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reassoc: Reassociate integral multiplies [PR95867] 

For floating point multiply, we have nice code in reassoc to reassociate
multiplications to almost optimal sequence of as few multiplications as
possible (or library call), but for integral types we just give up
because there is no __builtin_powi* for those types.

As there is no library routine we could use, instead of adding new internal
call just to hold it temporarily and then lower to multiplications again,
this patch for the integral types calls into the sincos pass routine that
expands it into multiplications right away.

2021-01-11  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/95867
	* tree-ssa-math-opts.h: New header.
	* tree-ssa-math-opts.c: Include tree-ssa-math-opts.h.
	(powi_as_mults): No longer static.  Use build_one_cst instead of
	build_real.  Formatting fix.
	* tree-ssa-reassoc.c: Include tree-ssa-math-opts.h.
	(attempt_builtin_powi): Handle multiplication reassociation without
	powi_fndecl using powi_as_mults.
	(reassociate_bb): For integral types don't require
	-funsafe-math-optimizations to call attempt_builtin_powi.

	* gcc.dg/tree-ssa/pr95867.c: New test.
This commit is contained in:
Jakub Jelinek 2021-01-11 10:35:10 +01:00
parent 9febe9e4be
commit 9a6c37e6ae
4 changed files with 102 additions and 22 deletions
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14
gcc/testsuite/gcc.dg/tree-ssa/pr95867.c Normal file
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@ -0,0 +1,14 @@
/* PR tree-optimization/95867 */
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
/* { dg-final { scan-tree-dump-times " \\* " 13 "optimized" } } */
#define A n * n * n * n * n * n * n * n
#define B A * A * A * A * A * A * A * A
#define C B * B * B * B * B * B * B * B
unsigned
foo (unsigned n)
{
return C * B * B * A * n * n * n * n * n;
}

7
gcc/tree-ssa-math-opts.c
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@ -115,6 +115,7 @@ along with GCC; see the file COPYING3. If not see
#include "tree-eh.h"
#include "targhooks.h"
#include "domwalk.h"
#include "tree-ssa-math-opts.h"
/* This structure represents one basic block that either computes a
division, or is a common dominator for basic block that compute a
@ -1527,7 +1528,7 @@ powi_as_mults_1 (gimple_stmt_iterator *gsi, location_t loc, tree type,
/* Convert ARG0**N to a tree of multiplications of ARG0 with itself.
This function needs to be kept in sync with powi_cost above. */
static tree
tree
powi_as_mults (gimple_stmt_iterator *gsi, location_t loc,
tree arg0, HOST_WIDE_INT n)
{
@ -1536,9 +1537,9 @@ powi_as_mults (gimple_stmt_iterator *gsi, location_t loc,
tree target;
if (n == 0)
return build_real (type, dconst1);
return build_one_cst (type);
memset (cache, 0, sizeof (cache));
memset (cache, 0, sizeof (cache));
cache[1] = arg0;
result = powi_as_mults_1 (gsi, loc, type, (n < 0) ? -n : n, cache);

26
gcc/tree-ssa-math-opts.h Normal file
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@ -0,0 +1,26 @@
/* Global, SSA-based optimizations using mathematical identities.
Copyright (C) 2021 Free Software Foundation, Inc.
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/>. */
#ifndef GCC_TREE_SSA_MATH_OPTS_H
#define GCC_TREE_SSA_MATH_OPTS_H
extern tree powi_as_mults (gimple_stmt_iterator *, location_t,
tree, HOST_WIDE_INT);
#endif /* GCC_TREE_SSA_MATH_OPTS_H */

