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Annotation of 43BSDTahoe/lib/libc/gen/gen.vax/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 the above copyright notice and this paragraph are
        !             7:  * duplicated in all such forms and that any documentation,
        !             8:  * advertising materials, and other materials related to such
        !             9:  * distribution and use acknowledge that the software was developed
        !            10:  * by the University of California, Berkeley.  The name of the
        !            11:  * University may not be used to endorse or promote products derived
        !            12:  * from this software without specific prior written permission.
        !            13:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
        !            14:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
        !            15:  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            16:  */
        !            17: 
        !            18: #if defined(LIBC_SCCS) && !defined(lint)
        !            19:        .asciz "@(#)ldexp.s     5.4 (Berkeley) 6/27/88"
        !            20: #endif /* LIBC_SCCS and not lint */
        !            21: 
        !            22: /*
        !            23:  * double ldexp (value, exp)
        !            24:  * double value;
        !            25:  * int exp;
        !            26:  *
        !            27:  * Ldexp returns value*2**exp, if that result is in range.
        !            28:  * If underflow occurs, it returns zero.  If overflow occurs,
        !            29:  * it returns a value of appropriate sign and largest
        !            30:  * possible magnitude.  In case of either overflow or underflow,
        !            31:  * errno is set to ERANGE.  Note that errno is not modified if
        !            32:  * no error occurs.
        !            33:  */
        !            34: 
        !            35: #include "DEFS.h"
        !            36: #include <errno.h>
        !            37: 
        !            38:        .globl  _errno
        !            39: 
        !            40: ENTRY(ldexp, 0)
        !            41:        movd    4(ap),r0        /* fetch "value" */
        !            42:        extzv   $7,$8,r0,r2     /* r2 := biased exponent */
        !            43:        jeql    1f              /* if zero, done */
        !            44: 
        !            45:        addl2   12(ap),r2       /* r2 := new biased exponent */
        !            46:        jleq    2f              /* if <= 0, underflow */
        !            47:        cmpl    r2,$256         /* otherwise check if too big */
        !            48:        jgeq    3f              /* jump if overflow */
        !            49:        insv    r2,$7,$8,r0     /* put exponent back in result */
        !            50: 1:
        !            51:        ret
        !            52: 2:
        !            53:        clrd    r0
        !            54:        jbr     1f
        !            55: 3:
        !            56:        movd    huge,r0         /* largest possible floating magnitude */
        !            57:        jbc     $15,4(ap),1f    /* jump if argument was positive */
        !            58:        mnegd   r0,r0           /* if arg < 0, make result negative */
        !            59: 1:
        !            60:        movl    $ERANGE,_errno
        !            61:        ret
        !            62: 
        !            63:        .data
        !            64: huge:  .word   0x7fff          /* the largest number that can */
        !            65:        .word   0xffff          /*   be represented in a long floating */
        !            66:        .word   0xffff          /*   number.  This is given in hex in order */
        !            67:        .word   0xffff          /*   to avoid floating conversions */

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