Unofficial MIPS Loongson Intrinsics Guide

This is an unofficial guide for the MIPS-era Loongson SIMD intrinsic headers in this repository. It follows the organization of the Unofficial LoongArch Intrinsics Guide, but the content is generated from the Loongson SX, Loongson ASX, MIPS MSA, MSA2, MSA Crypto, Loongson MMI, and Loongson CSR GCC-style headers.

The SX and ASX headers are early Loongson SIMD interfaces with 128-bit and 256-bit vector registers. Their intrinsic prefixes are still __lsx_ and __lasx_, even though these files target MIPS feature macros rather than LoongArch feature macros. MIPS MSA, MSA2, and MSA Crypto document the 128-bit MSA families supplied in msa.h, msa2.h, and msa-cryptointrin.h. MMI documents the older 64-bit paired-integer multimedia operations, while CSR documents scalar control/status helpers.

The operation blocks are generated from hardware probe results on a Loongson-3A4000 plus category-specific semantics validated by those probes. A separate header-mapping block shows the wrapper body from the header with argument names normalized for readability. When the header implements a builtin with inline assembly, the generator records the real instruction mnemonic used there. For compiler builtins without inline assembly in the header, the mnemonic is reconstructed from the builtin name.

Project Information

• Project repository: https://github.com/nihui/unofficial-mips-loongson-intrinsics-guide
• Inspired by and modeled after: https://github.com/jiegec/unofficial-loongarch-intrinsics-guide
• This guide was generated with assistance from OpenAI GPT-5 Codex.

Covered Headers

Extension	Header	Vector width	Feature macro	Intrinsics
Loongson SX	include/loongson-sxintrin.h	128 bit	__mips_loongson_sx	255
Loongson ASX	include/loongson-asxintrin.h	256 bit	__mips_loongson_asx	1165
MIPS MSA	include/msa.h	128 bit	__mips_msa	529
MSA2	include/msa2.h	128 bit	__mips_msa	371
MSA Crypto	include/msa-cryptointrin.h	128 bit	__mips_msa_crypto	29
Loongson MMI	include/loongson-mmiintrin.h	64 bit	__mips_loongson_mmi	99
Loongson CSR	include/loongson-csr.h	64 bit	__mips_loongson_csr	16

Total documented intrinsics: 2464.

Register Model

The pseudo descriptions assume vectors can be viewed through element arrays similar to the following C unions:

union loongson_64_register {
  uint8_t u8[8];
  int8_t i8[8];
  uint16_t u16[4];
  int16_t i16[4];
  uint32_t u32[2];
  int32_t i32[2];
  uint64_t u64[1];
  int64_t i64[1];
};

union loongson_128_register {
  uint8_t u8[16];
  int8_t i8[16];
  uint16_t u16[8];
  int16_t i16[8];
  uint32_t u32[4];
  int32_t i32[4];
  uint64_t u64[2];
  int64_t i64[2];
  unsigned __int128 u128[1];
  __int128 i128[1];
  float fp32[4];
  double fp64[2];
};

union loongson_256_register {
  uint8_t u8[32];
  int8_t i8[32];
  uint16_t u16[16];
  int16_t i16[16];
  uint32_t u32[8];
  int32_t i32[8];
  uint64_t u64[4];
  int64_t i64[4];
  unsigned __int128 u128[2];
  __int128 i128[2];
  float fp32[8];
  double fp64[4];
};

The source headers are GCC runtime headers and retain their original copyright notices.