1 /* Straight-line strength reduction.
2 Copyright (C) 2012-2013 Free Software Foundation, Inc.
3 Contributed by Bill Schmidt, IBM <wschmidt@linux.ibm.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 3, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 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 /* There are many algorithms for performing strength reduction on
22 loops. This is not one of them. IVOPTS handles strength reduction
23 of induction variables just fine. This pass is intended to pick
24 up the crumbs it leaves behind, by considering opportunities for
25 strength reduction along dominator paths.
27 Strength reduction addresses explicit multiplies, and certain
28 multiplies implicit in addressing expressions. It would also be
29 possible to apply strength reduction to divisions and modulos,
30 but such opportunities are relatively uncommon.
32 Strength reduction is also currently restricted to integer operations.
33 If desired, it could be extended to floating-point operations under
34 control of something like -funsafe-math-optimizations. */
38 #include "coretypes.h"
41 #include "basic-block.h"
42 #include "tree-pass.h"
44 #include "gimple-pretty-print.h"
45 #include "tree-flow.h"
47 #include "pointer-set.h"
50 #include "hash-table.h"
52 /* Information about a strength reduction candidate. Each statement
53 in the candidate table represents an expression of one of the
54 following forms (the special case of CAND_REF will be described
57 (CAND_MULT) S1: X = (B + i) * S
58 (CAND_ADD) S1: X = B + (i * S)
60 Here X and B are SSA names, i is an integer constant, and S is
61 either an SSA name or a constant. We call B the "base," i the
62 "index", and S the "stride."
64 Any statement S0 that dominates S1 and is of the form:
66 (CAND_MULT) S0: Y = (B + i') * S
67 (CAND_ADD) S0: Y = B + (i' * S)
69 is called a "basis" for S1. In both cases, S1 may be replaced by
71 S1': X = Y + (i - i') * S,
73 where (i - i') * S is folded to the extent possible.
75 All gimple statements are visited in dominator order, and each
76 statement that may contribute to one of the forms of S1 above is
77 given at least one entry in the candidate table. Such statements
78 include addition, pointer addition, subtraction, multiplication,
79 negation, copies, and nontrivial type casts. If a statement may
80 represent more than one expression of the forms of S1 above,
81 multiple "interpretations" are stored in the table and chained
84 * An add of two SSA names may treat either operand as the base.
85 * A multiply of two SSA names, likewise.
86 * A copy or cast may be thought of as either a CAND_MULT with
87 i = 0 and S = 1, or as a CAND_ADD with i = 0 or S = 0.
89 Candidate records are allocated from an obstack. They are addressed
90 both from a hash table keyed on S1, and from a vector of candidate
91 pointers arranged in predominator order.
95 Currently we don't recognize:
100 as a strength reduction opportunity, even though this S1 would
101 also be replaceable by the S1' above. This can be added if it
102 comes up in practice.
104 Strength reduction in addressing
105 --------------------------------
106 There is another kind of candidate known as CAND_REF. A CAND_REF
107 describes a statement containing a memory reference having
108 complex addressing that might benefit from strength reduction.
109 Specifically, we are interested in references for which
110 get_inner_reference returns a base address, offset, and bitpos as
113 base: MEM_REF (T1, C1)
114 offset: MULT_EXPR (PLUS_EXPR (T2, C2), C3)
115 bitpos: C4 * BITS_PER_UNIT
117 Here T1 and T2 are arbitrary trees, and C1, C2, C3, C4 are
118 arbitrary integer constants. Note that C2 may be zero, in which
119 case the offset will be MULT_EXPR (T2, C3).
121 When this pattern is recognized, the original memory reference
122 can be replaced with:
124 MEM_REF (POINTER_PLUS_EXPR (T1, MULT_EXPR (T2, C3)),
127 which distributes the multiply to allow constant folding. When
128 two or more addressing expressions can be represented by MEM_REFs
129 of this form, differing only in the constants C1, C2, and C4,
130 making this substitution produces more efficient addressing during
131 the RTL phases. When there are not at least two expressions with
132 the same values of T1, T2, and C3, there is nothing to be gained
135 Strength reduction of CAND_REFs uses the same infrastructure as
136 that used by CAND_MULTs and CAND_ADDs. We record T1 in the base (B)
137 field, MULT_EXPR (T2, C3) in the stride (S) field, and
138 C1 + (C2 * C3) + C4 in the index (i) field. A basis for a CAND_REF
139 is thus another CAND_REF with the same B and S values. When at
140 least two CAND_REFs are chained together using the basis relation,
141 each of them is replaced as above, resulting in improved code
142 generation for addressing.
144 Conditional candidates
145 ======================
147 Conditional candidates are best illustrated with an example.
148 Consider the code sequence:
151 (2) a_0 = x_0 * 5; MULT (B: x_0; i: 0; S: 5)
153 (3) x_1 = x_0 + 1; ADD (B: x_0, i: 1; S: 1)
154 (4) x_2 = PHI <x_0, x_1>; PHI (B: x_0, i: 0, S: 1)
155 (5) x_3 = x_2 + 1; ADD (B: x_2, i: 1, S: 1)
156 (6) a_1 = x_3 * 5; MULT (B: x_2, i: 1; S: 5)
158 Here strength reduction is complicated by the uncertain value of x_2.
159 A legitimate transformation is:
168 (4) [x_2 = PHI <x_0, x_1>;]
169 (4a) t_2 = PHI <a_0, t_1>;
173 where the bracketed instructions may go dead.
175 To recognize this opportunity, we have to observe that statement (6)
176 has a "hidden basis" (2). The hidden basis is unlike a normal basis
177 in that the statement and the hidden basis have different base SSA
178 names (x_2 and x_0, respectively). The relationship is established
179 when a statement's base name (x_2) is defined by a phi statement (4),
180 each argument of which (x_0, x_1) has an identical "derived base name."
181 If the argument is defined by a candidate (as x_1 is by (3)) that is a
182 CAND_ADD having a stride of 1, the derived base name of the argument is
183 the base name of the candidate (x_0). Otherwise, the argument itself
184 is its derived base name (as is the case with argument x_0).
186 The hidden basis for statement (6) is the nearest dominating candidate
187 whose base name is the derived base name (x_0) of the feeding phi (4),
188 and whose stride is identical to that of the statement. We can then
189 create the new "phi basis" (4a) and feeding adds along incoming arcs (3a),
190 allowing the final replacement of (6) by the strength-reduced (6r).
192 To facilitate this, a new kind of candidate (CAND_PHI) is introduced.
193 A CAND_PHI is not a candidate for replacement, but is maintained in the
194 candidate table to ease discovery of hidden bases. Any phi statement
195 whose arguments share a common derived base name is entered into the
196 table with the derived base name, an (arbitrary) index of zero, and a
197 stride of 1. A statement with a hidden basis can then be detected by
198 simply looking up its feeding phi definition in the candidate table,
199 extracting the derived base name, and searching for a basis in the
200 usual manner after substituting the derived base name.
202 Note that the transformation is only valid when the original phi and
203 the statements that define the phi's arguments are all at the same
204 position in the loop hierarchy. */
207 /* Index into the candidate vector, offset by 1. VECs are zero-based,
208 while cand_idx's are one-based, with zero indicating null. */
209 typedef unsigned cand_idx
;
211 /* The kind of candidate. */
222 /* The candidate statement S1. */
225 /* The base expression B: often an SSA name, but not always. */
231 /* The index constant i. */
234 /* The type of the candidate. This is normally the type of base_expr,
235 but casts may have occurred when combining feeding instructions.
236 A candidate can only be a basis for candidates of the same final type.
237 (For CAND_REFs, this is the type to be used for operand 1 of the
238 replacement MEM_REF.) */
241 /* The kind of candidate (CAND_MULT, etc.). */
244 /* Index of this candidate in the candidate vector. */
247 /* Index of the next candidate record for the same statement.
248 A statement may be useful in more than one way (e.g., due to
249 commutativity). So we can have multiple "interpretations"
251 cand_idx next_interp
;
253 /* Index of the basis statement S0, if any, in the candidate vector. */
256 /* First candidate for which this candidate is a basis, if one exists. */
259 /* Next candidate having the same basis as this one. */
262 /* If this is a conditional candidate, the CAND_PHI candidate
263 that defines the base SSA name B. */
266 /* Savings that can be expected from eliminating dead code if this
267 candidate is replaced. */
271 typedef struct slsr_cand_d slsr_cand
, *slsr_cand_t
;
272 typedef const struct slsr_cand_d
*const_slsr_cand_t
;
274 /* Pointers to candidates are chained together as part of a mapping
275 from base expressions to the candidates that use them. */
279 /* Base expression for the chain of candidates: often, but not
280 always, an SSA name. */
283 /* Pointer to a candidate. */
287 struct cand_chain_d
*next
;
291 typedef struct cand_chain_d cand_chain
, *cand_chain_t
;
292 typedef const struct cand_chain_d
*const_cand_chain_t
;
294 /* Information about a unique "increment" associated with candidates
295 having an SSA name for a stride. An increment is the difference
296 between the index of the candidate and the index of its basis,
297 i.e., (i - i') as discussed in the module commentary.
299 When we are not going to generate address arithmetic we treat
300 increments that differ only in sign as the same, allowing sharing
301 of the cost of initializers. The absolute value of the increment
302 is stored in the incr_info. */
306 /* The increment that relates a candidate to its basis. */
309 /* How many times the increment occurs in the candidate tree. */
312 /* Cost of replacing candidates using this increment. Negative and
313 zero costs indicate replacement should be performed. */
316 /* If this increment is profitable but is not -1, 0, or 1, it requires
317 an initializer T_0 = stride * incr to be found or introduced in the
318 nearest common dominator of all candidates. This field holds T_0
319 for subsequent use. */
322 /* If the initializer was found to already exist, this is the block
323 where it was found. */
327 typedef struct incr_info_d incr_info
, *incr_info_t
;
329 /* Candidates are maintained in a vector. If candidate X dominates
330 candidate Y, then X appears before Y in the vector; but the
331 converse does not necessarily hold. */
332 static vec
<slsr_cand_t
> cand_vec
;
346 enum phi_adjust_status
352 enum count_phis_status
358 /* Pointer map embodying a mapping from statements to candidates. */
359 static struct pointer_map_t
*stmt_cand_map
;
361 /* Obstack for candidates. */
362 static struct obstack cand_obstack
;
364 /* Obstack for candidate chains. */
365 static struct obstack chain_obstack
;
367 /* An array INCR_VEC of incr_infos is used during analysis of related
368 candidates having an SSA name for a stride. INCR_VEC_LEN describes
369 its current length. MAX_INCR_VEC_LEN is used to avoid costly
370 pathological cases. */
371 static incr_info_t incr_vec
;
372 static unsigned incr_vec_len
;
373 const int MAX_INCR_VEC_LEN
= 16;
375 /* For a chain of candidates with unknown stride, indicates whether or not
376 we must generate pointer arithmetic when replacing statements. */
377 static bool address_arithmetic_p
;
379 /* Forward function declarations. */
380 static slsr_cand_t
base_cand_from_table (tree
);
381 static tree
introduce_cast_before_cand (slsr_cand_t
, tree
, tree
);
383 /* Produce a pointer to the IDX'th candidate in the candidate vector. */
386 lookup_cand (cand_idx idx
)
388 return cand_vec
[idx
- 1];
391 /* Helper for hashing a candidate chain header. */
393 struct cand_chain_hasher
: typed_noop_remove
<cand_chain
>
395 typedef cand_chain value_type
;
396 typedef cand_chain compare_type
;
397 static inline hashval_t
hash (const value_type
*);
398 static inline bool equal (const value_type
*, const compare_type
*);
402 cand_chain_hasher::hash (const value_type
*p
)
404 tree base_expr
= p
->base_expr
;
405 return iterative_hash_expr (base_expr
, 0);
409 cand_chain_hasher::equal (const value_type
*chain1
, const compare_type
*chain2
)
411 return operand_equal_p (chain1
->base_expr
, chain2
->base_expr
, 0);
414 /* Hash table embodying a mapping from base exprs to chains of candidates. */
415 static hash_table
<cand_chain_hasher
> base_cand_map
;
417 /* Look in the candidate table for a CAND_PHI that defines BASE and
418 return it if found; otherwise return NULL. */
421 find_phi_def (tree base
)
425 if (TREE_CODE (base
) != SSA_NAME
)
428 c
= base_cand_from_table (base
);
430 if (!c
|| c
->kind
!= CAND_PHI
)
436 /* Helper routine for find_basis_for_candidate. May be called twice:
437 once for the candidate's base expr, and optionally again for the
438 candidate's phi definition. */
441 find_basis_for_base_expr (slsr_cand_t c
, tree base_expr
)
443 cand_chain mapping_key
;
445 slsr_cand_t basis
= NULL
;
447 // Limit potential of N^2 behavior for long candidate chains.
