On Mar 14, 5:53 pm, Bill Hart <goodwillh...@googlemail.com> wrote:
> This problem is quite difficult to deal with. I thought about it on
> the way home, and I don't want to have config.guess return:
>
> nocona-lahf-unknown-gnu-linux
>
> How does the 32 bit code decide if MMX is available etc? I suppose
> config.guess returns p4mmx. That's just nasty. Feature flags should be
> dealt with separately. I don't even really like passing flags to the
> yasm code because it means doctoring the yasm build system, which is
> already complicated enough. Hmm, how does it distinguish processors
> which support SSE in 32 bit mode? Surely it doesn't do p4mmxsse.
>
> If we could exclude all 64 bit models not having support for LAHF by
> having config.guess identify them as x86_64 only, i.e. not amd64,
> core2, nocona, etc, then they can just run with the default x86_64
> code.
>
> We need to remember to make all changes in fat.c as well as config.guess.
>
> Of course this doesn't help Brian much, who probably wants the core 2
> code to run on all 64 bit intel processors so that he doesn't need a
> separate build project for them. IIt may also slow those processors
> down (though who knows, really).
I had hoped it was not going to be an issue that we had to deal with
but the speed of the code is changed by using different instructions.
It goes from from 2.75 cycles/limb to 3.0 cycles per limb.
Brian
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