[NFC][HLSL] Move Sema work from ParseMicrosoftRootSignatureAttributeArgs (#143184)

This separates semantic analysis from parsing by moving `RootSignatureDecl` creation, scope storage, and lookup logic into
`SemaHLSL`.

For more context see:
https://github.com/llvm/llvm-project/issues/142834.

- Define `ActOnStartRootSignatureDecl` and `ActOnFinishRootSignatureDecl` on `SemaHLSL`
- NFC so no test changes.

Resolves: https://github.com/llvm/llvm-project/issues/142834

---------

Co-authored-by: Aaron Ballman <aaron@aaronballman.com>

clang/include/clang/Parse/Parser.h

@@ -3598,7 +3598,7 @@ private:
   /// keyword.
   bool isClassCompatibleKeyword(Token Tok) const;
 
-  void ParseMicrosoftRootSignatureAttributeArgs(ParsedAttributes &Attrs);
+  void ParseHLSLRootSignatureAttributeArgs(ParsedAttributes &Attrs);
 
   ///@}
 

clang/include/clang/Sema/SemaHLSL.h

@@ -119,6 +119,19 @@ public:
                                        bool IsCompAssign);
   void emitLogicalOperatorFixIt(Expr *LHS, Expr *RHS, BinaryOperatorKind Opc);
 
+  /// Computes the unique Root Signature identifier from the given signature,
+  /// then lookup if there is a previousy created Root Signature decl.
+  ///
+  /// Returns the identifier and if it was found
+  std::pair<IdentifierInfo *, bool>
+  ActOnStartRootSignatureDecl(StringRef Signature);
+
+  /// Creates the Root Signature decl of the parsed Root Signature elements
+  /// onto the AST and push it onto current Scope
+  void ActOnFinishRootSignatureDecl(
+      SourceLocation Loc, IdentifierInfo *DeclIdent,
+      SmallVector<llvm::hlsl::rootsig::RootElement> &Elements);
+
   void handleRootSignatureAttr(Decl *D, const ParsedAttr &AL);
   void handleNumThreadsAttr(Decl *D, const ParsedAttr &AL);
   void handleWaveSizeAttr(Decl *D, const ParsedAttr &AL);

clang/lib/Parse/ParseDeclCXX.cpp

@@ -29,6 +29,7 @@
 #include "clang/Sema/ParsedTemplate.h"
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/SemaCodeCompletion.h"
+#include "clang/Sema/SemaHLSL.h"
 #include "llvm/Support/TimeProfiler.h"
 #include <optional>
 
@@ -4903,7 +4904,7 @@ void Parser::ParseMicrosoftUuidAttributeArgs(ParsedAttributes &Attrs) {
   }
 }
 
-void Parser::ParseMicrosoftRootSignatureAttributeArgs(ParsedAttributes &Attrs) {
+void Parser::ParseHLSLRootSignatureAttributeArgs(ParsedAttributes &Attrs) {
   assert(Tok.is(tok::identifier) &&
          "Expected an identifier to denote which MS attribute to consider");
   IdentifierInfo *RootSignatureIdent = Tok.getIdentifierInfo();
@@ -4945,18 +4946,14 @@ void Parser::ParseMicrosoftRootSignatureAttributeArgs(ParsedAttributes &Attrs) {
 
   // Construct our identifier
   StringRef Signature = StrLiteral.value()->getString();
-  auto Hash = llvm::hash_value(Signature);
-  std::string IdStr = "__hlsl_rootsig_decl_" + std::to_string(Hash);
-  IdentifierInfo *DeclIdent = &(Actions.getASTContext().Idents.get(IdStr));
-
-  LookupResult R(Actions, DeclIdent, SourceLocation(),
-                 Sema::LookupOrdinaryName);
-  // Check if we have already found a decl of the same name, if we haven't
-  // then parse the root signature string and construct the in-memory elements
-  if (!Actions.LookupQualifiedName(R, Actions.CurContext)) {
+  auto [DeclIdent, Found] =
+      Actions.HLSL().ActOnStartRootSignatureDecl(Signature);
+  // If we haven't found an already defined DeclIdent then parse the root
+  // signature string and construct the in-memory elements
+  if (!Found) {
+    // Offset location 1 to account for '"'
     SourceLocation SignatureLoc =
-        StrLiteral.value()->getExprLoc().getLocWithOffset(
-            1); // offset 1 for '"'
+        StrLiteral.value()->getExprLoc().getLocWithOffset(1);
     // Invoke the root signature parser to construct the in-memory constructs
     hlsl::RootSignatureLexer Lexer(Signature, SignatureLoc);
     SmallVector<llvm::hlsl::rootsig::RootElement> RootElements;
@@ -4966,12 +4963,9 @@ void Parser::ParseMicrosoftRootSignatureAttributeArgs(ParsedAttributes &Attrs) {
       return;
     }
 
