PR bootstrap/50709 (bootstrap miscompare)

H.J. Lu hjl.tools@gmail.com
Tue Oct 25 16:47:00 GMT 2011


On Thu, Oct 20, 2011 at 5:23 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
>> @@ -1392,16 +1393,20 @@ inline_small_functions (void)
>>        if (!edge->inline_failed)
>>       continue;
>>
>> -      /* Be sure that caches are maintained consistent.  */
>>  #ifdef ENABLE_CHECKING
>> +      /* Be sure that caches are maintained conservatively consistent.
>> +      This means that cached badness is allways smaller or equal
>> +      to the real badness.  */
>> +      cached_badness = edge_badness (edge, false);
>> +#endif
>>        reset_edge_growth_cache (edge);
>>        reset_node_growth_cache (edge->callee);
>> -#endif
>>
>>        /* When updating the edge costs, we only decrease badness in the keys.
>>        Increases of badness are handled lazilly; when we see key with out
>>        of date value on it, we re-insert it now.  */
>>        current_badness = edge_badness (edge, false);
>> +      gcc_assert (cached_badness == -1 || cached_badness <= current_badness);
>
> This new check actually cathes a bug that is in tree since introduction of new
> ipa-inline-analysis code.  The inliner assume that when it produce a new inline
> copy, the overall growth estimates for all callees can only degrade.  This is
> not quite true: when a new knowledge is propagated, the callees might actually
> become cheaper and reduce the growth.
>
> This patch takes the easy but expensive way to plug the problem by forcing
> updating of all keys in the queue.  It increases LTO compile time of Mozilla to
> 10 minutes, so I will need to develop better sollution. (the trick saving
> recomputation was originally introduced to reduce copmile time particularly on
> this testcase) Just I should not keep tree ICEing on many C++ sources until I
> am done.
>
> Bootstrapped/regtested x86_64-linux, comitted.
>
> Honza
>
> Index: ChangeLog
> ===================================================================
> --- ChangeLog   (revision 180247)
> +++ ChangeLog   (working copy)
> @@ -1,5 +1,10 @@
>  2011-10-19  Jan Hubicka  <jh@suse.cz>
>
> +       * ipa-inline.c (inline_small_functions): Always update all calles after
> +       inlining.
> +
> +2011-10-19  Jan Hubicka  <jh@suse.cz>
> +
>        PR bootstrap/50709
>        * ipa-inline.c (inline_small_functions): Fix checking code to not make
>        effect on fibheap stability.

Those changes may have caused:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50868

-- 
H.J.



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