[llvm] [AMDGPU] Remove DPP DecoderNamespaces. NFC. (PR #82491)

[Ivan Kosarev via llvm-commits]

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@@ -222,6 +222,8 @@ class VOPCInstAlias <VOP3_Pseudo ps, Instruction inst,
 
   let AsmVariantName = AMDGPUAsmVariants.Default;
   let SubtargetPredicate = AssemblerPredicate;
+
+  string DecoderNamespace; // dummy
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kosarev wrote:

> It is quite a common pattern in our backend.

Oh, didn't notice that. Nevermind then. (But I still suspect improving is possible, so for example when `VOP2_Real`  takes `SIEncodingFamily.GFX9`, we know it's `DecoderNamespace = "GFX9"`.)

https://github.com/llvm/llvm-project/pull/82491