https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77568
--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #6)
> Note that all "bad" transforms can be done by users on the source level
> already. So the _only_ proper solution is to handle the situation in the
> passes that now refuse to do an important optimization (like combine).
For an example take:
float f(float x, float y, float z, int a)
{
float t = y * z;
if (a > 100)
x += t;
else
x -= t;
return x;
}
Note we are able to optimize the follow (use -O2) to use fmadds:
float f(float x, float y, float z, int a)
{
float t = y * z;
x += t;
x -= t;
return x;
}
---- CUT ----
and it is optimized in the widening_mul pass (which includes the FMA
optimization pass).
