FUCOM, FUCOMP, FUCOMPP

CASE (relation of operands) OF

    ST > SRC:  C3, C2, C0 := 000;

    ST < SRC:  C3, C2, C0 := 001;

    ST = SRC:  C3, C2, C0 := 100;

ESAC;

IF ST(0) or SRC = QNaN, but not SNaN or unsupported format

    THEN
          C3, C2, C0 := 111;

    ELSE (* ST(0) or SRC is SNaN or unsupported format *)
           #IA;

        IF FPUControlWord.IM = 1

                THEN
                      C3, C2, C0 := 111;

          FI;
FI;

IF Instruction = FUCOMP

    THEN

          PopRegisterStack;

FI;

IF Instruction = FUCOMPP

    THEN

          PopRegisterStack;

FI;

FPU Flags Affected

C1                  Set to 0 if stack underflow occurred.

C0, C2, C3          See Table 3-43.

#IS                 Stack underflow occurred.

#IA                 One or both operands are SNaN values or have unsupported formats. Detection of a QNaN

#D                  One or both operands are denormal values.