Author: Richard Smith Date: 2019-12-11T14:04:37-08:00 New Revision: e0e07a7e414e818788144511de0c6328285c43cd
URL: https://github.com/llvm/llvm-project/commit/e0e07a7e414e818788144511de0c6328285c43cd DIFF: https://github.com/llvm/llvm-project/commit/e0e07a7e414e818788144511de0c6328285c43cd.diff LOG: Fix detection of __attribute__((may_alias)) to properly look through type sugar. We previously missed the attribute in a lot of cases in C++, because there's often other type sugar there (eg, ElaboratedType). Added: clang/test/CodeGenCXX/may_alias.cpp Modified: clang/lib/CodeGen/CodeGenTBAA.cpp Removed: ################################################################################ diff --git a/clang/lib/CodeGen/CodeGenTBAA.cpp b/clang/lib/CodeGen/CodeGenTBAA.cpp index 09de9591de7e..7d730cb1ed15 100644 --- a/clang/lib/CodeGen/CodeGenTBAA.cpp +++ b/clang/lib/CodeGen/CodeGenTBAA.cpp @@ -78,17 +78,18 @@ llvm::MDNode *CodeGenTBAA::getChar() { 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; } diff --git a/clang/test/CodeGenCXX/may_alias.cpp b/clang/test/CodeGenCXX/may_alias.cpp new file mode 100644 index 000000000000..fbc4e22e731f --- /dev/null +++ b/clang/test/CodeGenCXX/may_alias.cpp @@ -0,0 +1,25 @@ +// 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} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
