1 /* Try to unroll loops, and split induction variables.
2 Copyright (C) 1992, 1993 Free Software Foundation, Inc.
3 Contributed by James E. Wilson, Cygnus Support/UC Berkeley.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
21 /* Try to unroll a loop, and split induction variables.
23 Loops for which the number of iterations can be calculated exactly are
24 handled specially. If the number of iterations times the insn_count is
25 less than MAX_UNROLLED_INSNS, then the loop is unrolled completely.
26 Otherwise, we try to unroll the loop a number of times modulo the number
27 of iterations, so that only one exit test will be needed. It is unrolled
28 a number of times approximately equal to MAX_UNROLLED_INSNS divided by
31 Otherwise, if the number of iterations can be calculated exactly at
32 run time, and the loop is always entered at the top, then we try to
33 precondition the loop. That is, at run time, calculate how many times
34 the loop will execute, and then execute the loop body a few times so
35 that the remaining iterations will be some multiple of 4 (or 2 if the
36 loop is large). Then fall through to a loop unrolled 4 (or 2) times,
37 with only one exit test needed at the end of the loop.
39 Otherwise, if the number of iterations can not be calculated exactly,
40 not even at run time, then we still unroll the loop a number of times
41 approximately equal to MAX_UNROLLED_INSNS divided by the insn count,
42 but there must be an exit test after each copy of the loop body.
44 For each induction variable, which is dead outside the loop (replaceable)
45 or for which we can easily calculate the final value, if we can easily
46 calculate its value at each place where it is set as a function of the
47 current loop unroll count and the variable's value at loop entry, then
48 the induction variable is split into `N' different variables, one for
49 each copy of the loop body. One variable is live across the backward
50 branch, and the others are all calculated as a function of this variable.
51 This helps eliminate data dependencies, and leads to further opportunities
54 /* Possible improvements follow: */
56 /* ??? Add an extra pass somewhere to determine whether unrolling will
57 give any benefit. E.g. after generating all unrolled insns, compute the
58 cost of all insns and compare against cost of insns in rolled loop.
60 - On traditional architectures, unrolling a non-constant bound loop
61 is a win if there is a giv whose only use is in memory addresses, the
62 memory addresses can be split, and hence giv increments can be
64 - It is also a win if the loop is executed many times, and preconditioning
65 can be performed for the loop.
66 Add code to check for these and similar cases. */
68 /* ??? Improve control of which loops get unrolled. Could use profiling
69 info to only unroll the most commonly executed loops. Perhaps have
70 a user specifyable option to control the amount of code expansion,
71 or the percent of loops to consider for unrolling. Etc. */
73 /* ??? Look at the register copies inside the loop to see if they form a
74 simple permutation. If so, iterate the permutation until it gets back to
75 the start state. This is how many times we should unroll the loop, for
76 best results, because then all register copies can be eliminated.
77 For example, the lisp nreverse function should be unrolled 3 times
86 ??? The number of times to unroll the loop may also be based on data
87 references in the loop. For example, if we have a loop that references
88 x[i-1], x[i], and x[i+1], we should unroll it a multiple of 3 times. */
90 /* ??? Add some simple linear equation solving capability so that we can
91 determine the number of loop iterations for more complex loops.
92 For example, consider this loop from gdb
93 #define SWAP_TARGET_AND_HOST(buffer,len)
96 char *p = (char *) buffer;
97 char *q = ((char *) buffer) + len - 1;
98 int iterations = (len + 1) >> 1;
100 for (p; p < q; p++, q--;)
108 start value = p = &buffer + current_iteration
109 end value = q = &buffer + len - 1 - current_iteration
110 Given the loop exit test of "p < q", then there must be "q - p" iterations,
111 set equal to zero and solve for number of iterations:
112 q - p = len - 1 - 2*current_iteration = 0
113 current_iteration = (len - 1) / 2
114 Hence, there are (len - 1) / 2 (rounded up to the nearest integer)
115 iterations of this loop. */
117 /* ??? Currently, no labels are marked as loop invariant when doing loop
118 unrolling. This is because an insn inside the loop, that loads the address
119 of a label inside the loop into a register, could be moved outside the loop
120 by the invariant code motion pass if labels were invariant. If the loop
121 is subsequently unrolled, the code will be wrong because each unrolled
122 body of the loop will use the same address, whereas each actually needs a
123 different address. A case where this happens is when a loop containing
124 a switch statement is unrolled.
126 It would be better to let labels be considered invariant. When we
127 unroll loops here, check to see if any insns using a label local to the
128 loop were moved before the loop. If so, then correct the problem, by
129 moving the insn back into the loop, or perhaps replicate the insn before
130 the loop, one copy for each time the loop is unrolled. */
132 /* The prime factors looked for when trying to unroll a loop by some
133 number which is modulo the total number of iterations. Just checking
134 for these 4 prime factors will find at least one factor for 75% of
135 all numbers theoretically. Practically speaking, this will succeed
136 almost all of the time since loops are generally a multiple of 2
139 #define NUM_FACTORS 4
141 struct _factor
{ int factor
, count
; } factors
[NUM_FACTORS
]
142 = { {2, 0}, {3, 0}, {5, 0}, {7, 0}};
144 /* Describes the different types of loop unrolling performed. */
146 enum unroll_types
{ UNROLL_COMPLETELY
, UNROLL_MODULO
, UNROLL_NAIVE
};
150 #include "insn-config.h"
151 #include "integrate.h"
158 /* This controls which loops are unrolled, and by how much we unroll
161 #ifndef MAX_UNROLLED_INSNS
162 #define MAX_UNROLLED_INSNS 100
165 /* Indexed by register number, if non-zero, then it contains a pointer
166 to a struct induction for a DEST_REG giv which has been combined with
167 one of more address givs. This is needed because whenever such a DEST_REG
168 giv is modified, we must modify the value of all split address givs
169 that were combined with this DEST_REG giv. */
171 static struct induction
**addr_combined_regs
;
173 /* Indexed by register number, if this is a splittable induction variable,
174 then this will hold the current value of the register, which depends on the
177 static rtx
*splittable_regs
;
179 /* Indexed by register number, if this is a splittable induction variable,
180 then this will hold the number of instructions in the loop that modify
181 the induction variable. Used to ensure that only the last insn modifying
182 a split iv will update the original iv of the dest. */
184 static int *splittable_regs_updates
;
186 /* Values describing the current loop's iteration variable. These are set up
187 by loop_iterations, and used by precondition_loop_p. */
189 static rtx loop_iteration_var
;
190 static rtx loop_initial_value
;
191 static rtx loop_increment
;
192 static rtx loop_final_value
;
194 /* Forward declarations. */
196 static void init_reg_map ();
197 static int precondition_loop_p ();
198 static void copy_loop_body ();
199 static void iteration_info ();
200 static rtx
approx_final_value ();
201 static int find_splittable_regs ();
202 static int find_splittable_givs ();
203 static rtx
fold_rtx_mult_add ();
205 /* Try to unroll one loop and split induction variables in the loop.
207 The loop is described by the arguments LOOP_END, INSN_COUNT, and
208 LOOP_START. END_INSERT_BEFORE indicates where insns should be added
209 which need to be executed when the loop falls through. STRENGTH_REDUCTION_P
210 indicates whether information generated in the strength reduction pass
213 This function is intended to be called from within `strength_reduce'
217 unroll_loop (loop_end
, insn_count
, loop_start
, end_insert_before
,
222 rtx end_insert_before
;
223 int strength_reduce_p
;
226 int unroll_number
= 1;
227 rtx copy_start
, copy_end
;
228 rtx insn
, copy
, sequence
, pattern
, tem
;
229 int max_labelno
, max_insnno
;
231 struct inline_remap
*map
;
239 int splitting_not_safe
= 0;
240 enum unroll_types unroll_type
;
241 int loop_preconditioned
= 0;
243 /* This points to the last real insn in the loop, which should be either
244 a JUMP_INSN (for conditional jumps) or a BARRIER (for unconditional
248 /* Don't bother unrolling huge loops. Since the minimum factor is
249 two, loops greater than one half of MAX_UNROLLED_INSNS will never
251 if (insn_count
> MAX_UNROLLED_INSNS
/ 2)
253 if (loop_dump_stream
)
254 fprintf (loop_dump_stream
, "Unrolling failure: Loop too big.\n");
258 /* When emitting debugger info, we can't unroll loops with unequal numbers
259 of block_beg and block_end notes, because that would unbalance the block
260 structure of the function. This can happen as a result of the
261 "if (foo) bar; else break;" optimization in jump.c. */
263 if (write_symbols
!= NO_DEBUG
)
265 int block_begins
= 0;
268 for (insn
= loop_start
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
270 if (GET_CODE (insn
) == NOTE
)
272 if (NOTE_LINE_NUMBER (insn
) == NOTE_INSN_BLOCK_BEG
)
274 else if (NOTE_LINE_NUMBER (insn
) == NOTE_INSN_BLOCK_END
)
279 if (block_begins
!= block_ends
)
281 if (loop_dump_stream
)
282 fprintf (loop_dump_stream
,
283 "Unrolling failure: Unbalanced block notes.\n");
288 /* Determine type of unroll to perform. Depends on the number of iterations
289 and the size of the loop. */
291 /* If there is no strength reduce info, then set loop_n_iterations to zero.
292 This can happen if strength_reduce can't find any bivs in the loop.
293 A value of zero indicates that the number of iterations could not be
296 if (! strength_reduce_p
)
297 loop_n_iterations
= 0;
299 if (loop_dump_stream
&& loop_n_iterations
> 0)
300 fprintf (loop_dump_stream
,
301 "Loop unrolling: %d iterations.\n", loop_n_iterations
);
303 /* Find and save a pointer to the last nonnote insn in the loop. */
305 last_loop_insn
= prev_nonnote_insn (loop_end
);
307 /* Calculate how many times to unroll the loop. Indicate whether or
308 not the loop is being completely unrolled. */
310 if (loop_n_iterations
== 1)
312 /* If number of iterations is exactly 1, then eliminate the compare and
313 branch at the end of the loop since they will never be taken.
314 Then return, since no other action is needed here. */
316 /* If the last instruction is not a BARRIER or a JUMP_INSN, then
317 don't do anything. */
319 if (GET_CODE (last_loop_insn
) == BARRIER
)
321 /* Delete the jump insn. This will delete the barrier also. */
322 delete_insn (PREV_INSN (last_loop_insn
));
324 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
327 /* The immediately preceding insn is a compare which must be
329 delete_insn (last_loop_insn
);
330 delete_insn (PREV_INSN (last_loop_insn
));
332 /* The immediately preceding insn may not be the compare, so don't
334 delete_insn (last_loop_insn
);
339 else if (loop_n_iterations
> 0
340 && loop_n_iterations
* insn_count
< MAX_UNROLLED_INSNS
)
342 unroll_number
= loop_n_iterations
;
343 unroll_type
= UNROLL_COMPLETELY
;
345 else if (loop_n_iterations
> 0)
347 /* Try to factor the number of iterations. Don't bother with the
348 general case, only using 2, 3, 5, and 7 will get 75% of all
349 numbers theoretically, and almost all in practice. */
351 for (i
= 0; i
< NUM_FACTORS
; i
++)
352 factors
[i
].count
= 0;
354 temp
= loop_n_iterations
;
355 for (i
= NUM_FACTORS
- 1; i
>= 0; i
--)
356 while (temp
% factors
[i
].factor
== 0)
359 temp
= temp
/ factors
[i
].factor
;
362 /* Start with the larger factors first so that we generally
363 get lots of unrolling. */
367 for (i
= 3; i
>= 0; i
--)
368 while (factors
[i
].count
--)
370 if (temp
* factors
[i
].factor
< MAX_UNROLLED_INSNS
)
372 unroll_number
*= factors
[i
].factor
;
373 temp
*= factors
[i
].factor
;
379 /* If we couldn't find any factors, then unroll as in the normal
381 if (unroll_number
== 1)
383 if (loop_dump_stream
)
384 fprintf (loop_dump_stream
,
385 "Loop unrolling: No factors found.\n");
388 unroll_type
= UNROLL_MODULO
;
392 /* Default case, calculate number of times to unroll loop based on its
394 if (unroll_number
== 1)
396 if (8 * insn_count
< MAX_UNROLLED_INSNS
)
398 else if (4 * insn_count
< MAX_UNROLLED_INSNS
)
403 unroll_type
= UNROLL_NAIVE
;
406 /* Now we know how many times to unroll the loop. */
408 if (loop_dump_stream
)
409 fprintf (loop_dump_stream
,
410 "Unrolling loop %d times.\n", unroll_number
);
413 if (unroll_type
== UNROLL_COMPLETELY
|| unroll_type
== UNROLL_MODULO
)
415 /* Loops of these types should never start with a jump down to
416 the exit condition test. For now, check for this case just to
417 be sure. UNROLL_NAIVE loops can be of this form, this case is
420 while (GET_CODE (insn
) != CODE_LABEL
&& GET_CODE (insn
) != JUMP_INSN
)
421 insn
= NEXT_INSN (insn
);
422 if (GET_CODE (insn
) == JUMP_INSN
)
426 if (unroll_type
== UNROLL_COMPLETELY
)
428 /* Completely unrolling the loop: Delete the compare and branch at
429 the end (the last two instructions). This delete must done at the
430 very end of loop unrolling, to avoid problems with calls to
431 back_branch_in_range_p, which is called by find_splittable_regs.
