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Clasp – A Common Lisp with LLVM back end and interoperation with C++

278 points| drmeister | 11 years ago |drmeister.wordpress.com | reply

74 comments

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[+] eudox|11 years ago|reply
>Programmers can expose C++ classes as well as functions and class methods with a single line of code that provides the Clasp name and a pointer to the function/method.

Hellooooo Qt without Smoke bindings.

[+] pnathan|11 years ago|reply
It would be really shiny to have a cross-platform GUI library in CL without grief. I've prodded that space repeatedly in the last 6 years and simply have not come away happy about any of it except LispWork's library.
[+] phkahler|11 years ago|reply
Sounded good until I saw this:

A faster Clasp compiler is coming soon – the current Clasp compiler generates slow native code that is about 100x slower than highly tuned Common Lisp compilers like Steel Bank Common Lisp.

No mention of the expected speedup, but 100x is a huge performance problem.

[+] drmeister|11 years ago|reply
The reason is that Clasp doesn't do Lisp language level optimizations like escape analysis yet. All bindings are stored on the heap and the stack/registers are underutilized. LLVM is a great library for implementing C and C++ but more work needs to be done to support Lisp features like closures and first-class functions. We are working on that now. The goal was first to "make it correct" and now we will "make it fast". Once we have a faster compiler (give us a couple of months) I don't see why it couldn't approach the speed of SBCL (a tall order).
[+] krig|11 years ago|reply
Considering that SBCL is among the fastest programming language implementations there is, 100x is actually not terrible for a first version.
[+] aidenn0|11 years ago|reply
I'm not too worried, since a) that makes it about as fast as cpython and b) there is a lot of low-hanging fruit. There is work being done on integrating the Cleavir compiler which does a number of tricks. In particular escape analysis and lambda lifting should both help a lot on certain types of code.
[+] wtbob|11 years ago|reply
This is extremely exciting, particularly if it can be made to work with emscripten. Common Lisp in the browser, here we come!
[+] aidenn0|11 years ago|reply
Almost certainly can't. The closest you can get is using clicc or ECL or something similar to generate C code, and then compile that with emscripten.

This invokes llvm at runtime, and AFAIK emscripten isn't ported to emscripten.

FWIW, I've tried other lisps under emscripten:

Most lisps generate machine code, store them in RAM, and then execute that RAM. This is not possible under emscripten.

Clisp is a good candidate, since it's byte-code interpreted rather than generating machine code, but clisp makes so many assumptions about how the machine works (in particular it strongly wants a C style stack and does manual stack-pointer manipulation). I actually got fairly far into the bootstrap process under emscripten, but the minimal lisp interpreter it compiles generated bizarre errors.

[+] drmeister|11 years ago|reply
I don't see why we couldn't do this. emscripten (https://github.com/kripken/emscripten) says it takes LLVM-IR to JavaScript. The Clasp (Common Lisp) function COMPILE-FILE compiles to LLVM-IR bitcode files. If you have some time and you would like to do this - hit me up with an email - I'd love to make this happen.
[+] mateuszf|11 years ago|reply
ClojureScript already exists, and even if it's not Common Lisp, its still Lisp with homoiconity, macros and what not.
[+] mcmancini|11 years ago|reply
Exciting work. CL on the LLVM has been needed.

Is this project something that you're doing to support your own research goals in computational chemistry? If so, can you share how this project fits into the bigger picture?

[+] yvdriess|11 years ago|reply
Finger crossed then that Azule can get a proper moving GC to work with LLVM then, until then a CL on LLVM (even Julia) are stuck with kinda bad GC.

I wonder why start from scratch for an LLVM backend, can't SBCL be used to generate LLVM code?

[+] drmeister|11 years ago|reply
SBCL doesn't generate LLVM code. My primary goal was Common Lisp with C++ interoperation. It seemed easier at the time to start from the ECL Common Lisp code base and write a new C++ core and a Common Lisp interpreter that always interoperated with C++. As I wrote the compiler and expanded the system I maintained C++ interoperation all the time. There were a hundred problems that I had to discover and solve along the way to maintain a Common Lisp that interoperated with C++. You can get some level of interoperation between ECL and C++ up in a weekend but it won't work with C++ exceptions and RAII and there are dozens of other problems. In retrospect I don't think I would have gotten here starting from ECL because I never really understood the ECL code.
[+] aidenn0|11 years ago|reply
It wasn't from scratch, it was from ECL. And did you mean Azul?
[+] ioddly|11 years ago|reply
Is the compacting garbage collector mentioned in the article not a proper moving GC? I am not familiar with it.
[+] masukomi|11 years ago|reply
I would point out that MOCL https://wukix.com/mocl pretty much provides this functionality only with full Common Lisp compatibility. It compiles the CL to C and adds methods to expose your functions to Obj-C / C code (if you want). Works just fine. Builds with Xcode, which as I understand, does everything on/via LLVM.
[+] lispm|11 years ago|reply
mocl is different from many other implementations: it is a batch compiler for whole programs to C. The generated code does contain a limited evaluator and no compiler. Some dynamic features are gone...
[+] aidenn0|11 years ago|reply
MOCL specifically does not have full CL compatibility.
[+] latiera|11 years ago|reply
MOCL is garbage, commercial garbage at that. No thanks.
[+] JabavuAdams|11 years ago|reply
> Clasp exposes the Clang AST library and the Clang ASTMatcher library. This allows programmers to write tools in Common Lisp that automatically analyze and refactor C++ programs. Clasp can be used to automatically clean-up and refactor large C++ codebases!

Niiice. I want to program C++, but not in C++.

[+] drmeister|11 years ago|reply
Yes, I'll post more on this and provide example code in the coming weeks on the blog. It's really exciting and it's something that Clasp can do right now even though the Clasp compiler isn't a highly optimizing one yet. Google uses automated Clang refactoring to clean up the googleplex (100 megaLOC). Clasp puts those capabilities into everyones hands now.
[+] tempodox|11 years ago|reply
Wow, this news almost makes me drool. I will keep my eye on that. I'm on SBCL right now, but I can't wait to see what Lisp can do with LLVM...
[+] fithisux|11 years ago|reply
I hope it turns out a good implementation since there is a lot of C++ code out there and I do not know C++. But I can comprehend Lisp.
[+] edwintorok|11 years ago|reply
The name is already taken unfortunately: http://www.cs.uni-potsdam.de/clasp/

  Package: clasp
  Version: 3.1.0-1
  Description-en: conflict-driven nogood learning answer set solver
  clasp is an answer set solver for (extended) normal logic
 programs.
[+] chc|11 years ago|reply
It was also already taken by a device for fastening things. And my name was already taken by at least three people before me. Somehow we all get along.
[+] andrewchambers|11 years ago|reply
All names are already taken, that's why Wikipedia has the disambiguation pages.
[+] 616c|11 years ago|reply
Someone has been building Ocaml's opam on Arch I see.