- Xtensa ISA manual: https://www.cadence.com/content/dam/cadence-www/global/en_US/documents/tools/ip/tensilica-ip/isa-summary.pdf
- espressif's xtensa ISA manual: https://dl.espressif.com/github_assets/espressif/xtensa-isa-doc/releases/download/latest/Xtensa.pdf
- ESP32でC/C++からアセンブラを使用する - Zenn: https://zenn.dev/lovyan03/articles/esp32-asm-001
- ESP32のアセンブラを読み解く - Zenn: https://zenn.dev/lovyan03/articles/esp32-asm-002
- libgcc's optimized routines: https://github.com/espressif/gcc/tree/esp-12_2_0/libgcc/config/xtensa
- No, the ESP32-S2 is not faster at floating point operations - The Weekend Writeup: https://blog.llandsmeer.com/tech/2021/04/08/esp32-s2-fpu.html
- GCC: https://github.com/espressif/gcc
- LLVM: https://github.com/espressif/llvm-project
- crosstool-NG: https://github.com/espressif/crosstool-NG
- Qemu: https://github.com/espressif/qemu
- OpenOCD: https://github.com/espressif/openocd-esp32
- Rust: https://github.com/esp-rs/rust
- Rust's xtensa-lx: https://github.com/esp-rs/xtensa-lx