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 global_const_equiv_map
= map
->const_equiv_map
;
1004 /* Search the list of bivs and givs to find ones which need to be remapped
1005 when split, and set their reg_map entry appropriately. */
1007 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
1009 if (REGNO (bl
->biv
->src_reg
) != bl
->regno
)
1010 map
->reg_map
[bl
->regno
] = bl
->biv
->src_reg
;
1012 /* Currently, non-reduced/final-value givs are never split. */
1013 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
1014 if (REGNO (v
->src_reg
) != bl
->regno
)
1015 map
->reg_map
[REGNO (v
->dest_reg
)] = v
->src_reg
;
1019 /* If the loop is being partially unrolled, and the iteration variables
1020 are being split, and are being renamed for the split, then must fix up
1021 the compare instruction at the end of the loop to refer to the new
1022 registers. This compare isn't copied, so the registers used in it
1023 will never be replaced if it isn't done here. */
1025 if (unroll_type
== UNROLL_MODULO
)
1027 insn
= NEXT_INSN (copy_end
);
1028 if (GET_CODE (insn
) == INSN
&& GET_CODE (PATTERN (insn
)) == SET
)
1031 /* If non-reduced/final-value givs were split, then this would also
1032 have to remap those givs. */
1035 tem
= SET_SRC (PATTERN (insn
));
1036 /* The set source is a register. */
1037 if (GET_CODE (tem
) == REG
)
1039 if (REGNO (tem
) < max_reg_before_loop
1040 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1041 SET_SRC (PATTERN (insn
))
1042 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1046 /* The set source is a compare of some sort. */
1047 tem
= XEXP (SET_SRC (PATTERN (insn
)), 0);
1048 if (GET_CODE (tem
) == REG
1049 && REGNO (tem
) < max_reg_before_loop
1050 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1051 XEXP (SET_SRC (PATTERN (insn
)), 0)
1052 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1054 tem
= XEXP (SET_SRC (PATTERN (insn
)), 1);
1055 if (GET_CODE (tem
) == REG
1056 && REGNO (tem
) < max_reg_before_loop
1057 && reg_iv_type
[REGNO (tem
)] == BASIC_INDUCT
)
1058 XEXP (SET_SRC (PATTERN (insn
)), 1)
1059 = reg_biv_class
[REGNO (tem
)]->biv
->src_reg
;
1064 /* For unroll_number - 1 times, make a copy of each instruction
1065 between copy_start and copy_end, and insert these new instructions
1066 before the end of the loop. */
1068 for (i
= 0; i
< unroll_number
; i
++)
1070 bzero (map
->insn_map
, max_insnno
* sizeof (rtx
));
1071 bzero (map
->const_equiv_map
, new_maxregnum
* sizeof (rtx
));
1072 bzero (map
->const_age_map
, new_maxregnum
* sizeof (unsigned));
1075 for (j
= 0; j
< max_labelno
; j
++)
1077 map
->label_map
[j
] = gen_label_rtx ();
1079 /* If loop starts with a branch to the test, then fix it so that
1080 it points to the test of the first unrolled copy of the loop. */
1081 if (i
== 0 && loop_start
!= copy_start
)
1083 insn
= PREV_INSN (copy_start
);
1084 pattern
= PATTERN (insn
);
1086 tem
= map
->label_map
[CODE_LABEL_NUMBER
1087 (XEXP (SET_SRC (pattern
), 0))];
1088 SET_SRC (pattern
) = gen_rtx (LABEL_REF
, VOIDmode
, tem
);
1090 /* Set the jump label so that it can be used by later loop unrolling
1092 JUMP_LABEL (insn
) = tem
;
1093 LABEL_NUSES (tem
)++;
1096 copy_loop_body (copy_start
, copy_end
, map
, exit_label
,
1097 i
== unroll_number
- 1, unroll_type
, start_label
,
1098 loop_end
, insert_before
, insert_before
);
1101 /* Before deleting any insns, emit a CODE_LABEL immediately after the last
1102 insn to be deleted. This prevents any runaway delete_insn call from
1103 more insns that it should, as it always stops at a CODE_LABEL. */
1105 /* Delete the compare and branch at the end of the loop if completely
1106 unrolling the loop. Deleting the backward branch at the end also
1107 deletes the code label at the start of the loop. This is done at
1108 the very end to avoid problems with back_branch_in_range_p. */
1110 if (unroll_type
== UNROLL_COMPLETELY
)
1111 safety_label
= emit_label_after (gen_label_rtx (), last_loop_insn
);
1113 safety_label
= emit_label_after (gen_label_rtx (), copy_end
);
1115 /* Delete all of the original loop instructions. Don't delete the
1116 LOOP_BEG note, or the first code label in the loop. */
1118 insn
= NEXT_INSN (copy_start
);
1119 while (insn
!= safety_label
)
1121 if (insn
!= start_label
)
1122 insn
= delete_insn (insn
);
1124 insn
= NEXT_INSN (insn
);
1127 /* Can now delete the 'safety' label emitted to protect us from runaway
1128 delete_insn calls. */
1129 if (INSN_DELETED_P (safety_label
))
1131 delete_insn (safety_label
);
1133 /* If exit_label exists, emit it after the loop. Doing the emit here
1134 forces it to have a higher INSN_UID than any insn in the unrolled loop.
1135 This is needed so that mostly_true_jump in reorg.c will treat jumps
1136 to this loop end label correctly, i.e. predict that they are usually
1139 emit_label_after (exit_label
, loop_end
);
1142 /* Return true if the loop can be safely, and profitably, preconditioned
1143 so that the unrolled copies of the loop body don't need exit tests.
1145 This only works if final_value, initial_value and increment can be
1146 determined, and if increment is a constant power of 2.
1147 If increment is not a power of 2, then the preconditioning modulo
1148 operation would require a real modulo instead of a boolean AND, and this
1149 is not considered `profitable'. */
1151 /* ??? If the loop is known to be executed very many times, or the machine
1152 has a very cheap divide instruction, then preconditioning is a win even
1153 when the increment is not a power of 2. Use RTX_COST to compute
1154 whether divide is cheap. */
1157 precondition_loop_p (initial_value
, final_value
, increment
, loop_start
,
1159 rtx
*initial_value
, *final_value
, *increment
;
1160 rtx loop_start
, loop_end
;
1162 int unsigned_compare
, compare_dir
;
1164 if (loop_n_iterations
> 0)
1166 *initial_value
= const0_rtx
;
1167 *increment
= const1_rtx
;
1168 *final_value
= GEN_INT (loop_n_iterations
);
1170 if (loop_dump_stream
)
1171 fprintf (loop_dump_stream
,
1172 "Preconditioning: Success, number of iterations known, %d.\n",
1177 if (loop_initial_value
== 0)
1179 if (loop_dump_stream
)
1180 fprintf (loop_dump_stream
,
1181 "Preconditioning: Could not find initial value.\n");
1184 else if (loop_increment
== 0)
1186 if (loop_dump_stream
)
1187 fprintf (loop_dump_stream
,
1188 "Preconditioning: Could not find increment value.\n");
1191 else if (GET_CODE (loop_increment
) != CONST_INT
)
1193 if (loop_dump_stream
)
1194 fprintf (loop_dump_stream
,
1195 "Preconditioning: Increment not a constant.\n");
1198 else if ((exact_log2 (INTVAL (loop_increment
)) < 0)
1199 && (exact_log2 (- INTVAL (loop_increment
)) < 0))
1201 if (loop_dump_stream
)
1202 fprintf (loop_dump_stream
,
1203 "Preconditioning: Increment not a constant power of 2.\n");
1207 /* Unsigned_compare and compare_dir can be ignored here, since they do
1208 not matter for preconditioning. */
1210 if (loop_final_value
== 0)
1212 if (loop_dump_stream
)
1213 fprintf (loop_dump_stream
,
1214 "Preconditioning: EQ comparison loop.\n");
1218 /* Must ensure that final_value is invariant, so call invariant_p to
1219 check. Before doing so, must check regno against max_reg_before_loop
1220 to make sure that the register is in the range covered by invariant_p.
1221 If it isn't, then it is most likely a biv/giv which by definition are
1223 if ((GET_CODE (loop_final_value
) == REG
1224 && REGNO (loop_final_value
) >= max_reg_before_loop
)
1225 || (GET_CODE (loop_final_value
) == PLUS
1226 && REGNO (XEXP (loop_final_value
, 0)) >= max_reg_before_loop
)
1227 || ! invariant_p (loop_final_value
))
1229 if (loop_dump_stream
)
1230 fprintf (loop_dump_stream
,
1231 "Preconditioning: Final value not invariant.\n");
1235 /* Fail for floating point values, since the caller of this function
1236 does not have code to deal with them. */
1237 if (GET_MODE_CLASS (GET_MODE (loop_final_value
)) == MODE_FLOAT
1238 || GET_MODE_CLASS (GET_MODE (loop_initial_value
)) == MODE_FLOAT
)
1240 if (loop_dump_stream
)
1241 fprintf (loop_dump_stream
,
1242 "Preconditioning: Floating point final or initial value.\n");
1246 /* Now set initial_value to be the iteration_var, since that may be a
1247 simpler expression, and is guaranteed to be correct if all of the
1248 above tests succeed.
1250 We can not use the initial_value as calculated, because it will be
1251 one too small for loops of the form "while (i-- > 0)". We can not
1252 emit code before the loop_skip_over insns to fix this problem as this
1253 will then give a number one too large for loops of the form
1256 Note that all loops that reach here are entered at the top, because
1257 this function is not called if the loop starts with a jump. */
1259 /* Fail if loop_iteration_var is not live before loop_start, since we need
1260 to test its value in the preconditioning code. */
1262 if (uid_luid
[regno_first_uid
[REGNO (loop_iteration_var
)]]
1263 > INSN_LUID (loop_start
))
1265 if (loop_dump_stream
)
1266 fprintf (loop_dump_stream
,
1267 "Preconditioning: Iteration var not live before loop start.\n");
1271 *initial_value
= loop_iteration_var
;
1272 *increment
= loop_increment
;
1273 *final_value
= loop_final_value
;
1276 if (loop_dump_stream
)
1277 fprintf (loop_dump_stream
, "Preconditioning: Successful.\n");
1282 /* All pseudo-registers must be mapped to themselves. Two hard registers
1283 must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
1284 REGNUM, to avoid function-inlining specific conversions of these
1285 registers. All other hard regs can not be mapped because they may be
1290 init_reg_map (map
, maxregnum
)
1291 struct inline_remap
*map
;
1296 for (i
= maxregnum
- 1; i
> LAST_VIRTUAL_REGISTER
; i
--)
1297 map
->reg_map
[i
] = regno_reg_rtx
[i
];
1298 /* Just clear the rest of the entries. */
1299 for (i
= LAST_VIRTUAL_REGISTER
; i
>= 0; i
--)
1300 map
->reg_map
[i
] = 0;
1302 map
->reg_map
[VIRTUAL_STACK_VARS_REGNUM
]
1303 = regno_reg_rtx
[VIRTUAL_STACK_VARS_REGNUM
];
1304 map
->reg_map
[VIRTUAL_INCOMING_ARGS_REGNUM
]
1305 = regno_reg_rtx
[VIRTUAL_INCOMING_ARGS_REGNUM
];
1308 /* Strength-reduction will often emit code for optimized biv/givs which
1309 calculates their value in a temporary register, and then copies the result
1310 to the iv. This procedure reconstructs the pattern computing the iv;
1311 verifying that all operands are of the proper form.
1313 The return value is the amount that the giv is incremented by. */
1316 calculate_giv_inc (pattern
, src_insn
, regno
)
1317 rtx pattern
, src_insn
;
1321 rtx increment_total
= 0;
1325 /* Verify that we have an increment insn here. First check for a plus
1326 as the set source. */
1327 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1329 /* SR sometimes computes the new giv value in a temp, then copies it
1331 src_insn
= PREV_INSN (src_insn
);
1332 pattern
= PATTERN (src_insn
);
1333 if (GET_CODE (SET_SRC (pattern
)) != PLUS
)
1336 /* The last insn emitted is not needed, so delete it to avoid confusing
1337 the second cse pass. This insn sets the giv unnecessarily. */
1338 delete_insn (get_last_insn ());
1341 /* Verify that we have a constant as the second operand of the plus. */
1342 increment
= XEXP (SET_SRC (pattern
), 1);
1343 if (GET_CODE (increment
) != CONST_INT
)
1345 /* SR sometimes puts the constant in a register, especially if it is
1346 too big to be an add immed operand. */
1347 src_insn
= PREV_INSN (src_insn
);
1348 increment
= SET_SRC (PATTERN (src_insn
));
1350 /* SR may have used LO_SUM to compute the constant if it is too large
1351 for a load immed operand. In this case, the constant is in operand
1352 one of the LO_SUM rtx. */
1353 if (GET_CODE (increment
) == LO_SUM
)
1354 increment
= XEXP (increment
, 1);
1356 if (GET_CODE (increment
) != CONST_INT
)
1359 /* The insn loading the constant into a register is not longer needed,
1361 delete_insn (get_last_insn ());
1364 if (increment_total
)
1365 increment_total
= GEN_INT (INTVAL (increment_total
) + INTVAL (increment
));
1367 increment_total
= increment
;
1369 /* Check that the source register is the same as the register we expected
1370 to see as the source. If not, something is seriously wrong. */
1371 if (GET_CODE (XEXP (SET_SRC (pattern
), 0)) != REG
1372 || REGNO (XEXP (SET_SRC (pattern
), 0)) != regno
)
1374 /* Some machines (e.g. the romp), may emit two add instructions for
1375 certain constants, so lets try looking for another add immediately
1376 before this one if we have only seen one add insn so far. */
1382 src_insn
= PREV_INSN (src_insn
);
1383 pattern
= PATTERN (src_insn
);
1385 delete_insn (get_last_insn ());
1393 return increment_total
;
1396 /* Copy REG_NOTES, except for insn references, because not all insn_map
1397 entries are valid yet. We do need to copy registers now though, because
1398 the reg_map entries can change during copying. */
1401 initial_reg_note_copy (notes
, map
)
1403 struct inline_remap
*map
;
1410 copy
= rtx_alloc (GET_CODE (notes
));
1411 PUT_MODE (copy
, GET_MODE (notes
));
1413 if (GET_CODE (notes
) == EXPR_LIST
)
1414 XEXP (copy
, 0) = copy_rtx_and_substitute (XEXP (notes
, 0), map
);
1415 else if (GET_CODE (notes
) == INSN_LIST
)
1416 /* Don't substitute for these yet. */
1417 XEXP (copy
, 0) = XEXP (notes
, 0);
1421 XEXP (copy
, 1) = initial_reg_note_copy (XEXP (notes
, 1), map
);
1426 /* Fixup insn references in copied REG_NOTES. */
1429 final_reg_note_copy (notes
, map
)
1431 struct inline_remap
*map
;
1435 for (note
= notes
; note
; note
= XEXP (note
, 1))
1436 if (GET_CODE (note
) == INSN_LIST
)
1437 XEXP (note
, 0) = map
->insn_map
[INSN_UID (XEXP (note
, 0))];
1440 /* Copy each instruction in the loop, substituting from map as appropriate.
1441 This is very similar to a loop in expand_inline_function. */
1444 copy_loop_body (copy_start
, copy_end
, map
, exit_label
, last_iteration
,
1445 unroll_type
, start_label
, loop_end
, insert_before
,
1447 rtx copy_start
, copy_end
;
1448 struct inline_remap
*map
;
1451 enum unroll_types unroll_type
;
1452 rtx start_label
, loop_end
, insert_before
, copy_notes_from
;
1456 int dest_reg_was_split
, i
;
1458 rtx final_label
= 0;
1459 rtx giv_inc
, giv_dest_reg
, giv_src_reg
;
1461 /* If this isn't the last iteration, then map any references to the
1462 start_label to final_label. Final label will then be emitted immediately
1463 after the end of this loop body if it was ever used.
1465 If this is the last iteration, then map references to the start_label
1467 if (! last_iteration
)
1469 final_label
= gen_label_rtx ();
1470 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = final_label
;
1473 map
->label_map
[CODE_LABEL_NUMBER (start_label
)] = start_label
;
1480 insn
= NEXT_INSN (insn
);
1482 map
->orig_asm_operands_vector
= 0;
1484 switch (GET_CODE (insn
))
1487 pattern
= PATTERN (insn
);
1491 /* Check to see if this is a giv that has been combined with
1492 some split address givs. (Combined in the sense that
1493 `combine_givs' in loop.c has put two givs in the same register.)
1494 In this case, we must search all givs based on the same biv to
1495 find the address givs. Then split the address givs.
1496 Do this before splitting the giv, since that may map the
1497 SET_DEST to a new register. */
1499 if (GET_CODE (pattern
) == SET
1500 && GET_CODE (SET_DEST (pattern
)) == REG
1501 && addr_combined_regs
[REGNO (SET_DEST (pattern
))])
1503 struct iv_class
*bl
;
1504 struct induction
*v
, *tv
;
1505 int regno
= REGNO (SET_DEST (pattern
));
1507 v
= addr_combined_regs
[REGNO (SET_DEST (pattern
))];
1508 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
1510 /* Although the giv_inc amount is not needed here, we must call
1511 calculate_giv_inc here since it might try to delete the
1512 last insn emitted. If we wait until later to call it,
1513 we might accidentally delete insns generated immediately
1514 below by emit_unrolled_add. */
1516 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1518 /* Now find all address giv's that were combined with this
1520 for (tv
= bl
->giv
; tv
; tv
= tv
->next_iv
)
1521 if (tv
->giv_type
== DEST_ADDR
&& tv
->same
== v
)
1523 int this_giv_inc
= INTVAL (giv_inc
);
1525 /* Scale this_giv_inc if the multiplicative factors of
1526 the two givs are different. */
1527 if (tv
->mult_val
!= v
->mult_val
)
1528 this_giv_inc
= (this_giv_inc
/ INTVAL (v
->mult_val
)
1529 * INTVAL (tv
->mult_val
));
1531 tv
->dest_reg
= plus_constant (tv
->dest_reg
, this_giv_inc
);
1532 *tv
->location
= tv
->dest_reg
;
1534 if (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)
1536 /* Must emit an insn to increment the split address
1537 giv. Add in the const_adjust field in case there
1538 was a constant eliminated from the address. */
1539 rtx value
, dest_reg
;
1541 /* tv->dest_reg will be either a bare register,
1542 or else a register plus a constant. */
1543 if (GET_CODE (tv
->dest_reg
) == REG
)
1544 dest_reg
= tv
->dest_reg
;
1546 dest_reg
= XEXP (tv
->dest_reg
, 0);
1548 /* tv->dest_reg may actually be a (PLUS (REG) (CONST))
1549 here, so we must call plus_constant to add
1550 the const_adjust amount before calling
1551 emit_unrolled_add below. */
1552 value
= plus_constant (tv
->dest_reg
, tv
->const_adjust
);
1554 /* The constant could be too large for an add
1555 immediate, so can't directly emit an insn here. */
1556 emit_unrolled_add (dest_reg
, XEXP (value
, 0),
1559 /* Reset the giv to be just the register again, in case
1560 it is used after the set we have just emitted.
