Terrible Golang performance

Stackoverflow: https://stackoverflow.com/questions/72266899/golang-performance-issues

Google group: https://groups.google.com/g/antlr-discussion/c/OdhAIsy2GfI

Example code: https://github.com/movelazar/perf-repro

A simple rule such as:

1 EQ 2 OR
1 EQ 2 OR
1 EQ 2 OR
1 EQ 2 OR
1 EQ 2

takes exponentially longer to parse the more 1 EQ 2 OR clauses there are. This does not happen in python (by my testing) or CSharp, Dart, Java (by stackoverflow comment).

On my machine, # of lines vs parse time:

11: 0.5s
12: 1.2s
13: 3.2s
14: 8.1s
15: 21.9s
16: 57.5s

Given that Python doesn’t face this issue I can’t imagine I’m doing something terrible in my grammar.

Issue goes away if I put parens on things but that’s not a real solution.

On 4.10.1, first noticed with 4.9.1.

Any help is greatly appreciated. Surprised I can’t find others with this issue.

[jimidle]

These fixes require Go 1.18+ but that should be no problem, given go’s backward compatibility guarantees.

[jimidle]

Thanks, @kaby76 for tracking this down! yeah, I was under impression Go target was kinda screwed up.

Does anybody know Go well enough to fix this hash issue?

I am pretty sure I do 😃. Now, do I have the time? Hmmm - I did the C runtime for v3 because nobody else had the time… It sounds like the consensus is that the Go runtime may need either a rewrite or some serious work.

What would those with an interest in the Go runtime vote for? A new runtime, or a revamp.

I can look at the hashing anyway - though this looks more like an oversight in how go and hashing works (that’s a guess - I have not looked at the problem that @kaby76 describes, but that description looks sound to me). I also agree with earlier comments that the structs and embedded structs may not be organized as well as they might - but that probably is better taken care of with a rewrite.