1969269 - Inline string character access built-ins when no arguments are passed

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, enhancement, P1)

Description

[André Bargull [:anba]]

JSC recently added this optimisation: https://github.com/WebKit/WebKit/commit/b6c35f4cd18125c7d3acb54ace62b9d74a67a45c

It looks like V8 already optimises for this pattern. Note that str.charAt(null), str.charAt(undefined), or str.charAt(NaN) aren't optimised in JSC and V8, so we don't have to worry about optimising for this case.

Comment 1

[André Bargull [:anba]]

Attachment: Bug 1969269: Support inlining String character built-ins when index argument is absent. r=jandem!

str.charAt() is sometimes used as a shorthand for str.charAt(0). The same
applies to str.charCodeAt(), str.codePointAt(), and str.at().

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/38ee6a959828
https://hg.mozilla.org/integration/autoland/rev/c73094ad1da9
Support inlining String character built-ins when index argument is absent. r=jandem

Comment 3

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/c73094ad1da9