https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79726
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's also a general -ffast-math missed optimization to demote the double
add to a float one. If you write
double f(double x[]) {
float p = 1.0;
for (int i = 0; i < 16; i++)
p += (float)x[i];
return p;
}
the loop is vectorized in a way you expect.
Note such demotion can result in +-Inf where it didn't appear before for
example when x[0] is less than float -Inf "+ 1." and thus (float)x[0] is
not representable but (float)(x[0] + 1.) is.
Still "correct" vectorization should also be possible but is not yet
implemented.
