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match.pd: Optimize (x < 0) ^ (y < 0) to (x ^ y) < 0 etc. [PR96681]

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This patch simplifies comparisons that test the sign bit xored together.
If the comparisons are both < 0 or both >= 0, then we should xor the operands
together and compare the result to < 0, if the comparisons are different,
we should compare to >= 0.

2021-01-15  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/96681
	* match.pd ((x < 0) ^ (y < 0) to (x ^ y) < 0): New simplification.
	((x >= 0) ^ (y >= 0) to (x ^ y) < 0): Likewise.
	((x < 0) ^ (y >= 0) to (x ^ y) >= 0): Likewise.
	((x >= 0) ^ (y < 0) to (x ^ y) >= 0): Likewise.

	* gcc.dg/tree-ssa/pr96681.c: New test.
This commit is contained in:
Jakub Jelinek 2021-01-15 21:10:44 +01:00
parent e63c2161d0
commit 5c046034e3
2 changed files with 53 additions and 0 deletions
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18
gcc/match.pd
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@ -3993,6 +3993,24 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(if (single_use (@2))
(cmp @0 @1)))))
/* Simplify (x < 0) ^ (y < 0) to (x ^ y) < 0 and
(x >= 0) ^ (y >= 0) to (x ^ y) < 0. */
(for cmp (lt ge)
(simplify
(bit_xor (cmp:s @0 integer_zerop) (cmp:s @1 integer_zerop))
(if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
&& !TYPE_UNSIGNED (TREE_TYPE (@0))
&& types_match (TREE_TYPE (@0), TREE_TYPE (@1)))
(lt (bit_xor @0 @1) { build_zero_cst (TREE_TYPE (@0)); }))))
/* Simplify (x < 0) ^ (y >= 0) to (x ^ y) >= 0 and
(x >= 0) ^ (y < 0) to (x ^ y) >= 0. */
(simplify
(bit_xor:c (lt:s @0 integer_zerop) (ge:s @1 integer_zerop))
(if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
&& !TYPE_UNSIGNED (TREE_TYPE (@0))
&& types_match (TREE_TYPE (@0), TREE_TYPE (@1)))
(ge (bit_xor @0 @1) { build_zero_cst (TREE_TYPE (@0)); })))
/* Transform comparisons of the form X * C1 CMP 0 to X CMP 0 in the
signed arithmetic case. That form is created by the compiler
often enough for folding it to be of value. One example is in

35
gcc/testsuite/gcc.dg/tree-ssa/pr96681.c Normal file
View file

@ -0,0 +1,35 @@
/* PR tree-optimization/96681 */
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
/* { dg-final { scan-tree-dump-times " \\^ " 5 "optimized" } } */
/* { dg-final { scan-tree-dump-times " (?:<|>=) 0" 5 "optimized" } } */
int
foo (int x, int y)
{
return (x < 0) ^ (y < 0);
}
int
bar (int x, int y)
{
return (x > -1) ^ (y > -1);
}
int
baz (int x, int y)
{
return (x ^ y) < 0;
}
int
qux (int x, int y)
{
return (x ^ y) >= 0;
}
int
corge (int x, int y)
{
return (x >= 0) ^ (y < 0);
}