[clang][NFC] Adjust TBAA Base Info API (#73263)

A couple of cleanups.

1) remove an unnecessary check from isValidBaseType.

2) Add a new internal entrypoint 'getValidBaseTypeInfo', for uses where the type is known to be valid.

Author: urnathan

clang/lib/CodeGen/CodeGenTBAA.cpp

@@ -98,8 +98,6 @@ static bool TypeHasMayAlias(QualType QTy) {
 
 /// Check if the given type is a valid base type to be used in access tags.
 static bool isValidBaseType(QualType QTy) {
-  if (QTy->isReferenceType())
-    return false;
   if (const RecordType *TTy = QTy->getAs<RecordType>()) {
     const RecordDecl *RD = TTy->getDecl()->getDefinition();
     // Incomplete types are not valid base access types.
@@ -243,9 +241,10 @@ llvm::MDNode *CodeGenTBAA::getTypeInfo(QualType QTy) {
   // aggregate will result into the may-alias access descriptor, meaning all
   // subsequent accesses to direct and indirect members of that aggregate will
   // be considered may-alias too.
-  // TODO: Combine getTypeInfo() and getBaseTypeInfo() into a single function.
+  // TODO: Combine getTypeInfo() and getValidBaseTypeInfo() into a single
+  // function.
   if (isValidBaseType(QTy))
-    return getBaseTypeInfo(QTy);
+    return getValidBaseTypeInfo(QTy);
 
   const Type *Ty = Context.getCanonicalType(QTy).getTypePtr();
   if (llvm::MDNode *N = MetadataCache[Ty])
@@ -394,7 +393,7 @@ llvm::MDNode *CodeGenTBAA::getBaseTypeInfoHelper(const Type *Ty) {
         if (BaseRD->isEmpty())
           continue;
         llvm::MDNode *TypeNode = isValidBaseType(BaseQTy)
-                                     ? getBaseTypeInfo(BaseQTy)
+                                     ? getValidBaseTypeInfo(BaseQTy)
                                      : getTypeInfo(BaseQTy);
         if (!TypeNode)
           return nullptr;
@@ -418,8 +417,9 @@ llvm::MDNode *CodeGenTBAA::getBaseTypeInfoHelper(const Type *Ty) {
       if (Field->isZeroSize(Context) || Field->isUnnamedBitfield())
         continue;
       QualType FieldQTy = Field->getType();
-      llvm::MDNode *TypeNode = isValidBaseType(FieldQTy) ?
-          getBaseTypeInfo(FieldQTy) : getTypeInfo(FieldQTy);
+      llvm::MDNode *TypeNode = isValidBaseType(FieldQTy)
+                                   ? getValidBaseTypeInfo(FieldQTy)
+                                   : getTypeInfo(FieldQTy);
       if (!TypeNode)
         return nullptr;
 
@@ -456,9 +456,8 @@ llvm::MDNode *CodeGenTBAA::getBaseTypeInfoHelper(const Type *Ty) {
   return nullptr;
 }
 
-llvm::MDNode *CodeGenTBAA::getBaseTypeInfo(QualType QTy) {
-  if (!isValidBaseType(QTy))
-    return nullptr;
+llvm::MDNode *CodeGenTBAA::getValidBaseTypeInfo(QualType QTy) {
+  assert(isValidBaseType(QTy) && "Must be a valid base type");
 
   const Type *Ty = Context.getCanonicalType(QTy).getTypePtr();
 
@@ -477,6 +476,10 @@ llvm::MDNode *CodeGenTBAA::getBaseTypeInfo(QualType QTy) {
   return TypeNode;
 }
 
+llvm::MDNode *CodeGenTBAA::getBaseTypeInfo(QualType QTy) {
+  return isValidBaseType(QTy) ? getValidBaseTypeInfo(QTy) : nullptr;
+}
+
 llvm::MDNode *CodeGenTBAA::getAccessTagInfo(TBAAAccessInfo Info) {
   assert(!Info.isIncomplete() && "Access to an object of an incomplete type!");
 

clang/lib/CodeGen/CodeGenTBAA.h

@@ -168,6 +168,10 @@ class CodeGenTBAA {
   /// used to describe accesses to objects of the given base type.
   llvm::MDNode *getBaseTypeInfoHelper(const Type *Ty);
 
+  /// getValidBaseTypeInfo - Return metadata that describes the given base
+  /// access type. The type must be suitable.
+  llvm::MDNode *getValidBaseTypeInfo(QualType QTy);
+
 public:
   CodeGenTBAA(ASTContext &Ctx, CodeGenTypes &CGTypes, llvm::Module &M,
               const CodeGenOptions &CGO, const LangOptions &Features,
@@ -190,8 +194,9 @@ class CodeGenTBAA {
   /// the given type.
   llvm::MDNode *getTBAAStructInfo(QualType QTy);
 
-  /// getBaseTypeInfo - Get metadata that describes the given base access type.
-  /// Return null if the type is not suitable for use in TBAA access tags.
+  /// getBaseTypeInfo - Get metadata that describes the given base access
+  /// type. Return null if the type is not suitable for use in TBAA access
+  /// tags.
   llvm::MDNode *getBaseTypeInfo(QualType QTy);
 
   /// getAccessTagInfo - Get TBAA tag for a given memory access.