RFR: 6983726: remove Proxy from MethodHandleProxies.asInterfaceInstance SAM conversion

[Rémi Forax]

On Mon, 27 Mar 2023 23:34:52 GMT, Chen Liang <liach at openjdk.org> wrote:

> As John Rose has pointed out in this issue, the current j.l.r.Proxy based implementation of MethodHandleProxies.asInterface has a few issues:
> 1. Exposes too much information via Proxy supertype (and WrapperInstance interface)
> 2. Does not allow future expansion to support SAM[^1] abstract classes
> 3. Slow (in fact, very slow)
> 
> This patch addresses all 3 problems:
> 1. It implements proxies with one hidden class for each requested interface and replaced WrapperInstance inheritance with an annotation. This can avoid unexpected passing of `instanceof`, and avoids the nasty problem of exporting a JDK interface to a dynamic module to ensure access.
> 2. This patch obtains already generated classes from a ClassValue by the requested interface type; the ClassValue can later be updated to compute implementation generation for abstract classes as well.
> 3. This patch's generated hidden classes has acceptable call and creation performance compared to the baseline; though the methods to access wrapper information see huge performance drops, they are not anticipated to be used in a very frequent basis, while the old implementation's wrapper access methods are more optimized (2ns/op) than interface implementation methods (6ns/op). [Oracle JDK 20 vs this](https://jmh.morethan.io/?gists=bf98de7b2128e7e5d14e697fd9921eb9,e5115a2a8fa0a45159e15fab0d95b5d8)
> 
> Additionally, an obsolete `ProxyForMethodHandle` test was removed, for it's no longer applicable. Tests in `jdk/java/lang/invoke` and `jdk/java/lang/reflect` pass.
> 
> Alternative implementation:
> [An alternative implementation](https://github.com/openjdk/jdk/commit/72dbf9d4e01c455854d9b865cb2a47c38f37a8e0) was to generate a proxy class for each methodhandle than sharing across methodhandles. That implementation was abandoned for its bad proxy creation performance, despite it having excellent call performance. [Alternative implementation vs this](https://jmh.morethan.io/?gists=08abb39f224574550925beb8be1b2f59,e5115a2a8fa0a45159e15fab0d95b5d8)
> 
> In addition, I have a question: in [8161245](https://bugs.openjdk.org/browse/JDK-8161245) it seems some fields can be optimized as seen in [ciField.cpp](https://github.com/openjdk/jdk/blob/6aec6f3a842ead30b26cd31dc57a2ab268f67875/src/hotspot/share/ci/ciField.cpp#L219). Does it affect the execution performance of MethodHandle in hidden classes' Condy vs. MethodHandle in regular final field in hidden classes?
> 
> [^1]: single abstract method

src/java.base/share/classes/java/lang/invoke/MethodHandleProxies.java line 206:

> 204:         try {
> 205:             proxy = (Object) info.ctor.invokeExact(mhs); // non-varargs
> 206:         } catch (Throwable e) {

At least Error should be directly propagated (especially OutOfMemoryError)

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PR Review Comment: https://git.openjdk.org/jdk/pull/13197#discussion_r1150405757