1 /* Predictive commoning.
2 Copyright (C) 2005, 2007, 2008, 2009, 2010, 2011, 2012
3 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by the
9 Free Software Foundation; either version 3, or (at your option) any
12 GCC is distributed in the hope that it will be useful, but WITHOUT
13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
21 /* This file implements the predictive commoning optimization. Predictive
22 commoning can be viewed as CSE around a loop, and with some improvements,
23 as generalized strength reduction-- i.e., reusing values computed in
24 earlier iterations of a loop in the later ones. So far, the pass only
25 handles the most useful case, that is, reusing values of memory references.
26 If you think this is all just a special case of PRE, you are sort of right;
27 however, concentrating on loops is simpler, and makes it possible to
28 incorporate data dependence analysis to detect the opportunities, perform
29 loop unrolling to avoid copies together with renaming immediately,
30 and if needed, we could also take register pressure into account.
32 Let us demonstrate what is done on an example:
34 for (i = 0; i < 100; i++)
36 a[i+2] = a[i] + a[i+1];
42 1) We find data references in the loop, and split them to mutually
43 independent groups (i.e., we find components of a data dependence
44 graph). We ignore read-read dependences whose distance is not constant.
45 (TODO -- we could also ignore antidependences). In this example, we
46 find the following groups:
48 a[i]{read}, a[i+1]{read}, a[i+2]{write}
49 b[10]{read}, b[10]{write}
50 c[99 - i]{read}, c[i]{write}
51 d[i + 1]{read}, d[i]{write}
53 2) Inside each of the group, we verify several conditions:
54 a) all the references must differ in indices only, and the indices
55 must all have the same step
56 b) the references must dominate loop latch (and thus, they must be
57 ordered by dominance relation).
58 c) the distance of the indices must be a small multiple of the step
59 We are then able to compute the difference of the references (# of
60 iterations before they point to the same place as the first of them).
61 Also, in case there are writes in the loop, we split the groups into
62 chains whose head is the write whose values are used by the reads in
63 the same chain. The chains are then processed independently,
64 making the further transformations simpler. Also, the shorter chains
65 need the same number of registers, but may require lower unrolling
66 factor in order to get rid of the copies on the loop latch.
68 In our example, we get the following chains (the chain for c is invalid).
70 a[i]{read,+0}, a[i+1]{read,-1}, a[i+2]{write,-2}
71 b[10]{read,+0}, b[10]{write,+0}
72 d[i + 1]{read,+0}, d[i]{write,+1}
74 3) For each read, we determine the read or write whose value it reuses,
75 together with the distance of this reuse. I.e. we take the last
76 reference before it with distance 0, or the last of the references
77 with the smallest positive distance to the read. Then, we remove
78 the references that are not used in any of these chains, discard the
79 empty groups, and propagate all the links so that they point to the
80 single root reference of the chain (adjusting their distance
81 appropriately). Some extra care needs to be taken for references with
82 step 0. In our example (the numbers indicate the distance of the
85 a[i] --> (*) 2, a[i+1] --> (*) 1, a[i+2] (*)
86 b[10] --> (*) 1, b[10] (*)
88 4) The chains are combined together if possible. If the corresponding
89 elements of two chains are always combined together with the same
90 operator, we remember just the result of this combination, instead
91 of remembering the values separately. We may need to perform
92 reassociation to enable combining, for example
94 e[i] + f[i+1] + e[i+1] + f[i]
96 can be reassociated as
98 (e[i] + f[i]) + (e[i+1] + f[i+1])
100 and we can combine the chains for e and f into one chain.
102 5) For each root reference (end of the chain) R, let N be maximum distance
103 of a reference reusing its value. Variables R0 up to RN are created,
104 together with phi nodes that transfer values from R1 .. RN to
106 Initial values are loaded to R0..R(N-1) (in case not all references
107 must necessarily be accessed and they may trap, we may fail here;
108 TODO sometimes, the loads could be guarded by a check for the number
109 of iterations). Values loaded/stored in roots are also copied to
110 RN. Other reads are replaced with the appropriate variable Ri.
111 Everything is put to SSA form.
113 As a small improvement, if R0 is dead after the root (i.e., all uses of
114 the value with the maximum distance dominate the root), we can avoid
115 creating RN and use R0 instead of it.
117 In our example, we get (only the parts concerning a and b are shown):
118 for (i = 0; i < 100; i++)
130 6) Factor F for unrolling is determined as the smallest common multiple of
131 (N + 1) for each root reference (N for references for that we avoided
132 creating RN). If F and the loop is small enough, loop is unrolled F
133 times. The stores to RN (R0) in the copies of the loop body are
134 periodically replaced with R0, R1, ... (R1, R2, ...), so that they can
135 be coalesced and the copies can be eliminated.
137 TODO -- copy propagation and other optimizations may change the live
138 ranges of the temporary registers and prevent them from being coalesced;
139 this may increase the register pressure.
141 In our case, F = 2 and the (main loop of the) result is
143 for (i = 0; i < ...; i += 2)
160 TODO -- stores killing other stores can be taken into account, e.g.,
161 for (i = 0; i < n; i++)
171 for (i = 0; i < n; i++)
181 The interesting part is that this would generalize store motion; still, since
182 sm is performed elsewhere, it does not seem that important.
184 Predictive commoning can be generalized for arbitrary computations (not
185 just memory loads), and also nontrivial transfer functions (e.g., replacing
186 i * i with ii_last + 2 * i + 1), to generalize strength reduction. */
190 #include "coretypes.h"
195 #include "tree-flow.h"
197 #include "tree-data-ref.h"
198 #include "tree-scalar-evolution.h"
199 #include "tree-chrec.h"
201 #include "gimple-pretty-print.h"
202 #include "tree-pass.h"
203 #include "tree-affine.h"
204 #include "tree-inline.h"
206 /* The maximum number of iterations between the considered memory
209 #define MAX_DISTANCE (target_avail_regs < 16 ? 4 : 8)
211 /* Data references (or phi nodes that carry data reference values across
214 typedef struct dref_d
216 /* The reference itself. */
217 struct data_reference
*ref
;
219 /* The statement in that the reference appears. */
222 /* In case that STMT is a phi node, this field is set to the SSA name
223 defined by it in replace_phis_by_defined_names (in order to avoid
224 pointing to phi node that got reallocated in the meantime). */
225 tree name_defined_by_phi
;
227 /* Distance of the reference from the root of the chain (in number of
228 iterations of the loop). */
231 /* Number of iterations offset from the first reference in the component. */
234 /* Number of the reference in a component, in dominance ordering. */
237 /* True if the memory reference is always accessed when the loop is
239 unsigned always_accessed
: 1;
243 DEF_VEC_ALLOC_P (dref
, heap
);
245 /* Type of the chain of the references. */
249 /* The addresses of the references in the chain are constant. */
252 /* There are only loads in the chain. */
255 /* Root of the chain is store, the rest are loads. */
258 /* A combination of two chains. */
262 /* Chains of data references. */
266 /* Type of the chain. */
267 enum chain_type type
;
269 /* For combination chains, the operator and the two chains that are
270 combined, and the type of the result. */
273 struct chain
*ch1
, *ch2
;
275 /* The references in the chain. */
276 VEC(dref
,heap
) *refs
;
278 /* The maximum distance of the reference in the chain from the root. */
281 /* The variables used to copy the value throughout iterations. */
282 VEC(tree
,heap
) *vars
;
284 /* Initializers for the variables. */
285 VEC(tree
,heap
) *inits
;
