usr/src/lib/libc/vax/gen/ldexp.s

#ifndef lint
        .asciz  "@(#)ldexp.s    5.1 (Berkeley) %G%"
#endif not lint

/*
 * double ldexp (value, exp)
 * double value;
 * int exp;
 *
 * Ldexp returns value*2**exp, if that result is in range.
 * If underflow occurs, it returns zero.  If overflow occurs,
 * it returns a value of appropriate sign and largest
 * possible magnitude.  In case of either overflow or underflow,
 * errno is set to ERANGE.  Note that errno is not modified if
 * no error occurs.
 */

#include "DEFS.h"
#include <errno.h>

        .globl  _errno

ENTRY(ldexp, 0)
        movd    4(ap),r0        /* fetch "value" */
        extzv   $7,$8,r0,r2     /* r2 := biased exponent */
        jeql    1f              /* if zero, done */

        addl2   12(ap),r2       /* r2 := new biased exponent */
        jleq    2f              /* if <= 0, underflow */
        cmpl    r2,$256         /* otherwise check if too big */
        jgeq    3f              /* jump if overflow */
        insv    r2,$7,$8,r0     /* put exponent back in result */
1:
        ret
2:
        clrd    r0
        jbr     1f
3:
        movd    huge,r0         /* largest possible floating magnitude */
        jbc     $15,4(ap),1f    /* jump if argument was positive */
        mnegd   r0,r0           /* if arg < 0, make result negative */
1:
        movl    $ERANGE,_errno
        ret

        .data
huge:   .word   0x7fff          /* the largest number that can */
        .word   0xffff          /*   be represented in a long floating */
        .word   0xffff          /*   number.  This is given in hex in order */
        .word   0xffff          /*   to avoid floating conversions */