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1 /* Predictive commoning.
2 Copyright (C) 2005-2020 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by the
8 Free Software Foundation; either version 3, or (at your option) any
9 later version.
11 GCC is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
20 /* This file implements the predictive commoning optimization. Predictive
21 commoning can be viewed as CSE around a loop, and with some improvements,
22 as generalized strength reduction-- i.e., reusing values computed in
23 earlier iterations of a loop in the later ones. So far, the pass only
24 handles the most useful case, that is, reusing values of memory references.
25 If you think this is all just a special case of PRE, you are sort of right;
26 however, concentrating on loops is simpler, and makes it possible to
27 incorporate data dependence analysis to detect the opportunities, perform
28 loop unrolling to avoid copies together with renaming immediately,
29 and if needed, we could also take register pressure into account.
31 Let us demonstrate what is done on an example:
33 for (i = 0; i < 100; i++)
35 a[i+2] = a[i] + a[i+1];
36 b[10] = b[10] + i;
37 c[i] = c[99 - i];
38 d[i] = d[i + 1];
41 1) We find data references in the loop, and split them to mutually
42 independent groups (i.e., we find components of a data dependence
43 graph). We ignore read-read dependences whose distance is not constant.
44 (TODO -- we could also ignore antidependences). In this example, we
45 find the following groups:
47 a[i]{read}, a[i+1]{read}, a[i+2]{write}
48 b[10]{read}, b[10]{write}
49 c[99 - i]{read}, c[i]{write}
50 d[i + 1]{read}, d[i]{write}
52 2) Inside each of the group, we verify several conditions:
53 a) all the references must differ in indices only, and the indices
54 must all have the same step
55 b) the references must dominate loop latch (and thus, they must be
56 ordered by dominance relation).
57 c) the distance of the indices must be a small multiple of the step
58 We are then able to compute the difference of the references (# of
59 iterations before they point to the same place as the first of them).
60 Also, in case there are writes in the loop, we split the groups into
61 chains whose head is the write whose values are used by the reads in
62 the same chain. The chains are then processed independently,
63 making the further transformations simpler. Also, the shorter chains
64 need the same number of registers, but may require lower unrolling
65 factor in order to get rid of the copies on the loop latch.
67 In our example, we get the following chains (the chain for c is invalid).
69 a[i]{read,+0}, a[i+1]{read,-1}, a[i+2]{write,-2}
70 b[10]{read,+0}, b[10]{write,+0}
71 d[i + 1]{read,+0}, d[i]{write,+1}
73 3) For each read, we determine the read or write whose value it reuses,
74 together with the distance of this reuse. I.e. we take the last
75 reference before it with distance 0, or the last of the references
76 with the smallest positive distance to the read. Then, we remove
77 the references that are not used in any of these chains, discard the
78 empty groups, and propagate all the links so that they point to the
79 single root reference of the chain (adjusting their distance
80 appropriately). Some extra care needs to be taken for references with
81 step 0. In our example (the numbers indicate the distance of the
82 reuse),
84 a[i] --> (*) 2, a[i+1] --> (*) 1, a[i+2] (*)
85 b[10] --> (*) 1, b[10] (*)
87 4) The chains are combined together if possible. If the corresponding
88 elements of two chains are always combined together with the same
89 operator, we remember just the result of this combination, instead
90 of remembering the values separately. We may need to perform
91 reassociation to enable combining, for example
93 e[i] + f[i+1] + e[i+1] + f[i]
95 can be reassociated as
97 (e[i] + f[i]) + (e[i+1] + f[i+1])
99 and we can combine the chains for e and f into one chain.
101 5) For each root reference (end of the chain) R, let N be maximum distance
102 of a reference reusing its value. Variables R0 up to RN are created,
103 together with phi nodes that transfer values from R1 .. RN to
104 R0 .. R(N-1).
105 Initial values are loaded to R0..R(N-1) (in case not all references
106 must necessarily be accessed and they may trap, we may fail here;
107 TODO sometimes, the loads could be guarded by a check for the number
108 of iterations). Values loaded/stored in roots are also copied to
109 RN. Other reads are replaced with the appropriate variable Ri.
110 Everything is put to SSA form.
112 As a small improvement, if R0 is dead after the root (i.e., all uses of
113 the value with the maximum distance dominate the root), we can avoid
114 creating RN and use R0 instead of it.
116 In our example, we get (only the parts concerning a and b are shown):
117 for (i = 0; i < 100; i++)
119 f = phi (a[0], s);
120 s = phi (a[1], f);
121 x = phi (b[10], x);
123 f = f + s;
124 a[i+2] = f;
125 x = x + i;
126 b[10] = x;
129 6) Factor F for unrolling is determined as the smallest common multiple of
130 (N + 1) for each root reference (N for references for that we avoided
131 creating RN). If F and the loop is small enough, loop is unrolled F
132 times. The stores to RN (R0) in the copies of the loop body are
133 periodically replaced with R0, R1, ... (R1, R2, ...), so that they can
134 be coalesced and the copies can be eliminated.
136 TODO -- copy propagation and other optimizations may change the live
137 ranges of the temporary registers and prevent them from being coalesced;
138 this may increase the register pressure.
140 In our case, F = 2 and the (main loop of the) result is
142 for (i = 0; i < ...; i += 2)
144 f = phi (a[0], f);
145 s = phi (a[1], s);
146 x = phi (b[10], x);
148 f = f + s;
149 a[i+2] = f;
150 x = x + i;
151 b[10] = x;
153 s = s + f;
154 a[i+3] = s;
155 x = x + i;
156 b[10] = x;
159 Apart from predictive commoning on Load-Load and Store-Load chains, we
160 also support Store-Store chains -- stores killed by other store can be
161 eliminated. Given below example:
163 for (i = 0; i < n; i++)
165 a[i] = 1;
166 a[i+2] = 2;
169 It can be replaced with:
171 t0 = a[0];
172 t1 = a[1];
173 for (i = 0; i < n; i++)
175 a[i] = 1;
176 t2 = 2;
177 t0 = t1;
178 t1 = t2;
180 a[n] = t0;
181 a[n+1] = t1;
183 If the loop runs more than 1 iterations, it can be further simplified into:
185 for (i = 0; i < n; i++)
187 a[i] = 1;
189 a[n] = 2;
190 a[n+1] = 2;
192 The interesting part is this can be viewed either as general store motion
193 or general dead store elimination in either intra/inter-iterations way.
195 With trivial effort, we also support load inside Store-Store chains if the
196 load is dominated by a store statement in the same iteration of loop. You
197 can see this as a restricted Store-Mixed-Load-Store chain.
199 TODO: For now, we don't support store-store chains in multi-exit loops. We
200 force to not unroll in case of store-store chain even if other chains might
201 ask for unroll.
203 Predictive commoning can be generalized for arbitrary computations (not
204 just memory loads), and also nontrivial transfer functions (e.g., replacing
205 i * i with ii_last + 2 * i + 1), to generalize strength reduction. */
207 #include "config.h"
208 #include "system.h"
209 #include "coretypes.h"
210 #include "backend.h"
211 #include "rtl.h"
212 #include "tree.h"
213 #include "gimple.h"
214 #include "predict.h"
215 #include "tree-pass.h"
216 #include "ssa.h"
217 #include "gimple-pretty-print.h"
218 #include "alias.h"
219 #include "fold-const.h"
220 #include "cfgloop.h"
221 #include "tree-eh.h"
222 #include "gimplify.h"
223 #include "gimple-iterator.h"
224 #include "gimplify-me.h"
225 #include "tree-ssa-loop-ivopts.h"
226 #include "tree-ssa-loop-manip.h"
227 #include "tree-ssa-loop-niter.h"
228 #include "tree-ssa-loop.h"
229 #include "tree-into-ssa.h"
230 #include "tree-dfa.h"
231 #include "tree-ssa.h"
232 #include "tree-data-ref.h"
233 #include "tree-scalar-evolution.h"
234 #include "tree-affine.h"
235 #include "builtins.h"
237 /* The maximum number of iterations between the considered memory
238 references. */
240 #define MAX_DISTANCE (target_avail_regs < 16 ? 4 : 8)
242 /* Data references (or phi nodes that carry data reference values across
243 loop iterations). */
245 typedef class dref_d
247 public:
248 /* The reference itself. */
249 struct data_reference *ref;
251 /* The statement in that the reference appears. */
252 gimple *stmt;
254 /* In case that STMT is a phi node, this field is set to the SSA name
255 defined by it in replace_phis_by_defined_names (in order to avoid
256 pointing to phi node that got reallocated in the meantime). */
257 tree name_defined_by_phi;
259 /* Distance of the reference from the root of the chain (in number of
260 iterations of the loop). */
261 unsigned distance;
263 /* Number of iterations offset from the first reference in the component. */
264 widest_int offset;
266 /* Number of the reference in a component, in dominance ordering. */
267 unsigned pos;
269 /* True if the memory reference is always accessed when the loop is
270 entered. */
271 unsigned always_accessed : 1;
272 } *dref;
275 /* Type of the chain of the references. */
277 enum chain_type
279 /* The addresses of the references in the chain are constant. */
280 CT_INVARIANT,
282 /* There are only loads in the chain. */
283 CT_LOAD,
285 /* Root of the chain is store, the rest are loads. */
286 CT_STORE_LOAD,
288 /* There are only stores in the chain. */
289 CT_STORE_STORE,
291 /* A combination of two chains. */
292 CT_COMBINATION
295 /* Chains of data references. */
297 typedef struct chain
299 /* Type of the chain. */
300 enum chain_type type;
302 /* For combination chains, the operator and the two chains that are
303 combined, and the type of the result. */
304 enum tree_code op;
305 tree rslt_type;
306 struct chain *ch1, *ch2;
308 /* The references in the chain. */
309 vec<dref> refs;
311 /* The maximum distance of the reference in the chain from the root. */
312 unsigned length;
314 /* The variables used to copy the value throughout iterations. */
315 vec<tree> vars;
317 /* Initializers for the variables. */
318 vec<tree> inits;
320 /* Finalizers for the eliminated stores. */
321 vec<tree> finis;
323 /* gimple stmts intializing the initial variables of the chain. */
324 gimple_seq init_seq;
326 /* gimple stmts finalizing the eliminated stores of the chain. */
327 gimple_seq fini_seq;
329 /* True if there is a use of a variable with the maximal distance
330 that comes after the root in the loop. */
331 unsigned has_max_use_after : 1;
333 /* True if all the memory references in the chain are always accessed. */
334 unsigned all_always_accessed : 1;
336 /* True if this chain was combined together with some other chain. */
337 unsigned combined : 1;
339 /* True if this is store elimination chain and eliminated stores store
340 loop invariant value into memory. */
341 unsigned inv_store_elimination : 1;
342 } *chain_p;
345 /* Describes the knowledge about the step of the memory references in
346 the component. */
348 enum ref_step_type
350 /* The step is zero. */
351 RS_INVARIANT,
353 /* The step is nonzero. */
354 RS_NONZERO,
356 /* The step may or may not be nonzero. */
357 RS_ANY
360 /* Components of the data dependence graph. */
362 struct component
364 /* The references in the component. */
365 vec<dref> refs;
367 /* What we know about the step of the references in the component. */
368 enum ref_step_type comp_step;
370 /* True if all references in component are stores and we try to do
371 intra/inter loop iteration dead store elimination. */
372 bool eliminate_store_p;
374 /* Next component in the list. */
375 struct component *next;
378 /* Bitmap of ssa names defined by looparound phi nodes covered by chains. */
380 static bitmap looparound_phis;
382 /* Cache used by tree_to_aff_combination_expand. */
384 static hash_map<tree, name_expansion *> *name_expansions;
386 /* Dumps data reference REF to FILE. */
388 extern void dump_dref (FILE *, dref);
389 void
390 dump_dref (FILE *file, dref ref)
392 if (ref->ref)
394 fprintf (file, " ");
395 print_generic_expr (file, DR_REF (ref->ref), TDF_SLIM);
