[Vm-dev] [Enh][VM] primitiveApplyToFromTo for the heart of the enumeration of collections?

[Klaus D. Witzel]

Attached is #primitiveApplyToFromTo as it compiles and runs using the  
win32 Squeak 3.7.1 build environment here; I'm testing it with the 3.8 and  
3.9 images.

The performance is compared against plain #do: (apples v.s. apples) and  
#to:do: (apples v.s. oranges) further down below.

Compared to #do: with block, #applyTo:from:to: with block is definitively  
faster (smaller hidden constants) and there also is at least one item  
waiting for optimization (and for me having time to do that).

I'd say that the factor can arrive at about 2 (#do: v.s.  
#applyTo:from:to:). But the primitive will not outperform an inlined  
#to:do: this was clear from the beginning. As Jon wrote, the primitive is  
good for "fixing" the standard enumeration methods so they all have (more  
or less) identical performance.

The current implementation is for non-Strings only (as dictated by an  
atCache parameter) but can of course be extended to work with Strings.  
Another item that's missing is returning self from the primitive, this is  
currently handled by falling into the shadow which then returns (and some  
superflous bytecode cycles are burned).

Example method in SequenceableCollection
applyTo: aBlock from: index to: limit
	<primitive: 164>
	[index <= limit] whileTrue:
		[aBlock value: (self basicAt: index).
		 thisContext tempAt: 2 put: index + 1]

The shadow code is exactly what is done by the primitive. As discussed  
ealier,the primitive can be called from #commonSend and from #commonReturn  
and in both cases might decide to exit with primitiveFail.

The overrides for #commonSend and #commonReturn are not attached but if  
you want them ask me.

Any questions?

/Klaus

--------------------

| time array sum |
	array := (1 to: 10565520) collect: [:none | 1].
	Smalltalk garbageCollect.
	time := Time millisecondsToRun: [
		sum := array sum].
	sum.
	time
=> 9093

--------------------

| time array sum |
	array := (1 to: 10565520) collect: [:none | 1].
	Smalltalk garbageCollect.
	time := Time millisecondsToRun: [
		sum := 0.
		array do: [:each | sum := sum + each]].
	sum.
	time
=> 4764

--------------------

| time array sum |
	array := (1 to: 10565520) collect: [:none | 1].
	Smalltalk garbageCollect.
	time := Time millisecondsToRun: [
		sum := 0.
		array applyTo: [:each | sum := sum + each]
			from: 1 to: array size].
	sum.
	time
=> 3499

--------------------

| time array sum |
	array := (1 to: 10565520) collect: [:none | 1].
	Smalltalk garbageCollect.
	time := Time millisecondsToRun: [
		sum := 0.
		1 to: array size do: [:index | sum := sum + (array at: index)]].
	sum.
	time
=> 2089

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