[FTL] Have a more generic fast path for compareStrictEq on Untyped/Untyped in FTLLowerDFGToB3

[Robin Morisset]

There is already such a path in the DFG, so currently the FTL is producing worse code than the DFG in this instance.

[Robin Morisset]

Technically there already is a fast path, but only for Int32/Int32.

[Robin Morisset]

Created attachment 430505 [details]
Patch

[Filip Pizlo]

Comment on attachment 430505 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=430505&action=review

> Source/JavaScriptCore/ChangeLog:23
> +        if (isCell(left) && isCell(right))

Isn't the thing that requires the slow path that both left and right are either strings or bigints?

[Robin Morisset]

Comment on attachment 430505 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=430505&action=review

>> Source/JavaScriptCore/ChangeLog:23
>> +        if (isCell(left) && isCell(right))
> 
> Isn't the thing that requires the slow path that both left and right are either strings or bigints?

Yes, but checking whether a Cell is either a HeapBigInt or a String would be quite a bit of code, so I am approximating here (going to the slow path even for things like Object == Object).
Note that I use the more precise condition when it comes to pruning that check with the abstract interpreter (so if we can prove it is Object == Object, we'll generate the ideal code without all of these checks).

[Radar WebKit Bug Importer]

<rdar://problem/79161356>