1853235 - Avoid repeated null checks and mIsAnyMemberPresent assignments in dictionary initializers (e.g. EventModifierInit::Init)

Status: NEW

(Core :: DOM: Bindings (WebIDL), enhancement)

Description

[Markus Stange [:mstange]]

Here's the generated code for EventModifierInit::Init: https://searchfox.org/mozilla-central/source/__GENERATED__/dom/bindings/UIEventBinding.cpp#253

You can see that it has lots of repeated if (!isNull) { ... } checks and mIsAnyMemberPresent = true; assignments.

In the profile in bug 1851236, some samples are associated with those mIsAnyMemberPresent lines, so it seems that the repeated assignments are not optimized out, and probably the isNull checks aren't either.

It may improve things a tiny bit if we tightened this up a bit. For example, if we only have one mIsAnyMemberPresent = true; assignment after the first property, then the remaining individual isNull checks will probably get folded into one check by the compiler.