8295302: Do not use ArrayList when LambdaForm has a single ClassData

[iklam]

Please review this small optimization. As shown in the JBS issue, most of the generated LambdaForm classes have a single ClassData, so we can get a small footprint/speed improvement.

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Issue

• JDK-8295302: Do not use ArrayList when LambdaForm has a single ClassData

Reviewers

• Vladimir Ivanov (@iwanowww - Reviewer)

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8295302: Do not use ArrayList when LambdaForm has a single ClassData

Reviewed-by: vlivanov, redestad, mchung

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[iklam]

Looks good, assuming there are tests calling in with no class data to check that defineClass is fine with null inputs?

Yes, we have two existing test cases that has no class data:

• java/lang/invoke/CompileThresholdBootstrapTest
• java/lang/invoke/LoopCombinatorLongSignatureTest

I found them by adding this to InvokerBytecodeGenerator::classDataValues()

    private Object classDataValues() {
        final List<ClassData> cd = classData;
        if (cd.size() == 0) {
            throw new RuntimeException("huh");
        }

If I remove the above hack but keep my patch, the tests passed. So I think this case is covered.

[iklam]

Thanks @cl4es @iwanowww @mlchung for the review, and @turbanoff for the suggestion. /integrate

[openjdk[bot]]

Going to push as commit 8d4c077218748d37617fc1bdb537a165706a5849. Since your change was applied there have been 16 commits pushed to the master branch:

• 017e7988b197427f6b464303788a418a1d892ab9: 8293939: Move continuation_enter_setup and friends
• f872467d69a6d8442f8004609ce819641cab568b: 8255746: Make PrintCompilation available on a per method level
• 388a56e4c4278f2a3da31946b15a45f3aee25e58: 8294467: Fix sequence-point warnings in Hotspot
• ceb5b08964e34dfae3819257e5df460f24f92a78: 8294468: Fix char-subscripts warnings in Hotspot
• 7b1c6767fc5ea90630776e5bfa0fcc47ffc89aa6: 8295662: jdk/incubator/vector tests fail "assert(VM_Version::supports_avx512vlbw()) failed"
• 5eaf5686656a10ee27977de23ed5290a723b96a8: 8295668: validate-source failure after JDK-8290011
• e238920bb69836e982138cb7e1fed2a39182df8f: 8295372: CompactNumberFormat handling of number one with decimal part
• a5f6e31ccbef27f4f363a80d41d5c9c1cae75151: 8295456: (ch) sun.nio.ch.Util::checkBufferPositionAligned gives misleading/incorrect error
• e27bea0c4db282e26d0d96611bb330e02c314d48: 8290011: IGV: Remove dead code and cleanup
• d37ce4cdd18afc4facf996598f79e72aae68f4ff: 8290368: Introduce LDAP and RMI protocol-specific object factory filters to JNDI implementation
• ... and 6 more: https://git.openjdk.org/jdk/compare/3f4964f83d6f03efbee2fb34aa8258d4fc923efb...master

Your commit was automatically rebased without conflicts.

[openjdk[bot]]

@iklam Pushed as commit 8d4c077218748d37617fc1bdb537a165706a5849.

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