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RE: Why is x86_sahf_1 pattern disabled in x86_64?
- From: "Lu, Hongjiu" <hongjiu dot lu at intel dot com>
- To: "Uros Bizjak" <uros at kss-loka dot si>
- Cc: "Jan Hubicka" <jh at suse dot cz>, "Michel Lespinasse" <walken at zoy dot org>, <gcc at gcc dot gnu dot org>
- Date: Tue, 18 May 2004 08:08:22 -0700
- Subject: RE: Why is x86_sahf_1 pattern disabled in x86_64?
Please make sure TARGET_USE_SAHF is only enabled for specific CPUs.
H.J. Lu
Intel Corporation
> -----Original Message-----
> From: Uros Bizjak [mailto:uros@kss-loka.si]
> Sent: Tuesday, May 18, 2004 1:37 AM
> To: Lu, Hongjiu
> Cc: Jan Hubicka; Michel Lespinasse; gcc@gcc.gnu.org
> Subject: Re: Why is x86_sahf_1 pattern disabled in x86_64?
>
> H. J. Lu wrote:
>
> >>This is the current Intel's position:
> >>
> >>Intel has no plans to support SAHF/LAHF on current processors or
> >>future processors that include EM64T. Intel advises against using
> >>those instructions. If those instructions are to be generated, they
> >>should be under an architecture specific flag and not be included
> when the
> >>compiler is expected to be generating portable code.
> >>
> >>
> >>
> I guess that "x86_sahf_1" instruction should stay disabled for
> TARGET_64BIT. The same functionality is now implemented with test
> instruction if !TARGET_USE_SAHF.
>
> Thanks,
> Uros.