1360620 - Reduce size of gfxTextRun by optimizing glyphrun storage

Status: RESOLVED FIXED

(Core :: Graphics: Text, enhancement)

Description

[Jonathan Kew [:jfkthame]]

See https://dxr.mozilla.org/mozilla-central/rev/2cca333f546f38860f84940d4c72d7470a3410f4/gfx/thebes/gfxTextRun.h#760-762.

I propose to reduce the size of gfxTextRun by replacing the AutoTArray<GlyphRun,1> (32 bytes in a 64-bit build) with a union that holds either a single GlyphRun *or* an nsTArray<GlyphRun>, with a flag elsewhere in gfxTextRun to record which is currently present (we have a spare padding byte available for that). There will be a bit of overhead in AddGlyphRun when transitioning from a single glyphrun (stored inline) to two glyphruns (in an array), but that will be essentially equivalent to the work AutoTArray does when its autobuffer oveflows.

This should reduce the size of gfxTextRun by 16 bytes, yet have the same allocation behavior as at present: when there's a single GlyphRun, it is stored directly in the textrun with no separate heap allocation, and when there are multiple glyph runs, we have to allocate heap storage for the array (just as the autoarray does when its one-element buffer overflows).

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: Optimize GlyphRun storage strategy in gfxTextRun, to reduce the overall size of the gfxTextRun object

Comment 2

[Jonathan Kew [:jfkthame]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=cc9944ab7313793b0873a53271a1376eac550adb

Comment 3

[Jonathan Kew [:jfkthame]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/dca52e4ed76197ec3e3629e659020c3d5c8d81bb
Bug 1360620 - Optimize GlyphRun storage strategy in gfxTextRun, to reduce the overall size of the gfxTextRun object. r=jrmuizel

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/dca52e4ed761
Optimize GlyphRun storage strategy in gfxTextRun, to reduce the overall size of the gfxTextRun object. r=jrmuizel

Comment 5

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/dca52e4ed761