A possible improvement at Tokens and Names

[Guoxiong Li]

Hi all,

When I read the code at `jdk.compiler/com.sun.tools.javac.parser.Tokens`
and ``jdk.compiler/com.sun.tools.javac.util.Names`, I find a  point which
can be possibly improved.

The constructor of the class `Tokens` invokes `Names.instance(context)` to
initialize `Names` which would initialize many unrelated names. Then, this
constructor uses the method `enterKeyword` to initialize the names about
`TokenKind` and to set `maxKey`. Because `Names.instance(context)`
initializes many unrelated names, the `Name.index` becomes very large so
that the `maxKey` also becomes very large. Then, the constructor creates an
array `key` by using the code `key =  new TokenKind[maxKey+1]`. We can
identify that the variable `key` is unnecessary to be so large.

I would like to initialize the related names, which are about `TokenKind`,
at the beginning of the constructor of the class `Names` to improve the
code. The complete patch is shown at the end of this email.

When using the code of the master branch, the length of the array
`Tokens.key` is 4280. When using my patch, the length of the array
`Tokens.key` is 383. The improvement is obvious.

Could I get your help to identify whether this improvement is feasible?
If so, could I get your help to file an issue at the bug tracker? Thanks a
lot.



The patch:

diff --git
a/src/jdk.compiler/share/classes/com/sun/tools/javac/parser/Tokens.java
b/src/jdk.compiler/share/classes/com/sun/tools/javac/parser/Tokens.java
index bd61dcf8ad2..3b4eb5bf4be 100644
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/parser/Tokens.java
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/parser/Tokens.java
@@ -60,7 +60,7 @@ public class Tokens {

     /** The names of all tokens.
      */
-    private Name[] tokenName = new Name[TokenKind.values().length];
+    private Name[] tokenName;

     public static final Context.Key<Tokens> tokensKey = new
Context.Key<>();

@@ -74,11 +74,10 @@ public class Tokens {
     protected Tokens(Context context) {
         context.put(tokensKey, this);
         names = Names.instance(context);
-        for (TokenKind t : TokenKind.values()) {
-            if (t.name != null)
-                enterKeyword(t.name, t);
-            else
-                tokenName[t.ordinal()] = null;
+        tokenName = names.tokenName;
+        for (Name n : tokenName) {
+            if (n != null && n.getIndex() > maxKey)
+                maxKey = n.getIndex();
         }

         key = new TokenKind[maxKey+1];
@@ -89,12 +88,6 @@ public class Tokens {
         }
     }

-    private void enterKeyword(String s, TokenKind token) {
-        Name n = names.fromString(s);
-        tokenName[token.ordinal()] = n;
-        if (n.getIndex() > maxKey) maxKey = n.getIndex();
-    }
-
     /**
      * Create a new token given a name; if the name corresponds to a token
name,
      * a new token of the corresponding kind is returned; otherwise, an
diff --git
a/src/jdk.compiler/share/classes/com/sun/tools/javac/util/Names.java
b/src/jdk.compiler/share/classes/com/sun/tools/javac/util/Names.java
index 26e0b7577aa..341817e8ff9 100644
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/util/Names.java
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/util/Names.java
@@ -25,6 +25,8 @@

 package com.sun.tools.javac.util;

+import com.sun.tools.javac.parser.Tokens.TokenKind;
+
 /**
  * Access to the compiler's name table.  Standard names are defined,
  * as well as methods to create new names.
@@ -47,6 +49,9 @@ public class Names {
         return instance;
     }

+    // the names about TokenKind
+    public final Name[] tokenName = new Name[TokenKind.values().length];
+
     // operators and punctuation
     public final Name asterisk;
     public final Name comma;
@@ -220,6 +225,15 @@ public class Names {
         Options options = Options.instance(context);
         table = createTable(options);

+        // set the names about TokenKind
+        for (TokenKind tokenKind : TokenKind.values()) {
+            Name tempName = null;
+            if (tokenKind.name != null) {
+                tempName = fromString(tokenKind.name);
+            }
+            tokenName[tokenKind.ordinal()] = tempName;
+        }
+
         // operators and punctuation
         asterisk = fromString("*");
         comma = fromString(",");
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