C++ TargetData::getTypeAllocSize方法代码示例

/// isObjectSmallerThan - Return true if we can prove that the object specified
/// by V is smaller than Size.
static bool isObjectSmallerThan(const Value *V, unsigned Size,
                                const TargetData &TD) {
  const Type *AccessTy;
  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
    AccessTy = GV->getType()->getElementType();
  } else if (const AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
    if (!AI->isArrayAllocation())
      AccessTy = AI->getType()->getElementType();
    else
      return false;
  } else if (const CallInst* CI = extractMallocCall(V)) {
    if (!isArrayMalloc(V, &TD))
      // The size is the argument to the malloc call.
      if (const ConstantInt* C = dyn_cast<ConstantInt>(CI->getOperand(1)))
        return (C->getZExtValue() < Size);
    return false;
  } else if (const Argument *A = dyn_cast<Argument>(V)) {
    if (A->hasByValAttr())
      AccessTy = cast<PointerType>(A->getType())->getElementType();
    else
      return false;
  } else {
    return false;
  }
  
  if (AccessTy->isSized())
    return TD.getTypeAllocSize(AccessTy) < Size;
  return false;
}

static int64_t GetOffsetFromIndex(const GEPOperator *GEP, unsigned Idx,
                                  bool &VariableIdxFound, const TargetData &TD) {
    // Skip over the first indices.
    gep_type_iterator GTI = gep_type_begin(GEP);
    for (unsigned i = 1; i != Idx; ++i, ++GTI)
        /*skip along*/;

    // Compute the offset implied by the rest of the indices.
    int64_t Offset = 0;
    for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
        ConstantInt *OpC = dyn_cast<ConstantInt>(GEP->getOperand(i));
        if (OpC == 0)
            return VariableIdxFound = true;
        if (OpC->isZero()) continue;  // No offset.

        // Handle struct indices, which add their field offset to the pointer.
        if (StructType *STy = dyn_cast<StructType>(*GTI)) {
            Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
            continue;
        }

        // Otherwise, we have a sequential type like an array or vector.  Multiply
        // the index by the ElementSize.
        uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
        Offset += Size*OpC->getSExtValue();
    }

    return Offset;
}

static unsigned getTypeSize(TargetData &TD, Type *type) {
  if (type->isFunctionTy()) /* it is not sized, weird */
    return TD.getPointerSize();

  if (!type->isSized())
    return 100; /* FIXME */

  if (StructType *ST = dyn_cast<StructType>(type))
    return TD.getStructLayout(ST)->getSizeInBytes();

  return TD.getTypeAllocSize(type);
}

void SVMBlockSizeAccumulator::AddConstant(const TargetData &TD,
    const MachineConstantPoolEntry &CPE)
{
    AddConstant(TD.getTypeAllocSize(CPE.getType()), CPE.getAlignment());
}

/// processByValArgument - This is called on every byval argument in call sites.
bool MemCpyOpt::processByValArgument(CallSite CS, unsigned ArgNo) {
  TargetData *TD = getAnalysisIfAvailable<TargetData>();
  if (!TD) return false;

  // Find out what feeds this byval argument.
  Value *ByValArg = CS.getArgument(ArgNo);
  const Type *ByValTy =cast<PointerType>(ByValArg->getType())->getElementType();
  uint64_t ByValSize = TD->getTypeAllocSize(ByValTy);
  MemDepResult DepInfo =
    MD->getPointerDependencyFrom(AliasAnalysis::Location(ByValArg, ByValSize),
                                 true, CS.getInstruction(),
                                 CS.getInstruction()->getParent());
  if (!DepInfo.isClobber())
    return false;

  // If the byval argument isn't fed by a memcpy, ignore it.  If it is fed by
  // a memcpy, see if we can byval from the source of the memcpy instead of the
  // result.
  MemCpyInst *MDep = dyn_cast<MemCpyInst>(DepInfo.getInst());
  if (MDep == 0 || MDep->isVolatile() ||
      ByValArg->stripPointerCasts() != MDep->getDest())
    return false;
  
  // The length of the memcpy must be larger or equal to the size of the byval.
  ConstantInt *C1 = dyn_cast<ConstantInt>(MDep->getLength());
  if (C1 == 0 || C1->getValue().getZExtValue() < ByValSize)
    return false;

  // Get the alignment of the byval.  If it is greater than the memcpy, then we
  // can't do the substitution.  If the call doesn't specify the alignment, then
  // it is some target specific value that we can't know.
  unsigned ByValAlign = CS.getParamAlignment(ArgNo+1);
  if (ByValAlign == 0 || MDep->getAlignment() < ByValAlign)
    return false;  
  
  // Verify that the copied-from memory doesn't change in between the memcpy and
  // the byval call.
  //    memcpy(a <- b)
  //    *b = 42;
  //    foo(*a)
  // It would be invalid to transform the second memcpy into foo(*b).
  //
  // NOTE: This is conservative, it will stop on any read from the source loc,
  // not just the defining memcpy.
  MemDepResult SourceDep =
    MD->getPointerDependencyFrom(AliasAnalysis::getLocationForSource(MDep),
                                 false, CS.getInstruction(), MDep->getParent());
  if (!SourceDep.isClobber() || SourceDep.getInst() != MDep)
    return false;
  
  Value *TmpCast = MDep->getSource();
  if (MDep->getSource()->getType() != ByValArg->getType())
    TmpCast = new BitCastInst(MDep->getSource(), ByValArg->getType(),
                              "tmpcast", CS.getInstruction());
  
  DEBUG(dbgs() << "MemCpyOpt: Forwarding memcpy to byval:\n"
               << "  " << *MDep << "\n"
               << "  " << *CS.getInstruction() << "\n");
  
  // Otherwise we're good!  Update the byval argument.
  CS.setArgument(ArgNo, TmpCast);
  ++NumMemCpyInstr;
  return true;
}