perf: shrink generated wrapper source#264
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This reduces iitm's per-module compile cost by emitting the export read / defer / override / set / get wiring once per wrapper rather than per export. On a 396-module / 3258-export graph (synchronous in-thread loader, Node 24.16): wrapper source 2.85 MiB -> 1.25 MiB, compileSourceTextModule 47.1 ms -> 24.8 ms, total wrap+load 192.8 ms -> 144.4 ms.
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bengl
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Jun 30, 2026
| __pending = next | ||
| } | ||
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| function __bind (key, write, read, useFallback) { |
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These double-underscores to hide things are going to break at some point.
bengl
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Jun 30, 2026
timfish
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Jun 30, 2026
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Summary
Every wrapped module makes Node compile a generated wrapper, and that compile is the dominant iitm startup cost once the parser is no longer Acorn. Each export inlined ~25 lines of identical read / defer / override / set / get wiring, so a realistic 396-module / 3258-export graph emitted 2.85 MiB of wrapper source for V8 to parse. This moves that wiring into a single
__bindhelper emitted once per wrapper; each export keeps only the liveletbinding and staticexportthe module system requires, plus a one-line__bindcall.Behavior is unchanged: live bindings, deferred resolution for circular imports, the Hook set/get proxy, and the Node 23+
module.exportsfallback all keep their existing semantics.Numbers
396-module / 3258-export graph, synchronous in-thread loader, Node 24.16,
--cpu-prof --cpu-prof-interval=50:compileSourceTextModuleself time: 47.1 ms -> 24.8 msTest plan
npm testtest/register/v22.15-sync-register-hooks*.mjs)module.exportsbuiltin fallback still resolveStacked on #259 (es-module-lexer); the compile win is what remains after the parser swap, so review/merge after that.