[Bug middle-end/79720] [5/6/7 Regression] complex division different at compile time / runtime

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79720

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #10)
> (In reply to Thomas Koenig from comment #7)
> > We also do a quite complex (sorry for the pun) and expensive
> > division routine, just in order not to lose any bits of precision.
> > If the compile-time simplification does not match that, it is
> > simply buggy.
> 
> If anything, I expect that the compile-time evaluation (using MPC) is more
> precise than what you get by chaining real add/sub/mul/div, even if that's a
> relatively expensive routine to reduce errors.

Yeah, exactly.  But then this is really NOTABUG.  The compile time evaluation
needs to be .5ulp precise, not emulate whatever precision issues the library
has.