Add a command line option `fregister_global_dtors_with_atexit` to register destructor functions annotated with __attribute__((destructor)) using __cxa_atexit or atexit.

[ahatanak]

Summary

The command line option makes IRGen register destructor functions
annotated with __attribute__((destructor)) calling __cxa_atexit in a
synthesized constructor function instead of emitting references to
the destructor functions in a special section (__mod_term_funcs on
Darwin).

The primary reason for adding this option is that we are planning to
deprecate __mod_term_funcs section on Darwin in the future. This feature
is enabled by default on Darwin and can be disabled using command line
option fno_register_global_dtors_with_atexit.

rdar://problem/33887655

[ahatanak]

Fix an error in emitGlobalDtorWithCXAAtExit and make sure @dso_handle is hidden.

[rjmccall]

include/clang/Driver/Options.td

1613 ↗

(On Diff #142218)

Probably worth spelling out that this is for *global* destructors, at least in the help text and maybe in the option names. At the very least, the option name should say "dtors" instead of just "dtor".

include/clang/Frontend/CodeGenOptions.def

46 ↗

(On Diff #142218)

Same thing: worth saying in the option name that this is just global dtors.

lib/CodeGen/CodeGenModule.h

1339 ↗

(On Diff #142218)

There's an llvm::TinyPtrVector which would be useful here.

lib/CodeGen/ItaniumCXXABI.cpp

2213 ↗

(On Diff #142218)

This is iterating over a DenseMap and therefore making the emission order dependent on details like how we hash ints for DenseMap.

Also, is this a correct way of handling Priority? You should at least justify that in comments.

[ahatanak]

Address review comments.

[ahatanak]

include/clang/Driver/Options.td

1613 ↗

(On Diff #142218)

I renamed the option to -fregister-global-dtors-with-atexit.

lib/CodeGen/ItaniumCXXABI.cpp

2213 ↗

(On Diff #142218)

I added a comment in registerGlobalDtorsWithAtExit that explains why destructor functions will be run in non-ascending order of their priority, which is what is expected.

[rjmccall]

Thank you. Minor request and then LGTM.

lib/CodeGen/ItaniumCXXABI.cpp

2202 ↗

(On Diff #142597)

You should probably mention that using null here is okay because this value is just passed back as an argument to the destructor function.

