[llvm] [DirectX] Scalarize `extractelement` with dynamic index (PR #141676)

[Deric C. via llvm-commits]

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@@ -173,6 +171,38 @@ bool DataScalarizerVisitor::visitStoreInst(StoreInst &SI) {
   return false;
 }
 
+bool DataScalarizerVisitor::visitExtractElementInst(ExtractElementInst &EEI) {
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Icohedron wrote:

```suggestion
bool DataScalarizerVisitor::visitExtractElementInst(ExtractElementInst &EEI) {
  // Shader Model 6.9 and above supports dynamic vector indexing and therefore
  // does not need to be scalarized
  VersionTuple ShaderModelVersion =
      EEI.getModule()->getTargetTriple().getOSVersion();
  if (ShaderModelVersion >= VersionTuple(6, 9))
    return false;
    
```
Should I add a shader model check here for 6.9? SM 6.9 isn't currently a supported target. Perhaps a TODO comment instead?

https://github.com/llvm/llvm-project/pull/141676