1 /* Try to unroll loops, and split induction variables.
2 Copyright (C) 1992, 1993 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, 675 Mass Ave, Cambridge, MA 02139, USA. */
21 /* Try to unroll a loop, and split induction variables.
23 Loops for which the number of iterations can be calculated exactly are
24 handled specially. If the number of iterations times the insn_count is
25 less than MAX_UNROLLED_INSNS, then the loop is unrolled completely.
26 Otherwise, we try to unroll the loop a number of times modulo the number
27 of iterations, so that only one exit test will be needed. It is unrolled
28 a number of times approximately equal to MAX_UNROLLED_INSNS divided by
31 Otherwise, if the number of iterations can be calculated exactly at
32 run time, and the loop is always entered at the top, then we try to
33 precondition the loop. That is, at run time, calculate how many times
34 the loop will execute, and then execute the loop body a few times so
35 that the remaining iterations will be some multiple of 4 (or 2 if the
36 loop is large). Then fall through to a loop unrolled 4 (or 2) times,
37 with only one exit test needed at the end of the loop.
39 Otherwise, if the number of iterations can not be calculated exactly,
40 not even at run time, then we still unroll the loop a number of times
41 approximately equal to MAX_UNROLLED_INSNS divided by the insn count,
42 but there must be an exit test after each copy of the loop body.
44 For each induction variable, which is dead outside the loop (replaceable)
45 or for which we can easily calculate the final value, if we can easily
46 calculate its value at each place where it is set as a function of the
47 current loop unroll count and the variable's value at loop entry, then
48 the induction variable is split into `N' different variables, one for
49 each copy of the loop body. One variable is live across the backward
50 branch, and the others are all calculated as a function of this variable.
51 This helps eliminate data dependencies, and leads to further opportunities
54 /* Possible improvements follow: */
56 /* ??? Add an extra pass somewhere to determine whether unrolling will
57 give any benefit. E.g. after generating all unrolled insns, compute the
58 cost of all insns and compare against cost of insns in rolled loop.
60 - On traditional architectures, unrolling a non-constant bound loop
61 is a win if there is a giv whose only use is in memory addresses, the
62 memory addresses can be split, and hence giv increments can be
64 - It is also a win if the loop is executed many times, and preconditioning
65 can be performed for the loop.
66 Add code to check for these and similar cases. */
68 /* ??? Improve control of which loops get unrolled. Could use profiling
69 info to only unroll the most commonly executed loops. Perhaps have
70 a user specifyable option to control the amount of code expansion,
71 or the percent of loops to consider for unrolling. Etc. */
73 /* ??? Look at the register copies inside the loop to see if they form a
74 simple permutation. If so, iterate the permutation until it gets back to
75 the start state. This is how many times we should unroll the loop, for
76 best results, because then all register copies can be eliminated.
77 For example, the lisp nreverse function should be unrolled 3 times
86 ??? The number of times to unroll the loop may also be based on data
87 references in the loop. For example, if we have a loop that references
88 x[i-1], x[i], and x[i+1], we should unroll it a multiple of 3 times. */
90 /* ??? Add some simple linear equation solving capability so that we can
91 determine the number of loop iterations for more complex loops.
92 For example, consider this loop from gdb
93 #define SWAP_TARGET_AND_HOST(buffer,len)
96 char *p = (char *) buffer;
97 char *q = ((char *) buffer) + len - 1;
98 int iterations = (len + 1) >> 1;
100 for (p; p < q; p++, q--;)
108 start value = p = &buffer + current_iteration
109 end value = q = &buffer + len - 1 - current_iteration
110 Given the loop exit test of "p < q", then there must be "q - p" iterations,
111 set equal to zero and solve for number of iterations:
112 q - p = len - 1 - 2*current_iteration = 0
113 current_iteration = (len - 1) / 2
114 Hence, there are (len - 1) / 2 (rounded up to the nearest integer)
115 iterations of this loop. */
117 /* ??? Currently, no labels are marked as loop invariant when doing loop
118 unrolling. This is because an insn inside the loop, that loads the address
119 of a label inside the loop into a register, could be moved outside the loop
120 by the invariant code motion pass if labels were invariant. If the loop
121 is subsequently unrolled, the code will be wrong because each unrolled
122 body of the loop will use the same address, whereas each actually needs a
123 different address. A case where this happens is when a loop containing
124 a switch statement is unrolled.
126 It would be better to let labels be considered invariant. When we
127 unroll loops here, check to see if any insns using a label local to the
128 loop were moved before the loop. If so, then correct the problem, by
129 moving the insn back into the loop, or perhaps replicate the insn before
130 the loop, one copy for each time the loop is unrolled. */
132 /* The prime factors looked for when trying to unroll a loop by some
133 number which is modulo the total number of iterations. Just checking
134 for these 4 prime factors will find at least one factor for 75% of
135 all numbers theoretically. Practically speaking, this will succeed
136 almost all of the time since loops are generally a multiple of 2
139 #define NUM_FACTORS 4
141 struct _factor
{ int factor
, count
; } factors
[NUM_FACTORS
]
142 = { {2, 0}, {3, 0}, {5, 0}, {7, 0}};
144 /* Describes the different types of loop unrolling performed. */
146 enum unroll_types
{ UNROLL_COMPLETELY
, UNROLL_MODULO
, UNROLL_NAIVE
};
150 #include "insn-config.h"
151 #include "integrate.h"
158 /* This controls which loops are unrolled, and by how much we unroll
161 #ifndef MAX_UNROLLED_INSNS
162 #define MAX_UNROLLED_INSNS 100
165 /* Indexed by register number, if non-zero, then it contains a pointer
166 to a struct induction for a DEST_REG giv which has been combined with
167 one of more address givs. This is needed because whenever such a DEST_REG
168 giv is modified, we must modify the value of all split address givs
169 that were combined with this DEST_REG giv. */
171 static struct induction
**addr_combined_regs
;
173 /* Indexed by register number, if this is a splittable induction variable,
174 then this will hold the current value of the register, which depends on the
177 static rtx
*splittable_regs
;
179 /* Indexed by register number, if this is a splittable induction variable,
180 then this will hold the number of instructions in the loop that modify
181 the induction variable. Used to ensure that only the last insn modifying
182 a split iv will update the original iv of the dest. */
184 static int *splittable_regs_updates
;
186 /* Values describing the current loop's iteration variable. These are set up
187 by loop_iterations, and used by precondition_loop_p. */
189 static rtx loop_iteration_var
;
190 static rtx loop_initial_value
;
191 static rtx loop_increment
;
192 static rtx loop_final_value
;
194 /* Forward declarations. */
196 static void init_reg_map ();
197 static int precondition_loop_p ();
198 static void copy_loop_body ();
199 static void iteration_info ();
200 static rtx
approx_final_value ();
201 static int find_splittable_regs ();
202 static int find_splittable_givs ();
203 static rtx
fold_rtx_mult_add ();
205 /* Try to unroll one loop and split induction variables in the loop.
207 The loop is described by the arguments LOOP_END, INSN_COUNT, and
208 LOOP_START. END_INSERT_BEFORE indicates where insns should be added
209 which need to be executed when the loop falls through. STRENGTH_REDUCTION_P
210 indicates whether information generated in the strength reduction pass
213 This function is intended to be called from within `strength_reduce'
217 unroll_loop (loop_end
, insn_count
, loop_start
, end_insert_before
,
222 rtx end_insert_before
;
223 int strength_reduce_p
;
226 int unroll_number
= 1;
227 rtx copy_start
, copy_end
;
228 rtx insn
, copy
, sequence
, pattern
, tem
;
229 int max_labelno
, max_insnno
;
231 struct inline_remap
*map
;
239 int splitting_not_safe
= 0;
240 enum unroll_types unroll_type
;
241 int loop_preconditioned
= 0;
243 /* This points to the last real insn in the loop, which should be either
244 a JUMP_INSN (for conditional jumps) or a BARRIER (for unconditional
248 /* Don't bother unrolling huge loops. Since the minimum factor is
249 two, loops greater than one half of MAX_UNROLLED_INSNS will never
251 if (insn_count
> MAX_UNROLLED_INSNS
/ 2)
253 if (loop_dump_stream
)
254 fprintf (loop_dump_stream
, "Unrolling failure: Loop too big.\n");
258 /* When emitting debugger info, we can't unroll loops with unequal numbers
259 of block_beg and block_end notes, because that would unbalance the block
260 structure of the function. This can happen as a result of the
261 "if (foo) bar; else break;" optimization in jump.c. */
263 if (write_symbols
!= NO_DEBUG
)
265 int block_begins
= 0;
268 for (insn
= loop_start
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
270 if (GET_CODE (insn
) == NOTE
)
272 if (NOTE_LINE_NUMBER (insn
) == NOTE_INSN_BLOCK_BEG
)
274 else if (NOTE_LINE_NUMBER (insn
) == NOTE_INSN_BLOCK_END
)
279 if (block_begins
!= block_ends
)
281 if (loop_dump_stream
)
282 fprintf (loop_dump_stream
,
283 "Unrolling failure: Unbalanced block notes.\n");
288 /* Determine type of unroll to perform. Depends on the number of iterations
289 and the size of the loop. */
291 /* If there is no strength reduce info, then set loop_n_iterations to zero.
292 This can happen if strength_reduce can't find any bivs in the loop.
293 A value of zero indicates that the number of iterations could not be
296 if (! strength_reduce_p
)
297 loop_n_iterations
= 0;
299 if (loop_dump_stream
&& loop_n_iterations
> 0)
300 fprintf (loop_dump_stream
,
301 "Loop unrolling: %d iterations.\n", loop_n_iterations
);
303 /* Find and save a pointer to the last nonnote insn in the loop. */
305 last_loop_insn
= prev_nonnote_insn (loop_end
);
307 /* Calculate how many times to unroll the loop. Indicate whether or
308 not the loop is being completely unrolled. */
310 if (loop_n_iterations
== 1)
312 /* If number of iterations is exactly 1, then eliminate the compare and
313 branch at the end of the loop since they will never be taken.
314 Then return, since no other action is needed here. */
316 /* If the last instruction is not a BARRIER or a JUMP_INSN, then
317 don't do anything. */
319 if (GET_CODE (last_loop_insn
) == BARRIER
)
321 /* Delete the jump insn. This will delete the barrier also. */
322 delete_insn (PREV_INSN (last_loop_insn
));
324 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
327 /* The immediately preceding insn is a compare which must be
329 delete_insn (last_loop_insn
);
330 delete_insn (PREV_INSN (last_loop_insn
));
332 /* The immediately preceding insn may not be the compare, so don't
334 delete_insn (last_loop_insn
);
339 else if (loop_n_iterations
> 0
340 && loop_n_iterations
* insn_count
< MAX_UNROLLED_INSNS
)
342 unroll_number
= loop_n_iterations
;
343 unroll_type
= UNROLL_COMPLETELY
;
345 else if (loop_n_iterations
> 0)
347 /* Try to factor the number of iterations. Don't bother with the
348 general case, only using 2, 3, 5, and 7 will get 75% of all
349 numbers theoretically, and almost all in practice. */
351 for (i
= 0; i
< NUM_FACTORS
; i
++)
352 factors
[i
].count
= 0;
354 temp
= loop_n_iterations
;
355 for (i
= NUM_FACTORS
- 1; i
>= 0; i
--)
356 while (temp
% factors
[i
].factor
== 0)
359 temp
= temp
/ factors
[i
].factor
;
362 /* Start with the larger factors first so that we generally
363 get lots of unrolling. */
367 for (i
= 3; i
>= 0; i
--)
368 while (factors
[i
].count
--)
370 if (temp
* factors
[i
].factor
< MAX_UNROLLED_INSNS
)
372 unroll_number
*= factors
[i
].factor
;
373 temp
*= factors
[i
].factor
;
379 /* If we couldn't find any factors, then unroll as in the normal
381 if (unroll_number
== 1)
383 if (loop_dump_stream
)
384 fprintf (loop_dump_stream
,
385 "Loop unrolling: No factors found.\n");
388 unroll_type
= UNROLL_MODULO
;
392 /* Default case, calculate number of times to unroll loop based on its
394 if (unroll_number
== 1)
396 if (8 * insn_count
< MAX_UNROLLED_INSNS
)
398 else if (4 * insn_count
< MAX_UNROLLED_INSNS
)
403 unroll_type
= UNROLL_NAIVE
;
406 /* Now we know how many times to unroll the loop. */
408 if (loop_dump_stream
)
409 fprintf (loop_dump_stream
,
410 "Unrolling loop %d times.\n", unroll_number
);
413 if (unroll_type
== UNROLL_COMPLETELY
|| unroll_type
== UNROLL_MODULO
)
415 /* Loops of these types should never start with a jump down to
416 the exit condition test. For now, check for this case just to
417 be sure. UNROLL_NAIVE loops can be of this form, this case is
420 while (GET_CODE (insn
) != CODE_LABEL
&& GET_CODE (insn
) != JUMP_INSN
)
421 insn
= NEXT_INSN (insn
);
422 if (GET_CODE (insn
) == JUMP_INSN
)
426 if (unroll_type
== UNROLL_COMPLETELY
)
428 /* Completely unrolling the loop: Delete the compare and branch at
429 the end (the last two instructions). This delete must done at the
430 very end of loop unrolling, to avoid problems with calls to
431 back_branch_in_range_p, which is called by find_splittable_regs.
