Here's a new version of the main strength reduction patch, addressing
previous comments. A couple of quick notes:
* I opened PR53773 and PR53774 for the cases where commutative
operations were encountered with a constant in rhs1. This version of
the patch still has the gcc_asserts in place to catch those cases, but
I'll plan to remove those once the patch is approved.
* You previously asked:
>>
>> +static slsr_cand_t
>> +base_cand_from_table (tree base_in)
>> +{
>> + slsr_cand mapping_key;
>> +
>> + gimple def = SSA_NAME_DEF_STMT (base_in);
>> + if (!def)
>> + return (slsr_cand_t) NULL;
>> +
>> + mapping_key.cand_stmt = def;
>> + return (slsr_cand_t) htab_find (stmt_cand_map, &mapping_key);
>>
>> isn't that reachable via the base-name -> chain mapping for base_in?
I had to review this a bit, but the answer is no. If you look at one of
the algebraic manipulations in create_mul_ssa_cand as an example,
base_in corresponds to Y. base_cand_from_table is looking for a
candidate that has Y for its LHS. The base-name -> chain mapping is
used to find all candidates that have B as the base_name.
* I added a detailed explanation of what's going on with legal_cast_p.
Hopefully this will be easier to understand now.
I've bootstrapped this on powerpc64-unknown-linux-gnu with three new
regressions (for which I opened the two bug reports). Ok for trunk
after removing the asserts?
Thanks,
Bill
gcc:
2012-06-25 Bill Schmidt <wschm...@linux.ibm.com>
* tree-pass.h (pass_strength_reduction): New decl.
* tree-ssa-loop-ivopts.c (initialize_costs): Make non-static.
(finalize_costs): Likewise.
* timevar.def (TV_TREE_SLSR): New timevar.
* gimple-ssa-strength-reduction.c: New.
* tree-flow.h (initialize_costs): New decl.
(finalize_costs): Likewise.
* Makefile.in (tree-ssa-strength-reduction.o): New dependencies.
* passes.c (init_optimization_passes): Add pass_strength_reduction.
gcc/testsuite:
2012-06-25 Bill Schmidt <wschm...@linux.ibm.com>
* gcc.dg/tree-ssa/slsr-1.c: New test.
* gcc.dg/tree-ssa/slsr-2.c: Likewise.
* gcc.dg/tree-ssa/slsr-3.c: Likewise.
* gcc.dg/tree-ssa/slsr-4.c: Likewise.
Index: gcc/tree-pass.h
===================================================================
--- gcc/tree-pass.h (revision 188890)
+++ gcc/tree-pass.h (working copy)
@@ -452,6 +452,7 @@ extern struct gimple_opt_pass pass_tm_memopt;
extern struct gimple_opt_pass pass_tm_edges;
extern struct gimple_opt_pass pass_split_functions;
extern struct gimple_opt_pass pass_feedback_split_functions;
+extern struct gimple_opt_pass pass_strength_reduction;
/* IPA Passes */
extern struct simple_ipa_opt_pass pass_ipa_lower_emutls;
Index: gcc/testsuite/gcc.dg/tree-ssa/slsr-1.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/slsr-1.c (revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/slsr-1.c (revision 0)
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
+
+extern void foo (int);
+
+void
+f (int *p, unsigned int n)
+{
+ foo (*(p + n * 4));
+ foo (*(p + 32 + n * 4));
+ if (n > 3)
+ foo (*(p + 16 + n * 4));
+ else
+ foo (*(p + 48 + n * 4));
+}
+
+/* { dg-final { scan-tree-dump-times "\\+ 128" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\+ 64" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\+ 192" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc/testsuite/gcc.dg/tree-ssa/slsr-2.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/slsr-2.c (revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/slsr-2.c (revision 0)
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
+
+extern void foo (int);
+
+void
+f (int *p, int n)
+{
+ foo (*(p + n++ * 4));
+ foo (*(p + 32 + n++ * 4));
+ foo (*(p + 16 + n * 4));
+}
+
+/* { dg-final { scan-tree-dump-times "\\+ 144" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\+ 96" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc/testsuite/gcc.dg/tree-ssa/slsr-3.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/slsr-3.c (revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/slsr-3.c (revision 0)
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
+
+int
+foo (int a[], int b[], int i)
+{
+ a[i] = b[i] + 2;
+ i++;
+ a[i] = b[i] + 2;
+ i++;
+ a[i] = b[i] + 2;
+ i++;
+ a[i] = b[i] + 2;
+ i++;
+ return i;
+}
+
+/* { dg-final { scan-tree-dump-times "\\* 4" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\+ 4" 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\+ 8" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\+ 12" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc/testsuite/gcc.dg/tree-ssa/slsr-4.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/slsr-4.c (revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/slsr-4.c (revision 0)
@@ -0,0 +1,37 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-slsr -fdump-tree-optimized" } */
+
+void foo (int);
+
+int
+f (int i)
+{
+ int x, y;
+
+ x = i * 4;
+ y = x * 10;
+ foo (y);
+
+ i = i + 5;
+ x = i * 4;
+ y = x * 10;
+ foo (y);
+
+ i = i - 4;
+ x = i * 4;
+ y = x * 10;
+ foo (y);
+}
+
+/* { dg-final { scan-tree-dump-times "\\* 4" 1 "slsr" } } */
+/* { dg-final { scan-tree-dump-times "\\* 10" 1 "slsr" } } */
+/* { dg-final { scan-tree-dump-times "\\+ 20;" 1 "slsr" } } */
+/* { dg-final { scan-tree-dump-times "\\+ 200" 1 "slsr" } } */
+/* { dg-final { scan-tree-dump-times "\\- 16;" 1 "slsr" } } */
+/* { dg-final { scan-tree-dump-times "\\- 160" 1 "slsr" } } */
+/* { dg-final { scan-tree-dump-times "\\* 4" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\* 10" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\+ 200" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "\\+ 40" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "slsr" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc/tree-ssa-loop-ivopts.c
===================================================================
--- gcc/tree-ssa-loop-ivopts.c (revision 188891)
+++ gcc/tree-ssa-loop-ivopts.c (working copy)
@@ -856,7 +856,7 @@ htab_inv_expr_hash (const void *ent)
/* Allocate data structures for the cost model. */
-static void
+void
initialize_costs (void)
{
mult_costs[0] = htab_create (100, mbc_entry_hash, mbc_entry_eq, free);
@@ -866,7 +866,7 @@ initialize_costs (void)
/* Release data structures for the cost model. */
-static void
+void
finalize_costs (void)
{
cost_tables_exist = false;
Index: gcc/timevar.def
===================================================================
--- gcc/timevar.def (revision 188890)
+++ gcc/timevar.def (working copy)
@@ -257,6 +257,7 @@ DEFTIMEVAR (TV_TREE_IFCOMBINE , "tree if-co
DEFTIMEVAR (TV_TREE_UNINIT , "uninit var analysis")
DEFTIMEVAR (TV_PLUGIN_INIT , "plugin initialization")
DEFTIMEVAR (TV_PLUGIN_RUN , "plugin execution")
+DEFTIMEVAR (TV_GIMPLE_SLSR , "straight-line strength reduction")
/* Everything else in rest_of_compilation not included above. */
DEFTIMEVAR (TV_EARLY_LOCAL , "early local passes")
Index: gcc/gimple-ssa-strength-reduction.c
===================================================================
--- gcc/gimple-ssa-strength-reduction.c (revision 0)
+++ gcc/gimple-ssa-strength-reduction.c (revision 0)
@@ -0,0 +1,1523 @@
+/* Straight-line strength reduction.
+ Copyright (C) 2012 Free Software Foundation, Inc.
