[tbb-bugs] #32053 [Applications/Tor Browser]: Tor Browser bundles based on Firefox 68 ESR are not reproducible (LLVM optimization issue)

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#32053: Tor Browser bundles based on Firefox 68 ESR are not reproducible (LLVM
optimization issue)
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 Reporter:  gk                                   |          Owner:  tbb-
                                                 |  team
     Type:  defect                               |         Status:  new
 Priority:  Immediate                            |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Critical                             |     Resolution:
 Keywords:  TorBrowserTeam201911, tbb-9.0-must,  |  Actual Points:
  tbb-9.0-issues, tbb-regression,                |
  tbb-9.0.1-can, GeorgKoppen201911               |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by gk):

 Replying to [comment:29 alexcrichton]:
 > The bug seems to be in the `-jump-threading` pass which I suspect is
 included in the O1 optimizations, yeah, but this technically only arose
 during O3 when presumably enough inlining had happened to then trigger the
 bug. I'm not really sure what the best way to avoid this bug would be
 unfortunately, but I suspect that an `-O1` build should be reproducible
 (albeit slow).

 Actually O2 is already enough. I can't trigger the issue with O1 nor with
 just `jump-threading` (and I tried pretty hard today). So, from those
 results I would say "something in O2 is the problem" which brings me to
 the thought that we might hunt different bugs. :) But on the positive side
 of things I think I have a setup ready now for actual bisecting LLVM which
 I will pick up tomorrow.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32053#comment:30>
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