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Annotation of 43BSDReno/lib/libm/mc68881/support.s, revision 1.1

1.1     ! root        1: /*-
        !             2:  * Copyright (c) 1990 The Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * This code is derived from software contributed to Berkeley by
        !             6:  * the Systems Programming Group of the University of Utah Computer
        !             7:  * Science Department.
        !             8:  *
        !             9:  * Redistribution and use in source and binary forms are permitted
        !            10:  * provided that: (1) source distributions retain this entire copyright
        !            11:  * notice and comment, and (2) distributions including binaries display
        !            12:  * the following acknowledgement:  ``This product includes software
        !            13:  * developed by the University of California, Berkeley and its contributors''
        !            14:  * in the documentation or other materials provided with the distribution
        !            15:  * and in all advertising materials mentioning features or use of this
        !            16:  * software. Neither the name of the University nor the names of its
        !            17:  * contributors may be used to endorse or promote products derived
        !            18:  * from this software without specific prior written permission.
        !            19:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
        !            20:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
        !            21:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            22:  *
        !            23:  *     @(#)support.s   5.2 (Berkeley) 5/17/90
        !            24:  */
        !            25: 
        !            26:        .text
        !            27:        .globl  _copysign, _finite, _scalb, _logb, _drem, _pow_p, _atan2__A
        !            28: 
        !            29: | copysign(x,y) 
        !            30: | returns x with the sign of y. 
        !            31: _copysign:
        !            32:        movl    sp@(4),d0
        !            33:        movl    sp@(8),d1
        !            34:        tstw    sp@(12)
        !            35:        jmi     Lneg
        !            36:        bclr    #31,d0
        !            37:        rts
        !            38: Lneg:
        !            39:        bset    #31,d0
        !            40:        rts
        !            41: 
        !            42: | finite(x)
        !            43: | returns the value TRUE if -INF < x < +INF and returns FALSE otherwise.
        !            44: _finite:
        !            45:        movw    #0x7FF0,d0
        !            46:        movw    sp@(4),d1
        !            47:        andw    d0,d1
        !            48:        cmpw    d0,d1
        !            49:        beq     Lnotfin
        !            50:        moveq   #1,d0
        !            51:        rts
        !            52: Lnotfin:
        !            53:        clrl    d0
        !            54:        rts
        !            55: 
        !            56: | scalb(x, N)
        !            57: | returns  x * (2**N), for integer values N.
        !            58: _scalb:
        !            59:        fmoved  sp@(4),fp0
        !            60:        fbeq    Ldone
        !            61:        fscalel sp@(12),fp0
        !            62: Ldone:
        !            63:        fmoved  fp0,sp@-
        !            64:        movel   sp@+,d0
        !            65:        movel   sp@+,d1
        !            66:        rts
        !            67: 
        !            68: | logb(x)
        !            69: | returns the unbiased exponent of x, a signed integer in double precision,
        !            70: | except that logb(0) is -INF, logb(INF) is +INF, and logb(NAN) is that NAN.
        !            71: _logb:
        !            72:        movw    sp@(4),d0
        !            73:        movw    #0x7FF0,d1      | exponent bits
        !            74:        andw    d1,d0           | mask off all else
        !            75:        cmpw    d1,d0           | max exponent?
        !            76:        bne     Lfinite         | no, is finite
        !            77:        fmoved  sp@(4),fp0      | yes, infinite or NaN
        !            78:        fbun    Ldone           | NaN returns NaN
        !            79:        fabsx   fp0             | +-inf returns inf
        !            80:        jra     Ldone
        !            81: Lfinite:
        !            82:        fmoved  sp@(4),fp0      | get entire number
        !            83:        fbne    Lnonz           | zero?
        !            84:        flog2x  fp0             | yes, log(0) a convenient source of -inf
        !            85:        jra     Ldone
        !            86: Lnonz:
        !            87:        fgetexpx        fp0     | get exponent
        !            88:        jra     Ldone
        !            89: 
        !            90: | drem(x,y)
        !            91: | returns  x REM y  =  x - [x/y]*y , where [x/y] is the integer nearest x/y;
        !            92: | in half way case, choose the even one.
        !            93: _drem:
        !            94:        fmoved  sp@(4),fp0
        !            95:        fremd   sp@(12),fp0
        !            96:        fmoved  fp0,sp@-
        !            97:        movel   sp@+,d0
        !            98:        movel   sp@+,d1
        !            99:        rts
        !           100: 
        !           101: | pow_p(x,y)
        !           102: | return x**y for x with sign=1 and finite y
        !           103: _pow_p:
        !           104:        flognd  sp@(4),fp0
        !           105:        fmuld   sp@(12),fp0
        !           106:        fetoxx  fp0
        !           107:        fmoved  fp0,sp@-
        !           108:        movel   sp@+,d0
        !           109:        movel   sp@+,d1
        !           110:        rts
        !           111: 
        !           112: | atan2__A(y,x)
        !           113: | compute atan2(y,x) where x,y are finite and non-zero
        !           114: | called by atan2() after weeding out all the special cases
        !           115: _atan2__A:
        !           116:        moveq   #0,d0           | sign of result
        !           117:        fmoved  sp@(4),fp0      | get y
        !           118:        fboge   Lypos           | <0?
        !           119:        moveq   #1,d0           | yes, result is neg
        !           120:        fnegx   fp0             | make y pos
        !           121: Lypos:
        !           122:        fmoved  sp@(12),fp1     | get x
        !           123:        fboge   Lxpos           | <0?
        !           124:        fnegx   fp1             | yes, make x pos
        !           125:        fdivx   fp1,fp0         | y/x
        !           126:        fatanx  fp0,fp1         | atan(y/x)
        !           127:        fmovecr #0,fp0          | get pi
        !           128:        fsubx   fp1,fp0         | pi - atan(y/x)
        !           129:        jra     Lsetsign
        !           130: Lxpos:
        !           131:        fdivx   fp1,fp0         | y/x
        !           132:        fatanx  fp0             | atan(y/x)
        !           133: Lsetsign:
        !           134:        tstl    d0              | should be neg?
        !           135:        jeq     Lrpos           | no, all done
        !           136:        fnegx   fp0             | yes, negate
        !           137: Lrpos:
        !           138:        fmoved  fp0,sp@-
        !           139:        movel   sp@+,d0
        !           140:        movel   sp@+,d1
        !           141:        rts

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