llvm

Included with Lifetime

$97 forever

LLVM IR and pass pipeline skill. Use when working directly with LLVM Intermediate Representation (IR), running opt passes, generating IR with llc, inspecting or writing LLVM IR for custom passes, or understanding how the LLVM backend lowers IR to assembly. Activates on queries about LLVM IR, opt, llc, llvm-dis, LLVM passes, IR transformations, or building LLVM-based tools.

Backend & APIs

What this skill does


# LLVM IR and Tooling

## Purpose

Guide agents through the LLVM IR pipeline: generating IR, running optimisation passes with `opt`, lowering to assembly with `llc`, and inspecting IR for debugging or performance work.

## Triggers

- "Show me the LLVM IR for this function"
- "How do I run an LLVM optimisation pass?"
- "What does this LLVM IR instruction mean?"
- "How do I write a custom LLVM pass?"
- "Why isn't auto-vectorisation happening in LLVM?"

## Workflow

### 1. Generate LLVM IR

```bash
# Emit textual IR (.ll)
clang -O0 -emit-llvm -S src.c -o src.ll

# Emit bitcode (.bc)
clang -O2 -emit-llvm -c src.c -o src.bc

# Disassemble bitcode to text
llvm-dis src.bc -o src.ll
```

### 2. Run optimisation passes with `opt`

```bash
# Apply a specific pass
opt -passes='mem2reg,instcombine,simplifycfg' src.ll -S -o out.ll

# Standard optimisation pipelines
opt -passes='default<O2>' src.ll -S -o out.ll
opt -passes='default<O3>' src.ll -S -o out.ll

# List available passes
opt --print-passes 2>&1 | less

# Print IR before and after a pass
opt -passes='instcombine' --print-before=instcombine --print-after=instcombine src.ll -S -o out.ll 2>&1 | less
```

### 3. Lower IR to assembly with `llc`

```bash
# Compile IR to object file
llc -filetype=obj src.ll -o src.o

# Compile to assembly
llc -filetype=asm -masm-syntax=intel src.ll -o src.s

# Target a specific CPU
llc -mcpu=skylake -mattr=+avx2 src.ll -o src.s

# Show available targets
llc --version
```

### 4. Inspect IR

Key IR constructs to understand:

| Construct | Meaning |
|-----------|---------|
| `alloca` | Stack allocation (pre-SSA; `mem2reg` promotes to registers) |
| `load`/`store` | Memory access |
| `getelementptr` (GEP) | Pointer arithmetic / field access |
| `phi` | SSA φ-node: merges values from predecessor blocks |
| `call`/`invoke` | Function call (`invoke` has exception edges) |
| `icmp`/`fcmp` | Integer/float comparison |
| `br` | Branch (conditional or unconditional) |
| `ret` | Return |
| `bitcast` | Reinterpret bits (no-op in codegen) |
| `ptrtoint`/`inttoptr` | Pointer↔integer (avoid where possible) |

### 5. Key passes

| Pass | Effect |
|------|--------|
| `mem2reg` | Promote alloca to SSA registers |
| `instcombine` | Instruction combining / peephole |
| `simplifycfg` | CFG cleanup, dead block removal |
| `loop-vectorize` | Auto-vectorisation |
| `slp-vectorize` | Superword-level parallelism (straight-line vectorisation) |
| `inline` | Function inlining |
| `gvn` | Global value numbering (common subexpression elimination) |
| `licm` | Loop-invariant code motion |
| `loop-unroll` | Loop unrolling |
| `argpromotion` | Promote pointer args to values |
| `sroa` | Scalar Replacement of Aggregates |

### 6. Debugging missed optimisations

```bash
# Why was a loop not vectorised?
clang -O2 -Rpass-missed=loop-vectorize -Rpass-analysis=loop-vectorize src.c

# Dump pass pipeline
clang -O2 -mllvm -debug-pass=Structure src.c -o /dev/null 2>&1 | less

# Print IR after each pass (very verbose)
opt -passes='default<O2>' -print-after-all src.ll -S 2>&1 | less
```

### 7. Useful llvm tools

| Tool | Purpose |
|------|---------|
| `llvm-dis` | Bitcode → textual IR |
| `llvm-as` | Textual IR → bitcode |
| `llvm-link` | Link multiple bitcode files |
| `llvm-lto` | Standalone LTO |
| `llvm-nm` | Symbols in bitcode/object |
| `llvm-objdump` | Disassemble objects |
| `llvm-profdata` | Merge/show PGO profiles |
| `llvm-cov` | Coverage reporting |
| `llvm-mca` | Machine code analyser (throughput/latency) |

For binutils equivalents, see `skills/binaries/binutils`.

