void CompiledLoop::removeLoopVarOverflow() {
// bug: should remove overflow only if increment is constant and not too large -- fix this
Node* n = _incNode->next();
assert(n->isBranchNode(), "must be branch");
BranchNode* overflowCheck = (BranchNode*)n;
assert(overflowCheck->op() == VSBranchOp, "should be overflow check");
if (CompilerDebug || PrintLoopOpts) {
cout(PrintLoopOpts)->print("*removing overflow check at node N%d\n", overflowCheck->id());
}
Node* taken = overflowCheck->next(1); // overflow handling code
taken->removeUpToMerge();
overflowCheck->removeNext(taken); // so overflowCheck can be eliminated
overflowCheck->eliminate(overflowCheck->bb(), NULL, true, false);
// since increment cannot fail anymore, directly increment loop counter if possible
// need to search for assignment of incremented value to loop var
Node* a = overflowCheck->next();
while (1) {
if (a->nPredecessors() > 1) break; // can't search beyond merge
if (a->nSuccessors() > 1) break; // can't search beyond branches
if (a->isAssignNode()) {
if (!a->deleted) {
AssignNode* assign = (AssignNode*)a;
if (assign->src() == _incNode->dest() && assign->dest() == _loopVar) {
if (CompilerDebug || PrintLoopOpts) {
cout(PrintLoopOpts)->print("*optimizing loopVar increment at N%d\n", _incNode->id());
}
_incNode->setDest(_incNode->bb(), _loopVar);
assign->eliminate(assign->bb(), NULL, true, false);
}
}
} else if (!a->isTrivial()) {
compiler_warning("unexpected nontrivial node N%d after loopVar increment\n", a->id());
}
a = a->next();
}
}
