adopt: "[JBS-8350118] Simplify the layout access VarHandle"

Author: fangerer

substratevm/src/com.oracle.svm.hosted.foreign/src/com/oracle/svm/hosted/foreign/ForeignFunctionsFeature.java

@@ -422,13 +422,44 @@ private static <S, T, U extends ResolvedJavaMethod> Map<S, U> createStubs(
         return created;
     }
 
+    private static final String JLI_PREFIX = "java.lang.invoke.";
+
+    /**
+     * List of (generated) classes that provide accessor methods for memory segments. Those methods
+     * are referenced with {@code java.lang.invoke.SegmentVarHandle}. Unfortunately, the classes
+     * containing the methods are not subclasses of {@link java.lang.invoke.VarHandle} and so the
+     * automatic registration for reflective access (see
+     * {@link com.oracle.svm.hosted.methodhandles.MethodHandleFeature#beforeAnalysis}) does not
+     * trigger.
+     */
+    @BasedOnJDKFile("https://github.com/openjdk/jdk/blob/jdk-25+13/src/java.base/share/classes/java/lang/invoke/VarHandles.java#L313-L344") //
+    private static final List<String> VAR_HANDLE_SEGMENT_ACCESSORS = List.of(
+                    "VarHandleSegmentAsBooleans",
+                    "VarHandleSegmentAsBytes",
+                    "VarHandleSegmentAsShorts",
+                    "VarHandleSegmentAsChars",
+                    "VarHandleSegmentAsInts",
+                    "VarHandleSegmentAsLongs",
+                    "VarHandleSegmentAsFloats",
+                    "VarHandleSegmentAsDoubles");
+
+    private static void registerVarHandleMethodsForReflection(FeatureAccess access, Class<?> subtype) {
+        assert subtype.getPackage().getName().equals(JLI_PREFIX.substring(0, JLI_PREFIX.length() - 1));
+        RuntimeReflection.register(subtype.getDeclaredMethods());
+    }
+
     @Override
     public void beforeAnalysis(BeforeAnalysisAccess a) {
         var access = (FeatureImpl.BeforeAnalysisAccessImpl) a;
         sealed = true;
 
         AbiUtils.singleton().checkLibrarySupport();
 
+        for (String simpleName : VAR_HANDLE_SEGMENT_ACCESSORS) {
+            Class<?> varHandleSegmentAsXClass = ReflectionUtil.lookupClass(JLI_PREFIX + simpleName);
+            access.registerSubtypeReachabilityHandler(ForeignFunctionsFeature::registerVarHandleMethodsForReflection, varHandleSegmentAsXClass);
+        }
+
         /*
          * Specializing an adapter would define a new class at runtime, which is not allowed in
          * SubstrateVM