[Vm-dev] how to add a new bytecode primitive?

Hi. I would like to add a new shortcut bytecode to do a little experiment to see if I can improve the speed of a serializer we are doing. In the serializer we call #basicNew for each object. I know that #new is in a bytecodePrim, and I wanted to see if doing the same with #basicNew give us some speed improvement. Just as an experiment.

Now, adding a new bytecode primitive seems complicated and I am not sure how to do it. Can someone help me? I seems I need

1) to add the selector in Smalltalk specialSelectors or in Smalltalk specialObjectsArray at: 24

2) Modify VariableNode >>#initialize the part of:

encoder fillDict: StdSelectors with: SelectorNode mapping: ((1 to: Smalltalk specialSelectorSize) collect: [:i | Smalltalk specialSelectorAt: i]) to: (SendPlus to: SendPlus + 31).

to:

encoder fillDict: StdSelectors with: SelectorNode mapping: ((1 to: Smalltalk specialSelectorSize) collect: [:i | Smalltalk specialSelectorAt: i]) to: (SendPlus to: SendPlus + 32).

3) Change ParserNode >>#initialize

from :

Send := 208.

to:

Send := 209.

4) Interpreter >>#

I need to change from:

..... (205 bytecodePrimNewWithArg) (206 bytecodePrimPointX) (207 bytecodePrimPointY)

(208 255 sendLiteralSelectorBytecode)

to

..... (205 bytecodePrimNewWithArg) (206 bytecodePrimPointX) (207 bytecodePrimPointY) (208 bytecodePrimBasicNew)

(209 255 sendLiteralSelectorBytecode)

What I am not sure here is if I am sure that the compiler will to still be poiting normal messages to bytecode 208 instead of starting in 209.

6) Evaluate:

ParserNode initialize. VariableNode initialize.

Am I missing something?

Finally, is there a bytecode primitive that it is not really used? because maybe it is easier to change for a moment an already existing one. The problem is that I want to see if we improve performance. So removing another bytecode primitive may have negatives effects too.

Thanks a lot in advance,

Mariano