Add a new flag and attributes to control static destructor registration

This commit adds the flag -fno-c++-static-destructors and the attributes
[[clang::no_destroy]] and [[clang::always_destroy]]. no_destroy specifies that a
specific static or thread duration variable shouldn't have it's destructor
registered, and is the default in -fno-c++-static-destructors mode.
always_destroy is the opposite, and is the default in -fc++-static-destructors
mode.

A variable whose destructor is disabled (either because of
-fno-c++-static-destructors or [[clang::no_destroy]]) doesn't count as a use of
the destructor, so we don't do any access checking or mark it referenced. We
also don't emit -Wexit-time-destructors for these variables.

rdar://21734598

Differential revision: https://reviews.llvm.org/D50994

llvm-svn: 340306

5 files changed, 110 insertions, 1 deletions

diff --git a/clang/test/CodeGenCXX/always_destroy.cpp b/clang/test/CodeGenCXX/always_destroy.cpp
new file mode 100644
index 00000000000..e84c4cf02c5
--- /dev/null
+++ b/clang/test/CodeGenCXX/always_destroy.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 %s -fno-c++-static-destructors -emit-llvm -triple x86_64-apple-macosx10.13.0 -o - | FileCheck %s
+
+struct NonTrivial {
+  ~NonTrivial();
+};
+
+// CHECK-NOT: __cxa_atexit{{.*}}_ZN10NonTrivialD1Ev
+NonTrivial nt1;
+// CHECK-NOT: _tlv_atexit{{.*}}_ZN10NonTrivialD1Ev
+thread_local NonTrivial nt2;
+
+struct NonTrivial2 {
+  ~NonTrivial2();
+};
+
+// CHECK: __cxa_atexit{{.*}}_ZN11NonTrivial2D1Ev
+[[clang::always_destroy]] NonTrivial2 nt21;
+// CHECK: _tlv_atexit{{.*}}_ZN11NonTrivial2D1Ev
+[[clang::always_destroy]] thread_local NonTrivial2 nt22;
+
+void f() {
+  // CHECK: __cxa_atexit{{.*}}_ZN11NonTrivial2D1Ev
+  [[clang::always_destroy]] static NonTrivial2 nt21;
+  // CHECK: _tlv_atexit{{.*}}_ZN11NonTrivial2D1Ev
+  [[clang::always_destroy]] thread_local NonTrivial2 nt22;
+}
+
+// CHECK-NOT: __cxa_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::no_destroy]] NonTrivial nt3;
+// CHECK-NOT: _tlv_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::no_destroy]] thread_local NonTrivial nt4;
diff --git a/clang/test/CodeGenCXX/no_destroy.cpp b/clang/test/CodeGenCXX/no_destroy.cpp
new file mode 100644
index 00000000000..93e6ce17bb6
--- /dev/null
+++ b/clang/test/CodeGenCXX/no_destroy.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 %s -emit-llvm -triple x86_64-apple-macosx10.13.0 -o - | FileCheck %s
+
+struct NonTrivial {
+  ~NonTrivial();
+};
+
+// CHECK-NOT: __cxa_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::no_destroy]] NonTrivial nt1;
+// CHECK-NOT: _tlv_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::no_destroy]] thread_local NonTrivial nt2;
+
+struct NonTrivial2 {
+  ~NonTrivial2();
+};
+
+// CHECK: __cxa_atexit{{.*}}_ZN11NonTrivial2D1Ev
+NonTrivial2 nt21;
+// CHECK: _tlv_atexit{{.*}}_ZN11NonTrivial2D1Ev
+thread_local NonTrivial2 nt22;
+
+void f() {
+  // CHECK: __cxa_atexit{{.*}}_ZN11NonTrivial2D1Ev
+  static NonTrivial2 nt21;
+  // CHECK: _tlv_atexit{{.*}}_ZN11NonTrivial2D1Ev
+  thread_local NonTrivial2 nt22;
+}
+
+// CHECK: __cxa_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::always_destroy]] NonTrivial nt3;
+// CHECK: _tlv_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::always_destroy]] thread_local NonTrivial nt4;
diff --git a/clang/test/Misc/pragma-attribute-supported-attributes-list.test b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
index 4a3846be8d9..d2c1fe6d27b 100644
--- a/clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -2,7 +2,7 @@
 
 // The number of supported attributes should never go down!
 