287 /* True if there is a use of a variable with the maximal distance
288 that comes after the root in the loop. */
289 unsigned has_max_use_after
: 1;
291 /* True if all the memory references in the chain are always accessed. */
292 unsigned all_always_accessed
: 1;
294 /* True if this chain was combined together with some other chain. */
295 unsigned combined
: 1;
299 DEF_VEC_ALLOC_P (chain_p
, heap
);
301 /* Describes the knowledge about the step of the memory references in
306 /* The step is zero. */
309 /* The step is nonzero. */
312 /* The step may or may not be nonzero. */
316 /* Components of the data dependence graph. */
320 /* The references in the component. */
321 VEC(dref
,heap
) *refs
;
323 /* What we know about the step of the references in the component. */
324 enum ref_step_type comp_step
;
326 /* Next component in the list. */
327 struct component
*next
;
330 /* Bitmap of ssa names defined by looparound phi nodes covered by chains. */
332 static bitmap looparound_phis
;
334 /* Cache used by tree_to_aff_combination_expand. */
336 static struct pointer_map_t
*name_expansions
;
338 /* Dumps data reference REF to FILE. */
340 extern void dump_dref (FILE *, dref
);
342 dump_dref (FILE *file
, dref ref
)
347 print_generic_expr (file
, DR_REF (ref
->ref
), TDF_SLIM
);
348 fprintf (file
, " (id %u%s)\n", ref
->pos
,
349 DR_IS_READ (ref
->ref
) ? "" : ", write");
351 fprintf (file
, " offset ");
352 dump_double_int (file
, ref
->offset
, false);
353 fprintf (file
, "\n");
355 fprintf (file
, " distance %u\n", ref
->distance
);
359 if (gimple_code (ref
->stmt
) == GIMPLE_PHI
)
360 fprintf (file
, " looparound ref\n");
362 fprintf (file
, " combination ref\n");
363 fprintf (file
, " in statement ");
364 print_gimple_stmt (file
, ref
->stmt
, 0, TDF_SLIM
);
365 fprintf (file
, "\n");
366 fprintf (file
, " distance %u\n", ref
->distance
);
371 /* Dumps CHAIN to FILE. */
373 extern void dump_chain (FILE *, chain_p
);
375 dump_chain (FILE *file
, chain_p chain
)
378 const char *chain_type
;
385 chain_type
= "Load motion";
389 chain_type
= "Loads-only";
393 chain_type
= "Store-loads";
397 chain_type
= "Combination";
404 fprintf (file
, "%s chain %p%s\n", chain_type
, (void *) chain
,
405 chain
->combined
? " (combined)" : "");
406 if (chain
->type
!= CT_INVARIANT
)
407 fprintf (file
, " max distance %u%s\n", chain
->length
,
408 chain
->has_max_use_after
? "" : ", may reuse first");
410 if (chain
->type
== CT_COMBINATION
)
412 fprintf (file
, " equal to %p %s %p in type ",
413 (void *) chain
->ch1
, op_symbol_code (chain
->op
),
414 (void *) chain
->ch2
);
415 print_generic_expr (file
, chain
->rslt_type
, TDF_SLIM
);
416 fprintf (file
, "\n");
421 fprintf (file
, " vars");
422 FOR_EACH_VEC_ELT (tree
, chain
->vars
, i
, var
)
425 print_generic_expr (file
, var
, TDF_SLIM
);
427 fprintf (file
, "\n");
432 fprintf (file
, " inits");
433 FOR_EACH_VEC_ELT (tree
, chain
->inits
, i
, var
)
436 print_generic_expr (file
, var
, TDF_SLIM
);
438 fprintf (file
, "\n");
441 fprintf (file
, " references:\n");
442 FOR_EACH_VEC_ELT (dref
, chain
->refs
, i
, a
)
445 fprintf (file
, "\n");
448 /* Dumps CHAINS to FILE. */
450 extern void dump_chains (FILE *, VEC (chain_p
, heap
) *);
452 dump_chains (FILE *file
, VEC (chain_p
, heap
) *chains
)
457 FOR_EACH_VEC_ELT (chain_p
, chains
, i
, chain
)
458 dump_chain (file
, chain
);
461 /* Dumps COMP to FILE. */
463 extern void dump_component (FILE *, struct component
*);
465 dump_component (FILE *file
, struct component
*comp
)
470 fprintf (file
, "Component%s:\n",
471 comp
->comp_step
== RS_INVARIANT
? " (invariant)" : "");
472 FOR_EACH_VEC_ELT (dref
, comp
->refs
, i
, a
)
474 fprintf (file
, "\n");
477 /* Dumps COMPS to FILE. */
479 extern void dump_components (FILE *, struct component
*);
481 dump_components (FILE *file
, struct component
*comps
)
483 struct component
*comp
;
485 for (comp
= comps
; comp
; comp
= comp
->next
)
486 dump_component (file
, comp
);
489 /* Frees a chain CHAIN. */
492 release_chain (chain_p chain
)
500 FOR_EACH_VEC_ELT (dref
, chain
->refs
, i
, ref
)
503 VEC_free (dref
, heap
, chain
->refs
);
504 VEC_free (tree
, heap
, chain
->vars
);
505 VEC_free (tree
, heap
, chain
->inits
);
513 release_chains (VEC (chain_p
, heap
) *chains
)
518 FOR_EACH_VEC_ELT (chain_p
, chains
, i
, chain
)
519 release_chain (chain
);
520 VEC_free (chain_p
, heap
, chains
);
523 /* Frees a component COMP. */
526 release_component (struct component
*comp
)
528 VEC_free (dref
, heap
, comp
->refs
);
532 /* Frees list of components COMPS. */
535 release_components (struct component
*comps
)
537 struct component
*act
, *next
;
539 for (act
= comps
; act
; act
= next
)
542 release_component (act
);
546 /* Finds a root of tree given by FATHERS containing A, and performs path
550 component_of (unsigned fathers
[], unsigned a
)
554 for (root
= a
; root
!= fathers
[root
]; root
= fathers
[root
])
557 for (; a
!= root
; a
= n
)
566 /* Join operation for DFU. FATHERS gives the tree, SIZES are sizes of the
567 components, A and B are components to merge. */
570 merge_comps (unsigned fathers
[], unsigned sizes
[], unsigned a
, unsigned b
)
572 unsigned ca
= component_of (fathers
, a
);
573 unsigned cb
= component_of (fathers
, b
);
578 if (sizes
[ca
] < sizes
[cb
])
580 sizes
[cb
] += sizes
[ca
];
585 sizes
[ca
] += sizes
[cb
];
590 /* Returns true if A is a reference that is suitable for predictive commoning
591 in the innermost loop that contains it. REF_STEP is set according to the
592 step of the reference A. */
595 suitable_reference_p (struct data_reference
*a
, enum ref_step_type
*ref_step
)
597 tree ref
= DR_REF (a
), step
= DR_STEP (a
);
600 || TREE_THIS_VOLATILE (ref
)
601 || !is_gimple_reg_type (TREE_TYPE (ref
))
602 || tree_could_throw_p (ref
))
605 if (integer_zerop (step
))
606 *ref_step
= RS_INVARIANT
;
607 else if (integer_nonzerop (step
))
608 *ref_step
= RS_NONZERO
;
615 /* Stores DR_OFFSET (DR) + DR_INIT (DR) to OFFSET. */
618 aff_combination_dr_offset (struct data_reference
*dr
, aff_tree
*offset
)
620 tree type
= TREE_TYPE (DR_OFFSET (dr
));
623 tree_to_aff_combination_expand (DR_OFFSET (dr
), type
, offset
,
625 aff_combination_const (&delta
, type
, tree_to_double_int (DR_INIT (dr
)));
626 aff_combination_add (offset
, &delta
);
629 /* Determines number of iterations of the innermost enclosing loop before B
630 refers to exactly the same location as A and stores it to OFF. If A and
631 B do not have the same step, they never meet, or anything else fails,
632 returns false, otherwise returns true. Both A and B are assumed to
633 satisfy suitable_reference_p. */
636 determine_offset (struct data_reference
*a
, struct data_reference
*b
,
639 aff_tree diff
, baseb
, step
;
642 /* Check that both the references access the location in the same type. */
643 typea
= TREE_TYPE (DR_REF (a
));
644 typeb
= TREE_TYPE (DR_REF (b
));
645 if (!useless_type_conversion_p (typeb
, typea
))
648 /* Check whether the base address and the step of both references is the
650 if (!operand_equal_p (DR_STEP (a
), DR_STEP (b
), 0)
651 || !operand_equal_p (DR_BASE_ADDRESS (a
), DR_BASE_ADDRESS (b
), 0))
654 if (integer_zerop (DR_STEP (a
)))
656 /* If the references have loop invariant address, check that they access
657 exactly the same location. */
658 *off
= double_int_zero
;
659 return (operand_equal_p (DR_OFFSET (a
), DR_OFFSET (b
), 0)
660 && operand_equal_p (DR_INIT (a
), DR_INIT (b
), 0));
663 /* Compare the offsets of the addresses, and check whether the difference
664 is a multiple of step. */
665 aff_combination_dr_offset (a
, &diff
);
666 aff_combination_dr_offset (b
, &baseb
);
667 aff_combination_scale (&baseb
, double_int_minus_one
);
668 aff_combination_add (&diff
, &baseb
);
670 tree_to_aff_combination_expand (DR_STEP (a
), TREE_TYPE (DR_STEP (a
)),
671 &step
, &name_expansions
);
672 return aff_combination_constant_multiple_p (&diff
, &step
, off
);
675 /* Returns the last basic block in LOOP for that we are sure that
676 it is executed whenever the loop is entered. */
679 last_always_executed_block (struct loop
*loop
)
682 VEC (edge
, heap
) *exits
= get_loop_exit_edges (loop
