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");
604 if (unroll_type
== UNROLL_NAIVE
605 && GET_CODE (last_loop_insn
) == BARRIER
606 && start_label
!= JUMP_LABEL (PREV_INSN (last_loop_insn
)))
608 /* In this case, we must copy the jump and barrier, because they will
609 not be converted to jumps to an immediately following label. */
611 insert_before
= NEXT_INSN (last_loop_insn
);
612 copy_end
= last_loop_insn
;
615 /* Allocate a translation table for the labels and insn numbers.
616 They will be filled in as we copy the insns in the loop. */
618 max_labelno
= max_label_num ();
619 max_insnno
= get_max_uid ();
621 map
= (struct inline_remap
*) alloca (sizeof (struct inline_remap
));
623 map
->integrating
= 0;
625 /* Allocate the label map. */
629 map
->label_map
= (rtx
*) alloca (max_labelno
* sizeof (rtx
));
631 local_label
= (char *) alloca (max_labelno
);
632 bzero (local_label
, max_labelno
);
637 /* Search the loop and mark all local labels, i.e. the ones which have to
638 be distinct labels when copied. For all labels which might be
639 non-local, set their label_map entries to point to themselves.
640 If they happen to be local their label_map entries will be overwritten
641 before the loop body is copied. The label_map entries for local labels
642 will be set to a different value each time the loop body is copied. */
644 for (insn
= copy_start
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
646 if (GET_CODE (insn
) == CODE_LABEL
)
647 local_label
[CODE_LABEL_NUMBER (insn
)] = 1;
648 else if (GET_CODE (insn
) == JUMP_INSN
)
650 if (JUMP_LABEL (insn
))
651 map
->label_map
[CODE_LABEL_NUMBER (JUMP_LABEL (insn
))]
653 else if (GET_CODE (PATTERN (insn
)) == ADDR_VEC
654 || GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
)
656 rtx pat
= PATTERN (insn
);
657 int diff_vec_p
= GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
;
658 int len
= XVECLEN (pat
, diff_vec_p
);
661 for (i
= 0; i
< len
; i
++)
663 label
= XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0);
664 map
->label_map
[CODE_LABEL_NUMBER (label
)] = label
;
670 /* Allocate space for the insn map. */
672 map
->insn_map
= (rtx
*) alloca (max_insnno
* sizeof (rtx
));
674 /* Set this to zero, to indicate that we are doing loop unrolling,
675 not function inlining. */
676 map
->inline_target
= 0;
678 /* The register and constant maps depend on the number of registers
679 present, so the final maps can't be created until after
680 find_splittable_regs is called. However, they are needed for
681 preconditioning, so we create temporary maps when preconditioning
684 /* The preconditioning code may allocate two new pseudo registers. */
685 maxregnum
= max_reg_num ();
687 /* Allocate and zero out the splittable_regs and addr_combined_regs
688 arrays. These must be zeroed here because they will be used if
689 loop preconditioning is performed, and must be zero for that case.
691 It is safe to do this here, since the extra registers created by the
692 preconditioning code and find_splittable_regs will never be used
693 to access the splittable_regs[] and addr_combined_regs[] arrays. */
695 splittable_regs
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
696 bzero (splittable_regs
, maxregnum
* sizeof (rtx
));
697 splittable_regs_updates
= (int *) alloca (maxregnum
* sizeof (int));
698 bzero (splittable_regs_updates
, maxregnum
* sizeof (int));
700 = (struct induction
**) alloca (maxregnum
* sizeof (struct induction
*));
701 bzero (addr_combined_regs
, maxregnum
* sizeof (struct induction
*));
703 /* If this loop requires exit tests when unrolled, check to see if we
704 can precondition the loop so as to make the exit tests unnecessary.
705 Just like variable splitting, this is not safe if the loop is entered
706 via a jump to the bottom. Also, can not do this if no strength
707 reduce info, because precondition_loop_p uses this info. */
709 /* Must copy the loop body for preconditioning before the following
710 find_splittable_regs call since that will emit insns which need to
711 be after the preconditioned loop copies, but immediately before the
712 unrolled loop copies. */
714 /* Also, it is not safe to split induction variables for the preconditioned
715 copies of the loop body. If we split induction variables, then the code
716 assumes that each induction variable can be represented as a function
717 of its initial value and the loop iteration number. This is not true
718 in this case, because the last preconditioned copy of the loop body
719 could be any iteration from the first up to the `unroll_number-1'th,
720 depending on the initial value of the iteration variable. Therefore
721 we can not split induction variables here, because we can not calculate
722 their value. Hence, this code must occur before find_splittable_regs
725 if (unroll_type
== UNROLL_NAIVE
&& ! splitting_not_safe
&& strength_reduce_p
)
727 rtx initial_value
, final_value
, increment
;
729 if (precondition_loop_p (&initial_value
, &final_value
, &increment
,
730 loop_start
, loop_end
))
732 register rtx diff
, temp
;
733 enum machine_mode mode
;
735 int abs_inc
, neg_inc
;
737 map
->reg_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
739 map
->const_equiv_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
740 map
->const_age_map
= (unsigned *) alloca (maxregnum
741 * sizeof (unsigned));
742 map
->const_equiv_map_size
= maxregnum
;
743 global_const_equiv_map
= map
->const_equiv_map
;
745 init_reg_map (map
, maxregnum
);
747 /* Limit loop unrolling to 4, since this will make 7 copies of
749 if (unroll_number
> 4)
752 /* Save the absolute value of the increment, and also whether or
753 not it is negative. */
755 abs_inc
= INTVAL (increment
);
764 /* Decide what mode to do these calculations in. Choose the larger
765 of final_value's mode and initial_value's mode, or a full-word if
766 both are constants. */
767 mode
= GET_MODE (final_value
);
768 if (mode
== VOIDmode
)
770 mode
= GET_MODE (initial_value
);
771 if (mode
== VOIDmode
)
774 else if (mode
!= GET_MODE (initial_value
)
775 && (GET_MODE_SIZE (mode
)
776 < GET_MODE_SIZE (GET_MODE (initial_value
))))
777 mode
= GET_MODE (initial_value
);
779 /* Calculate the difference between the final and initial values.
780 Final value may be a (plus (reg x) (const_int 1)) rtx.
781 Let the following cse pass simplify this if initial value is
784 We must copy the final and initial values here to avoid
785 improperly shared rtl. */
787 diff
= expand_binop (mode
, sub_optab
, copy_rtx (final_value
),
788 copy_rtx (initial_value
), NULL_RTX
, 0,
791 /* Now calculate (diff % (unroll * abs (increment))) by using an
793 diff
= expand_binop (GET_MODE (diff
), and_optab
, diff
,
794 GEN_INT (unroll_number
* abs_inc
- 1),
795 NULL_RTX
, 0, OPTAB_LIB_WIDEN
);
797 /* Now emit a sequence of branches to jump to the proper precond
800 labels
= (rtx
*) alloca (sizeof (rtx
) * unroll_number
);
801 for (i
= 0; i
< unroll_number
; i
++)
802 labels
[i
] = gen_label_rtx ();
804 /* Assuming the unroll_number is 4, and the increment is 2, then
805 for a negative increment: for a positive increment:
806 diff = 0,1 precond 0 diff = 0,7 precond 0
807 diff = 2,3 precond 3 diff = 1,2 precond 1
808 diff = 4,5 precond 2 diff = 3,4 precond 2
809 diff = 6,7 precond 1 diff = 5,6 precond 3 */
811 /* We only need to emit (unroll_number - 1) branches here, the
812 last case just falls through to the following code. */
814 /* ??? This would give better code if we emitted a tree of branches
815 instead of the current linear list of branches. */
817 for (i
= 0; i
< unroll_number
- 1; i
++)
821 /* For negative increments, must invert the constant compared
822 against, except when comparing against zero. */
826 cmp_const
= unroll_number
- i
;
830 emit_cmp_insn (diff
, GEN_INT (abs_inc
* cmp_const
),
831 EQ
, NULL_RTX
, mode
, 0, 0);
834 emit_jump_insn (gen_beq (labels
[i
]));
836 emit_jump_insn (gen_bge (labels
[i
]));
838 emit_jump_insn (gen_ble (labels
[i
]));
839 JUMP_LABEL (get_last_insn ()) = labels
[i
];
840 LABEL_NUSES (labels
[i
])++;
843 /* If the increment is greater than one, then we need another branch,
844 to handle other cases equivalent to 0. */
846 /* ??? This should be merged into the code above somehow to help
847 simplify the code here, and reduce the number of branches emitted.
848 For the negative increment case, the branch here could easily
849 be merged with the `0' case branch above. For the positive
850 increment case, it is not clear how this can be simplified. */
857 cmp_const
= abs_inc
- 1;
859 cmp_const
= abs_inc
* (unroll_number
- 1) + 1;
861 emit_cmp_insn (diff
, GEN_INT (cmp_const
), EQ
, NULL_RTX
,
865 emit_jump_insn (gen_ble (labels
[0]));
867 emit_jump_insn (gen_bge (labels
[0]));
868 JUMP_LABEL (get_last_insn ()) = labels
[0];
869 LABEL_NUSES (labels
[0])++;
872 sequence
= gen_sequence ();
874 emit_insn_before (sequence
, loop_start
);
876 /* Only the last copy of the loop body here needs the exit
877 test, so set copy_end to exclude the compare/branch here,
878 and then reset it inside the loop when get to the last
881 if (GET_CODE (last_loop_insn
) == BARRIER
)
882 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
883 else if (GET_CODE (last_loop_insn
) == JUMP_INSN
)
886 /* The immediately preceding insn is a compare which we do not
888 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
890 /* The immediately preceding insn may not be a compare, so we
892 copy_end
= PREV_INSN (last_loop_insn
);
898 for (i
= 1; i
< unroll_number
; i
++)
900 emit_label_after (labels
[unroll_number
- i
],
901 PREV_INSN (loop_start
));
903 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
904 bzero (map
->const_equiv_map
, maxregnum
* sizeof (rtx
));
905 bzero (map
->const_age_map
, maxregnum
* sizeof (unsigned));
908 for (j
= 0; j
< max_labelno
; j
++)
910 map
->label_map
[j
] = gen_label_rtx ();
912 /* The last copy needs the compare/branch insns at the end,
913 so reset copy_end here if the loop ends with a conditional
916 if (i
== unroll_number
- 1)
918 if (GET_CODE (last_loop_insn
) == BARRIER
)
919 copy_end
= PREV_INSN (PREV_INSN (last_loop_insn
));
921 copy_end
= last_loop_insn
;
924 /* None of the copies are the `last_iteration', so just
925 pass zero for that parameter. */
926 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, 0,
927 unroll_type
, start_label
, loop_end
,
928 loop_start
, copy_end
);
930 emit_label_after (labels
[0], PREV_INSN (loop_start
));
932 if (GET_CODE (last_loop_insn
) == BARRIER
)
934 insert_before
= PREV_INSN (last_loop_insn
);
935 copy_end
= PREV_INSN (insert_before
);
940 /* The immediately preceding insn is a compare which we do not
942 insert_before
= PREV_INSN (last_loop_insn
);
943 copy_end
= PREV_INSN (insert_before
);
945 /* The immediately preceding insn may not be a compare, so we
947 insert_before
= last_loop_insn
;
948 copy_end
= PREV_INSN (last_loop_insn
);
952 /* Set unroll type to MODULO now. */
953 unroll_type
= UNROLL_MODULO
;
954 loop_preconditioned
= 1;
958 /* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
959 the loop unless all loops are being unrolled. */
960 if (unroll_type
== UNROLL_NAIVE
&& ! flag_unroll_all_loops
)
962 if (loop_dump_stream
)
963 fprintf (loop_dump_stream
, "Unrolling failure: Naive unrolling not being done.\n");
967 /* At this point, we are guaranteed to unroll the loop. */
969 /* For each biv and giv, determine whether it can be safely split into
970 a different variable for each unrolled copy of the loop body.