432 All increments of splittable bivs/givs are changed to load constant
435 copy_start
= loop_start
;
437 /* Set insert_before to the instruction immediately after the JUMP_INSN
438 (or BARRIER), so that any NOTEs between the JUMP_INSN and the end of
439 the loop will be correctly handled by copy_loop_body. */
440 insert_before
= NEXT_INSN (last_loop_insn
);
442 /* Set copy_end to the insn before the jump at the end of the loop. */
443 if (GET_CODE (last_loop_insn
) == BARRIER
)
444 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
445 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
448 /* The instruction immediately before the JUMP_INSN is a compare
449 instruction which we do not want to copy. */
450 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
452 /* The instruction immediately before the JUMP_INSN may not be the
453 compare, so we must copy it. */
454 copy_end
= PREV_INSN (last_loop_insn
);
459 /* We currently can't unroll a loop if it doesn't end with a
460 JUMP_INSN. There would need to be a mechanism that recognizes
461 this case, and then inserts a jump after each loop body, which
462 jumps to after the last loop body. */
463 if (loop_dump_stream
)
464 fprintf (loop_dump_stream
,
465 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
469 else if (unroll_type
== UNROLL_MODULO
)
471 /* Partially unrolling the loop: The compare and branch at the end
472 (the last two instructions) must remain. Don't copy the compare
473 and branch instructions at the end of the loop. Insert the unrolled
474 code immediately before the compare/branch at the end so that the
475 code will fall through to them as before. */
477 copy_start
= loop_start
;
479 /* Set insert_before to the jump insn at the end of the loop.
480 Set copy_end to before the jump insn at the end of the loop. */
481 if (GET_CODE (last_loop_insn
) == BARRIER
)
483 insert_before
= PREV_INSN (last_loop_insn
);
484 copy_end
= PREV_INSN (insert_before
);
486 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
489 /* The instruction immediately before the JUMP_INSN is a compare
490 instruction which we do not want to copy or delete. */
491 insert_before
= PREV_INSN (last_loop_insn
);
492 copy_end
= PREV_INSN (insert_before
);
494 /* The instruction immediately before the JUMP_INSN may not be the
495 compare, so we must copy it. */
496 insert_before
= last_loop_insn
;
497 copy_end
= PREV_INSN (last_loop_insn
);
502 /* We currently can't unroll a loop if it doesn't end with a
503 JUMP_INSN. There would need to be a mechanism that recognizes
504 this case, and then inserts a jump after each loop body, which
505 jumps to after the last loop body. */
506 if (loop_dump_stream
)
507 fprintf (loop_dump_stream
,
508 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
514 /* Normal case: Must copy the compare and branch instructions at the
517 if (GET_CODE (last_loop_insn
) == BARRIER
)
519 /* Loop ends with an unconditional jump and a barrier.
520 Handle this like above, don't copy jump and barrier.
521 This is not strictly necessary, but doing so prevents generating
522 unconditional jumps to an immediately following label.
524 This will be corrected below if the target of this jump is
525 not the start_label. */
527 insert_before
= PREV_INSN (last_loop_insn
);
528 copy_end
= PREV_INSN (insert_before
);
530 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
532 /* Set insert_before to immediately after the JUMP_INSN, so that
533 NOTEs at the end of the loop will be correctly handled by
535 insert_before
= NEXT_INSN (last_loop_insn
);
536 copy_end
= last_loop_insn
;
540 /* We currently can't unroll a loop if it doesn't end with a
541 JUMP_INSN. There would need to be a mechanism that recognizes
542 this case, and then inserts a jump after each loop body, which
543 jumps to after the last loop body. */
544 if (loop_dump_stream
)
545 fprintf (loop_dump_stream
,
546 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
550 /* If copying exit test branches because they can not be eliminated,
551 then must convert the fall through case of the branch to a jump past
552 the end of the loop. Create a label to emit after the loop and save
553 it for later use. Do not use the label after the loop, if any, since
554 it might be used by insns outside the loop, or there might be insns
555 added before it later by final_[bg]iv_value which must be after
556 the real exit label. */
557 exit_label
= gen_label_rtx ();
560 while (GET_CODE (insn
) != CODE_LABEL
&& GET_CODE (insn
) != JUMP_INSN
)
561 insn
= NEXT_INSN (insn
);
563 if (GET_CODE (insn
) == JUMP_INSN
)
565 /* The loop starts with a jump down to the exit condition test.
566 Start copying the loop after the barrier following this
568 copy_start
= NEXT_INSN (insn
);
570 /* Splitting induction variables doesn't work when the loop is
571 entered via a jump to the bottom, because then we end up doing
572 a comparison against a new register for a split variable, but
573 we did not execute the set insn for the new register because
574 it was skipped over. */
575 splitting_not_safe
= 1;
576 if (loop_dump_stream
)
577 fprintf (loop_dump_stream
,
578 "Splitting not safe, because loop not entered at top.\n");
581 copy_start
= loop_start
;
584 /* This should always be the first label in the loop. */
585 start_label
= NEXT_INSN (copy_start
);
586 /* There may be a line number note and/or a loop continue note here. */
587 while (GET_CODE (start_label
) == NOTE
)
588 start_label
= NEXT_INSN (start_label
);
589 if (GET_CODE (start_label
) != CODE_LABEL
)
591 /* This can happen as a result of jump threading. If the first insns in
592 the loop test the same condition as the loop's backward jump, or the
593 opposite condition, then the backward jump will be modified to point
594 to elsewhere, and the loop's start label is deleted.
596 This case currently can not be handled by the loop unrolling code. */
598 if (loop_dump_stream
)
599 fprintf (loop_dump_stream
,
600 "Unrolling failure: unknown insns between BEG note and loop label.\n");
603 if (LABEL_NAME (start_label
))
605 /* The jump optimization pass must have combined the original start label
606 with a named label for a goto. We can't unroll this case because
607 jumps which go to the named label must be handled differently than
608 jumps to the loop start, and it is impossible to differentiate them
610 if (loop_dump_stream
)
611 fprintf (loop_dump_stream
,
612 "Unrolling failure: loop start label is gone\n");
616 if (unroll_type
== UNROLL_NAIVE
617 && GET_CODE (last_loop_insn
) == BARRIER
618 && start_label
!= JUMP_LABEL (PREV_INSN (last_loop_insn
)))
620 /* In this case, we must copy the jump and barrier, because they will
621 not be converted to jumps to an immediately following label. */
623 insert_before
= NEXT_INSN (last_loop_insn
);
624 copy_end
= last_loop_insn
;
627 /* Allocate a translation table for the labels and insn numbers.
628 They will be filled in as we copy the insns in the loop. */
630 max_labelno
= max_label_num ();
631 max_insnno
= get_max_uid ();
633 map
= (struct inline_remap
*) alloca (sizeof (struct inline_remap
));
635 map
->integrating
= 0;
637 /* Allocate the label map. */
641 map
->label_map
= (rtx
*) alloca (max_labelno
* sizeof (rtx
));
643 local_label
= (char *) alloca (max_labelno
);
644 bzero (local_label
, max_labelno
);
649 /* Search the loop and mark all local labels, i.e. the ones which have to
650 be distinct labels when copied. For all labels which might be
651 non-local, set their label_map entries to point to themselves.
652 If they happen to be local their label_map entries will be overwritten
653 before the loop body is copied. The label_map entries for local labels
654 will be set to a different value each time the loop body is copied. */
656 for (insn
= copy_start
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
658 if (GET_CODE (insn
) == CODE_LABEL
)
659 local_label
[CODE_LABEL_NUMBER (insn
)] = 1;
660 else if (GET_CODE (insn
) == JUMP_INSN
)
662 if (JUMP_LABEL (insn
))
663 map
->label_map
[CODE_LABEL_NUMBER (JUMP_LABEL (insn
))]
665 else if (GET_CODE (PATTERN (insn
)) == ADDR_VEC
666 || GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
)
668 rtx pat
= PATTERN (insn
);
669 int diff_vec_p
= GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
;
670 int len
= XVECLEN (pat
, diff_vec_p
);
673 for (i
= 0; i
< len
; i
++)
675 label
= XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0);
676 map
->label_map
[CODE_LABEL_NUMBER (label
)] = label
;
682 /* Allocate space for the insn map. */
684 map
->insn_map
= (rtx
*) alloca (max_insnno
* sizeof (rtx
));
686 /* Set this to zero, to indicate that we are doing loop unrolling,
687 not function inlining. */
688 map
->inline_target
= 0;
690 /* The register and constant maps depend on the number of registers
691 present, so the final maps can't be created until after
692 find_splittable_regs is called. However, they are needed for
693 preconditioning, so we create temporary maps when preconditioning
696 /* The preconditioning code may allocate two new pseudo registers. */
697 maxregnum
= max_reg_num ();
699 /* Allocate and zero out the splittable_regs and addr_combined_regs
700 arrays. These must be zeroed here because they will be used if
701 loop preconditioning is performed, and must be zero for that case.
703 It is safe to do this here, since the extra registers created by the
704 preconditioning code and find_splittable_regs will never be used
705 to access the splittable_regs[] and addr_combined_regs[] arrays. */
707 splittable_regs
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
708 bzero (splittable_regs
, maxregnum
* sizeof (rtx
));
709 splittable_regs_updates
= (int *) alloca (maxregnum
* sizeof (int));
710 bzero (splittable_regs_updates
, maxregnum
* sizeof (int));
712 = (struct induction
**) alloca (maxregnum
* sizeof (struct induction
*));
713 bzero (addr_combined_regs
, maxregnum
* sizeof (struct induction
*));
715 /* If this loop requires exit tests when unrolled, check to see if we
716 can precondition the loop so as to make the exit tests unnecessary.
717 Just like variable splitting, this is not safe if the loop is entered
718 via a jump to the bottom. Also, can not do this if no strength
719 reduce info, because precondition_loop_p uses this info. */
721 /* Must copy the loop body for preconditioning before the following
722 find_splittable_regs call since that will emit insns which need to
723 be after the preconditioned loop copies, but immediately before the
724 unrolled loop copies. */
726 /* Also, it is not safe to split induction variables for the preconditioned
727 copies of the loop body. If we split induction variables, then the code
728 assumes that each induction variable can be represented as a function
729 of its initial value and the loop iteration number. This is not true
730 in this case, because the last preconditioned copy of the loop body
731 could be any iteration from the first up to the `unroll_number-1'th,
732 depending on the initial value of the iteration variable. Therefore
733 we can not split induction variables here, because we can not calculate
734 their value. Hence, this code must occur before find_splittable_regs
737 if (unroll_type
== UNROLL_NAIVE
&& ! splitting_not_safe
&& strength_reduce_p
)
739 rtx initial_value
, final_value
, increment
;
741 if (precondition_loop_p (&initial_value
, &final_value
, &increment
,
742 loop_start
, loop_end
))
744 register rtx diff
, temp
;
745 enum machine_mode mode
;
747 int abs_inc
, neg_inc
;
749 map
->reg_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
751 map
->const_equiv_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
752 map
->const_age_map
= (unsigned *) alloca (maxregnum
753 * sizeof (unsigned));
754 map
->const_equiv_map_size
= maxregnum
;
755 global_const_equiv_map
= map
->const_equiv_map
;
756 global_const_equiv_map_size
= maxregnum
;
758 init_reg_map (map
, maxregnum
);
760 /* Limit loop unrolling to 4, since this will make 7 copies of
762 if (unroll_number
> 4)
765 /* Save the absolute value of the increment, and also whether or
766 not it is negative. */
768 abs_inc
= INTVAL (increment
);
777 /* Decide what mode to do these calculations in. Choose the larger
778 of final_value's mode and initial_value's mode, or a full-word if
779 both are constants. */
780 mode
= GET_MODE (final_value
);
781 if (mode
== VOIDmode
)
783 mode
= GET_MODE (initial_value
);
784 if (mode
== VOIDmode
)
787 else if (mode
!= GET_MODE (initial_value
)
788 && (GET_MODE_SIZE (mode
)
789 < GET_MODE_SIZE (GET_MODE (initial_value
))))
790 mode
= GET_MODE (initial_value
);
792 /* Calculate the difference between the final and initial values.