432 All increments of splittable bivs/givs are changed to load constant
435 copy_start
= loop_start
;
437 /* Set insert_before to the instruction immediately after the JUMP_INSN
438 (or BARRIER), so that any NOTEs between the JUMP_INSN and the end of
439 the loop will be correctly handled by copy_loop_body. */
440 insert_before
= NEXT_INSN (last_loop_insn
);
442 /* Set copy_end to the insn before the jump at the end of the loop. */
443 if (GET_CODE (last_loop_insn
) == BARRIER
)
444 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
445 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
448 /* The instruction immediately before the JUMP_INSN is a compare
449 instruction which we do not want to copy. */
450 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
452 /* The instruction immediately before the JUMP_INSN may not be the
453 compare, so we must copy it. */
454 copy_end
= PREV_INSN (last_loop_insn
);
459 /* We currently can't unroll a loop if it doesn't end with a
460 JUMP_INSN. There would need to be a mechanism that recognizes
461 this case, and then inserts a jump after each loop body, which
462 jumps to after the last loop body. */
463 if (loop_dump_stream
)
464 fprintf (loop_dump_stream
,
465 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
469 else if (unroll_type
== UNROLL_MODULO
)
471 /* Partially unrolling the loop: The compare and branch at the end
472 (the last two instructions) must remain. Don't copy the compare
473 and branch instructions at the end of the loop. Insert the unrolled
474 code immediately before the compare/branch at the end so that the
475 code will fall through to them as before. */
477 copy_start
= loop_start
;
479 /* Set insert_before to the jump insn at the end of the loop.
480 Set copy_end to before the jump insn at the end of the loop. */
481 if (GET_CODE (last_loop_insn
) == BARRIER
)
483 insert_before
= PREV_INSN (last_loop_insn
);
484 copy_end
= PREV_INSN (insert_before
);
486 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
489 /* The instruction immediately before the JUMP_INSN is a compare
490 instruction which we do not want to copy or delete. */
491 insert_before
= PREV_INSN (last_loop_insn
);
492 copy_end
= PREV_INSN (insert_before
);
494 /* The instruction immediately before the JUMP_INSN may not be the
495 compare, so we must copy it. */
496 insert_before
= last_loop_insn
;
497 copy_end
= PREV_INSN (last_loop_insn
);
502 /* We currently can't unroll a loop if it doesn't end with a
503 JUMP_INSN. There would need to be a mechanism that recognizes
504 this case, and then inserts a jump after each loop body, which
505 jumps to after the last loop body. */
506 if (loop_dump_stream
)
507 fprintf (loop_dump_stream
,
508 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
514 /* Normal case: Must copy the compare and branch instructions at the
517 if (GET_CODE (last_loop_insn
) == BARRIER
)
519 /* Loop ends with an unconditional jump and a barrier.
520 Handle this like above, don't copy jump and barrier.
521 This is not strictly necessary, but doing so prevents generating
522 unconditional jumps to an immediately following label.
524 This will be corrected below if the target of this jump is
525 not the start_label. */
527 insert_before
= PREV_INSN (last_loop_insn
);
528 copy_end
= PREV_INSN (insert_before
);
530 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
532 /* Set insert_before to immediately after the JUMP_INSN, so that
533 NOTEs at the end of the loop will be correctly handled by
535 insert_before
= NEXT_INSN (last_loop_insn
);
536 copy_end
= last_loop_insn
;
540 /* We currently can't unroll a loop if it doesn't end with a
541 JUMP_INSN. There would need to be a mechanism that recognizes
542 this case, and then inserts a jump after each loop body, which
543 jumps to after the last loop body. */
544 if (loop_dump_stream
)
545 fprintf (loop_dump_stream
,
546 "Unrolling failure: loop does not end with a JUMP_INSN.\n");
550 /* If copying exit test branches because they can not be eliminated,
551 then must convert the fall through case of the branch to a jump past
552 the end of the loop. Create a label to emit after the loop and save
553 it for later use. Do not use the label after the loop, if any, since
554 it might be used by insns outside the loop, or there might be insns
555 added before it later by final_[bg]iv_value which must be after
556 the real exit label. */
557 exit_label
= gen_label_rtx ();
560 while (GET_CODE (insn
) != CODE_LABEL
&& GET_CODE (insn
) != JUMP_INSN
)
561 insn
= NEXT_INSN (insn
);
563 if (GET_CODE (insn
) == JUMP_INSN
)
565 /* The loop starts with a jump down to the exit condition test.
566 Start copying the loop after the barrier following this
568 copy_start
= NEXT_INSN (insn
);
570 /* Splitting induction variables doesn't work when the loop is
571 entered via a jump to the bottom, because then we end up doing
572 a comparison against a new register for a split variable, but
573 we did not execute the set insn for the new register because
574 it was skipped over. */
575 splitting_not_safe
= 1;
576 if (loop_dump_stream
)
577 fprintf (loop_dump_stream
,
578 "Splitting not safe, because loop not entered at top.\n");
581 copy_start
= loop_start
;
584 /* This should always be the first label in the loop. */
585 start_label
= NEXT_INSN (copy_start
);
586 /* There may be a line number note and/or a loop continue note here. */
587 while (GET_CODE (start_label
) == NOTE
)
588 start_label
= NEXT_INSN (start_label
);
589 if (GET_CODE (start_label
) != CODE_LABEL
)
591 /* This can happen as a result of jump threading. If the first insns in
592 the loop test the same condition as the loop's backward jump, or the
593 opposite condition, then the backward jump will be modified to point
594 to elsewhere, and the loop's start label is deleted.
596 This case currently can not be handled by the loop unrolling code. */
598 if (loop_dump_stream
)
599 fprintf (loop_dump_stream
,
600 "Unrolling failure: unknown insns between BEG note and loop label.\n");
603 if (LABEL_NAME (start_label
))
605 /* The jump optimization pass must have combined the original start label
606 with a named label for a goto. We can't unroll this case because
607 jumps which go to the named label must be handled differently than
608 jumps to the loop start, and it is impossible to differentiate them
610 if (loop_dump_stream
)
611 fprintf (loop_dump_stream
,
612 "Unrolling failure: loop start label is gone\n");
616 if (unroll_type
== UNROLL_NAIVE
617 && GET_CODE (last_loop_insn
) == BARRIER
618 && start_label
!= JUMP_LABEL (PREV_INSN (last_loop_insn
)))
620 /* In this case, we must copy the jump and barrier, because they will
621 not be converted to jumps to an immediately following label. */
623 insert_before
= NEXT_INSN (last_loop_insn
);
624 copy_end
= last_loop_insn
;
627 /* Allocate a translation table for the labels and insn numbers.
628 They will be filled in as we copy the insns in the loop. */
630 max_labelno
= max_label_num ();
631 max_insnno
= get_max_uid ();
633 map
= (struct inline_remap
*) alloca (sizeof (struct inline_remap
));
635 map
->integrating
= 0;
637 /* Allocate the label map. */
641 map
->label_map
= (rtx
*) alloca (max_labelno
* sizeof (rtx
));
643 local_label
= (char *) alloca (max_labelno
);
644 bzero (local_label
, max_labelno
);
649 /* Search the loop and mark all local labels, i.e. the ones which have to
650 be distinct labels when copied. For all labels which might be
651 non-local, set their label_map entries to point to themselves.
652 If they happen to be local their label_map entries will be overwritten
653 before the loop body is copied. The label_map entries for local labels
654 will be set to a different value each time the loop body is copied. */
656 for (insn
= copy_start
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
658 if (GET_CODE (insn
) == CODE_LABEL
)
659 local_label
[CODE_LABEL_NUMBER (insn
)] = 1;
660 else if (GET_CODE (insn
) == JUMP_INSN
)
662 if (JUMP_LABEL (insn
))
663 map
->label_map
[CODE_LABEL_NUMBER (JUMP_LABEL (insn
))]
665 else if (GET_CODE (PATTERN (insn
)) == ADDR_VEC
666 || GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
)
668 rtx pat
= PATTERN (insn
);
669 int diff_vec_p
= GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
;
670 int len
= XVECLEN (pat
, diff_vec_p
);
673 for (i
= 0; i
< len
; i
++)
675 label
= XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0);
676 map
->label_map
[CODE_LABEL_NUMBER (label
)] = label
;
682 /* Allocate space for the insn map. */
684 map
->insn_map
= (rtx
*) alloca (max_insnno
* sizeof (rtx
));
686 /* Set this to zero, to indicate that we are doing loop unrolling,
687 not function inlining. */
688 map
->inline_target
= 0;
690 /* The register and constant maps depend on the number of registers
691 present, so the final maps can't be created until after
692 find_splittable_regs is called. However, they are needed for
693 preconditioning, so we create temporary maps when preconditioning
696 /* The preconditioning code may allocate two new pseudo registers. */
697 maxregnum
= max_reg_num ();
699 /* Allocate and zero out the splittable_regs and addr_combined_regs
700 arrays. These must be zeroed here because they will be used if
701 loop preconditioning is performed, and must be zero for that case.
703 It is safe to do this here, since the extra registers created by the
704 preconditioning code and find_splittable_regs will never be used
705 to access the splittable_regs[] and addr_combined_regs[] arrays. */
707 splittable_regs
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
708 bzero (splittable_regs
, maxregnum
* sizeof (rtx
));
709 splittable_regs_updates
= (int *) alloca (maxregnum
* sizeof (int));
710 bzero (splittable_regs_updates
, maxregnum
* sizeof (int));
712 = (struct induction
**) alloca (maxregnum
* sizeof (struct induction
*));
713 bzero (addr_combined_regs
, maxregnum
* sizeof (struct induction
*));
715 /* If this loop requires exit tests when unrolled, check to see if we
716 can precondition the loop so as to make the exit tests unnecessary.
717 Just like variable splitting, this is not safe if the loop is entered
718 via a jump to the bottom. Also, can not do this if no strength
719 reduce info, because precondition_loop_p uses this info. */
721 /* Must copy the loop body for preconditioning before the following
722 find_splittable_regs call since that will emit insns which need to
723 be after the preconditioned loop copies, but immediately before the
724 unrolled loop copies. */
726 /* Also, it is not safe to split induction variables for the preconditioned
727 copies of the loop body. If we split induction variables, then the code
728 assumes that each induction variable can be represented as a function
729 of its initial value and the loop iteration number. This is not true
730 in this case, because the last preconditioned copy of the loop body
731 could be any iteration from the first up to the `unroll_number-1'th,
732 depending on the initial value of the iteration variable. Therefore
733 we can not split induction variables here, because we can not calculate
734 their value. Hence, this code must occur before find_splittable_regs
737 if (unroll_type
== UNROLL_NAIVE
&& ! splitting_not_safe
&& strength_reduce_p
)
739 rtx initial_value
, final_value
, increment
;
741 if (precondition_loop_p (&initial_value
, &final_value
, &increment
,
742 loop_start
, loop_end
))
744 register rtx diff
, temp
;
745 enum machine_mode mode
;
747 int abs_inc
, neg_inc
;
749 map
->reg_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
751 map
->const_equiv_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
752 map
->const_age_map
= (unsigned *) alloca (maxregnum
753 * sizeof (unsigned));
754 map
->const_equiv_map_size
= maxregnum
;
755 global_const_equiv_map
= map
->const_equiv_map
;
757 init_reg_map (map
, maxregnum
);
759 /* Limit loop unrolling to 4, since this will make 7 copies of
761 if (unroll_number
> 4)
764 /* Save the absolute value of the increment, and also whether or
765 not it is negative. */
767 abs_inc
= INTVAL (increment
);
776 /* Decide what mode to do these calculations in. Choose the larger
777 of final_value's mode and initial_value's mode, or a full-word if
778 both are constants. */
779 mode
= GET_MODE (final_value
);
780 if (mode
== VOIDmode
)
782 mode
= GET_MODE (initial_value
);
783 if (mode
== VOIDmode
)
786 else if (mode
!= GET_MODE (initial_value
)
787 && (GET_MODE_SIZE (mode
)
788 < GET_MODE_SIZE (GET_MODE (initial_value
))))
789 mode
= GET_MODE (initial_value
);
791 /* Calculate the difference between the final and initial values.
792 Final value may be a (plus (reg x) (const_int 1)) rtx.
793 Let the following cse pass simplify this if initial value is
796 We must copy the final and initial values here to avoid
797 improperly shared rtl. */
799 diff
= expand_binop (mode
, sub_optab
, copy_rtx (final_value
),
800 copy_rtx (initial_value
), NULL_RTX
, 0,
803 /* Now calculate (diff % (unroll * abs (increment))) by using an
805 diff
= expand_binop (GET_MODE (diff
), and_optab
, diff
,
806 GEN_INT (unroll_number
* abs_inc
- 1),
807 NULL_RTX
, 0, OPTAB_LIB_WIDEN
);
809 /* Now emit a sequence of branches to jump to the proper precond
812 labels
= (rtx
*) alloca (sizeof (rtx
) * unroll_number
);
813 for (i
= 0; i
< unroll_number
; i
++)
814 labels
[i
] = gen_label_rtx ();
816 /* Assuming the unroll_number is 4, and the increment is 2, then
817 for a negative increment: for a positive increment:
818 diff = 0,1 precond 0 diff = 0,7 precond 0
819 diff = 2,3 precond 3 diff = 1,2 precond 1
820 diff = 4,5 precond 2 diff = 3,4 precond 2
821 diff = 6,7 precond 1 diff = 5,6 precond 3 */
823 /* We only need to emit (unroll_number - 1) branches here, the
824 last case just falls through to the following code. */
826 /* ??? This would give better code if we emitted a tree of branches
827 instead of the current linear list of branches. */
829 for (i
= 0; i
< unroll_number
- 1; i
++)
833 /* For negative increments, must invert the constant compared
834 against, except when comparing against zero. */
838 cmp_const
= unroll_number
- i
;
842 emit_cmp_insn (diff
, GEN_INT (abs_inc
* cmp_const
),
843 EQ
, NULL_RTX
, mode
, 0, 0);
846 emit_jump_insn (gen_beq (labels
[i
]));
848 emit_jump_insn (gen_bge (labels
[i
]));
850 emit_jump_insn (gen_ble (labels
[i
]));
851 JUMP_LABEL (get_last_insn ()) = labels
[i
];
852 LABEL_NUSES (labels
[i
])++;
855 /* If the increment is greater than one, then we need another branch,
856 to handle other cases equivalent to 0. */
858 /* ??? This should be merged into the code above somehow to help
859 simplify the code here, and reduce the number of branches emitted.
860 For the negative increment case, the branch here could easily
861 be merged with the `0' case branch above. For the positive
862 increment case, it is not clear how this can be simplified. */
869 cmp_const
= abs_inc
- 1;
871 cmp_const
= abs_inc
* (unroll_number
- 1) + 1;
873 emit_cmp_insn (diff
, GEN_INT (cmp_const
), EQ
, NULL_RTX
,
877 emit_jump_insn (gen_ble (labels
[0]));
879 emit_jump_insn (gen_bge (labels
[0]));
880 JUMP_LABEL (get_last_insn ()) = labels
[0];
881 LABEL_NUSES (labels
[0])++;
884 sequence
= gen_sequence ();
886 emit_insn_before (sequence
, loop_start
);
888 /* Only the last copy of the loop body here needs the exit
889 test, so set copy_end to exclude the compare/branch here,
890 and then reset it inside the loop when get to the last
893 if (GET_CODE (last_loop_insn
) == BARRIER
)
894 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
895 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
898 /* The immediately preceding insn is a compare which we do not
900 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
902 /* The immediately preceding insn may not be a compare, so we
904 copy_end
= PREV_INSN (last_loop_insn
);
910 for (i
= 1; i
< unroll_number
; i
++)
912 emit_label_after (labels
[unroll_number
- i
],
913 PREV_INSN (loop_start
));
915 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
916 bzero (map
->const_equiv_map
, maxregnum
* sizeof (rtx
));
917 bzero (map
->const_age_map
, maxregnum
* sizeof (unsigned));
920 for (j
= 0; j
< max_labelno
; j
++)
922 map
->label_map
[j
] = gen_label_rtx ();
924 /* The last copy needs the compare/branch insns at the end,
925 so reset copy_end here if the loop ends with a conditional
928 if (i
== unroll_number
- 1)
930 if (GET_CODE (last_loop_insn
) == BARRIER
)
931 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
933 copy_end
= last_loop_insn
;
936 /* None of the copies are the `last_iteration', so just
937 pass zero for that parameter. */
938 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, 0,
939 unroll_type
, start_label
, loop_end
,
940 loop_start
, copy_end
);
942 emit_label_after (labels
[0], PREV_INSN (loop_start
));
944 if (GET_CODE (last_loop_insn
) == BARRIER
)
946 insert_before
= PREV_INSN (last_loop_insn
);
947 copy_end
= PREV_INSN (insert_before
);
952 /* The immediately preceding insn is a compare which we do not
954 insert_before
= PREV_INSN (last_loop_insn
);
955 copy_end
= PREV_INSN (insert_before
);
957 /* The immediately preceding insn may not be a compare, so we
959 insert_before
= last_loop_insn
;
960 copy_end
= PREV_INSN (last_loop_insn
);
964 /* Set unroll type to MODULO now. */
965 unroll_type
= UNROLL_MODULO
;
966 loop_preconditioned
= 1;
970 /* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
971 the loop unless all loops are being unrolled. */
972 if (unroll_type
== UNROLL_NAIVE
&& ! flag_unroll_all_loops
)
974 if (loop_dump_stream
)
975 fprintf (loop_dump_stream
, "Unrolling failure: Naive unrolling not being done.\n");
979 /* At this point, we are guaranteed to unroll the loop. */
981 /* For each biv and giv, determine whether it can be safely split into
982 a different variable for each unrolled copy of the loop body.
983 We precalculate and save this info here, since computing it is
986 Do this before deleting any instructions from the loop, so that
987 back_branch_in_range_p will work correctly. */
989 if (splitting_not_safe
)
992 temp
= find_splittable_regs (unroll_type
, loop_start
, loop_end
,
993 end_insert_before
, unroll_number
);
995 /* find_splittable_regs may have created some new registers, so must
996 reallocate the reg_map with the new larger size, and must realloc
997 the constant maps also. */
999 maxregnum
= max_reg_num ();
1000 map
->reg_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
1002 init_reg_map (map
, maxregnum
);
1004 /* Space is needed in some of the map for new registers, so new_maxregnum
1005 is an (over)estimate of how many registers will exist at the end. */
1006 new_maxregnum
= maxregnum
+ (temp
* unroll_number
* 2);
1008 /* Must realloc space for the constant maps, because the number of registers
1009 may have changed. */
1011 map
->const_equiv_map
= (rtx
*) alloca (new_maxregnum
* sizeof (rtx
));
1012 map
->const_age_map
= (unsigned *) alloca (new_maxregnum
* sizeof (unsigned));
1014 map
->const_equiv_map_size
= new_maxregnum
;
1015 global_const_equiv_map
= map
->const_equiv_map
;
1017 /* Search the list of bivs and givs to find ones which need to be remapped
1018 when split, and set their reg_map entry appropriately. */
1020 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
1022 if (REGNO (bl
->biv
->src_reg
) != bl
->regno
)
1023 map
->reg_map
[bl
->regno
] = bl
->biv
->src_reg
;
1025 /* Currently, non-reduced/final-value givs are never split. */
1026 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
1027 if (REGNO (v
->src_reg
) != bl
->regno
)
1028 map
->reg_map
[REGNO (v
->dest_reg
)] = v
->src_reg
;
1032 /* If the loop is being partially unrolled, and the iteration variables
1033 are being split, and are being renamed for the split, then must fix up
1034 the compare instruction at the end of the loop to refer to the new
1035 registers. This compare isn't copied, so the registers used in it
1036 will never be replaced if it isn't done here. */
1038 if (unroll_type
== UNROLL_MODULO
)
1040 insn
= NEXT_INSN (copy_end
);
1041 if (GET_CODE (insn
) == INSN
&& GET_CODE (PATTERN (insn
)) == SET
)
1044 /* If non-reduced/final-value givs were split, then this would also
1045 have to remap those givs. */
1048 tem
= SET_SRC (PATTERN (insn
));
1049 /* The set source is a register. */
1050 if (GET_CODE (tem
) == REG
)
1052 if (REGNO (tem
) < max_reg_before_loop
1053 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1054 SET_SRC (PATTERN (insn
))
1055 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1059 /* The set source is a compare of some sort. */
1060 tem
= XEXP (SET_SRC (PATTERN (insn
)), 0);
1061 if (GET_CODE (tem
) == REG
1062 && REGNO (tem
) < max_reg_before_loop
1063 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1064 XEXP (SET_SRC (PATTERN (insn
)), 0)
1065 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1067 tem
= XEXP (SET_SRC (PATTERN (insn
)), 1);
1068 if (GET_CODE (tem
) == REG
1069 && REGNO (tem
) < max_reg_before_loop
1070 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1071 XEXP (SET_SRC (PATTERN (insn
)), 1)
1072 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1077 /* For unroll_number - 1 times, make a copy of each instruction
1078 between copy_start and copy_end, and insert these new instructions
1079 before the end of the loop. */
1081 for (i
= 0; i
< unroll_number
; i
++)
1083 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
1084 bzero (map
->const_equiv_map
, new_maxregnum
* sizeof (rtx
));
1085 bzero (map
->const_age_map
, new_maxregnum
* sizeof (unsigned));
1088 for (j
= 0; j
< max_labelno
; j
++)
1090 map
->label_map
[j
] = gen_label_rtx ();
1092 /* If loop starts with a branch to the test, then fix it so that
1093 it points to the test of the first unrolled copy of the loop. */
1094 if (i
== 0 && loop_start
!= copy_start
)
1096 insn
= PREV_INSN (copy_start
);
1097 pattern
= PATTERN (insn
);
1099 tem
= map
->label_map
[CODE_LABEL_NUMBER
1100 (XEXP (SET_SRC (pattern
), 0))];
1101 SET_SRC (pattern
) = gen_rtx (LABEL_REF
, VOIDmode
, tem
);
1103 /* Set the jump label so that it can be used by later loop unrolling
1105 JUMP_LABEL (insn
) = tem
;
1106 LABEL_NUSES (tem
)++;
1109 copy_loop_body (copy_start
, copy_end
, map
, exit_label
,
1110 i
== unroll_number
- 1, unroll_type
, start_label
,
1111 loop_end
, insert_before
, insert_before
);
1114 /* Before deleting any insns, emit a CODE_LABEL immediately after the last
1115 insn to be deleted. This prevents any runaway delete_insn call from
1116 more insns that it should, as it always stops at a CODE_LABEL. */
1118 /* Delete the compare and branch at the end of the loop if completely
1119 unrolling the loop. Deleting the backward branch at the end also
1120 deletes the code label at the start of the loop. This is done at
1121 the very end to avoid problems with back_branch_in_range_p. */
1123 if (unroll_type
== UNROLL_COMPLETELY
)
1124 safety_label
= emit_label_after (gen_label_rtx (), last_loop_insn
);
1126 safety_label
= emit_label_after (gen_label_rtx (), copy_end
);
1128 /* Delete all of the original loop instructions. Don't delete the
1129 LOOP_BEG note, or the first code label in the loop. */
1131 insn
= NEXT_INSN (copy_start
);
1132 while (insn
!= safety_label
)
1134 if (insn
!= start_label
)
1135 insn
= delete_insn (insn
);
1137 insn
= NEXT_INSN (insn
);
1140 /* Can now delete the 'safety' label emitted to protect us from runaway
1141 delete_insn calls. */
1142 if (INSN_DELETED_P (safety_label
))
1144 delete_insn (safety_label
);
1146 /* If exit_label exists, emit it after the loop. Doing the emit here
1147 forces it to have a higher INSN_UID than any insn in the unrolled loop.
1148 This is needed so that mostly_true_jump in reorg.c will treat jumps
1149 to this loop end label correctly, i.e. predict that they are usually
1152 emit_label_after (exit_label
, loop_end
);
1155 /* Return true if the loop can be safely, and profitably, preconditioned
1156 so that the unrolled copies of the loop body don't need exit tests.
1158 This only works if final_value, initial_value and increment can be
1159 determined, and if increment is a constant power of 2.
1160 If increment is not a power of 2, then the preconditioning modulo
1161 operation would require a real modulo instead of a boolean AND, and this
1162 is not considered `profitable'. */
1164 /* ??? If the loop is known to be executed very many times, or the machine
1165 has a very cheap divide instruction, then preconditioning is a win even
1166 when the increment is not a power of 2. Use RTX_COST to compute
1167 whether divide is cheap. */
1170 precondition_loop_p (initial_value
, final_value
, increment
, loop_start
,
1172 rtx
*initial_value
, *final_value
, *increment
;
1173 rtx loop_start
, loop_end
;
1175 int unsigned_compare
, compare_dir
;
1177 if (loop_n_iterations
> 0)
1179 *initial_value
= const0_rtx
;
1180 *increment
= const1_rtx
;
1181 *final_value
= GEN_INT (loop_n_iterations
);
1183 if (loop_dump_stream
)
1184 fprintf (loop_dump_stream
,
1185 "Preconditioning: Success, number of iterations known, %d.\n",
1190 if (loop_initial_value
== 0)
1192 if (loop_dump_stream
)
1193 fprintf (loop_dump_stream
,
1194 "Preconditioning: Could not find initial value.\n");
1197 else if (loop_increment
== 0)
1199 if (loop_dump_stream
)
1200 fprintf (loop_dump_stream
,
1201 "Preconditioning: Could not find increment value.\n");
1204 else if (GET_CODE (loop_increment
) != CONST_INT
)
1206 if (loop_dump_stream
)
1207 fprintf (loop_dump_stream
,
1208 "Preconditioning: Increment not a constant.\n");
1211 else if ((exact_log2 (INTVAL (loop_increment
)) < 0)
1212 && (exact_log2 (- INTVAL (loop_increment
)) < 0))
1214 if (loop_dump_stream
)
1215 fprintf (loop_dump_stream
,
1216 "Preconditioning: Increment not a constant power of 2.\n");
1220 /* Unsigned_compare and compare_dir can be ignored here, since they do
1221 not matter for preconditioning. */
1223 if (loop_final_value
== 0)
1225 if (loop_dump_stream
)
1226 fprintf (loop_dump_stream
,
1227 "Preconditioning: EQ comparison loop.\n");
1231 /* Must ensure that final_value is invariant, so call invariant_p to
1232 check. Before doing so, must check regno against max_reg_before_loop
1233 to make sure that the register is in the range covered by invariant_p.
