[Vm-dev] Request for review of VMMaker-dtl.262.mcz

[Stefan Marr]

Hi David,
Hi Eliot (this might related to my problem from yesterday):

Do you remember the discussion of primitivePerform and primitivePerformInSuperclass we had 8th to 12th December?

One implicit assumption, based on the implementation, I made was that I do not have to give an array of arguments to the primitives. It would just take the arguments from the stack and at least to my understanding, would do the right thing.

Your new implementation does not seem to do that anymore.

I am not sure whether that is the problem I am seeing with Cog right now (reported yesterday).
But your implementation looks like it breaks my code :(

What is the correct semantics for primitivePerform and primitivePerformInSuperclass with regard to arguments?
Is it really not supported to provide them on the stack?

Thanks
Stefan

On 05 Jan 2012, at 14:51, David T. Lewis wrote:


>> 
>> 
>> Reference Mantis 7429: Add Mirror Primitives to the VM
>> 
>> Update primitivePerformInSuperclass to support ContextPart>>object:perform:withArguments:inClass:
>> 
>> Implementation differs from that of oscog in that the original primitivePerformAt: is retained unmodified, and the necessary stack adjustments are done in primitivePerformInSuperclass for the special case of argumentCount 4 (mirror primitive call) rather than 3. The oscog approach may be prefered (not least for its clearer method naming), but making the change in primitivePerformInSuperclass is low risk and more easily implemented by a Sunday Squeaker.
>> 
>> All MirrorPrimitiveTests pass.
>> 
>> =============== Diff against VMMaker-dtl.261 ===============
>> 
>> Item was changed:
>>  ----- Method: Interpreter>>primitivePerformInSuperclass (in category 'control primitives') -----
>>  primitivePerformInSuperclass
>>  	| lookupClass rcvr currentClass |
>>  	lookupClass := self stackTop.
>> + 	rcvr := self stackValue: 3.
>> - 	rcvr := self stackValue: argumentCount.
>>  	currentClass := self fetchClassOf: rcvr.
>>  	[currentClass ~= lookupClass]
>>  		whileTrue:
>>  		[currentClass := self superclassOf: currentClass.
>>  		currentClass = nilObj ifTrue: [^ self primitiveFail]].
>> 
>> + 	argumentCount = 3
>> + 		ifTrue: ["normal primitive call with 3 arguments expected on the stack"
>> + 			self popStack.
>> + 			self primitivePerformAt: lookupClass.
>> + 			self successful ifFalse:
>> + 				[self push: lookupClass]]
>> + 		ifFalse: ["mirror primitive call with extra argument specifying object to serve as receiver"
>> + 			| s1 s2 s3 s4 s5 |
>> + 			"save stack contents"
>> + 			s1 := self popStack. "lookupClass"
>> + 			s2 := self popStack. "args"
>> + 			s3 := self popStack. "selector"
>> + 			s4 := self popStack. "mirror receiver"
>> + 			s5 := self popStack. "actual receiver"
>> + 			"slide stack up one, omitting the actual receiver parameter"
>> + 			self push: s4. "mirror receiver"
>> + 			self push: s3. "selector"
>> + 			self push: s2. "args"
>> + 			"perform as if mirror receiver had been the actual receiver"
>> + 			self primitivePerformAt: lookupClass.
>> + 			self successful ifFalse:
>> + 				["restore original stack"
>> + 				self pop: 3. "args, selector, mirror receiver"
>> + 				self push: s5. "actual receiver"
>> + 				self push: s4. "mirror receiver"				
>> + 				self push: s3. "selector"
>> + 				self push: s2. "args"
>> + 				self push: s1. "lookup class" ]]
>> + !
>> - 	self popStack.
>> - 	self primitivePerformAt: lookupClass.
>> - 	self successful ifFalse:
>> - 		[self push: lookupClass]!
>> 
>> Item was changed:
>>  ----- Method: VMMaker class>>versionString (in category 'version testing') -----
>>  versionString
>> 
>>  	"VMMaker versionString"
>> 
>> + 	^'4.7.19'!
>> - 	^'4.7.18'!

-- 
Stefan Marr
Software Languages Lab
Vrije Universiteit Brussel
Pleinlaan 2 / B-1050 Brussels / Belgium
http://soft.vub.ac.be/~smarr
Phone: +32 2 629 2974
Fax:   +32 2 629 3525