[GHC] #8131: T7571 with WAY=llvm fails, but not WAY=optllvm

[GHC]

#8131: T7571 with WAY=llvm fails, but not WAY=optllvm
-------------------------------------+-------------------------------------
        Reporter:  thoughtpolice     |                   Owner:  rwbarton
            Type:  bug               |                  Status:  patch
        Priority:  high              |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.7
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |  llvm/should_compile/T8131
                                     |                Blocking:
                                     |  Differential Revisions:  Phab:D624
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"681973c31c614185229bdae4f6b7ab4f6e64753d/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="681973c31c614185229bdae4f6b7ab4f6e64753d"
 Encode alignment in MO_Memcpy and friends

 Summary:
 Alignment needs to be a compile-time constant. Previously the code
 generators had to jump through hoops to ensure this was the case as the
 alignment was passed as a CmmExpr in the arguments list. Now we take
 care of this up front.

 This fixes #8131.

 Authored-by: Reid Barton <rwbarton at gmail.com>
 Dusted-off-by: Ben Gamari <ben at smart-cactus.org>

 Tests for T8131

 Test Plan: Validate

 Reviewers: rwbarton, austin

 Reviewed By: rwbarton, austin

 Subscribers: bgamari, carter, thomie

 Differential Revision: https://phabricator.haskell.org/D624

 GHC Trac Issues: #8131
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8131#comment:14>
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