From 97222f3fc11f4e19a16c6e2d2447e8d4dcb3bc92 Mon Sep 17 00:00:00 2001 From: Matteo Nicoli Date: Fri, 22 Aug 2025 20:42:12 +0200 Subject: [PATCH] tree-optimization/121595 - the optimization fabs(a+0.0) -> fabs(a) should apply only for non trapping case * added a match expression - gcc/match.pd * added tests - gcc/testsuite/gcc.dg/fabs-plus-zero-1.c - gcc/testsuite/gcc.dg/fabs-plus-zero-2.c Signed-off-by: Matteo Nicoli Reviewed-by: Andrew Pinski --- gcc/match.pd | 7 +++++++ gcc/testsuite/gcc.dg/fabs-plus-zero-1.c | 9 +++++++++ gcc/testsuite/gcc.dg/fabs-plus-zero-2.c | 10 ++++++++++ 3 files changed, 26 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/fabs-plus-zero-1.c create mode 100644 gcc/testsuite/gcc.dg/fabs-plus-zero-2.c diff --git a/gcc/match.pd b/gcc/match.pd index b1d7a3a1b73..cd2ddf5ee6e 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -2045,6 +2045,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (abs (negate @0)) (abs @0)) +/* fabs(x + 0.0) -> fabs(x), safe even with signed zeros when -fno-trapping-math. */ +(for op (plus minus) + (simplify + (abs (op @0 real_zerop@1)) + (if (!flag_trapping_math) + (abs @0)))) + (simplify (absu (negate @0)) (absu @0)) diff --git a/gcc/testsuite/gcc.dg/fabs-plus-zero-1.c b/gcc/testsuite/gcc.dg/fabs-plus-zero-1.c new file mode 100644 index 00000000000..c4a5a298334 --- /dev/null +++ b/gcc/testsuite/gcc.dg/fabs-plus-zero-1.c @@ -0,0 +1,9 @@ +/* With trapping-math enabled (default behavior), GCC must preserve the +0.0 */ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-optimized" } */ + +double f(double a) +{ + return __builtin_fabs(a + 0.0); +} +/* { dg-final { scan-tree-dump-times "\\+ 0\\.0" 1 "optimized" } } */ diff --git a/gcc/testsuite/gcc.dg/fabs-plus-zero-2.c b/gcc/testsuite/gcc.dg/fabs-plus-zero-2.c new file mode 100644 index 00000000000..c8f78dfbc1b --- /dev/null +++ b/gcc/testsuite/gcc.dg/fabs-plus-zero-2.c @@ -0,0 +1,10 @@ +/* With -fno-trapping-math it is safe to fold away +0.0 */ +/* { dg-do compile } */ +/* { dg-options "-O2 -fno-trapping-math -fdump-tree-optimized" } */ + +double f1(double a) { return __builtin_fabs(a + 0.0); } +double f2(double a) { return __builtin_fabs(a + -0.0); } +double f3(double a) { return __builtin_fabs(a - 0.0); } +double f4(double a) { return __builtin_fabs(a - -0.0); } + +/* { dg-final { scan-tree-dump-not "\\+ 0\\.0" "optimized" } } */ -- 2.39.5 (Apple Git-154)