1561 We must subtract the const_adjust factor added in
1563 tv
->dest_reg
= plus_constant (dest_reg
,
1564 - tv
->const_adjust
);
1565 *tv
->location
= tv
->dest_reg
;
1570 /* If this is a setting of a splittable variable, then determine
1571 how to split the variable, create a new set based on this split,
1572 and set up the reg_map so that later uses of the variable will
1573 use the new split variable. */
1575 dest_reg_was_split
= 0;
1577 if (GET_CODE (pattern
) == SET
1578 && GET_CODE (SET_DEST (pattern
)) == REG
1579 && splittable_regs
[REGNO (SET_DEST (pattern
))])
1581 int regno
= REGNO (SET_DEST (pattern
));
1583 dest_reg_was_split
= 1;
1585 /* Compute the increment value for the giv, if it wasn't
1586 already computed above. */
1589 giv_inc
= calculate_giv_inc (pattern
, insn
, regno
);
1590 giv_dest_reg
= SET_DEST (pattern
);
1591 giv_src_reg
= SET_DEST (pattern
);
1593 if (unroll_type
== UNROLL_COMPLETELY
)
1595 /* Completely unrolling the loop. Set the induction
1596 variable to a known constant value. */
1598 /* The value in splittable_regs may be an invariant
1599 value, so we must use plus_constant here. */
1600 splittable_regs
[regno
]
1601 = plus_constant (splittable_regs
[regno
], INTVAL (giv_inc
));
1603 if (GET_CODE (splittable_regs
[regno
]) == PLUS
)
1605 giv_src_reg
= XEXP (splittable_regs
[regno
], 0);
1606 giv_inc
= XEXP (splittable_regs
[regno
], 1);
1610 /* The splittable_regs value must be a REG or a
1611 CONST_INT, so put the entire value in the giv_src_reg
1613 giv_src_reg
= splittable_regs
[regno
];
1614 giv_inc
= const0_rtx
;
1619 /* Partially unrolling loop. Create a new pseudo
1620 register for the iteration variable, and set it to
1621 be a constant plus the original register. Except
1622 on the last iteration, when the result has to
1623 go back into the original iteration var register. */
1625 /* Handle bivs which must be mapped to a new register
1626 when split. This happens for bivs which need their
1627 final value set before loop entry. The new register
1628 for the biv was stored in the biv's first struct
1629 induction entry by find_splittable_regs. */
1631 if (regno
< max_reg_before_loop
1632 && reg_iv_type
[regno
] == BASIC_INDUCT
)
1634 giv_src_reg
= reg_biv_class
[regno
]->biv
->src_reg
;
1635 giv_dest_reg
= giv_src_reg
;
1639 /* If non-reduced/final-value givs were split, then
1640 this would have to remap those givs also. See
1641 find_splittable_regs. */
1644 splittable_regs
[regno
]
1645 = GEN_INT (INTVAL (giv_inc
)
1646 + INTVAL (splittable_regs
[regno
]));
1647 giv_inc
= splittable_regs
[regno
];
1649 /* Now split the induction variable by changing the dest
1650 of this insn to a new register, and setting its
1651 reg_map entry to point to this new register.
1653 If this is the last iteration, and this is the last insn
1654 that will update the iv, then reuse the original dest,
1655 to ensure that the iv will have the proper value when
1656 the loop exits or repeats.
1658 Using splittable_regs_updates here like this is safe,
1659 because it can only be greater than one if all
1660 instructions modifying the iv are always executed in
1663 if (! last_iteration
1664 || (splittable_regs_updates
[regno
]-- != 1))
1666 tem
= gen_reg_rtx (GET_MODE (giv_src_reg
));
1668 map
->reg_map
[regno
] = tem
;
1671 map
->reg_map
[regno
] = giv_src_reg
;
1674 /* The constant being added could be too large for an add
1675 immediate, so can't directly emit an insn here. */
1676 emit_unrolled_add (giv_dest_reg
, giv_src_reg
, giv_inc
);
1677 copy
= get_last_insn ();
1678 pattern
= PATTERN (copy
);
1682 pattern
= copy_rtx_and_substitute (pattern
, map
);
1683 copy
= emit_insn (pattern
);
1685 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1688 /* If this insn is setting CC0, it may need to look at
1689 the insn that uses CC0 to see what type of insn it is.
1690 In that case, the call to recog via validate_change will
1691 fail. So don't substitute constants here. Instead,
1692 do it when we emit the following insn.
1694 For example, see the pyr.md file. That machine has signed and
1695 unsigned compares. The compare patterns must check the
1696 following branch insn to see which what kind of compare to
1699 If the previous insn set CC0, substitute constants on it as
1701 if (sets_cc0_p (copy
) != 0)
1706 try_constants (cc0_insn
, map
);
1708 try_constants (copy
, map
);
1711 try_constants (copy
, map
);
1714 /* Make split induction variable constants `permanent' since we
1715 know there are no backward branches across iteration variable
1716 settings which would invalidate this. */
1717 if (dest_reg_was_split
)
1719 int regno
= REGNO (SET_DEST (pattern
));
1721 if (map
->const_age_map
[regno
] == map
->const_age
)
1722 map
->const_age_map
[regno
] = -1;
1727 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1728 copy
= emit_jump_insn (pattern
);
1729 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1731 if (JUMP_LABEL (insn
) == start_label
&& insn
== copy_end
1732 && ! last_iteration
)
1734 /* This is a branch to the beginning of the loop; this is the
1735 last insn being copied; and this is not the last iteration.
1736 In this case, we want to change the original fall through
1737 case to be a branch past the end of the loop, and the
1738 original jump label case to fall_through. */
1740 if (! invert_exp (pattern
, copy
)
1741 || ! redirect_exp (&pattern
,
1742 map
->label_map
[CODE_LABEL_NUMBER
1743 (JUMP_LABEL (insn
))],
1750 try_constants (cc0_insn
, map
);
1753 try_constants (copy
, map
);
1755 /* Set the jump label of COPY correctly to avoid problems with
1756 later passes of unroll_loop, if INSN had jump label set. */
1757 if (JUMP_LABEL (insn
))
1761 /* Can't use the label_map for every insn, since this may be
1762 the backward branch, and hence the label was not mapped. */
1763 if (GET_CODE (pattern
) == SET
)
1765 tem
= SET_SRC (pattern
);
1766 if (GET_CODE (tem
) == LABEL_REF
)
1767 label
= XEXP (tem
, 0);
1768 else if (GET_CODE (tem
) == IF_THEN_ELSE
)
1770 if (XEXP (tem
, 1) != pc_rtx
)
1771 label
= XEXP (XEXP (tem
, 1), 0);
1773 label
= XEXP (XEXP (tem
, 2), 0);
1777 if (label
&& GET_CODE (label
) == CODE_LABEL
)
1778 JUMP_LABEL (copy
) = label
;
1781 /* An unrecognizable jump insn, probably the entry jump
1782 for a switch statement. This label must have been mapped,
1783 so just use the label_map to get the new jump label. */
1784 JUMP_LABEL (copy
) = map
->label_map
[CODE_LABEL_NUMBER
1785 (JUMP_LABEL (insn
))];
1788 /* If this is a non-local jump, then must increase the label
1789 use count so that the label will not be deleted when the
1790 original jump is deleted. */
1791 LABEL_NUSES (JUMP_LABEL (copy
))++;
1793 else if (GET_CODE (PATTERN (copy
)) == ADDR_VEC
1794 || GET_CODE (PATTERN (copy
)) == ADDR_DIFF_VEC
)
1796 rtx pat
= PATTERN (copy
);
1797 int diff_vec_p
= GET_CODE (pat
) == ADDR_DIFF_VEC
;
1798 int len
= XVECLEN (pat
, diff_vec_p
);
1801 for (i
= 0; i
< len
; i
++)
1802 LABEL_NUSES (XEXP (XVECEXP (pat
, diff_vec_p
, i
), 0))++;
1805 /* If this used to be a conditional jump insn but whose branch
1806 direction is now known, we must do something special. */
1807 if (condjump_p (insn
) && !simplejump_p (insn
) && map
->last_pc_value
)
1810 /* The previous insn set cc0 for us. So delete it. */
1811 delete_insn (PREV_INSN (copy
));
1814 /* If this is now a no-op, delete it. */
1815 if (map
->last_pc_value
== pc_rtx
)
1821 /* Otherwise, this is unconditional jump so we must put a
1822 BARRIER after it. We could do some dead code elimination
1823 here, but jump.c will do it just as well. */
1829 pattern
= copy_rtx_and_substitute (PATTERN (insn
), map
);
1830 copy
= emit_call_insn (pattern
);
1831 REG_NOTES (copy
) = initial_reg_note_copy (REG_NOTES (insn
), map
);
1835 try_constants (cc0_insn
, map
);
1838 try_constants (copy
, map
);
1840 /* Be lazy and assume CALL_INSNs clobber all hard registers. */
1841 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
1842 map
->const_equiv_map
[i
] = 0;
1846 /* If this is the loop start label, then we don't need to emit a
1847 copy of this label since no one will use it. */
1849 if (insn
!= start_label
)
1851 copy
= emit_label (map
->label_map
[CODE_LABEL_NUMBER (insn
)]);
1857 copy
= emit_barrier ();
1861 /* VTOP notes are valid only before the loop exit test. If placed
1862 anywhere else, loop may generate bad code. */
1864 if (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
1865 && (NOTE_LINE_NUMBER (insn
) != NOTE_INSN_LOOP_VTOP
1866 || (last_iteration
&& unroll_type
!= UNROLL_COMPLETELY
)))
1867 copy
= emit_note (NOTE_SOURCE_FILE (insn
),
1868 NOTE_LINE_NUMBER (insn
));
1878 map
->insn_map
[INSN_UID (insn
)] = copy
;
1880 while (insn
!= copy_end
);
1882 /* Now finish coping the REG_NOTES. */
1886 insn
= NEXT_INSN (insn
);
1887 if ((GET_CODE (insn
) == INSN
|| GET_CODE (insn
) == JUMP_INSN
1888 || GET_CODE (insn
) == CALL_INSN
)
1889 && map
->insn_map
[INSN_UID (insn
)])
1890 final_reg_note_copy (REG_NOTES (map
->insn_map
[INSN_UID (insn
)]), map
);
1892 while (insn
!= copy_end
);
1894 /* There may be notes between copy_notes_from and loop_end. Emit a copy of
1895 each of these notes here, since there may be some important ones, such as
1896 NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
1897 iteration, because the original notes won't be deleted.
