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Re: REGRESSION in 3.2.1-pre on mips-irix6 (and elsewhere) compiling execute/20011219-1.c
- From: Jan Hubicka <jh at suse dot cz>
- To: Graham Stott <graham dot stott at btinternet dot com>
- Cc: Jan Hubicka <jh at suse dot cz>, Mark Mitchell <mark at codesourcery dot com>,"Kaveh R. Ghazi" <ghazi at caip dot rutgers dot edu>,"David dot Billinghurst at riotinto dot com" <David dot Billinghurst at riotinto dot com>,"Franz dot Sirl-kernel at lauterbach dot com" <Franz dot Sirl-kernel at lauterbach dot com>,"gcc-bugs at gcc dot gnu dot org" <gcc-bugs at gcc dot gnu dot org>,"gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Wed, 13 Nov 2002 20:33:08 +0100
- Subject: Re: REGRESSION in 3.2.1-pre on mips-irix6 (and elsewhere) compiling execute/20011219-1.c
- References: <200211130711.CAA03837@caip.rutgers.edu> <18800000.1037205214@warlock.codesourcery.com> <20021113180837.GH6534@kam.mff.cuni.cz> <3DD2A75D.2000705@btinternet.com>
> 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.
The jumptable issue ineed is very sick.
Perhaps we can add just code to add necesary hardjump around when this
happends.
>
> 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.
Most jumptables are referenced by the code preparing tablejump actually
and since no other code can refer to it, unfortunately. I don't see how
this can work without disabling the optimization entirely...
>
>
> I'll try and reproduce the problem on an mips cross compiler and
> see my idea fixes the problem.
THanks.
I will look into the other bugreport assigned to me tonight, so please
let me know what you got.
Honza
>
>
> Graham
>