[llvm] [AMDGPU][GlobalISel] Expand SGPR S1 exts into G_SELECT (PR #68858)

[Jay Foad via llvm-commits]

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@@ -2609,7 +2637,7 @@ void AMDGPURegisterBankInfo::applyMappingImpl(
         SrcBank->getID() == AMDGPU::SGPRRegBankID;
 
       // TODO: Should s16 select be legal?
-      LLT SelType = UseSel64 ? LLT::scalar(64) : LLT::scalar(32);
+      LLT SelType = UseSel64 ? LLT::scalar(64) : S32;
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jayfoad wrote:

```suggestion
      LLT SelType = UseSel64 ? S64 : S32;
```

https://github.com/llvm/llvm-project/pull/68858