[llvm] [DirectX][NFC] Refactor `DXILRootSignature` to follow the same pattern as other analysis (PR #146783)

[via llvm-commits]

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@@ -636,13 +635,14 @@ PreservedAnalyses RootSignatureAnalysisPrinter::run(Module &M,
 
 //===----------------------------------------------------------------------===//
 bool RootSignatureAnalysisWrapper::runOnModule(Module &M) {
-  FuncToRsMap = analyzeModule(M);
+  FuncToRsMap = std::make_unique<RootSignatureBindingInfo>(
+      RootSignatureBindingInfo(analyzeModule(M)));
   return false;
 }
 
 void RootSignatureAnalysisWrapper::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesAll();
-  AU.addRequired<DXILMetadataAnalysisWrapperPass>();
+  AU.addPreserved<DXILMetadataAnalysisWrapperPass>();
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joaosaffran wrote:

Yes, changing from `addRequired` to `addPreserved` means we will not run the analysis, we will just use existing analysis results. Since that Analysis already run in the pipeline, there is no actual logic change here.

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