On Fri, 17 Mar 2023 15:38:49 GMT, Doug Simon <[email protected]> wrote:
>> This PR extends JVMCI with new API (`jdk.vm.ci.meta.Annotated`) for
>> accessing annotations. The main differences from
>> `java.lang.reflect.AnnotatedElement` are:
>> * All methods in the `Annotated` interface explicitly specify requested
>> annotation type(s). That is, there is no equivalent of
>> `AnnotatedElement.getAnnotations()`.
>> * Annotation data is returned in a map-like object (of type
>> `jdk.vm.ci.meta.AnnotationData`) instead of in an `Annotation` object. This
>> works better for libgraal as it avoids the need for annotation types to be
>> loaded and included in libgraal.
>>
>> To demonstrate the new API, here's an example in terms
>> `java.lang.reflect.AnnotatedElement` (which `ResolvedJavaType` implements):
>>
>> ResolvedJavaMethod method = ...;
>> ExplodeLoop a = method.getAnnotation(ExplodeLoop.class);
>> return switch (a.kind()) {
>> case FULL_UNROLL -> LoopExplosionKind.FULL_UNROLL;
>> case FULL_UNROLL_UNTIL_RETURN ->
>> LoopExplosionKind.FULL_UNROLL_UNTIL_RETURN;
>> ...
>> }
>>
>>
>> The same code using the new API:
>>
>>
>> ResolvedJavaMethod method = ...;
>> ResolvedJavaType explodeLoopType = ...;
>> AnnotationData a = method.getAnnotationDataFor(explodeLoopType);
>> return switch (a.getEnum("kind").getName()) {
>> case "FULL_UNROLL" -> LoopExplosionKind.FULL_UNROLL;
>> case "FULL_UNROLL_UNTIL_RETURN" ->
>> LoopExplosionKind.FULL_UNROLL_UNTIL_RETURN;
>> ...
>> }
>>
>>
>> The implementation relies on new methods in `jdk.internal.vm.VMSupport` for
>> parsing annotations and serializing/deserializing to/from a byte array. This
>> allows the annotation data to be passed from the HotSpot heap to the
>> libgraal heap.
>
> Doug Simon has updated the pull request incrementally with one additional
> commit since the last revision:
>
> [skip ci] formatting fixes
A few higher-level comments:
>From the long-term perspective, it is likely that the set of kinds of elements
>that can occur in an annotation will be expanded, for example, method
>references are a repeated request. Easing future maintenance to gives more
>inter-source linkage in this situation and error handling for this case in the
>libgraal code would be prudent IMO.
The java.lang.reflect.AnnotatedElement API
(https://docs.oracle.com/en/java/javase/20/docs/api/java.base/java/lang/reflect/AnnotatedElement.html)
defines different ways an annotation can be affiliated with an element:
"The terms directly present, indirectly present, present, and associated are
used throughout this interface to describe precisely which annotations are
returned by methods: "
tl;dr these terms relate to which of inheriting annotations and looking through
repeated annotations the methods do on behalf of the caller. I think the
methods should phrase their operations in terms of these concepts, such as
"Construct the annotations present..." since inheritance is taken into account.
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PR Comment: https://git.openjdk.org/jdk/pull/12810#issuecomment-1511735022
