This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [patch 9/N][PA] convert to fma


On Thu, 11 Nov 2010, Richard Henderson wrote:

>  ;; Negating a multiply can be faked by adding zero in a fused multiply-add
>  ;; instruction.
> +;; ??? Only if we add -0.0 or can ignore the sign of zero.

Adding -0.0 can't be done with the fused multiply-add unless -0.0 is
already available in a floating register.  It would be better to just
condition the patterns on !flag_signed_zeros.

Dave
-- 
J. David Anglin                                  dave.anglin@nrc-cnrc.gc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6602)


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]