1 /* Try to unroll loops, and split induction variables.
2 Copyright (C) 1992, 1993, 1994 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 ();
204 static rtx
remap_split_bivs ();
206 /* Try to unroll one loop and split induction variables in the loop.
208 The loop is described by the arguments LOOP_END, INSN_COUNT, and
209 LOOP_START. END_INSERT_BEFORE indicates where insns should be added
210 which need to be executed when the loop falls through. STRENGTH_REDUCTION_P
211 indicates whether information generated in the strength reduction pass
214 This function is intended to be called from within `strength_reduce'
218 unroll_loop (loop_end
, insn_count
, loop_start
, end_insert_before
,
223 rtx end_insert_before
;
224 int strength_reduce_p
;
227 int unroll_number
= 1;
228 rtx copy_start
, copy_end
;
229 rtx insn
, copy
, sequence
, pattern
, tem
;
230 int max_labelno
, max_insnno
;
232 struct inline_remap
*map
;
239 int splitting_not_safe
= 0;
240 enum unroll_types unroll_type
;
241 int loop_preconditioned
= 0;
243 /* This points to the last real insn in the loop, which should be either
244 a JUMP_INSN (for conditional jumps) or a BARRIER (for unconditional
248 /* Don't bother unrolling huge loops. Since the minimum factor is
249 two, loops greater than one half of MAX_UNROLLED_INSNS will never
251 if (insn_count
> MAX_UNROLLED_INSNS
/ 2)
253 if (loop_dump_stream
)
254 fprintf (loop_dump_stream
, "Unrolling failure: Loop too big.\n");
258 /* When emitting debugger info, we can't unroll loops with unequal numbers
259 of block_beg and block_end notes, because that would unbalance the block
260 structure of the function. This can happen as a result of the
261 "if (foo) bar; else break;" optimization in jump.c. */
263 if (write_symbols
!= NO_DEBUG
)
265 int block_begins
= 0;
268 for (insn
= loop_start
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
270 if (GET_CODE (insn
) == NOTE
)
272 if (NOTE_LINE_NUMBER (insn
) == NOTE_INSN_BLOCK_BEG
)
274 else if (NOTE_LINE_NUMBER (insn
) == NOTE_INSN_BLOCK_END
)
279 if (block_begins
!= block_ends
)
281 if (loop_dump_stream
)
282 fprintf (loop_dump_stream
,
283 "Unrolling failure: Unbalanced block notes.\n");
288 /* Determine type of unroll to perform. Depends on the number of iterations
289 and the size of the loop. */
291 /* If there is no strength reduce info, then set loop_n_iterations to zero.
292 This can happen if strength_reduce can't find any bivs in the loop.
293 A value of zero indicates that the number of iterations could not be
296 if (! strength_reduce_p
)
297 loop_n_iterations
= 0;
299 if (loop_dump_stream
&& loop_n_iterations
> 0)
300 fprintf (loop_dump_stream
,
301 "Loop unrolling: %d iterations.\n", loop_n_iterations
);
303 /* Find and save a pointer to the last nonnote insn in the loop. */
305 last_loop_insn
= prev_nonnote_insn (loop_end
);
307 /* Calculate how many times to unroll the loop. Indicate whether or
308 not the loop is being completely unrolled. */
310 if (loop_n_iterations
== 1)
312 /* If number of iterations is exactly 1, then eliminate the compare and
313 branch at the end of the loop since they will never be taken.
314 Then return, since no other action is needed here. */
316 /* If the last instruction is not a BARRIER or a JUMP_INSN, then
317 don't do anything. */
319 if (GET_CODE (last_loop_insn
) == BARRIER
)
321 /* Delete the jump insn. This will delete the barrier also. */
322 delete_insn (PREV_INSN (last_loop_insn
));
324 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
327 /* The immediately preceding insn is a compare which must be
329 delete_insn (last_loop_insn
);
330 delete_insn (PREV_INSN (last_loop_insn
));
332 /* The immediately preceding insn may not be the compare, so don't
334 delete_insn (last_loop_insn
);
339 else if (loop_n_iterations
> 0
340 && loop_n_iterations
* insn_count
< MAX_UNROLLED_INSNS
)
342 unroll_number
= loop_n_iterations
;
343 unroll_type
= UNROLL_COMPLETELY
;
345 else if (loop_n_iterations
> 0)
347 /* Try to factor the number of iterations. Don't bother with the
348 general case, only using 2, 3, 5, and 7 will get 75% of all
349 numbers theoretically, and almost all in practice. */
351 for (i
= 0; i
< NUM_FACTORS
; i
++)
352 factors
[i
].count
= 0;
354 temp
= loop_n_iterations
;
355 for (i
= NUM_FACTORS
- 1; i
>= 0; i
--)
356 while (temp
% factors
[i
].factor
== 0)
359 temp
= temp
/ factors
[i
].factor
;
362 /* Start with the larger factors first so that we generally
363 get lots of unrolling. */
367 for (i
= 3; i
>= 0; i
--)
368 while (factors
[i
].count
--)
370 if (temp
* factors
[i
].factor
< MAX_UNROLLED_INSNS
)
372 unroll_number
*= factors
[i
].factor
;
373 temp
*= factors
[i
].factor
;
379 /* If we couldn't find any factors, then unroll as in the normal
381 if (unroll_number
== 1)
383 if (loop_dump_stream
)
384 fprintf (loop_dump_stream
,
385 "Loop unrolling: No factors found.\n");
388 unroll_type
= UNROLL_MODULO
;
392 /* Default case, calculate number of times to unroll loop based on its
394 if (unroll_number
== 1)
396 if (8 * insn_count
< MAX_UNROLLED_INSNS
)
398 else if (4 * insn_count
< MAX_UNROLLED_INSNS
)
403 unroll_type
= UNROLL_NAIVE
;
406 /* Now we know how many times to unroll the loop. */
408 if (loop_dump_stream
)
409 fprintf (loop_dump_stream
,
410 "Unrolling loop %d times.\n", unroll_number
);
413 if (unroll_type
== UNROLL_COMPLETELY
|| unroll_type
== UNROLL_MODULO
)
415 /* Loops of these types should never start with a jump down to
416 the exit condition test. For now, check for this case just to
417 be sure. UNROLL_NAIVE loops can be of this form, this case is
420 while (GET_CODE (insn
) != CODE_LABEL
&& GET_CODE (insn
) != JUMP_INSN
)
421 insn
= NEXT_INSN (insn
);
422 if (GET_CODE (insn
) == JUMP_INSN
)
426 if (unroll_type
== UNROLL_COMPLETELY
)
428 /* Completely unrolling the loop: Delete the compare and branch at
429 the end (the last two instructions). This delete must done at the
430 very end of loop unrolling, to avoid problems with calls to
431 back_branch_in_range_p, which is called by find_splittable_regs.
432 All increments of splittable bivs/givs are changed to load constant
435 copy_start
= loop_start
;
437 /* Set insert_before to the instruction immediately after the JUMP_INSN
438 (or BARRIER), so that any NOTEs between the JUMP_INSN and the end of
439 the loop will be correctly handled by copy_loop_body. */
440 insert_before
= NEXT_INSN (last_loop_insn
);
442 /* Set copy_end to the insn before the jump at the end of the loop. */
443 if (GET_CODE (last_loop_insn
) == BARRIER
)
444 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
445 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
448 /* The instruction immediately before the JUMP_INSN is a compare
449 instruction which we do not want to copy. */
450 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
452 /* The instruction immediately before the JUMP_INSN may not be the
453 compare, so we must copy it. */
454 copy_end
= PREV_INSN (last_loop_insn
);
459 /* We currently can't unroll a loop if it doesn't end with a
460 JUMP_INSN. There would need to be a mechanism that recognizes
461 this case, and then inserts a jump after each loop body, which
462 jumps to after the last loop body. */
463 if (loop_dump_stream
)
464 fprintf (loop_dump_stream
,
465 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
469 else if (unroll_type
== UNROLL_MODULO
)
471 /* Partially unrolling the loop: The compare and branch at the end
472 (the last two instructions) must remain. Don't copy the compare
473 and branch instructions at the end of the loop. Insert the unrolled
474 code immediately before the compare/branch at the end so that the
475 code will fall through to them as before. */
477 copy_start
= loop_start
;
479 /* Set insert_before to the jump insn at the end of the loop.
480 Set copy_end to before the jump insn at the end of the loop. */
481 if (GET_CODE (last_loop_insn
) == BARRIER
)
483 insert_before
= PREV_INSN (last_loop_insn
);
484 copy_end
= PREV_INSN (insert_before
);
486 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
489 /* The instruction immediately before the JUMP_INSN is a compare
490 instruction which we do not want to copy or delete. */
491 insert_before
= PREV_INSN (last_loop_insn
);
492 copy_end
= PREV_INSN (insert_before
);
494 /* The instruction immediately before the JUMP_INSN may not be the
495 compare, so we must copy it. */
496 insert_before
= last_loop_insn
;
497 copy_end
= PREV_INSN (last_loop_insn
);
502 /* We currently can't unroll a loop if it doesn't end with a
503 JUMP_INSN. There would need to be a mechanism that recognizes
504 this case, and then inserts a jump after each loop body, which
505 jumps to after the last loop body. */
506 if (loop_dump_stream
)
507 fprintf (loop_dump_stream
,
508 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
514 /* Normal case: Must copy the compare and branch instructions at the
517 if (GET_CODE (last_loop_insn
) == BARRIER
)
519 /* Loop ends with an unconditional jump and a barrier.
520 Handle this like above, don't copy jump and barrier.
521 This is not strictly necessary, but doing so prevents generating
522 unconditional jumps to an immediately following label.
524 This will be corrected below if the target of this jump is
525 not the start_label. */
527 insert_before
= PREV_INSN (last_loop_insn
);
528 copy_end
= PREV_INSN (insert_before
);
530 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
532 /* Set insert_before to immediately after the JUMP_INSN, so that
533 NOTEs at the end of the loop will be correctly handled by
535 insert_before
= NEXT_INSN (last_loop_insn
);
536 copy_end
= last_loop_insn
;
540 /* We currently can't unroll a loop if it doesn't end with a
541 JUMP_INSN. There would need to be a mechanism that recognizes
542 this case, and then inserts a jump after each loop body, which
543 jumps to after the last loop body. */
544 if (loop_dump_stream
)
545 fprintf (loop_dump_stream
,
546 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
550 /* If copying exit test branches because they can not be eliminated,
551 then must convert the fall through case of the branch to a jump past
552 the end of the loop. Create a label to emit after the loop and save
553 it for later use. Do not use the label after the loop, if any, since
554 it might be used by insns outside the loop, or there might be insns
555 added before it later by final_[bg]iv_value which must be after
556 the real exit label. */
557 exit_label
= gen_label_rtx ();
560 while (GET_CODE (insn
) != CODE_LABEL
&& GET_CODE (insn
) != JUMP_INSN
)
561 insn
= NEXT_INSN (insn
);
563 if (GET_CODE (insn
) == JUMP_INSN
)
565 /* The loop starts with a jump down to the exit condition test.
566 Start copying the loop after the barrier following this
568 copy_start
= NEXT_INSN (insn
);
570 /* Splitting induction variables doesn't work when the loop is
571 entered via a jump to the bottom, because then we end up doing
572 a comparison against a new register for a split variable, but
573 we did not execute the set insn for the new register because
574 it was skipped over. */
575 splitting_not_safe
= 1;
576 if (loop_dump_stream
)
577 fprintf (loop_dump_stream
,
578 "Splitting not safe, because loop not entered at top.\n");
581 copy_start
= loop_start
;
584 /* This should always be the first label in the loop. */
585 start_label
= NEXT_INSN (copy_start
);
586 /* There may be a line number note and/or a loop continue note here. */
587 while (GET_CODE (start_label
) == NOTE
)
588 start_label
= NEXT_INSN (start_label
);
589 if (GET_CODE (start_label
) != CODE_LABEL
)
591 /* This can happen as a result of jump threading. If the first insns in
592 the loop test the same condition as the loop's backward jump, or the
593 opposite condition, then the backward jump will be modified to point
594 to elsewhere, and the loop's start label is deleted.