cfe/trunk/include/clang/Driver/Options.td

 def fno_strict_enums : Flag<["-"], "fno-strict-enums">, Group<f_Group>;
 def fno_strict_vtable_pointers: Flag<["-"], "fno-strict-vtable-pointers">,
   Group<f_Group>;
 def fno_strict_overflow : Flag<["-"], "fno-strict-overflow">, Group<f_Group>;
 def fno_threadsafe_statics : Flag<["-"], "fno-threadsafe-statics">, Group<f_Group>,
   Flags<[CC1Option]>, HelpText<"Do not emit code to make initialization of local statics thread safe">;
 def fno_use_cxa_atexit : Flag<["-"], "fno-use-cxa-atexit">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Don't use __cxa_atexit for calling destructors">;
+def fno_register_global_dtors_with_atexit : Flag<["-"], "fno-register-global-dtors-with-atexit">, Group<f_Group>,
+  HelpText<"Don't use atexit or __cxa_atexit to register global destructors">;
 def fno_use_init_array : Flag<["-"], "fno-use-init-array">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Don't use .init_array instead of .ctors">;
 def fno_unit_at_a_time : Flag<["-"], "fno-unit-at-a-time">, Group<f_Group>;
 def fno_unwind_tables : Flag<["-"], "fno-unwind-tables">, Group<f_Group>;
 def fno_verbose_asm : Flag<["-"], "fno-verbose-asm">, Group<f_Group>;
 def fno_working_directory : Flag<["-"], "fno-working-directory">, Group<f_Group>;
 def fno_wrapv : Flag<["-"], "fno-wrapv">, Group<f_Group>;
 def fno_zero_initialized_in_bss : Flag<["-"], "fno-zero-initialized-in-bss">, Group<f_Group>;
def ftrigraphs : Flag<["-"], "ftrigraphs">, Group<f_Group>,
   HelpText<"Process trigraph sequences">, Flags<[CC1Option]>;
 def fno_trigraphs : Flag<["-"], "fno-trigraphs">, Group<f_Group>,
   HelpText<"Do not process trigraph sequences">, Flags<[CC1Option]>;
 def funsigned_bitfields : Flag<["-"], "funsigned-bitfields">, Group<f_Group>;
 def funsigned_char : Flag<["-"], "funsigned-char">, Group<f_Group>;
 def fno_unsigned_char : Flag<["-"], "fno-unsigned-char">;
 def funwind_tables : Flag<["-"], "funwind-tables">, Group<f_Group>;
 def fuse_cxa_atexit : Flag<["-"], "fuse-cxa-atexit">, Group<f_Group>;
+def fregister_global_dtors_with_atexit : Flag<["-"], "fregister-global-dtors-with-atexit">, Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Use atexit or __cxa_atexit to register global destructors">;
 def fuse_init_array : Flag<["-"], "fuse-init-array">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Use .init_array instead of .ctors">;
 def fno_var_tracking : Flag<["-"], "fno-var-tracking">, Group<clang_ignored_f_Group>;
 def fverbose_asm : Flag<["-"], "fverbose-asm">, Group<f_Group>;
 def fvisibility_EQ : Joined<["-"], "fvisibility=">, Group<f_Group>,
   HelpText<"Set the default symbol visibility for all global declarations">, Values<"hidden,default">;
 def fvisibility_inlines_hidden : Flag<["-"], "fvisibility-inlines-hidden">, Group<f_Group>,
   HelpText<"Give inline C++ member functions default visibility by default">,

cfe/trunk/include/clang/Frontend/CodeGenOptions.def

 CODEGENOPT(Autolink          , 1, 1) ///< -fno-autolink
 CODEGENOPT(ObjCAutoRefCountExceptions , 1, 0) ///< Whether ARC should be EH-safe.
 CODEGENOPT(Backchain         , 1, 0) ///< -mbackchain
 CODEGENOPT(ControlFlowGuard  , 1, 0) ///< -cfguard
 CODEGENOPT(CoverageExtraChecksum, 1, 0) ///< Whether we need a second checksum for functions in GCNO files.
 CODEGENOPT(CoverageNoFunctionNamesInData, 1, 0) ///< Do not include function names in GCDA files.
 CODEGENOPT(CoverageExitBlockBeforeBody, 1, 0) ///< Whether to emit the exit block before the body blocks in GCNO files.
 CODEGENOPT(CXAAtExit         , 1, 1) ///< Use __cxa_atexit for calling destructors.
+CODEGENOPT(RegisterGlobalDtorsWithAtExit, 1, 1) ///< Use atexit or __cxa_atexit to register global destructors.
 CODEGENOPT(CXXCtorDtorAliases, 1, 0) ///< Emit complete ctors/dtors as linker
                                      ///< aliases to base ctors when possible.
 CODEGENOPT(DataSections      , 1, 0) ///< Set when -fdata-sections is enabled.
 CODEGENOPT(UniqueSectionNames, 1, 1) ///< Set for -funique-section-names.
 CODEGENOPT(DisableFPElim     , 1, 0) ///< Set when -fomit-frame-pointer is enabled.
 CODEGENOPT(DisableFree       , 1, 0) ///< Don't free memory.
 CODEGENOPT(DiscardValueNames , 1, 0) ///< Discard Value Names from the IR (LLVMContext flag)
 CODEGENOPT(DisableGCov       , 1, 0) ///< Don't run the GCov pass, for testing.

cfe/trunk/lib/CodeGen/CGDeclCXX.cpp

 }
 
 /// Register a global destructor using the C atexit runtime function.
 void CodeGenFunction::registerGlobalDtorWithAtExit(const VarDecl &VD,
                                                    llvm::Constant *dtor,
                                                    llvm::Constant *addr) {
   // Create a function which calls the destructor.
   llvm::Constant *dtorStub = createAtExitStub(VD, dtor, addr);
+  registerGlobalDtorWithAtExit(dtorStub);
+}
 
