perf: optimize generated native dispatch

[DjDeveloperr]

Summary

• Adds engine-direct native dispatch paths so V8, Hermes, QuickJS, and JSC can bypass the generic Node-API call path for generated Objective-C/C function dispatch while keeping the Node-API backend available for non-direct builds.
• Extends generated signature dispatch with engine-specific backends, direct return handling, Hermes frame-argument dispatch, and fast block invoke support.
• Optimizes bridge hot paths: leaner primitive/object marshalling, cached receiver/object/selector lookups, direct function/block invocation, and Hermes NSArray/NSMutableArray indexed access without the Proxy path for normal arrays.
• Adds/updates the Objective-C dispatch benchmark harness for same-harness comparisons across NAPI engines and legacy iOS V8 AOT on/off.

Benchmark Results

Command family: node benchmarks/objc-dispatch/run.js --iterations 250000 using the same simulator/harness for all rows.

runtime	total ms	vs best	vs legacy AOT on
v8 gsd-on	392.30	0.00	-52.13%
hermes gsd-on	437.71	+45.40	-46.59%
quickjs gsd-on	484.62	+92.32	-40.87%
v8 gsd-off	491.81	+99.51	-39.99%
hermes gsd-off	524.35	+132.04	-36.02%
quickjs gsd-off	535.76	+143.45	-34.63%
jsc gsd-on	547.74	+155.43	-33.17%
jsc gsd-off	594.84	+202.54	-27.42%
legacy aot-on	819.54	+427.24	baseline
legacy aot-off	942.25	+549.95	+14.97%

GSD deltas:

target	on total ms	off total ms	win ms	win %
v8 GSD	392.30	491.81	99.51	25.37%
hermes GSD	437.71	524.35	86.64	19.79%
quickjs GSD	484.62	535.76	51.13	10.55%
jsc GSD	547.74	594.84	47.10	8.60%
legacy AOT	819.54	942.25	122.71	14.97%

Result files:

• build/benchmarks/objc-dispatch/results-2026-05-22T19-44-10-380Z.json
• build/benchmarks/objc-dispatch/results-2026-05-22T19-46-55-756Z.json
• build/benchmarks/objc-dispatch/results-2026-05-22T19-48-29-266Z.json
• build/benchmarks/objc-dispatch/results-2026-05-22T19-49-26-650Z.json
• build/benchmarks/objc-dispatch/results-2026-05-22T19-50-11-344Z.json

Validation

• git diff --check origin/main..HEAD
• IOS_TEST_ENGINE=hermes IOS_TEST_TIMEOUT_MS=900000 IOS_BUILD_TIMEOUT_MS=900000 npm run test:ios
  • SUCCESS: 705 specs, 0 failures, 14 skipped, 0 disabled
• Built and benchmarked NAPI iOS runtime for V8, Hermes, QuickJS, and JSC simulator engines.
• Built and benchmarked legacy iOS V8 runtime with AOT on/off.

Review Notes

• HostObject method dispatch was investigated and rejected because method property callbacks were dramatically slower than the optimized wrapper/prototype path.
• Hermes array optimization keeps placeholder arrays on the Proxy path and uses prototype numeric accessors only for initialized arrays.
• Direct paths are compile-gated per engine/backend; the generic Node-API path remains for non-direct/non-engine builds.