1899 We can't use insert_before here, because when from preconditioning,
1900 insert_before points before the loop. We can't use copy_end, because
1901 there may be insns already inserted after it (which we don't want to
1902 copy) when not from preconditioning code. */
1904 if (! last_iteration
)
1906 for (insn
= copy_notes_from
; insn
!= loop_end
; insn
= NEXT_INSN (insn
))
1908 if (GET_CODE (insn
) == NOTE
1909 && NOTE_LINE_NUMBER (insn
) != NOTE_INSN_DELETED
)
1910 emit_note (NOTE_SOURCE_FILE (insn
), NOTE_LINE_NUMBER (insn
));
1914 if (final_label
&& LABEL_NUSES (final_label
) > 0)
1915 emit_label (final_label
);
1917 tem
= gen_sequence ();
1919 emit_insn_before (tem
, insert_before
);
1922 /* Emit an insn, using the expand_binop to ensure that a valid insn is
1923 emitted. This will correctly handle the case where the increment value
1924 won't fit in the immediate field of a PLUS insns. */
1927 emit_unrolled_add (dest_reg
, src_reg
, increment
)
1928 rtx dest_reg
, src_reg
, increment
;
1932 result
= expand_binop (GET_MODE (dest_reg
), add_optab
, src_reg
, increment
,
1933 dest_reg
, 0, OPTAB_LIB_WIDEN
);
1935 if (dest_reg
!= result
)
1936 emit_move_insn (dest_reg
, result
);
1939 /* Searches the insns between INSN and LOOP_END. Returns 1 if there
1940 is a backward branch in that range that branches to somewhere between
1941 LOOP_START and INSN. Returns 0 otherwise. */
1943 /* ??? This is quadratic algorithm. Could be rewritten to be linear.
1944 In practice, this is not a problem, because this function is seldom called,
1945 and uses a negligible amount of CPU time on average. */
1948 back_branch_in_range_p (insn
, loop_start
, loop_end
)
1950 rtx loop_start
, loop_end
;
1952 rtx p
, q
, target_insn
;
1954 /* Stop before we get to the backward branch at the end of the loop. */
1955 loop_end
= prev_nonnote_insn (loop_end
);
1956 if (GET_CODE (loop_end
) == BARRIER
)
1957 loop_end
= PREV_INSN (loop_end
);
1959 /* Check in case insn has been deleted, search forward for first non
1960 deleted insn following it. */
1961 while (INSN_DELETED_P (insn
))
1962 insn
= NEXT_INSN (insn
);
1964 /* Check for the case where insn is the last insn in the loop. */
1965 if (insn
== loop_end
)
1968 for (p
= NEXT_INSN (insn
); p
!= loop_end
; p
= NEXT_INSN (p
))
1970 if (GET_CODE (p
) == JUMP_INSN
)
1972 target_insn
= JUMP_LABEL (p
);
1974 /* Search from loop_start to insn, to see if one of them is
1975 the target_insn. We can't use INSN_LUID comparisons here,
1976 since insn may not have an LUID entry. */
1977 for (q
= loop_start
; q
!= insn
; q
= NEXT_INSN (q
))
1978 if (q
== target_insn
)
1986 /* Try to generate the simplest rtx for the expression
1987 (PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
1991 fold_rtx_mult_add (mult1
, mult2
, add1
, mode
)
1992 rtx mult1
, mult2
, add1
;
1993 enum machine_mode mode
;
1998 /* The modes must all be the same. This should always be true. For now,
1999 check to make sure. */
2000 if ((GET_MODE (mult1
) != mode
&& GET_MODE (mult1
) != VOIDmode
)
2001 || (GET_MODE (mult2
) != mode
&& GET_MODE (mult2
) != VOIDmode
)
2002 || (GET_MODE (add1
) != mode
&& GET_MODE (add1
) != VOIDmode
))
2005 /* Ensure that if at least one of mult1/mult2 are constant, then mult2
2006 will be a constant. */
2007 if (GET_CODE (mult1
) == CONST_INT
)
2014 mult_res
= simplify_binary_operation (MULT
, mode
, mult1
, mult2
);
2016 mult_res
= gen_rtx (MULT
, mode
, mult1
, mult2
);
2018 /* Again, put the constant second. */
2019 if (GET_CODE (add1
) == CONST_INT
)
2026 result
= simplify_binary_operation (PLUS
, mode
, add1
, mult_res
);
2028 result
= gen_rtx (PLUS
, mode
, add1
, mult_res
);
2033 /* Searches the list of induction struct's for the biv BL, to try to calculate
2034 the total increment value for one iteration of the loop as a constant.
2036 Returns the increment value as an rtx, simplified as much as possible,
2037 if it can be calculated. Otherwise, returns 0. */
2040 biv_total_increment (bl
, loop_start
, loop_end
)
2041 struct iv_class
*bl
;
2042 rtx loop_start
, loop_end
;
2044 struct induction
*v
;
2047 /* For increment, must check every instruction that sets it. Each
2048 instruction must be executed only once each time through the loop.
2049 To verify this, we check that the the insn is always executed, and that
2050 there are no backward branches after the insn that branch to before it.
2051 Also, the insn must have a mult_val of one (to make sure it really is
2054 result
= const0_rtx
;
2055 for (v
= bl
->biv
; v
; v
= v
->next_iv
)
2057 if (v
->always_computable
&& v
->mult_val
== const1_rtx
2058 && ! back_branch_in_range_p (v
->insn
, loop_start
, loop_end
))
2059 result
= fold_rtx_mult_add (result
, const1_rtx
, v
->add_val
, v
->mode
);
2067 /* Determine the initial value of the iteration variable, and the amount
2068 that it is incremented each loop. Use the tables constructed by
2069 the strength reduction pass to calculate these values.