77
gcc/tree-ssa-reassoc.c
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@ -52,6 +52,7 @@ along with GCC; see the file COPYING3. If not see
#include "gimplify.h"
#include "case-cfn-macros.h"
#include "tree-ssa-reassoc.h"
#include "tree-ssa-math-opts.h"
/* This is a simple global reassociation pass. It is, in part, based
on the LLVM pass of the same name (They do some things more/less
@ -5976,8 +5977,8 @@ attempt_builtin_powi (gimple *stmt, vec<operand_entry *> *ops)
gimple *mul_stmt, *pow_stmt;
/* Nothing to do if BUILT_IN_POWI doesn't exist for this type and
target. */
if (!powi_fndecl)
target, unless type is integral. */
if (!powi_fndecl && !INTEGRAL_TYPE_P (type))
return NULL_TREE;
/* Allocate the repeated factor vector. */
@ -6086,14 +6087,33 @@ attempt_builtin_powi (gimple *stmt, vec<operand_entry *> *ops)
}
else
{
iter_result = make_temp_ssa_name (type, NULL, "reassocpow");
pow_stmt = gimple_build_call (powi_fndecl, 2, rf1->repr,
build_int_cst (integer_type_node,
power));
gimple_call_set_lhs (pow_stmt, iter_result);
gimple_set_location (pow_stmt, gimple_location (stmt));
gimple_set_uid (pow_stmt, gimple_uid (stmt));
gsi_insert_before (&gsi, pow_stmt, GSI_SAME_STMT);
if (INTEGRAL_TYPE_P (type))
{
gcc_assert (power > 1);
gimple_stmt_iterator gsip = gsi;
gsi_prev (&gsip);
iter_result = powi_as_mults (&gsi, gimple_location (stmt),
rf1->repr, power);
gimple_stmt_iterator gsic = gsi;
while (gsi_stmt (gsic) != gsi_stmt (gsip))
{
gimple_set_uid (gsi_stmt (gsic), gimple_uid (stmt));
gimple_set_visited (gsi_stmt (gsic), true);
gsi_prev (&gsic);
}
}
else
{
iter_result = make_temp_ssa_name (type, NULL, "reassocpow");
pow_stmt
= gimple_build_call (powi_fndecl, 2, rf1->repr,
build_int_cst (integer_type_node,
power));
gimple_call_set_lhs (pow_stmt, iter_result);
gimple_set_location (pow_stmt, gimple_location (stmt));
gimple_set_uid (pow_stmt, gimple_uid (stmt));
gsi_insert_before (&gsi, pow_stmt, GSI_SAME_STMT);
}
if (dump_file && (dump_flags & TDF_DETAILS))
{
@ -6188,14 +6208,32 @@ attempt_builtin_powi (gimple *stmt, vec<operand_entry *> *ops)
/* Form a call to __builtin_powi for the maximum product
just formed, raised to the power obtained earlier. */
rf1 = &repeat_factor_vec[j];
iter_result = make_temp_ssa_name (type, NULL, "reassocpow");
pow_stmt = gimple_build_call (powi_fndecl, 2, rf1->repr,
build_int_cst (integer_type_node,
power));
gimple_call_set_lhs (pow_stmt, iter_result);
gimple_set_location (pow_stmt, gimple_location (stmt));
gimple_set_uid (pow_stmt, gimple_uid (stmt));
gsi_insert_before (&gsi, pow_stmt, GSI_SAME_STMT);
if (INTEGRAL_TYPE_P (type))
{
gcc_assert (power > 1);
gimple_stmt_iterator gsip = gsi;
gsi_prev (&gsip);
iter_result = powi_as_mults (&gsi, gimple_location (stmt),
rf1->repr, power);
gimple_stmt_iterator gsic = gsi;
while (gsi_stmt (gsic) != gsi_stmt (gsip))
{
gimple_set_uid (gsi_stmt (gsic), gimple_uid (stmt));
gimple_set_visited (gsi_stmt (gsic), true);
gsi_prev (&gsic);
}
}
else
{
iter_result = make_temp_ssa_name (type, NULL, "reassocpow");
pow_stmt = gimple_build_call (powi_fndecl, 2, rf1->repr,
build_int_cst (integer_type_node,
power));
gimple_call_set_lhs (pow_stmt, iter_result);
gimple_set_location (pow_stmt, gimple_location (stmt));
gimple_set_uid (pow_stmt, gimple_uid (stmt));
gsi_insert_before (&gsi, pow_stmt, GSI_SAME_STMT);
}
}
/* If we previously formed at least one other builtin_powi call,
@ -6522,7 +6560,8 @@ reassociate_bb (basic_block bb)
attempt_builtin_copysign (&ops);
if (reassoc_insert_powi_p
&& flag_unsafe_math_optimizations)
&& (flag_unsafe_math_optimizations
|| (INTEGRAL_TYPE_P (TREE_TYPE (lhs)))))
powi_result = attempt_builtin_powi (stmt, &ops);
}