RFR: JDK-8318485: Narrow klass shift should be zero if encoding range extends to 0x1_0000_0000 [v2]

[Calvin Cheung]

On Mon, 23 Oct 2023 11:59:07 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> test/hotspot/jtreg/runtime/CompressedOops/CompressedClassPointersEncodingScheme.java line 78:
>> 
>>> 76:         test(4 * G - 128 * M, 128 * M, 0, 0);
>>> 77: 
>>> 78:         // add more...
>> 
>> The following works on my linux dev host.
>> 
>>         test(0xa0000000L, 1 * G, 0, 0);
>>         test(0x100000000L, 2 * G, 0, 3);
>> 
>> Maybe you can consider adding them to the test?
>
> I'd rather expand this in a separate RFE. Second one *should* work on all platforms, but I am not 100% sure some would encode this with base=4g shift=0 instead. Probably not, but it is better to stay focused on one issue. Makes also for clearer backporting.

That's fine.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/16261#discussion_r1368901907