971 We precalculate and save this info here, since computing it is
974 Do this before deleting any instructions from the loop, so that
975 back_branch_in_range_p will work correctly. */
977 if (splitting_not_safe
)
980 temp
= find_splittable_regs (unroll_type
, loop_start
, loop_end
,
981 end_insert_before
, unroll_number
);
983 /* find_splittable_regs may have created some new registers, so must
984 reallocate the reg_map with the new larger size, and must realloc
985 the constant maps also. */
987 maxregnum
= max_reg_num ();
988 map
->reg_map
= (rtx
*) alloca (maxregnum
* sizeof (rtx
));
990 init_reg_map (map
, maxregnum
);
992 /* Space is needed in some of the map for new registers, so new_maxregnum
993 is an (over)estimate of how many registers will exist at the end. */
994 new_maxregnum
= maxregnum
+ (temp
* unroll_number
* 2);
996 /* Must realloc space for the constant maps, because the number of registers
999 map
->const_equiv_map
= (rtx
*) alloca (new_maxregnum
* sizeof (rtx
));
1000 map
->const_age_map
= (unsigned *) alloca (new_maxregnum
* sizeof (unsigned));
1002 map
->const_equiv_map_size
= new_maxregnum
;
1003 global_const_equiv_map
= map
->const_equiv_map
;
1005 /* Search the list of bivs and givs to find ones which need to be remapped
1006 when split, and set their reg_map entry appropriately. */
1008 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
1010 if (REGNO (bl
->biv
->src_reg
) != bl
->regno
)
1011 map
->reg_map
[bl
->regno
] = bl
->biv
->src_reg
;
1013 /* Currently, non-reduced/final-value givs are never split. */
1014 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
1015 if (REGNO (v
->src_reg
) != bl
->regno
)
1016 map
->reg_map
[REGNO (v
->dest_reg
)] = v
->src_reg
;
1020 /* If the loop is being partially unrolled, and the iteration variables
1021 are being split, and are being renamed for the split, then must fix up
1022 the compare instruction at the end of the loop to refer to the new
1023 registers. This compare isn't copied, so the registers used in it
1024 will never be replaced if it isn't done here. */
1026 if (unroll_type
== UNROLL_MODULO
)
1028 insn
= NEXT_INSN (copy_end
);
1029 if (GET_CODE (insn
) == INSN
&& GET_CODE (PATTERN (insn
)) == SET
)
1032 /* If non-reduced/final-value givs were split, then this would also
1033 have to remap those givs. */
1036 tem
= SET_SRC (PATTERN (insn
));
1037 /* The set source is a register. */
1038 if (GET_CODE (tem
) == REG
)
1040 if (REGNO (tem
) < max_reg_before_loop
1041 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1042 SET_SRC (PATTERN (insn
))
1043 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1047 /* The set source is a compare of some sort. */
1048 tem
= XEXP (SET_SRC (PATTERN (insn
)), 0);
1049 if (GET_CODE (tem
) == REG
1050 && REGNO (tem
) < max_reg_before_loop
1051 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1052 XEXP (SET_SRC (PATTERN (insn
)), 0)
1053 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1055 tem
= XEXP (SET_SRC (PATTERN (insn
)), 1);
1056 if (GET_CODE (tem
) == REG
1057 && REGNO (tem
) < max_reg_before_loop
1058 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1059 XEXP (SET_SRC (PATTERN (insn
)), 1)
1060 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1065 /* For unroll_number - 1 times, make a copy of each instruction
1066 between copy_start and copy_end, and insert these new instructions
1067 before the end of the loop. */
1069 for (i
= 0; i
< unroll_number
; i
++)
1071 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
1072 bzero (map
->const_equiv_map
, new_maxregnum
* sizeof (rtx
));
1073 bzero (map
->const_age_map
, new_maxregnum
* sizeof (unsigned));
1076 for (j
= 0; j
< max_labelno
; j
++)
1078 map
->label_map
[j
] = gen_label_rtx ();
1080 /* If loop starts with a branch to the test, then fix it so that
1081 it points to the test of the first unrolled copy of the loop. */
1082 if (i
== 0 && loop_start
!= copy_start
)
1084 insn
= PREV_INSN (copy_start
);
1085 pattern
= PATTERN (insn
);
1087 tem
= map
->label_map
[CODE_LABEL_NUMBER
1088 (XEXP (SET_SRC (pattern
), 0))];
1089 SET_SRC (pattern
) = gen_rtx (LABEL_REF
, VOIDmode
, tem
);
1091 /* Set the jump label so that it can be used by later loop unrolling
1093 JUMP_LABEL (insn
) = tem
;
1094 LABEL_NUSES (tem
)++;
1097 copy_loop_body (copy_start
, copy_end
, map
, exit_label
,
1098 i
== unroll_number
- 1, unroll_type
, start_label
,
1099 loop_end
, insert_before
, insert_before
);
1102 /* Before deleting any insns, emit a CODE_LABEL immediately after the last
1103 insn to be deleted. This prevents any runaway delete_insn call from
1104 more insns that it should, as it always stops at a CODE_LABEL. */
1106 /* Delete the compare and branch at the end of the loop if completely
1107 unrolling the loop. Deleting the backward branch at the end also
1108 deletes the code label at the start of the loop. This is done at
1109 the very end to avoid problems with back_branch_in_range_p. */
1111 if (unroll_type
== UNROLL_COMPLETELY
)
1112 safety_label
= emit_label_after (gen_label_rtx (), last_loop_insn
);
1114 safety_label
= emit_label_after (gen_label_rtx (), copy_end
);
1116 /* Delete all of the original loop instructions. Don't delete the
1117 LOOP_BEG note, or the first code label in the loop. */
1119 insn
= NEXT_INSN (copy_start
);
1120 while (insn
!= safety_label
)
1122 if (insn
!= start_label
)
1123 insn
= delete_insn (insn
);
1125 insn
= NEXT_INSN (insn
);
1128 /* Can now delete the 'safety' label emitted to protect us from runaway
1129 delete_insn calls. */
1130 if (INSN_DELETED_P (safety_label
))
1132 delete_insn (safety_label
);
1134 /* If exit_label exists, emit it after the loop. Doing the emit here
1135 forces it to have a higher INSN_UID than any insn in the unrolled loop.
1136 This is needed so that mostly_true_jump in reorg.c will treat jumps
1137 to this loop end label correctly, i.e. predict that they are usually
1140 emit_label_after (exit_label
, loop_end
);
1143 /* Return true if the loop can be safely, and profitably, preconditioned
1144 so that the unrolled copies of the loop body don't need exit tests.
1146 This only works if final_value, initial_value and increment can be
1147 determined, and if increment is a constant power of 2.
1148 If increment is not a power of 2, then the preconditioning modulo
1149 operation would require a real modulo instead of a boolean AND, and this
1150 is not considered `profitable'. */
1152 /* ??? If the loop is known to be executed very many times, or the machine
1153 has a very cheap divide instruction, then preconditioning is a win even
1154 when the increment is not a power of 2. Use RTX_COST to compute
1155 whether divide is cheap. */
1158 precondition_loop_p (initial_value
, final_value
, increment
, loop_start
,
1160 rtx
*initial_value
, *final_value
, *increment
;
1161 rtx loop_start
, loop_end
;
1163 int unsigned_compare
, compare_dir
;
1165 if (loop_n_iterations
> 0)
1167 *initial_value
= const0_rtx
;
1168 *increment
= const1_rtx
;
1169 *final_value
= GEN_INT (loop_n_iterations
);
1171 if (loop_dump_stream
)
1172 fprintf (loop_dump_stream
,
1173 "Preconditioning: Success, number of iterations known, %d.\n",
1178 if (loop_initial_value
== 0)
1180 if (loop_dump_stream
)
1181 fprintf (loop_dump_stream
,
1182 "Preconditioning: Could not find initial value.\n");
1185 else if (loop_increment
== 0)
1187 if (loop_dump_stream
)
1188 fprintf (loop_dump_stream
,
1189 "Preconditioning: Could not find increment value.\n");
1192 else if (GET_CODE (loop_increment
) != CONST_INT
)
1194 if (loop_dump_stream
)
1195 fprintf (loop_dump_stream
,
1196 "Preconditioning: Increment not a constant.\n");
1199 else if ((exact_log2 (INTVAL (loop_increment
)) < 0)
1200 && (exact_log2 (- INTVAL (loop_increment
)) < 0))
1202 if (loop_dump_stream
)
1203 fprintf (loop_dump_stream
,
1204 "Preconditioning: Increment not a constant power of 2.\n");
1208 /* Unsigned_compare and compare_dir can be ignored here, since they do
1209 not matter for preconditioning. */
1211 if (loop_final_value
== 0)
1213 if (loop_dump_stream
)
1214 fprintf (loop_dump_stream
,
1215 "Preconditioning: EQ comparison loop.\n");
1219 /* Must ensure that final_value is invariant, so call invariant_p to
1220 check. Before doing so, must check regno against max_reg_before_loop
1221 to make sure that the register is in the range covered by invariant_p.
