Pull in r219512 from upstream llvm trunk (by Hal Finkel):

Pull in r219512 from upstream llvm trunk (by Hal Finkel):

  [MiSched] Fix a logic error in tryPressure()

  Fixes a logic error in the MachineScheduler found by Steve Montgomery
  (and confirmed by Andy). This has gone unfixed for months because the
  fix has been found to introduce some small performance regressions.
  However, Andy has recommended that, at this point, we fix this to
  avoid further dependence on the incorrect behavior (and then
  follow-up separately on any regressions), and I agree.

  Fixes PR18883.

This fixes a possible "ran out of registers" error when compiling
www/firefox 45.0 on i386.

Direct commit to stable/9, because head already has this fix since the
llvm/clang 3.6.0 import.

PR:		207837

git-svn-id: svn://svn.freebsd.org/base/stable/9@296801 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f