/*
	This C language subroutine computes the hyperbolic 
	tangent of its floating point input.
	
	The Run Time Library for the C Language.

	Gordon A. Sterling	(617) 461 - 3076
	DSP Development Tools Engineering

	Created on 6/9/90
	Updated on 5/94 by AS

	#include <math.h>	    <Header>
    	float tanhf(float x);	    <Prototype>
*/

#include "lib_glob.h"
#include "mth_glob.h"
#include "tanh.h"

.SEGMENT/CODE	Code_Space_Name;
.FILE 		RTL_FILENAME;

.GLOBAL	    _tanhf;

.EXTERN	    _expf;

_tanhf:		F8=PASS F4, put(R7);
		F4=ABS F4, put(R11);
		
		F2=bigx;
		COMP(F4,F2);
		IF GT JUMP (PC, return_one);
		F2=ln_3_over_2;
		COMP(F4,F2);
		IF GT JUMP (PC, return_exp);
		F2=eps;
		COMP(F4,F2);
		IF LE JUMP (PC, check_sign);
		F2=F4*F4;		/* g = f*f */
		F1=p1;
		F7=F1*F2;		/* p1*g */
		F1=p0;
		F7=F7+F1;		/* P(g) = p1*g + p0 */
		F7=F7*F2;		/* g*P(g) = (p1*g + p0)*g */
		F11=q0;
		CALL (PC, ___float_divide) (DB);
		F12=F2+F11;		/* Q(g) = g + q0 */
		F11=2.0;

		F7=F7*F4;		    /* R*f */
		F4=F7+F4;		    /* f+f*R */

check_sign:	F8=PASS F8;
		IF LT F4=-F4;
		F0=PASS F4, FETCH_RETURN

restore_state:	get(R11,1);
		get(R7,2);
		RETURN (DB);
		RESTORE_STACK
		RESTORE_FRAME

return_one:	JUMP (PC, check_sign) (DB);
		F4=1.0;
		NOP;

return_exp:	F4=F4+F4, CALLER_HOLD(R2)
		CALLER_SWAP
		RTLCALL (PC, _expf) (DB);
		SAVE_OLD_FRAME(R2)
		SAVE_RET_ADDR

		F7=1.0;
		CALL (PC, ___float_divide) (DB);
	    	F12=F0+F7;			/*Compute 1/(exp(f+f)+1.0) */
		F11=2.0;

		F4=0.5;
		JUMP (PC, check_sign) (DB);
		F4=F4-F7;		/*Compute 0.5 - 1.0/(exp(f+f)+1.0) */
		F4=F4+F4;		/*Result=result+result */
.ENDSEG;