+void CodeGenFunction::registerGlobalDtorWithAtExit(llvm::Constant *dtorStub) {
   // extern "C" int atexit(void (*f)(void));
   llvm::FunctionType *atexitTy =
     llvm::FunctionType::get(IntTy, dtorStub->getType(), false);
 
   llvm::Constant *atexit =
       CGM.CreateRuntimeFunction(atexitTy, "atexit", llvm::AttributeList(),
                                 /*Local=*/true);
   if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit))

cfe/trunk/lib/CodeGen/CodeGenFunction.h

public:
   llvm::Constant *createAtExitStub(const VarDecl &VD, llvm::Constant *Dtor,
                                    llvm::Constant *Addr);
 
   /// Call atexit() with a function that passes the given argument to
   /// the given function.
   void registerGlobalDtorWithAtExit(const VarDecl &D, llvm::Constant *fn,
                                     llvm::Constant *addr);
 
+  /// Call atexit() with function dtorStub.
+  void registerGlobalDtorWithAtExit(llvm::Constant *dtorStub);
+
   /// Emit code in this function to perform a guarded variable
   /// initialization.  Guarded initializations are used when it's not
   /// possible to prove that an initialization will be done exactly
   /// once, e.g. with a static local variable or a static data member
   /// of a class template.
   void EmitCXXGuardedInit(const VarDecl &D, llvm::GlobalVariable *DeclPtr,
                           bool PerformInit);
 

cfe/trunk/lib/CodeGen/CodeGenModule.h

private:
   /// Call replaceAllUsesWith on all pairs in Replacements.
   void applyReplacements();
 
   /// Call replaceAllUsesWith on all pairs in GlobalValReplacements.
   void applyGlobalValReplacements();
 
   void checkAliases();
 
+  std::map<int, llvm::TinyPtrVector<llvm::Function *>> DtorsUsingAtExit;
+
+  /// Register functions annotated with __attribute__((destructor)) using
+  /// __cxa_atexit, if it is available, or atexit otherwise.
+  void registerGlobalDtorsWithAtExit();
+
   void emitMultiVersionFunctions();
 
   /// Emit any vtables which we deferred and still have a use for.
   void EmitDeferredVTables();
 
   /// Emit a dummy function that reference a CoreFoundation symbol when
   /// @available is used on Darwin.
   void emitAtAvailableLinkGuard();

cfe/trunk/lib/CodeGen/CodeGenModule.cpp

void CodeGenModule::Release() {
   EmitDeferred();
   EmitVTablesOpportunistically();
   applyGlobalValReplacements();
   applyReplacements();
   checkAliases();
   emitMultiVersionFunctions();
   EmitCXXGlobalInitFunc();
   EmitCXXGlobalDtorFunc();
+  registerGlobalDtorsWithAtExit();
   EmitCXXThreadLocalInitFunc();
   if (ObjCRuntime)
     if (llvm::Function *ObjCInitFunction = ObjCRuntime->ModuleInitFunction())
       AddGlobalCtor(ObjCInitFunction);
   if (Context.getLangOpts().CUDA && !Context.getLangOpts().CUDAIsDevice &&
       CUDARuntime) {
     if (llvm::Function *CudaCtorFunction = CUDARuntime->makeModuleCtorFunction())
       AddGlobalCtor(CudaCtorFunction);
void CodeGenModule::AddGlobalCtor(llvm::Function *Ctor, int Priority,
                                   llvm::Constant *AssociatedData) {
   // FIXME: Type coercion of void()* types.
   GlobalCtors.push_back(Structor(Priority, Ctor, AssociatedData));
 }
 
