[llvm] [AMDGPU] Merge two V_CNDMASK instructions into V_DUAL_CNDMASK (PR #135007)

[Jay Foad via llvm-commits]

jayfoad wrote:

> > > for using vop2 instead of vop3 format
> > 
> > 
> > Normally this kind of shrinking would be done in SIShrinkInstructions. Is there a reason you can't do it there?
> 
> I wasn't sure if that would be proper because I am changing not only v_cndmask but also cmp instructions, but correct me if i'm wrong

I think it is OK to do it in SIShrinkInstructions. It does not have stricter rules than SIFoldOperands.

https://github.com/llvm/llvm-project/pull/135007