From 358d056c148bdeebb502ab94edd97eb1637f6f92 Mon Sep 17 00:00:00 2001 From: John McCall Date: Sun, 27 Mar 2011 09:00:25 +0000 Subject: [PATCH] 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. llvm-svn: 128374 --- clang/lib/CodeGen/CGVTT.cpp | 20 ++++++++++++++++---- clang/lib/CodeGen/CGVTables.cpp | 8 ++++++-- clang/lib/CodeGen/CGVTables.h | 3 ++- clang/lib/CodeGen/CodeGenModule.h | 1 + clang/test/CodeGenCXX/mangle-subst-std.cpp | 4 ++-- 5 files changed, 27 insertions(+), 9 deletions(-) diff --git a/clang/lib/CodeGen/CGVTT.cpp b/clang/lib/CodeGen/CGVTT.cpp index 3bc41e52544f..a6849f8f3d21 100644 --- a/clang/lib/CodeGen/CGVTT.cpp +++ b/clang/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/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp index 6c1b331be781..17d3cde8b0f3 100644 --- a/clang/lib/CodeGen/CGVTables.cpp +++ b/clang/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/clang/lib/CodeGen/CGVTables.h b/clang/lib/CodeGen/CGVTables.h index 7197a57298d0..b2f940185858 100644 --- a/clang/lib/CodeGen/CGVTables.h +++ b/clang/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/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h index e6fcf61473e8..aa6a0535a11c 100644 --- a/clang/lib/CodeGen/CodeGenModule.h +++ b/clang/lib/CodeGen/CodeGenModule.h @@ -313,6 +313,7 @@ public: enum TypeVisibilityKind { TVK_ForVTT, TVK_ForVTable, + TVK_ForConstructionVTable, TVK_ForRTTI, TVK_ForRTTIName }; diff --git a/clang/test/CodeGenCXX/mangle-subst-std.cpp b/clang/test/CodeGenCXX/mangle-subst-std.cpp index 8d79988da8e3..fea3582d321a 100644 --- a/clang/test/CodeGenCXX/mangle-subst-std.cpp +++ b/clang/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