Classfile API AttributedElement.Kind removal proposal

[Adam Sotona]

Actually we have no use case to benchmark.
Newly proposed code simply does not check for appropriate “where applicable” during bound attributes parsing and passes the Attribute instance on anyway. There was no other use of that information across the Classfile API.

Alternatively I can implement the check by single switch asking if the provided attribute is instanceof XyzElement according to the enclosing AttributedEleement type, and exchange it for UnknownAttribute if not appropriate. In comparison to Set::contains there should be no regression.

From: Brian Goetz <brian.goetz at oracle.com>
Date: Tuesday, 7 February 2023 16:02
To: Adam Sotona <adam.sotona at oracle.com>, classfile-api-dev at openjdk.org <classfile-api-dev at openjdk.org>
Subject: Re: Classfile API AttributedElement.Kind removal proposal
Just a little bit of history here.  We started writing this API before we had pattern support in the language, so we used the classic trick of having an enum constant per node type that could be switched over.  When patterns came along, we thought about removing them, but we were still a little diffident as we knew that the cost of switching over types was higher than switching over enums, and worried about performance-sensitive transformation code.

I wouldn't mind seeing a quick microbench comparing switching over bytecodes the two different ways, just to see if it still shows up on the profile.
On 2/7/2023 9:33 AM, Adam Sotona wrote:
Hi,
Based on discussion in the Classfile API PR: https://github.com/openjdk/jdk/pull/10982#discussion_r1098601988

I would like to propose removal of AttributedElement.Kind across all Classfile API.
The AttributedElement.Kind models Attributes “where applicable” and it is a duplication of each Attribute extending ClassElement, MethodElement, CodeElement, etc…

Classfile API is not actively using the AttributedElement.Kind except for parsing, where inappropriate AttributedElement.Kind is resolved as UnknownAttribute.

Following proposal removes all usages of AttributedElement.Kind from Classfile API:
https://github.com/openjdk/jdk-sandbox/pull/48/files

Please let me know is there are any objections.

Thanks,
Adam





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