 if (n_iterations != 0
3345 && ! uid_loop[INSN_UID (loop_start)]->exit_count
3346 && invariant_p (bl->initial_value))
3348 increment = biv_total_increment (bl, loop_start, loop_end);
3350 if (increment && invariant_p (increment))
3352 /* Can calculate the loop exit value, emit insns after loop
3353 end to calculate this value into a temporary register in
3354 case it is needed later. */
3356 tem = gen_reg_rtx (bl->biv->mode);
3357 record_base_value (REGNO (tem), bl->biv->add_val, 0);
3358 /* Make sure loop_end is not the last insn. */
3359 if (NEXT_INSN (loop_end) == 0)
3360 emit_note_after (NOTE_INSN_DELETED, loop_end);
3361 emit_iv_add_mult (increment, GEN_INT (n_iterations),
3362 bl->initial_value, tem, NEXT_INSN (loop_end));
3364 if (loop_dump_stream)
3365 fprintf (loop_dump_stream,
3366 "Final biv value for %d, calculated.\n", bl->regno);
3372 /* Check to see if the biv is dead at all loop exits. */
3373 if (reg_dead_after_loop (bl->biv->src_reg, loop_start, loop_end))
3375 if (loop_dump_stream)
3376 fprintf (loop_dump_stream,
3377 "Final biv value for %d, biv dead after loop exit.\n",
3386 /* Try to calculate the final value of the giv, the value it will have at
3387 the end of the loop. If we can do it, return that value. */
3390 final_giv_value (v, loop_start, loop_end, n_iterations)
3391 struct induction *v;
3392 rtx loop_start, loop_end;
3393 unsigned HOST_WIDE_INT n_iterations;
3395 struct iv_class *bl;
3398 rtx insert_before, seq;
3400 bl = reg_biv_class[REGNO (v->src_reg)];
3402 /* The final value for givs which depend on reversed bivs must be calculated
3403 differently than for ordinary givs. In this case, there is already an
3404 insn after the loop which sets this giv's final value (if necessary),
3405 and there are no other loop exits, so we can return any value. */
3408 if (loop_dump_stream)
3409 fprintf (loop_dump_stream,
3410 "Final giv value for %d, depends on reversed biv\n",
3411 REGNO (v->dest_reg));
3415 /* Try to calculate the final value as a function of the biv it depends
3416 upon. The only exit from the loop must be the fall through at the bottom
3417 (otherwise it may not have its final value when the loop exits). */
3419 /* ??? Can calculate the final giv value by subtracting off the
3420 extra biv increments times the giv's mult_val. The loop must have
3421 only one exit for this to work, but the loop iterations does not need
3424 if (n_iterations != 0
3425 && ! uid_loop[INSN_UID (loop_start)]->exit_count)
3427 /* ?? It is tempting to use the biv's value here since these insns will
3428 be put after the loop, and hence the biv will have its final value
3429 then. However, this fails if the biv is subsequently eliminated.
3430 Perhaps determine whether biv's are eliminable before trying to
3431 determine whether giv's are replaceable so that we can use the
3432 biv value here if it is not eliminable. */
3434 /* We are emitting code after the end of the loop, so we must make
3435 sure that bl->initial_value is still valid then. It will still
3436 be valid if it is invariant. */
3438 increment = biv_total_increment (bl, loop_start, loop_end);
3440 if (increment && invariant_p (increment)
3441 && invariant_p (bl->initial_value))
3443 /* Can calculate the loop exit value of its biv as
3444 (n_iterations * increment) + initial_value */
3446 /* The loop exit value of the giv is then
3447 (final_biv_value - extra increments) * mult_val + add_val.
3448 The extra increments are any increments to the biv which
3449 occur in the loop after the giv's value is calculated.
