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match.pd: Improve conditional_replacement for x ? 0 : -1 [PR796232]

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As mentioned in the PR, for boolean x we currently optimize
in phiopt x ? 0 : -1 into -(int)!x but it can be optimized as
(int) x - 1 which is one less operation both in GIMPLE and in x86 assembly.

This patch optimizes it in match.pd, by optimizing -(type)!x when
x has boolean range into (type)x - 1.

2020-12-06  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/96232
	* match.pd (-(type)!A -> (type)A - 1): New optimization.

	* gcc.dg/tree-ssa/pr96232-1.c: New test.
This commit is contained in:
Jakub Jelinek 2020-12-06 10:55:12 +01:00
parent bd0f024386
commit 9e12b8b181
2 changed files with 21 additions and 0 deletions
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10
gcc/match.pd
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@ -3812,6 +3812,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(cnd (logical_inverted_value truth_valued_p@0) @1 @2)
(cnd @0 @2 @1)))
/* -(type)!A -> (type)A - 1. */
(simplify
(negate (convert?:s (logical_inverted_value:s @0)))
(if (INTEGRAL_TYPE_P (type)
&& TREE_CODE (type) != BOOLEAN_TYPE
&& TYPE_PRECISION (type) > 1
&& TREE_CODE (@0) == SSA_NAME
&& ssa_name_has_boolean_range (@0))
(plus (convert:type @0) { build_all_ones_cst (type); })))
/* A + (B vcmp C ? 1 : 0) -> A - (B vcmp C ? -1 : 0), since vector comparisons
return all -1 or all 0 results. */
/* ??? We could instead convert all instances of the vec_cond to negate,

11
gcc/testsuite/gcc.dg/tree-ssa/pr96232-1.c Normal file
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@ -0,0 +1,11 @@
/* PR tree-optimization/96232 */
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
/* { dg-final { scan-tree-dump " \\+ -1;" "optimized" } } */
/* { dg-final { scan-tree-dump-not "~x_\[0-9]*\\\(D\\\)" "optimized" } } */
int
foo (_Bool x)
{
return x ? 0 : -1;
}