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https://issues.apache.org/jira/browse/GROOVY-12284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18106837#comment-18106837
]
ASF GitHub Bot commented on GROOVY-12284:
-----------------------------------------
daniellansun commented on code in PR #2822:
URL: https://github.com/apache/groovy/pull/2822#discussion_r3834984396
##########
src/main/java/org/codehaus/groovy/vmplugin/v8/Selector.java:
##########
@@ -1533,4 +1533,42 @@ private static Class<?> getThisType(Class<?> sender) {
}
return sender;
}
+
+ /**
+ * Builds a same-class guard that avoids {@code
asCollector(Object[].class, n)}
+ * for the common 1–4 argument shapes (receiver plus 0–3 parameters).
+ * The produced handle has type {@code (pt)boolean} and returns {@code
false}
+ * if any argument is {@code null} or has a different runtime class.
+ */
+ static MethodHandle sameClassesGuard(final Object[] args, final Class<?>[]
pt) {
+ int n = pt.length;
+ MethodType booleanType = MethodType.methodType(boolean.class, pt);
+ if (n == 0) {
+ return MethodHandles.constant(boolean.class, true);
+ }
+ if (n == 1) {
+ return SAME_CLASS.bindTo(args[0].getClass()).asType(booleanType);
+ }
+ if (n == 2) {
+ return SAME_CLASSES_2
+ .bindTo(args[0].getClass()).bindTo(args[1].getClass())
+ .asType(booleanType);
+ }
+ if (n == 3) {
+ return SAME_CLASSES_3
+
.bindTo(args[0].getClass()).bindTo(args[1].getClass()).bindTo(args[2].getClass())
+ .asType(booleanType);
+ }
+ if (n == 4) {
+ return SAME_CLASSES_4
+ .bindTo(args[0].getClass()).bindTo(args[1].getClass())
+ .bindTo(args[2].getClass()).bindTo(args[3].getClass())
+ .asType(booleanType);
+ }
+ Class<?>[] classes = new Class<?>[n];
+ for (int i = 0; i < n; i++) {
+ classes[i] = args[i].getClass();
+ }
+ return SAME_CLASSES.bindTo(classes).asCollector(Object[].class,
n).asType(booleanType);
+ }
Review Comment:
Thanks, Jochen — that is the better shape, and it already matches how
`IndyCompoundAssign` binds its class guard.
`Selector.sameClassesGuard` now does:
```java
return MethodHandles.insertArguments(SAME_CLASS_GUARDS[n], 0, classes)
.asType(callType.changeReturnType(boolean.class));
```
`SAME_CLASS_GUARDS` is `{null, SAME_CLASS, SAME_CLASSES_2, SAME_CLASSES_3,
SAME_CLASSES_4}`.
One adapter at arity 4 instead of four. Link-time only.
`SameClassesGuardMhBench.specialised_bindTo_arity4` keeps the old chained
`bindTo` so we can see if the single `insertArguments` actually moves the
needle. On this host the isolated arity-4 combinator is **0.99×**
(`insertArguments` vs chained `bindTo`, CIs overlap). Production uses
`insertArguments` for the idiomatic one-adapter shape; the end-to-end win
against the collector parent is unchanged (arity 4 still **4.68×**).
> 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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