Bug 279862 – [JSC] Add fast path for `array.concat()`

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Sosuke Suzuki]

This patch adds fast path for `array.concat()` using same way as `Array.from(array)` and
    `Iterator#toArray.call(array)`.
    
    According to microbench it is 1.5~6x faster.
    
                                                TipOfTree                  Patched
    
    array-prototype-concat-copy-obj           1.5511+-0.0177     ^      0.9972+-0.0240        ^ definitely 1.5555x faster
    array-prototype-concat-copy-double        1.5206+-0.0444     ^      0.9512+-0.0144        ^ definitely 1.5986x faster
    array-prototype-concat-copy-int32         1.5138+-0.0141     ^      0.9637+-0.0457        ^ definitely 1.5707x faster
    
    <geometric>                               1.5284+-0.0205     ^      0.9704+-0.0137        ^ definitely 1.5750x faster
    
    Other benchmarks of Arrray.prototype.concat show no performance regressions.

[Sosuke Suzuki]

Pull request: https://github.com/WebKit/WebKit/pull/33806

[EWS]

Committed 284060@main (21359545c81d): <https://commits.webkit.org/284060@main>

Reviewed commits have been landed. Closing PR #33806 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/136479133>