swift-runtime-performance

Name: swift-runtime-performance
Author: Livsy90

88stars5forks

How to install swift-runtime-performance?

livsy90/ios-performance-agent-skills/swift-runtime-performance

$npx -y skills add Livsy90/iOS-Performance-Agent-Skills --skill swift-runtime-performance

Installs into the current project.

Summary

Use this skill when reviewing Swift code for runtime-level performance costs, including heap allocation, ARC traffic, stack vs heap storage, closure capture contexts, method dispatch, protocol witness dispatch, existentials vs generics, opaque types, copy-on-write, SIL optimizer

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View on GitHub

SKILL.md

1	# Swift Runtime Performance
2
3	## Purpose
4
5	Use this skill to review Swift code for runtime-level performance costs without turning every abstraction into a problem. Focus on concrete costs such as allocation, ARC traffic, dispatch, specialization, copying, optimizer visibility, and unsafe memory boundaries.
6
7	This skill should help the agent distinguish real hot-path runtime costs from theoretical micro-optimizations.
8
9	## When to use this skill
10
11	Use this skill when the task involves Swift runtime behavior such as:
12
13	- heap allocation, stack vs heap storage, object layout, boxed values, or closure contexts;
14	- ARC retain/release traffic, ownership, lifetime, weak/unowned references, or closure captures;
15	- direct dispatch, class dispatch, Objective-C dispatch, witness dispatch, or dynamic dispatch in hot paths;
16	- `any Protocol`, `some Protocol`, generics, type erasure, specialization, or unspecialized hot code;
17	- copy-on-write collections, large values, custom COW storage, or repeated copies;
18	- optimized SIL inspection, compiler optimization, inlining, devirtualization, or specialization evidence;
19	- unsafe Swift, pointer lifetime, memory binding, aliasing, buffer mutation, or safe wrappers around unsafe regions;
20	- module boundaries that affect optimizer visibility, `@inlinable`, `@usableFromInline`, `@frozen`, or public API resilience trade-offs.
21
22	## When not to use this skill
23
24	Do not use this skill for:
25
26	- general Swift syntax or API usage questions with no runtime performance concern;
27	- app launch investigations where the main issue is pre-main, dyld, static initializers, SDK startup, first frame, or first interaction;
28	- SwiftUI performance issues where the main issue is identity, invalidation, state scope, layout, drawing, animation, or scrolling;
29	- Swift Concurrency issues where the main issue is task lifetime, actor isolation, MainActor responsiveness, cancellation, AsyncSequence cleanup, reentrancy, or executor behavior;
30	- profiling workflow questions where the main task is choosing tools, interpreting traces, designing signposts, XCTest metrics, MetricKit, or production signals;
31	- broad architecture questions unless there is a specific runtime cost in a hot path.
32
33	If another skill is more specific, route there first and use this skill only for the runtime subproblem.
34
35	## Neighbor skill boundaries
36
37	Use these boundaries before applying runtime advice:
38
39	- Use `swift-concurrency-performance` when the task centers on actors, tasks, MainActor, cancellation, AsyncSequence, continuations, task groups, executor behavior, or responsiveness under async work.
40	- Use `ios-launch-performance` when the task centers on cold launch, warm launch, pre-main, dyld, framework loading, static initializers, AppDelegate, SwiftUI `App`, first frame, first interaction, or launch metrics.
41	- Use `swiftui-performance` when the task centers on SwiftUI body evaluation, invalidation, identity, state ownership, dependency scope, `List`, `LazyVStack`, layout, drawing, animation, or lifecycle work in views.
42	- Use `ios-performance-profiling` when the task centers on choosing Instruments templates, interpreting traces, XCTest metrics, MetricKit, signposts, memory graphs, hangs, hitches, CPU, allocations, disk I/O, networking, or production telemetry.
43	- Use this skill when a neighboring task reveals a Swift runtime-level cost such as allocation churn, ARC traffic, existential boxing, witness dispatch, unspecialized generics, repeated COW copies, or unsafe memory boundaries.
44
45	## Core principle
46
47	Do not optimize based only on how the source code looks.
48
49	First identify:
50
51	1. whether the code is on a hot path;
52	2. what runtime cost is suspected;
53	3. whether the cost is visible in measurement, compiler output, or a small benchmark;
54	4. whether the proposed change preserves semantics and improves the measured path;
55	5. what trade-off the change introduces.
56
57	A runtime optimization is useful only when it reduces cost in a path that matters.
58
59	## Runtime cost taxonomy
60
61	Classify the suspected issue before recommending a change.
62
63	Use these categories:
64
65	- Allocation — heap objects, boxes, closure contexts, existential containers, temporary objects, intermediate collections.
66	- ARC — retain/release traffic, closure captures, weak/unowned access, bridged object lifetime, reference-backed value storage.
67	- Dispatch — dynamic dispatch, witness dispatch, Objective-C dispatch, closure calls, missed

