MS ABI: Remove nv adjustment from direct vdtor calls and prologues

Summary:
Generally the vector deleting dtor, which we model as a vtable thunk,
takes care of non-virtual adjustment and delegates to the other
destructor variants.  The other non-complete destructor variants assume
that 'this' on entry points to the virtual base subobject that first
declared the virtual destructor.

We need to change the adjustment in both the prologue and the vdtor call
setup.

Reviewers: timurrrr

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D2821

llvm-svn: 201612

1 files changed, 15 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index d8c7d6ee5ab..572bb098c93 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -601,6 +601,13 @@ llvm::Value *MicrosoftCXXABI::adjustThisArgumentForVirtualCall(
   unsigned AS = cast<llvm::PointerType>(This->getType())->getAddressSpace();
   llvm::Type *charPtrTy = CGF.Int8Ty->getPointerTo(AS);
   CharUnits StaticOffset = ML.VFPtrOffset;
+
+  // Base destructors expect 'this' to point to the beginning of the base
+  // subobject, not the first vfptr that happens to contain the virtual dtor.
+  // However, we still need to apply the virtual base adjustment.
+  if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
+    StaticOffset = CharUnits::Zero();
+
   if (ML.VBase) {
     bool AvoidVirtualOffset = false;
     if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base) {
@@ -729,6 +736,14 @@ llvm::Value *MicrosoftCXXABI::adjustThisParameterInVirtualFunctionPrologue(
   MicrosoftVTableContext::MethodVFTableLocation ML =
       CGM.getMicrosoftVTableContext().getMethodVFTableLocation(LookupGD);
   CharUnits Adjustment = ML.VFPtrOffset;
+
+  // Normal virtual instance methods need to adjust from the vfptr that first
+  // defined the virtual method to the virtual base subobject, but destructors
+  // do not.  The vector deleting destructor thunk applies this adjustment for
+  // us if necessary.
+  if (isa<CXXDestructorDecl>(MD))
+    Adjustment = CharUnits::Zero();
+
   if (ML.VBase) {
     const ASTRecordLayout &DerivedLayout =
         CGF.getContext().getASTRecordLayout(MD->getParent());