1 /* Try to unroll loops, and split induction variables.
2 Copyright (C) 1992 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");
604 if (unroll_type
== UNROLL_NAIVE
605 && GET_CODE (last_loop_insn
) == BARRIER
606 && start_label
!= JUMP_LABEL (PREV_INSN (last_loop_insn
)))
608 /* In this case, we must copy the jump and barrier, because they will
609 not be converted to jumps to an immediately following label. */
611 insert_before
= NEXT_INSN (last_loop_insn
);
612 copy_end
= last_loop_insn
;
615 /* Allocate a translation table for the labels and insn numbers.
616 They will be filled in as we copy the insns in the loop. */
618 max_labelno
= max_label_num ();
619 max_insnno
= get_max_uid ();
621 map
= (struct inline_remap
*) alloca (sizeof (struct inline_remap
));
623 map
->integrating
= 0;
625 /* Allocate the label map. */
629 map
->label_map
= (rtx
*) alloca (max_labelno
* sizeof (rtx
));
631 local_label
= (char *) alloca (max_labelno
);
632 bzero (local_label
, max_labelno
);
637 /* Search the loop and mark all local labels, i.e. the ones which have to
638 be distinct labels when copied. For all labels which might be
639 non-local, set their label_map entries to point to themselves.
640 If they happen to be local their label_map entries will be overwritten
641 before the loop body is copied. The label_map entries for local labels
642 will be set to a different value each time the loop body is copied. */
644 for (insn
= copy_start
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
646 if (GET_CODE (insn
) == CODE_LABEL
)
647 local_label
[CODE_LABEL_NUMBER (insn
)] = 1;
648 else if (GET_CODE (insn
) == JUMP_INSN
)
650 if (JUMP_LABEL (insn
))
651 map
->label_map
[CODE_LABEL_NUMBER (JUMP_LABEL (insn
))]
653 else if (GET_CODE (PATTERN (insn
)) == ADDR_VEC
654 || GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
)
656 rtx pat
= PATTERN (insn
);
657 int diff_vec_p
= GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
;
658 int len
= XVECLEN (pat
, diff_vec_p
);
661 for (i
= 0; i
< len
; i
++)
663 label
= XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0);
664 map
->label_map
[CODE_LABEL_NUMBER (label
)] = label
;
670 /* Allocate space for the insn map. */
672 map
->insn_map
= (rtx
*) alloca (max_insnno
* sizeof (rtx
));
674 /* Set this to zero, to indicate that we are doing loop unrolling,
675 not function inlining. */
676 map
->inline_target
= 0;
678 /* The register and constant maps depend on the number of registers
679 present, so the final maps can't be created until after
680 find_splittable_regs is called. However, they are needed for
681 preconditioning, so we create temporary maps when preconditioning
684 /* The preconditioning code may allocate two new pseudo registers. */
685 maxregnum
= max_reg_num ();
687 /* Allocate and zero out the splittable_regs and addr_combined_regs
688 arrays. These must be zeroed here because they will be used if
689 loop preconditioning is performed, and must be zero for that case.
691 It is safe to do this here, since the extra registers created by the
692 preconditioning code and find_splittable_regs will never be used
693 to access the splittable_regs[] and addr_combined_regs[] arrays. */
695 splittable_regs
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
696 bzero (splittable_regs
, maxregnum
* sizeof (rtx
));
697 splittable_regs_updates
= (int *) alloca (maxregnum
* sizeof (int));
698 bzero (splittable_regs_updates
, maxregnum
* sizeof (int));
700 = (struct induction
**) alloca (maxregnum
* sizeof (struct induction
*));
701 bzero (addr_combined_regs
, maxregnum
* sizeof (struct induction
*));
703 /* If this loop requires exit tests when unrolled, check to see if we
704 can precondition the loop so as to make the exit tests unnecessary.
705 Just like variable splitting, this is not safe if the loop is entered
706 via a jump to the bottom. Also, can not do this if no strength
707 reduce info, because precondition_loop_p uses this info. */
709 /* Must copy the loop body for preconditioning before the following
710 find_splittable_regs call since that will emit insns which need to
711 be after the preconditioned loop copies, but immediately before the
712 unrolled loop copies. */
714 /* Also, it is not safe to split induction variables for the preconditioned
715 copies of the loop body. If we split induction variables, then the code
716 assumes that each induction variable can be represented as a function
717 of its initial value and the loop iteration number. This is not true
718 in this case, because the last preconditioned copy of the loop body
719 could be any iteration from the first up to the `unroll_number-1'th,
720 depending on the initial value of the iteration variable. Therefore
721 we can not split induction variables here, because we can not calculate
722 their value. Hence, this code must occur before find_splittable_regs
725 if (unroll_type
== UNROLL_NAIVE
&& ! splitting_not_safe
&& strength_reduce_p
)
727 rtx initial_value
, final_value
, increment
;
729 if (precondition_loop_p (&initial_value
, &final_value
, &increment
,
730 loop_start
, loop_end
))
732 register rtx diff
, temp
;
733 enum machine_mode mode
;
735 int abs_inc
, neg_inc
;
737 map
->reg_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
739 map
->const_equiv_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
740 map
->const_age_map
= (unsigned *) alloca (maxregnum
741 * sizeof (unsigned));
742 map
->const_equiv_map_size
= maxregnum
;
743 global_const_equiv_map
= map
->const_equiv_map
;
745 init_reg_map (map
, maxregnum
);
747 /* Limit loop unrolling to 4, since this will make 7 copies of
749 if (unroll_number
> 4)
752 /* Save the absolute value of the increment, and also whether or
753 not it is negative. */
755 abs_inc
= INTVAL (increment
);
764 /* Decide what mode to do these calculations in. Choose the larger
765 of final_value's mode and initial_value's mode, or a full-word if
766 both are constants. */
767 mode
= GET_MODE (final_value
);
768 if (mode
== VOIDmode
)
770 mode
= GET_MODE (initial_value
);
771 if (mode
== VOIDmode
)
774 else if (mode
!= GET_MODE (initial_value
)
775 && (GET_MODE_SIZE (mode
)
776 < GET_MODE_SIZE (GET_MODE (initial_value
))))
777 mode
= GET_MODE (initial_value
);
779 /* Calculate the difference between the final and initial values.
780 Final value may be a (plus (reg x) (const_int 1)) rtx.
781 Let the following cse pass simplify this if initial value is
784 We must copy the final and initial values here to avoid
785 improperly shared rtl. */
787 diff
= expand_binop (mode
, sub_optab
, copy_rtx (final_value
),
788 copy_rtx (initial_value
), NULL_RTX
, 0,
791 /* Now calculate (diff % (unroll * abs (increment))) by using an
793 diff
= expand_binop (GET_MODE (diff
), and_optab
, diff
,
794 GEN_INT (unroll_number
* abs_inc
- 1),
795 NULL_RTX
, 0, OPTAB_LIB_WIDEN
);
797 /* Now emit a sequence of branches to jump to the proper precond
800 labels
= (rtx
*) alloca (sizeof (rtx
) * unroll_number
);
801 for (i
= 0; i
< unroll_number
; i
++)
802 labels
[i
] = gen_label_rtx ();
804 /* Assuming the unroll_number is 4, and the increment is 2, then
805 for a negative increment: for a positive increment:
806 diff = 0,1 precond 0 diff = 0,7 precond 0
807 diff = 2,3 precond 3 diff = 1,2 precond 1
808 diff = 4,5 precond 2 diff = 3,4 precond 2
809 diff = 6,7 precond 1 diff = 5,6 precond 3 */
811 /* We only need to emit (unroll_number - 1) branches here, the
812 last case just falls through to the following code. */
814 /* ??? This would give better code if we emitted a tree of branches
815 instead of the current linear list of branches. */
817 for (i
= 0; i
< unroll_number
- 1; i
++)
821 /* For negative increments, must invert the constant compared
822 against, except when comparing against zero. */
826 cmp_const
= unroll_number
- i
;
830 emit_cmp_insn (diff
, GEN_INT (abs_inc
* cmp_const
),
831 EQ
, NULL_RTX
, mode
, 0, 0);
834 emit_jump_insn (gen_beq (labels
[i
]));
836 emit_jump_insn (gen_bge (labels
[i
]));
838 emit_jump_insn (gen_ble (labels
[i
]));
839 JUMP_LABEL (get_last_insn ()) = labels
[i
];
840 LABEL_NUSES (labels
[i
])++;
843 /* If the increment is greater than one, then we need another branch,
844 to handle other cases equivalent to 0. */
846 /* ??? This should be merged into the code above somehow to help
847 simplify the code here, and reduce the number of branches emitted.
848 For the negative increment case, the branch here could easily
849 be merged with the `0' case branch above. For the positive
850 increment case, it is not clear how this can be simplified. */
857 cmp_const
= abs_inc
- 1;
859 cmp_const
= abs_inc
* (unroll_number
- 1) + 1;
861 emit_cmp_insn (diff
, GEN_INT (cmp_const
), EQ
, NULL_RTX
,
865 emit_jump_insn (gen_ble (labels
[0]));
867 emit_jump_insn (gen_bge (labels
[0]));
868 JUMP_LABEL (get_last_insn ()) = labels
[0];
869 LABEL_NUSES (labels
[0])++;
872 sequence
= gen_sequence ();
874 emit_insn_before (sequence
, loop_start
);
876 /* Only the last copy of the loop body here needs the exit
877 test, so set copy_end to exclude the compare/branch here,
878 and then reset it inside the loop when get to the last
881 if (GET_CODE (last_loop_insn
) == BARRIER
)
882 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
883 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
886 /* The immediately preceding insn is a compare which we do not
888 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
890 /* The immediately preceding insn may not be a compare, so we
892 copy_end
= PREV_INSN (last_loop_insn
);
898 for (i
= 1; i
< unroll_number
; i
++)
900 emit_label_after (labels
[unroll_number
- i
],
901 PREV_INSN (loop_start
));
903 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
904 bzero (map
->const_equiv_map
, maxregnum
* sizeof (rtx
));
905 bzero (map
->const_age_map
, maxregnum
* sizeof (unsigned));
908 for (j
= 0; j
< max_labelno
; j
++)
910 map
->label_map
[j
] = gen_label_rtx ();
912 /* The last copy needs the compare/branch insns at the end,
913 so reset copy_end here if the loop ends with a conditional
916 if (i
== unroll_number
- 1)
918 if (GET_CODE (last_loop_insn
) == BARRIER
)
919 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
921 copy_end
= last_loop_insn
;
924 /* None of the copies are the `last_iteration', so just
925 pass zero for that parameter. */
926 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, 0,
927 unroll_type
, start_label
, loop_end
,
928 loop_start
, copy_end
);
930 emit_label_after (labels
[0], PREV_INSN (loop_start
));
932 if (GET_CODE (last_loop_insn
) == BARRIER
)
934 insert_before
= PREV_INSN (last_loop_insn
);
935 copy_end
= PREV_INSN (insert_before
);
940 /* The immediately preceding insn is a compare which we do not
942 insert_before
= PREV_INSN (last_loop_insn
);
943 copy_end
= PREV_INSN (insert_before
);
945 /* The immediately preceding insn may not be a compare, so we
947 insert_before
= last_loop_insn
;
948 copy_end
= PREV_INSN (last_loop_insn
);
952 /* Set unroll type to MODULO now. */
953 unroll_type
= UNROLL_MODULO
;
954 loop_preconditioned
= 1;
958 /* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
959 the loop unless all loops are being unrolled. */
960 if (unroll_type
== UNROLL_NAIVE
&& ! flag_unroll_all_loops
)
962 if (loop_dump_stream
)
963 fprintf (loop_dump_stream
, "Unrolling failure: Naive unrolling not being done.\n");
967 /* At this point, we are guaranteed to unroll the loop. */
969 /* For each biv and giv, determine whether it can be safely split into
970 a different variable for each unrolled copy of the loop body.