);
684 basic_block last
= loop
->latch
;
686 FOR_EACH_VEC_ELT (edge
, exits
, i
, ex
)
687 last
= nearest_common_dominator (CDI_DOMINATORS
, last
, ex
->src
);
688 VEC_free (edge
, heap
, exits
);
693 /* Splits dependence graph on DATAREFS described by DEPENDS to components. */
695 static struct component
*
696 split_data_refs_to_components (struct loop
*loop
,
697 VEC (data_reference_p
, heap
) *datarefs
,
698 VEC (ddr_p
, heap
) *depends
)
700 unsigned i
, n
= VEC_length (data_reference_p
, datarefs
);
701 unsigned ca
, ia
, ib
, bad
;
702 unsigned *comp_father
= XNEWVEC (unsigned, n
+ 1);
703 unsigned *comp_size
= XNEWVEC (unsigned, n
+ 1);
704 struct component
**comps
;
705 struct data_reference
*dr
, *dra
, *drb
;
706 struct data_dependence_relation
*ddr
;
707 struct component
*comp_list
= NULL
, *comp
;
709 basic_block last_always_executed
= last_always_executed_block (loop
);
711 FOR_EACH_VEC_ELT (data_reference_p
, datarefs
, i
, dr
)
715 /* A fake reference for call or asm_expr that may clobber memory;
719 dr
->aux
= (void *) (size_t) i
;
724 /* A component reserved for the "bad" data references. */
728 FOR_EACH_VEC_ELT (data_reference_p
, datarefs
, i
, dr
)
730 enum ref_step_type dummy
;
732 if (!suitable_reference_p (dr
, &dummy
))
734 ia
= (unsigned) (size_t) dr
->aux
;
735 merge_comps (comp_father
, comp_size
, n
, ia
);
739 FOR_EACH_VEC_ELT (ddr_p
, depends
, i
, ddr
)
741 double_int dummy_off
;
743 if (DDR_ARE_DEPENDENT (ddr
) == chrec_known
)
748 ia
= component_of (comp_father
, (unsigned) (size_t) dra
->aux
);
749 ib
= component_of (comp_father
, (unsigned) (size_t) drb
->aux
);
753 bad
= component_of (comp_father
, n
);
755 /* If both A and B are reads, we may ignore unsuitable dependences. */
756 if (DR_IS_READ (dra
) && DR_IS_READ (drb
)
757 && (ia
== bad
|| ib
== bad
758 || !determine_offset (dra
, drb
, &dummy_off
)))
761 merge_comps (comp_father
, comp_size
, ia
, ib
);
764 comps
= XCNEWVEC (struct component
*, n
);
765 bad
= component_of (comp_father
, n
);
766 FOR_EACH_VEC_ELT (data_reference_p
, datarefs
, i
, dr
)
768 ia
= (unsigned) (size_t) dr
->aux
;
769 ca
= component_of (comp_father
, ia
);
776 comp
= XCNEW (struct component
);
777 comp
->refs
= VEC_alloc (dref
, heap
, comp_size
[ca
]);
781 dataref
= XCNEW (struct dref_d
);
783 dataref
->stmt
= DR_STMT (dr
);
784 dataref
->offset
= double_int_zero
;
785 dataref
->distance
= 0;
787 dataref
->always_accessed
788 = dominated_by_p (CDI_DOMINATORS
, last_always_executed
,
789 gimple_bb (dataref
->stmt
));
790 dataref
->pos
= VEC_length (dref
, comp
->refs
);
791 VEC_quick_push (dref
, comp
->refs
, dataref
);
794 for (i
= 0; i
< n
; i
++)
799 comp
->next
= comp_list
;
811 /* Returns true if the component COMP satisfies the conditions
812 described in 2) at the beginning of this file. LOOP is the current
816 suitable_component_p (struct loop
*loop
, struct component
*comp
)
820 basic_block ba
, bp
= loop
->header
;
821 bool ok
, has_write
= false;
823 FOR_EACH_VEC_ELT (dref
, comp
->refs
, i
, a
)
825 ba
= gimple_bb (a
->stmt
);
827 if (!just_once_each_iteration_p (loop
, ba
))
830 gcc_assert (dominated_by_p (CDI_DOMINATORS
, ba
, bp
));
833 if (DR_IS_WRITE (a
->ref
))
837 first
= VEC_index (dref
, comp
->refs
, 0);
838 ok
= suitable_reference_p (first
->ref
, &comp
->comp_step
);
840 first
->offset
= double_int_zero
;
842 for (i
= 1; VEC_iterate (dref
, comp
->refs
, i
, a
); i
++)
844 if (!determine_offset (first
->ref
, a
->ref
, &a
->offset
))
847 #ifdef ENABLE_CHECKING
849 enum ref_step_type a_step
;
850 ok
= suitable_reference_p (a
->ref
, &a_step
);
851 gcc_assert (ok
&& a_step
== comp
->comp_step
);
856 /* If there is a write inside the component, we must know whether the
857 step is nonzero or not -- we would not otherwise be able to recognize
858 whether the value accessed by reads comes from the OFFSET-th iteration
859 or the previous one. */
860 if (has_write
&& comp
->comp_step
== RS_ANY
)
866 /* Check the conditions on references inside each of components COMPS,
867 and remove the unsuitable components from the list. The new list
868 of components is returned. The conditions are described in 2) at
869 the beginning of this file. LOOP is the current loop. */
871 static struct component
*
872 filter_suitable_components (struct loop
*loop
, struct component
*comps
)
874 struct component
**comp
, *act
;
876 for (comp
= &comps
; *comp
; )
879 if (suitable_component_p (loop
, act
))
887 FOR_EACH_VEC_ELT (dref
, act
->refs
, i
, ref
)
889 release_component (act
);
896 /* Compares two drefs A and B by their offset and position. Callback for
900 order_drefs (const void *a
, const void *b
)
902 const dref
*const da
= (const dref
*) a
;
903 const dref
*const db
= (const dref
*) b
;
904 int offcmp
= (*da
)->offset
.scmp ((*db
)->offset
);
909 return (*da
)->pos
- (*db
)->pos
;
912 /* Returns root of the CHAIN. */
915 get_chain_root (chain_p chain
)
917 return VEC_index (dref
, chain
->refs
, 0);
920 /* Adds REF to the chain CHAIN. */
923 add_ref_to_chain (chain_p chain
, dref ref
)
925 dref root
= get_chain_root (chain
);
928 gcc_assert (root
->offset
.sle (ref
->offset
));
929 dist
= ref
->offset
- root
->offset
;
930 if (double_int::from_uhwi (MAX_DISTANCE
).ule (dist
))
935 gcc_assert (dist
.fits_uhwi ());
937 VEC_safe_push (dref
, heap
, chain
->refs
, ref
);
939 ref
->distance
= dist
.to_uhwi ();
941 if (ref
->distance
>= chain
->length
)
943 chain
->length
= ref
->distance
;
944 chain
->has_max_use_after
= false;
947 if (ref
->distance
== chain
->length
948 && ref
->pos
> root
->pos
)
949 chain
->has_max_use_after
= true;
951 chain
->all_always_accessed
&= ref
->always_accessed
;
954 /* Returns the chain for invariant component COMP. */
957 make_invariant_chain (struct component
*comp
)
959 chain_p chain
= XCNEW (struct chain
);
963 chain
->type
= CT_INVARIANT
;
965 chain
->all_always_accessed
= true;
967 FOR_EACH_VEC_ELT (dref
, comp
->refs
, i
, ref
)
969 VEC_safe_push (dref
, heap
, chain
->refs
, ref
);
970 chain
->all_always_accessed
&= ref
->always_accessed
;
976 /* Make a new chain rooted at REF. */
979 make_rooted_chain (dref ref
)
981 chain_p chain
= XCNEW (struct chain
);
983 chain
->type
= DR_IS_READ (ref
->ref
) ? CT_LOAD
: CT_STORE_LOAD
;
985 VEC_safe_push (dref
, heap
, chain
->refs
, ref
);
986 chain
->all_always_accessed
= ref
->always_accessed
;
993 /* Returns true if CHAIN is not trivial. */
996 nontrivial_chain_p (chain_p chain
)
998 return chain
!= NULL
&& VEC_length (dref
, chain
->refs
) > 1;
1001 /* Returns the ssa name that contains the value of REF, or NULL_TREE if there
1005 name_for_ref (dref ref
)
1009 if (is_gimple_assign (ref
->stmt
))
1011 if (!ref
->ref
|| DR_IS_READ (ref
->ref
))
1012 name
= gimple_assign_lhs (ref
->stmt
);
1014 name
= gimple_assign_rhs1 (ref
->stmt
);
1017 name
= PHI_RESULT (ref
->stmt
);
1019 return (TREE_CODE (name
) == SSA_NAME
? name
: NULL_TREE
);
1022 /* Returns true if REF is a valid initializer for ROOT with given DISTANCE (in
1023 iterations of the innermost enclosing loop). */
1026 valid_initializer_p (struct data_reference
*ref
,
1027 unsigned distance
, struct data_reference
*root
)
1029 aff_tree diff
, base
, step
;
1032 /* Both REF and ROOT must be accessing the same object. */
1033 if (!operand_equal_p (DR_BASE_ADDRESS (ref
), DR_BASE_ADDRESS (root
), 0))
1036 /* The initializer is defined outside of loop, hence its address must be
1037 invariant inside the loop. */
1038 gcc_assert (integer_zerop (DR_STEP (ref
)));
1040 /* If the address of the reference is invariant, initializer must access
1041 exactly the same location. */
1042 if (integer_zerop (DR_STEP (root
)))
1043 return (operand_equal_p (DR_OFFSET (ref
), DR_OFFSET (root
), 0)
1044 && operand_equal_p (DR_INIT (ref
), DR_INIT (root
), 0));
1046 /* Verify that this index of REF is equal to the root's index at
1047 -DISTANCE-th iteration. */
1048 aff_combination_dr_offset (root
, &diff
);
1049 aff_combination_dr_offset (ref
, &base
);
1050 aff_combination_scale (&base
, double_int_minus_one
);
1051 aff_combination_add (&diff
, &base
);
1053 tree_to_aff_combination_expand (DR_STEP (root