3450 We must search from the insn that sets the giv to the end
3451 of the loop to calculate this value. */
3453 insert_before = NEXT_INSN (loop_end);
3455 /* Put the final biv value in tem. */
3456 tem = gen_reg_rtx (bl->biv->mode);
3457 record_base_value (REGNO (tem), bl->biv->add_val, 0);
3458 emit_iv_add_mult (increment, GEN_INT (n_iterations),
3459 bl->initial_value, tem, insert_before);
3461 /* Subtract off extra increments as we find them. */
3462 for (insn = NEXT_INSN (v->insn); insn != loop_end;
3463 insn = NEXT_INSN (insn))
3465 struct induction *biv;
3467 for (biv = bl->biv; biv; biv = biv->next_iv)
3468 if (biv->insn == insn)
3471 tem = expand_binop (GET_MODE (tem), sub_optab, tem,
3472 biv->add_val, NULL_RTX, 0,
3474 seq = gen_sequence ();
3476 emit_insn_before (seq, insert_before);
3480 /* Now calculate the giv's final value. */
3481 emit_iv_add_mult (tem, v->mult_val, v->add_val, tem,
3484 if (loop_dump_stream)
3485 fprintf (loop_dump_stream,
3486 "Final giv value for %d, calc from biv's value.\n",
3487 REGNO (v->dest_reg));
3493 /* Replaceable giv's should never reach here. */
3497 /* Check to see if the biv is dead at all loop exits. */
3498 if (reg_dead_after_loop (v->dest_reg, loop_start, loop_end))
3500 if (loop_dump_stream)
3501 fprintf (loop_dump_stream,
3502 "Final giv value for %d, giv dead after loop exit.\n",
3503 REGNO (v->dest_reg));
3512 /* Look back before LOOP_START for then insn that sets REG and return
3513 the equivalent constant if there is a REG_EQUAL note otherwise just
3514 the SET_SRC of REG. */
3517 loop_find_equiv_value (loop_start, reg)
3525 for (insn = PREV_INSN (loop_start); insn ; insn = PREV_INSN (insn))
3527 if (GET_CODE (insn) == CODE_LABEL)
3530 else if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
3531 && reg_set_p (reg, insn))
3533 /* We found the last insn before the loop that sets the register.
3534 If it sets the entire register, and has a REG_EQUAL note,
3535 then use the value of the REG_EQUAL note. */
3536 if ((set = single_set (insn))
3537 && (SET_DEST (set) == reg))
3539 rtx note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
3541 /* Only use the REG_EQUAL note if it is a constant.
3542 Other things, divide in particular, will cause
3543 problems later if we use them. */
3544 if (note && GET_CODE (XEXP (note, 0)) != EXPR_LIST
3545 && CONSTANT_P (XEXP (note, 0)))
3546 ret = XEXP (note, 0);
3548 ret = SET_SRC (set);
3556 /* Return a simplified rtx for the expression OP - REG.
3558 REG must appear in OP, and OP must be a register or the sum of a register
3561 Thus, the return value must be const0_rtx or the second term.
3563 The caller is responsible for verifying that REG appears in OP and OP has
3567 subtract_reg_term (op, reg)
3572 if (GET_CODE (op) == PLUS)
3574 if (XEXP (op, 0) == reg)
3575 return XEXP (op, 1);
3576 else if (XEXP (op, 1) == reg)
3577 return XEXP (op, 0);
3579 /* OP does not contain REG as a term. */
3584 /* Find and return register term common to both expressions OP0 and
3585 OP1 or NULL_RTX if no such term exists. Each expression must be a
3586 REG or a PLUS of a REG. */
3589 find_common_reg_term (op0, op1)
3592 if ((GET_CODE (op0) == REG || GET_CODE (op0) == PLUS)
3593 && (GET_CODE (op1) == REG || GET_CODE (op1) == PLUS))
3600 if (GET_CODE (op0) == PLUS)
3601 op01 = XEXP (op0, 1), op00 = XEXP (op0, 0);
3603 op01 = const0_rtx, op00 = op0;
3605 if (GET_CODE (op1) == PLUS)
3606 op11 = XEXP (op1, 1), op10 = XEXP (op1, 0);
3608 op11 = const0_rtx, op10 = op1;
3610 /* Find and return common register term if present. */
3611 if (REG_P (op00) && (op00 == op10 || op00 == op11))
3613 else if (REG_P (op01) && (op01 == op10 || op01 == op11))
3617 /* No common register term found. */
3621 /* Calculate the number of loop iterations. Returns the exact number of loop