971 We precalculate and save this info here, since computing it is
974 Do this before deleting any instructions from the loop, so that
975 back_branch_in_range_p will work correctly. */
977 if (splitting_not_safe
)
980 temp
= find_splittable_regs (unroll_type
, loop_start
, loop_end
,
981 end_insert_before
, unroll_number
);
983 /* find_splittable_regs may have created some new registers, so must
984 reallocate the reg_map with the new larger size, and must realloc
985 the constant maps also. */
987 maxregnum
= max_reg_num ();
988 map
->reg_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
990 init_reg_map (map
, maxregnum
);
992 /* Space is needed in some of the map for new registers, so new_maxregnum
993 is an (over)estimate of how many registers will exist at the end. */
994 new_maxregnum
= maxregnum
+ (temp
* unroll_number
* 2);
996 /* Must realloc space for the constant maps, because the number of registers
999 map
->const_equiv_map
= (rtx
*) alloca (new_maxregnum
* sizeof (rtx
));
1000 map
->const_age_map
= (unsigned *) alloca (new_maxregnum
* sizeof (unsigned));
1002 global_const_equiv_map
= map
->const_equiv_map
;
1004 /* Search the list of bivs and givs to find ones which need to be remapped
1005 when split, and set their reg_map entry appropriately. */
1007 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
1009 if (REGNO (bl
->biv
->src_reg
) != bl
->regno
)
1010 map
->reg_map
[bl
->regno
] = bl
->biv
->src_reg
;
1012 /* Currently, non-reduced/final-value givs are never split. */
1013 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
1014 if (REGNO (v
->src_reg
) != bl
->regno
)
1015 map
->reg_map
[REGNO (v
->dest_reg
)] = v
->src_reg
;
1019 /* If the loop is being partially unrolled, and the iteration variables
1020 are being split, and are being renamed for the split, then must fix up
1021 the compare instruction at the end of the loop to refer to the new
1022 registers. This compare isn't copied, so the registers used in it
1023 will never be replaced if it isn't done here. */
1025 if (unroll_type
== UNROLL_MODULO
)
1027 insn
= NEXT_INSN (copy_end
);
1028 if (GET_CODE (insn
) == INSN
&& GET_CODE (PATTERN (insn
)) == SET
)
1031 /* If non-reduced/final-value givs were split, then this would also
1032 have to remap those givs. */
1035 tem
= SET_SRC (PATTERN (insn
));
1036 /* The set source is a register. */
1037 if (GET_CODE (tem
) == REG
)
1039 if (REGNO (tem
) < max_reg_before_loop
1040 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1041 SET_SRC (PATTERN (insn
))
1042 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1046 /* The set source is a compare of some sort. */
1047 tem
= XEXP (SET_SRC (PATTERN (insn
)), 0);
1048 if (GET_CODE (tem
) == REG
1049 && REGNO (tem
) < max_reg_before_loop
1050 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1051 XEXP (SET_SRC (PATTERN (insn
)), 0)
1052 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1054 tem
= XEXP (SET_SRC (PATTERN (insn
)), 1);
1055 if (GET_CODE (tem
) == REG
1056 && REGNO (tem
) < max_reg_before_loop
1057 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1058 XEXP (SET_SRC (PATTERN (insn
)), 1)
1059 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1064 /* For unroll_number - 1 times, make a copy of each instruction
1065 between copy_start and copy_end, and insert these new instructions
1066 before the end of the loop. */
1068 for (i
= 0; i
< unroll_number
; i
++)
1070 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
1071 bzero (map
->const_equiv_map
, new_maxregnum
* sizeof (rtx
));
1072 bzero (map
->const_age_map
, new_maxregnum
* sizeof (unsigned));
1075 for (j
= 0; j
< max_labelno
; j
++)
1077 map
->label_map
[j
] = gen_label_rtx ();
1079 /* If loop starts with a branch to the test, then fix it so that
1080 it points to the test of the first unrolled copy of the loop. */
1081 if (i
== 0 && loop_start
!= copy_start
)
1083 insn
= PREV_INSN (copy_start
);
1084 pattern
= PATTERN (insn
);
1086 tem
= map
->label_map
[CODE_LABEL_NUMBER
1087 (XEXP (SET_SRC (pattern
), 0))];
1088 SET_SRC (pattern
) = gen_rtx (LABEL_REF
, VOIDmode
, tem
);
1090 /* Set the jump label so that it can be used by later loop unrolling
1092 JUMP_LABEL (insn
) = tem
;
1093 LABEL_NUSES (tem
)++;
1096 copy_loop_body (copy_start
, copy_end
, map
, exit_label
,
1097 i
== unroll_number
- 1, unroll_type
, start_label
,
1098 loop_end
, insert_before
, insert_before
);
1101 /* Before deleting any insns, emit a CODE_LABEL immediately after the last
1102 insn to be deleted. This prevents any runaway delete_insn call from
1103 more insns that it should, as it always stops at a CODE_LABEL. */
1105 /* Delete the compare and branch at the end of the loop if completely
1106 unrolling the loop. Deleting the backward branch at the end also
1107 deletes the code label at the start of the loop. This is done at
1108 the very end to avoid problems with back_branch_in_range_p. */
1110 if (unroll_type
== UNROLL_COMPLETELY
)
1111 safety_label
= emit_label_after (gen_label_rtx (), last_loop_insn
);
1113 safety_label
= emit_label_after (gen_label_rtx (), copy_end
);
1115 /* Delete all of the original loop instructions. Don't delete the
1116 LOOP_BEG note, or the first code label in the loop. */
1118 insn
= NEXT_INSN (copy_start
);
1119 while (insn
!= safety_label
)
1121 if (insn
!= start_label
)
1122 insn
= delete_insn (insn
);
1124 insn
= NEXT_INSN (insn
);
1127 /* Can now delete the 'safety' label emitted to protect us from runaway
1128 delete_insn calls. */
1129 if (INSN_DELETED_P (safety_label
))
1131 delete_insn (safety_label
);
1133 /* If exit_label exists, emit it after the loop. Doing the emit here
1134 forces it to have a higher INSN_UID than any insn in the unrolled loop.
1135 This is needed so that mostly_true_jump in reorg.c will treat jumps
1136 to this loop end label correctly, i.e. predict that they are usually
1139 emit_label_after (exit_label
, loop_end
);
1142 /* Return true if the loop can be safely, and profitably, preconditioned
1143 so that the unrolled copies of the loop body don't need exit tests.
1145 This only works if final_value, initial_value and increment can be
1146 determined, and if increment is a constant power of 2.
1147 If increment is not a power of 2, then the preconditioning modulo
1148 operation would require a real modulo instead of a boolean AND, and this
1149 is not considered `profitable'. */
1151 /* ??? If the loop is known to be executed very many times, or the machine
1152 has a very cheap divide instruction, then preconditioning is a win even
1153 when the increment is not a power of 2. Use RTX_COST to compute
1154 whether divide is cheap. */
1157 precondition_loop_p (initial_value
, final_value
, increment
, loop_start
,
1159 rtx
*initial_value
, *final_value
, *increment
;
1160 rtx loop_start
, loop_end
;
1162 int unsigned_compare
, compare_dir
;
1164 if (loop_n_iterations
> 0)
1166 *initial_value
= const0_rtx
;
1167 *increment
= const1_rtx
;
1168 *final_value
= GEN_INT (loop_n_iterations
);
1170 if (loop_dump_stream
)
1171 fprintf (loop_dump_stream
,
1172 "Preconditioning: Success, number of iterations known, %d.\n",
1177 if (loop_initial_value
== 0)
1179 if (loop_dump_stream
)
1180 fprintf (loop_dump_stream
,
1181 "Preconditioning: Could not find initial value.\n");
1184 else if (loop_increment
== 0)
1186 if (loop_dump_stream
)
1187 fprintf (loop_dump_stream
,
1188 "Preconditioning: Could not find increment value.\n");
1191 else if (GET_CODE (loop_increment
) != CONST_INT
)
1193 if (loop_dump_stream
)
1194 fprintf (loop_dump_stream
,
1195 "Preconditioning: Increment not a constant.\n");
1198 else if ((exact_log2 (INTVAL (loop_increment
)) < 0)
1199 && (exact_log2 (- INTVAL (loop_increment
)) < 0))
1201 if (loop_dump_stream
)
1202 fprintf (loop_dump_stream
,
1203 "Preconditioning: Increment not a constant power of 2.\n");
1207 /* Unsigned_compare and compare_dir can be ignored here, since they do
1208 not matter for preconditioning. */
1210 if (loop_final_value
== 0)
1212 if (loop_dump_stream
)
1213 fprintf (loop_dump_stream
,
1214 "Preconditioning: EQ comparison loop.\n");
1218 /* Must ensure that final_value is invariant, so call invariant_p to
1219 check. Before doing so, must check regno against max_reg_before_loop
1220 to make sure that the register is in the range covered by invariant_p.
