1 files changed, 212 insertions, 0 deletions
diff --git a/clang/lib/AST/VTTBuilder.cpp b/clang/lib/AST/VTTBuilder.cpp
new file mode 100644
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+++ b/clang/lib/AST/VTTBuilder.cpp
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+//===--- VTTBuilder.cpp - C++ VTT layout builder --------------------------===//
+//
+//                     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 generation of the layout of virtual table
+// tables (VTT).
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/AST/VTTBuilder.h"
+#include "clang/AST/CXXInheritance.h"
+#include "clang/AST/RecordLayout.h"
+#include "clang/Basic/TargetInfo.h"
+#include "llvm/Support/Format.h"
+#include <algorithm>
+#include <cstdio>
+
+using namespace clang;
+
+#define DUMP_OVERRIDERS 0
+
+VTTBuilder::VTTBuilder(ASTContext &Ctx,
+                       const CXXRecordDecl *MostDerivedClass,
+                       bool GenerateDefinition)
+  : Ctx(Ctx), MostDerivedClass(MostDerivedClass), 
+  MostDerivedClassLayout(Ctx.getASTRecordLayout(MostDerivedClass)),
+    GenerateDefinition(GenerateDefinition) {
+  // Lay out this VTT.
+  LayoutVTT(BaseSubobject(MostDerivedClass, CharUnits::Zero()), 
+            /*BaseIsVirtual=*/false);
+}
+
+void VTTBuilder::AddVTablePointer(BaseSubobject Base, uint64_t VTableIndex,
+                                  const CXXRecordDecl *VTableClass) {
+  // Store the vtable pointer index if we're generating the primary VTT.
+  if (VTableClass == MostDerivedClass) {
+    assert(!SecondaryVirtualPointerIndices.count(Base) &&
+           "A virtual pointer index already exists for this base subobject!");
+    SecondaryVirtualPointerIndices[Base] = VTTComponents.size();
+  }
+
+  if (!GenerateDefinition) {
+    VTTComponents.push_back(VTTComponent());
+    return;
+  }
+
+  VTTComponents.push_back(VTTComponent(VTableIndex, Base));
+}
+
+void VTTBuilder::LayoutSecondaryVTTs(BaseSubobject Base) {
+  const CXXRecordDecl *RD = Base.getBase();
+
+  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
+       E = RD->bases_end(); I != E; ++I) {
+    
+    // Don't layout virtual bases.
+    if (I->isVirtual())
+        continue;
+
+    const CXXRecordDecl *BaseDecl =
+      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
+
+    const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(RD);
+    CharUnits BaseOffset = Base.getBaseOffset() + 
+      Layout.getBaseClassOffset(BaseDecl);
+   
+    // Layout the VTT for this base.
+    LayoutVTT(BaseSubobject(BaseDecl, BaseOffset), /*BaseIsVirtual=*/false);
+  }
+}
+
+void
+VTTBuilder::LayoutSecondaryVirtualPointers(BaseSubobject Base, 
+                                           bool BaseIsMorallyVirtual,
+                                           uint64_t VTableIndex,
+                                           const CXXRecordDecl *VTableClass,
+                                           VisitedVirtualBasesSetTy &VBases) {
+  const CXXRecordDecl *RD = Base.getBase();
+  
+  // We're not interested in bases that don't have virtual bases, and not
+  // morally virtual bases.
+  if (!RD->getNumVBases() && !BaseIsMorallyVirtual)
+    return;
+
+  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
+       E = RD->bases_end(); I != E; ++I) {
+    const CXXRecordDecl *BaseDecl =
+      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
+
+    // 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 (!BaseDecl->isDynamicClass())
+      continue;
+    
+    bool BaseDeclIsMorallyVirtual = BaseIsMorallyVirtual;
+    bool BaseDeclIsNonVirtualPrimaryBase = false;
+    CharUnits BaseOffset;
+    if (I->isVirtual()) {
+      // Ignore virtual bases that we've already visited.
