[Bug tree-optimization/107647] [12/13 Regression] GCC 12.2.0 may produce FMAs even with -ffp-contract=off

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107647

--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ah, we only fold those to internal functions _after_ vectorization.  SLP will
see

double x[2];

void foo (double a, double b, double * __restrict c)
{
  x[0] = __builtin_fma (a, b, c[0]);
  x[1] = __builtin_fma (a, b, -c[1]);
}

as two calls to FMA and thus fail to optimially vectorize it.