RFR: 6983726: Reimplement MethodHandleProxies.asInterfaceInstance [v18]

[Mandy Chung]

On Tue, 27 Jun 2023 16:33:11 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 updates the WrapperInstance methods to take an `Empty` to avoid method clashes
>> 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 faster than old implementation in general.
>> 
>> Benchmark for revision 17:
>> 
>> Benchmark                                                          Mode  Cnt      Score       Error  Units
>> MethodHandleProxiesAsIFInstance.baselineAllocCompute               avgt   15      1.503 ±     0.021  ns/op
>> MethodHandleProxiesAsIFInstance.baselineCompute                    avgt   15      0.269 ±     0.005  ns/op
>> MethodHandleProxiesAsIFInstance.testCall                           avgt   15      1.806 ±     0.018  ns/op
>> MethodHandleProxiesAsIFInstance.testCreate                         avgt   15     17.332 ±     0.210  ns/op
>> MethodHandleProxiesAsIFInstance.testCreateCall                     avgt   15     19.296 ±     1.371  ns/op
>> MethodHandleProxiesAsIFInstanceCall.callDoable                     avgt    5      0.419 ±     0.004  ns/op
>> MethodHandleProxiesAsIFInstanceCall.callHandle                     avgt    5      0.421 ±     0.004  ns/op
>> MethodHandleProxiesAsIFInstanceCall.callInterfaceInstance          avgt    5      1.731 ±     0.018  ns/op
>> MethodHandleProxiesAsIFInstanceCall.callLambda                     avgt    5      0.418 ±     0.003  ns/op
>> MethodHandleProxiesAsIFInstanceCall.constantDoable                 avgt    5      0.263 ±     0.003  ns/op
>> MethodHandleProxiesAsIFInstanceCall.constantHandle                 avgt    5      0.262 ±     0.002  ns/op
>> MethodHandleProxiesAsIFInstanceCall.constantInterfaceInstance      avgt    5      0.262 ±     0.002  ns/op
>> MethodHandleProxiesAsIFInstanceCall.constantLambda                 avgt    5      0.267 ±     0.019  ns/op
>> MethodHandleProxiesAsIFInstanceCall.direct                         avgt    5      0.266 ±     0.013  ns/op
>> MethodHandleProxiesAsIFInstanceCreate.createCallInterfaceInstance  avgt    5     18.057 ±     0.182 ...
>
> Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 38 commits:
> 
>  - SecurityManager fixed, minimize changes
>  - Merge branch 'master' into explore/mhp-iface
>  - Some changes per Mandy's review. SecurityManager test fails in this patch
>  - Merge branch 'master' into explore/mhp-iface
>  - Merge branch 'master' into explore/mhp-iface
>  - Merge branch 'master' into explore/mhp-iface
>  - stage, needs to fix is mh proxy instance check
>  - Merge branch 'master' into explore/mhp-iface
>  - Remove assertion, no longer true with teleport definition in MHP
>  - Fix tabs, and tests about modules and constructor access
>  - ... and 28 more: https://git.openjdk.org/jdk/compare/05e9c41e...07cc1279

Thanks for the update.

src/java.base/share/classes/java/lang/invoke/MethodHandleProxies.java line 481:

> 479:             MethodHandle originalTypeField;
> 480:             try {
> 481:                 originalTypeField = new Lookup(type).findStaticGetter(type, ORIGINAL_TYPE_NAME, Class.class);

If some random class `X` has the field "originalType" with value `I`, `isWrapperClass` would cause spinning a MH proxy class `I` as it calls `getProxyClassInfo` and return true.   `getProxyClassInfo` should be only called from `asInterfaceInstance`.

I think this can be done by having a `WeakHashMap<Class<?>, Boolean>` and `getProxyClassInfo` puts an entry with `TRUE` when a new proxy class is generated.

test/jdk/java/lang/reflect/Proxy/ProxyModuleMapping.java line 42:

> 40:         // unnamed module gets access to sun.invoke package (e.g. via --add-exports)
> 41:         new ProxyModuleMapping(sun.invoke.WrapperInstance.class).test();
> 42: 

The test case is to verify that proxy can access qualified exports.   So better to keep this test case and replace with an internal interface e.g. `jdk.internal.misc.VM.BufferPool`?

-------------

PR Review: https://git.openjdk.org/jdk/pull/13197#pullrequestreview-1503496814
PR Review Comment: https://git.openjdk.org/jdk/pull/13197#discussion_r1245624265
PR Review Comment: https://git.openjdk.org/jdk/pull/13197#discussion_r1245462594