'inf/inf' should raise an invalid operation exception at runtime. So it should not be folded during compilation unless -fno-trapping-math is used.
gcc/ PR middle-end/95115 * fold-const.cc (const_binop): Do not fold "inf/inf". gcc/testsuite * gcc.dg/pr95115.c: New test. --- gcc/fold-const.cc | 8 ++++++++ gcc/testsuite/gcc.dg/pr95115.c | 25 +++++++++++++++++++++++++ 2 files changed, 33 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/pr95115.c diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc index fd9c6352d4f..0e99d5a2e3d 100644 --- a/gcc/fold-const.cc +++ b/gcc/fold-const.cc @@ -1283,6 +1283,14 @@ const_binop (enum tree_code code, tree arg1, tree arg2) && (flag_trapping_math || ! MODE_HAS_INFINITIES (mode))) return NULL_TREE; + /* Don't perform "inf/inf", because it would raise an invalid + operation exception (IEEE 754 section 7.2 clause d). */ + if (code == RDIV_EXPR + && flag_trapping_math + && REAL_VALUE_ISINF (d1) + && REAL_VALUE_ISINF (d2)) + return NULL_TREE; + /* If either operand is a NaN, just return it. Otherwise, set up for floating-point trap; we return an overflow. */ if (REAL_VALUE_ISNAN (d1)) diff --git a/gcc/testsuite/gcc.dg/pr95115.c b/gcc/testsuite/gcc.dg/pr95115.c new file mode 100644 index 00000000000..46a95dfb698 --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr95115.c @@ -0,0 +1,25 @@ +/* { dg-do run } */ +/* { dg-options "-O2 -ftrapping-math" } */ +/* { dg-add-options ieee } */ +/* { dg-require-effective-target fenv_exceptions } */ + +#include <fenv.h> +#include <stdlib.h> + +double +x (void) +{ + double d = __builtin_inf (); + return d / d; +} + +int +main (void) +{ + double r = x (); + if (!__builtin_isnan (r)) + abort (); + if (!fetestexcept (FE_INVALID)) + abort (); + exit (0); +} -- 2.35.1