 /// AddGlobalDtor - Add a function to the list that will be called
 /// when the module is unloaded.
 void CodeGenModule::AddGlobalDtor(llvm::Function *Dtor, int Priority) {
+  if (CodeGenOpts.RegisterGlobalDtorsWithAtExit) {
+    DtorsUsingAtExit[Priority].push_back(Dtor);
+    return;
+  }
+
   // FIXME: Type coercion of void()* types.
   GlobalDtors.push_back(Structor(Priority, Dtor, nullptr));
 }
 
 void CodeGenModule::EmitCtorList(CtorList &Fns, const char *GlobalName) {
   if (Fns.empty()) return;
 
   // Ctor function type is void()*.

cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp

 #include "clang/AST/Mangle.h"
 #include "clang/AST/Type.h"
 #include "clang/AST/StmtCXX.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Value.h"
+#include "llvm/Support/ScopedPrinter.h"
 
 using namespace clang;
 using namespace CodeGen;
 
 namespace {
 class ItaniumCXXABI : public CodeGen::CGCXXABI {
   /// VTables - All the vtables which have been defined.
   llvm::DenseMap<const CXXRecordDecl *, llvm::GlobalVariable *> VTables;
if (llvm::Function *fn = dyn_cast<llvm::Function>(atexit))
     fn->setDoesNotThrow();
 
   // Create a variable that binds the atexit to this shared object.
   llvm::Constant *handle =
       CGF.CGM.CreateRuntimeVariable(CGF.Int8Ty, "__dso_handle");
   auto *GV = cast<llvm::GlobalValue>(handle->stripPointerCasts());
   GV->setVisibility(llvm::GlobalValue::HiddenVisibility);
 
+  if (!addr)
+    // addr is null when we are trying to register a dtor annotated with
+    // __attribute__((destructor)) in a constructor function. Using null here is
+    // okay because this argument is just passed back to the destructor
+    // function.
+    addr = llvm::Constant::getNullValue(CGF.Int8PtrTy);
+
   llvm::Value *args[] = {
     llvm::ConstantExpr::getBitCast(dtor, dtorTy),
     llvm::ConstantExpr::getBitCast(addr, CGF.Int8PtrTy),
     handle
   };
   CGF.EmitNounwindRuntimeCall(atexit, args);
 }
 
+void CodeGenModule::registerGlobalDtorsWithAtExit() {
+  for (const auto I : DtorsUsingAtExit) {
+    int Priority = I.first;
+    const llvm::TinyPtrVector<llvm::Function *> &Dtors = I.second;
+
+    // Create a function that registers destructors that have the same priority.
+    //
+    // Since constructor functions are run in non-descending order of their
+    // priorities, destructors are registered in non-descending order of their
+    // priorities, and since destructor functions are run in the reverse order
+    // of their registration, destructor functions are run in non-ascending
+    // order of their priorities.
+    CodeGenFunction CGF(*this);
+    std::string GlobalInitFnName =
+        std::string("__GLOBAL_init_") + llvm::to_string(Priority);
+    llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
+    llvm::Function *GlobalInitFn = CreateGlobalInitOrDestructFunction(
+        FTy, GlobalInitFnName, getTypes().arrangeNullaryFunction(),
+        SourceLocation());
+    ASTContext &Ctx = getContext();
+    FunctionDecl *FD = FunctionDecl::Create(
+        Ctx, Ctx.getTranslationUnitDecl(), SourceLocation(), SourceLocation(),
+        &Ctx.Idents.get(GlobalInitFnName), Ctx.VoidTy, nullptr, SC_Static,
+        false, false);
+    CGF.StartFunction(GlobalDecl(FD), getContext().VoidTy, GlobalInitFn,
+                      getTypes().arrangeNullaryFunction(), FunctionArgList(),
+                      SourceLocation(), SourceLocation());
+
+    for (auto *Dtor : Dtors) {
+      // Register the destructor function calling __cxa_atexit if it is
+      // available. Otherwise fall back on calling atexit.
+      if (getCodeGenOpts().CXAAtExit)
+        emitGlobalDtorWithCXAAtExit(CGF, Dtor, nullptr, false);
+      else
+        CGF.registerGlobalDtorWithAtExit(Dtor);
+    }
+
+    CGF.FinishFunction();
+    AddGlobalCtor(GlobalInitFn, Priority, nullptr);
+  }
+}
+
 /// Register a global destructor as best as we know how.
 void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
                                        const VarDecl &D,
                                        llvm::Constant *dtor,
                                        llvm::Constant *addr) {
   // Use __cxa_atexit if available.
   if (CGM.getCodeGenOpts().CXAAtExit)
     return emitGlobalDtorWithCXAAtExit(CGF, dtor, addr, D.getTLSKind());

