1832678 - Avoid InitCBReflowInput's call to nsIFrame::GetContainingBlock, if our parent frame could not possibly be a containing block

Status: RESOLVED FIXED

(Core :: Layout: Block and Inline, defect)

Description

[Daniel Holbert [:dholbert]]

In the profile links in bug 216418 , we spend a lot of time in ReflowInput::InitCBReflowInput()'s call to GetContainingBlock (and probably that time is mostly spent walking the ancestor frame tree to discover the nearest block which is quite far away due to how many layers of inline-level elements the content is wrapped in).

This call is almost entirely unnecessary in that case; we only use the return value for the purpose of checking if it matches our parent frame. In this case, our parent frame is almost always an inline-level frame, so it can't match.

We should optimize that call away by first checking whether our parent frame could possibly be something that GetContainingBlock could return (e.g. if it's block-level).

Comment 1

[u727415]

hmm! good

Comment 2

[Daniel Holbert [:dholbert]]

See more notes in bug 216418 comment 45, section (1), too.

Comment 3

[Timothy Nikkel (:tnikkel)]

Attachment: Bug 1832678. Avoid InitCBReflowInput's call to nsIFrame::GetContainingBlock, if our parent frame could not possibly be a containing block. r?#layout-reviewers

Comment 4

[Timothy Nikkel (:tnikkel)]

testcase 2 from bug 216418
trunk about 2900ms
with bug 1832685 about 2400ms
with bug 1832685 and the patch in this bug about 1900ms.

Comment 5

[Timothy Nikkel (:tnikkel)]

Attachment: Bug 1832678. Factor out an nsIFrame::IsBlockContainer helper. r?#layout-reviewers

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/e22a29df339c
Factor out an nsIFrame::IsBlockContainer helper. r=dholbert
https://hg.mozilla.org/integration/autoland/rev/2fbe220a08cf
Avoid InitCBReflowInput's call to nsIFrame::GetContainingBlock, if our parent frame could not possibly be a containing block. r=emilio

Comment 7

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/e22a29df339c
https://hg.mozilla.org/mozilla-central/rev/2fbe220a08cf