usr/src/usr.lib/liboldnm/badtan.s

#
# Copyright (c) 1980 Regents of the University of California.
# All rights reserved.  The Berkeley software License Agreement
# specifies the terms and conditions for redistribution.
#
#       @(#)badtan.s    5.1 (Berkeley) 5/8/85
#
#
# double tan(arg)
# double arg;
#method: range reduction to [0,pi/4] followed by polynomial
# approximation:  Hart&Cheney TAN 4285 D=19.74
.globl  _tan
.text
.align  1
_tan:
        .word   0x07c0
        bispsw  $0xe0
        clrl    r10     # sign flag, !=0 negate result
        movd    4(ap),r0
        jgeq    c1
        xorw2   $0x8000,r10
        mnegd   r0,r0
c1:
        emodd   fopi,fopix,r0,r2,r6
        bicl2   $~3,r2
        caseb   r2,$0,$3
a0:     .word   a1-a0,a2-a0,a3-a0,a4-a0
a2:     subd3   r6,$0d1.0e+0,r6
        jbr     b1
a3: xorw2       $0x8000,r10
b1:     bsbb    rtan
        jneq    b2      # tests final result cmptd in rtan
        movd    $0d1.7e+38,r0
        jmp     b3
b2:     divd3   r0,$0d1.0e+0,r0
b3:     xorw2   r10,r0  # negate result if flag != 0
        ret
a4:     subd3   r6,$0d1.0e+0,r6
        xorw2   $0x8000,r10
a1:     bsbb    rtan
        xorw2   r10,r0
        ret
rtan:
        muld3   r6,r6,r8
        polyd   r8,$4,pcoef
        muld2   r0,r6
        polyd   r8,$3,qcoef
        divd3   r0,r6,r0
        rsb
.data
.align  2
pcoef:
        .double 0d0.33866386426771720960e-4
        .double 0d0.34225543872410034353e-1
        .double 0d-0.15506856534832663769e+2
        .double 0d0.10559709017149531936e+4
        .double 0d-0.13068202647548256682e+5
qcoef:
        .double 0d1.0e+0
        .double 0d-0.15550331640317099669e+3
        .double 0d0.47657513629164836989e+4
        .double 0d-0.16638952389471190018e+5
fopi:
        .double 0d1.27323954473516268e+0
fopix: .byte 0x29