Recommit "[APInt] Add back the asserts that check that the APInt shift methods aren't called with values larger than BitWidth."

This includes a fix to clamp a right shift of larger than BitWidth in DAG combining.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300816 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed