[ammarahm-ed]

Wrapping an object a Java method returned looked up its class by name on every call: GetObjectClass, Class.getName() through a Java up-call, a string replace, and a metadata lookup keyed by that string.

When a method's declared return type is the object's exact runtime class, which is the common case, none of that is needed. The declared class and its MetadataNode are now resolved once per call site and stored on MetadataEntry (returnClass, returnNode, returnClassResolved). Each call compares the returned object's class to the cached one with a single IsSameObject and builds the wrapper from the cached node. A polymorphic return, where the runtime class is a subclass of the declared one, falls back to the name lookup as before. Array returns, whose declared type is not an L descriptor, never use the cache.

ObjectManager::CreateJSWrapper gets an overload that takes the node and class directly, in both the Node-API and the direct runtime.

Results

V8 release build on a Sony SO-01M (Android 11, arm64), AOT-compiled with cmd package compile -m speed. One warm-up launch is discarded, then 5 launches; values are the median ns per call.

Case	Node-API before	after	Δ	Direct before	after	Δ
Return a new object	31,356	28,552	-9%	23,765	22,441	-6%
Call a method on a new object	39,072	36,425	-7%	33,952	31,500	-7%
Return a Date Object	30,484	28,744	-6%	24,658	23,343	-5%
Return this	1,248	1,320	+6%	1,279	1,327	+4%
Return a String	812	808	-0%	794	781	-2%

Object returns that create a new wrapper are 5–9% faster, which is at the edge of this device's noise for allocation-heavy rows (up to ±15%). Return this hands back an existing wrapper and does not reach this code. The cost that dominates a new-object return is the wrapper itself, which the later PRs in this stack address.

All cases

Case	Node-API before	after	Δ	Direct before	after	Δ
Void Method on instance	671	664	-1%	575	606	+5%
Field on instance	824	810	-2%	860	845	-2%
Int Field on instance	380	376	-1%	368	372	+1%
Get Static Field	834	826	-1%	879	846	-4%
Void Static Method	346	317	-8%	303	304	+0%
multiply(a, b)	510	528	+4%	537	511	-5%
Pass and return string	1,211	1,208	-0%	1,144	1,184	+4%
Return a String	812	808	-0%	794	781	-2%
Return an Int	339	335	-1%	312	304	-3%
Pass a String	703	677	-4%	665	657	-1%
Return a Boolean	334	326	-2%	307	300	-2%
Return a Double	409	400	-2%	386	364	-6%
Pass an Int	436	422	-3%	414	418	+1%
Pass a Double	428	402	-6%	434	409	-6%
Pass a Boolean	500	502	+1%	446	429	-4%
Return an Int Array	28,417	27,806	-2%	18,199	18,681	+3%
Pass an Int Array	3,356	3,266	-3%	4,116	4,138	+1%
Return a String Array	29,365	28,082	-4%	19,965	20,078	+1%
Pass a String Array	5,624	5,468	-3%	6,732	6,578	-2%
Return a Double Array	28,102	26,814	-5%	19,561	19,978	+2%
Pass a Double Array	3,249	3,214	-1%	3,941	3,952	+0%
Return a Boolean Array	27,043	25,587	-5%	18,685	19,182	+3%
Pass a Boolean Array	3,162	3,102	-2%	3,793	3,760	-1%
Int Array[0] read	366	343	-6%	259	250	-4%
String Array[0] read	771	787	+2%	684	666	-3%
Double Array[0] read	444	435	-2%	362	361	-0%
Boolean Array[0] read	349	352	+1%	253	234	-7%
Int Array[0] write	452	459	+1%	377	364	-4%
String Array[0] write	1,155	1,138	-2%	1,077	1,058	-2%
Double Array[0] write	476	476	+0%	386	372	-3%
Boolean Array[0] write	478	466	-2%	390	372	-5%
Return a Date Object	30,484	28,744	-6%	24,658	23,343	-5%
Pass a Date Object	3,931	3,865	-2%	3,597	3,657	+2%
Invoke void callback	7,254	7,288	+0%	6,884	6,887	+0%
Instance add(a, b)	855	854	-0%	799	816	+2%
Pass and return non-ASCII string	1,228	1,189	-3%	1,141	1,177	+3%
Pass and return 1KB string	5,065	5,073	+0%	4,997	5,133	+3%
Return a Char	373	361	-3%	341	355	+4%
Return this	1,248	1,320	+6%	1,279	1,327	+4%
Return a new object	31,356	28,552	-9%	23,765	22,441	-6%
Call a method on a new object	39,072	36,425	-7%	33,952	31,500	-7%
Pass a 16 Int Array	4,558	4,543	-0%	5,152	5,141	-0%
Pass a 16 Double Array	5,130	5,304	+3%	5,796	5,780	-0%
Invoke int callback	10,264	10,346	+1%	10,772	11,232	+4%
Invoke string callback	8,610	8,676	+1%	8,336	8,262	-1%
Native heap after run (MB)	257 MB	257 MB	+0%	183 MB	208 MB	+14%

Only V8 was built and run.

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