Fix sign error.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117677 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveRangeEdit.h b/lib/CodeGen/LiveRangeEdit.h
index 3230a2e..7acf9e0 100644
--- a/lib/CodeGen/LiveRangeEdit.h
+++ b/lib/CodeGen/LiveRangeEdit.h
@@ -78,7 +78,7 @@
   iterator begin() const { return newRegs_.begin()+firstNew_; }
   iterator end() const { return newRegs_.end(); }
   unsigned size() const { return newRegs_.size()-firstNew_; }
-  LiveInterval *get(unsigned idx) const { return newRegs_[idx-firstNew_]; }
+  LiveInterval *get(unsigned idx) const { return newRegs_[idx+firstNew_]; }
 
   /// assignStackSlot - Ensure a stack slot is assigned to parent.
   /// @return the assigned stack slot number.