From c6c5af75f2c84d1b6204c20f1f31f23ee78b446e Mon Sep 17 00:00:00 2001
From: Martin Storsjo <martin@martin.st>
Date: Fri, 1 Sep 2017 06:41:55 +0000
Subject: [PATCH] Reland r312224 - [ItaniumCXXABI] Always use linkonce_odr
 linkage for RTTI data on MinGW

This fixes cases where dynamic classes produced RTTI data with
external linkage, producing linker errors about duplicate symbols.

This touches code close to what was changed in SVN r244266, but
this change doesn't break the tests added in that revision.

The previous version had missed to update CodeGenCXX/virt-dtor-key.cpp,
which had a behaviour change only when running the testsuite on windows.

Differential revision: https://reviews.llvm.org/D37327

llvm-svn: 312306
---
 clang/lib/CodeGen/ItaniumCXXABI.cpp     | 16 +++++++---------
 clang/test/CodeGenCXX/rtti-mingw64.cpp  |  5 +++++
 clang/test/CodeGenCXX/virt-dtor-key.cpp |  4 +++-
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index d78c032cec88..e07dbdd3abd0 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2998,15 +2998,13 @@ static llvm::GlobalVariable::LinkageTypes getTypeInfoLinkage(CodeGenModule &CGM,
         if (RD->hasAttr<DLLImportAttr>() &&
             ShouldUseExternalRTTIDescriptor(CGM, Ty))
           return llvm::GlobalValue::ExternalLinkage;
-      if (RD->isDynamicClass()) {
-        llvm::GlobalValue::LinkageTypes LT = CGM.getVTableLinkage(RD);
-        // MinGW won't export the RTTI information when there is a key function.
-        // Make sure we emit our own copy instead of attempting to dllimport it.
-        if (RD->hasAttr<DLLImportAttr>() &&
-            llvm::GlobalValue::isAvailableExternallyLinkage(LT))
-          LT = llvm::GlobalValue::LinkOnceODRLinkage;
-        return LT;
-      }
+      // MinGW always uses LinkOnceODRLinkage for type info.
+      if (RD->isDynamicClass() &&
+          !CGM.getContext()
+               .getTargetInfo()
+               .getTriple()
+               .isWindowsGNUEnvironment())
+        return CGM.getVTableLinkage(RD);
     }
 
     return llvm::GlobalValue::LinkOnceODRLinkage;
diff --git a/clang/test/CodeGenCXX/rtti-mingw64.cpp b/clang/test/CodeGenCXX/rtti-mingw64.cpp
index 818b11b64bc5..9f3e03961e89 100644
--- a/clang/test/CodeGenCXX/rtti-mingw64.cpp
+++ b/clang/test/CodeGenCXX/rtti-mingw64.cpp
@@ -2,7 +2,12 @@
 struct A { int a; };
 struct B : virtual A { int b; };
 B b;
+class C {
+  virtual ~C();
+};
+C::~C() {}
 
+// CHECK: @_ZTI1C = linkonce_odr
 // CHECK: @_ZTI1B = linkonce_odr constant { i8*, i8*, i32, i32, i8*, i64 }
 // CHECK-SAME:  i8* bitcast (i8** getelementptr inbounds (i8*, i8** @_ZTVN10__cxxabiv121__vmi_class_type_infoE, i64 2) to i8*),
 // CHECK-SAME:  i8* getelementptr inbounds ([3 x i8], [3 x i8]* @_ZTS1B, i32 0, i32 0),
diff --git a/clang/test/CodeGenCXX/virt-dtor-key.cpp b/clang/test/CodeGenCXX/virt-dtor-key.cpp
index 40c5a537cc53..d1055d4e30ca 100644
--- a/clang/test/CodeGenCXX/virt-dtor-key.cpp
+++ b/clang/test/CodeGenCXX/virt-dtor-key.cpp
@@ -1,5 +1,7 @@
-// RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang_cc1 -triple i386-linux -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang_cc1 -triple i386-windows-gnu -emit-llvm %s -o - | FileCheck %s -check-prefix CHECK-MINGW
 // CHECK: @_ZTI3foo = constant
+// CHECK-MINGW: @_ZTI3foo = linkonce_odr
 class foo {
    foo();
    virtual ~foo();