[Webkit-unassigned] [Bug 171421] New: [JSC] Add @isUndefinedOrNullIgnoringMasquerade()
bugzilla-daemon at webkit.org
bugzilla-daemon at webkit.org
Fri Apr 28 00:51:47 PDT 2017
https://bugs.webkit.org/show_bug.cgi?id=171421
Bug ID: 171421
Summary: [JSC] Add @isUndefinedOrNullIgnoringMasquerade()
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
In builtin JS, we have bunch of
if (object === null || object === @undefined)
thing. Previously, this is written as follows.
if (object == null)
However, the above one recognizes document.all as null/undefined due to its masquerade.
So, they are rewritten.
But the above thing is,
1. From JS developer, it looks very storange because it seems `== null` is better.
2. It bloats bytecodes, effectively prevents us from inlining. Keep builtin JS function small is a bit important in terms of inlining.
So, to make the meaning explicit and tighten bytecode size, we would like to introduce a new bytecode, op_is_undefined_or_null_ignoring_masquerade.
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