src/java.base/share/classes/sun/invoke/util/ValueConversions.java

rev 15320 : 8163370: Reduce number of classes loaded by common usage of java.lang.invoke
Reviewed-by: igerasim, psandoz

*** 27,59 ****
  
  import java.lang.invoke.MethodHandle;
  import java.lang.invoke.MethodHandles;
  import java.lang.invoke.MethodHandles.Lookup;
  import java.lang.invoke.MethodType;
! import java.util.EnumMap;
  
  public class ValueConversions {
      private static final Class<?> THIS_CLASS = ValueConversions.class;
      private static final Lookup IMPL_LOOKUP = MethodHandles.lookup();
  
!     /** Thread-safe canonicalized mapping from Wrapper to MethodHandle
       * with unsynchronized reads and synchronized writes.
!      * It's safe to publish MethodHandles by data race because they are immutable. */
      private static class WrapperCache {
!         /** EnumMap uses preconstructed array internally, which is constant during it's lifetime. */
!         private final EnumMap<Wrapper, MethodHandle> map = new EnumMap<>(Wrapper.class);
  
          public MethodHandle get(Wrapper w) {
!             return map.get(w);
          }
          public synchronized MethodHandle put(final Wrapper w, final MethodHandle mh) {
!             // Simulate CAS to avoid racy duplication
!             MethodHandle prev = map.putIfAbsent(w, mh);
!             if (prev != null)  return prev;
              return mh;
          }
      }
  
      private static WrapperCache[] newWrapperCaches(int n) {
          WrapperCache[] caches = new WrapperCache[n];
          for (int i = 0; i < n; i++)
              caches[i] = new WrapperCache();
--- 27,64 ----
  
  import java.lang.invoke.MethodHandle;
  import java.lang.invoke.MethodHandles;
  import java.lang.invoke.MethodHandles.Lookup;
  import java.lang.invoke.MethodType;
! import jdk.internal.vm.annotation.Stable;
  
  public class ValueConversions {
      private static final Class<?> THIS_CLASS = ValueConversions.class;
      private static final Lookup IMPL_LOOKUP = MethodHandles.lookup();
  
!     /**
!      * Thread-safe canonicalized mapping from Wrapper to MethodHandle
       * with unsynchronized reads and synchronized writes.
!      * It's safe to publish MethodHandles by data race because they are immutable.
!      */
      private static class WrapperCache {
!         @Stable
!         private final MethodHandle[] map = new MethodHandle[Wrapper.COUNT];
  
          public MethodHandle get(Wrapper w) {
!             return map[w.ordinal()];
          }
          public synchronized MethodHandle put(final Wrapper w, final MethodHandle mh) {
!             MethodHandle prev = map[w.ordinal()];
!             if (prev != null) {
!                 return prev;
!             } else {
!                 map[w.ordinal()] = mh;
                  return mh;
              }
          }
+     }
  
      private static WrapperCache[] newWrapperCaches(int n) {
          WrapperCache[] caches = new WrapperCache[n];
          for (int i = 0; i < n; i++)
              caches[i] = new WrapperCache();
*** 621,631 ****
      static byte fromBoolean(boolean x) {
          // see javadoc for MethodHandles.explicitCastArguments
          return (x ? (byte)1 : (byte)0);
      }
  
!     private static final WrapperCache[] CONVERT_PRIMITIVE_FUNCTIONS = newWrapperCaches(Wrapper.values().length);
  
      public static MethodHandle convertPrimitive(Wrapper wsrc, Wrapper wdst) {
          WrapperCache cache = CONVERT_PRIMITIVE_FUNCTIONS[wsrc.ordinal()];
          MethodHandle mh = cache.get(wdst);
          if (mh != null) {
--- 626,636 ----
      static byte fromBoolean(boolean x) {
          // see javadoc for MethodHandles.explicitCastArguments
          return (x ? (byte)1 : (byte)0);
      }
  
!     private static final WrapperCache[] CONVERT_PRIMITIVE_FUNCTIONS = newWrapperCaches(Wrapper.COUNT);
  
      public static MethodHandle convertPrimitive(Wrapper wsrc, Wrapper wdst) {
          WrapperCache cache = CONVERT_PRIMITIVE_FUNCTIONS[wsrc.ordinal()];
          MethodHandle mh = cache.get(wdst);
          if (mh != null) {