In combine_comparisons, under flag_trapping_math, we check whether the combined
comparison traps under the same conditions as the input comparisons:
bool trap = (compcode & COMPCODE_UNORD) == 0
&& (compcode != COMPCODE_EQ)
&& (compcode != COMPCODE_ORD);
When compcode is COMPCODE_FALSE or COMPCODE_TRUE trap is computed as true,
and combine_comparisons errorneously eliminates IEEE exceptions.
Bootstrapped and tested on x86_64-unknown-linux-gnu.
OK?
Thanks,
Richard.
PR tree-optimization/53805
* fold-const.cc (combine_comparisons): Do not treat COMPCODE_FALSE
or COMPCODE_TRUE as trapping.
* gcc.dg/tree-ssa/fp-trapping-and-1.c: New testcase.
---
gcc/fold-const.cc | 4 +++-
gcc/testsuite/gcc.dg/tree-ssa/fp-trapping-and-1.c | 11 +++++++++++
2 files changed, 14 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/fp-trapping-and-1.c
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 8c5e558647c..cfeafd5c1d1 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -3085,7 +3085,9 @@ combine_comparisons (enum tree_code code, enum tree_code
lcode,
&& (rcompcode != COMPCODE_ORD);
bool trap = (compcode & COMPCODE_UNORD) == 0
&& (compcode != COMPCODE_EQ)
- && (compcode != COMPCODE_ORD);
+ && (compcode != COMPCODE_ORD)
+ && (compcode != COMPCODE_FALSE)
+ && (compcode != COMPCODE_TRUE);
/* In a short-circuited boolean expression the LHS might be
such that the RHS, if evaluated, will never trap. For
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/fp-trapping-and-1.c
b/gcc/testsuite/gcc.dg/tree-ssa/fp-trapping-and-1.c
new file mode 100644
index 00000000000..84946dc7cc1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/fp-trapping-and-1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftrapping-math -fdump-tree-optimized" } */
+
+int
+f (double a, double b)
+{
+ return (a > b) & (a < b);
+}
+
+/* { dg-final { scan-tree-dump-times " > " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " < " 1 "optimized" } } */
--
2.51.0