), TREE_TYPE (DR_STEP (root
)),
1054 &step
, &name_expansions
);
1055 if (!aff_combination_constant_multiple_p (&diff
, &step
, &off
))
1058 if (off
!= double_int::from_uhwi (distance
))
1064 /* Finds looparound phi node of LOOP that copies the value of REF, and if its
1065 initial value is correct (equal to initial value of REF shifted by one
1066 iteration), returns the phi node. Otherwise, NULL_TREE is returned. ROOT
1067 is the root of the current chain. */
1070 find_looparound_phi (struct loop
*loop
, dref ref
, dref root
)
1072 tree name
, init
, init_ref
;
1073 gimple phi
= NULL
, init_stmt
;
1074 edge latch
= loop_latch_edge (loop
);
1075 struct data_reference init_dr
;
1076 gimple_stmt_iterator psi
;
1078 if (is_gimple_assign (ref
->stmt
))
1080 if (DR_IS_READ (ref
->ref
))
1081 name
= gimple_assign_lhs (ref
->stmt
);
1083 name
= gimple_assign_rhs1 (ref
->stmt
);
1086 name
= PHI_RESULT (ref
->stmt
);
1090 for (psi
= gsi_start_phis (loop
->header
); !gsi_end_p (psi
); gsi_next (&psi
))
1092 phi
= gsi_stmt (psi
);
1093 if (PHI_ARG_DEF_FROM_EDGE (phi
, latch
) == name
)
1097 if (gsi_end_p (psi
))
1100 init
= PHI_ARG_DEF_FROM_EDGE (phi
, loop_preheader_edge (loop
));
1101 if (TREE_CODE (init
) != SSA_NAME
)
1103 init_stmt
= SSA_NAME_DEF_STMT (init
);
1104 if (gimple_code (init_stmt
) != GIMPLE_ASSIGN
)
1106 gcc_assert (gimple_assign_lhs (init_stmt
) == init
);
1108 init_ref
= gimple_assign_rhs1 (init_stmt
);
1109 if (!REFERENCE_CLASS_P (init_ref
)
1110 && !DECL_P (init_ref
))
1113 /* Analyze the behavior of INIT_REF with respect to LOOP (innermost
1114 loop enclosing PHI). */
1115 memset (&init_dr
, 0, sizeof (struct data_reference
));
1116 DR_REF (&init_dr
) = init_ref
;
1117 DR_STMT (&init_dr
) = phi
;
1118 if (!dr_analyze_innermost (&init_dr
, loop
))
1121 if (!valid_initializer_p (&init_dr
, ref
->distance
+ 1, root
->ref
))
1127 /* Adds a reference for the looparound copy of REF in PHI to CHAIN. */
1130 insert_looparound_copy (chain_p chain
, dref ref
, gimple phi
)
1132 dref nw
= XCNEW (struct dref_d
), aref
;
1136 nw
->distance
= ref
->distance
+ 1;
1137 nw
->always_accessed
= 1;
1139 FOR_EACH_VEC_ELT (dref
, chain
->refs
, i
, aref
)
1140 if (aref
->distance
>= nw
->distance
)
1142 VEC_safe_insert (dref
, heap
, chain
->refs
, i
, nw
);
1144 if (nw
->distance
> chain
->length
)
1146 chain
->length
= nw
->distance
;
1147 chain
->has_max_use_after
= false;
1151 /* For references in CHAIN that are copied around the LOOP (created previously
1152 by PRE, or by user), add the results of such copies to the chain. This
1153 enables us to remove the copies by unrolling, and may need less registers
1154 (also, it may allow us to combine chains together). */
1157 add_looparound_copies (struct loop
*loop
, chain_p chain
)
1160 dref ref
, root
= get_chain_root (chain
);
1163 FOR_EACH_VEC_ELT (dref
, chain
->refs
, i
, ref
)
1165 phi
= find_looparound_phi (loop
, ref
, root
);
1169 bitmap_set_bit (looparound_phis
, SSA_NAME_VERSION (PHI_RESULT (phi
)));
1170 insert_looparound_copy (chain
, ref
, phi
);
1174 /* Find roots of the values and determine distances in the component COMP.
1175 The references are redistributed into CHAINS. LOOP is the current
1179 determine_roots_comp (struct loop
*loop
,
1180 struct component
*comp
,
1181 VEC (chain_p
, heap
) **chains
)
1185 chain_p chain
= NULL
;
1186 double_int last_ofs
= double_int_zero
;
1188 /* Invariants are handled specially. */
1189 if (comp
->comp_step
== RS_INVARIANT
)
1191 chain
= make_invariant_chain (comp
);
1192 VEC_safe_push (chain_p
, heap
, *chains
, chain
);
1196 VEC_qsort (dref
, comp
->refs
, order_drefs
);
1198 FOR_EACH_VEC_ELT (dref
, comp
->refs
, i
, a
)
1200 if (!chain
|| DR_IS_WRITE (a
->ref
)
1201 || double_int::from_uhwi (MAX_DISTANCE
).ule (a
->offset
- last_ofs
))
1203 if (nontrivial_chain_p (chain
))
1205 add_looparound_copies (loop
, chain
);
1206 VEC_safe_push (chain_p
, heap
, *chains
, chain
);
1209 release_chain (chain
);
1210 chain
= make_rooted_chain (a
);
1211 last_ofs
= a
->offset
;
1215 add_ref_to_chain (chain
, a
);
1218 if (nontrivial_chain_p (chain
))
1220 add_looparound_copies (loop
, chain
);
1221 VEC_safe_push (chain_p
, heap
, *chains
, chain
);
1224 release_chain (chain
);
1227 /* Find roots of the values and determine distances in components COMPS, and
1228 separates the references to CHAINS. LOOP is the current loop. */
1231 determine_roots (struct loop
*loop
,
1232 struct component
*comps
, VEC (chain_p
, heap
) **chains
)
1234 struct component
*comp
;
1236 for (comp
= comps
; comp
; comp
= comp
->next
)
1237 determine_roots_comp (loop
, comp
, chains
);
1240 /* Replace the reference in statement STMT with temporary variable
1241 NEW_TREE. If SET is true, NEW_TREE is instead initialized to the value of
1242 the reference in the statement. IN_LHS is true if the reference
1243 is in the lhs of STMT, false if it is in rhs. */
1246 replace_ref_with (gimple stmt
, tree new_tree
, bool set
, bool in_lhs
)
1250 gimple_stmt_iterator bsi
, psi
;
1252 if (gimple_code (stmt
) == GIMPLE_PHI
)
1254 gcc_assert (!in_lhs
&& !set
);
1256 val
= PHI_RESULT (stmt
);
1257 bsi
= gsi_after_labels (gimple_bb (stmt
));
1258 psi
= gsi_for_stmt (stmt
);
1259 remove_phi_node (&psi
, false);
1261 /* Turn the phi node into GIMPLE_ASSIGN. */
1262 new_stmt
= gimple_build_assign (val
, new_tree
);
1263 gsi_insert_before (&bsi
, new_stmt
, GSI_NEW_STMT
);
1267 /* Since the reference is of gimple_reg type, it should only
1268 appear as lhs or rhs of modify statement. */
1269 gcc_assert (is_gimple_assign (stmt
));
1271 bsi
= gsi_for_stmt (stmt
);
1273 /* If we do not need to initialize NEW_TREE, just replace the use of OLD. */
1276 gcc_assert (!in_lhs
);
1277 gimple_assign_set_rhs_from_tree (&bsi
, new_tree
);
1278 stmt
= gsi_stmt (bsi
);
1285 /* We have statement
1289 If OLD is a memory reference, then VAL is gimple_val, and we transform
1295 Otherwise, we are replacing a combination chain,
1296 VAL is the expression that performs the combination, and OLD is an
1297 SSA name. In this case, we transform the assignment to
1304 val
= gimple_assign_lhs (stmt
);
1305 if (TREE_CODE (val
) != SSA_NAME
)
1307 val
= gimple_assign_rhs1 (stmt
);
1308 gcc_assert (gimple_assign_single_p (stmt
));
1309 if (TREE_CLOBBER_P (val
))
1310 val
= get_or_create_ssa_default_def (cfun
, SSA_NAME_VAR (new_tree
));
1312 gcc_assert (gimple_assign_copy_p (stmt
));
1324 val
= gimple_assign_lhs (stmt
);
1327 new_stmt
= gimple_build_assign (new_tree
, unshare_expr (val
));
1328 gsi_insert_after (&bsi
, new_stmt
, GSI_NEW_STMT
);
1331 /* Returns the reference to the address of REF in the ITER-th iteration of
1332 LOOP, or NULL if we fail to determine it (ITER may be negative). We
1333 try to preserve the original shape of the reference (not rewrite it
1334 as an indirect ref to the address), to make tree_could_trap_p in
1335 prepare_initializers_chain return false more often. */
1338 ref_at_iteration (struct loop
*loop
, tree ref
, int iter
)
1340 tree idx
, *idx_p
, type
, val
, op0
= NULL_TREE
, ret
;
1344 if (handled_component_p (ref
))
1346 op0
= ref_at_iteration (loop
, TREE_OPERAND (ref
, 0), iter
);
1350 else if (!INDIRECT_REF_P (ref
)
1351 && TREE_CODE (ref
) != MEM_REF
)
1352 return unshare_expr (ref
);
1354 if (TREE_CODE (ref
) == MEM_REF
)
1356 ret
= unshare_expr (ref
);
1357 idx
= TREE_OPERAND (ref
, 0);
1358 idx_p
= &TREE_OPERAND (ret
, 0);
1360 else if (TREE_CODE (ref
) == COMPONENT_REF
)
1362 /* Check that the offset is loop invariant. */
1363 if (TREE_OPERAND (ref
, 2)
1364 && !expr_invariant_in_loop_p (loop
, TREE_OPERAND (ref
, 2)))
1367 return build3 (COMPONENT_REF
, TREE_TYPE (ref
), op0
,
1368 unshare_expr (TREE_OPERAND (ref
, 1)),
1369 unshare_expr (TREE_OPERAND (ref
, 2)));
1371 else if (TREE_CODE (ref
) == ARRAY_REF
)
1373 /* Check that the lower bound and the step are loop invariant. */
1374 if (TREE_OPERAND (ref
, 2)
1375 && !expr_invariant_in_loop_p (loop
, TREE_OPERAND (ref
, 2)))
1377 if (TREE_OPERAND (ref
, 3)
1378 && !expr_invariant_in_loop_p (loop
, TREE_OPERAND (ref
, 3)))
1381 ret
= build4 (ARRAY_REF
, TREE_TYPE (ref
), op0
