Switch to a WeakValueCache for interned strings.

Author: aardvark179

src/main/java/org/truffleruby/RubyContext.java

@@ -46,6 +46,7 @@
 import org.truffleruby.core.rope.PathToRopeCache;
 import org.truffleruby.core.rope.Rope;
 import org.truffleruby.core.rope.RopeCache;
+import org.truffleruby.core.rope.RopeKey;
 import org.truffleruby.core.string.CoreStrings;
 import org.truffleruby.core.string.FrozenStringLiterals;
 import org.truffleruby.core.symbol.SymbolTable;
@@ -119,6 +120,7 @@ public class RubyContext {
     private final PreInitializationManager preInitializationManager;
     private final NativeConfiguration nativeConfiguration;
     private final ValueWrapperManager valueWrapperManager = new ValueWrapperManager(this);
+    private final WeakValueCache<RopeKey, DynamicObject> internedStringCache = new WeakValueCache<>();
 
     private final CompilerOptions compilerOptions = Truffle.getRuntime().createCompilerOptions();
 
@@ -782,6 +784,10 @@ public ValueWrapperManager getValueWrapperManager() {
         return valueWrapperManager;
     }
 
+    public WeakValueCache<RopeKey, DynamicObject> getInternedStringCache() {
+        return internedStringCache;
+    }
+
     private static SecureRandom createRandomInstance() {
         try {
             /*

src/main/java/org/truffleruby/core/string/TruffleStringNodes.java

@@ -13,10 +13,12 @@
 import com.oracle.truffle.api.dsl.Cached;
 import com.oracle.truffle.api.dsl.Specialization;
 import com.oracle.truffle.api.object.DynamicObject;
+import org.truffleruby.Layouts;
 import org.truffleruby.builtins.CoreClass;
 import org.truffleruby.builtins.CoreMethod;
 import org.truffleruby.builtins.CoreMethodArrayArgumentsNode;
 import org.truffleruby.core.rope.Rope;
+import org.truffleruby.core.rope.RopeKey;
 import org.truffleruby.core.rope.RopeNodes;
 import org.truffleruby.language.RubyGuards;
 import org.truffleruby.language.control.RaiseException;
@@ -70,4 +72,12 @@ private String formatTooLongError(int count, final Rope rope) {
 
     }
 
+    @CoreMethod(names = "intern_string", onSingleton = true, required = 1)
+    public abstract static class InternNode extends CoreMethodArrayArgumentsNode {
+
+        @Specialization
+        public DynamicObject internString(DynamicObject string) {
+            return getContext().getInternedStringCache().addInCacheIfAbsent(new RopeKey(Layouts.STRING.getRope(string), getContext().getHashing(this)), string);
+        }
+    }
 }

src/main/ruby/core/truffle/string_operations.rb

@@ -11,12 +11,6 @@
 module Truffle
   module StringOperations
 
-    FROZEN_STRING_HASH = {}
-
-    def self.intern_string(str)
-      FROZEN_STRING_HASH[str] ||= str
-    end
-
     # Similar to MRI's Warning::buffer class
     class SimpleStringIO
       attr_reader :string