Berkeley Yacc (byacc) 2.0 had been ported:
"Berkeley Yacc (byacc) is generally conceded to be the best yacc variant available (YACC is an LALR parser generator). In contrast to bison, it is written to avoid dependencies upon a particular compiler. "
Official Project site: https://invisible-island.net/byacc/byacc.html
Source: eCSoft/2