396 fprintf (file, " (id %u%s)\n", ref->pos,
397 DR_IS_READ (ref->ref) ? "" : ", write");
399 fprintf (file, " offset ");
400 print_decs (ref->offset, file);
401 fprintf (file, "\n");
403 fprintf (file, " distance %u\n", ref->distance);
405 else
407 if (gimple_code (ref->stmt) == GIMPLE_PHI)
408 fprintf (file, " looparound ref\n");
409 else
410 fprintf (file, " combination ref\n");
411 fprintf (file, " in statement ");
412 print_gimple_stmt (file, ref->stmt, 0, TDF_SLIM);
413 fprintf (file, "\n");
414 fprintf (file, " distance %u\n", ref->distance);
419 /* Dumps CHAIN to FILE. */
421 extern void dump_chain (FILE *, chain_p);
422 void
423 dump_chain (FILE *file, chain_p chain)
425 dref a;
426 const char *chain_type;
427 unsigned i;
428 tree var;
430 switch (chain->type)
432 case CT_INVARIANT:
433 chain_type = "Load motion";
434 break;
436 case CT_LOAD:
437 chain_type = "Loads-only";
438 break;
440 case CT_STORE_LOAD:
441 chain_type = "Store-loads";
442 break;
444 case CT_STORE_STORE:
445 chain_type = "Store-stores";
446 break;
448 case CT_COMBINATION:
449 chain_type = "Combination";
450 break;
452 default:
453 gcc_unreachable ();
456 fprintf (file, "%s chain %p%s\n", chain_type, (void *) chain,
457 chain->combined ? " (combined)" : "");
458 if (chain->type != CT_INVARIANT)
459 fprintf (file, " max distance %u%s\n", chain->length,
460 chain->has_max_use_after ? "" : ", may reuse first");
462 if (chain->type == CT_COMBINATION)
464 fprintf (file, " equal to %p %s %p in type ",
465 (void *) chain->ch1, op_symbol_code (chain->op),
466 (void *) chain->ch2);
467 print_generic_expr (file, chain->rslt_type, TDF_SLIM);
468 fprintf (file, "\n");
471 if (chain->vars.exists ())
473 fprintf (file, " vars");
474 FOR_EACH_VEC_ELT (chain->vars, i, var)
476 fprintf (file, " ");
477 print_generic_expr (file, var, TDF_SLIM);
479 fprintf (file, "\n");
482 if (chain->inits.exists ())
484 fprintf (file, " inits");
485 FOR_EACH_VEC_ELT (chain->inits, i, var)
487 fprintf (file, " ");
488 print_generic_expr (file, var, TDF_SLIM);
490 fprintf (file, "\n");
493 fprintf (file, " references:\n");
494 FOR_EACH_VEC_ELT (chain->refs, i, a)
495 dump_dref (file, a);
497 fprintf (file, "\n");
500 /* Dumps CHAINS to FILE. */
502 extern void dump_chains (FILE *, vec<chain_p> );
503 void
504 dump_chains (FILE *file, vec<chain_p> chains)
506 chain_p chain;
507 unsigned i;
509 FOR_EACH_VEC_ELT (chains, i, chain)
510 dump_chain (file, chain);
513 /* Dumps COMP to FILE. */
515 extern void dump_component (FILE *, struct component *);
516 void
517 dump_component (FILE *file, struct component *comp)
519 dref a;
520 unsigned i;
522 fprintf (file, "Component%s:\n",
523 comp->comp_step == RS_INVARIANT ? " (invariant)" : "");
524 FOR_EACH_VEC_ELT (comp->refs, i, a)
525 dump_dref (file, a);
526 fprintf (file, "\n");
529 /* Dumps COMPS to FILE. */
531 extern void dump_components (FILE *, struct component *);
532 void
533 dump_components (FILE *file, struct component *comps)
535 struct component *comp;
537 for (comp = comps; comp; comp = comp->next)
538 dump_component (file, comp);
541 /* Frees a chain CHAIN. */
543 static void
544 release_chain (chain_p chain)
546 dref ref;
547 unsigned i;
549 if (chain == NULL)
550 return;
552 FOR_EACH_VEC_ELT (chain->refs, i, ref)
553 free (ref);
555 chain->refs.release ();
556 chain->vars.release ();
557 chain->inits.release ();
558 if (chain->init_seq)
559 gimple_seq_discard (chain->init_seq);
561 chain->finis.release ();
562 if (chain->fini_seq)
563 gimple_seq_discard (chain->fini_seq);
565 free (chain);
568 /* Frees CHAINS. */
570 static void
571 release_chains (vec<chain_p> chains)
573 unsigned i;
574 chain_p chain;
576 FOR_EACH_VEC_ELT (chains, i, chain)
577 release_chain (chain);
578 chains.release ();
581 /* Frees a component COMP. */
583 static void
584 release_component (struct component *comp)
586 comp->refs.release ();
587 free (comp);
590 /* Frees list of components COMPS. */
592 static void
593 release_components (struct component *comps)
595 struct component *act, *next;
597 for (act = comps; act; act = next)
599 next = act->next;
600 release_component (act);
604 /* Finds a root of tree given by FATHERS containing A, and performs path
605 shortening. */
607 static unsigned
608 component_of (unsigned fathers[], unsigned a)
610 unsigned root, n;
612 for (root = a; root != fathers[root]; root = fathers[root])
613 continue;
615 for (; a != root; a = n)
617 n = fathers[a];
618 fathers[a] = root;
621 return root;
624 /* Join operation for DFU. FATHERS gives the tree, SIZES are sizes of the
625 components, A and B are components to merge. */
627 static void
628 merge_comps (unsigned fathers[], unsigned sizes[], unsigned a, unsigned b)
630 unsigned ca = component_of (fathers, a);
631 unsigned cb = component_of (fathers, b);
633 if (ca == cb)
634 return;
636 if (sizes[ca] < sizes[cb])
638 sizes[cb] += sizes[ca];
639 fathers[ca] = cb;
641 else
643 sizes[ca] += sizes[cb];
644 fathers[cb] = ca;
648 /* Returns true if A is a reference that is suitable for predictive commoning
649 in the innermost loop that contains it. REF_STEP is set according to the
650 step of the reference A. */
652 static bool
653 suitable_reference_p (struct data_reference *a, enum ref_step_type *ref_step)
655 tree ref = DR_REF (a), step = DR_STEP (a);
657 if (!step
658 || TREE_THIS_VOLATILE (ref)
659 || !is_gimple_reg_type (TREE_TYPE (ref))
660 || tree_could_throw_p (ref))
661 return false;
663 if (integer_zerop (step))
664 *ref_step = RS_INVARIANT;
665 else if (integer_nonzerop (step))
666 *ref_step = RS_NONZERO;
667 else
668 *ref_step = RS_ANY;
670 return true;
673 /* Stores DR_OFFSET (DR) + DR_INIT (DR) to OFFSET. */
675 static void
676 aff_combination_dr_offset (struct data_reference *dr, aff_tree *offset)
678 tree type = TREE_TYPE (DR_OFFSET (dr));
679 aff_tree delta;
681 tree_to_aff_combination_expand (DR_OFFSET (dr), type, offset,
682 &name_expansions);
683 aff_combination_const (&delta, type, wi::to_poly_widest (DR_INIT (dr)));
684 aff_combination_add (offset, &delta);
687 /* Determines number of iterations of the innermost enclosing loop before B
688 refers to exactly the same location as A and stores it to OFF. If A and
689 B do not have the same step, they never meet, or anything else fails,
690 returns false, otherwise returns true. Both A and B are assumed to
691 satisfy suitable_reference_p. */
693 static bool
694 determine_offset (struct data_reference *a, struct data_reference *b,
695 poly_widest_int *off)
697 aff_tree diff, baseb, step;
698 tree typea, typeb;
700 /* Check that both the references access the location in the same type. */
701 typea = TREE_TYPE (DR_REF (a));
702 typeb = TREE_TYPE (DR_REF (b));
703 if (!useless_type_conversion_p (typeb, typea))
704 return false;
706 /* Check whether the base address and the step of both references is the
707 same. */
708 if (!operand_equal_p (DR_STEP (a), DR_STEP (b), 0)
709 || !operand_equal_p (DR_BASE_ADDRESS (a), DR_BASE_ADDRESS (b), 0))
710 return false;
712 if (integer_zerop (DR_STEP (a)))
714 /* If the references have loop invariant address, check that they access
715 exactly the same location. */
716 *off = 0;
717 return (operand_equal_p (DR_OFFSET (a), DR_OFFSET (b), 0)
718 && operand_equal_p (DR_INIT (a), DR_INIT (b), 0));
721 /* Compare the offsets of the addresses, and check whether the difference
722 is a multiple of step. */
723 aff_combination_dr_offset (a, &diff);
724 aff_combination_dr_offset (b, &baseb);
725 aff_combination_scale (&baseb, -1);
726 aff_combination_add (&diff, &baseb);
728 tree_to_aff_combination_expand (DR_STEP (a), TREE_TYPE (DR_STEP (a)),
729 &step, &name_expansions);
730 return aff_combination_constant_multiple_p (&diff, &step, off);
733 /* Returns the last basic block in LOOP for that we are sure that
734 it is executed whenever the loop is entered. */
736 static basic_block
737 last_always_executed_block (class loop *loop)
739 unsigned i;
740 vec<edge> exits = get_loop_exit_edges (loop);
741 edge ex;
742 basic_block last = loop->latch;
744 FOR_EACH_VEC_ELT (exits, i, ex)
745 last = nearest_common_dominator (CDI_DOMINATORS, last, ex->src);
746 exits.release ();
748 return last;
751 /* Splits dependence graph on DATAREFS described by DEPENDS to components. */
753 static struct component *
754 split_data_refs_to_components (class loop *loop,
755 vec<data_reference_p> datarefs,
756 vec<ddr_p> depends)
758 unsigned i, n = datarefs.length ();
759 unsigned ca, ia, ib, bad;
760 unsigned *comp_father = XNEWVEC (unsigned, n + 1);
761 unsigned *comp_size = XNEWVEC (unsigned, n + 1);
762 struct component **comps;
763 struct data_reference *dr, *dra, *drb;
764 struct data_dependence_relation *ddr;
765 struct component *comp_list = NULL, *comp;
766 dref dataref;
767 /* Don't do store elimination if loop has multiple exit edges. */
768 bool eliminate_store_p = single_exit (loop) != NULL;
769 basic_block last_always_executed = last_always_executed_block (loop);
770 auto_bitmap no_store_store_comps;
772 FOR_EACH_VEC_ELT (datarefs, i, dr)
774 if (!DR_REF (dr))
776 /* A fake reference for call or asm_expr that may clobber memory;
777 just fail. */
778 goto end;
780 /* predcom pass isn't prepared to handle calls with data references. */
781 if (is_gimple_call (DR_STMT (dr)))
782 goto end;
783 dr->aux = (void *) (size_t) i;
784 comp_father[i] = i;
785 comp_size[i] = 1;
788 /* A component reserved for the "bad" data references. */
789 comp_father[n] = n;
790 comp_size[n] = 1;
792 FOR_EACH_VEC_ELT (datarefs, i, dr)
794 enum ref_step_type dummy;
796 if (!suitable_reference_p (dr, &dummy))
798 ia = (unsigned) (size_t) dr->aux;
799 merge_comps (comp_father, comp_size, n, ia);
803 FOR_EACH_VEC_ELT (depends, i, ddr)
805 poly_widest_int dummy_off;
807 if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
808 continue;
810 dra = DDR_A (ddr);
811 drb = DDR_B (ddr);
813 /* Don't do store elimination if there is any unknown dependence for
814 any store data reference. */
815 if ((DR_IS_WRITE (dra) || DR_IS_WRITE (drb))
816 && (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know
817 || DDR_NUM_DIST_VECTS (ddr) == 0))
818 eliminate_store_p = false;
820 ia = component_of (comp_father, (unsigned) (size_t) dra->aux);
821 ib = component_of (comp_father, (unsigned) (size_t) drb->aux);
822 if (ia == ib)
823 continue;
825 bad = component_of (comp_father, n);
827 /* If both A and B are reads, we may ignore unsuitable dependences. */
828 if (DR_IS_READ (dra) && DR_IS_READ (drb))
830 if (ia == bad || ib == bad
831 || !determine_offset (dra, drb, &dummy_off))
832 continue;
834 /* If A is read and B write or vice versa and there is unsuitable
835 dependence, instead of merging both components into a component
836 that will certainly not pass suitable_component_p, just put the
837 read into bad component, perhaps at least the write together with
838 all the other data refs in it's component will be optimizable. */
839 else if (DR_IS_READ (dra) && ib != bad)
841 if (ia == bad)
843 bitmap_set_bit (no_store_store_comps, ib);
844 continue;
846 else if (!determine_offset (dra, drb, &dummy_off))
848 bitmap_set_bit (no_store_store_comps, ib);
849 merge_comps (comp_father, comp_size, bad, ia);
850 continue;
853 else if (DR_IS_READ (drb) && ia != bad)
855 if (ib == bad)
857 bitmap_set_bit (no_store_store_comps, ia);
858 continue;
860 else if (!determine_offset (dra, drb, &dummy_off))
862 bitmap_set_bit (no_store_store_comps, ia);
863 merge_comps (comp_father, comp_size, bad, ib);
864 continue;
867 else if (DR_IS_WRITE (dra) && DR_IS_WRITE (drb)
868 && ia != bad && ib != bad
869 && !determine_offset (dra, drb, &dummy_off))
871 merge_comps (comp_father, comp_size, bad, ia);
872 merge_comps (comp_father, comp_size, bad, ib);
873 continue;
876 merge_comps (comp_father, comp_size, ia, ib);
879 if (eliminate_store_p)
881 tree niters = number_of_latch_executions (loop);
883 /* Don't do store elimination if niters info is unknown because stores
884 in the last iteration can't be eliminated and we need to recover it
885 after loop. */
886 eliminate_store_p = (niters != NULL_TREE && niters != chrec_dont_know);
889 comps = XCNEWVEC (struct component *, n);