cfe/trunk/lib/Driver/ToolChains/Clang.cpp

if (!Args.hasFlag(
               RawTriple.getOS() != llvm::Triple::Solaris &&
               getToolChain().getArch() != llvm::Triple::hexagon &&
               getToolChain().getArch() != llvm::Triple::xcore &&
               ((RawTriple.getVendor() != llvm::Triple::MipsTechnologies) ||
                RawTriple.hasEnvironment())) ||
       KernelOrKext)
     CmdArgs.push_back("-fno-use-cxa-atexit");
 
+  if (Args.hasFlag(options::OPT_fregister_global_dtors_with_atexit,
+                   options::OPT_fno_register_global_dtors_with_atexit,
+                   RawTriple.isOSDarwin()))
+    CmdArgs.push_back("-fregister-global-dtors-with-atexit");
+
   // -fms-extensions=0 is default.
   if (Args.hasFlag(options::OPT_fms_extensions, options::OPT_fno_ms_extensions,
                    IsWindowsMSVC))
     CmdArgs.push_back("-fms-extensions");
 
   // -fno-use-line-directives is default.
   if (Args.hasFlag(options::OPT_fuse_line_directives,
                    options::OPT_fno_use_line_directives, false))

cfe/trunk/lib/Frontend/CompilerInvocation.cpp

static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.CoverageMapping =
       Args.hasFlag(OPT_fcoverage_mapping, OPT_fno_coverage_mapping, false);
   Opts.DumpCoverageMapping = Args.hasArg(OPT_dump_coverage_mapping);
   Opts.AsmVerbose = Args.hasArg(OPT_masm_verbose);
   Opts.PreserveAsmComments = !Args.hasArg(OPT_fno_preserve_as_comments);
   Opts.AssumeSaneOperatorNew = !Args.hasArg(OPT_fno_assume_sane_operator_new);
   Opts.ObjCAutoRefCountExceptions = Args.hasArg(OPT_fobjc_arc_exceptions);
   Opts.CXAAtExit = !Args.hasArg(OPT_fno_use_cxa_atexit);
+  Opts.RegisterGlobalDtorsWithAtExit =
+      Args.hasArg(OPT_fregister_global_dtors_with_atexit);
   Opts.CXXCtorDtorAliases = Args.hasArg(OPT_mconstructor_aliases);
   Opts.CodeModel = getCodeModel(Args, Diags);
   Opts.DebugPass = Args.getLastArgValue(OPT_mdebug_pass);
   Opts.DisableFPElim =
       (Args.hasArg(OPT_mdisable_fp_elim) || Args.hasArg(OPT_pg));
   Opts.DisableFree = Args.hasArg(OPT_disable_free);
   Opts.DiscardValueNames = Args.hasArg(OPT_discard_value_names);
   Opts.DisableTailCalls = Args.hasArg(OPT_mdisable_tail_calls);