1234 If it isn't, then it is most likely a biv/giv which by definition are
1236 if ((GET_CODE (loop_final_value
) == REG
1237 && REGNO (loop_final_value
) >= max_reg_before_loop
)
1238 || (GET_CODE (loop_final_value
) == PLUS
1239 && REGNO (XEXP (loop_final_value
, 0)) >= max_reg_before_loop
)
1240 || ! invariant_p (loop_final_value
))
1242 if (loop_dump_stream
)
1243 fprintf (loop_dump_stream
,
1244 "Preconditioning: Final value not invariant.\n");
1248 /* Fail for floating point values, since the caller of this function
1249 does not have code to deal with them. */
1250 if (GET_MODE_CLASS (GET_MODE (loop_final_value
)) == MODE_FLOAT
1251 || GET_MODE_CLASS (GET_MODE (loop_initial_value
)) == MODE_FLOAT
)
1253 if (loop_dump_stream
)
1254 fprintf (loop_dump_stream
,
1255 "Preconditioning: Floating point final or initial value.\n");
1259 /* Now set initial_value to be the iteration_var, since that may be a
1260 simpler expression, and is guaranteed to be correct if all of the
1261 above tests succeed.
1263 We can not use the initial_value as calculated, because it will be
1264 one too small for loops of the form "while (i-- > 0)". We can not
1265 emit code before the loop_skip_over insns to fix this problem as this
1266 will then give a number one too large for loops of the form
1269 Note that all loops that reach here are entered at the top, because
1270 this function is not called if the loop starts with a jump. */
1272 /* Fail if loop_iteration_var is not live before loop_start, since we need
1273 to test its value in the preconditioning code. */
1275 if (uid_luid
[regno_first_uid
[REGNO (loop_iteration_var
)]]
1276 > INSN_LUID (loop_start
))
1278 if (loop_dump_stream
)
1279 fprintf (loop_dump_stream
,
1280 "Preconditioning: Iteration var not live before loop start.\n");
1284 *initial_value
= loop_iteration_var
;
1285 *increment
= loop_increment
;
1286 *final_value
= loop_final_value
;
1289 if (loop_dump_stream
)
1290 fprintf (loop_dump_stream
, "Preconditioning: Successful.\n");
1295 /* All pseudo-registers must be mapped to themselves. Two hard registers
1296 must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
1297 REGNUM, to avoid function-inlining specific conversions of these
1298 registers. All other hard regs can not be mapped because they may be
1303 init_reg_map (map
, maxregnum
)
1304 struct inline_remap
*map
;
1309 for (i
= maxregnum
- 1; i
> LAST_VIRTUAL_REGISTER
; i
--)
1310 map
->reg_map
[i
] = regno_reg_rtx
[i
];
1311 /* Just clear the rest of the entries. */
1312 for (i
= LAST_VIRTUAL_REGISTER
; i
>= 0; i
--)
1313 map
->reg_map
[i
] = 0;
1315 map
->reg_map
[VIRTUAL_STACK_VARS_REGNUM
]
1316 = regno_reg_rtx
[VIRTUAL_STACK_VARS_REGNUM
];
1317 map
->reg_map
[VIRTUAL_INCOMING_ARGS_REGNUM
]
1318 = regno_reg_rtx
[VIRTUAL_INCOMING_ARGS_REGNUM
];
1321 /* Strength-reduction will often emit code for optimized biv/givs which
1322 calculates their value in a temporary register, and then copies the result
1323 to the iv. This procedure reconstructs the pattern computing the iv;
1324 verifying that all operands are of the proper form.
1326 The return value is the amount that the giv is incremented by. */
1329 calculate_giv_inc (pattern
, src_insn
, regno
)
1330 rtx pattern
, src_insn
;
1334 rtx increment_total
= 0;
1338 /* Verify that we have an increment insn here. First check for a plus
1339 as the set source. */
1340 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1342 /* SR sometimes computes the new giv value in a temp, then copies it
1344 src_insn
= PREV_INSN (src_insn
);
1345 pattern
= PATTERN (src_insn
);
1346 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1349 /* The last insn emitted is not needed, so delete it to avoid confusing
1350 the second cse pass. This insn sets the giv unnecessarily. */
1351 delete_insn (get_last_insn ());
1354 /* Verify that we have a constant as the second operand of the plus. */
1355 increment
= XEXP (SET_SRC (pattern
), 1);
1356 if (GET_CODE (increment
) != CONST_INT
)
1358 /* SR sometimes puts the constant in a register, especially if it is
1359 too big to be an add immed operand. */
1360 src_insn
= PREV_INSN (src_insn
);
1361 increment
= SET_SRC (PATTERN (src_insn
));
1363 /* SR may have used LO_SUM to compute the constant if it is too large
1364 for a load immed operand. In this case, the constant is in operand
1365 one of the LO_SUM rtx. */
1366 if (GET_CODE (increment
) == LO_SUM
)
1367 increment
= XEXP (increment
, 1);
1369 if (GET_CODE (increment
) != CONST_INT
)
1372 /* The insn loading the constant into a register is not longer needed,
1374 delete_insn (get_last_insn ());
1377 if (increment_total
)
1378 increment_total
= GEN_INT (INTVAL (increment_total
) + INTVAL (increment
));
1380 increment_total
= increment
;
1382 /* Check that the source register is the same as the register we expected
1383 to see as the source. If not, something is seriously wrong. */
1384 if (GET_CODE (XEXP (SET_SRC (pattern
), 0)) != REG
1385 || REGNO (XEXP (SET_SRC (pattern
), 0)) != regno
)
1387 /* Some machines (e.g. the romp), may emit two add instructions for
1388 certain constants, so lets try looking for another add immediately
1389 before this one if we have only seen one add insn so far. */
1395 src_insn
= PREV_INSN (src_insn
);
1396 pattern
= PATTERN (src_insn
);
1398 delete_insn (get_last_insn ());
1406 return increment_total
;
1409 /* Copy REG_NOTES, except for insn references, because not all insn_map
1410 entries are valid yet. We do need to copy registers now though, because
1411 the reg_map entries can change during copying. */
1414 initial_reg_note_copy (notes
, map
)
1416 struct inline_remap
*map
;
1423 copy
= rtx_alloc (GET_CODE (notes
));
1424 PUT_MODE (copy
, GET_MODE (notes
));
1426 if (GET_CODE (notes
) == EXPR_LIST
)
1427 XEXP (copy
, 0) = copy_rtx_and_substitute (XEXP (notes
, 0), map
);
1428 else if (GET_CODE (notes
) == INSN_LIST
)
1429 /* Don't substitute for these yet. */
1430 XEXP (copy
, 0) = XEXP (notes
, 0);
1434 XEXP (copy
, 1) = initial_reg_note_copy (XEXP (notes
, 1), map
);
1439 /* Fixup insn references in copied REG_NOTES. */
1442 final_reg_note_copy (notes
, map
)
1444 struct inline_remap
*map
;
1448 for (note
= notes
; note
; note
= XEXP (note
, 1))
1449 if (GET_CODE (note
) == INSN_LIST
)
1450 XEXP (note
, 0) = map
->insn_map
[INSN_UID (XEXP (note
, 0))];
1453 /* Copy each instruction in the loop, substituting from map as appropriate.
1454 This is very similar to a loop in expand_inline_function. */
1457 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, last_iteration
,
1458 unroll_type
, start_label
, loop_end
, insert_before
,
1460 rtx copy_start
, copy_end
;
1461 struct inline_remap
*map
;
1464 enum unroll_types unroll_type
;
1465 rtx start_label
, loop_end
, insert_before
, copy_notes_from
;
1469 int dest_reg_was_split
, i
;
1471 rtx final_label
= 0;
1472 rtx giv_inc
, giv_dest_reg
, giv_src_reg
;
1474 /* If this isn't the last iteration, then map any references to the
1475 start_label to final_label. Final label will then be emitted immediately
1476 after the end of this loop body if it was ever used.
1478 If this is the last iteration, then map references to the start_label
1480 if (! last_iteration
)
1482 final_label
= gen_label_rtx ();
1483 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = final_label
;
1486 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = start_label
;
1493 insn
= NEXT_INSN (insn
);
1495 map
->orig_asm_operands_vector
= 0;
1497 switch (GET_CODE (insn
))
1500 pattern
= PATTERN (insn
);
1504 /* Check to see if this is a giv that has been combined with
1505 some split address givs. (Combined in the sense that
1506 `combine_givs' in loop.c has put two givs in the same register.)
1507 In this case, we must search all givs based on the same biv to
1508 find the address givs. Then split the address givs.
1509 Do this before splitting the giv, since that may map the
1510 SET_DEST to a new register. */
1512 if (GET_CODE (pattern
) == SET
1513 && GET_CODE (SET_DEST (pattern
)) == REG
1514 && addr_combined_regs
[REGNO (SET_DEST (pattern
))])
1516 struct iv_class
*bl
;
1517 struct induction
*v
, *tv
;
1518 int regno
= REGNO (SET_DEST (pattern
));
1520 v
= addr_combined_regs
[REGNO (SET_DEST (pattern
))];
1521 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
1523 /* Although the giv_inc amount is not needed here, we must call
1524 calculate_giv_inc here since it might try to delete the
1525 last insn emitted. If we wait until later to call it,
1526 we might accidentally delete insns generated immediately
1527 below by emit_unrolled_add. */
1529 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1531 /* Now find all address giv's that were combined with this
1533 for (tv
= bl
->giv
; tv
; tv
= tv
->next_iv
)
1534 if (tv
->giv_type
== DEST_ADDR
&& tv
->same
== v
)
1536 int this_giv_inc
= INTVAL (giv_inc
);
1538 /* Scale this_giv_inc if the multiplicative factors of
1539 the two givs are different. */
1540 if (tv
->mult_val
!= v
->mult_val
)
1541 this_giv_inc
= (this_giv_inc
/ INTVAL (v
->mult_val
)
1542 * INTVAL (tv
->mult_val
));
1544 tv
->dest_reg
= plus_constant (tv
->dest_reg
, this_giv_inc
);
1545 *tv
->location
= tv
->dest_reg
;
1547 if (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)
1549 /* Must emit an insn to increment the split address
1550 giv. Add in the const_adjust field in case there
1551 was a constant eliminated from the address. */
1552 rtx value
, dest_reg
;
1554 /* tv->dest_reg will be either a bare register,
1555 or else a register plus a constant. */
1556 if (GET_CODE (tv
->dest_reg
) == REG
)
1557 dest_reg
= tv
->dest_reg
;
1559 dest_reg
= XEXP (tv
->dest_reg
, 0);
1561 /* tv->dest_reg may actually be a (PLUS (REG) (CONST))
1562 here, so we must call plus_constant to add
1563 the const_adjust amount before calling
1564 emit_unrolled_add below. */
1565 value
= plus_constant (tv
->dest_reg
, tv
->const_adjust
);
1567 /* The constant could be too large for an add
1568 immediate, so can't directly emit an insn here. */
1569 emit_unrolled_add (dest_reg
, XEXP (value
, 0),
1572 /* Reset the giv to be just the register again, in case
1573 it is used after the set we have just emitted.