890 bad = component_of (comp_father, n);
891 FOR_EACH_VEC_ELT (datarefs, i, dr)
893 ia = (unsigned) (size_t) dr->aux;
894 ca = component_of (comp_father, ia);
895 if (ca == bad)
896 continue;
898 comp = comps[ca];
899 if (!comp)
901 comp = XCNEW (struct component);
902 comp->refs.create (comp_size[ca]);
903 comp->eliminate_store_p = eliminate_store_p;
904 comps[ca] = comp;
907 dataref = XCNEW (class dref_d);
908 dataref->ref = dr;
909 dataref->stmt = DR_STMT (dr);
910 dataref->offset = 0;
911 dataref->distance = 0;
913 dataref->always_accessed
914 = dominated_by_p (CDI_DOMINATORS, last_always_executed,
915 gimple_bb (dataref->stmt));
916 dataref->pos = comp->refs.length ();
917 comp->refs.quick_push (dataref);
920 if (eliminate_store_p)
922 bitmap_iterator bi;
923 EXECUTE_IF_SET_IN_BITMAP (no_store_store_comps, 0, ia, bi)
925 ca = component_of (comp_father, ia);
926 if (ca != bad)
927 comps[ca]->eliminate_store_p = false;
931 for (i = 0; i < n; i++)
933 comp = comps[i];
934 if (comp)
936 comp->next = comp_list;
937 comp_list = comp;
940 free (comps);
942 end:
943 free (comp_father);
944 free (comp_size);
945 return comp_list;
948 /* Returns true if the component COMP satisfies the conditions
949 described in 2) at the beginning of this file. LOOP is the current
950 loop. */
952 static bool
953 suitable_component_p (class loop *loop, struct component *comp)
955 unsigned i;
956 dref a, first;
957 basic_block ba, bp = loop->header;
958 bool ok, has_write = false;
960 FOR_EACH_VEC_ELT (comp->refs, i, a)
962 ba = gimple_bb (a->stmt);
964 if (!just_once_each_iteration_p (loop, ba))
965 return false;
967 gcc_assert (dominated_by_p (CDI_DOMINATORS, ba, bp));
968 bp = ba;
970 if (DR_IS_WRITE (a->ref))
971 has_write = true;
974 first = comp->refs[0];
975 ok = suitable_reference_p (first->ref, &comp->comp_step);
976 gcc_assert (ok);
977 first->offset = 0;
979 for (i = 1; comp->refs.iterate (i, &a); i++)
981 /* Polynomial offsets are no use, since we need to know the
982 gap between iteration numbers at compile time. */
983 poly_widest_int offset;
984 if (!determine_offset (first->ref, a->ref, &offset)
985 || !offset.is_constant (&a->offset))
986 return false;
988 enum ref_step_type a_step;
989 gcc_checking_assert (suitable_reference_p (a->ref, &a_step)
990 && a_step == comp->comp_step);
993 /* If there is a write inside the component, we must know whether the
994 step is nonzero or not -- we would not otherwise be able to recognize
995 whether the value accessed by reads comes from the OFFSET-th iteration
996 or the previous one. */
997 if (has_write && comp->comp_step == RS_ANY)
998 return false;
1000 return true;
1003 /* Check the conditions on references inside each of components COMPS,
1004 and remove the unsuitable components from the list. The new list
1005 of components is returned. The conditions are described in 2) at
1006 the beginning of this file. LOOP is the current loop. */
1008 static struct component *
1009 filter_suitable_components (class loop *loop, struct component *comps)
1011 struct component **comp, *act;
1013 for (comp = &comps; *comp; )
1015 act = *comp;
1016 if (suitable_component_p (loop, act))
1017 comp = &act->next;
1018 else
1020 dref ref;
1021 unsigned i;
1023 *comp = act->next;
1024 FOR_EACH_VEC_ELT (act->refs, i, ref)
1025 free (ref);
1026 release_component (act);
1030 return comps;
1033 /* Compares two drefs A and B by their offset and position. Callback for
1034 qsort. */
1036 static int
1037 order_drefs (const void *a, const void *b)
1039 const dref *const da = (const dref *) a;
1040 const dref *const db = (const dref *) b;
1041 int offcmp = wi::cmps ((*da)->offset, (*db)->offset);
1043 if (offcmp != 0)
1044 return offcmp;
1046 return (*da)->pos - (*db)->pos;
1049 /* Compares two drefs A and B by their position. Callback for qsort. */
1051 static int
1052 order_drefs_by_pos (const void *a, const void *b)
1054 const dref *const da = (const dref *) a;
1055 const dref *const db = (const dref *) b;
1057 return (*da)->pos - (*db)->pos;
1060 /* Returns root of the CHAIN. */
1062 static inline dref
1063 get_chain_root (chain_p chain)
1065 return chain->refs[0];
1068 /* Given CHAIN, returns the last write ref at DISTANCE, or NULL if it doesn't
1069 exist. */
1071 static inline dref
1072 get_chain_last_write_at (chain_p chain, unsigned distance)
1074 for (unsigned i = chain->refs.length (); i > 0; i--)
1075 if (DR_IS_WRITE (chain->refs[i - 1]->ref)
1076 && distance == chain->refs[i - 1]->distance)
1077 return chain->refs[i - 1];
1079 return NULL;
1082 /* Given CHAIN, returns the last write ref with the same distance before load
1083 at index LOAD_IDX, or NULL if it doesn't exist. */
1085 static inline dref
1086 get_chain_last_write_before_load (chain_p chain, unsigned load_idx)
1088 gcc_assert (load_idx < chain->refs.length ());
1090 unsigned distance = chain->refs[load_idx]->distance;
1092 for (unsigned i = load_idx; i > 0; i--)
1093 if (DR_IS_WRITE (chain->refs[i - 1]->ref)
1094 && distance == chain->refs[i - 1]->distance)
1095 return chain->refs[i - 1];
1097 return NULL;
1100 /* Adds REF to the chain CHAIN. */
1102 static void
1103 add_ref_to_chain (chain_p chain, dref ref)
1105 dref root = get_chain_root (chain);
1107 gcc_assert (wi::les_p (root->offset, ref->offset));
1108 widest_int dist = ref->offset - root->offset;
1109 gcc_assert (wi::fits_uhwi_p (dist));
1111 chain->refs.safe_push (ref);
1113 ref->distance = dist.to_uhwi ();
1115 if (ref->distance >= chain->length)
1117 chain->length = ref->distance;
1118 chain->has_max_use_after = false;
1121 /* Promote this chain to CT_STORE_STORE if it has multiple stores. */
1122 if (DR_IS_WRITE (ref->ref))
1123 chain->type = CT_STORE_STORE;
1125 /* Don't set the flag for store-store chain since there is no use. */
1126 if (chain->type != CT_STORE_STORE
1127 && ref->distance == chain->length
1128 && ref->pos > root->pos)
1129 chain->has_max_use_after = true;
1131 chain->all_always_accessed &= ref->always_accessed;
1134 /* Returns the chain for invariant component COMP. */
1136 static chain_p
1137 make_invariant_chain (struct component *comp)
1139 chain_p chain = XCNEW (struct chain);
1140 unsigned i;
1141 dref ref;
1143 chain->type = CT_INVARIANT;
1145 chain->all_always_accessed = true;
1147 FOR_EACH_VEC_ELT (comp->refs, i, ref)
1149 chain->refs.safe_push (ref);
1150 chain->all_always_accessed &= ref->always_accessed;
1153 chain->inits = vNULL;
1154 chain->finis = vNULL;
1156 return chain;
1159 /* Make a new chain of type TYPE rooted at REF. */
1161 static chain_p
1162 make_rooted_chain (dref ref, enum chain_type type)
1164 chain_p chain = XCNEW (struct chain);
1166 chain->type = type;
1167 chain->refs.safe_push (ref);
1168 chain->all_always_accessed = ref->always_accessed;
1169 ref->distance = 0;
1171 chain->inits = vNULL;
1172 chain->finis = vNULL;
1174 return chain;
1177 /* Returns true if CHAIN is not trivial. */
1179 static bool
1180 nontrivial_chain_p (chain_p chain)
1182 return chain != NULL && chain->refs.length () > 1;
1185 /* Returns the ssa name that contains the value of REF, or NULL_TREE if there
1186 is no such name. */
1188 static tree
1189 name_for_ref (dref ref)
1191 tree name;
1193 if (is_gimple_assign (ref->stmt))
1195 if (!ref->ref || DR_IS_READ (ref->ref))
1196 name = gimple_assign_lhs (ref->stmt);
1197 else
1198 name = gimple_assign_rhs1 (ref->stmt);
1200 else
1201 name = PHI_RESULT (ref->stmt);
1203 return (TREE_CODE (name) == SSA_NAME ? name : NULL_TREE);
1206 /* Returns true if REF is a valid initializer for ROOT with given DISTANCE (in
1207 iterations of the innermost enclosing loop). */
1209 static bool
1210 valid_initializer_p (struct data_reference *ref,
1211 unsigned distance, struct data_reference *root)
1213 aff_tree diff, base, step;
1214 poly_widest_int off;
1216 /* Both REF and ROOT must be accessing the same object. */
1217 if (!operand_equal_p (DR_BASE_ADDRESS (ref), DR_BASE_ADDRESS (root), 0))
1218 return false;
1220 /* The initializer is defined outside of loop, hence its address must be
1221 invariant inside the loop. */
1222 gcc_assert (integer_zerop (DR_STEP (ref)));
1224 /* If the address of the reference is invariant, initializer must access
1225 exactly the same location. */
1226 if (integer_zerop (DR_STEP (root)))
1227 return (operand_equal_p (DR_OFFSET (ref), DR_OFFSET (root), 0)
1228 && operand_equal_p (DR_INIT (ref), DR_INIT (root), 0));
1230 /* Verify that this index of REF is equal to the root's index at
1231 -DISTANCE-th iteration. */
1232 aff_combination_dr_offset (root, &diff);
1233 aff_combination_dr_offset (ref, &base);
1234 aff_combination_scale (&base, -1);
1235 aff_combination_add (&diff, &base);
1237 tree_to_aff_combination_expand (DR_STEP (root), TREE_TYPE (DR_STEP (root)),
1238 &step, &name_expansions);
1239 if (!aff_combination_constant_multiple_p (&diff, &step, &off))
1240 return false;
1242 if (maybe_ne (off, distance))
1243 return false;
1245 return true;
1248 /* Finds looparound phi node of LOOP that copies the value of REF, and if its
1249 initial value is correct (equal to initial value of REF shifted by one
1250 iteration), returns the phi node. Otherwise, NULL_TREE is returned. ROOT
1251 is the root of the current chain. */
1253 static gphi *
1254 find_looparound_phi (class loop *loop, dref ref, dref root)
1256 tree name, init, init_ref;
1257 gphi *phi = NULL;
1258 gimple *init_stmt;
1259 edge latch = loop_latch_edge (loop);
1260 struct data_reference init_dr;
1261 gphi_iterator psi;
1263 if (is_gimple_assign (ref->stmt))
1265 if (DR_IS_READ (ref->ref))
1266 name = gimple_assign_lhs (ref->stmt);
1267 else
1268 name = gimple_assign_rhs1 (ref->stmt);
1270 else
1271 name = PHI_RESULT (ref->stmt);
1272 if (!name)
1273 return NULL;
1275 for (psi = gsi_start_phis (loop->header); !gsi_end_p (psi); gsi_next (&psi))
1277 phi = psi.phi ();
1278 if (PHI_ARG_DEF_FROM_EDGE (phi, latch) == name)
1279 break;
1282 if (gsi_end_p (psi))
1283 return NULL;
1285 init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
1286 if (TREE_CODE (init) != SSA_NAME)
1287 return NULL;
1288 init_stmt = SSA_NAME_DEF_STMT (init);
1289 if (gimple_code (init_stmt) != GIMPLE_ASSIGN)
1290 return NULL;
1291 gcc_assert (gimple_assign_lhs (init_stmt) == init);
1293 init_ref = gimple_assign_rhs1 (init_stmt);
1294 if (!REFERENCE_CLASS_P (init_ref)
1295 && !DECL_P (init_ref))
1296 return NULL;
1298 /* Analyze the behavior of INIT_REF with respect to LOOP (innermost
1299 loop enclosing PHI). */
1300 memset (&init_dr, 0, sizeof (struct data_reference));
1301 DR_REF (&init_dr) = init_ref;
1302 DR_STMT (&init_dr) = phi;
1303 if (!dr_analyze_innermost (&DR_INNERMOST (&init_dr), init_ref, loop,
1304 init_stmt))
1305 return NULL;
1307 if (!valid_initializer_p (&init_dr, ref->distance + 1, root->ref))
1308 return NULL;
1310 return phi;
1313 /* Adds a reference for the looparound copy of REF in PHI to CHAIN. */
1315 static void
1316 insert_looparound_copy (chain_p chain, dref ref, gphi *phi)
1318 dref nw = XCNEW (class dref_d), aref;
1319 unsigned i;
1321 nw->stmt = phi;
1322 nw->distance = ref->distance + 1;
1323 nw->always_accessed = 1;
1325 FOR_EACH_VEC_ELT (chain->refs, i, aref)
1326 if (aref->distance >= nw->distance)
1327 break;
1328 chain->refs.safe_insert (i, nw);
1330 if (nw->distance > chain->length)
1332 chain->length = nw->distance;
1333 chain->has_max_use_after = false;
1337 /* For references in CHAIN that are copied around the LOOP (created previously
1338 by PRE, or by user), add the results of such copies to the chain. This
1339 enables us to remove the copies by unrolling, and may need less registers
1340 (also, it may allow us to combine chains together). */
1342 static void
1343 add_looparound_copies (class loop *loop, chain_p chain)
1345 unsigned i;
1346 dref ref, root = get_chain_root (chain);
1347 gphi *phi;
1349 if (chain->type == CT_STORE_STORE)
1350 return;
1352 FOR_EACH_VEC_ELT (chain->refs, i, ref)
1354 phi = find_looparound_phi (loop, ref, root);
1355 if (!phi)
1356 continue;
1358 bitmap_set_bit (looparound_phis, SSA_NAME_VERSION (PHI_RESULT (phi)));
1359 insert_looparound_copy (chain, ref, phi);
1363 /* Find roots of the values and determine distances in the component COMP.
