REGRESSION in 3.2.1-pre on mips-irix6 (and elsewhere) compiling execute/20011219-1.c

[Graham Stott]

Jan,

Jan Hubicka wrote:
>>
>>--On Wednesday, November 13, 2002 02:11:26 AM -0500 "Kaveh R. Ghazi" 
>><ghazi@caip.rutgers.edu> wrote:
>>
>>
>>>Sometime in the last day or so, I'm getting a new regression from the
>>>gcc-3.2.1-pre testsuite on mips-irix6 when compiling
>>>execute/20011219-1.c.
>>
>>Jan, Graham -- I'd bet that this is fallout from your PR8502 patch.
>>
>>Would you please take a look?
> 
> I will do.  I tought it is failing in ppc, so tried it to reproduce on
> ppc croos that of course failed.  Another try.
> However the patch just prevents optimization to happen, so it is
> probably latent bug somewhere else :)
> 
> Honza
> 
>>-- 
>>Mark Mitchell                mark@codesourcery.com
>>CodeSourcery, LLC            http://www.codesourcery.com
> 
> 

Oh what a twisty maze our cfg jumptable tidying up cost is.

I'm wandering if it's caused by a deadjump table not getting deleted
perhaps we can refine the new test to be

   rtx label;

   ....

   if (reload_completed
       && (label = JUMP_LABEL (insn))
       && LABEL_NUSES (label) > LABEL_PRESERVE_P (label)
       && (table = NEXT_INSN (label)) != NULL_RTX
       && GET_CODE (table) == JUMP_INSN
       && (GET_CODE (PATTERN (table)) == ADDR_VEC
           || GET_CODE (PATTERN (table)) == ADDR_DIFF_VEC))
     return false;

This should allow a dead jump table to get deleted post reload
and also prevent a jump table that's referenced from being deleted.


I'll try and reproduce the problem on an mips cross compiler and
see my idea fixes the problem.


Graham