/*
* function meet
*
* Here we perform the meet operation in the interval lattice,
* using Cousot's narrowing operator. We meet the current abstract state
* with the new_abstract_state and update the current abstract state of
* the node.
*
* This function returns true if the current abstract state has changed.
*/
bool llvm::RangeAnalysis::meet(GraphNode* Node, Range new_abstract_state){
Range oldInterval = out_state[Node];
APInt oLower = out_state[Node].getLower();
APInt oUpper = out_state[Node].getUpper();
Range newInterval = new_abstract_state;
APInt nLower = newInterval.getLower();
APInt nUpper = newInterval.getUpper();
if (narrowing_count[Node] < MaxIterationCount) {
if (oLower.eq(Min) && nLower.ne(Min)) {
out_state[Node] = Range(nLower, oUpper);
} else {
APInt smin = APIntOps::smin(oLower, nLower);
if (oLower.ne(smin)) {
out_state[Node] = Range(smin, oUpper);
}
}
if (oUpper.eq(Max) && nUpper.ne(Max)) {
out_state[Node] = Range(out_state[Node].getLower(), nUpper);
} else {
APInt smax = APIntOps::smax(oUpper, nUpper);
if (oUpper.ne(smax)) {
out_state[Node] = Range(out_state[Node].getLower(), smax);
}
}
}
if (SigmaOpNode* Sigma = dyn_cast<SigmaOpNode>(Node)){
if (branchConstraints.count(Sigma) > 0) {
out_state[Node] = out_state[Node].intersectWith(branchConstraints[Sigma]->getRange());
}
}
bool hasChanged = oldInterval != out_state[Node];
if (hasChanged) narrowing_count[Node]++;
return hasChanged;
}
