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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