[GHC] #15864: Fix Int8#, Int16#, Word8#, Word16# tests under LLVM code generator

[GHC]

#15864: Fix Int8#, Int16#, Word8#, Word16# tests under LLVM code generator
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler (LLVM)   |              Version:  8.6.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"f424515fd8cbc2b7380cdf8427f972d062940bd5/ghc"
 f424515f/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="f424515fd8cbc2b7380cdf8427f972d062940bd5"
 [LlvmCodeGen] Fixes for Int8#/Word8#

 This fixes two isssues:

 - Using bitcast for MO_XX_Conv
   Arguments to a bitcast must be of the same size. We should be using
   `trunc` and `zext` instead.

 - Using unsupported MO_*_QuotRem for LLVM
   The two primops `MO_*_QuotRem` are not supported by the LLVM backend,
 so
   we shouldn't use them for `Int8#`/`Word8#` (just as we do not use
 them for
   `Int#`/`Word#`).

 Signed-off-by: Michal Terepeta <michal.terepeta at gmail.com>

 Test Plan: manually run tests with WAY=llvm

 Reviewers: bgamari, simonmar

 Reviewed By: bgamari

 Subscribers: rwbarton, carter

 GHC Trac Issues: #15864

 Differential Revision: https://phabricator.haskell.org/D5304
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15864#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler