#include "io.h" int main(void) { long long rd, rt; long long result; rt = 0x12345678; result = 0x00001E6A; __asm ("bitrev %0, %1\n\t" : "=r"(rd) : "r"(rt) ); if (rd != result) { printf("bitrev wrong\n"); return -1; } return 0; }