449 int max_iters
= PARAM_VALUE (PARAM_MAX_SLSR_CANDIDATE_SCAN
);
451 mapping_key
.base_expr
= base_expr
;
452 chain
= base_cand_map
.find (&mapping_key
);
454 for (; chain
&& iters
< max_iters
; chain
= chain
->next
, ++iters
)
456 slsr_cand_t one_basis
= chain
->cand
;
458 if (one_basis
->kind
!= c
->kind
459 || one_basis
->cand_stmt
== c
->cand_stmt
460 || !operand_equal_p (one_basis
->stride
, c
->stride
, 0)
461 || !types_compatible_p (one_basis
->cand_type
, c
->cand_type
)
462 || !dominated_by_p (CDI_DOMINATORS
,
463 gimple_bb (c
->cand_stmt
),
464 gimple_bb (one_basis
->cand_stmt
)))
467 if (!basis
|| basis
->cand_num
< one_basis
->cand_num
)
474 /* Use the base expr from candidate C to look for possible candidates
475 that can serve as a basis for C. Each potential basis must also
476 appear in a block that dominates the candidate statement and have
477 the same stride and type. If more than one possible basis exists,
478 the one with highest index in the vector is chosen; this will be
479 the most immediately dominating basis. */
482 find_basis_for_candidate (slsr_cand_t c
)
484 slsr_cand_t basis
= find_basis_for_base_expr (c
, c
->base_expr
);
486 /* If a candidate doesn't have a basis using its base expression,
487 it may have a basis hidden by one or more intervening phis. */
488 if (!basis
&& c
->def_phi
)
490 basic_block basis_bb
, phi_bb
;
491 slsr_cand_t phi_cand
= lookup_cand (c
->def_phi
);
492 basis
= find_basis_for_base_expr (c
, phi_cand
->base_expr
);
496 /* A hidden basis must dominate the phi-definition of the
497 candidate's base name. */
498 phi_bb
= gimple_bb (phi_cand
->cand_stmt
);
499 basis_bb
= gimple_bb (basis
->cand_stmt
);
501 if (phi_bb
== basis_bb
502 || !dominated_by_p (CDI_DOMINATORS
, phi_bb
, basis_bb
))
508 /* If we found a hidden basis, estimate additional dead-code
509 savings if the phi and its feeding statements can be removed. */
510 if (basis
&& has_single_use (gimple_phi_result (phi_cand
->cand_stmt
)))
511 c
->dead_savings
+= phi_cand
->dead_savings
;
517 c
->sibling
= basis
->dependent
;
518 basis
->dependent
= c
->cand_num
;
519 return basis
->cand_num
;
525 /* Record a mapping from the base expression of C to C itself, indicating that
526 C may potentially serve as a basis using that base expression. */
529 record_potential_basis (slsr_cand_t c
)
534 node
= (cand_chain_t
) obstack_alloc (&chain_obstack
, sizeof (cand_chain
));
535 node
->base_expr
= c
->base_expr
;
538 slot
= base_cand_map
.find_slot (node
, INSERT
);
542 cand_chain_t head
= (cand_chain_t
) (*slot
);
543 node
->next
= head
->next
;
550 /* Allocate storage for a new candidate and initialize its fields.
551 Attempt to find a basis for the candidate. */
554 alloc_cand_and_find_basis (enum cand_kind kind
, gimple gs
, tree base
,
555 double_int index
, tree stride
, tree ctype
,
558 slsr_cand_t c
= (slsr_cand_t
) obstack_alloc (&cand_obstack
,
564 c
->cand_type
= ctype
;
566 c
->cand_num
= cand_vec
.length () + 1;
570 c
->def_phi
= kind
== CAND_MULT
? find_phi_def (base
) : 0;
571 c
->dead_savings
= savings
;
573 cand_vec
.safe_push (c
);
575 if (kind
== CAND_PHI
)
578 c
->basis
= find_basis_for_candidate (c
);
580 record_potential_basis (c
);
585 /* Determine the target cost of statement GS when compiling according
589 stmt_cost (gimple gs
, bool speed
)
591 tree lhs
, rhs1
, rhs2
;
592 enum machine_mode lhs_mode
;
594 gcc_assert (is_gimple_assign (gs
));
595 lhs
= gimple_assign_lhs (gs
);
596 rhs1
= gimple_assign_rhs1 (gs
);
597 lhs_mode
= TYPE_MODE (TREE_TYPE (lhs
));
599 switch (gimple_assign_rhs_code (gs
))
602 rhs2
= gimple_assign_rhs2 (gs
);
604 if (host_integerp (rhs2
, 0))
605 return mult_by_coeff_cost (TREE_INT_CST_LOW (rhs2
), lhs_mode
, speed
);
607 gcc_assert (TREE_CODE (rhs1
) != INTEGER_CST
);
608 return mul_cost (speed
, lhs_mode
);
611 case POINTER_PLUS_EXPR
:
613 return add_cost (speed
, lhs_mode
);
616 return neg_cost (speed
, lhs_mode
);
619 return convert_cost (lhs_mode
, TYPE_MODE (TREE_TYPE (rhs1
)), speed
);
621 /* Note that we don't assign costs to copies that in most cases
631 /* Look up the defining statement for BASE_IN and return a pointer
632 to its candidate in the candidate table, if any; otherwise NULL.
633 Only CAND_ADD and CAND_MULT candidates are returned. */
636 base_cand_from_table (tree base_in
)
640 gimple def
= SSA_NAME_DEF_STMT (base_in
);
642 return (slsr_cand_t
) NULL
;
644 result
= (slsr_cand_t
*) pointer_map_contains (stmt_cand_map
, def
);
646 if (result
&& (*result
)->kind
!= CAND_REF
)
649 return (slsr_cand_t
) NULL
;
652 /* Add an entry to the statement-to-candidate mapping. */
655 add_cand_for_stmt (gimple gs
, slsr_cand_t c
)
657 void **slot
= pointer_map_insert (stmt_cand_map
, gs
);
662 /* Given PHI which contains a phi statement, determine whether it
663 satisfies all the requirements of a phi candidate. If so, create
664 a candidate. Note that a CAND_PHI never has a basis itself, but
665 is used to help find a basis for subsequent candidates. */
668 slsr_process_phi (gimple phi
, bool speed
)
671 tree arg0_base
= NULL_TREE
, base_type
;
673 struct loop
*cand_loop
= gimple_bb (phi
)->loop_father
;
674 unsigned savings
= 0;
676 /* A CAND_PHI requires each of its arguments to have the same
677 derived base name. (See the module header commentary for a
678 definition of derived base names.) Furthermore, all feeding
679 definitions must be in the same position in the loop hierarchy
682 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
684 slsr_cand_t arg_cand
;
685 tree arg
= gimple_phi_arg_def (phi
, i
);
686 tree derived_base_name
= NULL_TREE
;
687 gimple arg_stmt
= NULL
;
688 basic_block arg_bb
= NULL
;
690 if (TREE_CODE (arg
) != SSA_NAME
)
693 arg_cand
= base_cand_from_table (arg
);
697 while (arg_cand
->kind
!= CAND_ADD
&& arg_cand
->kind
!= CAND_PHI
)
699 if (!arg_cand
->next_interp
)
702 arg_cand
= lookup_cand (arg_cand
->next_interp
);
705 if (!integer_onep (arg_cand
->stride
))
708 derived_base_name
= arg_cand
->base_expr
;
709 arg_stmt
= arg_cand
->cand_stmt
;
710 arg_bb
= gimple_bb (arg_stmt
);
712 /* Gather potential dead code savings if the phi statement
713 can be removed later on. */
714 if (has_single_use (arg
))
716 if (gimple_code (arg_stmt
) == GIMPLE_PHI
)
717 savings
+= arg_cand
->dead_savings
;
719 savings
+= stmt_cost (arg_stmt
, speed
);
724 derived_base_name
= arg
;
726 if (SSA_NAME_IS_DEFAULT_DEF (arg
))
727 arg_bb
= single_succ (ENTRY_BLOCK_PTR
);
729 gimple_bb (SSA_NAME_DEF_STMT (arg
));
732 if (!arg_bb
|| arg_bb
->loop_father
!= cand_loop
)
736 arg0_base
= derived_base_name
;
737 else if (!operand_equal_p (derived_base_name
, arg0_base
, 0))
741 /* Create the candidate. "alloc_cand_and_find_basis" is named
742 misleadingly for this case, as no basis will be sought for a
744 base_type
= TREE_TYPE (arg0_base
);
746 c
= alloc_cand_and_find_basis (CAND_PHI
, phi
, arg0_base
, double_int_zero
,
747 integer_one_node
, base_type
, savings
);
749 /* Add the candidate to the statement-candidate mapping. */
750 add_cand_for_stmt (phi
, c
);
753 /* Look for the following pattern:
755 *PBASE: MEM_REF (T1, C1)
757 *POFFSET: MULT_EXPR (T2, C3) [C2 is zero]
759 MULT_EXPR (PLUS_EXPR (T2, C2), C3)
761 MULT_EXPR (MINUS_EXPR (T2, -C2), C3)
763 *PINDEX: C4 * BITS_PER_UNIT
765 If not present, leave the input values unchanged and return FALSE.
766 Otherwise, modify the input values as follows and return TRUE:
769 *POFFSET: MULT_EXPR (T2, C3)
770 *PINDEX: C1 + (C2 * C3) + C4 */
773 restructure_reference (tree
*pbase
, tree
*poffset
, double_int
*pindex
,
776 tree base
= *pbase
, offset
= *poffset
;
777 double_int index
= *pindex
;
778 double_int bpu
= double_int::from_uhwi (BITS_PER_UNIT
);
779 tree mult_op0
, mult_op1
, t1
, t2
, type
;
780 double_int c1
, c2
, c3
, c4
;
784 || TREE_CODE (base
) != MEM_REF
785 || TREE_CODE (offset
) != MULT_EXPR
786 || TREE_CODE (TREE_OPERAND (offset
, 1)) != INTEGER_CST
787 || !index
.umod (bpu
, FLOOR_MOD_EXPR
).is_zero ())
790 t1
= TREE_OPERAND (base
, 0);
791 c1
= mem_ref_offset (base
);
792 type
= TREE_TYPE (TREE_OPERAND (base
, 1));
794 mult_op0
= TREE_OPERAND (offset
, 0);
795 mult_op1
= TREE_OPERAND (offset
, 1);
797 c3
= tree_to_double_int (mult_op1
);
799 if (TREE_CODE (mult_op0
) == PLUS_EXPR
)
801 if (TREE_CODE (TREE_OPERAND (mult_op0
, 1)) == INTEGER_CST
)
803 t2
= TREE_OPERAND (mult_op0
, 0);
804 c2
= tree_to_double_int (TREE_OPERAND (mult_op0
, 1));
809 else if (TREE_CODE (mult_op0
) == MINUS_EXPR
)
811 if (TREE_CODE (TREE_OPERAND (mult_op0
, 1)) == INTEGER_CST
)
813 t2
= TREE_OPERAND (mult_op0
, 0);
814 c2
= -tree_to_double_int (TREE_OPERAND (mult_op0
, 1));
822 c2
= double_int_zero
;
825 c4
= index
.udiv (bpu
, FLOOR_DIV_EXPR
);
828 *poffset
= fold_build2 (MULT_EXPR
, sizetype
, t2
,
829 double_int_to_tree (sizetype
, c3
));
830 *pindex
= c1
+ c2
* c3
+ c4
;
836 /* Given GS which contains a data reference, create a CAND_REF entry in
837 the candidate table and attempt to find a basis. */
840 slsr_process_ref (gimple gs
)
842 tree ref_expr
, base
, offset
, type
;
843 HOST_WIDE_INT bitsize
, bitpos
;
844 enum machine_mode mode
;
845 int unsignedp
, volatilep
;
849 if (gimple_vdef (gs
))
850 ref_expr
= gimple_assign_lhs (gs
);
852 ref_expr
= gimple_assign_rhs1 (gs
);
854 if (!handled_component_p (ref_expr
)
855 || TREE_CODE (ref_expr
) == BIT_FIELD_REF
856 || (TREE_CODE (ref_expr
) == COMPONENT_REF
857 && DECL_BIT_FIELD (TREE_OPERAND (ref_expr
, 1))))
860 base
= get_inner_reference (ref_expr
, &bitsize
, &bitpos
, &offset
, &mode
,
861 &unsignedp
, &volatilep
, false);
862 index
= double_int::from_uhwi (bitpos
);
864 if (!restructure_reference (&base
, &offset
, &index
, &type
))
867 c
= alloc_cand_and_find_basis (CAND_REF
, gs
, base
, index
, offset
,
870 /* Add the candidate to the statement-candidate mapping. */
871 add_cand_for_stmt (gs
, c
);
874 /* Create a candidate entry for a statement GS, where GS multiplies
875 two SSA names BASE_IN and STRIDE_IN. Propagate any known information
876 about the two SSA names into the new candidate. Return the new
880 create_mul_ssa_cand (gimple gs
, tree base_in
, tree stride_in
, bool speed
)
882 tree base
= NULL_TREE
, stride
= NULL_TREE
, ctype
= NULL_TREE
;
884 unsigned savings
= 0;
886 slsr_cand_t base_cand
= base_cand_from_table (base_in
);
888 /* Look at all interpretations of the base candidate, if necessary,
889 to find information to propagate into this candidate. */
890 while (base_cand
&& !base
&& base_cand
->kind
!= CAND_PHI
)
893 if (base_cand
->kind
== CAND_MULT
&& integer_onep (base_cand
->stride
))
899 base
= base_cand
->base_expr
;
900 index
= base_cand
->index
;
902 ctype
= base_cand
->cand_type
;
903 if (has_single_use (base_in
))
904 savings
= (base_cand
->dead_savings
905 + stmt_cost (base_cand
->cand_stmt
, speed
));
907 else if (base_cand
->kind
== CAND_ADD
908 && TREE_CODE (base_cand
->stride
) == INTEGER_CST
)
910 /* Y = B + (i' * S), S constant
912 ============================
913 X = B + ((i' * S) * Z) */
914 base
= base_cand
->base_expr
;
915 index
= base_cand
->index
* tree_to_double_int (base_cand
->stride
);
917 ctype
= base_cand
->cand_type
;
918 if (has_single_use (base_in
))
919 savings
= (base_cand
->dead_savings
920 + stmt_cost (base_cand
->cand_stmt
, speed
));
923 if (base_cand
->next_interp
)
924 base_cand
= lookup_cand (base_cand
->next_interp
);
931 /* No interpretations had anything useful to propagate, so
932 produce X = (Y + 0) * Z. */
934 index
= double_int_zero
;
936 ctype
= TREE_TYPE (base_in
);
939 c
= alloc_cand_and_find_basis (CAND_MULT
, gs
, base
, index
, stride
,
944 /* Create a candidate entry for a statement GS, where GS multiplies
945 SSA name BASE_IN by constant STRIDE_IN. Propagate any known
946 information about BASE_IN into the new candidate. Return the new
950 create_mul_imm_cand (gimple gs
, tree base_in
, tree stride_in
, bool speed
)
952 tree base
= NULL_TREE
, stride
= NULL_TREE
, ctype
= NULL_TREE
;
953 double_int index
, temp
;
954 unsigned savings
= 0;
956 slsr_cand_t base_cand
= base_cand_from_table (base_in
);
958 /* Look at all interpretations of the base candidate, if necessary,
959 to find information to propagate into this candidate. */
960 while (base_cand
&& !base
&& base_cand
->kind
!= CAND_PHI
)
962 if (base_cand
->kind
== CAND_MULT
963 && TREE_CODE (base_cand
->stride
) == INTEGER_CST
)
965 /* Y = (B + i') * S, S constant
967 ============================
968 X = (B + i') * (S * c) */
969 base
= base_cand
->base_expr
;
970 index
= base_cand
->index
;
971 temp
= tree_to_double_int (base_cand
->stride
)
972 * tree_to_double_int (stride_in
);
973 stride
= double_int_to_tree (TREE_TYPE (stride_in
), temp
);
974 ctype
= base_cand
->cand_type
;
975 if (has_single_use (base_in
))
976 savings
= (base_cand
->dead_savings
977 + stmt_cost (base_cand
->cand_stmt
, speed
));
979 else if (base_cand
->kind
== CAND_ADD
&& integer_onep (base_cand
->stride
))
983 ===========================
985 base
= base_cand
->base_expr
;
986 index
= base_cand
->index
;
988 ctype
= base_cand
->cand_type
;
989 if (has_single_use (base_in
))
990 savings
= (base_cand
->dead_savings
991 + stmt_cost (base_cand
->cand_stmt
, speed
));
993 else if (base_cand
->kind
== CAND_ADD
994 && base_cand
->index
.is_one ()
995 && TREE_CODE (base_cand
->stride
) == INTEGER_CST
)
997 /* Y = B + (1 * S), S constant
999 ===========================
1001 base
= base_cand
->base_expr
;
1002 index
= tree_to_double_int (base_cand
->stride
);
1004 ctype
= base_cand
->cand_type
;
1005 if (has_single_use (base_in
))
1006 savings
= (base_cand
->dead_savings
1007 + stmt_cost (base_cand
->cand_stmt
, speed
));
1010 if (base_cand
->next_interp
)
1011 base_cand
= lookup_cand (base_cand
->next_interp
);
1018 /* No interpretations had anything useful to propagate, so
1019 produce X = (Y + 0) * c. */
1021 index
= double_int_zero
;
1023 ctype
= TREE_TYPE (base_in
);
1026 c
= alloc_cand_and_find_basis (CAND_MULT
, gs
, base
, index
, stride
,
1031 /* Given GS which is a multiply of scalar integers, make an appropriate
1032 entry in the candidate table. If this is a multiply of two SSA names,
1033 create two CAND_MULT interpretations and attempt to find a basis for
1034 each of them. Otherwise, create a single CAND_MULT and attempt to
1038 slsr_process_mul (gimple gs
, tree rhs1
, tree rhs2
, bool speed
)
1042 /* If this is a multiply of an SSA name with itself, it is highly
1043 unlikely that we will get a strength reduction opportunity, so
1044 don't record it as a candidate. This simplifies the logic for
1045 finding a basis, so if this is removed that must be considered. */
1049 if (TREE_CODE (rhs2
) == SSA_NAME
)
1051 /* Record an interpretation of this statement in the candidate table
1052 assuming RHS1 is the base expression and RHS2 is the stride. */
1053 c
= create_mul_ssa_cand (gs
, rhs1
, rhs2
, speed
);
1055 /* Add the first interpretation to the statement-candidate mapping. */
1056 add_cand_for_stmt (gs
, c
);
1058 /* Record another interpretation of this statement assuming RHS1
1059 is the stride and RHS2 is the base expression. */
1060 c2
= create_mul_ssa_cand (gs
, rhs2
, rhs1
, speed
);
1061 c
->next_interp
= c2
->cand_num
;
1065 /* Record an interpretation for the multiply-immediate. */
1066 c
= create_mul_imm_cand (gs
, rhs1
, rhs2
, speed
);
1068 /* Add the interpretation to the statement-candidate mapping. */
1069 add_cand_for_stmt (gs
, c
);
1073 /* Create a candidate entry for a statement GS, where GS adds two
1074 SSA names BASE_IN and ADDEND_IN if SUBTRACT_P is false, and
1075 subtracts ADDEND_IN from BASE_IN otherwise. Propagate any known
1076 information about the two SSA names into the new candidate.