793 Final value may be a (plus (reg x) (const_int 1)) rtx.
794 Let the following cse pass simplify this if initial value is
797 We must copy the final and initial values here to avoid
798 improperly shared rtl. */
800 diff
= expand_binop (mode
, sub_optab
, copy_rtx (final_value
),
801 copy_rtx (initial_value
), NULL_RTX
, 0,
804 /* Now calculate (diff % (unroll * abs (increment))) by using an
806 diff
= expand_binop (GET_MODE (diff
), and_optab
, diff
,
807 GEN_INT (unroll_number
* abs_inc
- 1),
808 NULL_RTX
, 0, OPTAB_LIB_WIDEN
);
810 /* Now emit a sequence of branches to jump to the proper precond
813 labels
= (rtx
*) alloca (sizeof (rtx
) * unroll_number
);
814 for (i
= 0; i
< unroll_number
; i
++)
815 labels
[i
] = gen_label_rtx ();
817 /* Assuming the unroll_number is 4, and the increment is 2, then
818 for a negative increment: for a positive increment:
819 diff = 0,1 precond 0 diff = 0,7 precond 0
820 diff = 2,3 precond 3 diff = 1,2 precond 1
821 diff = 4,5 precond 2 diff = 3,4 precond 2
822 diff = 6,7 precond 1 diff = 5,6 precond 3 */
824 /* We only need to emit (unroll_number - 1) branches here, the
825 last case just falls through to the following code. */
827 /* ??? This would give better code if we emitted a tree of branches
828 instead of the current linear list of branches. */
830 for (i
= 0; i
< unroll_number
- 1; i
++)
834 /* For negative increments, must invert the constant compared
835 against, except when comparing against zero. */
839 cmp_const
= unroll_number
- i
;
843 emit_cmp_insn (diff
, GEN_INT (abs_inc
* cmp_const
),
844 EQ
, NULL_RTX
, mode
, 0, 0);
847 emit_jump_insn (gen_beq (labels
[i
]));
849 emit_jump_insn (gen_bge (labels
[i
]));
851 emit_jump_insn (gen_ble (labels
[i
]));
852 JUMP_LABEL (get_last_insn ()) = labels
[i
];
853 LABEL_NUSES (labels
[i
])++;
856 /* If the increment is greater than one, then we need another branch,
857 to handle other cases equivalent to 0. */
859 /* ??? This should be merged into the code above somehow to help
860 simplify the code here, and reduce the number of branches emitted.
861 For the negative increment case, the branch here could easily
862 be merged with the `0' case branch above. For the positive
863 increment case, it is not clear how this can be simplified. */
870 cmp_const
= abs_inc
- 1;
872 cmp_const
= abs_inc
* (unroll_number
- 1) + 1;
874 emit_cmp_insn (diff
, GEN_INT (cmp_const
), EQ
, NULL_RTX
,
878 emit_jump_insn (gen_ble (labels
[0]));
880 emit_jump_insn (gen_bge (labels
[0]));
881 JUMP_LABEL (get_last_insn ()) = labels
[0];
882 LABEL_NUSES (labels
[0])++;
885 sequence
= gen_sequence ();
887 emit_insn_before (sequence
, loop_start
);
889 /* Only the last copy of the loop body here needs the exit
890 test, so set copy_end to exclude the compare/branch here,
891 and then reset it inside the loop when get to the last
894 if (GET_CODE (last_loop_insn
) == BARRIER
)
895 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
896 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
899 /* The immediately preceding insn is a compare which we do not
901 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
903 /* The immediately preceding insn may not be a compare, so we
905 copy_end
= PREV_INSN (last_loop_insn
);
911 for (i
= 1; i
< unroll_number
; i
++)
913 emit_label_after (labels
[unroll_number
- i
],
914 PREV_INSN (loop_start
));
916 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
917 bzero (map
->const_equiv_map
, maxregnum
* sizeof (rtx
));
918 bzero (map
->const_age_map
, maxregnum
* sizeof (unsigned));
921 for (j
= 0; j
< max_labelno
; j
++)
923 map
->label_map
[j
] = gen_label_rtx ();
925 /* The last copy needs the compare/branch insns at the end,
926 so reset copy_end here if the loop ends with a conditional
929 if (i
== unroll_number
- 1)
931 if (GET_CODE (last_loop_insn
) == BARRIER
)
932 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
934 copy_end
= last_loop_insn
;
937 /* None of the copies are the `last_iteration', so just
938 pass zero for that parameter. */
939 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, 0,
940 unroll_type
, start_label
, loop_end
,
941 loop_start
, copy_end
);
943 emit_label_after (labels
[0], PREV_INSN (loop_start
));
945 if (GET_CODE (last_loop_insn
) == BARRIER
)
947 insert_before
= PREV_INSN (last_loop_insn
);
948 copy_end
= PREV_INSN (insert_before
);
953 /* The immediately preceding insn is a compare which we do not
955 insert_before
= PREV_INSN (last_loop_insn
);
956 copy_end
= PREV_INSN (insert_before
);
958 /* The immediately preceding insn may not be a compare, so we
960 insert_before
= last_loop_insn
;
961 copy_end
= PREV_INSN (last_loop_insn
);
965 /* Set unroll type to MODULO now. */
966 unroll_type
= UNROLL_MODULO
;
967 loop_preconditioned
= 1;
971 /* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
972 the loop unless all loops are being unrolled. */
973 if (unroll_type
== UNROLL_NAIVE
&& ! flag_unroll_all_loops
)
975 if (loop_dump_stream
)
976 fprintf (loop_dump_stream
, "Unrolling failure: Naive unrolling not being done.\n");
980 /* At this point, we are guaranteed to unroll the loop. */
982 /* For each biv and giv, determine whether it can be safely split into
983 a different variable for each unrolled copy of the loop body.
984 We precalculate and save this info here, since computing it is
987 Do this before deleting any instructions from the loop, so that
988 back_branch_in_range_p will work correctly. */
990 if (splitting_not_safe
)
993 temp
= find_splittable_regs (unroll_type
, loop_start
, loop_end
,
994 end_insert_before
, unroll_number
);
996 /* find_splittable_regs may have created some new registers, so must
997 reallocate the reg_map with the new larger size, and must realloc
998 the constant maps also. */
1000 maxregnum
= max_reg_num ();
1001 map
->reg_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
1003 init_reg_map (map
, maxregnum
);
1005 /* Space is needed in some of the map for new registers, so new_maxregnum
1006 is an (over)estimate of how many registers will exist at the end. */
1007 new_maxregnum
= maxregnum
+ (temp
* unroll_number
* 2);
1009 /* Must realloc space for the constant maps, because the number of registers
1010 may have changed. */
1012 map
->const_equiv_map
= (rtx
*) alloca (new_maxregnum
* sizeof (rtx
));
1013 map
->const_age_map
= (unsigned *) alloca (new_maxregnum
* sizeof (unsigned));
1015 map
->const_equiv_map_size
= new_maxregnum
;
1016 global_const_equiv_map
= map
->const_equiv_map
;
1017 global_const_equiv_map_size
= new_maxregnum
;
1019 /* Search the list of bivs and givs to find ones which need to be remapped
1020 when split, and set their reg_map entry appropriately. */
1022 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
1024 if (REGNO (bl
->biv
->src_reg
) != bl
->regno
)
1025 map
->reg_map
[bl
->regno
] = bl
->biv
->src_reg
;
1027 /* Currently, non-reduced/final-value givs are never split. */
1028 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
1029 if (REGNO (v
->src_reg
) != bl
->regno
)
1030 map
->reg_map
[REGNO (v
->dest_reg
)] = v
->src_reg
;
1034 /* If the loop is being partially unrolled, and the iteration variables
1035 are being split, and are being renamed for the split, then must fix up
1036 the compare instruction at the end of the loop to refer to the new
1037 registers. This compare isn't copied, so the registers used in it
1038 will never be replaced if it isn't done here. */
1040 if (unroll_type
== UNROLL_MODULO
)
1042 insn
= NEXT_INSN (copy_end
);
1043 if (GET_CODE (insn
) == INSN
&& GET_CODE (PATTERN (insn
)) == SET
)
1046 /* If non-reduced/final-value givs were split, then this would also
1047 have to remap those givs. */
1050 tem
= SET_SRC (PATTERN (insn
));
1051 /* The set source is a register. */
1052 if (GET_CODE (tem
) == REG
)
1054 if (REGNO (tem
) < max_reg_before_loop
1055 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1056 SET_SRC (PATTERN (insn
))
1057 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1061 /* The set source is a compare of some sort. */
1062 tem
= XEXP (SET_SRC (PATTERN (insn
)), 0);
1063 if (GET_CODE (tem
) == REG
1064 && REGNO (tem
) < max_reg_before_loop
1065 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1066 XEXP (SET_SRC (PATTERN (insn
)), 0)
1067 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1069 tem
= XEXP (SET_SRC (PATTERN (insn
)), 1);
1070 if (GET_CODE (tem
) == REG
1071 && REGNO (tem
) < max_reg_before_loop
1072 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1073 XEXP (SET_SRC (PATTERN (insn
)), 1)
1074 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1079 /* For unroll_number - 1 times, make a copy of each instruction
1080 between copy_start and copy_end, and insert these new instructions
1081 before the end of the loop. */
1083 for (i
= 0; i
< unroll_number
; i
++)
1085 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
1086 bzero (map
->const_equiv_map
, new_maxregnum
* sizeof (rtx
));
1087 bzero (map
->const_age_map
, new_maxregnum
* sizeof (unsigned));
1090 for (j
= 0; j
< max_labelno
; j
++)
1092 map
->label_map
[j
] = gen_label_rtx ();
1094 /* If loop starts with a branch to the test, then fix it so that
1095 it points to the test of the first unrolled copy of the loop. */
1096 if (i
== 0 && loop_start
!= copy_start
)
1098 insn
= PREV_INSN (copy_start
);
1099 pattern
= PATTERN (insn
);
1101 tem
= map
->label_map
[CODE_LABEL_NUMBER
1102 (XEXP (SET_SRC (pattern
), 0))];
1103 SET_SRC (pattern
) = gen_rtx (LABEL_REF
, VOIDmode
, tem
);
1105 /* Set the jump label so that it can be used by later loop unrolling
1107 JUMP_LABEL (insn
) = tem
;
1108 LABEL_NUSES (tem
)++;
1111 copy_loop_body (copy_start
, copy_end
, map
, exit_label
,
1112 i
== unroll_number
- 1, unroll_type
, start_label
,
1113 loop_end
, insert_before
, insert_before
);
1116 /* Before deleting any insns, emit a CODE_LABEL immediately after the last
1117 insn to be deleted. This prevents any runaway delete_insn call from
1118 more insns that it should, as it always stops at a CODE_LABEL. */
1120 /* Delete the compare and branch at the end of the loop if completely
1121 unrolling the loop. Deleting the backward branch at the end also
1122 deletes the code label at the start of the loop. This is done at
1123 the very end to avoid problems with back_branch_in_range_p. */
1125 if (unroll_type
== UNROLL_COMPLETELY
)
1126 safety_label
= emit_label_after (gen_label_rtx (), last_loop_insn
);
1128 safety_label
= emit_label_after (gen_label_rtx (), copy_end
);
1130 /* Delete all of the original loop instructions. Don't delete the
1131 LOOP_BEG note, or the first code label in the loop. */
1133 insn
= NEXT_INSN (copy_start
);
1134 while (insn
!= safety_label
)
1136 if (insn
!= start_label
)
1137 insn
= delete_insn (insn
);
1139 insn
= NEXT_INSN (insn
);
1142 /* Can now delete the 'safety' label emitted to protect us from runaway
1143 delete_insn calls. */
1144 if (INSN_DELETED_P (safety_label
))
1146 delete_insn (safety_label
);
1148 /* If exit_label exists, emit it after the loop. Doing the emit here
1149 forces it to have a higher INSN_UID than any insn in the unrolled loop.
1150 This is needed so that mostly_true_jump in reorg.c will treat jumps
1151 to this loop end label correctly, i.e. predict that they are usually
1154 emit_label_after (exit_label
, loop_end
);
1157 /* Return true if the loop can be safely, and profitably, preconditioned
1158 so that the unrolled copies of the loop body don't need exit tests.
1160 This only works if final_value, initial_value and increment can be
1161 determined, and if increment is a constant power of 2.
1162 If increment is not a power of 2, then the preconditioning modulo
1163 operation would require a real modulo instead of a boolean AND, and this
1164 is not considered `profitable'. */
1166 /* ??? If the loop is known to be executed very many times, or the machine
1167 has a very cheap divide instruction, then preconditioning is a win even
1168 when the increment is not a power of 2. Use RTX_COST to compute
1169 whether divide is cheap. */
1172 precondition_loop_p (initial_value
, final_value
, increment
, loop_start
,
1174 rtx
*initial_value
, *final_value
, *increment
;
1175 rtx loop_start
, loop_end
;
1177 int unsigned_compare
, compare_dir
;
1179 if (loop_n_iterations
> 0)
1181 *initial_value
= const0_rtx
;
1182 *increment
= const1_rtx
;
1183 *final_value
= GEN_INT (loop_n_iterations
);
1185 if (loop_dump_stream
)
1186 fprintf (loop_dump_stream
,
1187 "Preconditioning: Success, number of iterations known, %d.\n",
1192 if (loop_initial_value
== 0)
1194 if (loop_dump_stream
)
1195 fprintf (loop_dump_stream
,
1196 "Preconditioning: Could not find initial value.\n");
1199 else if (loop_increment
== 0)
1201 if (loop_dump_stream
)
1202 fprintf (loop_dump_stream
,
1203 "Preconditioning: Could not find increment value.\n");
1206 else if (GET_CODE (loop_increment
) != CONST_INT
)
1208 if (loop_dump_stream
)
1209 fprintf (loop_dump_stream
,
1210 "Preconditioning: Increment not a constant.\n");
1213 else if ((exact_log2 (INTVAL (loop_increment
)) < 0)
1214 && (exact_log2 (- INTVAL (loop_increment
)) < 0))
1216 if (loop_dump_stream
)
1217 fprintf (loop_dump_stream
,
1218 "Preconditioning: Increment not a constant power of 2.\n");
1222 /* Unsigned_compare and compare_dir can be ignored here, since they do
1223 not matter for preconditioning. */
1225 if (loop_final_value
== 0)
1227 if (loop_dump_stream
)
1228 fprintf (loop_dump_stream
,
1229 "Preconditioning: EQ comparison loop.\n");
1233 /* Must ensure that final_value is invariant, so call invariant_p to
1234 check. Before doing so, must check regno against max_reg_before_loop
1235 to make sure that the register is in the range covered by invariant_p.
