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Annotation of researchv9/libc/sun/frexp.s, revision 1.1.1.1

1.1       root        1:        .data
                      2: /*     .asciz  "@(#)frexp.s 1.1 86/02/03 SMI"  */
                      3:        .text
                      4: 
                      5: #include "fpcrtdefs.h"
                      6: 
                      7:        NSAVED   = 5*4  | save registers d2-d7
                      8:        SAVEMASK = 0x3f00
                      9:        RESTMASK = 0x00fc
                     10: 
                     11:        M0      = d0
                     12:        M1      = d1
                     13:        EXP     = d2
                     14:        TYPE    = d3
                     15:        /* type values: */
                     16:            ZERO  = 1 | wonderful
                     17:            GU    = 2
                     18:            PLAIN = 3
                     19:            INF   = 4
                     20:            NAN   = 5
                     21: 
                     22: /*
                     23:  * double
                     24:  * frexp( value, eptr)
                     25:  *      double value;
                     26:  *      int *eptr;
                     27:  *
                     28:  * return a value v s.t. fabs(v) < 1.0
                     29:  * and return *eptr value e s.t.
                     30:  *       v * (2**e) == value
                     31:  */
                     32: 
                     33:        .globl  _frexp
                     34: _frexp:        link    a6,#0
                     35:        MCOUNT
                     36:        movl    a6@(8),d0       | suck parameters into registers
                     37:        movl    a6@(12),d1
                     38:        movl    a6@(16),a0
                     39:        moveml  #SAVEMASK,sp@-  | state save
                     40:        jbsr    d_unpk
                     41:        cmpb    #PLAIN,TYPE     | is it a funny number?
                     42:        beqs    2$              | Branch if normal.
                     43:        bgts    gohome          | yes -- repack and forget
                     44:        cmpb    #ZERO,TYPE
                     45:        beqs    gohome          | can't do much with zero, either
                     46: 1$:
                     47:        subqw   #1,EXP          | Subnormal requires normalization.
                     48:        lsll    #1,d1
                     49:        roxll   #1,d0
                     50:        btst    #20,d0
                     51:        beqs    1$              | Branch if not yet normalized.
                     52: 2$:                    | normal path through here
                     53:        addw    #(52+1),EXP     | return current exp val +1
                     54:                                | 52 is unpacked bias -- mantissa has point on right?
                     55:        extl    EXP
                     56:        movl    EXP,a0@
                     57:        movw    #-53,EXP        | repack with exp val of -1
                     58: gohome:
                     59:        jbsr    d_pack
                     60: gone:  moveml  sp@+,#RESTMASK
                     61:        unlk    a6
                     62:        rts

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