## Related skills

- Use `skills/compilers/clang` for source-level Clang flags
- Use `skills/binaries/linkers-lto` for LTO at link time
- Use `skills/profilers/linux-perf` combined with `llvm-mca` for micro-architectural analysis

Files: 2

Size: 7.9 KB

Complexity: 23/100

Category: Backend & APIs

Source: https://github.com/mohitmishra786/low-level-dev-skills/tree/main/skills/compilers/llvm

Related in Backend & APIs

jfrog

Included

Interact with the JFrog Platform via the JFrog CLI and REST/GraphQL APIs. Use this skill when the user wants to manage Artifactory repositories, upload or download artifacts, manage builds, configure permissions, manage users and groups, work with access tokens, configure JFrog CLI servers, search artifacts, manage properties, set up replication, manage JFrog Projects, run security audits or scans, look up CVE details, query exposures scan results from JFrog Advanced Security, manage release bundles and lifecycle operations, aggregate or export platform data, or perform any JFrog Platform administration task. Also use when the user mentions jf, jfrog, artifactory, xray, distribution, evidence, apptrust, onemodel, graphql, workers, mission control, curation, advanced security, exposures, or any JFrog product name.

Backend & APIsscripts

cupynumeric-migration-readiness

Included

Pre-migration readiness assessor for porting NumPy to cuPyNumeric. Use BEFORE substantial porting work begins when the user asks whether code will scale on GPU, whether they should migrate to cuPyNumeric, which NumPy patterns transfer cleanly, what must be refactored before porting, or mentions pre-port assessment, scaling analysis, or refactor planning. Inspect the user's source code, look up NumPy usage, cross-reference the cuPyNumeric API support manifest, and distinguish distributed-scaling-friendly patterns from blockers such as unsupported APIs, scalar synchronization, host round-trips, Python/object-heavy control flow, shape/data-dependent branching, and in-place mutation hazards. Produce a verdict of READY, LIGHT REFACTOR, SIGNIFICANT REFACTOR, or NOT RECOMMENDED, with concrete refactor pointers.

Backend & APIsscripts

alibabacloud-data-agent-skill

Included

Invoke Alibaba Cloud Apsara Data Agent for Analytics via CLI to perform natural language-driven data analysis on enterprise databases. Data Agent for Analytics is an intelligent data analysis agent developed by Alibaba Cloud Database team for enterprise users. It automatically completes requirement analysis, data understanding, analysis insights, and report generation based on natural language descriptions. This tool supports: discovering data resources (instances/databases/tables) managed in DMS, initiating query or deep analysis sessions, real-time progress tracking, and retrieving analysis conclusions and generated reports. Use this Skill when users need to query databases, analyze data trends, generate data reports, ask questions in natural language, or mention "Data Agent", "data analysis", "database query", "SQL analysis", "data insights".

Backend & APIsscripts

token-optimizer

Included

Reduce OpenClaw token usage and API costs through smart model routing, heartbeat optimization, budget tracking, and native 2026.2.15 features (session pruning, bootstrap size limits, cache TTL alignment). Use when token costs are high, API rate limits are being hit, or hosting multiple agents at scale. The 4 executable scripts (context_optimizer, model_router, heartbeat_optimizer, token_tracker) are local-only — no network requests, no subprocess calls, no system modifications. Reference files (PROVIDERS.md, config-patches.json) document optional multi-provider strategies that require external API keys and network access if you choose to use them. See SECURITY.md for full breakdown.

Backend & APIsscripts

resend-cli

Included

Use this skill when the task is specifically about operating Resend from an AI agent, terminal session, or CI job via the official resend CLI: installing/authenticating the CLI, sending/listing/updating/cancelling emails, batch sends, domains and DNS, webhooks and local listeners, inbound receiving, contacts, topics, segments, broadcasts, templates, API keys, profiles, or debugging Resend CLI/API failures. Trigger on mentions of Resend CLI, `resend`, `resend doctor`, `resend emails send`, `resend domains`, `resend webhooks listen`, `resend emails receiving`, or agent-friendly terminal automation.

Backend & APIsscripts

alibabacloud-odps-maxframe-coding

Included

Use this skill for MaxFrame SDK development and documentation navigation on Alibaba Cloud MaxCompute (ODPS). Helps answer MaxFrame API, concept, official example, and supported pandas API questions; create data processing programs; read/write MaxCompute tables; debug jobs (remote or local); and build custom DPE runtime images. Trigger when users mention MaxFrame, MaxCompute with MaxFrame, ODPS table processing, DPE runtime, MaxFrame docs/examples, DataFrame/Tensor operations, or GPU runtime setup. Works for both English and Chinese queries about Alibaba Cloud data processing with MaxFrame.

Backend & APIsscripts