On Fri, 8 Apr 2022 12:20:32 GMT, Claes Redestad <[email protected]> wrote:
>> A few additional enhancements aiming to improve VH performance in the
>> interpreter:
>>
>> - Flatten `TypeAndInvokers`: adds a pointer to `VarHandle` (a small increase
>> 40->48) but removes an object and an indirection on any instance actually
>> used - and might avoid allocating the `MethodHandle[]` unnecessarily on some
>> instances
>> - Have `checkExactAccessMode` return the directness of the `VarHandle` so
>> that we can avoid some `isDirect` method calls.
>>
>> Baseline, `-Xint`
>>
>> Benchmark Mode Cnt Score Error Units
>> VarHandleExact.exact_exactInvocation avgt 30 478.324 ? 5.762 ns/op
>> VarHandleExact.generic_exactInvocation avgt 30 392.114 ? 1.644 ns/op
>> VarHandleExact.generic_genericInvocation avgt 30 822.484 ? 1.865 ns/op
>>
>>
>> Patched, `-Xint`
>>
>> Benchmark Mode Cnt Score Error Units
>> VarHandleExact.exact_exactInvocation avgt 30 437.704 ? 5.320 ns/op
>> VarHandleExact.generic_exactInvocation avgt 30 374.512 ? 3.154 ns/op
>> VarHandleExact.generic_genericInvocation avgt 30 757.054 ? 1.237 ns/op
>>
>>
>> No significant performance difference in normal mode.
>
> Claes Redestad has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Simplified as suggested by @ExE-Boss
How would the performance change if the `isDirect` and `checkExactAccessMode`
merger was reverted?
src/java.base/share/classes/java/lang/invoke/VarHandle.java line 2075:
> 2073:
> 2074: @DontInline
> 2075: final void throwWrongMethodTypeException(VarHandle.AccessDescriptor
> ad) {
This can actually be `private` and `static`:
Suggestion:
private static final void
throwWrongMethodTypeException(VarHandle.AccessDescriptor ad) {
src/java.base/share/classes/java/lang/invoke/VarHandles.java line 719:
> 717: //
> MethodHandle.linkToStatic(<LINK_TO_STATIC_ARGS>);
> 718: // } else {
> 719: // MethodHandle mh =
> handle.getMethodHandle(ad.mode);
The `direct`‑ness check can be hoisted into an enclosing `if` statement:
Suggestion:
// if (direct) {
// if (handle.vform.methodType_table[ad.type] ==
ad.symbolicMethodTypeErased) {
// MethodHandle.linkToStatic(<LINK_TO_STATIC_ARGS>);
// return;
// } else if (handle.vform.getMethodType_V(ad.type) ==
ad.symbolicMethodTypeErased) {
// MethodHandle.linkToStatic(<LINK_TO_STATIC_ARGS>);
// return;
// }
// }
// MethodHandle mh = handle.getMethodHandle(ad.mode);
Also, any reason `GUARD_METHOD_TEMPLATE_V` uses `LINK_TO_STATIC_ARGS` instead
of `LINK_TO_STATIC_ARGS_V`?
-------------
PR: https://git.openjdk.java.net/jdk/pull/8160
