/// Test if V is always a pointer to allocated and suitably aligned memory for
/// a simple load or store.
static bool isDereferenceableAndAlignedPointer(
const Value *V, unsigned Align, const APInt &Size, const DataLayout &DL,
const Instruction *CtxI, const DominatorTree *DT,
SmallPtrSetImpl<const Value *> &Visited) {
// Already visited? Bail out, we've likely hit unreachable code.
if (!Visited.insert(V).second)
return false;
// Note that it is not safe to speculate into a malloc'd region because
// malloc may return null.
// bitcast instructions are no-ops as far as dereferenceability is concerned.
if (const BitCastOperator *BC = dyn_cast<BitCastOperator>(V))
return isDereferenceableAndAlignedPointer(BC->getOperand(0), Align, Size,
DL, CtxI, DT, Visited);
bool CheckForNonNull = false;
APInt KnownDerefBytes(Size.getBitWidth(),
V->getPointerDereferenceableBytes(DL, CheckForNonNull));
if (KnownDerefBytes.getBoolValue()) {
if (KnownDerefBytes.uge(Size))
if (!CheckForNonNull || isKnownNonZero(V, DL, 0, nullptr, CtxI, DT))
return isAligned(V, Align, DL);
}
// For GEPs, determine if the indexing lands within the allocated object.
if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
const Value *Base = GEP->getPointerOperand();
APInt Offset(DL.getIndexTypeSizeInBits(GEP->getType()), 0);
if (!GEP->accumulateConstantOffset(DL, Offset) || Offset.isNegative() ||
!Offset.urem(APInt(Offset.getBitWidth(), Align)).isMinValue())
return false;
// If the base pointer is dereferenceable for Offset+Size bytes, then the
// GEP (== Base + Offset) is dereferenceable for Size bytes. If the base
// pointer is aligned to Align bytes, and the Offset is divisible by Align
// then the GEP (== Base + Offset == k_0 * Align + k_1 * Align) is also
// aligned to Align bytes.
// Offset and Size may have different bit widths if we have visited an
// addrspacecast, so we can't do arithmetic directly on the APInt values.
return isDereferenceableAndAlignedPointer(
Base, Align, Offset + Size.sextOrTrunc(Offset.getBitWidth()),
DL, CtxI, DT, Visited);
}
// For gc.relocate, look through relocations
if (const GCRelocateInst *RelocateInst = dyn_cast<GCRelocateInst>(V))
return isDereferenceableAndAlignedPointer(
RelocateInst->getDerivedPtr(), Align, Size, DL, CtxI, DT, Visited);
if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V))
return isDereferenceableAndAlignedPointer(ASC->getOperand(0), Align, Size,
DL, CtxI, DT, Visited);
if (auto CS = ImmutableCallSite(V))
if (auto *RP = getArgumentAliasingToReturnedPointer(CS))
return isDereferenceableAndAlignedPointer(RP, Align, Size, DL, CtxI, DT,
Visited);
// If we don't know, assume the worst.
return false;
}
/*
* function evaluateNode
*
* Given a node, this function computes the abstract state of the node
* considering the abstract state of the node's predecessors and the
* semantics of the node.
*/
Range llvm::RangeAnalysis::evaluateNode(GraphNode* Node){
Range result;
/*
* VarNode: Constants generate constant ranges;
* otherwise, the output is a union of the predecessors
* */
if(VarNode* VN = dyn_cast<VarNode>(Node)){
Value* val = VN->getValue();
if (ConstantInt* CI = dyn_cast<ConstantInt>(val)){
APInt value = CI->getValue();
value = value.sextOrTrunc(MAX_BIT_INT);
result = Range(value,value);
} else {
result = getUnionOfPredecessors(Node);
}
}
/*
* Nodes that do not modify the data: PHI, Sigma, MemNode
* >> Just forward the state to the next node.
*/
else if (isa<MemNode>(Node) || isa<SigmaOpNode>(Node) || isa<PHIOpNode>(Node) || ( isa<OpNode>(Node) && dyn_cast<OpNode>(Node)->getOpCode() == Instruction::PHI ) ) {
result = getUnionOfPredecessors(Node);
}
/*
* CallNodes: We do not know the output
* >> [-inf, +inf]
*/
else if (isa<CallNode>(Node)) {
result = Range(Min, Max);
}
/*
* Binary operators: we will do the abstract interpretation
* to generate the result
*/
else if (BinaryOpNode* BOP = dyn_cast<BinaryOpNode>(Node)) {
GraphNode* Op1 = BOP->getOperand(0);
GraphNode* Op2 = BOP->getOperand(1);
result = abstractInterpretation(out_state[Op1], out_state[Op2], BOP->getBinaryOperator());
}
/*
* Unary operators: we will do the abstract interpretation
* to generate the result
*/
else if (UnaryOpNode* UOP = dyn_cast<UnaryOpNode>(Node)) {
GraphNode* Op = UOP->getIncomingNode(0);
result = abstractInterpretation(out_state[Op], UOP->getUnaryInstruction());
}
/*
* Generic operations: treat individually case by case
*/
else if (OpNode* OP = dyn_cast<OpNode>(Node)) {
if (Instruction* I = OP->getOperation()) {
switch (I->getOpcode()) {
case Instruction::Store:
GraphNode* Op = OP->getIncomingNode(0);
result = abstractInterpretation(out_state[Op], I);
break;
}
}
} else {
result = Range();
}
return result;
}
