[ms-cxxabi] Implement MSVC virtual base adjustment

While we can't yet emit vbtables, this allows us to find virtual bases
of objects constructed in other TUs.

This make iostream hello world work, since basic_ostream virtually
inherits from basic_ios.

Differential Revision: http://llvm-reviews.chandlerc.com/D795

llvm-svn: 182870

1 files changed, 6 insertions, 25 deletions

diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp
index e4180a0d72d..b3a14772ad0 100644
--- a/clang/lib/CodeGen/CGClass.cpp
+++ b/clang/lib/CodeGen/CGClass.cpp
@@ -198,7 +198,8 @@ CodeGenFunction::GetAddressOfBaseClass(llvm::Value *Value,
   // Compute the virtual offset.
   llvm::Value *VirtualOffset = 0;
   if (VBase) {
-    VirtualOffset = GetVirtualBaseClassOffset(Value, Derived, VBase);
+    VirtualOffset =
+      CGM.getCXXABI().GetVirtualBaseClassOffset(*this, Value, Derived, VBase);
   }
 
   // Apply both offsets.
@@ -1872,28 +1873,6 @@ void CodeGenFunction::PushDestructorCleanup(QualType T, llvm::Value *Addr) {
   PushDestructorCleanup(D, Addr);
 }
 
-llvm::Value *
-CodeGenFunction::GetVirtualBaseClassOffset(llvm::Value *This,
-                                           const CXXRecordDecl *ClassDecl,
-                                           const CXXRecordDecl *BaseClassDecl) {
-  llvm::Value *VTablePtr = GetVTablePtr(This, Int8PtrTy);
-  CharUnits VBaseOffsetOffset = 
-    CGM.getVTableContext().getVirtualBaseOffsetOffset(ClassDecl, BaseClassDecl);
-  
-  llvm::Value *VBaseOffsetPtr = 
-    Builder.CreateConstGEP1_64(VTablePtr, VBaseOffsetOffset.getQuantity(), 
-                               "vbase.offset.ptr");
-  llvm::Type *PtrDiffTy = 
-    ConvertType(getContext().getPointerDiffType());
-  
-  VBaseOffsetPtr = Builder.CreateBitCast(VBaseOffsetPtr, 
-                                         PtrDiffTy->getPointerTo());
-                                         
-  llvm::Value *VBaseOffset = Builder.CreateLoad(VBaseOffsetPtr, "vbase.offset");
-  
-  return VBaseOffset;
-}
-
 void
 CodeGenFunction::InitializeVTablePointer(BaseSubobject Base, 
                                          const CXXRecordDecl *NearestVBase,
@@ -1933,8 +1912,10 @@ CodeGenFunction::InitializeVTablePointer(BaseSubobject Base,
   if (CodeGenVTables::needsVTTParameter(CurGD) && NearestVBase) {
     // We need to use the virtual base offset offset because the virtual base
     // might have a different offset in the most derived class.
-    VirtualOffset = GetVirtualBaseClassOffset(LoadCXXThis(), VTableClass, 
-                                              NearestVBase);
+    VirtualOffset = CGM.getCXXABI().GetVirtualBaseClassOffset(*this,
+                                                              LoadCXXThis(),
+                                                              VTableClass,
+                                                              NearestVBase);
     NonVirtualOffset = OffsetFromNearestVBase;
   } else {
     // We can just use the base offset in the complete class.