4.4BSD/usr/src/lib/libm/vax/tan.s

# 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. All advertising materials mentioning features or use of this software
#    must display the following acknowledgement:
#	This product includes software developed by the University of
#	California, Berkeley and its contributors.
# 4. 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
#
	.data
	.align	2
_sccsid:
.asciz	"@(#)tan.s	1.1 (Berkeley) 8/21/85; 8.1 (ucb.elefunt) 6/4/93"

#  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
#
	.globl	_tan
	.text
	.align	1

_tan:	.word	0xffc		# save r2-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	$0x0060
	jsb	libm$argred
#
#  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	$0,r4
	jsb	libm$sincos
#
#  Save  sin(x)  in  r11/r10 .
#
	movd	r0,r10
#
#  Call cosine.  r4 = 1  implies cosine.
#
	movq	(sp)+,r0
	movq	(sp)+,r2
	movl	$1,r4
	jsb	libm$sincos
	divd3	r0,r10,r0
	bispsw	(sp)+
1:	ret