1222 If it isn't, then it is most likely a biv/giv which by definition are
1224 if ((GET_CODE (loop_final_value
) == REG
1225 && REGNO (loop_final_value
) >= max_reg_before_loop
)
1226 || (GET_CODE (loop_final_value
) == PLUS
1227 && REGNO (XEXP (loop_final_value
, 0)) >= max_reg_before_loop
)
1228 || ! invariant_p (loop_final_value
))
1230 if (loop_dump_stream
)
1231 fprintf (loop_dump_stream
,
1232 "Preconditioning: Final value not invariant.\n");
1236 /* Fail for floating point values, since the caller of this function
1237 does not have code to deal with them. */
1238 if (GET_MODE_CLASS (GET_MODE (loop_final_value
)) == MODE_FLOAT
1239 || GET_MODE_CLASS (GET_MODE (loop_initial_value
)) == MODE_FLOAT
)
1241 if (loop_dump_stream
)
1242 fprintf (loop_dump_stream
,
1243 "Preconditioning: Floating point final or initial value.\n");
1247 /* Now set initial_value to be the iteration_var, since that may be a
1248 simpler expression, and is guaranteed to be correct if all of the
1249 above tests succeed.
1251 We can not use the initial_value as calculated, because it will be
1252 one too small for loops of the form "while (i-- > 0)". We can not
1253 emit code before the loop_skip_over insns to fix this problem as this
1254 will then give a number one too large for loops of the form
1257 Note that all loops that reach here are entered at the top, because
1258 this function is not called if the loop starts with a jump. */
1260 /* Fail if loop_iteration_var is not live before loop_start, since we need
1261 to test its value in the preconditioning code. */
1263 if (uid_luid
[regno_first_uid
[REGNO (loop_iteration_var
)]]
1264 > INSN_LUID (loop_start
))
1266 if (loop_dump_stream
)
1267 fprintf (loop_dump_stream
,
1268 "Preconditioning: Iteration var not live before loop start.\n");
1272 *initial_value
= loop_iteration_var
;
1273 *increment
= loop_increment
;
1274 *final_value
= loop_final_value
;
1277 if (loop_dump_stream
)
1278 fprintf (loop_dump_stream
, "Preconditioning: Successful.\n");
1283 /* All pseudo-registers must be mapped to themselves. Two hard registers
1284 must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
1285 REGNUM, to avoid function-inlining specific conversions of these
1286 registers. All other hard regs can not be mapped because they may be
1291 init_reg_map (map
, maxregnum
)
1292 struct inline_remap
*map
;
1297 for (i
= maxregnum
- 1; i
> LAST_VIRTUAL_REGISTER
; i
--)
1298 map
->reg_map
[i
] = regno_reg_rtx
[i
];
1299 /* Just clear the rest of the entries. */
1300 for (i
= LAST_VIRTUAL_REGISTER
; i
>= 0; i
--)
1301 map
->reg_map
[i
] = 0;
1303 map
->reg_map
[VIRTUAL_STACK_VARS_REGNUM
]
1304 = regno_reg_rtx
[VIRTUAL_STACK_VARS_REGNUM
];
1305 map
->reg_map
[VIRTUAL_INCOMING_ARGS_REGNUM
]
1306 = regno_reg_rtx
[VIRTUAL_INCOMING_ARGS_REGNUM
];
1309 /* Strength-reduction will often emit code for optimized biv/givs which
1310 calculates their value in a temporary register, and then copies the result
1311 to the iv. This procedure reconstructs the pattern computing the iv;
1312 verifying that all operands are of the proper form.
1314 The return value is the amount that the giv is incremented by. */
1317 calculate_giv_inc (pattern
, src_insn
, regno
)
1318 rtx pattern
, src_insn
;
1322 rtx increment_total
= 0;
1326 /* Verify that we have an increment insn here. First check for a plus
1327 as the set source. */
1328 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1330 /* SR sometimes computes the new giv value in a temp, then copies it
1332 src_insn
= PREV_INSN (src_insn
);
1333 pattern
= PATTERN (src_insn
);
1334 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1337 /* The last insn emitted is not needed, so delete it to avoid confusing
1338 the second cse pass. This insn sets the giv unnecessarily. */
1339 delete_insn (get_last_insn ());
1342 /* Verify that we have a constant as the second operand of the plus. */
1343 increment
= XEXP (SET_SRC (pattern
), 1);
1344 if (GET_CODE (increment
) != CONST_INT
)
1346 /* SR sometimes puts the constant in a register, especially if it is
1347 too big to be an add immed operand. */
1348 src_insn
= PREV_INSN (src_insn
);
1349 increment
= SET_SRC (PATTERN (src_insn
));
1351 /* SR may have used LO_SUM to compute the constant if it is too large
1352 for a load immed operand. In this case, the constant is in operand
1353 one of the LO_SUM rtx. */
1354 if (GET_CODE (increment
) == LO_SUM
)
1355 increment
= XEXP (increment
, 1);
1357 if (GET_CODE (increment
) != CONST_INT
)
1360 /* The insn loading the constant into a register is not longer needed,
1362 delete_insn (get_last_insn ());
1365 if (increment_total
)
1366 increment_total
= GEN_INT (INTVAL (increment_total
) + INTVAL (increment
));
1368 increment_total
= increment
;
1370 /* Check that the source register is the same as the register we expected
1371 to see as the source. If not, something is seriously wrong. */
1372 if (GET_CODE (XEXP (SET_SRC (pattern
), 0)) != REG
1373 || REGNO (XEXP (SET_SRC (pattern
), 0)) != regno
)
1375 /* Some machines (e.g. the romp), may emit two add instructions for
1376 certain constants, so lets try looking for another add immediately
1377 before this one if we have only seen one add insn so far. */
1383 src_insn
= PREV_INSN (src_insn
);
1384 pattern
= PATTERN (src_insn
);
1386 delete_insn (get_last_insn ());
1394 return increment_total
;
1397 /* Copy REG_NOTES, except for insn references, because not all insn_map
1398 entries are valid yet. We do need to copy registers now though, because
1399 the reg_map entries can change during copying. */
1402 initial_reg_note_copy (notes
, map
)
1404 struct inline_remap
*map
;
1411 copy
= rtx_alloc (GET_CODE (notes
));
1412 PUT_MODE (copy
, GET_MODE (notes
));
1414 if (GET_CODE (notes
) == EXPR_LIST
)
1415 XEXP (copy
, 0) = copy_rtx_and_substitute (XEXP (notes
, 0), map
);
1416 else if (GET_CODE (notes
) == INSN_LIST
)
1417 /* Don't substitute for these yet. */
1418 XEXP (copy
, 0) = XEXP (notes
, 0);
1422 XEXP (copy
, 1) = initial_reg_note_copy (XEXP (notes
, 1), map
);
1427 /* Fixup insn references in copied REG_NOTES. */
1430 final_reg_note_copy (notes
, map
)
1432 struct inline_remap
*map
;
1436 for (note
= notes
; note
; note
= XEXP (note
, 1))
1437 if (GET_CODE (note
) == INSN_LIST
)
1438 XEXP (note
, 0) = map
->insn_map
[INSN_UID (XEXP (note
, 0))];
1441 /* Copy each instruction in the loop, substituting from map as appropriate.
1442 This is very similar to a loop in expand_inline_function. */
1445 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, last_iteration
,
1446 unroll_type
, start_label
, loop_end
, insert_before
,
1448 rtx copy_start
, copy_end
;
1449 struct inline_remap
*map
;
1452 enum unroll_types unroll_type
;
1453 rtx start_label
, loop_end
, insert_before
, copy_notes_from
;
1457 int dest_reg_was_split
, i
;
1459 rtx final_label
= 0;
1460 rtx giv_inc
, giv_dest_reg
, giv_src_reg
;
1462 /* If this isn't the last iteration, then map any references to the
1463 start_label to final_label. Final label will then be emitted immediately
1464 after the end of this loop body if it was ever used.
1466 If this is the last iteration, then map references to the start_label
1468 if (! last_iteration
)
1470 final_label
= gen_label_rtx ();
1471 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = final_label
;
1474 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = start_label
;
1481 insn
= NEXT_INSN (insn
);
1483 map
->orig_asm_operands_vector
= 0;
1485 switch (GET_CODE (insn
))
1488 pattern
= PATTERN (insn
);
1492 /* Check to see if this is a giv that has been combined with
1493 some split address givs. (Combined in the sense that
1494 `combine_givs' in loop.c has put two givs in the same register.)
1495 In this case, we must search all givs based on the same biv to
1496 find the address givs. Then split the address givs.
1497 Do this before splitting the giv, since that may map the
1498 SET_DEST to a new register. */
1500 if (GET_CODE (pattern
) == SET
1501 && GET_CODE (SET_DEST (pattern
)) == REG
1502 && addr_combined_regs
[REGNO (SET_DEST (pattern
))])
1504 struct iv_class
*bl
;
1505 struct induction
*v
, *tv
;
1506 int regno
= REGNO (SET_DEST (pattern
));
1508 v
= addr_combined_regs
[REGNO (SET_DEST (pattern
))];
1509 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
1511 /* Although the giv_inc amount is not needed here, we must call
1512 calculate_giv_inc here since it might try to delete the
1513 last insn emitted. If we wait until later to call it,
1514 we might accidentally delete insns generated immediately
1515 below by emit_unrolled_add. */
1517 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1519 /* Now find all address giv's that were combined with this
1521 for (tv
= bl
->giv
; tv
; tv
= tv
->next_iv
)
1522 if (tv
->giv_type
== DEST_ADDR
&& tv
->same
== v
)
1524 int this_giv_inc
= INTVAL (giv_inc
);
1526 /* Scale this_giv_inc if the multiplicative factors of
1527 the two givs are different. */
1528 if (tv
->mult_val
!= v
->mult_val
)
1529 this_giv_inc
= (this_giv_inc
/ INTVAL (v
->mult_val
)
1530 * INTVAL (tv
->mult_val
));
1532 tv
->dest_reg
= plus_constant (tv
->dest_reg
, this_giv_inc
);
1533 *tv
->location
= tv
->dest_reg
;
1535 if (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)
1537 /* Must emit an insn to increment the split address
1538 giv. Add in the const_adjust field in case there
1539 was a constant eliminated from the address. */
1540 rtx value
, dest_reg
;
1542 /* tv->dest_reg will be either a bare register,
1543 or else a register plus a constant. */
1544 if (GET_CODE (tv
->dest_reg
) == REG
)
1545 dest_reg
= tv
->dest_reg
;
1547 dest_reg
= XEXP (tv
->dest_reg
, 0);
1549 /* tv->dest_reg may actually be a (PLUS (REG) (CONST))
1550 here, so we must call plus_constant to add
1551 the const_adjust amount before calling
1552 emit_unrolled_add below. */
1553 value
= plus_constant (tv
->dest_reg
, tv
->const_adjust
);
1555 /* The constant could be too large for an add
1556 immediate, so can't directly emit an insn here. */
1557 emit_unrolled_add (dest_reg
, XEXP (value
, 0),
1560 /* Reset the giv to be just the register again, in case
1561 it is used after the set we have just emitted.
