RFR: JDK-8323497: On x64, use 32-bit immediate moves for narrow klass base if possible [v3]

[Thomas Stuefe]

On Tue, 20 Feb 2024 11:16:29 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Thomas Stuefe 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 four additional commits since the last revision:
>> 
>>  - Merge branch 'openjdk:master' into use-32bit-immediate-moves-on-x64-for-klass-encoding-base
>>  - Merge branch 'openjdk:master' into use-32bit-immediate-moves-on-x64-for-klass-encoding-base
>>  - remove obsolete comment
>>  - use-32bit-immediate-moves-on-x64-for-klass-encoding-base
>
> src/hotspot/cpu/x86/compressedKlass_x86.cpp line 44:
> 
>> 42:       result = reserve_address_space_for_zerobased_encoding(size, aslr);
>> 43:     }
>> 44:   } else {
> 
> This should be:
> 
>     if (result == nullptr) {
>         // If we cannot use zero-based encoding (when CDS is enabled), optimizing for an
>         ...
>     }

I don't think so. Why?

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PR Review Comment: https://git.openjdk.org/jdk/pull/17340#discussion_r1497027400