[llvm] [AMDGPU] Enable CSE in the GlobalISel post-legalizer combiner (PR #217258)

[Matt Arsenault via llvm-commits]

================
@@ -8240,6 +8226,17 @@ bool AMDGPULegalizerInfo::legalizeIntrinsic(LegalizerHelper &Helper,
 
       Register Def = MI.getOperand(1).getReg();
       Register Use = MI.getOperand(3).getReg();
+      const TargetRegisterClass *WaveMaskRC = TRI->getWaveMaskRegClass();
----------------
arsenm wrote:

I'm not sure why this case needs all of this machinery, new instructions are being created?

https://github.com/llvm/llvm-project/pull/217258