3622 iterations if it can be calculated, otherwise returns zero. */
3624 unsigned HOST_WIDE_INT
3625 loop_iterations (loop)
3628 rtx comparison, comparison_value;
3629 rtx iteration_var, initial_value, increment, final_value;
3630 enum rtx_code comparison_code;
3631 HOST_WIDE_INT abs_inc;
3632 unsigned HOST_WIDE_INT abs_diff;
3635 int unsigned_p, compare_dir, final_larger;
3638 struct loop_info *loop_info = loop->info;
3640 loop_info->n_iterations = 0;
3641 loop_info->initial_value = 0;
3642 loop_info->initial_equiv_value = 0;
3643 loop_info->comparison_value = 0;
3644 loop_info->final_value = 0;
3645 loop_info->final_equiv_value = 0;
3646 loop_info->increment = 0;
3647 loop_info->iteration_var = 0;
3648 loop_info->unroll_number = 1;
3650 /* We used to use prev_nonnote_insn here, but that fails because it might
3651 accidentally get the branch for a contained loop if the branch for this
3652 loop was deleted. We can only trust branches immediately before the
3654 last_loop_insn = PREV_INSN (loop->end);
3656 /* ??? We should probably try harder to find the jump insn
3657 at the end of the loop. The following code assumes that
3658 the last loop insn is a jump to the top of the loop. */
3659 if (GET_CODE (last_loop_insn) != JUMP_INSN)
3661 if (loop_dump_stream)
3662 fprintf (loop_dump_stream,
3663 "Loop iterations: No final conditional branch found.\n");
3667 /* If there is a more than a single jump to the top of the loop
3668 we cannot (easily) determine the iteration count. */
3669 if (LABEL_NUSES (JUMP_LABEL (last_loop_insn)) > 1)
3671 if (loop_dump_stream)
3672 fprintf (loop_dump_stream,
3673 "Loop iterations: Loop has multiple back edges.\n");
3677 /* Find the iteration variable. If the last insn is a conditional
3678 branch, and the insn before tests a register value, make that the
3679 iteration variable. */
3681 comparison = get_condition_for_loop (last_loop_insn);
3682 if (comparison == 0)
3684 if (loop_dump_stream)
3685 fprintf (loop_dump_stream,
3686 "Loop iterations: No final comparison found.\n");
3690 /* ??? Get_condition may switch position of induction variable and
3691 invariant register when it canonicalizes the comparison. */
3693 comparison_code = GET_CODE (comparison);
3694 iteration_var = XEXP (comparison, 0);
3695 comparison_value = XEXP (comparison, 1);
3697 if (GET_CODE (iteration_var) != REG)
3699 if (loop_dump_stream)
3700 fprintf (loop_dump_stream,
3701 "Loop iterations: Comparison not against register.\n");
3705 /* The only new registers that care created before loop iterations are
3706 givs made from biv increments, so this should never occur. */
3708 if ((unsigned) REGNO (iteration_var) >= reg_iv_type->num_elements)
3711 iteration_info (iteration_var, &initial_value, &increment,
3712 loop->start, loop->end);
3713 if (initial_value == 0)
3714 /* iteration_info already printed a message. */
3719 switch (comparison_code)
3734 /* Cannot determine loop iterations with this case. */
3753 /* If the comparison value is an invariant register, then try to find
3754 its value from the insns before the start of the loop. */
3756 final_value = comparison_value;
3757 if (GET_CODE (comparison_value) == REG && invariant_p (comparison_value))
3759 final_value = loop_find_equiv_value (loop->start, comparison_value);
3760 /* If we don't get an invariant final value, we are better
3761 off with the original register. */
3762 if (!invariant_p (final_value))
3763 final_value = comparison_value;
3766 /* Calculate the approximate final value of the induction variable
3767 (on the last successful iteration). The exact final value
3768 depends on the branch operator, and increment sign. It will be
3769 wrong if the iteration variable is not incremented by one each
3770 time through the loop and (comparison_value + off_by_one -
3771 initial_value) % increment != 0.
