515969 - Optimize UTF8 decoding in UTF8Utils

Status: RESOLVED WORKSFORME

(Core :: XPCOM, defect)

Description

[Alfred Kayser]

Attachment: V1: Fastpath and inlining for faster UTF8 to UTF16 conversion.

Optimize UTF8 decoding in UTF8Utils, by:
1. Add a simple fastpath for ASCII.
2. Inline CalcState.
3. Inline AddByte.

Ad 1. Very simple check for ascii bit, and then skip the call to UTF8CharEnumerator::NextChar with all the overhead of params and such.
Ad 2. Compiler doesn't inline, even if asked very politely, but manual inline allows to remove a lot of param pushing/popping.
Ad 3. AddByte is essentially a one-line, but compiler also refuses to inline this one.

Even with these 'inline's, the overall object code is smaller:

Before:
 830138 xpcomio_s.lib
3758212 build/xpcom_core.lib

After:
 829458 xpcomio_s.lib
3757032 build/xpcom_core.lib

So, overall less and faster code, especially for converting plain ascii to UTF16.


See also bug 514140 where need for UTF8 to UTF16 conversion is explained.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The bug assignee didn't login in Bugzilla in the last 7 months.
:nika, could you have a look please?
For more information, please visit auto_nag documentation.

Comment 2

[Nika Layzell [:nika] (ni? for response)]

We have completely replaced our UTF8->UTF16 infrastructure since this bug was filed.