1236 If it isn't, then it is most likely a biv/giv which by definition are
1238 if ((GET_CODE (loop_final_value
) == REG
1239 && REGNO (loop_final_value
) >= max_reg_before_loop
)
1240 || (GET_CODE (loop_final_value
) == PLUS
1241 && REGNO (XEXP (loop_final_value
, 0)) >= max_reg_before_loop
)
1242 || ! invariant_p (loop_final_value
))
1244 if (loop_dump_stream
)
1245 fprintf (loop_dump_stream
,
1246 "Preconditioning: Final value not invariant.\n");
1250 /* Fail for floating point values, since the caller of this function
1251 does not have code to deal with them. */
1252 if (GET_MODE_CLASS (GET_MODE (loop_final_value
)) == MODE_FLOAT
1253 || GET_MODE_CLASS (GET_MODE (loop_initial_value
)) == MODE_FLOAT
)
1255 if (loop_dump_stream
)
1256 fprintf (loop_dump_stream
,
1257 "Preconditioning: Floating point final or initial value.\n");
1261 /* Now set initial_value to be the iteration_var, since that may be a
1262 simpler expression, and is guaranteed to be correct if all of the
1263 above tests succeed.
1265 We can not use the initial_value as calculated, because it will be
1266 one too small for loops of the form "while (i-- > 0)". We can not
1267 emit code before the loop_skip_over insns to fix this problem as this
1268 will then give a number one too large for loops of the form
1271 Note that all loops that reach here are entered at the top, because
1272 this function is not called if the loop starts with a jump. */
1274 /* Fail if loop_iteration_var is not live before loop_start, since we need
1275 to test its value in the preconditioning code. */
1277 if (uid_luid
[regno_first_uid
[REGNO (loop_iteration_var
)]]
1278 > INSN_LUID (loop_start
))
1280 if (loop_dump_stream
)
1281 fprintf (loop_dump_stream
,
1282 "Preconditioning: Iteration var not live before loop start.\n");
1286 *initial_value
= loop_iteration_var
;
1287 *increment
= loop_increment
;
1288 *final_value
= loop_final_value
;
1291 if (loop_dump_stream
)
1292 fprintf (loop_dump_stream
, "Preconditioning: Successful.\n");
1297 /* All pseudo-registers must be mapped to themselves. Two hard registers
1298 must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
1299 REGNUM, to avoid function-inlining specific conversions of these
1300 registers. All other hard regs can not be mapped because they may be
1305 init_reg_map (map
, maxregnum
)
1306 struct inline_remap
*map
;
1311 for (i
= maxregnum
- 1; i
> LAST_VIRTUAL_REGISTER
; i
--)
1312 map
->reg_map
[i
] = regno_reg_rtx
[i
];
1313 /* Just clear the rest of the entries. */
1314 for (i
= LAST_VIRTUAL_REGISTER
; i
>= 0; i
--)
1315 map
->reg_map
[i
] = 0;
1317 map
->reg_map
[VIRTUAL_STACK_VARS_REGNUM
]
1318 = regno_reg_rtx
[VIRTUAL_STACK_VARS_REGNUM
];
1319 map
->reg_map
[VIRTUAL_INCOMING_ARGS_REGNUM
]
1320 = regno_reg_rtx
[VIRTUAL_INCOMING_ARGS_REGNUM
];
1323 /* Strength-reduction will often emit code for optimized biv/givs which
1324 calculates their value in a temporary register, and then copies the result
1325 to the iv. This procedure reconstructs the pattern computing the iv;
1326 verifying that all operands are of the proper form.
1328 The return value is the amount that the giv is incremented by. */
1331 calculate_giv_inc (pattern
, src_insn
, regno
)
1332 rtx pattern
, src_insn
;
1336 rtx increment_total
= 0;
1340 /* Verify that we have an increment insn here. First check for a plus
1341 as the set source. */
1342 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1344 /* SR sometimes computes the new giv value in a temp, then copies it
1346 src_insn
= PREV_INSN (src_insn
);
1347 pattern
= PATTERN (src_insn
);
1348 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1351 /* The last insn emitted is not needed, so delete it to avoid confusing
1352 the second cse pass. This insn sets the giv unnecessarily. */
1353 delete_insn (get_last_insn ());
1356 /* Verify that we have a constant as the second operand of the plus. */
1357 increment
= XEXP (SET_SRC (pattern
), 1);
1358 if (GET_CODE (increment
) != CONST_INT
)
1360 /* SR sometimes puts the constant in a register, especially if it is
1361 too big to be an add immed operand. */
1362 src_insn
= PREV_INSN (src_insn
);
1363 increment
= SET_SRC (PATTERN (src_insn
));
1365 /* SR may have used LO_SUM to compute the constant if it is too large
1366 for a load immed operand. In this case, the constant is in operand
1367 one of the LO_SUM rtx. */
1368 if (GET_CODE (increment
) == LO_SUM
)
1369 increment
= XEXP (increment
, 1);
1371 if (GET_CODE (increment
) != CONST_INT
)
1374 /* The insn loading the constant into a register is not longer needed,
1376 delete_insn (get_last_insn ());
1379 if (increment_total
)
1380 increment_total
= GEN_INT (INTVAL (increment_total
) + INTVAL (increment
));
1382 increment_total
= increment
;
1384 /* Check that the source register is the same as the register we expected
1385 to see as the source. If not, something is seriously wrong. */
1386 if (GET_CODE (XEXP (SET_SRC (pattern
), 0)) != REG
1387 || REGNO (XEXP (SET_SRC (pattern
), 0)) != regno
)
1389 /* Some machines (e.g. the romp), may emit two add instructions for
1390 certain constants, so lets try looking for another add immediately
1391 before this one if we have only seen one add insn so far. */
1397 src_insn
= PREV_INSN (src_insn
);
1398 pattern
= PATTERN (src_insn
);
1400 delete_insn (get_last_insn ());
1408 return increment_total
;
1411 /* Copy REG_NOTES, except for insn references, because not all insn_map
1412 entries are valid yet. We do need to copy registers now though, because
1413 the reg_map entries can change during copying. */
1416 initial_reg_note_copy (notes
, map
)
1418 struct inline_remap
*map
;
1425 copy
= rtx_alloc (GET_CODE (notes
));
1426 PUT_MODE (copy
, GET_MODE (notes
));
1428 if (GET_CODE (notes
) == EXPR_LIST
)
1429 XEXP (copy
, 0) = copy_rtx_and_substitute (XEXP (notes
, 0), map
);
1430 else if (GET_CODE (notes
) == INSN_LIST
)
1431 /* Don't substitute for these yet. */
1432 XEXP (copy
, 0) = XEXP (notes
, 0);
1436 XEXP (copy
, 1) = initial_reg_note_copy (XEXP (notes
, 1), map
);
1441 /* Fixup insn references in copied REG_NOTES. */
1444 final_reg_note_copy (notes
, map
)
1446 struct inline_remap
*map
;
1450 for (note
= notes
; note
; note
= XEXP (note
, 1))
1451 if (GET_CODE (note
) == INSN_LIST
)
1452 XEXP (note
, 0) = map
->insn_map
[INSN_UID (XEXP (note
, 0))];
1455 /* Copy each instruction in the loop, substituting from map as appropriate.
1456 This is very similar to a loop in expand_inline_function. */
1459 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, last_iteration
,
1460 unroll_type
, start_label
, loop_end
, insert_before
,
1462 rtx copy_start
, copy_end
;
1463 struct inline_remap
*map
;
1466 enum unroll_types unroll_type
;
1467 rtx start_label
, loop_end
, insert_before
, copy_notes_from
;
1471 int dest_reg_was_split
, i
;
1473 rtx final_label
= 0;
1474 rtx giv_inc
, giv_dest_reg
, giv_src_reg
;
1476 /* If this isn't the last iteration, then map any references to the
1477 start_label to final_label. Final label will then be emitted immediately
1478 after the end of this loop body if it was ever used.
1480 If this is the last iteration, then map references to the start_label
1482 if (! last_iteration
)
1484 final_label
= gen_label_rtx ();
1485 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = final_label
;
1488 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = start_label
;
1495 insn
= NEXT_INSN (insn
);
1497 map
->orig_asm_operands_vector
= 0;
1499 switch (GET_CODE (insn
))
1502 pattern
= PATTERN (insn
);
1506 /* Check to see if this is a giv that has been combined with
1507 some split address givs. (Combined in the sense that
1508 `combine_givs' in loop.c has put two givs in the same register.)
1509 In this case, we must search all givs based on the same biv to
1510 find the address givs. Then split the address givs.
1511 Do this before splitting the giv, since that may map the
1512 SET_DEST to a new register. */
1514 if (GET_CODE (pattern
) == SET
1515 && GET_CODE (SET_DEST (pattern
)) == REG
1516 && addr_combined_regs
[REGNO (SET_DEST (pattern
))])
1518 struct iv_class
*bl
;
1519 struct induction
*v
, *tv
;
1520 int regno
= REGNO (SET_DEST (pattern
));
1522 v
= addr_combined_regs
[REGNO (SET_DEST (pattern
))];
1523 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
1525 /* Although the giv_inc amount is not needed here, we must call
1526 calculate_giv_inc here since it might try to delete the
1527 last insn emitted. If we wait until later to call it,
1528 we might accidentally delete insns generated immediately
1529 below by emit_unrolled_add. */
1531 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1533 /* Now find all address giv's that were combined with this
1535 for (tv
= bl
->giv
; tv
; tv
= tv
->next_iv
)
1536 if (tv
->giv_type
== DEST_ADDR
&& tv
->same
== v
)
1538 int this_giv_inc
= INTVAL (giv_inc
);
1540 /* Scale this_giv_inc if the multiplicative factors of
1541 the two givs are different. */
1542 if (tv
->mult_val
!= v
->mult_val
)
1543 this_giv_inc
= (this_giv_inc
/ INTVAL (v
->mult_val
)
1544 * INTVAL (tv
->mult_val
));
1546 tv
->dest_reg
= plus_constant (tv
->dest_reg
, this_giv_inc
);
1547 *tv
->location
= tv
->dest_reg
;
1549 if (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)
1551 /* Must emit an insn to increment the split address
1552 giv. Add in the const_adjust field in case there
1553 was a constant eliminated from the address. */
1554 rtx value
, dest_reg
;
1556 /* tv->dest_reg will be either a bare register,
1557 or else a register plus a constant. */
1558 if (GET_CODE (tv
->dest_reg
) == REG
)
1559 dest_reg
= tv
->dest_reg
;
1561 dest_reg
= XEXP (tv
->dest_reg
, 0);
1563 /* tv->dest_reg may actually be a (PLUS (REG) (CONST))
1564 here, so we must call plus_constant to add
1565 the const_adjust amount before calling
1566 emit_unrolled_add below. */
1567 value
= plus_constant (tv
->dest_reg
, tv
->const_adjust
);
1569 /* The constant could be too large for an add
1570 immediate, so can't directly emit an insn here. */
1571 emit_unrolled_add (dest_reg
, XEXP (value
, 0),
1574 /* Reset the giv to be just the register again, in case
1575 it is used after the set we have just emitted.
