xref: /src/lib/libm/arch/vax/n_tan.S

/*	$NetBSD: n_tan.S,v 1.6 2003/08/07 16:44:45 agc Exp $	*/
/*
 * Copyright (c) 1985, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)tan.s	8.1 (Berkeley) 6/4/93
 */

#include <machine/asm.h>

/*  This is the implementation of Peter Tang's double precision
 *  tangent for the VAX using Bob Corbett's argument reduction.
 *
 *  Notes:
 *       under 1,024,000 random arguments testing on [0,2*pi]
 *       tan() observed maximum error = 2.15 ulps
 *
 * double tan(arg)
 * double arg;
 * method: true range reduction to [-pi/4,pi/4], P. Tang  &  B. Corbett
 * S. McDonald, April 4,  1985
 */
ENTRY(tan, 0x0fc0)		# save %r6-%r11
	movq	4(%ap),%r0
	bicw3	$0x807f,%r0,%r2
	beql	1f		# if x is zero or reserved operand then return x
/*
 * Save the PSL's IV & FU bits on the stack.
 */
	movpsl	%r2
	bicw3	$0xff9f,%r2,-(%sp)
/*
 *  Clear the IV & FU bits.
 */
	bicpsw	$0x0060
	jsb	_C_LABEL(__libm_argred)+2
/*
 *  At this point,
 *	   %r0  contains the quadrant number, 0, 1, 2, or 3;
 *	%r2/%r1  contains the reduced argument as a D-format number;
 *  	   %r3  contains a F-format extension to the reduced argument;
 *
 *  Save  %r3/%r0  so that we can call cosine after calling sine.
 */
	movq	%r2,-(%sp)
	movq	%r0,-(%sp)
/*
 *  Call sine.  %r4 = 0  implies sine.
 */
	movl	$0,%r4
	jsb	_C_LABEL(__libm_sincos)+2
/*
 *  Save  sin(x)  in  %r11/%r10 .
 */
	movd	%r0,%r10
/*
 *  Call cosine.  %r4 = 1  implies cosine.
 */
	movq	(%sp)+,%r0
	movq	(%sp)+,%r2
	movl	$1,%r4
	jsb	_C_LABEL(__libm_sincos)+2
	divd3	%r0,%r10,%r0
	bispsw	(%sp)+
1:	ret