1624793 - Simplify MThrow

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, task, P1)

Description

[Jan de Mooij [:jandem]]

Ion code for JSOp::Throw is complicated. We can clean this all up by making MThrow a plain, non-control instruction with its own resume point and then use MUnreachable as the control instruction terminating the block.

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1624793 part 1 - Simplify MThrow and IonBuilder::visitThrow. r?iain!

The changes:

• Make MThrow a non-control-instruction (followed by the MUnreachable control instruction).
• This allows us to remove the separate MNop and attach the resume point to MThrow itself.
• WarpBuilder only allows resumeAfter() on effectful instructions, so make sure MThrow isEffectful() by giving it a store AliasSet.

Comment 2

[Jan de Mooij [:jandem]]

Attachment: Bug 1624793 part 2 - Do the same thing for MThrowRuntimeLexicalError. r?iain!

We can now easily terminate the block for JSOp::ThrowSetConst too.

In theory we could also terminate the block after the MThrowRuntimeLexicalError
added in IonBuilder::addLexicalCheck, but because that depends on type information
instead of being a static property of the bytecode I'm not completely sure it's
always safe (considering arguments/definite-properties analysis, for example).

Depends on D68164

Comment 3

[Jan de Mooij [:jandem]]

Attachment: Bug 1624793 part 3 - Handle JSOp::ThrowSetConst in BytecodeFallsThrough. r?iain!

Just a drive-by change to be more consistent with JSOp::Throw and JSOp::ThrowMsg.
It also results in slightly more compact code in Baseline Interpreter and JIT.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f0a1f1eade8b
part 1 - Simplify MThrow and IonBuilder::visitThrow. r=iain
https://hg.mozilla.org/integration/autoland/rev/635cc9ec177c
part 2 - Do the same thing for MThrowRuntimeLexicalError. r=iain
https://hg.mozilla.org/integration/autoland/rev/f72280a54c6e
part 3 - Handle JSOp::ThrowSetConst in BytecodeFallsThrough. r=iain

Comment 5

[Alexandru Michis [:malexandru]]

https://hg.mozilla.org/mozilla-central/rev/f0a1f1eade8b
https://hg.mozilla.org/mozilla-central/rev/635cc9ec177c
https://hg.mozilla.org/mozilla-central/rev/f72280a54c6e