596 This case currently can not be handled by the loop unrolling code. */
598 if (loop_dump_stream
)
599 fprintf (loop_dump_stream
,
600 "Unrolling failure: unknown insns between BEG note and loop label.\n");
603 if (LABEL_NAME (start_label
))
605 /* The jump optimization pass must have combined the original start label
606 with a named label for a goto. We can't unroll this case because
607 jumps which go to the named label must be handled differently than
608 jumps to the loop start, and it is impossible to differentiate them
610 if (loop_dump_stream
)
611 fprintf (loop_dump_stream
,
612 "Unrolling failure: loop start label is gone\n");
616 if (unroll_type
== UNROLL_NAIVE
617 && GET_CODE (last_loop_insn
) == BARRIER
618 && start_label
!= JUMP_LABEL (PREV_INSN (last_loop_insn
)))
620 /* In this case, we must copy the jump and barrier, because they will
621 not be converted to jumps to an immediately following label. */
623 insert_before
= NEXT_INSN (last_loop_insn
);
624 copy_end
= last_loop_insn
;
627 /* Allocate a translation table for the labels and insn numbers.
628 They will be filled in as we copy the insns in the loop. */
630 max_labelno
= max_label_num ();
631 max_insnno
= get_max_uid ();
633 map
= (struct inline_remap
*) alloca (sizeof (struct inline_remap
));
635 map
->integrating
= 0;
637 /* Allocate the label map. */
641 map
->label_map
= (rtx
*) alloca (max_labelno
* sizeof (rtx
));
643 local_label
= (char *) alloca (max_labelno
);
644 bzero (local_label
, max_labelno
);
649 /* Search the loop and mark all local labels, i.e. the ones which have to
650 be distinct labels when copied. For all labels which might be
651 non-local, set their label_map entries to point to themselves.
652 If they happen to be local their label_map entries will be overwritten
653 before the loop body is copied. The label_map entries for local labels
654 will be set to a different value each time the loop body is copied. */
656 for (insn
= copy_start
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
658 if (GET_CODE (insn
) == CODE_LABEL
)
659 local_label
[CODE_LABEL_NUMBER (insn
)] = 1;
660 else if (GET_CODE (insn
) == JUMP_INSN
)
662 if (JUMP_LABEL (insn
))
663 map
->label_map
[CODE_LABEL_NUMBER (JUMP_LABEL (insn
))]
665 else if (GET_CODE (PATTERN (insn
)) == ADDR_VEC
666 || GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
)
668 rtx pat
= PATTERN (insn
);
669 int diff_vec_p
= GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
;
670 int len
= XVECLEN (pat
, diff_vec_p
);
673 for (i
= 0; i
< len
; i
++)
675 label
= XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0);
676 map
->label_map
[CODE_LABEL_NUMBER (label
)] = label
;
682 /* Allocate space for the insn map. */
684 map
->insn_map
= (rtx
*) alloca (max_insnno
* sizeof (rtx
));
686 /* Set this to zero, to indicate that we are doing loop unrolling,
687 not function inlining. */
688 map
->inline_target
= 0;
690 /* The register and constant maps depend on the number of registers
691 present, so the final maps can't be created until after
692 find_splittable_regs is called. However, they are needed for
693 preconditioning, so we create temporary maps when preconditioning
696 /* The preconditioning code may allocate two new pseudo registers. */
697 maxregnum
= max_reg_num ();
699 /* Allocate and zero out the splittable_regs and addr_combined_regs
700 arrays. These must be zeroed here because they will be used if
701 loop preconditioning is performed, and must be zero for that case.
703 It is safe to do this here, since the extra registers created by the
704 preconditioning code and find_splittable_regs will never be used
705 to access the splittable_regs[] and addr_combined_regs[] arrays. */
707 splittable_regs
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
708 bzero (splittable_regs
, maxregnum
* sizeof (rtx
));
709 splittable_regs_updates
= (int *) alloca (maxregnum
* sizeof (int));
710 bzero (splittable_regs_updates
, maxregnum
* sizeof (int));
712 = (struct induction
**) alloca (maxregnum
* sizeof (struct induction
*));
713 bzero (addr_combined_regs
, maxregnum
* sizeof (struct induction
*));
715 /* If this loop requires exit tests when unrolled, check to see if we
716 can precondition the loop so as to make the exit tests unnecessary.
717 Just like variable splitting, this is not safe if the loop is entered
718 via a jump to the bottom. Also, can not do this if no strength
719 reduce info, because precondition_loop_p uses this info. */
721 /* Must copy the loop body for preconditioning before the following
722 find_splittable_regs call since that will emit insns which need to
723 be after the preconditioned loop copies, but immediately before the
724 unrolled loop copies. */
726 /* Also, it is not safe to split induction variables for the preconditioned
727 copies of the loop body. If we split induction variables, then the code
728 assumes that each induction variable can be represented as a function
729 of its initial value and the loop iteration number. This is not true
730 in this case, because the last preconditioned copy of the loop body
731 could be any iteration from the first up to the `unroll_number-1'th,
732 depending on the initial value of the iteration variable. Therefore
733 we can not split induction variables here, because we can not calculate
734 their value. Hence, this code must occur before find_splittable_regs
737 if (unroll_type
== UNROLL_NAIVE
&& ! splitting_not_safe
&& strength_reduce_p
)
739 rtx initial_value
, final_value
, increment
;
741 if (precondition_loop_p (&initial_value
, &final_value
, &increment
,
742 loop_start
, loop_end
))
744 register rtx diff
, temp
;
745 enum machine_mode mode
;
747 int abs_inc
, neg_inc
;
749 map
->reg_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
751 map
->const_equiv_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
752 map
->const_age_map
= (unsigned *) alloca (maxregnum
753 * sizeof (unsigned));
754 map
->const_equiv_map_size
= maxregnum
;
755 global_const_equiv_map
= map
->const_equiv_map
;
756 global_const_equiv_map_size
= maxregnum
;
758 init_reg_map (map
, maxregnum
);
760 /* Limit loop unrolling to 4, since this will make 7 copies of
762 if (unroll_number
> 4)
765 /* Save the absolute value of the increment, and also whether or
766 not it is negative. */
768 abs_inc
= INTVAL (increment
);
777 /* Decide what mode to do these calculations in. Choose the larger
778 of final_value's mode and initial_value's mode, or a full-word if
779 both are constants. */
780 mode
= GET_MODE (final_value
);
781 if (mode
== VOIDmode
)
783 mode
= GET_MODE (initial_value
);
784 if (mode
== VOIDmode
)
787 else if (mode
!= GET_MODE (initial_value
)
788 && (GET_MODE_SIZE (mode
)
789 < GET_MODE_SIZE (GET_MODE (initial_value
))))
790 mode
= GET_MODE (initial_value
);
792 /* Calculate the difference between the final and initial values.
793 Final value may be a (plus (reg x) (const_int 1)) rtx.
794 Let the following cse pass simplify this if initial value is
797 We must copy the final and initial values here to avoid
798 improperly shared rtl. */
800 diff
= expand_binop (mode
, sub_optab
, copy_rtx (final_value
),
801 copy_rtx (initial_value
), NULL_RTX
, 0,
804 /* Now calculate (diff % (unroll * abs (increment))) by using an
806 diff
= expand_binop (GET_MODE (diff
), and_optab
, diff
,
807 GEN_INT (unroll_number
* abs_inc
- 1),
808 NULL_RTX
, 0, OPTAB_LIB_WIDEN
);
810 /* Now emit a sequence of branches to jump to the proper precond
813 labels
= (rtx
*) alloca (sizeof (rtx
) * unroll_number
);
814 for (i
= 0; i
< unroll_number
; i
++)
815 labels
[i
] = gen_label_rtx ();
817 /* Assuming the unroll_number is 4, and the increment is 2, then
818 for a negative increment: for a positive increment:
819 diff = 0,1 precond 0 diff = 0,7 precond 0
820 diff = 2,3 precond 3 diff = 1,2 precond 1
821 diff = 4,5 precond 2 diff = 3,4 precond 2
822 diff = 6,7 precond 1 diff = 5,6 precond 3 */
824 /* We only need to emit (unroll_number - 1) branches here, the
825 last case just falls through to the following code. */
827 /* ??? This would give better code if we emitted a tree of branches
828 instead of the current linear list of branches. */
830 for (i
= 0; i
< unroll_number
- 1; i
++)
834 /* For negative increments, must invert the constant compared
835 against, except when comparing against zero. */
839 cmp_const
= unroll_number
- i
;
843 emit_cmp_insn (diff
, GEN_INT (abs_inc
* cmp_const
),
844 EQ
, NULL_RTX
, mode
, 0, 0);
847 emit_jump_insn (gen_beq (labels
[i
]));
849 emit_jump_insn (gen_bge (labels
[i
]));
851 emit_jump_insn (gen_ble (labels
[i
]));
852 JUMP_LABEL (get_last_insn ()) = labels
[i
];
853 LABEL_NUSES (labels
[i
])++;
856 /* If the increment is greater than one, then we need another branch,
857 to handle other cases equivalent to 0. */
859 /* ??? This should be merged into the code above somehow to help
860 simplify the code here, and reduce the number of branches emitted.
861 For the negative increment case, the branch here could easily
862 be merged with the `0' case branch above. For the positive
863 increment case, it is not clear how this can be simplified. */
870 cmp_const
= abs_inc
- 1;
872 cmp_const
= abs_inc
* (unroll_number
- 1) + 1;
874 emit_cmp_insn (diff
, GEN_INT (cmp_const
), EQ
, NULL_RTX
,
878 emit_jump_insn (gen_ble (labels
[0]));
880 emit_jump_insn (gen_bge (labels
[0]));
881 JUMP_LABEL (get_last_insn ()) = labels
[0];
882 LABEL_NUSES (labels
[0])++;
885 sequence
= gen_sequence ();
887 emit_insn_before (sequence
, loop_start
);
889 /* Only the last copy of the loop body here needs the exit
890 test, so set copy_end to exclude the compare/branch here,
891 and then reset it inside the loop when get to the last
894 if (GET_CODE (last_loop_insn
) == BARRIER
)
895 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
896 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
899 /* The immediately preceding insn is a compare which we do not
901 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
903 /* The immediately preceding insn may not be a compare, so we
905 copy_end
= PREV_INSN (last_loop_insn
);
911 for (i
= 1; i
< unroll_number
; i
++)
913 emit_label_after (labels
[unroll_number
- i
],
914 PREV_INSN (loop_start
));
916 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
917 bzero (map
->const_equiv_map
, maxregnum
* sizeof (rtx
));
918 bzero (map
->const_age_map
, maxregnum
* sizeof (unsigned));
921 for (j
= 0; j
< max_labelno
; j
++)
923 map
->label_map
[j
] = gen_label_rtx ();
925 /* The last copy needs the compare/branch insns at the end,
926 so reset copy_end here if the loop ends with a conditional
929 if (i
== unroll_number
- 1)
931 if (GET_CODE (last_loop_insn
) == BARRIER
)
932 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
934 copy_end
= last_loop_insn
;
937 /* None of the copies are the `last_iteration', so just
938 pass zero for that parameter. */
939 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, 0,
940 unroll_type
, start_label
, loop_end
,
941 loop_start
, copy_end
);
943 emit_label_after (labels
[0], PREV_INSN (loop_start
));
945 if (GET_CODE (last_loop_insn
) == BARRIER
)
947 insert_before
= PREV_INSN (last_loop_insn
);
948 copy_end
= PREV_INSN (insert_before
);
953 /* The immediately preceding insn is a compare which we do not
955 insert_before
= PREV_INSN (last_loop_insn
);
956 copy_end
= PREV_INSN (insert_before
);
958 /* The immediately preceding insn may not be a compare, so we
960 insert_before
= last_loop_insn
;
961 copy_end
= PREV_INSN (last_loop_insn
);
965 /* Set unroll type to MODULO now. */
966 unroll_type
= UNROLL_MODULO
;
967 loop_preconditioned
= 1;
971 /* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
972 the loop unless all loops are being unrolled. */
973 if (unroll_type
== UNROLL_NAIVE
&& ! flag_unroll_all_loops
)
975 if (loop_dump_stream
)
976 fprintf (loop_dump_stream
, "Unrolling failure: Naive unrolling not being done.\n");
980 /* At this point, we are guaranteed to unroll the loop. */
982 /* For each biv and giv, determine whether it can be safely split into
983 a different variable for each unrolled copy of the loop body.
