Re-commit : [LICM] Allow sinking when foldable in loop

 This recommit r320823 after fixing a test failure.

 Original commit message:

    Continue trying to sink an instruction if its users in the loop is foldable.
    This will allow the instruction to be folded in the loop by decoupling it from
    the user outside of the loop.

    Reviewers: hfinkel, majnemer, davidxl, efriedma, danielcdh, bmakam, mcrosier

    Reviewed By: hfinkel

    Subscribers: javed.absar, bmakam, mcrosier, llvm-commits

    Differential Revision: https://reviews.llvm.org/D37076

llvm-svn: 320833