1077 Return the new candidate. */
1080 create_add_ssa_cand (gimple gs
, tree base_in
, tree addend_in
,
1081 bool subtract_p
, bool speed
)
1083 tree base
= NULL_TREE
, stride
= NULL_TREE
, ctype
= NULL
;
1085 unsigned savings
= 0;
1087 slsr_cand_t base_cand
= base_cand_from_table (base_in
);
1088 slsr_cand_t addend_cand
= base_cand_from_table (addend_in
);
1090 /* The most useful transformation is a multiply-immediate feeding
1091 an add or subtract. Look for that first. */
1092 while (addend_cand
&& !base
&& addend_cand
->kind
!= CAND_PHI
)
1094 if (addend_cand
->kind
== CAND_MULT
1095 && addend_cand
->index
.is_zero ()
1096 && TREE_CODE (addend_cand
->stride
) == INTEGER_CST
)
1098 /* Z = (B + 0) * S, S constant
1100 ===========================
1101 X = Y + ((+/-1 * S) * B) */
1103 index
= tree_to_double_int (addend_cand
->stride
);
1106 stride
= addend_cand
->base_expr
;
1107 ctype
= TREE_TYPE (base_in
);
1108 if (has_single_use (addend_in
))
1109 savings
= (addend_cand
->dead_savings
1110 + stmt_cost (addend_cand
->cand_stmt
, speed
));
1113 if (addend_cand
->next_interp
)
1114 addend_cand
= lookup_cand (addend_cand
->next_interp
);
1119 while (base_cand
&& !base
&& base_cand
->kind
!= CAND_PHI
)
1121 if (base_cand
->kind
== CAND_ADD
1122 && (base_cand
->index
.is_zero ()
1123 || operand_equal_p (base_cand
->stride
,
1124 integer_zero_node
, 0)))
1126 /* Y = B + (i' * S), i' * S = 0
1128 ============================
1129 X = B + (+/-1 * Z) */
1130 base
= base_cand
->base_expr
;
1131 index
= subtract_p
? double_int_minus_one
: double_int_one
;
1133 ctype
= base_cand
->cand_type
;
1134 if (has_single_use (base_in
))
1135 savings
= (base_cand
->dead_savings
1136 + stmt_cost (base_cand
->cand_stmt
, speed
));
1138 else if (subtract_p
)
1140 slsr_cand_t subtrahend_cand
= base_cand_from_table (addend_in
);
1142 while (subtrahend_cand
&& !base
&& subtrahend_cand
->kind
!= CAND_PHI
)
1144 if (subtrahend_cand
->kind
== CAND_MULT
1145 && subtrahend_cand
->index
.is_zero ()
1146 && TREE_CODE (subtrahend_cand
->stride
) == INTEGER_CST
)
1148 /* Z = (B + 0) * S, S constant
1150 ===========================
1151 Value: X = Y + ((-1 * S) * B) */
1153 index
= tree_to_double_int (subtrahend_cand
->stride
);
1155 stride
= subtrahend_cand
->base_expr
;
1156 ctype
= TREE_TYPE (base_in
);
1157 if (has_single_use (addend_in
))
1158 savings
= (subtrahend_cand
->dead_savings
1159 + stmt_cost (subtrahend_cand
->cand_stmt
, speed
));
1162 if (subtrahend_cand
->next_interp
)
1163 subtrahend_cand
= lookup_cand (subtrahend_cand
->next_interp
);
1165 subtrahend_cand
= NULL
;
1169 if (base_cand
->next_interp
)
1170 base_cand
= lookup_cand (base_cand
->next_interp
);
1177 /* No interpretations had anything useful to propagate, so
1178 produce X = Y + (1 * Z). */
1180 index
= subtract_p
? double_int_minus_one
: double_int_one
;
1182 ctype
= TREE_TYPE (base_in
);
1185 c
= alloc_cand_and_find_basis (CAND_ADD
, gs
, base
, index
, stride
,
1190 /* Create a candidate entry for a statement GS, where GS adds SSA
1191 name BASE_IN to constant INDEX_IN. Propagate any known information
1192 about BASE_IN into the new candidate. Return the new candidate. */
1195 create_add_imm_cand (gimple gs
, tree base_in
, double_int index_in
, bool speed
)
1197 enum cand_kind kind
= CAND_ADD
;
1198 tree base
= NULL_TREE
, stride
= NULL_TREE
, ctype
= NULL_TREE
;
1199 double_int index
, multiple
;
1200 unsigned savings
= 0;
1202 slsr_cand_t base_cand
= base_cand_from_table (base_in
);
1204 while (base_cand
&& !base
&& base_cand
->kind
!= CAND_PHI
)
1206 bool unsigned_p
= TYPE_UNSIGNED (TREE_TYPE (base_cand
->stride
));
1208 if (TREE_CODE (base_cand
->stride
) == INTEGER_CST
1209 && index_in
.multiple_of (tree_to_double_int (base_cand
->stride
),
1210 unsigned_p
, &multiple
))
1212 /* Y = (B + i') * S, S constant, c = kS for some integer k
1214 ============================
1215 X = (B + (i'+ k)) * S
1217 Y = B + (i' * S), S constant, c = kS for some integer k
1219 ============================
1220 X = (B + (i'+ k)) * S */
1221 kind
= base_cand
->kind
;
1222 base
= base_cand
->base_expr
;
1223 index
= base_cand
->index
+ multiple
;
1224 stride
= base_cand
->stride
;
1225 ctype
= base_cand
->cand_type
;
1226 if (has_single_use (base_in
))
1227 savings
= (base_cand
->dead_savings
1228 + stmt_cost (base_cand
->cand_stmt
, speed
));
1231 if (base_cand
->next_interp
)
1232 base_cand
= lookup_cand (base_cand
->next_interp
);
1239 /* No interpretations had anything useful to propagate, so
1240 produce X = Y + (c * 1). */
1244 stride
= integer_one_node
;
1245 ctype
= TREE_TYPE (base_in
);
1248 c
= alloc_cand_and_find_basis (kind
, gs
, base
, index
, stride
,
1253 /* Given GS which is an add or subtract of scalar integers or pointers,
1254 make at least one appropriate entry in the candidate table. */
1257 slsr_process_add (gimple gs
, tree rhs1
, tree rhs2
, bool speed
)
1259 bool subtract_p
= gimple_assign_rhs_code (gs
) == MINUS_EXPR
;
1260 slsr_cand_t c
= NULL
, c2
;
1262 if (TREE_CODE (rhs2
) == SSA_NAME
)
1264 /* First record an interpretation assuming RHS1 is the base expression
1265 and RHS2 is the stride. But it doesn't make sense for the
1266 stride to be a pointer, so don't record a candidate in that case. */
1267 if (!POINTER_TYPE_P (TREE_TYPE (rhs2
)))
1269 c
= create_add_ssa_cand (gs
, rhs1
, rhs2
, subtract_p
, speed
);
1271 /* Add the first interpretation to the statement-candidate
1273 add_cand_for_stmt (gs
, c
);
1276 /* If the two RHS operands are identical, or this is a subtract,
1278 if (operand_equal_p (rhs1
, rhs2
, 0) || subtract_p
)
1281 /* Otherwise, record another interpretation assuming RHS2 is the
1282 base expression and RHS1 is the stride, again provided that the
1283 stride is not a pointer. */
1284 if (!POINTER_TYPE_P (TREE_TYPE (rhs1
)))
1286 c2
= create_add_ssa_cand (gs
, rhs2
, rhs1
, false, speed
);
1288 c
->next_interp
= c2
->cand_num
;
1290 add_cand_for_stmt (gs
, c2
);
1297 /* Record an interpretation for the add-immediate. */
1298 index
= tree_to_double_int (rhs2
);
1302 c
= create_add_imm_cand (gs
, rhs1
, index
, speed
);
1304 /* Add the interpretation to the statement-candidate mapping. */
1305 add_cand_for_stmt (gs
, c
);
1309 /* Given GS which is a negate of a scalar integer, make an appropriate
1310 entry in the candidate table. A negate is equivalent to a multiply
1314 slsr_process_neg (gimple gs
, tree rhs1
, bool speed
)
1316 /* Record a CAND_MULT interpretation for the multiply by -1. */
1317 slsr_cand_t c
= create_mul_imm_cand (gs
, rhs1
, integer_minus_one_node
, speed
);
1319 /* Add the interpretation to the statement-candidate mapping. */
1320 add_cand_for_stmt (gs
, c
);
1323 /* Help function for legal_cast_p, operating on two trees. Checks
1324 whether it's allowable to cast from RHS to LHS. See legal_cast_p
1325 for more details. */
1328 legal_cast_p_1 (tree lhs
, tree rhs
)
1330 tree lhs_type
, rhs_type
;
1331 unsigned lhs_size
, rhs_size
;
1332 bool lhs_wraps
, rhs_wraps
;
1334 lhs_type
= TREE_TYPE (lhs
);
1335 rhs_type
= TREE_TYPE (rhs
);
1336 lhs_size
= TYPE_PRECISION (lhs_type
);
1337 rhs_size
= TYPE_PRECISION (rhs_type
);
1338 lhs_wraps
= TYPE_OVERFLOW_WRAPS (lhs_type
);
1339 rhs_wraps
= TYPE_OVERFLOW_WRAPS (rhs_type
);
1341 if (lhs_size
< rhs_size
1342 || (rhs_wraps
&& !lhs_wraps
)
1343 || (rhs_wraps
&& lhs_wraps
&& rhs_size
!= lhs_size
))
1349 /* Return TRUE if GS is a statement that defines an SSA name from
1350 a conversion and is legal for us to combine with an add and multiply
1351 in the candidate table. For example, suppose we have:
1357 Without the type-cast, we would create a CAND_MULT for D with base B,
1358 index i, and stride S. We want to record this candidate only if it
1359 is equivalent to apply the type cast following the multiply:
1365 We will record the type with the candidate for D. This allows us
1366 to use a similar previous candidate as a basis. If we have earlier seen
1372 we can replace D with
1374 D = D' + (i - i') * S;
1376 But if moving the type-cast would change semantics, we mustn't do this.
1378 This is legitimate for casts from a non-wrapping integral type to
1379 any integral type of the same or larger size. It is not legitimate
1380 to convert a wrapping type to a non-wrapping type, or to a wrapping
1381 type of a different size. I.e., with a wrapping type, we must
1382 assume that the addition B + i could wrap, in which case performing
1383 the multiply before or after one of the "illegal" type casts will
1384 have different semantics. */
1387 legal_cast_p (gimple gs
, tree rhs
)
1389 if (!is_gimple_assign (gs
)
1390 || !CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (gs
)))
1393 return legal_cast_p_1 (gimple_assign_lhs (gs
), rhs
);
1396 /* Given GS which is a cast to a scalar integer type, determine whether
1397 the cast is legal for strength reduction. If so, make at least one
1398 appropriate entry in the candidate table. */
1401 slsr_process_cast (gimple gs
, tree rhs1
, bool speed
)
1404 slsr_cand_t base_cand
, c
, c2
;
1405 unsigned savings
= 0;
1407 if (!legal_cast_p (gs
, rhs1
))
1410 lhs
= gimple_assign_lhs (gs
);
1411 base_cand
= base_cand_from_table (rhs1
);
1412 ctype
= TREE_TYPE (lhs
);
1414 if (base_cand
&& base_cand
->kind
!= CAND_PHI
)
1418 /* Propagate all data from the base candidate except the type,
1419 which comes from the cast, and the base candidate's cast,
1420 which is no longer applicable. */
1421 if (has_single_use (rhs1
))
1422 savings
= (base_cand
->dead_savings
1423 + stmt_cost (base_cand
->cand_stmt
, speed
));
1425 c
= alloc_cand_and_find_basis (base_cand
->kind
, gs
,
1426 base_cand
->base_expr
,
1427 base_cand
->index
, base_cand
->stride
,
1429 if (base_cand
->next_interp
)
1430 base_cand
= lookup_cand (base_cand
->next_interp
);
1437 /* If nothing is known about the RHS, create fresh CAND_ADD and
1438 CAND_MULT interpretations:
1443 The first of these is somewhat arbitrary, but the choice of
1444 1 for the stride simplifies the logic for propagating casts
1446 c
= alloc_cand_and_find_basis (CAND_ADD
, gs
, rhs1
, double_int_zero
,
1447 integer_one_node
, ctype
, 0);
1448 c2
= alloc_cand_and_find_basis (CAND_MULT
, gs
, rhs1
, double_int_zero
,
1449 integer_one_node
, ctype
, 0);
1450 c
->next_interp
= c2
->cand_num
;
1453 /* Add the first (or only) interpretation to the statement-candidate
1455 add_cand_for_stmt (gs
, c
);
1458 /* Given GS which is a copy of a scalar integer type, make at least one
1459 appropriate entry in the candidate table.
