Move the VTT related code into its own file, CGVTT.cpp

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@94079 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 398 insertions, 0 deletions

diff --git a/lib/CodeGen/CGVTT.cpp b/lib/CodeGen/CGVTT.cpp
new file mode 100644
index 0000000000..9714bd9d96
--- /dev/null
+++ b/lib/CodeGen/CGVTT.cpp
@@ -0,0 +1,398 @@
+//===--- CGVTT.cpp - Emit LLVM Code for C++ VTTs --------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This contains code dealing with C++ code generation of VTTs (vtable tables).
+//
+//===----------------------------------------------------------------------===//
+
+#include "CodeGenModule.h"
+#include "clang/AST/RecordLayout.h"
+using namespace clang;
+using namespace CodeGen;
+
+#define D1(x)
+
+namespace {
+class VTTBuilder {
+  /// Inits - The list of values built for the VTT.
+  std::vector<llvm::Constant *> &Inits;
+  /// Class - The most derived class that this vtable is being built for.
+  const CXXRecordDecl *Class;
+  CodeGenModule &CGM;  // Per-module state.
+  llvm::SmallSet<const CXXRecordDecl *, 32> SeenVBase;
+  /// BLayout - Layout for the most derived class that this vtable is being
+  /// built for.
+  const ASTRecordLayout &BLayout;
+  CGVtableInfo::AddrMap_t &AddressPoints;
+  // vtbl - A pointer to the vtable for Class.
+  llvm::Constant *ClassVtbl;
+  llvm::LLVMContext &VMContext;
+
+  /// SeenVBasesInSecondary - The seen virtual bases when building the 
+  /// secondary virtual pointers.
+  llvm::SmallPtrSet<const CXXRecordDecl *, 32> SeenVBasesInSecondary;
+
+  llvm::DenseMap<const CXXRecordDecl *, uint64_t> SubVTTIndicies;
+  
+  bool GenerateDefinition;
+
+  llvm::DenseMap<BaseSubobject, llvm::Constant *> CtorVtables;
+  llvm::DenseMap<std::pair<const CXXRecordDecl *, BaseSubobject>, uint64_t> 
+    CtorVtableAddressPoints;
+  
+  llvm::Constant *getCtorVtable(const BaseSubobject &Base) {
+    if (!GenerateDefinition)
+      return 0;
+
+    llvm::Constant *&CtorVtable = CtorVtables[Base];
+    if (!CtorVtable) {
+      // Build the vtable.
+      CGVtableInfo::CtorVtableInfo Info
+        = CGM.getVtableInfo().getCtorVtable(Class, Base);
+      
+      CtorVtable = Info.Vtable;
+      
+      // Add the address points for this base.
+      for (CGVtableInfo::AddressPointsMapTy::const_iterator I =
+           Info.AddressPoints.begin(), E = Info.AddressPoints.end(); 
+           I != E; ++I) {
+        uint64_t &AddressPoint = 
+          CtorVtableAddressPoints[std::make_pair(Base.getBase(), I->first)];
+        
+        // Check if we already have the address points for this base.
+        if (AddressPoint)
+          break;
+
+        // Otherwise, insert it.
+        AddressPoint = I->second;
+      }      
+    }
+    
+    return CtorVtable;
+  }
+  
+  
+  /// BuildVtablePtr - Build up a referene to the given secondary vtable
+  llvm::Constant *BuildVtablePtr(llvm::Constant *Vtable,
+                                 const CXXRecordDecl *VtableClass,
+                                 const CXXRecordDecl *RD,
+                                 uint64_t Offset) {
+    if (!GenerateDefinition)
+      return 0;
+
+    uint64_t AddressPoint;
+    
+    if (VtableClass != Class) {
+      // We have a ctor vtable, look for the address point in the ctor vtable
+      // address points.
+      AddressPoint = 
+        CtorVtableAddressPoints[std::make_pair(VtableClass, 
+                                               BaseSubobject(RD, Offset))];
+    } else { 
+      AddressPoint = 
+        (*AddressPoints[VtableClass])[std::make_pair(RD, Offset)];
+    }
+
+    // FIXME: We can never have 0 address point.  Do this for now so gepping
+    // retains the same structure.  Later we'll just assert.
