review: use TrailingObjects to store elements instead of on the context

Author: inbelic

clang/include/clang/AST/Decl.h

@@ -5179,22 +5179,35 @@ class HLSLBufferDecl final : public NamedDecl, public DeclContext {
   friend class ASTDeclWriter;
 };
 
-class HLSLRootSignatureDecl final : public NamedDecl {
-  ArrayRef<llvm::hlsl::rootsig::RootElement> RootElements;
+class HLSLRootSignatureDecl final
+    : public NamedDecl,
+      private llvm::TrailingObjects<HLSLRootSignatureDecl,
+                                    llvm::hlsl::rootsig::RootElement> {
+  friend TrailingObjects;
+
+  unsigned NumElems;
 
-  HLSLRootSignatureDecl(
-      DeclContext *DC, SourceLocation Loc, IdentifierInfo *ID,
-      ArrayRef<llvm::hlsl::rootsig::RootElement> RootElements);
+  llvm::hlsl::rootsig::RootElement *getElems() {
+    return getTrailingObjects<llvm::hlsl::rootsig::RootElement>();
+  }
+
+  const llvm::hlsl::rootsig::RootElement *getElems() const {
+    return getTrailingObjects<llvm::hlsl::rootsig::RootElement>();
+  }
+
+  HLSLRootSignatureDecl(DeclContext *DC, SourceLocation Loc, IdentifierInfo *ID,
+                        unsigned NumElems);
 
 public:
   static HLSLRootSignatureDecl *
   Create(ASTContext &C, DeclContext *DC, SourceLocation Loc, IdentifierInfo *ID,
          ArrayRef<llvm::hlsl::rootsig::RootElement> RootElements);
+
   static HLSLRootSignatureDecl *CreateDeserialized(ASTContext &C,
                                                    GlobalDeclID ID);
 
-  ArrayRef<llvm::hlsl::rootsig::RootElement> &getRootElements() {
-    return RootElements;
+  ArrayRef<llvm::hlsl::rootsig::RootElement> getRootElements() const {
+    return {getElems(), NumElems};
   }
 
   // Implement isa/cast/dyncast/etc.

clang/lib/AST/Decl.cpp

@@ -5851,24 +5851,31 @@ bool HLSLBufferDecl::buffer_decls_empty() {
 // HLSLRootSignatureDecl Implementation
 //===----------------------------------------------------------------------===//
 
-HLSLRootSignatureDecl::HLSLRootSignatureDecl(
-    DeclContext *DC, SourceLocation Loc, IdentifierInfo *ID,
-    ArrayRef<llvm::hlsl::rootsig::RootElement> RootElements)
+HLSLRootSignatureDecl::HLSLRootSignatureDecl(DeclContext *DC,
+                                             SourceLocation Loc,
+                                             IdentifierInfo *ID,
+                                             unsigned NumElems)
     : NamedDecl(Decl::Kind::HLSLRootSignature, DC, Loc, DeclarationName(ID)),
-      RootElements(RootElements) {}
+      NumElems(NumElems) {}
 
 HLSLRootSignatureDecl *HLSLRootSignatureDecl::Create(
     ASTContext &C, DeclContext *DC, SourceLocation Loc, IdentifierInfo *ID,
     ArrayRef<llvm::hlsl::rootsig::RootElement> RootElements) {
-  HLSLRootSignatureDecl *Result =
-      new (C, DC) HLSLRootSignatureDecl(DC, Loc, ID, RootElements);
-  return Result;
+  HLSLRootSignatureDecl *RSDecl =
+      new (C, DC,
+           additionalSizeToAlloc<llvm::hlsl::rootsig::RootElement>(
+               RootElements.size()))
+          HLSLRootSignatureDecl(DC, Loc, ID, RootElements.size());
+  auto *StoredElems = RSDecl->getElems();
+  std::uninitialized_copy(RootElements.begin(), RootElements.end(),
+                          StoredElems);
+  return RSDecl;
 }
 
 HLSLRootSignatureDecl *
 HLSLRootSignatureDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
-  HLSLRootSignatureDecl *Result =
-      new (C, ID) HLSLRootSignatureDecl(nullptr, SourceLocation(), nullptr, {});
+  HLSLRootSignatureDecl *Result = new (C, ID)
+      HLSLRootSignatureDecl(nullptr, SourceLocation(), nullptr, /*NumElems=*/0);
   return Result;
 }