gcc -O0 -c -mabm -mbmi retard.c -o retard.o ^ | | |
int code(unsigned long long number) { return (int) _tzcnt_u64(number); } objdump --disassemble-all retard.o 0000000000000000 <code>: 0: 55 push %rbp 1: 48 89 e5 mov %rsp,%rbp 4: 48 83 ec 10 sub $0x10,%rsp 8: 48 89 4d 10 mov %rcx,0x10(%rbp) c: 48 8b 45 10 mov 0x10(%rbp),%rax 10: 48 89 45 f8 mov %rax,-0x8(%rbp) 14: 31 c0 xor %eax,%eax 16: f3 48 0f bc 45 f8 tzcnt -0x8(%rbp),%rax <--------------------- 1c: 48 83 c4 10 add $0x10,%rsp 20: 5d pop %rbp Moron.