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Annotation of 43BSDReno/lib/libc/tahoe/fpe/addd.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 "@(#)addd.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(addd, 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,r1,r2,r3.
        !            34:  * r0,r1 - 'pure' fraction, r2 - exponent, r3 - sign).
        !            35:  * The smaller operand will be fetched into r4,r5,r6,r7.
        !            36:  */
        !            37:        andl3   $EXPMASK,4(fp),r0
        !            38:        andl3   $EXPMASK,12(fp),r1
        !            39:        cmpl    r0,r1
        !            40:        jgtr    first_greater
        !            41: 
        !            42:        movl    12(fp),r0       # bigger operand to r0,r1
        !            43:        movl    16(fp),r1
        !            44: 
        !            45:        movl    4(fp),r4        # smaller operand to r4,r5
        !            46:        movl    8(fp),r5
        !            47:        jmp     expo
        !            48: 
        !            49: first_greater:
        !            50:        movl    4(fp),r0        # bigger operand to r0,r1
        !            51:        movl    8(fp),r1
        !            52: 
        !            53:        movl    12(fp),r4       # smaller operand to r4,r5
        !            54:        movl    16(fp),r5
        !            55: 
        !            56: /*
        !            57:  * compute exponents:
        !            58:  */
        !            59: expo:
        !            60:        andl3   $EXPMASK,r0,r2  # r2 will hold the exponent.
        !            61:        jeql    is_res1         # check for reserved operand. 
        !            62:        shrl    $EXPSHIFT,r2,r2
        !            63: 
        !            64: 
        !            65:        andl3   $EXPMASK,r4,r6  # r6 will hold the exponent.
        !            66:        jeql    is_res2         # check for reserved operand. 
        !            67:        shrl    $EXPSHIFT,r6,r6
        !            68: /*
        !            69:  * compare the exponents:
        !            70:  */
        !            71:        subl3   r6,r2,r8
        !            72:        jeql    signs
        !            73:        cmpl    r8,$MAX_EXP_DIF
        !            74:        jlss    signs
        !            75:        ret                     # return the bigger number.
        !            76:  
        !            77: /*
        !            78:  * remember the signs:
        !            79:  */
        !            80: signs:
        !            81:        clrl    r3
        !            82:        bbc     $31,r0,sign2    # if negative remember it.
        !            83:        incl    r3
        !            84: sign2:
        !            85:        clrl    r7
        !            86:        bbc     $31,r4,frac     # if negative remember it.
        !            87:        incl    r7
        !            88: /*
        !            89:  * compute 'pure' fraction:
        !            90:  */
        !            91: frac:
        !            92:                                # clear the non fraction parts.
        !            93:        andl2   $(0!(EXPMASK | SIGNBIT)),r0
        !            94:                                # add the hidden bit.
        !            95:        orl2    $(0!CLEARHID),r0
        !            96:                                # clear the non fraction parts.
        !            97:        andl2   $(0!(EXPMASK | SIGNBIT)),r4
        !            98:                                # add the hidden bit.
        !            99:        orl2    $(0!CLEARHID),r4
        !           100: 
        !           101: /*
        !           102:  * shift the smaller operand:
        !           103:  */
        !           104:        shrq    r8,r4,r4
        !           105: eql_exps:
        !           106:        cmpl    r3,r7
        !           107:        jeql    add
        !           108:        bbc     $0,r3,negr4r5
        !           109: /*
        !           110:  * negate the pair r0,r1:
        !           111:  */
        !           112:        clrl    r3
        !           113:        mcoml   r1,r1
        !           114:        clrl    r9              # r9 - carry flag.
        !           115:        incl    r1
        !           116:        bcc     comr0
        !           117:        incl    r9              # remember the carry.
        !           118: comr0: mcoml   r0,r0
        !           119:        bbc     $0,r9,add
        !           120:        incl    r0
        !           121: 
        !           122: /*
        !           123:  * add the fractions:
        !           124:  */
        !           125: add:
        !           126:        clrl    r10             # to remember the sign of the result.
        !           127:        addl2   r5,r1
        !           128:        adwc    r4,r0
        !           129:        jgeq    norm            # if positive go to normelize.
        !           130:        incl    r10             # else remember it and negate the result.
        !           131: /*
        !           132:  * negate the pair r0,r1:
        !           133:  */
        !           134:        clrl    r3
        !           135:        mcoml   r1,r1
        !           136:        clrl    r9              # r9 - carry flag.
        !           137:        incl    r1
        !           138:        bcc     comr00
        !           139:        incl    r9              # remember the carry.
        !           140: comr00:        mcoml   r0,r0
        !           141:        bbc     $0,r9,norm
        !           142:        incl    r0
        !           143: norm:  callf   $4,fnorm
        !           144:  
        !           145: /*
        !           146:  * add the sign bit
        !           147:  */
        !           148:        bbs     $0,r10,negative
        !           149:        bbs     $0,r3,negative
        !           150:        ret
        !           151: negative:
        !           152:        orl2    $SIGNBIT,r0
        !           153:        ret
        !           154: 
        !           155: 
        !           156: /*
        !           157:  * negate the pair r4,r5:
        !           158:  */
        !           159: negr4r5:
        !           160:        clrl    r7
        !           161:        mcoml   r5,r5
        !           162:        clrl    r9              # r9 - carry flag.
        !           163:        incl    r5
        !           164:        bcc     comr4
        !           165:        incl    r9              # remember the carry.
        !           166: comr4: mcoml   r4,r4
        !           167:        bbc     $0,r9,add
        !           168:        incl    r4
        !           169:        jmp     add
        !           170:  
        !           171:  
        !           172: is_res1:
        !           173:        bbs     $31,r0,res_op
        !           174:        movl    r4,r0           # return the  smaller operand.
        !           175:        movl    r5,r1
        !           176:        ret
        !           177: 
        !           178: is_res2:
        !           179:        bbs     $31,r4,res_op
        !           180:        ret                     # we allready have the 'result' in r0,r1.
        !           181: 
        !           182: res_op:
        !           183:        callf   $4,fpresop
        !           184:        ret

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