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Annotation of 43BSDReno/lib/libc/tahoe/fpe/divf.s, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1986 Regents of the University of California.
                      3:  * All rights reserved.
                      4:  *
                      5:  * This code is derived from software contributed to Berkeley by
                      6:  * Computer Consoles Inc.
                      7:  *
                      8:  * Redistribution and use in source and binary forms are permitted
                      9:  * provided that: (1) source distributions retain this entire copyright
                     10:  * notice and comment, and (2) distributions including binaries display
                     11:  * the following acknowledgement:  ``This product includes software
                     12:  * developed by the University of California, Berkeley and its contributors''
                     13:  * in the documentation or other materials provided with the distribution
                     14:  * and in all advertising materials mentioning features or use of this
                     15:  * software. Neither the name of the University nor the names of its
                     16:  * contributors may be used to endorse or promote products derived
                     17:  * from this software without specific prior written permission.
                     18:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     19:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     20:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     21:  */
                     22: 
                     23: #if defined(SYSLIBC_SCCS) && !defined(lint)
                     24:        .asciz "@(#)divf.s      1.3 (Berkeley) 6/1/90"
                     25: #endif /* SYSLIBC_SCCS and not lint */
                     26: 
                     27: #include <tahoemath/fp.h>
                     28: #include "DEFS.h"
                     29: 
                     30: #define        HIDDEN  23      /* here we count from 0 not from 1 as in fp.h */
                     31: 
                     32: XENTRY(divf, R2|R3|R4|R5|R6|R7|R8|R9)
                     33:        clrl    r1
                     34:        clrl    r3              # r3 - sign: 0 for positive,1 for negative.
                     35:        movl    4(fp),r0
                     36:        jgeq    1f
                     37:        movl    $1,r3
                     38: 1:     movl    12(fp),r2
                     39:        jgeq    2f
                     40:        bbc     $0,r3,1f        # seconed operand is negative.
                     41:        clrl    r3              # if first was negative, make result positive.
                     42:        jmp     2f
                     43: 1:     movl    $1,r3           # if first was positive, make result negative.
                     44: 2:     andl2   $EXPMASK,r0     # compute first 'pure'exponent.
                     45:        jeql    is_res1
                     46:        shrl    $EXPSHIFT,r0,r0
                     47:        subl2   $BIAS,r0        
                     48:        andl2   $EXPMASK,r2     # compute seconed 'pure'exponent.
                     49:        jeql    is_res2
                     50:        shrl    $EXPSHIFT,r2,r2
                     51:        subl2   $BIAS,r2
                     52:        subl3   r2,r0,r2        # subtruct the exponents.
                     53:        addl2   $BIAS,r2
                     54:        jleq    underf
                     55:                                # normalization can make the exp. smaller.
                     56:  #
                     57:  #     We have the sign in r3,the exponent in r2,now is the time to
                     58:  #     perform the division...
                     59:  #
                     60:        # fetch dividend. (r0)
                     61:        andl3   $(0!(EXPMASK | SIGNBIT)),4(fp),r0
                     62:        orl2    $(0!CLEARHID),r0
                     63:        clrl    r1
                     64:  
                     65:        # fetch divisor : (r6)
                     66:        andl3   $(0!(EXPMASK | SIGNBIT)),12(fp),r6
                     67:        orl2    $(0!CLEARHID),r6
                     68: 
                     69:        shll    $2,r6,r6        # make the divisor bigger so we will not
                     70:                                # get overflow at the divission.
                     71:        ediv    r6,r0,r0,r7     # quo to r0, rem to r7
                     72:        subl2   $6,r2           # to compensate for: normalization (-24),
                     73:                                # ediv (+32), shifting r6 (-2).
                     74:        
                     75: over:
                     76:        callf   $4,fnorm        # we can use fnorm because we have data
                     77:                                # at r1 as well.(sfnorm takes care only 
                     78:                                # of r0).
                     79: sign:
                     80: 1:     bbc     $0,r3,done
                     81:        orl2    $SIGNBIT,r0
                     82: done:  ret
                     83: 
                     84: is_res1:
                     85:        bbc     $31,4(fp),retz
                     86:        callf   $4,sfpresop
                     87:        ret
                     88: is_res2:
                     89:        bbc     $31,12(fp),z_div
                     90:        callf   $4,sfpresop
                     91:        ret
                     92: retz:
                     93:          clrl  r0
                     94:          ret
                     95: underf:
                     96:        callf   $4,sfpunder
                     97:        ret
                     98: z_div:
                     99:        callf   $4,sfpzdiv
                    100:        ret

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