cfe/trunk/test/CodeGen/constructor-attribute.c

-// RUN: %clang_cc1 -emit-llvm -o %t %s
-// RUN: grep -e "global_ctors.*@A" %t
-// RUN: grep -e "global_dtors.*@B" %t
-// RUN: grep -e "global_ctors.*@C" %t
-// RUN: grep -e "global_dtors.*@D" %t
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=WITHOUTATEXIT %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -fregister-global-dtors-with-atexit -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=CXAATEXIT --check-prefix=WITHATEXIT %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -fno-use-cxa-atexit -fregister-global-dtors-with-atexit -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=ATEXIT --check-prefix=WITHATEXIT %s
+
+// WITHOUTATEXIT: global_ctors{{.*}}@A{{.*}}@C
+// WITHOUTATEXIT: @llvm.global_dtors = appending global [5 x { i32, void ()*, i8* }]{{.*}}@B{{.*}}@E{{.*}}@F{{.*}}@G{{.*}}@D
+// WITHATEXIT: @llvm.global_ctors = appending global [5 x { i32, void ()*, i8* }]{{.*}}i32 65535, void ()* @A,{{.*}}i32 65535, void ()* @C,{{.*}}i32 123, void ()* @__GLOBAL_init_123,{{.*}}i32 789, void ()* @[[GLOBAL_INIT_789:__GLOBAL_init_789.[0-9]+]],{{.*}}i32 65535, void ()* @__GLOBAL_init_65535,
+// WITHATEXIT-NOT: global_dtors
+
+// CHECK: define void @A()
+// CHECK: define void @B()
+// CHECK: define internal void @E()
+// CHECK: define internal void @F()
+// CHECK: define internal void @G()
+// CHECK: define i32 @__GLOBAL_init_789(i32 %{{.*}})
+// CHECK: define internal void @C()
+// CHECK: define internal void @D()
+// CHECK: define i32 @main()
+// CHECK: define internal i32 @foo()
+// WITHOUTATEXIT-NOT: define
+
+// WITHATEXIT: define internal void @__GLOBAL_init_123(){{.*}}section "__TEXT,__StaticInit,regular,pure_instructions"
+// CXAATEXIT: call i32 @__cxa_atexit(void (i8*)* bitcast (void ()* @E to void (i8*)*), i8* null, i8* @__dso_handle)
+// CXAATEXIT: call i32 @__cxa_atexit(void (i8*)* bitcast (void ()* @G to void (i8*)*), i8* null, i8* @__dso_handle)
+// ATEXIT: call i32 @atexit(void ()* @E)
+// ATEXIT: call i32 @atexit(void ()* @G)
+
+// WITHATEXIT: define internal void @[[GLOBAL_INIT_789]](){{.*}}section "__TEXT,__StaticInit,regular,pure_instructions"
+// CXAATEXIT: call i32 @__cxa_atexit(void (i8*)* bitcast (void ()* @F to void (i8*)*), i8* null, i8* @__dso_handle)
+// ATEXIT: call i32 @atexit(void ()* @F)
+
+// WITHATEXIT: define internal void @__GLOBAL_init_65535(){{.*}}section "__TEXT,__StaticInit,regular,pure_instructions"
+// CXAATEXIT: call i32 @__cxa_atexit(void (i8*)* bitcast (void ()* @B to void (i8*)*), i8* null, i8* @__dso_handle)
+// CXAATEXIT: call i32 @__cxa_atexit(void (i8*)* bitcast (void ()* @D to void (i8*)*), i8* null, i8* @__dso_handle)
+// ATEXIT: call i32 @atexit(void ()* @B)
+// ATEXIT: call i32 @atexit(void ()* @D)
 
 int printf(const char *, ...);
 
 void A() __attribute__((constructor));
 void B() __attribute__((destructor));
 
 void A() {
   printf("A\n");
 }
 
 void B() {
   printf("B\n");
 }
 
 static void C() __attribute__((constructor));
 
 static void D() __attribute__((destructor));
 
+static __attribute__((destructor(123))) void E() {
+}
+
+static __attribute__((destructor(789))) void F() {
+}
+
+static __attribute__((destructor(123))) void G() {
+}
+
+// Test that this function doesn't collide with the synthesized constructor
+// function for destructors with priority 789.
+int __GLOBAL_init_789(int a) {
+  return a * a;
+}
+
 static int foo() {
   return 10;
 }
 
 static void C() {
   printf("A: %d\n", foo());
 }
 
 static void D() {
   printf("B\n");
 }
 
 int main() {
   return 0;
 }

cfe/trunk/test/Driver/cxa-atexit.cpp

 
 // CHECK-WINDOWS: "-fno-use-cxa-atexit"
 // CHECK-SOLARIS: "-fno-use-cxa-atexit"
 // CHECK-HEXAGON: "-fno-use-cxa-atexit"
 // CHECK-XCORE: "-fno-use-cxa-atexit"
 // CHECK-MTI: "-fno-use-cxa-atexit"
 // CHECK-MIPS-NOT: "-fno-use-cxa-atexit"
 
