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

[GHC]

#14619: Output value of program changes upon compiling with -O optimizations
-------------------------------------+-------------------------------------
        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:                    |
-------------------------------------+-------------------------------------

Comment (by carter):

 1) phyx-  none of these register excerpts mention xmm0 .... whys that? the
 set of caller saved registers is xmm0  -xmm5 ... but here  the exceprts
 only work on xmm1-xmm6!  (is there some off by one error in the register
 abi encoding  stuff ?)

 2) i think we can probably assume / presume that the code at fault likely
 lies somewhere in
 https://github.com/ghc/ghc/blob/ghc-8.2/compiler/nativeGen/X86/CodeGen.hs#L2355-L2474
 (perma link
 https://github.com/ghc/ghc/blob/4d99a665986f66f403ad49f7d91a1fc069870274/compiler/nativeGen/X86/CodeGen.hs#L2355-L2474
 ) or something related in register/abi stuff

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14619#comment:28>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler