[lworld] RFR: 8351569: [lworld] Revisit atomic access modes in flat var handles [v5]

[Chen Liang]

On Thu, 20 Mar 2025 18:21:59 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> This PR is an attempt to put var handle support for flat values on a more solid footing. Some more notes in a comment below.
>
> Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Tighten the signature of VarHandles::checkAtomicFlatArray

src/java.base/share/classes/jdk/internal/misc/Unsafe.java line 2735:

> 2733:     @ForceInline
> 2734:     public final <V> Object getFlatValueOpaque(Object o, long offset, int layout, Class<?> valueType) {
> 2735:         // this is stronger that opaque semantics

Suggestion:

        // this is stronger than opaque semantics

src/java.base/share/classes/jdk/internal/misc/Unsafe.java line 2735:

> 2733:     @ForceInline
> 2734:     public final <V> Object getFlatValueOpaque(Object o, long offset, int layout, Class<?> valueType) {
> 2735:         // this is stronger that opaque semantics

Suggestion:

        // this is stronger than opaque semantics

src/java.base/share/classes/jdk/internal/misc/Unsafe.java line 2795:

> 2793:     @ForceInline
> 2794:     public final <V> void putFlatValueOpaque(Object o, long offset, int layout, Class<?> valueType, V x) {
> 2795:         // this is stronger that opaque semantics

Suggestion:

        // this is stronger than opaque semantics

src/java.base/share/classes/jdk/internal/misc/Unsafe.java line 2795:

> 2793:     @ForceInline
> 2794:     public final <V> void putFlatValueOpaque(Object o, long offset, int layout, Class<?> valueType, V x) {
> 2795:         // this is stronger that opaque semantics

Suggestion:

        // this is stronger than opaque semantics

src/java.base/share/classes/jdk/internal/misc/Unsafe.java line 3286:

> 3284:     }
> 3285: 
> 3286:     public Object getAndSetFlatValue(Object o, long offset, int layoutKind, Class<?> valueType, Object newValue) {

Why no more `@ForceInline`?

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

PR Review Comment: https://git.openjdk.org/valhalla/pull/1402#discussion_r2007837918
PR Review Comment: https://git.openjdk.org/valhalla/pull/1402#discussion_r2007838405
PR Review Comment: https://git.openjdk.org/valhalla/pull/1402#discussion_r2007838080
PR Review Comment: https://git.openjdk.org/valhalla/pull/1402#discussion_r2007838571
PR Review Comment: https://git.openjdk.org/valhalla/pull/1402#discussion_r2007840859