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Agent skill

Compiler Optimizations Deep

by mohitmishra786 in mohitmishra786/low-level-dev-skills

Deep compiler optimizations skill for RA, ISel, and PGO. An agent skill from mohitmishra786/low-level-dev-skills.

MITAuto-check passedDevelopment

Install Compiler Optimizations Deep

skills CLI
$ npx skills add mohitmishra786/low-level-dev-skills --skill compiler-optimizations-deep -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install mohitmishra786/low-level-dev-skills compiler-optimizations-deep --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/mohitmishra786/low-level-dev-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/compiler-internals/compiler-optimizations-deep .claude/skills/compiler-optimizations-deep && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
compiler-optimizations-deep
GitHub stars
253
Token cost
~839 tokens
SKILL.md length
237 words
Files
1
Skills in repo
138
Repo updated
First seen
Licence
MIT

At a glance

Deep compiler optimizations skill for RA, ISel, and PGO. An agent skill from mohitmishra786/low-level-dev-skills.

  • Works in 7 steps: Compiler pipeline map → Vectorization failure triage → Register allocation intuition → …
  • Explaining register allocation
  • SKILL.md covers Purpose, When to Use, Workflow and Common Problems, plus 1 more section
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Compiler Optimizations Deep is an agent skill from mohitmishra786/low-level-dev-skills. Deep compiler optimizations skill for RA, ISel, and PGO. Use when explaining register allocation, instruction selection, LICM, vectorization limits, or profile-guided optimization beyond -O3. Activates on queries about register allocation, instruction selection, LICM, auto-vectorization failure, PGO, or BOLT.

Its SKILL.md is about 840 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development. The repository describes itself as: A curated suite of AI agent skills for systems and low-level programming with C/C++, Rust, and Zig toolchains, covering compilers, debuggers, profilers, build systems…. The licence is MIT.

When your agent uses it

  • Explaining register allocation
  • Instruction selection
  • Vectorization limits
  • Profile-guided optimization beyond -O3

Example prompts

  • “/compiler-optimizations-deep”

Workflow steps

7 steps, taken from the step headings in SKILL.md.

  1. Compiler pipeline map
  2. Vectorization failure triage
  3. Register allocation intuition
  4. PGO workflow (Clang)
  5. BOLT (post-link)
  6. LICM example
  7. Agent usage

What it can do on your machine

Read from SKILL.md and the folder at commit bdc5847. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are bash).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Compiler Optimizations Deep loads about 839 tokens when it runs. Until then it costs about 85 tokens; SKILL.md has 237 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~85
When it runs · the whole SKILL.md, loaded when a task matches
~839

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from mohitmishra786/low-level-dev-skills at commit bdc5847, republished under its MIT licence (© mohitmishra786). 237 words, ~839 tokens.

Download SKILL.mdSave it as .claude/skills/compiler-optimizations-deep/SKILL.md (or your agent's skills folder).
name
compiler-optimizations-deep
description
Deep compiler optimizations skill for RA, ISel, and PGO. Use when explaining register allocation, instruction selection, LICM, vectorization limits, or profile-guided optimization beyond -O3. Activates on queries about register allocation, instruction selection, LICM, auto-vectorization failure, PGO, or BOLT.

Compiler Optimizations (Deep)

Purpose

Explain optimization phases beyond flags: mid-level IR opts, register allocation, instruction selection/scheduling, vectorization boundaries, PGO, and post-link BOLT — bridging skills/compilers/pgo and LLVM/GCC internals.

When to Use

  • -O3 did not vectorize a hot loop
  • Teaching why register pressure causes spills
  • Planning PGO or BOLT deployment
  • Understanding pass interaction (e.g., LICM before vectorize)

Workflow

1. Compiler pipeline map
Frontend → LLVM IR / GCC GIMPLE
├── Mid-level: DCE, GVN, LICM, inlining
├── Loop opts: unroll, vectorize
├── Codegen prep: legalize types
├── Instruction selection (DAG → machine ops)
├── Register allocation (greedy, linear scan)
└── Peephole / scheduling
2. Vectorization failure triage
bash
clang -O3 -Rpass=loop-vectorize -Rpass-missed=loop-vectorize foo.c
Miss reasonTypical fix
Unknown trip countpeel loop; assert count
Dependencereorder / separate accumulators
Function call in loopinline or outline
Alignment unknown__builtin_assume_aligned
3. Register allocation intuition

When live ranges exceed physical registers, the allocator spills to stack slots — costly loads/stores. Reducing live ranges (splitting variables, rematerialization) helps.

GCC/LLVM both use graph coloring variants (LLVM "greedy regalloc").

4. PGO workflow (Clang)
bash
clang -fprofile-instr-generate -O2 -o app foo.c
./app   # training workload
llvm-profdata merge default.profraw -o default.profdata
clang -fprofile-instr-use=default.profdata -O2 -o app_pgo foo.c

Improves branch layout, inlining, and vectorization thresholds.

