C++ MemCpyInst::getSource方法代码示例

void Lint::visitCallSite(CallSite CS) {
  Instruction &I = *CS.getInstruction();
  Value *Callee = CS.getCalledValue();

  visitMemoryReference(I, Callee, MemoryLocation::UnknownSize, 0, nullptr,
                       MemRef::Callee);

  if (Function *F = dyn_cast<Function>(findValue(Callee,
                                                 /*OffsetOk=*/false))) {
    Assert(CS.getCallingConv() == F->getCallingConv(),
           "Undefined behavior: Caller and callee calling convention differ",
           &I);

    FunctionType *FT = F->getFunctionType();
    unsigned NumActualArgs = CS.arg_size();

    Assert(FT->isVarArg() ? FT->getNumParams() <= NumActualArgs
                          : FT->getNumParams() == NumActualArgs,
           "Undefined behavior: Call argument count mismatches callee "
           "argument count",
           &I);

    Assert(FT->getReturnType() == I.getType(),
           "Undefined behavior: Call return type mismatches "
           "callee return type",
           &I);

    // Check argument types (in case the callee was casted) and attributes.
    // TODO: Verify that caller and callee attributes are compatible.
    Function::arg_iterator PI = F->arg_begin(), PE = F->arg_end();
    CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
    for (; AI != AE; ++AI) {
      Value *Actual = *AI;
      if (PI != PE) {
        Argument *Formal = &*PI++;
        Assert(Formal->getType() == Actual->getType(),
               "Undefined behavior: Call argument type mismatches "
               "callee parameter type",
               &I);

        // Check that noalias arguments don't alias other arguments. This is
        // not fully precise because we don't know the sizes of the dereferenced
        // memory regions.
        if (Formal->hasNoAliasAttr() && Actual->getType()->isPointerTy())
          for (CallSite::arg_iterator BI = CS.arg_begin(); BI != AE; ++BI)
            if (AI != BI && (*BI)->getType()->isPointerTy()) {
              AliasResult Result = AA->alias(*AI, *BI);
              Assert(Result != MustAlias && Result != PartialAlias,
                     "Unusual: noalias argument aliases another argument", &I);
            }

        // Check that an sret argument points to valid memory.
        if (Formal->hasStructRetAttr() && Actual->getType()->isPointerTy()) {
          Type *Ty =
            cast<PointerType>(Formal->getType())->getElementType();
          visitMemoryReference(I, Actual, DL->getTypeStoreSize(Ty),
                               DL->getABITypeAlignment(Ty), Ty,
                               MemRef::Read | MemRef::Write);
        }
      }
    }
  }

  if (CS.isCall() && cast<CallInst>(CS.getInstruction())->isTailCall())
    for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
         AI != AE; ++AI) {
      Value *Obj = findValue(*AI, /*OffsetOk=*/true);
      Assert(!isa<AllocaInst>(Obj),
             "Undefined behavior: Call with \"tail\" keyword references "
             "alloca",
             &I);
    }


  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I))
    switch (II->getIntrinsicID()) {
    default: break;

    // TODO: Check more intrinsics

    case Intrinsic::memcpy: {
      MemCpyInst *MCI = cast<MemCpyInst>(&I);
      // TODO: If the size is known, use it.
      visitMemoryReference(I, MCI->getDest(), MemoryLocation::UnknownSize,
                           MCI->getAlignment(), nullptr, MemRef::Write);
      visitMemoryReference(I, MCI->getSource(), MemoryLocation::UnknownSize,
                           MCI->getAlignment(), nullptr, MemRef::Read);

      // Check that the memcpy arguments don't overlap. The AliasAnalysis API
      // isn't expressive enough for what we really want to do. Known partial
      // overlap is not distinguished from the case where nothing is known.
      uint64_t Size = 0;
      if (const ConstantInt *Len =
              dyn_cast<ConstantInt>(findValue(MCI->getLength(),
                                              /*OffsetOk=*/false)))
        if (Len->getValue().isIntN(32))
          Size = Len->getValue().getZExtValue();
      Assert(AA->alias(MCI->getSource(), Size, MCI->getDest(), Size) !=
                 MustAlias,
             "Undefined behavior: memcpy source and destination overlap", &I);
//.........这里部分代码省略.........

