[Webkit-unassigned] [Bug 280144] New: Deleting existing entry from Map/Set followed by re-adding is slower than in v8

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=280144

            Bug ID: 280144
           Summary: Deleting existing entry from Map/Set followed by
                    re-adding is slower than in v8
           Product: WebKit
           Version: WebKit Local Build
          Hardware: Mac (Apple Silicon)
                OS: macOS 14
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: dylan.conway567 at gmail.com

Example minified from https://github.com/oven-sh/bun/issues/14063

```
var map = new Set();

for (var i = 0; i < 1000; i++) {
    for (var j = 0; j < 1000; j++) {
        map.delete(j);
        map.add(j);
    }
}
```

Running this on an m1 max takes about 1 second with JSC. With v8 it takes about 100 milliseconds.

Switching the order of `delete` and `add`, or combining the loops into a single loop to 1000000 does not seem to repro this behavior.

-- 
You are receiving this mail because:
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.webkit.org/pipermail/webkit-unassigned/attachments/20240922/28d46848/attachment.htm>