1576 We must subtract the const_adjust factor added in
1578 tv
->dest_reg
= plus_constant (dest_reg
,
1579 - tv
->const_adjust
);
1580 *tv
->location
= tv
->dest_reg
;
1585 /* If this is a setting of a splittable variable, then determine
1586 how to split the variable, create a new set based on this split,
1587 and set up the reg_map so that later uses of the variable will
1588 use the new split variable. */
1590 dest_reg_was_split
= 0;
1592 if (GET_CODE (pattern
) == SET
1593 && GET_CODE (SET_DEST (pattern
)) == REG
1594 && splittable_regs
[REGNO (SET_DEST (pattern
))])
1596 int regno
= REGNO (SET_DEST (pattern
));
1598 dest_reg_was_split
= 1;
1600 /* Compute the increment value for the giv, if it wasn't
1601 already computed above. */
1604 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1605 giv_dest_reg
= SET_DEST (pattern
);
1606 giv_src_reg
= SET_DEST (pattern
);
1608 if (unroll_type
== UNROLL_COMPLETELY
)
1610 /* Completely unrolling the loop. Set the induction
1611 variable to a known constant value. */
1613 /* The value in splittable_regs may be an invariant
1614 value, so we must use plus_constant here. */
1615 splittable_regs
[regno
]
1616 = plus_constant (splittable_regs
[regno
], INTVAL (giv_inc
));
1618 if (GET_CODE (splittable_regs
[regno
]) == PLUS
)
1620 giv_src_reg
= XEXP (splittable_regs
[regno
], 0);
1621 giv_inc
= XEXP (splittable_regs
[regno
], 1);
1625 /* The splittable_regs value must be a REG or a
1626 CONST_INT, so put the entire value in the giv_src_reg
1628 giv_src_reg
= splittable_regs
[regno
];
1629 giv_inc
= const0_rtx
;
1634 /* Partially unrolling loop. Create a new pseudo
1635 register for the iteration variable, and set it to
1636 be a constant plus the original register. Except
1637 on the last iteration, when the result has to
1638 go back into the original iteration var register. */
1640 /* Handle bivs which must be mapped to a new register
1641 when split. This happens for bivs which need their
1642 final value set before loop entry. The new register
1643 for the biv was stored in the biv's first struct
1644 induction entry by find_splittable_regs. */
1646 if (regno
< max_reg_before_loop
1647 && reg_iv_type
[regno
] == BASIC_INDUCT
)
1649 giv_src_reg
= reg_biv_class
[regno
]->biv
->src_reg
;
1650 giv_dest_reg
= giv_src_reg
;
1654 /* If non-reduced/final-value givs were split, then
1655 this would have to remap those givs also. See
1656 find_splittable_regs. */
1659 splittable_regs
[regno
]
1660 = GEN_INT (INTVAL (giv_inc
)
1661 + INTVAL (splittable_regs
[regno
]));
1662 giv_inc
= splittable_regs
[regno
];
1664 /* Now split the induction variable by changing the dest
1665 of this insn to a new register, and setting its
1666 reg_map entry to point to this new register.
1668 If this is the last iteration, and this is the last insn
1669 that will update the iv, then reuse the original dest,
1670 to ensure that the iv will have the proper value when
1671 the loop exits or repeats.
1673 Using splittable_regs_updates here like this is safe,
1674 because it can only be greater than one if all
1675 instructions modifying the iv are always executed in
1678 if (! last_iteration
1679 || (splittable_regs_updates
[regno
]-- != 1))
1681 tem
= gen_reg_rtx (GET_MODE (giv_src_reg
));
1683 map
->reg_map
[regno
] = tem
;
1686 map
->reg_map
[regno
] = giv_src_reg
;
1689 /* The constant being added could be too large for an add
1690 immediate, so can't directly emit an insn here. */
1691 emit_unrolled_add (giv_dest_reg
, giv_src_reg
, giv_inc
);
1692 copy
= get_last_insn ();
1693 pattern
= PATTERN (copy
);
1697 pattern
= copy_rtx_and_substitute (pattern
, map
);
1698 copy
= emit_insn (pattern
);
1700 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1703 /* If this insn is setting CC0, it may need to look at
1704 the insn that uses CC0 to see what type of insn it is.
1705 In that case, the call to recog via validate_change will
1706 fail. So don't substitute constants here. Instead,
1707 do it when we emit the following insn.
1709 For example, see the pyr.md file. That machine has signed and
1710 unsigned compares. The compare patterns must check the
1711 following branch insn to see which what kind of compare to
1714 If the previous insn set CC0, substitute constants on it as
1716 if (sets_cc0_p (copy
) != 0)
1721 try_constants (cc0_insn
, map
);
1723 try_constants (copy
, map
);
1726 try_constants (copy
, map
);
1729 /* Make split induction variable constants `permanent' since we
1730 know there are no backward branches across iteration variable
1731 settings which would invalidate this. */
1732 if (dest_reg_was_split
)
1734 int regno
= REGNO (SET_DEST (pattern
));
1736 if (regno
< map
->const_equiv_map_size
1737 && map
->const_age_map
[regno
] == map
->const_age
)
1738 map
->const_age_map
[regno
] = -1;
1743 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1744 copy
= emit_jump_insn (pattern
);
1745 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1747 if (JUMP_LABEL (insn
) == start_label
&& insn
== copy_end
1748 && ! last_iteration
)
1750 /* This is a branch to the beginning of the loop; this is the
1751 last insn being copied; and this is not the last iteration.
1752 In this case, we want to change the original fall through
1753 case to be a branch past the end of the loop, and the
1754 original jump label case to fall_through. */
1756 if (! invert_exp (pattern
, copy
)
1757 || ! redirect_exp (&pattern
,
1758 map
->label_map
[CODE_LABEL_NUMBER
1759 (JUMP_LABEL (insn
))],
1766 try_constants (cc0_insn
, map
);
1769 try_constants (copy
, map
);
1771 /* Set the jump label of COPY correctly to avoid problems with
1772 later passes of unroll_loop, if INSN had jump label set. */
1773 if (JUMP_LABEL (insn
))
1777 /* Can't use the label_map for every insn, since this may be
1778 the backward branch, and hence the label was not mapped. */
1779 if (GET_CODE (pattern
) == SET
)
1781 tem
= SET_SRC (pattern
);
1782 if (GET_CODE (tem
) == LABEL_REF
)
1783 label
= XEXP (tem
, 0);
1784 else if (GET_CODE (tem
) == IF_THEN_ELSE
)
1786 if (XEXP (tem
, 1) != pc_rtx
)
1787 label
= XEXP (XEXP (tem
, 1), 0);
1789 label
= XEXP (XEXP (tem
, 2), 0);
1793 if (label
&& GET_CODE (label
) == CODE_LABEL
)
1794 JUMP_LABEL (copy
) = label
;
1797 /* An unrecognizable jump insn, probably the entry jump
1798 for a switch statement. This label must have been mapped,
1799 so just use the label_map to get the new jump label. */
1800 JUMP_LABEL (copy
) = map
->label_map
[CODE_LABEL_NUMBER
1801 (JUMP_LABEL (insn
))];
1804 /* If this is a non-local jump, then must increase the label
1805 use count so that the label will not be deleted when the
1806 original jump is deleted. */
1807 LABEL_NUSES (JUMP_LABEL (copy
))++;
1809 else if (GET_CODE (PATTERN (copy
)) == ADDR_VEC
1810 || GET_CODE (PATTERN (copy
)) == ADDR_DIFF_VEC
)
1812 rtx pat
= PATTERN (copy
);
1813 int diff_vec_p
= GET_CODE (pat
) == ADDR_DIFF_VEC
;
1814 int len
= XVECLEN (pat
, diff_vec_p
);
1817 for (i
= 0; i
< len
; i
++)
1818 LABEL_NUSES (XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0))++;
1821 /* If this used to be a conditional jump insn but whose branch
1822 direction is now known, we must do something special. */
1823 if (condjump_p (insn
) && !simplejump_p (insn
) && map
->last_pc_value
)
1826 /* The previous insn set cc0 for us. So delete it. */
1827 delete_insn (PREV_INSN (copy
));
1830 /* If this is now a no-op, delete it. */
1831 if (map
->last_pc_value
== pc_rtx
)
1837 /* Otherwise, this is unconditional jump so we must put a
1838 BARRIER after it. We could do some dead code elimination
1839 here, but jump.c will do it just as well. */
1845 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1846 copy
= emit_call_insn (pattern
);
1847 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1851 try_constants (cc0_insn
, map
);
1854 try_constants (copy
, map
);
1856 /* Be lazy and assume CALL_INSNs clobber all hard registers. */
1857 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
1858 map
->const_equiv_map
[i
] = 0;
1862 /* If this is the loop start label, then we don't need to emit a
1863 copy of this label since no one will use it. */
1865 if (insn
!= start_label
)
1867 copy
= emit_label (map
->label_map
[CODE_LABEL_NUMBER (insn
)]);
1873 copy
= emit_barrier ();
1877 /* VTOP notes are valid only before the loop exit test. If placed
1878 anywhere else, loop may generate bad code. */
1880 if (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
1881 && (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_LOOP_VTOP
1882 || (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)))
1883 copy
= emit_note (NOTE_SOURCE_FILE (insn
),
1884 NOTE_LINE_NUMBER (insn
));
1894 map
->insn_map
[INSN_UID (insn
)] = copy
;
1896 while (insn
!= copy_end
);
1898 /* Now finish coping the REG_NOTES. */
1902 insn
= NEXT_INSN (insn
);
1903 if ((GET_CODE (insn
) == INSN
|| GET_CODE (insn
) == JUMP_INSN
1904 || GET_CODE (insn
) == CALL_INSN
)
1905 && map
->insn_map
[INSN_UID (insn
)])
1906 final_reg_note_copy (REG_NOTES (map
->insn_map
[INSN_UID (insn
)]), map
);
1908 while (insn
!= copy_end
);
1910 /* There may be notes between copy_notes_from and loop_end. Emit a copy of
1911 each of these notes here, since there may be some important ones, such as
1912 NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
1913 iteration, because the original notes won't be deleted.
1915 We can't use insert_before here, because when from preconditioning,
1916 insert_before points before the loop. We can't use copy_end, because
1917 there may be insns already inserted after it (which we don't want to
1918 copy) when not from preconditioning code. */
1920 if (! last_iteration
)
1922 for (insn
= copy_notes_from
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
1924 if (GET_CODE (insn
) == NOTE
1925 && NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
)
1926 emit_note (NOTE_SOURCE_FILE (insn
), NOTE_LINE_NUMBER (insn
));
1930 if (final_label
&& LABEL_NUSES (final_label
) > 0)
1931 emit_label (final_label
);
1933 tem
= gen_sequence ();
1935 emit_insn_before (tem
, insert_before
);
1938 /* Emit an insn, using the expand_binop to ensure that a valid insn is
1939 emitted. This will correctly handle the case where the increment value
1940 won't fit in the immediate field of a PLUS insns. */
1943 emit_unrolled_add (dest_reg
, src_reg
, increment
)
1944 rtx dest_reg
, src_reg
, increment
;
1948 result
= expand_binop (GET_MODE (dest_reg
), add_optab
, src_reg
, increment
,
1949 dest_reg
, 0, OPTAB_LIB_WIDEN
);
1951 if (dest_reg
!= result
)
1952 emit_move_insn (dest_reg
, result
);
1955 /* Searches the insns between INSN and LOOP_END. Returns 1 if there
1956 is a backward branch in that range that branches to somewhere between
1957 LOOP_START and INSN. Returns 0 otherwise. */
1959 /* ??? This is quadratic algorithm. Could be rewritten to be linear.
1960 In practice, this is not a problem, because this function is seldom called,
1961 and uses a negligible amount of CPU time on average. */
1964 back_branch_in_range_p (insn
, loop_start
, loop_end
)
1966 rtx loop_start
, loop_end
;
1968 rtx p
, q
, target_insn
;
1970 /* Stop before we get to the backward branch at the end of the loop. */
1971 loop_end
= prev_nonnote_insn (loop_end
);
1972 if (GET_CODE (loop_end
) == BARRIER
)
1973 loop_end
= PREV_INSN (loop_end
);
1975 /* Check in case insn has been deleted, search forward for first non
1976 deleted insn following it. */
1977 while (INSN_DELETED_P (insn
))
1978 insn
= NEXT_INSN (insn
);
1980 /* Check for the case where insn is the last insn in the loop. */
1981 if (insn
== loop_end
)
1984 for (p
= NEXT_INSN (insn
); p
!= loop_end
; p
= NEXT_INSN (p
))
1986 if (GET_CODE (p
) == JUMP_INSN
)
1988 target_insn
= JUMP_LABEL (p
);
1990 /* Search from loop_start to insn, to see if one of them is
1991 the target_insn. We can't use INSN_LUID comparisons here,
1992 since insn may not have an LUID entry. */
1993 for (q
= loop_start
; q
!= insn
; q
= NEXT_INSN (q
))
1994 if (q
== target_insn
)
2002 /* Try to generate the simplest rtx for the expression
2003 (PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
2007 fold_rtx_mult_add (mult1
, mult2
, add1
, mode
)
2008 rtx mult1
, mult2
, add1
;
2009 enum machine_mode mode
;
2014 /* The modes must all be the same. This should always be true. For now,
2015 check to make sure. */
2016 if ((GET_MODE (mult1
) != mode
&& GET_MODE (mult1
) != VOIDmode
)
2017 || (GET_MODE (mult2
) != mode
&& GET_MODE (mult2
) != VOIDmode
)
2018 || (GET_MODE (add1
) != mode
&& GET_MODE (add1
) != VOIDmode
))
2021 /* Ensure that if at least one of mult1/mult2 are constant, then mult2
2022 will be a constant. */
2023 if (GET_CODE (mult1
) == CONST_INT
)
2030 mult_res
= simplify_binary_operation (MULT
, mode
, mult1
, mult2
);
2032 mult_res
= gen_rtx (MULT
, mode
, mult1
, mult2
);
2034 /* Again, put the constant second. */
2035 if (GET_CODE (add1
) == CONST_INT
)
2042 result
= simplify_binary_operation (PLUS
, mode
, add1
, mult_res
);
2044 result
= gen_rtx (PLUS
, mode
, add1
, mult_res
);
2049 /* Searches the list of induction struct's for the biv BL, to try to calculate
2050 the total increment value for one iteration of the loop as a constant.