-// CHECK: #pragma clang attribute supports 72 attributes:
+// CHECK: #pragma clang attribute supports 74 attributes:
 // CHECK-NEXT: AMDGPUFlatWorkGroupSize (SubjectMatchRule_function)
 // CHECK-NEXT: AMDGPUNumSGPR (SubjectMatchRule_function)
 // CHECK-NEXT: AMDGPUNumVGPR (SubjectMatchRule_function)
@@ -11,6 +11,7 @@
 // CHECK-NEXT: AbiTag (SubjectMatchRule_record_not_is_union, SubjectMatchRule_variable, SubjectMatchRule_function, SubjectMatchRule_namespace)
 // CHECK-NEXT: AlignValue (SubjectMatchRule_variable, SubjectMatchRule_type_alias)
 // CHECK-NEXT: AllocSize (SubjectMatchRule_function)
+// CHECK-NEXT: AlwaysDestroy (SubjectMatchRule_variable)
 // CHECK-NEXT: Annotate ()
 // CHECK-NEXT: AnyX86NoCfCheck (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: AssumeAligned (SubjectMatchRule_objc_method, SubjectMatchRule_function)
@@ -38,6 +39,7 @@
 // CHECK-NEXT: MipsLongCall (SubjectMatchRule_function)
 // CHECK-NEXT: MipsShortCall (SubjectMatchRule_function)
 // CHECK-NEXT: NoDebug (SubjectMatchRule_hasType_functionType, SubjectMatchRule_objc_method, SubjectMatchRule_variable_not_is_parameter)
+// CHECK-NEXT: NoDestroy (SubjectMatchRule_variable)
 // CHECK-NEXT: NoDuplicate (SubjectMatchRule_function)
 // CHECK-NEXT: NoEscape (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: NoMicroMips (SubjectMatchRule_function)
diff --git a/clang/test/SemaCXX/no_destroy.cpp b/clang/test/SemaCXX/no_destroy.cpp
new file mode 100644
index 00000000000..bdb8077cb58
--- /dev/null
+++ b/clang/test/SemaCXX/no_destroy.cpp
@@ -0,0 +1,40 @@
+// RUN: %clang_cc1 -DNO_DTORS -fno-c++-static-destructors -verify %s
+// RUN: %clang_cc1 -verify %s
+
+struct SecretDestructor {
+#ifndef NO_DTORS
+  // expected-note@+2 4 {{private}}
+#endif
+private: ~SecretDestructor(); // expected-note 2 {{private}}
+};
+
+SecretDestructor sd1;
+thread_local SecretDestructor sd2;
+void locals() {
+  static SecretDestructor sd3;
+  thread_local SecretDestructor sd4;
+}
+
+#ifndef NO_DTORS
+// SecretDestructor sd1;                  // expected-error@-8 {{private}}
+// thread_local SecretDestructor sd2;     // expected-error@-8 {{private}}
+// void locals() {
+//   static SecretDestructor sd3;         // expected-error@-8 {{private}}
+//   thread_local SecretDestructor sd4;   // expected-error@-8 {{private}}
+// }
+#endif
+
+[[clang::always_destroy]] SecretDestructor sd6; // expected-error{{private}}
+[[clang::always_destroy]] thread_local SecretDestructor sd7; // expected-error{{private}}
+
+[[clang::no_destroy]] SecretDestructor sd8;
+
+int main() {
+  [[clang::no_destroy]] int p; // expected-error{{no_destroy attribute can only be applied to a variable with static or thread storage duration}}
+  [[clang::always_destroy]] int p2; // expected-error{{always_destroy attribute can only be applied to a variable with static or thread storage duration}}
+  [[clang::no_destroy]] static int p3;
+  [[clang::always_destroy]] static int p4;
+}
+
+[[clang::always_destroy]] [[clang::no_destroy]] int p; // expected-error{{'no_destroy' and 'always_destroy' attributes are not compatible}} // expected-note{{here}}
+[[clang::no_destroy]] [[clang::always_destroy]] int p2; // expected-error{{'always_destroy' and 'no_destroy' attributes are not compatible}} // expected-note{{here}}
diff --git a/clang/test/SemaCXX/warn-exit-time-destructors.cpp b/clang/test/SemaCXX/warn-exit-time-destructors.cpp
index 124576aa95b..17b3a940636 100644
--- a/clang/test/SemaCXX/warn-exit-time-destructors.cpp
+++ b/clang/test/SemaCXX/warn-exit-time-destructors.cpp
@@ -43,3 +43,8 @@ namespace test3 {
   };
   E e;
 }
+
+namespace test4 {
+struct A { ~A(); };
+[[clang::no_destroy]] A a; // no warning
+}