[GHC] #9346: AtomicPrimOps tests failing on 32-bit x86

[GHC]

#9346: AtomicPrimOps tests failing on 32-bit x86
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              Reporter:  niklasl     |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.9
            Resolution:              |          Keywords:
Differential Revisions:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |         Test Case:
            Difficulty:  Unknown     |          Blocking:
            Blocked By:              |
       Related Tickets:              |
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Comment (by tibbe):

 The `mov` instruction doesn't support a lock prefix. From: "Intel® 64 and
 IA-32 ArchitecturesSoftware Developer’s Manual":

 > The LOCK prefix can be prepended only to the following instructions and
 only to those forms of the instructions where the destination operand is a
 memory operand: ADD, ADC, AND, BTC, BTR, BTS, CMPXCHG, CMPXCH8B, DEC, INC,
 NEG, NOT, OR, SBB, SUB, XOR, XADD, and XCHG. If the LOCK prefix is used
 with one of these instructions and the source operand is a memory operand,
 an undefined opcode exception (#UD) may be generated. An undefined opcode
 exception will also be generated if the LOCK prefix is used with any
 instruction not in the above list. The XCHG instruction always asserts the
 LOCK# signal regardless of the presence or absence of the LOCK prefix

 However, I cannot see a place where we're adding one in the x86 codegen:
 https://github.com/ghc/ghc/blob/master/compiler/nativeGen/X86/CodeGen.hs

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9346#comment:3>
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