[vectorIntrinsics] RFR: Optimize mem barriers for ByteBuffer cases [v9]

[Radoslaw Smogura]

On Wed, 4 Aug 2021 21:16:19 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Radoslaw Smogura has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Code review changes:
>>   * make specied final static in test
>>   * use Unsafe to check if ByteBuffer is readOnly
>>   * remove if in X-ScopedMemory when loading / storing vectors,
>>      stay with byte[] cast
>>   * inline copyMemory in micro benchmark
>
> src/hotspot/share/opto/vectorIntrinsics.cpp line 837:
> 
>> 835:   const TypeInstPtr* vbox_type = TypeInstPtr::make_exact(TypePtr::NotNull, vbox_klass);
>> 836: 
>> 837:   if (mixed_access) {
> 
> I suggest the following shapes for the checks:
> 
> const bool in_native = (TypePtr::NULL_PTR == base_type);            // base always null
> const bool in_heap   = !TypePtr::NULL_PTR->higher_equal(base_type); // base never null
> 
> const bool is_mixed_access = !in_heap && !in_native;
> 
> const bool is_mismatched_access = in_heap && (addr_type->isa_aryptr() == NULL);
> 
> const bool needs_cpu_membar = is_mixed_access || is_mismatched_access;

Thank you, fixed, we were not sure if mismatched access should be there.

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PR: https://git.openjdk.java.net/panama-vector/pull/104