http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55760
--- Comment #5 from vincenzo Innocente <vincenzo.innocente at cern dot ch>
2013-01-08 15:29:18 UTC ---
we just got "hit" by this great type of code (copysign is unknown to
scientists)
most probably gcc could optimize it for -Ofast to return copysignf(1.f,x); (x/x
is optimized in 1)
cat one.cc;c++ -Ofast -mrecip -S one.cc; cat one.s
#include<cmath>
int one(float x) {
return x/std::abs(x);
}
.text
.align 4,0x90
.globl __Z3onef
__Z3onef:
LFB86:
movss LC0(%rip), %xmm2
andps %xmm0, %xmm2
rcpss %xmm2, %xmm1
mulss %xmm1, %xmm2
mulss %xmm1, %xmm2
addss %xmm1, %xmm1
subss %xmm2, %xmm1
mulss %xmm0, %xmm1
cvttss2si %xmm1, %eax
ret
