823465 - BaselineCompiler: Add string length stub

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Jan de Mooij [:jandem]]

Attachment: Patch

Comment 1

[Kannan Vijayan [:djvj]]

Comment on attachment 694321 [details] [diff] [review]
Patch

Review of attachment 694321 [details] [diff] [review]:
-----------------------------------------------------------------

::: js/src/ion/BaselineIC.cpp
@@ +348,5 @@
> +
> +            // Non-monitored stubs are used if the result has always the same type,
> +            // e.g. a StringLength stub will always return int32.
> +            if (!mainStub->isMonitored())
> +                continue;

This comment is not directly relevant to this patch, but the above code reminded me of this.

|DoGetPropFallback| should call |addMonitorStubForValue| on its TypeMonitor_Fallback stub, as |DoCallFallback| does, to avoid an extra trip to the type monitor fallback stub when some other monitored optimized stub ends up returning the same type.

Comment 2

[Jan de Mooij [:jandem]]

https://hg.mozilla.org/projects/ionmonkey/rev/7d714f0e176f

(In reply to Kannan Vijayan [:djvj] from comment #1)
>
> |DoGetPropFallback| should call |addMonitorStubForValue| on its
> TypeMonitor_Fallback stub, as |DoCallFallback| does, to avoid an extra trip
> to the type monitor fallback stub when some other monitored optimized stub
> ends up returning the same type.

The problem is that it may attach multiple stubs for the same type. We could check for existing stubs first, but just letting the fallback monitor path seems easier and shouldn't be noticeable. What do you think?