conversion open the door for many nasty implicit conversion issues, and
can be easily solved by initializing with (V.begin(), V.end()) when
needed.
This patch includes many small cleanups for sdisel also.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50340 91177308-0d34-0410-b5e6-96231b3b80d8