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>();
+ if (auto *TD = QTy->getAsTagDecl())
+ if (TD->hasAttr<MayAliasAttr>())
+ return true;
- // Typedef types have declarations, and therefore may have attributes.
- if (const TypedefType *TTy = dyn_cast<TypedefType>(QTy)) {
- if (TTy->getDecl()->hasAttr<MayAliasAttr>())
+ // Also look for may_alias as a declaration attribute on a typedef.
+ // FIXME: We should follow GCC and model may_alias as a type attribute
+ // rather than as a declaration attribute.
+ while (auto *TT = QTy->getAs<TypedefType>()) {
+ if (TT->getDecl()->hasAttr<MayAliasAttr>())
return true;
- // Also, their underlying types may have relevant attributes.
- return TypeHasMayAlias(TTy->desugar());
+ QTy = TT->desugar();
}
-
return false;
}
--- /dev/null
+// RUN: %clang_cc1 %s -triple %itanium_abi_triple -emit-llvm -O2 -disable-llvm-passes -o - | FileCheck %s
+// RUN: %clang_cc1 %s -triple %ms_abi_triple -emit-llvm -O2 -disable-llvm-passes -o - | FileCheck %s
+
+enum class __attribute__((may_alias)) E {};
+
+template<typename T> struct A {
+ using B __attribute__((may_alias)) = enum {};
+};
+
+template<typename T> using Alias = typename A<T>::B;
+
+// CHECK-LABEL: define {{.*}}foo
+// CHECK: load i{{[0-9]*}}, {{.*}}, !tbaa ![[MAY_ALIAS:[^ ,]*]]
+auto foo(E &r) { return r; }
+
+// CHECK-LABEL: define {{.*}}goo
+// CHECK: load i{{[0-9]*}}, {{.*}}, !tbaa ![[MAY_ALIAS]]
+auto goo(A<int>::B &r) { return r; }
+
+// CHECK-LABEL: define {{.*}}hoo
+// CHECK: load i{{[0-9]*}}, {{.*}}, !tbaa ![[MAY_ALIAS]]
+auto hoo(Alias<int> &r) { return r; }
+
+// CHECK: ![[CHAR:.*]] = !{!"omnipotent char", !{{.*}}, i64 0}
+// CHECK: ![[MAY_ALIAS]] = !{![[CHAR]], ![[CHAR]], i64 0}