Address reviewer feedback:

- Modify LiveRange::removeSegment so it handles intervals with no Segment
- Update code to remove overlaps() checks
- Remove addUsedIfAvailable of LiveIntervals

Author: perlfu

llvm/include/llvm/CodeGen/LiveInterval.h

@@ -520,8 +520,9 @@ namespace llvm {
         endIndex() < End.getBoundaryIndex();
     }
 
-    /// Remove the specified segment from this range.  Note that the segment
-    /// must be a single Segment in its entirety.
+    /// Remove the specified interval from this live range.
+    /// Does nothing if interval is not part of this live range.
+    /// Note that the interval must be within a single Segment in its entirety.
     void removeSegment(SlotIndex Start, SlotIndex End,
                        bool RemoveDeadValNo = false);
 

llvm/lib/CodeGen/LiveInterval.cpp

@@ -563,13 +563,18 @@ VNInfo *LiveRange::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
   return CalcLiveRangeUtilVector(this).extendInBlock(StartIdx, Kill);
 }
 
-/// Remove the specified segment from this range.  Note that the segment must
-/// be in a single Segment in its entirety.
+/// Remove the specified interval from this live range.
+/// Does nothing if interval is not part of this live range.
+/// Note that the interval must be within a single Segment in its entirety.
 void LiveRange::removeSegment(SlotIndex Start, SlotIndex End,
                               bool RemoveDeadValNo) {
   // Find the Segment containing this span.
   iterator I = find(Start);
-  assert(I != end() && "Segment is not in range!");
+
+  // No Segment found, so nothing to do.
+  if (I == end())
+    return;
+
   assert(I->containsInterval(Start, End)
          && "Segment is not entirely in range!");
 

llvm/lib/CodeGen/MachineBasicBlock.cpp

@@ -1312,10 +1312,8 @@ MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(
         }
       } else if (!isLiveOut && !isLastMBB) {
         LI.removeSegment(StartIndex, EndIndex);
-        for (auto &SR : LI.subranges()) {
-          if (SR.overlaps(StartIndex, EndIndex))
-            SR.removeSegment(StartIndex, EndIndex);
-        }
+        for (auto &SR : LI.subranges())
+          SR.removeSegment(StartIndex, EndIndex);
       }
     }
 

llvm/lib/CodeGen/PHIElimination.cpp

@@ -136,7 +136,6 @@ INITIALIZE_PASS_END(PHIElimination, DEBUG_TYPE,
 
 void PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addUsedIfAvailable<LiveVariables>();
-  AU.addUsedIfAvailable<LiveIntervals>();
   AU.addPreserved<LiveVariables>();
   AU.addPreserved<SlotIndexes>();
   AU.addPreserved<LiveIntervals>();