From e99f6a65a8307e6b31a08a677914dfd20d46687f Mon Sep 17 00:00:00 2001
From: Maurizio Cimadamore <mcimadamore@openjdk.org>
Date: Fri, 31 May 2024 17:53:35 +0000
Subject: [PATCH] 8333236: Test java/foreign/TestAccessModes.java is timing out
 after passing

Reviewed-by: jvernee
---
 .../jdk/internal/foreign/LayoutPath.java      |  2 +-
 .../classes/jdk/internal/foreign/Utils.java   | 28 +++++++++++++++++--
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/java.base/share/classes/jdk/internal/foreign/LayoutPath.java b/src/java.base/share/classes/jdk/internal/foreign/LayoutPath.java
index 92b94fe612e..ebd83d1c5da 100644
--- a/src/java.base/share/classes/jdk/internal/foreign/LayoutPath.java
+++ b/src/java.base/share/classes/jdk/internal/foreign/LayoutPath.java
@@ -205,7 +205,7 @@ public class LayoutPath {
                     String.format("Path does not select a value layout: %s", breadcrumbs()));
         }
 
-        VarHandle handle = Utils.makeSegmentViewVarHandle(valueLayout);
+        VarHandle handle = Utils.makeRawSegmentViewVarHandle(valueLayout);
         handle = MethodHandles.collectCoordinates(handle, 1, offsetHandle());
 
         // we only have to check the alignment of the root layout for the first dereference we do,
diff --git a/src/java.base/share/classes/jdk/internal/foreign/Utils.java b/src/java.base/share/classes/jdk/internal/foreign/Utils.java
index f05666b88b6..2ed65e3dd04 100644
--- a/src/java.base/share/classes/jdk/internal/foreign/Utils.java
+++ b/src/java.base/share/classes/jdk/internal/foreign/Utils.java
@@ -28,6 +28,7 @@ package jdk.internal.foreign;
 
 import java.lang.foreign.AddressLayout;
 import java.lang.foreign.MemoryLayout;
+import java.lang.foreign.MemoryLayout.PathElement;
 import java.lang.foreign.MemorySegment;
 import java.lang.foreign.StructLayout;
 import java.lang.foreign.ValueLayout;
@@ -37,6 +38,8 @@ import java.lang.invoke.MethodType;
 import java.lang.invoke.VarHandle;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Supplier;
 
 import jdk.internal.access.SharedSecrets;
@@ -87,7 +90,28 @@ public final class Utils {
         return ms.asSlice(alignUp(offset, alignment) - offset);
     }
 
-    public static VarHandle makeSegmentViewVarHandle(ValueLayout layout) {
+    /**
+     * This method returns a <em>raw var handle</em>, that is, a var handle that does not perform any size
+     * or alignment checks. Such checks are added (using adaptation) by {@link LayoutPath#dereferenceHandle()}.
+     * <p>
+     * We provide two level of caching of the generated var handles. First, the var handle associated
+     * with a {@link ValueLayout#varHandle()} call is cached inside a stable field of the value layout implementation.
+     * This optimizes common code idioms like {@code JAVA_INT.varHandle().getInt(...)}. A second layer of caching
+     * is then provided by this method: after all, var handles constructed by {@link MemoryLayout#varHandle(PathElement...)}
+     * will be obtained by adapting some raw var handle generated by this method.
+     *
+     * @param layout the value layout for which a raw memory segment var handle is to be created.
+     * @return a raw memory segment var handle.
+     */
+    public static VarHandle makeRawSegmentViewVarHandle(ValueLayout layout) {
+        final class VarHandleCache {
+            private static final Map<ValueLayout, VarHandle> HANDLE_MAP = new ConcurrentHashMap<>();
+        }
+        return VarHandleCache.HANDLE_MAP
+                .computeIfAbsent(layout.withoutName(), Utils::makeRawSegmentViewVarHandleInternal);
+    }
+
+    private static VarHandle makeRawSegmentViewVarHandleInternal(ValueLayout layout) {
         Class<?> baseCarrier = layout.carrier();
         if (layout.carrier() == MemorySegment.class) {
             baseCarrier = switch ((int) ValueLayout.ADDRESS.byteSize()) {
@@ -108,7 +132,7 @@ public final class Utils {
             handle = MethodHandles.filterValue(handle,
                     MethodHandles.explicitCastArguments(ADDRESS_TO_LONG, MethodType.methodType(baseCarrier, MemorySegment.class)),
                     MethodHandles.explicitCastArguments(MethodHandles.insertArguments(LONG_TO_ADDRESS, 1,
-                            pointeeByteSize(addressLayout), pointeeByteAlign(addressLayout)),
+                                    pointeeByteSize(addressLayout), pointeeByteAlign(addressLayout)),
                             MethodType.methodType(MemorySegment.class, baseCarrier)));
         }
         return handle;