path: root/lib/CodeGen/CGExprCXX.cpp

//===--- CGExprCXX.cpp - Emit LLVM Code for C++ expressions ---------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This contains code dealing with code generation of C++ expressions
//
//===----------------------------------------------------------------------===//

#include "CodeGenFunction.h"
#include "CGObjCRuntime.h"
using namespace clang;
using namespace CodeGen;

RValue CodeGenFunction::EmitCXXMemberCall(const CXXMethodDecl *MD,
                                          llvm::Value *Callee,
                                          ReturnValueSlot ReturnValue,
                                          llvm::Value *This,
                                          llvm::Value *VTT,
                                          CallExpr::const_arg_iterator ArgBeg,
                                          CallExpr::const_arg_iterator ArgEnd) {
  assert(MD->isInstance() &&
         "Trying to emit a member call expr on a static method!");

  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();

  CallArgList Args;

  // Push the this ptr.
  Args.push_back(std::make_pair(RValue::get(This),
                                MD->getThisType(getContext())));

  // If there is a VTT parameter, emit it.
  if (VTT) {
    QualType T = getContext().getPointerType(getContext().VoidPtrTy);
    Args.push_back(std::make_pair(RValue::get(VTT), T));
  }
  
  // And the rest of the call args
  EmitCallArgs(Args, FPT, ArgBeg, ArgEnd);

  QualType ResultType = FPT->getResultType();
  return EmitCall(CGM.getTypes().getFunctionInfo(ResultType, Args,
                                                 FPT->getExtInfo()),
                  Callee, ReturnValue, Args, MD);
}

/// canDevirtualizeMemberFunctionCalls - Checks whether virtual calls on given
/// expr can be devirtualized.
static bool canDevirtualizeMemberFunctionCalls(const Expr *Base) {
  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Base)) {
    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
      // This is a record decl. We know the type and can devirtualize it.
      return VD->getType()->isRecordType();
    }
    
    return false;
  }
  
  // We can always devirtualize calls on temporary object expressions.
  if (isa<CXXConstructExpr>(Base))
    return true;
  
  // And calls on bound temporaries.
  if (isa<CXXBindTemporaryExpr>(Base))
    return true;
  
  // Check if this is a call expr that returns a record type.
  if (const CallExpr *CE = dyn_cast<CallExpr>(Base))
    return CE->getCallReturnType()->isRecordType();
  
  // We can't devirtualize the call.
  return false;
}

RValue CodeGenFunction::EmitCXXMemberCallExpr(const CXXMemberCallExpr *CE,
                                              ReturnValueSlot ReturnValue) {
  if (isa<BinaryOperator>(CE->getCallee()->IgnoreParens())) 
    return EmitCXXMemberPointerCallExpr(CE, ReturnValue);
      
  const MemberExpr *ME = cast<MemberExpr>(CE->getCallee()->IgnoreParens());
  const CXXMethodDecl *MD = cast<CXXMethodDecl>(ME->getMemberDecl());

  if (MD->isStatic()) {
    // The method is static, emit it as we would a regular call.
    llvm::Value *Callee = CGM.GetAddrOfFunction(MD);
    return EmitCall(getContext().getPointerType(MD->getType()), Callee,
                    ReturnValue, CE->arg_begin(), CE->arg_end());
  }
  
  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();

  const llvm::Type *Ty =
    CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(MD),
                                   FPT->isVariadic());
  llvm::Value *This;

  if (ME->isArrow())
    This = EmitScalarExpr(ME->getBase());
  else {
    LValue BaseLV = EmitLValue(ME->getBase());
    This = BaseLV.getAddress();
  }

  if (MD->isCopyAssignment() && MD->isTrivial()) {
    // We don't like to generate the trivial copy assignment operator when
    // it isn't necessary; just produce the proper effect here.
    llvm::Value *RHS = EmitLValue(*CE->arg_begin()).getAddress();
    EmitAggregateCopy(This, RHS, CE->getType());
    return RValue::get(This);
  }

  // C++ [class.virtual]p12:
  //   Explicit qualification with the scope operator (5.1) suppresses the
  //   virtual call mechanism.