1461 This interface is included for completeness, but is unnecessary
1462 if this pass immediately follows a pass that performs copy
1463 propagation, such as DOM. */
1466 slsr_process_copy (gimple gs
, tree rhs1
, bool speed
)
1468 slsr_cand_t base_cand
, c
, c2
;
1469 unsigned savings
= 0;
1471 base_cand
= base_cand_from_table (rhs1
);
1473 if (base_cand
&& base_cand
->kind
!= CAND_PHI
)
1477 /* Propagate all data from the base candidate. */
1478 if (has_single_use (rhs1
))
1479 savings
= (base_cand
->dead_savings
1480 + stmt_cost (base_cand
->cand_stmt
, speed
));
1482 c
= alloc_cand_and_find_basis (base_cand
->kind
, gs
,
1483 base_cand
->base_expr
,
1484 base_cand
->index
, base_cand
->stride
,
1485 base_cand
->cand_type
, savings
);
1486 if (base_cand
->next_interp
)
1487 base_cand
= lookup_cand (base_cand
->next_interp
);
1494 /* If nothing is known about the RHS, create fresh CAND_ADD and
1495 CAND_MULT interpretations:
1500 The first of these is somewhat arbitrary, but the choice of
1501 1 for the stride simplifies the logic for propagating casts
1503 c
= alloc_cand_and_find_basis (CAND_ADD
, gs
, rhs1
, double_int_zero
,
1504 integer_one_node
, TREE_TYPE (rhs1
), 0);
1505 c2
= alloc_cand_and_find_basis (CAND_MULT
, gs
, rhs1
, double_int_zero
,
1506 integer_one_node
, TREE_TYPE (rhs1
), 0);
1507 c
->next_interp
= c2
->cand_num
;
1510 /* Add the first (or only) interpretation to the statement-candidate
1512 add_cand_for_stmt (gs
, c
);
1515 /* Find strength-reduction candidates in block BB. */
1518 find_candidates_in_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
1521 bool speed
= optimize_bb_for_speed_p (bb
);
1522 gimple_stmt_iterator gsi
;
1524 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1525 slsr_process_phi (gsi_stmt (gsi
), speed
);
1527 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1529 gimple gs
= gsi_stmt (gsi
);
1531 if (gimple_vuse (gs
) && gimple_assign_single_p (gs
))
1532 slsr_process_ref (gs
);
1534 else if (is_gimple_assign (gs
)
1535 && SCALAR_INT_MODE_P
1536 (TYPE_MODE (TREE_TYPE (gimple_assign_lhs (gs
)))))
1538 tree rhs1
= NULL_TREE
, rhs2
= NULL_TREE
;
1540 switch (gimple_assign_rhs_code (gs
))
1544 rhs1
= gimple_assign_rhs1 (gs
);
1545 rhs2
= gimple_assign_rhs2 (gs
);
1546 /* Should never happen, but currently some buggy situations
1547 in earlier phases put constants in rhs1. */
1548 if (TREE_CODE (rhs1
) != SSA_NAME
)
1552 /* Possible future opportunity: rhs1 of a ptr+ can be
1554 case POINTER_PLUS_EXPR
:
1556 rhs2
= gimple_assign_rhs2 (gs
);
1562 rhs1
= gimple_assign_rhs1 (gs
);
1563 if (TREE_CODE (rhs1
) != SSA_NAME
)
1571 switch (gimple_assign_rhs_code (gs
))
1574 slsr_process_mul (gs
, rhs1
, rhs2
, speed
);
1578 case POINTER_PLUS_EXPR
:
1580 slsr_process_add (gs
, rhs1
, rhs2
, speed
);
1584 slsr_process_neg (gs
, rhs1
, speed
);
1588 slsr_process_cast (gs
, rhs1
, speed
);
1592 slsr_process_copy (gs
, rhs1
, speed
);
1602 /* Dump a candidate for debug. */
1605 dump_candidate (slsr_cand_t c
)
1607 fprintf (dump_file
, "%3d [%d] ", c
->cand_num
,
1608 gimple_bb (c
->cand_stmt
)->index
);
1609 print_gimple_stmt (dump_file
, c
->cand_stmt
, 0, 0);
1613 fputs (" MULT : (", dump_file
);
1614 print_generic_expr (dump_file
, c
->base_expr
, 0);
1615 fputs (" + ", dump_file
);
1616 dump_double_int (dump_file
, c
->index
, false);
1617 fputs (") * ", dump_file
);
1618 print_generic_expr (dump_file
, c
->stride
, 0);
1619 fputs (" : ", dump_file
);
1622 fputs (" ADD : ", dump_file
);
1623 print_generic_expr (dump_file
, c
->base_expr
, 0);
1624 fputs (" + (", dump_file
);
1625 dump_double_int (dump_file
, c
->index
, false);
1626 fputs (" * ", dump_file
);
1627 print_generic_expr (dump_file
, c
->stride
, 0);
1628 fputs (") : ", dump_file
);
1631 fputs (" REF : ", dump_file
);
1632 print_generic_expr (dump_file
, c
->base_expr
, 0);
1633 fputs (" + (", dump_file
);
1634 print_generic_expr (dump_file
, c
->stride
, 0);
1635 fputs (") + ", dump_file
);
1636 dump_double_int (dump_file
, c
->index
, false);
1637 fputs (" : ", dump_file
);
1640 fputs (" PHI : ", dump_file
);
1641 print_generic_expr (dump_file
, c
->base_expr
, 0);
1642 fputs (" + (unknown * ", dump_file
);
1643 print_generic_expr (dump_file
, c
->stride
, 0);
1644 fputs (") : ", dump_file
);
1649 print_generic_expr (dump_file
, c
->cand_type
, 0);
1650 fprintf (dump_file
, "\n basis: %d dependent: %d sibling: %d\n",
1651 c
->basis
, c
->dependent
, c
->sibling
);
1652 fprintf (dump_file
, " next-interp: %d dead-savings: %d\n",
1653 c
->next_interp
, c
->dead_savings
);
1655 fprintf (dump_file
, " phi: %d\n", c
->def_phi
);
1656 fputs ("\n", dump_file
);
1659 /* Dump the candidate vector for debug. */
1662 dump_cand_vec (void)
1667 fprintf (dump_file
, "\nStrength reduction candidate vector:\n\n");
1669 FOR_EACH_VEC_ELT (cand_vec
, i
, c
)
1673 /* Callback used to dump the candidate chains hash table. */
1676 ssa_base_cand_dump_callback (cand_chain
**slot
, void *ignored ATTRIBUTE_UNUSED
)
1678 const_cand_chain_t chain
= *slot
;
1681 print_generic_expr (dump_file
, chain
->base_expr
, 0);
1682 fprintf (dump_file
, " -> %d", chain
->cand
->cand_num
);
1684 for (p
= chain
->next
; p
; p
= p
->next
)
1685 fprintf (dump_file
, " -> %d", p
->cand
->cand_num
);
1687 fputs ("\n", dump_file
);
1691 /* Dump the candidate chains. */
1694 dump_cand_chains (void)
1696 fprintf (dump_file
, "\nStrength reduction candidate chains:\n\n");
1697 base_cand_map
.traverse_noresize
<void *, ssa_base_cand_dump_callback
> (NULL
);
1698 fputs ("\n", dump_file
);
1701 /* Dump the increment vector for debug. */
1704 dump_incr_vec (void)
1706 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1710 fprintf (dump_file
, "\nIncrement vector:\n\n");
1712 for (i
= 0; i
< incr_vec_len
; i
++)
1714 fprintf (dump_file
, "%3d increment: ", i
);
1715 dump_double_int (dump_file
, incr_vec
[i
].incr
, false);
1716 fprintf (dump_file
, "\n count: %d", incr_vec
[i
].count
);
1717 fprintf (dump_file
, "\n cost: %d", incr_vec
[i
].cost
);
1718 fputs ("\n initializer: ", dump_file
);
1719 print_generic_expr (dump_file
, incr_vec
[i
].initializer
, 0);
1720 fputs ("\n\n", dump_file
);
1725 /* Replace *EXPR in candidate C with an equivalent strength-reduced
1729 replace_ref (tree
*expr
, slsr_cand_t c
)
1731 tree add_expr
= fold_build2 (POINTER_PLUS_EXPR
, TREE_TYPE (c
->base_expr
),
1732 c
->base_expr
, c
->stride
);
1733 tree mem_ref
= fold_build2 (MEM_REF
, TREE_TYPE (*expr
), add_expr
,
1734 double_int_to_tree (c
->cand_type
, c
->index
));
1736 /* Gimplify the base addressing expression for the new MEM_REF tree. */
1737 gimple_stmt_iterator gsi
= gsi_for_stmt (c
->cand_stmt
);
1738 TREE_OPERAND (mem_ref
, 0)
1739 = force_gimple_operand_gsi (&gsi
, TREE_OPERAND (mem_ref
, 0),
1740 /*simple_p=*/true, NULL
,
1741 /*before=*/true, GSI_SAME_STMT
);
1742 copy_ref_info (mem_ref
, *expr
);
1744 update_stmt (c
->cand_stmt
);
1747 /* Replace CAND_REF candidate C, each sibling of candidate C, and each
1748 dependent of candidate C with an equivalent strength-reduced data
1752 replace_refs (slsr_cand_t c
)
1754 if (gimple_vdef (c
->cand_stmt
))
1756 tree
*lhs
= gimple_assign_lhs_ptr (c
->cand_stmt
);
1757 replace_ref (lhs
, c
);
1761 tree
*rhs
= gimple_assign_rhs1_ptr (c
->cand_stmt
);
1762 replace_ref (rhs
, c
);
1766 replace_refs (lookup_cand (c
->sibling
));
1769 replace_refs (lookup_cand (c
->dependent
));
1772 /* Return TRUE if candidate C is dependent upon a PHI. */
1775 phi_dependent_cand_p (slsr_cand_t c
)
1777 /* A candidate is not necessarily dependent upon a PHI just because
1778 it has a phi definition for its base name. It may have a basis
1779 that relies upon the same phi definition, in which case the PHI
1780 is irrelevant to this candidate. */
1783 && lookup_cand (c
->basis
)->def_phi
!= c
->def_phi
);
1786 /* Calculate the increment required for candidate C relative to
1790 cand_increment (slsr_cand_t c
)
1794 /* If the candidate doesn't have a basis, just return its own
1795 index. This is useful in record_increments to help us find
1796 an existing initializer. Also, if the candidate's basis is
1797 hidden by a phi, then its own index will be the increment
1798 from the newly introduced phi basis. */
1799 if (!c
->basis
|| phi_dependent_cand_p (c
))
1802 basis
= lookup_cand (c
->basis
);
1803 gcc_assert (operand_equal_p (c
->base_expr
, basis
->base_expr
, 0));
1804 return c
->index
- basis
->index
;
1807 /* Calculate the increment required for candidate C relative to
1808 its basis. If we aren't going to generate pointer arithmetic
1809 for this candidate, return the absolute value of that increment
1812 static inline double_int
1813 cand_abs_increment (slsr_cand_t c
)
1815 double_int increment
= cand_increment (c
);
1817 if (!address_arithmetic_p
&& increment
.is_negative ())
1818 increment
= -increment
;
1823 /* Return TRUE iff candidate C has already been replaced under
1824 another interpretation. */
1827 cand_already_replaced (slsr_cand_t c
)
1829 return (gimple_bb (c
->cand_stmt
) == 0);
1832 /* Common logic used by replace_unconditional_candidate and
1833 replace_conditional_candidate. */
1836 replace_mult_candidate (slsr_cand_t c
, tree basis_name
, double_int bump
)
1838 tree target_type
= TREE_TYPE (gimple_assign_lhs (c
->cand_stmt
));
1839 enum tree_code cand_code
= gimple_assign_rhs_code (c
->cand_stmt
);
1841 /* It is highly unlikely, but possible, that the resulting
1842 bump doesn't fit in a HWI. Abandon the replacement
1843 in this case. This does not affect siblings or dependents
1844 of C. Restriction to signed HWI is conservative for unsigned
1845 types but allows for safe negation without twisted logic. */
1846 if (bump
.fits_shwi ()
1847 && bump
.to_shwi () != HOST_WIDE_INT_MIN
1848 /* It is not useful to replace casts, copies, or adds of
1849 an SSA name and a constant. */
1850 && cand_code
!= MODIFY_EXPR
1851 && cand_code
!= NOP_EXPR
1852 && cand_code
!= PLUS_EXPR
1853 && cand_code
!= POINTER_PLUS_EXPR
1854 && cand_code
!= MINUS_EXPR
)
1856 enum tree_code code
= PLUS_EXPR
;
1858 gimple stmt_to_print
= NULL
;
1860 /* If the basis name and the candidate's LHS have incompatible
1861 types, introduce a cast. */
1862 if (!useless_type_conversion_p (target_type
, TREE_TYPE (basis_name
)))
1863 basis_name
= introduce_cast_before_cand (c
, target_type
, basis_name
);
1864 if (bump
.is_negative ())
1870 bump_tree
= double_int_to_tree (target_type
, bump
);
1872 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1874 fputs ("Replacing: ", dump_file
);
1875 print_gimple_stmt (dump_file
, c
->cand_stmt
, 0, 0);
1878 if (bump
.is_zero ())
1880 tree lhs
= gimple_assign_lhs (c
->cand_stmt
);
1881 gimple copy_stmt
= gimple_build_assign (lhs
, basis_name
);
1882 gimple_stmt_iterator gsi
= gsi_for_stmt (c
->cand_stmt
);
1883 gimple_set_location (copy_stmt
, gimple_location (c
->cand_stmt
));
1884 gsi_replace (&gsi
, copy_stmt
, false);
1885 c
->cand_stmt
= copy_stmt
;
1886 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1887 stmt_to_print
= copy_stmt
;
1892 if (cand_code
!= NEGATE_EXPR
) {
1893 rhs1
= gimple_assign_rhs1 (c
->cand_stmt
);
1894 rhs2
= gimple_assign_rhs2 (c
->cand_stmt
);
1896 if (cand_code
!= NEGATE_EXPR
1897 && ((operand_equal_p (rhs1
, basis_name
, 0)
1898 && operand_equal_p (rhs2
, bump_tree
, 0))
1899 || (operand_equal_p (rhs1
, bump_tree
, 0)
1900 && operand_equal_p (rhs2
, basis_name
, 0))))
1902 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1904 fputs ("(duplicate, not actually replacing)", dump_file
);
1905 stmt_to_print
= c
->cand_stmt
;
1910 gimple_stmt_iterator gsi
= gsi_for_stmt (c
->cand_stmt
);
1911 gimple_assign_set_rhs_with_ops (&gsi
, code
,
1912 basis_name
, bump_tree
);
1913 update_stmt (gsi_stmt (gsi
));
1914 c
->cand_stmt
= gsi_stmt (gsi
);
1915 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1916 stmt_to_print
= gsi_stmt (gsi
);
1920 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1922 fputs ("With: ", dump_file
);
1923 print_gimple_stmt (dump_file
, stmt_to_print
, 0, 0);
1924 fputs ("\n", dump_file
);
1929 /* Replace candidate C with an add or subtract. Note that we only
1930 operate on CAND_MULTs with known strides, so we will never generate
1931 a POINTER_PLUS_EXPR. Each candidate X = (B + i) * S is replaced by
1932 X = Y + ((i - i') * S), as described in the module commentary. The
1933 folded value ((i - i') * S) is referred to here as the "bump." */
1936 replace_unconditional_candidate (slsr_cand_t c
)
1939 double_int stride
, bump
;
1941 if (cand_already_replaced (c
))
1944 basis
= lookup_cand (c
->basis
);
1945 stride
= tree_to_double_int (c
->stride
);
1946 bump
= cand_increment (c
) * stride
;
1948 replace_mult_candidate (c
, gimple_assign_lhs (basis
->cand_stmt
), bump
);
1951 /* Return the index in the increment vector of the given INCREMENT,
1952 or -1 if not found. The latter can occur if more than
1953 MAX_INCR_VEC_LEN increments have been found. */
1956 incr_vec_index (double_int increment
)
1960 for (i
= 0; i
< incr_vec_len
&& increment
!= incr_vec
[i
].incr
; i
++)
1963 if (i
< incr_vec_len
)
