8295302: Do not use ArrayList when LambdaForm has a single ClassData #10706

iklam · 2022-10-13T21:53:47Z

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) ⚠️ Review applies to 5a800f0d
Claes Redestad (@cl4es - Reviewer) ⚠️ Review applies to 5a800f0d
Mandy Chung (@mlchung - Reviewer) ⚠️ Review applies to eb05b9ef

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bridgekeeper · 2022-10-13T21:54:09Z

👋 Welcome back iklam! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2022-10-13T21:57:17Z

@iklam The following label will be automatically applied to this pull request:

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mlbridge · 2022-10-13T22:01:53Z

Webrevs

iwanowww · 2022-10-13T22:29:03Z

src/java.base/share/classes/java/lang/invoke/InvokerBytecodeGenerator.java

        Class<?> invokerClass = LOOKUP.makeHiddenClassDefiner(className, classFile, Set.of())
-                                      .defineClass(true, classDataValues());


Why not just put it in classDataValues() instead?

Object classDataValues() { final List<ClassData> cd = classData; return switch(cd.size()) { case 0 -> null; // flatten for zero case case 1 -> cd.get(0).value; // flatten for single value case case 2 -> List.of(cd.get(0).value, cd.get(1).value); ...

And it also covers zero case for free.

I fixed it as you suggested. I also changed the method to private to make sure no one else is using this method.

iwanowww · 2022-10-13T22:30:43Z

src/java.base/share/classes/java/lang/invoke/InvokerBytecodeGenerator.java

-            emitIconstInsn(mv, index++);
-            mv.visitMethodInsn(Opcodes.INVOKEINTERFACE, "java/util/List",
-                               "get", "(I)Ljava/lang/Object;", true);
+        if (classData.size() == 1) {


if (classData.size() < 2) {

It works for zero case, because checkcast always succeeds on nulls.

Actually the zero case is already handled here:

static void clinit(ClassWriter cw, String className, List<ClassData> classData) { if (classData.isEmpty()) return;

No <clinit> method is generated because we have no static field to initialize.

iwanowww

Looks good.

openjdk · 2022-10-14T04:50:49Z

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

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

Reviewed-by: vlivanov, redestad, mchung

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been no new commits pushed to the master branch. If another commit should be pushed before you perform the /integrate command, your PR will be automatically rebased. If you prefer to avoid any potential automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

mlchung · 2022-10-14T16:57:47Z

src/java.base/share/classes/java/lang/invoke/InvokerBytecodeGenerator.java

        final List<ClassData> cd = classData;
        return switch(cd.size()) {
-            case 0 -> List.of();
-            case 1 -> List.of(cd.get(0).value);
+            case 0 -> null;


List.of() always returns the same singleton instance and does not cause any object allocation. I prefer to keep the classDataValues() to return List<Object>

Ah, I now see why you have to change the signature because of the single element case. I made my comment too quickly.

A couple of suggestions:
Please add a javadoc for this method to describe what this method returns for different cases. It's better to move this method close to clinit as they are tightly coupled.

I moved the method and added in javadoc. Could you check if the wording is OK?

cl4es

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

iklam · 2022-10-17T21:10:22Z

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.

…for-lambdaform

mlchung · 2022-10-18T02:03:06Z

src/java.base/share/classes/java/lang/invoke/InvokerBytecodeGenerator.java

@@ -360,6 +342,29 @@ private void methodEpilogue() {
        mv.visitEnd();
    }

+    /**
+     * Returns an object to pass this.classData to the <clinit> method of the


What about:

Suggested change

* Returns an object to pass this.classData to the <clinit> method of the

* Returns the class data object that will be passed to `Lookup.defineHiddenClass`.

* The classData is loaded in the <clinit> method of the generated class.

* If the class data contains only one single object, this method returns that single object.

* If the class data contains more than one objects, this method returns a List.

*

* This method returns null if no class data.

Actually, the classData is passed here:

private MemberName loadMethod(byte[] classFile) { Class<?> invokerClass = LOOKUP.makeHiddenClassDefiner(className, classFile, Set.of()) .defineClass(true, classDataValues()); return resolveInvokerMember(invokerClass, invokerName, invokerType); }

So it doesn't go through Lookup.defineHiddenClass.

yes, it's an internal version that defines a hidden class, equivalent to calling Lookup::defineHiddenClassWithClassData (typo in my suggested wording), but it will bypass the security permission check and also returns the Class instead of Lookup (saving not to allocate a Lookup object).

mlchung

Thanks for the update. I made the suggested wording. You can push once it's updated.

turbanoff · 2022-10-18T20:12:48Z

src/java.base/share/classes/java/lang/invoke/InvokerBytecodeGenerator.java

+     */
+    private Object classDataValues() {
+        final List<ClassData> cd = classData;
+        return switch(cd.size()) {


Suggested change

return switch(cd.size()) {

return switch (cd.size()) {

…for-lambdaform

iklam · 2022-10-19T21:10:38Z

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

openjdk · 2022-10-19T21:11:50Z

Going to push as commit 8d4c077.
Since your change was applied there have been 16 commits pushed to the master branch:

017e798: 8293939: Move continuation_enter_setup and friends
f872467: 8255746: Make PrintCompilation available on a per method level
388a56e: 8294467: Fix sequence-point warnings in Hotspot
ceb5b08: 8294468: Fix char-subscripts warnings in Hotspot
7b1c676: 8295662: jdk/incubator/vector tests fail "assert(VM_Version::supports_avx512vlbw()) failed"
5eaf568: 8295668: validate-source failure after JDK-8290011
e238920: 8295372: CompactNumberFormat handling of number one with decimal part
a5f6e31: 8295456: (ch) sun.nio.ch.Util::checkBufferPositionAligned gives misleading/incorrect error
e27bea0: 8290011: IGV: Remove dead code and cleanup
d37ce4c: 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 · 2022-10-19T21:12:11Z

@iklam Pushed as commit 8d4c077.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

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

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openjdk bot added the rfr Pull request is ready for review label Oct 13, 2022

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iklam added 2 commits October 17, 2022 14:41

@mlchung comments

605a5f9

Merge branch 'master' into 8295302-no-arraylist-for-single-classdata-…

eb05b9e

…for-lambdaform

mlchung reviewed Oct 18, 2022

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iklam added 2 commits October 18, 2022 22:05

javadoc from @mlchung; fix code format per @turbanoff

a339fc6

Merge branch 'master' into 8295302-no-arraylist-for-single-classdata-…

51f1835

…for-lambdaform

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8295302: Do not use ArrayList when LambdaForm has a single ClassData #10706

8295302: Do not use ArrayList when LambdaForm has a single ClassData #10706

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		Class<?> invokerClass = LOOKUP.makeHiddenClassDefiner(className, classFile, Set.of())
		.defineClass(true, classDataValues());

-     * Returns an object to pass this.classData to the <clinit> method of the
+     * Returns the class data object that will be passed to `Lookup.defineHiddenClass`.
+     * The classData is loaded in the <clinit> method of the generated class.
+     * If the class data contains only one single object, this method returns  that single object.
+     * If the class data contains more than one objects, this method returns a List.
+     *
+     * This method returns null if no class data.

8295302: Do not use ArrayList when LambdaForm has a single ClassData #10706

8295302: Do not use ArrayList when LambdaForm has a single ClassData #10706

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iklam commented Oct 13, 2022 • edited by openjdk bot Loading

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