8297784: Optimize @Stable field for Method.isCallerSensitive

[shipilev]

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:

• Ad-hoc benchmarks
• Linux x86_64 fastdebug java/lang/reflect
• Linux x86_64 fastdebug tier1, tier2

---

Progress

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Issue

• JDK-8297784: Optimize @stable field for Method.isCallerSensitive

Reviewers

• Claes Redestad (@cl4es - Reviewer) ⚠️ Review applies to 51ccc4b9
• Jorn Vernee (@JornVernee - Reviewer) ⚠️ Review applies to 51ccc4b9
• Alan Bateman (@AlanBateman - Reviewer)

Reviewing

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[mlbridge]

Webrevs

• 01: Full - Incremental (be0bb88b)
• 00: Full (51ccc4b9)

[cl4es]

LGTM.

[openjdk]

@shipilev This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8297784: Optimize @Stable field for Method.isCallerSensitive

Reviewed-by: redestad, jvernee, alanb

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At the time when this comment was updated there had been 20 new commits pushed to the master branch:

• f05bfb1: 8297515: serialVersionUID fields are not annotated with @serial
• 22f5d01: 8252584: HotSpot Style Guide should permit alignas
• 8ffed34: 8297681: Unnecessary color conversion during 4BYTE_ABGR_PRE to INT_ARGB_PRE blit
• abe532a: 8296924: C2: assert(is_valid_AArch64_address(dest.target())) failed: bad address
• 5dcaf6c: 8297749: Remove duplicate space in the ProtocolException message being thrown from HttpURLConnection
• c7a679f: 8297290: Use int indices to reference CDS archived primitive mirrors
• 37f613b: 8297676: DataBuffer.TYPE_SHORT/TYPE_FLOAT/TYPE_DOUBLE are not placeholders
• 87f00f4: 8296878: Document Filter attached to JPasswordField and setText("") is not cleared instead inserted characters replaced with unicode null characters
• 9ced2ea: 8297311: Improve exception message thrown by java.net.HostPortrange::toLowerCase(String s)
• defe060: 8296905: Replace the native LCMS#getProfileID() method with the accessor
• ... and 10 more: https://git.openjdk.org/jdk/compare/69ede5baeda6645aa3e961a02cbd40db965fc6a1...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[shipilev]

/integrate

[openjdk]

Going to push as commit 9bbcb54.
Since your change was applied there have been 73 commits pushed to the master branch:

• 11ba759: 8297992: Tests fail after JDK-8297215 due to lack of @enablePreview
• b035056: 8297455: Use the official ToolProvider API to call javac
• 257aa15: 8297444: Refactor the javacserver build tool
• e846b04: 8297875: jar should not compress the manifest directory entry
• 82031d3: 8297294: compiler/c2/irTests/TestMulNodeIdealization.java failed compilation
• 337ca10: 8297978: Exclude vmTestbase/nsk/stress/except/except012.java until 8297977 is fixed
• 770ff5a: 8297215: Update libs tests to use @enablePreview
• c69aa42: 8297968: Crash in PrintOptoAssembly
• 5a5ced3: 8297830: aarch64: Make Address a discriminated union internally
• 391599b: 8297313: Refactor APIs for calculating address of CDS archive heap regions
• ... and 63 more: https://git.openjdk.org/jdk/compare/69ede5baeda6645aa3e961a02cbd40db965fc6a1...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 9bbcb54.

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