Quick and dirty brainfuck jit compiler for x64 linux.
Machine code is built in memory from the brainfuck program. The memory region is made exectuable by a call to mprotect and is the code is run.
| Brainfuck | C | Machine code |
|---|---|---|
> |
ptr++; |
lea bx,[rbx+1] |
< |
ptr--; |
lea bx,[rbx-1] |
+ |
tape[ptr]++; |
add BYTE PTR [r12+rbx],1 |
- |
tape[ptr]--; |
sub BYTE PTR [r12+rbx],1 |
. |
putchar(tape[ptr]); |
syscall |
[ |
while(tape[ptr]){ |
cmp BYTE PTR [r12+rbx],0x0; jz loop_end |
] |
} |
cmp BYTE PTR [r12+rbx],0x0; jnz loop_start |
# |
breakpoint |
int 3 |
- Adjacent
>,<,+or-are combined. For example>>>would becomelea bx,[rbx+3] - The cmp part of
[and]is skipped if the zero flag is still valid from a+or- - The tape is 65536 (2^16) bytes long and the tape pointer is stored in
bx(16 bits), enabling quick wrapping [-]and[+]emitmov BYTE PTR [r12+rbx],0x0