1364 The references are redistributed into CHAINS. LOOP is the current
1365 loop. */
1367 static void
1368 determine_roots_comp (class loop *loop,
1369 struct component *comp,
1370 vec<chain_p> *chains)
1372 unsigned i;
1373 dref a;
1374 chain_p chain = NULL;
1375 widest_int last_ofs = 0;
1376 enum chain_type type;
1378 /* Invariants are handled specially. */
1379 if (comp->comp_step == RS_INVARIANT)
1381 chain = make_invariant_chain (comp);
1382 chains->safe_push (chain);
1383 return;
1386 /* Trivial component. */
1387 if (comp->refs.length () <= 1)
1389 if (comp->refs.length () == 1)
1391 free (comp->refs[0]);
1392 comp->refs.truncate (0);
1394 return;
1397 comp->refs.qsort (order_drefs);
1399 /* For Store-Store chain, we only support load if it is dominated by a
1400 store statement in the same iteration of loop. */
1401 if (comp->eliminate_store_p)
1402 for (a = NULL, i = 0; i < comp->refs.length (); i++)
1404 if (DR_IS_WRITE (comp->refs[i]->ref))
1405 a = comp->refs[i];
1406 else if (a == NULL || a->offset != comp->refs[i]->offset)
1408 /* If there is load that is not dominated by a store in the
1409 same iteration of loop, clear the flag so no Store-Store
1410 chain is generated for this component. */
1411 comp->eliminate_store_p = false;
1412 break;
1416 /* Determine roots and create chains for components. */
1417 FOR_EACH_VEC_ELT (comp->refs, i, a)
1419 if (!chain
1420 || (chain->type == CT_LOAD && DR_IS_WRITE (a->ref))
1421 || (!comp->eliminate_store_p && DR_IS_WRITE (a->ref))
1422 || wi::leu_p (MAX_DISTANCE, a->offset - last_ofs))
1424 if (nontrivial_chain_p (chain))
1426 add_looparound_copies (loop, chain);
1427 chains->safe_push (chain);
1429 else
1430 release_chain (chain);
1432 /* Determine type of the chain. If the root reference is a load,
1433 this can only be a CT_LOAD chain; other chains are intialized
1434 to CT_STORE_LOAD and might be promoted to CT_STORE_STORE when
1435 new reference is added. */
1436 type = DR_IS_READ (a->ref) ? CT_LOAD : CT_STORE_LOAD;
1437 chain = make_rooted_chain (a, type);
1438 last_ofs = a->offset;
1439 continue;
1442 add_ref_to_chain (chain, a);
1445 if (nontrivial_chain_p (chain))
1447 add_looparound_copies (loop, chain);
1448 chains->safe_push (chain);
1450 else
1451 release_chain (chain);
1454 /* Find roots of the values and determine distances in components COMPS, and
1455 separates the references to CHAINS. LOOP is the current loop. */
1457 static void
1458 determine_roots (class loop *loop,
1459 struct component *comps, vec<chain_p> *chains)
1461 struct component *comp;
1463 for (comp = comps; comp; comp = comp->next)
1464 determine_roots_comp (loop, comp, chains);
1467 /* Replace the reference in statement STMT with temporary variable
1468 NEW_TREE. If SET is true, NEW_TREE is instead initialized to the value of
1469 the reference in the statement. IN_LHS is true if the reference
1470 is in the lhs of STMT, false if it is in rhs. */
1472 static void
1473 replace_ref_with (gimple *stmt, tree new_tree, bool set, bool in_lhs)
1475 tree val;
1476 gassign *new_stmt;
1477 gimple_stmt_iterator bsi, psi;
1479 if (gimple_code (stmt) == GIMPLE_PHI)
1481 gcc_assert (!in_lhs && !set);
1483 val = PHI_RESULT (stmt);
1484 bsi = gsi_after_labels (gimple_bb (stmt));
1485 psi = gsi_for_stmt (stmt);
1486 remove_phi_node (&psi, false);
1488 /* Turn the phi node into GIMPLE_ASSIGN. */
1489 new_stmt = gimple_build_assign (val, new_tree);
1490 gsi_insert_before (&bsi, new_stmt, GSI_NEW_STMT);
1491 return;
1494 /* Since the reference is of gimple_reg type, it should only
1495 appear as lhs or rhs of modify statement. */
1496 gcc_assert (is_gimple_assign (stmt));
1498 bsi = gsi_for_stmt (stmt);
1500 /* If we do not need to initialize NEW_TREE, just replace the use of OLD. */
1501 if (!set)
1503 gcc_assert (!in_lhs);
1504 gimple_assign_set_rhs_from_tree (&bsi, new_tree);
1505 stmt = gsi_stmt (bsi);
1506 update_stmt (stmt);
1507 return;
1510 if (in_lhs)
1512 /* We have statement
1514 OLD = VAL
1516 If OLD is a memory reference, then VAL is gimple_val, and we transform
1517 this to
1519 OLD = VAL
1520 NEW = VAL
1522 Otherwise, we are replacing a combination chain,
1523 VAL is the expression that performs the combination, and OLD is an
1524 SSA name. In this case, we transform the assignment to
1526 OLD = VAL
1527 NEW = OLD
1531 val = gimple_assign_lhs (stmt);
1532 if (TREE_CODE (val) != SSA_NAME)
1534 val = gimple_assign_rhs1 (stmt);
1535 gcc_assert (gimple_assign_single_p (stmt));
1536 if (TREE_CLOBBER_P (val))
1537 val = get_or_create_ssa_default_def (cfun, SSA_NAME_VAR (new_tree));
1538 else
1539 gcc_assert (gimple_assign_copy_p (stmt));
1542 else
1544 /* VAL = OLD
1546 is transformed to
1548 VAL = OLD
1549 NEW = VAL */
1551 val = gimple_assign_lhs (stmt);
1554 new_stmt = gimple_build_assign (new_tree, unshare_expr (val));
1555 gsi_insert_after (&bsi, new_stmt, GSI_NEW_STMT);
1558 /* Returns a memory reference to DR in the (NITERS + ITER)-th iteration
1559 of the loop it was analyzed in. Append init stmts to STMTS. */
1561 static tree
1562 ref_at_iteration (data_reference_p dr, int iter,
1563 gimple_seq *stmts, tree niters = NULL_TREE)
1565 tree off = DR_OFFSET (dr);
1566 tree coff = DR_INIT (dr);
1567 tree ref = DR_REF (dr);
1568 enum tree_code ref_code = ERROR_MARK;
1569 tree ref_type = NULL_TREE;
1570 tree ref_op1 = NULL_TREE;
1571 tree ref_op2 = NULL_TREE;
1572 tree new_offset;
1574 if (iter != 0)
1576 new_offset = size_binop (MULT_EXPR, DR_STEP (dr), ssize_int (iter));
1577 if (TREE_CODE (new_offset) == INTEGER_CST)
1578 coff = size_binop (PLUS_EXPR, coff, new_offset);
1579 else
1580 off = size_binop (PLUS_EXPR, off, new_offset);
1583 if (niters != NULL_TREE)
1585 niters = fold_convert (ssizetype, niters);
1586 new_offset = size_binop (MULT_EXPR, DR_STEP (dr), niters);
1587 if (TREE_CODE (niters) == INTEGER_CST)
1588 coff = size_binop (PLUS_EXPR, coff, new_offset);
1589 else
1590 off = size_binop (PLUS_EXPR, off, new_offset);
1593 /* While data-ref analysis punts on bit offsets it still handles
1594 bitfield accesses at byte boundaries. Cope with that. Note that
1595 if the bitfield object also starts at a byte-boundary we can simply
1596 replicate the COMPONENT_REF, but we have to subtract the component's
1597 byte-offset from the MEM_REF address first.
1598 Otherwise we simply build a BIT_FIELD_REF knowing that the bits
1599 start at offset zero. */
1600 if (TREE_CODE (ref) == COMPONENT_REF
1601 && DECL_BIT_FIELD (TREE_OPERAND (ref, 1)))
1603 unsigned HOST_WIDE_INT boff;
1604 tree field = TREE_OPERAND (ref, 1);
1605 tree offset = component_ref_field_offset (ref);
1606 ref_type = TREE_TYPE (ref);
1607 boff = tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field));
1608 /* This can occur in Ada. See the comment in get_bit_range. */
1609 if (boff % BITS_PER_UNIT != 0
1610 || !tree_fits_uhwi_p (offset))
1612 ref_code = BIT_FIELD_REF;
1613 ref_op1 = DECL_SIZE (field);
1614 ref_op2 = bitsize_zero_node;
1616 else
1618 boff >>= LOG2_BITS_PER_UNIT;
1619 boff += tree_to_uhwi (offset);
1620 coff = size_binop (MINUS_EXPR, coff, ssize_int (boff));
1621 ref_code = COMPONENT_REF;
1622 ref_op1 = field;
1623 ref_op2 = TREE_OPERAND (ref, 2);
1624 ref = TREE_OPERAND (ref, 0);
1627 tree addr = fold_build_pointer_plus (DR_BASE_ADDRESS (dr), off);
1628 addr = force_gimple_operand_1 (unshare_expr (addr), stmts,
1629 is_gimple_mem_ref_addr, NULL_TREE);
1630 tree alias_ptr = fold_convert (reference_alias_ptr_type (ref), coff);
1631 tree type = build_aligned_type (TREE_TYPE (ref),
1632 get_object_alignment (ref));
1633 ref = build2 (MEM_REF, type, addr, alias_ptr);
1634 if (ref_type)
1635 ref = build3 (ref_code, ref_type, ref, ref_op1, ref_op2);
1636 return ref;
1639 /* Get the initialization expression for the INDEX-th temporary variable
1640 of CHAIN. */
1642 static tree
1643 get_init_expr (chain_p chain, unsigned index)
1645 if (chain->type == CT_COMBINATION)
1647 tree e1 = get_init_expr (chain->ch1, index);
1648 tree e2 = get_init_expr (chain->ch2, index);
1650 return fold_build2 (chain->op, chain->rslt_type, e1, e2);
1652 else
1653 return chain->inits[index];
1656 /* Returns a new temporary variable used for the I-th variable carrying
1657 value of REF. The variable's uid is marked in TMP_VARS. */
1659 static tree
1660 predcom_tmp_var (tree ref, unsigned i, bitmap tmp_vars)
1662 tree type = TREE_TYPE (ref);
1663 /* We never access the components of the temporary variable in predictive
1664 commoning. */
1665 tree var = create_tmp_reg (type, get_lsm_tmp_name (ref, i));
1666 bitmap_set_bit (tmp_vars, DECL_UID (var));
1667 return var;
1670 /* Creates the variables for CHAIN, as well as phi nodes for them and
1671 initialization on entry to LOOP. Uids of the newly created
1672 temporary variables are marked in TMP_VARS. */
1674 static void
1675 initialize_root_vars (class loop *loop, chain_p chain, bitmap tmp_vars)
1677 unsigned i;
1678 unsigned n = chain->length;
1679 dref root = get_chain_root (chain);
1680 bool reuse_first = !chain->has_max_use_after;
1681 tree ref, init, var, next;
1682 gphi *phi;
1683 gimple_seq stmts;
1684 edge entry = loop_preheader_edge (loop), latch = loop_latch_edge (loop);
1686 /* If N == 0, then all the references are within the single iteration. And
1687 since this is an nonempty chain, reuse_first cannot be true. */
1688 gcc_assert (n > 0 || !reuse_first);
1690 chain->vars.create (n + 1);
1692 if (chain->type == CT_COMBINATION)
1693 ref = gimple_assign_lhs (root->stmt);
1694 else
1695 ref = DR_REF (root->ref);
1697 for (i = 0; i < n + (reuse_first ? 0 : 1); i++)
1699 var = predcom_tmp_var (ref, i, tmp_vars);
1700 chain->vars.quick_push (var);
1702 if (reuse_first)
1703 chain->vars.quick_push (chain->vars[0]);
1705 FOR_EACH_VEC_ELT (chain->vars, i, var)
1706 chain->vars[i] = make_ssa_name (var);
1708 for (i = 0; i < n; i++)
1710 var = chain->vars[i];
1711 next = chain->vars[i + 1];
1712 init = get_init_expr (chain, i);
1714 init = force_gimple_operand (init, &stmts, true, NULL_TREE);
1715 if (stmts)
1716 gsi_insert_seq_on_edge_immediate (entry, stmts);
1718 phi = create_phi_node (var, loop->header);
1719 add_phi_arg (phi, init, entry, UNKNOWN_LOCATION);
1720 add_phi_arg (phi, next, latch, UNKNOWN_LOCATION);
1724 /* For inter-iteration store elimination CHAIN in LOOP, returns true if
1725 all stores to be eliminated store loop invariant values into memory.
