Don't use the third field of llvm.global_ctors for MachO.

The field is defined as:

If the third field is present, non-null, and points to a global variable or function, the initializer function will only run if the associated data from the current module is not discarded.

And without COMDATs we can't implement that.

llvm-svn: 218097

3 files changed, 16 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index 3e5f42e18c2..91ae6a8c2fa 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -301,6 +301,9 @@ CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
   auto *ISA = D->getAttr<InitSegAttr>();
   CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
                                                           PerformInit);
+
+  llvm::GlobalVariable *Key = supportsCOMDAT() ? Addr : nullptr;
+
   if (D->getTLSKind()) {
     // FIXME: Should we support init_priority for thread_local?
     // FIXME: Ideally, initialization of instantiated thread_local static data
@@ -330,12 +333,12 @@ CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
     // being initialized.  On most platforms, this is a minor startup time
     // optimization.  In the MS C++ ABI, there are no guard variables, so this
     // COMDAT key is required for correctness.
-    AddGlobalCtor(Fn, 65535, Addr);
+    AddGlobalCtor(Fn, 65535, Key);
     DelayedCXXInitPosition.erase(D);
   } else if (D->hasAttr<SelectAnyAttr>()) {
     // SelectAny globals will be comdat-folded. Put the initializer into a COMDAT
     // group associated with the global, so the initializers get folded too.
-    AddGlobalCtor(Fn, 65535, Addr);
+    AddGlobalCtor(Fn, 65535, Key);
     DelayedCXXInitPosition.erase(D);
   } else {
     llvm::DenseMap<const Decl *, unsigned>::iterator I =
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index b36d4a66cd8..a095c9ddbb9 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -599,6 +599,9 @@ public:
   DiagnosticsEngine &getDiags() const { return Diags; }
   const llvm::DataLayout &getDataLayout() const { return TheDataLayout; }
   const TargetInfo &getTarget() const { return Target; }
+  const llvm::Triple &getTriple() const;
+  bool supportsCOMDAT() const;
+
   CGCXXABI &getCXXABI() const { return *ABI; }
   llvm::LLVMContext &getLLVMContext() { return VMContext; }
 
diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 9bf1dbbd0d8..cca825c1c56 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -6868,6 +6868,14 @@ static bool getTypeString(SmallStringEnc &Enc, const Decl *D,
 // Driver code
 //===----------------------------------------------------------------------===//
 
+const llvm::Triple &CodeGenModule::getTriple() const {
+  return getTarget().getTriple();
+}
+
+bool CodeGenModule::supportsCOMDAT() const {
+  return !getTriple().isOSBinFormatMachO();
+}
+
 const TargetCodeGenInfo &CodeGenModule::getTargetCodeGenInfo() {
   if (TheTargetCodeGenInfo)
     return *TheTargetCodeGenInfo;