https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128315
Bug ID: 128315
Summary: wrong code at -O1 and above with -frounding-math: sin
and cos of +Inf after feclearexcept leave FE_INVALID
clear
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: kyuwoncho18 at gmail dot com
Target Milestone: ---
Target: x86_64-pc-linux-gnu
#include <fenv.h>
#include <math.h>
#include <stdio.h>
volatile double v = INFINITY;
volatile double s, c;
int main(void)
{
double x = v;
feclearexcept(FE_ALL_EXCEPT);
s = sin(x);
c = cos(x);
printf("%d\n", fetestexcept(FE_INVALID) != 0);
return 0;
}
godbolt: https://godbolt.org/z/srj5znrGP
sin(+Inf) and cos(+Inf) raise FE_INVALID (C17 F.10.1.5, F.10.1.6), so with
-ftrapping-math -frounding-math -lm the program must print 1, as it does at
-O0, with -O2 -fdisable-tree-sincos, and at -O2 when the cos call is removed.
At -O1, -O2, -O3 and -Os it prints 0, and the -fdump-tree-sincos dump shows the
__builtin_cexpi call that replaces sin and cos placed before the feclearexcept
call.