+ Contributed by Bill Schmidt, IBM <wschm...@linux.ibm.com>
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
+
+/* There are many algorithms for performing strength reduction on
+ loops. This is not one of them. IVOPTS handles strength reduction
+ of induction variables just fine. This pass is intended to pick
+ up the crumbs it leaves behind, by considering opportunities for
+ strength reduction along dominator paths.
+
+ Strength reduction will be implemented in four stages, gradually
+ adding more complex candidates:
+
+ 1) Explicit multiplies, known constant multipliers, no
+ conditional increments. (complete)
+ 2) Explicit multiplies, unknown constant multipliers,
+ no conditional increments. (data gathering complete,
+ replacements pending)
+ 3) Implicit multiplies in addressing expressions. (pending)
+ 4) Explicit multiplies, conditional increments. (pending)
+
+ It would also be possible to apply strength reduction to divisions
+ and modulos, but such opportunities are relatively uncommon.
+
+ Strength reduction is also currently restricted to integer operations.
+ If desired, it could be extended to floating-point operations under
+ control of something like -funsafe-math-optimizations. */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree.h"
+#include "gimple.h"
+#include "basic-block.h"
+#include "tree-pass.h"
+#include "timevar.h"
+#include "cfgloop.h"
+#include "tree-pretty-print.h"
+#include "gimple-pretty-print.h"
+#include "tree-flow.h"
+#include "domwalk.h"
+#include "pointer-set.h"
+
+/* Information about a strength reduction candidate. Each statement
+ in the candidate table represents an expression of one of the
+ following forms (the special case of CAND_REF will be described
+ later):
+
+ (CAND_MULT) S1: X = (B + i) * S
+ (CAND_ADD) S1: X = B + (i * S)
+
+ Here X and B are SSA names, i is an integer constant, and S is
+ either an SSA name or a constant. We call B the "base," i the
+ "index", and S the "stride."
+
+ Any statement S0 that dominates S1 and is of the form:
+
+ (CAND_MULT) S0: Y = (B + i') * S
+ (CAND_ADD) S0: Y = B + (i' * S)
+
+ is called a "basis" for S1. In both cases, S1 may be replaced by
+
+ S1': X = Y + (i - i') * S,
+
+ where (i - i') * S is folded to the extent possible.
+
+ All gimple statements are visited in dominator order, and each
+ statement that may contribute to one of the forms of S1 above is
+ given at least one entry in the candidate table. Such statements
+ include addition, pointer addition, subtraction, multiplication,
+ negation, copies, and nontrivial type casts. If a statement may
+ represent more than one expression of the forms of S1 above,
+ multiple "interpretations" are stored in the table and chained
+ together. Examples:
+
+ * An add of two SSA names may treat either operand as the base.
+ * A multiply of two SSA names, likewise.
+ * A copy or cast may be thought of as either a CAND_MULT with
+ i = 0 and S = 1, or as a CAND_ADD with i = 0 or S = 0.
+
+ Candidate records are allocated from an obstack. They are addressed
+ both from a hash table keyed on S1, and from a vector of candidate
+ pointers arranged in predominator order.
+
+ Opportunity note
+ ----------------
+ Currently we don't recognize:
+
+ S0: Y = (S * i') - B
+ S1: X = (S * i) - B
+
+ as a strength reduction opportunity, even though this S1 would
+ also be replaceable by the S1' above. This can be added if it
+ comes up in practice. */
+
+
+/* Index into the candidate vector, offset by 1. VECs are zero-based,
+ while cand_idx's are one-based, with zero indicating null. */
+typedef unsigned cand_idx;
+
+/* The kind of candidate. */
+enum cand_kind
+{
+ CAND_MULT,
+ CAND_ADD
+};
+
+struct slsr_cand_d
+{
+ /* The candidate statement S1. */
+ gimple cand_stmt;
+
+ /* The base SSA name B. */
+ tree base_name;
+
+ /* The stride S. */
+ tree stride;
+
+ /* The index constant i. */
+ double_int index;
+
+ /* The type of the candidate. This is normally the type of base_name,
+ but casts may have occurred when combining feeding instructions.
+ A candidate can only be a basis for candidates of the same final type. */
+ tree cand_type;
+
+ /* The kind of candidate (CAND_MULT, etc.). */
+ enum cand_kind kind;
+
+ /* Index of this candidate in the candidate vector. */
+ cand_idx cand_num;
+
+ /* Index of the next candidate record for the same statement.
+ A statement may be useful in more than one way (e.g., due to
+ commutativity). So we can have multiple "interpretations"
+ of a statement. */
+ cand_idx next_interp;
+
+ /* Index of the basis statement S0, if any, in the candidate vector. */
+ cand_idx basis;
+
+ /* First candidate for which this candidate is a basis, if one exists. */
+ cand_idx dependent;
+
+ /* Next candidate having the same basis as this one. */
+ cand_idx sibling;
+
+ /* If this is a conditional candidate, the defining PHI statement
+ for the base SSA name B. For future use; always NULL for now. */
+ gimple def_phi;
+
+ /* Savings that can be expected from eliminating dead code if this
+ candidate is replaced. */
+ int dead_savings;
+};
+
+typedef struct slsr_cand_d slsr_cand, *slsr_cand_t;
+typedef const struct slsr_cand_d *const_slsr_cand_t;
+
+/* Pointers to candidates are chained together as part of a mapping
+ from SSA names to the candidates that use them as a base name. */
+
+struct cand_chain_d
+{
+ /* SSA name that serves as a base name for the chain of candidates. */
+ tree base_name;
+
+ /* Pointer to a candidate. */
+ slsr_cand_t cand;
+
+ /* Chain pointer. */
+ struct cand_chain_d *next;
+
+};
+
+typedef struct cand_chain_d cand_chain, *cand_chain_t;
+typedef const struct cand_chain_d *const_cand_chain_t;
+
+/* Candidates are maintained in a vector. If candidate X dominates
+ candidate Y, then X appears before Y in the vector; but the
+ converse does not necessarily hold. */
+DEF_VEC_P (slsr_cand_t);
+DEF_VEC_ALLOC_P (slsr_cand_t, heap);
+static VEC (slsr_cand_t, heap) *cand_vec;
+
+enum cost_consts
+{
+ COST_NEUTRAL = 0,
+ COST_INFINITE = 1000
+};
+
+/* Pointer map embodying a mapping from statements to candidates. */
+static struct pointer_map_t *stmt_cand_map;
+
+/* Obstack for candidates. */
+static struct obstack cand_obstack;
+
+/* Array mapping from base SSA names to chains of candidates. */
+static cand_chain_t *base_cand_map;
+
+/* Obstack for candidate chains. */
+static struct obstack chain_obstack;
+
+/* Produce a pointer to the IDX'th candidate in the candidate vector. */
+
+static slsr_cand_t
+lookup_cand (cand_idx idx)
+{
+ return VEC_index (slsr_cand_t, cand_vec, idx - 1);
+}
+
+/* Use the base name from candidate C to look for possible candidates
+ that can serve as a basis for C. Each potential basis must also
+ appear in a block that dominates the candidate statement and have
+ the same stride and type. If more than one possible basis exists,
+ the one with highest index in the vector is chosen; this will be
+ the most immediately dominating basis. */
+
+static int
+find_basis_for_candidate (slsr_cand_t c)
+{
+ cand_chain_t chain;
+ slsr_cand_t basis = NULL;
+
+ gcc_assert (TREE_CODE (c->base_name) == SSA_NAME);
+ chain = base_cand_map[SSA_NAME_VERSION (c->base_name)];
+
+ for (; chain; chain = chain->next)
+ {
+ slsr_cand_t one_basis = chain->cand;
+
+ if (one_basis->kind != c->kind
+ || !operand_equal_p (one_basis->stride, c->stride, 0)
+ || !types_compatible_p (one_basis->cand_type, c->cand_type)
+ || !dominated_by_p (CDI_DOMINATORS,
+ gimple_bb (c->cand_stmt),
+ gimple_bb (one_basis->cand_stmt)))
+ continue;
+
+ if (!basis || basis->cand_num < one_basis->cand_num)
+ basis = one_basis;
+ }
+
+ if (basis)
+ {
+ c->sibling = basis->dependent;
+ basis->dependent = c->cand_num;
+ return basis->cand_num;
+ }
+
+ return 0;
+}
+
+/* Record a mapping from the base name of C to C itself, indicating that
+ C may potentially serve as a basis using that base name. */
+
+static void
+record_potential_basis (slsr_cand_t c)
+{
+ cand_chain_t node, head;
+ int index;
+
+ node = (cand_chain_t) obstack_alloc (&chain_obstack, sizeof (cand_chain));
+ node->base_name = c->base_name;
+ node->cand = c;
+ node->next = NULL;
+ index = SSA_NAME_VERSION (c->base_name);
+ head = base_cand_map[index];
+
+ if (head)
+ {
+ node->next = head->next;
+ head->next = node;
+ }
+ else
+ base_cand_map[index] = node;
+}
+
+/* Allocate storage for a new candidate and initialize its fields.
+ Attempt to find a basis for the candidate. */
+
+static slsr_cand_t
+alloc_cand_and_find_basis (enum cand_kind kind, gimple gs, tree base,
+ double_int index, tree stride, tree ctype,
+ unsigned savings)
+{
+ slsr_cand_t c = (slsr_cand_t) obstack_alloc (&cand_obstack,
+ sizeof (slsr_cand));
+ c->cand_stmt = gs;
+ c->base_name = base;
+ c->stride = stride;
+ c->index = index;
+ c->cand_type = ctype;
+ c->kind = kind;
+ c->cand_num = VEC_length (slsr_cand_t, cand_vec) + 1;
+ c->next_interp = 0;
+ c->dependent = 0;
+ c->sibling = 0;
+ c->def_phi = NULL;
+ c->dead_savings = savings;
+
+ VEC_safe_push (slsr_cand_t, heap, cand_vec, c);
+ c->basis = find_basis_for_candidate (c);
+ record_potential_basis (c);
+
+ return c;
+}
+
+/* Determine the target cost of statement GS when compiling according
+ to SPEED. */
+
+static int
+stmt_cost (gimple gs, bool speed)
+{
+ tree lhs, rhs1, rhs2;
+ enum machine_mode lhs_mode;
+
+ gcc_assert (is_gimple_assign (gs));
+ lhs = gimple_assign_lhs (gs);
+ rhs1 = gimple_assign_rhs1 (gs);
+ lhs_mode = TYPE_MODE (TREE_TYPE (lhs));
+
+ switch (gimple_assign_rhs_code (gs))
+ {
+ case MULT_EXPR:
+ rhs2 = gimple_assign_rhs2 (gs);
+
+ if (host_integerp (rhs2, 0))
+ return multiply_by_const_cost (TREE_INT_CST_LOW (rhs2), lhs_mode,
+ speed);
+
+ gcc_assert (TREE_CODE (rhs1) != INTEGER_CST);
+ return multiply_regs_cost (TYPE_MODE (TREE_TYPE (lhs)), speed);
+
+ case PLUS_EXPR:
+ case POINTER_PLUS_EXPR:
+ case MINUS_EXPR:
+ rhs2 = gimple_assign_rhs2 (gs);
+
+ if (host_integerp (rhs2, 0))
+ return add_const_cost (TYPE_MODE (TREE_TYPE (rhs1)), speed);
+
+ gcc_assert (TREE_CODE (rhs1) != INTEGER_CST);
+ return add_regs_cost (lhs_mode, speed);
+
+ case NEGATE_EXPR:
+ return negate_reg_cost (lhs_mode, speed);
+
+ case NOP_EXPR:
+ return extend_or_trunc_reg_cost (TREE_TYPE (lhs), TREE_TYPE (rhs1),
+ speed);
+
+ /* Note that we don't assign costs to copies that in most cases
+ will go away. */
+ default:
+ ;
+ }
+
+ gcc_unreachable ();
+ return 0;
+}
+
+/* Look up the defining statement for BASE_IN and return a pointer
+ to its candidate in the candidate table, if any; otherwise NULL.
+ Only CAND_ADD and CAND_MULT candidates are returned. */
+
+static slsr_cand_t
+base_cand_from_table (tree base_in)
+{
+ slsr_cand_t *result;
+
+ gimple def = SSA_NAME_DEF_STMT (base_in);
+ if (!def)
+ return (slsr_cand_t) NULL;
+
+ result = (slsr_cand_t *) pointer_map_contains (stmt_cand_map, def);
+ if (!result)
+ return (slsr_cand_t) NULL;
+
+ return *result;
+}
+
+/* Add an entry to the statement-to-candidate mapping. */
+
+static void
+add_cand_for_stmt (gimple gs, slsr_cand_t c)
+{
+ void **slot = pointer_map_insert (stmt_cand_map, gs);
+ gcc_assert (!*slot);
+ *slot = c;
+}
+
+/* Create a candidate entry for a statement GS, where GS multiplies
+ two SSA names BASE_IN and STRIDE_IN. Propagate any known information
+ about the two SSA names into the new candidate. Return the new
+ candidate. */
+
+static slsr_cand_t
+create_mul_ssa_cand (gimple gs, tree base_in, tree stride_in, bool speed)
+{
+ tree base = NULL_TREE, stride = NULL_TREE, ctype = NULL_TREE;
+ double_int index;
+ unsigned savings = 0;
+ slsr_cand_t c;
+ slsr_cand_t base_cand = base_cand_from_table (base_in);
+
+ /* Look at all interpretations of the base candidate, if necessary,
+ to find information to propagate into this candidate. */
+ while (base_cand && !base)
+ {
+
+ if (base_cand->kind == CAND_MULT
+ && operand_equal_p (base_cand->stride, integer_one_node, 0))
+ {
+ /* Y = (B + i') * 1
+ X = Y * Z
+ ================
+ X = (B + i') * Z */
+ base = base_cand->base_name;
+ index = base_cand->index;
+ stride = stride_in;
+ ctype = base_cand->cand_type;
+ if (has_single_use (base_in))
+ savings = (base_cand->dead_savings
+ + stmt_cost (base_cand->cand_stmt, speed));
+ }
+ else if (base_cand->kind == CAND_ADD
+ && TREE_CODE (base_cand->stride) == INTEGER_CST)
+ {
+ /* Y = B + (i' * S), S constant
+ X = Y * Z
+ ============================
+ X = B + ((i' * S) * Z) */
+ base = base_cand->base_name;
+ index = double_int_mul (base_cand->index,
+ tree_to_double_int (base_cand->stride));
+ stride = stride_in;
+ ctype = base_cand->cand_type;
+ if (has_single_use (base_in))
+ savings = (base_cand->dead_savings
+ + stmt_cost (base_cand->cand_stmt, speed));
+ }
+
+ if (base_cand->next_interp)
+ base_cand = lookup_cand (base_cand->next_interp);
+ else
+ base_cand = NULL;
+ }
+
+ if (!base)
+ {
+ /* No interpretations had anything useful to propagate, so
+ produce X = (Y + 0) * Z. */
+ base = base_in;
+ index = double_int_zero;
+ stride = stride_in;
+ ctype = TREE_TYPE (SSA_NAME_VAR (base_in));
+ }
+
+ c = alloc_cand_and_find_basis (CAND_MULT, gs, base, index, stride,
+ ctype, savings);
+ return c;
+}
+
+/* Create a candidate entry for a statement GS, where GS multiplies
+ SSA name BASE_IN by constant STRIDE_IN. Propagate any known
+ information about BASE_IN into the new candidate. Return the new
+ candidate. */
+
+static slsr_cand_t
+create_mul_imm_cand (gimple gs, tree base_in, tree stride_in, bool speed)
+{
+ tree base = NULL_TREE, stride = NULL_TREE, ctype = NULL_TREE;
+ double_int index, temp;
+ unsigned savings = 0;
+ slsr_cand_t c;
+ slsr_cand_t base_cand = base_cand_from_table (base_in);
+
+ /* Look at all interpretations of the base candidate, if necessary,
+ to find information to propagate into this candidate. */
+ while (base_cand && !base)
+ {
+ if (base_cand->kind == CAND_MULT
+ && TREE_CODE (base_cand->stride) == INTEGER_CST)
+ {
+ /* Y = (B + i') * S, S constant
+ X = Y * c
+ ============================
+ X = (B + i') * (S * c) */
+ base = base_cand->base_name;
