On Mon, Nov 3, 2014 at 1:11 PM, Nicolas Cellier <
nicolas.cellier.aka.nice at gmail.com> wrote:

> I think Eliot already explained this in this vm-dev thread
> [Vm-dev] About primitive for cleaning compiled method cache
> http://lists.squeakfoundation.org/pipermail/vm-dev/2013-March/012333.html
>

Right.
http://lists.squeakfoundation.org/pipermail/vm-dev/2013-March/012359.html

>
>
> 2014-11-03 19:42 GMT+01:00 Eliot Miranda <eliot.miranda at gmail.com>:
>
>>
>>
>> On Mon, Nov 3, 2014 at 10:32 AM, Levente Uzonyi <leves at elte.hu> wrote:
>>
>>> Hi All,
>>>
>>> We have three primitives for three different versions of #flushCache:
>>> - primitive 89 used by Behavior >> #flushCache
>>> - primitive 116 used by CompiledMethod >> #flushCache
>>> - primitive 119 used by Symbol >> #flushCache
>>>
>>> Based on the comment in CompiledMethod >> #flushCache, and Symbol >>
>>> #flushCache, primitive 119 is not used since Squeak 2.3, and Symbol >>
>>> #flushCache can safely be removed.
>>>
>>
>> NO!!!  This is completely wrong.  Symbol>>#flushCache is the one that
>> *must* be there.  The use of 116 is IMO completely bogus.  For the VM to
>> use 116 effectively it must be able to find the selector in the method; in
>> general not possible because the selector is only optional in a method,
>> optionally in the penultimate literal, but perhaps inside the penultimate
>> literal, and perhaps the method is an anonymous accessor only copied into a
>> method dictionary.
>> Caches in the VM are based on *selectors* (arguably these may not even be
>> symbols; see below) and flushing entries that refer to a particular
>> compiled method may not correctly update caches on subclass or superclass
>> methods.  Whereas flushing based on selector, even if it does more work,
>> always reliably upates caches correctly.
>>
>> In general message selectors can be any object, so one could aggressively
>> shrink by e.g. replacing all selectors by SmallIntegers.  This was done
>> back in the day with the ActiveBook system, an early tablet implemented
>> largely in Smalltalk.  So primitive 119 should IMO be implemented in Object.
>>
>>
>>> But the method is still in the image, and it is being sent whenever a
>>> method is removed or added to a class.
>>> Is the comment wrong, or the method is really not needed?
>>>
>>
>>  The comment is wrong.
>>
>> Also the last comments in Behavior >> #basicAddSelector:withMethod: and
>>> Behavior >> #basicRemoveSelector: suggest that either the method's or the
>>> selector's cache should be flushed, but not both, which is actually the
>>> case in both methods.
>>> The comment in Symbol >> #flushCache suggests the same. So what's the
>>> truth? Do we still need primitive 119?
>>
>>
>> Yes, we do, and only it should be used in Behavior >>
>> #basicAddSelector:withMethod: and Behavior >> #basicRemoveSelector:.
>>
>>
>>>
>>> Levente
>>>
>>>
>>
>>
>> --
>> best,
>> Eliot
>>
>>
>>
>>
>
>
>
>


-- 
best,
Eliot
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