1562 We must subtract the const_adjust factor added in
1564 tv
->dest_reg
= plus_constant (dest_reg
,
1565 - tv
->const_adjust
);
1566 *tv
->location
= tv
->dest_reg
;
1571 /* If this is a setting of a splittable variable, then determine
1572 how to split the variable, create a new set based on this split,
1573 and set up the reg_map so that later uses of the variable will
1574 use the new split variable. */
1576 dest_reg_was_split
= 0;
1578 if (GET_CODE (pattern
) == SET
1579 && GET_CODE (SET_DEST (pattern
)) == REG
1580 && splittable_regs
[REGNO (SET_DEST (pattern
))])
1582 int regno
= REGNO (SET_DEST (pattern
));
1584 dest_reg_was_split
= 1;
1586 /* Compute the increment value for the giv, if it wasn't
1587 already computed above. */
1590 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1591 giv_dest_reg
= SET_DEST (pattern
);
1592 giv_src_reg
= SET_DEST (pattern
);
1594 if (unroll_type
== UNROLL_COMPLETELY
)
1596 /* Completely unrolling the loop. Set the induction
1597 variable to a known constant value. */
1599 /* The value in splittable_regs may be an invariant
1600 value, so we must use plus_constant here. */
1601 splittable_regs
[regno
]
1602 = plus_constant (splittable_regs
[regno
], INTVAL (giv_inc
));
1604 if (GET_CODE (splittable_regs
[regno
]) == PLUS
)
1606 giv_src_reg
= XEXP (splittable_regs
[regno
], 0);
1607 giv_inc
= XEXP (splittable_regs
[regno
], 1);
1611 /* The splittable_regs value must be a REG or a
1612 CONST_INT, so put the entire value in the giv_src_reg
1614 giv_src_reg
= splittable_regs
[regno
];
1615 giv_inc
= const0_rtx
;
1620 /* Partially unrolling loop. Create a new pseudo
1621 register for the iteration variable, and set it to
1622 be a constant plus the original register. Except
1623 on the last iteration, when the result has to
1624 go back into the original iteration var register. */
1626 /* Handle bivs which must be mapped to a new register
1627 when split. This happens for bivs which need their
1628 final value set before loop entry. The new register
1629 for the biv was stored in the biv's first struct
1630 induction entry by find_splittable_regs. */
1632 if (regno
< max_reg_before_loop
1633 && reg_iv_type
[regno
] == BASIC_INDUCT
)
1635 giv_src_reg
= reg_biv_class
[regno
]->biv
->src_reg
;
1636 giv_dest_reg
= giv_src_reg
;
1640 /* If non-reduced/final-value givs were split, then
1641 this would have to remap those givs also. See
1642 find_splittable_regs. */
1645 splittable_regs
[regno
]
1646 = GEN_INT (INTVAL (giv_inc
)
1647 + INTVAL (splittable_regs
[regno
]));
1648 giv_inc
= splittable_regs
[regno
];
1650 /* Now split the induction variable by changing the dest
1651 of this insn to a new register, and setting its
1652 reg_map entry to point to this new register.
1654 If this is the last iteration, and this is the last insn
1655 that will update the iv, then reuse the original dest,
1656 to ensure that the iv will have the proper value when
1657 the loop exits or repeats.
1659 Using splittable_regs_updates here like this is safe,
1660 because it can only be greater than one if all
1661 instructions modifying the iv are always executed in
1664 if (! last_iteration
1665 || (splittable_regs_updates
[regno
]-- != 1))
1667 tem
= gen_reg_rtx (GET_MODE (giv_src_reg
));
1669 map
->reg_map
[regno
] = tem
;
1672 map
->reg_map
[regno
] = giv_src_reg
;
1675 /* The constant being added could be too large for an add
1676 immediate, so can't directly emit an insn here. */
1677 emit_unrolled_add (giv_dest_reg
, giv_src_reg
, giv_inc
);
1678 copy
= get_last_insn ();
1679 pattern
= PATTERN (copy
);
1683 pattern
= copy_rtx_and_substitute (pattern
, map
);
1684 copy
= emit_insn (pattern
);
1686 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1689 /* If this insn is setting CC0, it may need to look at
1690 the insn that uses CC0 to see what type of insn it is.
1691 In that case, the call to recog via validate_change will
1692 fail. So don't substitute constants here. Instead,
1693 do it when we emit the following insn.
1695 For example, see the pyr.md file. That machine has signed and
1696 unsigned compares. The compare patterns must check the
1697 following branch insn to see which what kind of compare to
1700 If the previous insn set CC0, substitute constants on it as
1702 if (sets_cc0_p (copy
) != 0)
1707 try_constants (cc0_insn
, map
);
1709 try_constants (copy
, map
);
1712 try_constants (copy
, map
);
1715 /* Make split induction variable constants `permanent' since we
1716 know there are no backward branches across iteration variable
1717 settings which would invalidate this. */
1718 if (dest_reg_was_split
)
1720 int regno
= REGNO (SET_DEST (pattern
));
1722 if (regno
< map
->const_equiv_map_size
1723 && map
->const_age_map
[regno
] == map
->const_age
)
1724 map
->const_age_map
[regno
] = -1;
1729 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1730 copy
= emit_jump_insn (pattern
);
1731 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1733 if (JUMP_LABEL (insn
) == start_label
&& insn
== copy_end
1734 && ! last_iteration
)
1736 /* This is a branch to the beginning of the loop; this is the
1737 last insn being copied; and this is not the last iteration.
1738 In this case, we want to change the original fall through
1739 case to be a branch past the end of the loop, and the
1740 original jump label case to fall_through. */
1742 if (! invert_exp (pattern
, copy
)
1743 || ! redirect_exp (&pattern
,
1744 map
->label_map
[CODE_LABEL_NUMBER
1745 (JUMP_LABEL (insn
))],
1752 try_constants (cc0_insn
, map
);
1755 try_constants (copy
, map
);
1757 /* Set the jump label of COPY correctly to avoid problems with
1758 later passes of unroll_loop, if INSN had jump label set. */
1759 if (JUMP_LABEL (insn
))
1763 /* Can't use the label_map for every insn, since this may be
1764 the backward branch, and hence the label was not mapped. */
1765 if (GET_CODE (pattern
) == SET
)
1767 tem
= SET_SRC (pattern
);
1768 if (GET_CODE (tem
) == LABEL_REF
)
1769 label
= XEXP (tem
, 0);
1770 else if (GET_CODE (tem
) == IF_THEN_ELSE
)
1772 if (XEXP (tem
, 1) != pc_rtx
)
1773 label
= XEXP (XEXP (tem
, 1), 0);
1775 label
= XEXP (XEXP (tem
, 2), 0);
1779 if (label
&& GET_CODE (label
) == CODE_LABEL
)
1780 JUMP_LABEL (copy
) = label
;
1783 /* An unrecognizable jump insn, probably the entry jump
1784 for a switch statement. This label must have been mapped,
1785 so just use the label_map to get the new jump label. */
1786 JUMP_LABEL (copy
) = map
->label_map
[CODE_LABEL_NUMBER
1787 (JUMP_LABEL (insn
))];
1790 /* If this is a non-local jump, then must increase the label
1791 use count so that the label will not be deleted when the
1792 original jump is deleted. */
1793 LABEL_NUSES (JUMP_LABEL (copy
))++;
1795 else if (GET_CODE (PATTERN (copy
)) == ADDR_VEC
1796 || GET_CODE (PATTERN (copy
)) == ADDR_DIFF_VEC
)
1798 rtx pat
= PATTERN (copy
);
1799 int diff_vec_p
= GET_CODE (pat
) == ADDR_DIFF_VEC
;
1800 int len
= XVECLEN (pat
, diff_vec_p
);
1803 for (i
= 0; i
< len
; i
++)
1804 LABEL_NUSES (XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0))++;
1807 /* If this used to be a conditional jump insn but whose branch
1808 direction is now known, we must do something special. */
1809 if (condjump_p (insn
) && !simplejump_p (insn
) && map
->last_pc_value
)
1812 /* The previous insn set cc0 for us. So delete it. */
1813 delete_insn (PREV_INSN (copy
));
1816 /* If this is now a no-op, delete it. */
1817 if (map
->last_pc_value
== pc_rtx
)
1823 /* Otherwise, this is unconditional jump so we must put a
1824 BARRIER after it. We could do some dead code elimination
1825 here, but jump.c will do it just as well. */
1831 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1832 copy
= emit_call_insn (pattern
);
1833 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1837 try_constants (cc0_insn
, map
);
1840 try_constants (copy
, map
);
1842 /* Be lazy and assume CALL_INSNs clobber all hard registers. */
1843 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
1844 map
->const_equiv_map
[i
] = 0;
1848 /* If this is the loop start label, then we don't need to emit a
1849 copy of this label since no one will use it. */
1851 if (insn
!= start_label
)
1853 copy
= emit_label (map
->label_map
[CODE_LABEL_NUMBER (insn
)]);
1859 copy
= emit_barrier ();
1863 /* VTOP notes are valid only before the loop exit test. If placed
1864 anywhere else, loop may generate bad code. */
1866 if (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
1867 && (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_LOOP_VTOP
1868 || (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)))
1869 copy
= emit_note (NOTE_SOURCE_FILE (insn
),
1870 NOTE_LINE_NUMBER (insn
));
1880 map
->insn_map
[INSN_UID (insn
)] = copy
;
1882 while (insn
!= copy_end
);
1884 /* Now finish coping the REG_NOTES. */
1888 insn
= NEXT_INSN (insn
);
1889 if ((GET_CODE (insn
) == INSN
|| GET_CODE (insn
) == JUMP_INSN
1890 || GET_CODE (insn
) == CALL_INSN
)
1891 && map
->insn_map
[INSN_UID (insn
)])
1892 final_reg_note_copy (REG_NOTES (map
->insn_map
[INSN_UID (insn
)]), map
);
1894 while (insn
!= copy_end
);
1896 /* There may be notes between copy_notes_from and loop_end. Emit a copy of
1897 each of these notes here, since there may be some important ones, such as
1898 NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
1899 iteration, because the original notes won't be deleted.