1221 If it isn't, then it is most likely a biv/giv which by definition are
1223 if ((GET_CODE (loop_final_value
) == REG
1224 && REGNO (loop_final_value
) >= max_reg_before_loop
)
1225 || (GET_CODE (loop_final_value
) == PLUS
1226 && REGNO (XEXP (loop_final_value
, 0)) >= max_reg_before_loop
)
1227 || ! invariant_p (loop_final_value
))
1229 if (loop_dump_stream
)
1230 fprintf (loop_dump_stream
,
1231 "Preconditioning: Final value not invariant.\n");
1235 /* Fail for floating point values, since the caller of this function
1236 does not have code to deal with them. */
1237 if (GET_MODE_CLASS (GET_MODE (loop_final_value
)) == MODE_FLOAT
1238 || GET_MODE_CLASS (GET_MODE (loop_initial_value
)) == MODE_FLOAT
)
1240 if (loop_dump_stream
)
1241 fprintf (loop_dump_stream
,
1242 "Preconditioning: Floating point final or initial value.\n");
1246 /* Now set initial_value to be the iteration_var, since that may be a
1247 simpler expression, and is guaranteed to be correct if all of the
1248 above tests succeed.
1250 We can not use the initial_value as calculated, because it will be
1251 one too small for loops of the form "while (i-- > 0)". We can not
1252 emit code before the loop_skip_over insns to fix this problem as this
1253 will then give a number one too large for loops of the form
1256 Note that all loops that reach here are entered at the top, because
1257 this function is not called if the loop starts with a jump. */
1259 /* Fail if loop_iteration_var is not live before loop_start, since we need
1260 to test its value in the preconditioning code. */
1262 if (uid_luid
[regno_first_uid
[REGNO (loop_iteration_var
)]]
1263 > INSN_LUID (loop_start
))
1265 if (loop_dump_stream
)
1266 fprintf (loop_dump_stream
,
1267 "Preconditioning: Iteration var not live before loop start.\n");
1271 *initial_value
= loop_iteration_var
;
1272 *increment
= loop_increment
;
1273 *final_value
= loop_final_value
;
1276 if (loop_dump_stream
)
1277 fprintf (loop_dump_stream
, "Preconditioning: Successful.\n");
1282 /* All pseudo-registers must be mapped to themselves. Two hard registers
1283 must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
1284 REGNUM, to avoid function-inlining specific conversions of these
1285 registers. All other hard regs can not be mapped because they may be
1290 init_reg_map (map
, maxregnum
)
1291 struct inline_remap
*map
;
1296 for (i
= maxregnum
- 1; i
> LAST_VIRTUAL_REGISTER
; i
--)
1297 map
->reg_map
[i
] = regno_reg_rtx
[i
];
1298 /* Just clear the rest of the entries. */
1299 for (i
= LAST_VIRTUAL_REGISTER
; i
>= 0; i
--)
1300 map
->reg_map
[i
] = 0;
1302 map
->reg_map
[VIRTUAL_STACK_VARS_REGNUM
]
1303 = regno_reg_rtx
[VIRTUAL_STACK_VARS_REGNUM
];
1304 map
->reg_map
[VIRTUAL_INCOMING_ARGS_REGNUM
]
1305 = regno_reg_rtx
[VIRTUAL_INCOMING_ARGS_REGNUM
];
1308 /* Strength-reduction will often emit code for optimized biv/givs which
1309 calculates their value in a temporary register, and then copies the result
1310 to the iv. This procedure reconstructs the pattern computing the iv;
1311 verifying that all operands are of the proper form.
1313 The return value is the amount that the giv is incremented by. */
1316 calculate_giv_inc (pattern
, src_insn
, regno
)
1317 rtx pattern
, src_insn
;
1322 /* Verify that we have an increment insn here. First check for a plus
1323 as the set source. */
1324 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1326 /* SR sometimes computes the new giv value in a temp, then copies it
1328 src_insn
= PREV_INSN (src_insn
);
1329 pattern
= PATTERN (src_insn
);
1330 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1333 /* The last insn emitted is not needed, so delete it to avoid confusing
1334 the second cse pass. This insn sets the giv unnecessarily. */
1335 delete_insn (get_last_insn ());
1338 /* Verify that we have a constant as the second operand of the plus. */
1339 increment
= XEXP (SET_SRC (pattern
), 1);
1340 if (GET_CODE (increment
) != CONST_INT
)
1342 /* SR sometimes puts the constant in a register, especially if it is
1343 too big to be an add immed operand. */
1344 increment
= SET_SRC (PATTERN (PREV_INSN (src_insn
)));
1346 /* SR may have used LO_SUM to compute the constant if it is too large
1347 for a load immed operand. In this case, the constant is in operand
1348 one of the LO_SUM rtx. */
1349 if (GET_CODE (increment
) == LO_SUM
)
1350 increment
= XEXP (increment
, 1);
1352 if (GET_CODE (increment
) != CONST_INT
)
1355 /* The insn loading the constant into a register is not longer needed,
1357 delete_insn (get_last_insn ());
1360 /* Check that the source register is the same as the dest register. */
1361 if (GET_CODE (XEXP (SET_SRC (pattern
), 0)) != REG
1362 || REGNO (XEXP (SET_SRC (pattern
), 0)) != regno
)
1368 /* Copy REG_NOTES, except for insn references, because not all insn_map
1369 entries are valid yet. We do need to copy registers now though, because
1370 the reg_map entries can change during copying. */
1373 initial_reg_note_copy (notes
, map
)
1375 struct inline_remap
*map
;
1382 copy
= rtx_alloc (GET_CODE (notes
));
1383 PUT_MODE (copy
, GET_MODE (notes
));
1385 if (GET_CODE (notes
) == EXPR_LIST
)
1386 XEXP (copy
, 0) = copy_rtx_and_substitute (XEXP (notes
, 0), map
);
1387 else if (GET_CODE (notes
) == INSN_LIST
)
1388 /* Don't substitute for these yet. */
1389 XEXP (copy
, 0) = XEXP (notes
, 0);
1393 XEXP (copy
, 1) = initial_reg_note_copy (XEXP (notes
, 1), map
);
1398 /* Fixup insn references in copied REG_NOTES. */
1401 final_reg_note_copy (notes
, map
)
1403 struct inline_remap
*map
;
1407 for (note
= notes
; note
; note
= XEXP (note
, 1))
1408 if (GET_CODE (note
) == INSN_LIST
)
1409 XEXP (note
, 0) = map
->insn_map
[INSN_UID (XEXP (note
, 0))];
1412 /* Copy each instruction in the loop, substituting from map as appropriate.
1413 This is very similar to a loop in expand_inline_function. */
1416 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, last_iteration
,
1417 unroll_type
, start_label
, loop_end
, insert_before
,
1419 rtx copy_start
, copy_end
;
1420 struct inline_remap
*map
;
1423 enum unroll_types unroll_type
;
1424 rtx start_label
, loop_end
, insert_before
, copy_notes_from
;
1428 int dest_reg_was_split
, i
;
1430 rtx final_label
= 0;
1431 rtx giv_inc
, giv_dest_reg
, giv_src_reg
;
1433 /* If this isn't the last iteration, then map any references to the
1434 start_label to final_label. Final label will then be emitted immediately
1435 after the end of this loop body if it was ever used.
1437 If this is the last iteration, then map references to the start_label
1439 if (! last_iteration
)
1441 final_label
= gen_label_rtx ();
1442 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = final_label
;
1445 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = start_label
;
1452 insn
= NEXT_INSN (insn
);
1454 map
->orig_asm_operands_vector
= 0;
1456 switch (GET_CODE (insn
))
1459 pattern
= PATTERN (insn
);
1463 /* Check to see if this is a giv that has been combined with
1464 some split address givs. (Combined in the sense that
1465 `combine_givs' in loop.c has put two givs in the same register.)
1466 In this case, we must search all givs based on the same biv to
1467 find the address givs. Then split the address givs.
1468 Do this before splitting the giv, since that may map the
1469 SET_DEST to a new register. */
1471 if (GET_CODE (pattern
) == SET
1472 && GET_CODE (SET_DEST (pattern
)) == REG
1473 && addr_combined_regs
[REGNO (SET_DEST (pattern
))])
1475 struct iv_class
*bl
;
1476 struct induction
*v
, *tv
;
1477 int regno
= REGNO (SET_DEST (pattern
));
1479 v
= addr_combined_regs
[REGNO (SET_DEST (pattern
))];
1480 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
1482 /* Although the giv_inc amount is not needed here, we must call
1483 calculate_giv_inc here since it might try to delete the
1484 last insn emitted. If we wait until later to call it,
1485 we might accidentally delete insns generated immediately
1486 below by emit_unrolled_add. */
1488 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1490 /* Now find all address giv's that were combined with this
1492 for (tv
= bl
->giv
; tv
; tv
= tv
->next_iv
)
1493 if (tv
->giv_type
== DEST_ADDR
&& tv
->same
== v
)
1495 int this_giv_inc
= INTVAL (giv_inc
);
1497 /* Scale this_giv_inc if the multiplicative factors of
1498 the two givs are different. */
1499 if (tv
->mult_val
!= v
->mult_val
)
1500 this_giv_inc
= (this_giv_inc
/ INTVAL (v
->mult_val
)
1501 * INTVAL (tv
->mult_val
));
1503 tv
->dest_reg
= plus_constant (tv
->dest_reg
, this_giv_inc
);
1504 *tv
->location
= tv
->dest_reg
;
1506 if (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)
1508 /* Must emit an insn to increment the split address
1509 giv. Add in the const_adjust field in case there
1510 was a constant eliminated from the address. */
1511 rtx value
, dest_reg
;
1513 /* tv->dest_reg will be either a bare register,
1514 or else a register plus a constant. */
1515 if (GET_CODE (tv
->dest_reg
) == REG
)
1516 dest_reg
= tv
->dest_reg
;
1518 dest_reg
= XEXP (tv
->dest_reg
, 0);
1520 /* tv->dest_reg may actually be a (PLUS (REG) (CONST))
1521 here, so we must call plus_constant to add
1522 the const_adjust amount before calling
1523 emit_unrolled_add below. */
1524 value
= plus_constant (tv
->dest_reg
, tv
->const_adjust
);
1526 /* The constant could be too large for an add
1527 immediate, so can't directly emit an insn here. */
1528 emit_unrolled_add (dest_reg
, XEXP (value
, 0),
1531 /* Reset the giv to be just the register again, in case
1532 it is used after the set we have just emitted.