See skills/compilers/pgo for GCC and BOLT.

5. BOLT (post-link)
bash
llvm-bolt -instrument app -o app.inst
./app.inst
llvm-bolt -data=perf.fdata -reorder-blocks=+ -o app.bolt app

Optimizes layout after linker — needs relocations (-Wl,--emit-relocs).

6. LICM example

Loop-invariant code motion hoists x * scale out of inner loop when legal — reduces work per iteration.

7. Agent usage
/compiler-optimizations-deep Why did LLVM fail to vectorize this reduction loop?

Common Problems

SymptomCauseFix
PGO no gainUnrepresentative trainingMatch production input
BOLT crashStripped binaryKeep symbols + relocs
Spills in asmRegister pressureSimplify live ranges
-O3 slowerCode bloat / cacheTry -O2 or PGO
Different GCC/ClangPass ordering differsCompare IR + asm
  • skills/compilers/pgo — PGO and BOLT detail
  • skills/compiler-internals/llvm-ir-and-passes — IR-level opts
  • skills/compiler-internals/code-generation-and-backends — ISel and backends
  • skills/computer-architecture/cpu-pipelines-and-hazards — scheduling context
  • skills/low-level-programming/simd-intrinsics — manual vectorization

© mohitmishra786, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/compiler-internals/compiler-optimizations-deep of mohitmishra786/low-level-dev-skills.

Open the folder on GitHubat commit bdc5847

Compare with similar skills

Compiler Optimizations Deep next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Compiler Optimizations Deep compared with similar skills
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Compiler Optimizations Deep this skillmohitmishra786/low-level-dev-skills253—~839Automated safety check: PassMIT
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PR Babysitteropeninterpreter/openinterpreter69k3 repos~4.2kAutomated safety check: PassApache-2.0
Code Review ChecklistshareAI-lab/learn-claude-code78k5 repos~1.1kAutomated safety check: PassMIT

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Categories

Questions about Compiler Optimizations Deep

What does Compiler Optimizations Deep do?

Deep compiler optimizations skill for RA, ISel, and PGO. An agent skill from mohitmishra786/low-level-dev-skills. Compiler Optimizations Deep is an agent skill from mohitmishra786/low-level-dev-skills. Deep compiler optimizations skill for RA, ISel, and PGO.

When should I use Compiler Optimizations Deep?

Compiler Optimizations Deep fits situations like: explaining register allocation; instruction selection; vectorization limits; profile-guided optimization beyond -O3.

How do I install Compiler Optimizations Deep in Claude Code?

Run `npx skills add mohitmishra786/low-level-dev-skills --skill compiler-optimizations-deep -a claude-code`. Or copy the skill folder (skills/compiler-internals/compiler-optimizations-deep in mohitmishra786/low-level-dev-skills) into .claude/skills/compiler-optimizations-deep in your project. Claude Code loads it when a task matches its description.

How do I install Compiler Optimizations Deep in Codex?

Run `npx skills add mohitmishra786/low-level-dev-skills --skill compiler-optimizations-deep -a codex`. Or copy the skill folder (skills/compiler-internals/compiler-optimizations-deep in mohitmishra786/low-level-dev-skills) into .agents/skills/compiler-optimizations-deep in your project. Codex loads it when a task matches its description.

Can I use Compiler Optimizations Deep in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add mohitmishra786/low-level-dev-skills --skill compiler-optimizations-deep -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/compiler-optimizations-deep, .gemini/skills/compiler-optimizations-deep, .github/skills/compiler-optimizations-deep and .opencode/skills/compiler-optimizations-deep in your project.

What does Compiler Optimizations Deep need to run?

SKILL.md names no scripts, command-line tools or credentials: Compiler Optimizations Deep is instructions for the agent only.

Does Compiler Optimizations Deep access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Compiler Optimizations Deep safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Compiler Optimizations Deep use?

Compiler Optimizations Deep is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Compiler Optimizations Deep use?

About 839 tokens (SKILL.md is roughly 3.4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Compiler Optimizations Deep?

Skills that share tags, products or a category with Compiler Optimizations Deep: Vercel Composition Patterns (supabase/supabase, 111k stars), Finishing a Development Branch (obra/superpowers, 296k stars), Typescript Advanced Types (rolling-scopes/rsschool-app, 10k stars) and PR Babysitter (openinterpreter/openinterpreter, 69k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Compiler Optimizations Deep?

mohitmishra786 (a GitHub user) maintains it in mohitmishra786/low-level-dev-skills, which has 253 GitHub stars. The repository holds 138 skills in this directory. The repository was last updated on June 27, 2026.

Source: mohitmishra786/low-level-dev-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.