[squeak-dev] Re: [Pharo-project] Issue 4538 and CompiledMethod equality

Mariano Martinez Peck marianopeck at gmail.com
Thu Sep 15 21:27:51 UTC 2011


>
>>
>> BUT, it doesn't mean that Association is always used for globals.
>> CompiledMethod equality is failing because of the last literal, the one that
>> maps class name (symbol) and point to the real class. So...when I
>> materialize, both CMs have non-identical associations for the last literal,
>> but equal.
>>
>
> As Henrik says the last literals are ideally #== to each other.  However,
> no Squeak dialect makes any attempt to keep the class0side associations
> equal. Look at a class-side method and you'll see it's last literal is
> nil->SomeClass class.  Now since this association doesn't exist in Smalltalk
> (unlike last literals on the instance side) the compiler merely creates
> distinct ones for each class-side method.
>


Thanks Eliot for that point. In fact, I have just checked and you are right.
The tests that are failing for me is those where class side methods are
involded. In this case, the last literal of the original CM and the
materialized, gives false in #literalEqual:   hence,  originalCM =
materializedCM is false :(



>
> Personally I don't think one can defend the position where method equality
> is different for instance-side or class-side methods so there must be some
> solutions:
>
> 1. special case comparison of the last literal (the methodClass literal),
> comparing keys and insisting that the keys be #== and the values be #==
> (can't just define it as keys #== since all similar class-side methods will
> be equal irrespective of their actual class).
>
>
This one seems the easier and fixes my problem :)

sameLiteralsAs: method
    "Compare my literals to those of method. This is needed to compare
compiled methods."

    | numLits literal1 literal2 |
    (numLits := self numLiterals) ~= method numLiterals
        ifTrue: [ ^ false ].
    "The last literal requires special checking instead of using
#literalEqual:"
    1 to: numLits - 1 do: [ :index |
        literal1 := self literalAt: index.
        literal2 := method literalAt: index.
        (literal1 == literal2 or: [ literal1 literalEqual: literal2 ])
            ifFalse: [
                (index = 1 and: [ #(117 120) includes: self primitive ])
                    ifTrue: [
                        literal1 isArray
                            ifTrue: [
                                (literal2 isArray and: [ literal1 allButLast
= literal2 allButLast ])
                                    ifFalse: [ self halt. ^ false ] ]
                            ifFalse: [
                                "ExternalLibraryFunction"
                                (literal1 analogousCodeTo: literal2)
                                    ifFalse: [ self halt. ^ false ] ] ]
                    ifFalse: [
                        index = (numLits - 1)
                            ifTrue: [
                                "properties"
                                (self properties analogousCodeTo: method
properties)
                                    ifFalse: [ self halt. ^ false ] ]
                            ifFalse: [ self halt. ^ false ] ] ] ].
    literal1 := self literalAt: numLits.
    literal2 := method literalAt: numLits.
    ^ ((literal1 key == literal2 key) and: [literal1 value == literal2
value]).




> 2. special case comparison of the last literal (the methodClass literal),
> insisting only that the class of the literal be the same if it
> isVariableBinding.
>
> 3. make the compile unique class-side methodClass literals.  i.e. if a
> class already has a class-side method then the compiler or method dictionary
> insertion code must find that existing association and reuse it
>
> Other ideas?
>
>
>> >From my point of view, that literal, the last one does not need to be
>> identical to assume 2 CMs are equal. They just need to be equal.
>>
>>
>> --
>> Mariano
>> http://marianopeck.wordpress.com
>>
>>
>
>
> --
> best,
> Eliot
>
>
>
>
>


-- 
Mariano
http://marianopeck.wordpress.com
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