[squeak-dev] A small idea how to get closer to hardware with small efforts :)

Igor Stasenko siguctua at gmail.com
Mon Apr 5 08:13:06 UTC 2010

Hello again,

it is about running a native code , stored in compiled methods.

All we need is:

a) allow code execution for object memory. On most platforms this is
trivial - just pass additional flags to virtual memory allocation
b) add a single primitive 'call a native code'
c) use a special compiled method trailer, which will store the native
code inside itself

Then we could place any native code inside a compiled method and use a
single primitive to run this code.
This is quite simple thing, given that both pharo and squeak adopted
method trailers, so
a primitive, before running the code, needs few checks:
 - a method's trailer format is valid (we could reserve a terminal
byte value for that)
 - a native code, placed inside a method trailer is targeted for same
platform as currently running on

if not, then primitive will simply fail, and interpreter will run the
method's bytecode, which , depending on a situation, can check if it
can recompile the code
(if platform doesn't match) or use a workaround.
The only limitation of such approach, that native code, placed in
compiled method should be relocate-agnostic, i.e.
never use absolute jumps, only relative ones and so on.

Also, we could force, that code using a specific calling convention,
so it will be easy to fetch values from stack and other useful stuff
from interpreter/object memory (like passing an interpreterProxy
This could be a good answer in generating a trampoline code for
FFI/Alien on the fly.

What you think?

Best regards,
Igor Stasenko AKA sig.

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