1574 We must subtract the const_adjust factor added in
1576 tv
->dest_reg
= plus_constant (dest_reg
,
1577 - tv
->const_adjust
);
1578 *tv
->location
= tv
->dest_reg
;
1583 /* If this is a setting of a splittable variable, then determine
1584 how to split the variable, create a new set based on this split,
1585 and set up the reg_map so that later uses of the variable will
1586 use the new split variable. */
1588 dest_reg_was_split
= 0;
1590 if (GET_CODE (pattern
) == SET
1591 && GET_CODE (SET_DEST (pattern
)) == REG
1592 && splittable_regs
[REGNO (SET_DEST (pattern
))])
1594 int regno
= REGNO (SET_DEST (pattern
));
1596 dest_reg_was_split
= 1;
1598 /* Compute the increment value for the giv, if it wasn't
1599 already computed above. */
1602 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1603 giv_dest_reg
= SET_DEST (pattern
);
1604 giv_src_reg
= SET_DEST (pattern
);
1606 if (unroll_type
== UNROLL_COMPLETELY
)
1608 /* Completely unrolling the loop. Set the induction
1609 variable to a known constant value. */
1611 /* The value in splittable_regs may be an invariant
1612 value, so we must use plus_constant here. */
1613 splittable_regs
[regno
]
1614 = plus_constant (splittable_regs
[regno
], INTVAL (giv_inc
));
1616 if (GET_CODE (splittable_regs
[regno
]) == PLUS
)
1618 giv_src_reg
= XEXP (splittable_regs
[regno
], 0);
1619 giv_inc
= XEXP (splittable_regs
[regno
], 1);
1623 /* The splittable_regs value must be a REG or a
1624 CONST_INT, so put the entire value in the giv_src_reg
1626 giv_src_reg
= splittable_regs
[regno
];
1627 giv_inc
= const0_rtx
;
1632 /* Partially unrolling loop. Create a new pseudo
1633 register for the iteration variable, and set it to
1634 be a constant plus the original register. Except
1635 on the last iteration, when the result has to
1636 go back into the original iteration var register. */
1638 /* Handle bivs which must be mapped to a new register
1639 when split. This happens for bivs which need their
1640 final value set before loop entry. The new register
1641 for the biv was stored in the biv's first struct
1642 induction entry by find_splittable_regs. */
1644 if (regno
< max_reg_before_loop
1645 && reg_iv_type
[regno
] == BASIC_INDUCT
)
1647 giv_src_reg
= reg_biv_class
[regno
]->biv
->src_reg
;
1648 giv_dest_reg
= giv_src_reg
;
1652 /* If non-reduced/final-value givs were split, then
1653 this would have to remap those givs also. See
1654 find_splittable_regs. */
1657 splittable_regs
[regno
]
1658 = GEN_INT (INTVAL (giv_inc
)
1659 + INTVAL (splittable_regs
[regno
]));
1660 giv_inc
= splittable_regs
[regno
];
1662 /* Now split the induction variable by changing the dest
1663 of this insn to a new register, and setting its
1664 reg_map entry to point to this new register.
1666 If this is the last iteration, and this is the last insn
1667 that will update the iv, then reuse the original dest,
1668 to ensure that the iv will have the proper value when
1669 the loop exits or repeats.
1671 Using splittable_regs_updates here like this is safe,
1672 because it can only be greater than one if all
1673 instructions modifying the iv are always executed in
1676 if (! last_iteration
1677 || (splittable_regs_updates
[regno
]-- != 1))
1679 tem
= gen_reg_rtx (GET_MODE (giv_src_reg
));
1681 map
->reg_map
[regno
] = tem
;
1684 map
->reg_map
[regno
] = giv_src_reg
;
1687 /* The constant being added could be too large for an add
1688 immediate, so can't directly emit an insn here. */
1689 emit_unrolled_add (giv_dest_reg
, giv_src_reg
, giv_inc
);
1690 copy
= get_last_insn ();
1691 pattern
= PATTERN (copy
);
1695 pattern
= copy_rtx_and_substitute (pattern
, map
);
1696 copy
= emit_insn (pattern
);
1698 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1701 /* If this insn is setting CC0, it may need to look at
1702 the insn that uses CC0 to see what type of insn it is.
1703 In that case, the call to recog via validate_change will
1704 fail. So don't substitute constants here. Instead,
1705 do it when we emit the following insn.
1707 For example, see the pyr.md file. That machine has signed and
1708 unsigned compares. The compare patterns must check the
1709 following branch insn to see which what kind of compare to
1712 If the previous insn set CC0, substitute constants on it as
1714 if (sets_cc0_p (copy
) != 0)
1719 try_constants (cc0_insn
, map
);
1721 try_constants (copy
, map
);
1724 try_constants (copy
, map
);
1727 /* Make split induction variable constants `permanent' since we
1728 know there are no backward branches across iteration variable
1729 settings which would invalidate this. */
1730 if (dest_reg_was_split
)
1732 int regno
= REGNO (SET_DEST (pattern
));
1734 if (regno
< map
->const_equiv_map_size
1735 && map
->const_age_map
[regno
] == map
->const_age
)
1736 map
->const_age_map
[regno
] = -1;
1741 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1742 copy
= emit_jump_insn (pattern
);
1743 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1745 if (JUMP_LABEL (insn
) == start_label
&& insn
== copy_end
1746 && ! last_iteration
)
1748 /* This is a branch to the beginning of the loop; this is the
1749 last insn being copied; and this is not the last iteration.
1750 In this case, we want to change the original fall through
1751 case to be a branch past the end of the loop, and the
1752 original jump label case to fall_through. */
1754 if (! invert_exp (pattern
, copy
)
1755 || ! redirect_exp (&pattern
,
1756 map
->label_map
[CODE_LABEL_NUMBER
1757 (JUMP_LABEL (insn
))],
1764 try_constants (cc0_insn
, map
);
1767 try_constants (copy
, map
);
1769 /* Set the jump label of COPY correctly to avoid problems with
1770 later passes of unroll_loop, if INSN had jump label set. */
1771 if (JUMP_LABEL (insn
))
1775 /* Can't use the label_map for every insn, since this may be
1776 the backward branch, and hence the label was not mapped. */
1777 if (GET_CODE (pattern
) == SET
)
1779 tem
= SET_SRC (pattern
);
1780 if (GET_CODE (tem
) == LABEL_REF
)
1781 label
= XEXP (tem
, 0);
1782 else if (GET_CODE (tem
) == IF_THEN_ELSE
)
1784 if (XEXP (tem
, 1) != pc_rtx
)
1785 label
= XEXP (XEXP (tem
, 1), 0);
1787 label
= XEXP (XEXP (tem
, 2), 0);
1791 if (label
&& GET_CODE (label
) == CODE_LABEL
)
1792 JUMP_LABEL (copy
) = label
;
1795 /* An unrecognizable jump insn, probably the entry jump
1796 for a switch statement. This label must have been mapped,
1797 so just use the label_map to get the new jump label. */
1798 JUMP_LABEL (copy
) = map
->label_map
[CODE_LABEL_NUMBER
1799 (JUMP_LABEL (insn
))];
1802 /* If this is a non-local jump, then must increase the label
1803 use count so that the label will not be deleted when the
1804 original jump is deleted. */
1805 LABEL_NUSES (JUMP_LABEL (copy
))++;
1807 else if (GET_CODE (PATTERN (copy
)) == ADDR_VEC
1808 || GET_CODE (PATTERN (copy
)) == ADDR_DIFF_VEC
)
1810 rtx pat
= PATTERN (copy
);
1811 int diff_vec_p
= GET_CODE (pat
) == ADDR_DIFF_VEC
;
1812 int len
= XVECLEN (pat
, diff_vec_p
);
1815 for (i
= 0; i
< len
; i
++)
1816 LABEL_NUSES (XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0))++;
1819 /* If this used to be a conditional jump insn but whose branch
1820 direction is now known, we must do something special. */
1821 if (condjump_p (insn
) && !simplejump_p (insn
) && map
->last_pc_value
)
1824 /* The previous insn set cc0 for us. So delete it. */
1825 delete_insn (PREV_INSN (copy
));
1828 /* If this is now a no-op, delete it. */
1829 if (map
->last_pc_value
== pc_rtx
)
1835 /* Otherwise, this is unconditional jump so we must put a
1836 BARRIER after it. We could do some dead code elimination
1837 here, but jump.c will do it just as well. */
1843 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1844 copy
= emit_call_insn (pattern
);
1845 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1849 try_constants (cc0_insn
, map
);
1852 try_constants (copy
, map
);
1854 /* Be lazy and assume CALL_INSNs clobber all hard registers. */
1855 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
1856 map
->const_equiv_map
[i
] = 0;
1860 /* If this is the loop start label, then we don't need to emit a
1861 copy of this label since no one will use it. */
1863 if (insn
!= start_label
)
1865 copy
= emit_label (map
->label_map
[CODE_LABEL_NUMBER (insn
)]);
1871 copy
= emit_barrier ();
1875 /* VTOP notes are valid only before the loop exit test. If placed
1876 anywhere else, loop may generate bad code. */
1878 if (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
1879 && (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_LOOP_VTOP
1880 || (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)))
1881 copy
= emit_note (NOTE_SOURCE_FILE (insn
),
1882 NOTE_LINE_NUMBER (insn
));
1892 map
->insn_map
[INSN_UID (insn
)] = copy
;
1894 while (insn
!= copy_end
);
1896 /* Now finish coping the REG_NOTES. */
1900 insn
= NEXT_INSN (insn
);
1901 if ((GET_CODE (insn
) == INSN
|| GET_CODE (insn
) == JUMP_INSN
1902 || GET_CODE (insn
) == CALL_INSN
)
1903 && map
->insn_map
[INSN_UID (insn
)])
1904 final_reg_note_copy (REG_NOTES (map
->insn_map
[INSN_UID (insn
)]), map
);
1906 while (insn
!= copy_end
);
1908 /* There may be notes between copy_notes_from and loop_end. Emit a copy of
1909 each of these notes here, since there may be some important ones, such as
1910 NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
1911 iteration, because the original notes won't be deleted.
1913 We can't use insert_before here, because when from preconditioning,
1914 insert_before points before the loop. We can't use copy_end, because
1915 there may be insns already inserted after it (which we don't want to
1916 copy) when not from preconditioning code. */
1918 if (! last_iteration
)
1920 for (insn
= copy_notes_from
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
1922 if (GET_CODE (insn
) == NOTE
1923 && NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
)
1924 emit_note (NOTE_SOURCE_FILE (insn
), NOTE_LINE_NUMBER (insn
));
1928 if (final_label
&& LABEL_NUSES (final_label
) > 0)
1929 emit_label (final_label
);
1931 tem
= gen_sequence ();
1933 emit_insn_before (tem
, insert_before
);
1936 /* Emit an insn, using the expand_binop to ensure that a valid insn is
1937 emitted. This will correctly handle the case where the increment value
1938 won't fit in the immediate field of a PLUS insns. */
1941 emit_unrolled_add (dest_reg
, src_reg
, increment
)
1942 rtx dest_reg
, src_reg
, increment
;
1946 result
= expand_binop (GET_MODE (dest_reg
), add_optab
, src_reg
, increment
,
1947 dest_reg
, 0, OPTAB_LIB_WIDEN
);
1949 if (dest_reg
!= result
)
1950 emit_move_insn (dest_reg
, result
);
1953 /* Searches the insns between INSN and LOOP_END. Returns 1 if there
1954 is a backward branch in that range that branches to somewhere between
1955 LOOP_START and INSN. Returns 0 otherwise. */
1957 /* ??? This is quadratic algorithm. Could be rewritten to be linear.
1958 In practice, this is not a problem, because this function is seldom called,
1959 and uses a negligible amount of CPU time on average. */
1962 back_branch_in_range_p (insn
, loop_start
, loop_end
)
1964 rtx loop_start
, loop_end
;
1966 rtx p
, q
, target_insn
;
1968 /* Stop before we get to the backward branch at the end of the loop. */
1969 loop_end
= prev_nonnote_insn (loop_end
);
1970 if (GET_CODE (loop_end
) == BARRIER
)
1971 loop_end
= PREV_INSN (loop_end
);
1973 /* Check in case insn has been deleted, search forward for first non
1974 deleted insn following it. */
1975 while (INSN_DELETED_P (insn
))
1976 insn
= NEXT_INSN (insn
);
1978 /* Check for the case where insn is the last insn in the loop. */
1979 if (insn
== loop_end
)
1982 for (p
= NEXT_INSN (insn
); p
!= loop_end
; p
= NEXT_INSN (p
))
1984 if (GET_CODE (p
) == JUMP_INSN
)
1986 target_insn
= JUMP_LABEL (p
);
1988 /* Search from loop_start to insn, to see if one of them is
1989 the target_insn. We can't use INSN_LUID comparisons here,
1990 since insn may not have an LUID entry. */
1991 for (q
= loop_start
; q
!= insn
; q
= NEXT_INSN (q
))
1992 if (q
== target_insn
)
2000 /* Try to generate the simplest rtx for the expression
2001 (PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
2005 fold_rtx_mult_add (mult1
, mult2
, add1
, mode
)
2006 rtx mult1
, mult2
, add1
;
2007 enum machine_mode mode
;
2012 /* The modes must all be the same. This should always be true. For now,
2013 check to make sure. */
2014 if ((GET_MODE (mult1
) != mode
&& GET_MODE (mult1
) != VOIDmode
)
2015 || (GET_MODE (mult2
) != mode
&& GET_MODE (mult2
) != VOIDmode
)
2016 || (GET_MODE (add1
) != mode
&& GET_MODE (add1
) != VOIDmode
))
2019 /* Ensure that if at least one of mult1/mult2 are constant, then mult2
2020 will be a constant. */
2021 if (GET_CODE (mult1
) == CONST_INT
)
2028 mult_res
= simplify_binary_operation (MULT
, mode
, mult1
, mult2
);
2030 mult_res
= gen_rtx (MULT
, mode
, mult1
, mult2
);
2032 /* Again, put the constant second. */
2033 if (GET_CODE (add1
) == CONST_INT
)
2040 result
= simplify_binary_operation (PLUS
, mode
, add1
, mult_res
);
2042 result
= gen_rtx (PLUS
, mode
, add1
, mult_res
);
2047 /* Searches the list of induction struct's for the biv BL, to try to calculate
2048 the total increment value for one iteration of the loop as a constant.
