1604760 - Remove unreachable code in JSFunction::isDerivedClassConstructor testing for self-hosted lazy scripts

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P2)

Description

[André Bargull [:anba]]

Default class constructors have their SELF_HOSTED flag cleared in js::MakeDefaultConstructor, which means JSFunction::hasSelfHostedLazyScript() when called in JSFunction::isDerivedClassConstructor always returns false, cf. hasSelfHostedLazyScript and isSelfHostedOrIntrinsic:

bool hasSelfHostedLazyScript() const {
  return isInterpretedLazy() && isSelfHostedOrIntrinsic();
}

bool isSelfHostedOrIntrinsic() const {
  return hasFlags(SELF_HOSTED);
}

Comment 1

[André Bargull [:anba]]

Attachment: Bug 1604760: Remove unreachable code in JSFunction::isDerivedClassConstructor testing for self-hosted lazy scripts. r=tcampbell!

Additionally assert we don't try to relazify default class constructors, so it's
more clear we don't have to worry about this case in isDerivedClassConstructor().

We don't relaziy default class constructors, because JSScript::canRelazify()
returns false for these functions. canRelazify() requires either a lazy
script (default class constructors originate from self-hosted code, so they
don't have a lazy script) or a script with ImmutableFlags::SelfHosted set.
But ImmutableFlags::SelfHosted is cleared from default class constructors in
JSScript::setDefaultClassConstructorSpan().

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/a52aae1039fc
Remove unreachable code in JSFunction::isDerivedClassConstructor testing for self-hosted lazy scripts. r=tcampbell

Comment 3

[Andrei Ciure[:aciure]]

https://hg.mozilla.org/mozilla-central/rev/a52aae1039fc