We were emitting construction v-tables with internal linkage all the time.

Emit them instead with the linkage of the VTT.

I'm actually really ambivalent about this;  it's what GCC does, but outside
of improving code size (if the linkage is coalescing), I'm not sure it's
at all relevant.  Construction vtables are naturally referenced only by the
VTT, which is itself only referenced by complete-object constructors and
destructors;  giving the construction vtables possibly-external linkage is
important if you have an optimization that drills through the VTT to a
reference to a particular construction vtable which it cannot just emit
itself.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@128374 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGVTT.cpp b/lib/CodeGen/CGVTT.cpp
index 3bc41e52544f7838e2659bddf14dd5f0107eea83..a6849f8f3d2118365ae638a4a315411f19829b3a 100644 (file)
--- a/lib/CodeGen/CGVTT.cpp
+++ b/lib/CodeGen/CGVTT.cpp
@@ -53,6 +53,10 @@ class VTTBuilder {
   /// GenerateDefinition - Whether the VTT builder should generate LLVM IR for
   /// the VTT.
   bool GenerateDefinition;
+
+  /// The linkage to use for any construction vtables required by this VTT.
+  /// Only required if we're building a definition.
+  llvm::GlobalVariable::LinkageTypes LinkageForConstructionVTables;
   
   /// GetAddrOfVTable - Returns the address of the vtable for the base class in
   /// the given vtable class.
@@ -109,7 +113,9 @@ class VTTBuilder {
   
 public:
   VTTBuilder(CodeGenModule &CGM, const CXXRecordDecl *MostDerivedClass,
-             bool GenerateDefinition);
+             bool GenerateDefinition,
+             llvm::GlobalVariable::LinkageTypes LinkageForConstructionVTables
+               = (llvm::GlobalVariable::LinkageTypes) -1);
 
   // getVTTComponents - Returns a reference to the VTT components.
   const VTTComponentsVectorTy &getVTTComponents() const {
@@ -132,10 +138,15 @@ public:
 
 VTTBuilder::VTTBuilder(CodeGenModule &CGM,
                        const CXXRecordDecl *MostDerivedClass,
-                       bool GenerateDefinition)
+                       bool GenerateDefinition,
+          llvm::GlobalVariable::LinkageTypes LinkageForConstructionVTables)
   : CGM(CGM), MostDerivedClass(MostDerivedClass), 
   MostDerivedClassLayout(CGM.getContext().getASTRecordLayout(MostDerivedClass)),
-  GenerateDefinition(GenerateDefinition) {
+    GenerateDefinition(GenerateDefinition),
+    LinkageForConstructionVTables(LinkageForConstructionVTables) {
+  assert(!GenerateDefinition ||
+         LinkageForConstructionVTables
+           != (llvm::GlobalVariable::LinkageTypes) -1);
     
   // Lay out this VTT.
   LayoutVTT(BaseSubobject(MostDerivedClass, CharUnits::Zero()), 
@@ -157,6 +168,7 @@ VTTBuilder::GetAddrOfVTable(BaseSubobject Base, bool BaseIsVirtual,
   
   return CGM.getVTables().GenerateConstructionVTable(MostDerivedClass, 
                                                      Base, BaseIsVirtual,
+                                           LinkageForConstructionVTables,
                                                      AddressPoints);
 }
 
@@ -371,7 +383,7 @@ void
 CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
                                   llvm::GlobalVariable::LinkageTypes Linkage,
                                   const CXXRecordDecl *RD) {
-  VTTBuilder Builder(CGM, RD, /*GenerateDefinition=*/true);
+  VTTBuilder Builder(CGM, RD, /*GenerateDefinition=*/true, Linkage);
 
   const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
   const llvm::ArrayType *ArrayType = 

