Don't use comdats for initializers on platforms that don't support it

In particular, pre-.init_array ELF uses the .ctors section mechanism.
MinGW COFF also uses .ctors, now that I think about it. Therefore,
restrict this optimization to the two platforms that are currently known
to work: ELF with .init_array and COFF with .CRT$XCU.

llvm-svn: 218287

4 files changed, 12 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index 91ae6a8c2fa..7b8d3d57a97 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -302,7 +302,7 @@ CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
   CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
                                                           PerformInit);
 
-  llvm::GlobalVariable *Key = supportsCOMDAT() ? Addr : nullptr;
+  llvm::GlobalVariable *Key = supportsCOMDATInitializers() ? Addr : nullptr;
 
   if (D->getTLSKind()) {
     // FIXME: Should we support init_priority for thread_local?
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index afd5b5d404f..d62d68a408a 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -601,6 +601,7 @@ public:
   const TargetInfo &getTarget() const { return Target; }
   const llvm::Triple &getTriple() const;
   bool supportsCOMDAT() const;
+  bool supportsCOMDATInitializers() const;
 
   CGCXXABI &getCXXABI() const { return *ABI; }
   llvm::LLVMContext &getLLVMContext() { return VMContext; }
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index 84bfb6aa505..6d73a4b184c 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -1668,7 +1668,8 @@ void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
 
     // The ABI says: It is suggested that it be emitted in the same COMDAT group
     // as the associated data object
-    if (!D.isLocalVarDecl() && var->isWeakForLinker() && CGM.supportsCOMDAT()) {
+    if (!D.isLocalVarDecl() && var->isWeakForLinker() &&
+        CGM.supportsCOMDATInitializers()) {
       llvm::Comdat *C = CGM.getModule().getOrInsertComdat(var->getName());
       guard->setComdat(C);
       var->setComdat(C);
diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 17552a50692..de129e57cbb 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -6877,6 +6877,14 @@ bool CodeGenModule::supportsCOMDAT() const {
   return !getTriple().isOSBinFormatMachO();
 }
 
+bool CodeGenModule::supportsCOMDATInitializers() const {
+  // We can only put initializers in comdat groups on ELF with .init_array and
+  // COFF with .CRT$XCU.
+  return supportsCOMDAT() &&
+         ((getTriple().isOSBinFormatELF() && getCodeGenOpts().UseInitArray) ||
+          (getTriple().isWindowsMSVCEnvironment()));
+}
+
 const TargetCodeGenInfo &CodeGenModule::getTargetCodeGenInfo() {
   if (TheTargetCodeGenInfo)
     return *TheTargetCodeGenInfo;