[llvm] [AMDGPU] Create AMDGPUMnemonicAlias tablegen class (PR #89288)

[Joe Nash via llvm-commits]

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@@ -143,14 +143,14 @@ multiclass VOP1Inst <string opName, VOPProfile P,
       def _e64_dpp  : VOP3_DPP_Pseudo <opName, P>;
   } // End SubtargetPredicate = isGFX11Plus
 
-  def : MnemonicAlias<opName#"_e32", opName>, LetDummies;
-  def : MnemonicAlias<opName#"_e64", opName>, LetDummies;
+  def : LetDummies, AMDGPUMnemonicAlias<opName#"_e32", opName>;
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Sisyph wrote:

There are various fields set as outer lets such as isReMaterializable, mayRaiseFPException etc. set on VOP1Inst. I briefly tried to add LetDummies to AMDGPUMnemonicInst, but it was not trivial.

https://github.com/llvm/llvm-project/pull/89288