Stream: git-wasmtime

Topic: wasmtime / PR #5252 Cranelift(Aarch64): Optimize lowering...

Wasmtime GitHub notifications bot (Nov 10 2022 at 23:58):

fitzgen opened PR #5252 from optimize-comparisons-with-immediates-on-aarch64 to main:

We can encode more constants into 12-bit immediates if we do the following rewrite for comparisons with odd constants:

    A >= B + 1
==> A - 1 >= B
==> A > B

(And similar for less-than-or-equals.)

<!--

Please ensure that the following steps are all taken care of before submitting
the PR.

• [ ] This has been discussed in issue #..., or if not, please tell us why
  here.

• [ ] A short description of what this does, why it is needed; if the
  description becomes long, the matter should probably be discussed in an issue
  first.

• [ ] This PR contains test cases, if meaningful.

• [ ] A reviewer from the core maintainer team has been assigned for this PR.
  If you don't know who could review this, please indicate so. The list of
  suggested reviewers on the right can help you.

Please ensure all communication adheres to the code of conduct.
-->

Wasmtime GitHub notifications bot (Nov 10 2022 at 23:58):

fitzgen requested elliottt for a review on PR #5252.

Wasmtime GitHub notifications bot (Nov 10 2022 at 23:59):

fitzgen created PR review comment:

I'm not sure why these changed here, but also I think it is benign since movz is zero-extending the value?

Wasmtime GitHub notifications bot (Nov 10 2022 at 23:59):

fitzgen submitted PR review.

Wasmtime GitHub notifications bot (Nov 11 2022 at 00:46):

elliottt submitted PR review.

Wasmtime GitHub notifications bot (Nov 15 2022 at 16:36):

fitzgen updated PR #5252 from optimize-comparisons-with-immediates-on-aarch64 to main.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:17):

jameysharp submitted PR review.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:17):

jameysharp created PR review comment:

Why is make_imm12_from_u64 separate from imm12_from_u64? They look identical to me.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:18):

fitzgen created PR review comment:

One is a pure constructor and the other is a fallible extractor. They are identical but can't replace one another in ISLE's type system.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:18):

fitzgen submitted PR review.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:18):

fitzgen merged PR #5252.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:19):

elliottt created PR review comment:

Couldn't it be an infallible extractor? Then there'd be no Option in the return type, and the same rust function could be reused for the extractor and constructor in isle.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:19):

elliottt submitted PR review.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:20):

elliottt created PR review comment:

Scratch that -- I just realized that we're relying on the failure behavior in the extractor case :)

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:20):

elliottt submitted PR review.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:21):

fitzgen submitted PR review.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:21):

fitzgen created PR review comment:

It can't be infallible because not all u64s can be represented with Imm12s

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:21):

fitzgen edited PR review comment.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:29):

jameysharp submitted PR review.

Wasmtime GitHub notifications bot (Nov 15 2022 at 17:29):

jameysharp created PR review comment:

Ah, I see. But then you could have used the extractor instead of a constructor, right?

(if-let (imm12_from_u64 imm) (u64_sub b 1))

Last updated: Nov 22 2024 at 16:03 UTC