1901 We can't use insert_before here, because when from preconditioning,
1902 insert_before points before the loop. We can't use copy_end, because
1903 there may be insns already inserted after it (which we don't want to
1904 copy) when not from preconditioning code. */
1906 if (! last_iteration
)
1908 for (insn
= copy_notes_from
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
1910 if (GET_CODE (insn
) == NOTE
1911 && NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
)
1912 emit_note (NOTE_SOURCE_FILE (insn
), NOTE_LINE_NUMBER (insn
));
1916 if (final_label
&& LABEL_NUSES (final_label
) > 0)
1917 emit_label (final_label
);
1919 tem
= gen_sequence ();
1921 emit_insn_before (tem
, insert_before
);
1924 /* Emit an insn, using the expand_binop to ensure that a valid insn is
1925 emitted. This will correctly handle the case where the increment value
1926 won't fit in the immediate field of a PLUS insns. */
1929 emit_unrolled_add (dest_reg
, src_reg
, increment
)
1930 rtx dest_reg
, src_reg
, increment
;
1934 result
= expand_binop (GET_MODE (dest_reg
), add_optab
, src_reg
, increment
,
1935 dest_reg
, 0, OPTAB_LIB_WIDEN
);
1937 if (dest_reg
!= result
)
1938 emit_move_insn (dest_reg
, result
);
1941 /* Searches the insns between INSN and LOOP_END. Returns 1 if there
1942 is a backward branch in that range that branches to somewhere between
1943 LOOP_START and INSN. Returns 0 otherwise. */
1945 /* ??? This is quadratic algorithm. Could be rewritten to be linear.
1946 In practice, this is not a problem, because this function is seldom called,
1947 and uses a negligible amount of CPU time on average. */
1950 back_branch_in_range_p (insn
, loop_start
, loop_end
)
1952 rtx loop_start
, loop_end
;
1954 rtx p
, q
, target_insn
;
1956 /* Stop before we get to the backward branch at the end of the loop. */
1957 loop_end
= prev_nonnote_insn (loop_end
);
1958 if (GET_CODE (loop_end
) == BARRIER
)
1959 loop_end
= PREV_INSN (loop_end
);
1961 /* Check in case insn has been deleted, search forward for first non
1962 deleted insn following it. */
1963 while (INSN_DELETED_P (insn
))
1964 insn
= NEXT_INSN (insn
);
1966 /* Check for the case where insn is the last insn in the loop. */
1967 if (insn
== loop_end
)
1970 for (p
= NEXT_INSN (insn
); p
!= loop_end
; p
= NEXT_INSN (p
))
1972 if (GET_CODE (p
) == JUMP_INSN
)
1974 target_insn
= JUMP_LABEL (p
);
1976 /* Search from loop_start to insn, to see if one of them is
1977 the target_insn. We can't use INSN_LUID comparisons here,
1978 since insn may not have an LUID entry. */
1979 for (q
= loop_start
; q
!= insn
; q
= NEXT_INSN (q
))
1980 if (q
== target_insn
)
1988 /* Try to generate the simplest rtx for the expression
1989 (PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
1993 fold_rtx_mult_add (mult1
, mult2
, add1
, mode
)
1994 rtx mult1
, mult2
, add1
;
1995 enum machine_mode mode
;
2000 /* The modes must all be the same. This should always be true. For now,
2001 check to make sure. */
2002 if ((GET_MODE (mult1
) != mode
&& GET_MODE (mult1
) != VOIDmode
)
2003 || (GET_MODE (mult2
) != mode
&& GET_MODE (mult2
) != VOIDmode
)
2004 || (GET_MODE (add1
) != mode
&& GET_MODE (add1
) != VOIDmode
))
2007 /* Ensure that if at least one of mult1/mult2 are constant, then mult2
2008 will be a constant. */
2009 if (GET_CODE (mult1
) == CONST_INT
)
2016 mult_res
= simplify_binary_operation (MULT
, mode
, mult1
, mult2
);
2018 mult_res
= gen_rtx (MULT
, mode
, mult1
, mult2
);
2020 /* Again, put the constant second. */
2021 if (GET_CODE (add1
) == CONST_INT
)
2028 result
= simplify_binary_operation (PLUS
, mode
, add1
, mult_res
);
2030 result
= gen_rtx (PLUS
, mode
, add1
, mult_res
);
2035 /* Searches the list of induction struct's for the biv BL, to try to calculate
2036 the total increment value for one iteration of the loop as a constant.
2038 Returns the increment value as an rtx, simplified as much as possible,
2039 if it can be calculated. Otherwise, returns 0. */
2042 biv_total_increment (bl
, loop_start
, loop_end
)
2043 struct iv_class
*bl
;
2044 rtx loop_start
, loop_end
;
2046 struct induction
*v
;
2049 /* For increment, must check every instruction that sets it. Each
2050 instruction must be executed only once each time through the loop.
2051 To verify this, we check that the the insn is always executed, and that
2052 there are no backward branches after the insn that branch to before it.
2053 Also, the insn must have a mult_val of one (to make sure it really is
2056 result
= const0_rtx
;
2057 for (v
= bl
->biv
; v
; v
= v
->next_iv
)
2059 if (v
->always_computable
&& v
->mult_val
== const1_rtx
2060 && ! back_branch_in_range_p (v
->insn
, loop_start
, loop_end
))
2061 result
= fold_rtx_mult_add (result
, const1_rtx
, v
->add_val
, v
->mode
);
2069 /* Determine the initial value of the iteration variable, and the amount
2070 that it is incremented each loop. Use the tables constructed by
2071 the strength reduction pass to calculate these values.
2073 Initial_value and/or increment are set to zero if their values could not
2077 iteration_info (iteration_var
, initial_value
, increment
, loop_start
, loop_end
)
2078 rtx iteration_var
, *initial_value
, *increment
;
2079 rtx loop_start
, loop_end
;
2081 struct iv_class
*bl
;
2082 struct induction
*v
, *b
;
2084 /* Clear the result values, in case no answer can be found. */
2088 /* The iteration variable can be either a giv or a biv. Check to see
2089 which it is, and compute the variable's initial value, and increment
2090 value if possible. */
2092 /* If this is a new register, can't handle it since we don't have any
2093 reg_iv_type entry for it. */
2094 if (REGNO (iteration_var
) >= max_reg_before_loop
)
2096 if (loop_dump_stream
)
2097 fprintf (loop_dump_stream
,
2098 "Loop unrolling: No reg_iv_type entry for iteration var.\n");
2101 /* Reject iteration variables larger than the host long size, since they
2102 could result in a number of iterations greater than the range of our
2103 `unsigned long' variable loop_n_iterations. */
2104 else if (GET_MODE_BITSIZE (GET_MODE (iteration_var
)) > HOST_BITS_PER_LONG
)
2106 if (loop_dump_stream
)
2107 fprintf (loop_dump_stream
,
2108 "Loop unrolling: Iteration var rejected because mode larger than host long.\n");
2111 else if (GET_MODE_CLASS (GET_MODE (iteration_var
)) != MODE_INT
)
2113 if (loop_dump_stream
)
2114 fprintf (loop_dump_stream
,
2115 "Loop unrolling: Iteration var not an integer.\n");
2118 else if (reg_iv_type
[REGNO (iteration_var
)] == BASIC_INDUCT
)
2120 /* Grab initial value, only useful if it is a constant. */
2121 bl
= reg_biv_class
[REGNO (iteration_var
)];
2122 *initial_value
= bl
->initial_value
;
2124 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2126 else if (reg_iv_type
[REGNO (iteration_var
)] == GENERAL_INDUCT
)
2129 /* ??? The code below does not work because the incorrect number of
2130 iterations is calculated when the biv is incremented after the giv
2131 is set (which is the usual case). This can probably be accounted
2132 for by biasing the initial_value by subtracting the amount of the
2133 increment that occurs between the giv set and the giv test. However,
2134 a giv as an iterator is very rare, so it does not seem worthwhile
2136 /* ??? An example failure is: i = 6; do {;} while (i++ < 9). */
2137 if (loop_dump_stream
)
2138 fprintf (loop_dump_stream
,
2139 "Loop unrolling: Giv iterators are not handled.\n");
2142 /* Initial value is mult_val times the biv's initial value plus
2143 add_val. Only useful if it is a constant. */
2144 v
= reg_iv_info
[REGNO (iteration_var
)];
2145 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2146 *initial_value
= fold_rtx_mult_add (v
->mult_val
, bl
->initial_value
,
2147 v
->add_val
, v
->mode
);
2149 /* Increment value is mult_val times the increment value of the biv. */
2151 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2153 *increment
= fold_rtx_mult_add (v
->mult_val
, *increment
, const0_rtx
,
2159 if (loop_dump_stream
)
2160 fprintf (loop_dump_stream
,
2161 "Loop unrolling: Not basic or general induction var.\n");
2166 /* Calculate the approximate final value of the iteration variable
2167 which has an loop exit test with code COMPARISON_CODE and comparison value
2168 of COMPARISON_VALUE. Also returns an indication of whether the comparison
2169 was signed or unsigned, and the direction of the comparison. This info is
2170 needed to calculate the number of loop iterations. */
2173 approx_final_value (comparison_code
, comparison_value
, unsigned_p
, compare_dir
)
2174 enum rtx_code comparison_code
;
2175 rtx comparison_value
;
2179 /* Calculate the final value of the induction variable.
2180 The exact final value depends on the branch operator, and increment sign.
2181 This is only an approximate value. It will be wrong if the iteration
2182 variable is not incremented by one each time through the loop, and
2183 approx final value - start value % increment != 0. */
2186 switch (comparison_code
)
2192 return plus_constant (comparison_value
, 1);
2197 return plus_constant (comparison_value
, -1);
2199 /* Can not calculate a final value for this case. */
2206 return comparison_value
;
2212 return comparison_value
;
2215 return comparison_value
;
2221 /* For each biv and giv, determine whether it can be safely split into
2222 a different variable for each unrolled copy of the loop body. If it
2223 is safe to split, then indicate that by saving some useful info
2224 in the splittable_regs array.
2226 If the loop is being completely unrolled, then splittable_regs will hold
2227 the current value of the induction variable while the loop is unrolled.
2228 It must be set to the initial value of the induction variable here.
2229 Otherwise, splittable_regs will hold the difference between the current
2230 value of the induction variable and the value the induction variable had
2231 at the top of the loop. It must be set to the value 0 here.
2233 Returns the total number of instructions that set registers that are
2236 /* ?? If the loop is only unrolled twice, then most of the restrictions to
2237 constant values are unnecessary, since we can easily calculate increment
2238 values in this case even if nothing is constant. The increment value
2239 should not involve a multiply however. */
2241 /* ?? Even if the biv/giv increment values aren't constant, it may still
2242 be beneficial to split the variable if the loop is only unrolled a few
2243 times, since multiplies by small integers (1,2,3,4) are very cheap. */
2246 find_splittable_regs (unroll_type
, loop_start
, loop_end
, end_insert_before
,
2248 enum unroll_types unroll_type
;
2249 rtx loop_start
, loop_end
;
2250 rtx end_insert_before
;
2253 struct iv_class
*bl
;
2254 struct induction
*v
;
2256 rtx biv_final_value
;
2260 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
2262 /* Biv_total_increment must return a constant value,
2263 otherwise we can not calculate the split values. */
2265 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2266 if (! increment
|| GET_CODE (increment
) != CONST_INT
)
2269 /* The loop must be unrolled completely, or else have a known number
2270 of iterations and only one exit, or else the biv must be dead
2271 outside the loop, or else the final value must be known. Otherwise,
2272 it is unsafe to split the biv since it may not have the proper
2273 value on loop exit. */
2275 /* loop_number_exit_labels is non-zero if the loop has an exit other than
2276 a fall through at the end. */
2279 biv_final_value
= 0;
2280 if (unroll_type
!= UNROLL_COMPLETELY
2281 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2282 || unroll_type
== UNROLL_NAIVE
)
2283 && (uid_luid
[regno_last_uid
[bl
->regno
]] >= INSN_LUID (loop_end
)
2285 || INSN_UID (bl
->init_insn
) >= max_uid_for_loop
2286 || (uid_luid
[regno_first_uid
[bl
->regno
]]
2287 < INSN_LUID (bl
->init_insn
))
2288 || reg_mentioned_p (bl
->biv
->dest_reg
, SET_SRC (bl
->init_set
)))
2289 && ! (biv_final_value
= final_biv_value (bl
, loop_start
, loop_end
)))
2292 /* If any of the insns setting the BIV don't do so with a simple
2293 PLUS, we don't know how to split it. */
2294 for (v
= bl
->biv
; biv_splittable
&& v
; v
= v
->next_iv
)
2295 if ((tem
= single_set (v
->insn
)) == 0
2296 || GET_CODE (SET_DEST (tem
)) != REG
2297 || REGNO (SET_DEST (tem
)) != bl
->regno
2298 || GET_CODE (SET_SRC (tem
)) != PLUS
)
2301 /* If final value is non-zero, then must emit an instruction which sets
2302 the value of the biv to the proper value. This is done after
2303 handling all of the givs, since some of them may need to use the
2304 biv's value in their initialization code. */
2306 /* This biv is splittable. If completely unrolling the loop, save
2307 the biv's initial value. Otherwise, save the constant zero. */
2309 if (biv_splittable
== 1)
2311 if (unroll_type
== UNROLL_COMPLETELY
)
2313 /* If the initial value of the biv is itself (i.e. it is too
2314 complicated for strength_reduce to compute), or is a hard
2315 register, then we must create a new pseudo reg to hold the
2316 initial value of the biv. */
2318 if (GET_CODE (bl
->initial_value
) == REG
2319 && (REGNO (bl
->initial_value
) == bl
->regno
2320 || REGNO (bl
->initial_value
) < FIRST_PSEUDO_REGISTER
))
2322 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2324 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2327 if (loop_dump_stream
)
2328 fprintf (loop_dump_stream
, "Biv %d initial value remapped to %d.\n",
2329 bl
->regno
, REGNO (tem
));
2331 splittable_regs
[bl
->regno
] = tem
;
2334 splittable_regs
[bl
->regno
] = bl
->initial_value
;
2337 splittable_regs
[bl
->regno
] = const0_rtx
;
2339 /* Save the number of instructions that modify the biv, so that
2340 we can treat the last one specially. */
2342 splittable_regs_updates
[bl
->regno
] = bl
->biv_count
;
2343 result
+= bl
->biv_count
;
2345 if (loop_dump_stream
)
2346 fprintf (loop_dump_stream
,
2347 "Biv %d safe to split.\n", bl
->regno
);
2350 /* Check every giv that depends on this biv to see whether it is
2351 splittable also. Even if the biv isn't splittable, givs which
2352 depend on it may be splittable if the biv is live outside the
2353 loop, and the givs aren't. */
2355 result
+= find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
,
2356 increment
, unroll_number
);
2358 /* If final value is non-zero, then must emit an instruction which sets
2359 the value of the biv to the proper value. This is done after
2360 handling all of the givs, since some of them may need to use the
2361 biv's value in their initialization code. */
2362 if (biv_final_value
)
2364 /* If the loop has multiple exits, emit the insns before the
2365 loop to ensure that it will always be executed no matter
2366 how the loop exits. Otherwise emit the insn after the loop,
2367 since this is slightly more efficient. */
2368 if (! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2369 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2374 /* Create a new register to hold the value of the biv, and then
2375 set the biv to its final value before the loop start. The biv
2376 is set to its final value before loop start to ensure that
2377 this insn will always be executed, no matter how the loop
2379 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2380 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2382 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2386 if (loop_dump_stream
)
2387 fprintf (loop_dump_stream
, "Biv %d mapped to %d for split.\n",
2388 REGNO (bl
->biv
->src_reg
), REGNO (tem
));
2390 /* Set up the mapping from the original biv register to the new
2392 bl
->biv
->src_reg
= tem
;
2399 /* For every giv based on the biv BL, check to determine whether it is
2400 splittable. This is a subroutine to find_splittable_regs ().
2402 Return the number of instructions that set splittable registers. */
2405 find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
, increment
,
2407 struct iv_class
*bl
;
2408 enum unroll_types unroll_type
;
2409 rtx loop_start
, loop_end
;
2413 struct induction
*v
;
2418 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
2422 /* Only split the giv if it has already been reduced, or if the loop is
2423 being completely unrolled. */
2424 if (unroll_type
!= UNROLL_COMPLETELY
&& v
->ignore
)
2427 /* The giv can be split if the insn that sets the giv is executed once
2428 and only once on every iteration of the loop. */
2429 /* An address giv can always be split. v->insn is just a use not a set,
2430 and hence it does not matter whether it is always executed. All that
2431 matters is that all the biv increments are always executed, and we
2432 won't reach here if they aren't. */
2433 if (v
->giv_type
!= DEST_ADDR
2434 && (! v
->always_computable
2435 || back_branch_in_range_p (v
->insn
, loop_start
, loop_end
)))
2438 /* The giv increment value must be a constant. */
2439 giv_inc
= fold_rtx_mult_add (v
->mult_val
, increment
, const0_rtx
,
2441 if (! giv_inc
|| GET_CODE (giv_inc
) != CONST_INT
)
2444 /* The loop must be unrolled completely, or else have a known number of
2445 iterations and only one exit, or else the giv must be dead outside
2446 the loop, or else the final value of the giv must be known.
2447 Otherwise, it is not safe to split the giv since it may not have the
2448 proper value on loop exit. */
2450 /* The used outside loop test will fail for DEST_ADDR givs. They are
2451 never used outside the loop anyways, so it is always safe to split a
2455 if (unroll_type
!= UNROLL_COMPLETELY
2456 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2457 || unroll_type
== UNROLL_NAIVE
)
2458 && v
->giv_type
!= DEST_ADDR
2459 && ((regno_first_uid
[REGNO (v
->dest_reg
)] != INSN_UID (v
->insn
)
2460 /* Check for the case where the pseudo is set by a shift/add
2461 sequence, in which case the first insn setting the pseudo
2462 is the first insn of the shift/add sequence. */
2463 && (! (tem
= find_reg_note (v
->insn
, REG_RETVAL
, NULL_RTX
))
2464 || (regno_first_uid
[REGNO (v
->dest_reg
)]
2465 != INSN_UID (XEXP (tem
, 0)))))
2466 /* Line above always fails if INSN was moved by loop opt. */
2467 || (uid_luid
[regno_last_uid
[REGNO (v
->dest_reg
)]]
2468 >= INSN_LUID (loop_end
)))
2469 && ! (final_value
= v
->final_value
))
2473 /* Currently, non-reduced/final-value givs are never split. */
2474 /* Should emit insns after the loop if possible, as the biv final value
2477 /* If the final value is non-zero, and the giv has not been reduced,
2478 then must emit an instruction to set the final value. */
2479 if (final_value
&& !v
->new_reg
)
2481 /* Create a new register to hold the value of the giv, and then set
2482 the giv to its final value before the loop start. The giv is set
2483 to its final value before loop start to ensure that this insn
2484 will always be executed, no matter how we exit. */
2485 tem
= gen_reg_rtx (v
->mode
);
2486 emit_insn_before (gen_move_insn (tem
, v
->dest_reg
), loop_start
);
2487 emit_insn_before (gen_move_insn (v
->dest_reg
, final_value
),
2490 if (loop_dump_stream
)
2491 fprintf (loop_dump_stream
, "Giv %d mapped to %d for split.\n",
2492 REGNO (v
->dest_reg
), REGNO (tem
));
2498 /* This giv is splittable. If completely unrolling the loop, save the
2499 giv's initial value. Otherwise, save the constant zero for it. */
2501 if (unroll_type
== UNROLL_COMPLETELY
)
2503 /* It is not safe to use bl->initial_value here, because it may not
2504 be invariant. It is safe to use the initial value stored in
2505 the splittable_regs array if it is set. In rare cases, it won't
2506 be set, so then we do exactly the same thing as
2507 find_splittable_regs does to get a safe value. */
2508 rtx biv_initial_value
;
2510 if (splittable_regs
[bl
->regno
])
2511 biv_initial_value
= splittable_regs
[bl
->regno
];
2512 else if (GET_CODE (bl
->initial_value
) != REG
2513 || (REGNO (bl
->initial_value
) != bl
->regno
2514 && REGNO (bl
->initial_value
) >= FIRST_PSEUDO_REGISTER
))
2515 biv_initial_value
= bl
->initial_value
;
2518 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2520 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2522 biv_initial_value
= tem
;
2524 value
= fold_rtx_mult_add (v
->mult_val
, biv_initial_value
,
2525 v
->add_val
, v
->mode
);
2532 /* If a giv was combined with another giv, then we can only split
2533 this giv if the giv it was combined with was reduced. This
2534 is because the value of v->new_reg is meaningless in this
2536 if (v
->same
&& ! v
->same
->new_reg
)
2538 if (loop_dump_stream
)
2539 fprintf (loop_dump_stream
,
2540 "giv combined with unreduced giv not split.\n");
2543 /* If the giv is an address destination, it could be something other
2544 than a simple register, these have to be treated differently. */
2545 else if (v
->giv_type
== DEST_REG
)
2547 /* If value is not a constant, register, or register plus
2548 constant, then compute its value into a register before
2549 loop start. This prevents illegal rtx sharing, and should
2550 generate better code. We can use bl->initial_value here
2551 instead of splittable_regs[bl->regno] because this code
2552 is going before the loop start. */
2553 if (unroll_type
== UNROLL_COMPLETELY
2554 && GET_CODE (value
) != CONST_INT
2555 && GET_CODE (value
) != REG
2556 && (GET_CODE (value
) != PLUS
2557 || GET_CODE (XEXP (value
, 0)) != REG
2558 || GET_CODE (XEXP (value
, 1)) != CONST_INT
))
2560 rtx tem
= gen_reg_rtx (v
->mode
);
2561 emit_iv_add_mult (bl
->initial_value
, v
->mult_val
,
2562 v
->add_val
, tem
, loop_start
);
2566 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2570 /* Splitting address givs is useful since it will often allow us
2571 to eliminate some increment insns for the base giv as
2574 /* If the addr giv is combined with a dest_reg giv, then all
2575 references to that dest reg will be remapped, which is NOT
2576 what we want for split addr regs. We always create a new
2577 register for the split addr giv, just to be safe. */
2579 /* ??? If there are multiple address givs which have been
2580 combined with the same dest_reg giv, then we may only need
2581 one new register for them. Pulling out constants below will
2582 catch some of the common cases of this. Currently, I leave
2583 the work of simplifying multiple address givs to the
2584 following cse pass. */
2586 v
->const_adjust
= 0;
2587 if (unroll_type
!= UNROLL_COMPLETELY
)
2589 /* If not completely unrolling the loop, then create a new
2590 register to hold the split value of the DEST_ADDR giv.
