[SLSR] handle (B | i) * S

Summary:
Consider (B | i) * S as (B + i) * S if B and i have no bits set in
common.

Test Plan: @or in slsr-mul.ll

Reviewers: broune, meheff

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D9788

llvm-svn: 237456