> [JDK-8271820](https://bugs.openjdk.org/browse/JDK-8271820) introduced the > `@Stable private Boolean callerSensitive;` cache in `Method`. That field is > essentially a tri-state `Boolean` that relies on its `null` value to serve as > "not initialized" value for `@Stable`. > > This works well when the holder `Method` instance is constant: JIT compilers > fold `@Stable` well. But if such folding fails, we always dereference the > full-blown reference to "boxed" `Boolean` from the field on every access. We > can instead do a more lean tri-state primitive field to improve that > non-optimized case without sacrificing optimized case. > > I chose `byte` and `-1`, `0`, `1` to let the fastpath encode well on most > (all?) architectures. > > On adhoc benchmark like: > > > @State(Scope.Thread) > public class WrapperConstness { > static final Method CONST; > static Method NON_CONST; > > static { > try { > CONST = WrapperConstness.class.getDeclaredMethod("target"); > NON_CONST = CONST; > } catch (NoSuchMethodException e) { > throw new RuntimeException(e); > } > } > > public void target() {} > > @Benchmark > public void nonConstant() throws Exception { > NON_CONST.invoke(this); > } > > @Benchmark > public void constant() throws Exception { > CONST.invoke(this); > } > } > > > We have a minor improvement for non-const case, confirmed due to better > `isCallerSensitive` access: > > > Benchmark Mode Cnt Score Error Units > > # Baseline > WrapperConstness.constant avgt 25 0.410 ± 0.010 ns/op > WrapperConstness.nonConstant avgt 25 7.283 ± 0.025 ns/op > > # Patched > WrapperConstness.constant avgt 5 0.407 ± 0.008 ns/op > WrapperConstness.nonConstant avgt 5 7.054 ± 0.027 ns/op ; -3% > > > Additional testing: > - [x] Ad-hoc benchmarks > - [x] Linux x86_64 fastdebug `java/lang/reflect` > - [x] Linux x86_64 fastdebug `tier1`, `tier2`
Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision: Add a newline ------------- Changes: - all: https://git.openjdk.org/jdk/pull/11422/files - new: https://git.openjdk.org/jdk/pull/11422/files/51ccc4b9..be0bb88b Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=11422&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11422&range=00-01 Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/11422.diff Fetch: git fetch https://git.openjdk.org/jdk pull/11422/head:pull/11422 PR: https://git.openjdk.org/jdk/pull/11422
