From 6c2ab1d578c6cc1f3ddcc948532cd625f1092ef2 Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Tue, 31 Aug 2010 21:07:20 +0000
Subject: [PATCH] Amusingly, I missed this point of abstraction in all my
 earlier member-pointer refactoring:  dereferencing a member data pointer.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@112640 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGCXX.cpp         |  9 +++++++++
 lib/CodeGen/CGCXXABI.h        |  6 ++++++
 lib/CodeGen/CGExpr.cpp        | 17 ++++++++---------
 lib/CodeGen/ItaniumCXXABI.cpp | 30 ++++++++++++++++++++++++++++++
 4 files changed, 53 insertions(+), 9 deletions(-)

diff --git a/lib/CodeGen/CGCXX.cpp b/lib/CodeGen/CGCXX.cpp
index fbea42065b..f8d81fa796 100644
--- a/lib/CodeGen/CGCXX.cpp
+++ b/lib/CodeGen/CGCXX.cpp
@@ -359,6 +359,15 @@ llvm::Value *CGCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
   return llvm::Constant::getNullValue(FTy->getPointerTo());
 }
 
+llvm::Value *CGCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
+                                                    llvm::Value *Base,
+                                                    llvm::Value *MemPtr,
+                                              const MemberPointerType *MPT) {
+  ErrorUnsupportedABI(CGF, "loads of member pointers");
+  const llvm::Type *Ty = CGF.ConvertType(MPT->getPointeeType())->getPointerTo();
+  return llvm::Constant::getNullValue(Ty);
+}
+
 llvm::Value *CGCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
                                                    const CastExpr *E,
                                                    llvm::Value *Src) {
diff --git a/lib/CodeGen/CGCXXABI.h b/lib/CodeGen/CGCXXABI.h
index b87d6c0259..8d3e70f0b3 100644
--- a/lib/CodeGen/CGCXXABI.h
+++ b/lib/CodeGen/CGCXXABI.h
@@ -88,6 +88,12 @@ public:
                                   llvm::Value *MemPtr,
                                   const MemberPointerType *MPT);
 
+  /// Calculate an l-value from an object and a data member pointer.
+  virtual llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF,
+                                                    llvm::Value *Base,
+                                                    llvm::Value *MemPtr,
+                                            const MemberPointerType *MPT);
+
   /// Perform a derived-to-base or base-to-derived member pointer
   /// conversion.
   virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index a676333f49..1af0d56b44 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -2090,16 +2090,15 @@ EmitPointerToDataMemberBinaryExpr(const BinaryOperator *E) {
     BaseV = EmitScalarExpr(E->getLHS());
   else
     BaseV = EmitLValue(E->getLHS()).getAddress();
-  const llvm::Type *i8Ty = llvm::Type::getInt8PtrTy(getLLVMContext());
-  BaseV = Builder.CreateBitCast(BaseV, i8Ty);
+
   llvm::Value *OffsetV = EmitScalarExpr(E->getRHS());
-  llvm::Value *AddV = Builder.CreateInBoundsGEP(BaseV, OffsetV, "add.ptr");
 
-  QualType Ty = E->getRHS()->getType();
-  Ty = Ty->getAs<MemberPointerType>()->getPointeeType();
-  
-  const llvm::Type *PType = ConvertType(getContext().getPointerType(Ty));
-  AddV = Builder.CreateBitCast(AddV, PType);
-  return MakeAddrLValue(AddV, Ty);
+  const MemberPointerType *MPT
+    = E->getRHS()->getType()->getAs<MemberPointerType>();
+
+  llvm::Value *AddV =
+    CGM.getCXXABI().EmitMemberDataPointerAddress(*this, BaseV, OffsetV, MPT);
+
+  return MakeAddrLValue(AddV, MPT->getPointeeType());
 }
 
diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index 920b833b25..13768006f4 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -66,6 +66,11 @@ public:
                                                llvm::Value *MemFnPtr,
                                                const MemberPointerType *MPT);
 
+  llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF,
+                                            llvm::Value *Base,
+                                            llvm::Value *MemPtr,
+                                            const MemberPointerType *MPT);
+
   llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
                                            const CastExpr *E,
                                            llvm::Value *Src);
@@ -261,6 +266,31 @@ ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
   return Callee;
 }
 
+/// Compute an l-value by applying the given pointer-to-member to a
+/// base object.
+llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
+                                                         llvm::Value *Base,
+                                                         llvm::Value *MemPtr,
+                                           const MemberPointerType *MPT) {
+  assert(MemPtr->getType() == getPtrDiffTy());
+
+  CGBuilderTy &Builder = CGF.Builder;
+
+  unsigned AS = cast<llvm::PointerType>(Base->getType())->getAddressSpace();
+
+  // Cast to char*.
+  Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS));
+
+  // Apply the offset, which we assume is non-null.
+  llvm::Value *Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset");
+
+  // Cast the address to the appropriate pointer type, adopting the
+  // address space of the base pointer.
+  const llvm::Type *PType
+    = CGF.ConvertType(MPT->getPointeeType())->getPointerTo(AS);
+  return Builder.CreateBitCast(Addr, PType);
+}
+
 /// Perform a derived-to-base or base-to-derived member pointer conversion.
 ///
 /// Obligatory offset/adjustment diagram:
-- 
2.40.0