swift

d6b4f163 - [region-isolation] Add a SILLocation to SequenceBoundary in IsolationHistory.

[region-isolation] Add a SILLocation to SequenceBoundary in IsolationHistory. We package all isolation history nodes from a single instruction by placing a sequence boundary at the bottom. When ever we pop, we actually pop a PartitionOp at a time meaning that we pop until we see a SequenceBoundary. Thus the sequence boundary will always be the last element visited when popping meaning that it is a convenient place to stick the SILLocation associated with the entire PartitionOp. As a benefit, there was some unused space in IsolationHistory::Node for that case since we were not using the std::variant field at all.