[tor-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:31 gk]:
 > Okay, so before I speculate further I double-check your results using
 `-opt-bisect-limit` at least figuring out which optimization is the
 culprit for the tests I am currently running.

 Yeah, I can confirm that this is the `-jump-threading` operation here,
 too, good. Then let's get the LLVM bisecting going.

 Alex: So, I tried to extract the problematic function name with `llvm-
 extract` but I failed so far due to my lack of knowledge of LLVM tools.
 How do I properly demangle the function name so that `llvm-extract` likes
 it? I tried `llvm-cxxfilt` but no dice. The `opt` output for the
 problematic function I get is:
 {{{
 BISECT: running pass (1208271) Jump Threading on function
 (_ZN83_$LT$style..values..specified..box_..Appearance$u20$as$u20$style..parser..Parse$GT$5parse17ha60227de7ee101e5E)
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32053#comment:36>
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