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Re: PR bootstrap/50709 (bootstrap miscompare)


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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