984 We precalculate and save this info here, since computing it is
987 Do this before deleting any instructions from the loop, so that
988 back_branch_in_range_p will work correctly. */
990 if (splitting_not_safe
)
993 temp
= find_splittable_regs (unroll_type
, loop_start
, loop_end
,
994 end_insert_before
, unroll_number
);
996 /* find_splittable_regs may have created some new registers, so must
997 reallocate the reg_map with the new larger size, and must realloc
998 the constant maps also. */
1000 maxregnum
= max_reg_num ();
1001 map
->reg_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
1003 init_reg_map (map
, maxregnum
);
1005 /* Space is needed in some of the map for new registers, so new_maxregnum
1006 is an (over)estimate of how many registers will exist at the end. */
1007 new_maxregnum
= maxregnum
+ (temp
* unroll_number
* 2);
1009 /* Must realloc space for the constant maps, because the number of registers
1010 may have changed. */
1012 map
->const_equiv_map
= (rtx
*) alloca (new_maxregnum
* sizeof (rtx
));
1013 map
->const_age_map
= (unsigned *) alloca (new_maxregnum
* sizeof (unsigned));
1015 map
->const_equiv_map_size
= new_maxregnum
;
1016 global_const_equiv_map
= map
->const_equiv_map
;
1017 global_const_equiv_map_size
= new_maxregnum
;
1019 /* Search the list of bivs and givs to find ones which need to be remapped
1020 when split, and set their reg_map entry appropriately. */
1022 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
1024 if (REGNO (bl
->biv
->src_reg
) != bl
->regno
)
1025 map
->reg_map
[bl
->regno
] = bl
->biv
->src_reg
;
1027 /* Currently, non-reduced/final-value givs are never split. */
1028 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
1029 if (REGNO (v
->src_reg
) != bl
->regno
)
1030 map
->reg_map
[REGNO (v
->dest_reg
)] = v
->src_reg
;
1034 /* If the loop is being partially unrolled, and the iteration variables
1035 are being split, and are being renamed for the split, then must fix up
1036 the compare/jump instruction at the end of the loop to refer to the new
1037 registers. This compare isn't copied, so the registers used in it
1038 will never be replaced if it isn't done here. */
1040 if (unroll_type
== UNROLL_MODULO
)
1042 insn
= NEXT_INSN (copy_end
);
1043 if (GET_CODE (insn
) == INSN
|| GET_CODE (insn
) == JUMP_INSN
)
1044 PATTERN (insn
) = remap_split_bivs (PATTERN (insn
));
1047 /* For unroll_number - 1 times, make a copy of each instruction
1048 between copy_start and copy_end, and insert these new instructions
1049 before the end of the loop. */
1051 for (i
= 0; i
< unroll_number
; i
++)
1053 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
1054 bzero (map
->const_equiv_map
, new_maxregnum
* sizeof (rtx
));
1055 bzero (map
->const_age_map
, new_maxregnum
* sizeof (unsigned));
1058 for (j
= 0; j
< max_labelno
; j
++)
1060 map
->label_map
[j
] = gen_label_rtx ();
1062 /* If loop starts with a branch to the test, then fix it so that
1063 it points to the test of the first unrolled copy of the loop. */
1064 if (i
== 0 && loop_start
!= copy_start
)
1066 insn
= PREV_INSN (copy_start
);
1067 pattern
= PATTERN (insn
);
1069 tem
= map
->label_map
[CODE_LABEL_NUMBER
1070 (XEXP (SET_SRC (pattern
), 0))];
1071 SET_SRC (pattern
) = gen_rtx (LABEL_REF
, VOIDmode
, tem
);
1073 /* Set the jump label so that it can be used by later loop unrolling
1075 JUMP_LABEL (insn
) = tem
;
1076 LABEL_NUSES (tem
)++;
1079 copy_loop_body (copy_start
, copy_end
, map
, exit_label
,
1080 i
== unroll_number
- 1, unroll_type
, start_label
,
1081 loop_end
, insert_before
, insert_before
);
1084 /* Before deleting any insns, emit a CODE_LABEL immediately after the last
1085 insn to be deleted. This prevents any runaway delete_insn call from
1086 more insns that it should, as it always stops at a CODE_LABEL. */
1088 /* Delete the compare and branch at the end of the loop if completely
1089 unrolling the loop. Deleting the backward branch at the end also
1090 deletes the code label at the start of the loop. This is done at
1091 the very end to avoid problems with back_branch_in_range_p. */
1093 if (unroll_type
== UNROLL_COMPLETELY
)
1094 safety_label
= emit_label_after (gen_label_rtx (), last_loop_insn
);
1096 safety_label
= emit_label_after (gen_label_rtx (), copy_end
);
1098 /* Delete all of the original loop instructions. Don't delete the
1099 LOOP_BEG note, or the first code label in the loop. */
1101 insn
= NEXT_INSN (copy_start
);
1102 while (insn
!= safety_label
)
1104 if (insn
!= start_label
)
1105 insn
= delete_insn (insn
);
1107 insn
= NEXT_INSN (insn
);
1110 /* Can now delete the 'safety' label emitted to protect us from runaway
1111 delete_insn calls. */
1112 if (INSN_DELETED_P (safety_label
))
1114 delete_insn (safety_label
);
1116 /* If exit_label exists, emit it after the loop. Doing the emit here
1117 forces it to have a higher INSN_UID than any insn in the unrolled loop.
1118 This is needed so that mostly_true_jump in reorg.c will treat jumps
1119 to this loop end label correctly, i.e. predict that they are usually
1122 emit_label_after (exit_label
, loop_end
);
1125 /* Return true if the loop can be safely, and profitably, preconditioned
1126 so that the unrolled copies of the loop body don't need exit tests.
1128 This only works if final_value, initial_value and increment can be
1129 determined, and if increment is a constant power of 2.
1130 If increment is not a power of 2, then the preconditioning modulo
1131 operation would require a real modulo instead of a boolean AND, and this
1132 is not considered `profitable'. */
1134 /* ??? If the loop is known to be executed very many times, or the machine
1135 has a very cheap divide instruction, then preconditioning is a win even
1136 when the increment is not a power of 2. Use RTX_COST to compute
1137 whether divide is cheap. */
1140 precondition_loop_p (initial_value
, final_value
, increment
, loop_start
,
1142 rtx
*initial_value
, *final_value
, *increment
;
1143 rtx loop_start
, loop_end
;
1146 if (loop_n_iterations
> 0)
1148 *initial_value
= const0_rtx
;
1149 *increment
= const1_rtx
;
1150 *final_value
= GEN_INT (loop_n_iterations
);
1152 if (loop_dump_stream
)
1153 fprintf (loop_dump_stream
,
1154 "Preconditioning: Success, number of iterations known, %d.\n",
1159 if (loop_initial_value
== 0)
1161 if (loop_dump_stream
)
1162 fprintf (loop_dump_stream
,
1163 "Preconditioning: Could not find initial value.\n");
1166 else if (loop_increment
== 0)
1168 if (loop_dump_stream
)
1169 fprintf (loop_dump_stream
,
1170 "Preconditioning: Could not find increment value.\n");
1173 else if (GET_CODE (loop_increment
) != CONST_INT
)
1175 if (loop_dump_stream
)
1176 fprintf (loop_dump_stream
,
1177 "Preconditioning: Increment not a constant.\n");
1180 else if ((exact_log2 (INTVAL (loop_increment
)) < 0)
1181 && (exact_log2 (- INTVAL (loop_increment
)) < 0))
1183 if (loop_dump_stream
)
1184 fprintf (loop_dump_stream
,
1185 "Preconditioning: Increment not a constant power of 2.\n");
1189 /* Unsigned_compare and compare_dir can be ignored here, since they do
1190 not matter for preconditioning. */
1192 if (loop_final_value
== 0)
1194 if (loop_dump_stream
)
1195 fprintf (loop_dump_stream
,
1196 "Preconditioning: EQ comparison loop.\n");
1200 /* Must ensure that final_value is invariant, so call invariant_p to
1201 check. Before doing so, must check regno against max_reg_before_loop
1202 to make sure that the register is in the range covered by invariant_p.
1203 If it isn't, then it is most likely a biv/giv which by definition are
1205 if ((GET_CODE (loop_final_value
) == REG
1206 && REGNO (loop_final_value
) >= max_reg_before_loop
)
1207 || (GET_CODE (loop_final_value
) == PLUS
1208 && REGNO (XEXP (loop_final_value
, 0)) >= max_reg_before_loop
)
1209 || ! invariant_p (loop_final_value
))
1211 if (loop_dump_stream
)
1212 fprintf (loop_dump_stream
,
1213 "Preconditioning: Final value not invariant.\n");
1217 /* Fail for floating point values, since the caller of this function
1218 does not have code to deal with them. */
1219 if (GET_MODE_CLASS (GET_MODE (loop_final_value
)) == MODE_FLOAT
1220 || GET_MODE_CLASS (GET_MODE (loop_initial_value
)) == MODE_FLOAT
)
1222 if (loop_dump_stream
)
1223 fprintf (loop_dump_stream
,
1224 "Preconditioning: Floating point final or initial value.\n");
1228 /* Now set initial_value to be the iteration_var, since that may be a
1229 simpler expression, and is guaranteed to be correct if all of the
1230 above tests succeed.
1232 We can not use the initial_value as calculated, because it will be
1233 one too small for loops of the form "while (i-- > 0)". We can not
1234 emit code before the loop_skip_over insns to fix this problem as this
1235 will then give a number one too large for loops of the form
1238 Note that all loops that reach here are entered at the top, because
1239 this function is not called if the loop starts with a jump. */
1241 /* Fail if loop_iteration_var is not live before loop_start, since we need
1242 to test its value in the preconditioning code. */
1244 if (uid_luid
[regno_first_uid
[REGNO (loop_iteration_var
)]]
1245 > INSN_LUID (loop_start
))
1247 if (loop_dump_stream
)
1248 fprintf (loop_dump_stream
,
1249 "Preconditioning: Iteration var not live before loop start.\n");
1253 *initial_value
= loop_iteration_var
;
1254 *increment
= loop_increment
;
1255 *final_value
= loop_final_value
;
1258 if (loop_dump_stream
)
1259 fprintf (loop_dump_stream
, "Preconditioning: Successful.\n");
1264 /* All pseudo-registers must be mapped to themselves. Two hard registers
1265 must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
1266 REGNUM, to avoid function-inlining specific conversions of these
1267 registers. All other hard regs can not be mapped because they may be
1272 init_reg_map (map
, maxregnum
)
1273 struct inline_remap
*map
;
1278 for (i
= maxregnum
- 1; i
> LAST_VIRTUAL_REGISTER
; i
--)
1279 map
->reg_map
[i
] = regno_reg_rtx
[i
];
1280 /* Just clear the rest of the entries. */
1281 for (i
= LAST_VIRTUAL_REGISTER
; i
>= 0; i
--)
1282 map
->reg_map
[i
] = 0;
1284 map
->reg_map
[VIRTUAL_STACK_VARS_REGNUM
]
1285 = regno_reg_rtx
[VIRTUAL_STACK_VARS_REGNUM
];
1286 map
->reg_map
[VIRTUAL_INCOMING_ARGS_REGNUM
]
1287 = regno_reg_rtx
[VIRTUAL_INCOMING_ARGS_REGNUM
];
1290 /* Strength-reduction will often emit code for optimized biv/givs which
1291 calculates their value in a temporary register, and then copies the result
1292 to the iv. This procedure reconstructs the pattern computing the iv;
1293 verifying that all operands are of the proper form.
