Tracing special messages [WAS] Re: [Vm-dev] Re: normalSend, specialObjectsArray and VM

[Eliot Miranda]

On Tue, Oct 5, 2010 at 12:00 PM, Mariano Martinez Peck <
marianopeck at gmail.com> wrote:

>
>
>
> On Tue, Oct 5, 2010 at 8:48 PM, Eliot Miranda <eliot.miranda at gmail.com>wrote:
>
>>
>>
>>
>> On Tue, Oct 5, 2010 at 11:20 AM, Mariano Martinez Peck <
>> marianopeck at gmail.com> wrote:
>>
>>>
>>>
>>>
>>> On Tue, Oct 5, 2010 at 7:50 PM, Eliot Miranda <eliot.miranda at gmail.com>wrote:
>>>
>>>>
>>>>
>>>>
>>>> On Tue, Oct 5, 2010 at 9:23 AM, Mariano Martinez Peck <
>>>> marianopeck at gmail.com> wrote:
>>>>
>>>>>
>>>>> Hi. So....if I want to intercept ALL message sends....going to
>>>>> #normalSend is not enough since I have #class, #==, Float>>#+   etc that are
>>>>> executed directly like bytecodes. So...my questions are now:
>>>>>
>>>>> 1) Those special selectors are those that are in "Smalltalk
>>>>> specialSelectors" ?  are there more?  all from there are special?
>>>>>
>>>>> 2) All those "Smalltalk specialSelectors"  have their associated
>>>>> bytecode primitive in Interpreter??  If true, then I should modify all
>>>>> bytecodePrim*  in Interpreter. I am right?   If I do that, that's all ? I am
>>>>> intercepting everything?
>>>>>
>>>>
>>>> Right.  Just modify all of them to eliminate the optimized code and to
>>>> revert to normalSend.
>>>>
>>>
>>> Thanks Eliot. I didn't understand. What is the optimized code?   I
>>> checked all bytecodePrim* and the ones that DO NOT send "self normalSend" at
>>> the end, are very few. The problem is that some return before returning
>>> "self normalSend". So...I should modify all those who DO NOT call "self
>>> normalSend" at the end and those which return before.
>>>
>>
>> Change them all so they do a normalSend and nothing else, e.g.
>>
>> bytecodePrimAdd
>> messageSelector := self specialSelector: 0.
>>  argumentCount := 1.
>> self normalSend
>>
>>
> Ok, but suppose I DON'T want to slow down the system.... what if I change
> to this for example
>
> bytecodePrimAdd
>     | rcvr arg result |
>     rcvr := self internalStackValue: 1.
>     arg := self internalStackValue: 0.
>     (self areIntegers: rcvr and: arg)
>         ifTrue: [result := (self integerValueOf: rcvr) + (self
> integerValueOf: arg).
>                 (self isIntegerValue: result) ifTrue:
>                     [self internalPop: 2 thenPush: (self integerObjectOf:
> result).
>                     self markObjectUsage: rcvr.
>                     ^ self fetchNextBytecode "success"]]
>         ifFalse: [successFlag := true.
>                 self externalizeIPandSP.
>                 self primitiveFloatAdd: rcvr toArg: arg.
>                 self internalizeIPandSP.
>                 successFlag ifTrue: [self markObjectUsage: rcvr. ^ self
> fetchNextBytecode "success"]].
>
>     messageSelector := self specialSelector: 0.
>     argumentCount := 1.
>     self normalSend
>
> Ok...I have to manually check each method, but I don't have problem.
>
> Should that work and be almost as fast as normally?
>

But it doesn't mark the method right?  It only marks the objects.  However
if you analyse the bytecodePrimFoo implementations you should be able to
work out which methods are used, SmallInteger>>#+, Float>>#+ et al.



> Or change the part of the bytecode table that specifies the special
>> selector primitives to read
>>  (176 207 sendSpecialSelectorBytecode)
>>
>> sendSpecialSelectorBytecode
>> | selectorIndex specialSelectors |
>>  selectorIndex := (currentBytecode - 176) * 2.
>> specialSelectors := self splObj: SpecialSelectors.
>>  messageSelector := self fetchPointer: selectorIndex
>> ofObject: specialSelectors.
>>  argumentCount := self fetchInteger: selectorIndex + 1
>> ofObject: specialSelectors.
>>  self normalSend
>>
>> But most of all try and slow down and understand what is going on; then
>> you will be able to answer your own questions.  Reading the blue book<http://www.mirandabanda.org/bluebook/bluebook_imp_toc.html>will help.
>>
>>
>
> hehehehehe what an idea :) I didn't know I could do that. Thanks for the
> blue book. I read the vm chapters but several months ago. I should read it
> again since the first time I didn't understand very much hehehehe.
>
>
>>
>>>
>>>
>>>> Providing you also look at the perform and method evaluation primitives
>>>> I think you'll get all sends.
>>>>
>>>>
>>> #primitivePerform*   and #primitiveExecuteMethod*    ???
>>>
>>>
>>>> There is another way.  Modify the Smalltalk compiler to to use the
>>>> special selector sends.
>>>>
>>>>
>>> Thanks Eliot for the idea. Can you explain me a little more (sorry,
>>> newbie here!). You mean that with the Compiler I can do that all method
>>> sends use the normal send instead of special bytecodes or primitives?
>>>
>>
>> Yes.  If you modify the compiler not to use the StdSelectors then the
>> compiler will emit normal sends for all the special selectors.   Again I
>> think if you slowed down and started playing ore you would discover this for
>> yourself and in the end be more productive.  I know its hard and frustrating
>> initially.  But my own competence comes directly from having played around
>> in this way.
>>
>>
> Thanks Eliot. I will consider this alternative also.
>
> Best regards.
>
> Mariano
>
>
>> best,
>> Eliot
>>
>>
>>> Thank you very much.
>>>
>>> Mariano
>>>
>>>
>>>>
>>>>> Thanks a lot in advance,
>>>>>
>>>>> Mariano
>>>>>
>>>>>
>>>>>
>>>>> On Sun, Oct 3, 2010 at 11:09 PM, Craig Latta <craig at netjam.org> wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> > Craig Latta has done all this work, talk to him.
>>>>>>
>>>>>>     Sure, I'd be happy to discuss it.
>>>>>>
>>>>>>
>>>>>> -C
>>>>>>
>>>>>> --
>>>>>> Craig Latta
>>>>>> www.netjam.org
>>>>>> + 31 020 894 6247
>>>>>> +  1 415 287 3547
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>
>
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