fp64_tanx.S

/* Copyright (c) 2020  Uwe Bissinger
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   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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/* $Id$ */

#include "fp64def.h"
#include "asmdef.h"

/* float64_t fp64_tan (float64_t x);
     The fp64_tan() function returns the tangent of x, which is
     defined mathematically as sin(x) / cos(x).
 */

FUNCTION fp64_tan
ENTRY fp64_tan
	XCALL _U(__fp64_pushB)		; preserve registers

	push rA7					; save x
	push rA6
	push rA5
	push rA4
	push rA3
	push rA2
	push rA1
	push rA0

	XCALL _U(fp64_cos)			; calculate cos(x) 

	pop rB0						; restore x
	pop rB1	
	pop rB2
	pop rB3
	pop rB4
	pop rB5
	pop rB6
	pop rB7
	
	push rA7					; save cos(x)
	push rA6
	push rA5
	push rA4
	push rA3
	push rA2
	push rA1
	push rA0
	
	XCALL _U(__fp64_movAB)		; move x into A
	XCALL _U(fp64_sin)			; calculate sin(x) 
	
	pop rB0						; restore cos(x)
	pop rB1	
	pop rB2
	pop rB3
	pop rB4
	pop rB5
	pop rB6
	pop rB7
	
	XCALL _U(__fp64_isBzero)	; is cos(x) == 0?
	sec
	breq 1f						; yes, no need to calculate sin(x)/cos(x), return +/-Inf.

	XCALL _U(fp64_div)			; calculate sin(x)/cos(x)

1:	
	XJMP _U(__fp64_popBret)		; restore registers and return

ENDFUNC