1295 The return value is the amount that the giv is incremented by. */
1298 calculate_giv_inc (pattern
, src_insn
, regno
)
1299 rtx pattern
, src_insn
;
1303 rtx increment_total
= 0;
1307 /* Verify that we have an increment insn here. First check for a plus
1308 as the set source. */
1309 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1311 /* SR sometimes computes the new giv value in a temp, then copies it
1313 src_insn
= PREV_INSN (src_insn
);
1314 pattern
= PATTERN (src_insn
);
1315 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1318 /* The last insn emitted is not needed, so delete it to avoid confusing
1319 the second cse pass. This insn sets the giv unnecessarily. */
1320 delete_insn (get_last_insn ());
1323 /* Verify that we have a constant as the second operand of the plus. */
1324 increment
= XEXP (SET_SRC (pattern
), 1);
1325 if (GET_CODE (increment
) != CONST_INT
)
1327 /* SR sometimes puts the constant in a register, especially if it is
1328 too big to be an add immed operand. */
1329 src_insn
= PREV_INSN (src_insn
);
1330 increment
= SET_SRC (PATTERN (src_insn
));
1332 /* SR may have used LO_SUM to compute the constant if it is too large
1333 for a load immed operand. In this case, the constant is in operand
1334 one of the LO_SUM rtx. */
1335 if (GET_CODE (increment
) == LO_SUM
)
1336 increment
= XEXP (increment
, 1);
1338 if (GET_CODE (increment
) != CONST_INT
)
1341 /* The insn loading the constant into a register is not longer needed,
1343 delete_insn (get_last_insn ());
1346 if (increment_total
)
1347 increment_total
= GEN_INT (INTVAL (increment_total
) + INTVAL (increment
));
1349 increment_total
= increment
;
1351 /* Check that the source register is the same as the register we expected
1352 to see as the source. If not, something is seriously wrong. */
1353 if (GET_CODE (XEXP (SET_SRC (pattern
), 0)) != REG
1354 || REGNO (XEXP (SET_SRC (pattern
), 0)) != regno
)
1356 /* Some machines (e.g. the romp), may emit two add instructions for
1357 certain constants, so lets try looking for another add immediately
1358 before this one if we have only seen one add insn so far. */
1364 src_insn
= PREV_INSN (src_insn
);
1365 pattern
= PATTERN (src_insn
);
1367 delete_insn (get_last_insn ());
1375 return increment_total
;
1378 /* Copy REG_NOTES, except for insn references, because not all insn_map
1379 entries are valid yet. We do need to copy registers now though, because
1380 the reg_map entries can change during copying. */
1383 initial_reg_note_copy (notes
, map
)
1385 struct inline_remap
*map
;
1392 copy
= rtx_alloc (GET_CODE (notes
));
1393 PUT_MODE (copy
, GET_MODE (notes
));
1395 if (GET_CODE (notes
) == EXPR_LIST
)
1396 XEXP (copy
, 0) = copy_rtx_and_substitute (XEXP (notes
, 0), map
);
1397 else if (GET_CODE (notes
) == INSN_LIST
)
1398 /* Don't substitute for these yet. */
1399 XEXP (copy
, 0) = XEXP (notes
, 0);
1403 XEXP (copy
, 1) = initial_reg_note_copy (XEXP (notes
, 1), map
);
1408 /* Fixup insn references in copied REG_NOTES. */
1411 final_reg_note_copy (notes
, map
)
1413 struct inline_remap
*map
;
1417 for (note
= notes
; note
; note
= XEXP (note
, 1))
1418 if (GET_CODE (note
) == INSN_LIST
)
1419 XEXP (note
, 0) = map
->insn_map
[INSN_UID (XEXP (note
, 0))];
1422 /* Copy each instruction in the loop, substituting from map as appropriate.
1423 This is very similar to a loop in expand_inline_function. */
1426 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, last_iteration
,
1427 unroll_type
, start_label
, loop_end
, insert_before
,
1429 rtx copy_start
, copy_end
;
1430 struct inline_remap
*map
;
1433 enum unroll_types unroll_type
;
1434 rtx start_label
, loop_end
, insert_before
, copy_notes_from
;
1438 int dest_reg_was_split
, i
;
1440 rtx final_label
= 0;
1441 rtx giv_inc
, giv_dest_reg
, giv_src_reg
;
1443 /* If this isn't the last iteration, then map any references to the
1444 start_label to final_label. Final label will then be emitted immediately
1445 after the end of this loop body if it was ever used.
1447 If this is the last iteration, then map references to the start_label
1449 if (! last_iteration
)
1451 final_label
= gen_label_rtx ();
1452 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = final_label
;
1455 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = start_label
;
1462 insn
= NEXT_INSN (insn
);
1464 map
->orig_asm_operands_vector
= 0;
1466 switch (GET_CODE (insn
))
1469 pattern
= PATTERN (insn
);
1473 /* Check to see if this is a giv that has been combined with
1474 some split address givs. (Combined in the sense that
1475 `combine_givs' in loop.c has put two givs in the same register.)
1476 In this case, we must search all givs based on the same biv to
1477 find the address givs. Then split the address givs.
1478 Do this before splitting the giv, since that may map the
1479 SET_DEST to a new register. */
1481 if (GET_CODE (pattern
) == SET
1482 && GET_CODE (SET_DEST (pattern
)) == REG
1483 && addr_combined_regs
[REGNO (SET_DEST (pattern
))])
1485 struct iv_class
*bl
;
1486 struct induction
*v
, *tv
;
1487 int regno
= REGNO (SET_DEST (pattern
));
1489 v
= addr_combined_regs
[REGNO (SET_DEST (pattern
))];
1490 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
1492 /* Although the giv_inc amount is not needed here, we must call
1493 calculate_giv_inc here since it might try to delete the
1494 last insn emitted. If we wait until later to call it,
1495 we might accidentally delete insns generated immediately
1496 below by emit_unrolled_add. */
1498 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1500 /* Now find all address giv's that were combined with this
1502 for (tv
= bl
->giv
; tv
; tv
= tv
->next_iv
)
1503 if (tv
->giv_type
== DEST_ADDR
&& tv
->same
== v
)
1505 int this_giv_inc
= INTVAL (giv_inc
);
1507 /* Scale this_giv_inc if the multiplicative factors of
1508 the two givs are different. */
1509 if (tv
->mult_val
!= v
->mult_val
)
1510 this_giv_inc
= (this_giv_inc
/ INTVAL (v
->mult_val
)
1511 * INTVAL (tv
->mult_val
));
1513 tv
->dest_reg
= plus_constant (tv
->dest_reg
, this_giv_inc
);
1514 *tv
->location
= tv
->dest_reg
;
1516 if (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)
1518 /* Must emit an insn to increment the split address
1519 giv. Add in the const_adjust field in case there
1520 was a constant eliminated from the address. */
1521 rtx value
, dest_reg
;
1523 /* tv->dest_reg will be either a bare register,
1524 or else a register plus a constant. */
1525 if (GET_CODE (tv
->dest_reg
) == REG
)
1526 dest_reg
= tv
->dest_reg
;
1528 dest_reg
= XEXP (tv
->dest_reg
, 0);
1530 /* Check for shared address givs, and avoid
1531 incrementing the shared psuedo reg more than
1533 if (! (tv
!= v
&& tv
->insn
== v
->insn
1534 && tv
->new_reg
== v
->new_reg
))
1536 /* tv->dest_reg may actually be a (PLUS (REG)
1537 (CONST)) here, so we must call plus_constant
1538 to add the const_adjust amount before calling
1539 emit_unrolled_add below. */
1540 value
= plus_constant (tv
->dest_reg
,
1543 /* The constant could be too large for an add
1544 immediate, so can't directly emit an insn
1546 emit_unrolled_add (dest_reg
, XEXP (value
, 0),
1550 /* Reset the giv to be just the register again, in case
1551 it is used after the set we have just emitted.
1552 We must subtract the const_adjust factor added in
1554 tv
->dest_reg
= plus_constant (dest_reg
,
1555 - tv
->const_adjust
);
1556 *tv
->location
= tv
->dest_reg
;
1561 /* If this is a setting of a splittable variable, then determine
1562 how to split the variable, create a new set based on this split,
1563 and set up the reg_map so that later uses of the variable will
1564 use the new split variable. */
1566 dest_reg_was_split
= 0;
1568 if (GET_CODE (pattern
) == SET
1569 && GET_CODE (SET_DEST (pattern
)) == REG
1570 && splittable_regs
[REGNO (SET_DEST (pattern
))])
1572 int regno
= REGNO (SET_DEST (pattern
));
1574 dest_reg_was_split
= 1;
1576 /* Compute the increment value for the giv, if it wasn't
1577 already computed above. */
1580 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1581 giv_dest_reg
= SET_DEST (pattern
);
1582 giv_src_reg
= SET_DEST (pattern
);
1584 if (unroll_type
== UNROLL_COMPLETELY
)
1586 /* Completely unrolling the loop. Set the induction
1587 variable to a known constant value. */
1589 /* The value in splittable_regs may be an invariant
1590 value, so we must use plus_constant here. */
1591 splittable_regs
[regno
]
1592 = plus_constant (splittable_regs
[regno
], INTVAL (giv_inc
));
1594 if (GET_CODE (splittable_regs
[regno
]) == PLUS
)
1596 giv_src_reg
= XEXP (splittable_regs
[regno
], 0);
1597 giv_inc
= XEXP (splittable_regs
[regno
], 1);
1601 /* The splittable_regs value must be a REG or a
1602 CONST_INT, so put the entire value in the giv_src_reg
1604 giv_src_reg
= splittable_regs
[regno
];
1605 giv_inc
= const0_rtx
;
1610 /* Partially unrolling loop. Create a new pseudo
1611 register for the iteration variable, and set it to
1612 be a constant plus the original register. Except
1613 on the last iteration, when the result has to
1614 go back into the original iteration var register. */
1616 /* Handle bivs which must be mapped to a new register
1617 when split. This happens for bivs which need their
1618 final value set before loop entry. The new register
1619 for the biv was stored in the biv's first struct
1620 induction entry by find_splittable_regs. */
1622 if (regno
< max_reg_before_loop
1623 && reg_iv_type
[regno
] == BASIC_INDUCT
)
1625 giv_src_reg
= reg_biv_class
[regno
]->biv
->src_reg
;
1626 giv_dest_reg
= giv_src_reg
;
1630 /* If non-reduced/final-value givs were split, then
1631 this would have to remap those givs also. See
1632 find_splittable_regs. */
1635 splittable_regs
[regno
]
1636 = GEN_INT (INTVAL (giv_inc
)
1637 + INTVAL (splittable_regs
[regno
]));
1638 giv_inc
= splittable_regs
[regno
];
1640 /* Now split the induction variable by changing the dest
1641 of this insn to a new register, and setting its
1642 reg_map entry to point to this new register.
1644 If this is the last iteration, and this is the last insn
1645 that will update the iv, then reuse the original dest,
1646 to ensure that the iv will have the proper value when
1647 the loop exits or repeats.
1649 Using splittable_regs_updates here like this is safe,
1650 because it can only be greater than one if all
1651 instructions modifying the iv are always executed in
1654 if (! last_iteration
1655 || (splittable_regs_updates
[regno
]-- != 1))
1657 tem
= gen_reg_rtx (GET_MODE (giv_src_reg
));
1659 map
->reg_map
[regno
] = tem
;
1662 map
->reg_map
[regno
] = giv_src_reg
;
1665 /* The constant being added could be too large for an add
1666 immediate, so can't directly emit an insn here. */
1667 emit_unrolled_add (giv_dest_reg
, giv_src_reg
, giv_inc
);
1668 copy
= get_last_insn ();
1669 pattern
= PATTERN (copy
);
1673 pattern
= copy_rtx_and_substitute (pattern
, map
);
1674 copy
= emit_insn (pattern
);
1676 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1679 /* If this insn is setting CC0, it may need to look at
1680 the insn that uses CC0 to see what type of insn it is.
1681 In that case, the call to recog via validate_change will
1682 fail. So don't substitute constants here. Instead,
1683 do it when we emit the following insn.
1685 For example, see the pyr.md file. That machine has signed and
1686 unsigned compares. The compare patterns must check the
1687 following branch insn to see which what kind of compare to
1690 If the previous insn set CC0, substitute constants on it as
1692 if (sets_cc0_p (copy
) != 0)
1697 try_constants (cc0_insn
, map
);
1699 try_constants (copy
, map
);
1702 try_constants (copy
, map
);
1705 /* Make split induction variable constants `permanent' since we
1706 know there are no backward branches across iteration variable
1707 settings which would invalidate this. */
1708 if (dest_reg_was_split
)
1710 int regno
= REGNO (SET_DEST (pattern
));
1712 if (regno
< map
->const_equiv_map_size
1713 && map
->const_age_map
[regno
] == map
->const_age
)
1714 map
->const_age_map
[regno
] = -1;
1719 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1720 copy
= emit_jump_insn (pattern
);
1721 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1723 if (JUMP_LABEL (insn
) == start_label
&& insn
== copy_end
1724 && ! last_iteration
)
1726 /* This is a branch to the beginning of the loop; this is the
1727 last insn being copied; and this is not the last iteration.
1728 In this case, we want to change the original fall through
1729 case to be a branch past the end of the loop, and the
1730 original jump label case to fall_through. */
1732 if (! invert_exp (pattern
, copy
)
1733 || ! redirect_exp (&pattern
,
1734 map
->label_map
[CODE_LABEL_NUMBER
1735 (JUMP_LABEL (insn
))],
1742 try_constants (cc0_insn
, map
);
1745 try_constants (copy
, map
);
1747 /* Set the jump label of COPY correctly to avoid problems with
1748 later passes of unroll_loop, if INSN had jump label set. */
1749 if (JUMP_LABEL (insn
))
1753 /* Can't use the label_map for every insn, since this may be
1754 the backward branch, and hence the label was not mapped. */
1755 if (GET_CODE (pattern
) == SET
)
1757 tem
= SET_SRC (pattern
);
1758 if (GET_CODE (tem
) == LABEL_REF
)
1759 label
= XEXP (tem
, 0);
1760 else if (GET_CODE (tem
) == IF_THEN_ELSE
)
1762 if (XEXP (tem
, 1) != pc_rtx
)
1763 label
= XEXP (XEXP (tem
, 1), 0);
1765 label
= XEXP (XEXP (tem
, 2), 0);
1769 if (label
&& GET_CODE (label
) == CODE_LABEL
)
1770 JUMP_LABEL (copy
) = label
;
1773 /* An unrecognizable jump insn, probably the entry jump
1774 for a switch statement. This label must have been mapped,
1775 so just use the label_map to get the new jump label. */
1776 JUMP_LABEL (copy
) = map
->label_map
[CODE_LABEL_NUMBER
1777 (JUMP_LABEL (insn
))];
1780 /* If this is a non-local jump, then must increase the label
1781 use count so that the label will not be deleted when the
1782 original jump is deleted. */
1783 LABEL_NUSES (JUMP_LABEL (copy
))++;
1785 else if (GET_CODE (PATTERN (copy
)) == ADDR_VEC
1786 || GET_CODE (PATTERN (copy
)) == ADDR_DIFF_VEC
)
1788 rtx pat
= PATTERN (copy
);
1789 int diff_vec_p
= GET_CODE (pat
) == ADDR_DIFF_VEC
;
1790 int len
= XVECLEN (pat
, diff_vec_p
);
1793 for (i
= 0; i
< len
; i
++)
1794 LABEL_NUSES (XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0))++;
1797 /* If this used to be a conditional jump insn but whose branch
1798 direction is now known, we must do something special. */
1799 if (condjump_p (insn
) && !simplejump_p (insn
) && map
->last_pc_value
)
1802 /* The previous insn set cc0 for us. So delete it. */
1803 delete_insn (PREV_INSN (copy
));
1806 /* If this is now a no-op, delete it. */
1807 if (map
->last_pc_value
== pc_rtx
)
1809 /* Don't let delete_insn delete the label referenced here,
1810 because we might possibly need it later for some other
1811 instruction in the loop. */
1812 if (JUMP_LABEL (copy
))
1813 LABEL_NUSES (JUMP_LABEL (copy
))++;
1815 if (JUMP_LABEL (copy
))
1816 LABEL_NUSES (JUMP_LABEL (copy
))--;
1820 /* Otherwise, this is unconditional jump so we must put a
1821 BARRIER after it. We could do some dead code elimination
1822 here, but jump.c will do it just as well. */
1828 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1829 copy
= emit_call_insn (pattern
);
1830 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1832 /* Because the USAGE information potentially contains objects other
1833 than hard registers, we need to copy it. */
1834 CALL_INSN_FUNCTION_USAGE (copy
) =
1835 copy_rtx_and_substitute (CALL_INSN_FUNCTION_USAGE (insn
), map
);
1839 try_constants (cc0_insn
, map
);
1842 try_constants (copy
, map
);
1844 /* Be lazy and assume CALL_INSNs clobber all hard registers. */
1845 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
1846 map
->const_equiv_map
[i
] = 0;
1850 /* If this is the loop start label, then we don't need to emit a
1851 copy of this label since no one will use it. */
1853 if (insn
!= start_label
)
1855 copy
= emit_label (map
->label_map
[CODE_LABEL_NUMBER (insn
)]);
1861 copy
= emit_barrier ();
1865 /* VTOP notes are valid only before the loop exit test. If placed
1866 anywhere else, loop may generate bad code. */
1868 if (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
1869 && (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_LOOP_VTOP
1870 || (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)))
1871 copy
= emit_note (NOTE_SOURCE_FILE (insn
),
1872 NOTE_LINE_NUMBER (insn
));
1882 map
->insn_map
[INSN_UID (insn
)] = copy
;
1884 while (insn
!= copy_end
);
1886 /* Now finish coping the REG_NOTES. */
1890 insn
= NEXT_INSN (insn
);
1891 if ((GET_CODE (insn
) == INSN
|| GET_CODE (insn
) == JUMP_INSN
1892 || GET_CODE (insn
) == CALL_INSN
)
1893 && map
->insn_map
[INSN_UID (insn
)])
1894 final_reg_note_copy (REG_NOTES (map
->insn_map
[INSN_UID (insn
)]), map
);
1896 while (insn
!= copy_end
);
1898 /* There may be notes between copy_notes_from and loop_end. Emit a copy of
1899 each of these notes here, since there may be some important ones, such as
1900 NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
1901 iteration, because the original notes won't be deleted.
1903 We can't use insert_before here, because when from preconditioning,
1904 insert_before points before the loop. We can't use copy_end, because
1905 there may be insns already inserted after it (which we don't want to
1906 copy) when not from preconditioning code. */
1908 if (! last_iteration
)
1910 for (insn
= copy_notes_from
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
1912 if (GET_CODE (insn
) == NOTE
1913 && NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
)
1914 emit_note (NOTE_SOURCE_FILE (insn
), NOTE_LINE_NUMBER (insn
));
1918 if (final_label
&& LABEL_NUSES (final_label
) > 0)
1919 emit_label (final_label
);
1921 tem
= gen_sequence ();
1923 emit_insn_before (tem
, insert_before
);
1926 /* Emit an insn, using the expand_binop to ensure that a valid insn is
1927 emitted. This will correctly handle the case where the increment value
1928 won't fit in the immediate field of a PLUS insns. */
1931 emit_unrolled_add (dest_reg
, src_reg
, increment
)
1932 rtx dest_reg
, src_reg
, increment
;
1936 result
= expand_binop (GET_MODE (dest_reg
), add_optab
, src_reg
, increment
,
1937 dest_reg
, 0, OPTAB_LIB_WIDEN
);
1939 if (dest_reg
!= result
)
1940 emit_move_insn (dest_reg
, result
);
1943 /* Searches the insns between INSN and LOOP_END. Returns 1 if there
1944 is a backward branch in that range that branches to somewhere between
1945 LOOP_START and INSN. Returns 0 otherwise. */
1947 /* ??? This is quadratic algorithm. Could be rewritten to be linear.
1948 In practice, this is not a problem, because this function is seldom called,
1949 and uses a negligible amount of CPU time on average. */
1952 back_branch_in_range_p (insn
, loop_start
, loop_end
)
1954 rtx loop_start
, loop_end
;
1956 rtx p
, q
, target_insn
;
1958 /* Stop before we get to the backward branch at the end of the loop. */
1959 loop_end
= prev_nonnote_insn (loop_end
);
1960 if (GET_CODE (loop_end
) == BARRIER
)
1961 loop_end
= PREV_INSN (loop_end
);
1963 /* Check in case insn has been deleted, search forward for first non
1964 deleted insn following it. */
1965 while (INSN_DELETED_P (insn
))
1966 insn
= NEXT_INSN (insn
);
1968 /* Check for the case where insn is the last insn in the loop. */
1969 if (insn
== loop_end
)
1972 for (p
= NEXT_INSN (insn
); p
!= loop_end
; p
= NEXT_INSN (p
))
1974 if (GET_CODE (p
) == JUMP_INSN
)
1976 target_insn
= JUMP_LABEL (p
);
1978 /* Search from loop_start to insn, to see if one of them is
1979 the target_insn. We can't use INSN_LUID comparisons here,
1980 since insn may not have an LUID entry. */
1981 for (q
= loop_start
; q
!= insn
; q
= NEXT_INSN (q
))
1982 if (q
== target_insn
)
1990 /* Try to generate the simplest rtx for the expression
1991 (PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
1995 fold_rtx_mult_add (mult1
, mult2
, add1
, mode
)
1996 rtx mult1
, mult2
, add1
;
1997 enum machine_mode mode
;
2002 /* The modes must all be the same. This should always be true. For now,
2003 check to make sure. */
2004 if ((GET_MODE (mult1
) != mode
&& GET_MODE (mult1
) != VOIDmode
)
2005 || (GET_MODE (mult2
) != mode
&& GET_MODE (mult2
) != VOIDmode
)
2006 || (GET_MODE (add1
) != mode
&& GET_MODE (add1
) != VOIDmode
))
2009 /* Ensure that if at least one of mult1/mult2 are constant, then mult2
2010 will be a constant. */
2011 if (GET_CODE (mult1
) == CONST_INT
)
2018 mult_res
= simplify_binary_operation (MULT
, mode
, mult1
, mult2
);
2020 mult_res
= gen_rtx (MULT
, mode
, mult1
, mult2
);
2022 /* Again, put the constant second. */
2023 if (GET_CODE (add1
) == CONST_INT
)
2030 result
= simplify_binary_operation (PLUS
, mode
, add1
, mult_res
);
2032 result
= gen_rtx (PLUS
, mode
, add1
, mult_res
);
2037 /* Searches the list of induction struct's for the biv BL, to try to calculate
2038 the total increment value for one iteration of the loop as a constant.
2040 Returns the increment value as an rtx, simplified as much as possible,
2041 if it can be calculated. Otherwise, returns 0. */
2044 biv_total_increment (bl
, loop_start
, loop_end
)
2045 struct iv_class
*bl
;
2046 rtx loop_start
, loop_end
;
2048 struct induction
*v
;
2051 /* For increment, must check every instruction that sets it. Each
2052 instruction must be executed only once each time through the loop.
2053 To verify this, we check that the the insn is always executed, and that
2054 there are no backward branches after the insn that branch to before it.
2055 Also, the insn must have a mult_val of one (to make sure it really is
2058 result
= const0_rtx
;
2059 for (v
= bl
->biv
; v
; v
= v
->next_iv
)
2061 if (v
->always_computable
&& v
->mult_val
== const1_rtx
2062 && ! back_branch_in_range_p (v
->insn
, loop_start
, loop_end
))
2063 result
= fold_rtx_mult_add (result
, const1_rtx
, v
->add_val
, v
->mode
);
2071 /* Determine the initial value of the iteration variable, and the amount
2072 that it is incremented each loop. Use the tables constructed by
2073 the strength reduction pass to calculate these values.
2075 Initial_value and/or increment are set to zero if their values could not
2079 iteration_info (iteration_var
, initial_value
, increment
, loop_start
, loop_end
)
2080 rtx iteration_var
, *initial_value
, *increment
;
2081 rtx loop_start
, loop_end
;
2083 struct iv_class
*bl
;
2084 struct induction
*v
, *b
;
2086 /* Clear the result values, in case no answer can be found. */
2090 /* The iteration variable can be either a giv or a biv. Check to see
2091 which it is, and compute the variable's initial value, and increment
2092 value if possible. */
2094 /* If this is a new register, can't handle it since we don't have any
2095 reg_iv_type entry for it. */
2096 if (REGNO (iteration_var
) >= max_reg_before_loop
)
2098 if (loop_dump_stream
)
2099 fprintf (loop_dump_stream
,
2100 "Loop unrolling: No reg_iv_type entry for iteration var.\n");
2103 /* Reject iteration variables larger than the host long size, since they
2104 could result in a number of iterations greater than the range of our
2105 `unsigned long' variable loop_n_iterations. */
2106 else if (GET_MODE_BITSIZE (GET_MODE (iteration_var
)) > HOST_BITS_PER_LONG
)
2108 if (loop_dump_stream
)
2109 fprintf (loop_dump_stream
,
2110 "Loop unrolling: Iteration var rejected because mode larger than host long.\n");
2113 else if (GET_MODE_CLASS (GET_MODE (iteration_var
)) != MODE_INT
)
2115 if (loop_dump_stream
)
2116 fprintf (loop_dump_stream
,
2117 "Loop unrolling: Iteration var not an integer.\n");
2120 else if (reg_iv_type
[REGNO (iteration_var
)] == BASIC_INDUCT
)
2122 /* Grab initial value, only useful if it is a constant. */
2123 bl
= reg_biv_class
[REGNO (iteration_var
)];
2124 *initial_value
= bl
->initial_value
;
2126 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2128 else if (reg_iv_type
[REGNO (iteration_var
)] == GENERAL_INDUCT
)
2131 /* ??? The code below does not work because the incorrect number of
2132 iterations is calculated when the biv is incremented after the giv
2133 is set (which is the usual case). This can probably be accounted
2134 for by biasing the initial_value by subtracting the amount of the
2135 increment that occurs between the giv set and the giv test. However,
2136 a giv as an iterator is very rare, so it does not seem worthwhile
2138 /* ??? An example failure is: i = 6; do {;} while (i++ < 9). */
2139 if (loop_dump_stream
)
2140 fprintf (loop_dump_stream
,
2141 "Loop unrolling: Giv iterators are not handled.\n");
2144 /* Initial value is mult_val times the biv's initial value plus
2145 add_val. Only useful if it is a constant. */
2146 v
= reg_iv_info
[REGNO (iteration_var
)];
2147 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2148 *initial_value
= fold_rtx_mult_add (v
->mult_val
, bl
->initial_value
,
2149 v
->add_val
, v
->mode
);
2151 /* Increment value is mult_val times the increment value of the biv. */
2153 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2155 *increment
= fold_rtx_mult_add (v
->mult_val
, *increment
, const0_rtx
,
2161 if (loop_dump_stream
)
2162 fprintf (loop_dump_stream
,
2163 "Loop unrolling: Not basic or general induction var.\n");
2168 /* Calculate the approximate final value of the iteration variable
2169 which has an loop exit test with code COMPARISON_CODE and comparison value
2170 of COMPARISON_VALUE. Also returns an indication of whether the comparison
2171 was signed or unsigned, and the direction of the comparison. This info is
2172 needed to calculate the number of loop iterations. */
2175 approx_final_value (comparison_code
, comparison_value
, unsigned_p
, compare_dir
)
2176 enum rtx_code comparison_code
;
2177 rtx comparison_value
;
2181 /* Calculate the final value of the induction variable.