+ index = base_cand->index;
+ temp = double_int_mul (tree_to_double_int (base_cand->stride),
+ tree_to_double_int (stride_in));
+ stride = double_int_to_tree (TREE_TYPE (stride_in), temp);
+ ctype = base_cand->cand_type;
+ if (has_single_use (base_in))
+ savings = (base_cand->dead_savings
+ + stmt_cost (base_cand->cand_stmt, speed));
+ }
+ else if (base_cand->kind == CAND_ADD
+ && operand_equal_p (base_cand->stride, integer_one_node, 0))
+ {
+ /* Y = B + (i' * 1)
+ X = Y * c
+ ===========================
+ X = (B + i') * c */
+ base = base_cand->base_name;
+ index = base_cand->index;
+ stride = stride_in;
+ ctype = base_cand->cand_type;
+ if (has_single_use (base_in))
+ savings = (base_cand->dead_savings
+ + stmt_cost (base_cand->cand_stmt, speed));
+ }
+ else if (base_cand->kind == CAND_ADD
+ && double_int_one_p (base_cand->index)
+ && TREE_CODE (base_cand->stride) == INTEGER_CST)
+ {
+ /* Y = B + (1 * S), S constant
+ X = Y * c
+ ===========================
+ X = (B + S) * c */
+ base = base_cand->base_name;
+ index = tree_to_double_int (base_cand->stride);
+ stride = stride_in;
+ ctype = base_cand->cand_type;
+ if (has_single_use (base_in))
+ savings = (base_cand->dead_savings
+ + stmt_cost (base_cand->cand_stmt, speed));
+ }
+
+ if (base_cand->next_interp)
+ base_cand = lookup_cand (base_cand->next_interp);
+ else
+ base_cand = NULL;
+ }
+
+ if (!base)
+ {
+ /* No interpretations had anything useful to propagate, so
+ produce X = (Y + 0) * c. */
+ base = base_in;
+ index = double_int_zero;
+ stride = stride_in;
+ ctype = TREE_TYPE (SSA_NAME_VAR (base_in));
+ }
+
+ c = alloc_cand_and_find_basis (CAND_MULT, gs, base, index, stride,
+ ctype, savings);
+ return c;
+}
+
+/* Given GS which is a multiply of scalar integers, make an appropriate
+ entry in the candidate table. If this is a multiply of two SSA names,
+ create two CAND_MULT interpretations and attempt to find a basis for
+ each of them. Otherwise, create a single CAND_MULT and attempt to
+ find a basis. */
+
+static void
+slsr_process_mul (gimple gs, tree rhs1, tree rhs2, bool speed)
+{
+ slsr_cand_t c, c2;
+
+ /* If this is a multiply of an SSA name with itself, it is highly
+ unlikely that we will get a strength reduction opportunity, so
+ don't record it as a candidate. This simplifies the logic for
+ finding a basis, so if this is removed that must be considered. */
+ if (rhs1 == rhs2)
+ return;
+
+ if (TREE_CODE (rhs2) == SSA_NAME)
+ {
+ /* Record an interpretation of this statement in the candidate table
+ assuming RHS1 is the base name and RHS2 is the stride. */
+ c = create_mul_ssa_cand (gs, rhs1, rhs2, speed);
+
+ /* Add the first interpretation to the statement-candidate mapping. */
+ add_cand_for_stmt (gs, c);
+
+ /* Record another interpretation of this statement assuming RHS1
+ is the stride and RHS2 is the base name. */
+ c2 = create_mul_ssa_cand (gs, rhs2, rhs1, speed);
+ c->next_interp = c2->cand_num;
+ }
+ else
+ {
+ /* Record an interpretation for the multiply-immediate. */
+ c = create_mul_imm_cand (gs, rhs1, rhs2, speed);
+
+ /* Add the interpretation to the statement-candidate mapping. */
+ add_cand_for_stmt (gs, c);
+ }
+}
+
+/* Create a candidate entry for a statement GS, where GS adds two
+ SSA names BASE_IN and ADDEND_IN if SUBTRACT_P is false, and
+ subtracts ADDEND_IN from BASE_IN otherwise. Propagate any known
+ information about the two SSA names into the new candidate.
+ Return the new candidate. */
+
+static slsr_cand_t
+create_add_ssa_cand (gimple gs, tree base_in, tree addend_in,
+ bool subtract_p, bool speed)
+{
+ tree base = NULL_TREE, stride = NULL_TREE, ctype = NULL;
+ double_int index;
+ unsigned savings = 0;
+ slsr_cand_t c;
+ slsr_cand_t base_cand = base_cand_from_table (base_in);
+ slsr_cand_t addend_cand = base_cand_from_table (addend_in);
+
+ /* The most useful transformation is a multiply-immediate feeding
+ an add or subtract. Look for that first. */
+ while (addend_cand && !base)
+ {
+ if (addend_cand->kind == CAND_MULT
+ && double_int_zero_p (addend_cand->index)
+ && TREE_CODE (addend_cand->stride) == INTEGER_CST)
+ {
+ /* Z = (B + 0) * S, S constant
+ X = Y +/- Z
+ ===========================
+ X = Y + ((+/-1 * S) * B) */
+ base = base_in;
+ index = tree_to_double_int (addend_cand->stride);
+ if (subtract_p)
+ index = double_int_neg (index);
+ stride = addend_cand->base_name;
+ ctype = TREE_TYPE (SSA_NAME_VAR (base_in));
+ if (has_single_use (addend_in))
+ savings = (addend_cand->dead_savings
+ + stmt_cost (addend_cand->cand_stmt, speed));
+ }
+
+ if (addend_cand->next_interp)
+ addend_cand = lookup_cand (addend_cand->next_interp);
+ else
+ addend_cand = NULL;
+ }
+
+ while (base_cand && !base)
+ {
+ if (base_cand->kind == CAND_ADD
+ && (double_int_zero_p (base_cand->index)
+ || operand_equal_p (base_cand->stride,
+ integer_zero_node, 0)))
+ {
+ /* Y = B + (i' * S), i' * S = 0
+ X = Y +/- Z
+ ============================
+ X = B + (+/-1 * Z) */
+ base = base_cand->base_name;
+ index = subtract_p ? double_int_minus_one : double_int_one;
+ stride = addend_in;
+ ctype = base_cand->cand_type;
+ if (has_single_use (base_in))
+ savings = (base_cand->dead_savings
+ + stmt_cost (base_cand->cand_stmt, speed));
+ }
+ else if (subtract_p)
+ {
+ slsr_cand_t subtrahend_cand = base_cand_from_table (addend_in);
+
+ while (subtrahend_cand && !base)
+ {
+ if (subtrahend_cand->kind == CAND_MULT
+ && double_int_zero_p (subtrahend_cand->index)
+ && TREE_CODE (subtrahend_cand->stride) == INTEGER_CST)
+ {
+ /* Z = (B + 0) * S, S constant
+ X = Y - Z
+ ===========================
+ Value: X = Y + ((-1 * S) * B) */
+ base = base_in;
+ index = tree_to_double_int (subtrahend_cand->stride);
