[jira] [Created] (GROOVY-12288) Cache ClassWriter getCommonSuperClass lookups per class

["Daniel Sun (Jira)" <ji...@apache.org>]

Daniel Sun created GROOVY-12288:
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             Summary: Cache ClassWriter getCommonSuperClass lookups per class
                 Key: GROOVY-12288
                 URL: https://issues.apache.org/jira/browse/GROOVY-12288
             Project: Groovy
          Issue Type: Improvement
            Reporter: Daniel Sun


Bytecode generation uses an ASM {{ClassWriter}} with {{{}COMPUTE_FRAMES{}}}. Frame computation calls {{getCommonSuperClass}} at every control-flow merge. Groovy overrides that method so types still being compiled are resolved through {{ClassNode}} ({{{}CompileUnit{}}}, generated inner classes, {{{}ClassNodeResolver{}}}) rather than {{{}Class.forName{}}}.

{{COMPUTE_FRAMES}} asks for the same binary-name pairs many times inside one class. Each call converts slashes to dots, resolves two \{{ClassNode}}s, and walks superclasses with isDerivedFrom. Class generation is about half of compile wall time.
h3. Approach

Memoize both steps on the {{ClassWriter}} created by {{{}CompilationUnit.createClassVisitor{}}}. One writer is allocated per generated class and discarded afterwards, so the maps cannot go stale across classes.
||Cache||Key||Value||
|{{classNodeByName}}|binary name (dot form)|{{ClassNode}} (successful lookups only)|
|{{commonSuperByPair}}|canonical pair of internal names|internal name of the common superclass|

The key is order-independent: {{(A,B)}} and {{(B,A)}} share one entry. Names are joined with {{{}>{}}}, which cannot appear in a JVM internal name.
{code:java}
// before (every merge point)
ClassNode a = getClassNode(arg1.replace('/', '.'));
ClassNode b = getClassNode(arg2.replace('/', '.'));
return getCommonSuperClassNode(a, b).getName().replace('.', '/');

// after
String key = arg1.compareTo(arg2) < 0 ? arg1 + '>' + arg2 : arg2 + '>' + arg1;
String cached = commonSuperByPair.get(key);
if (cached != null) {
    return cached;
}
// resolve, compute, store, return
{code}
The common-superclass algorithm is unchanged.
h3. Impact

Compile-time only. {{getCommonSuperClass}} results and generated bytecode stay the same.

 



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