[GHC] #14272: GHC goes out of memory while compiling simple program with optimizations

[GHC]

#14272: GHC goes out of memory while compiling simple program with optimizations
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        Reporter:  39aldo39          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4021,
       Wiki Page:                    |  Phab:D4025
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Changes (by bgamari):

 * differential:  Phab:D4021 => Phab:D4021, Phab:D4025


Comment:

 Alright, so the problem is fairly obvious: after some amount of
 simplification we end up with `... (GHC.Prim.uncheckedIShiftL# 1# x_a3q9)
 ...`. After a bit more simplification we learn (due to case analysis) that
 `x_a3q9 = 9223372036854775807#`. This allows the `uncheckedIShiftL#`
 constant folding rule to fire, which then blows up as the result is
 absurdly large.

 This is fixed by adding another constant folding rule to catch this case
 (which should result in `0#`). This is done in Phab:D4025.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14272#comment:10>
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