-// Find the first intersection, and cache interference info
-// (retain segment iterators into both lvr_ and liu_).
-LiveIntervalUnion::InterferenceResult
-LiveIntervalUnion::Query::firstInterference() {
- if (firstInterference_ != LiveIntervalUnion::InterferenceResult()) {
- return firstInterference_;
+ LiveInterval::iterator VirtRegEnd = VirtReg->end();
+ LiveInterval *RecentReg = 0;
+ while (LiveUnionI.valid()) {
+ assert(VirtRegI != VirtRegEnd && "Reached end of VirtReg");
+
+ // Check for overlapping interference.
+ while (VirtRegI->start < LiveUnionI.stop() &&
+ VirtRegI->end > LiveUnionI.start()) {
+ // This is an overlap, record the interfering register.
+ LiveInterval *VReg = LiveUnionI.value();
+ if (VReg != RecentReg && !isSeenInterference(VReg)) {
+ RecentReg = VReg;
+ InterferingVRegs.push_back(VReg);
+ if (InterferingVRegs.size() >= MaxInterferingRegs)
+ return InterferingVRegs.size();
+ }
+ // This LiveUnion segment is no longer interesting.
+ if (!(++LiveUnionI).valid()) {
+ SeenAllInterferences = true;
+ return InterferingVRegs.size();
+ }
+ }
+
+ // The iterators are now not overlapping, LiveUnionI has been advanced
+ // beyond VirtRegI.
+ assert(VirtRegI->end <= LiveUnionI.start() && "Expected non-overlap");
+
+ // Advance the iterator that ends first.
+ VirtRegI = VirtReg->advanceTo(VirtRegI, LiveUnionI.start());
+ if (VirtRegI == VirtRegEnd)
+ break;
+
+ // Detect overlap, handle above.
+ if (VirtRegI->start < LiveUnionI.stop())
+ continue;
+
+ // Still not overlapping. Catch up LiveUnionI.
+ LiveUnionI.advanceTo(VirtRegI->start);