From 8a91585a7208986181e58e4055f57534e62471bc Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Thu, 15 Jan 2015 21:36:08 +0000
Subject: [PATCH] Use a trivial comdat for inline ctor/dtor when not using
 C5/D5.

When combined with llvm not producing implicit comdats, not doing this would
cause code bloat on ELF and link errors on COFF.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@226211 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CodeGenModule.cpp       | 13 +++++++++----
 lib/CodeGen/CodeGenModule.h         |  1 +
 lib/CodeGen/ItaniumCXXABI.cpp       |  2 ++
 test/CodeGenCXX/ctor-dtor-alias.cpp | 13 ++++++++-----
 4 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index 8981bfe89c..7a97aa64ea 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -1953,6 +1953,13 @@ static bool shouldBeInCOMDAT(CodeGenModule &CGM, const Decl &D) {
   llvm_unreachable("No such linkage");
 }
 
+void CodeGenModule::maybeSetTrivialComdat(const Decl &D,
+                                          llvm::GlobalObject &GO) {
+  if (!shouldBeInCOMDAT(*this, D))
+    return;
+  GO.setComdat(TheModule.getOrInsertComdat(GO.getName()));
+}
+
 void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
   llvm::Constant *Init = nullptr;
   QualType ASTTy = D->getType();
@@ -2096,8 +2103,7 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
     setTLSMode(GV, *D);
   }
 
-  if (shouldBeInCOMDAT(*this, *D))
-    GV->setComdat(TheModule.getOrInsertComdat(GV->getName()));
+  maybeSetTrivialComdat(*D, *GV);
 
   // Emit the initializer function if necessary.
   if (NeedsGlobalCtor || NeedsGlobalDtor)
@@ -2433,8 +2439,7 @@ void CodeGenModule::EmitGlobalFunctionDefinition(GlobalDecl GD,
 
   MaybeHandleStaticInExternC(D, Fn);
 
-  if (shouldBeInCOMDAT(*this, *D))
-    Fn->setComdat(TheModule.getOrInsertComdat(Fn->getName()));
+  maybeSetTrivialComdat(*D, *Fn);
 
   CodeGenFunction(*this).GenerateCode(D, Fn, FI);
 
diff --git a/lib/CodeGen/CodeGenModule.h b/lib/CodeGen/CodeGenModule.h
index ddcb414508..4559aecff1 100644
--- a/lib/CodeGen/CodeGenModule.h
+++ b/lib/CodeGen/CodeGenModule.h
@@ -606,6 +606,7 @@ public:
   const TargetInfo &getTarget() const { return Target; }
   const llvm::Triple &getTriple() const;
   bool supportsCOMDAT() const;
+  void maybeSetTrivialComdat(const Decl &D, llvm::GlobalObject &GO);
 
   CGCXXABI &getCXXABI() const { return *ABI; }
   llvm::LLVMContext &getLLVMContext() { return VMContext; }
diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index f2ffabcf3e..7d8ad465bf 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -3202,5 +3202,7 @@ void ItaniumCXXABI::emitCXXStructor(const CXXMethodDecl *MD,
       getMangleContext().mangleCXXCtorComdat(CD, Out);
     llvm::Comdat *C = CGM.getModule().getOrInsertComdat(Out.str());
     Fn->setComdat(C);
+  } else {
+    CGM.maybeSetTrivialComdat(*MD, *Fn);
   }
 }
diff --git a/test/CodeGenCXX/ctor-dtor-alias.cpp b/test/CodeGenCXX/ctor-dtor-alias.cpp
index bd60cb88bb..6f8aedc071 100644
--- a/test/CodeGenCXX/ctor-dtor-alias.cpp
+++ b/test/CodeGenCXX/ctor-dtor-alias.cpp
@@ -22,7 +22,10 @@ namespace test1 {
 // CHECK1-NOT: comdat
 
 // COFF doesn't support comdats with arbitrary names (C5/D5).
-// COFF-NOT: comdat
+// COFF: define weak_odr {{.*}} void @_ZN5test16foobarIvEC2Ev({{.*}} comdat align
+// COFF: define weak_odr {{.*}} void @_ZN5test16foobarIvEC1Ev({{.*}} comdat align
+// COFF: define weak_odr {{.*}} void @_ZN5test16foobarIvED2Ev({{.*}} comdat align
+// COFF: define weak_odr {{.*}} void @_ZN5test16foobarIvED0Ev({{.*}} comdat align
 
 template <typename T>
 struct foobar {
@@ -39,7 +42,7 @@ namespace test2 {
 
 // CHECK1: define internal void @__cxx_global_var_init()
 // CHECK1: call void @_ZN5test26foobarIvEC2Ev
-// CHECK1: define linkonce_odr void @_ZN5test26foobarIvEC2Ev(
+// CHECK1: define linkonce_odr void @_ZN5test26foobarIvEC2Ev({{.*}} comdat align
 void g();
 template <typename T> struct foobar {
   foobar() { g(); }
@@ -72,13 +75,13 @@ namespace test4 {
 
   // CHECK1: define internal void @__cxx_global_var_init2()
   // CHECK1: call i32 @__cxa_atexit{{.*}}_ZN5test41AD2Ev
-  // CHECK1: define linkonce_odr void @_ZN5test41AD2Ev(
+  // CHECK1: define linkonce_odr void @_ZN5test41AD2Ev({{.*}} comdat align
 
   // test that we don't do this optimization at -O0 so that the debugger can
   // see both destructors.
   // NOOPT: define internal void @__cxx_global_var_init2()
   // NOOPT: call i32 @__cxa_atexit{{.*}}@_ZN5test41BD2Ev
-  // NOOPT: define linkonce_odr void @_ZN5test41BD2Ev
+  // NOOPT: define linkonce_odr void @_ZN5test41BD2Ev({{.*}} comdat align
   struct A {
     virtual ~A() {}
   };
@@ -93,7 +96,7 @@ namespace test5 {
 
   // CHECK2: define internal void @__cxx_global_var_init3()
   // CHECK2: call i32 @__cxa_atexit{{.*}}_ZN5test51AD2Ev
-  // CHECK2: define linkonce_odr void @_ZN5test51AD2Ev(
+  // CHECK2: define linkonce_odr void @_ZN5test51AD2Ev({{.*}} comdat align
   struct A {
     virtual ~A() {}
   };
-- 
2.40.0