Bug 198770 – [JSC] Polymorphic call stub's slow path should restore callee saves before performing tail call

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Yusuke Suzuki]

When linkPolymorphicCall gives up compiling polymorphic call, we fall back to virtual call. But `linkVirtualCall` does not restore the callee saves before calling the tail call, while polymorphic call does it.
If the caller CodeBlock clobbers the callee saves (e.g. FTL), we forget restoring it, and caller's caller will see garbage in callee saves.

[Yusuke Suzuki]

And polymorphic call stub's slow path seems not restoring it too.

[Yusuke Suzuki]

<rdar://problem/51260313>

[Yusuke Suzuki]

Created attachment 371914 [details]
Patch

[Yusuke Suzuki]

The change of virtual call is not necessary. Only polymorphic call is problematic.

[Yusuke Suzuki]

Created attachment 371934 [details]
Patch

[Yusuke Suzuki]

Created attachment 371935 [details]
Patch

[Saam Barati]

Comment on attachment 371934 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=371934&action=review

> Source/JavaScriptCore/ChangeLog:30
> +        This patch does that skips after restoring callee saves.

“does that skips” => “makes branches to the slow path happen”

> JSTests/stress/poly-call-stub-slow-path-should-restore-callee-saves-when-doing-tail-call.js:5
> +        var a = WeakSet.bind();

Maybe also two other tests:
- One where the poly call is in the test itself instead of a built in (in case we change the built in in the future)
- A test with a non cell callee

[Saam Barati]

Comment on attachment 371935 [details]
Patch

r=me with comments from previous patch

[Yusuke Suzuki]

Comment on attachment 371934 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=371934&action=review

Thanks!

>> Source/JavaScriptCore/ChangeLog:30
>> +        This patch does that skips after restoring callee saves.
> 
> “does that skips” => “makes branches to the slow path happen”

Fixed.

>> JSTests/stress/poly-call-stub-slow-path-should-restore-callee-saves-when-doing-tail-call.js:5
>> +        var a = WeakSet.bind();
> 
> Maybe also two other tests:
> - One where the poly call is in the test itself instead of a built in (in case we change the built in in the future)
> - A test with a non cell callee

Nice, added.

[Yusuke Suzuki]

Committed r246372: <https://trac.webkit.org/changeset/246372>