[Newcompiler] Re: NewCompiler-ms.273.mcz

[Mathieu Suen]

Hi Klaus

On Sep 8, 2007, at 9:12 AM, Klaus D. Witzel wrote:

>> - Add a more powerfull way for comparing compiled method
> ...
>>
>> Article:
>> * http://www.squeaksource.com/NewCompiler.html
>>
>> Download:
>> * http://www.squeaksource.com/NewCompiler/NewCompiler-ms.273.mcz
>
> Hi Math,
>
> the same primitive can be used by many methods but with different  
> fallback code (in case the primitive fails). This so can make two  
> methods unequal. I'd suggest to eliminate the check for
>
> (self primitive > 0 and: [self primitive = method primitive])
> 		ifTrue:[^true].

I know but the decompiler seems to produce different method for quick  
return.
It must be fix but it will not really change so I change it to:

"Dont bother checking quick return"
	(self isReturnSpecial and: [self primitive = method primitive])
		ifTrue:[^true].


>
> Now since comparision of primitive numbers was formerly subsummed by
>
> self header = method header ifFalse: [^false].

Yes but the decompiler, some time added a temporary variable but the  
method is the same.

>
> , I'd suggest to put primitive number comparision back as
>
>  self primitive = method primitive
> 		ifFalse: [^false].

added.

>
> Also,
>
>  self initialPC to: self endPC do:
>
> was formerly guarded by
>
>  self size = method size ifFalse: [^false].
>
> Without such a guard, it's not impossible that you compare elements  
> which are not bytecode.

Yes some bytecode is the same but depending on the offset of the  
temporary the bycode use the extend bytecode and size is different  
but method are the same.

The decompiler change the order of the temporary that is why it can  
happen.

So I have added:

self size = method size ifFalse: [^(InstructionCompaire compaire:  
self with: method)].

>
> Last but not least: comparing the literals must parallel the way  
> the compiler compares the literals, see call sites of #addLiteral:,  
> i.e. #pushLiteral: in BytecodeGenerator. With other words, not  
> using #= for literal comparision but instead use #literalEqual:.

I remove the literal comparison since my InstructionCompaire dose it  
implicitly.
but #literalEqual: dose the same than #=:

Object>>literalEqual: other

	^ self class == other class and: [self = other]



>
> For the case of float literal comparision (which should be done by  
> Float itself in its override of #literalEqual:) I'd suggest to ask  
> the Squeak community about their opinion, their use cases and their  
> numerical tolerance.
>
> As always, I'm open to critique :)

Thanks :) It is a pleasure to read your remarks.
Tell me if you are not agree with my changes.

>
> /Klaus


	

	
		
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