+ index = double_int_neg (index);
+ stride = subtrahend_cand->base_name;
+ ctype = TREE_TYPE (SSA_NAME_VAR (base_in));
+ if (has_single_use (addend_in))
+ savings = (subtrahend_cand->dead_savings
+ + stmt_cost (subtrahend_cand->cand_stmt, speed));
+ }
+
+ if (subtrahend_cand->next_interp)
+ subtrahend_cand = lookup_cand (subtrahend_cand->next_interp);
+ else
+ subtrahend_cand = NULL;
+ }
+ }
+
+ if (base_cand->next_interp)
+ base_cand = lookup_cand (base_cand->next_interp);
+ else
+ base_cand = NULL;
+ }
+
+ if (!base)
+ {
+ /* No interpretations had anything useful to propagate, so
+ produce X = Y + (1 * Z). */
+ base = base_in;
+ index = subtract_p ? double_int_minus_one : double_int_one;
+ stride = addend_in;
+ ctype = TREE_TYPE (SSA_NAME_VAR (base_in));
+ }
+
+ c = alloc_cand_and_find_basis (CAND_ADD, gs, base, index, stride,
+ ctype, savings);
+ return c;
+}
+
+/* Create a candidate entry for a statement GS, where GS adds SSA
+ name BASE_IN to constant INDEX_IN. Propagate any known information
+ about BASE_IN into the new candidate. Return the new candidate. */
+
+static slsr_cand_t
+create_add_imm_cand (gimple gs, tree base_in, double_int index_in, bool speed)
+{
+ enum cand_kind kind = CAND_ADD;
+ tree base = NULL_TREE, stride = NULL_TREE, ctype = NULL_TREE;
+ double_int index, multiple;
+ unsigned savings = 0;
+ slsr_cand_t c;
+ slsr_cand_t base_cand = base_cand_from_table (base_in);
+
+ while (base_cand && !base)
+ {
+ bool unsigned_p = TYPE_UNSIGNED (TREE_TYPE (base_cand->stride));
+
+ if (TREE_CODE (base_cand->stride) == INTEGER_CST
+ && double_int_multiple_of (index_in,
+ tree_to_double_int (base_cand->stride),
+ unsigned_p,
+ &multiple))
+ {
+ /* Y = (B + i') * S, S constant, c = kS for some integer k
+ X = Y + c
+ ============================
+ X = (B + (i'+ k)) * S
+ OR
+ Y = B + (i' * S), S constant, c = kS for some integer k
+ X = Y + c
+ ============================
+ X = (B + (i'+ k)) * S */
+ kind = base_cand->kind;
+ base = base_cand->base_name;
+ index = double_int_add (base_cand->index, multiple);
+ stride = base_cand->stride;
+ ctype = base_cand->cand_type;
+ if (has_single_use (base_in))
+ savings = (base_cand->dead_savings
+ + stmt_cost (base_cand->cand_stmt, speed));
+ }
+
+ if (base_cand->next_interp)
+ base_cand = lookup_cand (base_cand->next_interp);
+ else
+ base_cand = NULL;
+ }
+
+ if (!base)
+ {
+ /* No interpretations had anything useful to propagate, so
+ produce X = Y + (c * 1). */
+ kind = CAND_ADD;
+ base = base_in;
+ index = index_in;
+ stride = integer_one_node;
+ ctype = TREE_TYPE (SSA_NAME_VAR (base_in));
+ }
+
+ c = alloc_cand_and_find_basis (kind, gs, base, index, stride,
+ ctype, savings);
+ return c;
+}
+
+/* Given GS which is an add or subtract of scalar integers or pointers,
+ make at least one appropriate entry in the candidate table. */
+
+static void
+slsr_process_add (gimple gs, tree rhs1, tree rhs2, bool speed)
+{
+ bool subtract_p = gimple_assign_rhs_code (gs) == MINUS_EXPR;
+ slsr_cand_t c = NULL, c2;
+
+ if (TREE_CODE (rhs2) == SSA_NAME)
+ {
+ /* First record an interpretation assuming RHS1 is the base name
+ and RHS2 is the stride. But it doesn't make sense for the
+ stride to be a pointer, so don't record a candidate in that case. */
+ if (!POINTER_TYPE_P (TREE_TYPE (SSA_NAME_VAR (rhs2))))
+ {
+ c = create_add_ssa_cand (gs, rhs1, rhs2, subtract_p, speed);
+
+ /* Add the first interpretation to the statement-candidate
+ mapping. */
+ add_cand_for_stmt (gs, c);
+ }
+
+ /* If the two RHS operands are identical, or this is a subtract,
+ we're done. */
+ if (operand_equal_p (rhs1, rhs2, 0) || subtract_p)
+ return;
+
+ /* Otherwise, record another interpretation assuming RHS2 is the
+ base name and RHS1 is the stride, again provided that the
+ stride is not a pointer. */
+ if (!POINTER_TYPE_P (TREE_TYPE (SSA_NAME_VAR (rhs1))))
+ {
+ c2 = create_add_ssa_cand (gs, rhs2, rhs1, false, speed);
+ if (c)
+ c->next_interp = c2->cand_num;
+ else
+ add_cand_for_stmt (gs, c2);
+ }
+ }
+ else
+ {
+ double_int index;
+
+ /* Record an interpretation for the add-immediate. */
+ index = tree_to_double_int (rhs2);
+ if (subtract_p)
+ index = double_int_neg (index);
+
+ c = create_add_imm_cand (gs, rhs1, index, speed);
+
+ /* Add the interpretation to the statement-candidate mapping. */
+ add_cand_for_stmt (gs, c);
+ }
+}
+
+/* Given GS which is a negate of a scalar integer, make an appropriate
+ entry in the candidate table. A negate is equivalent to a multiply
+ by -1. */
+
+static void
+slsr_process_neg (gimple gs, tree rhs1, bool speed)
+{
+ /* Record a CAND_MULT interpretation for the multiply by -1. */
+ slsr_cand_t c = create_mul_imm_cand (gs, rhs1, integer_minus_one_node,
speed);
+
+ /* Add the interpretation to the statement-candidate mapping. */
+ add_cand_for_stmt (gs, c);
+}
+
+/* Return TRUE if GS is a statement that defines an SSA name from
+ a conversion and is legal for us to combine with an add and multiply
+ in the candidate table. For example, suppose we have:
+
+ A = B + i;
+ C = (type) A;
+ D = C * S;
+
+ Without the type-cast, we would create a CAND_MULT for D with base B,
+ index i, and stride S. We want to record this candidate only if it
+ is equivalent to apply the type cast following the multiply:
+
+ A = B + i;
+ E = A * S;
+ D = (type) E;
+
+ We will record the type with the candidate for D. This allows us
+ to use a similar previous candidate as a basis. If we have earlier seen
+
+ A' = B + i';
+ C' = (type) A';
+ D' = C' * S;
+
+ we can replace D with
+
+ D = D' + (i - i') * S;
+
+ But if moving the type-cast would change semantics, we mustn't do this.
