r260388 - [MS ABI] Never reference dllimport'd vtables
David Majnemer via cfe-commits
cfe-commits at lists.llvm.org
Wed Feb 10 09:40:48 PST 2016
Author: majnemer
Date: Wed Feb 10 11:40:47 2016
New Revision: 260388
URL: http://llvm.org/viewvc/llvm-project?rev=260388&view=rev
Log:
[MS ABI] Never reference dllimport'd vtables
Referencing a dllimported vtable is impossible in a constexpr
constructor. It would be friendlier to C++ programmers if we
synthesized a copy of the vftable which referenced imported virtual
functions. This would let us initialize the object in a way which
preserves both the intent to import functionality from another DLL while
also making constexpr work.
Differential Revision: http://reviews.llvm.org/D17061
Modified:
cfe/trunk/lib/AST/MicrosoftMangle.cpp
cfe/trunk/lib/AST/VTableBuilder.cpp
cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp
cfe/trunk/test/CodeGenCXX/dllimport-rtti.cpp
cfe/trunk/test/CodeGenCXX/dllimport.cpp
cfe/trunk/test/CodeGenCXX/microsoft-abi-vftables.cpp
Modified: cfe/trunk/lib/AST/MicrosoftMangle.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/MicrosoftMangle.cpp?rev=260388&r1=260387&r2=260388&view=diff
==============================================================================
--- cfe/trunk/lib/AST/MicrosoftMangle.cpp (original)
+++ cfe/trunk/lib/AST/MicrosoftMangle.cpp Wed Feb 10 11:40:47 2016
@@ -2599,7 +2599,10 @@ void MicrosoftMangleContextImpl::mangleC
// NOTE: <cvr-qualifiers> here is always 'B' (const). <storage-class>
// is always '6' for vftables.
MicrosoftCXXNameMangler Mangler(*this, Out);
- Mangler.getStream() << "\01??_7";
+ if (Derived->hasAttr<DLLImportAttr>())
+ Mangler.getStream() << "\01??_S";
+ else
+ Mangler.getStream() << "\01??_7";
Mangler.mangleName(Derived);
Mangler.getStream() << "6B"; // '6' for vftable, 'B' for const.
for (const CXXRecordDecl *RD : BasePath)
Modified: cfe/trunk/lib/AST/VTableBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/VTableBuilder.cpp?rev=260388&r1=260387&r2=260388&view=diff
==============================================================================
--- cfe/trunk/lib/AST/VTableBuilder.cpp (original)
+++ cfe/trunk/lib/AST/VTableBuilder.cpp Wed Feb 10 11:40:47 2016
@@ -2548,7 +2548,6 @@ public:
// Only include the RTTI component if we know that we will provide a
// definition of the vftable.
HasRTTIComponent = Context.getLangOpts().RTTIData &&
- !MostDerivedClass->hasAttr<DLLImportAttr>() &&
MostDerivedClass->getTemplateSpecializationKind() !=
TSK_ExplicitInstantiationDeclaration;
Modified: cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp?rev=260388&r1=260387&r2=260388&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp (original)
+++ cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp Wed Feb 10 11:40:47 2016
@@ -1673,7 +1673,16 @@ llvm::GlobalVariable *MicrosoftCXXABI::g
SmallString<256> VFTableName;
mangleVFTableName(getMangleContext(), RD, VFPtr, VFTableName);
- llvm::GlobalValue::LinkageTypes VFTableLinkage = CGM.getVTableLinkage(RD);
+ // Classes marked __declspec(dllimport) need vftables generated on the
+ // import-side in order to support features like constexpr. No other
+ // translation unit relies on the emission of the local vftable, translation
+ // units are expected to generate them as needed.
+ //
+ // Because of this unique behavior, we maintain this logic here instead of
+ // getVTableLinkage.
