[SCCP] Remove code in visitBinaryOperator (and add tests).

We visit and/or, we try to derive a lattice value for the
instruction even if one of the operands is overdefined.
If the non-overdefined value is still 'unknown' just return and wait
for ResolvedUndefsIn to "plug in" the correct value. This simplifies
the logic a bit. While I'm here add tests for missing cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@287709 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed