[GHC] #15482: the_gc_thread variable from GC.c is not aligned to 64

[GHC]

#15482: the_gc_thread variable from GC.c is not aligned to 64
-------------------------------------+-------------------------------------
           Reporter:  arrowd         |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.4.3
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:  x86_64         |   Type of failure:  None/Unknown
  (amd64)                            |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 When compiling GHC with clang and -march=native flag, the compiler emits
 vmovaps instruction with unaligned operand for this code:


 {{{
 * thread #1, name = 'ghc-pkg', stop reason = signal SIGBUS: hardware error
     frame #0: 0x0000000804e476c6 libHSrts-ghc8.0.2.so`initGcThreads
 [inlined] new_gc_thread(n=0) at GC.c:818
    815          ws->todo_q = newWSDeque(128);
    816          ws->todo_overflow = NULL;
    817          ws->n_todo_overflow = 0;
 -> 818          ws->todo_large_objects = NULL;
    819
    820          ws->part_list = NULL;
    821          ws->n_part_blocks = 0;
 }}}


 Research done by another FreeBSD developer suggested that this is due

 {{{

 StgWord8 the_gc_thread[sizeof(gc_thread) + 64 * sizeof(gen_workspace)];
 }}}


 not being aligned to 64 bytes, because struct gc_thread have no alignment
 specifier.

 Detailed information can be found in FreeBSD bugzilla:
 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=226059

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15482>
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