-    // Create the Root Signature
-    auto *SignatureDecl = HLSLRootSignatureDecl::Create(
-        Actions.getASTContext(), /*DeclContext=*/Actions.CurContext,
-        RootSignatureLoc, DeclIdent, RootElements);
-    SignatureDecl->setImplicit();
-    Actions.PushOnScopeChains(SignatureDecl, getCurScope());
+    // Construct the declaration.
+    Actions.HLSL().ActOnFinishRootSignatureDecl(RootSignatureLoc, DeclIdent,
+                                                RootElements);
   }
 
   // Create the arg for the ParsedAttr
@@ -5014,7 +5008,7 @@ void Parser::ParseMicrosoftAttributes(ParsedAttributes &Attrs) {
       if (Tok.getIdentifierInfo()->getName() == "uuid")
         ParseMicrosoftUuidAttributeArgs(Attrs);
       else if (Tok.getIdentifierInfo()->getName() == "RootSignature")
-        ParseMicrosoftRootSignatureAttributeArgs(Attrs);
+        ParseHLSLRootSignatureAttributeArgs(Attrs);
       else {
         IdentifierInfo *II = Tok.getIdentifierInfo();
         SourceLocation NameLoc = Tok.getLocation();

clang/lib/Sema/SemaDecl.cpp

@@ -62,6 +62,7 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/Frontend/HLSL/HLSLRootSignature.h"
 #include "llvm/Support/SaveAndRestore.h"
 #include "llvm/TargetParser/Triple.h"
 #include <algorithm>

clang/lib/Sema/SemaHLSL.cpp

@@ -978,6 +978,31 @@ void SemaHLSL::emitLogicalOperatorFixIt(Expr *LHS, Expr *RHS,
       << NewFnName << FixItHint::CreateReplacement(FullRange, OS.str());
 }
 
+std::pair<IdentifierInfo *, bool>
+SemaHLSL::ActOnStartRootSignatureDecl(StringRef Signature) {
+  llvm::hash_code Hash = llvm::hash_value(Signature);
+  std::string IdStr = "__hlsl_rootsig_decl_" + std::to_string(Hash);
+  IdentifierInfo *DeclIdent = &(getASTContext().Idents.get(IdStr));
+
+  // Check if we have already found a decl of the same name.
+  LookupResult R(SemaRef, DeclIdent, SourceLocation(),
+                 Sema::LookupOrdinaryName);
+  bool Found = SemaRef.LookupQualifiedName(R, SemaRef.CurContext);
+  return {DeclIdent, Found};
+}
+
+void SemaHLSL::ActOnFinishRootSignatureDecl(
+    SourceLocation Loc, IdentifierInfo *DeclIdent,
+    SmallVector<llvm::hlsl::rootsig::RootElement> &Elements) {
+
+  auto *SignatureDecl = HLSLRootSignatureDecl::Create(
+      SemaRef.getASTContext(), /*DeclContext=*/SemaRef.CurContext, Loc,
+      DeclIdent, Elements);
+
+  SignatureDecl->setImplicit();
+  SemaRef.PushOnScopeChains(SignatureDecl, SemaRef.getCurScope());
+}
+
 void SemaHLSL::handleRootSignatureAttr(Decl *D, const ParsedAttr &AL) {
   if (AL.getNumArgs() != 1) {
     Diag(AL.getLoc(), diag::err_attribute_wrong_number_arguments) << AL << 1;