SBCL: The Assembly Code Breadboard - https://news.ycombinator.com/item?id=39859849 - March 2024 (19 comments)
SBCL: Assembly code breadboard (2014) - https://news.ycombinator.com/item?id=28450473 - Sept 2021 (4 comments)
SBCL: The Ultimate Assembly Code Breadboard (2014) - https://news.ycombinator.com/item?id=11959147 - June 2016 (2 comments)
SBCL: The Ultimate Assembly Code Breadboard - https://news.ycombinator.com/item?id=7408807 - March 2014 (75 comments)
Using SBCL as a macro-assembler is extremely cool, and then allowing CL code to call into the VM is where it really blows my mind.
Obviously it’s been over a decade since this article was written. For someone less familiar with SBCL internals (or CL in general), would something like AsmJit or Iced be a good way to achieve similar things?
Absolutely. I think TFA is hooking into the actual code emitter used by SBCL's evaluator-compiler, since it's not actually primitive, but implemented in Lisp and loaded into the image itself.
My guess at context: from the earliest days of Lisp, I think there was an expectation that Lisp systems would expose as much of their internals as possible... including their internal JIT, which is being plugged into here. I think the name for it was the "LISP Assembly Program" (LAP).
The approach is similar to Forth.
You have a few key forms that provide the required integration points with the hardware, those are the few ones written in Assembly.
Including the reader and at least some of the macro capabilities.
Then everything else is built from them.
For a time travel into those days see the recovered Interlisp-D system from Xerox PARC, https://interlisp.org/
I remember stopping with a friend to chat with Dave one day not too long after he joined the team and he was over the moon about how the Lisp exposed not just an assembler, but an interactive assembler: he could write assembly routines, evaluate them, and see them run immediately, and also inspect the in-memory data that they operated on. He seemed so happy.
I have started learning SBCL internal from the beginning of this year with the help of GPT, and I really want to contribute to SBCL compiler someday in future.
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