Fix MSVC warning.

This patch is to fix the following warning when compiled with MSVC 64 bit.

  warning C4334: '<<' : result of 32-bit shift implicitly converted to 64
  bits (was 64-bit shift intended?)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205245 91177308-0d34-0410-b5e6-96231b3b80d8