RFR: 8254693: Add Panama feature to pass heap segments to native code [v2]

[Jorn Vernee]

On Wed, 18 Oct 2023 09:45:25 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   drop unused in_reg_spiller
>
> test/micro/org/openjdk/bench/java/lang/foreign/CriticalCalls.java line 101:
> 
>> 99:     public int callNotPinned() throws Throwable {
>> 100:         try (Arena arena = Arena.ofConfined()) {
>> 101:             MemorySegment nativeArr = arena.allocate(JAVA_INT, arr.length);
> 
> This allocation method will zero the segment. I think that's a bit unfair and will bias the results against non-pinned, right?

Good point. I made this benchmark a while ago, before we had the more optimized allocate variants

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PR Review Comment: https://git.openjdk.org/jdk/pull/16201#discussion_r1363582375