When to define the macro NO_ICE40_DEFAULT_ASSIGNMENTS?

[zapta]

The ICE40 library file cells_sim.v contains this macro NO_ICE40_DEFAULT_ASSIGNMENTS. Are we as users supposed to use it, e.g. for lint or sim, or is it an internal Yosys definition?

`ifndef NO_ICE40_DEFAULT_ASSIGNMENTS
`define ICE40_DEFAULT_ASSIGNMENT_V(v) = v
`define ICE40_DEFAULT_ASSIGNMENT_0 = 1'b0
`define ICE40_DEFAULT_ASSIGNMENT_1 = 1'b1
`else
`define ICE40_DEFAULT_ASSIGNMENT_V(v)
`define ICE40_DEFAULT_ASSIGNMENT_0
`define ICE40_DEFAULT_ASSIGNMENT_1
`endif

yosys/techlibs/ice40/cells_sim.v

Line 5 in 106f289

`ifndef NO_ICE40_DEFAULT_ASSIGNMENTS