[ms-cxxabi] Implement member pointer conversions

Summary:
This only supports converting along non-virtual inheritance paths by
changing the field offset or the non-virtual base adjustment.

This implements three kinds of conversions:
- codegen for Value conversions
- Constant emission for APValue
- Constant folding for CastExprs

In almost all constant initialization settings
EmitMemberPointer(APValue) is called, except when the expression
contains a reinterpret cast.

reinterpret casts end up being a big corner case because the null value
changes between different kinds of member pointers.

Reviewers: rsmith

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D741

llvm-svn: 181543

1 files changed, 22 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGCXXABI.cpp b/clang/lib/CodeGen/CGCXXABI.cpp
index 68fecb2d0cb..4a125e6d7fa 100644
--- a/clang/lib/CodeGen/CGCXXABI.cpp
+++ b/clang/lib/CodeGen/CGCXXABI.cpp
@@ -251,6 +251,28 @@ llvm::Constant *CGCXXABI::getMemberPointerAdjustment(const CastExpr *E) {
                                           E->path_end());
 }
 
+CharUnits CGCXXABI::getMemberPointerPathAdjustment(const APValue &MP) {
+  // TODO: Store base specifiers in APValue member pointer paths so we can
+  // easily reuse CGM.GetNonVirtualBaseClassOffset().
+  const ValueDecl *MPD = MP.getMemberPointerDecl();
+  CharUnits ThisAdjustment = CharUnits::Zero();
+  ArrayRef<const CXXRecordDecl*> Path = MP.getMemberPointerPath();
+  bool DerivedMember = MP.isMemberPointerToDerivedMember();
+  const CXXRecordDecl *RD = cast<CXXRecordDecl>(MPD->getDeclContext());
+  for (unsigned I = 0, N = Path.size(); I != N; ++I) {
+    const CXXRecordDecl *Base = RD;
+    const CXXRecordDecl *Derived = Path[I];
+    if (DerivedMember)
+      std::swap(Base, Derived);
+    ThisAdjustment +=
+      getContext().getASTRecordLayout(Derived).getBaseClassOffset(Base);
+    RD = Path[I];
+  }
+  if (DerivedMember)
+    ThisAdjustment = -ThisAdjustment;
+  return ThisAdjustment;
+}
+
 llvm::BasicBlock *CGCXXABI::EmitCtorCompleteObjectHandler(
                                                          CodeGenFunction &CGF) {
   if (CGM.getTarget().getCXXABI().hasConstructorVariants())