[clang] [HLSL] Implement HLSL Flat casting (excluding splat cases) (PR #118842)

[Sarah Spall via cfe-commits]

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@@ -6358,3 +6359,81 @@ RValue CodeGenFunction::EmitPseudoObjectRValue(const PseudoObjectExpr *E,
 LValue CodeGenFunction::EmitPseudoObjectLValue(const PseudoObjectExpr *E) {
   return emitPseudoObjectExpr(*this, E, true, AggValueSlot::ignored()).LV;
 }
+
+void CodeGenFunction::FlattenAccessAndType(
+    Address Addr, QualType AddrType,
+    SmallVectorImpl<std::pair<Address, llvm::Value *>> &AccessList,
+    SmallVectorImpl<QualType> &FlatTypes) {
+  // WorkList is list of type we are processing + the Index List to access
+  // the field of that type in Addr for use in a GEP
+  llvm::SmallVector<std::pair<QualType, llvm::SmallVector<llvm::Value *, 4>>,
+                    16>
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spall wrote:

The 16 was borrowed from 'BuildFlattenedTypeList' in SemaHLSL.cpp

https://github.com/llvm/llvm-project/pull/118842