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Proper Tail Optimization doesn't work #2140

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amirouche opened this issue Sep 2, 2017 · 7 comments
Open

Proper Tail Optimization doesn't work #2140

amirouche opened this issue Sep 2, 2017 · 7 comments

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@amirouche
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amirouche commented Sep 2, 2017 •
edited

GNU Guile has now a working prototype of a compiler backend that generates JavaScript.

It use lots of tail calls. I compiled it with traceur using the following command:

$ traceur --out script.js --script out.prettier.js --proper-tail-calls  --experimental

I run it in chrome using the following html file:

<html>
  <body>
    <script src="https://google.github.io/traceur-compiler/bin/traceur.js"></script>
    <script src="https://google.github.io/traceur-compiler/bin/BrowserSystem.js"></script>
    <script src="/script.js" type="text/javascript"></script>
  </body>
</html>

It fails with a Uncaught RangeError: Maximum call stack size exceeded.

The original scheme program is:

(js-invoke (js-eval "console") "log" "héllo world")

The input JavaScript file can be found here. That input file is correctly intrepreted by nodejs v8.4.0 using the --harmony_tailcalls flag.
@arv
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arv commented Sep 2, 2017

The option for tail calls is not enabled by default. How did you coming your ES6 code?

@amirouche
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The option for tail calls is not enabled by default.

I enabled it with --proper-tail-calls flag, it's not enough?

How did you coming your ES6 code?

I don't understand the question.

@arv
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arv commented Sep 2, 2017

Oops. Typo, should have been "how did you compile your code"

If I remember correctly the tall call implementation in traceur did not cover all cases. I have to look closer at your code.

Note, no one is really maintaining this project at the moment. If you have some time your contribution would be appreciated.

@amirouche
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Actually the compilation is ok, it's just that I don't have a correct traceur-runtime.js. I had to replace some string with traceur-runtime@0.0.112/src/. I don't know how to build the "traceur/dist/common" version of the runtime.

Yes hopefully I can help.

I just successfully ran the following program:

"use strict";

function foo(n) {
  if (n===0) {
    return "done"
  } else {
    return foo(n-1)
  }
}

console.log(foo(100000));

I guess I need to find out what is not optmised in the other case.

@amirouche
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amirouche commented Sep 3, 2017 •
edited

By the way the code is written using CPS. Someone told me cheney on the MTA should be the way to go. But I don't understand how in the context of JavaScript it makes sens.

@amirouche
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amirouche commented Jul 25, 2019 •
edited

Hopefully, it will be helpful to someone on the same quest.

For what it's worth, I managed to translate a subset of Scheme (!) to JavaScript using Continuation-Passing-Style and a trampoline. Here is the Scheme description of the transformation in nanopass framework syntax:

https://github.com/scheme-live/ruse-scheme/blob/5921af59c8586c1e76996e446df76d40601f93a9/rusec.scm#L987-L1101

It works. The thing is that as-is it is very slow, proof: https://www.measurethat.net/Benchmarks/Show/5674/0/ruse-compiler-factorial

The rest of the compiler can be found at https://github.com/scheme-live/ruse-scheme/blob/master/rusec.scm

edit: change link to code to updated version and replace benchmark link with something that is not buggy

@amirouche
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Ideas on how to optimize the code is 💯 welcome.

Here is another jsperf link because the other is broken: https://jsperf.com/ruse-scheme-factorial-v0

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@arv @amirouche