blog/2023/11/03/C2-AutoVectorizer-Improvement-Ideas

[utterances-bot]

C2 AutoVectorizer Improvement Ideas | Emanuel’s Blog

Motivation

https://eme64.github.io/blog/2023/11/03/C2-AutoVectorizer-Improvement-Ideas.html

[arkie-dev]

Hi,
I think that big part of making auto-vectorization successful is finding as many opportunities to vectorize as we can. So issues like if conversion and flattening control flow are very important.
Could you tell me if there is some work currently done with if-conversion or other improvements to control flow. In JDK-8347116 you mention that
if-conversion is blocked by cost model but I don't see why it need to be blocked. We can have working If-conversion without cost model.
Br,
Krystian

[eme64]

@fdevro Thanks for your interest!

I'm currently focusing on aliasing analysis, and after that I will work on reductions / cost-model, then probably if-conversion.

Please also see:
https://eme64.github.io/blog/2025/01/01/AutoVectorization-Status.html

I'm not sure if if-conversion is profitable in all cases. That is why I would like to have a cost-model in place first.

[eme64]

That said, one step is also JDK-8308841, ensuring that cases where we already have integer CMove (essentially already if-converted) can be vectorized. I hope that someone can take this one on soon.