Bug 44037 – JSC: Move the static_cast into to(U)Int32 fast case

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

[Andreas Kling]

Converting a double JSValue to an int32 (or uint32) is fairly expensive since it includes the overhead of calling to(U)Int32SlowCase.

We could move the ideal case (static_cast<(u)int32_t> of double value within range) out of the slow case for a performance boost on conversion-heavy pages such as http://www.bel.fi/~alankila/plasma.html

[Andreas Kling]

Created attachment 64453 [details]
Proposed patch

[Geoffrey Garen]

Comment on attachment 64453 [details]
Proposed patch

For changes that are likely to affect performance, we usually require a performance measurement.

Please at least post SunSpider results with and without this patch, though I'd also be interested to see measurements of the website you mentioned.

[Andreas Kling]

(In reply to comment #2)
> (From update of attachment 64453 [details])
> Please at least post SunSpider results with and without this patch, though I'd also be interested to see measurements of the website you mentioned.

Callgrind says: SunSpider is an amazing 0.0000072283% faster with this change.

Results for the linked page are pretty much uninteresting until something is done about bug 43742.

[Andreas Kling]

Comment on attachment 64453 [details]
Proposed patch

With the fix for 43742 landed, this patch yields a 1.6% speedup for the plasma demo - http://www.bel.fi/~alankila/plasma.html

[Geoffrey Garen]

Comment on attachment 64453 [details]
Proposed patch

r=me

[WebKit Commit Bot]

Comment on attachment 64453 [details]
Proposed patch

Clearing flags on attachment: 64453

Committed r65698: <http://trac.webkit.org/changeset/65698>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.