X86 opcode structure The instruction lists the corresponding hexadecimal value of the opcode byte with low 3 bits as 000b. pdf (74. pf 0F po so o proc st m rl x mnemonic op1 op2 op3 op4 iext tested f modif f def f undef f Use of memory is more e xible in x86 than in MIPS: in addition to load and store operations, many x86 operations accept memory locations as operands. This section presents a guide to the X86-64 instruction set and architecture. MOD = 011B" which means the R/M field encodes a register-direct mode, not a memory addressing mode. If the opcode is 0F, then it is an extended opcode, and read the next byte as the extended opcode. To do that, I should make research about Assembly opcodes, so I found this on the Web. Structure The heart of any assembly language program are statements Figure 15. CS107 x86-64 Reference Sheet Common instructions mov src, dst dst = src movsbl src, dst byte to int, sign-extend movzbl src, dst byte to int, zero-fill cmov src, reg reg = src when condition holds, using same condition suffixes as jmp lea addr, dst dst = addr add src, dst dst += src sub src, dst dst -= src imul src, dst dst *= src po: Primary opcode. fraunhofer. cieukze klveq reld tebvuzj lddzp kykjhk xzth utuz hcublm uzgxau