/// processByValArgument - This is called on every byval argument in call sites.
bool MemCpyOpt::processByValArgument(CallSite CS, unsigned ArgNo) {
    if (TD == 0) return false;

    // Find out what feeds this byval argument.
    Value *ByValArg = CS.getArgument(ArgNo);
    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 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) return false;

    // If it is greater than the memcpy, then we check to see if we can force the
    // source of the memcpy to the alignment we need.  If we fail, we bail out.
    if (MDep->getAlignment() < ByValAlign &&
            getOrEnforceKnownAlignment(MDep->getSource(),ByValAlign, TD) < 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;
}

void Lint::visitCallSite(CallSite CS) {
  Instruction &I = *CS.getInstruction();
  Value *Callee = CS.getCalledValue();

  // TODO: Check function alignment?
  visitMemoryReference(I, Callee, 0, 0);

  if (Function *F = dyn_cast<Function>(Callee->stripPointerCasts())) {
    Assert1(CS.getCallingConv() == F->getCallingConv(),
            "Undefined behavior: Caller and callee calling convention differ",
            &I);

    const FunctionType *FT = F->getFunctionType();
    unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());

    Assert1(FT->isVarArg() ?
              FT->getNumParams() <= NumActualArgs :
              FT->getNumParams() == NumActualArgs,
            "Undefined behavior: Call argument count mismatches callee "
            "argument count", &I);
      
    // TODO: Check argument types (in case the callee was casted)

    // TODO: Check ABI-significant attributes.

    // TODO: Check noalias attribute.

    // TODO: Check sret attribute.
  }

  // TODO: Check the "tail" keyword constraints.

  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I))
    switch (II->getIntrinsicID()) {
    default: break;

    // TODO: Check more intrinsics

    case Intrinsic::memcpy: {
      MemCpyInst *MCI = cast<MemCpyInst>(&I);
      visitMemoryReference(I, MCI->getSource(), MCI->getAlignment(), 0);
      visitMemoryReference(I, MCI->getDest(), MCI->getAlignment(), 0);

      // Check that the memcpy arguments don't overlap. The AliasAnalysis API
      // isn't expressive enough for what we really want to do. Known partial
      // overlap is not distinguished from the case where nothing is known.
      unsigned Size = 0;
      if (const ConstantInt *Len =
            dyn_cast<ConstantInt>(MCI->getLength()->stripPointerCasts()))
        if (Len->getValue().isIntN(32))
          Size = Len->getValue().getZExtValue();
      Assert1(AA->alias(MCI->getSource(), Size, MCI->getDest(), Size) !=
              AliasAnalysis::MustAlias,
              "Undefined behavior: memcpy source and destination overlap", &I);
      break;
    }
    case Intrinsic::memmove: {
      MemMoveInst *MMI = cast<MemMoveInst>(&I);
      visitMemoryReference(I, MMI->getSource(), MMI->getAlignment(), 0);
      visitMemoryReference(I, MMI->getDest(), MMI->getAlignment(), 0);
      break;
    }
    case Intrinsic::memset: {
      MemSetInst *MSI = cast<MemSetInst>(&I);
      visitMemoryReference(I, MSI->getDest(), MSI->getAlignment(), 0);
      break;
    }

    case Intrinsic::vastart:
      Assert1(I.getParent()->getParent()->isVarArg(),
              "Undefined behavior: va_start called in a non-varargs function",
              &I);

      visitMemoryReference(I, CS.getArgument(0), 0, 0);
      break;
    case Intrinsic::vacopy:
      visitMemoryReference(I, CS.getArgument(0), 0, 0);
      visitMemoryReference(I, CS.getArgument(1), 0, 0);
      break;
    case Intrinsic::vaend:
      visitMemoryReference(I, CS.getArgument(0), 0, 0);
      break;

    case Intrinsic::stackrestore:
      visitMemoryReference(I, CS.getArgument(0), 0, 0);
      break;
    }
}