This is a JIT compiler for brainfuck written in python with llvmlite.
There are several optimization when generating IR.
The default whitelist (0,0) in branch code generation makes it possible to cheat compiler and avoid to generate ptrBoundCheck.
Specifically, we can use N <s to move stack point out of buffer (when moving there is no check generated), then a followed [. In branch code, we first give N >s to extend whitelist, thus the memory between [buf-N, buf] could be accessed freely.