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Annotation of 43BSDReno/lib/libc/tahoe/fpe/cvtld.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 "@(#)cvtld.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(cvtld, R2|R3|R4|R5)
        !            31:  #
        !            32:  #Some initializations:
        !            33:  #
        !            34:        clrl    r4              # r4 - negative flag.
        !            35:        clrl    r2              # r2 - exponent.
        !            36:        movl    4(fp),r0        # fetch operand.
        !            37:        movl    r0,r5           # need another copy.
        !            38:        jeql    retzero         # return zero.
        !            39:        jgtr    positive
        !            40:        mnegl   r0,r0
        !            41:        jvs     retmin          # return minimum integer.
        !            42:        incl    r4              # remember it was negative.
        !            43:        movl    r0,r5           # remember the negated value.
        !            44:  #
        !            45:  #Compute exponent:
        !            46:  #
        !            47: positive:
        !            48:        ffs     r0,r1
        !            49:        incl    r1
        !            50:        addl2   r1,r2
        !            51:        shrl    r1,r0,r0
        !            52:        jneq    positive        # look for more set bits.
        !            53:  #
        !            54:  #we have the exponent in r2.
        !            55:  #
        !            56:        movl    r5,r0           # r0,r1 will hold the resulting f.p. number.
        !            57:        clrl    r1
        !            58:  #
        !            59:  #Shift the fraction part to its proper place:
        !            60:  #
        !            61:        subl3   r2,$HID_POS,r3
        !            62:        jlss    shiftr          # if less then zero we have to shift right.
        !            63:        shll    r3,r0,r0        # else we shift left.
        !            64:        jmp     shifted
        !            65: shiftr:
        !            66:        mnegl   r3,r3
        !            67:        shrq    r3,r0,r0
        !            68: shifted:
        !            69:        andl2   $CLEARHID,r0    # clear the hidden bit.
        !            70:        shal    $EXPSHIFT,r2,r2 # shift the exponent to its proper place.
        !            71:        orl2    $EXPSIGN,r2     # set the exponent sign bit(to bias it).
        !            72:        orl2    r2,r0           # combine exponent & fraction.
        !            73:        bbc     $0,r4,sign_ok   # do we  have to set the sign bit?
        !            74:        orl2    $SIGNBIT,r0     # yes...
        !            75: sign_ok:
        !            76:        ret
        !            77: 
        !            78: retzero:
        !            79:        clrl    r0
        !            80:        clrl    r1
        !            81:        ret
        !            82: 
        !            83: retmin:
        !            84:        movl    $0xd0000000,r0
        !            85:        clrl    r1
        !            86:        ret
        !            87: 
        !            88: 
        !            89:        

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