Combine VM with Statics, and rely on JIT inlining of releaseFence

scala · SethTisue · Aug 18, 2018 · May 4, 2018 · May 4, 2018 · Aug 16, 2018
commit 2c6d90cacce308c68e6c25d92d47f985e79eda5d
@@ -7,7 +7,7 @@ import java.io.{ObjectInputStream, ObjectOutputStream}
 import scala.annotation.unchecked.uncheckedVariance
 import scala.annotation.tailrec
 import mutable.{Builder, ListBuffer}
-import scala.runtime.ScalaRunTime
+import scala.runtime.Statics.releaseFence
 
 /** A class for immutable linked lists representing ordered collections
   *  of elements of type `A`.
@@ -148,7 +148,7 @@ sealed abstract class List[+A]
       t = nx
       rest = rest.tail
     }
-    ScalaRunTime.releaseFence()
+    releaseFence()
     h
   }
 
@@ -218,7 +218,7 @@ sealed abstract class List[+A]
         t = nx
         rest = rest.tail
       }
-      ScalaRunTime.releaseFence()
+      releaseFence()
       h
     }
   }
@@ -245,7 +245,7 @@ sealed abstract class List[+A]
         }
         rest = rest.tail
       } while (rest ne Nil)
-      {ScalaRunTime.releaseFence(); h}
+      {releaseFence(); h}
     }
   }
   final override def flatMap[B](f: A => IterableOnce[B]): List[B] = {
@@ -269,7 +269,7 @@ sealed abstract class List[+A]
         }
         rest = rest.tail
       }
-      if (!found) Nil else {ScalaRunTime.releaseFence(); h}
+      if (!found) Nil else {releaseFence(); h}
     }
   }
 
@@ -453,7 +453,7 @@ sealed abstract class List[+A]
       }
     }
     val result = loop(null, null, this, this)
-    ScalaRunTime.releaseFence()
+    releaseFence()
     result
   }
 
@@ -537,7 +537,7 @@ sealed abstract class List[+A]
     }
 
     val result = noneIn(this)
-    ScalaRunTime.releaseFence()
+    releaseFence()
     result
   }
 
@@ -565,11 +565,11 @@ sealed abstract class List[+A]
 
 }
 
-// Internal code that mutates `next` _must_ call `ScalaRunTime.releaseFence()` if either immediately, or
+// Internal code that mutates `next` _must_ call `Statics.releaseFence()` if either immediately, or
 // before a newly-allocated, thread-local :: instance is aliased (e.g. in ListBuffer.toList)
 final case class :: [+A](override val head: A, private[scala] var next: List[A @uncheckedVariance]) // sound because `next` is used only locally
   extends List[A] {
-  ScalaRunTime.releaseFence()
+  releaseFence()
   override def isEmpty: Boolean = false
   override def headOption: Some[A] = Some(head)
   override def tail: List[A] = next

@@ -6,7 +6,7 @@ import java.io.{ObjectInputStream, ObjectOutputStream}
 
 import scala.collection.mutable.{Builder, ReusableBuilder}
 import scala.annotation.unchecked.uncheckedVariance
-import scala.runtime.ScalaRunTime
+import scala.runtime.Statics.releaseFence
 
 /** $factoryInfo
   * @define Coll `Vector`
@@ -71,12 +71,12 @@ final class Vector[+A] private[immutable] (private[collection] val startIndex: I
 
   override def iterableFactory: SeqFactory[Vector] = Vector
 
-  // Code paths that mutates `dirty` _must_ call `ScalaRunTime.releaseFence()` before returning from
+  // Code paths that mutates `dirty` _must_ call `Statics.releaseFence()` before returning from
   // the public method.
   private[immutable] var dirty = false
   // While most JDKs would implicit add this fence because of >= 1 final field, the spec only mandates
   // it if all fields are final, so let's add this in explicitly.
-  ScalaRunTime.releaseFence()
+  releaseFence()
 
   def length: Int = endIndex - startIndex
 
@@ -225,7 +225,7 @@ final class Vector[+A] private[immutable] (private[collection] val startIndex: I
     s.dirty = dirty
     s.gotoPosWritable(focus, idx, focus ^ idx)  // if dirty commit changes; go to new pos and prepare for writing
     s.display0(idx & 31) = elem.asInstanceOf[AnyRef]
-    ScalaRunTime.releaseFence()
+    releaseFence()
     s
   }
 
@@ -319,7 +319,7 @@ final class Vector[+A] private[immutable] (private[collection] val startIndex: I
       s.display0 = elems
       s
     }
-    ScalaRunTime.releaseFence()
+    releaseFence()
     result
   }
 
@@ -383,7 +383,7 @@ final class Vector[+A] private[immutable] (private[collection] val startIndex: I
       s.display0 = elems
       s
     }
-    ScalaRunTime.releaseFence()
+    releaseFence()
     result
   }
 
@@ -521,7 +521,7 @@ final class Vector[+A] private[immutable] (private[collection] val startIndex: I
     s.gotoPosWritable(focus, blockIndex, focus ^ blockIndex)
     s.preClean(d)
     s.cleanLeftEdge(cutIndex - shift)
-    ScalaRunTime.releaseFence()
+    releaseFence()
     s
   }
 
@@ -537,7 +537,7 @@ final class Vector[+A] private[immutable] (private[collection] val startIndex: I
     s.gotoPosWritable(focus, blockIndex, focus ^ blockIndex)
     s.preClean(d)
     s.cleanRightEdge(cutIndex - shift)
-    ScalaRunTime.releaseFence()
+    releaseFence()
     s
   }
 
