# Code Review Asm Xtensa > Review Xtensa assembly code for ESP32 platforms. Checks for critical errors in inline assembly, ABI compliance, and optimization opportunities. Use after modifying ESP32 assembly or inline asm code. Use when this capability is needed. - Skill: `tomevault-io/code-review-asm-xtensa` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/code-review-asm-xtensa` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/code-review-asm-xtensa/raw - Safety review: pending (external: skill-scanner PASS, skillspector CAUTION) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/code-review-asm-xtensa --- Perform comprehensive manual review of Xtensa assembly code in FastLED ESP32 platforms for correctness, ABI compliance, safety, and performance. ## What Gets Checked ### Critical Errors (Must Fix) - **E001**: Invalid `movi` for 32-bit addresses - **E002**: Wrong return instruction in interrupts - **E003**: Missing `memw` memory barriers for MMIO writes - **E004**: Windowed ABI used in interrupt handlers - **E005**: Unaligned memory access - **E006**: Missing `IRAM_ATTR` on interrupt handlers - **E007**: Mixed ABI usage in same function ### Performance Warnings - **W001-W005**: Load-use hazards, loop overhead, nesting depth, register pressure, dependency chains ### Optimization Opportunities - **O001-O004**: Array indexing, conditional moves, loop unrolling, code density Search for Xtensa assembly code in git changes (inline asm and .S files) and perform deep analysis. --- > Source: [FastLED/FastLED](https://github.com/FastLED/FastLED) — distributed by [TomeVault](https://tomevault.io).