3772 ??? Note that the final_value may overflow and thus final_larger
3773 will be bogus. A potentially infinite loop will be classified
3774 as immediate, e.g. for (i = 0x7ffffff0; i <= 0x7fffffff; i++) */
3776 final_value = plus_constant (final_value, off_by_one);
3778 /* Save the calculated values describing this loop's bounds, in case
3779 precondition_loop_p will need them later. These values can not be
3780 recalculated inside precondition_loop_p because strength reduction
3781 optimizations may obscure the loop's structure.
3783 These values are only required by precondition_loop_p and insert_bct
3784 whenever the number of iterations cannot be computed at compile time.
3785 Only the difference between final_value and initial_value is
3786 important. Note that final_value is only approximate. */
3787 loop_info->initial_value = initial_value;
3788 loop_info->comparison_value = comparison_value;
3789 loop_info->final_value = plus_constant (comparison_value, off_by_one);
3790 loop_info->increment = increment;
3791 loop_info->iteration_var = iteration_var;
3792 loop_info->comparison_code = comparison_code;
3794 /* Try to determine the iteration count for loops such
3795 as (for i = init; i < init + const; i++). When running the
3796 loop optimization twice, the first pass often converts simple
3797 loops into this form. */
3799 if (REG_P (initial_value))
3805 reg1 = initial_value;
3806 if (GET_CODE (final_value) == PLUS)
3807 reg2 = XEXP (final_value, 0), const2 = XEXP (final_value, 1);
3809 reg2 = final_value, const2 = const0_rtx;
3811 /* Check for initial_value = reg1, final_value = reg2 + const2,
3812 where reg1 != reg2. */
3813 if (REG_P (reg2) && reg2 != reg1)
3817 /* Find what reg1 is equivalent to. Hopefully it will
3818 either be reg2 or reg2 plus a constant. */
3819 temp = loop_find_equiv_value (loop->start, reg1);
3820 if (find_common_reg_term (temp, reg2))
3821 initial_value = temp;
3824 /* Find what reg2 is equivalent to. Hopefully it will
3825 either be reg1 or reg1 plus a constant. Let's ignore
3826 the latter case for now since it is not so common. */
3827 temp = loop_find_equiv_value (loop->start, reg2);
3828 if (temp == loop_info->iteration_var)
3829 temp = initial_value;
3831 final_value = (const2 == const0_rtx)
3832 ? reg1 : gen_rtx_PLUS (GET_MODE (reg1), reg1, const2);
3835 else if (loop->vtop && GET_CODE (reg2) == CONST_INT)
3839 /* When running the loop optimizer twice, check_dbra_loop
3840 further obfuscates reversible loops of the form:
3841 for (i = init; i < init + const; i++). We often end up with
3842 final_value = 0, initial_value = temp, temp = temp2 - init,
3843 where temp2 = init + const. If the loop has a vtop we
3844 can replace initial_value with const. */
3846 temp = loop_find_equiv_value (loop->start, reg1);
3847 if (GET_CODE (temp) == MINUS && REG_P (XEXP (temp, 0)))
3849 rtx temp2 = loop_find_equiv_value (loop->start, XEXP (temp, 0));
3850 if (GET_CODE (temp2) == PLUS
3851 && XEXP (temp2, 0) == XEXP (temp, 1))
3852 initial_value = XEXP (temp2, 1);
3857 /* If have initial_value = reg + const1 and final_value = reg +
3858 const2, then replace initial_value with const1 and final_value
3859 with const2. This should be safe since we are protected by the
3860 initial comparison before entering the loop if we have a vtop.
3861 For example, a + b < a + c is not equivalent to b < c for all a
3862 when using modulo arithmetic.
