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 "CGObjCRuntime.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/StmtVisitor.h"
#include "llvm/Constants.h"
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Intrinsics.h"
using namespace clang;
using namespace CodeGen;

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

namespace  {
class AggExprEmitter : public StmtVisitor<AggExprEmitter> {
  CodeGenFunction &CGF;
  CGBuilderTy &Builder;
  AggValueSlot Dest;
  bool IgnoreResult;

  /// We want to use 'dest' as the return slot except under two
  /// conditions:
  ///   - The destination slot requires garbage collection, so we
  ///     need to use the GC API.
  ///   - The destination slot is potentially aliased.
  bool shouldUseDestForReturnSlot() const {
    return !(Dest.requiresGCollection() || Dest.isPotentiallyAliased());
  }

  ReturnValueSlot getReturnValueSlot() const {
    if (!shouldUseDestForReturnSlot())
      return ReturnValueSlot();

    return ReturnValueSlot(Dest.getAddr(), Dest.isVolatile());
  }

  AggValueSlot EnsureSlot(QualType T) {
    if (!Dest.isIgnored()) return Dest;
    return CGF.CreateAggTemp(T, "agg.tmp.ensured");
  }

public:
  AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest,
                 bool ignore)
    : CGF(cgf), Builder(CGF.Builder), Dest(Dest),
      IgnoreResult(ignore) {
  }

  //===--------------------------------------------------------------------===//
  //                               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);

  /// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
  void EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore = false);
  void EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore = false,
                         unsigned Alignment = 0);

  void EmitMoveFromReturnSlot(const Expr *E, RValue Src);

  AggValueSlot::NeedsGCBarriers_t needsGC(QualType T) {
    if (CGF.getLangOptions().getGC() && TypeRequiresGCollection(T))
      return AggValueSlot::NeedsGCBarriers;
    return AggValueSlot::DoesNotNeedGCBarriers;
  }

  bool TypeRequiresGCollection(QualType T);

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

  void VisitStmt(Stmt *S) {
    CGF.ErrorUnsupported(S, "aggregate expression");
  }
  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
  void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
    Visit(GE->getResultExpr());
  }
  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
  void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
    return Visit(E->getReplacement());
  }

  // l-values.
  void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLVa