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

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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