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Annotation of 43BSDReno/lib/libc/i386/gen/ldexp.c, revision 1.1.1.1

1.1       root        1: /*-
                      2:  * Copyright (c) 1990 The Regents of the University of California.
                      3:  * All rights reserved.
                      4:  *
                      5:  * This code is derived from software contributed to Berkeley by
                      6:  * Sean Eric Fagan.
                      7:  *
                      8:  * Redistribution and use in source and binary forms are permitted
                      9:  * provided that: (1) source distributions retain this entire copyright
                     10:  * notice and comment, and (2) distributions including binaries display
                     11:  * the following acknowledgement:  ``This product includes software
                     12:  * developed by the University of California, Berkeley and its contributors''
                     13:  * in the documentation or other materials provided with the distribution
                     14:  * and in all advertising materials mentioning features or use of this
                     15:  * software. Neither the name of the University nor the names of its
                     16:  * contributors may be used to endorse or promote products derived
                     17:  * from this software without specific prior written permission.
                     18:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     19:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     20:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     21:  */
                     22: 
                     23: #if defined(LIBC_SCCS) && !defined(lint)
                     24: static char sccsid[] = "@(#)ldexp.c    5.1 (Berkeley) 4/23/90";
                     25: #endif /* LIBC_SCCS and not lint */
                     26: 
                     27: /*
                     28:  * ldexp(value, exp): return value * (2 ** exp).
                     29:  *
                     30:  * Written by Sean Eric Fagan ([email protected])
                     31:  * Sun Mar 11 20:27:09 PST 1990
                     32:  */
                     33: 
                     34: /*
                     35:  * We do the conversion in C to let gcc optimize it away, if possible.
                     36:  * The "fxch ; fstp" stuff is because value is still on the stack
                     37:  * (stupid 8087!).
                     38:  */
                     39: double
                     40: ldexp (double value, int exp)
                     41: {
                     42:        double temp, texp, temp2;
                     43:        texp = exp;
                     44:        asm ("fscale ; fxch %%st(1) ; fstp%L1 %1 "
                     45:                : "=f" (temp), "=0" (temp2)
                     46:                : "0" (texp), "f" (value));
                     47:        return (temp);
                     48: }

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