2182 The exact final value depends on the branch operator, and increment sign.
2183 This is only an approximate value. It will be wrong if the iteration
2184 variable is not incremented by one each time through the loop, and
2185 approx final value - start value % increment != 0. */
2188 switch (comparison_code
)
2194 return plus_constant (comparison_value
, 1);
2199 return plus_constant (comparison_value
, -1);
2201 /* Can not calculate a final value for this case. */
2208 return comparison_value
;
2214 return comparison_value
;
2217 return comparison_value
;
2223 /* For each biv and giv, determine whether it can be safely split into
2224 a different variable for each unrolled copy of the loop body. If it
2225 is safe to split, then indicate that by saving some useful info
2226 in the splittable_regs array.
2228 If the loop is being completely unrolled, then splittable_regs will hold
2229 the current value of the induction variable while the loop is unrolled.
2230 It must be set to the initial value of the induction variable here.
2231 Otherwise, splittable_regs will hold the difference between the current
2232 value of the induction variable and the value the induction variable had
2233 at the top of the loop. It must be set to the value 0 here.
2235 Returns the total number of instructions that set registers that are
2238 /* ?? If the loop is only unrolled twice, then most of the restrictions to
2239 constant values are unnecessary, since we can easily calculate increment
2240 values in this case even if nothing is constant. The increment value
2241 should not involve a multiply however. */
2243 /* ?? Even if the biv/giv increment values aren't constant, it may still
2244 be beneficial to split the variable if the loop is only unrolled a few
2245 times, since multiplies by small integers (1,2,3,4) are very cheap. */
2248 find_splittable_regs (unroll_type
, loop_start
, loop_end
, end_insert_before
,
2250 enum unroll_types unroll_type
;
2251 rtx loop_start
, loop_end
;
2252 rtx end_insert_before
;
2255 struct iv_class
*bl
;
2256 struct induction
*v
;
2258 rtx biv_final_value
;
2262 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
2264 /* Biv_total_increment must return a constant value,
2265 otherwise we can not calculate the split values. */
2267 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2268 if (! increment
|| GET_CODE (increment
) != CONST_INT
)
2271 /* The loop must be unrolled completely, or else have a known number
2272 of iterations and only one exit, or else the biv must be dead
2273 outside the loop, or else the final value must be known. Otherwise,
2274 it is unsafe to split the biv since it may not have the proper
2275 value on loop exit. */
2277 /* loop_number_exit_labels is non-zero if the loop has an exit other than
2278 a fall through at the end. */
2281 biv_final_value
= 0;
2282 if (unroll_type
!= UNROLL_COMPLETELY
2283 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2284 || unroll_type
== UNROLL_NAIVE
)
2285 && (uid_luid
[regno_last_uid
[bl
->regno
]] >= INSN_LUID (loop_end
)
2287 || INSN_UID (bl
->init_insn
) >= max_uid_for_loop
2288 || (uid_luid
[regno_first_uid
[bl
->regno
]]
2289 < INSN_LUID (bl
->init_insn
))
2290 || reg_mentioned_p (bl
->biv
->dest_reg
, SET_SRC (bl
->init_set
)))
2291 && ! (biv_final_value
= final_biv_value (bl
, loop_start
, loop_end
)))
2294 /* If any of the insns setting the BIV don't do so with a simple
2295 PLUS, we don't know how to split it. */
2296 for (v
= bl
->biv
; biv_splittable
&& v
; v
= v
->next_iv
)
2297 if ((tem
= single_set (v
->insn
)) == 0
2298 || GET_CODE (SET_DEST (tem
)) != REG
2299 || REGNO (SET_DEST (tem
)) != bl
->regno
2300 || GET_CODE (SET_SRC (tem
)) != PLUS
)
2303 /* If final value is non-zero, then must emit an instruction which sets
2304 the value of the biv to the proper value. This is done after
2305 handling all of the givs, since some of them may need to use the
2306 biv's value in their initialization code. */
2308 /* This biv is splittable. If completely unrolling the loop, save
2309 the biv's initial value. Otherwise, save the constant zero. */
2311 if (biv_splittable
== 1)
2313 if (unroll_type
== UNROLL_COMPLETELY
)
2315 /* If the initial value of the biv is itself (i.e. it is too
2316 complicated for strength_reduce to compute), or is a hard
2317 register, then we must create a new pseudo reg to hold the
2318 initial value of the biv. */
2320 if (GET_CODE (bl
->initial_value
) == REG
2321 && (REGNO (bl
->initial_value
) == bl
->regno
2322 || REGNO (bl
->initial_value
) < FIRST_PSEUDO_REGISTER
))
2324 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2326 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2329 if (loop_dump_stream
)
2330 fprintf (loop_dump_stream
, "Biv %d initial value remapped to %d.\n",
2331 bl
->regno
, REGNO (tem
));
2333 splittable_regs
[bl
->regno
] = tem
;
2336 splittable_regs
[bl
->regno
] = bl
->initial_value
;
2339 splittable_regs
[bl
->regno
] = const0_rtx
;
2341 /* Save the number of instructions that modify the biv, so that
2342 we can treat the last one specially. */
2344 splittable_regs_updates
[bl
->regno
] = bl
->biv_count
;
2345 result
+= bl
->biv_count
;
2347 if (loop_dump_stream
)
2348 fprintf (loop_dump_stream
,
2349 "Biv %d safe to split.\n", bl
->regno
);
2352 /* Check every giv that depends on this biv to see whether it is
2353 splittable also. Even if the biv isn't splittable, givs which
2354 depend on it may be splittable if the biv is live outside the
2355 loop, and the givs aren't. */
2357 result
+= find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
,
2358 increment
, unroll_number
);
2360 /* If final value is non-zero, then must emit an instruction which sets
2361 the value of the biv to the proper value. This is done after
2362 handling all of the givs, since some of them may need to use the
2363 biv's value in their initialization code. */
2364 if (biv_final_value
)
2366 /* If the loop has multiple exits, emit the insns before the
2367 loop to ensure that it will always be executed no matter
2368 how the loop exits. Otherwise emit the insn after the loop,
2369 since this is slightly more efficient. */
2370 if (! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2371 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2376 /* Create a new register to hold the value of the biv, and then
2377 set the biv to its final value before the loop start. The biv
2378 is set to its final value before loop start to ensure that
2379 this insn will always be executed, no matter how the loop
2381 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2382 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2384 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2388 if (loop_dump_stream
)
2389 fprintf (loop_dump_stream
, "Biv %d mapped to %d for split.\n",
2390 REGNO (bl
->biv
->src_reg
), REGNO (tem
));
2392 /* Set up the mapping from the original biv register to the new
2394 bl
->biv
->src_reg
= tem
;
2401 /* For every giv based on the biv BL, check to determine whether it is
2402 splittable. This is a subroutine to find_splittable_regs ().
2404 Return the number of instructions that set splittable registers. */
2407 find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
, increment
,
2409 struct iv_class
*bl
;
2410 enum unroll_types unroll_type
;
2411 rtx loop_start
, loop_end
;
2415 struct induction
*v
;
2420 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
2424 /* Only split the giv if it has already been reduced, or if the loop is
2425 being completely unrolled. */
2426 if (unroll_type
!= UNROLL_COMPLETELY
&& v
->ignore
)
2429 /* The giv can be split if the insn that sets the giv is executed once
2430 and only once on every iteration of the loop. */
2431 /* An address giv can always be split. v->insn is just a use not a set,
2432 and hence it does not matter whether it is always executed. All that
2433 matters is that all the biv increments are always executed, and we
2434 won't reach here if they aren't. */
2435 if (v
->giv_type
!= DEST_ADDR
2436 && (! v
->always_computable
2437 || back_branch_in_range_p (v
->insn
, loop_start
, loop_end
)))
2440 /* The giv increment value must be a constant. */
2441 giv_inc
= fold_rtx_mult_add (v
->mult_val
, increment
, const0_rtx
,
2443 if (! giv_inc
|| GET_CODE (giv_inc
) != CONST_INT
)
2446 /* The loop must be unrolled completely, or else have a known number of
2447 iterations and only one exit, or else the giv must be dead outside
2448 the loop, or else the final value of the giv must be known.
