Find anchoring end points for repairIntervalsInRange and repairIndexesInRange
automatically.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175673 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index e07922b..a716e8b 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1038,6 +1038,13 @@
                                       MachineBasicBlock::iterator Begin,
                                       MachineBasicBlock::iterator End,
                                       ArrayRef<unsigned> OrigRegs) {
+  // Find anchor points, which are at the beginning/end of blocks or at
+  // instructions that already have indexes.
+  while (Begin != MBB->begin() && !Indexes->hasIndex(Begin))
+    --Begin;
+  while (End != MBB->end() && !Indexes->hasIndex(End))
+    ++End;
+
   SlotIndex endIdx;
   if (End == MBB->end())
     endIdx = getMBBEndIdx(MBB).getPrevSlot();