1533 We must subtract the const_adjust factor added in
1535 tv
->dest_reg
= plus_constant (dest_reg
,
1536 - tv
->const_adjust
);
1537 *tv
->location
= tv
->dest_reg
;
1542 /* If this is a setting of a splittable variable, then determine
1543 how to split the variable, create a new set based on this split,
1544 and set up the reg_map so that later uses of the variable will
1545 use the new split variable. */
1547 dest_reg_was_split
= 0;
1549 if (GET_CODE (pattern
) == SET
1550 && GET_CODE (SET_DEST (pattern
)) == REG
1551 && splittable_regs
[REGNO (SET_DEST (pattern
))])
1553 int regno
= REGNO (SET_DEST (pattern
));
1555 dest_reg_was_split
= 1;
1557 /* Compute the increment value for the giv, if it wasn't
1558 already computed above. */
1561 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1562 giv_dest_reg
= SET_DEST (pattern
);
1563 giv_src_reg
= SET_DEST (pattern
);
1565 if (unroll_type
== UNROLL_COMPLETELY
)
1567 /* Completely unrolling the loop. Set the induction
1568 variable to a known constant value. */
1570 /* The value in splittable_regs may be an invariant
1571 value, so we must use plus_constant here. */
1572 splittable_regs
[regno
]
1573 = plus_constant (splittable_regs
[regno
], INTVAL (giv_inc
));
1575 if (GET_CODE (splittable_regs
[regno
]) == PLUS
)
1577 giv_src_reg
= XEXP (splittable_regs
[regno
], 0);
1578 giv_inc
= XEXP (splittable_regs
[regno
], 1);
1582 /* The splittable_regs value must be a REG or a
1583 CONST_INT, so put the entire value in the giv_src_reg
1585 giv_src_reg
= splittable_regs
[regno
];
1586 giv_inc
= const0_rtx
;
1591 /* Partially unrolling loop. Create a new pseudo
1592 register for the iteration variable, and set it to
1593 be a constant plus the original register. Except
1594 on the last iteration, when the result has to
1595 go back into the original iteration var register. */
1597 /* Handle bivs which must be mapped to a new register
1598 when split. This happens for bivs which need their
1599 final value set before loop entry. The new register
1600 for the biv was stored in the biv's first struct
1601 induction entry by find_splittable_regs. */
1603 if (regno
< max_reg_before_loop
1604 && reg_iv_type
[regno
] == BASIC_INDUCT
)
1606 giv_src_reg
= reg_biv_class
[regno
]->biv
->src_reg
;
1607 giv_dest_reg
= giv_src_reg
;
1611 /* If non-reduced/final-value givs were split, then
1612 this would have to remap those givs also. See
1613 find_splittable_regs. */
1616 splittable_regs
[regno
]
1617 = GEN_INT (INTVAL (giv_inc
)
1618 + INTVAL (splittable_regs
[regno
]));
1619 giv_inc
= splittable_regs
[regno
];
1621 /* Now split the induction variable by changing the dest
1622 of this insn to a new register, and setting its
1623 reg_map entry to point to this new register.
1625 If this is the last iteration, and this is the last insn
1626 that will update the iv, then reuse the original dest,
1627 to ensure that the iv will have the proper value when
1628 the loop exits or repeats.
1630 Using splittable_regs_updates here like this is safe,
1631 because it can only be greater than one if all
1632 instructions modifying the iv are always executed in
1635 if (! last_iteration
1636 || (splittable_regs_updates
[regno
]-- != 1))
1638 tem
= gen_reg_rtx (GET_MODE (giv_src_reg
));
1640 map
->reg_map
[regno
] = tem
;
1643 map
->reg_map
[regno
] = giv_src_reg
;
1646 /* The constant being added could be too large for an add
1647 immediate, so can't directly emit an insn here. */
1648 emit_unrolled_add (giv_dest_reg
, giv_src_reg
, giv_inc
);
1649 copy
= get_last_insn ();
1650 pattern
= PATTERN (copy
);
1654 pattern
= copy_rtx_and_substitute (pattern
, map
);
1655 copy
= emit_insn (pattern
);
1657 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1660 /* If this insn is setting CC0, it may need to look at
1661 the insn that uses CC0 to see what type of insn it is.
1662 In that case, the call to recog via validate_change will
1663 fail. So don't substitute constants here. Instead,
1664 do it when we emit the following insn.
1666 For example, see the pyr.md file. That machine has signed and
1667 unsigned compares. The compare patterns must check the
1668 following branch insn to see which what kind of compare to
1671 If the previous insn set CC0, substitute constants on it as
1673 if (sets_cc0_p (copy
) != 0)
1678 try_constants (cc0_insn
, map
);
1680 try_constants (copy
, map
);
1683 try_constants (copy
, map
);
1686 /* Make split induction variable constants `permanent' since we
1687 know there are no backward branches across iteration variable
1688 settings which would invalidate this. */
1689 if (dest_reg_was_split
)
1691 int regno
= REGNO (SET_DEST (pattern
));
1693 if (map
->const_age_map
[regno
] == map
->const_age
)
1694 map
->const_age_map
[regno
] = -1;
1699 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1700 copy
= emit_jump_insn (pattern
);
1701 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1703 if (JUMP_LABEL (insn
) == start_label
&& insn
== copy_end
1704 && ! last_iteration
)
1706 /* This is a branch to the beginning of the loop; this is the
1707 last insn being copied; and this is not the last iteration.
1708 In this case, we want to change the original fall through
1709 case to be a branch past the end of the loop, and the
1710 original jump label case to fall_through. */
1712 if (! invert_exp (pattern
, copy
)
1713 || ! redirect_exp (&pattern
,
1714 map
->label_map
[CODE_LABEL_NUMBER
1715 (JUMP_LABEL (insn
))],
1722 try_constants (cc0_insn
, map
);
1725 try_constants (copy
, map
);
1727 /* Set the jump label of COPY correctly to avoid problems with
1728 later passes of unroll_loop, if INSN had jump label set. */
1729 if (JUMP_LABEL (insn
))
1733 /* Can't use the label_map for every insn, since this may be
1734 the backward branch, and hence the label was not mapped. */
1735 if (GET_CODE (pattern
) == SET
)
1737 tem
= SET_SRC (pattern
);
1738 if (GET_CODE (tem
) == LABEL_REF
)
1739 label
= XEXP (tem
, 0);
1740 else if (GET_CODE (tem
) == IF_THEN_ELSE
)
1742 if (XEXP (tem
, 1) != pc_rtx
)
1743 label
= XEXP (XEXP (tem
, 1), 0);
1745 label
= XEXP (XEXP (tem
, 2), 0);
1749 if (label
&& GET_CODE (label
) == CODE_LABEL
)
1750 JUMP_LABEL (copy
) = label
;
1753 /* An unrecognizable jump insn, probably the entry jump
1754 for a switch statement. This label must have been mapped,
1755 so just use the label_map to get the new jump label. */
1756 JUMP_LABEL (copy
) = map
->label_map
[CODE_LABEL_NUMBER
1757 (JUMP_LABEL (insn
))];
1760 /* If this is a non-local jump, then must increase the label
1761 use count so that the label will not be deleted when the
1762 original jump is deleted. */
1763 LABEL_NUSES (JUMP_LABEL (copy
))++;
1765 else if (GET_CODE (PATTERN (copy
)) == ADDR_VEC
1766 || GET_CODE (PATTERN (copy
)) == ADDR_DIFF_VEC
)
1768 rtx pat
= PATTERN (copy
);
1769 int diff_vec_p
= GET_CODE (pat
) == ADDR_DIFF_VEC
;
1770 int len
= XVECLEN (pat
, diff_vec_p
);
1773 for (i
= 0; i
< len
; i
++)
1774 LABEL_NUSES (XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0))++;
1777 /* If this used to be a conditional jump insn but whose branch
1778 direction is now known, we must do something special. */
1779 if (condjump_p (insn
) && !simplejump_p (insn
) && map
->last_pc_value
)
1782 /* The previous insn set cc0 for us. So delete it. */
1783 delete_insn (PREV_INSN (copy
));
1786 /* If this is now a no-op, delete it. */
1787 if (map
->last_pc_value
== pc_rtx
)
1793 /* Otherwise, this is unconditional jump so we must put a
1794 BARRIER after it. We could do some dead code elimination
1795 here, but jump.c will do it just as well. */
1801 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1802 copy
= emit_call_insn (pattern
);
1803 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1807 try_constants (cc0_insn
, map
);
1810 try_constants (copy
, map
);
1812 /* Be lazy and assume CALL_INSNs clobber all hard registers. */
1813 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
1814 map
->const_equiv_map
[i
] = 0;
1818 /* If this is the loop start label, then we don't need to emit a
1819 copy of this label since no one will use it. */
1821 if (insn
!= start_label
)
1823 copy
= emit_label (map
->label_map
[CODE_LABEL_NUMBER (insn
)]);
1829 copy
= emit_barrier ();
1833 /* VTOP notes are valid only before the loop exit test. If placed
1834 anywhere else, loop may generate bad code. */
1836 if (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
1837 && (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_LOOP_VTOP
1838 || (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)))
1839 copy
= emit_note (NOTE_SOURCE_FILE (insn
),
1840 NOTE_LINE_NUMBER (insn
));
1850 map
->insn_map
[INSN_UID (insn
)] = copy
;
1852 while (insn
!= copy_end
);
1854 /* Now finish coping the REG_NOTES. */
1858 insn
= NEXT_INSN (insn
);
1859 if ((GET_CODE (insn
) == INSN
|| GET_CODE (insn
) == JUMP_INSN
1860 || GET_CODE (insn
) == CALL_INSN
)
1861 && map
->insn_map
[INSN_UID (insn
)])
1862 final_reg_note_copy (REG_NOTES (map
->insn_map
[INSN_UID (insn
)]), map
);
1864 while (insn
!= copy_end
);
1866 /* There may be notes between copy_notes_from and loop_end. Emit a copy of
1867 each of these notes here, since there may be some important ones, such as
1868 NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
1869 iteration, because the original notes won't be deleted.
1871 We can't use insert_before here, because when from preconditioning,
1872 insert_before points before the loop. We can't use copy_end, because
1873 there may be insns already inserted after it (which we don't want to
1874 copy) when not from preconditioning code. */
1876 if (! last_iteration
)
1878 for (insn
= copy_notes_from
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
1880 if (GET_CODE (insn
) == NOTE
1881 && NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
)
1882 emit_note (NOTE_SOURCE_FILE (insn
), NOTE_LINE_NUMBER (insn
));
1886 if (final_label
&& LABEL_NUSES (final_label
) > 0)
1887 emit_label (final_label
);
1889 tem
= gen_sequence ();
1891 emit_insn_before (tem
, insert_before
);
1894 /* Emit an insn, using the expand_binop to ensure that a valid insn is
1895 emitted. This will correctly handle the case where the increment value
1896 won't fit in the immediate field of a PLUS insns. */
1899 emit_unrolled_add (dest_reg
, src_reg
, increment
)
1900 rtx dest_reg
, src_reg
, increment
;
1904 result
= expand_binop (GET_MODE (dest_reg
), add_optab
, src_reg
, increment
,
1905 dest_reg
, 0, OPTAB_LIB_WIDEN
);
1907 if (dest_reg
!= result
)
1908 emit_move_insn (dest_reg
, result
);
1911 /* Searches the insns between INSN and LOOP_END. Returns 1 if there
1912 is a backward branch in that range that branches to somewhere between
1913 LOOP_START and INSN. Returns 0 otherwise. */
1915 /* ??? This is quadratic algorithm. Could be rewritten to be linear.