2591 Emit insn to initialize its value before loop start. */
2592 tem
= gen_reg_rtx (v
->mode
);
2594 /* If the address giv has a constant in its new_reg value,
2595 then this constant can be pulled out and put in value,
2596 instead of being part of the initialization code. */
2598 if (GET_CODE (v
->new_reg
) == PLUS
2599 && GET_CODE (XEXP (v
->new_reg
, 1)) == CONST_INT
)
2602 = plus_constant (tem
, INTVAL (XEXP (v
->new_reg
,1)));
2604 /* Only succeed if this will give valid addresses.
2605 Try to validate both the first and the last
2606 address resulting from loop unrolling, if
2607 one fails, then can't do const elim here. */
2608 if (memory_address_p (v
->mem_mode
, v
->dest_reg
)
2609 && memory_address_p (v
->mem_mode
,
2610 plus_constant (v
->dest_reg
,
2612 * (unroll_number
- 1))))
2614 /* Save the negative of the eliminated const, so
2615 that we can calculate the dest_reg's increment
2617 v
->const_adjust
= - INTVAL (XEXP (v
->new_reg
, 1));
2619 v
->new_reg
= XEXP (v
->new_reg
, 0);
2620 if (loop_dump_stream
)
2621 fprintf (loop_dump_stream
,
2622 "Eliminating constant from giv %d\n",
2631 /* If the address hasn't been checked for validity yet, do so
2632 now, and fail completely if either the first or the last
2633 unrolled copy of the address is not a valid address. */
2634 if (v
->dest_reg
== tem
2635 && (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2636 || ! memory_address_p (v
->mem_mode
,
2637 plus_constant (v
->dest_reg
,
2639 * (unroll_number
-1)))))
2641 if (loop_dump_stream
)
2642 fprintf (loop_dump_stream
,
2643 "Illegal address for giv at insn %d\n",
2644 INSN_UID (v
->insn
));
2648 /* To initialize the new register, just move the value of
2649 new_reg into it. This is not guaranteed to give a valid
2650 instruction on machines with complex addressing modes.
2651 If we can't recognize it, then delete it and emit insns
2652 to calculate the value from scratch. */
2653 emit_insn_before (gen_rtx (SET
, VOIDmode
, tem
,
2654 copy_rtx (v
->new_reg
)),
2656 if (recog_memoized (PREV_INSN (loop_start
)) < 0)
2658 delete_insn (PREV_INSN (loop_start
));
2659 emit_iv_add_mult (bl
->initial_value
, v
->mult_val
,
2660 v
->add_val
, tem
, loop_start
);
2661 if (loop_dump_stream
)
2662 fprintf (loop_dump_stream
,
2663 "Illegal init insn, rewritten.\n");
2668 v
->dest_reg
= value
;
2670 /* Check the resulting address for validity, and fail
2671 if the resulting address would be illegal. */
2672 if (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2673 || ! memory_address_p (v
->mem_mode
,
2674 plus_constant (v
->dest_reg
,
2676 (unroll_number
-1))))
2678 if (loop_dump_stream
)
2679 fprintf (loop_dump_stream
,
2680 "Illegal address for giv at insn %d\n",
2681 INSN_UID (v
->insn
));
2686 /* Store the value of dest_reg into the insn. This sharing
2687 will not be a problem as this insn will always be copied
2690 *v
->location
= v
->dest_reg
;
2692 /* If this address giv is combined with a dest reg giv, then
2693 save the base giv's induction pointer so that we will be
2694 able to handle this address giv properly. The base giv
2695 itself does not have to be splittable. */
2697 if (v
->same
&& v
->same
->giv_type
== DEST_REG
)
2698 addr_combined_regs
[REGNO (v
->same
->new_reg
)] = v
->same
;
2700 if (GET_CODE (v
->new_reg
) == REG
)
2702 /* This giv maybe hasn't been combined with any others.
2703 Make sure that it's giv is marked as splittable here. */
2705 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2707 /* Make it appear to depend upon itself, so that the
2708 giv will be properly split in the main loop above. */
2712 addr_combined_regs
[REGNO (v
->new_reg
)] = v
;
2716 if (loop_dump_stream
)
2717 fprintf (loop_dump_stream
, "DEST_ADDR giv being split.\n");
2723 /* Currently, unreduced giv's can't be split. This is not too much
2724 of a problem since unreduced giv's are not live across loop
2725 iterations anyways. When unrolling a loop completely though,
2726 it makes sense to reduce&split givs when possible, as this will
2727 result in simpler instructions, and will not require that a reg
2728 be live across loop iterations. */
2730 splittable_regs
[REGNO (v
->dest_reg
)] = value
;
2731 fprintf (stderr
, "Giv %d at insn %d not reduced\n",
2732 REGNO (v
->dest_reg
), INSN_UID (v
->insn
));
2738 /* Givs are only updated once by definition. Mark it so if this is
2739 a splittable register. Don't need to do anything for address givs
2740 where this may not be a register. */
2742 if (GET_CODE (v
->new_reg
) == REG
)
2743 splittable_regs_updates
[REGNO (v
->new_reg
)] = 1;
2747 if (loop_dump_stream
)
2751 if (GET_CODE (v
->dest_reg
) == CONST_INT
)
2753 else if (GET_CODE (v
->dest_reg
) != REG
)
2754 regnum
= REGNO (XEXP (v
->dest_reg
, 0));
2756 regnum
= REGNO (v
->dest_reg
);
2757 fprintf (loop_dump_stream
, "Giv %d at insn %d safe to split.\n",
2758 regnum
, INSN_UID (v
->insn
));
2765 /* Try to prove that the register is dead after the loop exits. Trace every
2766 loop exit looking for an insn that will always be executed, which sets
2767 the register to some value, and appears before the first use of the register
2768 is found. If successful, then return 1, otherwise return 0. */
2770 /* ?? Could be made more intelligent in the handling of jumps, so that
2771 it can search past if statements and other similar structures. */
2774 reg_dead_after_loop (reg
, loop_start
, loop_end
)
2775 rtx reg
, loop_start
, loop_end
;
2781 /* HACK: Must also search the loop fall through exit, create a label_ref
2782 here which points to the loop_end, and append the loop_number_exit_labels
2784 label
= gen_rtx (LABEL_REF
, VOIDmode
, loop_end
);
2785 LABEL_NEXTREF (label
)
2786 = loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]];
2788 for ( ; label
; label
= LABEL_NEXTREF (label
))
2790 /* Succeed if find an insn which sets the biv or if reach end of
2791 function. Fail if find an insn that uses the biv, or if come to
2792 a conditional jump. */
2794 insn
= NEXT_INSN (XEXP (label
, 0));
2797 code
= GET_CODE (insn
);
2798 if (GET_RTX_CLASS (code
) == 'i')
2802 if (reg_referenced_p (reg
, PATTERN (insn
)))
2805 set
= single_set (insn
);
2806 if (set
&& rtx_equal_p (SET_DEST (set
), reg
))
2810 if (code
== JUMP_INSN
)
2812 if (GET_CODE (PATTERN (insn
)) == RETURN
)
2814 else if (! simplejump_p (insn
)
2815 /* Prevent infinite loop following infinite loops. */
2816 || jump_count
++ > 20)
2819 insn
= JUMP_LABEL (insn
);
2822 insn
= NEXT_INSN (insn
);
2826 /* Success, the register is dead on all loop exits. */
2830 /* Try to calculate the final value of the biv, the value it will have at
2831 the end of the loop. If we can do it, return that value. */
2834 final_biv_value (bl
, loop_start
, loop_end
)
2835 struct iv_class
*bl
;
2836 rtx loop_start
, loop_end
;
2840 /* ??? This only works for MODE_INT biv's. Reject all others for now. */
2842 if (GET_MODE_CLASS (bl
->biv
->mode
) != MODE_INT
)
2845 /* The final value for reversed bivs must be calculated differently than
2846 for ordinary bivs. In this case, there is already an insn after the
2847 loop which sets this biv's final value (if necessary), and there are
2848 no other loop exits, so we can return any value. */
2851 if (loop_dump_stream
)
2852 fprintf (loop_dump_stream
,
2853 "Final biv value for %d, reversed biv.\n", bl
->regno
);
2858 /* Try to calculate the final value as initial value + (number of iterations
2859 * increment). For this to work, increment must be invariant, the only
2860 exit from the loop must be the fall through at the bottom (otherwise
2861 it may not have its final value when the loop exits), and the initial
2862 value of the biv must be invariant. */
2864 if (loop_n_iterations
!= 0
2865 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2866 && invariant_p (bl
->initial_value
))
2868 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2870 if (increment
&& invariant_p (increment
))
2872 /* Can calculate the loop exit value, emit insns after loop
2873 end to calculate this value into a temporary register in
2874 case it is needed later. */
2876 tem
= gen_reg_rtx (bl
->biv
->mode
);
2877 /* Make sure loop_end is not the last insn. */
2878 if (NEXT_INSN (loop_end
) == 0)
2879 emit_note_after (NOTE_INSN_DELETED
, loop_end
);
2880 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2881 bl
->initial_value
, tem
, NEXT_INSN (loop_end
));
2883 if (loop_dump_stream
)
2884 fprintf (loop_dump_stream
,
2885 "Final biv value for %d, calculated.\n", bl
->regno
);
2891 /* Check to see if the biv is dead at all loop exits. */
2892 if (reg_dead_after_loop (bl
->biv
->src_reg
, loop_start
, loop_end
))
2894 if (loop_dump_stream
)
2895 fprintf (loop_dump_stream
,
2896 "Final biv value for %d, biv dead after loop exit.\n",
2905 /* Try to calculate the final value of the giv, the value it will have at
2906 the end of the loop. If we can do it, return that value. */
2909 final_giv_value (v
, loop_start
, loop_end
)
2910 struct induction
*v
;
2911 rtx loop_start
, loop_end
;
2913 struct iv_class
*bl
;
2917 rtx insert_before
, seq
;
2919 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2921 /* The final value for givs which depend on reversed bivs must be calculated
2922 differently than for ordinary givs. In this case, there is already an
2923 insn after the loop which sets this giv's final value (if necessary),
2924 and there are no other loop exits, so we can return any value. */
2927 if (loop_dump_stream
)
2928 fprintf (loop_dump_stream
,
2929 "Final giv value for %d, depends on reversed biv\n",
2930 REGNO (v
->dest_reg
));
2934 /* Try to calculate the final value as a function of the biv it depends
2935 upon. The only exit from the loop must be the fall through at the bottom
2936 (otherwise it may not have its final value when the loop exits). */
2938 /* ??? Can calculate the final giv value by subtracting off the
2939 extra biv increments times the giv's mult_val. The loop must have
2940 only one exit for this to work, but the loop iterations does not need
2943 if (loop_n_iterations
!= 0
2944 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2946 /* ?? It is tempting to use the biv's value here since these insns will
2947 be put after the loop, and hence the biv will have its final value
2948 then. However, this fails if the biv is subsequently eliminated.
