Implement CodeGen support for the may_alias attribute.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@121734 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CodeGenTBAA.cpp b/lib/CodeGen/CodeGenTBAA.cpp
index d4d71a7..61dc41e 100644
--- a/lib/CodeGen/CodeGenTBAA.cpp
+++ b/lib/CodeGen/CodeGenTBAA.cpp
@@ -77,8 +77,29 @@
return llvm::MDNode::get(VMContext, Ops, llvm::array_lengthof(Ops) - !Flags);
}
+static bool TypeHasMayAlias(QualType QTy) {
+ // Tagged types have declarations, and therefore may have attributes.
+ if (const TagType *TTy = dyn_cast<TagType>(QTy))
+ return TTy->getDecl()->hasAttr<MayAliasAttr>();
+
+ // Typedef types have declarations, and therefore may have attributes.
+ if (const TypedefType *TTy = dyn_cast<TypedefType>(QTy)) {
+ if (TTy->getDecl()->hasAttr<MayAliasAttr>())
+ return true;
+ // Also, their underlying types may have relevant attributes.
+ return TypeHasMayAlias(TTy->desugar());
+ }
+
+ return false;
+}
+
llvm::MDNode *
CodeGenTBAA::getTBAAInfo(QualType QTy) {
+ // If the type has the may_alias attribute (even on a typedef), it is
+ // effectively in the general char alias class.
+ if (TypeHasMayAlias(QTy))
+ return getChar();
+
Type *Ty = Context.getCanonicalType(QTy).getTypePtr();
if (llvm::MDNode *N = MetadataCache[Ty])