Re: #16258: PowerPC Big-Endian: ArithInt16, ArithInt8, ArithWord16, and ArithWord8 fail

#16258: PowerPC Big-Endian: ArithInt16, ArithInt8, ArithWord16, and ArithWord8 fail
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        Reporter:  trommler          |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.10.1
       Component:  Compiler          |              Version:  8.7
      Resolution:                    |             Keywords:  Big-endian
Operating System:  Unknown/Multiple  |         Architecture:  powerpc64
 Type of failure:  Incorrect result  |            Test Case:
  at runtime                         |  primops/should_run/ArithInt16,
                                     |  primops/should_run/ArithWord16,
                                     |  primops/should_run/ArithWord8,
                                     |  primops/should_run/ArithInt8
      Blocked By:                    |             Blocking:
 Related Tickets:  #16222            |  Differential Rev(s):
       Wiki Page:                    |  https://gitlab.haskell.org/ghc/ghc/merge_requests/286
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Comment (by Marge Bot <ben+marge-bot@…>):

 In [changeset:"af7b0fdb64ad1c57f5829e8bd89e8e0fa96b11d2/ghc"
 af7b0fdb/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="af7b0fdb64ad1c57f5829e8bd89e8e0fa96b11d2"
 Cmm: Promote stack arguments to word size

 Smaller than word size integers must be promoted to word size
 when passed on the stack. While on little endian systems we can
 get away with writing a small integer to a word size stack slot
 and read it as a word ignoring the upper bits, on big endian
 systems a small integer write ends up in the most significant
 bits and a word size read that ignores the upper bits delivers
 a random value.

 On little endian systems a smaller than word size write to
 the stack might be more efficient but that decision is
 system specific and should be done as an optimization in the
 respective backends.

 Fixes #16258
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16258#comment:7>