Use index to get Encoding literal value at runtime

Author: bjfish

src/main/java/org/truffleruby/core/encoding/EncodingManager.java

@@ -51,6 +51,8 @@ public class EncodingManager {
     private static final int INITIAL_NUMBER_OF_ENCODINGS = EncodingDB.getEncodings().size();
 
     private final List<RubyEncoding> ENCODING_LIST_BY_ENCODING_INDEX = new ArrayList<>(INITIAL_NUMBER_OF_ENCODINGS);
+    @CompilationFinal(dimensions = 1) private final RubyEncoding[] BUILT_IN_ENCODINGS = //
+            new RubyEncoding[INITIAL_NUMBER_OF_ENCODINGS];
     private final Map<String, RubyEncoding> LOOKUP = new ConcurrentHashMap<>();
 
     private final RubyContext context;
@@ -79,7 +81,7 @@ private void initializeEncodings(RubyClass encodingClass) {
             final CaseInsensitiveBytesHashEntry<EncodingDB.Entry> e = hei.next();
             final EncodingDB.Entry encodingEntry = e.value;
             final RubyEncoding rubyEncoding = defineEncoding(encodingEntry, e.bytes, e.p, e.end);
-
+            BUILT_IN_ENCODINGS[encodingEntry.getEncoding().getIndex()] = rubyEncoding;
             for (String constName : EncodingUtils.encodingNames(e.bytes, e.p, e.end)) {
                 encodingClass.fields.setConstant(context, null, constName, rubyEncoding);
             }
@@ -318,4 +320,9 @@ public void setDefaultInternalEncoding(Encoding defaultInternalEncoding) {
     public Encoding getDefaultInternalEncoding() {
         return defaultInternalEncoding;
     }
+
+    public RubyEncoding getBuiltInEncoding(int index) {
+        return BUILT_IN_ENCODINGS[index];
+    }
+
 }

src/main/java/org/truffleruby/language/literal/EncodingLiteralNode.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2020 Oracle and/or its affiliates. All rights reserved. This
+ * code is released under a tri EPL/GPL/LGPL license. You can use it,
+ * redistribute it and/or modify it under the terms of the:
+ *
+ * Eclipse Public License version 2.0, or
+ * GNU General Public License version 2, or
+ * GNU Lesser General Public License version 2.1.
+ */
+package org.truffleruby.language.literal;
+
+import com.oracle.truffle.api.frame.VirtualFrame;
+import org.truffleruby.language.RubyContextSourceNode;
+
+public class EncodingLiteralNode extends RubyContextSourceNode {
+
+    private final int index;
+
+    public EncodingLiteralNode(int index) {
+        this.index = index;
+    }
+
+    @Override
+    public Object execute(VirtualFrame frame) {
+        return getContext().getEncodingManager().getBuiltInEncoding(index);
+    }
+
+}

src/main/java/org/truffleruby/parser/BodyTranslator.java

@@ -111,6 +111,7 @@
 import org.truffleruby.language.globals.ReadMatchReferenceNodes;
 import org.truffleruby.language.globals.WriteGlobalVariableNodeGen;
 import org.truffleruby.language.literal.BooleanLiteralNode;
+import org.truffleruby.language.literal.EncodingLiteralNode;
 import org.truffleruby.language.literal.FloatLiteralNode;
 import org.truffleruby.language.literal.IntegerFixnumLiteralNode;
 import org.truffleruby.language.literal.LongFixnumLiteralNode;
@@ -1308,7 +1309,7 @@ public RubyNode visitDotNode(DotParseNode node) {
     @Override
     public RubyNode visitEncodingNode(EncodingParseNode node) {
         SourceIndexLength sourceSection = node.getPosition();
-        final RubyNode ret = new ObjectLiteralNode(context.getEncodingManager().getRubyEncoding(node.getEncoding()));
+        final RubyNode ret = new EncodingLiteralNode(node.getEncoding().getIndex());
         ret.unsafeSetSourceSection(sourceSection);
         return addNewlineIfNeeded(node, ret);
     }