On Fri, 24 Mar 2023 08:35:06 GMT, ExE Boss <d...@openjdk.org> wrote:
>> Per Minborg has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> Improve javadocs for Linker::captureStateLayout
>
> src/java.base/share/classes/jdk/internal/foreign/abi/SharedUtils.java line
> 297:
>
>> 295: MethodType mtype = mh.type();
>> 296: int[] perms = new int[mtype.parameterCount()];
>> 297: MethodType swappedType =
>> MethodType.methodType(mtype.returnType());
>
> Instead of `MethodType::appendParameterTypes(…)` (which performs an expensive
> lookup of a new cached `MethodType` value per call), this method should
> instead use a `Class<?>[]` for the arguments, which avoids that overhead
> inside a loop:
>
> public static MethodHandle swapArguments(MethodHandle mh, int firstArg,
> int secondArg) {
> MethodType mtype = mh.type();
> int[] perms = new int[mtype.parameterCount()];
> Class<?>[] ptypes = new Class<?>[perms.length];
> for (int i = 0 ; i < perms.length ; i++) {
> int dst = i;
> if (i == firstArg) dst = secondArg;
> else if (i == secondArg) dst = firstArg;
> perms[i] = dst;
> ptypes[i] = mtype.parameterType(dst);
> }
> // This should use `JavaLangInvokeAccess` to invoke the internal
> // `MethodType.methodType(Class<?> rtype, Class<?>[] ptypes,
> boolean trusted)`
> // method with a `trusted` value of `true`:
> MethodType swappedType =
> MethodType.methodType(mtype.returnType(), ptypes);
> return permuteArguments(mh, swappedType, perms);
> }
Thanks for this enhancement proposal. I hope you do not mind me asking if you
could file a separate issue about this where you describe the above? We can
then merge that proposal independent of this PR.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/13079#discussion_r1150341545
