bool LLVMReachingDefsAnalysis::handleStoreInst(LLVMNode *storeNode, DefMap *df,
PointsToSetT *&strong_update)
{
bool changed = false;
llvm::StoreInst *SI = cast<StoreInst>(storeNode->getValue());
LLVMNode *ptrNode = getOperand(storeNode, SI->getPointerOperand(), 0);
assert(ptrNode && "No pointer operand");
// update definitions
PointsToSetT& S = ptrNode->getPointsTo();
// if we have only one concrete pointer (known pointer
// with known offset), it is safe to do strong update
if (S.size() == 1) {
const Pointer& ptr = *S.begin();
// NOTE: we don't have good mechanism to diferentiate
// heap-allocated objects yet, so if the pointer points to heap,
// we must do weak update
if (ptr.isKnown() && !ptr.offset.isUnknown() && !ptr.pointsToHeap()) {
changed |= df->update(ptr, storeNode);
strong_update = &S;
return changed;
}
// else fall-through to weak update
}
// weak update
for (const Pointer& ptr : ptrNode->getPointsTo())
changed |= df->add(ptr, storeNode);
return changed;
}
bool LLVMReachingDefsAnalysis::handleIntrinsicCall(LLVMNode *callNode,
CallInst *CI,
DefMap *df)
{
bool changed = false;
IntrinsicInst *I = cast<IntrinsicInst>(CI);
Value *dest;
switch (I->getIntrinsicID())
{
case Intrinsic::memmove:
case Intrinsic::memcpy:
case Intrinsic::memset:
dest = I->getOperand(0);
break;
default:
return handleUndefinedCall(callNode, CI, df);
}
LLVMNode *destNode = getOperand(callNode, dest, 1);
assert(destNode && "No operand for intrinsic call");
for (const Pointer& ptr : destNode->getPointsTo()) {
// we could compute all the concrete offsets, but
// these functions usually set the whole memory,
// so if we use UNKNOWN_OFFSET, the effect is the same
changed |= df->add(Pointer(ptr.obj, UNKNOWN_OFFSET), callNode);
}
return changed;
}
bool LLVMReachingDefsAnalysis::handleUndefinedCall(LLVMNode *callNode,
CallInst *CI,
DefMap *df)
{
bool changed = false;
for (unsigned n = 1, e = callNode->getOperandsNum(); n < e; ++n) {
Value *llvmOp = CI->getOperand(n - 1);
if (!llvmOp->getType()->isPointerTy())
continue;
if (isa<Constant>(llvmOp->stripInBoundsOffsets()))
continue;
LLVMNode *op = getOperand(callNode, llvmOp, n);
assert(op && "unhandled pointer operand in undef call");
// with undefined call we must assume that any
// memory that was passed via pointer was modified
// and on unknown offset
// XXX we should handle external globals too
for (const Pointer& ptr : op->getPointsTo())
changed |= df->add(Pointer(ptr.obj, UNKNOWN_OFFSET), callNode);
}
return changed;
}
