From 84080ec16ede6a6fe85a1d991690c6bda82a59ee Mon Sep 17 00:00:00 2001
From: Anders Carlsson <andersca@mac.com>
Date: Tue, 29 Sep 2009 03:13:20 +0000
Subject: [PATCH] Handle CK_BaseToDerivedMemberPointer for member function
 pointers. Fixes PR5091.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@83041 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGCXXClass.cpp    | 33 +++++++++++++++++++++++----------
 lib/CodeGen/CGExprAgg.cpp     | 35 ++++++++++++++++++++++++++++++++++-
 lib/CodeGen/CodeGenFunction.h |  5 +++++
 3 files changed, 62 insertions(+), 11 deletions(-)

diff --git a/lib/CodeGen/CGCXXClass.cpp b/lib/CodeGen/CGCXXClass.cpp
index 6d53e83e7c..5d7b8a022c 100644
--- a/lib/CodeGen/CGCXXClass.cpp
+++ b/lib/CodeGen/CGCXXClass.cpp
@@ -69,21 +69,38 @@ static uint64_t ComputeBaseClassOffset(ASTContext &Context,
     return Offset;
 }
 
+llvm::Constant *
+CodeGenFunction::GetCXXBaseClassOffset(const CXXRecordDecl *ClassDecl,
+                                       const CXXRecordDecl *BaseClassDecl) {
+  if (ClassDecl == BaseClassDecl)
+    return 0;
+
+  QualType BTy =
+    getContext().getCanonicalType(
+      getContext().getTypeDeclType(const_cast<CXXRecordDecl*>(BaseClassDecl)));
+
+  uint64_t Offset = ComputeBaseClassOffset(getContext(), 
+                                           ClassDecl, BaseClassDecl);
+  if (!Offset)
+    return 0;
+
+  const llvm::Type *PtrDiffTy = ConvertType(getContext().getPointerDiffType());
+
+  return llvm::ConstantInt::get(PtrDiffTy, Offset);
+}
+
 llvm::Value *
 CodeGenFunction::GetAddressCXXOfBaseClass(llvm::Value *BaseValue,
                                           const CXXRecordDecl *ClassDecl,
                                           const CXXRecordDecl *BaseClassDecl,
                                           bool NullCheckValue) {
-  if (ClassDecl == BaseClassDecl)
-    return BaseValue;
-
+  llvm::Constant *Offset = GetCXXBaseClassOffset(ClassDecl, BaseClassDecl);
+  
   QualType BTy =
     getContext().getCanonicalType(
       getContext().getTypeDeclType(const_cast<CXXRecordDecl*>(BaseClassDecl)));
   const llvm::Type *BasePtrTy = llvm::PointerType::getUnqual(ConvertType(BTy));
 
-  uint64_t Offset = ComputeBaseClassOffset(getContext(), 
-                                           ClassDecl, BaseClassDecl);
   if (!Offset) {
     // Just cast back.
     return Builder.CreateBitCast(BaseValue, BasePtrTy);
@@ -105,16 +122,12 @@ CodeGenFunction::GetAddressCXXOfBaseClass(llvm::Value *BaseValue,
     EmitBlock(CastNotNull);
   }
   
-  const llvm::Type *LongTy = 
-    CGM.getTypes().ConvertType(CGM.getContext().LongTy);
   const llvm::Type *Int8PtrTy = 
     llvm::PointerType::getUnqual(llvm::Type::getInt8Ty(VMContext));
   
-  llvm::Value *OffsetVal = llvm::ConstantInt::get(LongTy, Offset);
-  
   // Apply the offset.
   BaseValue = Builder.CreateBitCast(BaseValue, Int8PtrTy);
-  BaseValue = Builder.CreateGEP(BaseValue, OffsetVal, "add.ptr");
+  BaseValue = Builder.CreateGEP(BaseValue, Offset, "add.ptr");
   
   // Cast back.
   BaseValue = Builder.CreateBitCast(BaseValue, BasePtrTy);
diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp
index 3bc8c12974..017efd3c88 100644
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@@ -200,7 +200,6 @@ void AggExprEmitter::VisitCastExpr(CastExpr *E) {
     break;
 
   case CastExpr::CK_NullToMemberPointer: {
-    QualType T = E->getType();
     const llvm::Type *PtrDiffTy = 
       CGF.ConvertType(CGF.getContext().getPointerDiffType());
 
@@ -213,6 +212,40 @@ void AggExprEmitter::VisitCastExpr(CastExpr *E) {
 
     break;
   }
+      
+  case CastExpr::CK_BaseToDerivedMemberPointer: {
+    QualType SrcType = E->getSubExpr()->getType();
+    
+    llvm::Value *Src = CGF.CreateTempAlloca(CGF.ConvertTypeForMem(SrcType), 
+                                            "tmp");
+    CGF.EmitAggExpr(E->getSubExpr(), Src, SrcType.isVolatileQualified());
+    
+    llvm::Value *SrcPtr = Builder.CreateStructGEP(Src, 0, "src.ptr");
+    SrcPtr = Builder.CreateLoad(SrcPtr);
+    
+    llvm::Value *SrcAdj = Builder.CreateStructGEP(Src, 1, "src.adj");
+    SrcAdj = Builder.CreateLoad(SrcAdj);
+    
+    llvm::Value *DstPtr = Builder.CreateStructGEP(DestPtr, 0, "dst.ptr");
+    Builder.CreateStore(SrcPtr, DstPtr, VolatileDest);
+    
+    llvm::Value *DstAdj = Builder.CreateStructGEP(DestPtr, 1, "dst.adj");
+    
+    // Now See if we need to update the adjustment.
+    const CXXRecordDecl *SrcDecl = 
+      cast<CXXRecordDecl>(SrcType->getAs<MemberPointerType>()->
+                          getClass()->getAs<RecordType>()->getDecl());
+    const CXXRecordDecl *DstDecl = 
+      cast<CXXRecordDecl>(E->getType()->getAs<MemberPointerType>()->
+                          getClass()->getAs<RecordType>()->getDecl());
+    
+    llvm::Constant *Adj = CGF.GetCXXBaseClassOffset(DstDecl, SrcDecl);
+    if (Adj)
+      SrcAdj = Builder.CreateAdd(SrcAdj, Adj, "adj");
+    
+    Builder.CreateStore(SrcAdj, DstAdj, VolatileDest);
+    break;
+  }
   }
 }
 
diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index 73cac24431..faad45ad96 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -589,6 +589,11 @@ public:
                                         const CXXRecordDecl *BaseClassDecl,
                                         bool NullCheckValue);
 
+  /// GetCXXBaseClassOffset - Returns the offset from a derived class to its
+  /// base class. Returns null if the offset is 0.
+  llvm::Constant *GetCXXBaseClassOffset(const CXXRecordDecl *ClassDecl,
+                                        const CXXRecordDecl *BaseClassDecl);
+  
   void EmitClassAggrMemberwiseCopy(llvm::Value *DestValue,
                                    llvm::Value *SrcValue,
                                    const ArrayType *Array,
-- 
2.40.0