/**
* Merges the given register set into the set for the block with the given label. If there was not
* already an associated set, then this is the same as calling {@link #setStarts}. Otherwise, this
* will merge the two sets and call {@link #setStarts} on the result of the merge.
*
* @param label >= 0; the block label
* @param specs non-null; the register set to merge into the start set for the block
* @return <code>true</code> if the merge resulted in an actual change to the associated set
* (including storing one for the first time) or <code>false</code> if there was no change
*/
public boolean mergeStarts(int label, RegisterSpecSet specs) {
RegisterSpecSet start = getStarts0(label);
boolean changed = false;
if (start == null) {
setStarts(label, specs);
return true;
}
RegisterSpecSet newStart = start.mutableCopy();
newStart.intersect(specs, true);
if (start.equals(newStart)) {
return false;
}
newStart.setImmutable();
setStarts(label, newStart);
return true;
}
/**
* Gets a mutable copy of the register set associated with the start of the block with the given
* label. This returns a newly-allocated empty {@link RegisterSpecSet} of appropriate max size if
* there is not yet any set associated with the block.
*
* @param label >= 0; the block label
* @return non-null; the associated register set
*/
public RegisterSpecSet mutableCopyOfStarts(int label) {
RegisterSpecSet result = getStarts0(label);
return (result != null) ? result.mutableCopy() : new RegisterSpecSet(regCount);
}
