[clang] [HLSL] Add support for elementwise and aggregate splat casting struct types with bitfields (PR #161263)

[Helena Kotas via cfe-commits]

================
@@ -2392,39 +2392,36 @@ bool CodeGenFunction::ShouldNullCheckClassCastValue(const CastExpr *CE) {
 }
 
 // RHS is an aggregate type
-static Value *EmitHLSLElementwiseCast(CodeGenFunction &CGF, Address RHSVal,
-                                      QualType RHSTy, QualType LHSTy,
-                                      SourceLocation Loc) {
-  SmallVector<std::pair<Address, llvm::Value *>, 16> LoadGEPList;
-  SmallVector<QualType, 16> SrcTypes; // Flattened type
-  CGF.FlattenAccessAndType(RHSVal, RHSTy, LoadGEPList, SrcTypes);
-  // LHS is either a vector or a builtin?
+static Value *EmitHLSLElementwiseCast(CodeGenFunction &CGF, LValue SrcVal,
+                                      QualType DestTy, SourceLocation Loc) {
+  SmallVector<LValue, 16> LoadList;
+  CGF.FlattenAccessAndTypeLValue(SrcVal, LoadList);
+  // Dest is either a vector or a builtin?
   // if its a vector create a temp alloca to store into and return that
-  if (auto *VecTy = LHSTy->getAs<VectorType>()) {
-    assert(SrcTypes.size() >= VecTy->getNumElements() &&
+  if (auto *VecTy = DestTy->getAs<VectorType>()) {
+    assert(LoadList.size() >= VecTy->getNumElements() &&
            "Flattened type on RHS must have more elements than vector on LHS.");
----------------
hekota wrote:

```suggestion
           "Flattened type on RHS must have the same number or more elements than vector on LHS.");
```

https://github.com/llvm/llvm-project/pull/161263