[PATCH] D35824: [Sema] Implicitly apply the may_alias attribute to std::byte
David Majnemer via Phabricator via cfe-commits
cfe-commits at lists.llvm.org
Tue Jul 25 16:34:39 PDT 2017
This revision was automatically updated to reflect the committed changes.
Closed by commit rL309058: [CodeGen] Correctly model std::byte's aliasing properties (authored by majnemer).
Changed prior to commit:
https://reviews.llvm.org/D35824?vs=108166&id=108185#toc
Repository:
rL LLVM
https://reviews.llvm.org/D35824
Files:
cfe/trunk/include/clang/AST/Type.h
cfe/trunk/lib/AST/Type.cpp
cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp
cfe/trunk/test/CodeGenCXX/std-byte.cpp
Index: cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp
+++ cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp
@@ -139,6 +139,12 @@
}
}
+ // C++1z [basic.lval]p10: "If a program attempts to access the stored value of
+ // an object through a glvalue of other than one of the following types the
+ // behavior is undefined: [...] a char, unsigned char, or std::byte type."
+ if (Ty->isStdByteType())
+ return MetadataCache[Ty] = getChar();
+
// Handle pointers.
// TODO: Implement C++'s type "similarity" and consider dis-"similar"
// pointers distinct.
Index: cfe/trunk/lib/AST/Type.cpp
===================================================================
--- cfe/trunk/lib/AST/Type.cpp
+++ cfe/trunk/lib/AST/Type.cpp
@@ -2313,6 +2313,15 @@
return false;
}
+bool Type::isStdByteType() const {
+ if (auto *ET = getAs<EnumType>()) {
+ auto *II = ET->getDecl()->getIdentifier();
+ if (II && II->isStr("byte") && ET->getDecl()->isInStdNamespace())
+ return true;
+ }
+ return false;
+}
+
bool Type::isPromotableIntegerType() const {
if (const BuiltinType *BT = getAs<BuiltinType>())
switch (BT->getKind()) {
Index: cfe/trunk/include/clang/AST/Type.h
===================================================================
--- cfe/trunk/include/clang/AST/Type.h
+++ cfe/trunk/include/clang/AST/Type.h
@@ -1752,6 +1752,7 @@
bool isTemplateTypeParmType() const; // C++ template type parameter
bool isNullPtrType() const; // C++11 std::nullptr_t
bool isAlignValT() const; // C++17 std::align_val_t
+ bool isStdByteType() const; // C++17 std::byte
bool isAtomicType() const; // C11 _Atomic()
#define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
Index: cfe/trunk/test/CodeGenCXX/std-byte.cpp
===================================================================
--- cfe/trunk/test/CodeGenCXX/std-byte.cpp
+++ cfe/trunk/test/CodeGenCXX/std-byte.cpp
@@ -0,0 +1,41 @@
+// RUN: %clang_cc1 -std=c++1z -Werror -triple i386-unknown-unknown -emit-llvm -O1 -disable-llvm-passes -o - %s | FileCheck %s
+
+// std::byte should be considered equivalent to char for aliasing.
+
+namespace std {
+enum byte : unsigned char {};
+}
+
+// CHECK-LABEL: define void @test0(
+extern "C" void test0(std::byte *sb, int *i) {
+ // CHECK: store i8 0, i8* %{{.*}} !tbaa [[TAG_CHAR:!.*]]
+ *sb = std::byte{0};
+
+ // CHECK: store i32 1, i32* %{{.*}} !tbaa [[TAG_INT:!.*]]
+ *i = 1;
+}
+
+enum byte : unsigned char {};
+namespace my {
+enum byte : unsigned char {};
+namespace std {
+enum byte : unsigned char {};
+} // namespace std
+} // namespace my
+
+// Make sure we don't get confused with other enums named 'byte'.
+
+// CHECK-LABEL: define void @test1(
+extern "C" void test1(::byte *b, ::my::byte *mb, ::my::std::byte *msb) {
+ *b = ::byte{0};
+ *mb = ::my::byte{0};
+ *msb = ::my::std::byte{0};
+ // CHECK-NOT: store i8 0, i8* %{{.*}} !tbaa [[TAG_CHAR]]
+}
+
+// CHECK: !"any pointer", [[TYPE_CHAR:!.*]],
+// CHECK: [[TYPE_CHAR]] = !{!"omnipotent char", [[TAG_CXX_TBAA:!.*]],
+// CHECK: [[TAG_CXX_TBAA]] = !{!"Simple C++ TBAA"}
+// CHECK: [[TAG_CHAR]] = !{[[TYPE_CHAR:!.*]], [[TYPE_CHAR]], i64 0}
+// CHECK: [[TAG_INT]] = !{[[TYPE_INT:!.*]], [[TYPE_INT]], i64 0}
+// CHECK: [[TYPE_INT]] = !{!"int", [[TYPE_CHAR]]
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