FFREE
Usage: FFREE src Modifies flags:
Sets the tag in the FPU tag register associated with register 'src' to empty (11B). The contents of ST(i) and the FPU stack-top pointer (TOP) are not affected.
Flag Floating-Point Register as Unused
FFREE fpureg ; DD C0+r [8086,FPU]
FFREEP fpureg ; DF C0+r [286,FPU,UNDOC]
FFREE marks the given register as being empty.
FFREEP marks the given register as being empty, and then pops the register stack.
C0, C1, C2, C3 undefined.
Example:
ffree st4