Re: Fix one of problems in profile updating code

["Giovanni Bajo" <rasky at develer dot com>]

Jan Hubicka <jh@suse.cz> wrote:

>>>> with one of updates you killed code computing counts of duplicated
block
>>>> in thread updating code.  Please try to mind profile when modifying the
>>>> code further as it is getting bit dificult to figure out what jump
>>>> threading does and how to fix it and the code broke several times in
the
>>>> past.  This bug was responsible for quite large regression of art
>>>> benchmark and there still seems to be other problem described in
>>>> PR22401.
>>>
>>> Jeff, Honza --
>>>
>>> Is there something that can be done here to make it harder for people to
>>> make mistakes with profiling?  This is an important feature, but one
>>> that not everyone uses.  Like, is it possible to create a test case for
>
> Well, almost everyone uses the guessed profile at -O2.  Missupdating it
> can cause similar problems as missupdating the real profile...


I think these problems are going to exist forever until you either add a
verify pass which makes the compiler ICE (in a default bootstrap & regtest)
when the profile information is screwed, or you add a specific testsuite
(executed by default in make check) which can check for problems by
inspecting the compiler logs.

Otherwise, people are simply not going to notice the problem.
-- 
Giovanni Bajo