+    if (AddressPoint == 0)
+      AddressPoint = 1;
+    D1(printf("XXX address point for %s in %s layout %s at offset %d was %d\n",
+              RD->getNameAsCString(), VtblClass->getNameAsCString(),
+              Class->getNameAsCString(), (int)Offset, (int)AddressPoint));
+
+    llvm::Value *Idxs[] = {
+      llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), 0),
+      llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), AddressPoint)
+    };
+    
+    llvm::Constant *Init = 
+      llvm::ConstantExpr::getInBoundsGetElementPtr(Vtable, Idxs, 2);
+
+    const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(VMContext);
+    return llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
+  }
+
+  /// Secondary - Add the secondary vtable pointers to Inits.  Offset is the
+  /// current offset in bits to the object we're working on.
+  void Secondary(const CXXRecordDecl *RD, llvm::Constant *vtbl,
+                 const CXXRecordDecl *VtblClass, uint64_t Offset=0,
+                 bool MorallyVirtual=false) {
+    if (RD->getNumVBases() == 0 && ! MorallyVirtual)
+      return;
+
+    for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
+           e = RD->bases_end(); i != e; ++i) {
+      const CXXRecordDecl *Base =
+        cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
+
+      // We only want to visit each virtual base once.
+      if (i->isVirtual() && SeenVBasesInSecondary.count(Base))
+        continue;
+      
+      // Itanium C++ ABI 2.6.2:
+      //   Secondary virtual pointers are present for all bases with either
+      //   virtual bases or virtual function declarations overridden along a 
+      //   virtual path.
+      //
+      // If the base class is not dynamic, we don't want to add it, nor any
+      // of its base classes.
+      if (!Base->isDynamicClass())
+        continue;
+
+      const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
+      const CXXRecordDecl *PrimaryBase = Layout.getPrimaryBase();
+      const bool PrimaryBaseWasVirtual = Layout.getPrimaryBaseWasVirtual();
+      bool NonVirtualPrimaryBase;
+      NonVirtualPrimaryBase = !PrimaryBaseWasVirtual && Base == PrimaryBase;
+      bool BaseMorallyVirtual = MorallyVirtual | i->isVirtual();
+      uint64_t BaseOffset;
+      if (!i->isVirtual()) {
+        const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
+        BaseOffset = Offset + Layout.getBaseClassOffset(Base);
+      } else
+        BaseOffset = BLayout.getVBaseClassOffset(Base);
+      llvm::Constant *subvtbl = vtbl;
+      const CXXRecordDecl *subVtblClass = VtblClass;
+      if ((Base->getNumVBases() || BaseMorallyVirtual)
+          && !NonVirtualPrimaryBase) {
+        llvm::Constant *init;
+        if (BaseMorallyVirtual || VtblClass == Class)
+          init = BuildVtablePtr(vtbl, VtblClass, Base, BaseOffset);
+        else {
+          init = getCtorVtable(BaseSubobject(Base, BaseOffset));
+          
+          subvtbl = init;
+          subVtblClass = Base;
+          
+          init = BuildVtablePtr(init, Class, Base, BaseOffset);
+        }
+
+        Inits.push_back(init);
+      }
+      
+      if (i->isVirtual())
+        SeenVBasesInSecondary.insert(Base);
+      
+      Secondary(Base, subvtbl, subVtblClass, BaseOffset, BaseMorallyVirtual);
+    }
+  }
+
+  /// BuiltVTT - Add the VTT to Inits.  Offset is the offset in bits to the
+  /// currnet object we're working on.
+  void BuildVTT(const CXXRecordDecl *RD, uint64_t Offset, bool MorallyVirtual) {
+    // Itanium C++ ABI 2.6.2:
+    //   An array of virtual table addresses, called the VTT, is declared for 
+    //   each class type that has indirect or direct virtual base classes.
