Implement code generation of member function pointer calls. Fixes PR5121.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@83271 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 109 insertions, 0 deletions

diff --git a/lib/CodeGen/CGCXX.cpp b/lib/CodeGen/CGCXX.cpp
index 1ea60eff56..2d5c62e3e2 100644
--- a/lib/CodeGen/CGCXX.cpp
+++ b/lib/CodeGen/CGCXX.cpp
@@ -199,6 +199,9 @@ RValue CodeGenFunction::EmitCXXMemberCall(const CXXMethodDecl *MD,
 }
 
 RValue CodeGenFunction::EmitCXXMemberCallExpr(const CXXMemberCallExpr *CE) {
+  if (isa<BinaryOperator>(CE->getCallee())) 
+    return EmitCXXMemberPointerCallExpr(CE);
+      
   const MemberExpr *ME = cast<MemberExpr>(CE->getCallee());
   const CXXMethodDecl *MD = cast<CXXMethodDecl>(ME->getMemberDecl());
 
@@ -242,6 +245,112 @@ RValue CodeGenFunction::EmitCXXMemberCallExpr(const CXXMemberCallExpr *CE) {
 }
 
 RValue
+CodeGenFunction::EmitCXXMemberPointerCallExpr(const CXXMemberCallExpr *E) {
+  const BinaryOperator *BO = cast<BinaryOperator>(E->getCallee());
+  const DeclRefExpr *BaseExpr = cast<DeclRefExpr>(BO->getLHS());
+  const DeclRefExpr *MemFn = cast<DeclRefExpr>(BO->getRHS());
+  
+  const MemberPointerType *MPT = MemFn->getType()->getAs<MemberPointerType>();
+  const FunctionProtoType *FPT = 
+    MPT->getPointeeType()->getAs<FunctionProtoType>();
+  const CXXRecordDecl *RD = 
+    cast<CXXRecordDecl>(cast<RecordType>(MPT->getClass())->getDecl());
+
+  const llvm::FunctionType *FTy = 
+    CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(RD, FPT),
+                                   FPT->isVariadic());
+
+  const llvm::Type *Int8PtrTy = 
+    llvm::Type::getInt8Ty(VMContext)->getPointerTo();
+
+  // Get the member function pointer.
+  llvm::Value *MemFnPtr = 
+    CreateTempAlloca(ConvertType(MemFn->getType()), "mem.fn");
+  EmitAggExpr(MemFn, MemFnPtr, /*VolatileDest=*/false);
+
+  // Emit the 'this' pointer.
+  llvm::Value *This;
+  
+  if (BO->getOpcode() == BinaryOperator::PtrMemI)
+    This = EmitScalarExpr(BaseExpr);
+  else 
+    This = EmitLValue(BaseExpr).getAddress();
+  
+  // Adjust it.
+  llvm::Value *Adj = Builder.CreateStructGEP(MemFnPtr, 1);
+  Adj = Builder.CreateLoad(Adj, "mem.fn.adj");
+  
+  llvm::Value *Ptr = Builder.CreateBitCast(This, Int8PtrTy, "ptr");
+  Ptr = Builder.CreateGEP(Ptr, Adj, "adj");
+  
+  This = Builder.CreateBitCast(Ptr, This->getType(), "this");
+  
+  llvm::Value *FnPtr = Builder.CreateStructGEP(MemFnPtr, 0, "mem.fn.ptr");
+  
+  const llvm::Type *PtrDiffTy = ConvertType(getContext().getPointerDiffType());
+
+  llvm::Value *FnAsInt = Builder.CreateLoad(FnPtr, "fn");
+  
+  // If the LSB in the function pointer is 1, the function pointer points to
+  // a virtual function.
+  llvm::Value *IsVirtual 
+    = Builder.CreateAnd(FnAsInt, llvm::ConstantInt::get(PtrDiffTy, 1),
+                        "and");
+  
+  IsVirtual = Builder.CreateTrunc(IsVirtual,
+                                  llvm::Type::getInt1Ty(VMContext));
+  
+  llvm::BasicBlock *FnVirtual = createBasicBlock("fn.virtual");
+  llvm::BasicBlock *FnNonVirtual = createBasicBlock("fn.nonvirtual");
+  llvm::BasicBlock *FnEnd = createBasicBlock("fn.end");
+  
+  Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
+  EmitBlock(FnVirtual);
+  
+  const llvm::Type *VTableTy = 
+    FTy->getPointerTo()->getPointerTo()->getPointerTo();
+
+  llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy);
+  VTable = Builder.CreateLoad(VTable);
+  
+  VTable = Builder.CreateGEP(VTable, FnAsInt, "fn");
+  
+  // Since the function pointer is 1 plus the virtual table offset, we
+  // subtract 1 by using a GEP.
+  VTable = Builder.CreateConstGEP1_64(VTable, -1);
+  
+  llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "virtualfn");
+  
+  EmitBranch(FnEnd);
+  EmitBlock(FnNonVirtual);
+  
+  // If the function is not virtual, just load the pointer.
+  llvm::Value *NonVirtualFn = Builder.CreateLoad(FnPtr, "fn");
+  NonVirtualFn = Builder.CreateIntToPtr(NonVirtualFn, FTy->getPointerTo());
+  
+  EmitBlock(FnEnd);
+
+  llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo());
+  Callee->reserveOperandSpace(2);
+  Callee->addIncoming(VirtualFn, FnVirtual);
+  Callee->addIncoming(NonVirtualFn, FnNonVirtual);
+
+  CallArgList Args;
+
+  QualType ThisType = 
+    getContext().getPointerType(getContext().getTagDeclType(RD));
+
+  // Push the this ptr.
+  Args.push_back(std::make_pair(RValue::get(This), ThisType));
+  
+  // And the rest of the call args
+  EmitCallArgs(Args, FPT, E->arg_begin(), E->arg_end());
+  QualType ResultType = BO->getType()->getAs<FunctionType>()->getResultType();
+  return EmitCall(CGM.getTypes().getFunctionInfo(ResultType, Args),
+                  Callee, Args, 0);
+}
+
+RValue
 CodeGenFunction::EmitCXXOperatorMemberCallExpr(const CXXOperatorCallExpr *E,
                                                const CXXMethodDecl *MD) {
   assert(MD->isInstance() &&