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re PR tree-optimization/59100 (requesting optimization of safe rotate function) 

2014-05-08  Marc Glisse  <marc.glisse@inria.fr>

	PR tree-optimization/59100
gcc/
	* tree-ssa-phiopt.c: Include tree-inline.h.
	(neutral_element_p, absorbing_element_p): New functions.
	(value_replacement): Handle conditional binary operations with a
	neutral or absorbing element.
gcc/testsuite/
	* gcc.dg/tree-ssa/phi-opt-12.c: New file.
	* gcc.dg/tree-ssa/phi-opt-13.c: Likewise.

From-SVN: r210212
This commit is contained in:
Marc Glisse 2014-05-08 15:17:01 +02:00 committed by Marc Glisse
parent a5eaec4266
commit 421bf78009
5 changed files with 157 additions and 3 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2014-05-08 Marc Glisse <marc.glisse@inria.fr>
PR tree-optimization/59100
* tree-ssa-phiopt.c: Include tree-inline.h.
(neutral_element_p, absorbing_element_p): New functions.
(value_replacement): Handle conditional binary operations with a
neutral or absorbing element.
2014-05-08 Richard Biener <rguenther@suse.de>
* tree-ssa-sccvn.c (vn_get_expr_for): Valueize operands before

6
gcc/testsuite/ChangeLog
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@ -1,3 +1,9 @@
2014-05-08 Marc Glisse <marc.glisse@inria.fr>
PR tree-optimization/59100
* gcc.dg/tree-ssa/phi-opt-12.c: New file.
* gcc.dg/tree-ssa/phi-opt-13.c: Likewise.
2014-05-08 Richard Sandiford <rdsandiford@googlemail.com>
PR tree-optimization/61095

23
gcc/testsuite/gcc.dg/tree-ssa/phi-opt-12.c Normal file
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@ -0,0 +1,23 @@
/* { dg-do compile } */
/* { dg-options "-O -fdump-tree-phiopt1" } */
int f(int a, int b, int c) {
if (c > 5) return c;
if (a == 0) return b;
return a + b;
}
unsigned rot(unsigned x, int n) {
const int bits = __CHAR_BIT__ * __SIZEOF_INT__;
return (n == 0) ? x : ((x << n) | (x >> (bits - n)));
}
unsigned m(unsigned a, unsigned b) {
if (a == 0)
return 0;
else
return a & b;
}
/* { dg-final { scan-tree-dump-times "goto" 2 "phiopt1" } } */
/* { dg-final { cleanup-tree-dump "phiopt1" } } */

11
gcc/testsuite/gcc.dg/tree-ssa/phi-opt-13.c Normal file
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@ -0,0 +1,11 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
// Division is expensive
long f(long a, long b) {
if (__builtin_expect(b == 1, 1)) return a;
return a / b;
}
/* { dg-final { scan-tree-dump-times "goto " 2 "optimized" } } */
/* { dg-final { cleanup-tree-dump "optimized" } } */

