shared scope prototype

[jbolda]

Motivation

Playing around with @e18e/deopt to see if we can squeeze out a bit more perf. With scope being hit so often, having a shared prototype avoids some deopt.

Approach

• this seemed to be the biggest gain, and presume it will be a situation that continues to exist in the future
• other items raised seemed to not make as much of a difference and/or felt like they could change in the future

Deoptimization report

deopt: dependent allocation site transition changed (high)

• build/npm/esm/lib/api.js:53:24 dispatch

deopt: unexpected name in keyed access (high)

• build/npm/esm/lib/api.js:55:65

deopt: wrong map (high)

The optimized code was specialized for objects of one shape here, but got an object with a different shape, so it had to deoptimize. Keep the objects reaching this line consistent (the same properties added in the same order) so V8 can rely on their shape.

• build/npm/esm/lib/api.js:57:21 $scope.reduce.min

ic: megamorphic (high)

This access saw too many different object shapes, so its inline cache went megamorphic and V8 can no longer optimize it. Keep the objects reaching this line consistent (the same properties added in the same order) so the access can stay monomorphic.

• build/npm/esm/lib/api.js:55:65
• build/npm/esm/lib/api.js:67:28 createHandle
• build/npm/esm/lib/api.js:68:25 createHandle
• build/npm/esm/lib/api.js:68:63 handle.
• build/npm/esm/lib/scope-internal.js:12:30 get
• build/npm/esm/lib/scope-internal.js:97:35 reduce
• build/npm/esm/lib/scope-internal.js:134:32 destroy
• build/npm/esm/lib/delimiter.js:100:27 close
• build/npm/esm/lib/delimiter.js:107:25 close
• build/npm/esm/lib/api/scope.js:8:39 set
• build/npm/esm/lib/box.js:4:26 box

code: optimization churn (medium)

V8 re-optimized this function repeatedly without settling on a single optimized version. This churn wastes compilation work and usually points to types or object shapes that keep changing between calls. Keep the values reaching this function consistent so V8 can optimize it once and keep that code.

• build/npm/esm/lib/api.js:53:24 dispatch

ic: polymorphic (medium)

• build/npm/esm/lib/delimiter.js:134:28
• build/npm/esm/lib/task.js:41:25

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/effection@1197

commit: 000e3c4

[codspeed-hq]

Merging this PR will not alter performance

✅ 6 untouched benchmarks

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_{Comparing shared-scope-prototype (000e3c4) with v4 (49fe66f)}