1969 /* Create a new statement along edge E to add BASIS_NAME to the product
1970 of INCREMENT and the stride of candidate C. Create and return a new
1971 SSA name from *VAR to be used as the LHS of the new statement.
1972 KNOWN_STRIDE is true iff C's stride is a constant. */
1975 create_add_on_incoming_edge (slsr_cand_t c
, tree basis_name
,
1976 double_int increment
, edge e
, location_t loc
,
1979 basic_block insert_bb
;
1980 gimple_stmt_iterator gsi
;
1981 tree lhs
, basis_type
;
1984 /* If the add candidate along this incoming edge has the same
1985 index as C's hidden basis, the hidden basis represents this
1987 if (increment
.is_zero ())
1990 basis_type
= TREE_TYPE (basis_name
);
1991 lhs
= make_temp_ssa_name (basis_type
, NULL
, "slsr");
1996 enum tree_code code
= PLUS_EXPR
;
1997 double_int bump
= increment
* tree_to_double_int (c
->stride
);
1998 if (bump
.is_negative ())
2004 bump_tree
= double_int_to_tree (basis_type
, bump
);
2005 new_stmt
= gimple_build_assign_with_ops (code
, lhs
, basis_name
,
2011 bool negate_incr
= (!address_arithmetic_p
&& increment
.is_negative ());
2012 i
= incr_vec_index (negate_incr
? -increment
: increment
);
2013 gcc_assert (i
>= 0);
2015 if (incr_vec
[i
].initializer
)
2017 enum tree_code code
= negate_incr
? MINUS_EXPR
: PLUS_EXPR
;
2018 new_stmt
= gimple_build_assign_with_ops (code
, lhs
, basis_name
,
2019 incr_vec
[i
].initializer
);
2021 else if (increment
.is_one ())
2022 new_stmt
= gimple_build_assign_with_ops (PLUS_EXPR
, lhs
, basis_name
,
2024 else if (increment
.is_minus_one ())
2025 new_stmt
= gimple_build_assign_with_ops (MINUS_EXPR
, lhs
, basis_name
,
2031 insert_bb
= single_succ_p (e
->src
) ? e
->src
: split_edge (e
);
2032 gsi
= gsi_last_bb (insert_bb
);
2034 if (!gsi_end_p (gsi
) && is_ctrl_stmt (gsi_stmt (gsi
)))
2035 gsi_insert_before (&gsi
, new_stmt
, GSI_NEW_STMT
);
2037 gsi_insert_after (&gsi
, new_stmt
, GSI_NEW_STMT
);
2039 gimple_set_location (new_stmt
, loc
);
2041 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2043 fprintf (dump_file
, "Inserting in block %d: ", insert_bb
->index
);
2044 print_gimple_stmt (dump_file
, new_stmt
, 0, 0);
2050 /* Given a candidate C with BASIS_NAME being the LHS of C's basis which
2051 is hidden by the phi node FROM_PHI, create a new phi node in the same
2052 block as FROM_PHI. The new phi is suitable for use as a basis by C,
2053 with its phi arguments representing conditional adjustments to the
2054 hidden basis along conditional incoming paths. Those adjustments are
2055 made by creating add statements (and sometimes recursively creating
2056 phis) along those incoming paths. LOC is the location to attach to
2057 the introduced statements. KNOWN_STRIDE is true iff C's stride is a
2061 create_phi_basis (slsr_cand_t c
, gimple from_phi
, tree basis_name
,
2062 location_t loc
, bool known_stride
)
2068 slsr_cand_t basis
= lookup_cand (c
->basis
);
2069 int nargs
= gimple_phi_num_args (from_phi
);
2070 basic_block phi_bb
= gimple_bb (from_phi
);
2071 slsr_cand_t phi_cand
= base_cand_from_table (gimple_phi_result (from_phi
));
2072 phi_args
.create (nargs
);
2074 /* Process each argument of the existing phi that represents
2075 conditionally-executed add candidates. */
2076 for (i
= 0; i
< nargs
; i
++)
2078 edge e
= (*phi_bb
->preds
)[i
];
2079 tree arg
= gimple_phi_arg_def (from_phi
, i
);
2082 /* If the phi argument is the base name of the CAND_PHI, then
2083 this incoming arc should use the hidden basis. */
2084 if (operand_equal_p (arg
, phi_cand
->base_expr
, 0))
2085 if (basis
->index
.is_zero ())
2086 feeding_def
= gimple_assign_lhs (basis
->cand_stmt
);
2089 double_int incr
= -basis
->index
;
2090 feeding_def
= create_add_on_incoming_edge (c
, basis_name
, incr
,
2091 e
, loc
, known_stride
);
2095 gimple arg_def
= SSA_NAME_DEF_STMT (arg
);
2097 /* If there is another phi along this incoming edge, we must
2098 process it in the same fashion to ensure that all basis
2099 adjustments are made along its incoming edges. */
2100 if (gimple_code (arg_def
) == GIMPLE_PHI
)
2101 feeding_def
= create_phi_basis (c
, arg_def
, basis_name
,
2105 slsr_cand_t arg_cand
= base_cand_from_table (arg
);
2106 double_int diff
= arg_cand
->index
- basis
->index
;
2107 feeding_def
= create_add_on_incoming_edge (c
, basis_name
, diff
,
2108 e
, loc
, known_stride
);
2112 /* Because of recursion, we need to save the arguments in a vector
2113 so we can create the PHI statement all at once. Otherwise the
2114 storage for the half-created PHI can be reclaimed. */
2115 phi_args
.safe_push (feeding_def
);
2118 /* Create the new phi basis. */
2119 name
= make_temp_ssa_name (TREE_TYPE (basis_name
), NULL
, "slsr");
2120 phi
= create_phi_node (name
, phi_bb
);
2121 SSA_NAME_DEF_STMT (name
) = phi
;
2123 FOR_EACH_VEC_ELT (phi_args
, i
, phi_arg
)
2125 edge e
= (*phi_bb
->preds
)[i
];
2126 add_phi_arg (phi
, phi_arg
, e
, loc
);
2131 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2133 fputs ("Introducing new phi basis: ", dump_file
);
2134 print_gimple_stmt (dump_file
, phi
, 0, 0);
2140 /* Given a candidate C whose basis is hidden by at least one intervening
2141 phi, introduce a matching number of new phis to represent its basis
2142 adjusted by conditional increments along possible incoming paths. Then
2143 replace C as though it were an unconditional candidate, using the new
2147 replace_conditional_candidate (slsr_cand_t c
)
2149 tree basis_name
, name
;
2152 double_int stride
, bump
;
2154 /* Look up the LHS SSA name from C's basis. This will be the
2155 RHS1 of the adds we will introduce to create new phi arguments. */
2156 basis
= lookup_cand (c
->basis
);
2157 basis_name
= gimple_assign_lhs (basis
->cand_stmt
);
2159 /* Create a new phi statement which will represent C's true basis
2160 after the transformation is complete. */
2161 loc
= gimple_location (c
->cand_stmt
);
2162 name
= create_phi_basis (c
, lookup_cand (c
->def_phi
)->cand_stmt
,
2163 basis_name
, loc
, KNOWN_STRIDE
);
2164 /* Replace C with an add of the new basis phi and a constant. */
2165 stride
= tree_to_double_int (c
->stride
);
2166 bump
= c
->index
* stride
;
2168 replace_mult_candidate (c
, name
, bump
);
2171 /* Compute the expected costs of inserting basis adjustments for
2172 candidate C with phi-definition PHI. The cost of inserting
2173 one adjustment is given by ONE_ADD_COST. If PHI has arguments
2174 which are themselves phi results, recursively calculate costs
2175 for those phis as well. */
2178 phi_add_costs (gimple phi
, slsr_cand_t c
, int one_add_cost
)
2182 slsr_cand_t phi_cand
= base_cand_from_table (gimple_phi_result (phi
));
2184 /* If we work our way back to a phi that isn't dominated by the hidden
2185 basis, this isn't a candidate for replacement. Indicate this by
2186 returning an unreasonably high cost. It's not easy to detect
2187 these situations when determining the basis, so we defer the
2188 decision until now. */
2189 basic_block phi_bb
= gimple_bb (phi
);
2190 slsr_cand_t basis
= lookup_cand (c
->basis
);
2191 basic_block basis_bb
= gimple_bb (basis
->cand_stmt
);
2193 if (phi_bb
== basis_bb
|| !dominated_by_p (CDI_DOMINATORS
, phi_bb
, basis_bb
))
2194 return COST_INFINITE
;
2196 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
2198 tree arg
= gimple_phi_arg_def (phi
, i
);
2200 if (arg
!= phi_cand
->base_expr
)
2202 gimple arg_def
= SSA_NAME_DEF_STMT (arg
);
2204 if (gimple_code (arg_def
) == GIMPLE_PHI
)
2205 cost
+= phi_add_costs (arg_def
, c
, one_add_cost
);
2208 slsr_cand_t arg_cand
= base_cand_from_table (arg
);
2210 if (arg_cand
->index
!= c
->index
)
2211 cost
+= one_add_cost
;
2219 /* For candidate C, each sibling of candidate C, and each dependent of
2220 candidate C, determine whether the candidate is dependent upon a
2221 phi that hides its basis. If not, replace the candidate unconditionally.