1916 In practice, this is not a problem, because this function is seldom called,
1917 and uses a negligible amount of CPU time on average. */
1920 back_branch_in_range_p (insn
, loop_start
, loop_end
)
1922 rtx loop_start
, loop_end
;
1924 rtx p
, q
, target_insn
;
1926 /* Stop before we get to the backward branch at the end of the loop. */
1927 loop_end
= prev_nonnote_insn (loop_end
);
1928 if (GET_CODE (loop_end
) == BARRIER
)
1929 loop_end
= PREV_INSN (loop_end
);
1931 /* Check in case insn has been deleted, search forward for first non
1932 deleted insn following it. */
1933 while (INSN_DELETED_P (insn
))
1934 insn
= NEXT_INSN (insn
);
1936 /* Check for the case where insn is the last insn in the loop. */
1937 if (insn
== loop_end
)
1940 for (p
= NEXT_INSN (insn
); p
!= loop_end
; p
= NEXT_INSN (p
))
1942 if (GET_CODE (p
) == JUMP_INSN
)
1944 target_insn
= JUMP_LABEL (p
);
1946 /* Search from loop_start to insn, to see if one of them is
1947 the target_insn. We can't use INSN_LUID comparisons here,
1948 since insn may not have an LUID entry. */
1949 for (q
= loop_start
; q
!= insn
; q
= NEXT_INSN (q
))
1950 if (q
== target_insn
)
1958 /* Try to generate the simplest rtx for the expression
1959 (PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
1963 fold_rtx_mult_add (mult1
, mult2
, add1
, mode
)
1964 rtx mult1
, mult2
, add1
;
1965 enum machine_mode mode
;
1970 /* The modes must all be the same. This should always be true. For now,
1971 check to make sure. */
1972 if ((GET_MODE (mult1
) != mode
&& GET_MODE (mult1
) != VOIDmode
)
1973 || (GET_MODE (mult2
) != mode
&& GET_MODE (mult2
) != VOIDmode
)
1974 || (GET_MODE (add1
) != mode
&& GET_MODE (add1
) != VOIDmode
))
1977 /* Ensure that if at least one of mult1/mult2 are constant, then mult2
1978 will be a constant. */
1979 if (GET_CODE (mult1
) == CONST_INT
)
1986 mult_res
= simplify_binary_operation (MULT
, mode
, mult1
, mult2
);
1988 mult_res
= gen_rtx (MULT
, mode
, mult1
, mult2
);
1990 /* Again, put the constant second. */
1991 if (GET_CODE (add1
) == CONST_INT
)
1998 result
= simplify_binary_operation (PLUS
, mode
, add1
, mult_res
);
2000 result
= gen_rtx (PLUS
, mode
, add1
, mult_res
);
2005 /* Searches the list of induction struct's for the biv BL, to try to calculate
2006 the total increment value for one iteration of the loop as a constant.
2008 Returns the increment value as an rtx, simplified as much as possible,
2009 if it can be calculated. Otherwise, returns 0. */
2012 biv_total_increment (bl
, loop_start
, loop_end
)
2013 struct iv_class
*bl
;
2014 rtx loop_start
, loop_end
;
2016 struct induction
*v
;
2019 /* For increment, must check every instruction that sets it. Each
2020 instruction must be executed only once each time through the loop.
2021 To verify this, we check that the the insn is always executed, and that
2022 there are no backward branches after the insn that branch to before it.
2023 Also, the insn must have a mult_val of one (to make sure it really is
2026 result
= const0_rtx
;
2027 for (v
= bl
->biv
; v
; v
= v
->next_iv
)
2029 if (v
->always_computable
&& v
->mult_val
== const1_rtx
2030 && ! back_branch_in_range_p (v
->insn
, loop_start
, loop_end
))
2031 result
= fold_rtx_mult_add (result
, const1_rtx
, v
->add_val
, v
->mode
);
2039 /* Determine the initial value of the iteration variable, and the amount
2040 that it is incremented each loop. Use the tables constructed by
2041 the strength reduction pass to calculate these values.
2043 Initial_value and/or increment are set to zero if their values could not
2047 iteration_info (iteration_var
, initial_value
, increment
, loop_start
, loop_end
)
2048 rtx iteration_var
, *initial_value
, *increment
;
2049 rtx loop_start
, loop_end
;
2051 struct iv_class
*bl
;
2052 struct induction
*v
, *b
;
2054 /* Clear the result values, in case no answer can be found. */
2058 /* The iteration variable can be either a giv or a biv. Check to see
2059 which it is, and compute the variable's initial value, and increment
2060 value if possible. */
2062 /* If this is a new register, can't handle it since we don't have any
2063 reg_iv_type entry for it. */
2064 if (REGNO (iteration_var
) >= max_reg_before_loop
)
2066 if (loop_dump_stream
)
2067 fprintf (loop_dump_stream
,
2068 "Loop unrolling: No reg_iv_type entry for iteration var.\n");
2071 /* Reject iteration variables larger than the host long size, since they
2072 could result in a number of iterations greater than the range of our
2073 `unsigned long' variable loop_n_iterations. */
2074 else if (GET_MODE_BITSIZE (GET_MODE (iteration_var
)) > HOST_BITS_PER_LONG
)
2076 if (loop_dump_stream
)
2077 fprintf (loop_dump_stream
,
2078 "Loop unrolling: Iteration var rejected because mode larger than host long.\n");
2081 else if (GET_MODE_CLASS (GET_MODE (iteration_var
)) != MODE_INT
)
2083 if (loop_dump_stream
)
2084 fprintf (loop_dump_stream
,
2085 "Loop unrolling: Iteration var not an integer.\n");
2088 else if (reg_iv_type
[REGNO (iteration_var
)] == BASIC_INDUCT
)
2090 /* Grab initial value, only useful if it is a constant. */
2091 bl
= reg_biv_class
[REGNO (iteration_var
)];
2092 *initial_value
= bl
->initial_value
;
2094 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2096 else if (reg_iv_type
[REGNO (iteration_var
)] == GENERAL_INDUCT
)
2099 /* ??? The code below does not work because the incorrect number of
2100 iterations is calculated when the biv is incremented after the giv
2101 is set (which is the usual case). This can probably be accounted
2102 for by biasing the initial_value by subtracting the amount of the
2103 increment that occurs between the giv set and the giv test. However,
2104 a giv as an iterator is very rare, so it does not seem worthwhile
2106 /* ??? An example failure is: i = 6; do {;} while (i++ < 9). */
2107 if (loop_dump_stream
)
2108 fprintf (loop_dump_stream
,
2109 "Loop unrolling: Giv iterators are not handled.\n");
2112 /* Initial value is mult_val times the biv's initial value plus
2113 add_val. Only useful if it is a constant. */
2114 v
= reg_iv_info
[REGNO (iteration_var
)];
2115 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2116 *initial_value
= fold_rtx_mult_add (v
->mult_val
, bl
->initial_value
,
2117 v
->add_val
, v
->mode
);
2119 /* Increment value is mult_val times the increment value of the biv. */
2121 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2123 *increment
= fold_rtx_mult_add (v
->mult_val
, *increment
, const0_rtx
,
2129 if (loop_dump_stream
)
2130 fprintf (loop_dump_stream
,
2131 "Loop unrolling: Not basic or general induction var.\n");
2136 /* Calculate the approximate final value of the iteration variable
2137 which has an loop exit test with code COMPARISON_CODE and comparison value
2138 of COMPARISON_VALUE. Also returns an indication of whether the comparison
2139 was signed or unsigned, and the direction of the comparison. This info is
2140 needed to calculate the number of loop iterations. */
2143 approx_final_value (comparison_code
, comparison_value
, unsigned_p
, compare_dir
)
2144 enum rtx_code comparison_code
;
2145 rtx comparison_value
;
2149 /* Calculate the final value of the induction variable.
2150 The exact final value depends on the branch operator, and increment sign.
2151 This is only an approximate value. It will be wrong if the iteration
2152 variable is not incremented by one each time through the loop, and
2153 approx final value - start value % increment != 0. */
2156 switch (comparison_code
)
2162 return plus_constant (comparison_value
, 1);
2167 return plus_constant (comparison_value
, -1);
2169 /* Can not calculate a final value for this case. */
2176 return comparison_value
;
2182 return comparison_value
;
2185 return comparison_value
;
2191 /* For each biv and giv, determine whether it can be safely split into
2192 a different variable for each unrolled copy of the loop body. If it
2193 is safe to split, then indicate that by saving some useful info
2194 in the splittable_regs array.
2196 If the loop is being completely unrolled, then splittable_regs will hold
2197 the current value of the induction variable while the loop is unrolled.