+
+ This is legitimate for casts from a non-wrapping integral type to
+ any integral type of the same or larger size. It is not legitimate
+ to convert a wrapping type to a non-wrapping type, or to a wrapping
+ type of a different size. I.e., with a wrapping type, we must
+ assume that the addition B + i could wrap, in which case performing
+ the multiply before or after one of the "illegal" type casts will
+ have different semantics. */
+
+static bool
+legal_cast_p (gimple gs, tree rhs)
+{
+ tree lhs, lhs_type, rhs_type;
+ unsigned lhs_size, rhs_size;
+ bool lhs_wraps, rhs_wraps;
+
+ if (!is_gimple_assign (gs)
+ || !CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (gs)))
+ return false;
+
+ lhs = gimple_assign_lhs (gs);
+ lhs_type = TREE_TYPE (lhs);
+ rhs_type = TREE_TYPE (rhs);
+ lhs_size = TYPE_PRECISION (lhs_type);
+ rhs_size = TYPE_PRECISION (rhs_type);
+ lhs_wraps = TYPE_OVERFLOW_WRAPS (lhs_type);
+ rhs_wraps = TYPE_OVERFLOW_WRAPS (rhs_type);
+
+ if (lhs_size < rhs_size
+ || (rhs_wraps && !lhs_wraps)
+ || (rhs_wraps && lhs_wraps && rhs_size != lhs_size))
+ return false;
+
+ return true;
+}
+
+/* Given GS which is a cast to a scalar integer type, determine whether
+ the cast is legal for strength reduction. If so, make at least one
+ appropriate entry in the candidate table. */
+
+static void
+slsr_process_cast (gimple gs, tree rhs1, bool speed)
+{
+ tree lhs, ctype;
+ slsr_cand_t base_cand, c, c2;
+ unsigned savings = 0;
+
+ if (!legal_cast_p (gs, rhs1))
+ return;
+
+ lhs = gimple_assign_lhs (gs);
+ base_cand = base_cand_from_table (rhs1);
+ ctype = TREE_TYPE (lhs);
+
+ if (base_cand)
+ {
+ while (base_cand)
+ {
+ /* Propagate all data from the base candidate except the type,
+ which comes from the cast, and the base candidate's cast,
+ which is no longer applicable. */
+ if (has_single_use (rhs1))
+ savings = (base_cand->dead_savings
+ + stmt_cost (base_cand->cand_stmt, speed));
+
+ c = alloc_cand_and_find_basis (base_cand->kind, gs,
+ base_cand->base_name,
+ base_cand->index, base_cand->stride,
+ ctype, savings);
+ if (base_cand->next_interp)
+ base_cand = lookup_cand (base_cand->next_interp);
+ else
+ base_cand = NULL;
+ }
+ }
+ else
+ {
+ /* If nothing is known about the RHS, create fresh CAND_ADD and
+ CAND_MULT interpretations:
+
+ X = Y + (0 * 1)
+ X = (Y + 0) * 1
+
+ The first of these is somewhat arbitrary, but the choice of
+ 1 for the stride simplifies the logic for propagating casts
+ into their uses. */
+ c = alloc_cand_and_find_basis (CAND_ADD, gs, rhs1, double_int_zero,
+ integer_one_node, ctype, 0);
+ c2 = alloc_cand_and_find_basis (CAND_MULT, gs, rhs1, double_int_zero,
+ integer_one_node, ctype, 0);
+ c->next_interp = c2->cand_num;
+ }
+
+ /* Add the first (or only) interpretation to the statement-candidate
+ mapping. */
+ add_cand_for_stmt (gs, c);
+}
+
+/* Given GS which is a copy of a scalar integer type, make at least one
+ appropriate entry in the candidate table.
+
+ This interface is included for completeness, but is unnecessary
+ if this pass immediately follows a pass that performs copy
+ propagation, such as DOM. */
+
+static void
+slsr_process_copy (gimple gs, tree rhs1, bool speed)
+{
+ slsr_cand_t base_cand, c, c2;
+ unsigned savings = 0;
+
+ base_cand = base_cand_from_table (rhs1);
+
+ if (base_cand)
+ {
+ while (base_cand)
+ {
+ /* Propagate all data from the base candidate. */
+ if (has_single_use (rhs1))
+ savings = (base_cand->dead_savings
+ + stmt_cost (base_cand->cand_stmt, speed));
+
+ c = alloc_cand_and_find_basis (base_cand->kind, gs,
+ base_cand->base_name,
+ base_cand->index, base_cand->stride,
+ base_cand->cand_type, savings);
+ if (base_cand->next_interp)
+ base_cand = lookup_cand (base_cand->next_interp);
+ else
+ base_cand = NULL;
+ }
+ }
+ else
+ {
+ /* If nothing is known about the RHS, create fresh CAND_ADD and
+ CAND_MULT interpretations:
+
+ X = Y + (0 * 1)
+ X = (Y + 0) * 1
+
+ The first of these is somewhat arbitrary, but the choice of
+ 1 for the stride simplifies the logic for propagating casts
+ into their uses. */
+ c = alloc_cand_and_find_basis (CAND_ADD, gs, rhs1, double_int_zero,
+ integer_one_node, TREE_TYPE (rhs1), 0);
+ c2 = alloc_cand_and_find_basis (CAND_MULT, gs, rhs1, double_int_zero,
+ integer_one_node, TREE_TYPE (rhs1), 0);
+ c->next_interp = c2->cand_num;
+ }
+
+ /* Add the first (or only) interpretation to the statement-candidate
+ mapping. */
+ add_cand_for_stmt (gs, c);
+}
+
+/* Find strength-reduction candidates in block BB. */
+
+static void
+find_candidates_in_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
+ basic_block bb)
+{
+ bool speed = optimize_bb_for_speed_p (bb);
+ gimple_stmt_iterator gsi;
+
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ gimple gs = gsi_stmt (gsi);
+
+ if (is_gimple_assign (gs)
+ && SCALAR_INT_MODE_P (TYPE_MODE (TREE_TYPE (gimple_assign_lhs (gs)))))
+ {
+ tree rhs1 = NULL_TREE, rhs2 = NULL_TREE;
+
+ switch (gimple_assign_rhs_code (gs))
+ {
+ case MULT_EXPR:
+ case PLUS_EXPR:
+ rhs1 = gimple_assign_rhs1 (gs);
+ rhs2 = gimple_assign_rhs2 (gs);
+ gcc_assert (TREE_CODE (rhs1) == SSA_NAME);
+ break;
+
+ /* Possible future opportunity: rhs1 of a ptr+ can be
+ an ADDR_EXPR. */
+ case POINTER_PLUS_EXPR:
+ case MINUS_EXPR:
+ rhs2 = gimple_assign_rhs2 (gs);
+ /* Fall-through. */
+
+ case NOP_EXPR:
+ case MODIFY_EXPR:
+ case NEGATE_EXPR:
+ rhs1 = gimple_assign_rhs1 (gs);
+ if (TREE_CODE (rhs1) != SSA_NAME)
+ continue;
+ break;
+
+ default:
+ ;
+ }
+
+ switch (gimple_assign_rhs_code (gs))
+ {
+ case MULT_EXPR:
+ slsr_process_mul (gs, rhs1, rhs2, speed);
+ break;
+
+ case PLUS_EXPR:
+ case POINTER_PLUS_EXPR:
+ case MINUS_EXPR:
+ slsr_process_add (gs, rhs1, rhs2, speed);
+ break;
+
+ case NEGATE_EXPR:
+ slsr_process_neg (gs, rhs1, speed);
+ break;
+
+ case NOP_EXPR:
+ slsr_process_cast (gs, rhs1, speed);
+ break;
+
+ case MODIFY_EXPR:
+ slsr_process_copy (gs, rhs1, speed);
+ break;
+
+ default:
+ ;
+ }
+ }
+ }
+}
+
+/* Dump a candidate for debug. */
+
+static void
+dump_candidate (slsr_cand_t c)
+{
+ fprintf (dump_file, "%3d [%d] ", c->cand_num,
+ gimple_bb (c->cand_stmt)->index);
+ print_gimple_stmt (dump_file, c->cand_stmt, 0, 0);
+ switch (c->kind)
+ {
+ case CAND_MULT:
+ fputs (" MULT : (", dump_file);
+ print_generic_expr (dump_file, c->base_name, 0);
+ fputs (" + ", dump_file);
+ dump_double_int (dump_file, c->index, false);
+ fputs (") * ", dump_file);
+ print_generic_expr (dump_file, c->stride, 0);
+ fputs (" : ", dump_file);
+ break;
+ case CAND_ADD:
+ fputs (" ADD : ", dump_file);
+ print_generic_expr (dump_file, c->base_name, 0);
+ fputs (" + (", dump_file);
+ dump_double_int (dump_file, c->index, false);
+ fputs (" * ", dump_file);
+ print_generic_expr (dump_file, c->stride, 0);
