RFR: 8272723: Don't use Access API to access primitive fields [v2]

[Stefan Karlsson]

On Thu, 19 Aug 2021 16:05:54 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> For earlier incarnations of Shenandoah, we needed to put barriers before accessing primitive fields. This is no longer necessary nor implemented/used by any GC, and we should simplify the code to do plain access instead.
>> 
>> (We may want to remove remaining primitive access machinery in the Access API soon)
>> 
>> Testing:
>>  - [x] tier1
>>  - [ ] tier2
>>  - [ ] hotspot_gc
>
> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove remaining primitive Access API uses

src/hotspot/share/oops/oop.inline.hpp line 240:

> 238: inline void     oopDesc::bool_field_put(int offset, jboolean value) { *field_addr<jboolean>(offset) = jboolean(value & 1); }
> 239: inline jboolean oopDesc::bool_field_volatile(int offset) const      { return Atomic::load_acquire(field_addr<jboolean>(offset)); }
> 240: inline void     oopDesc::bool_field_put_volatile(int offset, jboolean value) { Atomic::release_store_fence(field_addr<jboolean>(offset), jboolean(value & 1)); }

bool_field_volatile doesn't match the old HeapAccess<MO_SEQ_CST::load_at:

RawAccessBarrier<decorators>::load_internal(void* addr) {
  if (support_IRIW_for_not_multiple_copy_atomic_cpu) {
    OrderAccess::fence();
  }
  return Atomic::load_acquire(reinterpret_cast<const volatile T*>(addr));
}

src/hotspot/share/oops/typeArrayOop.inline.hpp line 93:

> 91: 
> 92: inline jbyte typeArrayOopDesc::byte_at(int which) const {
> 93:   assert(is_within_bounds(which), "index %d out of bounds %d", which, length());

byte_at_addr already asserts this.

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PR: https://git.openjdk.java.net/jdk/pull/5187