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Simd contains fix #104735

Merged
merged 2 commits into from
Nov 22, 2022
Merged

Simd contains fix #104735

merged 2 commits into from
Nov 22, 2022

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the8472
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@the8472 the8472 commented Nov 22, 2022

Fixes #104726

The bug was introduced by an improvement late in the original PR (#103779) which added the backtracking when the last and first byte of the needle were the same. That changed the meaning of the variable for the last probe offset, which I should have split into the last byte offset and last probe offset. Not doing so lead to incorrect loop conditions.

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rustbot commented Nov 22, 2022

r? @Mark-Simulacrum

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Nov 22, 2022
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rustbot commented Nov 22, 2022

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

  • Stabilizing library features
  • Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
  • Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
  • Changing public documentation in ways that create new stability guarantees
  • Changing observable runtime behavior of library APIs

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thomcc commented Nov 22, 2022

r? @thomcc

@rustbot rustbot assigned thomcc and unassigned Mark-Simulacrum Nov 22, 2022
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thomcc commented Nov 22, 2022

Great catch. Really subtle but makes sense after your fix.

Marking as p=10 following the rationale in #104727 (comment) (soundness fix), but this patch shouldn't impact perf since it's not reverting an optimization.

@bors r+ p=10

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bors commented Nov 22, 2022

📌 Commit 3ed8fcc has been approved by thomcc

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 22, 2022
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bors commented Nov 22, 2022

⌛ Testing commit 3ed8fcc with merge ff8c8df...

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bors commented Nov 22, 2022

☀️ Test successful - checks-actions
Approved by: thomcc
Pushing ff8c8df to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Nov 22, 2022
@bors bors merged commit ff8c8df into rust-lang:master Nov 22, 2022
@rustbot rustbot added this to the 1.67.0 milestone Nov 22, 2022
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Finished benchmarking commit (ff8c8df): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
- - 0
Regressions ❌
(secondary)
1.5% [1.3%, 1.6%] 2
Improvements ✅
(primary)
- - 0
Improvements ✅
(secondary)
-1.8% [-2.1%, -1.6%] 2
All ❌✅ (primary) - - 0

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
- - 0
Regressions ❌
(secondary)
4.4% [2.9%, 7.7%] 4
Improvements ✅
(primary)
- - 0
Improvements ✅
(secondary)
- - 0
All ❌✅ (primary) - - 0

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Successfully merging this pull request may close these issues.

Unsafe precondition violated in the x86_64 SIMD implementation of str.contains
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