+ fputs (") : ", dump_file);
+ break;
+ default:
+ gcc_unreachable ();
+ }
+ print_generic_expr (dump_file, c->cand_type, 0);
+ fprintf (dump_file, "\n basis: %d dependent: %d sibling: %d\n",
+ c->basis, c->dependent, c->sibling);
+ fprintf (dump_file, " next-interp: %d dead-savings: %d\n",
+ c->next_interp, c->dead_savings);
+ if (c->def_phi)
+ {
+ fputs (" phi: ", dump_file);
+ print_gimple_stmt (dump_file, c->def_phi, 0, 0);
+ }
+ fputs ("\n", dump_file);
+}
+
+/* Dump the candidate vector for debug. */
+
+static void
+dump_cand_vec (void)
+{
+ unsigned i;
+ slsr_cand_t c;
+
+ fprintf (dump_file, "\nStrength reduction candidate vector:\n\n");
+
+ FOR_EACH_VEC_ELT (slsr_cand_t, cand_vec, i, c)
+ dump_candidate (c);
+}
+
+/* Dump the candidate chains. */
+
+static void
+dump_cand_chains (void)
+{
+ unsigned i;
+
+ fprintf (dump_file, "\nStrength reduction candidate chains:\n\n");
+
+ for (i = 0; i < num_ssa_names; i++)
+ {
+ const_cand_chain_t chain = base_cand_map[i];
+
+ if (chain)
+ {
+ cand_chain_t p;
+
+ print_generic_expr (dump_file, chain->base_name, 0);
+ fprintf (dump_file, " -> %d", chain->cand->cand_num);
+
+ for (p = chain->next; p; p = p->next)
+ fprintf (dump_file, " -> %d", p->cand->cand_num);
+
+ fputs ("\n", dump_file);
+ }
+ }
+
+ fputs ("\n", dump_file);
+}
+
+
+/* Recursive helper for unconditional_cands_with_known_stride_p.
+ Returns TRUE iff C, its siblings, and its dependents are all
+ unconditional candidates. */
+
+static bool
+unconditional_cands (slsr_cand_t c)
+{
+ if (c->def_phi)
+ return false;
+
+ if (c->sibling && !unconditional_cands (lookup_cand (c->sibling)))
+ return false;
+
+ if (c->dependent && !unconditional_cands (lookup_cand (c->dependent)))
+ return false;
+
+ return true;
+}
+
+/* Determine whether or not the tree of candidates rooted at
+ ROOT consists entirely of unconditional increments with
+ an INTEGER_CST stride. */
+
+static bool
+unconditional_cands_with_known_stride_p (slsr_cand_t root)
+{
+ /* The stride is identical for all related candidates, so
+ check it once. */
+ if (TREE_CODE (root->stride) != INTEGER_CST)
+ return false;
+
+ return unconditional_cands (lookup_cand (root->dependent));
+}
+
+/* Calculate the increment required for candidate C relative to
+ its basis. */
+
+static double_int
+cand_increment (slsr_cand_t c)
+{
+ slsr_cand_t basis;
+
+ /* If the candidate doesn't have a basis, just return its own
+ index. This is useful in record_increments to help us find
+ an existing initializer. */
+ if (!c->basis)
+ return c->index;
+
+ basis = lookup_cand (c->basis);
+ gcc_assert (operand_equal_p (c->base_name, basis->base_name, 0));
+ return double_int_sub (c->index, basis->index);
+}
+
+/* Return TRUE iff candidate C has already been replaced under
+ another interpretation. */
+
+static inline bool
+cand_already_replaced (slsr_cand_t c)
+{
+ return (gimple_bb (c->cand_stmt) == 0);
+}
+
+/* Helper routine for replace_dependents, doing the work for a
+ single candidate C. */
+
+static void
+replace_dependent (slsr_cand_t c, enum tree_code cand_code)
+{
+ double_int stride = tree_to_double_int (c->stride);
+ double_int bump = double_int_mul (cand_increment (c), stride);
+ gimple stmt_to_print = NULL;
+ slsr_cand_t basis;
+ tree basis_name, incr_type, bump_tree;
+ enum tree_code code;
+
+ /* It is highly unlikely, but possible, that the resulting
+ bump doesn't fit in a HWI. Abandon the replacement
+ in this case. Restriction to signed HWI is conservative
+ for unsigned types but allows for safe negation without
+ twisted logic. */
+ if (!double_int_fits_in_shwi_p (bump))
+ return;
+
+ basis = lookup_cand (c->basis);
+ basis_name = gimple_assign_lhs (basis->cand_stmt);
+ incr_type = TREE_TYPE (gimple_assign_rhs1 (c->cand_stmt));
+ code = PLUS_EXPR;
+
+ if (double_int_negative_p (bump))
+ {
+ code = MINUS_EXPR;
+ bump = double_int_neg (bump);
+ }
+
+ bump_tree = double_int_to_tree (incr_type, bump);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fputs ("Replacing: ", dump_file);
+ print_gimple_stmt (dump_file, c->cand_stmt, 0, 0);
+ }
+
+ if (double_int_zero_p (bump))
+ {
+ tree lhs = gimple_assign_lhs (c->cand_stmt);
+ gimple copy_stmt = gimple_build_assign (lhs, basis_name);
+ gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt);
+ gimple_set_location (copy_stmt, gimple_location (c->cand_stmt));
+ gsi_replace (&gsi, copy_stmt, false);
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ stmt_to_print = copy_stmt;
+ }
+ else
+ {
+ tree rhs1 = gimple_assign_rhs1 (c->cand_stmt);
+ tree rhs2 = gimple_assign_rhs2 (c->cand_stmt);
+ if (cand_code != NEGATE_EXPR
+ && ((operand_equal_p (rhs1, basis_name, 0)
+ && operand_equal_p (rhs2, bump_tree, 0))
+ || (operand_equal_p (rhs1, bump_tree, 0)
+ && operand_equal_p (rhs2, basis_name, 0))))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fputs ("(duplicate, not actually replacing)", dump_file);
+ stmt_to_print = c->cand_stmt;
+ }
+ }
+ else
+ {
+ gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt);
+ gimple_assign_set_rhs_with_ops (&gsi, code, basis_name, bump_tree);
+ update_stmt (gsi_stmt (gsi));
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ stmt_to_print = gsi_stmt (gsi);
+ }
+ }
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fputs ("With: ", dump_file);
+ print_gimple_stmt (dump_file, stmt_to_print, 0, 0);
+ fputs ("\n", dump_file);
+ }
+}
+
+/* Replace candidate C, each sibling of candidate C, and each
+ dependent of candidate C with an add or subtract. Note that we
+ only operate on CAND_MULTs with known strides, so we will never
+ generate a POINTER_PLUS_EXPR. Each candidate X = (B + i) * S is
+ replaced by X = Y + ((i - i') * S), as described in the module
+ commentary. The folded value ((i - i') * S) is referred to here
+ as the "bump." */
+
+static void
+replace_dependents (slsr_cand_t c)
+{
+ enum tree_code cand_code = gimple_assign_rhs_code (c->cand_stmt);
+
+ /* It is not useful to replace casts, copies, or adds of an SSA name
+ and a constant. Also skip candidates that have already been
+ replaced under another interpretation. */
+ if (cand_code != MODIFY_EXPR
+ && cand_code != NOP_EXPR
+ && c->kind == CAND_MULT
+ && !cand_already_replaced (c))
+ replace_dependent (c, cand_code);
+
+ if (c->sibling)
+ replace_dependents (lookup_cand (c->sibling));
+
+ if (c->dependent)
+ replace_dependents (lookup_cand (c->dependent));
+}
+
+/* Analyze costs of related candidates in the candidate vector,
+ and make beneficial replacements. */
+
+static void
+analyze_candidates_and_replace (void)
+{
+ unsigned i;
+ slsr_cand_t c;
+
+ /* Each candidate that has a null basis and a non-null
+ dependent is the root of a tree of related statements.
