https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128304
Bug ID: 128304
Summary: [16/17 Regression] wrong code for _Complex float d[i]
-= x[i] * y[i] at -O3 -ffast-math -march=armv8.3-a
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: yuki.tanaka at defaultcase dot de
Target Milestone: ---
__attribute__((noipa)) void a(_Complex float *__restrict d, _Complex float *x,
_Complex float *y, int n)
{
for (int i = 0; i < n; i++)
d[i] -= x[i] * y[i];
}
int main(void)
{
_Complex float x[1] = { 1 + 2i };
_Complex float y[1] = { 2 + 3i };
_Complex float d[1] = { 100 + 50i };
a(d, x, y, 1);
if (__real__ d[0] != 104 || __imag__ d[0] != 43)
__builtin_abort();
return 0;
}
ASM generation compiler returned: 0
Execution build compiler returned: 0
Program returned: 134
Program terminated with signal SIGABRT (6)
(100 + 50i) - (1 + 2i) * (2 + 3i) is 104 + 43i, so d[0] must be 104 + 43i.
Instead d[0] is something else and main aborts. This happens with -O3
-ffast-math (also -Ofast) and -march=armv8.3-a.
Compiler Explorer:
https://godbolt.org/z/W1EhjWGq3
