From 5c046034e3ea61dd68965154a398f8f813daf8f2 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Fri, 15 Jan 2021 21:10:44 +0100 Subject: [PATCH] match.pd: Optimize (x < 0) ^ (y < 0) to (x ^ y) < 0 etc. [PR96681] 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 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. --- gcc/match.pd | 18 +++++++++++++++++ gcc/testsuite/gcc.dg/tree-ssa/pr96681.c | 35 +++++++++++++++++++++++++++++++++ 2 files changed, 53 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr96681.c diff --git a/gcc/match.pd b/gcc/match.pd index f08ab67..e731bdb 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -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 diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96681.c b/gcc/testsuite/gcc.dg/tree-ssa/pr96681.c new file mode 100644 index 0000000..6d72a1a --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96681.c @@ -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); +} -- 2.7.4