2449 Otherwise, it is not safe to split the giv since it may not have the
2450 proper value on loop exit. */
2452 /* The used outside loop test will fail for DEST_ADDR givs. They are
2453 never used outside the loop anyways, so it is always safe to split a
2457 if (unroll_type
!= UNROLL_COMPLETELY
2458 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2459 || unroll_type
== UNROLL_NAIVE
)
2460 && v
->giv_type
!= DEST_ADDR
2461 && ((regno_first_uid
[REGNO (v
->dest_reg
)] != INSN_UID (v
->insn
)
2462 /* Check for the case where the pseudo is set by a shift/add
2463 sequence, in which case the first insn setting the pseudo
2464 is the first insn of the shift/add sequence. */
2465 && (! (tem
= find_reg_note (v
->insn
, REG_RETVAL
, NULL_RTX
))
2466 || (regno_first_uid
[REGNO (v
->dest_reg
)]
2467 != INSN_UID (XEXP (tem
, 0)))))
2468 /* Line above always fails if INSN was moved by loop opt. */
2469 || (uid_luid
[regno_last_uid
[REGNO (v
->dest_reg
)]]
2470 >= INSN_LUID (loop_end
)))
2471 && ! (final_value
= v
->final_value
))
2475 /* Currently, non-reduced/final-value givs are never split. */
2476 /* Should emit insns after the loop if possible, as the biv final value
2479 /* If the final value is non-zero, and the giv has not been reduced,
2480 then must emit an instruction to set the final value. */
2481 if (final_value
&& !v
->new_reg
)
2483 /* Create a new register to hold the value of the giv, and then set
2484 the giv to its final value before the loop start. The giv is set
2485 to its final value before loop start to ensure that this insn
2486 will always be executed, no matter how we exit. */
2487 tem
= gen_reg_rtx (v
->mode
);
2488 emit_insn_before (gen_move_insn (tem
, v
->dest_reg
), loop_start
);
2489 emit_insn_before (gen_move_insn (v
->dest_reg
, final_value
),
2492 if (loop_dump_stream
)
2493 fprintf (loop_dump_stream
, "Giv %d mapped to %d for split.\n",
2494 REGNO (v
->dest_reg
), REGNO (tem
));
2500 /* This giv is splittable. If completely unrolling the loop, save the
2501 giv's initial value. Otherwise, save the constant zero for it. */
2503 if (unroll_type
== UNROLL_COMPLETELY
)
2505 /* It is not safe to use bl->initial_value here, because it may not
2506 be invariant. It is safe to use the initial value stored in
2507 the splittable_regs array if it is set. In rare cases, it won't
2508 be set, so then we do exactly the same thing as
2509 find_splittable_regs does to get a safe value. */
2510 rtx biv_initial_value
;
2512 if (splittable_regs
[bl
->regno
])
2513 biv_initial_value
= splittable_regs
[bl
->regno
];
2514 else if (GET_CODE (bl
->initial_value
) != REG
2515 || (REGNO (bl
->initial_value
) != bl
->regno
2516 && REGNO (bl
->initial_value
) >= FIRST_PSEUDO_REGISTER
))
2517 biv_initial_value
= bl
->initial_value
;
2520 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2522 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2524 biv_initial_value
= tem
;
2526 value
= fold_rtx_mult_add (v
->mult_val
, biv_initial_value
,
2527 v
->add_val
, v
->mode
);
2534 /* If a giv was combined with another giv, then we can only split
2535 this giv if the giv it was combined with was reduced. This
2536 is because the value of v->new_reg is meaningless in this
2538 if (v
->same
&& ! v
->same
->new_reg
)
2540 if (loop_dump_stream
)
2541 fprintf (loop_dump_stream
,
2542 "giv combined with unreduced giv not split.\n");
2545 /* If the giv is an address destination, it could be something other
2546 than a simple register, these have to be treated differently. */
2547 else if (v
->giv_type
== DEST_REG
)
2549 /* If value is not a constant, register, or register plus
2550 constant, then compute its value into a register before
2551 loop start. This prevents illegal rtx sharing, and should
2552 generate better code. We can use bl->initial_value here
2553 instead of splittable_regs[bl->regno] because this code
2554 is going before the loop start. */
2555 if (unroll_type
== UNROLL_COMPLETELY
2556 && GET_CODE (value
) != CONST_INT
2557 && GET_CODE (value
) != REG
2558 && (GET_CODE (value
) != PLUS
2559 || GET_CODE (XEXP (value
, 0)) != REG
2560 || GET_CODE (XEXP (value
, 1)) != CONST_INT
))
2562 rtx tem
= gen_reg_rtx (v
->mode
);
2563 emit_iv_add_mult (bl
->initial_value
, v
->mult_val
,
2564 v
->add_val
, tem
, loop_start
);
2568 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2572 /* Splitting address givs is useful since it will often allow us
2573 to eliminate some increment insns for the base giv as
2576 /* If the addr giv is combined with a dest_reg giv, then all
2577 references to that dest reg will be remapped, which is NOT
2578 what we want for split addr regs. We always create a new
2579 register for the split addr giv, just to be safe. */
2581 /* ??? If there are multiple address givs which have been
2582 combined with the same dest_reg giv, then we may only need
2583 one new register for them. Pulling out constants below will
2584 catch some of the common cases of this. Currently, I leave
2585 the work of simplifying multiple address givs to the
2586 following cse pass. */
2588 /* As a special case, if we have multiple identical address givs
2589 within a single instruction, then we do use a single psuedo
2590 reg for both. This is necessary in case one is a match_dup
2593 v
->const_adjust
= 0;
2595 if (v
->same
&& v
->same
->insn
== v
->insn
2596 && v
->new_reg
== v
->same
->new_reg
)
2598 v
->dest_reg
= v
->same
->dest_reg
;
2599 if (loop_dump_stream
)
2600 fprintf (loop_dump_stream
,
2601 "Sharing address givs with reg %d\n",
2602 REGNO (v
->dest_reg
));
2604 else if (unroll_type
!= UNROLL_COMPLETELY
)
2606 /* If not completely unrolling the loop, then create a new
2607 register to hold the split value of the DEST_ADDR giv.
2608 Emit insn to initialize its value before loop start. */
2609 tem
= gen_reg_rtx (v
->mode
);
2611 /* If the address giv has a constant in its new_reg value,
2612 then this constant can be pulled out and put in value,
2613 instead of being part of the initialization code. */
2615 if (GET_CODE (v
->new_reg
) == PLUS
2616 && GET_CODE (XEXP (v
->new_reg
, 1)) == CONST_INT
)
2619 = plus_constant (tem
, INTVAL (XEXP (v
->new_reg
,1)));
2621 /* Only succeed if this will give valid addresses.
2622 Try to validate both the first and the last
2623 address resulting from loop unrolling, if
2624 one fails, then can't do const elim here. */
2625 if (memory_address_p (v
->mem_mode
, v
->dest_reg
)
2626 && memory_address_p (v
->mem_mode
,
2627 plus_constant (v
->dest_reg
,
2629 * (unroll_number
- 1))))
2631 /* Save the negative of the eliminated const, so
2632 that we can calculate the dest_reg's increment
2634 v
->const_adjust
= - INTVAL (XEXP (v
->new_reg
, 1));
2636 v
->new_reg
= XEXP (v
->new_reg
, 0);
2637 if (loop_dump_stream
)
2638 fprintf (loop_dump_stream
,
2639 "Eliminating constant from giv %d\n",
2648 /* If the address hasn't been checked for validity yet, do so
2649 now, and fail completely if either the first or the last
2650 unrolled copy of the address is not a valid address. */
2651 if (v
->dest_reg
== tem
2652 && (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2653 || ! memory_address_p (v
->mem_mode
,
2654 plus_constant (v
->dest_reg
,
2656 * (unroll_number
-1)))))
2658 if (loop_dump_stream
)
2659 fprintf (loop_dump_stream
,
2660 "Illegal address for giv at insn %d\n",
2661 INSN_UID (v
->insn
));
2665 /* To initialize the new register, just move the value of
2666 new_reg into it. This is not guaranteed to give a valid
2667 instruction on machines with complex addressing modes.
2668 If we can't recognize it, then delete it and emit insns
2669 to calculate the value from scratch. */
2670 emit_insn_before (gen_rtx (SET
, VOIDmode
, tem
,
2671 copy_rtx (v
->new_reg
)),
2673 if (recog_memoized (PREV_INSN (loop_start
)) < 0)
2677 /* We can't use bl->initial_value to compute the initial
2678 value, because the loop may have been preconditioned.
2679 We must calculate it from NEW_REG. Try using
2680 force_operand instead of emit_iv_add_mult. */
2681 delete_insn (PREV_INSN (loop_start
));
2684 ret
= force_operand (v
->new_reg
, tem
);
2686 emit_move_insn (tem
, ret
);
2687 sequence
= gen_sequence ();
2689 emit_insn_before (sequence
, loop_start
);
2691 if (loop_dump_stream
)
2692 fprintf (loop_dump_stream
,
2693 "Illegal init insn, rewritten.\n");
2698 v
->dest_reg
= value
;
2700 /* Check the resulting address for validity, and fail
2701 if the resulting address would be illegal. */
2702 if (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2703 || ! memory_address_p (v
->mem_mode
,
2704 plus_constant (v
->dest_reg
,
2706 (unroll_number
-1))))
2708 if (loop_dump_stream
)
2709 fprintf (loop_dump_stream
,
2710 "Illegal address for giv at insn %d\n",
2711 INSN_UID (v
->insn
));
2716 /* Store the value of dest_reg into the insn. This sharing
2717 will not be a problem as this insn will always be copied
2720 *v
->location
= v
->dest_reg
;
2722 /* If this address giv is combined with a dest reg giv, then
2723 save the base giv's induction pointer so that we will be
2724 able to handle this address giv properly. The base giv
2725 itself does not have to be splittable. */
2727 if (v
->same
&& v
->same
->giv_type
== DEST_REG
)
2728 addr_combined_regs
[REGNO (v
->same
->new_reg
)] = v
->same
;
2730 if (GET_CODE (v
->new_reg
) == REG
)
2732 /* This giv maybe hasn't been combined with any others.
2733 Make sure that it's giv is marked as splittable here. */
2735 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2737 /* Make it appear to depend upon itself, so that the
2738 giv will be properly split in the main loop above. */
2742 addr_combined_regs
[REGNO (v
->new_reg
)] = v
;
2746 if (loop_dump_stream
)
2747 fprintf (loop_dump_stream
, "DEST_ADDR giv being split.\n");
2753 /* Currently, unreduced giv's can't be split. This is not too much
2754 of a problem since unreduced giv's are not live across loop
2755 iterations anyways. When unrolling a loop completely though,
2756 it makes sense to reduce&split givs when possible, as this will
2757 result in simpler instructions, and will not require that a reg
2758 be live across loop iterations. */
2760 splittable_regs
[REGNO (v
->dest_reg
)] = value
;
2761 fprintf (stderr
, "Giv %d at insn %d not reduced\n",
2762 REGNO (v
->dest_reg
), INSN_UID (v
->insn
));
2768 /* Givs are only updated once by definition. Mark it so if this is
2769 a splittable register. Don't need to do anything for address givs
2770 where this may not be a register. */
2772 if (GET_CODE (v
->new_reg
) == REG
)
2773 splittable_regs_updates
[REGNO (v
->new_reg
)] = 1;
2777 if (loop_dump_stream
)
2781 if (GET_CODE (v
->dest_reg
) == CONST_INT
)
2783 else if (GET_CODE (v
->dest_reg
) != REG
)
2784 regnum
= REGNO (XEXP (v
->dest_reg
, 0));
2786 regnum
= REGNO (v
->dest_reg
);
2787 fprintf (loop_dump_stream
, "Giv %d at insn %d safe to split.\n",
2788 regnum
, INSN_UID (v
->insn
));
2795 /* Try to prove that the register is dead after the loop exits. Trace every
2796 loop exit looking for an insn that will always be executed, which sets
2797 the register to some value, and appears before the first use of the register
2798 is found. If successful, then return 1, otherwise return 0. */
2800 /* ?? Could be made more intelligent in the handling of jumps, so that
2801 it can search past if statements and other similar structures. */
2804 reg_dead_after_loop (reg
, loop_start
, loop_end
)
2805 rtx reg
, loop_start
, loop_end
;
2811 /* HACK: Must also search the loop fall through exit, create a label_ref
2812 here which points to the loop_end, and append the loop_number_exit_labels
2814 label
= gen_rtx (LABEL_REF
, VOIDmode
, loop_end
);
2815 LABEL_NEXTREF (label
)
2816 = loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]];
2818 for ( ; label
; label
= LABEL_NEXTREF (label
))
2820 /* Succeed if find an insn which sets the biv or if reach end of
2821 function. Fail if find an insn that uses the biv, or if come to
2822 a conditional jump. */
2824 insn
= NEXT_INSN (XEXP (label
, 0));
2827 code
= GET_CODE (insn
);
2828 if (GET_RTX_CLASS (code
) == 'i')
2832 if (reg_referenced_p (reg
, PATTERN (insn
)))
2835 set
= single_set (insn
);
2836 if (set
&& rtx_equal_p (SET_DEST (set
), reg
))
2840 if (code
== JUMP_INSN
)
2842 if (GET_CODE (PATTERN (insn
)) == RETURN
)
2844 else if (! simplejump_p (insn
)
2845 /* Prevent infinite loop following infinite loops. */
2846 || jump_count
++ > 20)
2849 insn
= JUMP_LABEL (insn
);
2852 insn
= NEXT_INSN (insn
);
2856 /* Success, the register is dead on all loop exits. */
2860 /* Try to calculate the final value of the biv, the value it will have at
2861 the end of the loop. If we can do it, return that value. */
2864 final_biv_value (bl
, loop_start
, loop_end
)
2865 struct iv_class
*bl
;
2866 rtx loop_start
, loop_end
;
2870 /* ??? This only works for MODE_INT biv's. Reject all others for now. */
2872 if (GET_MODE_CLASS (bl
->biv
->mode
) != MODE_INT
)
2875 /* The final value for reversed bivs must be calculated differently than
2876 for ordinary bivs. In this case, there is already an insn after the
2877 loop which sets this biv's final value (if necessary), and there are
2878 no other loop exits, so we can return any value. */
2881 if (loop_dump_stream
)
2882 fprintf (loop_dump_stream
,
2883 "Final biv value for %d, reversed biv.\n", bl
->regno
);
2888 /* Try to calculate the final value as initial value + (number of iterations
2889 * increment). For this to work, increment must be invariant, the only
2890 exit from the loop must be the fall through at the bottom (otherwise
2891 it may not have its final value when the loop exits), and the initial
2892 value of the biv must be invariant. */
2894 if (loop_n_iterations
!= 0
2895 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2896 && invariant_p (bl
->initial_value
))
2898 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2900 if (increment
&& invariant_p (increment
))
2902 /* Can calculate the loop exit value, emit insns after loop
2903 end to calculate this value into a temporary register in
2904 case it is needed later. */
2906 tem
= gen_reg_rtx (bl
->biv
->mode
);
2907 /* Make sure loop_end is not the last insn. */
2908 if (NEXT_INSN (loop_end
) == 0)
2909 emit_note_after (NOTE_INSN_DELETED
, loop_end
);
2910 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2911 bl
->initial_value
, tem
, NEXT_INSN (loop_end
));
2913 if (loop_dump_stream
)
2914 fprintf (loop_dump_stream
,
2915 "Final biv value for %d, calculated.\n", bl
->regno
);
2921 /* Check to see if the biv is dead at all loop exits. */
2922 if (reg_dead_after_loop (bl
->biv
->src_reg
, loop_start
, loop_end
))
2924 if (loop_dump_stream
)
2925 fprintf (loop_dump_stream
,
2926 "Final biv value for %d, biv dead after loop exit.\n",
2935 /* Try to calculate the final value of the giv, the value it will have at
2936 the end of the loop. If we can do it, return that value. */
2939 final_giv_value (v
, loop_start
, loop_end
)
2940 struct induction
*v
;
2941 rtx loop_start
, loop_end
;
2943 struct iv_class
*bl
;
2946 rtx insert_before
, seq
;
2948 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2950 /* The final value for givs which depend on reversed bivs must be calculated
2951 differently than for ordinary givs. In this case, there is already an
2952 insn after the loop which sets this giv's final value (if necessary),
2953 and there are no other loop exits, so we can return any value. */
2956 if (loop_dump_stream
)
2957 fprintf (loop_dump_stream
,
2958 "Final giv value for %d, depends on reversed biv\n",
2959 REGNO (v
->dest_reg
));
2963 /* Try to calculate the final value as a function of the biv it depends
2964 upon. The only exit from the loop must be the fall through at the bottom
2965 (otherwise it may not have its final value when the loop exits). */
2967 /* ??? Can calculate the final giv value by subtracting off the
2968 extra biv increments times the giv's mult_val. The loop must have
2969 only one exit for this to work, but the loop iterations does not need
2972 if (loop_n_iterations
!= 0
2973 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2975 /* ?? It is tempting to use the biv's value here since these insns will
2976 be put after the loop, and hence the biv will have its final value
2977 then. However, this fails if the biv is subsequently eliminated.
