Remove TailCall.TailPosition.NotTail metadata.

[Akirathan]

Pull Request Description

TailCall.TailPosition.NotTail metadata is attached to every IR element that is not in tail position. Which is true for most IR elements. This is inefficient and unnecessary. This PR removes this metadata and keeps only TailCall.TailPosition.Tail. This removes few bytes from MetadataStorage from most of IR elements

Important Notes

To check whether ir element is not in tail position, we used to check it with something like this ir.getMetadata(TailCall) == Some(TailCall.TailPosition.NotTail), now, we simply can do it with ir.getMetadata(TailCall) == None

Checklist

Please ensure that the following checklist has been satisfied before submitting the PR:

• The documentation has been updated, if necessary.
• Screenshots/screencasts have been attached, if there are any visual changes. For interactive or animated visual changes, a screencast is preferred.
• All code follows the
  Scala,
  Java,
  TypeScript,
  and
  Rust
  style guides. In case you are using a language not listed above, follow the Rust style guide.
• Unit tests have been written where possible.

[Akirathan]

This is the gist of this PR. There is no NotTail attached anymore.

[JaroslavTulach]

Thank you for extracting the discovery you made while working on @Tail_Call mini passes and applying it for the benefit of size of .bindings caches. Have you measured the effect on the size of the caches? I'd assume it is at least five bytes per each non-tail statement. E.g. it might be a lot.

[JaroslavTulach]

There is no NotTail anymore. TailPosition has only one instance and that's the case object Tail.

[Akirathan]

Have you measured the effect on the size of the caches? I'd assume it is at least five bytes per each non-tail statement. E.g. it might be a lot.

@JaroslavTulach I have not measured it. If you are interested, I will do the measurements, but for me, it is enough to know that it will definitely be smaller. However, I don't think the change will be that dramatic, because previously, the TailCall.TailPosition metadata was persisted as a simple boolean value (see https://github.com/enso-org/enso/blob/develop/engine/runtime-compiler/src/main/java/org/enso/compiler/pass/analyse/PassPersistance.java#L107).

GitHub

enso/engine/runtime-compiler/src/main/java/org/enso/compiler/pass/analyse/PassPersistance.java at develop · enso-org/enso

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[JaroslavTulach]

Have you measured the effect on the size of the caches? I'd assume it is at least five bytes per each non-tail statement. E.g. it might be a lot.

If you are interested ... will do the measurements, but for me, it is enough to know that it will definitely be smaller.

In general I see 5% decrease in .bindings size. Base went down from 34MB to 32MB. The biggest effect is on Visualizations library:

• before 3086432 bytes
• after 2239275 bytes
• smaller by 28%