[GHC] #10647: Notice about lack of SIMD support.

[GHC]

#10647: Notice about lack of SIMD support.
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              Reporter:  mniip       |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.8.4
              Keywords:              |  Operating System:  Linux
          Architecture:  x86_64      |   Type of failure:  Compile-time
  (amd64)                            |  crash
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 In some cases, when SIMD primitives are used without the `-fllvm` flag,
 instead of giving the friendly `SIMD vector instructions require the LLVM
 back-end.`, GHC crashes with varying messages.

 The simplest example is

 {{{#!hs
 {-# LANGUAGE MagicHash #-}
 module Foo where
 import GHC.Prim
 data V = V Int8X16#
 }}}

 In 7.8.4 this crashes with
 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.8.4 for x86_64-unknown-linux):
         Size.intSize W128
 }}}

 According to osa1, in HEAD this still crashes, but with
 {{{
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 7.11.20150717 for x86_64-unknown-linux):
         Format.intFormat W128
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10647>
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