2071 Initial_value and/or increment are set to zero if their values could not
2075 iteration_info (iteration_var
, initial_value
, increment
, loop_start
, loop_end
)
2076 rtx iteration_var
, *initial_value
, *increment
;
2077 rtx loop_start
, loop_end
;
2079 struct iv_class
*bl
;
2080 struct induction
*v
, *b
;
2082 /* Clear the result values, in case no answer can be found. */
2086 /* The iteration variable can be either a giv or a biv. Check to see
2087 which it is, and compute the variable's initial value, and increment
2088 value if possible. */
2090 /* If this is a new register, can't handle it since we don't have any
2091 reg_iv_type entry for it. */
2092 if (REGNO (iteration_var
) >= max_reg_before_loop
)
2094 if (loop_dump_stream
)
2095 fprintf (loop_dump_stream
,
2096 "Loop unrolling: No reg_iv_type entry for iteration var.\n");
2099 /* Reject iteration variables larger than the host long size, since they
2100 could result in a number of iterations greater than the range of our
2101 `unsigned long' variable loop_n_iterations. */
2102 else if (GET_MODE_BITSIZE (GET_MODE (iteration_var
)) > HOST_BITS_PER_LONG
)
2104 if (loop_dump_stream
)
2105 fprintf (loop_dump_stream
,
2106 "Loop unrolling: Iteration var rejected because mode larger than host long.\n");
2109 else if (GET_MODE_CLASS (GET_MODE (iteration_var
)) != MODE_INT
)
2111 if (loop_dump_stream
)
2112 fprintf (loop_dump_stream
,
2113 "Loop unrolling: Iteration var not an integer.\n");
2116 else if (reg_iv_type
[REGNO (iteration_var
)] == BASIC_INDUCT
)
2118 /* Grab initial value, only useful if it is a constant. */
2119 bl
= reg_biv_class
[REGNO (iteration_var
)];
2120 *initial_value
= bl
->initial_value
;
2122 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2124 else if (reg_iv_type
[REGNO (iteration_var
)] == GENERAL_INDUCT
)
2127 /* ??? The code below does not work because the incorrect number of
2128 iterations is calculated when the biv is incremented after the giv
2129 is set (which is the usual case). This can probably be accounted
2130 for by biasing the initial_value by subtracting the amount of the
2131 increment that occurs between the giv set and the giv test. However,
2132 a giv as an iterator is very rare, so it does not seem worthwhile
2134 /* ??? An example failure is: i = 6; do {;} while (i++ < 9). */
2135 if (loop_dump_stream
)
2136 fprintf (loop_dump_stream
,
2137 "Loop unrolling: Giv iterators are not handled.\n");
2140 /* Initial value is mult_val times the biv's initial value plus
2141 add_val. Only useful if it is a constant. */
2142 v
= reg_iv_info
[REGNO (iteration_var
)];
2143 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2144 *initial_value
= fold_rtx_mult_add (v
->mult_val
, bl
->initial_value
,
2145 v
->add_val
, v
->mode
);
2147 /* Increment value is mult_val times the increment value of the biv. */
2149 *increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2151 *increment
= fold_rtx_mult_add (v
->mult_val
, *increment
, const0_rtx
,
2157 if (loop_dump_stream
)
2158 fprintf (loop_dump_stream
,
2159 "Loop unrolling: Not basic or general induction var.\n");
2164 /* Calculate the approximate final value of the iteration variable
2165 which has an loop exit test with code COMPARISON_CODE and comparison value
2166 of COMPARISON_VALUE. Also returns an indication of whether the comparison
2167 was signed or unsigned, and the direction of the comparison. This info is
2168 needed to calculate the number of loop iterations. */
2171 approx_final_value (comparison_code
, comparison_value
, unsigned_p
, compare_dir
)
2172 enum rtx_code comparison_code
;
2173 rtx comparison_value
;
2177 /* Calculate the final value of the induction variable.
2178 The exact final value depends on the branch operator, and increment sign.
2179 This is only an approximate value. It will be wrong if the iteration
2180 variable is not incremented by one each time through the loop, and
2181 approx final value - start value % increment != 0. */
2184 switch (comparison_code
)
2190 return plus_constant (comparison_value
, 1);
2195 return plus_constant (comparison_value
, -1);
2197 /* Can not calculate a final value for this case. */
2204 return comparison_value
;
2210 return comparison_value
;
2213 return comparison_value
;
2219 /* For each biv and giv, determine whether it can be safely split into
2220 a different variable for each unrolled copy of the loop body. If it
2221 is safe to split, then indicate that by saving some useful info
2222 in the splittable_regs array.
2224 If the loop is being completely unrolled, then splittable_regs will hold
2225 the current value of the induction variable while the loop is unrolled.
2226 It must be set to the initial value of the induction variable here.
2227 Otherwise, splittable_regs will hold the difference between the current
2228 value of the induction variable and the value the induction variable had
2229 at the top of the loop. It must be set to the value 0 here. */
2231 /* ?? If the loop is only unrolled twice, then most of the restrictions to
2232 constant values are unnecessary, since we can easily calculate increment
2233 values in this case even if nothing is constant. The increment value
2234 should not involve a multiply however. */
2236 /* ?? Even if the biv/giv increment values aren't constant, it may still
2237 be beneficial to split the variable if the loop is only unrolled a few
2238 times, since multiplies by small integers (1,2,3,4) are very cheap. */
2241 find_splittable_regs (unroll_type
, loop_start
, loop_end
, end_insert_before
,
2243 enum unroll_types unroll_type
;
2244 rtx loop_start
, loop_end
;
2245 rtx end_insert_before
;
2248 struct iv_class
*bl
;
2249 struct induction
*v
;
2251 rtx biv_final_value
;
2255 for (bl
= loop_iv_list
; bl
; bl
= bl
->next
)
2257 /* Biv_total_increment must return a constant value,
2258 otherwise we can not calculate the split values. */
2260 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2261 if (! increment
|| GET_CODE (increment
) != CONST_INT
)
2264 /* The loop must be unrolled completely, or else have a known number
2265 of iterations and only one exit, or else the biv must be dead
2266 outside the loop, or else the final value must be known. Otherwise,
2267 it is unsafe to split the biv since it may not have the proper
2268 value on loop exit. */
2270 /* loop_number_exit_labels is non-zero if the loop has an exit other than
2271 a fall through at the end. */
2274 biv_final_value
= 0;
2275 if (unroll_type
!= UNROLL_COMPLETELY
2276 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2277 || unroll_type
== UNROLL_NAIVE
)
2278 && (uid_luid
[regno_last_uid
[bl
->regno
]] >= INSN_LUID (loop_end
)
2280 || INSN_UID (bl
->init_insn
) >= max_uid_for_loop
2281 || (uid_luid
[regno_first_uid
[bl
->regno
]]
2282 < INSN_LUID (bl
->init_insn
))
2283 || reg_mentioned_p (bl
->biv
->dest_reg
, SET_SRC (bl
->init_set
)))
2284 && ! (biv_final_value
= final_biv_value (bl
, loop_start
, loop_end
)))
2287 /* If any of the insns setting the BIV don't do so with a simple
2288 PLUS, we don't know how to split it. */
2289 for (v
= bl
->biv
; biv_splittable
&& v
; v
= v
->next_iv
)
2290 if ((tem
= single_set (v
->insn
)) == 0
2291 || GET_CODE (SET_DEST (tem
)) != REG
2292 || REGNO (SET_DEST (tem
)) != bl
->regno
2293 || GET_CODE (SET_SRC (tem
)) != PLUS
)
2296 /* If final value is non-zero, then must emit an instruction which sets
2297 the value of the biv to the proper value. This is done after
2298 handling all of the givs, since some of them may need to use the
2299 biv's value in their initialization code. */
2301 /* This biv is splittable. If completely unrolling the loop, save
2302 the biv's initial value. Otherwise, save the constant zero. */
2304 if (biv_splittable
== 1)
2306 if (unroll_type
== UNROLL_COMPLETELY
)
2308 /* If the initial value of the biv is itself (i.e. it is too
2309 complicated for strength_reduce to compute), or is a hard
2310 register, then we must create a new pseudo reg to hold the
2311 initial value of the biv. */
2313 if (GET_CODE (bl
->initial_value
) == REG
2314 && (REGNO (bl
->initial_value
) == bl
->regno
2315 || REGNO (bl
->initial_value
) < FIRST_PSEUDO_REGISTER
))
2317 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2319 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2322 if (loop_dump_stream
)
2323 fprintf (loop_dump_stream
, "Biv %d initial value remapped to %d.\n",
2324 bl
->regno
, REGNO (tem
));
2326 splittable_regs
[bl
->regno
] = tem
;
2329 splittable_regs
[bl
->regno
] = bl
->initial_value
;
2332 splittable_regs
[bl
->regno
] = const0_rtx
;
2334 /* Save the number of instructions that modify the biv, so that
2335 we can treat the last one specially. */
2337 splittable_regs_updates
[bl
->regno
] = bl
->biv_count
;
2341 if (loop_dump_stream
)
2342 fprintf (loop_dump_stream
,
2343 "Biv %d safe to split.\n", bl
->regno
);
2346 /* Check every giv that depends on this biv to see whether it is
2347 splittable also. Even if the biv isn't splittable, givs which
2348 depend on it may be splittable if the biv is live outside the
2349 loop, and the givs aren't. */
2351 result
= find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
,
2352 increment
, unroll_number
, result
);
2354 /* If final value is non-zero, then must emit an instruction which sets
2355 the value of the biv to the proper value. This is done after
2356 handling all of the givs, since some of them may need to use the
2357 biv's value in their initialization code. */
2358 if (biv_final_value
)
2360 /* If the loop has multiple exits, emit the insns before the
2361 loop to ensure that it will always be executed no matter
2362 how the loop exits. Otherwise emit the insn after the loop,
2363 since this is slightly more efficient. */
2364 if (! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2365 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2370 /* Create a new register to hold the value of the biv, and then
2371 set the biv to its final value before the loop start. The biv
2372 is set to its final value before loop start to ensure that
2373 this insn will always be executed, no matter how the loop
2375 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2376 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2378 emit_insn_before (gen_move_insn (bl
->biv
->src_reg
,
2382 if (loop_dump_stream
)
2383 fprintf (loop_dump_stream
, "Biv %d mapped to %d for split.\n",
2384 REGNO (bl
->biv
->src_reg
), REGNO (tem
));
2386 /* Set up the mapping from the original biv register to the new
2388 bl
->biv
->src_reg
= tem
;
2395 /* For every giv based on the biv BL, check to determine whether it is
2396 splittable. This is a subroutine to find_splittable_regs (). */
2399 find_splittable_givs (bl
, unroll_type
, loop_start
, loop_end
, increment
,
2400 unroll_number
, result
)
2401 struct iv_class
*bl
;
2402 enum unroll_types unroll_type
;
2403 rtx loop_start
, loop_end
;
2405 int unroll_number
, result
;
2407 struct induction
*v
;
2411 for (v
= bl
->giv
; v
; v
= v
->next_iv
)
2415 /* Only split the giv if it has already been reduced, or if the loop is
2416 being completely unrolled. */
2417 if (unroll_type
!= UNROLL_COMPLETELY
&& v
->ignore
)
2420 /* The giv can be split if the insn that sets the giv is executed once
2421 and only once on every iteration of the loop. */
2422 /* An address giv can always be split. v->insn is just a use not a set,
2423 and hence it does not matter whether it is always executed. All that
2424 matters is that all the biv increments are always executed, and we
2425 won't reach here if they aren't. */
2426 if (v
->giv_type
!= DEST_ADDR
2427 && (! v
->always_computable
2428 || back_branch_in_range_p (v
->insn
, loop_start
, loop_end
)))
2431 /* The giv increment value must be a constant. */
2432 giv_inc
= fold_rtx_mult_add (v
->mult_val
, increment
, const0_rtx
,
2434 if (! giv_inc
|| GET_CODE (giv_inc
) != CONST_INT
)
2437 /* The loop must be unrolled completely, or else have a known number of
2438 iterations and only one exit, or else the giv must be dead outside
2439 the loop, or else the final value of the giv must be known.
