1707562 - Fix maybeDensifySparseElements to not reshape for each element

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P2)

Description

[Jan de Mooij [:jandem]]

In NativeObject::maybeDensifySparseElements, we remove each sparse-element property one by one. Because the object is in dictionary mode, this will result in a new shape being allocated for each property we remove. This is slow and adds unnecessary GC pressure; we can change this to allocate just a single new shape.

Densification is rare; most websites don't hit this code at all. However it's easy to fix and this refactoring will also make it easier to change this code for the ReShape work.

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1707562 part 1 - Use AutoCheckShapeConsistency in NativeObject::removeProperty. r?jonco!

Comment 2

[Jan de Mooij [:jandem]]

Attachment: Bug 1707562 part 2 - Handle non-dictionary property removal first with an early return. r?jonco!

Depends on D113347

Comment 3

[Jan de Mooij [:jandem]]

Attachment: Bug 1707562 part 3 - Rename freeSlot to freeDictionarySlot and simplify it a bit. r?jonco!

After the previous patch this is only called for dictionary objects.

The caller already has the ShapeTable it can pass in.

Depends on D113348

Comment 4

[Jan de Mooij [:jandem]]

Attachment: Bug 1707562 part 4 - Add NativeObject::densifySparseElements. r?jonco!

This is just moving code, no other changes.

Depends on D113349

Comment 5

[Jan de Mooij [:jandem]]

Attachment: Bug 1707562 part 5 - Add removeDictionaryPropertyWithoutReshape helper method. r?jonco!

Depends on D113350

Comment 6

[Jan de Mooij [:jandem]]

Attachment: Bug 1707562 part 6 - Use |continue| in densifySparseElements. r?jonco!

Depends on D113351

Comment 7

[Jan de Mooij [:jandem]]

Attachment: Bug 1707562 part 7 - Optimize sparse element densification. r?jonco!

Densify all properties and then assign a new shape to the object, instead of
allocating a new shape for each property being densified. This is faster and
avoids some GC pressure.

Depends on D113352

Comment 8

[Jan de Mooij [:jandem]]

Attachment: Bug 1707562 part 8 - Use HandleId for removeProperty argument. r?jonco!

Depends on D113353

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/6804ae862058
part 1 - Use AutoCheckShapeConsistency in NativeObject::removeProperty. r=jonco
https://hg.mozilla.org/integration/autoland/rev/9ca23b2a317a
part 2 - Handle non-dictionary property removal first with an early return. r=jonco
https://hg.mozilla.org/integration/autoland/rev/6e77fb213892
part 3 - Rename freeSlot to freeDictionarySlot and simplify it a bit. r=jonco
https://hg.mozilla.org/integration/autoland/rev/877d6461487e
part 4 - Add NativeObject::densifySparseElements. r=jonco
https://hg.mozilla.org/integration/autoland/rev/4b56f6c94f2e
part 5 - Add removeDictionaryPropertyWithoutReshape helper method. r=jonco
https://hg.mozilla.org/integration/autoland/rev/b5521fed2101
part 6 - Use |continue| in densifySparseElements. r=jonco
https://hg.mozilla.org/integration/autoland/rev/60ceda12b56d
part 7 - Optimize sparse element densification. r=jonco
https://hg.mozilla.org/integration/autoland/rev/a76135d2790a
part 8 - Use HandleId for removeProperty argument. r=jonco

Comment 10

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/6804ae862058
https://hg.mozilla.org/mozilla-central/rev/9ca23b2a317a
https://hg.mozilla.org/mozilla-central/rev/6e77fb213892
https://hg.mozilla.org/mozilla-central/rev/877d6461487e
https://hg.mozilla.org/mozilla-central/rev/4b56f6c94f2e
https://hg.mozilla.org/mozilla-central/rev/b5521fed2101
https://hg.mozilla.org/mozilla-central/rev/60ceda12b56d
https://hg.mozilla.org/mozilla-central/rev/a76135d2790a