1114574 - Improve MCompare::tryFold

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect)

Description

[Jan de Mooij [:jandem]]

Attachment: Patch

I think the code was written before we had TypeSets in MIR instructions. Now we can rewrite it to use mightBeType, which is both simpler/shorter (no need to list all types) and more effective, because we can now fold things like:

(object|null) === undefined
(int32|string) === true

etc.

Comment 1

[Hannes Verschore [:h4writer]]

Comment on attachment 8540130 [details] [diff] [review]
Patch

Review of attachment 8540130 [details] [diff] [review]:
-----------------------------------------------------------------

Nice

::: js/src/jit/MIR.cpp
@@ +3017,5 @@
> +                *result = (op == JSOP_EQ);
> +                return true;
> +            }
> +            if (!lhs()->mightBeType(MIRType_Null) && !lhs()->mightBeType(MIRType_Undefined) &&
> +                !operandMightEmulateUndefined())

Nit: maybe put every test on a new line? So put "!lhs()->mightBeType(MIRType_Undefined) &&" on a new line. I find that easier to read.

Comment 2

[Jan de Mooij [:jandem]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/f8e5c5ed14cb

Comment 3

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/f8e5c5ed14cb