Bug 154674 – Consider using a jump table in element factories

• Status: RESOLVED
• Resolution: WONTFIX
• Component: DOM

[Ryosuke Niwa]

Created attachment 272199 [details]
WIP

We've always said that it's silly to be using HashMap for looking up the atomic string name.

Here's a super crude prototype of using alphabet jump table & one-level binary search.

This appears to be ~0.5% improvement on PerformanceTests/Bindings/create-element.html but this test only creates div so we need a more comprehensive testing.

[Ryosuke Niwa]

Created attachment 272281 [details]
WIP

Here's a new WIP patch with tests.

I was observing a consistent 1-2% gain but I'm no longer seeing that now :(
I don't know whether my testing was busted.
I'm somehow seeing a lot more variance on my test results now.

[Ryosuke Niwa]

Created attachment 336357 [details]
WIP2

[Ryosuke Niwa]

Created attachment 336359 [details]
WIP3

With this patch, we avoid creating AtomicString when creating built-in HTML elements in the HTML parser & createElement. In the case of createElement, we also avoid lowercasing the string.

[EWS Watchlist]

Attachment 336359 [details] did not pass style-queue:


ERROR: Source/WebCore/dom/TagNameLookupTable.h:26:  Use #pragma once instead of #ifndef for header guard.  [build/header_guard] [5]
ERROR: Source/WebCore/dom/TagNameLookupTable.cpp:29:  Alphabetical sorting problem.  [build/include_order] [4]
ERROR: Source/WebCore/html/parser/AtomicHTMLToken.h:30:  Alphabetical sorting problem.  [build/include_order] [4]
Total errors found: 3 in 13 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Ryosuke Niwa]

Created attachment 336429 [details]
WIP4 (fixed build)

[Ryosuke Niwa]

Hm... this appears to be an overall regression in Speedometer because there are enough non-standard attributes set. I guess we won't do this.