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(nasm.info)Section B.4.77

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B.4.77. `FDIV', `FDIVP', `FDIVR', `FDIVRP': Floating-Point Division
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     FDIV mem32                    ; D8 /6                [8086,FPU]
     FDIV mem64                    ; DC /6                [8086,FPU]

     FDIV fpureg                   ; D8 F0+r              [8086,FPU]
     FDIV ST0,fpureg               ; D8 F0+r              [8086,FPU]

     FDIV TO fpureg                ; DC F8+r              [8086,FPU]
     FDIV fpureg,ST0               ; DC F8+r              [8086,FPU]

     FDIVR mem32                   ; D8 /0                [8086,FPU]
     FDIVR mem64                   ; DC /0                [8086,FPU]

     FDIVR fpureg                  ; D8 F8+r              [8086,FPU]
     FDIVR ST0,fpureg              ; D8 F8+r              [8086,FPU]

     FDIVR TO fpureg               ; DC F0+r              [8086,FPU]
     FDIVR fpureg,ST0              ; DC F0+r              [8086,FPU]

     FDIVP fpureg                  ; DE F8+r              [8086,FPU]
     FDIVP fpureg,ST0              ; DE F8+r              [8086,FPU]

     FDIVRP fpureg                 ; DE F0+r              [8086,FPU]
     FDIVRP fpureg,ST0             ; DE F0+r              [8086,FPU]

   * `FDIV' divides `ST0' by the given operand and stores the result
     back in `ST0', unless the `TO' qualifier is given, in which case
     it divides the given operand by `ST0' and stores the result in the
     operand.

   * `FDIVR' does the same thing, but does the division the other way
     up: so if `TO' is not given, it divides the given operand by `ST0'
     and stores the result in `ST0', whereas if `TO' is given it
     divides `ST0' by its operand and stores the result in the operand.

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

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

   For FP/Integer divisions, see `FIDIV' (*Note Section B.4.82::).