A possible improvement at Tokens and Names

[Jonathan Gibbons]

Hi,

I'll create a JBS issue to track this. In itself, that does not imply a 
review or an endorsement of the idea, but it does provide a place to 
record the discussion.
https://bugs.openjdk.java.net/browse/JDK-8260053

Can you post the patch as a PR?

-- Jon

On 1/20/21 4:10 AM, Guoxiong Li wrote:
> 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 <http://t.name> != null)
> -                enterKeyword(t.name <http://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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