def _parfor_use_alloca(parfor, alloca_set):
    """
    Reduction variables for parfors and the reduction variables within
    nested parfors must be stack allocated.
    """
    alloca_set |= set(parfor.redvars)

    blocks = wrap_parfor_blocks(parfor)
    alloca_set |= analysis.must_use_alloca(blocks)

    unwrap_parfor_blocks(parfor)

    Reduction variables for parfors and the reduction variables within
    nested parfors must be stack allocated.
    
numba/parfors/parfor.py