It affects code generated by the OCaml native compiler, which includes the OCaml compiler itself since it is written in OCaml. See also: https://caml.inria.fr/mantis/view.php?id=7452
It also affects code generated by GCC, but apparently GCC is less likely to generate code sequences which trigger the CPU bug.
> It affects code generated by the OCaml native compiler
Possibly, but that was not the issue here. It's clear from your own link that the crashes were due to C code in the OCaml runtime (used by the compiler itself), which is written in C and was compiled with GCC at -O2. See https://caml.inria.fr/mantis/view.php?id=7452#c17129
It also affects code generated by GCC, but apparently GCC is less likely to generate code sequences which trigger the CPU bug.