[JVM] Do a modern object-oriented atomic ops (i.e. eliminate Unsafe)

As commented, VarHandle can handle the atomic ops that we would've been forced to depend on Unsafe to accomplish (racily!) prior to Java 9.
Raku · Jul 27, 2022 · 572d61d · 572d61d
1 parent f3bcaa1
commit 572d61d
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Showing 4 changed files with 51 additions and 78 deletions.
diff --git a/src/vm/jvm/runtime/org/raku/nqp/runtime/Intrinsics.java b/src/vm/jvm/runtime/org/raku/nqp/runtime/Intrinsics.java
diff --git a/src/vm/jvm/runtime/org/raku/nqp/runtime/Ops.java b/src/vm/jvm/runtime/org/raku/nqp/runtime/Ops.java
@@ -14,6 +14,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.UnsupportedEncodingException;
+import java.lang.invoke.VarHandle;
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.MethodType;
@@ -6039,7 +6040,7 @@ public static SixModelObject atomicbindattr(SixModelObject obj, SixModelObject c
         return value;
     }
     public static SixModelObject barrierfull(ThreadContext tc) {
-        Intrinsics.itsUnsafe(tc, (unsafe) -> { unsafe.fullFence(); });
+        VarHandle.fullFence();
         return createNull(tc);
     }
 

diff --git a/src/vm/jvm/runtime/org/raku/nqp/sixmodel/SixModelObject.java b/src/vm/jvm/runtime/org/raku/nqp/sixmodel/SixModelObject.java
@@ -33,25 +33,28 @@ public SixModelObject get_attribute_boxed(ThreadContext tc, SixModelObject class
     public void get_attribute_native(ThreadContext tc, SixModelObject class_handle, String name, long hint) {
         throw ExceptionHandling.dieInternal(tc, this.st.REPR.name + " representation does not support natively typed attributes");
     }
-    public void bind_attribute_boxed(ThreadContext tc,SixModelObject class_handle,
+    public void bind_attribute_boxed(ThreadContext tc, SixModelObject class_handle,
             String name, long hint, SixModelObject value) {
         throw ExceptionHandling.dieInternal(tc, this.st.REPR.name + " representation does not support attributes");
     }
-    public void bind_attribute_native(ThreadContext tc,SixModelObject class_handle, String name, long hint) {
+    public void bind_attribute_native(ThreadContext tc, SixModelObject class_handle, String name, long hint) {
         throw ExceptionHandling.dieInternal(tc, this.st.REPR.name + " representation does not support natively typed attributes");
     }
     public long is_attribute_initialized(ThreadContext tc, SixModelObject class_handle,
             String name, long hint) {
         throw ExceptionHandling.dieInternal(tc, this.st.REPR.name + " representation does not support attributes");
     }
-    public SixModelObject cas_attribute_boxed(ThreadContext tc,SixModelObject class_handle,
+    public SixModelObject cas_attribute_boxed(ThreadContext tc, SixModelObject class_handle,
             String name, SixModelObject expected, SixModelObject value) {
         throw ExceptionHandling.dieInternal(tc, this.st.REPR.name + " representation does not support cas of attributes");
     }
-    public void atomic_bind_attribute_boxed(ThreadContext tc,SixModelObject class_handle,
+    public void atomic_bind_attribute_boxed(ThreadContext tc, SixModelObject class_handle,
             String name, SixModelObject value) {
         throw ExceptionHandling.dieInternal(tc, this.st.REPR.name + " representation does not support atomic binding to attributes");
     }
+    public SixModelObject atomic_load_attribute_boxed(ThreadContext tc, SixModelObject class_handle, String name) {
+        throw ExceptionHandling.dieInternal(tc, this.st.REPR.name + " representation does not support atomic loading of attributes");
+    }
 
     /**
      * Boxing related functions.

diff --git a/src/vm/jvm/runtime/org/raku/nqp/sixmodel/reprs/P6OpaqueBaseInstance.java b/src/vm/jvm/runtime/org/raku/nqp/sixmodel/reprs/P6OpaqueBaseInstance.java
@@ -1,6 +1,8 @@
 package org.raku.nqp.sixmodel.reprs;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
 import org.raku.nqp.runtime.ExceptionHandling;
-import org.raku.nqp.runtime.Intrinsics;
 import org.raku.nqp.runtime.Ops;
 import org.raku.nqp.runtime.ThreadContext;
 import org.raku.nqp.sixmodel.STable;
@@ -115,41 +117,53 @@ public long is_attribute_initialized(ThreadContext tc, SixModelObject class_hand
             return super.is_attribute_initialized(tc, class_handle, name, hint);
     }
 
-    private long scalarValueOffset;
-
     @Override
     public SixModelObject cas_attribute_boxed(ThreadContext tc, SixModelObject class_handle,
                                               String name, SixModelObject expected, SixModelObject value) {
-        return Intrinsics.butUnsafe(tc, (unsafe) -> {
-            try {
-                long offset = unsafe.objectFieldOffset(this.getClass().getDeclaredField(
-                    "field_" + resolveAttribute(class_handle, name)));
-                return unsafe.compareAndSwapObject(this, offset, expected, value)
-                    ? expected
-                    : (SixModelObject)unsafe.getObjectVolatile(this, offset);
-            }
-            catch (Exception e) {
-                throw ExceptionHandling.dieInternal(tc, e);
-            }
-            finally {
-                return Ops.createNull(tc);
-            }
-        });
+        SixModelObject result = null;
+        try {
+            String attribute = "field_" + resolveAttribute(class_handle, name);
+            VarHandle variable = MethodHandles.lookup().in(this.getClass())
+                .findVarHandle(this.getClass(), attribute, SixModelObject.class);
+            result = (SixModelObject)variable.compareAndExchange(this, expected, value);
+        }
+        catch (Exception e) {
+            throw ExceptionHandling.dieInternal(tc, e);
+        }
+        finally {
+            return result == null ? Ops.createNull(tc) : result;
+        }
     }
 
     @Override
     public void atomic_bind_attribute_boxed(ThreadContext tc, SixModelObject class_handle,
                                             String name, SixModelObject value) {
-        Intrinsics.itsUnsafe(tc, (unsafe) -> {
-            try {
-                long offset = unsafe.objectFieldOffset(this.getClass().getDeclaredField(
-                    "field_" + resolveAttribute(class_handle, name)));
-                unsafe.putObjectVolatile(this, offset, value);
-            }
-            catch (Exception e) {
-                throw ExceptionHandling.dieInternal(tc, e);
-            }
-        });
+        try {
+            String attribute = "field_" + resolveAttribute(class_handle, name);
+            VarHandle variable = MethodHandles.lookup().in(this.getClass())
+                .findVarHandle(this.getClass(), attribute, SixModelObject.class);
+            variable.setRelease(this, value);
+        }
+        catch (Exception e) {
+            throw ExceptionHandling.dieInternal(tc, e);
+        }
+    }
+
+    @Override
+    public SixModelObject atomic_load_attribute_boxed(ThreadContext tc, SixModelObject class_handle, String name) {
+        SixModelObject result = null;
+        try {
+            String attribute = "field_" + resolveAttribute(class_handle, name);
+            VarHandle variable = MethodHandles.lookup().in(this.getClass())
+                .findVarHandle(this.getClass(), attribute, SixModelObject.class);
+            result = (SixModelObject)variable.getAcquire(this);
+        }
+        catch (Exception e) {
+            throw ExceptionHandling.dieInternal(tc, e);
+        }
+        finally {
+            return result == null ? Ops.createNull(tc) : result;
+        }
     }
 
     public SixModelObject posDelegate() {