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Re: Darwin problem (Re: PATCH: Select the default x86 arch/cpu based on target)


On Fri, Feb 26, 2010 at 06:00:58AM -0800, H.J. Lu wrote:
> On Fri, Feb 26, 2010 at 5:45 AM, Jason Merrill <jason@redhat.com> wrote:
> > On 02/25/2010 09:56 PM, H.J. Lu wrote:
> >>
> >> 1. in i386/darwin.h, there are
> >>
> >> /* For darwin we want to target specific processor features as a minimum,
> >> ? ?but these unfortunately don't correspond to a specific processor. ?*/
> >> #undef TARGET_SUBTARGET32_ISA_DEFAULT
> >> #define TARGET_SUBTARGET32_ISA_DEFAULT (OPTION_MASK_ISA_MMX ? ? ? ? ? ? \
> >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? | OPTION_MASK_ISA_SSE ? ? ? ? ? \
> >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? | OPTION_MASK_ISA_SSE2)
> >
> > Is this still needed? ?Users configuring for Darwin should get that minimum
> > functionality now because of your patch.
> >
> 
> ".../configure i686-darwin" will pass -march=pentiumpro to cc1 and
> ix86_arch_specified will be set to 1. We want ix86_arch_specified
> to be 0 in this case. A patch is posted at
> 
> http://gcc.gnu.org/ml/gcc-patches/2010-02/msg01111.html

That patch is horribly ugly, leaking default_* to what users can use
in -march= they pass the compiler is a terrible idea.
I'd say much better would be for i[3456] target_cpu not to do
--with-arch=i[3456] by default on darwin, unless --with-arch= has been used
explicitly.

	Jakub


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