848319 - IonMonkey: Use MRegExp::UseSource instead of MRegExp::UseClone

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Hannes Verschore [:h4writer]]

A MRegExp cannot get moved, unless it is flagged not being cloned, i.e. UseSource. It is actually very simple to enable moving, without doing something wrong. We only need to make sure re.lastIndex is correct. Therefore adding a MStoreFixedSlot to set lastIndex to 0 is enough. MRegExp can get hoisted, as long as the MStoreFixedSlot isn't.

Comment 1

[Hannes Verschore [:h4writer]]

Attachment: Enable hoisting MRegExp

Like we discussed. Setting lastIndex to 0 on the place the MRegExp would be created. This yields only a 1% increase on v8-regexp, though. But it's very simple change.

Comment 2

[Sean Stangl [:sstangl]]

Comment on attachment 721681 [details] [diff] [review]
Enable hoisting MRegExp

Review of attachment 721681 [details] [diff] [review]:
-----------------------------------------------------------------

::: js/src/ion/IonBuilder.cpp
@@ +6890,5 @@
>      current->push(ins);
>  
> +    // MRegExp::UseSource makes the regexp moveable.
> +    // That would be incorrect for global/sticky, because lastIndex could be wrong.
> +    // Therefore setting the lastIndex to 0. That is faster than using MRegExp::UseClone.

Previously, the only used option was UseClone, but now the only option is UseSource. Since nothing even bothers checking these options, could we just remove the parameter?

Comment 3

[Hannes Verschore [:h4writer]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/738733ab166d

Comment 4

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/738733ab166d