3864 ??? Without a vtop we could still perform the optimization if we check
3865 the initial and final values carefully. */
3867 && (reg_term = find_common_reg_term (initial_value, final_value)))
3869 initial_value = subtract_reg_term (initial_value, reg_term);
3870 final_value = subtract_reg_term (final_value, reg_term);
3873 loop_info->initial_equiv_value = initial_value;
3874 loop_info->final_equiv_value = final_value;
3876 /* For EQ comparison loops, we don't have a valid final value.
3877 Check this now so that we won't leave an invalid value if we
3878 return early for any other reason. */
3879 if (comparison_code == EQ)
3880 loop_info->final_equiv_value = loop_info->final_value = 0;
3884 if (loop_dump_stream)
3885 fprintf (loop_dump_stream,
3886 "Loop iterations: Increment value can't be calculated.\n");
3890 if (GET_CODE (increment) != CONST_INT)
3892 /* If we have a REG, check to see if REG holds a constant value. */
3893 /* ??? Other RTL, such as (neg (reg)) is possible here, but it isn't
3894 clear if it is worthwhile to try to handle such RTL. */
3895 if (GET_CODE (increment) == REG || GET_CODE (increment) == SUBREG)
3896 increment = loop_find_equiv_value (loop->start, increment);
3898 if (GET_CODE (increment) != CONST_INT)
3900 if (loop_dump_stream)
3902 fprintf (loop_dump_stream,
3903 "Loop iterations: Increment value not constant ");
3904 print_rtl (loop_dump_stream, increment);
3905 fprintf (loop_dump_stream, ".\n");
3909 loop_info->increment = increment;
3912 if (GET_CODE (initial_value) != CONST_INT)
3914 if (loop_dump_stream)
3916 fprintf (loop_dump_stream,
3917 "Loop iterations: Initial value not constant ");
3918 print_rtl (loop_dump_stream, initial_value);
3919 fprintf (loop_dump_stream, ".\n");
3923 else if (comparison_code == EQ)
3925 if (loop_dump_stream)
3926 fprintf (loop_dump_stream,
3927 "Loop iterations: EQ comparison loop.\n");
3930 else if (GET_CODE (final_value) != CONST_INT)
3932 if (loop_dump_stream)
3934 fprintf (loop_dump_stream,
3935 "Loop iterations: Final value not constant ");
3936 print_rtl (loop_dump_stream, final_value);
3937 fprintf (loop_dump_stream, ".\n");
3942 /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
3945 = ((unsigned HOST_WIDE_INT) INTVAL (final_value)
3946 > (unsigned HOST_WIDE_INT) INTVAL (initial_value))
3947 - ((unsigned HOST_WIDE_INT) INTVAL (final_value)
3948 < (unsigned HOST_WIDE_INT) INTVAL (initial_value));
3950 final_larger = (INTVAL (final_value) > INTVAL (initial_value))
3951 - (INTVAL (final_value) < INTVAL (initial_value));
3953 if (INTVAL (increment) > 0)
3955 else if (INTVAL (increment) == 0)
3960 /* There are 27 different cases: compare_dir = -1, 0, 1;
3961 final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
3962 There are 4 normal cases, 4 reverse cases (where the iteration variable
3963 will overflow before the loop exits), 4 infinite loop cases, and 15
3964 immediate exit (0 or 1 iteration depending on loop type) cases.
3965 Only try to optimize the normal cases. */
3967 /* (compare_dir/final_larger/increment_dir)
3968 Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
3969 Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
3970 Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
3971 Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
3973 /* ?? If the meaning of reverse loops (where the iteration variable
3974 will overflow before the loop exits) is undefined, then could
3975 eliminate all of these special checks, and just always assume
3976 the loops are normal/immediate/infinite. Note that this means
3977 the sign of increment_dir does not have to be known. Also,
3978 since it does not really hurt if immediate exit loops or infinite loops
3979 are optimized, then that case could be ignored also, and hence all
3980 loops can be optimized.
3982 According to ANSI Spec, the reverse loop case result is undefined,
3983 because the action on overflow is undefined.
