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)
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 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.