, NULL_TREE
,
1382 unshare_expr (TREE_OPERAND (ref
, 2)),
1383 unshare_expr (TREE_OPERAND (ref
, 3)));
1384 idx
= TREE_OPERAND (ref
, 1);
1385 idx_p
= &TREE_OPERAND (ret
, 1);
1390 ok
= simple_iv (loop
, loop
, idx
, &iv
, true);
1393 iv
.base
= expand_simple_operations (iv
.base
);
1394 if (integer_zerop (iv
.step
))
1395 *idx_p
= unshare_expr (iv
.base
);
1398 type
= TREE_TYPE (iv
.base
);
1399 if (POINTER_TYPE_P (type
))
1401 val
= fold_build2 (MULT_EXPR
, sizetype
, iv
.step
,
1403 val
= fold_build_pointer_plus (iv
.base
, val
);
1407 val
= fold_build2 (MULT_EXPR
, type
, iv
.step
,
1408 build_int_cst_type (type
, iter
));
1409 val
= fold_build2 (PLUS_EXPR
, type
, iv
.base
, val
);
1411 *idx_p
= unshare_expr (val
);
1417 /* Get the initialization expression for the INDEX-th temporary variable
1421 get_init_expr (chain_p chain
, unsigned index
)
1423 if (chain
->type
== CT_COMBINATION
)
1425 tree e1
= get_init_expr (chain
->ch1
, index
);
1426 tree e2
= get_init_expr (chain
->ch2
, index
);
1428 return fold_build2 (chain
->op
, chain
->rslt_type
, e1
, e2
);
1431 return VEC_index (tree
, chain
->inits
, index
);
1434 /* Returns a new temporary variable used for the I-th variable carrying
1435 value of REF. The variable's uid is marked in TMP_VARS. */
1438 predcom_tmp_var (tree ref
, unsigned i
, bitmap tmp_vars
)
1440 tree type
= TREE_TYPE (ref
);
1441 /* We never access the components of the temporary variable in predictive
1443 tree var
= create_tmp_reg (type
, get_lsm_tmp_name (ref
, i
));
1444 bitmap_set_bit (tmp_vars
, DECL_UID (var
));
1448 /* Creates the variables for CHAIN, as well as phi nodes for them and
1449 initialization on entry to LOOP. Uids of the newly created
1450 temporary variables are marked in TMP_VARS. */
1453 initialize_root_vars (struct loop
*loop
, chain_p chain
, bitmap tmp_vars
)
1456 unsigned n
= chain
->length
;
1457 dref root
= get_chain_root (chain
);
1458 bool reuse_first
= !chain
->has_max_use_after
;
1459 tree ref
, init
, var
, next
;
1462 edge entry
= loop_preheader_edge (loop
), latch
= loop_latch_edge (loop
);
1464 /* If N == 0, then all the references are within the single iteration. And
1465 since this is an nonempty chain, reuse_first cannot be true. */
1466 gcc_assert (n
> 0 || !reuse_first
);
1468 chain
->vars
= VEC_alloc (tree
, heap
, n
+ 1);
1470 if (chain
->type
== CT_COMBINATION
)
1471 ref
= gimple_assign_lhs (root
->stmt
);
1473 ref
= DR_REF (root
->ref
);
1475 for (i
= 0; i
< n
+ (reuse_first
? 0 : 1); i
++)
1477 var
= predcom_tmp_var (ref
, i
, tmp_vars
);
1478 VEC_quick_push (tree
, chain
->vars
, var
);
1481 VEC_quick_push (tree
, chain
->vars
, VEC_index (tree
, chain
->vars
, 0));
1483 FOR_EACH_VEC_ELT (tree
, chain
->vars
, i
, var
)
1484 VEC_replace (tree
, chain
->vars
, i
, make_ssa_name (var
, NULL
));
1486 for (i
= 0; i
< n
; i
++)
1488 var
= VEC_index (tree
, chain
->vars
, i
);
1489 next
= VEC_index (tree
, chain
->vars
, i
+ 1);
1490 init
= get_init_expr (chain
, i
);
1492 init
= force_gimple_operand (init
, &stmts
, true, NULL_TREE
);
1494 gsi_insert_seq_on_edge_immediate (entry
, stmts
);
1496 phi
= create_phi_node (var
, loop
->header
);
1497 add_phi_arg (phi
, init
, entry
, UNKNOWN_LOCATION
);
1498 add_phi_arg (phi
, next
, latch
, UNKNOWN_LOCATION
);
1502 /* Create the variables and initialization statement for root of chain
1503 CHAIN. Uids of the newly created temporary variables are marked
1507 initialize_root (struct loop
*loop
, chain_p chain
, bitmap tmp_vars
)
1509 dref root
= get_chain_root (chain
);
1510 bool in_lhs
= (chain
->type
== CT_STORE_LOAD
1511 || chain
->type
== CT_COMBINATION
);
1513 initialize_root_vars (loop
, chain
, tmp_vars
);
1514 replace_ref_with (root
->stmt
,
1515 VEC_index (tree
, chain
->vars
, chain
->length
),
1519 /* Initializes a variable for load motion for ROOT and prepares phi nodes and
1520 initialization on entry to LOOP if necessary. The ssa name for the variable
1521 is stored in VARS. If WRITTEN is true, also a phi node to copy its value
1522 around the loop is created. Uid of the newly created temporary variable
1523 is marked in TMP_VARS. INITS is the list containing the (single)
1527 initialize_root_vars_lm (struct loop
*loop
, dref root
, bool written
,
1528 VEC(tree
, heap
) **vars
, VEC(tree
, heap
) *inits
,
1532 tree ref
= DR_REF (root
->ref
), init
, var
, next
;
1535 edge entry
= loop_preheader_edge (loop
), latch
= loop_latch_edge (loop
);
1537 /* Find the initializer for the variable, and check that it cannot
1539 init
= VEC_index (tree
, inits
, 0);
1541 *vars
= VEC_alloc (tree
, heap
, written
? 2 : 1);
1542 var
= predcom_tmp_var (ref
, 0, tmp_vars
);
1543 VEC_quick_push (tree
, *vars
, var
);
1545 VEC_quick_push (tree
, *vars
, VEC_index (tree
, *vars
, 0));
1547 FOR_EACH_VEC_ELT (tree
, *vars
, i
, var
)
1548 VEC_replace (tree
, *vars
, i
, make_ssa_name (var
, NULL
));
1550 var
= VEC_index (tree
, *vars
, 0);
1552 init
= force_gimple_operand (init
, &stmts
, written
, NULL_TREE
);
1554 gsi_insert_seq_on_edge_immediate (entry
, stmts
);
1558 next
= VEC_index (tree
, *vars
, 1);
1559 phi
= create_phi_node (var
, loop
->header
);
1560 add_phi_arg (phi
, init
, entry
, UNKNOWN_LOCATION
);
1561 add_phi_arg (phi
, next
, latch
, UNKNOWN_LOCATION
);
1565 gimple init_stmt
= gimple_build_assign (var
, init
);
1566 gsi_insert_on_edge_immediate (entry
, init_stmt
);
1571 /* Execute load motion for references in chain CHAIN. Uids of the newly
1572 created temporary variables are marked in TMP_VARS. */
1575 execute_load_motion (struct loop
*loop
, chain_p chain
, bitmap tmp_vars
)
1577 VEC (tree
, heap
) *vars
;
1579 unsigned n_writes
= 0, ridx
, i
;
1582 gcc_assert (chain
->type
== CT_INVARIANT
);
1583 gcc_assert (!chain
->combined
);
1584 FOR_EACH_VEC_ELT (dref
, chain
->refs
, i
, a
)
1585 if (DR_IS_WRITE (a
->ref
))
1588 /* If there are no reads in the loop, there is nothing to do. */
1589 if (n_writes
== VEC_length (dref
, chain
->refs
))
1592 initialize_root_vars_lm (loop
, get_chain_root (chain
), n_writes
> 0,
1593 &vars
, chain
->inits
, tmp_vars
);
1596 FOR_EACH_VEC_ELT (dref
, chain
->refs
, i
, a
)
1598 bool is_read
= DR_IS_READ (a
->ref
);
1600 if (DR_IS_WRITE (a
->ref
))
1605 var
= VEC_index (tree
, vars
, 0);
1606 var
= make_ssa_name (SSA_NAME_VAR (var
), NULL
);
1607 VEC_replace (tree
, vars
, 0, var
);
1613 replace_ref_with (a
->stmt
, VEC_index (tree
, vars
, ridx
),
1614 !is_read
, !is_read
);
1617 VEC_free (tree
, heap
, vars
);
1620 /* Returns the single statement in that NAME is used, excepting
1621 the looparound phi nodes contained in one of the chains. If there is no
1622 such statement, or more statements, NULL is returned. */
1625 single_nonlooparound_use (tree name
)
1628 imm_use_iterator it
;
1629 gimple stmt
, ret
= NULL
;
1631 FOR_EACH_IMM_USE_FAST (use
, it
, name
)
1633 stmt
= USE_STMT (use
);
1635 if (gimple_code (stmt
) == GIMPLE_PHI
)
1637 /* Ignore uses in looparound phi nodes. Uses in other phi nodes
1638 could not be processed anyway, so just fail for them. */
1639 if (bitmap_bit_p (looparound_phis
,
1640 SSA_NAME_VERSION (PHI_RESULT (stmt
))))
1645 else if (is_gimple_debug (stmt
))
1647 else if (ret
!= NULL
)
1656 /* Remove statement STMT, as well as the chain of assignments in that it is
1660 remove_stmt (gimple stmt
)
1664 gimple_stmt_iterator psi
;
1666 if (gimple_code (stmt
) == GIMPLE_PHI
)
1668 name
= PHI_RESULT (stmt
);
1669 next
= single_nonlooparound_use (name
);
1670 reset_debug_uses (stmt
);
1671 psi
= gsi_for_stmt (stmt
);
1672 remove_phi_node (&psi
, true);
1675 || !gimple_assign_ssa_name_copy_p (next
)
1676 || gimple_assign_rhs1 (next
) != name
)
1684 gimple_stmt_iterator bsi
;
1686 bsi
= gsi_for_stmt (stmt
);
1688 name
= gimple_assign_lhs (stmt
);
1689 gcc_assert (TREE_CODE (name
) == SSA_NAME
);
1691 next
= single_nonlooparound_use (name
);
1692 reset_debug_uses (stmt
);
1694 unlink_stmt_vdef (stmt
);
1695 gsi_remove (&bsi
, true);
1696 release_defs (stmt
);
1699 || !gimple_assign_ssa_name_copy_p (next
)
1700 || gimple_assign_rhs1 (next
) != name
)
1707 /* Perform the predictive commoning optimization for a chain CHAIN.