2198 It must be set to the initial value of the induction variable here.
2199 Otherwise, splittable_regs will hold the difference between the current
2200 value of the induction variable and the value the induction variable had
2201 at the top of the loop. It must be set to the value 0 here. */
2203 /* ?? If the loop is only unrolled twice, then most of the restrictions to
2204 constant values are unnecessary, since we can easily calculate increment
2205 values in this case even if nothing is constant. The increment value
2206 should not involve a multiply however. */
2208 /* ?? Even if the biv/giv increment values aren't constant, it may still
2209 be beneficial to split the variable if the loop is only unrolled a few
2210 times, since multiplies by small integers (1,2,3,4) are very cheap. */
2213 find_splittable_regs (unroll_type
, loop_start
, loop_end
, end_insert_before
,
2215 enum unroll_types unroll_type
;
2216 rtx loop_start
, loop_end
;
2217 rtx end_insert_before
;
2220 struct iv_class
*bl
;
2221 struct induction
*v
;
2223 rtx biv_final_value
;
2227 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
2229 /* Biv_total_increment must return a constant value,
2230 otherwise we can not calculate the split values. */
2232 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2233 if (! increment
|| GET_CODE (increment
) != CONST_INT
)
2236 /* The loop must be unrolled completely, or else have a known number
2237 of iterations and only one exit, or else the biv must be dead
2238 outside the loop, or else the final value must be known. Otherwise,
2239 it is unsafe to split the biv since it may not have the proper
2240 value on loop exit. */
2242 /* loop_number_exit_labels is non-zero if the loop has an exit other than
2243 a fall through at the end. */
2246 biv_final_value
= 0;
2247 if (unroll_type
!= UNROLL_COMPLETELY
2248 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2249 || unroll_type
== UNROLL_NAIVE
)
2250 && (uid_luid
[regno_last_uid
[bl
->regno
]] >= INSN_LUID (loop_end
)
2252 || INSN_UID (bl
->init_insn
) >= max_uid_for_loop
2253 || (uid_luid
[regno_first_uid
[bl
->regno
]]
2254 < INSN_LUID (bl
->init_insn
))
2255 || reg_mentioned_p (bl
->biv
->dest_reg
, SET_SRC (bl
->init_set
)))
2256 && ! (biv_final_value
= final_biv_value (bl
, loop_start
, loop_end
)))
2259 /* If any of the insns setting the BIV don't do so with a simple
2260 PLUS, we don't know how to split it. */
2261 for (v
= bl
->biv
; biv_splittable
&& v
; v
= v
->next_iv
)
2262 if ((tem
= single_set (v
->insn
)) == 0
2263 || GET_CODE (SET_DEST (tem
)) != REG
2264 || REGNO (SET_DEST (tem
)) != bl
->regno
2265 || GET_CODE (SET_SRC (tem
)) != PLUS
)
2268 /* If final value is non-zero, then must emit an instruction which sets
2269 the value of the biv to the proper value. This is done after
2270 handling all of the givs, since some of them may need to use the
2271 biv's value in their initialization code. */
2273 /* This biv is splittable. If completely unrolling the loop, save
2274 the biv's initial value. Otherwise, save the constant zero. */
2276 if (biv_splittable
== 1)
2278 if (unroll_type
== UNROLL_COMPLETELY
)
2280 /* If the initial value of the biv is itself (i.e. it is too
2281 complicated for strength_reduce to compute), or is a hard
2282 register, then we must create a new pseudo reg to hold the
2283 initial value of the biv. */
2285 if (GET_CODE (bl
->initial_value
) == REG
2286 && (REGNO (bl
->initial_value
) == bl
->regno
2287 || REGNO (bl
->initial_value
) < FIRST_PSEUDO_REGISTER
))
2289 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2291 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2294 if (loop_dump_stream
)
2295 fprintf (loop_dump_stream
, "Biv %d initial value remapped to %d.\n",
2296 bl
->regno
, REGNO (tem
));
2298 splittable_regs
[bl
->regno
] = tem
;
2301 splittable_regs
[bl
->regno
] = bl
->initial_value
;
2304 splittable_regs
[bl
->regno
] = const0_rtx
;
2306 /* Save the number of instructions that modify the biv, so that
2307 we can treat the last one specially. */
2309 splittable_regs_updates
[bl
->regno
] = bl
->biv_count
;
2313 if (loop_dump_stream
)
2314 fprintf (loop_dump_stream
,
2315 "Biv %d safe to split.\n", bl
->regno
);
2318 /* Check every giv that depends on this biv to see whether it is
2319 splittable also. Even if the biv isn't splittable, givs which
2320 depend on it may be splittable if the biv is live outside the
2321 loop, and the givs aren't. */
2323 result
= find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
,
2324 increment
, unroll_number
, result
);
2326 /* If final value is non-zero, then must emit an instruction which sets
2327 the value of the biv to the proper value. This is done after
2328 handling all of the givs, since some of them may need to use the
2329 biv's value in their initialization code. */
2330 if (biv_final_value
)
2332 /* If the loop has multiple exits, emit the insns before the
2333 loop to ensure that it will always be executed no matter
2334 how the loop exits. Otherwise emit the insn after the loop,
2335 since this is slightly more efficient. */
2336 if (! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2337 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2342 /* Create a new register to hold the value of the biv, and then
2343 set the biv to its final value before the loop start. The biv
2344 is set to its final value before loop start to ensure that
2345 this insn will always be executed, no matter how the loop
2347 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2348 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2350 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2354 if (loop_dump_stream
)
2355 fprintf (loop_dump_stream
, "Biv %d mapped to %d for split.\n",
2356 REGNO (bl
->biv
->src_reg
), REGNO (tem
));
2358 /* Set up the mapping from the original biv register to the new
2360 bl
->biv
->src_reg
= tem
;
2367 /* For every giv based on the biv BL, check to determine whether it is
2368 splittable. This is a subroutine to find_splittable_regs (). */
2371 find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
, increment
,
2372 unroll_number
, result
)
2373 struct iv_class
*bl
;
2374 enum unroll_types unroll_type
;
2375 rtx loop_start
, loop_end
;
2377 int unroll_number
, result
;
2379 struct induction
*v
;
2383 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
2387 /* Only split the giv if it has already been reduced, or if the loop is
2388 being completely unrolled. */
2389 if (unroll_type
!= UNROLL_COMPLETELY
&& v
->ignore
)
2392 /* The giv can be split if the insn that sets the giv is executed once
2393 and only once on every iteration of the loop. */
2394 /* An address giv can always be split. v->insn is just a use not a set,
2395 and hence it does not matter whether it is always executed. All that
2396 matters is that all the biv increments are always executed, and we
2397 won't reach here if they aren't. */
2398 if (v
->giv_type
!= DEST_ADDR
2399 && (! v
->always_computable
2400 || back_branch_in_range_p (v
->insn
, loop_start
, loop_end
)))
2403 /* The giv increment value must be a constant. */
2404 giv_inc
= fold_rtx_mult_add (v
->mult_val
, increment
, const0_rtx
,
2406 if (! giv_inc
|| GET_CODE (giv_inc
) != CONST_INT
)
2409 /* The loop must be unrolled completely, or else have a known number of
2410 iterations and only one exit, or else the giv must be dead outside
2411 the loop, or else the final value of the giv must be known.
2412 Otherwise, it is not safe to split the giv since it may not have the
2413 proper value on loop exit. */
2415 /* The used outside loop test will fail for DEST_ADDR givs. They are
2416 never used outside the loop anyways, so it is always safe to split a
2420 if (unroll_type
!= UNROLL_COMPLETELY
2421 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2422 || unroll_type
== UNROLL_NAIVE
)
2423 && v
->giv_type
!= DEST_ADDR
2424 && ((regno_first_uid
[REGNO (v
->dest_reg
)] != INSN_UID (v
->insn
)
2425 /* Check for the case where the pseudo is set by a shift/add
2426 sequence, in which case the first insn setting the pseudo
2427 is the first insn of the shift/add sequence. */
2428 && (! (tem
= find_reg_note (v
->insn
, REG_RETVAL
, NULL_RTX
))
2429 || (regno_first_uid
[REGNO (v
->dest_reg
)]
2430 != INSN_UID (XEXP (tem
, 0)))))
2431 /* Line above always fails if INSN was moved by loop opt. */
2432 || (uid_luid
[regno_last_uid
[REGNO (v
->dest_reg
)]]
2433 >= INSN_LUID (loop_end
)))
2434 && ! (final_value
= v
->final_value
))
2438 /* Currently, non-reduced/final-value givs are never split. */
2439 /* Should emit insns after the loop if possible, as the biv final value
2442 /* If the final value is non-zero, and the giv has not been reduced,
2443 then must emit an instruction to set the final value. */
2444 if (final_value
&& !v
->new_reg
)
2446 /* Create a new register to hold the value of the giv, and then set
2447 the giv to its final value before the loop start. The giv is set
2448 to its final value before loop start to ensure that this insn
2449 will always be executed, no matter how we exit. */
2450 tem
= gen_reg_rtx (v
->mode
);
2451 emit_insn_before (gen_move_insn (tem
, v
->dest_reg
), loop_start
);
2452 emit_insn_before (gen_move_insn (v
->dest_reg
, final_value
),
2455 if (loop_dump_stream
)
2456 fprintf (loop_dump_stream
, "Giv %d mapped to %d for split.\n",
2457 REGNO (v
->dest_reg
), REGNO (tem
));
2463 /* This giv is splittable. If completely unrolling the loop, save the
2464 giv's initial value. Otherwise, save the constant zero for it. */
2466 if (unroll_type
== UNROLL_COMPLETELY
)
2468 /* It is not safe to use bl->initial_value here, because it may not
2469 be invariant. It is safe to use the initial value stored in
2470 the splittable_regs array if it is set. In rare cases, it won't
2471 be set, so then we do exactly the same thing as
2472 find_splittable_regs does to get a safe value. */
2473 rtx biv_initial_value
;
2475 if (splittable_regs
[bl
->regno
])
2476 biv_initial_value
= splittable_regs
[bl
->regno
];
2477 else if (GET_CODE (bl
->initial_value
) != REG
2478 || (REGNO (bl
->initial_value
) != bl
->regno
2479 && REGNO (bl
->initial_value
) >= FIRST_PSEUDO_REGISTER
))
2480 biv_initial_value
= bl
->initial_value
;
2483 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2485 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2487 biv_initial_value
= tem
;
2489 value
= fold_rtx_mult_add (v
->mult_val
, biv_initial_value
,
2490 v
->add_val
, v
->mode
);
2497 /* If a giv was combined with another giv, then we can only split
2498 this giv if the giv it was combined with was reduced. This
2499 is because the value of v->new_reg is meaningless in this
2501 if (v
->same
&& ! v
->same
->new_reg
)
2503 if (loop_dump_stream
)
2504 fprintf (loop_dump_stream
,
2505 "giv combined with unreduced giv not split.\n");
2508 /* If the giv is an address destination, it could be something other
2509 than a simple register, these have to be treated differently. */
2510 else if (v
->giv_type
== DEST_REG
)
2512 /* If value is not a constant, register, or register plus
2513 constant, then compute its value into a register before
2514 loop start. This prevents illegal rtx sharing, and should
2515 generate better code. We can use bl->initial_value here
2516 instead of splittable_regs[bl->regno] because this code
2517 is going before the loop start. */
2518 if (unroll_type
== UNROLL_COMPLETELY
2519 && GET_CODE (value
) != CONST_INT
2520 && GET_CODE (value
) != REG
2521 && (GET_CODE (value
) != PLUS
2522 || GET_CODE (XEXP (value
, 0)) != REG
2523 || GET_CODE (XEXP (value
, 1)) != CONST_INT
))
2525 rtx tem
= gen_reg_rtx (v
->mode
);
2526 emit_iv_add_mult (bl
->initial_value
, v
->mult_val
,
2527 v
->add_val
, tem
, loop_start
);
2531 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2535 /* Splitting address givs is useful since it will often allow us
2536 to eliminate some increment insns for the base giv as
2539 /* If the addr giv is combined with a dest_reg giv, then all
2540 references to that dest reg will be remapped, which is NOT
2541 what we want for split addr regs. We always create a new
2542 register for the split addr giv, just to be safe. */
2544 /* ??? If there are multiple address givs which have been
2545 combined with the same dest_reg giv, then we may only need
2546 one new register for them. Pulling out constants below will
2547 catch some of the common cases of this. Currently, I leave
2548 the work of simplifying multiple address givs to the
2549 following cse pass. */
2551 v
->const_adjust
= 0;
2552 if (unroll_type
!= UNROLL_COMPLETELY
)
2554 /* If not completely unrolling the loop, then create a new
2555 register to hold the split value of the DEST_ADDR giv.