2052 Returns the increment value as an rtx, simplified as much as possible,
2053 if it can be calculated. Otherwise, returns 0. */
2056 biv_total_increment (bl
, loop_start
, loop_end
)
2057 struct iv_class
*bl
;
2058 rtx loop_start
, loop_end
;
2060 struct induction
*v
;
2063 /* For increment, must check every instruction that sets it. Each
2064 instruction must be executed only once each time through the loop.
2065 To verify this, we check that the the insn is always executed, and that
2066 there are no backward branches after the insn that branch to before it.
2067 Also, the insn must have a mult_val of one (to make sure it really is
2070 result
= const0_rtx
;
2071 for (v
= bl
->biv
; v
; v
= v
->next_iv
)
2073 if (v
->always_computable
&& v
->mult_val
== const1_rtx
2074 && ! back_branch_in_range_p (v
->insn
, loop_start
, loop_end
))
2075 result
= fold_rtx_mult_add (result
, const1_rtx
, v
->add_val
, v
->mode
);
2083 /* Determine the initial value of the iteration variable, and the amount
2084 that it is incremented each loop. Use the tables constructed by
2085 the strength reduction pass to calculate these values.
2087 Initial_value and/or increment are set to zero if their values could not
2091 iteration_info (iteration_var
, initial_value
, increment
, loop_start
, loop_end
)
2092 rtx iteration_var
, *initial_value
, *increment
;
2093 rtx loop_start
, loop_end
;
2095 struct iv_class
*bl
;
2096 struct induction
*v
, *b
;
2098 /* Clear the result values, in case no answer can be found. */
2102 /* The iteration variable can be either a giv or a biv. Check to see
2103 which it is, and compute the variable's initial value, and increment
2104 value if possible. */
2106 /* If this is a new register, can't handle it since we don't have any
2107 reg_iv_type entry for it. */
2108 if (REGNO (iteration_var
) >= max_reg_before_loop
)
2110 if (loop_dump_stream
)
2111 fprintf (loop_dump_stream
,
2112 "Loop unrolling: No reg_iv_type entry for iteration var.\n");
2115 /* Reject iteration variables larger than the host long size, since they
2116 could result in a number of iterations greater than the range of our
2117 `unsigned long' variable loop_n_iterations. */
2118 else if (GET_MODE_BITSIZE (GET_MODE (iteration_var
)) > HOST_BITS_PER_LONG
)
2120 if (loop_dump_stream
)
2121 fprintf (loop_dump_stream
,
2122 "Loop unrolling: Iteration var rejected because mode larger than host long.\n");
2125 else if (GET_MODE_CLASS (GET_MODE (iteration_var
)) != MODE_INT
)
2127 if (loop_dump_stream
)
2128 fprintf (loop_dump_stream
,
2129 "Loop unrolling: Iteration var not an integer.\n");
2132 else if (reg_iv_type
[REGNO (iteration_var
)] == BASIC_INDUCT
)
2134 /* Grab initial value, only useful if it is a constant. */
2135 bl
= reg_biv_class
[REGNO (iteration_var
)];
2136 *initial_value
= bl
->initial_value
;
2138 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2140 else if (reg_iv_type
[REGNO (iteration_var
)] == GENERAL_INDUCT
)
2143 /* ??? The code below does not work because the incorrect number of
2144 iterations is calculated when the biv is incremented after the giv
2145 is set (which is the usual case). This can probably be accounted
2146 for by biasing the initial_value by subtracting the amount of the
2147 increment that occurs between the giv set and the giv test. However,
2148 a giv as an iterator is very rare, so it does not seem worthwhile
2150 /* ??? An example failure is: i = 6; do {;} while (i++ < 9). */
2151 if (loop_dump_stream
)
2152 fprintf (loop_dump_stream
,
2153 "Loop unrolling: Giv iterators are not handled.\n");
2156 /* Initial value is mult_val times the biv's initial value plus
2157 add_val. Only useful if it is a constant. */
2158 v
= reg_iv_info
[REGNO (iteration_var
)];
2159 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2160 *initial_value
= fold_rtx_mult_add (v
->mult_val
, bl
->initial_value
,
2161 v
->add_val
, v
->mode
);
2163 /* Increment value is mult_val times the increment value of the biv. */
2165 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2167 *increment
= fold_rtx_mult_add (v
->mult_val
, *increment
, const0_rtx
,
2173 if (loop_dump_stream
)
2174 fprintf (loop_dump_stream
,
2175 "Loop unrolling: Not basic or general induction var.\n");
2180 /* Calculate the approximate final value of the iteration variable
2181 which has an loop exit test with code COMPARISON_CODE and comparison value
2182 of COMPARISON_VALUE. Also returns an indication of whether the comparison
2183 was signed or unsigned, and the direction of the comparison. This info is
2184 needed to calculate the number of loop iterations. */
2187 approx_final_value (comparison_code
, comparison_value
, unsigned_p
, compare_dir
)
2188 enum rtx_code comparison_code
;
2189 rtx comparison_value
;
2193 /* Calculate the final value of the induction variable.
2194 The exact final value depends on the branch operator, and increment sign.
2195 This is only an approximate value. It will be wrong if the iteration
2196 variable is not incremented by one each time through the loop, and
2197 approx final value - start value % increment != 0. */
2200 switch (comparison_code
)
2206 return plus_constant (comparison_value
, 1);
2211 return plus_constant (comparison_value
, -1);
2213 /* Can not calculate a final value for this case. */
2220 return comparison_value
;
2226 return comparison_value
;
2229 return comparison_value
;
2235 /* For each biv and giv, determine whether it can be safely split into
2236 a different variable for each unrolled copy of the loop body. If it
2237 is safe to split, then indicate that by saving some useful info
2238 in the splittable_regs array.
2240 If the loop is being completely unrolled, then splittable_regs will hold
2241 the current value of the induction variable while the loop is unrolled.
2242 It must be set to the initial value of the induction variable here.
2243 Otherwise, splittable_regs will hold the difference between the current
2244 value of the induction variable and the value the induction variable had
2245 at the top of the loop. It must be set to the value 0 here.
2247 Returns the total number of instructions that set registers that are
2250 /* ?? If the loop is only unrolled twice, then most of the restrictions to
2251 constant values are unnecessary, since we can easily calculate increment
2252 values in this case even if nothing is constant. The increment value
2253 should not involve a multiply however. */
2255 /* ?? Even if the biv/giv increment values aren't constant, it may still
2256 be beneficial to split the variable if the loop is only unrolled a few
2257 times, since multiplies by small integers (1,2,3,4) are very cheap. */
2260 find_splittable_regs (unroll_type
, loop_start
, loop_end
, end_insert_before
,
2262 enum unroll_types unroll_type
;
2263 rtx loop_start
, loop_end
;
2264 rtx end_insert_before
;
2267 struct iv_class
*bl
;
2268 struct induction
*v
;
2270 rtx biv_final_value
;
2274 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
2276 /* Biv_total_increment must return a constant value,
2277 otherwise we can not calculate the split values. */
2279 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2280 if (! increment
|| GET_CODE (increment
) != CONST_INT
)
2283 /* The loop must be unrolled completely, or else have a known number
2284 of iterations and only one exit, or else the biv must be dead
2285 outside the loop, or else the final value must be known. Otherwise,
2286 it is unsafe to split the biv since it may not have the proper
2287 value on loop exit. */
2289 /* loop_number_exit_labels is non-zero if the loop has an exit other than
2290 a fall through at the end. */
2293 biv_final_value
= 0;
2294 if (unroll_type
!= UNROLL_COMPLETELY
2295 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2296 || unroll_type
== UNROLL_NAIVE
)
2297 && (uid_luid
[regno_last_uid
[bl
->regno
]] >= INSN_LUID (loop_end
)
2299 || INSN_UID (bl
->init_insn
) >= max_uid_for_loop
2300 || (uid_luid
[regno_first_uid
[bl
->regno
]]
2301 < INSN_LUID (bl
->init_insn
))
2302 || reg_mentioned_p (bl
->biv
->dest_reg
, SET_SRC (bl
->init_set
)))
2303 && ! (biv_final_value
= final_biv_value (bl
, loop_start
, loop_end
)))
2306 /* If any of the insns setting the BIV don't do so with a simple
2307 PLUS, we don't know how to split it. */
2308 for (v
= bl
->biv
; biv_splittable
&& v
; v
= v
->next_iv
)
2309 if ((tem
= single_set (v
->insn
)) == 0
2310 || GET_CODE (SET_DEST (tem
)) != REG
2311 || REGNO (SET_DEST (tem
)) != bl
->regno
2312 || GET_CODE (SET_SRC (tem
)) != PLUS
)
2315 /* If final value is non-zero, then must emit an instruction which sets
2316 the value of the biv to the proper value. This is done after
2317 handling all of the givs, since some of them may need to use the
2318 biv's value in their initialization code. */
2320 /* This biv is splittable. If completely unrolling the loop, save
2321 the biv's initial value. Otherwise, save the constant zero. */
2323 if (biv_splittable
== 1)
2325 if (unroll_type
== UNROLL_COMPLETELY
)
2327 /* If the initial value of the biv is itself (i.e. it is too
2328 complicated for strength_reduce to compute), or is a hard
2329 register, then we must create a new pseudo reg to hold the
2330 initial value of the biv. */
2332 if (GET_CODE (bl
->initial_value
) == REG
2333 && (REGNO (bl
->initial_value
) == bl
->regno
2334 || REGNO (bl
->initial_value
) < FIRST_PSEUDO_REGISTER
))
2336 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2338 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2341 if (loop_dump_stream
)
2342 fprintf (loop_dump_stream
, "Biv %d initial value remapped to %d.\n",
2343 bl
->regno
, REGNO (tem
));
2345 splittable_regs
[bl
->regno
] = tem
;
2348 splittable_regs
[bl
->regno
] = bl
->initial_value
;
2351 splittable_regs
[bl
->regno
] = const0_rtx
;
2353 /* Save the number of instructions that modify the biv, so that
2354 we can treat the last one specially. */
2356 splittable_regs_updates
[bl
->regno
] = bl
->biv_count
;
2357 result
+= bl
->biv_count
;
2359 if (loop_dump_stream
)
2360 fprintf (loop_dump_stream
,
2361 "Biv %d safe to split.\n", bl
->regno
);
2364 /* Check every giv that depends on this biv to see whether it is
2365 splittable also. Even if the biv isn't splittable, givs which
2366 depend on it may be splittable if the biv is live outside the
2367 loop, and the givs aren't. */
2369 result
+= find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
,
2370 increment
, unroll_number
);
2372 /* If final value is non-zero, then must emit an instruction which sets
2373 the value of the biv to the proper value. This is done after
2374 handling all of the givs, since some of them may need to use the
2375 biv's value in their initialization code. */
2376 if (biv_final_value
)
2378 /* If the loop has multiple exits, emit the insns before the
2379 loop to ensure that it will always be executed no matter
2380 how the loop exits. Otherwise emit the insn after the loop,
2381 since this is slightly more efficient. */
2382 if (! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2383 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2388 /* Create a new register to hold the value of the biv, and then
2389 set the biv to its final value before the loop start. The biv
2390 is set to its final value before loop start to ensure that
2391 this insn will always be executed, no matter how the loop
2393 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2394 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2396 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2400 if (loop_dump_stream
)
2401 fprintf (loop_dump_stream
, "Biv %d mapped to %d for split.\n",
2402 REGNO (bl
->biv
->src_reg
), REGNO (tem
));
2404 /* Set up the mapping from the original biv register to the new
2406 bl
->biv
->src_reg
= tem
;
2413 /* For every giv based on the biv BL, check to determine whether it is
2414 splittable. This is a subroutine to find_splittable_regs ().
2416 Return the number of instructions that set splittable registers. */
2419 find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
, increment
,
2421 struct iv_class
*bl
;
2422 enum unroll_types unroll_type
;
2423 rtx loop_start
, loop_end
;
2427 struct induction
*v
;
2432 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
2436 /* Only split the giv if it has already been reduced, or if the loop is
2437 being completely unrolled. */
2438 if (unroll_type
!= UNROLL_COMPLETELY
&& v
->ignore
)
2441 /* The giv can be split if the insn that sets the giv is executed once
2442 and only once on every iteration of the loop. */
2443 /* An address giv can always be split. v->insn is just a use not a set,
2444 and hence it does not matter whether it is always executed. All that
2445 matters is that all the biv increments are always executed, and we
2446 won't reach here if they aren't. */
2447 if (v
->giv_type
!= DEST_ADDR
2448 && (! v
->always_computable
2449 || back_branch_in_range_p (v
->insn
, loop_start
, loop_end
)))
2452 /* The giv increment value must be a constant. */
2453 giv_inc
= fold_rtx_mult_add (v
->mult_val
, increment
, const0_rtx
,
2455 if (! giv_inc
|| GET_CODE (giv_inc
) != CONST_INT
)
2458 /* The loop must be unrolled completely, or else have a known number of
2459 iterations and only one exit, or else the giv must be dead outside
2460 the loop, or else the final value of the giv must be known.
