[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, 6 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGCXXABI.h b/clang/lib/CodeGen/CGCXXABI.h
index 1e4da631d6f..7f72e1db6e9 100644
--- a/clang/lib/CodeGen/CGCXXABI.h
+++ b/clang/lib/CodeGen/CGCXXABI.h
@@ -192,6 +192,12 @@ protected:
   /// is required.
   llvm::Constant *getMemberPointerAdjustment(const CastExpr *E);
 
+  /// \brief Computes the non-virtual adjustment needed for a member pointer
+  /// conversion along an inheritance path stored in an APValue.  Unlike
+  /// getMemberPointerAdjustment(), the adjustment can be negative if the path
+  /// is from a derived type to a base type.
+  CharUnits getMemberPointerPathAdjustment(const APValue &MP);
+
 public:
   /// Adjust the given non-null pointer to an object of polymorphic
   /// type to point to the complete object.