On Mon, 2023-11-13 at 07:09 +0000, Tamar Christina wrote:
> In the case of e.g. longaarch64 It looks like the target actually has an
> fcopysign
> Instruction, so wouldn't this rewriting by simplify-rtx be a de-optimization?
Yes it seems a de-optimization on LoongArch. For this micro-benchmark:
int main()
{
#pragma GCC unroll(100)
for (int i = 0; i < 1000000000; i++) {
float x = -1, a = 1.23456;
asm volatile ("":"+f"(a));
#ifdef DISALLOW_COPYSIGN_OPTIMIZATION
asm("":"+f"(x));
#endif
a = __builtin_copysignf(a, x);
asm(""::"f"(a));
}
}
If DISALLOW_COPYSIGN_OPTIMIZATION is defined, the result is faster for
0.23 seconds.
I'll submit another patch to disable this.
--
Xi Ruoyao <xry...@xry111.site>
School of Aerospace Science and Technology, Xidian University
