Fix a crash when building 177.mesa for armv6.

When splitting a live range immediately before an LDR_POST instruction
that redefines the address register, make sure to use the correct value
number in leaveIntvBefore.

We need the value number entering the instruction.

<rdar://problem/9793765>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135413 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SplitKit.cpp

@@ -730,7 +730,7 @@ SlotIndex SplitEditor::leaveIntvBefore(SlotIndex Idx) {
   DEBUG(dbgs() << "    leaveIntvBefore " << Idx);
 
   // The interval must be live into the instruction at Idx.
-  Idx = Idx.getBoundaryIndex();
+  Idx = Idx.getBaseIndex();
   VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Idx);
   if (!ParentVNI) {
     DEBUG(dbgs() << ": not live\n");