2440 Otherwise, it is not safe to split the giv since it may not have the
2441 proper value on loop exit. */
2443 /* The used outside loop test will fail for DEST_ADDR givs. They are
2444 never used outside the loop anyways, so it is always safe to split a
2448 if (unroll_type
!= UNROLL_COMPLETELY
2449 && (loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2450 || unroll_type
== UNROLL_NAIVE
)
2451 && v
->giv_type
!= DEST_ADDR
2452 && ((regno_first_uid
[REGNO (v
->dest_reg
)] != INSN_UID (v
->insn
)
2453 /* Check for the case where the pseudo is set by a shift/add
2454 sequence, in which case the first insn setting the pseudo
2455 is the first insn of the shift/add sequence. */
2456 && (! (tem
= find_reg_note (v
->insn
, REG_RETVAL
, NULL_RTX
))
2457 || (regno_first_uid
[REGNO (v
->dest_reg
)]
2458 != INSN_UID (XEXP (tem
, 0)))))
2459 /* Line above always fails if INSN was moved by loop opt. */
2460 || (uid_luid
[regno_last_uid
[REGNO (v
->dest_reg
)]]
2461 >= INSN_LUID (loop_end
)))
2462 && ! (final_value
= v
->final_value
))
2466 /* Currently, non-reduced/final-value givs are never split. */
2467 /* Should emit insns after the loop if possible, as the biv final value
2470 /* If the final value is non-zero, and the giv has not been reduced,
2471 then must emit an instruction to set the final value. */
2472 if (final_value
&& !v
->new_reg
)
2474 /* Create a new register to hold the value of the giv, and then set
2475 the giv to its final value before the loop start. The giv is set
2476 to its final value before loop start to ensure that this insn
2477 will always be executed, no matter how we exit. */
2478 tem
= gen_reg_rtx (v
->mode
);
2479 emit_insn_before (gen_move_insn (tem
, v
->dest_reg
), loop_start
);
2480 emit_insn_before (gen_move_insn (v
->dest_reg
, final_value
),
2483 if (loop_dump_stream
)
2484 fprintf (loop_dump_stream
, "Giv %d mapped to %d for split.\n",
2485 REGNO (v
->dest_reg
), REGNO (tem
));
2491 /* This giv is splittable. If completely unrolling the loop, save the
2492 giv's initial value. Otherwise, save the constant zero for it. */
2494 if (unroll_type
== UNROLL_COMPLETELY
)
2496 /* It is not safe to use bl->initial_value here, because it may not
2497 be invariant. It is safe to use the initial value stored in
2498 the splittable_regs array if it is set. In rare cases, it won't
2499 be set, so then we do exactly the same thing as
2500 find_splittable_regs does to get a safe value. */
2501 rtx biv_initial_value
;
2503 if (splittable_regs
[bl
->regno
])
2504 biv_initial_value
= splittable_regs
[bl
->regno
];
2505 else if (GET_CODE (bl
->initial_value
) != REG
2506 || (REGNO (bl
->initial_value
) != bl
->regno
2507 && REGNO (bl
->initial_value
) >= FIRST_PSEUDO_REGISTER
))
2508 biv_initial_value
= bl
->initial_value
;
2511 rtx tem
= gen_reg_rtx (bl
->biv
->mode
);
2513 emit_insn_before (gen_move_insn (tem
, bl
->biv
->src_reg
),
2515 biv_initial_value
= tem
;
2517 value
= fold_rtx_mult_add (v
->mult_val
, biv_initial_value
,
2518 v
->add_val
, v
->mode
);
2525 /* If a giv was combined with another giv, then we can only split
2526 this giv if the giv it was combined with was reduced. This
2527 is because the value of v->new_reg is meaningless in this
2529 if (v
->same
&& ! v
->same
->new_reg
)
2531 if (loop_dump_stream
)
2532 fprintf (loop_dump_stream
,
2533 "giv combined with unreduced giv not split.\n");
2536 /* If the giv is an address destination, it could be something other
2537 than a simple register, these have to be treated differently. */
2538 else if (v
->giv_type
== DEST_REG
)
2540 /* If value is not a constant, register, or register plus
2541 constant, then compute its value into a register before
2542 loop start. This prevents illegal rtx sharing, and should
2543 generate better code. We can use bl->initial_value here
2544 instead of splittable_regs[bl->regno] because this code
2545 is going before the loop start. */
2546 if (unroll_type
== UNROLL_COMPLETELY
2547 && GET_CODE (value
) != CONST_INT
2548 && GET_CODE (value
) != REG
2549 && (GET_CODE (value
) != PLUS
2550 || GET_CODE (XEXP (value
, 0)) != REG
2551 || GET_CODE (XEXP (value
, 1)) != CONST_INT
))
2553 rtx tem
= gen_reg_rtx (v
->mode
);
2554 emit_iv_add_mult (bl
->initial_value
, v
->mult_val
,
2555 v
->add_val
, tem
, loop_start
);
2559 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2563 /* Splitting address givs is useful since it will often allow us
2564 to eliminate some increment insns for the base giv as
2567 /* If the addr giv is combined with a dest_reg giv, then all
2568 references to that dest reg will be remapped, which is NOT
2569 what we want for split addr regs. We always create a new
2570 register for the split addr giv, just to be safe. */
2572 /* ??? If there are multiple address givs which have been
2573 combined with the same dest_reg giv, then we may only need
2574 one new register for them. Pulling out constants below will
2575 catch some of the common cases of this. Currently, I leave
2576 the work of simplifying multiple address givs to the
2577 following cse pass. */
2579 v
->const_adjust
= 0;
2580 if (unroll_type
!= UNROLL_COMPLETELY
)
2582 /* If not completely unrolling the loop, then create a new
2583 register to hold the split value of the DEST_ADDR giv.
2584 Emit insn to initialize its value before loop start. */
2585 tem
= gen_reg_rtx (v
->mode
);
2587 /* If the address giv has a constant in its new_reg value,
2588 then this constant can be pulled out and put in value,
2589 instead of being part of the initialization code. */
2591 if (GET_CODE (v
->new_reg
) == PLUS
2592 && GET_CODE (XEXP (v
->new_reg
, 1)) == CONST_INT
)
2595 = plus_constant (tem
, INTVAL (XEXP (v
->new_reg
,1)));
2597 /* Only succeed if this will give valid addresses.
2598 Try to validate both the first and the last
2599 address resulting from loop unrolling, if
2600 one fails, then can't do const elim here. */
2601 if (memory_address_p (v
->mem_mode
, v
->dest_reg
)
2602 && memory_address_p (v
->mem_mode
,
2603 plus_constant (v
->dest_reg
,
2605 * (unroll_number
- 1))))
2607 /* Save the negative of the eliminated const, so
2608 that we can calculate the dest_reg's increment
2610 v
->const_adjust
= - INTVAL (XEXP (v
->new_reg
, 1));
2612 v
->new_reg
= XEXP (v
->new_reg
, 0);
2613 if (loop_dump_stream
)
2614 fprintf (loop_dump_stream
,
2615 "Eliminating constant from giv %d\n",
2624 /* If the address hasn't been checked for validity yet, do so
2625 now, and fail completely if either the first or the last
2626 unrolled copy of the address is not a valid address. */
2627 if (v
->dest_reg
== tem
2628 && (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2629 || ! memory_address_p (v
->mem_mode
,
2630 plus_constant (v
->dest_reg
,
2632 * (unroll_number
-1)))))
2634 if (loop_dump_stream
)
2635 fprintf (loop_dump_stream
,
2636 "Illegal address for giv at insn %d\n",
2637 INSN_UID (v
->insn
));
2641 /* To initialize the new register, just move the value of
2642 new_reg into it. This is not guaranteed to give a valid
2643 instruction on machines with complex addressing modes.