2461 Otherwise, it is not safe to split the giv since it may not have the
2462 proper value on loop exit. */
2464 /* The used outside loop test will fail for DEST_ADDR givs. They are
2465 never used outside the loop anyways, so it is always safe to split a
2469 if (unroll_type
!= UNROLL_COMPLETELY
2470 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2471 || unroll_type
== UNROLL_NAIVE
)
2472 && v
->giv_type
!= DEST_ADDR
2473 && ((regno_first_uid
[REGNO (v
->dest_reg
)] != INSN_UID (v
->insn
)
2474 /* Check for the case where the pseudo is set by a shift/add
2475 sequence, in which case the first insn setting the pseudo
2476 is the first insn of the shift/add sequence. */
2477 && (! (tem
= find_reg_note (v
->insn
, REG_RETVAL
, NULL_RTX
))
2478 || (regno_first_uid
[REGNO (v
->dest_reg
)]
2479 != INSN_UID (XEXP (tem
, 0)))))
2480 /* Line above always fails if INSN was moved by loop opt. */
2481 || (uid_luid
[regno_last_uid
[REGNO (v
->dest_reg
)]]
2482 >= INSN_LUID (loop_end
)))
2483 && ! (final_value
= v
->final_value
))
2487 /* Currently, non-reduced/final-value givs are never split. */
2488 /* Should emit insns after the loop if possible, as the biv final value
2491 /* If the final value is non-zero, and the giv has not been reduced,
2492 then must emit an instruction to set the final value. */
2493 if (final_value
&& !v
->new_reg
)
2495 /* Create a new register to hold the value of the giv, and then set
2496 the giv to its final value before the loop start. The giv is set
2497 to its final value before loop start to ensure that this insn
2498 will always be executed, no matter how we exit. */
2499 tem
= gen_reg_rtx (v
->mode
);
2500 emit_insn_before (gen_move_insn (tem
, v
->dest_reg
), loop_start
);
2501 emit_insn_before (gen_move_insn (v
->dest_reg
, final_value
),
2504 if (loop_dump_stream
)
2505 fprintf (loop_dump_stream
, "Giv %d mapped to %d for split.\n",
2506 REGNO (v
->dest_reg
), REGNO (tem
));
2512 /* This giv is splittable. If completely unrolling the loop, save the
2513 giv's initial value. Otherwise, save the constant zero for it. */
2515 if (unroll_type
== UNROLL_COMPLETELY
)
2517 /* It is not safe to use bl->initial_value here, because it may not
2518 be invariant. It is safe to use the initial value stored in
2519 the splittable_regs array if it is set. In rare cases, it won't
2520 be set, so then we do exactly the same thing as
2521 find_splittable_regs does to get a safe value. */
2522 rtx biv_initial_value
;
2524 if (splittable_regs
[bl
->regno
])
2525 biv_initial_value
= splittable_regs
[bl
->regno
];
2526 else if (GET_CODE (bl
->initial_value
) != REG
2527 || (REGNO (bl
->initial_value
) != bl
->regno
2528 && REGNO (bl
->initial_value
) >= FIRST_PSEUDO_REGISTER
))
2529 biv_initial_value
= bl
->initial_value
;
2532 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2534 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2536 biv_initial_value
= tem
;
2538 value
= fold_rtx_mult_add (v
->mult_val
, biv_initial_value
,
2539 v
->add_val
, v
->mode
);
2546 /* If a giv was combined with another giv, then we can only split
2547 this giv if the giv it was combined with was reduced. This
2548 is because the value of v->new_reg is meaningless in this
2550 if (v
->same
&& ! v
->same
->new_reg
)
2552 if (loop_dump_stream
)
2553 fprintf (loop_dump_stream
,
2554 "giv combined with unreduced giv not split.\n");
2557 /* If the giv is an address destination, it could be something other
2558 than a simple register, these have to be treated differently. */
2559 else if (v
->giv_type
== DEST_REG
)
2561 /* If value is not a constant, register, or register plus
2562 constant, then compute its value into a register before
2563 loop start. This prevents illegal rtx sharing, and should
2564 generate better code. We can use bl->initial_value here
2565 instead of splittable_regs[bl->regno] because this code
2566 is going before the loop start. */
2567 if (unroll_type
== UNROLL_COMPLETELY
2568 && GET_CODE (value
) != CONST_INT
2569 && GET_CODE (value
) != REG
2570 && (GET_CODE (value
) != PLUS
2571 || GET_CODE (XEXP (value
, 0)) != REG
2572 || GET_CODE (XEXP (value
, 1)) != CONST_INT
))
2574 rtx tem
= gen_reg_rtx (v
->mode
);
2575 emit_iv_add_mult (bl
->initial_value
, v
->mult_val
,
2576 v
->add_val
, tem
, loop_start
);
2580 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2584 /* Splitting address givs is useful since it will often allow us
2585 to eliminate some increment insns for the base giv as
2588 /* If the addr giv is combined with a dest_reg giv, then all
2589 references to that dest reg will be remapped, which is NOT
2590 what we want for split addr regs. We always create a new
2591 register for the split addr giv, just to be safe. */
2593 /* ??? If there are multiple address givs which have been
2594 combined with the same dest_reg giv, then we may only need
2595 one new register for them. Pulling out constants below will
2596 catch some of the common cases of this. Currently, I leave
2597 the work of simplifying multiple address givs to the
2598 following cse pass. */
2600 v
->const_adjust
= 0;
2601 if (unroll_type
!= UNROLL_COMPLETELY
)
2603 /* If not completely unrolling the loop, then create a new
2604 register to hold the split value of the DEST_ADDR giv.
2605 Emit insn to initialize its value before loop start. */
2606 tem
= gen_reg_rtx (v
->mode
);
2608 /* If the address giv has a constant in its new_reg value,
2609 then this constant can be pulled out and put in value,
2610 instead of being part of the initialization code. */
2612 if (GET_CODE (v
->new_reg
) == PLUS
2613 && GET_CODE (XEXP (v
->new_reg
, 1)) == CONST_INT
)
2616 = plus_constant (tem
, INTVAL (XEXP (v
->new_reg
,1)));
2618 /* Only succeed if this will give valid addresses.
2619 Try to validate both the first and the last
2620 address resulting from loop unrolling, if
2621 one fails, then can't do const elim here. */
2622 if (memory_address_p (v
->mem_mode
, v
->dest_reg
)
2623 && memory_address_p (v
->mem_mode
,
2624 plus_constant (v
->dest_reg
,
2626 * (unroll_number
- 1))))
2628 /* Save the negative of the eliminated const, so
2629 that we can calculate the dest_reg's increment
2631 v
->const_adjust
= - INTVAL (XEXP (v
->new_reg
, 1));
2633 v
->new_reg
= XEXP (v
->new_reg
, 0);
2634 if (loop_dump_stream
)
2635 fprintf (loop_dump_stream
,
2636 "Eliminating constant from giv %d\n",
2645 /* If the address hasn't been checked for validity yet, do so
2646 now, and fail completely if either the first or the last
2647 unrolled copy of the address is not a valid address. */
2648 if (v
->dest_reg
== tem
2649 && (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2650 || ! memory_address_p (v
->mem_mode
,
2651 plus_constant (v
->dest_reg
,
2653 * (unroll_number
-1)))))
2655 if (loop_dump_stream
)
2656 fprintf (loop_dump_stream
,
2657 "Illegal address for giv at insn %d\n",
2658 INSN_UID (v
->insn
));
2662 /* To initialize the new register, just move the value of
2663 new_reg into it. This is not guaranteed to give a valid
2664 instruction on machines with complex addressing modes.
2665 If we can't recognize it, then delete it and emit insns
2666 to calculate the value from scratch. */
2667 emit_insn_before (gen_rtx (SET
, VOIDmode
, tem
,
2668 copy_rtx (v
->new_reg
)),
2670 if (recog_memoized (PREV_INSN (loop_start
)) < 0)
2674 /* We can't use bl->initial_value to compute the initial
2675 value, because the loop may have been preconditioned.
2676 We must calculate it from NEW_REG. Try using
2677 force_operand instead of emit_iv_add_mult. */
2678 delete_insn (PREV_INSN (loop_start
));
2681 ret
= force_operand (v
->new_reg
, tem
);
2683 emit_move_insn (tem
, ret
);
2684 sequence
= gen_sequence ();
2686 emit_insn_before (sequence
, loop_start
);
2688 if (loop_dump_stream
)
2689 fprintf (loop_dump_stream
,
2690 "Illegal init insn, rewritten.\n");
2695 v
->dest_reg
= value
;
2697 /* Check the resulting address for validity, and fail
2698 if the resulting address would be illegal. */
2699 if (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2700 || ! memory_address_p (v
->mem_mode
,
2701 plus_constant (v
->dest_reg
,
2703 (unroll_number
-1))))
2705 if (loop_dump_stream
)
2706 fprintf (loop_dump_stream
,
2707 "Illegal address for giv at insn %d\n",
2708 INSN_UID (v
->insn
));
2713 /* Store the value of dest_reg into the insn. This sharing
2714 will not be a problem as this insn will always be copied
2717 *v
->location
= v
->dest_reg
;
2719 /* If this address giv is combined with a dest reg giv, then
2720 save the base giv's induction pointer so that we will be
2721 able to handle this address giv properly. The base giv
2722 itself does not have to be splittable. */
2724 if (v
->same
&& v
->same
->giv_type
== DEST_REG
)
2725 addr_combined_regs
[REGNO (v
->same
->new_reg
)] = v
->same
;
2727 if (GET_CODE (v
->new_reg
) == REG
)
2729 /* This giv maybe hasn't been combined with any others.
