[llvm] [DirectX] Update `DXILRootSignature` to not run analysis after data has been parsed (PR #146783)

[Sarah Spall via llvm-commits]

================
@@ -33,17 +35,47 @@ enum class RootSignatureElementKind {
   CBV = 5,
   DescriptorTable = 6,
 };
+
+class RootSignatureBindingInfo {
+private:
+  SmallDenseMap<const Function *, mcdxbc::RootSignatureDesc> FuncToRsMap;
+
+public:
+  using iterator =
+      SmallDenseMap<const Function *, mcdxbc::RootSignatureDesc>::iterator;
+
+  RootSignatureBindingInfo() = default;
+  RootSignatureBindingInfo(
+      SmallDenseMap<const Function *, mcdxbc::RootSignatureDesc> Map)
+      : FuncToRsMap(Map) {};
+
+  iterator find(const Function *F) { return FuncToRsMap.find(F); }
+
+  iterator end() { return FuncToRsMap.end(); }
+
+  std::optional<mcdxbc::RootSignatureDesc>
+  getDescForFunction(const Function *F) {
+    const auto FuncRs = find(F);
+    if (FuncRs == end())
+      return std::nullopt;
+
+    return FuncRs->second;
+  }
+};
+
 class RootSignatureAnalysis : public AnalysisInfoMixin<RootSignatureAnalysis> {
   friend AnalysisInfoMixin<RootSignatureAnalysis>;
   static AnalysisKey Key;
 
 public:
   RootSignatureAnalysis() = default;
 
-  using Result = SmallDenseMap<const Function *, mcdxbc::RootSignatureDesc>;
+  using Result = RootSignatureBindingInfo;
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spall wrote:

Why create a type alias here? Why not just put 'RootSignatureBindingInfo' inline? It looks like its only used one place.

https://github.com/llvm/llvm-project/pull/146783