Use unchecked-*-int functions for real 32-bit math

Question

Currently the unchecked-* functions and macros simply alias the primitive js operators. It would be nice if the unchecked-**-int family of functions and macros implemented C/Java-like signed int operations with silent overflows (just like in Clojure) using asm.js coersion idioms. This should also allow us to share such code between clojure and clojurescript without worrying about their different numerics.

A use case is that porting hash algorithms from java to clojurescript is trickier and more verbose than it needs to be.

Answer 1

Comment made by: dnolen

This sounds interesting, would like to see more thoughts on approach, benchmarks etc.

Answer 2

Comment made by: dnolen

Bump, this enhancements sound simple & fine.

Answer 3

Comment made by: favila

I'll have time to do this in about a week. The implementation is straightforward (basically use xor 0 everywhere). The goal is correctness, but I expect performance to be as good as or better than it is now on most platforms. I'm not sure if advanced mode will drop intermediate truncations or what impact this has on performance.

Some higher-level numeric analysis using the asm.js type system is possible but I doubt it's worth it.

Answer 4

Comment made by: favila

I completely forgot about this, sorry. I see you have scheduled it for the "next" release. Are you assigning it as well or will you still accept a patch?

Answer 5

Comment made by: dnolen

Be my guest :)

Answer 6

Reference: https://clojure.atlassian.net/browse/CLJS-773 (reported by favila)