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