+ llvm::GlobalValue::LinkageTypes VFTableLinkage =
+ RD->hasAttr<DLLImportAttr>() ? llvm::GlobalValue::LinkOnceODRLinkage
+ : CGM.getVTableLinkage(RD);
bool VFTableComesFromAnotherTU =
llvm::GlobalValue::isAvailableExternallyLinkage(VFTableLinkage) ||
llvm::GlobalValue::isExternalLinkage(VFTableLinkage);
@@ -1746,9 +1755,7 @@ llvm::GlobalVariable *MicrosoftCXXABI::g
if (C)
VTable->setComdat(C);
- if (RD->hasAttr<DLLImportAttr>())
- VFTable->setDLLStorageClass(llvm::GlobalValue::DLLImportStorageClass);
- else if (RD->hasAttr<DLLExportAttr>())
+ if (RD->hasAttr<DLLExportAttr>())
VFTable->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
VFTablesMap[ID] = VFTable;
Modified: cfe/trunk/test/CodeGenCXX/dllimport-rtti.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/dllimport-rtti.cpp?rev=260388&r1=260387&r2=260388&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/dllimport-rtti.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/dllimport-rtti.cpp Wed Feb 10 11:40:47 2016
@@ -4,7 +4,8 @@
struct __declspec(dllimport) S {
virtual void f() {}
} s;
-// MSVC-DAG: @"\01??_7S@@6B@" = available_externally dllimport
+// MSVC: [[VF_S:.*]] = private unnamed_addr constant [2 x i8*]
+// MSVC-DAG: @"\01??_SS@@6B@" = unnamed_addr alias i8*, getelementptr inbounds ([2 x i8*], [2 x i8*]* [[VF_S]], i32 0, i32 1)
// MSVC-DAG: @"\01??_R0?AUS@@@8" = linkonce_odr
// MSVC-DAG: @"\01??_R1A@?0A at EA@S@@8" = linkonce_odr
// MSVC-DAG: @"\01??_R2S@@8" = linkonce_odr
Modified: cfe/trunk/test/CodeGenCXX/dllimport.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/dllimport.cpp?rev=260388&r1=260387&r2=260388&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/dllimport.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/dllimport.cpp Wed Feb 10 11:40:47 2016
@@ -614,7 +614,7 @@ USEMEMFUNC(V, foo)
struct __declspec(dllimport) W { virtual void foo() {} };
USECLASS(W)
// vftable:
-// MO1-DAG: @"\01??_7W@@6B@" = available_externally dllimport unnamed_addr constant [1 x i8*] [i8* bitcast (void (%struct.W*)* @"\01?foo at W@@UAEXXZ" to i8*)]
+// MO1-DAG: @"\01??_SW@@6B@" = linkonce_odr unnamed_addr constant [1 x i8*] [i8* bitcast (void (%struct.W*)* @"\01?foo at W@@UAEXXZ" to i8*)]
// GO1-DAG: @_ZTV1W = available_externally dllimport unnamed_addr constant [3 x i8*] [i8* null, i8* null, i8* bitcast (void (%struct.W*)* @_ZN1W3fooEv to i8*)]
struct __declspec(dllimport) KeyFuncClass {
Modified: cfe/trunk/test/CodeGenCXX/microsoft-abi-vftables.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/microsoft-abi-vftables.cpp?rev=260388&r1=260387&r2=260388&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/microsoft-abi-vftables.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/microsoft-abi-vftables.cpp Wed Feb 10 11:40:47 2016
@@ -4,8 +4,6 @@
// RTTI-DAG: $"\01??_7S@@6B@" = comdat largest
// RTTI-DAG: $"\01??_7V@@6B@" = comdat largest
-// RTTI-NOT: @"\01??_R4U@@6B@"
-
struct S {
virtual ~S();
} s;
@@ -19,9 +17,10 @@ struct __declspec(dllimport) U {
virtual ~U();
} u;
-// RTTI-DAG: @"\01??_7U@@6B@" = available_externally dllimport unnamed_addr constant [1 x i8*] [i8* bitcast ({{.*}} @"\01??_GU@@UAEPAXI at Z" to i8*)]
+// RTTI-DAG: [[VTABLE_U:@.*]] = private unnamed_addr constant [2 x i8*] [i8* bitcast ({{.*}} @"\01??_R4U@@6B@" to i8*), i8* bitcast ({{.*}} @"\01??_GU@@UAEPAXI at Z" to i8*)]
+// RTTI-DAG: @"\01??_SU@@6B@" = unnamed_addr alias i8*, getelementptr inbounds ([2 x i8*], [2 x i8*]* [[VTABLE_U]], i32 0, i32 1)
-// NO-RTTI-DAG: @"\01??_7U@@6B@" = available_externally dllimport unnamed_addr constant [1 x i8*] [i8* bitcast ({{.*}} @"\01??_GU@@UAEPAXI at Z" to i8*)]
+// NO-RTTI-DAG: @"\01??_SU@@6B@" = linkonce_odr unnamed_addr constant [1 x i8*] [i8* bitcast ({{.*}} @"\01??_GU@@UAEPAXI at Z" to i8*)]
struct __declspec(dllexport) V {
virtual ~V();
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