def _parse_refprune_flags():
    """Parse refprune flags from the `config`.

    Invalid values are ignored an warn via a `NumbaInvalidConfigWarning`
    category.

    Returns
    -------
    flags : llvmlite.binding.RefPruneSubpasses
    """
    flags = config.LLVM_REFPRUNE_FLAGS.split(',')
    if not flags:
        return 0
    val = 0
    for item in flags:
        item = item.strip()
        try:
            val |= getattr(ll.RefPruneSubpasses, item.upper())
        except AttributeError:
            warnings.warn(f"invalid refprune flags {item!r}",
                          NumbaInvalidConfigWarning)
    return val
Parse refprune flags from the `config`.

    Invalid values are ignored an warn via a `NumbaInvalidConfigWarning`
    category.

    Returns
    -------
    flags : llvmlite.binding.RefPruneSubpasses
    
numba/core/codegen.py