[LLVMdev] RFC: X86InstrFormats.td Refactoring
Dan Gohman
gohman at apple.com
Tue Mar 31 13:35:03 PDT 2009
On Mar 31, 2009, at 1:01 PM, David Greene wrote:
> On Tuesday 31 March 2009 13:53, Dan Gohman wrote:
>
>>> class SSI<bits<8> o, Format F, dag outs, dag ins, string asm,
>>> list<dag> pattern>
>>>
>>> : SSIb<o, F, outs, ins, asm, pattern>, Requires<HasSSE1>;
>>
>> Is this just factoring out the ", XS" part? As presented, it looks
>> like
>> this change would introduce more redundancy that it would eliminate.
>
> It's factoring out XS and the other encoding bits, but the real goal
> is to
> separate out the Requires<> predicates. Doing this will help AVX
> quite a bit
> as we'd like to build AVX format classes off of the existing ones.
> Most of
> AVX simply recodes existing SSE instructions using the VEX prefix so
> it makes
> sense to use the infrastructure already there. The problem is the
> Requires<>
> parts are all inappropriate so we need to factor them out.
Ok. I have no real objection to this. I look
forward to seeing how it helps in the context of
the rest of the changes :-).
Dan
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