From 1bfd05a5a24fec130f673fb0c8133c50fb09f763 Mon Sep 17 00:00:00 2001
From: Hans Wennborg <hans@hanshq.net>
Date: Mon, 5 Feb 2018 09:59:14 +0000
Subject: Merging r324059:
 ------------------------------------------------------------------------
 r324059 | mstorsjo | 2018-02-02 07:22:35 +0100 (Fri, 02 Feb 2018) | 21 lines

[MinGW] Emit typeinfo locally for dllimported classes without key functions

This fixes building Qt as shared libraries with clang in MinGW
mode; previously subclasses of the QObjectData class (in other
DLLs than the base DLL) failed to find the typeinfo symbols
(that neither were emitted in the base DLL nor in the DLL
containing the subclass).

If the virtual destructor in the newly added testcase wouldn't
be pure (or if there'd be another non-pure virtual method),
it'd be a key function and things would work out even before this
change. Make sure to locally emit the typeinfo for these classes
as well.

This matches what GCC does in this specific testcase.

This fixes the root issue that spawned PR35146. (The difference
to GCC that is initially described in that bug still is present
though.)

Differential Revision: https://reviews.llvm.org/D42641
------------------------------------------------------------------------


git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_60@324219 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/ItaniumCXXABI.cpp             |  5 +++++
 test/CodeGenCXX/dllimport-missing-key.cpp | 20 ++++++++++++++++++++
 test/CodeGenCXX/dllimport-rtti.cpp        |  2 +-
 3 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGenCXX/dllimport-missing-key.cpp

diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index c375b82ea9..a3c2766dbb 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2761,6 +2761,11 @@ static bool ShouldUseExternalRTTIDescriptor(CodeGenModule &CGM,
     // N.B. We must always emit the RTTI data ourselves if there exists a key
     // function.
     bool IsDLLImport = RD->hasAttr<DLLImportAttr>();
+
+    // Don't import the RTTI but emit it locally.
+    if (CGM.getTriple().isWindowsGNUEnvironment() && IsDLLImport)
+      return false;
+
     if (CGM.getVTables().isVTableExternal(RD))
       return IsDLLImport && !CGM.getTriple().isWindowsItaniumEnvironment()
                  ? false
diff --git a/test/CodeGenCXX/dllimport-missing-key.cpp b/test/CodeGenCXX/dllimport-missing-key.cpp
new file mode 100644
index 0000000000..d8ef7aa7ea
--- /dev/null
+++ b/test/CodeGenCXX/dllimport-missing-key.cpp
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -triple i686-windows-gnu -emit-llvm -std=c++1y -O0 -o - %s -w | FileCheck --check-prefix=GNU %s
+
+class __declspec(dllimport) QObjectData {
+public:
+    virtual ~QObjectData() = 0;
+    void *ptr;
+
+    int method() const;
+};
+
+class LocalClass : public QObjectData {
+};
+
+void call() {
+    (new LocalClass())->method();
+}
+
+// GNU-DAG: @_ZTV11QObjectData = available_externally dllimport
+// GNU-DAG: @_ZTS11QObjectData = linkonce_odr
+// GNU-DAG: @_ZTI11QObjectData = linkonce_odr
diff --git a/test/CodeGenCXX/dllimport-rtti.cpp b/test/CodeGenCXX/dllimport-rtti.cpp
index 91e747ae1c..dfb39a15ed 100644
--- a/test/CodeGenCXX/dllimport-rtti.cpp
+++ b/test/CodeGenCXX/dllimport-rtti.cpp
@@ -12,7 +12,7 @@ struct __declspec(dllimport) S {
 // MSVC-DAG: @"\01??_R3S@@8" = linkonce_odr
 
 // GNU-DAG: @_ZTV1S = available_externally dllimport
-// GNU-DAG: @_ZTI1S = external dllimport
+// GNU-DAG: @_ZTI1S = linkonce_odr
 
 struct U : S {
 } u;
-- 
cgit v1.2.3