+ // Update LiveIntervals for the new copy or implicit def.
+ if (LIS) {
+ MachineInstr *NewInstr = std::prev(AfterPHIsIt);
+ SlotIndex DestCopyIndex = LIS->InsertMachineInstrInMaps(NewInstr);
+
+ SlotIndex MBBStartIndex = LIS->getMBBStartIdx(&MBB);
+ if (IncomingReg) {
+ // Add the region from the beginning of MBB to the copy instruction to
+ // IncomingReg's live interval.
+ LiveInterval &IncomingLI = LIS->createEmptyInterval(IncomingReg);
+ VNInfo *IncomingVNI = IncomingLI.getVNInfoAt(MBBStartIndex);
+ if (!IncomingVNI)
+ IncomingVNI = IncomingLI.getNextValue(MBBStartIndex,
+ LIS->getVNInfoAllocator());
+ IncomingLI.addSegment(LiveInterval::Segment(MBBStartIndex,
+ DestCopyIndex.getRegSlot(),
+ IncomingVNI));
+ }
+
+ LiveInterval &DestLI = LIS->getInterval(DestReg);
+ assert(DestLI.begin() != DestLI.end() &&
+ "PHIs should have nonempty LiveIntervals.");
+ if (DestLI.endIndex().isDead()) {
+ // A dead PHI's live range begins and ends at the start of the MBB, but
+ // the lowered copy, which will still be dead, needs to begin and end at
+ // the copy instruction.
+ VNInfo *OrigDestVNI = DestLI.getVNInfoAt(MBBStartIndex);
+ assert(OrigDestVNI && "PHI destination should be live at block entry.");
+ DestLI.removeSegment(MBBStartIndex, MBBStartIndex.getDeadSlot());
+ DestLI.createDeadDef(DestCopyIndex.getRegSlot(),
+ LIS->getVNInfoAllocator());
+ DestLI.removeValNo(OrigDestVNI);
+ } else {
+ // Otherwise, remove the region from the beginning of MBB to the copy
+ // instruction from DestReg's live interval.
+ DestLI.removeSegment(MBBStartIndex, DestCopyIndex.getRegSlot());
+ VNInfo *DestVNI = DestLI.getVNInfoAt(DestCopyIndex.getRegSlot());
+ assert(DestVNI && "PHI destination should be live at its definition.");
+ DestVNI->def = DestCopyIndex.getRegSlot();
+ }
+ }
+