[llvm] AMDGPU: Move spill pseudo special case out of adjustAllocatableRegClass (PR #158246)

[Christudasan Devadasan via llvm-commits]

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@@ -6012,10 +6011,9 @@ const TargetRegisterClass *SIInstrInfo::getRegClass(const MCInstrDesc &TID,
   if (OpNum >= TID.getNumOperands())
     return nullptr;
   auto RegClass = TID.operands()[OpNum].RegClass;
-  if (TID.getOpcode() == AMDGPU::AV_MOV_B64_IMM_PSEUDO) {
-    // Special pseudos have no alignment requirement
+  // Special pseudos have no alignment requirement
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cdevadas wrote:

```suggestion
  // Special pseudos have no alignment requirement.
```

https://github.com/llvm/llvm-project/pull/158246