Re: [PATCH] ipa-icf: skip variables with body_removed

["Martin Liška" <mliska@suse.cz>]

@Honza: PING

On 5/20/22 09:46, Martin Liška wrote:
> On 5/19/22 17:02, Jan Hubicka wrote:
>>> Similarly to cgraph_nodes, it may happen that body_removed is set
>>> during merging of symbols.
>>>
>>> 	PR ipa/105600
>>>
>>> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
>>>
>>> Ready to be installed?
>>> Thanks,
>>> Martin
>>>
>>> gcc/ChangeLog:
>>>
>>> 	* ipa-icf.cc (sem_item_optimizer::filter_removed_items):
>>> 	Skip variables with body_removed.
>>> ---
>>>  gcc/ipa-icf.cc | 7 ++++---
>>>  1 file changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/gcc/ipa-icf.cc b/gcc/ipa-icf.cc
>>> index 765ae746745..6528a7a10b2 100644
>>> --- a/gcc/ipa-icf.cc
>>> +++ b/gcc/ipa-icf.cc
>>> @@ -2411,10 +2411,11 @@ sem_item_optimizer::filter_removed_items (void)
>>>  	    {
>>>  	      /* Filter out non-readonly variables.  */
>>>  	      tree decl = item->decl;
>>> -	      if (TREE_READONLY (decl))
>>> -		filtered.safe_push (item);
>>> -	      else
>>> +	      varpool_node *vnode = static_cast <sem_variable *>(item)->get_node ();
>>> +	      if (!TREE_READONLY (decl) || vnode->body_removed)
>>>  		remove_item (item);
>>> +	      else
>>> +		filtered.safe_push (item);
>>
>> So the situation here is that we merge symbols but keep syntactic alias
>> because the declarations are not compatible (have different attributes
>> perhaps because of fortify source)?
> 
> The test-case is more about a constexpr symbol or so, I'm not familiar enough
> with these modern C++.
> 
> cgraph_node looks like:
> 
> (gdb) p item->node->debug()
> _ZN8nlohmann6detail12static_constINS0_10to_json_fnEE5valueE/10 (value) @0x7ffff7fb3200
>   Type: variable
>   Body removed by symtab_remove_unreachable_nodes
>   Visibility: externally_visible semantic_interposition preempted_reg external public weak comdat comdat_group:_ZN8nlohmann6detail12static_constINS0_10to_json_fnEE5valueE one_only
>   References: 
>   Referring: _Z7to_jsonRN8nlohmann10basic_jsonISt3mapSt6vectorNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEblmiSaNS_14adl_serializerES2_IhSaIhEEEERK8Settings/1 (addr) _Z7to_jsonRN8nlohmann10basic_jsonISt3mapSt6vectorNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEblmiSaNS_14adl_serializerES2_IhSaIhEEEERK8Settings/1 (addr) 
>   Read from file: a.o
>   Availability: not_available
>   Varpool flags: initialized read-only
> 
> 
>>
>> Will ICF still see through the aliases and do merging?
> 
> No.
> 
>> I think you can
>> craft a testcase by triggering the attribute mismatch and see what
>> happens.  At the time we implemented ICF these aliases did not exists,
>> so maybe some TLC is needed here.
> 
> Please come up with such test case :)
> 
> Thanks,
> Martin
> 
>>
>> Honza
>