[LLVMdev] RFC: X86InstrFormats.td Refactoring

[Dan Gohman]

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