[PATCH] Fix backtracking of instruction scheduling (pre-RA-sched)

[Andrew Trick]

Author: Andrew Trick <atrick at apple.com>
Date:   Thu Mar 26 20:44:13 2015

  Fix a bug in SelectionDAG scheduling backtracking code: PR22304.
  
  It can happen (by line CurSU->isPending = true; // This SU is not in
  AvailableQueue right now.) that a SUnit is mark as available but is
  not in the AvailableQueue. For SUnit being selected for scheduling
  both conditions must be met.
  
  This patch mainly defensively protects from invalid removing a node
  from a queue. Sometimes nodes are marked isAvailable but are not in
  the queue because they have been defered due to some hazard.
  
  Patch by Pawel Bylica!
  
  git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233351 91177308-0d34-0410-b5e6-96231b3b80d8


REPOSITORY
  rL LLVM

http://reviews.llvm.org/D8556

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