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Annotation of 43BSDReno/lib/libc/tahoe/fpe/addf.s, revision 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 "@(#)addf.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: XENTRY(addf, R2|R3|R4|R5|R6|R7|R8|R9|R10)
        !            31: /*
        !            32:  * see which operand has a greater exponent
        !            33:  * The greater one will be fetched into r0,r2,r3.
        !            34:  * r0- 'pure' fraction, r2 - exponent, r3 - sign).
        !            35:  * The smaller operand will be fetched into r4,r6,r7.
        !            36:  */
        !            37:        clrl    r1
        !            38:        andl3   $EXPMASK,4(fp),r0
        !            39:        andl3   $EXPMASK,12(fp),r1
        !            40:        cmpl    r0,r1
        !            41:        jgtr    first_greater
        !            42: 
        !            43:        movl    12(fp),r0       # bigger operand to r0
        !            44: 
        !            45:        movl    4(fp),r4        # smaller operand to r4
        !            46:        jmp     expo
        !            47: 
        !            48: first_greater:
        !            49:        movl    4(fp),r0        # bigger operand to r0
        !            50: 
        !            51:        movl    12(fp),r4       # smaller operand to r4
        !            52: 
        !            53: 
        !            54: /*
        !            55:  *compute exponents:
        !            56:  */
        !            57: expo:
        !            58:        andl3   $EXPMASK,r0,r2  # r2 will hold the exponent of greater operand.
        !            59:        jeql    is_res1         # check for reserved operand. 
        !            60:        shrl    $EXPSHIFT,r2,r2
        !            61: 
        !            62: 
        !            63:        andl3   $EXPMASK,r4,r6  # r6 will hold the exponent of smaller operand.
        !            64:        jeql    is_res2         # check for reserved operand. 
        !            65:        shrl    $EXPSHIFT,r6,r6
        !            66: /*
        !            67:  *compare the exponents:
        !            68:  */
        !            69:        subl3   r6,r2,r8
        !            70:        jeql    signs
        !            71:        cmpl    r8,$MAX_EXP_DIF
        !            72:        jlss    signs
        !            73:        ret                     # return the bigger number.
        !            74:  
        !            75: /*
        !            76:  *remember the signs:
        !            77:  */
        !            78: signs:
        !            79:        clrl    r3
        !            80:        bbc     $31,r0,sign2    # if negative remember it.(R3=1)
        !            81:        incl    r3
        !            82: sign2:
        !            83:        clrl    r7
        !            84:        bbc     $31,r4,frac     # if negative remember it.(R7=1)
        !            85:        incl    r7
        !            86: /*
        !            87:  *compute 'pure' fraction:
        !            88:  */
        !            89: frac:
        !            90:                                # clear the non fraction parts.
        !            91:        andl2   $(0!(EXPMASK | SIGNBIT)),r0
        !            92:                                # add the hidden bit.
        !            93:        orl2    $(0!CLEARHID),r0
        !            94:                                # clear the non fraction parts.
        !            95:        andl2   $(0!(EXPMASK | SIGNBIT)),r4
        !            96:                                # add the hidden bit.
        !            97:        orl2    $(0!CLEARHID),r4
        !            98: 
        !            99: /*
        !           100:  *shift the smaller operand:
        !           101:  */
        !           102:        shar    r8,r4,r4
        !           103: eql_exps:
        !           104:        cmpl    r3,r7
        !           105:        jeql    add
        !           106:        bbc     $0,r3,negr4
        !           107: /*
        !           108:  *negate r0:
        !           109:  */
        !           110:        clrl    r3
        !           111:        mnegl   r0,r0
        !           112: 
        !           113: /*
        !           114:  *add the fractions:
        !           115:  */
        !           116: add:
        !           117:        clrl    r10
        !           118:        addl2   r4,r0
        !           119:        jgeq    norm
        !           120:        incl    r10
        !           121: /*
        !           122:  *negate the pair r0,r1:
        !           123:  */
        !           124:        mnegl   r0,r0
        !           125: norm:  callf   $4,sfnorm
        !           126:  
        !           127: /*
        !           128:  *add the sign bit
        !           129:  */
        !           130:        bbs     $0,r10,negative
        !           131:        bbs     $0,r3,negative  # the bigger operand was negative.
        !           132:        ret
        !           133: negative:
        !           134:        orl2    $SIGNBIT,r0
        !           135:        ret
        !           136:  
        !           137:  
        !           138: /*
        !           139:  *negate r4:
        !           140:  */
        !           141: negr4:
        !           142:        mnegl   r4,r4
        !           143:        jmp     add
        !           144:  
        !           145:  
        !           146: is_res1:
        !           147:        bbs     $31,r0,res_op
        !           148:        movl    r4,r0           # return the  smaller operand.
        !           149:        ret
        !           150: 
        !           151: is_res2:
        !           152:        bbs     $31,r4,res_op
        !           153:        ret                     # we allready have the 'result' in r0,r1.
        !           154: 
        !           155: res_op:
        !           156:        callf   $4,sfpresop
        !           157:        ret

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