2556 Emit insn to initialize its value before loop start. */
2557 tem
= gen_reg_rtx (v
->mode
);
2559 /* If the address giv has a constant in its new_reg value,
2560 then this constant can be pulled out and put in value,
2561 instead of being part of the initialization code. */
2563 if (GET_CODE (v
->new_reg
) == PLUS
2564 && GET_CODE (XEXP (v
->new_reg
, 1)) == CONST_INT
)
2567 = plus_constant (tem
, INTVAL (XEXP (v
->new_reg
,1)));
2569 /* Only succeed if this will give valid addresses.
2570 Try to validate both the first and the last
2571 address resulting from loop unrolling, if
2572 one fails, then can't do const elim here. */
2573 if (memory_address_p (v
->mem_mode
, v
->dest_reg
)
2574 && memory_address_p (v
->mem_mode
,
2575 plus_constant (v
->dest_reg
,
2577 * (unroll_number
- 1))))
2579 /* Save the negative of the eliminated const, so
2580 that we can calculate the dest_reg's increment
2582 v
->const_adjust
= - INTVAL (XEXP (v
->new_reg
, 1));
2584 v
->new_reg
= XEXP (v
->new_reg
, 0);
2585 if (loop_dump_stream
)
2586 fprintf (loop_dump_stream
,
2587 "Eliminating constant from giv %d\n",
2596 /* If the address hasn't been checked for validity yet, do so
2597 now, and fail completely if either the first or the last
2598 unrolled copy of the address is not a valid address. */
2599 if (v
->dest_reg
== tem
2600 && (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2601 || ! memory_address_p (v
->mem_mode
,
2602 plus_constant (v
->dest_reg
,
2604 * (unroll_number
-1)))))
2606 if (loop_dump_stream
)
2607 fprintf (loop_dump_stream
,
2608 "Illegal address for giv at insn %d\n",
2609 INSN_UID (v
->insn
));
2613 /* To initialize the new register, just move the value of
2614 new_reg into it. This is not guaranteed to give a valid
2615 instruction on machines with complex addressing modes.
2616 If we can't recognize it, then delete it and emit insns
2617 to calculate the value from scratch. */
2618 emit_insn_before (gen_rtx (SET
, VOIDmode
, tem
,
2619 copy_rtx (v
->new_reg
)),
2621 if (recog_memoized (PREV_INSN (loop_start
)) < 0)
2623 delete_insn (PREV_INSN (loop_start
));
2624 emit_iv_add_mult (bl
->initial_value
, v
->mult_val
,
2625 v
->add_val
, tem
, loop_start
);
2626 if (loop_dump_stream
)
2627 fprintf (loop_dump_stream
,
2628 "Illegal init insn, rewritten.\n");
2633 v
->dest_reg
= value
;
2635 /* Check the resulting address for validity, and fail
2636 if the resulting address would be illegal. */
2637 if (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2638 || ! memory_address_p (v
->mem_mode
,
2639 plus_constant (v
->dest_reg
,
2641 (unroll_number
-1))))
2643 if (loop_dump_stream
)
2644 fprintf (loop_dump_stream
,
2645 "Illegal address for giv at insn %d\n",
2646 INSN_UID (v
->insn
));
2651 /* Store the value of dest_reg into the insn. This sharing
2652 will not be a problem as this insn will always be copied
2655 *v
->location
= v
->dest_reg
;
2657 /* If this address giv is combined with a dest reg giv, then
2658 save the base giv's induction pointer so that we will be
2659 able to handle this address giv properly. The base giv
2660 itself does not have to be splittable. */
2662 if (v
->same
&& v
->same
->giv_type
== DEST_REG
)
2663 addr_combined_regs
[REGNO (v
->same
->new_reg
)] = v
->same
;
2665 if (GET_CODE (v
->new_reg
) == REG
)
2667 /* This giv maybe hasn't been combined with any others.
2668 Make sure that it's giv is marked as splittable here. */
2670 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2672 /* Make it appear to depend upon itself, so that the
2673 giv will be properly split in the main loop above. */
2677 addr_combined_regs
[REGNO (v
->new_reg
)] = v
;
2681 if (loop_dump_stream
)
2682 fprintf (loop_dump_stream
, "DEST_ADDR giv being split.\n");
2688 /* Currently, unreduced giv's can't be split. This is not too much
2689 of a problem since unreduced giv's are not live across loop
2690 iterations anyways. When unrolling a loop completely though,
2691 it makes sense to reduce&split givs when possible, as this will
2692 result in simpler instructions, and will not require that a reg
2693 be live across loop iterations. */
2695 splittable_regs
[REGNO (v
->dest_reg
)] = value
;
2696 fprintf (stderr
, "Giv %d at insn %d not reduced\n",
2697 REGNO (v
->dest_reg
), INSN_UID (v
->insn
));
2703 /* Givs are only updated once by definition. Mark it so if this is
2704 a splittable register. Don't need to do anything for address givs
2705 where this may not be a register. */
2707 if (GET_CODE (v
->new_reg
) == REG
)
2708 splittable_regs_updates
[REGNO (v
->new_reg
)] = 1;
2712 if (loop_dump_stream
)
2716 if (GET_CODE (v
->dest_reg
) == CONST_INT
)
2718 else if (GET_CODE (v
->dest_reg
) != REG
)
2719 regnum
= REGNO (XEXP (v
->dest_reg
, 0));
2721 regnum
= REGNO (v
->dest_reg
);
2722 fprintf (loop_dump_stream
, "Giv %d at insn %d safe to split.\n",
2723 regnum
, INSN_UID (v
->insn
));
2730 /* Try to prove that the register is dead after the loop exits. Trace every
2731 loop exit looking for an insn that will always be executed, which sets
2732 the register to some value, and appears before the first use of the register
2733 is found. If successful, then return 1, otherwise return 0. */
2735 /* ?? Could be made more intelligent in the handling of jumps, so that
2736 it can search past if statements and other similar structures. */
2739 reg_dead_after_loop (reg
, loop_start
, loop_end
)
2740 rtx reg
, loop_start
, loop_end
;
2746 /* HACK: Must also search the loop fall through exit, create a label_ref
2747 here which points to the loop_end, and append the loop_number_exit_labels
2749 label
= gen_rtx (LABEL_REF
, VOIDmode
, loop_end
);
2750 LABEL_NEXTREF (label
)
2751 = loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]];
2753 for ( ; label
; label
= LABEL_NEXTREF (label
))
2755 /* Succeed if find an insn which sets the biv or if reach end of
2756 function. Fail if find an insn that uses the biv, or if come to
2757 a conditional jump. */
2759 insn
= NEXT_INSN (XEXP (label
, 0));
2762 code
= GET_CODE (insn
);
2763 if (GET_RTX_CLASS (code
) == 'i')
2767 if (reg_referenced_p (reg
, PATTERN (insn
)))
2770 set
= single_set (insn
);
2771 if (set
&& rtx_equal_p (SET_DEST (set
), reg
))
2775 if (code
== JUMP_INSN
)
2777 if (GET_CODE (PATTERN (insn
)) == RETURN
)
2779 else if (! simplejump_p (insn
)
2780 /* Prevent infinite loop following infinite loops. */
2781 || jump_count
++ > 20)
2784 insn
= JUMP_LABEL (insn
);
2787 insn
= NEXT_INSN (insn
);
2791 /* Success, the register is dead on all loop exits. */
2795 /* Try to calculate the final value of the biv, the value it will have at
2796 the end of the loop. If we can do it, return that value. */
2799 final_biv_value (bl
, loop_start
, loop_end
)
2800 struct iv_class
*bl
;
2801 rtx loop_start
, loop_end
;
2805 /* ??? This only works for MODE_INT biv's. Reject all others for now. */
2807 if (GET_MODE_CLASS (bl
->biv
->mode
) != MODE_INT
)
2810 /* The final value for reversed bivs must be calculated differently than
2811 for ordinary bivs. In this case, there is already an insn after the
2812 loop which sets this biv's final value (if necessary), and there are
2813 no other loop exits, so we can return any value. */
2816 if (loop_dump_stream
)
2817 fprintf (loop_dump_stream
,
2818 "Final biv value for %d, reversed biv.\n", bl
->regno
);
2823 /* Try to calculate the final value as initial value + (number of iterations
2824 * increment). For this to work, increment must be invariant, the only
2825 exit from the loop must be the fall through at the bottom (otherwise
2826 it may not have its final value when the loop exits), and the initial
2827 value of the biv must be invariant. */
2829 if (loop_n_iterations
!= 0
2830 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2831 && invariant_p (bl
->initial_value
))
2833 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2835 if (increment
&& invariant_p (increment
))
2837 /* Can calculate the loop exit value, emit insns after loop
2838 end to calculate this value into a temporary register in
2839 case it is needed later. */
2841 tem
= gen_reg_rtx (bl
->biv
->mode
);
2842 /* Make sure loop_end is not the last insn. */
2843 if (NEXT_INSN (loop_end
) == 0)
2844 emit_note_after (NOTE_INSN_DELETED
, loop_end
);
2845 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2846 bl
->initial_value
, tem
, NEXT_INSN (loop_end
));
2848 if (loop_dump_stream
)
2849 fprintf (loop_dump_stream
,
2850 "Final biv value for %d, calculated.\n", bl
->regno
);
2856 /* Check to see if the biv is dead at all loop exits. */
2857 if (reg_dead_after_loop (bl
->biv
->src_reg
, loop_start
, loop_end
))
2859 if (loop_dump_stream
)
2860 fprintf (loop_dump_stream
,
2861 "Final biv value for %d, biv dead after loop exit.\n",
2870 /* Try to calculate the final value of the giv, the value it will have at
2871 the end of the loop. If we can do it, return that value. */
2874 final_giv_value (v
, loop_start
, loop_end
)
2875 struct induction
*v
;
2876 rtx loop_start
, loop_end
;
2878 struct iv_class
*bl
;
2882 rtx insert_before
, seq
;
2884 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2886 /* The final value for givs which depend on reversed bivs must be calculated
2887 differently than for ordinary givs. In this case, there is already an
2888 insn after the loop which sets this giv's final value (if necessary),
2889 and there are no other loop exits, so we can return any value. */
2892 if (loop_dump_stream
)
2893 fprintf (loop_dump_stream
,
2894 "Final giv value for %d, depends on reversed biv\n",
2895 REGNO (v
->dest_reg
));
2899 /* Try to calculate the final value as a function of the biv it depends
2900 upon. The only exit from the loop must be the fall through at the bottom
2901 (otherwise it may not have its final value when the loop exits). */
2903 /* ??? Can calculate the final giv value by subtracting off the
2904 extra biv increments times the giv's mult_val. The loop must have
2905 only one exit for this to work, but the loop iterations does not need
2908 if (loop_n_iterations
!= 0
2909 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2911 /* ?? It is tempting to use the biv's value here since these insns will
2912 be put after the loop, and hence the biv will have its final value
2913 then. However, this fails if the biv is subsequently eliminated.
