diff --git a/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h b/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
index c837e13cb43..19d17036585 100644
--- a/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
+++ b/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
@@ -216,6 +216,14 @@ public:
     iterator_range<SmallVectorImpl<unsigned>::iterator>
     getVRegsMem(unsigned OpIdx);
 
+    /// Get the end iterator for a range starting at \p StartIdx and
+    /// spannig \p NumVal in NewVRegs.
+    /// \pre StartIdx + NumVal <= NewVRegs.size()
+    SmallVectorImpl<unsigned>::const_iterator
+    getNewVRegsEnd(unsigned StartIdx, unsigned NumVal) const;
+    SmallVectorImpl<unsigned>::iterator getNewVRegsEnd(unsigned StartIdx,
+                                                       unsigned NumVal);
+
   public:
     /// Create an OperandsMapper that will hold the information to apply \p
     /// InstrMapping to \p MI.
diff --git a/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp b/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
index f945a087e60..6173369f9cc 100644
--- a/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
+++ b/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
@@ -538,13 +538,26 @@ RegisterBankInfo::OperandsMapper::getVRegsMem(unsigned OpIdx) {
       NewVRegs.push_back(0);
   }
   SmallVectorImpl<unsigned>::iterator End =
-      NewVRegs.size() <= StartIdx + NumPartialVal + 1
-          ? NewVRegs.end()
-          : &NewVRegs[StartIdx + NumPartialVal + 1];
+      getNewVRegsEnd(StartIdx, NumPartialVal);
 
   return make_range(&NewVRegs[StartIdx], End);
 }
 
+SmallVectorImpl<unsigned>::const_iterator
+RegisterBankInfo::OperandsMapper::getNewVRegsEnd(unsigned StartIdx,
+                                                 unsigned NumVal) const {
+  return const_cast<OperandsMapper *>(this)->getNewVRegsEnd(StartIdx, NumVal);
+}
+SmallVectorImpl<unsigned>::iterator
+RegisterBankInfo::OperandsMapper::getNewVRegsEnd(unsigned StartIdx,
+                                                 unsigned NumVal) {
+  assert((NewVRegs.size() == StartIdx + NumVal ||
+          NewVRegs.size() > StartIdx + NumVal) &&
+         "NewVRegs too small to contain all the partial mapping");
+  return NewVRegs.size() <= StartIdx + NumVal ? NewVRegs.end()
+                                              : &NewVRegs[StartIdx + NumVal];
+}
+
 void RegisterBankInfo::OperandsMapper::createVRegs(unsigned OpIdx) {
   assert(OpIdx < getMI().getNumOperands() && "Out-of-bound access");
   iterator_range<SmallVectorImpl<unsigned>::iterator> NewVRegsForOpIdx =
@@ -588,9 +601,7 @@ RegisterBankInfo::OperandsMapper::getVRegs(unsigned OpIdx,
   unsigned PartMapSize =
       getInstrMapping().getOperandMapping(OpIdx).BreakDown.size();
   SmallVectorImpl<unsigned>::const_iterator End =
-      NewVRegs.size() <= StartIdx + PartMapSize + 1
-          ? NewVRegs.end()
-          : &NewVRegs[StartIdx + PartMapSize + 1];
+      getNewVRegsEnd(StartIdx, PartMapSize);
   iterator_range<SmallVectorImpl<unsigned>::const_iterator> Res =
       make_range(&NewVRegs[StartIdx], End);
 #ifndef NDEBUG