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Compiler profiling and hotspot analysis.
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Based on SOC occupation classification
Use whenever adding an e2e compiler-output test (our JS vs the reference compiler) — a new cluster case under `tasks/compiler_tests/`.
🧩 PARITY · Turn one divergence from the Original into a test per affected case (does not fix).
Use when starting any compiler task or session before touching parser/analyze/transform/ast/codegen/css/diagnostics code, before proposing a design or writing code, and when the task grows into a new layer and you need its PRD invariants.
🔪 SDT · verdict-directed review of backend codegen/transform. Use when auditing codegen/transform for smart-analyzer / dumb-codegen violations, or when porting a transform/codegen visitor from the Original.
The required unit-test format for `crates/**/src/**` — use when writing or reviewing a Rust `#[test]`, a test helper, or an `assert_*`. Not for `tasks/compiler_tests/` (use add-test) or `tasks/diagnostic_tests/` (use add-diagnostic-test).
PRD editorial standard for docs/. Use when writing a new PRD, extending one, or reviewing changes under docs/ — and when another skill needs the PRD rules.
| name | profile |
| description | Compiler profiling and hotspot analysis. |
| argument-hint | [fresh] |
| allowed-tools | Bash, Read, Grep, Glob, mcp__narsil-mcp__* |
| disable-model-invocation | true |
./profile/ layout./profile/all/ — all cases × prod/dev (just bench-flame-all):
aggregate.top.txt — aggregated top across all cases<slug>_<mode>/top.txt — top of a single case<slug>_<mode>/profile.folded — folded stacks (can be up to 6 MB; do NOT read whole, only Grep by function name)<slug>_<mode>/profile.json, profile.json.syms.json — raw dumps, do NOT read whole; work through jq/grep surgically./profile/one/ — a single case (just bench-flame <path> [--dev]):
<slug>_<mode>/ aboveslug = path from tasks/benchmark/benches/compiler/ with / → _, without .svelte/.svelte.js.
mode = prod | dev.
If $ARGUMENTS == "fresh" — run just bench-flame-all. Tell the user the run takes ~4 min and start immediately, without asking for confirmation. After the run — read ./profile/all/aggregate.top.txt.
Otherwise — read the existing ./profile/all/aggregate.top.txt. If the file is missing — tell the user to run /profile fresh or just bench-flame-all manually and stop.
Analyze ./profile/all/. Work through the top-5 hotspots from aggregate.top.txt — every one, not just the first.
For each, find the driver-case: compare <slug>_<mode>/top.txt across subdirectories and pick where this function's self-% is highest.
Report on the hotspots: what's hot, why, and what to do about it.
When the user picks an option — dig into the driver-case of that hotspot and propose concrete changes.
To profile a single case in isolation — just bench-flame <path> [--dev] (artifacts in ./profile/one/, see above).