3985 See also the special test for NE loops below. */
3987 if (final_larger == increment_dir && final_larger != 0
3988 && (final_larger == compare_dir || compare_dir == 0))
3993 if (loop_dump_stream)
3994 fprintf (loop_dump_stream,
3995 "Loop iterations: Not normal loop.\n");
3999 /* Calculate the number of iterations, final_value is only an approximation,
4000 so correct for that. Note that abs_diff and n_iterations are
4001 unsigned, because they can be as large as 2^n - 1. */
4003 abs_inc = INTVAL (increment);
4005 abs_diff = INTVAL (final_value) - INTVAL (initial_value);
4006 else if (abs_inc < 0)
4008 abs_diff = INTVAL (initial_value) - INTVAL (final_value);
4014 /* For NE tests, make sure that the iteration variable won't miss
4015 the final value. If abs_diff mod abs_incr is not zero, then the
4016 iteration variable will overflow before the loop exits, and we
4017 can not calculate the number of iterations. */
4018 if (compare_dir == 0 && (abs_diff % abs_inc) != 0)
4021 /* Note that the number of iterations could be calculated using
4022 (abs_diff + abs_inc - 1) / abs_inc, provided care was taken to
4023 handle potential overflow of the summation. */
4024 loop_info->n_iterations = abs_diff / abs_inc + ((abs_diff % abs_inc) != 0);
4025 return loop_info->n_iterations;
4029 /* Replace uses of split bivs with their split pseudo register. This is
4030 for original instructions which remain after loop unrolling without
4034 remap_split_bivs (x)
4037 register enum rtx_code code;
4039 register const char *fmt;
4044 code = GET_CODE (x);
4059 /* If non-reduced/final-value givs were split, then this would also
4060 have to remap those givs also. */
4062 if (REGNO (x) < max_reg_before_loop
4063 && REG_IV_TYPE (REGNO (x)) == BASIC_INDUCT)
4064 return reg_biv_class[REGNO (x)]->biv->src_reg;
4071 fmt = GET_RTX_FORMAT (code);
4072 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
4075 XEXP (x, i) = remap_split_bivs (XEXP (x, i));
4076 else if (fmt[i] == 'E')
4079 for (j = 0; j < XVECLEN (x, i); j++)
4080 XVECEXP (x, i, j) = remap_split_bivs (XVECEXP (x, i, j));
4086 /* If FIRST_UID is a set of REGNO, and FIRST_UID dominates LAST_UID (e.g.
4087 FIST_UID is always executed if LAST_UID is), then return 1. Otherwise
4088 return 0. COPY_START is where we can start looking for the insns
4089 FIRST_UID and LAST_UID. COPY_END is where we stop looking for these
4092 If there is no JUMP_INSN between LOOP_START and FIRST_UID, then FIRST_UID
4093 must dominate LAST_UID.
4095 If there is a CODE_LABEL between FIRST_UID and LAST_UID, then FIRST_UID
4096 may not dominate LAST_UID.
4098 If there is no CODE_LABEL between FIRST_UID and LAST_UID, then FIRST_UID
4099 must dominate LAST_UID. */
4102 set_dominates_use (regno, first_uid, last_uid, copy_start, copy_end)
4109 int passed_jump = 0;
4110 rtx p = NEXT_INSN (copy_start);
4112 while (INSN_UID (p) != first_uid)
4114 if (GET_CODE (p) == JUMP_INSN)
4116 /* Could not find FIRST_UID. */
4122 /* Verify that FIRST_UID is an insn that entirely sets REGNO. */
4123 if (GET_RTX_CLASS (GET_CODE (p)) != 'i'
4124 || ! dead_or_set_regno_p (p, regno))
4127 /* FIRST_UID is always executed. */
4128 if (passed_jump == 0)
4131 while (INSN_UID (p) != last_uid)
4133 /* If we see a CODE_LABEL between FIRST_UID and LAST_UID, then we
4134 can not be sure that FIRST_UID dominates LAST_UID. */
4135 if (GET_CODE (p) == CODE_LABEL)
4137 /* Could not find LAST_UID, but we reached the end of the loop, so
4139 else if (p == copy_end)
4144 /* FIRST_UID is always executed if LAST_UID is executed. */