Initial commit

Initial commit

Copied lib/Fuzzer sources from LLVM repo, master branch, rev:

    commit 1df940a102a8bf84dd51df273fa21f438ec83005
    Author: Mikael Holmen <mikael.holmen@ericsson.com>
    Date:   Wed May 10 06:33:43 2017 +0000

    [UnreachableBlockElim] Check return value of constrainRegClass().

    Summary:
    MachineRegisterInfo::constrainRegClass() can fail if two register classes
    don't have a common subclass or if the register class doesn't contain
    enough registers. Check the return value before trying to remove Phi nodes,
    and if we can't constrain, we output a COPY instead of simply replacing
    registers.

    Reviewers: kparzysz, david2050, wmi

    Reviewed By: kparzysz

    Subscribers: llvm-commits

    Differential Revision: https://reviews.llvm.org/D32999

    git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302622 91177308-0d34-0410-b5e6-96231b3b80