Review request for JDK-8025435

[Marcus Lagergren]

Please review JDK-8025435 at http://cr.openjdk.java.net/~lagergren/8025435/

https://bugs.openjdk.java.net/browse/JDK-8025435

This is the framework for optimistic builtin functions. Summary of work

* Introduced SpecializedFunction and SpecializedFunction.Guard for fast optimistic implementations
* Modified ScriptFunction so that it picks the best specialization first, and checks if it can link using the above datastructures
* Modified Nasgen to recognize the SpecializedFunction and its annotations
* Implemented fast versions of Array.push/pop and String.charCodeAt as proof of concepts
* Added a switchpoint based rather than guard based framework for invalidation of builtin functions (on a per context basis), to get rid of previous guard overhead
* Added primitive linkage without proto filter as long as builtins acting upon them haven’t been rewritten
* Currently there is support for invalidation of both entire builtins e.g. Array.prototype = something and proerties Array.prototype.push = something, but the granularity right now, to save switchpoints, uses the same switchpoint for an entire builtin and all its properties, as any other cases are rare. Granularity can easily be increased by adding keys to the builtinSwitchPoints table in the Context
* Prefer to invalidate callsite by ClassCastException and failed type checks instead of explicit guards.

I’m saving further specializations for later dates.

Added various microbenchmarks to prove performance of the implementations of the current functions.

Before patch:

zann:make marcus$ sh ../bin/runopt.sh ../test/examples/push-pop-benchmark.js
18997 ms

Verified OK - result is correct

After patch:

zann:make marcus$ sh ../bin/runopt.sh ../test/examples/push-pop-benchmark.js
2327 ms

Verified OK - result is correct
zann:make marcus$ d8 ../test/examples/push-pop-benchmark.js
9672 ms

Verified OK - result is correct

Similar benchmark exists for charCodeAt - my other proof of concept, which runs about 5x faster too. 

Test and test262 are clean after some horror corner cases with lengths and array like objects.

Regards
Marcus