2644 If we can't recognize it, then delete it and emit insns
2645 to calculate the value from scratch. */
2646 emit_insn_before (gen_rtx (SET
, VOIDmode
, tem
,
2647 copy_rtx (v
->new_reg
)),
2649 if (recog_memoized (PREV_INSN (loop_start
)) < 0)
2651 delete_insn (PREV_INSN (loop_start
));
2652 emit_iv_add_mult (bl
->initial_value
, v
->mult_val
,
2653 v
->add_val
, tem
, loop_start
);
2654 if (loop_dump_stream
)
2655 fprintf (loop_dump_stream
,
2656 "Illegal init insn, rewritten.\n");
2661 v
->dest_reg
= value
;
2663 /* Check the resulting address for validity, and fail
2664 if the resulting address would be illegal. */
2665 if (! memory_address_p (v
->mem_mode
, v
->dest_reg
)
2666 || ! memory_address_p (v
->mem_mode
,
2667 plus_constant (v
->dest_reg
,
2669 (unroll_number
-1))))
2671 if (loop_dump_stream
)
2672 fprintf (loop_dump_stream
,
2673 "Illegal address for giv at insn %d\n",
2674 INSN_UID (v
->insn
));
2679 /* Store the value of dest_reg into the insn. This sharing
2680 will not be a problem as this insn will always be copied
2683 *v
->location
= v
->dest_reg
;
2685 /* If this address giv is combined with a dest reg giv, then
2686 save the base giv's induction pointer so that we will be
2687 able to handle this address giv properly. The base giv
2688 itself does not have to be splittable. */
2690 if (v
->same
&& v
->same
->giv_type
== DEST_REG
)
2691 addr_combined_regs
[REGNO (v
->same
->new_reg
)] = v
->same
;
2693 if (GET_CODE (v
->new_reg
) == REG
)
2695 /* This giv maybe hasn't been combined with any others.
2696 Make sure that it's giv is marked as splittable here. */
2698 splittable_regs
[REGNO (v
->new_reg
)] = value
;
2700 /* Make it appear to depend upon itself, so that the
2701 giv will be properly split in the main loop above. */
2705 addr_combined_regs
[REGNO (v
->new_reg
)] = v
;
2709 if (loop_dump_stream
)
2710 fprintf (loop_dump_stream
, "DEST_ADDR giv being split.\n");
2716 /* Currently, unreduced giv's can't be split. This is not too much
2717 of a problem since unreduced giv's are not live across loop
2718 iterations anyways. When unrolling a loop completely though,
2719 it makes sense to reduce&split givs when possible, as this will
2720 result in simpler instructions, and will not require that a reg
2721 be live across loop iterations. */
2723 splittable_regs
[REGNO (v
->dest_reg
)] = value
;
2724 fprintf (stderr
, "Giv %d at insn %d not reduced\n",
2725 REGNO (v
->dest_reg
), INSN_UID (v
->insn
));
2731 /* Givs are only updated once by definition. Mark it so if this is
2732 a splittable register. Don't need to do anything for address givs
2733 where this may not be a register. */
2735 if (GET_CODE (v
->new_reg
) == REG
)
2736 splittable_regs_updates
[REGNO (v
->new_reg
)] = 1;
2740 if (loop_dump_stream
)
2744 if (GET_CODE (v
->dest_reg
) == CONST_INT
)
2746 else if (GET_CODE (v
->dest_reg
) != REG
)
2747 regnum
= REGNO (XEXP (v
->dest_reg
, 0));
2749 regnum
= REGNO (v
->dest_reg
);
2750 fprintf (loop_dump_stream
, "Giv %d at insn %d safe to split.\n",
2751 regnum
, INSN_UID (v
->insn
));
2758 /* Try to prove that the register is dead after the loop exits. Trace every
2759 loop exit looking for an insn that will always be executed, which sets
2760 the register to some value, and appears before the first use of the register
2761 is found. If successful, then return 1, otherwise return 0. */
2763 /* ?? Could be made more intelligent in the handling of jumps, so that
2764 it can search past if statements and other similar structures. */
2767 reg_dead_after_loop (reg
, loop_start
, loop_end
)
2768 rtx reg
, loop_start
, loop_end
;
2774 /* HACK: Must also search the loop fall through exit, create a label_ref
2775 here which points to the loop_end, and append the loop_number_exit_labels
2777 label
= gen_rtx (LABEL_REF
, VOIDmode
, loop_end
);
2778 LABEL_NEXTREF (label
)
2779 = loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]];
2781 for ( ; label
; label
= LABEL_NEXTREF (label
))
2783 /* Succeed if find an insn which sets the biv or if reach end of
2784 function. Fail if find an insn that uses the biv, or if come to
2785 a conditional jump. */
2787 insn
= NEXT_INSN (XEXP (label
, 0));
2790 code
= GET_CODE (insn
);
2791 if (GET_RTX_CLASS (code
) == 'i')
2795 if (reg_referenced_p (reg
, PATTERN (insn
)))
2798 set
= single_set (insn
);
2799 if (set
&& rtx_equal_p (SET_DEST (set
), reg
))
2803 if (code
== JUMP_INSN
)
2805 if (GET_CODE (PATTERN (insn
)) == RETURN
)
2807 else if (! simplejump_p (insn
)
2808 /* Prevent infinite loop following infinite loops. */
2809 || jump_count
++ > 20)
2812 insn
= JUMP_LABEL (insn
);
2815 insn
= NEXT_INSN (insn
);
2819 /* Success, the register is dead on all loop exits. */
2823 /* Try to calculate the final value of the biv, the value it will have at
2824 the end of the loop. If we can do it, return that value. */
2827 final_biv_value (bl
, loop_start
, loop_end
)
2828 struct iv_class
*bl
;
2829 rtx loop_start
, loop_end
;
2833 /* ??? This only works for MODE_INT biv's. Reject all others for now. */
2835 if (GET_MODE_CLASS (bl
->biv
->mode
) != MODE_INT
)
2838 /* The final value for reversed bivs must be calculated differently than
2839 for ordinary bivs. In this case, there is already an insn after the
2840 loop which sets this biv's final value (if necessary), and there are
2841 no other loop exits, so we can return any value. */
2844 if (loop_dump_stream
)
2845 fprintf (loop_dump_stream
,
2846 "Final biv value for %d, reversed biv.\n", bl
->regno
);
2851 /* Try to calculate the final value as initial value + (number of iterations
2852 * increment). For this to work, increment must be invariant, the only
2853 exit from the loop must be the fall through at the bottom (otherwise
2854 it may not have its final value when the loop exits), and the initial
2855 value of the biv must be invariant. */
2857 if (loop_n_iterations
!= 0
2858 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]]
2859 && invariant_p (bl
->initial_value
))
2861 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2863 if (increment
&& invariant_p (increment
))
2865 /* Can calculate the loop exit value, emit insns after loop
2866 end to calculate this value into a temporary register in
2867 case it is needed later. */
2869 tem
= gen_reg_rtx (bl
->biv
->mode
);
2870 /* Make sure loop_end is not the last insn. */
2871 if (NEXT_INSN (loop_end
) == 0)
2872 emit_note_after (NOTE_INSN_DELETED
, loop_end
);
2873 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2874 bl
->initial_value
, tem
, NEXT_INSN (loop_end
));
2876 if (loop_dump_stream
)
2877 fprintf (loop_dump_stream
,
2878 "Final biv value for %d, calculated.\n", bl
->regno
);
2884 /* Check to see if the biv is dead at all loop exits. */
2885 if (reg_dead_after_loop (bl
->biv
->src_reg
, loop_start
, loop_end
))
2887 if (loop_dump_stream
)
2888 fprintf (loop_dump_stream
,
2889 "Final biv value for %d, biv dead after loop exit.\n",
2898 /* Try to calculate the final value of the giv, the value it will have at
2899 the end of the loop. If we can do it, return that value. */
2902 final_giv_value (v
, loop_start
, loop_end
)
2903 struct induction
*v
;
2904 rtx loop_start
, loop_end
;
2906 struct iv_class
*bl
;
2910 rtx insert_before
, seq
;
2912 bl
= reg_biv_class
[REGNO (v
->src_reg
)];
2914 /* The final value for givs which depend on reversed bivs must be calculated
2915 differently than for ordinary givs. In this case, there is already an
2916 insn after the loop which sets this giv's final value (if necessary),
2917 and there are no other loop exits, so we can return any value. */
2920 if (loop_dump_stream
)
2921 fprintf (loop_dump_stream
,
2922 "Final giv value for %d, depends on reversed biv\n",
2923 REGNO (v
->dest_reg
));
2927 /* Try to calculate the final value as a function of the biv it depends
2928 upon. The only exit from the loop must be the fall through at the bottom
2929 (otherwise it may not have its final value when the loop exits). */
2931 /* ??? Can calculate the final giv value by subtracting off the
2932 extra biv increments times the giv's mult_val. The loop must have
2933 only one exit for this to work, but the loop iterations does not need
2936 if (loop_n_iterations
!= 0
2937 && ! loop_number_exit_labels
[uid_loop_num
[INSN_UID (loop_start
)]])
2939 /* ?? It is tempting to use the biv's value here since these insns will
2940 be put after the loop, and hence the biv will have its final value
2941 then. However, this fails if the biv is subsequently eliminated.
2942 Perhaps determine whether biv's are eliminable before trying to
2943 determine whether giv's are replaceable so that we can use the
2944 biv value here if it is not eliminable. */
2946 increment
= biv_total_increment (bl
, loop_start
, loop_end
);
2948 if (increment
&& invariant_p (increment
))
2950 /* Can calculate the loop exit value of its biv as
2951 (loop_n_iterations * increment) + initial_value */
2953 /* The loop exit value of the giv is then
2954 (final_biv_value - extra increments) * mult_val + add_val.
