title: x86 decoding instruction opcode byte
body: <p>I'm creating an x86 decoder and I'm struggling on understanding and finding an efficient way to calculate the mnemonic of an instruction.</p>
  
  <p>I know that the opcode 6 MSBs are the opcode bits, but I can't find anywhere that use those 6 bits in a mnemonic table. The only mnemonic table I find is for the whole opcode byte itself and not just the 6 MSBs.</p>
  
  <p>I wanted to ask what are some efficient ways I can go on decoding the mnemonics encoded in the opcode byte, and if there're any table references using the 6 MSBs and not the whole opcode byte.</p>