Replacing the x86 bswap Assembly Instruction

Symptom

Error: unknown mnemonic 'bswap' -- 'bswap x3'

Cause

bswap is the reverse byte order instruction of the x86 and needs to be replaced with the REV instruction of the ARM64.

Procedure

• bswap instruction on the x86:

  inline uint32_t bswap(uint32_t val) { 
      __asm__("bswap %0" : "=r" (val) : "0" (val));
      return val; 
  }

• Code on the Kunpeng platform:

  static inline uint32_t bswap(uint32_t val) { 
      __asm__("rev %w[dst], %w[src]" : [dst]"=r"(val) : [src]"r"(val)); 
      return val;
  }