[llvm] [DirectX] Simplify and correct the flattening of GEPs in DXILFlattenArrays (PR #146173)

[Finn Plummer via llvm-commits]

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@@ -40,18 +41,19 @@ class DXILFlattenArraysLegacy : public ModulePass {
   static char ID; // Pass identification.
 };
 
-struct GEPData {
-  ArrayType *ParentArrayType;
-  Value *ParentOperand;
-  SmallVector<Value *> Indices;
-  SmallVector<uint64_t> Dims;
-  bool AllIndicesAreConstInt;
+struct GEPInfo {
+  ArrayType *RootFlattenedArrayType;
+  Value *RootPointerOperand;
+  SmallMapVector<Value *, APInt, 4> VariableOffsets;
+  APInt ConstantOffset;
 };
 
 class DXILFlattenArraysVisitor
     : public InstVisitor<DXILFlattenArraysVisitor, bool> {
 public:
-  DXILFlattenArraysVisitor() {}
+  DXILFlattenArraysVisitor(
+      DenseMap<GlobalVariable *, GlobalVariable *> &GlobalMap)
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inbelic wrote:

nit: Can we use `SmallDenseMap` here (and elsewhere)?

https://github.com/llvm/llvm-project/pull/146173