1373095 - nsTableCellFrame::GetRowSpan() is a tad slow

Status: RESOLVED FIXED

(Core :: Layout: Tables, enhancement, P3)

Description

[Mats Palmgren (:mats)]

It's at ~1.5% on the perf log for the Netflix use case reported in bug 1373058,
which seems a bit too much.

GetRowSpan/GetColSpan are virtual because nsMathMLmtdFrame overrides it.
http://searchfox.org/mozilla-central/rev/c49a70b53f67dd5550eec8a08793805f2aca8d42/layout/mathml/nsMathMLmtableFrame.cpp#1170
It seems we could devirtualize these fairly easily, by adding that code
in an else-branch in the base class:
http://searchfox.org/mozilla-central/rev/c49a70b53f67dd5550eec8a08793805f2aca8d42/layout/tables/nsTableCellFrame.cpp#712

Or perhaps hookup <mtd> so that it parses the attr like <td>:
http://searchfox.org/mozilla-central/rev/c49a70b53f67dd5550eec8a08793805f2aca8d42/dom/html/HTMLTableCellElement.cpp#404
so that the existing code in nsTableCellFrame just works as is.

Comment 1

[Mats Palmgren (:mats)]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=46174017a113acd4229393fbc91cc5894f635fd4

Comment 2

[Mats Palmgren (:mats)]

Attachment: Devirtualize GetRowSpan/GetColSpan

FYI, I intentionally skipped this HTML quirk:
http://searchfox.org/mozilla-central/rev/20d16dadd336e0c6b97e3e19dc4ff907744b5734/dom/html/HTMLTableCellElement.cpp#406-408
since we currently don't do that for MathML <mtd>.
Let me know if you think we should.

Comment 3

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 8878496 [details] [diff] [review]
Devirtualize GetRowSpan/GetColSpan

>+    if (IsMathMLElement(nsGkAtoms::mtd_)) {

No point testing the namespace again, given where we are.  Just use:

  if (mNodeInfo->Equals(nsGkAtoms::mtd_)) {

r=me

Comment 4

[Mats Palmgren (:mats)]

Ah, good point.  I'll update the other three places likewise then:
http://searchfox.org/mozilla-central/rev/20d16dadd336e0c6b97e3e19dc4ff907744b5734/dom/mathml/nsMathMLElement.cpp#150,239,242

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/c0bb73483afb
Devirtualize GetRowSpan/GetColSpan.  r=bz

Comment 6

[Sebastian Hengst [:aryx] (needinfo on intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/c0bb73483afb