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Re: Another switch testcase failure with enable-checking


Jan Hubicka <jh@suse.cz> writes:

>> Jan Hubicka wrote:
>> >>All,
>> >>
>> >>I've stumbled on another interesting switch testcase which triggers an 
>> >>enable-checking abort
>> >>on all the ports I've tried so far x86, mips, sh, s390.
>> >>
>> >>For this testcase I get at -O2 with enable-checking enabled
>> >>
>> >>bug2.c: In function `foo':
>> >>bug2.c:28: warning: verify_flow_info: Wrong probability of edge 1->19 
>> >>10008
>> >>bug2.c:28: internal compiler error: verify_flow_info failed
>> >>
>> >>Jan any ideas what's wrong with the edge probability calcs
>> >
>> >
>> >This is commonly just some roundoff error around.  I will track it down
>> >tomorrow.
>> >
>> Yes it's an around-off error somewhere I tracked down where rhe bad 
>> probability is
>> being set. It's in cfg.c:redirect_edge_succ_nodup the stmt
>> 
>> 	"s->probability += e->probability;"
>> 
>> results in a probability > 10000 because s->probability is 9942 and 
>> e->probaility
>> is 566 which add up to 10008.
>> 
>> This happens on any target where the switch gets collapsed to an 
>> if-then-else.
> Hi,
> I am attaching patch I will install shortly.
> Regstested/bootstrapped i386
>
> Honza
>
> Sat Aug 10 19:43:09 CEST 2002  Jan Hubicka  <jh@suse.cz>
> 			       Graham Scott
> 	* cfg.c (redirect_edge_succ_nodup): Avoid overflows due to roundoff
> 	errors.
>
> *** cfg.c.old	Sat Aug 10 20:55:22 2002
> --- cfg.c	Sat Aug 10 20:55:46 2002
> *************** redirect_edge_succ_nodup (e, new_succ)
> *** 455,460 ****
> --- 455,462 ----
>       {
>         s->flags |= e->flags;
>         s->probability += e->probability;
> +       if (s->probability > REG_BR_PROB_BASE)
> + 	s->probability = REG_BR_PROB_BASE;
>         s->count += e->count;
>         remove_edge (e);
>         e = s;
>

Isn't this also needed for 3.2?  I propose to queue this for GCC
3.2.1,

Andreas
-- 
 Andreas Jaeger
  SuSE Labs aj@suse.de
   private aj@arthur.inka.de
    http://www.suse.de/~aj


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