Re: Static sem_item_optimizer instance in ipa-icf pass

[Martin Liška <mliska at suse dot cz>]

On 08/01/2018 02:17 PM, Florian Rommel wrote:
> Hi,
> 
> I stumbled across this during my work on a gcc compiler plugin [1].
> 
> During the ipa-icf pass semantic items (`sem_function` and `sem_variable`) are generated to find potential candidates for function or variable merging.

Hello.

Sorry for late answer.

> 
> In `ipa-icf.c` there is a static variable `optimizer` (of type `sem_item_optimizer`) which is initialized before and destroyed after the ipa-icf pass.  This variable is used by the semantic items.  Therefore it is not possible to use `sem_function` or `sem_variable` outside of the icf pass (as the static optimizer is NULL).  E.g. create a `sem_function` variable with `sem_function::parse`.
> 
> Is this intended?  I would like to use `sem_function` objects (independently from the icf pass) to compare functions that were generated by our gcc plugin (or is this a bad idea).

That can definitely done better, if I see correctly only reference from sem_item, sem_function and sem_variable
is in sem_item::add_type. That can be removed.

> 
> It seems that (non-static) member functions like `sem_item_optimizer::parse_func_and_vars` use this static `optimizer` instance (through some indirections [2]) which looks kinda wrong to me.

Sure, that's strange. But I can't find the reference in current trunk.

Can you please update to trunk and check the remaining problematic references?

Thanks,
Martin

> 
> Regards,
> Flo
> 
> 
> [1] https://github.com/luhsra/multiverse
> 
> [2] Calls:
>    sem_item_optimizer::parse_funcs_and_vars  [ipa_icf.c:2666]
>    sem_function::parse                       [ipa_icf.c:1691]
>    sem_function::init                        [ipa_icf.c:1387]
>    sem_function::hash_stmt                   [ipa_icf.c:1617]
>    sem_function::add_type                    [ipa_icf.c:1547]
>      uses static sem_item_optimizer optimzer [ipa_icf.c:94]
> 
> 
>