Class description
A tuple that holds info necessary for a gc cycle to figure out where the gc root pointers are. It has the following slots:
gc-rootssequence of vregs or spill-slots
derived-rootsAn assoc of pairs of vregs or spill slots.

The 'gc-roots' and 'derived-roots' slots are initially vreg integers referencing objects that are live during the gc call and needs to be spilled so that they can be traced. In the emit-gc-map-insn word in compiler.cfg.linear-scan.assignment they are converted to spill slots which the collector is able to trace.

See also
emit-gc-info-bitmap, fill-gc-map