[Bug tree-optimization/88713] Vectorized code slow vs. flang

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88713

--- Comment #50 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Thomas Koenig from comment #49)
> (In reply to Uroš Bizjak from comment #48)
> > (In reply to rguenther@suse.de from comment #47)
> > > >But why don't we generate sqrtps for vector sqrtf?
> > > 
> > > That's the default for - mrecip back in time we benchmarked it and scalar
> > > recip miscompares sth.
> > 
> > It was polyhedron benchmark, in one benchmark, the index was calculated from
> > square root, and that was too sensitive for 2 ULP difference.
> 
> Argh.  Sacrificing performance for the sake of bugware...

The details are in [1] and all the drama is documented in PR32352.

[1] https://gcc.gnu.org/ml/gcc-patches/2007-06/msg01044.html