2050 Returns the increment value as an rtx, simplified as much as possible,
2051 if it can be calculated. Otherwise, returns 0. */
2054 biv_total_increment (bl
, loop_start
, loop_end
)
2055 struct iv_class
*bl
;
2056 rtx loop_start
, loop_end
;
2058 struct induction
*v
;
2061 /* For increment, must check every instruction that sets it. Each
2062 instruction must be executed only once each time through the loop.
2063 To verify this, we check that the the insn is always executed, and that
2064 there are no backward branches after the insn that branch to before it.
2065 Also, the insn must have a mult_val of one (to make sure it really is
2068 result
= const0_rtx
;
2069 for (v
= bl
->biv
; v
; v
= v
->next_iv
)
2071 if (v
->always_computable
&& v
->mult_val
== const1_rtx
2072 && ! back_branch_in_range_p (v
->insn
, loop_start
, loop_end
))
2073 result
= fold_rtx_mult_add (result
, const1_rtx
, v
->add_val
, v
->mode
);
2081 /* Determine the initial value of the iteration variable, and the amount
2082 that it is incremented each loop. Use the tables constructed by
2083 the strength reduction pass to calculate these values.
2085 Initial_value and/or increment are set to zero if their values could not
2089 iteration_info (iteration_var
, initial_value
, increment
, loop_start
, loop_end
)
2090 rtx iteration_var
, *initial_value
, *increment
;
2091 rtx loop_start
, loop_end
;
2093 struct iv_class
*bl
;
2094 struct induction
*v
, *b
;
2096 /* Clear the result values, in case no answer can be found. */
2100 /* The iteration variable can be either a giv or a biv. Check to see
2101 which it is, and compute the variable's initial value, and increment
2102 value if possible. */
2104 /* If this is a new register, can't handle it since we don't have any
2105 reg_iv_type entry for it. */
2106 if (REGNO (iteration_var
) >= max_reg_before_loop
)
2108 if (loop_dump_stream
)
2109 fprintf (loop_dump_stream
,
2110 "Loop unrolling: No reg_iv_type entry for iteration var.\n");
2113 /* Reject iteration variables larger than the host long size, since they
2114 could result in a number of iterations greater than the range of our
2115 `unsigned long' variable loop_n_iterations. */
2116 else if (GET_MODE_BITSIZE (GET_MODE (iteration_var
)) > HOST_BITS_PER_LONG
)
2118 if (loop_dump_stream
)
2119 fprintf (loop_dump_stream
,
2120 "Loop unrolling: Iteration var rejected because mode larger than host long.\n");
2123 else if (GET_MODE_CLASS (GET_MODE (iteration_var
)) != MODE_INT
)
2125 if (loop_dump_stream
)
2126 fprintf (loop_dump_stream
,
2127 "Loop unrolling: Iteration var not an integer.\n");
2130 else if (reg_iv_type
[REGNO (iteration_var
)] == BASIC_INDUCT
)
2132 /* Grab initial value, only useful if it is a constant. */
2133 bl
= reg_biv_class
[REGNO (iteration_var
)];
2134 *initial_value
= bl
->initial_value
;
2136 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2138 else if (reg_iv_type
[REGNO (iteration_var
)] == GENERAL_INDUCT
)
2141 /* ??? The code below does not work because the incorrect number of
2142 iterations is calculated when the biv is incremented after the giv
2143 is set (which is the usual case). This can probably be accounted
2144 for by biasing the initial_value by subtracting the amount of the
2145 increment that occurs between the giv set and the giv test. However,
2146 a giv as an iterator is very rare, so it does not seem worthwhile
2148 /* ??? An example failure is: i = 6; do {;} while (i++ < 9). */
2149 if (loop_dump_stream
)
2150 fprintf (loop_dump_stream
,
2151 "Loop unrolling: Giv iterators are not handled.\n");
2154 /* Initial value is mult_val times the biv's initial value plus
2155 add_val. Only useful if it is a constant. */
2156 v
= reg_iv_info
[REGNO (iteration_var
)];
2157 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2158 *initial_value
= fold_rtx_mult_add (v
->mult_val
, bl
->initial_value
,
2159 v
->add_val
, v
->mode
);
2161 /* Increment value is mult_val times the increment value of the biv. */
2163 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2165 *increment
= fold_rtx_mult_add (v
->mult_val
, *increment
, const0_rtx
,
2171 if (loop_dump_stream
)
2172 fprintf (loop_dump_stream
,
2173 "Loop unrolling: Not basic or general induction var.\n");
2178 /* Calculate the approximate final value of the iteration variable
2179 which has an loop exit test with code COMPARISON_CODE and comparison value
2180 of COMPARISON_VALUE. Also returns an indication of whether the comparison
2181 was signed or unsigned, and the direction of the comparison. This info is
2182 needed to calculate the number of loop iterations. */
2185 approx_final_value (comparison_code
, comparison_value
, unsigned_p
, compare_dir
)
2186 enum rtx_code comparison_code
;
2187 rtx comparison_value
;
2191 /* Calculate the final value of the induction variable.
2192 The exact final value depends on the branch operator, and increment sign.
2193 This is only an approximate value. It will be wrong if the iteration
2194 variable is not incremented by one each time through the loop, and
2195 approx final value - start value % increment != 0. */
2198 switch (comparison_code
)
2204 return plus_constant (comparison_value
, 1);
2209 return plus_constant (comparison_value
, -1);
2211 /* Can not calculate a final value for this case. */
2218 return comparison_value
;
2224 return comparison_value
;
2227 return comparison_value
;
2233 /* For each biv and giv, determine whether it can be safely split into
2234 a different variable for each unrolled copy of the loop body. If it
2235 is safe to split, then indicate that by saving some useful info
2236 in the splittable_regs array.
2238 If the loop is being completely unrolled, then splittable_regs will hold
2239 the current value of the induction variable while the loop is unrolled.
2240 It must be set to the initial value of the induction variable here.
2241 Otherwise, splittable_regs will hold the difference between the current
2242 value of the induction variable and the value the induction variable had
2243 at the top of the loop. It must be set to the value 0 here.
2245 Returns the total number of instructions that set registers that are
2248 /* ?? If the loop is only unrolled twice, then most of the restrictions to
2249 constant values are unnecessary, since we can easily calculate increment
2250 values in this case even if nothing is constant. The increment value
2251 should not involve a multiply however. */
2253 /* ?? Even if the biv/giv increment values aren't constant, it may still
2254 be beneficial to split the variable if the loop is only unrolled a few
2255 times, since multiplies by small integers (1,2,3,4) are very cheap. */
2258 find_splittable_regs (unroll_type
, loop_start
, loop_end
, end_insert_before
,
2260 enum unroll_types unroll_type
;
2261 rtx loop_start
, loop_end
;
2262 rtx end_insert_before
;
2265 struct iv_class
*bl
;
2266 struct induction
*v
;
2268 rtx biv_final_value
;
2272 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
2274 /* Biv_total_increment must return a constant value,
2275 otherwise we can not calculate the split values. */
2277 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2278 if (! increment
|| GET_CODE (increment
) != CONST_INT
)
2281 /* The loop must be unrolled completely, or else have a known number
2282 of iterations and only one exit, or else the biv must be dead
2283 outside the loop, or else the final value must be known. Otherwise,
2284 it is unsafe to split the biv since it may not have the proper
2285 value on loop exit. */
2287 /* loop_number_exit_labels is non-zero if the loop has an exit other than
2288 a fall through at the end. */
2291 biv_final_value
= 0;
2292 if (unroll_type
!= UNROLL_COMPLETELY
2293 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2294 || unroll_type
== UNROLL_NAIVE
)
2295 && (uid_luid
[regno_last_uid
[bl
->regno
]] >= INSN_LUID (loop_end
)
2297 || INSN_UID (bl
->init_insn
) >= max_uid_for_loop
2298 || (uid_luid
[regno_first_uid
[bl
->regno
]]
2299 < INSN_LUID (bl
->init_insn
))
2300 || reg_mentioned_p (bl
->biv
->dest_reg
, SET_SRC (bl
->init_set
)))
2301 && ! (biv_final_value
= final_biv_value (bl
, loop_start
, loop_end
)))
2304 /* If any of the insns setting the BIV don't do so with a simple
2305 PLUS, we don't know how to split it. */
2306 for (v
= bl
->biv
; biv_splittable
&& v
; v
= v
->next_iv
)
2307 if ((tem
= single_set (v
->insn
)) == 0
2308 || GET_CODE (SET_DEST (tem
)) != REG
2309 || REGNO (SET_DEST (tem
)) != bl
->regno
2310 || GET_CODE (SET_SRC (tem
)) != PLUS
)
2313 /* If final value is non-zero, then must emit an instruction which sets
2314 the value of the biv to the proper value. This is done after
2315 handling all of the givs, since some of them may need to use the
2316 biv's value in their initialization code. */
2318 /* This biv is splittable. If completely unrolling the loop, save
2319 the biv's initial value. Otherwise, save the constant zero. */
2321 if (biv_splittable
== 1)
2323 if (unroll_type
== UNROLL_COMPLETELY
)
2325 /* If the initial value of the biv is itself (i.e. it is too
2326 complicated for strength_reduce to compute), or is a hard
2327 register, then we must create a new pseudo reg to hold the
2328 initial value of the biv. */
2330 if (GET_CODE (bl
->initial_value
) == REG
2331 && (REGNO (bl
->initial_value
) == bl
->regno
2332 || REGNO (bl
->initial_value
) < FIRST_PSEUDO_REGISTER
))
2334 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2336 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2339 if (loop_dump_stream
)
2340 fprintf (loop_dump_stream
, "Biv %d initial value remapped to %d.\n",
2341 bl
->regno
, REGNO (tem
));
2343 splittable_regs
[bl
->regno
] = tem
;
2346 splittable_regs
[bl
->regno
] = bl
->initial_value
;
2349 splittable_regs
[bl
->regno
] = const0_rtx
;
2351 /* Save the number of instructions that modify the biv, so that
2352 we can treat the last one specially. */
2354 splittable_regs_updates
[bl
->regno
] = bl
->biv_count
;
2355 result
+= bl
->biv_count
;
2357 if (loop_dump_stream
)
2358 fprintf (loop_dump_stream
,
2359 "Biv %d safe to split.\n", bl
->regno
);
2362 /* Check every giv that depends on this biv to see whether it is
2363 splittable also. Even if the biv isn't splittable, givs which
2364 depend on it may be splittable if the biv is live outside the
2365 loop, and the givs aren't. */
2367 result
+= find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
,
2368 increment
, unroll_number
);
2370 /* If final value is non-zero, then must emit an instruction which sets
2371 the value of the biv to the proper value. This is done after
2372 handling all of the givs, since some of them may need to use the
2373 biv's value in their initialization code. */
2374 if (biv_final_value
)
2376 /* If the loop has multiple exits, emit the insns before the
2377 loop to ensure that it will always be executed no matter
2378 how the loop exits. Otherwise emit the insn after the loop,
2379 since this is slightly more efficient. */
2380 if (! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2381 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2386 /* Create a new register to hold the value of the biv, and then
2387 set the biv to its final value before the loop start. The biv
2388 is set to its final value before loop start to ensure that
2389 this insn will always be executed, no matter how the loop
2391 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2392 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2394 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2398 if (loop_dump_stream
)
2399 fprintf (loop_dump_stream
, "Biv %d mapped to %d for split.\n",
2400 REGNO (bl
->biv
->src_reg
), REGNO (tem
));
2402 /* Set up the mapping from the original biv register to the new
2404 bl
->biv
->src_reg
= tem
;
2411 /* For every giv based on the biv BL, check to determine whether it is
2412 splittable. This is a subroutine to find_splittable_regs ().
2414 Return the number of instructions that set splittable registers. */
2417 find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
, increment
,
2419 struct iv_class
*bl
;
2420 enum unroll_types unroll_type
;
2421 rtx loop_start
, loop_end
;
2425 struct induction
*v
;
2430 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
2434 /* Only split the giv if it has already been reduced, or if the loop is
2435 being completely unrolled. */
2436 if (unroll_type
!= UNROLL_COMPLETELY
&& v
->ignore
)
2439 /* The giv can be split if the insn that sets the giv is executed once
2440 and only once on every iteration of the loop. */
2441 /* An address giv can always be split. v->insn is just a use not a set,
2442 and hence it does not matter whether it is always executed. All that
2443 matters is that all the biv increments are always executed, and we
2444 won't reach here if they aren't. */
2445 if (v
->giv_type
!= DEST_ADDR
2446 && (! v
->always_computable
2447 || back_branch_in_range_p (v
->insn
, loop_start
, loop_end
)))
2450 /* The giv increment value must be a constant. */
2451 giv_inc
= fold_rtx_mult_add (v
->mult_val
, increment
, const0_rtx
,
2453 if (! giv_inc
|| GET_CODE (giv_inc
) != CONST_INT
)
2456 /* The loop must be unrolled completely, or else have a known number of
2457 iterations and only one exit, or else the giv must be dead outside
2458 the loop, or else the final value of the giv must be known.
