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Annotation of 43BSDReno/lib/libm/vax/tan.s, revision 1.1.1.1

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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