Inline compile-time constant values into the code model by asotona · Pull Request #1203 · openjdk/babylon

asotona · 2026-10-02T09:20:55Z

This PR puts constants known to javac directly into the model instead of loading them from variables or fields.
OpWriter required a fix related to byte and short constants.
Affected tests are updated.

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bridgekeeper · 2026-10-02T09:24:11Z

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

openjdk · 2026-10-02T09:25:18Z

@asotona 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:

Inline compile-time constant values into the code model

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

At the time when this comment was updated there had been 3 new commits pushed to the code-reflection branch:

01756cc: Fix specification of Reflect
8eb9611: 8392553: javac crashes on an inferred recursive intersection
f03b08d: Support Interpretation of switch operation

Please see this link for an up-to-date comparison between the source branch of this pull request and the code-reflection branch.
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➡️ To integrate this PR with the above commit message to the code-reflection branch, type /integrate in a new comment.

mlbridge · 2026-10-02T09:33:01Z

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PaulSandoz · 2026-10-05T15:27:31Z

         * variable.
         *</ul>
         *
+         * @apiNote Compiler-generated Java code models may inline constant-variable reads as {@link ConstantOp} operations.


We can link to the definition of "Java code model" in the jdk.incubator.code package doc and state:

Java code models(<- link) model access to a constant variable as a constant operation whose constant value is the same as the constant variable's value

…pressions not replaced with values

mabbay · 2026-10-06T09:14:55Z

-                        %88 : java.type:"boolean" = eq %86 %87;
-                        yield %88;
+                    (%85 : java.type:"int")java.type:"boolean" -> {
+                        %86 : java.type:"int" = constant @11;


value %4 is not used, instead a new constant op is appended, is that deliberate ?

mabbay · 2026-10-06T10:59:49Z

                case FIELD, ENUM_CONSTANT -> {
                    if (sym.name.equals(names._this) || sym.name.equals(names._super)) {
                        result = thisValue();
                    } else if (top.localToOp.containsKey(sym)) {


else-if at line 1053 can be removed

…and inline constant captures

PaulSandoz · 2026-10-07T17:21:11Z

            Method intfMethod = funcIntfMethod(intfClass, mtd);
-            List<Value> captures = lop.capturedValues();
+            // filter out constant captures
+            List<Value> captures = lop.capturedValues().stream().filter(v -> constants.evaluate(v).isEmpty()).toList();


We should avoid evaluating constants three times.

The evaluation cached in a map, there is no need to construct arbitrary maps on top of it.

Ah, I missed that, although computing the captured values is not cached.

PaulSandoz · 2026-10-07T18:21:25Z

                lambdaMetafactory = DMHD_REFLECTABLE_LAMBDA_METAFACTORY;
                intfMethodName = intfMethodName + "=" + modelName;
            }
            functions.add(lambdaToFuncOp(implName, lop).transform(this));


It would be preferable to have just one lambda model to work from i.e. the quoting function model. That complicates the "purity" of the functions added and the bytecode transformation of those quoting functions, but I believe the quoting function model has all that is needed to generate the same bytecode. Follow on work?

PaulSandoz · 2026-10-07T18:28:04Z

+import jdk.incubator.code.dialect.java.JavaType;
+import jdk.incubator.code.dialect.java.PrimitiveType;
+
+public final class ConstantValueAnalysis {


As follow on work we can consider adding a method to JavaExpression that evaluates constants without a lookup, which shares the same underlying code as those that do.

PaulSandoz · 2026-10-07T19:24:01Z

+    }
+
+    /**
+     * Embeds the given operation into a quoting code model whose behavior quotes the operation.


The specification needs adjustment to say how it uses embeddedConstants.

Let's rename embeddedConstants to capturedConstants, then it becomes easier to state that there is an intersection between the set of the lambda's captured values and the given key set of capturedConstants, and then what happens to the capture values that are members of that intersection.

PaulSandoz · 2026-10-07T20:00:33Z

+
+public final class ConstantValueAnalysis {
+    private final Function<Block, List<List<Value>>> incomingArguments;
+    private final Map<Value, Optional<Object>> cache = new IdentityHashMap<>();


No need to use IdentityHashMap. Value instances and CodeElements instances are identity-based objects whose equals/hashCode methods use identity.

asotona added 6 commits October 2, 2026 10:53

ReflectMethods inlines compile-time constants

6e69c66

fixed constant values serialization

ce97aaf

fixed related tests

1c1d2f0

fixed javac reflect tests

f8dc160

removed redundant conversion

7862d39

tests fix

4c23a57

openjdk Bot added ready Pull request is ready to be integrated rfr Pull request is ready for review labels Oct 2, 2026

asotona added 3 commits October 5, 2026 15:35

added JavaOp javadoc api notes

5d53c3a

simplified Quoted::extractOp

14f8b01

fixed tests

825a012

PaulSandoz reviewed Oct 5, 2026

View reviewed changes

asotona added 4 commits October 5, 2026 17:56

added link to the relevant package info paragraph

088bb33

fixed API note text

7b2f853

VarOp declarations for compile-time constants dropped and constant ex…

0048e63

…pressions not replaced with values

accepting unused receiver + tests

569f108

mabbay reviewed Oct 6, 2026

View reviewed changes

asotona added 8 commits October 7, 2026 09:18

picked ConstantValueAnalysis from followup CFP work

7e307f2

ReflectMethods reuse constant definition across bodies

c2b3e3c

ConstantValueAnalysis used in LambdaExpansionTransformer to identify …

0a823af

…and inline constant captures

fixed tests

659e434

Quoted::embedOp extended to support embedded captured constants

0a95092

added constant capture tests to LambdaTest

28926be

added test for nested constants-capturing reflective lambdas

c38a622

ConstantValueAnalysis extended to cover JLS 15.29 expressions + test

4356746

PaulSandoz reviewed Oct 7, 2026

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Inline compile-time constant values into the code model - #1203

Inline compile-time constant values into the code model#1203
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