From 3b2a33806e86660ba9b675cc9a098195541326be Mon Sep 17 00:00:00 2001
From: Maurizio Cimadamore <maurizio.cimadamore@oracle.com>
Date: Fri, 31 May 2024 17:14:12 +0100
Subject: [PATCH] Address review comments

---
 .../jdk/internal/foreign/LayoutPath.java      |  2 +-
 .../classes/jdk/internal/foreign/Utils.java   | 20 ++++++++++++++++---
 2 files changed, 18 insertions(+), 4 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 92b94fe612e24..ebd83d1c5da5f 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 VarHandle dereferenceHandle(boolean adapt) {
                     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 4e4f77ef0906b..8c339a8ce6215 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 @@
 
 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;
@@ -89,15 +90,28 @@ public static MemorySegment alignUp(MemorySegment ms, long alignment) {
         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
+     * to 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::makeSegmentViewVarHandleInternal);
+                .computeIfAbsent(layout.withoutName(), Utils::makeRawSegmentViewVarHandleInternal);
     }
 
-    private static VarHandle makeSegmentViewVarHandleInternal(ValueLayout layout) {
+    private static VarHandle makeRawSegmentViewVarHandleInternal(ValueLayout layout) {
         Class<?> baseCarrier = layout.carrier();
         if (layout.carrier() == MemorySegment.class) {
             baseCarrier = switch ((int) ValueLayout.ADDRESS.byteSize()) {