RFR: 8358032: Use crypto pmull for CRC32/CRC32C intrinsics on Ampere CPU [v2]
Liming Liu
lliu at openjdk.org
Thu Jun 5 05:18:52 UTC 2025
On Wed, 4 Jun 2025 08:47:13 GMT, Andrew Haley <aph at openjdk.org> wrote:
>> src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp line 4355:
>>
>>> 4353: add(buf, buf, 32);
>>> 4354: crc32x(crc, crc, tmp2);
>>> 4355: subs(len, len, 32);
>>
>> What is the point of these changes?
>
> To be more precise: converting these adjustments to post-increment operations isn't obviously an improvement on AArch64 generally. How does it help?
According to perf, post-increment ops help to reduce the access to TLB on Ampere1 in this case.
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PR Review Comment: https://git.openjdk.org/jdk/pull/25609#discussion_r2127971345
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