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https://issues.apache.org/jira/browse/GROOVY-12284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18106839#comment-18106839
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ASF GitHub Bot commented on GROOVY-12284:
-----------------------------------------
daniellansun commented on code in PR #2822:
URL: https://github.com/apache/groovy/pull/2822#discussion_r3834991427
##########
src/main/java/org/codehaus/groovy/vmplugin/v8/Selector.java:
##########
@@ -1314,11 +1317,8 @@ public void setGuards(Object receiver) {
handle = MethodHandles.guardWithTest(test, handle,
fallback);
}
} else if (Arrays.stream(pt).anyMatch(nonFinalOrNullUnsafe)) {
- MethodHandle test = SAME_CLASSES
-
.bindTo(Arrays.stream(args).map(Object::getClass).toArray(Class[]::new))
- .asCollector(Object[].class, pt.length)
- .asType(MethodType.methodType(boolean.class, pt));
- handle = MethodHandles.guardWithTest(test, handle, fallback);
+ handle = MethodHandles.guardWithTest(
+ Selector.sameClassesGuard(args, pt), handle, fallback);
Review Comment:
Agreed.
- **Arity 0:** `anyMatch` on an empty `pt` is already false, and a receiver
is always present, so this branch never ran for a parameterless handle.
The helper no longer special-cases `n == 0` with a constant-`true`
combinator. If it is called with no parameters it falls through to an
empty collector (returns `true`); that path is tested. No no-op
`guardWithTest` is installed on the live call site.
- **`MethodType`:** the helper now takes `handle.type()` and uses
`callType.changeReturnType(boolean.class)` for the guard signature,
including primitive slots (GROOVY-11782).
- **`ClassValue` / call-site index:** agreed, that is a different change
(an extra argument on the bootstrap, a table on the host class). Not
something I would mix into this PR.
> 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
> Priority: Major
>
> 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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