{
    Subroutine to compute one over the square root of x.

	    X=1/sqrt(Y)

	Calling Registers
    F0 = Y Input Value
    F8 = 3.0
    F1 = 0.5

	Result Registers
    F0 = 1/sqrt(Y)

	Altered Registers
    F0, F4, F12

	Computation Time
    13 Cycles

    Version 0.02    7/6/90	Gordon A. Sterling
}

#include "asm_glob.h"

.SEGMENT/PM	Assembly_Library_Code_Space;

.PRECISION=MACHINE_PRECISION;

.GLOBAL	recip_sqrt;

recip_sqrt:	F4=RSQRTS F0;			{Fetch seed}
		F12=F4*F4;			{F12=X0^2}
		F12=F12*F0;			{F12=C*X0^2}
		F4=F1*F4, F12=F8-F12;		{F4=.5*X0, F10=3-C*X0^2}
		F4=F4*F12;			{F4=X1=.5*X0(3-C*X0^2)}
		F12=F4*F4;			{F12=X1^2}
		F12=F12*F0;			{F12=C*X1^2}
		F4=F1*F4, F12=F8-F12;		{F4=.5*X1, F10=3-C*X1^2}
		F4=F4*F12;			{F4=X2=.5*X1(3-C*X1^2)}
		F12=F4*F4;			{F12=X2^2}
		RTS (DB), F12=F12*F0;		{F12=C*X2^2}
		F4=F1*F4, F12=F8-F12;		{F4=.5*X2, F10=3-C*X2^2}
		F0=F4*F12;			{F0=X3=.5*X2(3-C*X2^2)}

.ENDSEG;