[GHC] #12184: unsafeCoerce# causing invalid assembly generation

[GHC]

#12184: unsafeCoerce# causing invalid assembly generation
-------------------------------------+-------------------------------------
           Reporter:  osa1           |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Discovered by MichaelBurge on IRC:

 {{{#!haskell
 {-# LANGUAGE MagicHash #-}

 import GHC.Prim
 import GHC.Types

 x = D# ((unsafeCoerce# (5# :: Int#) :: Double#) +## 5.0##)

 main = putStrLn $ show x
 }}}

 Compile with GHC 7.8, 8.0.1 or HEAD:

 {{{
 [1 of 1] Compiling Main             ( weird.hs, weird.o )
 /tmp/ghc23262_0/ghc_2.s: Assembler messages:

 /tmp/ghc23262_0/ghc_2.s:43:0: error:
      Error: junk `naughty x86_64 register' after expression
 `gcc' failed in phase `Assembler'. (Exit code: 1)
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12184>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler