path: root/lib/CodeGen/CGExprConstant.cpp

//===--- CGExprConstant.cpp - Emit LLVM Code from Constant 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 Constant Expr nodes as LLVM code.
//
//===----------------------------------------------------------------------===//

#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "CGObjCRuntime.h"
#include "clang/AST/APValue.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/Target/TargetData.h"
using namespace clang;
using namespace CodeGen;

namespace  {
class VISIBILITY_HIDDEN ConstExprEmitter : 
  public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
  CodeGenModule &CGM;
  CodeGenFunction *CGF;
public:
  ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
    : CGM(cgm), CGF(cgf) {
  }
    
  //===--------------------------------------------------------------------===//
  //                            Visitor Methods
  //===--------------------------------------------------------------------===//
    
  llvm::Constant *VisitStmt(Stmt *S) {
    CGM.ErrorUnsupported(S, "constant expression");
    QualType T = cast<Expr>(S)->getType();
    return llvm::UndefValue::get(CGM.getTypes().ConvertType(T));
  }
  
  llvm::Constant *VisitParenExpr(ParenExpr *PE) { 
    return Visit(PE->getSubExpr()); 
  }
  
  // Leaves
  llvm::Constant *VisitIntegerLiteral(const IntegerLiteral *E) {
    return llvm::ConstantInt::get(E->getValue());
  }
  llvm::Constant *VisitFloatingLiteral(const FloatingLiteral *E) {
    return llvm::ConstantFP::get(E->getValue());
  }
  llvm::Constant *VisitCharacterLiteral(const CharacterLiteral *E) {
    return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
  }
  llvm::Constant *VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *E) {
    return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
  }
  llvm::Constant *VisitCXXZeroInitValueExpr(const CXXZeroInitValueExpr *E) {
    return llvm::Constant::getNullValue(ConvertType(E->getType()));
  }
  llvm::Constant *VisitObjCStringLiteral(const ObjCStringLiteral *E) {
    std::string S(E->getString()->getStrData(), 
                  E->getString()->getByteLength());
    llvm::Constant *C = CGM.getObjCRuntime().GenerateConstantString(S);
    return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
  }
  
  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
    return Visit(E->getInitializer());
  }
  
  llvm::Constant *VisitCastExpr(CastExpr* E) {
    llvm::Constant *C = Visit(E->getSubExpr());
    
    return EmitConversion(C, E->getSubExpr()->getType(), E->getType());    
  }

  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
    return Visit(DAE->getExpr());
  }

  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
    std::vector<llvm::Constant*> Elts;
    const llvm::ArrayType *AType =
        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
    unsigned NumInitElements = ILE->getNumInits();
    // FIXME: Check for wide strings
    if (NumInitElements > 0 && isa<StringLiteral>(ILE->getInit(0)) &&
        ILE->getType()->getArrayElementTypeNoTypeQual()->isCharType())
      return Visit(ILE->getInit(0));
    const llvm::Type *ElemTy = AType->getElementType();
    unsigned NumElements = AType->getNumElements();

    // Initialising an array requires us to automatically 
    // initialise any elements that have not been initialised explicitly
    unsigned NumInitableElts = std::min(NumInitElements, NumElements);

    // Copy initializer elements.
    unsigned i = 0;
    bool RewriteType = false;
    for (; i < NumInitableElts; ++i) {
      llvm::Constant *C = CGM.EmitConstantExpr(ILE->getInit(i), CGF);
      RewriteType |= (C->getType() != ElemTy);
      Elts.push_back(C);
    }

    // Initialize remaining array elements.
    for (; i < NumElements; ++i)
      Elts.push_back(llvm::Constant::getNullValue(ElemTy));

    if (RewriteType) {
      // FIXME: Try to avoid packing the array
      std::vector<const llvm::Type*> Types;
      for (unsigned i = 0; i < Elts.size(); ++i)
        Types.push_back(Elts[i]->getType());
      const