[GHC] #14989: "Each block should be reachable from only one ProcPoint" compiling `integer` with `-fllvm`

[GHC]

#14989: "Each block should be reachable from only one ProcPoint" compiling
`integer` with `-fllvm`
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        Reporter:  sgraf             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.5
      Resolution:                    |             Keywords:
Operating System:  Windows           |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by sgraf):

 This is probably the culprit:
 https://github.com/ghc/ghc/blob/ca535f95a742d885c4082c9dc296c151fb3c1e12/compiler/cmm/CmmPipeline.hs#L122-L127

 `cbe_fix` doesn't quite cut it because of the change in dominance
 frontiers outlined above.

 The most efficient solution would be to only consider the merged blocks
 and their successors.

 I just realized that the second CBE pass is new and also that stack layout
 happens before.
 Doesn't a change in proc points affect stack layout? I'd do the fix myself
 (inserting a proper call to `minimalProcPointSet`), but I feel like I
 don't understand enough of the interactions and where to conjure
 `new_proc_points` from after that.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14989#comment:2>
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