https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103605
--- Comment #3 from pc at gcc dot gnu.org ---
Here's a test which exercises all three options:
- fmin () (glibc 2.28)
- xsmincdp (ironically, via __builtin_vsx_xsmindp)
- xsmindp (via asm)
--
$ cat xsmindp.c
#include <stdio.h>
#include <math.h>
int main (int argc) {
double d0 = argc, d1 = argc+1;
double rf, rb, rx;
printf ("(src1, src2): fmin b-in asm\n");
rf = fmin (d0, d1);
rb = __builtin_vsx_xsmindp (d0, d1);
asm ("xsmindp %0,%1,%2" : "=wa" (rx) : "wa" (d0), "wa" (d1));
printf ("(+3.0, +3.0): %+3.1f %+3.1f %+3.1f\n", rf, rb, rx);
d1 = NAN;
rf = fmin (d0, d1);
rb = __builtin_vsx_xsmindp (d0, d1);
asm ("xsmindp %0,%1,%2" : "=wa" (rx) : "wa" (d0), "wa" (d1));
printf ("(+3.0, NAN): %+3.1f %+3.1f %+3.1f\n", rf, rb, rx);
rf = fmin (d1, d0);
rb = __builtin_vsx_xsmindp (d1, d0);
asm ("xsmindp %0,%1,%2" : "=wa" (rx) : "wa" (d1), "wa" (d0));
printf ("( NAN, +3.0): %+3.1f %+3.1f %+3.1f\n", rf, rb, rx);
d0 = NAN;
rf = fmin (d0, d1);
rb = __builtin_vsx_xsmindp (d0, d1);
asm ("xsmindp %0,%1,%2" : "=wa" (rx) : "wa" (d0), "wa" (d1));
printf ("( NAN, NAN): %+3.1f %+3.1f %+3.1f\n", rf, rb, rx);
d0 = argc, d1 = argc+1;
d1 = __builtin_nans ("0");
rf = fmin (d0, d1);
rb = __builtin_vsx_xsmindp (d0, d1);
asm ("xsmindp %0,%1,%2" : "=wa" (rx) : "wa" (d0), "wa" (d1));
printf ("(+3.0, SNAN): %+3.1f %+3.1f %+3.1f\n", rf, rb, rx);
rf = fmin (d1, d0);
rb = __builtin_vsx_xsmindp (d1, d0);
asm ("xsmindp %0,%1,%2" : "=wa" (rx) : "wa" (d1), "wa" (d0));
printf ("(SNAN, +3.0): %+3.1f %+3.1f %+3.1f\n", rf, rb, rx);
d0 = __builtin_nans ("0");
rf = fmin (d0, d1);
rb = __builtin_vsx_xsmindp (d0, d1);
asm ("xsmindp %0,%1,%2" : "=wa" (rx) : "wa" (d0), "wa" (d1));
printf ("(SNAN, SNAN): %+3.1f %+3.1f %+3.1f\n", rf, rb, rx);
return 0;
}
$ /opt/gcc-nightly/trunk/bin/gcc --version
gcc (GCC) 12.0.1 20220426 (experimental) [remotes/origin/HEAD
r12-8269-gcd4acb8cd9]
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ /opt/gcc-nightly/trunk/bin/gcc -fsignaling-nans -D_WANT_SNAN -o xsmindp
xsmindp.c -O0 -lm && ./xsmindp
(src1, src2): fmin b-in asm
(+3.0, +3.0): +1.0 +1.0 +1.0
(+3.0, NAN): +1.0 +nan +1.0
( NAN, +3.0): +1.0 +1.0 +1.0
( NAN, NAN): +nan +nan +nan
(+3.0, SNAN): +nan +nan +nan
(SNAN, +3.0): +nan +1.0 +nan
(SNAN, SNAN): +nan +nan +nan
$ /opt/gcc-nightly/trunk/bin/gcc -fsignaling-nans -D_WANT_SNAN -o xsmindp
xsmindp.c -O3 -mcpu=power10 -lm && ./xsmindp
(src1, src2): fmin b-in asm
(+3.0, +3.0): +1.0 +1.0 +1.0
(+3.0, NAN): +1.0 +nan +1.0
( NAN, +3.0): +1.0 +nan +1.0
( NAN, NAN): +nan +nan +nan
(+3.0, SNAN): +nan +nan +nan
(SNAN, +3.0): +nan +1.0 +nan
(SNAN, SNAN): +nan +nan +nan
$ /opt/gcc-nightly/trunk/bin/gcc -fsignaling-nans -D_WANT_SNAN -o xsmindp
xsmindp.c -O3 -mcpu=power10 -lm -ffast-math && ./xsmindp
(src1, src2): fmin b-in asm
(+3.0, +3.0): +1.0 +1.0 +1.0
(+3.0, NAN): +nan +nan +1.0
( NAN, +3.0): +nan +nan +1.0
( NAN, NAN): +nan +nan +nan
(+3.0, SNAN): +nan +nan +nan
(SNAN, +3.0): +nan +nan +nan
(SNAN, SNAN): +nan +nan +nan
--
Without -ffast-math, the current semantics of fmin() match those of xsmindp.
With -ffast-math, the current semantics of fmin() match those of xsmincdp.