+    if (RD->getNumVBases() == 0)
+      return;
+
+    // Remember the sub-VTT index.
+    SubVTTIndicies[RD] = Inits.size();
+
+    llvm::Constant *Vtable;
+    const CXXRecordDecl *VtableClass;
+
+    // First comes the primary virtual table pointer...
+    if (MorallyVirtual) {
+      Vtable = ClassVtbl;
+      VtableClass = Class;
+    } else {
+      Vtable = getCtorVtable(BaseSubobject(RD, Offset));
+      VtableClass = RD;
+    }
+    
+    llvm::Constant *Init = BuildVtablePtr(Vtable, VtableClass, RD, Offset);
+    Inits.push_back(Init);
+
+    // then the secondary VTTs....
+    SecondaryVTTs(RD, Offset, MorallyVirtual);
+
+    // Make sure to clear the set of seen virtual bases.
+    SeenVBasesInSecondary.clear();
+
+    // and last the secondary vtable pointers.
+    Secondary(RD, Vtable, VtableClass, Offset, MorallyVirtual);
+  }
+
+  /// SecondaryVTTs - Add the secondary VTTs to Inits.  The secondary VTTs are
+  /// built from each direct non-virtual proper base that requires a VTT in
+  /// declaration order.
+  void SecondaryVTTs(const CXXRecordDecl *RD, uint64_t Offset=0,
+                     bool MorallyVirtual=false) {
+    for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
+           e = RD->bases_end(); i != e; ++i) {
+      const CXXRecordDecl *Base =
+        cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
+      if (i->isVirtual())
+        continue;
+      const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
+      uint64_t BaseOffset = Offset + Layout.getBaseClassOffset(Base);
+      
+      BuildVTT(Base, BaseOffset, MorallyVirtual);
+    }
+  }
+
+  /// VirtualVTTs - Add the VTT for each proper virtual base in inheritance
+  /// graph preorder.
+  void VirtualVTTs(const CXXRecordDecl *RD) {
+    for (CXXRecordDecl::base_class_const_iterator i = RD->bases_begin(),
+           e = RD->bases_end(); i != e; ++i) {
+      const CXXRecordDecl *Base =
+        cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
+      if (i->isVirtual() && !SeenVBase.count(Base)) {
+        SeenVBase.insert(Base);
+        uint64_t BaseOffset = BLayout.getVBaseClassOffset(Base);
+        BuildVTT(Base, BaseOffset, false);
+      }
+      VirtualVTTs(Base);
+    }
+  }
+
+public:
+  VTTBuilder(std::vector<llvm::Constant *> &inits, const CXXRecordDecl *c,
+             CodeGenModule &cgm, bool GenerateDefinition)
+    : Inits(inits), Class(c), CGM(cgm),
+      BLayout(cgm.getContext().getASTRecordLayout(c)),
+      AddressPoints(*cgm.getVtableInfo().AddressPoints[c]),
+      VMContext(cgm.getModule().getContext()),
+      GenerateDefinition(GenerateDefinition) {
+    
+    // First comes the primary virtual table pointer for the complete class...
+    ClassVtbl = GenerateDefinition ? CGM.getVtableInfo().getVtable(Class) : 0;
+
+    llvm::Constant *Init = BuildVtablePtr(ClassVtbl, Class, Class, 0);
+    Inits.push_back(Init);
+    
+    // then the secondary VTTs...
+    SecondaryVTTs(Class);
+
+    // Make sure to clear the set of seen virtual bases.
+    SeenVBasesInSecondary.clear();
+
+    // then the secondary vtable pointers...
+    Secondary(Class, ClassVtbl, Class);
+
+    // and last, the virtual VTTs.
+    VirtualVTTs(Class);
+  }
+  
+  llvm::DenseMap<const CXXRecordDecl *, uint64_t> &getSubVTTIndicies() {
+    return SubVTTIndicies;
+  }
+};
+}
+
+llvm::GlobalVariable *
+CGVtableInfo::GenerateVTT(llvm::GlobalVariable::LinkageTypes Linkage,
+                          bool GenerateDefinition,
+                          const CXXRecordDecl *RD) {
+  // Only classes that have virtual bases need a VTT.
