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Re: [PATCH] Add FMA_EXPR, un-cse multiplications before expansion
On Thu, 21 Oct 2010, Geert Bosch wrote:
> On Oct 21, 2010, at 18:14, Joseph S. Myers wrote:
> > (It might make sense to add -ffp-contract={on,off,fast} at an early stage,
> > with "off" disabling the GIMPLE-level FMA formation. Implementation of
> > the pragma, and distinguishing "on" (C99-conforming, contracting
> > restricted to source expressions) from "fast" (no such restriction on
> > contracting, the present state) could follow later.)
>
> Yes, that would be great. It is essential for some numerical code to
> avoid automatic contractions. As such code is typically library code
> that is compiled separately, it would be acceptable to have a compile-time
> option for now.
>
> Can't wait for pragma STDC FP_CONTRACT implementation, as well as working
> fma{,f,l} implementations! :-)
You have working fma functions right now in git glibc, except for:
* fmal for IBM long double (double double)
* targets without exceptions and rounding mode support (generally using
software floating point), where I suspect a pure soft-fp implementation
may be best.
--
Joseph S. Myers
joseph@codesourcery.com