[Bug middle-end/91250] Missed optimization: is not used vfnmsub213ss

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91250

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Target|                            |x86_64-*-*, i?86-*-*
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2019-07-24
          Component|tree-optimization           |middle-end
            Version|unknown                     |10.0
     Ever confirmed|0                           |1

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  We're canonicalizing this as

  _1 = .FMA (b_3(D), a_4(D), c_5(D));
  _6 = -_1;

which expansion doesn't handle.  It works without -ffast-math.

When trying to fix also consider

float foo(float a, float b, float c)
{
    return -(a * b + c);
}