+  if (RD->getNumVBases() == 0)
+    return 0;
+
+  llvm::SmallString<256> OutName;
+  CGM.getMangleContext().mangleCXXVTT(RD, OutName);
+  llvm::StringRef Name = OutName.str();
+
+  D1(printf("vtt %s\n", RD->getNameAsCString()));
+
+  llvm::GlobalVariable *GV = CGM.getModule().getGlobalVariable(Name);
+  if (GV == 0 || GV->isDeclaration()) {
+    const llvm::Type *Int8PtrTy = 
+      llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
+
+    std::vector<llvm::Constant *> inits;
+    VTTBuilder b(inits, RD, CGM, GenerateDefinition);
+
+    const llvm::ArrayType *Type = llvm::ArrayType::get(Int8PtrTy, inits.size());
+    llvm::Constant *Init = 0;
+    if (GenerateDefinition)
+      Init = llvm::ConstantArray::get(Type, inits);
+
+    llvm::GlobalVariable *OldGV = GV;
+    GV = new llvm::GlobalVariable(CGM.getModule(), Type, /*isConstant=*/true, 
+                                  Linkage, Init, Name);
+    CGM.setGlobalVisibility(GV, RD);
+    
+    if (OldGV) {
+      GV->takeName(OldGV);
+      llvm::Constant *NewPtr = 
+        llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
+      OldGV->replaceAllUsesWith(NewPtr);
+      OldGV->eraseFromParent();
+    }
+  }
+  
+  return GV;
+}
+
+CGVtableInfo::CtorVtableInfo 
+CGVtableInfo::getCtorVtable(const CXXRecordDecl *RD, 
+                            const BaseSubobject &Base) {
+  CtorVtableInfo Info;
+  
+  Info.Vtable = GenerateVtable(llvm::GlobalValue::InternalLinkage,
+                               /*GenerateDefinition=*/true,
+                               RD, Base.getBase(), Base.getBaseOffset(),
+                               Info.AddressPoints);
+  return Info;
+}
+
+llvm::GlobalVariable *CGVtableInfo::getVTT(const CXXRecordDecl *RD) {
+  return GenerateVTT(llvm::GlobalValue::ExternalLinkage, 
+                     /*GenerateDefinition=*/false, RD);
+  
+}
+
+
+bool CGVtableInfo::needsVTTParameter(GlobalDecl GD) {
+  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
+  
+  // We don't have any virtual bases, just return early.
+  if (!MD->getParent()->getNumVBases())
+    return false;
+  
+  // Check if we have a base constructor.
+  if (isa<CXXConstructorDecl>(MD) && GD.getCtorType() == Ctor_Base)
+    return true;
+
+  // Check if we have a base destructor.
+  if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
+    return true;
+  
+  return false;
+}
+
+uint64_t CGVtableInfo::getSubVTTIndex(const CXXRecordDecl *RD, 
+                                      const CXXRecordDecl *Base) {
+  ClassPairTy ClassPair(RD, Base);
+
+  SubVTTIndiciesTy::iterator I = 
+    SubVTTIndicies.find(ClassPair);
+  if (I != SubVTTIndicies.end())
+    return I->second;
+  
+  std::vector<llvm::Constant *> inits;
+  VTTBuilder Builder(inits, RD, CGM, /*GenerateDefinition=*/false);
+
+  for (llvm::DenseMap<const CXXRecordDecl *, uint64_t>::iterator I =
+       Builder.getSubVTTIndicies().begin(), 
+       E = Builder.getSubVTTIndicies().end(); I != E; ++I) {
+    // Insert all indices.
+    ClassPairTy ClassPair(RD, I->first);
+    
+    SubVTTIndicies.insert(std::make_pair(ClassPair, I->second));
+  }
+    
+  I = SubVTTIndicies.find(ClassPair);
+  assert(I != SubVTTIndicies.end() && "Did not find index!");
+  
+  return I->second;
+}