GNU Info

(nasm.info)Section B.4.106

---

Next: Section B.4.107 Prev: Section B.4.105 Up: Section B.4

---

Enter node , (file) or (file)node

B.4.106. `FSUB', `FSUBP', `FSUBR', `FSUBRP': Floating-Point Subtract
--------------------------------------------------------------------

     FSUB mem32                    ; D8 /4                [8086,FPU]
     FSUB mem64                    ; DC /4                [8086,FPU]

     FSUB fpureg                   ; D8 E0+r              [8086,FPU]
     FSUB ST0,fpureg               ; D8 E0+r              [8086,FPU]

     FSUB TO fpureg                ; DC E8+r              [8086,FPU]
     FSUB fpureg,ST0               ; DC E8+r              [8086,FPU]

     FSUBR mem32                   ; D8 /5                [8086,FPU]
     FSUBR mem64                   ; DC /5                [8086,FPU]

     FSUBR fpureg                  ; D8 E8+r              [8086,FPU]
     FSUBR ST0,fpureg              ; D8 E8+r              [8086,FPU]

     FSUBR TO fpureg               ; DC E0+r              [8086,FPU]
     FSUBR fpureg,ST0              ; DC E0+r              [8086,FPU]

     FSUBP fpureg                  ; DE E8+r              [8086,FPU]
     FSUBP fpureg,ST0              ; DE E8+r              [8086,FPU]

     FSUBRP fpureg                 ; DE E0+r              [8086,FPU]
     FSUBRP fpureg,ST0             ; DE E0+r              [8086,FPU]

   * `FSUB' subtracts the given operand from `ST0' and stores the
     result back in `ST0', unless the `TO' qualifier is given, in which
     case it subtracts `ST0' from the given operand and stores the
     result in the operand.

   * `FSUBR' does the same thing, but does the subtraction the other way
     up: so if `TO' is not given, it subtracts `ST0' from the given
     operand and stores the result in `ST0', whereas if `TO' is given
     it subtracts its operand from `ST0' and stores the result in the
     operand.

   * `FSUBP' operates like `FSUB TO', but pops the register stack once
     it has finished.

   * `FSUBRP' operates like `FSUBR TO', but pops the register stack
     once it has finished.