+ Analyze each tree to determine a subset of those
+ statements that can be replaced with maximum benefit. */
+ FOR_EACH_VEC_ELT (slsr_cand_t, cand_vec, i, c)
+ {
+ slsr_cand_t first_dep;
+
+ if (c->basis != 0 || c->dependent == 0)
+ continue;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "\nProcessing dependency tree rooted at %d.\n",
+ c->cand_num);
+
+ first_dep = lookup_cand (c->dependent);
+
+ /* If the common stride of all related candidates is a
+ known constant, and none of these has a phi-dependence,
+ then all replacements are considered profitable.
+ Each replaces a multiply by a single add, with the
+ possibility that a feeding add also goes dead as a
+ result. */
+ if (unconditional_cands_with_known_stride_p (c))
+ replace_dependents (first_dep);
+
+ /* TODO: When the stride is an SSA name, it may still be
+ profitable to replace some or all of the dependent
+ candidates, depending on whether the introduced increments
+ can be reused, or are less expensive to calculate than
+ the replaced statements. */
+
+ /* TODO: Strength-reduce data references with implicit
+ multiplication in their addressing expressions. */
+
+ /* TODO: When conditional increments occur so that a
+ candidate is dependent upon a phi-basis, the cost of
+ introducing a temporary must be accounted for. */
+ }
+}
+
+static unsigned
+execute_strength_reduction (void)
+{
+ struct dom_walk_data walk_data;
+
+ /* Create the obstack where candidates will reside. */
+ gcc_obstack_init (&cand_obstack);
+
+ /* Allocate the candidate vector. */
+ cand_vec = VEC_alloc (slsr_cand_t, heap, 128);
+
+ /* Allocate the mapping from statements to candidate indices. */
+ stmt_cand_map = pointer_map_create ();
+
+ /* Create the obstack where candidate chains will reside. */
+ gcc_obstack_init (&chain_obstack);
+
+ /* Allocate the mapping from base names to candidate chains. */
+ base_cand_map = XNEWVEC (cand_chain_t, num_ssa_names);
+ memset (base_cand_map, 0, num_ssa_names * sizeof (cand_chain_t));
+
+ /* Initialize the loop optimizer. We need to detect flow across
+ back edges, and this gives us dominator information as well. */
+ loop_optimizer_init (AVOID_CFG_MODIFICATIONS);
+
+ /* Initialize costs tables in IVOPTS. */
+ initialize_costs ();
+
+ /* Set up callbacks for the generic dominator tree walker. */
+ walk_data.dom_direction = CDI_DOMINATORS;
+ walk_data.initialize_block_local_data = NULL;
+ walk_data.before_dom_children = find_candidates_in_block;
+ walk_data.after_dom_children = NULL;
+ walk_data.global_data = NULL;
+ walk_data.block_local_data_size = 0;
+ init_walk_dominator_tree (&walk_data);
+
+ /* Walk the CFG in predominator order looking for strength reduction
+ candidates. */
+ walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ dump_cand_vec ();
+ dump_cand_chains ();
+ }
+
+ /* Analyze costs and make appropriate replacements. */
+ analyze_candidates_and_replace ();
+
+ /* Free resources. */
+ fini_walk_dominator_tree (&walk_data);
+ loop_optimizer_finalize ();
+ free (base_cand_map);
+ obstack_free (&chain_obstack, NULL);
+ pointer_map_destroy (stmt_cand_map);
+ VEC_free (slsr_cand_t, heap, cand_vec);
+ obstack_free (&cand_obstack, NULL);
+ finalize_costs ();
+
+ return 0;
+}
+
+static bool
+gate_strength_reduction (void)
+{
+ return optimize > 0;
+}
+
+struct gimple_opt_pass pass_strength_reduction =
+{
+ {
+ GIMPLE_PASS,
+ "slsr", /* name */
+ gate_strength_reduction, /* gate */
+ execute_strength_reduction, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_GIMPLE_SLSR, /* tv_id */
+ PROP_cfg | PROP_ssa, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_verify_ssa /* todo_flags_finish */
+ }
+};
Index: gcc/tree-flow.h
===================================================================
--- gcc/tree-flow.h (revision 188891)
+++ gcc/tree-flow.h (working copy)
@@ -810,6 +810,8 @@ bool expr_invariant_in_loop_p (struct loop *, tree
bool stmt_invariant_in_loop_p (struct loop *, gimple);
bool multiplier_allowed_in_address_p (HOST_WIDE_INT, enum machine_mode,
addr_space_t);
+void initialize_costs (void);
+void finalize_costs (void);
unsigned multiply_by_const_cost (HOST_WIDE_INT, enum machine_mode, bool);
unsigned add_regs_cost (enum machine_mode, bool);
unsigned multiply_regs_cost (enum machine_mode, bool);
Index: gcc/Makefile.in
===================================================================
--- gcc/Makefile.in (revision 188890)
+++ gcc/Makefile.in (working copy)
@@ -1243,6 +1243,7 @@ OBJS = \
gimple-fold.o \
gimple-low.o \
gimple-pretty-print.o \
+ gimple-ssa-strength-reduction.o \
gimple-streamer-in.o \
gimple-streamer-out.o \
gimplify.o \
@@ -2432,6 +2433,11 @@ tree-ssa-sccvn.o : tree-ssa-sccvn.c $(TREE_FLOW_H)
alloc-pool.h $(BASIC_BLOCK_H) $(BITMAP_H) langhooks.h $(HASHTAB_H)
$(GIMPLE_H) \
$(TREE_INLINE_H) tree-iterator.h tree-ssa-propagate.h tree-ssa-sccvn.h \
$(PARAMS_H) $(GIMPLE_PRETTY_PRINT_H) gimple-fold.h
+gimple-ssa-strength-reduction.o : gimple-ssa-strength-reduction.c $(CONFIG_H) \
+ $(SYSTEM_H) coretypes.h $(TREE_H) $(GIMPLE_H) $(BASIC_BLOCK_H) \
+ $(TREE_PASS_H) $(TIMEVAR_H) $(CFGLOOP_H) $(TREE_PRETTY_PRINT_H) \
+ $(GIMPLE_PRETTY_PRINT_H) alloc-pool.h $(TREE_FLOW_H) domwalk.h \
+ pointer-set.h
tree-vrp.o : tree-vrp.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(TREE_H) \
$(TREE_FLOW_H) $(TREE_PASS_H) $(TREE_DUMP_H) $(DIAGNOSTIC_CORE_H) $(GGC_H) \
$(BASIC_BLOCK_H) tree-ssa-propagate.h $(FLAGS_H) $(TREE_DUMP_H) \
Index: gcc/passes.c
===================================================================
--- gcc/passes.c (revision 188890)
+++ gcc/passes.c (working copy)
@@ -1463,6 +1463,7 @@ init_optimization_passes (void)
NEXT_PASS (pass_cse_reciprocals);
NEXT_PASS (pass_reassoc);
NEXT_PASS (pass_vrp);
+ NEXT_PASS (pass_strength_reduction);
NEXT_PASS (pass_dominator);
/* The only const/copy propagation opportunities left after
DOM should be due to degenerate PHI nodes. So rather than