2222 Otherwise, determine whether the cost of introducing compensation code
2223 for the candidate is offset by the gains from strength reduction. If
2224 so, replace the candidate and introduce the compensation code. */
2227 replace_uncond_cands_and_profitable_phis (slsr_cand_t c
)
2229 if (phi_dependent_cand_p (c
))
2231 if (c
->kind
== CAND_MULT
)
2233 /* A candidate dependent upon a phi will replace a multiply by
2234 a constant with an add, and will insert at most one add for
2235 each phi argument. Add these costs with the potential dead-code
2236 savings to determine profitability. */
2237 bool speed
= optimize_bb_for_speed_p (gimple_bb (c
->cand_stmt
));
2238 int mult_savings
= stmt_cost (c
->cand_stmt
, speed
);
2239 gimple phi
= lookup_cand (c
->def_phi
)->cand_stmt
;
2240 tree phi_result
= gimple_phi_result (phi
);
2241 int one_add_cost
= add_cost (speed
,
2242 TYPE_MODE (TREE_TYPE (phi_result
)));
2243 int add_costs
= one_add_cost
+ phi_add_costs (phi
, c
, one_add_cost
);
2244 int cost
= add_costs
- mult_savings
- c
->dead_savings
;
2246 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2248 fprintf (dump_file
, " Conditional candidate %d:\n", c
->cand_num
);
2249 fprintf (dump_file
, " add_costs = %d\n", add_costs
);
2250 fprintf (dump_file
, " mult_savings = %d\n", mult_savings
);
2251 fprintf (dump_file
, " dead_savings = %d\n", c
->dead_savings
);
2252 fprintf (dump_file
, " cost = %d\n", cost
);
2253 if (cost
<= COST_NEUTRAL
)
2254 fputs (" Replacing...\n", dump_file
);
2256 fputs (" Not replaced.\n", dump_file
);
2259 if (cost
<= COST_NEUTRAL
)
2260 replace_conditional_candidate (c
);
2264 replace_unconditional_candidate (c
);
2267 replace_uncond_cands_and_profitable_phis (lookup_cand (c
->sibling
));
2270 replace_uncond_cands_and_profitable_phis (lookup_cand (c
->dependent
));
2273 /* Count the number of candidates in the tree rooted at C that have
2274 not already been replaced under other interpretations. */
2277 count_candidates (slsr_cand_t c
)
2279 unsigned count
= cand_already_replaced (c
) ? 0 : 1;
2282 count
+= count_candidates (lookup_cand (c
->sibling
));
2285 count
+= count_candidates (lookup_cand (c
->dependent
));
2290 /* Increase the count of INCREMENT by one in the increment vector.
2291 INCREMENT is associated with candidate C. If INCREMENT is to be
2292 conditionally executed as part of a conditional candidate replacement,
2293 IS_PHI_ADJUST is true, otherwise false. If an initializer
2294 T_0 = stride * I is provided by a candidate that dominates all
2295 candidates with the same increment, also record T_0 for subsequent use. */
2298 record_increment (slsr_cand_t c
, double_int increment
, bool is_phi_adjust
)
2303 /* Treat increments that differ only in sign as identical so as to
2304 share initializers, unless we are generating pointer arithmetic. */
2305 if (!address_arithmetic_p
&& increment
.is_negative ())
2306 increment
= -increment
;
2308 for (i
= 0; i
< incr_vec_len
; i
++)
2310 if (incr_vec
[i
].incr
== increment
)
2312 incr_vec
[i
].count
++;
2315 /* If we previously recorded an initializer that doesn't
2316 dominate this candidate, it's not going to be useful to
2318 if (incr_vec
[i
].initializer
2319 && !dominated_by_p (CDI_DOMINATORS
,
2320 gimple_bb (c
->cand_stmt
),
2321 incr_vec
[i
].init_bb
))
2323 incr_vec
[i
].initializer
= NULL_TREE
;
2324 incr_vec
[i
].init_bb
= NULL
;
2331 if (!found
&& incr_vec_len
< MAX_INCR_VEC_LEN
- 1)
2333 /* The first time we see an increment, create the entry for it.
2334 If this is the root candidate which doesn't have a basis, set
2335 the count to zero. We're only processing it so it can possibly
2336 provide an initializer for other candidates. */
2337 incr_vec
[incr_vec_len
].incr
= increment
;
2338 incr_vec
[incr_vec_len
].count
= c
->basis
|| is_phi_adjust
? 1 : 0;
2339 incr_vec
[incr_vec_len
].cost
= COST_INFINITE
;
2341 /* Optimistically record the first occurrence of this increment
2342 as providing an initializer (if it does); we will revise this
2343 opinion later if it doesn't dominate all other occurrences.
2344 Exception: increments of -1, 0, 1 never need initializers;
2345 and phi adjustments don't ever provide initializers. */
2346 if (c
->kind
== CAND_ADD
2348 && c
->index
== increment
2349 && (increment
.sgt (double_int_one
)
2350 || increment
.slt (double_int_minus_one
))
2351 && (gimple_assign_rhs_code (c
->cand_stmt
) == PLUS_EXPR
2352 || gimple_assign_rhs_code (c
->cand_stmt
) == POINTER_PLUS_EXPR
))
2354 tree t0
= NULL_TREE
;
2355 tree rhs1
= gimple_assign_rhs1 (c
->cand_stmt
);
2356 tree rhs2
= gimple_assign_rhs2 (c
->cand_stmt
);
2357 if (operand_equal_p (rhs1
, c
->base_expr
, 0))
2359 else if (operand_equal_p (rhs2
, c
->base_expr
, 0))
2362 && SSA_NAME_DEF_STMT (t0
)
2363 && gimple_bb (SSA_NAME_DEF_STMT (t0
)))
2365 incr_vec
[incr_vec_len
].initializer
= t0
;
2366 incr_vec
[incr_vec_len
++].init_bb
2367 = gimple_bb (SSA_NAME_DEF_STMT (t0
));
2371 incr_vec
[incr_vec_len
].initializer
= NULL_TREE
;
2372 incr_vec
[incr_vec_len
++].init_bb
= NULL
;
2377 incr_vec
[incr_vec_len
].initializer
= NULL_TREE
;
2378 incr_vec
[incr_vec_len
++].init_bb
= NULL
;
2383 /* Given phi statement PHI that hides a candidate from its BASIS, find
2384 the increments along each incoming arc (recursively handling additional
2385 phis that may be present) and record them. These increments are the
2386 difference in index between the index-adjusting statements and the
2387 index of the basis. */
2390 record_phi_increments (slsr_cand_t basis
, gimple phi
)
2393 slsr_cand_t phi_cand
= base_cand_from_table (gimple_phi_result (phi
));
2395 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
2397 tree arg
= gimple_phi_arg_def (phi
, i
);
2399 if (!operand_equal_p (arg
, phi_cand
->base_expr
, 0))
2401 gimple arg_def
= SSA_NAME_DEF_STMT (arg
);
2403 if (gimple_code (arg_def
) == GIMPLE_PHI
)
2404 record_phi_increments (basis
, arg_def
);
2407 slsr_cand_t arg_cand
= base_cand_from_table (arg
);
2408 double_int diff
= arg_cand
->index
- basis
->index
;
2409 record_increment (arg_cand
, diff
, PHI_ADJUST
);
2415 /* Determine how many times each unique increment occurs in the set
2416 of candidates rooted at C's parent, recording the data in the
2417 increment vector. For each unique increment I, if an initializer
2418 T_0 = stride * I is provided by a candidate that dominates all
2419 candidates with the same increment, also record T_0 for subsequent
2423 record_increments (slsr_cand_t c
)
2425 if (!cand_already_replaced (c
))
2427 if (!phi_dependent_cand_p (c
))
2428 record_increment (c
, cand_increment (c
), NOT_PHI_ADJUST
);
2431 /* A candidate with a basis hidden by a phi will have one
2432 increment for its relationship to the index represented by
2433 the phi, and potentially additional increments along each
2434 incoming edge. For the root of the dependency tree (which
2435 has no basis), process just the initial index in case it has
2436 an initializer that can be used by subsequent candidates. */
2437 record_increment (c
, c
->index
, NOT_PHI_ADJUST
);
2440 record_phi_increments (lookup_cand (c
->basis
),
2441 lookup_cand (c
->def_phi
)->cand_stmt
);
2446 record_increments (lookup_cand (c
->sibling
));
2449 record_increments (lookup_cand (c
->dependent
));
2452 /* Add up and return the costs of introducing add statements that
2453 require the increment INCR on behalf of candidate C and phi
2454 statement PHI. Accumulate into *SAVINGS the potential savings
2455 from removing existing statements that feed PHI and have no other
2459 phi_incr_cost (slsr_cand_t c
, double_int incr
, gimple phi
, int *savings
)
2463 slsr_cand_t basis
= lookup_cand (c
->basis
);
2464 slsr_cand_t phi_cand
= base_cand_from_table (gimple_phi_result (phi
));
2466 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
2468 tree arg
= gimple_phi_arg_def (phi
, i
);
2470 if (!operand_equal_p (arg
, phi_cand
->base_expr
, 0))
2472 gimple arg_def
= SSA_NAME_DEF_STMT (arg
);
2474 if (gimple_code (arg_def
) == GIMPLE_PHI
)
2476 int feeding_savings
= 0;
2477 cost
+= phi_incr_cost (c
, incr
, arg_def
, &feeding_savings
);
2478 if (has_single_use (gimple_phi_result (arg_def
)))
2479 *savings
+= feeding_savings
;
2483 slsr_cand_t arg_cand
= base_cand_from_table (arg
);
2484 double_int diff
= arg_cand
->index
- basis
->index
;
2488 tree basis_lhs
= gimple_assign_lhs (basis
->cand_stmt
);
2489 tree lhs
= gimple_assign_lhs (arg_cand
->cand_stmt
);
2490 cost
+= add_cost (true, TYPE_MODE (TREE_TYPE (basis_lhs
)));
2491 if (has_single_use (lhs
))
2492 *savings
+= stmt_cost (arg_cand
->cand_stmt
, true);
2501 /* Return the first candidate in the tree rooted at C that has not
2502 already been replaced, favoring siblings over dependents. */
2505 unreplaced_cand_in_tree (slsr_cand_t c
)
2507 if (!cand_already_replaced (c
))
2512 slsr_cand_t sib
= unreplaced_cand_in_tree (lookup_cand (c
->sibling
));
2519 slsr_cand_t dep
= unreplaced_cand_in_tree (lookup_cand (c
->dependent
));
2527 /* Return TRUE if the candidates in the tree rooted at C should be
2528 optimized for speed, else FALSE. We estimate this based on the block
2529 containing the most dominant candidate in the tree that has not yet
2533 optimize_cands_for_speed_p (slsr_cand_t c
)
2535 slsr_cand_t c2
= unreplaced_cand_in_tree (c
);
2537 return optimize_bb_for_speed_p (gimple_bb (c2
->cand_stmt
));
2540 /* Add COST_IN to the lowest cost of any dependent path starting at
2541 candidate C or any of its siblings, counting only candidates along
2542 such paths with increment INCR. Assume that replacing a candidate
2543 reduces cost by REPL_SAVINGS. Also account for savings from any
2544 statements that would go dead. If COUNT_PHIS is true, include
2545 costs of introducing feeding statements for conditional candidates. */
2548 lowest_cost_path (int cost_in
, int repl_savings
, slsr_cand_t c
,
2549 double_int incr
, bool count_phis
)
2551 int local_cost
, sib_cost
, savings
= 0;
2552 double_int cand_incr
= cand_abs_increment (c
);
2554 if (cand_already_replaced (c
))
2555 local_cost
= cost_in
;
2556 else if (incr
== cand_incr
)
2557 local_cost
= cost_in
- repl_savings
- c
->dead_savings
;
2559 local_cost
= cost_in
- c
->dead_savings
;
2562 && phi_dependent_cand_p (c
)
2563 && !cand_already_replaced (c
))
2565 gimple phi
= lookup_cand (c
->def_phi
)->cand_stmt
;
2566 local_cost
+= phi_incr_cost (c
, incr
, phi
, &savings
);
2568 if (has_single_use (gimple_phi_result (phi
)))
2569 local_cost
-= savings
;
2573 local_cost
= lowest_cost_path (local_cost
, repl_savings
,
2574 lookup_cand (c
->dependent
), incr
,
2579 sib_cost
= lowest_cost_path (cost_in
, repl_savings
,
2580 lookup_cand (c
->sibling
), incr
,
2582 local_cost
= MIN (local_cost
, sib_cost
);
2588 /* Compute the total savings that would accrue from all replacements
2589 in the candidate tree rooted at C, counting only candidates with
2590 increment INCR. Assume that replacing a candidate reduces cost
2591 by REPL_SAVINGS. Also account for savings from statements that
2595 total_savings (int repl_savings
, slsr_cand_t c
, double_int incr
,
2599 double_int cand_incr
= cand_abs_increment (c
);
2601 if (incr
== cand_incr
&& !cand_already_replaced (c
))
2602 savings
+= repl_savings
+ c
->dead_savings
;
2605 && phi_dependent_cand_p (c
)
2606 && !cand_already_replaced (c
))
2608 int phi_savings
= 0;
2609 gimple phi
= lookup_cand (c
->def_phi
)->cand_stmt
;
2610 savings
-= phi_incr_cost (c
, incr
, phi
, &phi_savings
);
2612 if (has_single_use (gimple_phi_result (phi
)))
2613 savings
+= phi_savings
;
2617 savings
+= total_savings (repl_savings
, lookup_cand (c
->dependent
), incr
,
2621 savings
+= total_savings (repl_savings
, lookup_cand (c
->sibling
), incr
,
2627 /* Use target-specific costs to determine and record which increments
2628 in the current candidate tree are profitable to replace, assuming
2629 MODE and SPEED. FIRST_DEP is the first dependent of the root of
2632 One slight limitation here is that we don't account for the possible
2633 introduction of casts in some cases. See replace_one_candidate for
2634 the cases where these are introduced. This should probably be cleaned
2638 analyze_increments (slsr_cand_t first_dep
, enum machine_mode mode
, bool speed
)
2642 for (i
= 0; i
< incr_vec_len
; i
++)
2644 HOST_WIDE_INT incr
= incr_vec
[i
].incr
.to_shwi ();
2646 /* If somehow this increment is bigger than a HWI, we won't
2647 be optimizing candidates that use it. And if the increment
2648 has a count of zero, nothing will be done with it. */
2649 if (!incr_vec
[i
].incr
.fits_shwi () || !incr_vec
[i
].count
)
2650 incr_vec
[i
].cost
= COST_INFINITE
;
2652 /* Increments of 0, 1, and -1 are always profitable to replace,
2653 because they always replace a multiply or add with an add or
2654 copy, and may cause one or more existing instructions to go
2655 dead. Exception: -1 can't be assumed to be profitable for
2656 pointer addition. */
2660 && (gimple_assign_rhs_code (first_dep
->cand_stmt
)
2661 != POINTER_PLUS_EXPR
)))
2662 incr_vec
[i
].cost
= COST_NEUTRAL
;
2664 /* FORNOW: If we need to add an initializer, give up if a cast from
2665 the candidate's type to its stride's type can lose precision.
