RFR: 8329331: Intrinsify Unsafe::setMemory [v2]

[ExE Boss]

On Mon, 1 Apr 2024 21:30:19 GMT, Scott Gibbons <sgibbons at openjdk.org> wrote:

>> This code makes an intrinsic stub for `Unsafe::setMemory`.  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:
> 
>   Use non-sse fill (old left in)

src/hotspot/share/opto/library_call.hpp line 235:

> 233:   bool inline_unsafe_copyMemory();
> 234: 
> 235:   bool inline_unsafe_setMemory();

Maybe remove the empty line between these `inline_unsafe_*Memory` methods?
Suggestion:

  bool inline_unsafe_copyMemory();
  bool inline_unsafe_setMemory();

src/hotspot/share/prims/unsafe.cpp line 391:

> 389:   size_t sz = (size_t)size;
> 390: 
> 391: 

Suggestion:

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

PR Review Comment: https://git.openjdk.org/jdk/pull/18555#discussion_r1546092398
PR Review Comment: https://git.openjdk.org/jdk/pull/18555#discussion_r1546093297