1726 In this case, we can use these invariant values directly after LOOP. */
1728 static bool
1729 is_inv_store_elimination_chain (class loop *loop, chain_p chain)
1731 if (chain->length == 0 || chain->type != CT_STORE_STORE)
1732 return false;
1734 gcc_assert (!chain->has_max_use_after);
1736 /* If loop iterates for unknown times or fewer times than chain->length,
1737 we still need to setup root variable and propagate it with PHI node. */
1738 tree niters = number_of_latch_executions (loop);
1739 if (TREE_CODE (niters) != INTEGER_CST
1740 || wi::leu_p (wi::to_wide (niters), chain->length))
1741 return false;
1743 /* Check stores in chain for elimination if they only store loop invariant
1744 values. */
1745 for (unsigned i = 0; i < chain->length; i++)
1747 dref a = get_chain_last_write_at (chain, i);
1748 if (a == NULL)
1749 continue;
1751 gimple *def_stmt, *stmt = a->stmt;
1752 if (!gimple_assign_single_p (stmt))
1753 return false;
1755 tree val = gimple_assign_rhs1 (stmt);
1756 if (TREE_CLOBBER_P (val))
1757 return false;
1759 if (CONSTANT_CLASS_P (val))
1760 continue;
1762 if (TREE_CODE (val) != SSA_NAME)
1763 return false;
1765 def_stmt = SSA_NAME_DEF_STMT (val);
1766 if (gimple_nop_p (def_stmt))
1767 continue;
1769 if (flow_bb_inside_loop_p (loop, gimple_bb (def_stmt)))
1770 return false;
1772 return true;
1775 /* Creates root variables for store elimination CHAIN in which stores for
1776 elimination only store loop invariant values. In this case, we neither
1777 need to load root variables before loop nor propagate it with PHI nodes. */
1779 static void
1780 initialize_root_vars_store_elim_1 (chain_p chain)
1782 tree var;
1783 unsigned i, n = chain->length;
1785 chain->vars.create (n);
1786 chain->vars.safe_grow_cleared (n);
1788 /* Initialize root value for eliminated stores at each distance. */
1789 for (i = 0; i < n; i++)
1791 dref a = get_chain_last_write_at (chain, i);
1792 if (a == NULL)
1793 continue;
1795 var = gimple_assign_rhs1 (a->stmt);
1796 chain->vars[a->distance] = var;
1799 /* We don't propagate values with PHI nodes, so manually propagate value
1800 to bubble positions. */
1801 var = chain->vars[0];
1802 for (i = 1; i < n; i++)
1804 if (chain->vars[i] != NULL_TREE)
1806 var = chain->vars[i];
1807 continue;
1809 chain->vars[i] = var;
1812 /* Revert the vector. */
1813 for (i = 0; i < n / 2; i++)
1814 std::swap (chain->vars[i], chain->vars[n - i - 1]);
1817 /* Creates root variables for store elimination CHAIN in which stores for
1818 elimination store loop variant values. In this case, we may need to
1819 load root variables before LOOP and propagate it with PHI nodes. Uids
1820 of the newly created root variables are marked in TMP_VARS. */
1822 static void
1823 initialize_root_vars_store_elim_2 (class loop *loop,
1824 chain_p chain, bitmap tmp_vars)
1826 unsigned i, n = chain->length;
1827 tree ref, init, var, next, val, phi_result;
1828 gimple *stmt;
1829 gimple_seq stmts;
1831 chain->vars.create (n);
1833 ref = DR_REF (get_chain_root (chain)->ref);
1834 for (i = 0; i < n; i++)
1836 var = predcom_tmp_var (ref, i, tmp_vars);
1837 chain->vars.quick_push (var);
1840 FOR_EACH_VEC_ELT (chain->vars, i, var)
1841 chain->vars[i] = make_ssa_name (var);
1843 /* Root values are either rhs operand of stores to be eliminated, or
1844 loaded from memory before loop. */
1845 auto_vec<tree> vtemps;
1846 vtemps.safe_grow_cleared (n);
1847 for (i = 0; i < n; i++)
1849 init = get_init_expr (chain, i);
1850 if (init == NULL_TREE)
1852 /* Root value is rhs operand of the store to be eliminated if
1853 it isn't loaded from memory before loop. */
1854 dref a = get_chain_last_write_at (chain, i);
1855 val = gimple_assign_rhs1 (a->stmt);
1856 if (TREE_CLOBBER_P (val))
1858 val = get_or_create_ssa_default_def (cfun, SSA_NAME_VAR (var));
1859 gimple_assign_set_rhs1 (a->stmt, val);
1862 vtemps[n - i - 1] = val;
1864 else
1866 edge latch = loop_latch_edge (loop);
1867 edge entry = loop_preheader_edge (loop);
1869 /* Root value is loaded from memory before loop, we also need
1870 to add PHI nodes to propagate the value across iterations. */
1871 init = force_gimple_operand (init, &stmts, true, NULL_TREE);
1872 if (stmts)
1873 gsi_insert_seq_on_edge_immediate (entry, stmts);
1875 next = chain->vars[n - i];
1876 phi_result = copy_ssa_name (next);
1877 gphi *phi = create_phi_node (phi_result, loop->header);
1878 add_phi_arg (phi, init, entry, UNKNOWN_LOCATION);
1879 add_phi_arg (phi, next, latch, UNKNOWN_LOCATION);
1880 vtemps[n - i - 1] = phi_result;
1884 /* Find the insertion position. */
1885 dref last = get_chain_root (chain);
1886 for (i = 0; i < chain->refs.length (); i++)
1888 if (chain->refs[i]->pos > last->pos)
1889 last = chain->refs[i];
1892 gimple_stmt_iterator gsi = gsi_for_stmt (last->stmt);
1894 /* Insert statements copying root value to root variable. */
1895 for (i = 0; i < n; i++)
1897 var = chain->vars[i];
1898 val = vtemps[i];
1899 stmt = gimple_build_assign (var, val);
1900 gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
1904 /* Generates stores for CHAIN's eliminated stores in LOOP's last
1905 (CHAIN->length - 1) iterations. */
1907 static void
1908 finalize_eliminated_stores (class loop *loop, chain_p chain)
1910 unsigned i, n = chain->length;
1912 for (i = 0; i < n; i++)
1914 tree var = chain->vars[i];
1915 tree fini = chain->finis[n - i - 1];
1916 gimple *stmt = gimple_build_assign (fini, var);
1918 gimple_seq_add_stmt_without_update (&chain->fini_seq, stmt);
1921 if (chain->fini_seq)
1923 gsi_insert_seq_on_edge_immediate (single_exit (loop), chain->fini_seq);
1924 chain->fini_seq = NULL;
1928 /* Initializes a variable for load motion for ROOT and prepares phi nodes and
1929 initialization on entry to LOOP if necessary. The ssa name for the variable
1930 is stored in VARS. If WRITTEN is true, also a phi node to copy its value
1931 around the loop is created. Uid of the newly created temporary variable
1932 is marked in TMP_VARS. INITS is the list containing the (single)
1933 initializer. */
1935 static void
1936 initialize_root_vars_lm (class loop *loop, dref root, bool written,
1937 vec<tree> *vars, vec<tree> inits,
1938 bitmap tmp_vars)
1940 unsigned i;
1941 tree ref = DR_REF (root->ref), init, var, next;
1942 gimple_seq stmts;
1943 gphi *phi;
1944 edge entry = loop_preheader_edge (loop), latch = loop_latch_edge (loop);
1946 /* Find the initializer for the variable, and check that it cannot
1947 trap. */
1948 init = inits[0];
1950 vars->create (written ? 2 : 1);
1951 var = predcom_tmp_var (ref, 0, tmp_vars);
1952 vars->quick_push (var);
1953 if (written)
1954 vars->quick_push ((*vars)[0]);
1956 FOR_EACH_VEC_ELT (*vars, i, var)
1957 (*vars)[i] = make_ssa_name (var);
1959 var = (*vars)[0];
1961 init = force_gimple_operand (init, &stmts, written, NULL_TREE);
1962 if (stmts)
1963 gsi_insert_seq_on_edge_immediate (entry, stmts);
1965 if (written)
1967 next = (*vars)[1];
1968 phi = create_phi_node (var, loop->header);
1969 add_phi_arg (phi, init, entry, UNKNOWN_LOCATION);
1970 add_phi_arg (phi, next, latch, UNKNOWN_LOCATION);
1972 else
1974 gassign *init_stmt = gimple_build_assign (var, init);
1975 gsi_insert_on_edge_immediate (entry, init_stmt);
1980 /* Execute load motion for references in chain CHAIN. Uids of the newly
1981 created temporary variables are marked in TMP_VARS. */
1983 static void
1984 execute_load_motion (class loop *loop, chain_p chain, bitmap tmp_vars)
1986 auto_vec<tree> vars;
1987 dref a;
1988 unsigned n_writes = 0, ridx, i;
1989 tree var;
1991 gcc_assert (chain->type == CT_INVARIANT);
1992 gcc_assert (!chain->combined);
1993 FOR_EACH_VEC_ELT (chain->refs, i, a)
1994 if (DR_IS_WRITE (a->ref))
1995 n_writes++;
1997 /* If there are no reads in the loop, there is nothing to do. */
1998 if (n_writes == chain->refs.length ())
1999 return;
2001 initialize_root_vars_lm (loop, get_chain_root (chain), n_writes > 0,
2002 &vars, chain->inits, tmp_vars);
2004 ridx = 0;
2005 FOR_EACH_VEC_ELT (chain->refs, i, a)
2007 bool is_read = DR_IS_READ (a->ref);
2009 if (DR_IS_WRITE (a->ref))
2011 n_writes--;
2012 if (n_writes)
2014 var = vars[0];
2015 var = make_ssa_name (SSA_NAME_VAR (var));
2016 vars[0] = var;
2018 else
2019 ridx = 1;
2022 replace_ref_with (a->stmt, vars[ridx],
2023 !is_read, !is_read);
2027 /* Returns the single statement in that NAME is used, excepting
2028 the looparound phi nodes contained in one of the chains. If there is no
2029 such statement, or more statements, NULL is returned. */
2031 static gimple *
2032 single_nonlooparound_use (tree name)
2034 use_operand_p use;
2035 imm_use_iterator it;
2036 gimple *stmt, *ret = NULL;
2038 FOR_EACH_IMM_USE_FAST (use, it, name)
2040 stmt = USE_STMT (use);
2042 if (gimple_code (stmt) == GIMPLE_PHI)
2044 /* Ignore uses in looparound phi nodes. Uses in other phi nodes
2045 could not be processed anyway, so just fail for them. */
2046 if (bitmap_bit_p (looparound_phis,
2047 SSA_NAME_VERSION (PHI_RESULT (stmt))))
2048 continue;
2050 return NULL;
2052 else if (is_gimple_debug (stmt))
2053 continue;
2054 else if (ret != NULL)
2055 return NULL;
2056 else
2057 ret = stmt;
2060 return ret;
2063 /* Remove statement STMT, as well as the chain of assignments in that it is
2064 used. */
2066 static void
2067 remove_stmt (gimple *stmt)
2069 tree name;
2070 gimple *next;
2071 gimple_stmt_iterator psi;
2073 if (gimple_code (stmt) == GIMPLE_PHI)
2075 name = PHI_RESULT (stmt);
2076 next = single_nonlooparound_use (name);
2077 reset_debug_uses (stmt);
2078 psi = gsi_for_stmt (stmt);
2079 remove_phi_node (&psi, true);
2081 if (!next
2082 || !gimple_assign_ssa_name_copy_p (next)
2083 || gimple_assign_rhs1 (next) != name)
2084 return;
2086 stmt = next;
2089 while (1)
2091 gimple_stmt_iterator bsi;
2093 bsi = gsi_for_stmt (stmt);
2095 name = gimple_assign_lhs (stmt);
2096 if (TREE_CODE (name) == SSA_NAME)
2098 next = single_nonlooparound_use (name);
2099 reset_debug_uses (stmt);
2101 else
2103 /* This is a store to be eliminated. */
2104 gcc_assert (gimple_vdef (stmt) != NULL);
2105 next = NULL;
2108 unlink_stmt_vdef (stmt);
2109 gsi_remove (&bsi, true);
2110 release_defs (stmt);
2112 if (!next
2113 || !gimple_assign_ssa_name_copy_p (next)
2114 || gimple_assign_rhs1 (next) != name)
2115 return;
2117 stmt = next;
2121 /* Perform the predictive commoning optimization for a chain CHAIN.
2122 Uids of the newly created temporary variables are marked in TMP_VARS.*/
2124 static void
2125 execute_pred_commoning_chain (class loop *loop, chain_p chain,
2126 bitmap tmp_vars)
2128 unsigned i;
2129 dref a;
2130 tree var;
2131 bool in_lhs;
2133 if (chain->combined)
2135 /* For combined chains, just remove the statements that are used to
2136 compute the values of the expression (except for the root one).
2137 We delay this until after all chains are processed. */
2139 else if (chain->type == CT_STORE_STORE)
2141 if (chain->length > 0)
2143 if (chain->inv_store_elimination)
2145 /* If dead stores in this chain only store loop invariant
2146 values, we can simply record the invariant value and use
2147 it directly after loop. */
2148 initialize_root_vars_store_elim_1 (chain);
2150 else
2152 /* If dead stores in this chain store loop variant values,
2153 we need to set up the variables by loading from memory
2154 before loop and propagating it with PHI nodes. */
2155 initialize_root_vars_store_elim_2 (loop, chain, tmp_vars);
2158 /* For inter-iteration store elimination chain, stores at each
2159 distance in loop's last (chain->length - 1) iterations can't
2160 be eliminated, because there is no following killing store.