2666 This could eventually be handled better by expressly retaining the
2667 result of a cast to a wider type in the stride. Example:
2672 _4 = x + _3; ADD: x + (10 * _1) : int
2674 _6 = x + _3; ADD: x + (15 * _1) : int
2676 Right now replacing _6 would cause insertion of an initializer
2677 of the form "short int T = _1 * 5;" followed by a cast to
2678 int, which could overflow incorrectly. Had we recorded _2 or
2679 (int)_1 as the stride, this wouldn't happen. However, doing
2680 this breaks other opportunities, so this will require some
2682 else if (!incr_vec
[i
].initializer
2683 && TREE_CODE (first_dep
->stride
) != INTEGER_CST
2684 && !legal_cast_p_1 (first_dep
->stride
,
2685 gimple_assign_lhs (first_dep
->cand_stmt
)))
2687 incr_vec
[i
].cost
= COST_INFINITE
;
2689 /* If we need to add an initializer, make sure we don't introduce
2690 a multiply by a pointer type, which can happen in certain cast
2691 scenarios. FIXME: When cleaning up these cast issues, we can
2692 afford to introduce the multiply provided we cast out to an
2693 unsigned int of appropriate size. */
2694 else if (!incr_vec
[i
].initializer
2695 && TREE_CODE (first_dep
->stride
) != INTEGER_CST
2696 && POINTER_TYPE_P (TREE_TYPE (first_dep
->stride
)))
2698 incr_vec
[i
].cost
= COST_INFINITE
;
2700 /* For any other increment, if this is a multiply candidate, we
2701 must introduce a temporary T and initialize it with
2702 T_0 = stride * increment. When optimizing for speed, walk the
2703 candidate tree to calculate the best cost reduction along any
2704 path; if it offsets the fixed cost of inserting the initializer,
2705 replacing the increment is profitable. When optimizing for
2706 size, instead calculate the total cost reduction from replacing
2707 all candidates with this increment. */
2708 else if (first_dep
->kind
== CAND_MULT
)
2710 int cost
= mult_by_coeff_cost (incr
, mode
, speed
);
2711 int repl_savings
= mul_cost (speed
, mode
) - add_cost (speed
, mode
);
2713 cost
= lowest_cost_path (cost
, repl_savings
, first_dep
,
2714 incr_vec
[i
].incr
, COUNT_PHIS
);
2716 cost
-= total_savings (repl_savings
, first_dep
, incr_vec
[i
].incr
,
2719 incr_vec
[i
].cost
= cost
;
2722 /* If this is an add candidate, the initializer may already
2723 exist, so only calculate the cost of the initializer if it
2724 doesn't. We are replacing one add with another here, so the
2725 known replacement savings is zero. We will account for removal
2726 of dead instructions in lowest_cost_path or total_savings. */
2730 if (!incr_vec
[i
].initializer
)
2731 cost
= mult_by_coeff_cost (incr
, mode
, speed
);
2734 cost
= lowest_cost_path (cost
, 0, first_dep
, incr_vec
[i
].incr
,
2737 cost
-= total_savings (0, first_dep
, incr_vec
[i
].incr
,
2740 incr_vec
[i
].cost
= cost
;
2745 /* Return the nearest common dominator of BB1 and BB2. If the blocks
2746 are identical, return the earlier of C1 and C2 in *WHERE. Otherwise,
2747 if the NCD matches BB1, return C1 in *WHERE; if the NCD matches BB2,
2748 return C2 in *WHERE; and if the NCD matches neither, return NULL in
2749 *WHERE. Note: It is possible for one of C1 and C2 to be NULL. */
2752 ncd_for_two_cands (basic_block bb1
, basic_block bb2
,
2753 slsr_cand_t c1
, slsr_cand_t c2
, slsr_cand_t
*where
)
2769 ncd
= nearest_common_dominator (CDI_DOMINATORS
, bb1
, bb2
);
2771 /* If both candidates are in the same block, the earlier
2773 if (bb1
== ncd
&& bb2
== ncd
)
2775 if (!c1
|| (c2
&& c2
->cand_num
< c1
->cand_num
))
2781 /* Otherwise, if one of them produced a candidate in the
2782 dominator, that one wins. */
2783 else if (bb1
== ncd
)
2786 else if (bb2
== ncd
)
2789 /* If neither matches the dominator, neither wins. */
2796 /* Consider all candidates that feed PHI. Find the nearest common
2797 dominator of those candidates requiring the given increment INCR.
2798 Further find and return the nearest common dominator of this result
2799 with block NCD. If the returned block contains one or more of the
2800 candidates, return the earliest candidate in the block in *WHERE. */
2803 ncd_with_phi (slsr_cand_t c
, double_int incr
, gimple phi
,
2804 basic_block ncd
, slsr_cand_t
*where
)
2807 slsr_cand_t basis
= lookup_cand (c
->basis
);
2808 slsr_cand_t phi_cand
= base_cand_from_table (gimple_phi_result (phi
));
2810 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
2812 tree arg
= gimple_phi_arg_def (phi
, i
);
2814 if (!operand_equal_p (arg
, phi_cand
->base_expr
, 0))
2816 gimple arg_def
= SSA_NAME_DEF_STMT (arg
);
2818 if (gimple_code (arg_def
) == GIMPLE_PHI
)
2819 ncd
= ncd_with_phi (c
, incr
, arg_def
, ncd
, where
);
2822 slsr_cand_t arg_cand
= base_cand_from_table (arg
);
2823 double_int diff
= arg_cand
->index
- basis
->index
;
2825 if ((incr
== diff
) || (!address_arithmetic_p
&& incr
== -diff
))
2826 ncd
= ncd_for_two_cands (ncd
, gimple_bb (arg_cand
->cand_stmt
),
2827 *where
, arg_cand
, where
);
2835 /* Consider the candidate C together with any candidates that feed
2836 C's phi dependence (if any). Find and return the nearest common
2837 dominator of those candidates requiring the given increment INCR.
2838 If the returned block contains one or more of the candidates,
2839 return the earliest candidate in the block in *WHERE. */
2842 ncd_of_cand_and_phis (slsr_cand_t c
, double_int incr
, slsr_cand_t
*where
)
2844 basic_block ncd
= NULL
;
2846 if (cand_abs_increment (c
) == incr
)
2848 ncd
= gimple_bb (c
->cand_stmt
);
2852 if (phi_dependent_cand_p (c
))
2853 ncd
= ncd_with_phi (c
, incr
, lookup_cand (c
->def_phi
)->cand_stmt
,
2859 /* Consider all candidates in the tree rooted at C for which INCR
2860 represents the required increment of C relative to its basis.
2861 Find and return the basic block that most nearly dominates all
2862 such candidates. If the returned block contains one or more of
2863 the candidates, return the earliest candidate in the block in
2867 nearest_common_dominator_for_cands (slsr_cand_t c
, double_int incr
,
2870 basic_block sib_ncd
= NULL
, dep_ncd
= NULL
, this_ncd
= NULL
, ncd
;
2871 slsr_cand_t sib_where
= NULL
, dep_where
= NULL
, this_where
= NULL
, new_where
;
2873 /* First find the NCD of all siblings and dependents. */
2875 sib_ncd
= nearest_common_dominator_for_cands (lookup_cand (c
->sibling
),
2878 dep_ncd
= nearest_common_dominator_for_cands (lookup_cand (c
->dependent
),
2880 if (!sib_ncd
&& !dep_ncd
)
2885 else if (sib_ncd
&& !dep_ncd
)
2887 new_where
= sib_where
;
2890 else if (dep_ncd
&& !sib_ncd
)
2892 new_where
= dep_where
;
2896 ncd
= ncd_for_two_cands (sib_ncd
, dep_ncd
, sib_where
,
2897 dep_where
, &new_where
);
2899 /* If the candidate's increment doesn't match the one we're interested
2900 in (and nor do any increments for feeding defs of a phi-dependence),
2901 then the result depends only on siblings and dependents. */
2902 this_ncd
= ncd_of_cand_and_phis (c
, incr
, &this_where
);
2904 if (!this_ncd
|| cand_already_replaced (c
))
2910 /* Otherwise, compare this candidate with the result from all siblings
2912 ncd
= ncd_for_two_cands (ncd
, this_ncd
, new_where
, this_where
, where
);
2917 /* Return TRUE if the increment indexed by INDEX is profitable to replace. */
2920 profitable_increment_p (unsigned index
)
2922 return (incr_vec
[index
].cost
<= COST_NEUTRAL
);
2925 /* For each profitable increment in the increment vector not equal to
2926 0 or 1 (or -1, for non-pointer arithmetic), find the nearest common
2927 dominator of all statements in the candidate chain rooted at C
2928 that require that increment, and insert an initializer
2929 T_0 = stride * increment at that location. Record T_0 with the
2930 increment record. */
2933 insert_initializers (slsr_cand_t c
)
2937 for (i
= 0; i
< incr_vec_len
; i
++)
2940 slsr_cand_t where
= NULL
;
2942 tree stride_type
, new_name
, incr_tree
;
2943 double_int incr
= incr_vec
[i
].incr
;
2945 if (!profitable_increment_p (i
)
2947 || (incr
.is_minus_one ()
2948 && gimple_assign_rhs_code (c
->cand_stmt
) != POINTER_PLUS_EXPR
)
2952 /* We may have already identified an existing initializer that
2954 if (incr_vec
[i
].initializer
)
2956 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2958 fputs ("Using existing initializer: ", dump_file
);
2959 print_gimple_stmt (dump_file
,
2960 SSA_NAME_DEF_STMT (incr_vec
[i
].initializer
),
2966 /* Find the block that most closely dominates all candidates
2967 with this increment. If there is at least one candidate in
2968 that block, the earliest one will be returned in WHERE. */
2969 bb
= nearest_common_dominator_for_cands (c
, incr
, &where
);
2971 /* Create a new SSA name to hold the initializer's value. */
2972 stride_type
= TREE_TYPE (c
->stride
);
2973 new_name
= make_temp_ssa_name (stride_type
, NULL
, "slsr");
2974 incr_vec
[i
].initializer
= new_name
;
2976 /* Create the initializer and insert it in the latest possible
2977 dominating position. */
2978 incr_tree
= double_int_to_tree (stride_type
, incr
);
2979 init_stmt
= gimple_build_assign_with_ops (MULT_EXPR
, new_name
,
2980 c
->stride
, incr_tree
);
2983 gimple_stmt_iterator gsi
= gsi_for_stmt (where
->cand_stmt
);
2984 gsi_insert_before (&gsi
, init_stmt
, GSI_SAME_STMT
);
2985 gimple_set_location (init_stmt
, gimple_location (where
->cand_stmt
));
2989 gimple_stmt_iterator gsi
= gsi_last_bb (bb
);
2990 gimple basis_stmt
= lookup_cand (c
->basis
)->cand_stmt
;
2992 if (!gsi_end_p (gsi
) && is_ctrl_stmt (gsi_stmt (gsi
)))
2993 gsi_insert_before (&gsi
, init_stmt
, GSI_SAME_STMT
);
2995 gsi_insert_after (&gsi
, init_stmt
, GSI_SAME_STMT
);
2997 gimple_set_location (init_stmt
, gimple_location (basis_stmt
));
3000 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3002 fputs ("Inserting initializer: ", dump_file
);
3003 print_gimple_stmt (dump_file
, init_stmt
, 0, 0);
3008 /* Return TRUE iff all required increments for candidates feeding PHI
3009 are profitable to replace on behalf of candidate C. */
3012 all_phi_incrs_profitable (slsr_cand_t c
, gimple phi
)
3015 slsr_cand_t basis
= lookup_cand (c
->basis
);
3016 slsr_cand_t phi_cand
= base_cand_from_table (gimple_phi_result (phi
));
3018 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
3020 tree arg
= gimple_phi_arg_def (phi
, i
);
3022 if (!operand_equal_p (arg
, phi_cand
->base_expr
, 0))
3024 gimple arg_def
= SSA_NAME_DEF_STMT (arg
);
3026 if (gimple_code (arg_def
) == GIMPLE_PHI
)
3028 if (!all_phi_incrs_profitable (c
, arg_def
))
3034 slsr_cand_t arg_cand
= base_cand_from_table (arg
);
3035 double_int increment
= arg_cand
->index
- basis
->index
;
3037 if (!address_arithmetic_p
&& increment
.is_negative ())
3038 increment
= -increment
;
3040 j
= incr_vec_index (increment
);
3042 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3044 fprintf (dump_file
, " Conditional candidate %d, phi: ",
3046 print_gimple_stmt (dump_file
, phi
, 0, 0);
3047 fputs (" increment: ", dump_file
);
3048 dump_double_int (dump_file
, increment
, false);
3051 "\n Not replaced; incr_vec overflow.\n");
3053 fprintf (dump_file
, "\n cost: %d\n", incr_vec
[j
].cost
);
3054 if (profitable_increment_p (j
))
3055 fputs (" Replacing...\n", dump_file
);
3057 fputs (" Not replaced.\n", dump_file
);
3061 if (j
< 0 || !profitable_increment_p (j
))
3070 /* Create a NOP_EXPR that copies FROM_EXPR into a new SSA name of
3071 type TO_TYPE, and insert it in front of the statement represented
3072 by candidate C. Use *NEW_VAR to create the new SSA name. Return
3073 the new SSA name. */
3076 introduce_cast_before_cand (slsr_cand_t c
, tree to_type
, tree from_expr
)
3080 gimple_stmt_iterator gsi
= gsi_for_stmt (c
->cand_stmt
);
3082 cast_lhs
= make_temp_ssa_name (to_type
, NULL
, "slsr");
3083 cast_stmt
= gimple_build_assign_with_ops (NOP_EXPR
, cast_lhs
,
3084 from_expr
, NULL_TREE
);
3085 gimple_set_location (cast_stmt
, gimple_location (c
->cand_stmt
));
3086 gsi_insert_before (&gsi
, cast_stmt
, GSI_SAME_STMT
);
3088 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3090 fputs (" Inserting: ", dump_file
);
3091 print_gimple_stmt (dump_file
, cast_stmt
, 0, 0);
3097 /* Replace the RHS of the statement represented by candidate C with
3098 NEW_CODE, NEW_RHS1, and NEW_RHS2, provided that to do so doesn't
3099 leave C unchanged or just interchange its operands. The original
3100 operation and operands are in OLD_CODE, OLD_RHS1, and OLD_RHS2.
