[GHC] #7684: cgrun071 segfaults

[GHC]

#7684: cgrun071 segfaults
----------------------------------+----------------------------------
        Reporter:  tibbe          |            Owner:
            Type:  bug            |           Status:  new
        Priority:  normal         |        Milestone:  7.8.1
       Component:  Compiler       |          Version:  7.7
      Resolution:                 |         Keywords:
Operating System:  MacOS X        |     Architecture:  x86_64 (amd64)
 Type of failure:  Runtime crash  |       Difficulty:  Unknown
       Test Case:  cgrun071       |       Blocked By:
        Blocking:                 |  Related Tickets:
----------------------------------+----------------------------------

Comment (by rwbarton):

 I don't understand how the first 8 or so lines of gdb output are
 consistent with the rest, so I'm going to assume that gdb was temporarily
 confused.  The `info registers` output looks much more plausible.

 Replying to [comment:15 simonmar]:
 > The native code generator is supposed to emit code to mask out the extra
 bits.  If it isn't doing that, that's a bug.  See commit
 085e8145f63c8f42d8bc19cd3cff52b8cd5b6455

 Going by leroux's `info registers` output, it sure looks like it isn't
 masking them out, since the argument register `rdi` is
 `0x98b7fa5e6c84f828`.

 From the assembly diff I see that gcc 4.8 outputs code to do the masking
 in the callee (`movzbl  %dil, %edi`) where gcc 4.2 does not.  Oddly the
 System V x86_64 ABI doesn't seem to specify whether arguments in registers
 that are smaller than the register size should be masked/sign-extended by
 the caller, but I gather that we are working under the assumption that
 they should be (which is consistent with the 386 ABI).

 leroux, could you attach the entire `cgrun071.S` disassembly output?  Or
 if it's very large, at least the disassembly of the function which calls
 `hs_popcnt8`?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7684#comment:29>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler