[GHC] #7588: GHC HEAD built with LLVM on Mac OS X miscompiles RTS: SIGSEGV in stg_PAP_apply

[GHC]

#7588: GHC HEAD built with LLVM on Mac OS X miscompiles RTS: SIGSEGV in
stg_PAP_apply
--------------------------+-------------------------------------------------
Reporter:  thoughtpolice  |          Owner:                  
    Type:  bug            |         Status:  new             
Priority:  normal         |      Component:  Compiler (LLVM) 
 Version:  7.7            |       Keywords:  sigsegv         
      Os:  MacOS X        |   Architecture:  Unknown/Multiple
 Failure:  Runtime crash  |      Blockedby:  7571, 7580      
Blocking:                 |        Related:                  
--------------------------+-------------------------------------------------
 After fixing #7571 and #7580, with those two patches, I now get a working
 stage1 compiler that can produce binaries using the LLVM backend. But all
 of them segfault:

 {{{
 $ cat no-op.hs
 main = return ()
 $ ~/code/haskell/ghc/inplace/bin/ghc-stage1 -fforce-recomp -fllvm no-op.hs
 [1 of 1] Compiling Main             ( no-op.hs, no-op.o )
 Linking no-op ...
 $ ./no-op
 [1]    12434 segmentation fault  ./no-op
 $
 }}}

 This looks like an error in stg_PAP_apply:

 {{{
 gdb -q ./no-op
 ⏎
 Reading symbols for shared libraries .... done
 (gdb) r
 Starting program: /Users/a/t/no-op
 Reading symbols for shared libraries +++............................. done

 Program received signal EXC_BAD_ACCESS, Could not access memory.
 Reason: 13 at address: 0x0000000000000000
 0x00000001002917d4 in stg_PAP_apply ()
 (gdb)
 }}}

 I imagine this is due to some miscompilation of ```rts/Apply.cmm``` using
 LLVM.

 I'll rebuild the stage1 compiler with debugging support for sanity, and
 also enable the debug RTS in the test, and report back soon.

 (I imagine this failure is certainly possible *because* of my patches in
 the other tickets, although my intuition tells me those are strictly
 correctness fixes and something else is afoot here.)

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7588>
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