path: root/lib/CodeGen/CGExprAgg.cpp

//===--- CGExprAgg.cpp - Emit LLVM Code from Aggregate 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 to emit Aggregate Expr nodes as LLVM code.
//
//===----------------------------------------------------------------------===//

#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/StmtVisitor.h"
#include "llvm/Constants.h"
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Intrinsics.h"
using namespace clang;
using namespace CodeGen;

//===----------------------------------------------------------------------===//
//                        Aggregate Expression Emitter
//===----------------------------------------------------------------------===//

namespace  {
class VISIBILITY_HIDDEN AggExprEmitter : public StmtVisitor<AggExprEmitter> {
  CodeGenFunction &CGF;
  llvm::IRBuilder<> &Builder;
  llvm::Value *DestPtr;
  bool VolatileDest;
public:
  AggExprEmitter(CodeGenFunction &cgf, llvm::Value *destPtr, bool volatileDest)
    : CGF(cgf), Builder(CGF.Builder),
      DestPtr(destPtr), VolatileDest(volatileDest) {
  }

  //===--------------------------------------------------------------------===//
  //                               Utilities
  //===--------------------------------------------------------------------===//

  /// EmitAggLoadOfLValue - Given an expression with aggregate type that
  /// represents a value lvalue, this method emits the address of the lvalue,
  /// then loads the result into DestPtr.
  void EmitAggLoadOfLValue(const Expr *E);
  
  void EmitAggregateCopy(llvm::Value *DestPtr, llvm::Value *SrcPtr,
                         QualType EltTy);

  void EmitAggregateClear(llvm::Value *DestPtr, QualType Ty);

  void EmitNonConstInit(InitListExpr *E);

  //===--------------------------------------------------------------------===//
  //                            Visitor Methods
  //===--------------------------------------------------------------------===//
  
  void VisitStmt(Stmt *S) {
    CGF.ErrorUnsupported(S, "aggregate expression");
  }
  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }

  // l-values.
  void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E)
      { EmitAggLoadOfLValue(E); }

  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
    EmitAggLoadOfLValue(E);
  }

  // Operators.
  //  case Expr::UnaryOperatorClass:
  //  case Expr::CastExprClass: 
  void VisitImplicitCastExpr(ImplicitCastExpr *E);
  void VisitCallExpr(const CallExpr *E);
  void VisitStmtExpr(const StmtExpr *E);
  void VisitBinaryOperator(const BinaryOperator *BO);
  void VisitBinAssign(const BinaryOperator *E);
  void VisitOverloadExpr(const OverloadExpr *E);
  void VisitBinComma(const BinaryOperator *E);

  void VisitObjCMessageExpr(ObjCMessageExpr *E);
  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
    EmitAggLoadOfLValue(E);
  }
  void VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E);
  
  void VisitConditionalOperator(const ConditionalOperator *CO);
  void VisitInitListExpr(InitListExpr *E);
  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
    Visit(DAE->getExpr());
  }
  void VisitVAArgExpr(VAArgExpr *E);

  void EmitInitializationToLValue(Expr *E, LValue Address);
  void EmitNullInitializationToLValue(LValue Address, QualType T);
  //  case Expr::ChooseExprClass:

};
}  // end anonymous namespace.

//===----------------------------------------------------------------------===//
//                                Utilities
//===----------------------------------------------------------------------===//

void AggExprEmitter::EmitAggregateClear(llvm::Value *DestPtr, QualType Ty) {
  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");

  // Aggregate assignment turns into llvm.memset.
  const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
  if (DestPtr->getType() != BP)
    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");

  // Get size and alignment info for this aggregate.
  std::pair<uint64_t, unsigned> TypeInfo = CGF.getContext().getTypeInfo(Ty);

  // FIXME: Handle variable sized types.
  const llvm::Type *IntPtr = llvm::IntegerType::get(CGF.LLVMPointerWidth);

  llvm::Value *MemSetOps[4] = {
    DestPtr,
    llvm::ConstantInt::getNullValue(llvm::Type::Int8Ty),
    // TypeInfo.first describes size in bits.
    llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
    llvm::ConstantInt::get(llvm::Type::Int32Ty, TypeInfo.second/8)
  };
 
  Builder.CreateCall(CGF.CGM.getMemSetFn(), MemSetOps, MemSetOps+4);
}

void AggExprEmitter::EmitAggregateCopy(llvm::Value *DestPtr,
                                       llvm::Value *SrcPtr, QualType Ty) {
  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
  
  // Aggregate assignment turns into llvm.memmove.
  const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
  if (DestPtr->getType() != BP)
    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
  if (SrcPtr->getType() != BP)
    SrcPtr = Builder.CreateBitCast(SrcPtr, BP, "tmp");
  
  // Get size and alignment info for this aggregate.
  std::pair<uint64_t, unsigned> TypeInfo = CGF.getContext().getTypeInfo(Ty);
  
  // FIXME: Handle variable sized types.
  const llvm::Type *IntPtr = llvm::IntegerType::get(CGF.LLVMPointerWidth);
  
  llvm::Value *MemMoveOps[4] = {
    DestPtr, SrcPtr,
    // TypeInfo.first describes size in bits.
    llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
    llvm::ConstantInt::get(llvm::Type::Int32Ty, TypeInfo.second/8)
  };
  
  Builder.CreateCall(CGF.CGM.getMemMoveFn(), MemMoveOps, MemMoveOps+4);
}


/// EmitAggLoadOfLValue - Given an expression with aggregate type that
/// represents a value lvalue, this method emits the address of the lvalue,
/// then loads the result into DestPtr.
void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
  LValue LV = CGF.EmitLValue(E);
  assert(LV.isSimple() && "Can't have aggregate bitfield, vector, etc");
  llvm::Value *SrcPtr = LV.getAddress();
  
  // If the result is ignored, don't copy from the value.
  if (DestPtr == 0)
    // FIXME: If the source is volatile, we must read from it.
    return;

  EmitAggregateCopy(DestPtr, SrcPtr, E->getType());
}

//===----------------------------------------------------------------------===//
//                            Visitor Methods
//===----------------------------------------------------------------------===//

void AggExprEmitter::VisitImplicitCastExpr(ImplicitCastExpr *E) {
  assert(CGF.getContext().typesAreCompatible(
                          E->getSubExpr()->getType().getUnqualifiedType(),
                          E->getType().getUnqualifiedType()) &&
         "Implicit cast types must be compatible");
  Visit(E->getSubExpr());
}

void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
  RValue RV = CGF.EmitCallExpr(E);
  assert(RV.isAggregate() && "Return value must be aggregate value!");
  
  // If the result is ignored, don't copy from the value.
  if (DestPtr == 0)
    // FIXME: If the source is volatile, we must read from it.
    return;
  
  EmitAggregateCopy(DestPtr, RV.getAggregateAddr(), E->getType());
}

void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
  RValue RV = CGF.EmitObjCMessageExpr(E);
  assert(RV.isAggregate() && "Return value must be aggregate value!");

  // If the result is ignored, don't copy from the value.
  if (DestPtr == 0)
    // FIXME: If the source is volatile, we must read from it.
    return;
  
  EmitAggregateCopy(DestPtr, RV.getAggregateAddr(), E->getType());
}

void AggExprEmitter