2955 The extra increments are any increments to the biv which
2956 occur in the loop after the giv's value is calculated.
2957 We must search from the insn that sets the giv to the end
2958 of the loop to calculate this value. */
2960 insert_before
= NEXT_INSN (loop_end
);
2962 /* Put the final biv value in tem. */
2963 tem
= gen_reg_rtx (bl
->biv
->mode
);
2964 emit_iv_add_mult (increment
, GEN_INT (loop_n_iterations
),
2965 bl
->initial_value
, tem
, insert_before
);
2967 /* Subtract off extra increments as we find them. */
2968 for (insn
= NEXT_INSN (v
->insn
); insn
!= loop_end
;
2969 insn
= NEXT_INSN (insn
))
2971 struct induction
*biv
;
2973 for (biv
= bl
->biv
; biv
; biv
= biv
->next_iv
)
2974 if (biv
->insn
== insn
)
2977 tem
= expand_binop (GET_MODE (tem
), sub_optab
, tem
,
2978 biv
->add_val
, NULL_RTX
, 0,
2980 seq
= gen_sequence ();
2982 emit_insn_before (seq
, insert_before
);
2986 /* Now calculate the giv's final value. */
2987 emit_iv_add_mult (tem
, v
->mult_val
, v
->add_val
, tem
,
2990 if (loop_dump_stream
)
2991 fprintf (loop_dump_stream
,
2992 "Final giv value for %d, calc from biv's value.\n",
2993 REGNO (v
->dest_reg
));
2999 /* Replaceable giv's should never reach here. */
3003 /* Check to see if the biv is dead at all loop exits. */
3004 if (reg_dead_after_loop (v
->dest_reg
, loop_start
, loop_end
))
3006 if (loop_dump_stream
)
3007 fprintf (loop_dump_stream
,
3008 "Final giv value for %d, giv dead after loop exit.\n",
3009 REGNO (v
->dest_reg
));
3018 /* Calculate the number of loop iterations. Returns the exact number of loop
3019 iterations if it can be calculated, otherwise returns zero. */
3021 unsigned HOST_WIDE_INT
3022 loop_iterations (loop_start
, loop_end
)
3023 rtx loop_start
, loop_end
;
3025 rtx comparison
, comparison_value
;
3026 rtx iteration_var
, initial_value
, increment
, final_value
;
3027 enum rtx_code comparison_code
;
3030 int unsigned_compare
, compare_dir
, final_larger
;
3031 unsigned long tempu
;
3034 /* First find the iteration variable. If the last insn is a conditional
3035 branch, and the insn before tests a register value, make that the
3036 iteration variable. */
3038 loop_initial_value
= 0;
3040 loop_final_value
= 0;
3041 loop_iteration_var
= 0;
3043 last_loop_insn
= prev_nonnote_insn (loop_end
);
3045 comparison
= get_condition_for_loop (last_loop_insn
);
3046 if (comparison
== 0)
3048 if (loop_dump_stream
)
3049 fprintf (loop_dump_stream
,
3050 "Loop unrolling: No final conditional branch found.\n");
3054 /* ??? Get_condition may switch position of induction variable and
3055 invariant register when it canonicalizes the comparison. */
3057 comparison_code
= GET_CODE (comparison
);
3058 iteration_var
= XEXP (comparison
, 0);
3059 comparison_value
= XEXP (comparison
, 1);
3061 if (GET_CODE (iteration_var
) != REG
)
3063 if (loop_dump_stream
)
3064 fprintf (loop_dump_stream
,
3065 "Loop unrolling: Comparison not against register.\n");
3069 /* Loop iterations is always called before any new registers are created
3070 now, so this should never occur. */
3072 if (REGNO (iteration_var
) >= max_reg_before_loop
)
3075 iteration_info (iteration_var
, &initial_value
, &increment
,
3076 loop_start
, loop_end
);
3077 if (initial_value
== 0)
3078 /* iteration_info already printed a message. */
3083 if (loop_dump_stream
)
3084 fprintf (loop_dump_stream
,
3085 "Loop unrolling: Increment value can't be calculated.\n");
3088 if (GET_CODE (increment
) != CONST_INT
)
3090 if (loop_dump_stream
)
3091 fprintf (loop_dump_stream
,
3092 "Loop unrolling: Increment value not constant.\n");
3095 if (GET_CODE (initial_value
) != CONST_INT
)
3097 if (loop_dump_stream
)
3098 fprintf (loop_dump_stream
,
3099 "Loop unrolling: Initial value not constant.\n");
3103 /* If the comparison value is an invariant register, then try to find
3104 its value from the insns before the start of the loop. */
3106 if (GET_CODE (comparison_value
) == REG
&& invariant_p (comparison_value
))
3110 for (insn
= PREV_INSN (loop_start
); insn
; insn
= PREV_INSN (insn
))
3112 if (GET_CODE (insn
) == CODE_LABEL
)
3115 else if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i'
3116 && reg_set_p (comparison_value
, insn
))
3118 /* We found the last insn before the loop that sets the register.
3119 If it sets the entire register, and has a REG_EQUAL note,
3120 then use the value of the REG_EQUAL note. */
3121 if ((set
= single_set (insn
))
3122 && (SET_DEST (set
) == comparison_value
))
3124 rtx note
= find_reg_note (insn
, REG_EQUAL
, NULL_RTX
);
3126 if (note
&& GET_CODE (XEXP (note
, 0)) != EXPR_LIST
)
3127 comparison_value
= XEXP (note
, 0);
3134 final_value
= approx_final_value (comparison_code
, comparison_value
,
3135 &unsigned_compare
, &compare_dir
);
3137 /* Save the calculated values describing this loop's bounds, in case
3138 precondition_loop_p will need them later. These values can not be
3139 recalculated inside precondition_loop_p because strength reduction
3140 optimizations may obscure the loop's structure. */
3142 loop_iteration_var
= iteration_var
;
3143 loop_initial_value
= initial_value
;
3144 loop_increment
= increment
;
3145 loop_final_value
= final_value
;
3147 if (final_value
== 0)
3149 if (loop_dump_stream
)
3150 fprintf (loop_dump_stream
,
3151 "Loop unrolling: EQ comparison loop.\n");
3154 else if (GET_CODE (final_value
) != CONST_INT
)
3156 if (loop_dump_stream
)
3157 fprintf (loop_dump_stream
,
3158 "Loop unrolling: Final value not constant.\n");
3162 /* ?? Final value and initial value do not have to be constants.
3163 Only their difference has to be constant. When the iteration variable
3164 is an array address, the final value and initial value might both
3165 be addresses with the same base but different constant offsets.
3166 Final value must be invariant for this to work.
3168 To do this, need some way to find the values of registers which are
3171 /* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
3172 if (unsigned_compare
)
3174 = ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3175 > (unsigned HOST_WIDE_INT
) INTVAL (initial_value
))
3176 - ((unsigned HOST_WIDE_INT
) INTVAL (final_value
)
3177 < (unsigned HOST_WIDE_INT
) INTVAL (initial_value
));
3179 final_larger
= (INTVAL (final_value
) > INTVAL (initial_value
))
3180 - (INTVAL (final_value
) < INTVAL (initial_value
));
3182 if (INTVAL (increment
) > 0)
3184 else if (INTVAL (increment
) == 0)
3189 /* There are 27 different cases: compare_dir = -1, 0, 1;
3190 final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
3191 There are 4 normal cases, 4 reverse cases (where the iteration variable
3192 will overflow before the loop exits), 4 infinite loop cases, and 15
3193 immediate exit (0 or 1 iteration depending on loop type) cases.
3194 Only try to optimize the normal cases. */
3196 /* (compare_dir/final_larger/increment_dir)
3197 Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
3198 Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
3199 Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
3200 Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
3202 /* ?? If the meaning of reverse loops (where the iteration variable
3203 will overflow before the loop exits) is undefined, then could
3204 eliminate all of these special checks, and just always assume
3205 the loops are normal/immediate/infinite. Note that this means
3206 the sign of increment_dir does not have to be known. Also,
3207 since it does not really hurt if immediate exit loops or infinite loops
3208 are optimized, then that case could be ignored also, and hence all
3209 loops can be optimized.
3211 According to ANSI Spec, the reverse loop case result is undefined,
3212 because the action on overflow is undefined.
3214 See also the special test for NE loops below. */
3216 if (final_larger
== increment_dir
&& final_larger
!= 0
3217 && (final_larger
== compare_dir
|| compare_dir
== 0))
3222 if (loop_dump_stream
)
3223 fprintf (loop_dump_stream
,
3224 "Loop unrolling: Not normal loop.\n");
3228 /* Calculate the number of iterations, final_value is only an approximation,
3229 so correct for that. Note that tempu and loop_n_iterations are
3230 unsigned, because they can be as large as 2^n - 1. */
3232 i
= INTVAL (increment
);
3234 tempu
= INTVAL (final_value
) - INTVAL (initial_value
);
3237 tempu
= INTVAL (initial_value
) - INTVAL (final_value
);
3243 /* For NE tests, make sure that the iteration variable won't miss the
3244 final value. If tempu mod i is not zero, then the iteration variable
3245 will overflow before the loop exits, and we can not calculate the
3246 number of iterations. */
3247 if (compare_dir
== 0 && (tempu
% i
) != 0)
3250 return tempu
/ i
+ ((tempu
% i
) != 0);