2161 We need to generate these stores after loop. */
2162 finalize_eliminated_stores (loop, chain);
2165 bool last_store_p = true;
2166 for (i = chain->refs.length (); i > 0; i--)
2168 a = chain->refs[i - 1];
2169 /* Preserve the last store of the chain. Eliminate other stores
2170 which are killed by the last one. */
2171 if (DR_IS_WRITE (a->ref))
2173 if (last_store_p)
2174 last_store_p = false;
2175 else
2176 remove_stmt (a->stmt);
2178 continue;
2181 /* Any load in Store-Store chain must be dominated by a previous
2182 store, we replace the load reference with rhs of the store. */
2183 dref b = get_chain_last_write_before_load (chain, i - 1);
2184 gcc_assert (b != NULL);
2185 var = gimple_assign_rhs1 (b->stmt);
2186 replace_ref_with (a->stmt, var, false, false);
2189 else
2191 /* For non-combined chains, set up the variables that hold its value. */
2192 initialize_root_vars (loop, chain, tmp_vars);
2193 a = get_chain_root (chain);
2194 in_lhs = (chain->type == CT_STORE_LOAD
2195 || chain->type == CT_COMBINATION);
2196 replace_ref_with (a->stmt, chain->vars[chain->length], true, in_lhs);
2198 /* Replace the uses of the original references by these variables. */
2199 for (i = 1; chain->refs.iterate (i, &a); i++)
2201 var = chain->vars[chain->length - a->distance];
2202 replace_ref_with (a->stmt, var, false, false);
2207 /* Determines the unroll factor necessary to remove as many temporary variable
2208 copies as possible. CHAINS is the list of chains that will be
2209 optimized. */
2211 static unsigned
2212 determine_unroll_factor (vec<chain_p> chains)
2214 chain_p chain;
2215 unsigned factor = 1, af, nfactor, i;
2216 unsigned max = param_max_unroll_times;
2218 FOR_EACH_VEC_ELT (chains, i, chain)
2220 if (chain->type == CT_INVARIANT)
2221 continue;
2222 /* For now we can't handle unrolling when eliminating stores. */
2223 else if (chain->type == CT_STORE_STORE)
2224 return 1;
2226 if (chain->combined)
2228 /* For combined chains, we can't handle unrolling if we replace
2229 looparound PHIs. */
2230 dref a;
2231 unsigned j;
2232 for (j = 1; chain->refs.iterate (j, &a); j++)
2233 if (gimple_code (a->stmt) == GIMPLE_PHI)
2234 return 1;
2235 continue;
2238 /* The best unroll factor for this chain is equal to the number of
2239 temporary variables that we create for it. */
2240 af = chain->length;
2241 if (chain->has_max_use_after)
2242 af++;
2244 nfactor = factor * af / gcd (factor, af);
2245 if (nfactor <= max)
2246 factor = nfactor;
2249 return factor;
2252 /* Perform the predictive commoning optimization for CHAINS.
2253 Uids of the newly created temporary variables are marked in TMP_VARS. */
2255 static void
2256 execute_pred_commoning (class loop *loop, vec<chain_p> chains,
2257 bitmap tmp_vars)
2259 chain_p chain;
2260 unsigned i;
2262 FOR_EACH_VEC_ELT (chains, i, chain)
2264 if (chain->type == CT_INVARIANT)
2265 execute_load_motion (loop, chain, tmp_vars);
2266 else
2267 execute_pred_commoning_chain (loop, chain, tmp_vars);
2270 FOR_EACH_VEC_ELT (chains, i, chain)
2272 if (chain->type == CT_INVARIANT)
2274 else if (chain->combined)
2276 /* For combined chains, just remove the statements that are used to
2277 compute the values of the expression (except for the root one). */
2278 dref a;
2279 unsigned j;
2280 for (j = 1; chain->refs.iterate (j, &a); j++)
2281 remove_stmt (a->stmt);
2285 update_ssa (TODO_update_ssa_only_virtuals);
2288 /* For each reference in CHAINS, if its defining statement is
2289 phi node, record the ssa name that is defined by it. */
2291 static void
2292 replace_phis_by_defined_names (vec<chain_p> chains)
2294 chain_p chain;
2295 dref a;
2296 unsigned i, j;
2298 FOR_EACH_VEC_ELT (chains, i, chain)
2299 FOR_EACH_VEC_ELT (chain->refs, j, a)
2301 if (gimple_code (a->stmt) == GIMPLE_PHI)
2303 a->name_defined_by_phi = PHI_RESULT (a->stmt);
2304 a->stmt = NULL;
2309 /* For each reference in CHAINS, if name_defined_by_phi is not
2310 NULL, use it to set the stmt field. */
2312 static void
2313 replace_names_by_phis (vec<chain_p> chains)
2315 chain_p chain;
2316 dref a;
2317 unsigned i, j;
2319 FOR_EACH_VEC_ELT (chains, i, chain)
2320 FOR_EACH_VEC_ELT (chain->refs, j, a)
2321 if (a->stmt == NULL)
2323 a->stmt = SSA_NAME_DEF_STMT (a->name_defined_by_phi);
2324 gcc_assert (gimple_code (a->stmt) == GIMPLE_PHI);
2325 a->name_defined_by_phi = NULL_TREE;
2329 /* Wrapper over execute_pred_commoning, to pass it as a callback
2330 to tree_transform_and_unroll_loop. */
2332 struct epcc_data
2334 vec<chain_p> chains;
2335 bitmap tmp_vars;
2338 static void
2339 execute_pred_commoning_cbck (class loop *loop, void *data)
2341 struct epcc_data *const dta = (struct epcc_data *) data;
2343 /* Restore phi nodes that were replaced by ssa names before
2344 tree_transform_and_unroll_loop (see detailed description in
2345 tree_predictive_commoning_loop). */
2346 replace_names_by_phis (dta->chains);
2347 execute_pred_commoning (loop, dta->chains, dta->tmp_vars);
2350 /* Base NAME and all the names in the chain of phi nodes that use it
2351 on variable VAR. The phi nodes are recognized by being in the copies of
2352 the header of the LOOP. */
2354 static void
2355 base_names_in_chain_on (class loop *loop, tree name, tree var)
2357 gimple *stmt, *phi;
2358 imm_use_iterator iter;
2360 replace_ssa_name_symbol (name, var);
2362 while (1)
2364 phi = NULL;
2365 FOR_EACH_IMM_USE_STMT (stmt, iter, name)
2367 if (gimple_code (stmt) == GIMPLE_PHI
2368 && flow_bb_inside_loop_p (loop, gimple_bb (stmt)))
2370 phi = stmt;
2371 BREAK_FROM_IMM_USE_STMT (iter);
2374 if (!phi)
2375 return;
2377 name = PHI_RESULT (phi);
2378 replace_ssa_name_symbol (name, var);
2382 /* Given an unrolled LOOP after predictive commoning, remove the
2383 register copies arising from phi nodes by changing the base
2384 variables of SSA names. TMP_VARS is the set of the temporary variables
2385 for those we want to perform this. */
2387 static void
2388 eliminate_temp_copies (class loop *loop, bitmap tmp_vars)
2390 edge e;
2391 gphi *phi;
2392 gimple *stmt;
2393 tree name, use, var;
2394 gphi_iterator psi;
2396 e = loop_latch_edge (loop);
2397 for (psi = gsi_start_phis (loop->header); !gsi_end_p (psi); gsi_next (&psi))
2399 phi = psi.phi ();
2400 name = PHI_RESULT (phi);
2401 var = SSA_NAME_VAR (name);
2402 if (!var || !bitmap_bit_p (tmp_vars, DECL_UID (var)))
2403 continue;
2404 use = PHI_ARG_DEF_FROM_EDGE (phi, e);
2405 gcc_assert (TREE_CODE (use) == SSA_NAME);
2407 /* Base all the ssa names in the ud and du chain of NAME on VAR. */
2408 stmt = SSA_NAME_DEF_STMT (use);
2409 while (gimple_code (stmt) == GIMPLE_PHI
2410 /* In case we could not unroll the loop enough to eliminate
2411 all copies, we may reach the loop header before the defining
2412 statement (in that case, some register copies will be present
2413 in loop latch in the final code, corresponding to the newly
2414 created looparound phi nodes). */
2415 && gimple_bb (stmt) != loop->header)
2417 gcc_assert (single_pred_p (gimple_bb (stmt)));
2418 use = PHI_ARG_DEF (stmt, 0);
2419 stmt = SSA_NAME_DEF_STMT (use);
2422 base_names_in_chain_on (loop, use, var);
2426 /* Returns true if CHAIN is suitable to be combined. */
2428 static bool
2429 chain_can_be_combined_p (chain_p chain)
2431 return (!chain->combined
2432 && (chain->type == CT_LOAD || chain->type == CT_COMBINATION));
2435 /* Returns the modify statement that uses NAME. Skips over assignment
2436 statements, NAME is replaced with the actual name used in the returned
2437 statement. */
2439 static gimple *
2440 find_use_stmt (tree *name)
2442 gimple *stmt;
2443 tree rhs, lhs;
2445 /* Skip over assignments. */
2446 while (1)
2448 stmt = single_nonlooparound_use (*name);
2449 if (!stmt)
2450 return NULL;
2452 if (gimple_code (stmt) != GIMPLE_ASSIGN)
2453 return NULL;
2455 lhs = gimple_assign_lhs (stmt);
2456 if (TREE_CODE (lhs) != SSA_NAME)
2457 return NULL;
2459 if (gimple_assign_copy_p (stmt))
2461 rhs = gimple_assign_rhs1 (stmt);
2462 if (rhs != *name)
2463 return NULL;
2465 *name = lhs;
2467 else if (get_gimple_rhs_class (gimple_assign_rhs_code (stmt))
2468 == GIMPLE_BINARY_RHS)
2469 return stmt;
2470 else
2471 return NULL;
2475 /* Returns true if we may perform reassociation for operation CODE in TYPE. */
2477 static bool
2478 may_reassociate_p (tree type, enum tree_code code)
2480 if (FLOAT_TYPE_P (type)
2481 && !flag_unsafe_math_optimizations)
2482 return false;
2484 return (commutative_tree_code (code)
2485 && associative_tree_code (code));
2488 /* If the operation used in STMT is associative and commutative, go through the
2489 tree of the same operations and returns its root. Distance to the root
2490 is stored in DISTANCE. */
2492 static gimple *
2493 find_associative_operation_root (gimple *stmt, unsigned *distance)
2495 tree lhs;
2496 gimple *next;
2497 enum tree_code code = gimple_assign_rhs_code (stmt);
2498 tree type = TREE_TYPE (gimple_assign_lhs (stmt));
2499 unsigned dist = 0;
2501 if (!may_reassociate_p (type, code))
2502 return NULL;
2504 while (1)
2506 lhs = gimple_assign_lhs (stmt);
2507 gcc_assert (TREE_CODE (lhs) == SSA_NAME);
2509 next = find_use_stmt (&lhs);
2510 if (!next
2511 || gimple_assign_rhs_code (next) != code)
2512 break;
2514 stmt = next;
2515 dist++;
2518 if (distance)
2519 *distance = dist;
2520 return stmt;
2523 /* Returns the common statement in that NAME1 and NAME2 have a use. If there
2524 is no such statement, returns NULL_TREE. In case the operation used on
2525 NAME1 and NAME2 is associative and commutative, returns the root of the
2526 tree formed by this operation instead of the statement that uses NAME1 or
2527 NAME2. */
2529 static gimple *
2530 find_common_use_stmt (tree *name1, tree *name2)
2532 gimple *stmt1, *stmt2;
2534 stmt1 = find_use_stmt (name1);
2535 if (!stmt1)
2536 return NULL;
2538 stmt2 = find_use_stmt (name2);
2539 if (!stmt2)
2540 return NULL;
2542 if (stmt1 == stmt2)
2543 return stmt1;
2545 stmt1 = find_associative_operation_root (stmt1, NULL);
2546 if (!stmt1)
2547 return NULL;
2548 stmt2 = find_associative_operation_root (stmt2, NULL);
2549 if (!stmt2)
2550 return NULL;
2552 return (stmt1 == stmt2 ? stmt1 : NULL);
2555 /* Checks whether R1 and R2 are combined together using CODE, with the result
2556 in RSLT_TYPE, in order R1 CODE R2 if SWAP is false and in order R2 CODE R1
2557 if it is true. If CODE is ERROR_MARK, set these values instead. */
2559 static bool
2560 combinable_refs_p (dref r1, dref r2,
2561 enum tree_code *code, bool *swap, tree *rslt_type)
2563 enum tree_code acode;
2564 bool aswap;
2565 tree atype;
2566 tree name1, name2;
2567 gimple *stmt;
2569 name1 = name_for_ref (r1);
2570 name2 = name_for_ref (r2);
2571 gcc_assert (name1 != NULL_TREE && name2 != NULL_TREE);
2573 stmt = find_common_use_stmt (&name1, &name2);