@@ -630,7 +630,7 @@ final class VectorBuilder[A]() extends ReusableBuilder[A, Vector[A]] with Vector
     val s = new Vector[A](0, size, 0) // should focus front or back?
     s.initFrom(this)
     if (depth > 1) s.gotoPos(0, size - 1) // we're currently focused to size - 1, not size!
-    ScalaRunTime.releaseFence()
+    releaseFence()
     s
   }
 

@@ -5,7 +5,7 @@ import scala.annotation.tailrec
 import scala.collection.immutable.{List, Nil, ::}
 import scala.annotation.tailrec
 import java.lang.{IllegalArgumentException, IndexOutOfBoundsException}
-import scala.runtime.ScalaRunTime
+import scala.runtime.Statics.releaseFence
 
 /** A `Buffer` implementation backed by a list. It provides constant time
   *  prepend and append. Most other operations are linear.
@@ -65,7 +65,7 @@ class ListBuffer[A]
     // We've accumulated a number of mutations to `List.tail` by this stage.
     // Make sure they are visible to threads that the client of this ListBuffer might be about
     // to share this List with.
-    ScalaRunTime.releaseFence()
+    releaseFence()
     first
   }
 

@@ -268,9 +268,4 @@ object ScalaRunTime {
   def wrapShortArray(xs: Array[Short]): ArraySeq[Short] = if (xs ne null) new ArraySeq.ofShort(xs) else null
   def wrapBooleanArray(xs: Array[Boolean]): ArraySeq[Boolean] = if (xs ne null) new ArraySeq.ofBoolean(xs) else null
   def wrapUnitArray(xs: Array[Unit]): ArraySeq[Unit] = if (xs ne null) new ArraySeq.ofUnit(xs) else null
-
-  /**
-    * Forwards to `VarHandle.releaseFence` or `sun.misc.Unsafe.storeFence` on JDK9+ or JDK8 respectively.
-    */
-  @inline def releaseFence(): Unit = VM.RELEASE_FENCE.invoke()
 }
@@ -1,5 +1,10 @@
 package scala.runtime;
 
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
+import java.lang.reflect.Field;
+
 /** Not for public consumption.  Usage by the runtime only.
  */
 
@@ -117,4 +122,48 @@ public static int anyHash(Object x) {
 
   /** Used as a marker object to return from PartialFunctions */
   public static final Object pfMarker = new Object();
+
+  // @ForceInline would be nice here.
+  public static void releaseFence() throws Throwable {
+    VM.RELEASE_FENCE.invoke();
+  }
+
+  final static class VM {
+      static final MethodHandle RELEASE_FENCE;
+
+      static {
+          RELEASE_FENCE = mkHandle();
+      }
+
+      private static MethodHandle mkHandle() {
+          MethodHandles.Lookup lookup = MethodHandles.lookup();
+          try {
+              return lookup.findStatic(Class.forName("java.lang.invoke.VarHandle"), "releaseFence", MethodType.methodType(Void.TYPE));
+          } catch (ClassNotFoundException e) {
+              try {
+                  Class<?> unsafeClass = Class.forName("sun.misc.Unsafe");
+                  return lookup.findVirtual(unsafeClass, "storeFence", MethodType.methodType(void.class)).bindTo(findUnsafe(unsafeClass));
+              } catch (NoSuchMethodException | ClassNotFoundException | IllegalAccessException e1) {
+                  ExceptionInInitializerError error = new ExceptionInInitializerError(e1);
+                  error.addSuppressed(e);
+                  throw error;
+              }
+          } catch (NoSuchMethodException | IllegalAccessException e) {
+              throw new ExceptionInInitializerError(e);
+          }
+      }
+
+      private static Object findUnsafe(Class<?> unsafeClass) throws IllegalAccessException {
+          Object found = null;
+          for (Field field : unsafeClass.getDeclaredFields()) {
+              if (field.getType() == unsafeClass) {
+                  field.setAccessible(true);
+                  found = field.get(null);
+                  break;
+              }
+          }
+          if (found == null) throw new IllegalStateException("No instance of Unsafe found");
+          return found;
+      }
+  }
 }
diff --git a/src/reflect/scala/reflect/internal/tpe/FindMembers.scala b/src/reflect/scala/reflect/internal/tpe/FindMembers.scala
@@ -7,7 +7,7 @@ package tpe
 
 import util.StatisticsStatics
 import Flags._
-import scala.runtime.ScalaRunTime
+import scala.runtime.Statics.releaseFence
 
 trait FindMembers {
   this: SymbolTable =>
@@ -282,7 +282,7 @@ trait FindMembers {
     } else {
       if (StatisticsStatics.areSomeColdStatsEnabled) statistics.incCounter(multMemberCount)
       lastM.next = Nil
-      ScalaRunTime.releaseFence()
+      releaseFence()
       initBaseClasses.head.newOverloaded(tpe, members)
     }
   }

diff --git a/src/reflect/scala/reflect/internal/util/Collections.scala b/src/reflect/scala/reflect/internal/util/Collections.scala
@@ -9,7 +9,7 @@ package reflect.internal.util
 import scala.collection.{immutable, mutable}
 import scala.annotation.tailrec
 import mutable.ListBuffer
-import scala.runtime.ScalaRunTime
+import scala.runtime.Statics.releaseFence
 
 /** Profiler driven changes.
  *  TODO - inlining doesn't work from here because of the bug that
@@ -59,7 +59,7 @@ trait Collections {
       tail = next
       rest = rest.tail
     }
-    ScalaRunTime.releaseFence()
+    releaseFence()
     head
   }
 
@@ -131,7 +131,7 @@ trait Collections {
       }
     }
     val result = loop(null, xs, xs, ys)
-    ScalaRunTime.releaseFence()
+    releaseFence()
     result
   }