diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1321,10 +1321,11 @@
         if (auto Fragment = Expr->getFragmentInfo())
           BitsToDescribe = Fragment->SizeInBits;
         for (auto RegAndSize : RFV.getRegsAndSizes()) {
-          unsigned RegisterSize = RegAndSize.second;
           // Bail out if all bits are described already.
           if (Offset >= BitsToDescribe)
             break;
+          // TODO: handle scalable vectors.
+          unsigned RegisterSize = RegAndSize.second;
           unsigned FragmentSize = (Offset + RegisterSize > BitsToDescribe)
               ? BitsToDescribe - Offset
               : RegisterSize;