RFR: JDK-8320368: Per-CPU optimization of Klass range reservation [v2]

[Thomas Stuefe]

On Wed, 22 Nov 2023 09:49:56 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Thomas Stuefe has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Merge branch 'JDK-8320368-Per-CPU-optimization-of-Klass-range-reservation' of github.com:tstuefe/jdk into JDK-8320368-Per-CPU-optimization-of-Klass-range-reservation
>>  - Regression Test
>
> src/hotspot/cpu/aarch64/compressedKlass_aarch64.cpp line 49:
> 
>> 47:   }
>> 48: 
>> 49:   // If that failed, attempt to allocate at any 4G-aligned address. Let the system decide where. For ASLR,
> 
> One small nit here: encoding in MOVK mode may require more instructions than XOR mode because XOR is `eor dst, src, 0x800000000` but MOVK is `mov dst, src; eor dst, src, 0x800000000`. XOR is always the best, and we should perhaps try it first.

Oh, you are right. Okay, I will add that. Being able to do CPU-specific stuff without ifdef is like a breath of fresh air.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16743#discussion_r1401794854