On Mon, 22 Sep 2025 08:02:57 GMT, Johan Sjölen <[email protected]> wrote:
>> Hi,
>>
>> This is a refactoring of the way that we store the Bootstrap method
>> attribute in the ConstantPool class. We used to have a single `Array<u2>`
>> which was divided into a section of `u4` offsets and a section which was the
>> actual data. In this refactoring we make this split more clear, by actually
>> allocating an `Array<u4>` to store the offsets in and an `Array<u2>` to
>> store the data in. These arrays are then put into a `BSMAttributeEntries`
>> class, which allows us to separate out the API from that of the rest of the
>> `ConstantPool`.
>>
>> We had multiple instances of the code knowing the layout of the operands
>> array and using this to do 'clever' ways of copying and inserting data into
>> it. See `ConstantPool::copy_operands` and `ConstantPool::resize_operands`. I
>> felt like we could do things in a simpler way, so I added the
>> `start_/end_extension` protocol and added the `InsertionIterator` for this.
>> See `ClassFileParser::parse_classfile_bootstrap_methods_attribute` for how
>> this works. I put several relevant definitions into the inline file in hopes
>> of encouraging the compiler to optimize these appropriately.
>>
>> For the Java SA code, I had to add a `U4Array` class. I also had to fix the
>> vmstructs definitions, etc.
>>
>> On the whole, while this code is a bit less terse, I think it's a good API
>> improvement and the underlying implementation of splitting up the operands
>> array is also an improvement.
>>
>> Testing: Oracle Tier1-Tier5 has been run succesfully multiple times. Before
>> integration, I will merge with master and run these tiers again.
>
> Johan Sjölen has updated the pull request incrementally with two additional
> commits since the last revision:
>
> - Merge remote-tracking branch 'origin/operands-again' into operands-again
> - Fix BSM naming
src/hotspot/share/prims/jvmtiClassFileReconstituter.cpp line 393:
> 391: void JvmtiClassFileReconstituter::write_bootstrapmethod_attribute() {
> 392: write_attribute_name_index("BootstrapMethods");
> 393: u4 length = sizeof(u2) + // Size of num_bootstrap_methods
Nit: The comment update is confusing. Should it remain as it was? :
u4 length = sizeof(u2); // num_bootstrap_methods
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PR Review Comment: https://git.openjdk.org/jdk/pull/27198#discussion_r2371115648