2575 if (!stmt
2576 /* A simple post-dominance check - make sure the combination
2577 is executed under the same condition as the references. */
2578 || (gimple_bb (stmt) != gimple_bb (r1->stmt)
2579 && gimple_bb (stmt) != gimple_bb (r2->stmt)))
2580 return false;
2582 acode = gimple_assign_rhs_code (stmt);
2583 aswap = (!commutative_tree_code (acode)
2584 && gimple_assign_rhs1 (stmt) != name1);
2585 atype = TREE_TYPE (gimple_assign_lhs (stmt));
2587 if (*code == ERROR_MARK)
2589 *code = acode;
2590 *swap = aswap;
2591 *rslt_type = atype;
2592 return true;
2595 return (*code == acode
2596 && *swap == aswap
2597 && *rslt_type == atype);
2600 /* Remove OP from the operation on rhs of STMT, and replace STMT with
2601 an assignment of the remaining operand. */
2603 static void
2604 remove_name_from_operation (gimple *stmt, tree op)
2606 tree other_op;
2607 gimple_stmt_iterator si;
2609 gcc_assert (is_gimple_assign (stmt));
2611 if (gimple_assign_rhs1 (stmt) == op)
2612 other_op = gimple_assign_rhs2 (stmt);
2613 else
2614 other_op = gimple_assign_rhs1 (stmt);
2616 si = gsi_for_stmt (stmt);
2617 gimple_assign_set_rhs_from_tree (&si, other_op);
2619 /* We should not have reallocated STMT. */
2620 gcc_assert (gsi_stmt (si) == stmt);
2622 update_stmt (stmt);
2625 /* Reassociates the expression in that NAME1 and NAME2 are used so that they
2626 are combined in a single statement, and returns this statement. */
2628 static gimple *
2629 reassociate_to_the_same_stmt (tree name1, tree name2)
2631 gimple *stmt1, *stmt2, *root1, *root2, *s1, *s2;
2632 gassign *new_stmt, *tmp_stmt;
2633 tree new_name, tmp_name, var, r1, r2;
2634 unsigned dist1, dist2;
2635 enum tree_code code;
2636 tree type = TREE_TYPE (name1);
2637 gimple_stmt_iterator bsi;
2639 stmt1 = find_use_stmt (&name1);
2640 stmt2 = find_use_stmt (&name2);
2641 root1 = find_associative_operation_root (stmt1, &dist1);
2642 root2 = find_associative_operation_root (stmt2, &dist2);
2643 code = gimple_assign_rhs_code (stmt1);
2645 gcc_assert (root1 && root2 && root1 == root2
2646 && code == gimple_assign_rhs_code (stmt2));
2648 /* Find the root of the nearest expression in that both NAME1 and NAME2
2649 are used. */
2650 r1 = name1;
2651 s1 = stmt1;
2652 r2 = name2;
2653 s2 = stmt2;
2655 while (dist1 > dist2)
2657 s1 = find_use_stmt (&r1);
2658 r1 = gimple_assign_lhs (s1);
2659 dist1--;
2661 while (dist2 > dist1)
2663 s2 = find_use_stmt (&r2);
2664 r2 = gimple_assign_lhs (s2);
2665 dist2--;
2668 while (s1 != s2)
2670 s1 = find_use_stmt (&r1);
2671 r1 = gimple_assign_lhs (s1);
2672 s2 = find_use_stmt (&r2);
2673 r2 = gimple_assign_lhs (s2);
2676 /* Remove NAME1 and NAME2 from the statements in that they are used
2677 currently. */
2678 remove_name_from_operation (stmt1, name1);
2679 remove_name_from_operation (stmt2, name2);
2681 /* Insert the new statement combining NAME1 and NAME2 before S1, and
2682 combine it with the rhs of S1. */
2683 var = create_tmp_reg (type, "predreastmp");
2684 new_name = make_ssa_name (var);
2685 new_stmt = gimple_build_assign (new_name, code, name1, name2);
2687 var = create_tmp_reg (type, "predreastmp");
2688 tmp_name = make_ssa_name (var);
2690 /* Rhs of S1 may now be either a binary expression with operation
2691 CODE, or gimple_val (in case that stmt1 == s1 or stmt2 == s1,
2692 so that name1 or name2 was removed from it). */
2693 tmp_stmt = gimple_build_assign (tmp_name, gimple_assign_rhs_code (s1),
2694 gimple_assign_rhs1 (s1),
2695 gimple_assign_rhs2 (s1));
2697 bsi = gsi_for_stmt (s1);
2698 gimple_assign_set_rhs_with_ops (&bsi, code, new_name, tmp_name);
2699 s1 = gsi_stmt (bsi);
2700 update_stmt (s1);
2702 gsi_insert_before (&bsi, new_stmt, GSI_SAME_STMT);
2703 gsi_insert_before (&bsi, tmp_stmt, GSI_SAME_STMT);
2705 return new_stmt;
2708 /* Returns the statement that combines references R1 and R2. In case R1
2709 and R2 are not used in the same statement, but they are used with an
2710 associative and commutative operation in the same expression, reassociate
2711 the expression so that they are used in the same statement. */
2713 static gimple *
2714 stmt_combining_refs (dref r1, dref r2)
2716 gimple *stmt1, *stmt2;
2717 tree name1 = name_for_ref (r1);
2718 tree name2 = name_for_ref (r2);
2720 stmt1 = find_use_stmt (&name1);
2721 stmt2 = find_use_stmt (&name2);
2722 if (stmt1 == stmt2)
2723 return stmt1;
2725 return reassociate_to_the_same_stmt (name1, name2);
2728 /* Tries to combine chains CH1 and CH2 together. If this succeeds, the
2729 description of the new chain is returned, otherwise we return NULL. */
2731 static chain_p
2732 combine_chains (chain_p ch1, chain_p ch2)
2734 dref r1, r2, nw;
2735 enum tree_code op = ERROR_MARK;
2736 bool swap = false;
2737 chain_p new_chain;
2738 unsigned i;
2739 tree rslt_type = NULL_TREE;
2741 if (ch1 == ch2)
2742 return NULL;
2743 if (ch1->length != ch2->length)
2744 return NULL;
2746 if (ch1->refs.length () != ch2->refs.length ())
2747 return NULL;
2749 for (i = 0; (ch1->refs.iterate (i, &r1)
2750 && ch2->refs.iterate (i, &r2)); i++)
2752 if (r1->distance != r2->distance)
2753 return NULL;
2755 if (!combinable_refs_p (r1, r2, &op, &swap, &rslt_type))
2756 return NULL;
2759 if (swap)
2760 std::swap (ch1, ch2);
2762 new_chain = XCNEW (struct chain);
2763 new_chain->type = CT_COMBINATION;
2764 new_chain->op = op;
2765 new_chain->ch1 = ch1;
2766 new_chain->ch2 = ch2;
2767 new_chain->rslt_type = rslt_type;
2768 new_chain->length = ch1->length;
2770 for (i = 0; (ch1->refs.iterate (i, &r1)
2771 && ch2->refs.iterate (i, &r2)); i++)
2773 nw = XCNEW (class dref_d);
2774 nw->stmt = stmt_combining_refs (r1, r2);
2775 nw->distance = r1->distance;
2777 new_chain->refs.safe_push (nw);
2780 ch1->combined = true;
2781 ch2->combined = true;
2782 return new_chain;
2785 /* Recursively update position information of all offspring chains to ROOT
2786 chain's position information. */
2788 static void
2789 update_pos_for_combined_chains (chain_p root)
2791 chain_p ch1 = root->ch1, ch2 = root->ch2;
2792 dref ref, ref1, ref2;
2793 for (unsigned j = 0; (root->refs.iterate (j, &ref)
2794 && ch1->refs.iterate (j, &ref1)
2795 && ch2->refs.iterate (j, &ref2)); ++j)
2796 ref1->pos = ref2->pos = ref->pos;
2798 if (ch1->type == CT_COMBINATION)
2799 update_pos_for_combined_chains (ch1);
2800 if (ch2->type == CT_COMBINATION)
2801 update_pos_for_combined_chains (ch2);
2804 /* Returns true if statement S1 dominates statement S2. */
2806 static bool
2807 pcom_stmt_dominates_stmt_p (gimple *s1, gimple *s2)
2809 basic_block bb1 = gimple_bb (s1), bb2 = gimple_bb (s2);
2811 if (!bb1 || s1 == s2)
2812 return true;
2814 if (bb1 == bb2)
2815 return gimple_uid (s1) < gimple_uid (s2);
2817 return dominated_by_p (CDI_DOMINATORS, bb2, bb1);
2820 /* Try to combine the CHAINS in LOOP. */
2822 static void
2823 try_combine_chains (class loop *loop, vec<chain_p> *chains)
2825 unsigned i, j;
2826 chain_p ch1, ch2, cch;
2827 auto_vec<chain_p> worklist;
2828 bool combined_p = false;
2830 FOR_EACH_VEC_ELT (*chains, i, ch1)
2831 if (chain_can_be_combined_p (ch1))
2832 worklist.safe_push (ch1);
2834 while (!worklist.is_empty ())
2836 ch1 = worklist.pop ();
2837 if (!chain_can_be_combined_p (ch1))
2838 continue;
2840 FOR_EACH_VEC_ELT (*chains, j, ch2)
2842 if (!chain_can_be_combined_p (ch2))
2843 continue;
2845 cch = combine_chains (ch1, ch2);
2846 if (cch)
2848 worklist.safe_push (cch);
2849 chains->safe_push (cch);
2850 combined_p = true;
2851 break;
2855 if (!combined_p)
2856 return;
2858 /* Setup UID for all statements in dominance order. */
2859 basic_block *bbs = get_loop_body_in_dom_order (loop);
2860 renumber_gimple_stmt_uids_in_blocks (bbs, loop->num_nodes);
2861 free (bbs);
2863 /* Re-association in combined chains may generate statements different to
2864 order of references of the original chain. We need to keep references
2865 of combined chain in dominance order so that all uses will be inserted
2866 after definitions. Note:
2867 A) This is necessary for all combined chains.
2868 B) This is only necessary for ZERO distance references because other
2869 references inherit value from loop carried PHIs.
2871 We first update position information for all combined chains. */
2872 dref ref;
2873 for (i = 0; chains->iterate (i, &ch1); ++i)
2875 if (ch1->type != CT_COMBINATION || ch1->combined)
2876 continue;
2878 for (j = 0; ch1->refs.iterate (j, &ref); ++j)
2879 ref->pos = gimple_uid (ref->stmt);
2881 update_pos_for_combined_chains (ch1);
2883 /* Then sort references according to newly updated position information. */
2884 for (i = 0; chains->iterate (i, &ch1); ++i)
2886 if (ch1->type != CT_COMBINATION && !ch1->combined)
2887 continue;
2889 /* Find the first reference with non-ZERO distance. */
2890 if (ch1->length == 0)
2891 j = ch1->refs.length();
2892 else
2894 for (j = 0; ch1->refs.iterate (j, &ref); ++j)
2895 if (ref->distance != 0)
2896 break;
2899 /* Sort all ZERO distance references by position. */
2900 qsort (&ch1->refs[0], j, sizeof (ch1->refs[0]), order_drefs_by_pos);
2902 if (ch1->combined)
2903 continue;
2905 /* For ZERO length chain, has_max_use_after must be true since root
2906 combined stmt must dominates others. */
2907 if (ch1->length == 0)
2909 ch1->has_max_use_after = true;
2910 continue;
2912 /* Check if there is use at max distance after root for combined chains
2913 and set flag accordingly. */
2914 ch1->has_max_use_after = false;
2915 gimple *root_stmt = get_chain_root (ch1)->stmt;
2916 for (j = 1; ch1->refs.iterate (j, &ref); ++j)
2918 if (ref->distance == ch1->length
2919 && !pcom_stmt_dominates_stmt_p (ref->stmt, root_stmt))
2921 ch1->has_max_use_after = true;
2922 break;
2928 /* Prepare initializers for store elimination CHAIN in LOOP. Returns false
2929 if this is impossible because one of these initializers may trap, true
2930 otherwise. */
2932 static bool
2933 prepare_initializers_chain_store_elim (class loop *loop, chain_p chain)
2935 unsigned i, n = chain->length;
2937 /* For now we can't eliminate stores if some of them are conditional
2938 executed. */
2939 if (!chain->all_always_accessed)
2940 return false;
2942 /* Nothing to intialize for intra-iteration store elimination. */
2943 if (n == 0 && chain->type == CT_STORE_STORE)
2944 return true;
2946 /* For store elimination chain, there is nothing to initialize if stores
2947 to be eliminated only store loop invariant values into memory. */
2948 if (chain->type == CT_STORE_STORE
2949 && is_inv_store_elimination_chain (loop, chain))
2951 chain->inv_store_elimination = true;
2952 return true;
2955 chain->inits.create (n);
2956 chain->inits.safe_grow_cleared (n);
2958 /* For store eliminatin chain like below:
2960 for (i = 0; i < len; i++)
2962 a[i] = 1;
2963 // a[i + 1] = ...