+      if (!VBases.insert(BaseDecl))
+        continue;
+      
+      BaseOffset = MostDerivedClassLayout.getVBaseClassOffset(BaseDecl);
+      BaseDeclIsMorallyVirtual = true;
+    } else {
+      const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(RD);
+      
+      BaseOffset = Base.getBaseOffset() + 
+        Layout.getBaseClassOffset(BaseDecl);
+      
+      if (!Layout.isPrimaryBaseVirtual() &&
+          Layout.getPrimaryBase() == BaseDecl)
+        BaseDeclIsNonVirtualPrimaryBase = true;
+    }
+
+    // Itanium C++ ABI 2.6.2:
+    //   Secondary virtual pointers: for each base class X which (a) has virtual
+    //   bases or is reachable along a virtual path from D, and (b) is not a
+    //   non-virtual primary base, the address of the virtual table for X-in-D
+    //   or an appropriate construction virtual table.
+    if (!BaseDeclIsNonVirtualPrimaryBase &&
+        (BaseDecl->getNumVBases() || BaseDeclIsMorallyVirtual)) {
+      // Add the vtable pointer.
+      AddVTablePointer(BaseSubobject(BaseDecl, BaseOffset), VTableIndex, 
+                       VTableClass);
+    }
+
+    // And lay out the secondary virtual pointers for the base class.
+    LayoutSecondaryVirtualPointers(BaseSubobject(BaseDecl, BaseOffset),
+                                   BaseDeclIsMorallyVirtual, VTableIndex, 
+                                   VTableClass, VBases);
+  }
+}
+
+void 
+VTTBuilder::LayoutSecondaryVirtualPointers(BaseSubobject Base, 
+                                           uint64_t VTableIndex) {
+  VisitedVirtualBasesSetTy VBases;
+  LayoutSecondaryVirtualPointers(Base, /*BaseIsMorallyVirtual=*/false,
+                                 VTableIndex, Base.getBase(), VBases);
+}
+
+void VTTBuilder::LayoutVirtualVTTs(const CXXRecordDecl *RD,
+                                   VisitedVirtualBasesSetTy &VBases) {
+  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
+       E = RD->bases_end(); I != E; ++I) {
+    const CXXRecordDecl *BaseDecl = 
+      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
+    
+    // Check if this is a virtual base.
+    if (I->isVirtual()) {
+      // Check if we've seen this base before.
+      if (!VBases.insert(BaseDecl))
+        continue;
+    
+      CharUnits BaseOffset = 
+        MostDerivedClassLayout.getVBaseClassOffset(BaseDecl);
+      
+      LayoutVTT(BaseSubobject(BaseDecl, BaseOffset), /*BaseIsVirtual=*/true);
+    }
+    
+    // We only need to layout virtual VTTs for this base if it actually has
+    // virtual bases.
+    if (BaseDecl->getNumVBases())
+      LayoutVirtualVTTs(BaseDecl, VBases);
+  }
+}
+
+void VTTBuilder::LayoutVTT(BaseSubobject Base, bool BaseIsVirtual) {
+  const CXXRecordDecl *RD = Base.getBase();
+
+  // 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;
+
+  bool IsPrimaryVTT = Base.getBase() == MostDerivedClass;
+
+  if (!IsPrimaryVTT) {
+    // Remember the sub-VTT index.
+    SubVTTIndicies[Base] = VTTComponents.size();
+  }
+
+  uint64_t VTableIndex = VTTVTables.size();
+  VTTVTables.push_back(VTTVTable(Base, BaseIsVirtual));
+
+  // Add the primary vtable pointer.
+  AddVTablePointer(Base, VTableIndex, RD);
+
+  // Add the secondary VTTs.
+  LayoutSecondaryVTTs(Base);
+  
+  // Add the secondary virtual pointers.
+  LayoutSecondaryVirtualPointers(Base, VTableIndex);
+  
+  // If this is the primary VTT, we want to lay out virtual VTTs as well.
+  if (IsPrimaryVTT) {
+    VisitedVirtualBasesSetTy VBases;
+    LayoutVirtualVTTs(Base.getBase(), VBases);
+  }
+}