2 levels of Slate

[Lee Salzman]

C is the only reason these levels exist. They will become significantly
more blurry once Slate is able to compile itself. There will be no more
executable, just an image.

Lee

On Mon, Nov 08, 2004 at 12:51:42AM -0500, Todd Fleming wrote:
> Right now, Slate code has 2 levels: VM and user. Methods in the VM 
> level, after generation into machine language and loaded into an OS 
> process, have necessary assumptions about certain slot offsets and the 
> addresses of other methods contained in the VM level. For example, the 
> machine code for "i@(Interpreter pointer) returnFrom: n" knows the 
> address of "i@(Interpreter pointer) applyUnwindBlockFrom: 
> lexicalContext" and the offset of  the unwindBlock slot within 
> LexicalContext. Methods in the user level have no such knowledge; they 
> have to search for roles and slots. Compiled code at the VM level is 
> fast, but it is static; you can't modify VM methods at runtime or change 
> the layout of objects at runtime in a way that violate the assumptions 
> made by these methods. Compiled code at the user level is a lot more 
> flexible, but may not be fast enough for some operations, such as 
> rendering curved areas to a bitmap.
> 
> Right now, the line between VM and non-VM is defined by what gets 
> compiled into C. C is going away; Slate will generate its VM directly 
> into machine code (or, at least that's what I think you guys are doing). 
> Eventually, if I understand correctly, Slate will also compile 
> user-level code into machine languate (JIT?). At this stage, will there 
> still be a hard line between these two levels, or will it start to 
> blurr? Will the whole VM still live in an executable, or will part of it 
> live in the image?
> 
> Todd
>