If you don't care about performance, you can do the method lookup in C, and have the asm implementation of objc_msgSend simply call that C function and then the returned method.

A working implementation of this minimal objc_msgSend can be found in Cocotron sources:

http://code.google.com/p/cocotron/source/browse/objc/platfor...

It's the commented-out piece of code at line 10. Here's the C function it calls:

http://code.google.com/p/cocotron/source/browse/objc/objc_ms...