2949 Perhaps determine whether biv's are eliminable before trying to
2950 determine whether giv's are replaceable so that we can use the
2951 biv value here if it is not eliminable. */
2953 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2955 if (increment
&& invariant_p (increment
))
2957 /* Can calculate the loop exit value of its biv as
2958 (loop_n_iterations * increment) + initial_value */
2960 /* The loop exit value of the giv is then
2961 (final_biv_value - extra increments) * mult_val + add_val.
2962 The extra increments are any increments to the biv which
2963 occur in the loop after the giv's value is calculated.
2964 We must search from the insn that sets the giv to the end
2965 of the loop to calculate this value. */
2967 insert_before
= NEXT_INSN (loop_end
);
2969 /* Put the final biv value in tem. */
2970 tem
= gen_reg_rtx (bl
->biv
->mode
);
2971 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2972 bl
->initial_value
, tem
, insert_before
);
2974 /* Subtract off extra increments as we find them. */
2975 for (insn
= NEXT_INSN (v
->insn
); insn
!= loop_end
;
2976 insn
= NEXT_INSN (insn
))
2978 struct induction
*biv
;
2980 for (biv
= bl
->biv
; biv
; biv
= biv
->next_iv
)
2981 if (biv
->insn
== insn
)
2984 tem
= expand_binop (GET_MODE (tem
), sub_optab
, tem
,
2985 biv
->add_val
, NULL_RTX
, 0,
2987 seq
= gen_sequence ();
2989 emit_insn_before (seq
, insert_before
);
2993 /* Now calculate the giv's final value. */
2994 emit_iv_add_mult (tem
, v
->mult_val
, v
->add_val
, tem
,
2997 if (loop_dump_stream
)
2998 fprintf (loop_dump_stream
,
2999 "Final giv value for %d, calc from biv's value.\n",
3000 REGNO (v
->dest_reg
));
3006 /* Replaceable giv's should never reach here. */
3010 /* Check to see if the biv is dead at all loop exits. */
3011 if (reg_dead_after_loop (v
->dest_reg
, loop_start
, loop_end
))
3013 if (loop_dump_stream
)
3014 fprintf (loop_dump_stream
,
3015 "Final giv value for %d, giv dead after loop exit.\n",
3016 REGNO (v
->dest_reg
));
3025 /* Calculate the number of loop iterations. Returns the exact number of loop
3026 iterations if it can be calculated, otherwise returns zero. */
3028 unsigned HOST_WIDE_INT
3029 loop_iterations (loop_start
, loop_end
)
3030 rtx loop_start
, loop_end
;
3032 rtx comparison
, comparison_value
;
3033 rtx iteration_var
, initial_value
, increment
, final_value
;
3034 enum rtx_code comparison_code
;
3037 int unsigned_compare
, compare_dir
, final_larger
;
3038 unsigned long tempu
;
3041 /* First find the iteration variable. If the last insn is a conditional
3042 branch, and the insn before tests a register value, make that the
3043 iteration variable. */
3045 loop_initial_value
= 0;
3047 loop_final_value
= 0;
3048 loop_iteration_var
= 0;
3050 last_loop_insn
= prev_nonnote_insn (loop_end
);
3052 comparison
= get_condition_for_loop (last_loop_insn
);
3053 if (comparison
== 0)
3055 if (loop_dump_stream
)
3056 fprintf (loop_dump_stream
,
3057 "Loop unrolling: No final conditional branch found.\n");
3061 /* ??? Get_condition may switch position of induction variable and
3062 invariant register when it canonicalizes the comparison. */
3064 comparison_code
= GET_CODE (comparison
);
3065 iteration_var
= XEXP (comparison
, 0);
3066 comparison_value
= XEXP (comparison
, 1);
3068 if (GET_CODE (iteration_var
) != REG
)
3070 if (loop_dump_stream
)
3071 fprintf (loop_dump_stream
,
3072 "Loop unrolling: Comparison not against register.\n");
3076 /* Loop iterations is always called before any new registers are created
3077 now, so this should never occur. */
3079 if (REGNO (iteration_var
) >= max_reg_before_loop
)
3082 iteration_info (iteration_var
, &initial_value
, &increment
,
3083 loop_start
, loop_end
);
3084 if (initial_value
== 0)
3085 /* iteration_info already printed a message. */
3090 if (loop_dump_stream
)
3091 fprintf (loop_dump_stream
,
3092 "Loop unrolling: Increment value can't be calculated.\n");
3095 if (GET_CODE (increment
) != CONST_INT
)
3097 if (loop_dump_stream
)
3098 fprintf (loop_dump_stream
,
3099 "Loop unrolling: Increment value not constant.\n");
3102 if (GET_CODE (initial_value
) != CONST_INT
)
3104 if (loop_dump_stream
)
3105 fprintf (loop_dump_stream
,
3106 "Loop unrolling: Initial value not constant.\n");
3110 /* If the comparison value is an invariant register, then try to find
3111 its value from the insns before the start of the loop. */
3113 if (GET_CODE (comparison_value
) == REG
&& invariant_p (comparison_value
))
3117 for (insn
= PREV_INSN (loop_start
); insn
; insn
= PREV_INSN (insn
))
3119 if (GET_CODE (insn
) == CODE_LABEL
)
3122 else if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i'
3123 && reg_set_p (comparison_value
, insn
))
3125 /* We found the last insn before the loop that sets the register.
3126 If it sets the entire register, and has a REG_EQUAL note,
3127 then use the value of the REG_EQUAL note. */
3128 if ((set
= single_set (insn
))
3129 && (SET_DEST (set
) == comparison_value
))
3131 rtx note
= find_reg_note (insn
, REG_EQUAL
, NULL_RTX
);
3133 if (note
&& GET_CODE (XEXP (note
, 0)) != EXPR_LIST
)
3134 comparison_value
= XEXP (note
, 0);
3141 final_value
= approx_final_value (comparison_code
, comparison_value
,
3142 &unsigned_compare
, &compare_dir
);
3144 /* Save the calculated values describing this loop's bounds, in case
3145 precondition_loop_p will need them later. These values can not be
3146 recalculated inside precondition_loop_p because strength reduction
3147 optimizations may obscure the loop's structure. */
3149 loop_iteration_var
= iteration_var
;
3150 loop_initial_value
= initial_value
;
3151 loop_increment
= increment
;
3152 loop_final_value
= final_value
;
3154 if (final_value
== 0)
3156 if (loop_dump_stream
)
3157 fprintf (loop_dump_stream
,
3158 "Loop unrolling: EQ comparison loop.\n");
3161 else if (GET_CODE (final_value
) != CONST_INT
)
3163 if (loop_dump_stream
)
3164 fprintf (loop_dump_stream
,
3165 "Loop unrolling: Final value not constant.\n");
3169 /* ?? Final value and initial value do not have to be constants.
3170 Only their difference has to be constant. When the iteration variable
3171 is an array address, the final value and initial value might both
3172 be addresses with the same base but different constant offsets.
3173 Final value must be invariant for this to work.
3175 To do this, need some way to find the values of registers which are
3178 /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
3179 if (unsigned_compare
)
3181 = ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3182 > (unsigned HOST_WIDE_INT
) INTVAL (initial_value
))
3183 - ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3184 < (unsigned HOST_WIDE_INT
) INTVAL (initial_value
));
3186 final_larger
= (INTVAL (final_value
) > INTVAL (initial_value
))
3187 - (INTVAL (final_value
) < INTVAL (initial_value
));
3189 if (INTVAL (increment
) > 0)
3191 else if (INTVAL (increment
) == 0)
3196 /* There are 27 different cases: compare_dir = -1, 0, 1;
3197 final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
3198 There are 4 normal cases, 4 reverse cases (where the iteration variable
3199 will overflow before the loop exits), 4 infinite loop cases, and 15
3200 immediate exit (0 or 1 iteration depending on loop type) cases.
3201 Only try to optimize the normal cases. */
3203 /* (compare_dir/final_larger/increment_dir)
3204 Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
3205 Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
3206 Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
3207 Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
3209 /* ?? If the meaning of reverse loops (where the iteration variable
3210 will overflow before the loop exits) is undefined, then could
3211 eliminate all of these special checks, and just always assume
3212 the loops are normal/immediate/infinite. Note that this means
3213 the sign of increment_dir does not have to be known. Also,
3214 since it does not really hurt if immediate exit loops or infinite loops
3215 are optimized, then that case could be ignored also, and hence all
3216 loops can be optimized.
3218 According to ANSI Spec, the reverse loop case result is undefined,
3219 because the action on overflow is undefined.
3221 See also the special test for NE loops below. */
3223 if (final_larger
== increment_dir
&& final_larger
!= 0
3224 && (final_larger
== compare_dir
|| compare_dir
== 0))
3229 if (loop_dump_stream
)
3230 fprintf (loop_dump_stream
,
3231 "Loop unrolling: Not normal loop.\n");
3235 /* Calculate the number of iterations, final_value is only an approximation,
3236 so correct for that. Note that tempu and loop_n_iterations are
3237 unsigned, because they can be as large as 2^n - 1. */
3239 i
= INTVAL (increment
);
3241 tempu
= INTVAL (final_value
) - INTVAL (initial_value
);
3244 tempu
= INTVAL (initial_value
) - INTVAL (final_value
);
3250 /* For NE tests, make sure that the iteration variable won't miss the
3251 final value. If tempu mod i is not zero, then the iteration variable
3252 will overflow before the loop exits, and we can not calculate the
3253 number of iterations. */
3254 if (compare_dir
== 0 && (tempu
% i
) != 0)
3257 return tempu
/ i
+ ((tempu
% i
) != 0);