Opcodes currently supported by SubX: 01: add r32 to rm32 (add) 03: add rm32 to r32 (add) 05: add imm32 to EAX (add) 09: rm32 = bitwise OR of r32 with rm32 (or) 0b: r32 = bitwise OR of r32 with rm32 (or) 0d: EAX = bitwise OR of imm32 with EAX (or) 21: rm32 = bitwise AND of r32 with rm32 (and) 23: r32 = bitwise AND of r32 with rm32 (and) 25: EAX = bitwise AND of imm32 with EAX (and) 29: subtract r32 from rm32 (sub) 2b: subtract rm32 from r32 (sub) 2d: subtract imm32 from EAX (sub) 31: rm32 = bitwise XOR of r32 with rm32 (xor) 33: r32 = bitwise XOR of r32 with rm32 (xor) 35: EAX = bitwise XOR of imm32 with EAX (xor) 39: compare: set SF if rm32 < r32 (cmp) 3b: compare: set SF if r32 < rm32 (cmp) 3d: compare: set SF if EAX < imm32 (cmp) 40: increment EAX (inc) 41: increment ECX (inc) 42: increment EDX (inc) 43: increment EBX (inc) 44: increment ESP (inc) 45: increment EBP (inc) 46: increment ESI (inc) 47: increment EDI (inc) 48: decrement EAX (dec) 49: decrement ECX (dec) 4a: decrement EDX (dec) 4b: decrement EBX (dec) 4c: decrement ESP (dec) 4d: decrement EBP (dec) 4e: decrement ESI (dec) 4f: decrement EDI (dec) 50: push EAX to stack (push) 51: push ECX to stack (push) 52: push EDX to stack (push) 53: push EBX to stack (push) 54: push ESP to stack (push) 55: push EBP to stack (push) 56: push ESI to stack (push) 57: push EDI to stack (push) 58: pop top of stack to EAX (pop) 59: pop top of stack to ECX (pop) 5a: pop top of stack to EDX (pop) 5b: pop top of stack to EBX (pop) 5c: pop top of stack to ESP (pop) 5d: pop top of stack to EBP (pop) 5e: pop top of stack to ESI (pop) 5f: pop top of stack to EDI (pop) 68: push imm32 to stack (push) 69: multiply rm32 by imm32 and store result in r32 (imul) 70: jump disp8 bytes away if OF is set (jcc/jo) 71: jump disp8 bytes away if OF is unset (jcc/jno) 72: jump disp8 bytes away if lesser (addr, float), if CF is set (jcc/jb/jnae) 73: jump disp8 bytes away if greater or equal (addr, float), if CF is unset (jcc/jae/jnb) 74: jump disp8 bytes away if equal, if ZF is set (jcc/jz/je) 75: jump disp8 bytes away if not equal, if ZF is not set (jcc/jnz/jne) 76: jump disp8 bytes away if lesser or equal (addr, float), if ZF is set or CF is set (jcc/jbe/jna) 77: jump disp8 bytes away if greater (addr, float), if ZF is unset and CF is unset (jcc/ja/jnbe) 7c: jump disp8 bytes away if lesser, if SF != OF (jcc/jl/jnge) 7d: jump disp8 bytes away if greater or equal, if SF == OF (jcc/jge/jnl) 7e: jump disp8 bytes away if lesser or equal, if ZF is set or SF != OF (jcc/jle/jng) 7f: jump disp8 bytes away if greater, if ZF is unset and SF == OF (jcc/jg/jnle) 81: combine rm32 with imm32 based on subop (add/sub/and/or/xor/cmp) 87: swap the contents of r32 and rm32 (xchg) 88: copy r8 to r8/m8-at-r32 89: copy r32 to rm32 (mov) 8a: copy r8/m8-at-r32 to r8 8b: copy rm32 to r32 (mov) 8d: copy address in rm32 into r32 (lea) 8f: pop top of stack to rm32 (pop) 99: sign-extend EAX into EDX (cdq) b8: copy imm32 to EAX (mov) b9: copy imm32 to ECX (mov) ba: copy imm32 to EDX (mov) bb: copy imm32 to EBX (mov) bc: copy imm32 to ESP (mov) bd: copy imm32 to EBP (mov) be: copy imm32 to ESI (mov) bf: copy imm32 to EDI (mov) c1: shift rm32 by imm8 bits depending on subop (sal/sar/shl/shr) c3: return from most recent unfinished call (ret) c6: copy imm8 to r8/m8-at-r32 with subop 0 (mov) c7: copy imm32 to rm32 with subop 0 (mov) cd: software interrupt (int) d3: shift rm32 by CL bits depending on subop (sal/sar/shl/shr) e8: call disp32 (call) e9: jump disp32 bytes away (jmp) eb: jump disp8 bytes away (jmp) f4: halt (hlt) f7: negate/multiply/divide rm32 (with EAX and EDX if necessary) depending on subop (neg/mul/idiv) ff: increment/decrement/jump/push/call rm32 based on subop (inc/dec/jmp/push/call) 0f 2f: compare: set CF if x32 < xm32 (comiss) 0f 80: jump disp32 bytes away if OF is set (jcc/jo) 0f 81: jump disp32 bytes away if OF is unset (jcc/jno) 0f 82: jump disp32 bytes away if lesser (addr, float), if CF is set (jcc/jb/jnae) 0f 83: jump disp32 bytes away if greater or equal (addr, float), if CF is unset (jcc/jae/jnb) 0f 84: jump disp32 bytes away if equal, if ZF is set (jcc/jz/je) 0f 85: jump disp32 bytes away if not equal, if ZF is not set (jcc/jnz/jne) 0f 86: jump disp32 bytes away if lesser or equal (addr, float), if ZF is set or CF is set (jcc/jbe/jna) 0f 87: jump disp32 bytes away if greater (addr, float), if ZF is unset and CF is unset (jcc/ja/jnbe) 0f 8c: jump disp32 bytes away if lesser, if SF != OF (jcc/jl/jnge) 0f 8d: jump disp32 bytes away if greater or equal, if SF == OF (jcc/jge/jnl) 0f 8e: jump disp32 bytes away if lesser or equal, if ZF is set or SF != OF (jcc/jle/jng) 0f 8f: jump disp32 bytes away if greater, if ZF is unset and SF == OF (jcc/jg/jnle) 0f 92: set r8/m8-at-rm32 to 1 if lesser (addr, float), if CF is set, 0 otherwise (setcc/setb/setnae) 0f 93: set r8/m8-at-rm32 to 1 if greater or equal (addr, float), if CF is unset, 0 otherwise (setcc/setae/setnb) 0f 94: set r8/m8-at-rm32 to 1 if equal, if ZF is set, 0 otherwise (setcc/setz/sete) 0f 95: set r8/m8-at-rm32 to 1 if not equal, if ZF is not set, 0 otherwise (setcc/setnz/setne) 0f 96: set r8/m8-at-rm32 to 1 if lesser or equal (addr, float), if ZF is set or CF is set, 0 otherwise (setcc/setbe/setna) 0f 97: set r8/m8-at-rm32 to 1 if greater (addr, float), if ZF is unset and CF is unset, 0 otherwise (setcc/seta/setnbe) 0f 9c: set r8/m8-at-rm32 to 1 if lesser, if SF != OF, 0 otherwise (setcc/setl/setnge) 0f 9d: set r8/m8-at-rm32 to 1 if greater or equal, if SF == OF, 0 otherwise (setcc/setge/setnl) 0f 9e: set r8/m8-at-rm32 to 1 if lesser or equal, if ZF is set or SF != OF, 0 otherwise (setcc/setle/setng) 0f 9f: set r8/m8-at-rm32 to 1 if greater, if ZF is unset and SF == OF, 0 otherwise (setcc/setg/setnle) 0f af: multiply rm32 into r32 (imul) f3 0f 10: copy xm32 to x32 (movss) f3 0f 11: copy x32 to xm32 (movss) f3 0f 2a: convert integer to floating-point (cvtsi2ss) f3 0f 2c: truncate floating-point to int (cvttss2si) f3 0f 2d: convert floating-point to int (cvtss2si) f3 0f 51: square root of float (sqrtss) f3 0f 52: inverse square root of float (rsqrtss) f3 0f 53: reciprocal of float (rcpss) f3 0f 58: add floats (addss) f3 0f 59: multiply floats (mulss) f3 0f 5c: subtract floats (subss) f3 0f 5d: minimum of two floats (minss) f3 0f 5e: divide floats (divss) f3 0f 5f: maximum of two floats (maxss) Run `bootstrap help instructions` for details on words like 'r32' and 'disp8'. For complete details on these instructions, consult the IA-32 manual (volume 2). There's various versions of it online, such as https://c9x.me/x86. The mnemonics in brackets will help you locate each instruction.