This CL is associated with a fuzzing effort to find bugs in LLVM. The
first step is to fuzz llvm-as to find potential issues in generating
IR. Both afl-fuzz and LLVM's lib/Fuzzer are being used.
This CL introduces the executable that implements the in-process
fuzzer using LLVM's lib/Fuzzer. The motivation for using lib/Fuzzer is
based on time comparisons between afl-fuzz and lib/Fuzzer. Early
results show that per-process, the lib/Fuzzer implemenation of llvm-as
(i.e. this CL) generates over 30 times the number of mutations found
by afl-fuzz, per hour runtime. The speedup is due to the removal of
overhead of forking a process, and loading the executable into memory.
I placed this under the tools directory, since it is an executable. It
is also only conditionally built if (using cmake) the flag
LLVM_USEE_SANITIZE_COVERAGE is used, so that it isn't built by
default.
ideally, shit should be done outside of this function,
so that the first input does not get credit for additional coverage.
You can do this by having a constructor of a global object do this,
or by defining your own main and using fuzzer::FuzzerDriver,
However in practice this won't hurt much, if at all.
So feel free to just add a FIXME in the comment