1275248 - Use MustAlias in mightAlias

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect)

Description

[Hannes Verschore [:h4writer]]

Since flow alias analysis mightAlias can return 3 values. NoAlias, MayAlias and MustAlias. We currently don't use MustAlias. One of the next steps is to test for this in flow alias analysis. As a result it would be good to start using this.

This moves the logic from foldsTo to mightAlias. And foldsTo only checks if mightAlias is MustAlias to decide to replace it.

Comment 1

[Hannes Verschore [:h4writer]]

Attachment: Patch

Comment 2

[Jan de Mooij [:jandem]]

Comment on attachment 8755839 [details] [diff] [review]
Patch

Review of attachment 8755839 [details] [diff] [review]:
-----------------------------------------------------------------

::: js/src/jit/MIR.cpp
@@ +4908,5 @@
>  MDefinition*
>  MLoadUnboxedObjectOrNull::foldsTo(TempAllocator& alloc)
>  {
> +    if (MDefinition* def = foldsToStore(alloc)) {
> +        if (def->type() != MIRType::ObjectOrNull)

Can you add a comment explaining why we need the ObjectOrNull check?

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/67b41b80d37c
IonMonkey: Use MustAlias in Alias Analysis, r=jandem
https://hg.mozilla.org/integration/mozilla-inbound/rev/130a21afe562
IonMonkey: Don't alias loading of elements with different indexes, r=jandem

Comment 4

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/67b41b80d37c
https://hg.mozilla.org/mozilla-central/rev/130a21afe562