2009/12/11 Eliot Miranda <eliot.miranda at gmail.com>:
> Hi Igor,
>
> On Thu, Dec 10, 2009 at 3:40 PM, Igor Stasenko <siguctua at gmail.com> wrote:
>>
>> This question is mostly to Eliot,
>> since he the last who dare to touch the Compiler deeply..
>> My concern is use pattern:
>>
>>        method := methodNode generate: #(0 0 0 0).
>>        ^method copyWithTempsFromMethodNode: methodNode
>>
>> the point of nitpicking is the need of generating a dummy
>> CompiledMethod instance,
>> which used for nothing else than making a copy and attachment of temp
>> names.
>>
>> And, the question, is there a way to skip generating the dummy
>> compiled method and just do:
>>
>>  method := methodNode generateWithTempNames.
>>
>> or:
>>
>>  method := methodNode generate: (methodNode tempsTrailer).
>>
>> ?
>>
>
> I think so, but is it worth-while?  The temp names can only be generated
> correctly once the closure analysis is done, see ensureClosureAnalysisDone
> in generate:.  So you'd have to pass in a flag to generate: saying you
> wanted to append temps, compute the temps after ensureClosureAnalysisDone,
> derive how many bytes they would compress to, and add that to the size of
> the method being computed.  But that would open up details of the
> compression scheme to the generate: method.  But saving one instantiation
> amongst hundreds, perhaps thousands, in an average compile is probably not
> worth it.
> I expect that more worth-while would be to rip out my hack of Dan's hack
> compression algorithm for temp names and replace it with the use of gzip,
> which is built into the system and does a far better job than my
> modification of Dan's scheme.

I doubt that gzip will be able to compress well anything which is less
than 100 bytes long.Most of smalltalk methods contain very few temps,
and gzip compression is not working well with very small portions of
data

|str|
str := 'a b c d e f g h '.
{ str size.  str zipped size } "print it"

okay, as you said its not possible to determine the right number of
temps without generating the method (a more correct would be - hard ,
not impossible ;) ) however , i think that hiding this behavior inside
method node is worthwhile, because usage pattern, like:

result := something foo.
result := result bar: something.

crying for being replaced with just:
result := something zork.

because otherwise it brings unnecessary detail out of scope of method
generation, which forcing users to repeat same elaborate pattern in
different places.

The trailing bytes generation is a cryptic stuff.. for instance, why i
see (#0 0 0 0) sent to #generate: everywhere?
Any person who sees it, start asking questions, what if i send #(1 2 3
4) instead , or send #(1).. and generally,
is it safe to pass something else than #(0 0 0 0)?
So, in order to reduce confusion, it is worthwhile to hide
implementation detail from eyes of user.

If one wants to put a method source pointer, then he should tell
method node to generate method with it:

methodNode generateWithSourcePointer: anInteger
and if user wants to generate method with temp names, then he can do
it by telling:
methodNode generateWithTempNames

and if user wants to generate method with arbitrary trailing bytes,
then user should be exterminated and replaced by advanced version
(iUser) :)


>>
>> --
>> Best regards,
>> Igor Stasenko AKA sig.
>>
>


-- 
Best regards,
Igor Stasenko AKA sig.