[LLVMdev] RFC: X86InstrFormats.td Refactoring

[David Greene]

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.

                                                        -Dave