RFR: 8304932: MethodTypeDescImpl can be mutated by argument passed to MethodTypeDesc.of

[Chen Liang]

On Sun, 26 Mar 2023 05:23:54 GMT, Chen Liang <liach at openjdk.org> wrote:

> Fixed the bug where if a caller keeps a reference to the array passed into `MethodTypeDesc.of`, the caller may mutate the Desc via the array and can create invalid MethodTypeDesc.
> 
> Unfortunately, since the input array now needs to be copied, the `of` factory suffers from a performance drop. But otherwise, this patch has minor performance gains on `ofDescriptor` factory, even compared to Adam's patch that optimized `ofDescriptor` in #12945.
> 
> This patch moves the parameters to an immutable list, to avoid allocations on `parameterList` as well.
> 
> Benchmark of Oracle JDK 20: https://gist.github.com/683c6219e183cbc2b336224fc2c0d50a
> Benchmark of this patch: https://gist.github.com/22be9371a2370fb4a7b44f1684750ec4
> Benchmark of [asotona's patch](https://github.com/openjdk/jdk/pull/12945/files#diff-ac8e413d3e13532a2b0d34a90253c6ddd7a4f04082f792b9d076e9b5a33f2078): https://gist.github.com/eb98579c3b51cafae481049a95a78f80
> 
> [sotona vs this](https://jmh.morethan.io/?gists=eb98579c3b51cafae481049a95a78f80,22be9371a2370fb4a7b44f1684750ec4); [20 vs this](https://jmh.morethan.io/?gists=683c6219e183cbc2b336224fc2c0d50a,22be9371a2370fb4a7b44f1684750ec4); [20 vs sotona](https://jmh.morethan.io/?gists=683c6219e183cbc2b336224fc2c0d50a,eb98579c3b51cafae481049a95a78f80), for reference

Additional comments:
1. Maybe it's feasible to add another factory:

static MethodTypeDesc of(ClassDesc returnType, List<ClassDesc> parameterTypes) {
    return new MethodTypeDescImpl(returnType, List.copyOf(parameterTypes));
}

which would avoid another copy if `parameterTypes` is already a list from `List.of` factories.

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PR Comment: https://git.openjdk.org/jdk/pull/13186#issuecomment-1484001253