2459 Otherwise, it is not safe to split the giv since it may not have the
2460 proper value on loop exit. */
2462 /* The used outside loop test will fail for DEST_ADDR givs. They are
2463 never used outside the loop anyways, so it is always safe to split a
2467 if (unroll_type
!= UNROLL_COMPLETELY
2468 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2469 || unroll_type
== UNROLL_NAIVE
)
2470 && v
->giv_type
!= DEST_ADDR
2471 && ((regno_first_uid
[REGNO (v
->dest_reg
)] != INSN_UID (v
->insn
)
2472 /* Check for the case where the pseudo is set by a shift/add
2473 sequence, in which case the first insn setting the pseudo
2474 is the first insn of the shift/add sequence. */
2475 && (! (tem
= find_reg_note (v
->insn
, REG_RETVAL
, NULL_RTX
))
2476 || (regno_first_uid
[REGNO (v
->dest_reg
)]
2477 != INSN_UID (XEXP (tem
, 0)))))
2478 /* Line above always fails if INSN was moved by loop opt. */
2479 || (uid_luid
[regno_last_uid
[REGNO (v
->dest_reg
)]]
2480 >= INSN_LUID (loop_end
)))
2481 && ! (final_value
= v
->final_value
))
2485 /* Currently, non-reduced/final-value givs are never split. */
2486 /* Should emit insns after the loop if possible, as the biv final value
2489 /* If the final value is non-zero, and the giv has not been reduced,
2490 then must emit an instruction to set the final value. */
2491 if (final_value
&& !v
->new_reg
)
2493 /* Create a new register to hold the value of the giv, and then set
2494 the giv to its final value before the loop start. The giv is set
2495 to its final value before loop start to ensure that this insn
2496 will always be executed, no matter how we exit. */
2497 tem
= gen_reg_rtx (v
->mode
);
2498 emit_insn_before (gen_move_insn (tem
, v
->dest_reg
), loop_start
);
2499 emit_insn_before (gen_move_insn (v
->dest_reg
, final_value
),
2502 if (loop_dump_stream
)
2503 fprintf (loop_dump_stream
, "Giv %d mapped to %d for split.\n",
2504 REGNO (v
->dest_reg
), REGNO (tem
));
2510 /* This giv is splittable. If completely unrolling the loop, save the
2511 giv's initial value. Otherwise, save the constant zero for it. */
2513 if (unroll_type
== UNROLL_COMPLETELY
)
2515 /* It is not safe to use bl->initial_value here, because it may not
2516 be invariant. It is safe to use the initial value stored in
2517 the splittable_regs array if it is set. In rare cases, it won't
2518 be set, so then we do exactly the same thing as
2519 find_splittable_regs does to get a safe value. */
2520 rtx biv_initial_value
;
2522 if (splittable_regs
[bl
->regno
])
2523 biv_initial_value
= splittable_regs
[bl
->regno
];
2524 else if (GET_CODE (bl
->initial_value
) != REG
2525 || (REGNO (bl
->initial_value
) != bl
->regno
2526 && REGNO (bl
->initial_value
) >= FIRST_PSEUDO_REGISTER
))
2527 biv_initial_value
= bl
->initial_value
;
2530 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2532 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2534 biv_initial_value
= tem
;
2536 value
= fold_rtx_mult_add (v
->mult_val
, biv_initial_value
,
2537 v
->add_val
, v
->mode
);
2544 /* If a giv was combined with another giv, then we can only split
2545 this giv if the giv it was combined with was reduced. This
2546 is because the value of v->new_reg is meaningless in this
2548 if (v
->same
&& ! v
->same
->new_reg
)
2550 if (loop_dump_stream
)
2551 fprintf (loop_dump_stream
,
2552 "giv combined with unreduced giv not split.\n");
2555 /* If the giv is an address destination, it could be something other
2556 than a simple register, these have to be treated differently. */
2557 else if (v
->giv_type
== DEST_REG
)
2559 /* If value is not a constant, register, or register plus
2560 constant, then compute its value into a register before
2561 loop start. This prevents illegal rtx sharing, and should
2562 generate better code. We can use bl->initial_value here
2563 instead of splittable_regs[bl->regno] because this code
2564 is going before the loop start. */
2565 if (unroll_type
== UNROLL_COMPLETELY
2566 && GET_CODE (value
) != CONST_INT
2567 && GET_CODE (value
) != REG
2568 && (GET_CODE (value
) != PLUS
2569 || GET_CODE (XEXP (value
, 0)) != REG
2570 || GET_CODE (XEXP (value
, 1)) != CONST_INT
))
2572 rtx tem
= gen_reg_rtx (v
->mode
);
2573 emit_iv_add_mult (bl
->initial_value
, v
->mult_val
,
2574 v
->add_val
, tem
, loop_start
);
2578 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2582 /* Splitting address givs is useful since it will often allow us
2583 to eliminate some increment insns for the base giv as
2586 /* If the addr giv is combined with a dest_reg giv, then all
2587 references to that dest reg will be remapped, which is NOT
2588 what we want for split addr regs. We always create a new
2589 register for the split addr giv, just to be safe. */
2591 /* ??? If there are multiple address givs which have been
2592 combined with the same dest_reg giv, then we may only need
2593 one new register for them. Pulling out constants below will
2594 catch some of the common cases of this. Currently, I leave
2595 the work of simplifying multiple address givs to the
2596 following cse pass. */
2598 v
->const_adjust
= 0;
2599 if (unroll_type
!= UNROLL_COMPLETELY
)
2601 /* If not completely unrolling the loop, then create a new
2602 register to hold the split value of the DEST_ADDR giv.
2603 Emit insn to initialize its value before loop start. */
2604 tem
= gen_reg_rtx (v
->mode
);
2606 /* If the address giv has a constant in its new_reg value,
2607 then this constant can be pulled out and put in value,
2608 instead of being part of the initialization code. */
2610 if (GET_CODE (v
->new_reg
) == PLUS
2611 && GET_CODE (XEXP (v
->new_reg
, 1)) == CONST_INT
)
2614 = plus_constant (tem
, INTVAL (XEXP (v
->new_reg
,1)));
2616 /* Only succeed if this will give valid addresses.
2617 Try to validate both the first and the last
2618 address resulting from loop unrolling, if
2619 one fails, then can't do const elim here. */
2620 if (memory_address_p (v
->mem_mode
, v
->dest_reg
)
2621 && memory_address_p (v
->mem_mode
,
2622 plus_constant (v
->dest_reg
,
2624 * (unroll_number
- 1))))
2626 /* Save the negative of the eliminated const, so
2627 that we can calculate the dest_reg's increment
2629 v
->const_adjust
= - INTVAL (XEXP (v
->new_reg
, 1));
2631 v
->new_reg
= XEXP (v
->new_reg
, 0);
2632 if (loop_dump_stream
)
2633 fprintf (loop_dump_stream
,
2634 "Eliminating constant from giv %d\n",
2643 /* If the address hasn't been checked for validity yet, do so
2644 now, and fail completely if either the first or the last
2645 unrolled copy of the address is not a valid address. */
2646 if (v
->dest_reg
== tem
2647 && (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2648 || ! memory_address_p (v
->mem_mode
,
2649 plus_constant (v
->dest_reg
,
2651 * (unroll_number
-1)))))
2653 if (loop_dump_stream
)
2654 fprintf (loop_dump_stream
,
2655 "Illegal address for giv at insn %d\n",
2656 INSN_UID (v
->insn
));
2660 /* To initialize the new register, just move the value of
2661 new_reg into it. This is not guaranteed to give a valid
2662 instruction on machines with complex addressing modes.
2663 If we can't recognize it, then delete it and emit insns
2664 to calculate the value from scratch. */
2665 emit_insn_before (gen_rtx (SET
, VOIDmode
, tem
,
2666 copy_rtx (v
->new_reg
)),
2668 if (recog_memoized (PREV_INSN (loop_start
)) < 0)
2670 delete_insn (PREV_INSN (loop_start
));
2671 emit_iv_add_mult (bl
->initial_value
, v
->mult_val
,
2672 v
->add_val
, tem
, loop_start
);
2673 if (loop_dump_stream
)
2674 fprintf (loop_dump_stream
,
2675 "Illegal init insn, rewritten.\n");
2680 v
->dest_reg
= value
;
2682 /* Check the resulting address for validity, and fail
2683 if the resulting address would be illegal. */
2684 if (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2685 || ! memory_address_p (v
->mem_mode
,
2686 plus_constant (v
->dest_reg
,
2688 (unroll_number
-1))))
2690 if (loop_dump_stream
)
2691 fprintf (loop_dump_stream
,
2692 "Illegal address for giv at insn %d\n",
2693 INSN_UID (v
->insn
));
2698 /* Store the value of dest_reg into the insn. This sharing
2699 will not be a problem as this insn will always be copied
2702 *v
->location
= v
->dest_reg
;
2704 /* If this address giv is combined with a dest reg giv, then
2705 save the base giv's induction pointer so that we will be
2706 able to handle this address giv properly. The base giv
2707 itself does not have to be splittable. */
2709 if (v
->same
&& v
->same
->giv_type
== DEST_REG
)
2710 addr_combined_regs
[REGNO (v
->same
->new_reg
)] = v
->same
;
2712 if (GET_CODE (v
->new_reg
) == REG
)
2714 /* This giv maybe hasn't been combined with any others.
2715 Make sure that it's giv is marked as splittable here. */
2717 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2719 /* Make it appear to depend upon itself, so that the
2720 giv will be properly split in the main loop above. */
2724 addr_combined_regs
[REGNO (v
->new_reg
)] = v
;
2728 if (loop_dump_stream
)
2729 fprintf (loop_dump_stream
, "DEST_ADDR giv being split.\n");
2735 /* Currently, unreduced giv's can't be split. This is not too much
2736 of a problem since unreduced giv's are not live across loop
2737 iterations anyways. When unrolling a loop completely though,
2738 it makes sense to reduce&split givs when possible, as this will
2739 result in simpler instructions, and will not require that a reg
2740 be live across loop iterations. */
2742 splittable_regs
[REGNO (v
->dest_reg
)] = value
;
2743 fprintf (stderr
, "Giv %d at insn %d not reduced\n",
2744 REGNO (v
->dest_reg
), INSN_UID (v
->insn
));
2750 /* Givs are only updated once by definition. Mark it so if this is
2751 a splittable register. Don't need to do anything for address givs
2752 where this may not be a register. */
2754 if (GET_CODE (v
->new_reg
) == REG
)
2755 splittable_regs_updates
[REGNO (v
->new_reg
)] = 1;
2759 if (loop_dump_stream
)
2763 if (GET_CODE (v
->dest_reg
) == CONST_INT
)
2765 else if (GET_CODE (v
->dest_reg
) != REG
)
2766 regnum
= REGNO (XEXP (v
->dest_reg
, 0));
2768 regnum
= REGNO (v
->dest_reg
);
2769 fprintf (loop_dump_stream
, "Giv %d at insn %d safe to split.\n",
2770 regnum
, INSN_UID (v
->insn
));
2777 /* Try to prove that the register is dead after the loop exits. Trace every
2778 loop exit looking for an insn that will always be executed, which sets
2779 the register to some value, and appears before the first use of the register
2780 is found. If successful, then return 1, otherwise return 0. */
2782 /* ?? Could be made more intelligent in the handling of jumps, so that
2783 it can search past if statements and other similar structures. */
2786 reg_dead_after_loop (reg
, loop_start
, loop_end
)
2787 rtx reg
, loop_start
, loop_end
;
2793 /* HACK: Must also search the loop fall through exit, create a label_ref
2794 here which points to the loop_end, and append the loop_number_exit_labels
2796 label
= gen_rtx (LABEL_REF
, VOIDmode
, loop_end
);
2797 LABEL_NEXTREF (label
)
2798 = loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]];
2800 for ( ; label
; label
= LABEL_NEXTREF (label
))
2802 /* Succeed if find an insn which sets the biv or if reach end of
2803 function. Fail if find an insn that uses the biv, or if come to
2804 a conditional jump. */
2806 insn
= NEXT_INSN (XEXP (label
, 0));
2809 code
= GET_CODE (insn
);
2810 if (GET_RTX_CLASS (code
) == 'i')
2814 if (reg_referenced_p (reg
, PATTERN (insn
)))
2817 set
= single_set (insn
);
2818 if (set
&& rtx_equal_p (SET_DEST (set
), reg
))
2822 if (code
== JUMP_INSN
)
2824 if (GET_CODE (PATTERN (insn
)) == RETURN
)
2826 else if (! simplejump_p (insn
)
2827 /* Prevent infinite loop following infinite loops. */
2828 || jump_count
++ > 20)
2831 insn
= JUMP_LABEL (insn
);
2834 insn
= NEXT_INSN (insn
);
2838 /* Success, the register is dead on all loop exits. */
2842 /* Try to calculate the final value of the biv, the value it will have at
2843 the end of the loop. If we can do it, return that value. */
2846 final_biv_value (bl
, loop_start
, loop_end
)
2847 struct iv_class
*bl
;
2848 rtx loop_start
, loop_end
;
2852 /* ??? This only works for MODE_INT biv's. Reject all others for now. */
2854 if (GET_MODE_CLASS (bl
->biv
->mode
) != MODE_INT
)
2857 /* The final value for reversed bivs must be calculated differently than
2858 for ordinary bivs. In this case, there is already an insn after the
2859 loop which sets this biv's final value (if necessary), and there are
2860 no other loop exits, so we can return any value. */
2863 if (loop_dump_stream
)
2864 fprintf (loop_dump_stream
,
2865 "Final biv value for %d, reversed biv.\n", bl
->regno
);
2870 /* Try to calculate the final value as initial value + (number of iterations
2871 * increment). For this to work, increment must be invariant, the only
2872 exit from the loop must be the fall through at the bottom (otherwise
2873 it may not have its final value when the loop exits), and the initial
2874 value of the biv must be invariant. */
2876 if (loop_n_iterations
!= 0
2877 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2878 && invariant_p (bl
->initial_value
))
2880 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2882 if (increment
&& invariant_p (increment
))
2884 /* Can calculate the loop exit value, emit insns after loop
2885 end to calculate this value into a temporary register in
2886 case it is needed later. */
2888 tem
= gen_reg_rtx (bl
->biv
->mode
);
2889 /* Make sure loop_end is not the last insn. */
2890 if (NEXT_INSN (loop_end
) == 0)
2891 emit_note_after (NOTE_INSN_DELETED
, loop_end
);
2892 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2893 bl
->initial_value
, tem
, NEXT_INSN (loop_end
));
2895 if (loop_dump_stream
)
2896 fprintf (loop_dump_stream
,
2897 "Final biv value for %d, calculated.\n", bl
->regno
);
2903 /* Check to see if the biv is dead at all loop exits. */
2904 if (reg_dead_after_loop (bl
->biv
->src_reg
, loop_start
, loop_end
))
2906 if (loop_dump_stream
)
2907 fprintf (loop_dump_stream
,
2908 "Final biv value for %d, biv dead after loop exit.\n",
2917 /* Try to calculate the final value of the giv, the value it will have at
2918 the end of the loop. If we can do it, return that value. */
2921 final_giv_value (v
, loop_start
, loop_end
)
2922 struct induction
*v
;
2923 rtx loop_start
, loop_end
;
2925 struct iv_class
*bl
;
2929 rtx insert_before
, seq
;
2931 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2933 /* The final value for givs which depend on reversed bivs must be calculated
2934 differently than for ordinary givs. In this case, there is already an
2935 insn after the loop which sets this giv's final value (if necessary),
2936 and there are no other loop exits, so we can return any value. */
2939 if (loop_dump_stream
)
2940 fprintf (loop_dump_stream
,
2941 "Final giv value for %d, depends on reversed biv\n",
2942 REGNO (v
->dest_reg
));
2946 /* Try to calculate the final value as a function of the biv it depends
2947 upon. The only exit from the loop must be the fall through at the bottom
2948 (otherwise it may not have its final value when the loop exits). */
2950 /* ??? Can calculate the final giv value by subtracting off the
2951 extra biv increments times the giv's mult_val. The loop must have
2952 only one exit for this to work, but the loop iterations does not need
2955 if (loop_n_iterations
!= 0
2956 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2958 /* ?? It is tempting to use the biv's value here since these insns will
2959 be put after the loop, and hence the biv will have its final value
2960 then. However, this fails if the biv is subsequently eliminated.
