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Annotation of 43BSDReno/lib/libc/vax/gen/ldexp.s, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1983 Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms are permitted
        !             6:  * provided that: (1) source distributions retain this entire copyright
        !             7:  * notice and comment, and (2) distributions including binaries display
        !             8:  * the following acknowledgement:  ``This product includes software
        !             9:  * developed by the University of California, Berkeley and its contributors''
        !            10:  * in the documentation or other materials provided with the distribution
        !            11:  * and in all advertising materials mentioning features or use of this
        !            12:  * software. Neither the name of the University nor the names of its
        !            13:  * contributors may be used to endorse or promote products derived
        !            14:  * from this software without specific prior written permission.
        !            15:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
        !            16:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
        !            17:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            18:  */
        !            19: 
        !            20: #if defined(LIBC_SCCS) && !defined(lint)
        !            21:        .asciz "@(#)ldexp.s     5.6 (Berkeley) 6/1/90"
        !            22: #endif /* LIBC_SCCS and not lint */
        !            23: 
        !            24: /*
        !            25:  * double ldexp (value, exp)
        !            26:  * double value;
        !            27:  * int exp;
        !            28:  *
        !            29:  * Ldexp returns value*2**exp, if that result is in range.
        !            30:  * If underflow occurs, it returns zero.  If overflow occurs,
        !            31:  * it returns a value of appropriate sign and largest
        !            32:  * possible magnitude.  In case of either overflow or underflow,
        !            33:  * errno is set to ERANGE.  Note that errno is not modified if
        !            34:  * no error occurs.
        !            35:  */
        !            36: 
        !            37: #include "DEFS.h"
        !            38: 
        !            39: /*
        !            40:  * don't include errno.h, ANSI C says it defines errno.
        !            41:  *
        !            42:  * #include <errno.h>
        !            43:  */
        !            44: #define        ERANGE  34
        !            45: 
        !            46:        .globl  _errno
        !            47: 
        !            48: ENTRY(ldexp, 0)
        !            49:        movd    4(ap),r0        /* fetch "value" */
        !            50:        extzv   $7,$8,r0,r2     /* r2 := biased exponent */
        !            51:        jeql    1f              /* if zero, done */
        !            52: 
        !            53:        addl2   12(ap),r2       /* r2 := new biased exponent */
        !            54:        jleq    2f              /* if <= 0, underflow */
        !            55:        cmpl    r2,$256         /* otherwise check if too big */
        !            56:        jgeq    3f              /* jump if overflow */
        !            57:        insv    r2,$7,$8,r0     /* put exponent back in result */
        !            58: 1:
        !            59:        ret
        !            60: 2:
        !            61:        clrd    r0
        !            62:        jbr     1f
        !            63: 3:
        !            64:        movd    huge,r0         /* largest possible floating magnitude */
        !            65:        jbc     $15,4(ap),1f    /* jump if argument was positive */
        !            66:        mnegd   r0,r0           /* if arg < 0, make result negative */
        !            67: 1:
        !            68:        movl    $ERANGE,_errno
        !            69:        ret
        !            70: 
        !            71:        .data
        !            72: huge:  .word   0x7fff          /* the largest number that can */
        !            73:        .word   0xffff          /*   be represented in a long floating */
        !            74:        .word   0xffff          /*   number.  This is given in hex in order */
        !            75:        .word   0xffff          /*   to avoid floating conversions */

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