RFR: 8266530: HotSpot changes for JEP 306 [v7]

[Joe Darcy]

Hi David,

Yes; this state of the changes reflects the final spec.

Thanks,

-Joe

On 5/18/2021 7:45 PM, David Holmes wrote:
> On Wed, 19 May 2021 00:30:10 GMT, Joe Darcy <darcy at openjdk.org> wrote:
>
>>> Please review these VM changes in support of JEP 306: Restore Always-Strict Floating-Point Semantics.
>>>
>>> JEP 306 is considering the following changes to the JVMS:
>>>
>>> 1) Require "strict" floating-point evaluation in all circumstances.
>>> 2) For class file version 61 and higher, undefine ACC_STRICT, moving that bit position back to undefined for methods. For class file versions, 46 through, ACC_STRICT would remain a defined modifier.
>>>
>>> Since all floating-point evaluation is done strictly, a modifier bit is not needed to indicate this anymore. There are a few mandated modifier checks when ACC_STRICT is defined, such as not allowing an "abstract strictfp" method. These checks in classFileParser are now conditional on the class file version.
>>>
>>> The tests verify  "abstract strictfp" triggers a ClassFormatError  for version 60 and does not trigger an error or exception for version 61. (As an undefined bit in version 61, the VM is supposed to ignore it.)
>>>
>>> FYI, the javac and core libs portions of JEP 306 are out for review under https://github.com/openjdk/jdk/pull/3831.
>>>
>>> The HotSpot and javac/core libs parts of JEP 306 are independent in that neither relies on the other:
>>>   * javac will not output class files which expose the difference in class parsing behavior; the ACC_STRICT modifier will not be set in any version 61 class file emitted by javac.
>>>   *  since HotSpot already does all floating-point evaluation strictly, no changes are needed to support strict evaluation.
>> Joe Darcy has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains ten additional commits since the last revision:
>>
>>   - Respond to review feedback.
>>   - Merge branch 'master' into 8266530
>>   - Restore previous is_strict cdoe in method.hpp.
>>   - Merge branch 'master' into 8266530
>>   - Make methods strict on IA32.
>>   - Merge branch 'master' into 8266530
>>   - Merge branch 'master' into 8266530
>>   - Respond to review feedback.
>>   - 8266530: HotSpot changes for JEP 306
> Latest update seems fine.
>
> Approving under the assumption these changes reflect the final spec.
>
> Thanks,
> David
>
> -------------
>
> Marked as reviewed by dholmes (Reviewer).
>
> PR: https://git.openjdk.java.net/jdk/pull/3891