+ // Fall back to the regular add method if the live range
+ // is using the segment set instead of the segment vector.
+ if (LR->segmentSet != nullptr) {
+ LR->addSegmentToSet(Seg);
+ return;
+ }
+
+ // Flush the state if Start moves backwards.
+ if (!LastStart.isValid() || LastStart > Seg.start) {
+ if (isDirty())
+ flush();
+ // This brings us to an uninitialized state. Reinitialize.
+ assert(Spills.empty() && "Leftover spilled segments");
+ WriteI = ReadI = LR->begin();
+ }
+
+ // Remember start for next time.
+ LastStart = Seg.start;
+
+ // Advance ReadI until it ends after Seg.start.
+ LiveRange::iterator E = LR->end();
+ if (ReadI != E && ReadI->end <= Seg.start) {
+ // First try to close the gap between WriteI and ReadI with spills.
+ if (ReadI != WriteI)
+ mergeSpills();
+ // Then advance ReadI.
+ if (ReadI == WriteI)
+ ReadI = WriteI = LR->find(Seg.start);
+ else
+ while (ReadI != E && ReadI->end <= Seg.start)
+ *WriteI++ = *ReadI++;
+ }
+
+ assert(ReadI == E || ReadI->end > Seg.start);
+
+ // Check if the ReadI segment begins early.
+ if (ReadI != E && ReadI->start <= Seg.start) {
+ assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
+ // Bail if Seg is completely contained in ReadI.
+ if (ReadI->end >= Seg.end)
+ return;
+ // Coalesce into Seg.
+ Seg.start = ReadI->start;
+ ++ReadI;
+ }
+
+ // Coalesce as much as possible from ReadI into Seg.
+ while (ReadI != E && coalescable(Seg, *ReadI)) {
+ Seg.end = std::max(Seg.end, ReadI->end);
+ ++ReadI;
+ }
+
+ // Try coalescing Spills.back() into Seg.
+ if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
+ Seg.start = Spills.back().start;
+ Seg.end = std::max(Spills.back().end, Seg.end);
+ Spills.pop_back();
+ }
+
+ // Try coalescing Seg into WriteI[-1].
+ if (WriteI != LR->begin() && coalescable(WriteI[-1], Seg)) {
+ WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
+ return;
+ }
+
+ // Seg doesn't coalesce with anything, and needs to be inserted somewhere.
+ if (WriteI != ReadI) {
+ *WriteI++ = Seg;
+ return;
+ }
+
+ // Finally, append to LR or Spills.
+ if (WriteI == E) {
+ LR->segments.push_back(Seg);
+ WriteI = ReadI = LR->end();
+ } else
+ Spills.push_back(Seg);
+}
+
+// Merge as many spilled segments as possible into the gap between WriteI
+// and ReadI. Advance WriteI to reflect the inserted instructions.
+void LiveRangeUpdater::mergeSpills() {
+ // Perform a backwards merge of Spills and [SpillI;WriteI).
+ size_t GapSize = ReadI - WriteI;
+ size_t NumMoved = std::min(Spills.size(), GapSize);
+ LiveRange::iterator Src = WriteI;
+ LiveRange::iterator Dst = Src + NumMoved;
+ LiveRange::iterator SpillSrc = Spills.end();
+ LiveRange::iterator B = LR->begin();
+
+ // This is the new WriteI position after merging spills.
+ WriteI = Dst;
+
+ // Now merge Src and Spills backwards.
+ while (Src != Dst) {
+ if (Src != B && Src[-1].start > SpillSrc[-1].start)
+ *--Dst = *--Src;
+ else
+ *--Dst = *--SpillSrc;
+ }
+ assert(NumMoved == size_t(Spills.end() - SpillSrc));
+ Spills.erase(SpillSrc, Spills.end());
+}
+
+void LiveRangeUpdater::flush() {
+ if (!isDirty())
+ return;
+ // Clear the dirty state.
+ LastStart = SlotIndex();
+
+ assert(LR && "Cannot add to a null destination");
+
+ // Nothing to merge?
+ if (Spills.empty()) {
+ LR->segments.erase(WriteI, ReadI);
+ LR->verify();
+ return;
+ }
+
+ // Resize the WriteI - ReadI gap to match Spills.
+ size_t GapSize = ReadI - WriteI;
+ if (GapSize < Spills.size()) {
+ // The gap is too small. Make some room.
+ size_t WritePos = WriteI - LR->begin();
+ LR->segments.insert(ReadI, Spills.size() - GapSize, LiveRange::Segment());
+ // This also invalidated ReadI, but it is recomputed below.
+ WriteI = LR->begin() + WritePos;
+ } else {
+ // Shrink the gap if necessary.
+ LR->segments.erase(WriteI + Spills.size(), ReadI);
+ }
+ ReadI = WriteI + Spills.size();
+ mergeSpills();
+ LR->verify();