[Unroll] Follow-up for r247769: fix a bug in UnrolledInstAnalyzer::visitLoad.

Apart from checking that GlobalVariable is a constant, we should check
that it's not a weak constant, in which case we can't propagate its
value.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248327 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed