[InstCombine] Improve the expansion in SimplifyUsingDistributiveLaws to handle cases where one side doesn't simplify, but the other side resolves to an identity value
Summary:
If one side simplifies to the identity value for inner opcode, we can replace the value with just the operation that can't be simplified.
I've removed a couple now unneeded special cases in visitAnd and visitOr. There are probably other cases I missed.
Reviewers: spatel, majnemer, hfinkel, dberlin
Reviewed By: spatel
Subscribers: grandinj, llvm-commits, spatel
Differential Revision: https://reviews.llvm.org/D35451
llvm-svn: 308111