1708 Uids of the newly created temporary variables are marked in TMP_VARS.*/
1711 execute_pred_commoning_chain (struct loop
*loop
, chain_p chain
,
1718 if (chain
->combined
)
1720 /* For combined chains, just remove the statements that are used to
1721 compute the values of the expression (except for the root one). */
1722 for (i
= 1; VEC_iterate (dref
, chain
->refs
, i
, a
); i
++)
1723 remove_stmt (a
->stmt
);
1727 /* For non-combined chains, set up the variables that hold its value,
1728 and replace the uses of the original references by these
1730 initialize_root (loop
, chain
, tmp_vars
);
1731 for (i
= 1; VEC_iterate (dref
, chain
->refs
, i
, a
); i
++)
1733 var
= VEC_index (tree
, chain
->vars
, chain
->length
- a
->distance
);
1734 replace_ref_with (a
->stmt
, var
, false, false);
1739 /* Determines the unroll factor necessary to remove as many temporary variable
1740 copies as possible. CHAINS is the list of chains that will be
1744 determine_unroll_factor (VEC (chain_p
, heap
) *chains
)
1747 unsigned factor
= 1, af
, nfactor
, i
;
1748 unsigned max
= PARAM_VALUE (PARAM_MAX_UNROLL_TIMES
);
1750 FOR_EACH_VEC_ELT (chain_p
, chains
, i
, chain
)
1752 if (chain
->type
== CT_INVARIANT
|| chain
->combined
)
1755 /* The best unroll factor for this chain is equal to the number of
1756 temporary variables that we create for it. */
1758 if (chain
->has_max_use_after
)
1761 nfactor
= factor
* af
/ gcd (factor
, af
);
1769 /* Perform the predictive commoning optimization for CHAINS.
1770 Uids of the newly created temporary variables are marked in TMP_VARS. */
1773 execute_pred_commoning (struct loop
*loop
, VEC (chain_p
, heap
) *chains
,
1779 FOR_EACH_VEC_ELT (chain_p
, chains
, i
, chain
)
1781 if (chain
->type
== CT_INVARIANT
)
1782 execute_load_motion (loop
, chain
, tmp_vars
);
1784 execute_pred_commoning_chain (loop
, chain
, tmp_vars
);
1787 update_ssa (TODO_update_ssa_only_virtuals
);
1790 /* For each reference in CHAINS, if its defining statement is
1791 phi node, record the ssa name that is defined by it. */
1794 replace_phis_by_defined_names (VEC (chain_p
, heap
) *chains
)
1800 FOR_EACH_VEC_ELT (chain_p
, chains
, i
, chain
)
1801 FOR_EACH_VEC_ELT (dref
, chain
->refs
, j
, a
)
1803 if (gimple_code (a
->stmt
) == GIMPLE_PHI
)
1805 a
->name_defined_by_phi
= PHI_RESULT (a
->stmt
);
1811 /* For each reference in CHAINS, if name_defined_by_phi is not
1812 NULL, use it to set the stmt field. */
1815 replace_names_by_phis (VEC (chain_p
, heap
) *chains
)
1821 FOR_EACH_VEC_ELT (chain_p
, chains
, i
, chain
)
1822 FOR_EACH_VEC_ELT (dref
, chain
->refs
, j
, a
)
1823 if (a
->stmt
== NULL
)
1825 a
->stmt
= SSA_NAME_DEF_STMT (a
->name_defined_by_phi
);
1826 gcc_assert (gimple_code (a
->stmt
) == GIMPLE_PHI
);
1827 a
->name_defined_by_phi
= NULL_TREE
;
1831 /* Wrapper over execute_pred_commoning, to pass it as a callback
1832 to tree_transform_and_unroll_loop. */
1836 VEC (chain_p
, heap
) *chains
;
1841 execute_pred_commoning_cbck (struct loop
*loop
, void *data
)
1843 struct epcc_data
*const dta
= (struct epcc_data
*) data
;
1845 /* Restore phi nodes that were replaced by ssa names before
1846 tree_transform_and_unroll_loop (see detailed description in
1847 tree_predictive_commoning_loop). */
1848 replace_names_by_phis (dta
->chains
);
1849 execute_pred_commoning (loop
, dta
->chains
, dta
->tmp_vars
);
1852 /* Base NAME and all the names in the chain of phi nodes that use it
1853 on variable VAR. The phi nodes are recognized by being in the copies of
1854 the header of the LOOP. */
1857 base_names_in_chain_on (struct loop
*loop
, tree name
, tree var
)
1860 imm_use_iterator iter
;
1862 replace_ssa_name_symbol (name
, var
);
1867 FOR_EACH_IMM_USE_STMT (stmt
, iter
, name
)
1869 if (gimple_code (stmt
) == GIMPLE_PHI
1870 && flow_bb_inside_loop_p (loop
, gimple_bb (stmt
)))
1873 BREAK_FROM_IMM_USE_STMT (iter
);
1879 name
= PHI_RESULT (phi
);
1880 replace_ssa_name_symbol (name
, var
);
1884 /* Given an unrolled LOOP after predictive commoning, remove the
1885 register copies arising from phi nodes by changing the base
1886 variables of SSA names. TMP_VARS is the set of the temporary variables
1887 for those we want to perform this. */
1890 eliminate_temp_copies (struct loop
*loop
, bitmap tmp_vars
)
1894 tree name
, use
, var
;
1895 gimple_stmt_iterator psi
;
1897 e
= loop_latch_edge (loop
);
1898 for (psi
= gsi_start_phis (loop
->header
); !gsi_end_p (psi
); gsi_next (&psi
))
1900 phi
= gsi_stmt (psi
);
1901 name
= PHI_RESULT (phi
);
1902 var
= SSA_NAME_VAR (name
);
1903 if (!var
|| !bitmap_bit_p (tmp_vars
, DECL_UID (var
)))
1905 use
= PHI_ARG_DEF_FROM_EDGE (phi
, e
);
1906 gcc_assert (TREE_CODE (use
) == SSA_NAME
);
1908 /* Base all the ssa names in the ud and du chain of NAME on VAR. */
1909 stmt
= SSA_NAME_DEF_STMT (use
);
1910 while (gimple_code (stmt
) == GIMPLE_PHI
1911 /* In case we could not unroll the loop enough to eliminate
1912 all copies, we may reach the loop header before the defining
1913 statement (in that case, some register copies will be present
1914 in loop latch in the final code, corresponding to the newly
1915 created looparound phi nodes). */
1916 && gimple_bb (stmt
) != loop
->header
)
1918 gcc_assert (single_pred_p (gimple_bb (stmt
)));
1919 use
= PHI_ARG_DEF (stmt
, 0);
1920 stmt
= SSA_NAME_DEF_STMT (use
);
1923 base_names_in_chain_on (loop
, use
, var
);
1927 /* Returns true if CHAIN is suitable to be combined. */
1930 chain_can_be_combined_p (chain_p chain
)
1932 return (!chain
->combined
1933 && (chain
->type
== CT_LOAD
|| chain
->type
== CT_COMBINATION
));
1936 /* Returns the modify statement that uses NAME. Skips over assignment
1937 statements, NAME is replaced with the actual name used in the returned
1941 find_use_stmt (tree
*name
)
1946 /* Skip over assignments. */
1949 stmt
= single_nonlooparound_use (*name
);
1953 if (gimple_code (stmt
) != GIMPLE_ASSIGN
)
1956 lhs
= gimple_assign_lhs (stmt
);
1957 if (TREE_CODE (lhs
) != SSA_NAME
)
1960 if (gimple_assign_copy_p (stmt
))
1962 rhs
= gimple_assign_rhs1 (stmt
);
1968 else if (get_gimple_rhs_class (gimple_assign_rhs_code (stmt
))
1969 == GIMPLE_BINARY_RHS
)
1976 /* Returns true if we may perform reassociation for operation CODE in TYPE. */
1979 may_reassociate_p (tree type
, enum tree_code code
)
1981 if (FLOAT_TYPE_P (type
)
1982 && !flag_unsafe_math_optimizations
)
1985 return (commutative_tree_code (code
)
1986 && associative_tree_code (code
));
1989 /* If the operation used in STMT is associative and commutative, go through the
1990 tree of the same operations and returns its root. Distance to the root
1991 is stored in DISTANCE. */
1994 find_associative_operation_root (gimple stmt
, unsigned *distance
)
1998 enum tree_code code
= gimple_assign_rhs_code (stmt
);
1999 tree type
= TREE_TYPE (gimple_assign_lhs (stmt
));
2002 if (!may_reassociate_p (type
, code
))
2007 lhs
= gimple_assign_lhs (stmt
);
2008 gcc_assert (TREE_CODE (lhs
) == SSA_NAME
);
2010 next
= find_use_stmt (&lhs
);
2012 || gimple_assign_rhs_code (next
) != code
)
2024 /* Returns the common statement in that NAME1 and NAME2 have a use. If there
2025 is no such statement, returns NULL_TREE. In case the operation used on
2026 NAME1 and NAME2 is associative and commutative, returns the root of the
2027 tree formed by this operation instead of the statement that uses NAME1 or
2031 find_common_use_stmt (tree
*name1
, tree
*name2
)
2033 gimple stmt1
, stmt2
;
2035 stmt1
= find_use_stmt (name1
);
2039 stmt2
= find_use_stmt (name2
);
2046 stmt1
= find_associative_operation_root (stmt1
, NULL
);
2049 stmt2
= find_associative_operation_root (stmt2
, NULL
);
2053 return (stmt1
== stmt2
? stmt1
: NULL
);
2056 /* Checks whether R1 and R2 are combined together using CODE, with the result
2057 in RSLT_TYPE, in order R1 CODE R2 if SWAP is false and in order R2 CODE R1
2058 if it is true. If CODE is ERROR_MARK, set these values instead. */
2061 combinable_refs_p (dref r1
, dref r2
,
2062 enum tree_code
*code
, bool *swap
, tree
*rslt_type
)
2064 enum tree_code acode
;
2070 name1
= name_for_ref (r1
);
2071 name2
= name_for_ref (r2
);
2072 gcc_assert (name1
!= NULL_TREE
&& name2
!= NULL_TREE
);
2074 stmt
= find_common_use_stmt (&name1
, &name2
);
2079 acode
= gimple_assign_rhs_code (stmt
);
2080 aswap
= (!commutative_tree_code (acode
)
2081 && gimple_assign_rhs1 (stmt
) != name1
);
2082 atype
= TREE_TYPE (gimple_assign_lhs (stmt
));
2084 if (*code
== ERROR_MARK
)
2092 return (*code
== acode
2094 && *rslt_type
== atype
);
2097 /* Remove OP from the operation on rhs of STMT, and replace STMT with
2098 an assignment of the remaining operand. */
2101 remove_name_from_operation (gimple stmt
, tree op
)
2104 gimple_stmt_iterator si
;
2106 gcc_assert (is_gimple_assign (stmt
));
2108 if (gimple_assign_rhs1 (stmt
) == op
)
2109 other_op
= gimple_assign_rhs2 (stmt
);
2111 other_op
= gimple_assign_rhs1 (stmt
);
2113 si
= gsi_for_stmt (stmt
);
2114 gimple_assign_set_rhs_from_tree (&si
, other_op
);
2116 /* We should not have reallocated STMT. */
2117 gcc_assert (gsi_stmt (si
) == stmt
);
2122 /* Reassociates the expression in that NAME1 and NAME2 are used so that they
2123 are combined in a single statement, and returns this statement. */
2126 reassociate_to_the_same_stmt (tree name1
, tree name2
)
2128 gimple stmt1
, stmt2
, root1
, root2
, s1
, s2
;
2129 gimple new_stmt
, tmp_stmt
;
2130 tree new_name
, tmp_name
, var
, r1
, r2
;
2131 unsigned dist1
, dist2
;
2132 enum tree_code code
;
2133 tree type
= TREE_TYPE (name1
);
2134 gimple_stmt_iterator bsi
;
2136 stmt1
= find_use_stmt (&name1
);
2137 stmt2
= find_use_stmt (&name2
);
2138 root1
= find_associative_operation_root (stmt1
, &dist1
);
2139 root2
= find_associative_operation_root (stmt2
, &dist2
);
2140 code
= gimple_assign_rhs_code (stmt1
);
2142 gcc_assert (root1
&& root2
&& root1
== root2
2143 && code
== gimple_assign_rhs_code (stmt2
));
2145 /* Find the root of the nearest expression in that both NAME1 and NAME2
2152 while (dist1
> dist2
)
2154 s1
= find_use_stmt (&r1
);
2155 r1
= gimple_assign_lhs (s1
);
2158 while (dist2
> dist1
)
2160 s2
= find_use_stmt (&r2
);
2161 r2
= gimple_assign_lhs (s2
);
2167 s1
= find_use_stmt (&r1
);
2168 r1
= gimple_assign_lhs (s1
);
2169 s2
= find_use_stmt (&r2
);
2170 r2
= gimple_assign_lhs (s2
);
2173 /* Remove NAME1 and NAME2 from the statements in that they are used
2175 remove_name_from_operation (stmt1
, name1
);
2176 remove_name_from_operation (stmt2
, name2
);
2178 /* Insert the new statement combining NAME1 and NAME2 before S1, and
2179 combine it with the rhs of S1. */
2180 var
= create_tmp_reg (type
, "predreastmp");
2181 new_name
= make_ssa_name (var
, NULL
);
2182 new_stmt
= gimple_build_assign_with_ops (code
, new_name
, name1
, name2
);
2184 var
= create_tmp_reg (type
, "predreastmp");
2185 tmp_name
= make_ssa_name (var
, NULL
);
2187 /* Rhs of S1 may now be either a binary expression with operation
2188 CODE, or gimple_val (in case that stmt1 == s1 or stmt2 == s1,
2189 so that name1 or name2 was removed from it). */
2190 tmp_stmt
= gimple_build_assign_with_ops (gimple_assign_rhs_code (s1
),
2192 gimple_assign_rhs1 (s1
),
2193 gimple_assign_rhs2 (s1
));
2195 bsi
= gsi_for_stmt (s1
);
2196 gimple_assign_set_rhs_with_ops (&bsi
, code
, new_name
, tmp_name
);
2197 s1
= gsi_stmt (bsi
);
2200 gsi_insert_before (&bsi
, new_stmt
, GSI_SAME_STMT
);
2201 gsi_insert_before (&bsi
, tmp_stmt
, GSI_SAME_STMT
);
2206 /* Returns the statement that combines references R1 and R2. In case R1
2207 and R2 are not used in the same statement, but they are used with an
2208 associative and commutative operation in the same expression, reassociate
2209 the expression so that they are used in the same statement. */
2212 stmt_combining_refs (dref r1
, dref r2
)
2214 gimple stmt1
, stmt2
;
2215 tree name1
= name_for_ref (r1
);
2216 tree name2
= name_for_ref (r2
);
2218 stmt1
= find_use_stmt (&name1
);
2219 stmt2
= find_use_stmt (&name2
);
2223 return reassociate_to_the_same_stmt (name1
, name2
);
2226 /* Tries to combine chains CH1 and CH2 together. If this succeeds, the
2227 description of the new chain is returned, otherwise we return NULL. */
2230 combine_chains (chain_p ch1
, chain_p ch2
)
2233 enum tree_code op
= ERROR_MARK
;
2238 tree rslt_type
= NULL_TREE
;
2242 if (ch1
->length
!= ch2
->length
)
2245 if (VEC_length (dref
, ch1
->refs
) != VEC_length (dref
, ch2
->refs
))
2248 for (i
= 0; (VEC_iterate (dref
, ch1
->refs
, i
, r1
)
2249 && VEC_iterate (dref
, ch2
->refs
, i
, r2
)); i
++)
2251 if (r1
->distance
!= r2
->distance
)
2254 if (!combinable_refs_p (r1
, r2
, &op
, &swap
, &rslt_type
))
2265 new_chain
= XCNEW (struct chain
);
2266 new_chain
->type
= CT_COMBINATION
;
2268 new_chain
->ch1
= ch1
;
2269 new_chain
->ch2
= ch2
;
2270 new_chain
->rslt_type
= rslt_type
;
2271 new_chain
->length
= ch1
->length
;
2273 for (i
= 0; (VEC_iterate (dref
, ch1
->refs
, i
, r1
)
2274 && VEC_iterate (dref
, ch2
->refs
, i
, r2
)); i
++)
2276 nw
= XCNEW (struct dref_d
);
2277 nw
->stmt
= stmt_combining_refs (r1
, r2
);
2278 nw
->distance
= r1
->distance
;
2280 VEC_safe_push (dref
, heap
, new_chain
->refs
, nw
);
2283 new_chain
->has_max_use_after
= false;
2284 root_stmt
= get_chain_root (new_chain
)->stmt
;
2285 for (i
= 1; VEC_iterate (dref
, new_chain
->refs
, i
, nw
); i
++)
2287 if (nw
->distance
== new_chain
->length
2288 && !stmt_dominates_stmt_p (nw
->stmt
, root_stmt
))
2290 new_chain
->has_max_use_after
= true;
2295 ch1
->combined
= true;
2296 ch2
->combined
= true;
2300 /* Try to combine the CHAINS. */
2303 try_combine_chains (VEC (chain_p
, heap
) **chains
)
2306 chain_p ch1
, ch2
, cch
;
2307 VEC (chain_p