2730 Make sure that it's giv is marked as splittable here. */
2732 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2734 /* Make it appear to depend upon itself, so that the
2735 giv will be properly split in the main loop above. */
2739 addr_combined_regs
[REGNO (v
->new_reg
)] = v
;
2743 if (loop_dump_stream
)
2744 fprintf (loop_dump_stream
, "DEST_ADDR giv being split.\n");
2750 /* Currently, unreduced giv's can't be split. This is not too much
2751 of a problem since unreduced giv's are not live across loop
2752 iterations anyways. When unrolling a loop completely though,
2753 it makes sense to reduce&split givs when possible, as this will
2754 result in simpler instructions, and will not require that a reg
2755 be live across loop iterations. */
2757 splittable_regs
[REGNO (v
->dest_reg
)] = value
;
2758 fprintf (stderr
, "Giv %d at insn %d not reduced\n",
2759 REGNO (v
->dest_reg
), INSN_UID (v
->insn
));
2765 /* Givs are only updated once by definition. Mark it so if this is
2766 a splittable register. Don't need to do anything for address givs
2767 where this may not be a register. */
2769 if (GET_CODE (v
->new_reg
) == REG
)
2770 splittable_regs_updates
[REGNO (v
->new_reg
)] = 1;
2774 if (loop_dump_stream
)
2778 if (GET_CODE (v
->dest_reg
) == CONST_INT
)
2780 else if (GET_CODE (v
->dest_reg
) != REG
)
2781 regnum
= REGNO (XEXP (v
->dest_reg
, 0));
2783 regnum
= REGNO (v
->dest_reg
);
2784 fprintf (loop_dump_stream
, "Giv %d at insn %d safe to split.\n",
2785 regnum
, INSN_UID (v
->insn
));
2792 /* Try to prove that the register is dead after the loop exits. Trace every
2793 loop exit looking for an insn that will always be executed, which sets
2794 the register to some value, and appears before the first use of the register
2795 is found. If successful, then return 1, otherwise return 0. */
2797 /* ?? Could be made more intelligent in the handling of jumps, so that
2798 it can search past if statements and other similar structures. */
2801 reg_dead_after_loop (reg
, loop_start
, loop_end
)
2802 rtx reg
, loop_start
, loop_end
;
2808 /* HACK: Must also search the loop fall through exit, create a label_ref
2809 here which points to the loop_end, and append the loop_number_exit_labels
2811 label
= gen_rtx (LABEL_REF
, VOIDmode
, loop_end
);
2812 LABEL_NEXTREF (label
)
2813 = loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]];
2815 for ( ; label
; label
= LABEL_NEXTREF (label
))
2817 /* Succeed if find an insn which sets the biv or if reach end of
2818 function. Fail if find an insn that uses the biv, or if come to
2819 a conditional jump. */
2821 insn
= NEXT_INSN (XEXP (label
, 0));
2824 code
= GET_CODE (insn
);
2825 if (GET_RTX_CLASS (code
) == 'i')
2829 if (reg_referenced_p (reg
, PATTERN (insn
)))
2832 set
= single_set (insn
);
2833 if (set
&& rtx_equal_p (SET_DEST (set
), reg
))
2837 if (code
== JUMP_INSN
)
2839 if (GET_CODE (PATTERN (insn
)) == RETURN
)
2841 else if (! simplejump_p (insn
)
2842 /* Prevent infinite loop following infinite loops. */
2843 || jump_count
++ > 20)
2846 insn
= JUMP_LABEL (insn
);
2849 insn
= NEXT_INSN (insn
);
2853 /* Success, the register is dead on all loop exits. */
2857 /* Try to calculate the final value of the biv, the value it will have at
2858 the end of the loop. If we can do it, return that value. */
2861 final_biv_value (bl
, loop_start
, loop_end
)
2862 struct iv_class
*bl
;
2863 rtx loop_start
, loop_end
;
2867 /* ??? This only works for MODE_INT biv's. Reject all others for now. */
2869 if (GET_MODE_CLASS (bl
->biv
->mode
) != MODE_INT
)
2872 /* The final value for reversed bivs must be calculated differently than
2873 for ordinary bivs. In this case, there is already an insn after the
2874 loop which sets this biv's final value (if necessary), and there are
2875 no other loop exits, so we can return any value. */
2878 if (loop_dump_stream
)
2879 fprintf (loop_dump_stream
,
2880 "Final biv value for %d, reversed biv.\n", bl
->regno
);
2885 /* Try to calculate the final value as initial value + (number of iterations
2886 * increment). For this to work, increment must be invariant, the only
2887 exit from the loop must be the fall through at the bottom (otherwise
2888 it may not have its final value when the loop exits), and the initial
2889 value of the biv must be invariant. */
2891 if (loop_n_iterations
!= 0
2892 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2893 && invariant_p (bl
->initial_value
))
2895 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2897 if (increment
&& invariant_p (increment
))
2899 /* Can calculate the loop exit value, emit insns after loop
2900 end to calculate this value into a temporary register in
2901 case it is needed later. */
2903 tem
= gen_reg_rtx (bl
->biv
->mode
);
2904 /* Make sure loop_end is not the last insn. */
2905 if (NEXT_INSN (loop_end
) == 0)
2906 emit_note_after (NOTE_INSN_DELETED
, loop_end
);
2907 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2908 bl
->initial_value
, tem
, NEXT_INSN (loop_end
));
2910 if (loop_dump_stream
)
2911 fprintf (loop_dump_stream
,
2912 "Final biv value for %d, calculated.\n", bl
->regno
);
2918 /* Check to see if the biv is dead at all loop exits. */
2919 if (reg_dead_after_loop (bl
->biv
->src_reg
, loop_start
, loop_end
))
2921 if (loop_dump_stream
)
2922 fprintf (loop_dump_stream
,
2923 "Final biv value for %d, biv dead after loop exit.\n",
2932 /* Try to calculate the final value of the giv, the value it will have at
2933 the end of the loop. If we can do it, return that value. */
2936 final_giv_value (v
, loop_start
, loop_end
)
2937 struct induction
*v
;
2938 rtx loop_start
, loop_end
;
2940 struct iv_class
*bl
;
2944 rtx insert_before
, seq
;
2946 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2948 /* The final value for givs which depend on reversed bivs must be calculated
2949 differently than for ordinary givs. In this case, there is already an
2950 insn after the loop which sets this giv's final value (if necessary),
2951 and there are no other loop exits, so we can return any value. */
2954 if (loop_dump_stream
)
2955 fprintf (loop_dump_stream
,
2956 "Final giv value for %d, depends on reversed biv\n",
2957 REGNO (v
->dest_reg
));
2961 /* Try to calculate the final value as a function of the biv it depends
2962 upon. The only exit from the loop must be the fall through at the bottom
2963 (otherwise it may not have its final value when the loop exits). */
2965 /* ??? Can calculate the final giv value by subtracting off the
2966 extra biv increments times the giv's mult_val. The loop must have
2967 only one exit for this to work, but the loop iterations does not need
2970 if (loop_n_iterations
!= 0
2971 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2973 /* ?? It is tempting to use the biv's value here since these insns will
2974 be put after the loop, and hence the biv will have its final value
2975 then. However, this fails if the biv is subsequently eliminated.
2976 Perhaps determine whether biv's are eliminable before trying to
2977 determine whether giv's are replaceable so that we can use the
2978 biv value here if it is not eliminable. */
2980 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2982 if (increment
&& invariant_p (increment
))
2984 /* Can calculate the loop exit value of its biv as
2985 (loop_n_iterations * increment) + initial_value */
2987 /* The loop exit value of the giv is then
2988 (final_biv_value - extra increments) * mult_val + add_val.
2989 The extra increments are any increments to the biv which
2990 occur in the loop after the giv's value is calculated.
2991 We must search from the insn that sets the giv to the end
2992 of the loop to calculate this value. */
2994 insert_before
= NEXT_INSN (loop_end
);
2996 /* Put the final biv value in tem. */
2997 tem
= gen_reg_rtx (bl
->biv
->mode
);
2998 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2999 bl
->initial_value
, tem
, insert_before
);
3001 /* Subtract off extra increments as we find them. */
3002 for (insn
= NEXT_INSN (v
->insn
); insn
!= loop_end
;
3003 insn
= NEXT_INSN (insn
))
3005 struct induction
*biv
;
3007 for (biv
= bl
->biv
; biv
; biv
= biv
->next_iv
)
3008 if (biv
->insn
== insn
)
3011 tem
= expand_binop (GET_MODE (tem
), sub_optab
, tem
,
3012 biv
->add_val
, NULL_RTX
, 0,
3014 seq
= gen_sequence ();
3016 emit_insn_before (seq
, insert_before
);
3020 /* Now calculate the giv's final value. */
3021 emit_iv_add_mult (tem
, v
->mult_val
, v
->add_val
, tem
,
3024 if (loop_dump_stream
)
3025 fprintf (loop_dump_stream
,
3026 "Final giv value for %d, calc from biv's value.\n",
3027 REGNO (v
->dest_reg
));
3033 /* Replaceable giv's should never reach here. */
3037 /* Check to see if the biv is dead at all loop exits. */
3038 if (reg_dead_after_loop (v
->dest_reg
, loop_start
, loop_end
))
3040 if (loop_dump_stream
)
3041 fprintf (loop_dump_stream
,
3042 "Final giv value for %d, giv dead after loop exit.\n",
3043 REGNO (v
->dest_reg
));
3052 /* Calculate the number of loop iterations. Returns the exact number of loop
3053 iterations if it can be calculated, otherwise returns zero. */
3055 unsigned HOST_WIDE_INT
3056 loop_iterations (loop_start
, loop_end
)
3057 rtx loop_start
, loop_end
;
3059 rtx comparison
, comparison_value
;
3060 rtx iteration_var
, initial_value
, increment
, final_value
;
3061 enum rtx_code comparison_code
;
3064 int unsigned_compare
, compare_dir
, final_larger
;
3065 unsigned long tempu
;
3068 /* First find the iteration variable. If the last insn is a conditional
3069 branch, and the insn before tests a register value, make that the
3070 iteration variable. */
3072 loop_initial_value
= 0;
3074 loop_final_value
= 0;
3075 loop_iteration_var
= 0;
3077 last_loop_insn
= prev_nonnote_insn (loop_end
);
3079 comparison
= get_condition_for_loop (last_loop_insn
);
3080 if (comparison
== 0)
3082 if (loop_dump_stream
)
3083 fprintf (loop_dump_stream
,
3084 "Loop unrolling: No final conditional branch found.\n");
3088 /* ??? Get_condition may switch position of induction variable and
3089 invariant register when it canonicalizes the comparison. */
3091 comparison_code
= GET_CODE (comparison
);
3092 iteration_var
= XEXP (comparison
, 0);
3093 comparison_value
= XEXP (comparison
, 1);
3095 if (GET_CODE (iteration_var
) != REG
)
3097 if (loop_dump_stream
)
3098 fprintf (loop_dump_stream
,
3099 "Loop unrolling: Comparison not against register.\n");
3103 /* Loop iterations is always called before any new registers are created
3104 now, so this should never occur. */
3106 if (REGNO (iteration_var
) >= max_reg_before_loop
)
3109 iteration_info (iteration_var
, &initial_value
, &increment
,
3110 loop_start
, loop_end
);
3111 if (initial_value
== 0)
3112 /* iteration_info already printed a message. */
3117 if (loop_dump_stream
)
3118 fprintf (loop_dump_stream
,
3119 "Loop unrolling: Increment value can't be calculated.\n");
3122 if (GET_CODE (increment
) != CONST_INT
)
3124 if (loop_dump_stream
)
3125 fprintf (loop_dump_stream
,
3126 "Loop unrolling: Increment value not constant.\n");
3129 if (GET_CODE (initial_value
) != CONST_INT
)
3131 if (loop_dump_stream
)
3132 fprintf (loop_dump_stream
,
3133 "Loop unrolling: Initial value not constant.\n");
3137 /* If the comparison value is an invariant register, then try to find
3138 its value from the insns before the start of the loop. */
3140 if (GET_CODE (comparison_value
) == REG
&& invariant_p (comparison_value
))
3144 for (insn
= PREV_INSN (loop_start
); insn
; insn
= PREV_INSN (insn
))
3146 if (GET_CODE (insn
) == CODE_LABEL
)
3149 else if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i'
3150 && reg_set_p (comparison_value
, insn
))
3152 /* We found the last insn before the loop that sets the register.
3153 If it sets the entire register, and has a REG_EQUAL note,
3154 then use the value of the REG_EQUAL note. */
3155 if ((set
= single_set (insn
))
3156 && (SET_DEST (set
) == comparison_value
))
3158 rtx note
= find_reg_note (insn
, REG_EQUAL
, NULL_RTX
);
3160 if (note
&& GET_CODE (XEXP (note
, 0)) != EXPR_LIST
)
3161 comparison_value
= XEXP (note
, 0);
3168 final_value
= approx_final_value (comparison_code
, comparison_value
,
3169 &unsigned_compare
, &compare_dir
);
3171 /* Save the calculated values describing this loop's bounds, in case
3172 precondition_loop_p will need them later. These values can not be
3173 recalculated inside precondition_loop_p because strength reduction
3174 optimizations may obscure the loop's structure. */
3176 loop_iteration_var
= iteration_var
;
3177 loop_initial_value
= initial_value
;
3178 loop_increment
= increment
;
3179 loop_final_value
= final_value
;
3181 if (final_value
== 0)
3183 if (loop_dump_stream
)
3184 fprintf (loop_dump_stream
,
3185 "Loop unrolling: EQ comparison loop.\n");
3188 else if (GET_CODE (final_value
) != CONST_INT
)
3190 if (loop_dump_stream
)
3191 fprintf (loop_dump_stream
,
3192 "Loop unrolling: Final value not constant.\n");
3196 /* ?? Final value and initial value do not have to be constants.
3197 Only their difference has to be constant. When the iteration variable
3198 is an array address, the final value and initial value might both
3199 be addresses with the same base but different constant offsets.
3200 Final value must be invariant for this to work.
3202 To do this, need some way to find the values of registers which are
3205 /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
3206 if (unsigned_compare
)
3208 = ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3209 > (unsigned HOST_WIDE_INT
) INTVAL (initial_value
))
3210 - ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3211 < (unsigned HOST_WIDE_INT
) INTVAL (initial_value
));
3213 final_larger
= (INTVAL (final_value
) > INTVAL (initial_value
))
3214 - (INTVAL (final_value
) < INTVAL (initial_value
));
3216 if (INTVAL (increment
) > 0)
3218 else if (INTVAL (increment
) == 0)
3223 /* There are 27 different cases: compare_dir = -1, 0, 1;
3224 final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
3225 There are 4 normal cases, 4 reverse cases (where the iteration variable
3226 will overflow before the loop exits), 4 infinite loop cases, and 15
3227 immediate exit (0 or 1 iteration depending on loop type) cases.
3228 Only try to optimize the normal cases. */
3230 /* (compare_dir/final_larger/increment_dir)
3231 Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
3232 Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
3233 Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
3234 Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
3236 /* ?? If the meaning of reverse loops (where the iteration variable
3237 will overflow before the loop exits) is undefined, then could
3238 eliminate all of these special checks, and just always assume
3239 the loops are normal/immediate/infinite. Note that this means
3240 the sign of increment_dir does not have to be known. Also,
3241 since it does not really hurt if immediate exit loops or infinite loops
3242 are optimized, then that case could be ignored also, and hence all
3243 loops can be optimized.
3245 According to ANSI Spec, the reverse loop case result is undefined,
3246 because the action on overflow is undefined.
3248 See also the special test for NE loops below. */
3250 if (final_larger
== increment_dir
&& final_larger
!= 0
3251 && (final_larger
== compare_dir
|| compare_dir
== 0))
3256 if (loop_dump_stream
)
3257 fprintf (loop_dump_stream
,
3258 "Loop unrolling: Not normal loop.\n");
3262 /* Calculate the number of iterations, final_value is only an approximation,
3263 so correct for that. Note that tempu and loop_n_iterations are
3264 unsigned, because they can be as large as 2^n - 1. */
3266 i
= INTVAL (increment
);
3268 tempu
= INTVAL (final_value
) - INTVAL (initial_value
);
3271 tempu
= INTVAL (initial_value
) - INTVAL (final_value
);
3277 /* For NE tests, make sure that the iteration variable won't miss the
3278 final value. If tempu mod i is not zero, then the iteration variable
3279 will overflow before the loop exits, and we can not calculate the
3280 number of iterations. */
3281 if (compare_dir
== 0 && (tempu
% i
) != 0)
3284 return tempu
/ i
+ ((tempu
% i
) != 0);