[Webkit-unassigned] [Bug 173414] New: [JSC] Implement Object.assign in C++

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Thu Jun 15 05:09:33 PDT 2017


https://bugs.webkit.org/show_bug.cgi?id=173414

            Bug ID: 173414
           Summary: [JSC] Implement Object.assign in C++
           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: utatane.tea at gmail.com

Implementing Object.assign in JS is not so good compared to C++ version because,

1. JS version allocates JS array for object own keys. And we allocate JSString / Symbol for each key.
But basically, they can be handled as UniquedStringImpl in C++. Allocating these cells are wasteful.

2. While implementing builtins in JS offers some good type speculation chances, Object.assign is inherently super polymorphic.
So JS's type profile doesn't help well.

3. We have a chance to introduce various fast path for Object.assign in C++.

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