[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:  AndreasK
            Type:  bug               |               Status:  patch
        Priority:  highest           |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.2.2
  (CodeGen)                          |
      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):  Phab:D4348
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"add4e1f11b88cd603f6c01bc135eb576e1922a8e/ghc" add4e1f/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="add4e1f11b88cd603f6c01bc135eb576e1922a8e"
 Mark xmm6 as caller saved in the register allocator for windows.

 This prevents the register being picked up as a scratch register.
 Otherwise the allocator would be free to use it before a call. This
 fixes #14619.

 Test Plan: ci, repro case on #14619

 Reviewers: bgamari, Phyx, erikd, simonmar, RyanGlScott, simonpj

 Reviewed By: Phyx, RyanGlScott, simonpj

 Subscribers: simonpj, RyanGlScott, Phyx, rwbarton, thomie, carter

 GHC Trac Issues: #14619

 Differential Revision: https://phabricator.haskell.org/D4348
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14619#comment:39>
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