https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127791
Bug ID: 127791
Summary: Separate IEEE alternate exception handling from
-ftrapping-math
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
CC: ebotcazou at gcc dot gnu.org, jsm28 at gcc dot gnu.org
Target Milestone: ---
When using -fnon-call-exceptions together with -ftrapping-math (the default),
any operation with a possible IEEE exception will cause EH code to be emitted
regardless of whether alternate IEEE exception handling is enabled and thus
an exception would be delivered. The -fnon-call-exceptions + -ftrapping-math
combination does _not_ raise exceptions when just IEEE flags are set.
Testcase:
double z;
double foo (double x, double y)
{
try
{
z = x + y;
return z;
}
catch (...)
{
return 0.;
}
}
Proposal: -ftrapping-math[={standard,trap,[no-]trap-<exception-kind>}]
with -ftrapping-math aliasing to -ftrapping-math=standard and in that
mode -fnon-call-exceptions should not consider IEEE exceptions to raise
exceptions.
Ada seems to do
/* Assume that FP operations can trap if S'Machine_Overflow is true,
but don't override the user if not. */
if (Machine_Overflows_On_Target)
flag_trapping_math = 1;
else if (!OPTION_SET_P (flag_trapping_math))
flag_trapping_math = 0;
but I'm not sure if it requires/enables alternate exception handling?
