Mapping Python to LLVM • Hacker News Board

Re: Mapping Python to LLVM

#31

Post by maximilianburke » Tue, Jan 10, 2023, 4:35 PM UTC

orra wrote: post #30

maximilianburke wrote: post #8

I recall that Google had a project to compile Python to LLVM (Unladen Swallow @ https://code.google.com/archive/p/unladen-swallow/ ), but work stopped on it a long time ago. If I recall it really wasn't that much faster than CPython given the overhead, but it's been a long time; if it was faster I assume it wouldn't have been abandoned.

Quite. Unladen Swallow was unfortunately a failure, in part because LLVM at the time was quite buggy, and in part because LLVM wasn't (isn't?) magic enough to speed up a dynamic language. The blog post here mentions they do their own optimization passes, before handing over to LLVM. I imagine that's pretty important.

LLVM really wasn't that buggy at the time (circa 2009); the project I was using it for at the time, a .NET compiler that targeted video game consoles, was quite stable from a code generation point of view, and we were shipping games with it.

Re: Mapping Python to LLVM

#32

Post by orra » Tue, Jan 10, 2023, 5:04 PM UTC

maximilianburke wrote: post #31

orra wrote: post #30

Earlier quoted context omitted.

Quite. Unladen Swallow was unfortunately a failure, in part because LLVM at the time was quite buggy, and in part because LLVM wasn't (isn't?) magic enough to speed up a dynamic language. The blog post here mentions they do their own optimization passes, before handing over to LLVM. I imagine that's pretty important.

LLVM really wasn't that buggy at the time (circa 2009); the project I was using it for at the time, a .NET compiler that targeted video game consoles, was quite stable from a code generation point of view, and we were shipping games with it.

Ah, that's cool. Thanks for the correction. I was misremembering the Unladen Swallow retrospective[1]. It's fair to say they used a lot fo their available time contributing to LLVM, but it sounds like that was feature work, not bug focused.

[1] https://qinsb.blogspot.com/2011/03/unladen-swallow-retrospec...

Re: Mapping Python to LLVM

#33

Post by lowbloodsugar » Tue, Jan 10, 2023, 10:04 PM UTC

int_19h wrote: post #24

lowbloodsugar wrote: post #18

Have to assign variables to a bit of memory on the stack because SSA??

LLVM has an optimization pass that takes care of that. https://llvm.org/docs/Passes.html#passes-mem2reg

That's not the only way to do that tho? Or is that the recommended way to do it?

Re: Mapping Python to LLVM

#34

Post by int_19h » Tue, Jan 10, 2023, 11:43 PM UTC

lowbloodsugar wrote: post #33

int_19h wrote: post #24

Earlier quoted context omitted.

LLVM has an optimization pass that takes care of that. https://llvm.org/docs/Passes.html#passes-mem2reg

That's not the only way to do that tho? Or is that the recommended way to do it?

You can write your code generator to produce the optimized output right away, of course. But the whole point of LLVM is to not have every compiler worry about doing stuff like this well.