2964 a[i + 2] = 3;
2967 store to a[i + 1] is missed in loop body, it acts like bubbles. The
2968 content of a[i + 1] remain the same if the loop iterates fewer times
2969 than chain->length. We need to set up root variables for such stores
2970 by loading from memory before loop. Note we only need to load bubble
2971 elements because loop body is guaranteed to be executed at least once
2972 after loop's preheader edge. */
2973 auto_vec<bool> bubbles;
2974 bubbles.safe_grow_cleared (n + 1);
2975 for (i = 0; i < chain->refs.length (); i++)
2976 bubbles[chain->refs[i]->distance] = true;
2978 struct data_reference *dr = get_chain_root (chain)->ref;
2979 for (i = 0; i < n; i++)
2981 if (bubbles[i])
2982 continue;
2984 gimple_seq stmts = NULL;
2986 tree init = ref_at_iteration (dr, (int) 0 - i, &stmts);
2987 if (stmts)
2988 gimple_seq_add_seq_without_update (&chain->init_seq, stmts);
2990 chain->inits[i] = init;
2993 return true;
2996 /* Prepare initializers for CHAIN in LOOP. Returns false if this is
2997 impossible because one of these initializers may trap, true otherwise. */
2999 static bool
3000 prepare_initializers_chain (class loop *loop, chain_p chain)
3002 unsigned i, n = (chain->type == CT_INVARIANT) ? 1 : chain->length;
3003 struct data_reference *dr = get_chain_root (chain)->ref;
3004 tree init;
3005 dref laref;
3006 edge entry = loop_preheader_edge (loop);
3008 if (chain->type == CT_STORE_STORE)
3009 return prepare_initializers_chain_store_elim (loop, chain);
3011 /* Find the initializers for the variables, and check that they cannot
3012 trap. */
3013 chain->inits.create (n);
3014 for (i = 0; i < n; i++)
3015 chain->inits.quick_push (NULL_TREE);
3017 /* If we have replaced some looparound phi nodes, use their initializers
3018 instead of creating our own. */
3019 FOR_EACH_VEC_ELT (chain->refs, i, laref)
3021 if (gimple_code (laref->stmt) != GIMPLE_PHI)
3022 continue;
3024 gcc_assert (laref->distance > 0);
3025 chain->inits[n - laref->distance]
3026 = PHI_ARG_DEF_FROM_EDGE (laref->stmt, entry);
3029 for (i = 0; i < n; i++)
3031 gimple_seq stmts = NULL;
3033 if (chain->inits[i] != NULL_TREE)
3034 continue;
3036 init = ref_at_iteration (dr, (int) i - n, &stmts);
3037 if (!chain->all_always_accessed && tree_could_trap_p (init))
3039 gimple_seq_discard (stmts);
3040 return false;
3043 if (stmts)
3044 gimple_seq_add_seq_without_update (&chain->init_seq, stmts);
3046 chain->inits[i] = init;
3049 return true;
3052 /* Prepare initializers for CHAINS in LOOP, and free chains that cannot
3053 be used because the initializers might trap. */
3055 static void
3056 prepare_initializers (class loop *loop, vec<chain_p> chains)
3058 chain_p chain;
3059 unsigned i;
3061 for (i = 0; i < chains.length (); )
3063 chain = chains[i];
3064 if (prepare_initializers_chain (loop, chain))
3065 i++;
3066 else
3068 release_chain (chain);
3069 chains.unordered_remove (i);
3074 /* Generates finalizer memory references for CHAIN in LOOP. Returns true
3075 if finalizer code for CHAIN can be generated, otherwise false. */
3077 static bool
3078 prepare_finalizers_chain (class loop *loop, chain_p chain)
3080 unsigned i, n = chain->length;
3081 struct data_reference *dr = get_chain_root (chain)->ref;
3082 tree fini, niters = number_of_latch_executions (loop);
3084 /* For now we can't eliminate stores if some of them are conditional
3085 executed. */
3086 if (!chain->all_always_accessed)
3087 return false;
3089 chain->finis.create (n);
3090 for (i = 0; i < n; i++)
3091 chain->finis.quick_push (NULL_TREE);
3093 /* We never use looparound phi node for store elimination chains. */
3095 /* Find the finalizers for the variables, and check that they cannot
3096 trap. */
3097 for (i = 0; i < n; i++)
3099 gimple_seq stmts = NULL;
3100 gcc_assert (chain->finis[i] == NULL_TREE);
3102 if (TREE_CODE (niters) != INTEGER_CST && TREE_CODE (niters) != SSA_NAME)
3104 niters = unshare_expr (niters);
3105 niters = force_gimple_operand (niters, &stmts, true, NULL);
3106 if (stmts)
3108 gimple_seq_add_seq_without_update (&chain->fini_seq, stmts);
3109 stmts = NULL;
3112 fini = ref_at_iteration (dr, (int) 0 - i, &stmts, niters);
3113 if (stmts)
3114 gimple_seq_add_seq_without_update (&chain->fini_seq, stmts);
3116 chain->finis[i] = fini;
3119 return true;
3122 /* Generates finalizer memory reference for CHAINS in LOOP. Returns true
3123 if finalizer code generation for CHAINS breaks loop closed ssa form. */
3125 static bool
3126 prepare_finalizers (class loop *loop, vec<chain_p> chains)
3128 chain_p chain;
3129 unsigned i;
3130 bool loop_closed_ssa = false;
3132 for (i = 0; i < chains.length ();)
3134 chain = chains[i];
3136 /* Finalizer is only necessary for inter-iteration store elimination
3137 chains. */
3138 if (chain->length == 0 || chain->type != CT_STORE_STORE)
3140 i++;
3141 continue;
3144 if (prepare_finalizers_chain (loop, chain))
3146 i++;
3147 /* Be conservative, assume loop closed ssa form is corrupted
3148 by store-store chain. Though it's not always the case if
3149 eliminated stores only store loop invariant values into
3150 memory. */
3151 loop_closed_ssa = true;
3153 else
3155 release_chain (chain);
3156 chains.unordered_remove (i);
3159 return loop_closed_ssa;
3162 /* Insert all initializing gimple stmts into loop's entry edge. */
3164 static void
3165 insert_init_seqs (class loop *loop, vec<chain_p> chains)
3167 unsigned i;
3168 edge entry = loop_preheader_edge (loop);
3170 for (i = 0; i < chains.length (); ++i)
3171 if (chains[i]->init_seq)
3173 gsi_insert_seq_on_edge_immediate (entry, chains[i]->init_seq);
3174 chains[i]->init_seq = NULL;
3178 /* Performs predictive commoning for LOOP. Sets bit 1<<0 of return value
3179 if LOOP was unrolled; Sets bit 1<<1 of return value if loop closed ssa
3180 form was corrupted. */
3182 static unsigned
3183 tree_predictive_commoning_loop (class loop *loop)
3185 vec<data_reference_p> datarefs;
3186 vec<ddr_p> dependences;
3187 struct component *components;
3188 vec<chain_p> chains = vNULL;
3189 unsigned unroll_factor;
3190 class tree_niter_desc desc;
3191 bool unroll = false, loop_closed_ssa = false;
3192 edge exit;
3194 if (dump_file && (dump_flags & TDF_DETAILS))
3195 fprintf (dump_file, "Processing loop %d\n", loop->num);
3197 /* Nothing for predicitive commoning if loop only iterates 1 time. */
3198 if (get_max_loop_iterations_int (loop) == 0)
3200 if (dump_file && (dump_flags & TDF_DETAILS))
3201 fprintf (dump_file, "Loop iterates only 1 time, nothing to do.\n");
3203 return 0;
3206 /* Find the data references and split them into components according to their
3207 dependence relations. */
3208 auto_vec<loop_p, 3> loop_nest;
3209 dependences.create (10);
3210 datarefs.create (10);
3211 if (! compute_data_dependences_for_loop (loop, true, &loop_nest, &datarefs,
3212 &dependences))
3214 if (dump_file && (dump_flags & TDF_DETAILS))
3215 fprintf (dump_file, "Cannot analyze data dependencies\n");
3216 free_data_refs (datarefs);
3217 free_dependence_relations (dependences);
3218 return 0;
3221 if (dump_file && (dump_flags & TDF_DETAILS))
3222 dump_data_dependence_relations (dump_file, dependences);
3224 components = split_data_refs_to_components (loop, datarefs, dependences);
3225 loop_nest.release ();
3226 free_dependence_relations (dependences);
3227 if (!components)
3229 free_data_refs (datarefs);
3230 free_affine_expand_cache (&name_expansions);
3231 return 0;
3234 if (dump_file && (dump_flags & TDF_DETAILS))
3236 fprintf (dump_file, "Initial state:\n\n");
3237 dump_components (dump_file, components);
3240 /* Find the suitable components and split them into chains. */
3241 components = filter_suitable_components (loop, components);
3243 auto_bitmap tmp_vars;
3244 looparound_phis = BITMAP_ALLOC (NULL);
3245 determine_roots (loop, components, &chains);
3246 release_components (components);
3248 if (!chains.exists ())
3250 if (dump_file && (dump_flags & TDF_DETAILS))
3251 fprintf (dump_file,
3252 "Predictive commoning failed: no suitable chains\n");
3253 goto end;
3255 prepare_initializers (loop, chains);
3256 loop_closed_ssa = prepare_finalizers (loop, chains);
3258 /* Try to combine the chains that are always worked with together. */
3259 try_combine_chains (loop, &chains);
3261 insert_init_seqs (loop, chains);
3263 if (dump_file && (dump_flags & TDF_DETAILS))
3265 fprintf (dump_file, "Before commoning:\n\n");
3266 dump_chains (dump_file, chains);
3269 /* Determine the unroll factor, and if the loop should be unrolled, ensure
3270 that its number of iterations is divisible by the factor. */
3271 unroll_factor = determine_unroll_factor (chains);
3272 scev_reset ();
3273 unroll = (unroll_factor > 1
3274 && can_unroll_loop_p (loop, unroll_factor, &desc));
3275 exit = single_dom_exit (loop);
3277 /* Execute the predictive commoning transformations, and possibly unroll the
3278 loop. */
3279 if (unroll)
3281 struct epcc_data dta;
3283 if (dump_file && (dump_flags & TDF_DETAILS))
3284 fprintf (dump_file, "Unrolling %u times.\n", unroll_factor);
3286 dta.chains = chains;
3287 dta.tmp_vars = tmp_vars;
3289 update_ssa (TODO_update_ssa_only_virtuals);
3291 /* Cfg manipulations performed in tree_transform_and_unroll_loop before
3292 execute_pred_commoning_cbck is called may cause phi nodes to be
3293 reallocated, which is a problem since CHAINS may point to these
3294 statements. To fix this, we store the ssa names defined by the
3295 phi nodes here instead of the phi nodes themselves, and restore
3296 the phi nodes in execute_pred_commoning_cbck. A bit hacky. */
3297 replace_phis_by_defined_names (chains);
3299 tree_transform_and_unroll_loop (loop, unroll_factor, exit, &desc,
3300 execute_pred_commoning_cbck, &dta);
3301 eliminate_temp_copies (loop, tmp_vars);
3303 else
3305 if (dump_file && (dump_flags & TDF_DETAILS))
3306 fprintf (dump_file,
3307 "Executing predictive commoning without unrolling.\n");
3308 execute_pred_commoning (loop, chains, tmp_vars);
3311 end: ;
3312 release_chains (chains);
3313 free_data_refs (datarefs);
3314 BITMAP_FREE (looparound_phis);
3316 free_affine_expand_cache (&name_expansions);
3318 return (unroll ? 1 : 0) | (loop_closed_ssa ? 2 : 0);
3321 /* Runs predictive commoning. */
3323 unsigned
3324 tree_predictive_commoning (void)
3326 class loop *loop;
3327 unsigned ret = 0, changed = 0;
3329 initialize_original_copy_tables ();
3330 FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
3331 if (optimize_loop_for_speed_p (loop))
3333 changed |= tree_predictive_commoning_loop (loop);
3335 free_original_copy_tables ();
3337 if (changed > 0)
3339 scev_reset ();
3341 if (changed > 1)
3342 rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa);
3344 ret = TODO_cleanup_cfg;
3347 return ret;
3350 /* Predictive commoning Pass. */
3352 static unsigned
3353 run_tree_predictive_commoning (struct function *fun)
3355 if (number_of_loops (fun) <= 1)
3356 return 0;
3358 return tree_predictive_commoning ();
3361 namespace {
3363 const pass_data pass_data_predcom =
3365 GIMPLE_PASS, /* type */
3366 "pcom", /* name */
3367 OPTGROUP_LOOP, /* optinfo_flags */
3368 TV_PREDCOM, /* tv_id */
3369 PROP_cfg, /* properties_required */
3370 0, /* properties_provided */
3371 0, /* properties_destroyed */
3372 0, /* todo_flags_start */
3373 TODO_update_ssa_only_virtuals, /* todo_flags_finish */
3376 class pass_predcom : public gimple_opt_pass
3378 public:
3379 pass_predcom (gcc::context *ctxt)
3380 : gimple_opt_pass (pass_data_predcom, ctxt)
3383 /* opt_pass methods: */
3384 virtual bool gate (function *) { return flag_predictive_commoning != 0; }
3385 virtual unsigned int execute (function *fun)
3387 return run_tree_predictive_commoning (fun);
3390 }; // class pass_predcom
3392 } // anon namespace
3394 gimple_opt_pass *
3395 make_pass_predcom (gcc::context *ctxt)
3397 return new pass_predcom (ctxt);