hilomap - technology mapping of constant hi- and/or lo-drivers

yosys> help hilomap
hilomap [options] [selection]
Map constants to 'tielo' and 'tiehi' driver cells.
-hicell <celltype> <portname>
Replace constant hi bits with this cell.
-locell <celltype> <portname>
Replace constant lo bits with this cell.
Create only one hi/lo cell and connect all constant bits
to that cell. Per default a separate cell is created for
each constant bit.