2961 Perhaps determine whether biv's are eliminable before trying to
2962 determine whether giv's are replaceable so that we can use the
2963 biv value here if it is not eliminable. */
2965 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2967 if (increment
&& invariant_p (increment
))
2969 /* Can calculate the loop exit value of its biv as
2970 (loop_n_iterations * increment) + initial_value */
2972 /* The loop exit value of the giv is then
2973 (final_biv_value - extra increments) * mult_val + add_val.
2974 The extra increments are any increments to the biv which
2975 occur in the loop after the giv's value is calculated.
2976 We must search from the insn that sets the giv to the end
2977 of the loop to calculate this value. */
2979 insert_before
= NEXT_INSN (loop_end
);
2981 /* Put the final biv value in tem. */
2982 tem
= gen_reg_rtx (bl
->biv
->mode
);
2983 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2984 bl
->initial_value
, tem
, insert_before
);
2986 /* Subtract off extra increments as we find them. */
2987 for (insn
= NEXT_INSN (v
->insn
); insn
!= loop_end
;
2988 insn
= NEXT_INSN (insn
))
2990 struct induction
*biv
;
2992 for (biv
= bl
->biv
; biv
; biv
= biv
->next_iv
)
2993 if (biv
->insn
== insn
)
2996 tem
= expand_binop (GET_MODE (tem
), sub_optab
, tem
,
2997 biv
->add_val
, NULL_RTX
, 0,
2999 seq
= gen_sequence ();
3001 emit_insn_before (seq
, insert_before
);
3005 /* Now calculate the giv's final value. */
3006 emit_iv_add_mult (tem
, v
->mult_val
, v
->add_val
, tem
,
3009 if (loop_dump_stream
)
3010 fprintf (loop_dump_stream
,
3011 "Final giv value for %d, calc from biv's value.\n",
3012 REGNO (v
->dest_reg
));
3018 /* Replaceable giv's should never reach here. */
3022 /* Check to see if the biv is dead at all loop exits. */
3023 if (reg_dead_after_loop (v
->dest_reg
, loop_start
, loop_end
))
3025 if (loop_dump_stream
)
3026 fprintf (loop_dump_stream
,
3027 "Final giv value for %d, giv dead after loop exit.\n",
3028 REGNO (v
->dest_reg
));
3037 /* Calculate the number of loop iterations. Returns the exact number of loop
3038 iterations if it can be calculated, otherwise returns zero. */
3040 unsigned HOST_WIDE_INT
3041 loop_iterations (loop_start
, loop_end
)
3042 rtx loop_start
, loop_end
;
3044 rtx comparison
, comparison_value
;
3045 rtx iteration_var
, initial_value
, increment
, final_value
;
3046 enum rtx_code comparison_code
;
3049 int unsigned_compare
, compare_dir
, final_larger
;
3050 unsigned long tempu
;
3053 /* First find the iteration variable. If the last insn is a conditional
3054 branch, and the insn before tests a register value, make that the
3055 iteration variable. */
3057 loop_initial_value
= 0;
3059 loop_final_value
= 0;
3060 loop_iteration_var
= 0;
3062 last_loop_insn
= prev_nonnote_insn (loop_end
);
3064 comparison
= get_condition_for_loop (last_loop_insn
);
3065 if (comparison
== 0)
3067 if (loop_dump_stream
)
3068 fprintf (loop_dump_stream
,
3069 "Loop unrolling: No final conditional branch found.\n");
3073 /* ??? Get_condition may switch position of induction variable and
3074 invariant register when it canonicalizes the comparison. */
3076 comparison_code
= GET_CODE (comparison
);
3077 iteration_var
= XEXP (comparison
, 0);
3078 comparison_value
= XEXP (comparison
, 1);
3080 if (GET_CODE (iteration_var
) != REG
)
3082 if (loop_dump_stream
)
3083 fprintf (loop_dump_stream
,
3084 "Loop unrolling: Comparison not against register.\n");
3088 /* Loop iterations is always called before any new registers are created
3089 now, so this should never occur. */
3091 if (REGNO (iteration_var
) >= max_reg_before_loop
)
3094 iteration_info (iteration_var
, &initial_value
, &increment
,
3095 loop_start
, loop_end
);
3096 if (initial_value
== 0)
3097 /* iteration_info already printed a message. */
3102 if (loop_dump_stream
)
3103 fprintf (loop_dump_stream
,
3104 "Loop unrolling: Increment value can't be calculated.\n");
3107 if (GET_CODE (increment
) != CONST_INT
)
3109 if (loop_dump_stream
)
3110 fprintf (loop_dump_stream
,
3111 "Loop unrolling: Increment value not constant.\n");
3114 if (GET_CODE (initial_value
) != CONST_INT
)
3116 if (loop_dump_stream
)
3117 fprintf (loop_dump_stream
,
3118 "Loop unrolling: Initial value not constant.\n");
3122 /* If the comparison value is an invariant register, then try to find
3123 its value from the insns before the start of the loop. */
3125 if (GET_CODE (comparison_value
) == REG
&& invariant_p (comparison_value
))
3129 for (insn
= PREV_INSN (loop_start
); insn
; insn
= PREV_INSN (insn
))
3131 if (GET_CODE (insn
) == CODE_LABEL
)
3134 else if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i'
3135 && reg_set_p (comparison_value
, insn
))
3137 /* We found the last insn before the loop that sets the register.
3138 If it sets the entire register, and has a REG_EQUAL note,
3139 then use the value of the REG_EQUAL note. */
3140 if ((set
= single_set (insn
))
3141 && (SET_DEST (set
) == comparison_value
))
3143 rtx note
= find_reg_note (insn
, REG_EQUAL
, NULL_RTX
);
3145 if (note
&& GET_CODE (XEXP (note
, 0)) != EXPR_LIST
)
3146 comparison_value
= XEXP (note
, 0);
3153 final_value
= approx_final_value (comparison_code
, comparison_value
,
3154 &unsigned_compare
, &compare_dir
);
3156 /* Save the calculated values describing this loop's bounds, in case
3157 precondition_loop_p will need them later. These values can not be
3158 recalculated inside precondition_loop_p because strength reduction
3159 optimizations may obscure the loop's structure. */
3161 loop_iteration_var
= iteration_var
;
3162 loop_initial_value
= initial_value
;
3163 loop_increment
= increment
;
3164 loop_final_value
= final_value
;
3166 if (final_value
== 0)
3168 if (loop_dump_stream
)
3169 fprintf (loop_dump_stream
,
3170 "Loop unrolling: EQ comparison loop.\n");
3173 else if (GET_CODE (final_value
) != CONST_INT
)
3175 if (loop_dump_stream
)
3176 fprintf (loop_dump_stream
,
3177 "Loop unrolling: Final value not constant.\n");
3181 /* ?? Final value and initial value do not have to be constants.
3182 Only their difference has to be constant. When the iteration variable
3183 is an array address, the final value and initial value might both
3184 be addresses with the same base but different constant offsets.
3185 Final value must be invariant for this to work.
3187 To do this, need some way to find the values of registers which are
3190 /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
3191 if (unsigned_compare
)
3193 = ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3194 > (unsigned HOST_WIDE_INT
) INTVAL (initial_value
))
3195 - ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3196 < (unsigned HOST_WIDE_INT
) INTVAL (initial_value
));
3198 final_larger
= (INTVAL (final_value
) > INTVAL (initial_value
))
3199 - (INTVAL (final_value
) < INTVAL (initial_value
));
3201 if (INTVAL (increment
) > 0)
3203 else if (INTVAL (increment
) == 0)
3208 /* There are 27 different cases: compare_dir = -1, 0, 1;
3209 final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
3210 There are 4 normal cases, 4 reverse cases (where the iteration variable
3211 will overflow before the loop exits), 4 infinite loop cases, and 15
3212 immediate exit (0 or 1 iteration depending on loop type) cases.
3213 Only try to optimize the normal cases. */
3215 /* (compare_dir/final_larger/increment_dir)
3216 Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
3217 Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
3218 Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
3219 Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
3221 /* ?? If the meaning of reverse loops (where the iteration variable
3222 will overflow before the loop exits) is undefined, then could
3223 eliminate all of these special checks, and just always assume
3224 the loops are normal/immediate/infinite. Note that this means
3225 the sign of increment_dir does not have to be known. Also,
3226 since it does not really hurt if immediate exit loops or infinite loops
3227 are optimized, then that case could be ignored also, and hence all
3228 loops can be optimized.
3230 According to ANSI Spec, the reverse loop case result is undefined,
3231 because the action on overflow is undefined.
3233 See also the special test for NE loops below. */
3235 if (final_larger
== increment_dir
&& final_larger
!= 0
3236 && (final_larger
== compare_dir
|| compare_dir
== 0))
3241 if (loop_dump_stream
)
3242 fprintf (loop_dump_stream
,
3243 "Loop unrolling: Not normal loop.\n");
3247 /* Calculate the number of iterations, final_value is only an approximation,
3248 so correct for that. Note that tempu and loop_n_iterations are
3249 unsigned, because they can be as large as 2^n - 1. */
3251 i
= INTVAL (increment
);
3253 tempu
= INTVAL (final_value
) - INTVAL (initial_value
);
3256 tempu
= INTVAL (initial_value
) - INTVAL (final_value
);
3262 /* For NE tests, make sure that the iteration variable won't miss the
3263 final value. If tempu mod i is not zero, then the iteration variable
3264 will overflow before the loop exits, and we can not calculate the
3265 number of iterations. */
3266 if (compare_dir
== 0 && (tempu
% i
) != 0)
3269 return tempu
/ i
+ ((tempu
% i
) != 0);