[Webkit-unassigned] [Bug 151233] New: Set existence with numeric values slower than numeric object property existence

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=151233

            Bug ID: 151233
           Summary: Set existence with numeric values slower than numeric
                    object property existence
    Classification: Unclassified
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: joepeck at webkit.org
                CC: keith_miller at apple.com, sbarati at apple.com,
                    utatane.tea at gmail.com

Created attachment 265448
  --> https://bugs.webkit.org/attachment.cgi?id=265448&action=review
[TEST] Set Existence Benchmark

* SUMMARY
Set existence with numeric values slower than numeric object property existence.

In Web Inspector we were converting a bunch of uses of "Object as Set" and "Object as Map" to Set/Map objects. I wrote a small benchmark to compare possible performance differences. Existence checks for large dense Sets with primitives is worse than existence checks in large dense Objects.

    object[number]    - 17ms
    number in object  - 84ms
    set.has(number)   - 622ms

For numeric keys object was significantly faster than Set.
For other key types the effect was not as large.

See attached test case.

* NOTES
- Not sure how realistic the test is for real world code. Especially given Set's major advantage is non-primitive keys.

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