[GHC] #14619: Output value of program changes upon compiling with -O optimizations

[GHC]

#14619: Output value of program changes upon compiling with -O optimizations
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        Reporter:  sheaf             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Windows           |         Architecture:  x86_64
 Type of failure:  Incorrect result  |  (amd64)
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by carter):

 summary notes of findings / information so far.

 1) reproducible in 64bit windows/ mingw32 windows 64bit build.  Phyx-
 indicated that the bug is observable with ghc 8.2 and old, but not with
 8.4/head?

 2) O2 and disabling the CMM SINK optimization pass makes the bug go away,
 which seems to indicate / hint at the issue being some piece of
 compilation / optimization that interacts with the CMM Sink algorithm
 using platform dependent data is incorrect

 theres not that many places (seemingly) where the information / action
 differs at this layer between different x86_64 compiler targets. So i
 think one of the spots in cmm/ native code gen  that does something
 different when the platform in MinGW32 is the culptrit?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14619#comment:23>
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