lib/CodeGen/CGObjC.cpp

//===---- CGBuiltin.cpp - Emit LLVM Code for builtins ---------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This contains code to emit Objective-C code as LLVM code.
//
//===----------------------------------------------------------------------===//

#include "CGObjCRuntime.h"
#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "clang/AST/ExprObjC.h"
#include "llvm/Constant.h"
#include "llvm/Function.h"

using namespace clang;
using namespace CodeGen;

/// Emits an instance of NSConstantString representing the object.
llvm::Value *CodeGenFunction::EmitObjCStringLiteral(const ObjCStringLiteral *E){
  return CGM.getObjCRuntime()->GenerateConstantString(
      E->getString()->getStrData(), E->getString()->getByteLength());
}

/// Emit a selector.
llvm::Value *CodeGenFunction::EmitObjCSelectorExpr(const ObjCSelectorExpr *E) {
  // Untyped selector.
  // Note that this implementation allows for non-constant strings to be passed
  // as arguments to @selector().  Currently, the only thing preventing this
  // behaviour is the type checking in the front end.
  return CGM.getObjCRuntime()->GetSelector(Builder,
      CGM.GetAddrOfConstantString(E->getSelector().getName()), 0);
}



llvm::Value *CodeGenFunction::EmitObjCMessageExpr(const ObjCMessageExpr *E) {
  // Only the lookup mechanism and first two arguments of the method
  // implementation vary between runtimes.  We can get the receiver and
  // arguments in generic code.
  
  CGObjCRuntime *Runtime = CGM.getObjCRuntime();
  const Expr *ReceiverExpr = E->getReceiver();
  bool isSuperMessage = false;
  // Find the receiver
  llvm::Value *Receiver;
  if (!ReceiverExpr) {
    const char * classname = E->getClassName()->getName();
    if (!strcmp(classname, "super")) {
      classname = E->getMethodDecl()->getClassInterface()->getName();
    }
    llvm::Value *ClassName = CGM.GetAddrOfConstantString(classname);
    ClassName = Builder.CreateStructGEP(ClassName, 0);
    Receiver = Runtime->LookupClass(Builder, ClassName);
  } else if (dyn_cast<PreDefinedExpr>(E->getReceiver())) {
    isSuperMessage = true;
    Receiver = LoadObjCSelf();
  } else {
   Receiver = EmitScalarExpr(E->getReceiver());
  }

  // Process the arguments
  unsigned ArgC = E->getNumArgs();
  llvm::SmallVector<llvm::Value*, 16> Args;
  for (unsigned i = 0; i != ArgC; ++i) {
    const Expr *ArgExpr = E->getArg(i);
    QualType ArgTy = ArgExpr->getType();
    if (!hasAggregateLLVMType(ArgTy)) {
      // Scalar argument is passed by-value.
      Args.push_back(EmitScalarExpr(ArgExpr));
    } else if (ArgTy->isAnyComplexType()) {
      // Make a temporary alloca to pass the argument.
      llvm::Value *DestMem = CreateTempAlloca(ConvertType(ArgTy));
      EmitComplexExprIntoAddr(ArgExpr, DestMem, false);
      Args.push_back(DestMem);
    } else {
      llvm::Value *DestMem = CreateTempAlloca(ConvertType(ArgTy));
      EmitAggExpr(ArgExpr, DestMem, false);
      Args.push_back(DestMem);
    }
  }

  // Get the selector string
  std::string SelStr = E->getSelector().getName();
  llvm::Constant *Selector = CGM.GetAddrOfConstantString(SelStr);

  llvm::Value *SelPtr = Builder.CreateStructGEP(Selector, 0);
  if (isSuperMessage) {
    const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(CurFuncDecl);
    assert(OMD && "super is only valid in an Objective-C method");
    const char *SuperClass = OMD->getClassInterface()->getSuperClass()->getName();
    return Runtime->GenerateMessageSendSuper(Builder, ConvertType(E->getType()),
                                        Receiver, SuperClass,
                                        Receiver, SelPtr,
                                        &Args[0], Args.size());
  }
  return Runtime->GenerateMessageSend(Builder, ConvertType(E->getType()),
                                      LoadObjCSelf(),
                                      Receiver, SelPtr,
                                      &Args[0], Args.size());
}

/// Generate an Objective-C method.  An Objective-C method is a C function with
/// its pointer, name, and types registered in the class struture.  
void CodeGenFunction::GenerateObjCMethod(const ObjCMethodDecl *OMD) {

  llvm::SmallVector<const llvm::Type *, 16> ParamTypes;
  for (unsigned i=0 ; i<OMD->param_size() ; i++) {
    const llvm::Type *Ty = ConvertType(OMD->getParamDecl(i)->getType());
    if (Ty->isFirstClassType())
      ParamTypes.push_back(Ty);
    else
      ParamTypes.push_back(llvm::PointerType::getUnqual(Ty));
  }
  std::string CategoryName = "";
  if (ObjCCategoryImplDecl *OCD =
      dyn_cast<ObjCCategoryImplDecl>(OMD->getMethodContext())) {
    CategoryName = OCD->getName();
  }
  const llvm::Type *ReturnTy = CGM.getTypes().ConvertReturnType(OMD->getResultType());
  CurFn = CGM.getObjCRuntime()->MethodPreamble(
                                              OMD->getClassInterface()->getName(),
                                              CategoryName,
                                              OMD->getSelector().getName(),
                                              ReturnTy,
                                              llvm::PointerType::getUnqual(
                                              llvm::Type::Int32Ty),
                                              ParamTypes.begin(),
                                              OMD->param_size(),
                                              !OMD->isInstance(),
                                              OMD->isVariadic());
  llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
  
  // Create a marker to make it easy to insert allocas into the entryblock
  // later.  Don't create this with the builder, because we don't want it
  // folded.
  llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
  AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
                                         EntryBB);

  FnRetTy = OMD->getResultType();
  CurFuncDecl = OMD;

  Builder.SetInsertPoint(EntryBB);
  
  // Emit allocs for param decls.  Give the LLVM Argument nodes names.
  llvm::Function::arg_iterator AI = CurFn->arg_begin();
  
  if (hasAggregateLLVMType(OMD->getResultType())) {
    ++AI;
  }
  // Add implicit parameters to the decl map.
  // TODO: Add something to AST to let the runtime specify the names and types
  // of these.

  llvm::Value *&SelfEntry = LocalDeclMap[OMD->getSelfDecl()];
  const llvm::Type *IPTy = AI->getType();
  llvm::Value *DeclPtr = new llvm::AllocaInst(IPTy, 0, AI->getName() +
      ".addr", AllocaInsertPt);
  // Store the initial value into the alloca.
  Builder.CreateStore(AI, DeclPtr);
  SelfEntry = DeclPtr;
  ++AI;
  llvm::Value *&CmdEntry = LocalDeclMap[OMD->getCmdDecl()];
  IPTy = AI->getType();
  DeclPtr = new llvm::AllocaInst(IPTy, 0, AI->getName() +
      ".addr", AllocaInsertPt);
  // Store the initial value into the alloca.
  Builder.CreateStore(AI, DeclPtr);
  CmdEntry = DeclPtr;

  for (unsigned i = 0, e = OMD->getNumParams(); i != e; ++i, ++AI) {
    assert(AI != CurFn->arg_end() && "Argument mismatch!");
    EmitParmDecl(*OMD->getParamDecl(i), AI);
  }
  
  GenerateFunction(OMD->getBody());
}

llvm::Value *CodeGenFunction::LoadObjCSelf(void)
{
  if (const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(CurFuncDecl)) {
    ValueDecl *Decl = OMD->getSelfDecl();
    llvm::Value *SelfPtr = LocalDeclMap[&(*(Decl))];
    return Builder.CreateLoad(SelfPtr, "self");
  }
  return NULL;
}

CGObjCRuntime::~CGObjCRuntime() {}