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

[Ana Mihajlovic via llvm-commits]

mihajlovicana 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.

okay, will try and migrate that there 

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