Re: Another switch testcase failure with enable-checking

[Jan Hubicka <jh at suse dot cz>]

> 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.

I see.   We need simple check for overflow here as we do on the other
places.  I will bootstrap the patch and check in as default once
checkout of GCC tree finishes.
We can not avoid such thing to happen and I am keeping the check for
probability to be in the range in verify_flow_info to most importantly
catch cases where we compute absolute nonsenses (so the result is way
off the allowed range)

Thanks!
Honza
> 
> >Honza
> >
> 
> Graham
> 
>