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Annotation of 43BSDReno/lib/libm/vax/tan.s, revision 1.1

1.1     ! root        1: # Copyright (c) 1985 Regents of the University of California.
        !             2: # All rights reserved.
        !             3: #
        !             4: # Redistribution and use in source and binary forms are permitted
        !             5: # provided that the above copyright notice and this paragraph are
        !             6: # duplicated in all such forms and that any documentation,
        !             7: # advertising materials, and other materials related to such
        !             8: # distribution and use acknowledge that the software was developed
        !             9: # by the University of California, Berkeley.  The name of the
        !            10: # University may not be used to endorse or promote products derived
        !            11: # from this software without specific prior written permission.
        !            12: # THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
        !            13: # IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
        !            14: # WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            15: #
        !            16: # All recipients should regard themselves as participants in an ongoing
        !            17: # research project and hence should feel obligated to report their
        !            18: # experiences (good or bad) with these elementary function codes, using
        !            19: # the sendbug(8) program, to the authors.
        !            20: #
        !            21: #      @(#)tan.s       5.3 (Berkeley) 6/30/88
        !            22: #
        !            23:        .data
        !            24:        .align  2
        !            25: _sccsid:
        !            26: .asciz "@(#)tan.s      1.1 (Berkeley) 8/21/85; 5.3 (ucb.elefunt) 6/30/88"
        !            27: 
        !            28: #  This is the implementation of Peter Tang's double precision  
        !            29: #  tangent for the VAX using Bob Corbett's argument reduction.
        !            30: #  
        !            31: #  Notes:
        !            32: #       under 1,024,000 random arguments testing on [0,2*pi] 
        !            33: #       tan() observed maximum error = 2.15 ulps
        !            34: #
        !            35: # double tan(arg)
        !            36: # double arg;
        !            37: # method: true range reduction to [-pi/4,pi/4], P. Tang  &  B. Corbett
        !            38: # S. McDonald, April 4,  1985
        !            39: #
        !            40:        .globl  _tan
        !            41:        .text
        !            42:        .align  1
        !            43: 
        !            44: _tan:  .word   0xffc           # save r2-r11
        !            45:        movq    4(ap),r0
        !            46:        bicw3   $0x807f,r0,r2
        !            47:        beql    1f              # if x is zero or reserved operand then return x
        !            48: #
        !            49: # Save the PSL's IV & FU bits on the stack.
        !            50: #
        !            51:        movpsl  r2
        !            52:        bicw3   $0xff9f,r2,-(sp)
        !            53: #
        !            54: #  Clear the IV & FU bits.
        !            55: #
        !            56:        bicpsw  $0x0060
        !            57:        jsb     libm$argred
        !            58: #
        !            59: #  At this point,
        !            60: #         r0  contains the quadrant number, 0, 1, 2, or 3;
        !            61: #      r2/r1  contains the reduced argument as a D-format number;
        !            62: #         r3  contains a F-format extension to the reduced argument;
        !            63: #
        !            64: #  Save  r3/r0  so that we can call cosine after calling sine.
        !            65: #
        !            66:        movq    r2,-(sp)
        !            67:        movq    r0,-(sp)
        !            68: #
        !            69: #  Call sine.  r4 = 0  implies sine.
        !            70: #
        !            71:        movl    $0,r4
        !            72:        jsb     libm$sincos
        !            73: #
        !            74: #  Save  sin(x)  in  r11/r10 .
        !            75: #
        !            76:        movd    r0,r10
        !            77: #
        !            78: #  Call cosine.  r4 = 1  implies cosine.
        !            79: #
        !            80:        movq    (sp)+,r0
        !            81:        movq    (sp)+,r2
        !            82:        movl    $1,r4
        !            83:        jsb     libm$sincos
        !            84:        divd3   r0,r10,r0
        !            85:        bispsw  (sp)+
        !            86: 1:     ret

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