RFR: 8329331: Intrinsify Unsafe::setMemory [v11]

[Sandhya Viswanathan]

On Thu, 11 Apr 2024 18:42:56 GMT, Scott Gibbons <sgibbons at openjdk.org> wrote:

>> This code makes an intrinsic stub for `Unsafe::setMemory` for x86_64.  See [this PR](https://github.com/openjdk/jdk/pull/16760) for discussion around this change.
>> 
>> Overall, making this an intrinsic improves overall performance of `Unsafe::setMemory` by up to 4x for all buffer sizes.
>> 
>> Tested with tier-1 (and full CI).  I've added a table of the before and after numbers for the JMH I ran (`MemorySegmentZeroUnsafe`).
>> 
>> [setMemoryBM.txt](https://github.com/openjdk/jdk/files/14808974/setMemoryBM.txt)
>
> Scott Gibbons has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix whitespace error.

src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp line 8343:

> 8341:       UnsafeCopyMemory::create_table(8);
> 8342:     }
> 8343: 

Did you mean to initialize UnsafeSetMemory::_table here instead?

src/hotspot/cpu/x86/stubGenerator_x86_64_arraycopy.cpp line 155:

> 153:   StubRoutines::_arrayof_jint_fill = generate_fill(T_INT, true, "arrayof_jint_fill");
> 154: 
> 155: // #ifdef _LP64

We could remove the #ifdef _LP64, #endif commented pair.

src/hotspot/cpu/x86/stubGenerator_x86_64_arraycopy.cpp line 735:

> 733: 
> 734:   if (MaxVectorSize == 64) {
> 735:     UnsafeCopyMemoryMark ucmm(this, !is_oop && !aligned, false, ucme_exit_pc);

This is not related to Unsafe::setMemory?

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PR Review Comment: https://git.openjdk.org/jdk/pull/18555#discussion_r1561587296
PR Review Comment: https://git.openjdk.org/jdk/pull/18555#discussion_r1561606554
PR Review Comment: https://git.openjdk.org/jdk/pull/18555#discussion_r1561620598