+// RUN: %clang -target x86_64-apple-darwin -fregister-global-dtors-with-atexit -fno-register-global-dtors-with-atexit -c -### %s 2>&1 | \
+// RUN: FileCheck --check-prefix=WITHOUTATEXIT %s
+// RUN: %clang -target x86_64-apple-darwin -fno-register-global-dtors-with-atexit -fregister-global-dtors-with-atexit -c -### %s 2>&1 | \
+// RUN: FileCheck --check-prefix=WITHATEXIT %s
+// RUN: %clang -target x86_64-apple-darwin -c -### %s 2>&1 | \
+// RUN: FileCheck --check-prefix=WITHATEXIT %s
+// RUN: %clang -target x86_64-pc-linux-gnu -fregister-global-dtors-with-atexit -fno-register-global-dtors-with-atexit -c -### %s 2>&1 | \
+// RUN: FileCheck --check-prefix=WITHOUTATEXIT %s
+// RUN: %clang -target x86_64-pc-linux-gnu -fno-register-global-dtors-with-atexit -fregister-global-dtors-with-atexit -c -### %s 2>&1 | \
+// RUN: FileCheck --check-prefix=WITHATEXIT %s
+// RUN: %clang -target x86_64-pc-linux-gnu -c -### %s 2>&1 | \
+// RUN: FileCheck --check-prefix=WITHOUTATEXIT %s
+
+// WITHATEXIT: -fregister-global-dtors-with-atexit
+// WITHOUTATEXIT-NOT: -fregister-global-dtors-with-atexit

cfe/trunk/test/Driver/rewrite-legacy-objc.m

 // RUN: %clang -no-canonical-prefixes -target x86_64-apple-macosx10.7.0 -rewrite-legacy-objc %s -o - -### 2>&1 | \
 // RUN:   FileCheck -check-prefix=TEST0 %s
 // TEST0: clang{{.*}}" "-cc1"
 // TEST0: "-rewrite-objc"
 // FIXME: CHECK-NOT is broken somehow, it doesn't work here. Check adjacency instead.
-// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx-fragile" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fobjc-runtime=macosx-fragile" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
 // TEST0: rewrite-legacy-objc.m"
 // RUN: %clang -no-canonical-prefixes -target i386-apple-macosx10.9.0 -rewrite-legacy-objc %s -o - -### 2>&1 | \
 // RUN:   FileCheck -check-prefix=TEST1 %s
 // RUN: %clang -no-canonical-prefixes -target i386-apple-macosx10.6.0 -rewrite-legacy-objc %s -o - -### 2>&1 | \
 // RUN:   FileCheck -check-prefix=TEST2 %s
-// TEST1: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx-fragile" "-fobjc-subscripting-legacy-runtime" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
-// TEST2: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx-fragile" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST1: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fobjc-runtime=macosx-fragile" "-fobjc-subscripting-legacy-runtime" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST2: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fobjc-runtime=macosx-fragile" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"

cfe/trunk/test/Driver/rewrite-objc.m

 // RUN: %clang -no-canonical-prefixes -target x86_64-apple-macosx10.7.0 -rewrite-objc %s -o - -### 2>&1 | \
 // RUN:   FileCheck -check-prefix=TEST0 %s
 // TEST0: clang{{.*}}" "-cc1"
 // TEST0: "-rewrite-objc"
 // FIXME: CHECK-NOT is broken somehow, it doesn't work here. Check adjacency instead.
-// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fobjc-runtime=macosx" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"