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Annotation of 43BSD/lib/libc/vax/gen/ldexp.s, revision 1.1.1.1

1.1       root        1: #ifdef LIBC_SCCS
                      2:        .asciz  "@(#)ldexp.s    5.2 (Berkeley) 3/9/86"
                      3: #endif LIBC_SCCS
                      4: 
                      5: /*
                      6:  * double ldexp (value, exp)
                      7:  * double value;
                      8:  * int exp;
                      9:  *
                     10:  * Ldexp returns value*2**exp, if that result is in range.
                     11:  * If underflow occurs, it returns zero.  If overflow occurs,
                     12:  * it returns a value of appropriate sign and largest
                     13:  * possible magnitude.  In case of either overflow or underflow,
                     14:  * errno is set to ERANGE.  Note that errno is not modified if
                     15:  * no error occurs.
                     16:  */
                     17: 
                     18: #include "DEFS.h"
                     19: #include <errno.h>
                     20: 
                     21:        .globl  _errno
                     22: 
                     23: ENTRY(ldexp, 0)
                     24:        movd    4(ap),r0        /* fetch "value" */
                     25:        extzv   $7,$8,r0,r2     /* r2 := biased exponent */
                     26:        jeql    1f              /* if zero, done */
                     27: 
                     28:        addl2   12(ap),r2       /* r2 := new biased exponent */
                     29:        jleq    2f              /* if <= 0, underflow */
                     30:        cmpl    r2,$256         /* otherwise check if too big */
                     31:        jgeq    3f              /* jump if overflow */
                     32:        insv    r2,$7,$8,r0     /* put exponent back in result */
                     33: 1:
                     34:        ret
                     35: 2:
                     36:        clrd    r0
                     37:        jbr     1f
                     38: 3:
                     39:        movd    huge,r0         /* largest possible floating magnitude */
                     40:        jbc     $15,4(ap),1f    /* jump if argument was positive */
                     41:        mnegd   r0,r0           /* if arg < 0, make result negative */
                     42: 1:
                     43:        movl    $ERANGE,_errno
                     44:        ret
                     45: 
                     46:        .data
                     47: huge:  .word   0x7fff          /* the largest number that can */
                     48:        .word   0xffff          /*   be represented in a long floating */
                     49:        .word   0xffff          /*   number.  This is given in hex in order */
                     50:        .word   0xffff          /*   to avoid floating conversions */

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