Sgnstore
From WikiManual
Takes a memory location and sets its value to 1,0, or -1 depending if the memory location is positive or negative or zero.
examples:
Given 10 .up store
.up sgnstore same as *.up sgn .up store is equal to 1
Given 0 .up store
.up sgnstore same as *.up sgn .up store is equal to 0
Given -1 .up store
.up sgnstore same as *.up sgn .up store is equal to -1