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Re: [patch] Hookize SMALL_REGISTER_CLASSES


On Mon, May 3, 2010 at 9:54 PM, Jakub Jelinek <jakub@redhat.com> wrote:
>> Yes, I know. So what does that mean? Should I change this to always
>> return false for SCALAR_INT_MODE_P modes?
>
> Aren't
> ?AREG, DREG, CREG, BREG, SIREG, DIREG,
> ?AD_REGS, ? ? ? ? ? ? ? ? ? ? ?/* %eax/%edx for DImode */
> ?SSE_FIRST_REG,
> classes small though? ?Aren't we going to ICE frequently whenever x86-64
> code uses these classes say in inline asm?

We had this discussion one and a half year ago, too. The consensus
appeared to be that, yes, those classes are small, but there are
enough registers around to spill to for the register allocator. The
discussion focused mainly on xmm0, but the same applies to AREG in
modes wider than 32 bits (this is why I proposed only >32 bits modes
as not small). But I don't recall the details and I may not remember
correctly...

Ciao!
Steven


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