112
gcc/tree-ssa-phiopt.c
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@ -54,6 +54,7 @@ along with GCC; see the file COPYING3. If not see
#include "expr.h"
#include "optabs.h"
#include "tree-scalar-evolution.h"
#include "tree-inline.h"
#ifndef HAVE_conditional_move
#define HAVE_conditional_move (0)
@ -659,6 +660,64 @@ operand_equal_for_value_replacement (const_tree arg0, const_tree arg1,
return false;
}
/* Returns true if ARG is a neutral element for operation CODE
on the RIGHT side. */
static bool
neutral_element_p (tree_code code, tree arg, bool right)
{
switch (code)
{
case PLUS_EXPR:
case BIT_IOR_EXPR:
case BIT_XOR_EXPR:
return integer_zerop (arg);
case LROTATE_EXPR:
case RROTATE_EXPR:
case LSHIFT_EXPR:
case RSHIFT_EXPR:
case MINUS_EXPR:
case POINTER_PLUS_EXPR:
return right && integer_zerop (arg);
case MULT_EXPR:
return integer_onep (arg);
case TRUNC_DIV_EXPR:
case CEIL_DIV_EXPR:
case FLOOR_DIV_EXPR:
case ROUND_DIV_EXPR:
case EXACT_DIV_EXPR:
return right && integer_onep (arg);
case BIT_AND_EXPR:
return integer_all_onesp (arg);
default:
return false;
}
}
/* Returns true if ARG is an absorbing element for operation CODE. */
static bool
absorbing_element_p (tree_code code, tree arg)
{
switch (code)
{
case BIT_IOR_EXPR:
return integer_all_onesp (arg);
case MULT_EXPR:
case BIT_AND_EXPR:
return integer_zerop (arg);
default:
return false;
}
}
/* The function value_replacement does the main work of doing the value
replacement. Return non-zero if the replacement is done. Otherwise return
0. If we remove the middle basic block, return 2.
@ -683,9 +742,7 @@ value_replacement (basic_block cond_bb, basic_block middle_bb,
/* If there is a statement in MIDDLE_BB that defines one of the PHI
arguments, then adjust arg0 or arg1. */
gsi = gsi_after_labels (middle_bb);
if (!gsi_end_p (gsi) && is_gimple_debug (gsi_stmt (gsi)))
gsi_next_nondebug (&gsi);
gsi = gsi_start_nondebug_after_labels_bb (middle_bb);
while (!gsi_end_p (gsi))
{
gimple stmt = gsi_stmt (gsi);
@ -781,6 +838,55 @@ value_replacement (basic_block cond_bb, basic_block middle_bb,
}
}
/* Now optimize (x != 0) ? x + y : y to just y.
The following condition is too restrictive, there can easily be another
stmt in middle_bb, for instance a CONVERT_EXPR for the second argument. */
gimple assign = last_and_only_stmt (middle_bb);
if (!assign || gimple_code (assign) != GIMPLE_ASSIGN
|| gimple_assign_rhs_class (assign) != GIMPLE_BINARY_RHS
|| (!INTEGRAL_TYPE_P (TREE_TYPE (arg0))
&& !POINTER_TYPE_P (TREE_TYPE (arg0))))
return 0;
/* Size-wise, this is always profitable. */
if (optimize_bb_for_speed_p (cond_bb)
/* The special case is useless if it has a low probability. */
&& profile_status_for_fn (cfun) != PROFILE_ABSENT
&& EDGE_PRED (middle_bb, 0)->probability < PROB_EVEN
/* If assign is cheap, there is no point avoiding it. */
&& estimate_num_insns (assign, &eni_time_weights)
>= 3 * estimate_num_insns (cond, &eni_time_weights))
return 0;
tree lhs = gimple_assign_lhs (assign);
tree rhs1 = gimple_assign_rhs1 (assign);
tree rhs2 = gimple_assign_rhs2 (assign);
enum tree_code code_def = gimple_assign_rhs_code (assign);
tree cond_lhs = gimple_cond_lhs (cond);
tree cond_rhs = gimple_cond_rhs (cond);
if (((code == NE_EXPR && e1 == false_edge)
|| (code == EQ_EXPR && e1 == true_edge))
&& arg0 == lhs
&& ((arg1 == rhs1
&& operand_equal_for_phi_arg_p (rhs2, cond_lhs)
&& neutral_element_p (code_def, cond_rhs, true))
|| (arg1 == rhs2
&& operand_equal_for_phi_arg_p (rhs1, cond_lhs)
&& neutral_element_p (code_def, cond_rhs, false))
|| (operand_equal_for_phi_arg_p (arg1, cond_rhs)
&& (operand_equal_for_phi_arg_p (rhs2, cond_lhs)
|| operand_equal_for_phi_arg_p (rhs1, cond_lhs))
&& absorbing_element_p (code_def, cond_rhs))))
{
gsi = gsi_for_stmt (cond);
gimple_stmt_iterator gsi_from = gsi_for_stmt (assign);
gsi_move_before (&gsi_from, &gsi);
replace_phi_edge_with_variable (cond_bb, e1, phi, lhs);
return 2;
}
return 0;
}