3101 If the replacement was made and we are doing a details dump,
3102 return the revised statement, else NULL. */
3105 replace_rhs_if_not_dup (enum tree_code new_code
, tree new_rhs1
, tree new_rhs2
,
3106 enum tree_code old_code
, tree old_rhs1
, tree old_rhs2
,
3109 if (new_code
!= old_code
3110 || ((!operand_equal_p (new_rhs1
, old_rhs1
, 0)
3111 || !operand_equal_p (new_rhs2
, old_rhs2
, 0))
3112 && (!operand_equal_p (new_rhs1
, old_rhs2
, 0)
3113 || !operand_equal_p (new_rhs2
, old_rhs1
, 0))))
3115 gimple_stmt_iterator gsi
= gsi_for_stmt (c
->cand_stmt
);
3116 gimple_assign_set_rhs_with_ops (&gsi
, new_code
, new_rhs1
, new_rhs2
);
3117 update_stmt (gsi_stmt (gsi
));
3118 c
->cand_stmt
= gsi_stmt (gsi
);
3120 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3121 return gsi_stmt (gsi
);
3124 else if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3125 fputs (" (duplicate, not actually replacing)\n", dump_file
);
3130 /* Strength-reduce the statement represented by candidate C by replacing
3131 it with an equivalent addition or subtraction. I is the index into
3132 the increment vector identifying C's increment. NEW_VAR is used to
3133 create a new SSA name if a cast needs to be introduced. BASIS_NAME
3134 is the rhs1 to use in creating the add/subtract. */
3137 replace_one_candidate (slsr_cand_t c
, unsigned i
, tree basis_name
)
3139 gimple stmt_to_print
= NULL
;
3140 tree orig_rhs1
, orig_rhs2
;
3142 enum tree_code orig_code
, repl_code
;
3143 double_int cand_incr
;
3145 orig_code
= gimple_assign_rhs_code (c
->cand_stmt
);
3146 orig_rhs1
= gimple_assign_rhs1 (c
->cand_stmt
);
3147 orig_rhs2
= gimple_assign_rhs2 (c
->cand_stmt
);
3148 cand_incr
= cand_increment (c
);
3150 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3152 fputs ("Replacing: ", dump_file
);
3153 print_gimple_stmt (dump_file
, c
->cand_stmt
, 0, 0);
3154 stmt_to_print
= c
->cand_stmt
;
3157 if (address_arithmetic_p
)
3158 repl_code
= POINTER_PLUS_EXPR
;
3160 repl_code
= PLUS_EXPR
;
3162 /* If the increment has an initializer T_0, replace the candidate
3163 statement with an add of the basis name and the initializer. */
3164 if (incr_vec
[i
].initializer
)
3166 tree init_type
= TREE_TYPE (incr_vec
[i
].initializer
);
3167 tree orig_type
= TREE_TYPE (orig_rhs2
);
3169 if (types_compatible_p (orig_type
, init_type
))
3170 rhs2
= incr_vec
[i
].initializer
;
3172 rhs2
= introduce_cast_before_cand (c
, orig_type
,
3173 incr_vec
[i
].initializer
);
3175 if (incr_vec
[i
].incr
!= cand_incr
)
3177 gcc_assert (repl_code
== PLUS_EXPR
);
3178 repl_code
= MINUS_EXPR
;
3181 stmt_to_print
= replace_rhs_if_not_dup (repl_code
, basis_name
, rhs2
,
3182 orig_code
, orig_rhs1
, orig_rhs2
,
3186 /* Otherwise, the increment is one of -1, 0, and 1. Replace
3187 with a subtract of the stride from the basis name, a copy
3188 from the basis name, or an add of the stride to the basis
3189 name, respectively. It may be necessary to introduce a
3190 cast (or reuse an existing cast). */
3191 else if (cand_incr
.is_one ())
3193 tree stride_type
= TREE_TYPE (c
->stride
);
3194 tree orig_type
= TREE_TYPE (orig_rhs2
);
3196 if (types_compatible_p (orig_type
, stride_type
))
3199 rhs2
= introduce_cast_before_cand (c
, orig_type
, c
->stride
);
3201 stmt_to_print
= replace_rhs_if_not_dup (repl_code
, basis_name
, rhs2
,
3202 orig_code
, orig_rhs1
, orig_rhs2
,
3206 else if (cand_incr
.is_minus_one ())
3208 tree stride_type
= TREE_TYPE (c
->stride
);
3209 tree orig_type
= TREE_TYPE (orig_rhs2
);
3210 gcc_assert (repl_code
!= POINTER_PLUS_EXPR
);
3212 if (types_compatible_p (orig_type
, stride_type
))
3215 rhs2
= introduce_cast_before_cand (c
, orig_type
, c
->stride
);
3217 if (orig_code
!= MINUS_EXPR
3218 || !operand_equal_p (basis_name
, orig_rhs1
, 0)
3219 || !operand_equal_p (rhs2
, orig_rhs2
, 0))
3221 gimple_stmt_iterator gsi
= gsi_for_stmt (c
->cand_stmt
);
3222 gimple_assign_set_rhs_with_ops (&gsi
, MINUS_EXPR
, basis_name
, rhs2
);
3223 update_stmt (gsi_stmt (gsi
));
3224 c
->cand_stmt
= gsi_stmt (gsi
);
3226 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3227 stmt_to_print
= gsi_stmt (gsi
);
3229 else if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3230 fputs (" (duplicate, not actually replacing)\n", dump_file
);
3233 else if (cand_incr
.is_zero ())
3235 tree lhs
= gimple_assign_lhs (c
->cand_stmt
);
3236 tree lhs_type
= TREE_TYPE (lhs
);
3237 tree basis_type
= TREE_TYPE (basis_name
);
3239 if (types_compatible_p (lhs_type
, basis_type
))
3241 gimple copy_stmt
= gimple_build_assign (lhs
, basis_name
);
3242 gimple_stmt_iterator gsi
= gsi_for_stmt (c
->cand_stmt
);
3243 gimple_set_location (copy_stmt
, gimple_location (c
->cand_stmt
));
3244 gsi_replace (&gsi
, copy_stmt
, false);
3245 c
->cand_stmt
= copy_stmt
;
3247 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3248 stmt_to_print
= copy_stmt
;
3252 gimple_stmt_iterator gsi
= gsi_for_stmt (c
->cand_stmt
);
3253 gimple cast_stmt
= gimple_build_assign_with_ops (NOP_EXPR
, lhs
,
3256 gimple_set_location (cast_stmt
, gimple_location (c
->cand_stmt
));
3257 gsi_replace (&gsi
, cast_stmt
, false);
3258 c
->cand_stmt
= cast_stmt
;
3260 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3261 stmt_to_print
= cast_stmt
;
3267 if (dump_file
&& (dump_flags
& TDF_DETAILS
) && stmt_to_print
)
3269 fputs ("With: ", dump_file
);
3270 print_gimple_stmt (dump_file
, stmt_to_print
, 0, 0);
3271 fputs ("\n", dump_file
);
3275 /* For each candidate in the tree rooted at C, replace it with
3276 an increment if such has been shown to be profitable. */
3279 replace_profitable_candidates (slsr_cand_t c
)
3281 if (!cand_already_replaced (c
))
3283 double_int increment
= cand_abs_increment (c
);
3284 enum tree_code orig_code
= gimple_assign_rhs_code (c
->cand_stmt
);
3287 i
= incr_vec_index (increment
);
3289 /* Only process profitable increments. Nothing useful can be done
3290 to a cast or copy. */
3292 && profitable_increment_p (i
)
3293 && orig_code
!= MODIFY_EXPR
3294 && orig_code
!= NOP_EXPR
)
3296 if (phi_dependent_cand_p (c
))
3298 gimple phi
= lookup_cand (c
->def_phi
)->cand_stmt
;
3300 if (all_phi_incrs_profitable (c
, phi
))
3302 /* Look up the LHS SSA name from C's basis. This will be
3303 the RHS1 of the adds we will introduce to create new
3305 slsr_cand_t basis
= lookup_cand (c
->basis
);
3306 tree basis_name
= gimple_assign_lhs (basis
->cand_stmt
);
3308 /* Create a new phi statement that will represent C's true
3309 basis after the transformation is complete. */
3310 location_t loc
= gimple_location (c
->cand_stmt
);
3311 tree name
= create_phi_basis (c
, phi
, basis_name
,
3312 loc
, UNKNOWN_STRIDE
);
3314 /* Replace C with an add of the new basis phi and the
3316 replace_one_candidate (c
, i
, name
);
3321 slsr_cand_t basis
= lookup_cand (c
->basis
);
3322 tree basis_name
= gimple_assign_lhs (basis
->cand_stmt
);
3323 replace_one_candidate (c
, i
, basis_name
);
3329 replace_profitable_candidates (lookup_cand (c
->sibling
));
3332 replace_profitable_candidates (lookup_cand (c
->dependent
));
3335 /* Analyze costs of related candidates in the candidate vector,
3336 and make beneficial replacements. */
3339 analyze_candidates_and_replace (void)
3344 /* Each candidate that has a null basis and a non-null
3345 dependent is the root of a tree of related statements.
3346 Analyze each tree to determine a subset of those
3347 statements that can be replaced with maximum benefit. */
3348 FOR_EACH_VEC_ELT (cand_vec
, i
, c
)
3350 slsr_cand_t first_dep
;
3352 if (c
->basis
!= 0 || c
->dependent
== 0)
3355 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3356 fprintf (dump_file
, "\nProcessing dependency tree rooted at %d.\n",
3359 first_dep
= lookup_cand (c
->dependent
);
3361 /* If this is a chain of CAND_REFs, unconditionally replace
3362 each of them with a strength-reduced data reference. */
3363 if (c
->kind
== CAND_REF
)
3366 /* If the common stride of all related candidates is a known
3367 constant, each candidate without a phi-dependence can be
3368 profitably replaced. Each replaces a multiply by a single
3369 add, with the possibility that a feeding add also goes dead.
3370 A candidate with a phi-dependence is replaced only if the
3371 compensation code it requires is offset by the strength
3372 reduction savings. */
3373 else if (TREE_CODE (c
->stride
) == INTEGER_CST
)
3374 replace_uncond_cands_and_profitable_phis (first_dep
);
3376 /* When the stride is an SSA name, it may still be profitable
3377 to replace some or all of the dependent candidates, depending
3378 on whether the introduced increments can be reused, or are
3379 less expensive to calculate than the replaced statements. */
3382 enum machine_mode mode
;
3385 /* Determine whether we'll be generating pointer arithmetic
3386 when replacing candidates. */
3387 address_arithmetic_p
= (c
->kind
== CAND_ADD
3388 && POINTER_TYPE_P (c
->cand_type
));
3390 /* If all candidates have already been replaced under other
3391 interpretations, nothing remains to be done. */
3392 if (!count_candidates (c
))
3395 /* Construct an array of increments for this candidate chain. */
3396 incr_vec
= XNEWVEC (incr_info
, MAX_INCR_VEC_LEN
);
3398 record_increments (c
);
3400 /* Determine which increments are profitable to replace. */
3401 mode
= TYPE_MODE (TREE_TYPE (gimple_assign_lhs (c
->cand_stmt
)));
3402 speed
= optimize_cands_for_speed_p (c
);
3403 analyze_increments (first_dep
, mode
, speed
);
3405 /* Insert initializers of the form T_0 = stride * increment
3406 for use in profitable replacements. */
3407 insert_initializers (first_dep
);
3410 /* Perform the replacements. */
3411 replace_profitable_candidates (first_dep
);
3418 execute_strength_reduction (void)
3420 struct dom_walk_data walk_data
;
3422 /* Create the obstack where candidates will reside. */
3423 gcc_obstack_init (&cand_obstack
);
3425 /* Allocate the candidate vector. */
3426 cand_vec
.create (128);
3428 /* Allocate the mapping from statements to candidate indices. */
3429 stmt_cand_map
= pointer_map_create ();
3431 /* Create the obstack where candidate chains will reside. */
3432 gcc_obstack_init (&chain_obstack
);
3434 /* Allocate the mapping from base expressions to candidate chains. */
3435 base_cand_map
.create (500);
3437 /* Initialize the loop optimizer. We need to detect flow across
3438 back edges, and this gives us dominator information as well. */
3439 loop_optimizer_init (AVOID_CFG_MODIFICATIONS
);
3441 /* Set up callbacks for the generic dominator tree walker. */
3442 walk_data
.dom_direction
= CDI_DOMINATORS
;
3443 walk_data
.initialize_block_local_data
= NULL
;
3444 walk_data
.before_dom_children
= find_candidates_in_block
;
3445 walk_data
.after_dom_children
= NULL
;
3446 walk_data
.global_data
= NULL
;
3447 walk_data
.block_local_data_size
= 0;
3448 init_walk_dominator_tree (&walk_data
);
3450 /* Walk the CFG in predominator order looking for strength reduction
3452 walk_dominator_tree (&walk_data
, ENTRY_BLOCK_PTR
);
3454 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3457 dump_cand_chains ();
3460 /* Analyze costs and make appropriate replacements. */
3461 analyze_candidates_and_replace ();
3463 /* Free resources. */
3464 fini_walk_dominator_tree (&walk_data
);
3465 loop_optimizer_finalize ();
3466 base_cand_map
.dispose ();
3467 obstack_free (&chain_obstack
, NULL
);
3468 pointer_map_destroy (stmt_cand_map
);
3469 cand_vec
.release ();
3470 obstack_free (&cand_obstack
, NULL
);
3476 gate_strength_reduction (void)
3478 return flag_tree_slsr
;
3483 const pass_data pass_data_strength_reduction
=
3485 GIMPLE_PASS
, /* type */
3487 OPTGROUP_NONE
, /* optinfo_flags */
3488 true, /* has_gate */
3489 true, /* has_execute */
3490 TV_GIMPLE_SLSR
, /* tv_id */
3491 ( PROP_cfg
| PROP_ssa
), /* properties_required */
3492 0, /* properties_provided */
3493 0, /* properties_destroyed */
3494 0, /* todo_flags_start */
3495 TODO_verify_ssa
, /* todo_flags_finish */
3498 class pass_strength_reduction
: public gimple_opt_pass
3501 pass_strength_reduction(gcc::context
*ctxt
)
3502 : gimple_opt_pass(pass_data_strength_reduction
, ctxt
)
3505 /* opt_pass methods: */
3506 bool gate () { return gate_strength_reduction (); }
3507 unsigned int execute () { return execute_strength_reduction (); }
3509 }; // class pass_strength_reduction
3514 make_pass_strength_reduction (gcc::context
*ctxt
)
3516 return new pass_strength_reduction (ctxt
);