------- Comment #1 from dwarak dot rajagopal at amd dot com 2008-11-20 16:48
-------
1) -msse5 includes -mfma switch (because fma is a part of sse5 instructions).
So having "-msse5 -mfma" is same as having just "msse5", though you can just
have -fma (without -msse5).
2) "-mavx -msse5" => Yes. This would not make sense since no machine can run
this.
- Dwarak
(In reply to comment #0)
> Both Intel FMA and AMD SSE5 support FMA. For -mfma, which enables
> Intel FMA and is a dummy at the moment, or -msse5, we will
> generate FMA instructions for
>
> double f;
>
> void
> foo (double x, double y, double z)
> {
> f = x * y + z;
> }
>
> What FMA should "-mfma -msse5" generate? Also currently, with
> "-O2 -mavx -msse5", we generate
>
> foo:
> fmaddsd %xmm2, %xmm1, %xmm0, %xmm0
> vmovsd %xmm0, f(%rip)
> ret
>
> which won't run on any machines. For "-mfma -msse5" and
> "-mavx -msse5",
>
> 1. Should these combinations be allowed? If allowed,
> 2. Should the last option turn off the first one?
>
(In reply to comment #0)
> Both Intel FMA and AMD SSE5 support FMA. For -mfma, which enables
> Intel FMA and is a dummy at the moment, or -msse5, we will
> generate FMA instructions for
>
> double f;
>
> void
> foo (double x, double y, double z)
> {
> f = x * y + z;
> }
>
> What FMA should "-mfma -msse5" generate? Also currently, with
> "-O2 -mavx -msse5", we generate
>
> foo:
> fmaddsd %xmm2, %xmm1, %xmm0, %xmm0
> vmovsd %xmm0, f(%rip)
> ret
>
> which won't run on any machines. For "-mfma -msse5" and
> "-mavx -msse5",
>
> 1. Should these combinations be allowed? If allowed,
> 2. Should the last option turn off the first one?
>
--
dwarak dot rajagopal at amd dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |dwarak dot rajagopal at amd
| |dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38201