2978 Perhaps determine whether biv's are eliminable before trying to
2979 determine whether giv's are replaceable so that we can use the
2980 biv value here if it is not eliminable. */
2982 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2984 if (increment
&& invariant_p (increment
))
2986 /* Can calculate the loop exit value of its biv as
2987 (loop_n_iterations * increment) + initial_value */
2989 /* The loop exit value of the giv is then
2990 (final_biv_value - extra increments) * mult_val + add_val.
2991 The extra increments are any increments to the biv which
2992 occur in the loop after the giv's value is calculated.
2993 We must search from the insn that sets the giv to the end
2994 of the loop to calculate this value. */
2996 insert_before
= NEXT_INSN (loop_end
);
2998 /* Put the final biv value in tem. */
2999 tem
= gen_reg_rtx (bl
->biv
->mode
);
3000 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
3001 bl
->initial_value
, tem
, insert_before
);
3003 /* Subtract off extra increments as we find them. */
3004 for (insn
= NEXT_INSN (v
->insn
); insn
!= loop_end
;
3005 insn
= NEXT_INSN (insn
))
3007 struct induction
*biv
;
3009 for (biv
= bl
->biv
; biv
; biv
= biv
->next_iv
)
3010 if (biv
->insn
== insn
)
3013 tem
= expand_binop (GET_MODE (tem
), sub_optab
, tem
,
3014 biv
->add_val
, NULL_RTX
, 0,
3016 seq
= gen_sequence ();
3018 emit_insn_before (seq
, insert_before
);
3022 /* Now calculate the giv's final value. */
3023 emit_iv_add_mult (tem
, v
->mult_val
, v
->add_val
, tem
,
3026 if (loop_dump_stream
)
3027 fprintf (loop_dump_stream
,
3028 "Final giv value for %d, calc from biv's value.\n",
3029 REGNO (v
->dest_reg
));
3035 /* Replaceable giv's should never reach here. */
3039 /* Check to see if the biv is dead at all loop exits. */
3040 if (reg_dead_after_loop (v
->dest_reg
, loop_start
, loop_end
))
3042 if (loop_dump_stream
)
3043 fprintf (loop_dump_stream
,
3044 "Final giv value for %d, giv dead after loop exit.\n",
3045 REGNO (v
->dest_reg
));
3054 /* Calculate the number of loop iterations. Returns the exact number of loop
3055 iterations if it can be calculated, otherwise returns zero. */
3057 unsigned HOST_WIDE_INT
3058 loop_iterations (loop_start
, loop_end
)
3059 rtx loop_start
, loop_end
;
3061 rtx comparison
, comparison_value
;
3062 rtx iteration_var
, initial_value
, increment
, final_value
;
3063 enum rtx_code comparison_code
;
3066 int unsigned_compare
, compare_dir
, final_larger
;
3067 unsigned long tempu
;
3070 /* First find the iteration variable. If the last insn is a conditional
3071 branch, and the insn before tests a register value, make that the
3072 iteration variable. */
3074 loop_initial_value
= 0;
3076 loop_final_value
= 0;
3077 loop_iteration_var
= 0;
3079 last_loop_insn
= prev_nonnote_insn (loop_end
);
3081 comparison
= get_condition_for_loop (last_loop_insn
);
3082 if (comparison
== 0)
3084 if (loop_dump_stream
)
3085 fprintf (loop_dump_stream
,
3086 "Loop unrolling: No final conditional branch found.\n");
3090 /* ??? Get_condition may switch position of induction variable and
3091 invariant register when it canonicalizes the comparison. */
3093 comparison_code
= GET_CODE (comparison
);
3094 iteration_var
= XEXP (comparison
, 0);
3095 comparison_value
= XEXP (comparison
, 1);
3097 if (GET_CODE (iteration_var
) != REG
)
3099 if (loop_dump_stream
)
3100 fprintf (loop_dump_stream
,
3101 "Loop unrolling: Comparison not against register.\n");
3105 /* Loop iterations is always called before any new registers are created
3106 now, so this should never occur. */
3108 if (REGNO (iteration_var
) >= max_reg_before_loop
)
3111 iteration_info (iteration_var
, &initial_value
, &increment
,
3112 loop_start
, loop_end
);
3113 if (initial_value
== 0)
3114 /* iteration_info already printed a message. */
3119 if (loop_dump_stream
)
3120 fprintf (loop_dump_stream
,
3121 "Loop unrolling: Increment value can't be calculated.\n");
3124 if (GET_CODE (increment
) != CONST_INT
)
3126 if (loop_dump_stream
)
3127 fprintf (loop_dump_stream
,
3128 "Loop unrolling: Increment value not constant.\n");
3131 if (GET_CODE (initial_value
) != CONST_INT
)
3133 if (loop_dump_stream
)
3134 fprintf (loop_dump_stream
,
3135 "Loop unrolling: Initial value not constant.\n");
3139 /* If the comparison value is an invariant register, then try to find
3140 its value from the insns before the start of the loop. */
3142 if (GET_CODE (comparison_value
) == REG
&& invariant_p (comparison_value
))
3146 for (insn
= PREV_INSN (loop_start
); insn
; insn
= PREV_INSN (insn
))
3148 if (GET_CODE (insn
) == CODE_LABEL
)
3151 else if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i'
3152 && reg_set_p (comparison_value
, insn
))
3154 /* We found the last insn before the loop that sets the register.
3155 If it sets the entire register, and has a REG_EQUAL note,
3156 then use the value of the REG_EQUAL note. */
3157 if ((set
= single_set (insn
))
3158 && (SET_DEST (set
) == comparison_value
))
3160 rtx note
= find_reg_note (insn
, REG_EQUAL
, NULL_RTX
);
3162 if (note
&& GET_CODE (XEXP (note
, 0)) != EXPR_LIST
)
3163 comparison_value
= XEXP (note
, 0);
3170 final_value
= approx_final_value (comparison_code
, comparison_value
,
3171 &unsigned_compare
, &compare_dir
);
3173 /* Save the calculated values describing this loop's bounds, in case
3174 precondition_loop_p will need them later. These values can not be
3175 recalculated inside precondition_loop_p because strength reduction
3176 optimizations may obscure the loop's structure. */
3178 loop_iteration_var
= iteration_var
;
3179 loop_initial_value
= initial_value
;
3180 loop_increment
= increment
;
3181 loop_final_value
= final_value
;
3183 if (final_value
== 0)
3185 if (loop_dump_stream
)
3186 fprintf (loop_dump_stream
,
3187 "Loop unrolling: EQ comparison loop.\n");
3190 else if (GET_CODE (final_value
) != CONST_INT
)
3192 if (loop_dump_stream
)
3193 fprintf (loop_dump_stream
,
3194 "Loop unrolling: Final value not constant.\n");
3198 /* ?? Final value and initial value do not have to be constants.
3199 Only their difference has to be constant. When the iteration variable
3200 is an array address, the final value and initial value might both
3201 be addresses with the same base but different constant offsets.
3202 Final value must be invariant for this to work.
3204 To do this, need some way to find the values of registers which are
3207 /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
3208 if (unsigned_compare
)
3210 = ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3211 > (unsigned HOST_WIDE_INT
) INTVAL (initial_value
))
3212 - ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3213 < (unsigned HOST_WIDE_INT
) INTVAL (initial_value
));
3215 final_larger
= (INTVAL (final_value
) > INTVAL (initial_value
))
3216 - (INTVAL (final_value
) < INTVAL (initial_value
));
3218 if (INTVAL (increment
) > 0)
3220 else if (INTVAL (increment
) == 0)
3225 /* There are 27 different cases: compare_dir = -1, 0, 1;
3226 final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
3227 There are 4 normal cases, 4 reverse cases (where the iteration variable
3228 will overflow before the loop exits), 4 infinite loop cases, and 15
3229 immediate exit (0 or 1 iteration depending on loop type) cases.
3230 Only try to optimize the normal cases. */
3232 /* (compare_dir/final_larger/increment_dir)
3233 Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
3234 Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
3235 Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
3236 Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
3238 /* ?? If the meaning of reverse loops (where the iteration variable
3239 will overflow before the loop exits) is undefined, then could
3240 eliminate all of these special checks, and just always assume
3241 the loops are normal/immediate/infinite. Note that this means
3242 the sign of increment_dir does not have to be known. Also,
3243 since it does not really hurt if immediate exit loops or infinite loops
3244 are optimized, then that case could be ignored also, and hence all
3245 loops can be optimized.
3247 According to ANSI Spec, the reverse loop case result is undefined,
3248 because the action on overflow is undefined.
3250 See also the special test for NE loops below. */
3252 if (final_larger
== increment_dir
&& final_larger
!= 0
3253 && (final_larger
== compare_dir
|| compare_dir
== 0))
3258 if (loop_dump_stream
)
3259 fprintf (loop_dump_stream
,
3260 "Loop unrolling: Not normal loop.\n");
3264 /* Calculate the number of iterations, final_value is only an approximation,
3265 so correct for that. Note that tempu and loop_n_iterations are
3266 unsigned, because they can be as large as 2^n - 1. */
3268 i
= INTVAL (increment
);
3270 tempu
= INTVAL (final_value
) - INTVAL (initial_value
);
3273 tempu
= INTVAL (initial_value
) - INTVAL (final_value
);
3279 /* For NE tests, make sure that the iteration variable won't miss the
3280 final value. If tempu mod i is not zero, then the iteration variable
3281 will overflow before the loop exits, and we can not calculate the
3282 number of iterations. */
3283 if (compare_dir
== 0 && (tempu
% i
) != 0)
3286 return tempu
/ i
+ ((tempu
% i
) != 0);
3289 /* Replace uses of split bivs with their split psuedo register. This is
3290 for original instructions which remain after loop unrolling without
3294 remap_split_bivs (x
)
3297 register enum rtx_code code
;
3304 code
= GET_CODE (x
);
3319 /* If non-reduced/final-value givs were split, then this would also
3320 have to remap those givs also. */
3322 if (REGNO (x
) < max_reg_before_loop
3323 && reg_iv_type
[REGNO (x
)] == BASIC_INDUCT
)
3324 return reg_biv_class
[REGNO (x
)]->biv
->src_reg
;
3327 fmt
= GET_RTX_FORMAT (code
);
3328 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
3331 XEXP (x
, i
) = remap_split_bivs (XEXP (x
, i
));
3335 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
3336 XVECEXP (x
, i
, j
) = remap_split_bivs (XVECEXP (x
, i
, j
));