Re: [Squeak-VMdev] bytecodes and contexts

[Ian P. <ian...@in...>]

[subject line changed to reduce the stress on Craig's mail client ;-]

Hi Anthony,

> Also, I haven't heard anyone mention refactoring the bytecodes (eg.
> getting rid of doubleExtendedDoAnythingBytecode).  I bet a JIT would
> prefer an alternative encoding.

I think you know that's true. ;)

To get anywhere with even the simplest code analysis, the first thing a 
JIT will do is to convert the bytecodes into a "canonical form" where 
there's only 1 form of each operation and (probably) all bytecodes are 
the same size (e.g., a word for each operation containing 1 byte of 
opcode and up to 3 bytes of operands).

This kind of transformation reduces 253 or so bytecodes down to about 
20 or so "canonical" operations.

> Code in the block and its outer
> methods access these changeable values by sending get and set messages
> to the ValueHolder.

Is the only reason to send messages to these things the lack of 
bytecodes to encode the additional indirections?  (Type: 
"load/store/pop free var N from enclosing environment at level M".)

Or have I missed something?

> If we change the
> bytecodes, maybe we should add the ValueHolder create, get, and set
> messages, and the createBlockClosure message as special common selector
> bytecodes.

Certainly.  (Or maybe we could do even better...)

Cheers,
Ian