, heap
) *worklist
= NULL
;
2309 FOR_EACH_VEC_ELT (chain_p
, *chains
, i
, ch1
)
2310 if (chain_can_be_combined_p (ch1
))
2311 VEC_safe_push (chain_p
, heap
, worklist
, ch1
);
2313 while (!VEC_empty (chain_p
, worklist
))
2315 ch1
= VEC_pop (chain_p
, worklist
);
2316 if (!chain_can_be_combined_p (ch1
))
2319 FOR_EACH_VEC_ELT (chain_p
, *chains
, j
, ch2
)
2321 if (!chain_can_be_combined_p (ch2
))
2324 cch
= combine_chains (ch1
, ch2
);
2327 VEC_safe_push (chain_p
, heap
, worklist
, cch
);
2328 VEC_safe_push (chain_p
, heap
, *chains
, cch
);
2334 VEC_free (chain_p
, heap
, worklist
);
2337 /* Prepare initializers for CHAIN in LOOP. Returns false if this is
2338 impossible because one of these initializers may trap, true otherwise. */
2341 prepare_initializers_chain (struct loop
*loop
, chain_p chain
)
2343 unsigned i
, n
= (chain
->type
== CT_INVARIANT
) ? 1 : chain
->length
;
2344 struct data_reference
*dr
= get_chain_root (chain
)->ref
;
2348 edge entry
= loop_preheader_edge (loop
);
2350 /* Find the initializers for the variables, and check that they cannot
2352 chain
->inits
= VEC_alloc (tree
, heap
, n
);
2353 for (i
= 0; i
< n
; i
++)
2354 VEC_quick_push (tree
, chain
->inits
, NULL_TREE
);
2356 /* If we have replaced some looparound phi nodes, use their initializers
2357 instead of creating our own. */
2358 FOR_EACH_VEC_ELT (dref
, chain
->refs
, i
, laref
)
2360 if (gimple_code (laref
->stmt
) != GIMPLE_PHI
)
2363 gcc_assert (laref
->distance
> 0);
2364 VEC_replace (tree
, chain
->inits
, n
- laref
->distance
,
2365 PHI_ARG_DEF_FROM_EDGE (laref
->stmt
, entry
));
2368 for (i
= 0; i
< n
; i
++)
2370 if (VEC_index (tree
, chain
->inits
, i
) != NULL_TREE
)
2373 init
= ref_at_iteration (loop
, DR_REF (dr
), (int) i
- n
);
2377 if (!chain
->all_always_accessed
&& tree_could_trap_p (init
))
2380 init
= force_gimple_operand (init
, &stmts
, false, NULL_TREE
);
2382 gsi_insert_seq_on_edge_immediate (entry
, stmts
);
2384 VEC_replace (tree
, chain
->inits
, i
, init
);
2390 /* Prepare initializers for CHAINS in LOOP, and free chains that cannot
2391 be used because the initializers might trap. */
2394 prepare_initializers (struct loop
*loop
, VEC (chain_p
, heap
) *chains
)
2399 for (i
= 0; i
< VEC_length (chain_p
, chains
); )
2401 chain
= VEC_index (chain_p
, chains
, i
);
2402 if (prepare_initializers_chain (loop
, chain
))
2406 release_chain (chain
);
2407 VEC_unordered_remove (chain_p
, chains
, i
);
2412 /* Performs predictive commoning for LOOP. Returns true if LOOP was
2416 tree_predictive_commoning_loop (struct loop
*loop
)
2418 VEC (loop_p
, heap
) *loop_nest
;
2419 VEC (data_reference_p
, heap
) *datarefs
;
2420 VEC (ddr_p
, heap
) *dependences
;
2421 struct component
*components
;
2422 VEC (chain_p
, heap
) *chains
= NULL
;
2423 unsigned unroll_factor
;
2424 struct tree_niter_desc desc
;
2425 bool unroll
= false;
2429 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2430 fprintf (dump_file
, "Processing loop %d\n", loop
->num
);
2432 /* Find the data references and split them into components according to their
2433 dependence relations. */
2434 datarefs
= VEC_alloc (data_reference_p
, heap
, 10);
2435 dependences
= VEC_alloc (ddr_p
, heap
, 10);
2436 loop_nest
= VEC_alloc (loop_p
, heap
, 3);
2437 if (! compute_data_dependences_for_loop (loop
, true, &loop_nest
, &datarefs
,
2440 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2441 fprintf (dump_file
, "Cannot analyze data dependencies\n");
2442 VEC_free (loop_p
, heap
, loop_nest
);
2443 free_data_refs (datarefs
);
2444 free_dependence_relations (dependences
);
2448 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2449 dump_data_dependence_relations (dump_file
, dependences
);
2451 components
= split_data_refs_to_components (loop
, datarefs
, dependences
);
2452 VEC_free (loop_p
, heap
, loop_nest
);
2453 free_dependence_relations (dependences
);
2456 free_data_refs (datarefs
);
2460 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2462 fprintf (dump_file
, "Initial state:\n\n");
2463 dump_components (dump_file
, components
);
2466 /* Find the suitable components and split them into chains. */
2467 components
= filter_suitable_components (loop
, components
);
2469 tmp_vars
= BITMAP_ALLOC (NULL
);
2470 looparound_phis
= BITMAP_ALLOC (NULL
);
2471 determine_roots (loop
, components
, &chains
);
2472 release_components (components
);
2476 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2478 "Predictive commoning failed: no suitable chains\n");
2481 prepare_initializers (loop
, chains
);
2483 /* Try to combine the chains that are always worked with together. */
2484 try_combine_chains (&chains
);
2486 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2488 fprintf (dump_file
, "Before commoning:\n\n");
2489 dump_chains (dump_file
, chains
);
2492 /* Determine the unroll factor, and if the loop should be unrolled, ensure
2493 that its number of iterations is divisible by the factor. */
2494 unroll_factor
= determine_unroll_factor (chains
);
2496 unroll
= (unroll_factor
> 1
2497 && can_unroll_loop_p (loop
, unroll_factor
, &desc
));
2498 exit
= single_dom_exit (loop
);
2500 /* Execute the predictive commoning transformations, and possibly unroll the
2504 struct epcc_data dta
;
2506 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2507 fprintf (dump_file
, "Unrolling %u times.\n", unroll_factor
);
2509 dta
.chains
= chains
;
2510 dta
.tmp_vars
= tmp_vars
;
2512 update_ssa (TODO_update_ssa_only_virtuals
);
2514 /* Cfg manipulations performed in tree_transform_and_unroll_loop before
2515 execute_pred_commoning_cbck is called may cause phi nodes to be
2516 reallocated, which is a problem since CHAINS may point to these
2517 statements. To fix this, we store the ssa names defined by the
2518 phi nodes here instead of the phi nodes themselves, and restore
2519 the phi nodes in execute_pred_commoning_cbck. A bit hacky. */
2520 replace_phis_by_defined_names (chains
);
2522 tree_transform_and_unroll_loop (loop
, unroll_factor
, exit
, &desc
,
2523 execute_pred_commoning_cbck
, &dta
);
2524 eliminate_temp_copies (loop
, tmp_vars
);
2528 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2530 "Executing predictive commoning without unrolling.\n");
2531 execute_pred_commoning (loop
, chains
, tmp_vars
);
2535 release_chains (chains
);
2536 free_data_refs (datarefs
);
2537 BITMAP_FREE (tmp_vars
);
2538 BITMAP_FREE (looparound_phis
);
2540 free_affine_expand_cache (&name_expansions
);
2545 /* Runs predictive commoning. */
2548 tree_predictive_commoning (void)
2550 bool unrolled
= false;
2555 initialize_original_copy_tables ();
2556 FOR_EACH_LOOP (li
, loop
, LI_ONLY_INNERMOST
)
2557 if (optimize_loop_for_speed_p (loop
))
2559 unrolled
|= tree_predictive_commoning_loop (loop
);
2565 ret
= TODO_cleanup_cfg
;
2567 free_original_copy_tables ();