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swift-runtime-performance

88stars5forks

View on GitHub

How to install swift-runtime-performance?

livsy90/ios-performance-agent-skills/swift-runtime-performance

$npx -y skills add Livsy90/iOS-Performance-Agent-Skills --skill swift-runtime-performance

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# Swift Runtime Performance
2
3	## Purpose
4
5	Use this skill to review Swift code for runtime-level performance costs without turning every abstraction into a problem. Focus on concrete costs such as allocation, ARC traffic, dispatch, specialization, copying, optimizer visibility, and unsafe memory boundaries.
6
7	This skill should help the agent distinguish real hot-path runtime costs from theoretical micro-optimizations.
8
9	## When to use this skill
10
11	Use this skill when the task involves Swift runtime behavior such as:
12
13	- heap allocation, stack vs heap storage, object layout, boxed values, or closure contexts;
14	- ARC retain/release traffic, ownership, lifetime, weak/unowned references, or closure captures;
15	- direct dispatch, class dispatch, Objective-C dispatch, witness dispatch, or dynamic dispatch in hot paths;
16	- `any Protocol`, `some Protocol`, generics, type erasure, specialization, or unspecialized hot code;
17	- copy-on-write collections, large values, custom COW storage, or repeated copies;
18	- optimized SIL inspection, compiler optimization, inlining, devirtualization, or specialization evidence;
19	- unsafe Swift, pointer lifetime, memory binding, aliasing, buffer mutation, or safe wrappers around unsafe regions;
20	- module boundaries that affect optimizer visibility, `@inlinable`, `@usableFromInline`, `@frozen`, or public API resilience trade-offs.
21
22	## When not to use this skill
23
24	Do not use this skill for:
25
26	- general Swift syntax or API usage questions with no runtime performance concern;
27	- app launch investigations where the main issue is pre-main, dyld, static initializers, SDK startup, first frame, or first interaction;
28	- SwiftUI performance issues where the main issue is identity, invalidation, state scope, layout, drawing, animation, or scrolling;
29	- Swift Concurrency issues where the main issue is task lifetime, actor isolation, MainActor responsiveness, cancellation, AsyncSequence cleanup, reentrancy, or executor behavior;
30	- profiling workflow questions where the main task is choosing tools, interpreting traces, designing signposts, XCTest metrics, MetricKit, or production signals;
31	- broad architecture questions unless there is a specific runtime cost in a hot path.
32
33	If another skill is more specific, route there first and use this skill only for the runtime subproblem.
34
35	## Neighbor skill boundaries
36
37	Use these boundaries before applying runtime advice:
38
39	- Use `swift-concurrency-performance` when the task centers on actors, tasks, MainActor, cancellation, AsyncSequence, continuations, task groups, executor behavior, or responsiveness under async work.
40	- Use `ios-launch-performance` when the task centers on cold launch, warm launch, pre-main, dyld, framework loading, static initializers, AppDelegate, SwiftUI `App`, first frame, first interaction, or launch metrics.
41	- Use `swiftui-performance` when the task centers on SwiftUI body evaluation, invalidation, identity, state ownership, dependency scope, `List`, `LazyVStack`, layout, drawing, animation, or lifecycle work in views.
42	- Use `ios-performance-profiling` when the task centers on choosing Instruments templates, interpreting traces, XCTest metrics, MetricKit, signposts, memory graphs, hangs, hitches, CPU, allocations, disk I/O, networking, or production telemetry.
43	- Use this skill when a neighboring task reveals a Swift runtime-level cost such as allocation churn, ARC traffic, existential boxing, witness dispatch, unspecialized generics, repeated COW copies, or unsafe memory boundaries.
44
45	## Core principle
46
47	Do not optimize based only on how the source code looks.
48
49	First identify:
50
51	1. whether the code is on a hot path;
52	2. what runtime cost is suspected;
53	3. whether the cost is visible in measurement, compiler output, or a small benchmark;
54	4. whether the proposed change preserves semantics and improves the measured path;
55	5. what trade-off the change introduces.
56
57	A runtime optimization is useful only when it reduces cost in a path that matters.
58
59	## Runtime cost taxonomy
60
61	Classify the suspected issue before recommending a change.
62
63	Use these categories:
64
65	- Allocation — heap objects, boxes, closure contexts, existential containers, temporary objects, intermediate collections.
66	- ARC — retain/release traffic, closure captures, weak/unowned access, bridged object lifetime, reference-backed value storage.
67	- Dispatch — dynamic dispatch, witness dispatch, Objective-C dispatch, closure calls, missed

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6 picks

Type