1626587 - Replace mozilla::IsPod with <type_traits> alternatives

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P2)

Description

[André Bargull [:anba]]

Unless needed for the mozilla::Vector POD optimisation, we should replace mozilla::IsPod with appropriate <type_traits> alternatives.

Comment 1

[André Bargull [:anba]]

Attachment: Bug 1626587 - Part 1: Replace mozilla::IsPod in LifoAlloc. r=jwalden!

Replace mozilla::IsPod with std::is_trivial and std::is_trivially_destructible,
which should cover the requirements for LifoAlloc. (std::is_trivial implies
is_trivially_default_constructible and is_trivially_copyable.)

IsPod<OffsetAndDefIndex> can then be removed.

Comment 2

[André Bargull [:anba]]

Attachment: Bug 1626587 - Part 2: Replace mozilla::IsPod in VectorPool. r=jwalden!

Similar to part 1, use both std::is_trivial and std::is_trivially_destructible
instead of mozilla::IsPod to ensure the vector elements are POD values, so we
can skip constructor/destructor calls.

There's no mozilla::IsPod specialisation to remove for this part.

Depends on D69198

Comment 3

[André Bargull [:anba]]

Attachment: Bug 1626587 - Part 3: Replace mozilla::IsPod in InlineTablePool. r=jwalden!

We can't use std::is_trivial for the table entry type, because the entry value
isn't trivially default constructible. (Neither mozilla::HashMapEntry nor
RecyclableAtomMapValueWrapper are trivially default constructible.)

So instead of using std::is_trivial<EntryType> directly, we have to check
std::is_trivial<KeyType> and std::is_trivial<ValueType> separately, where
we potentially need to unwrap ValueType in case it's
IsRecyclableAtomMapValueWrapper.

This allows to remove the mozilla::IsPod specialisations for NameLocation,
DeclaredNameInfo, MaybeCheckTDZ, and RecyclableAtomMapValueWrapper.

Depends on D69199

Comment 4

[André Bargull [:anba]]

Attachment: Bug 1626587 - Part 4: Remove mozilla::IsPod for HashMapEntry. r=jwalden!

The mozilla::IsPod<HashMapEntry specialisation was only needed for the static
assertions in "js/src/frontend/NameCollections.h". Part 3 removed those, so we
can now also remove mozilla::IsPod<HashMapEntry.

Drive-by change:

• Remove no longer needed "mozilla/PodOperations.h" include in mfbt/HashTable.h.
• And then fix up previously transitively included files for RootingAPI.h,
  jsfriendapi.h, and Bench.cpp.

Depends on D69200

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d49eebe62ba3
Part 1: Replace mozilla::IsPod in LifoAlloc. r=jwalden
https://hg.mozilla.org/integration/autoland/rev/1e75beb9d311
Part 2: Replace mozilla::IsPod in VectorPool. r=jwalden
https://hg.mozilla.org/integration/autoland/rev/239b37c87f58
Part 3: Replace mozilla::IsPod in InlineTablePool. r=jwalden
https://hg.mozilla.org/integration/autoland/rev/1e75de42137c
Part 4: Remove mozilla::IsPod for HashMapEntry. r=jwalden

Comment 6

[Stefan Hindli [:stefan_hindli]]

https://hg.mozilla.org/mozilla-central/rev/d49eebe62ba3
https://hg.mozilla.org/mozilla-central/rev/1e75beb9d311
https://hg.mozilla.org/mozilla-central/rev/239b37c87f58
https://hg.mozilla.org/mozilla-central/rev/1e75de42137c