2914 Perhaps determine whether biv's are eliminable before trying to
2915 determine whether giv's are replaceable so that we can use the
2916 biv value here if it is not eliminable. */
2918 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2920 if (increment
&& invariant_p (increment
))
2922 /* Can calculate the loop exit value of its biv as
2923 (loop_n_iterations * increment) + initial_value */
2925 /* The loop exit value of the giv is then
2926 (final_biv_value - extra increments) * mult_val + add_val.
2927 The extra increments are any increments to the biv which
2928 occur in the loop after the giv's value is calculated.
2929 We must search from the insn that sets the giv to the end
2930 of the loop to calculate this value. */
2932 insert_before
= NEXT_INSN (loop_end
);
2934 /* Put the final biv value in tem. */
2935 tem
= gen_reg_rtx (bl
->biv
->mode
);
2936 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2937 bl
->initial_value
, tem
, insert_before
);
2939 /* Subtract off extra increments as we find them. */
2940 for (insn
= NEXT_INSN (v
->insn
); insn
!= loop_end
;
2941 insn
= NEXT_INSN (insn
))
2943 struct induction
*biv
;
2945 for (biv
= bl
->biv
; biv
; biv
= biv
->next_iv
)
2946 if (biv
->insn
== insn
)
2949 tem
= expand_binop (GET_MODE (tem
), sub_optab
, tem
,
2950 biv
->add_val
, NULL_RTX
, 0,
2952 seq
= gen_sequence ();
2954 emit_insn_before (seq
, insert_before
);
2958 /* Now calculate the giv's final value. */
2959 emit_iv_add_mult (tem
, v
->mult_val
, v
->add_val
, tem
,
2962 if (loop_dump_stream
)
2963 fprintf (loop_dump_stream
,
2964 "Final giv value for %d, calc from biv's value.\n",
2965 REGNO (v
->dest_reg
));
2971 /* Replaceable giv's should never reach here. */
2975 /* Check to see if the biv is dead at all loop exits. */
2976 if (reg_dead_after_loop (v
->dest_reg
, loop_start
, loop_end
))
2978 if (loop_dump_stream
)
2979 fprintf (loop_dump_stream
,
2980 "Final giv value for %d, giv dead after loop exit.\n",
2981 REGNO (v
->dest_reg
));
2990 /* Calculate the number of loop iterations. Returns the exact number of loop
2991 iterations if it can be calculated, otherwise returns zero. */
2993 unsigned HOST_WIDE_INT
2994 loop_iterations (loop_start
, loop_end
)
2995 rtx loop_start
, loop_end
;
2997 rtx comparison
, comparison_value
;
2998 rtx iteration_var
, initial_value
, increment
, final_value
;
2999 enum rtx_code comparison_code
;
3002 int unsigned_compare
, compare_dir
, final_larger
;
3003 unsigned long tempu
;
3006 /* First find the iteration variable. If the last insn is a conditional
3007 branch, and the insn before tests a register value, make that the
3008 iteration variable. */
3010 loop_initial_value
= 0;
3012 loop_final_value
= 0;
3013 loop_iteration_var
= 0;
3015 last_loop_insn
= prev_nonnote_insn (loop_end
);
3017 comparison
= get_condition_for_loop (last_loop_insn
);
3018 if (comparison
== 0)
3020 if (loop_dump_stream
)
3021 fprintf (loop_dump_stream
,
3022 "Loop unrolling: No final conditional branch found.\n");
3026 /* ??? Get_condition may switch position of induction variable and
3027 invariant register when it canonicalizes the comparison. */
3029 comparison_code
= GET_CODE (comparison
);
3030 iteration_var
= XEXP (comparison
, 0);
3031 comparison_value
= XEXP (comparison
, 1);
3033 if (GET_CODE (iteration_var
) != REG
)
3035 if (loop_dump_stream
)
3036 fprintf (loop_dump_stream
,
3037 "Loop unrolling: Comparison not against register.\n");
3041 /* Loop iterations is always called before any new registers are created
3042 now, so this should never occur. */
3044 if (REGNO (iteration_var
) >= max_reg_before_loop
)
3047 iteration_info (iteration_var
, &initial_value
, &increment
,
3048 loop_start
, loop_end
);
3049 if (initial_value
== 0)
3050 /* iteration_info already printed a message. */
3055 if (loop_dump_stream
)
3056 fprintf (loop_dump_stream
,
3057 "Loop unrolling: Increment value can't be calculated.\n");
3060 if (GET_CODE (increment
) != CONST_INT
)
3062 if (loop_dump_stream
)
3063 fprintf (loop_dump_stream
,
3064 "Loop unrolling: Increment value not constant.\n");
3067 if (GET_CODE (initial_value
) != CONST_INT
)
3069 if (loop_dump_stream
)
3070 fprintf (loop_dump_stream
,
3071 "Loop unrolling: Initial value not constant.\n");
3075 /* If the comparison value is an invariant register, then try to find
3076 its value from the insns before the start of the loop. */
3078 if (GET_CODE (comparison_value
) == REG
&& invariant_p (comparison_value
))
3082 for (insn
= PREV_INSN (loop_start
); insn
; insn
= PREV_INSN (insn
))
3084 if (GET_CODE (insn
) == CODE_LABEL
)
3087 else if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i'
3088 && reg_set_p (comparison_value
, insn
))
3090 /* We found the last insn before the loop that sets the register.
3091 If it sets the entire register, and has a REG_EQUAL note,
3092 then use the value of the REG_EQUAL note. */
3093 if ((set
= single_set (insn
))
3094 && (SET_DEST (set
) == comparison_value
))
3096 rtx note
= find_reg_note (insn
, REG_EQUAL
, NULL_RTX
);
3098 if (note
&& GET_CODE (XEXP (note
, 0)) != EXPR_LIST
)
3099 comparison_value
= XEXP (note
, 0);
3106 final_value
= approx_final_value (comparison_code
, comparison_value
,
3107 &unsigned_compare
, &compare_dir
);
3109 /* Save the calculated values describing this loop's bounds, in case
3110 precondition_loop_p will need them later. These values can not be
3111 recalculated inside precondition_loop_p because strength reduction
3112 optimizations may obscure the loop's structure. */
3114 loop_iteration_var
= iteration_var
;
3115 loop_initial_value
= initial_value
;
3116 loop_increment
= increment
;
3117 loop_final_value
= final_value
;
3119 if (final_value
== 0)
3121 if (loop_dump_stream
)
3122 fprintf (loop_dump_stream
,
3123 "Loop unrolling: EQ comparison loop.\n");
3126 else if (GET_CODE (final_value
) != CONST_INT
)
3128 if (loop_dump_stream
)
3129 fprintf (loop_dump_stream
,
3130 "Loop unrolling: Final value not constant.\n");
3134 /* ?? Final value and initial value do not have to be constants.
3135 Only their difference has to be constant. When the iteration variable
3136 is an array address, the final value and initial value might both
3137 be addresses with the same base but different constant offsets.
3138 Final value must be invariant for this to work.
3140 To do this, need some way to find the values of registers which are
3143 /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
3144 if (unsigned_compare
)
3146 = ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3147 > (unsigned HOST_WIDE_INT
) INTVAL (initial_value
))
3148 - ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3149 < (unsigned HOST_WIDE_INT
) INTVAL (initial_value
));
3151 final_larger
= (INTVAL (final_value
) > INTVAL (initial_value
))
3152 - (INTVAL (final_value
) < INTVAL (initial_value
));
3154 if (INTVAL (increment
) > 0)
3156 else if (INTVAL (increment
) == 0)
3161 /* There are 27 different cases: compare_dir = -1, 0, 1;
3162 final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
3163 There are 4 normal cases, 4 reverse cases (where the iteration variable
3164 will overflow before the loop exits), 4 infinite loop cases, and 15
3165 immediate exit (0 or 1 iteration depending on loop type) cases.
3166 Only try to optimize the normal cases. */
3168 /* (compare_dir/final_larger/increment_dir)
3169 Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
3170 Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
3171 Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
3172 Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
3174 /* ?? If the meaning of reverse loops (where the iteration variable
3175 will overflow before the loop exits) is undefined, then could
3176 eliminate all of these special checks, and just always assume
3177 the loops are normal/immediate/infinite. Note that this means
3178 the sign of increment_dir does not have to be known. Also,
3179 since it does not really hurt if immediate exit loops or infinite loops
3180 are optimized, then that case could be ignored also, and hence all
3181 loops can be optimized.
3183 According to ANSI Spec, the reverse loop case result is undefined,
3184 because the action on overflow is undefined.
3186 See also the special test for NE loops below. */
3188 if (final_larger
== increment_dir
&& final_larger
!= 0
3189 && (final_larger
== compare_dir
|| compare_dir
== 0))
3194 if (loop_dump_stream
)
3195 fprintf (loop_dump_stream
,
3196 "Loop unrolling: Not normal loop.\n");
3200 /* Calculate the number of iterations, final_value is only an approximation,
3201 so correct for that. Note that tempu and loop_n_iterations are
3202 unsigned, because they can be as large as 2^n - 1. */
3204 i
= INTVAL (increment
);
3206 tempu
= INTVAL (final_value
) - INTVAL (initial_value
);
3209 tempu
= INTVAL (initial_value
) - INTVAL (final_value
);
3215 /* For NE tests, make sure that the iteration variable won't miss the
3216 final value. If tempu mod i is not zero, then the iteration variable
3217 will overflow before the loop exits, and we can not calculate the
3218 number of iterations. */
3219 if (compare_dir
== 0 && (tempu
% i
) != 0)
3222 return tempu
/ i
+ ((tempu
% i
) != 0);