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https://issues.apache.org/jira/browse/GROOVY-12284?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daniel Sun resolved GROOVY-12284.
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Fix Version/s: 6.0.0-beta-3
Assignee: Daniel Sun
Resolution: Fixed
> Specialize indy sameClasses guards for arity 1-4
> ------------------------------------------------
>
> Key: GROOVY-12284
> URL: https://issues.apache.org/jira/browse/GROOVY-12284
> Project: Groovy
> Issue Type: Improvement
> Reporter: Daniel Sun
> Assignee: Daniel Sun
> Priority: Major
> Fix For: 6.0.0-beta-3
>
>
> h3. Problem
> When an invokedynamic site is linked with all arguments non-null and at least
> one parameter type that is non-final (or a primitive wrapper — GROOVY-11782),
> {{Selector}} installs a same-class guard:
> {code:java}
> SAME_CLASSES
> .bindTo(expectedClasses)
> .asCollector(Object[].class, n)
> .asType(MethodType.methodType(boolean.class, pt));
> {code}
> {{asCollector}} of an {{Object}} array of length {{n}} allocates a fresh
> array on *every later invocation* of that site; the array overload of
> {{sameClasses}} then walks it.
> That is the hot path for ordinary dynamic Groovy calls of the shapes
> {{recv.foo()}}, {{recv.foo(a)}}, {{recv.foo(a, b)}}, {{recv.foo(a, b, c)}} —
> arity 1-4 (receiver plus 0-3 arguments). Dynamic indy sites almost always
> have {{Object}} parameter types, so this guard is the common case, not a rare
> fallback.
> (If any argument is {{null}} at link time, {{Selector}} already installs
> per-slot {{SAME_CLASS}} / {{IS_NULL}} tests and does not use the collector.)
> The classic MOP already specializes this check:
> {{MetaClassHelper.sameClasses}} has overloads for 0-4 arguments so the
> call-site cache does not box arguments into an array. The indy guard did not.
> h3. Goal
> Keep the same guard semantics (return {{false}} if any argument is {{null}}
> or has a different runtime class) without allocating an {{Object}} array on
> the common 1-4 arity shapes.
> h3. Approach
> ||Arity (incl. receiver)||Guard||
> |0|constant {{true}}|
> |1|existing {{SAME_CLASS}}|
> |2|new {{SAME_CLASSES_2}}|
> |3|new {{SAME_CLASSES_3}}|
> |4|new {{SAME_CLASSES_4}}|
> |5 or more|existing {{SAME_CLASSES}} plus {{asCollector}} (unchanged)|
> Expected classes are bound with {{bindTo}}. One {{guardWithTest}} at the
> site, via a single {{Selector.sameClassesGuard(args, pt)}} helper.
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