1577389 - nsStyleMargin::GetMargin and nsStylePadding::GetPadding are a bit slow

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, enhancement, P3)

Description

[Cameron McCormack (:heycam)]

We call these for most elements during reflow. Values of 0 for margin and padding are very common, and we can check for such values and return nsMargin(0, 0, 0, 0) without having to do all the FP math for converting the LengthPercentage to an in-range nscoord.

The upcoming patch makes time spent under StyleCSSPixelLength::ToAppUnits (which is where all the time under GetMargin and GetPadding is taken) drop from 62 ms to 4 ms on https://en.wikipedia.org/wiki/Barack_Obama page load on my machine.

Comment 1

[Cameron McCormack (:heycam)]

Attachment: Bug 1577389 - Return early from StyleCSSPixelLength::ToAppUnits for zero lengths.

Zero lengths are common, and we can avoid doing all the FP math.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d4a2b6867f3e
Return early from StyleCSSPixelLength::ToAppUnits for zero lengths. r=emilio

Comment 3

[Stefan Hindli [:stefan_hindli]]

https://hg.mozilla.org/mozilla-central/rev/d4a2b6867f3e

Comment 4

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/releases/mozilla-beta/rev/d4a2b6867f3e