diff --git a/lib/CodeGen/CGVTables.cpp b/lib/CodeGen/CGVTables.cpp
index 6c1b331be7815dc397511b8971b5dee373abe547..17d3cde8b0f38dc59d6370f85309ca9b07a8cdda 100644 (file)
--- a/lib/CodeGen/CGVTables.cpp
+++ b/lib/CodeGen/CGVTables.cpp
@@ -3065,6 +3065,7 @@ llvm::GlobalVariable *
 CodeGenVTables::GenerateConstructionVTable(const CXXRecordDecl *RD, 
                                       const BaseSubobject &Base, 
                                       bool BaseIsVirtual, 
+                                   llvm::GlobalVariable::LinkageTypes Linkage,
                                       VTableAddressPointsMapTy& AddressPoints) {
   VTableBuilder Builder(*this, Base.getBase(), 
                         CGM.getContext().toBits(Base.getBaseOffset()), 
@@ -3093,8 +3094,11 @@ CodeGenVTables::GenerateConstructionVTable(const CXXRecordDecl *RD,
 
   // Create the variable that will hold the construction vtable.
   llvm::GlobalVariable *VTable = 
-    CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType, 
-                                          llvm::GlobalValue::InternalLinkage);
+    CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType, Linkage);
+  CGM.setTypeVisibility(VTable, RD, CodeGenModule::TVK_ForConstructionVTable);
+
+  // V-tables are always unnamed_addr.
+  VTable->setUnnamedAddr(true);
 
   // Add the thunks.
   VTableThunksTy VTableThunks;

diff --git a/lib/CodeGen/CGVTables.h b/lib/CodeGen/CGVTables.h
index 7197a57298d0822f36705e2ee53ee97300f5b415..b2f940185858b1f90d125ed50f22d08387d81aca 100644 (file)
--- a/lib/CodeGen/CGVTables.h
+++ b/lib/CodeGen/CGVTables.h
@@ -1,4 +1,4 @@
-//===--- CGVTables.h - Emit LLVM Code for C++ vtables ---------------------===//
+//===--- CGVTables.h - Emit LLVM Code for C++ vtables -----------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -260,6 +260,7 @@ public:
   llvm::GlobalVariable *
   GenerateConstructionVTable(const CXXRecordDecl *RD, const BaseSubobject &Base, 
                              bool BaseIsVirtual, 
+                             llvm::GlobalVariable::LinkageTypes Linkage,
                              VTableAddressPointsMapTy& AddressPoints);
 
     

diff --git a/lib/CodeGen/CodeGenModule.h b/lib/CodeGen/CodeGenModule.h
index e6fcf61473e8a811a68de58fdf636935a7d55cc2..aa6a0535a11c476232701d94d686358017b99406 100644 (file)
--- a/lib/CodeGen/CodeGenModule.h
+++ b/lib/CodeGen/CodeGenModule.h
@@ -313,6 +313,7 @@ public:
   enum TypeVisibilityKind {
     TVK_ForVTT,
     TVK_ForVTable,
+    TVK_ForConstructionVTable,
     TVK_ForRTTI,
     TVK_ForRTTIName
   };

diff --git a/test/CodeGenCXX/mangle-subst-std.cpp b/test/CodeGenCXX/mangle-subst-std.cpp
index 8d79988da8e344d93749b75a8e887ff5897f3dac..fea3582d321a38efce41d5ee1d942eb753246d88 100644 (file)
--- a/test/CodeGenCXX/mangle-subst-std.cpp
+++ b/test/CodeGenCXX/mangle-subst-std.cpp
@@ -5,8 +5,8 @@
 
 // CHECK: @_ZTTSd = linkonce_odr unnamed_addr constant
 // CHECK: @_ZTVSd = linkonce_odr unnamed_addr constant 
-// CHECK: @_ZTCSd0_Si = internal constant 
-// CHECK: @_ZTCSd16_So = internal constant
+// CHECK: @_ZTCSd0_Si = linkonce_odr unnamed_addr constant 
+// CHECK: @_ZTCSd16_So = linkonce_odr unnamed_addr constant
 // CHECK: @_ZTTSo = linkonce_odr unnamed_addr constant
 // CHECK: @_ZTVSo = linkonce_odr unnamed_addr constant
 // CHECK: @_ZTTSi = linkonce_odr unnamed_addr constant