5 ms·

SBCL "user-guided optimization" notice

BoingBoomTschak 2y ago
Thought this was quite fun. In general, following SBCL development (via the useful Atom feed) has been a very instructive and sometimes entertaining endeavour!
phoe-krk 2y ago
https://github.com/search?q=lang%3A%22Common+Lisp%22+%22%28lambda+%28%29%29%22&type=code https://github.com/search?q=lang%3A%22Common+Lisp%22+%22%28l... and https://github.com/search?q=lang%3A%22Common+Lisp%22+%22(lambda+()+nil)%22&type=code https://github.com/search?q=lang%3A%22Common+Lisp%22+%22(lam... indeed gives quite a lot of results. A (possibly stupid) question: is it possible to generalize this pattern and will it bring any kind of improvements? I'm thinking that for functions shaped like (LAMBDA () X), where X is a literal object or a lexical variable, COMPILE can keep a hash-table with the X being its weak keys and the respective compiled functions being their values. Whenever a form like (LAMBDA () X) is encountered as an argument to COMPILE, it can "intern" the function in the table (if necessary) and return it. I have no idea if it would bring any or a lot of gains besides the cases for NIL (and maybe T) because of CONSTANTLY and closures, but it's a thought that came to my mind upon first reading this commit.
nxobject 2y ago
If that's what an industrial-strength compiler for a relatively niche language has to do, imagine what special cases LLVM and GCC have to deal with!
- BoingBoomTschak 2y ago
  I'd love to see a list of such curious commits!
- MonkeyClub 2y ago
  > for a relatively niche language Thinking of the queen of languages relegated to "a relatively niche language" really made me sad.
  - nxobject 2y ago
    Tell me about it: I still think in Scheme when I’m writing any other of CL’s dynamically typed, garbage-collected, first-class function progeny. I just wish that more languages had symbols.
    - NikkiA 2y ago
      > I just wish that more languages had symbols. They're just a global enum, almost all languages have enums.
      - jmercouris 2y ago
        Is the implementation specified that they are a global enum? I don't believe so.
      - BoingBoomTschak 2y ago
        Symbols are dynamic, not static. And uninterned symbols exist. You could say that it's a global (per package) weak hash table, from my understanding.
      - dreamcompiler 2y ago
        Symbols exist as data structures at runtime that can be inspected, have their names compared, and have a value that is separate from their name. Enums typically don't do any of that.
sherburt3 2y ago
You would expect there to be some mutual respect between SBCL developers and users because it’s such a tiny group of people who are intelligent and capable programmers.

Thought this was quite fun. In general, following SBCL development (via the useful Atom feed) has been a very instructive and sometimes entertaining endeavour!

phoe-krk 2y ago

https://github.com/search?q=lang%3A%22Common+Lisp%22+%22%28lambda+%28%29%29%22&type=code https://github.com/search?q=lang%3A%22Common+Lisp%22+%22%28l... and https://github.com/search?q=lang%3A%22Common+Lisp%22+%22(lambda+()+nil)%22&type=code https://github.com/search?q=lang%3A%22Common+Lisp%22+%22(lam... indeed gives quite a lot of results. A (possibly stupid) question: is it possible to generalize this pattern and will it bring any kind of improvements? I'm thinking that for functions shaped like (LAMBDA () X), where X is a literal object or a lexical variable, COMPILE can keep a hash-table with the X being its weak keys and the respective compiled functions being their values. Whenever a form like (LAMBDA () X) is encountered as an argument to COMPILE, it can "intern" the function in the table (if necessary) and return it. I have no idea if it would bring any or a lot of gains besides the cases for NIL (and maybe T) because of CONSTANTLY and closures, but it's a thought that came to my mind upon first reading this commit.

nxobject 2y ago

If that's what an industrial-strength compiler for a relatively niche language has to do, imagine what special cases LLVM and GCC have to deal with!

BoingBoomTschak 2y ago
I'd love to see a list of such curious commits!
MonkeyClub 2y ago
> for a relatively niche language Thinking of the queen of languages relegated to "a relatively niche language" really made me sad.
- nxobject 2y ago
  Tell me about it: I still think in Scheme when I’m writing any other of CL’s dynamically typed, garbage-collected, first-class function progeny. I just wish that more languages had symbols.
  - NikkiA 2y ago
    > I just wish that more languages had symbols. They're just a global enum, almost all languages have enums.
    - jmercouris 2y ago
      Is the implementation specified that they are a global enum? I don't believe so.
    - BoingBoomTschak 2y ago
      Symbols are dynamic, not static. And uninterned symbols exist. You could say that it's a global (per package) weak hash table, from my understanding.
    - dreamcompiler 2y ago
      Symbols exist as data structures at runtime that can be inspected, have their names compared, and have a value that is separate from their name. Enums typically don't do any of that.

sherburt3 2y ago

You would expect there to be some mutual respect between SBCL developers and users because it’s such a tiny group of people who are intelligent and capable programmers.