e_exp.S - vx32 - Local 9vx git repository for patches.
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       ---
       e_exp.S (3027B)
       ---
            1 /*
            2  * Copyright (c) 1993,94 Winning Strategies, Inc.
            3  * All rights reserved.
            4  *
            5  * Redistribution and use in source and binary forms, with or without
            6  * modification, are permitted provided that the following conditions
            7  * are met:
            8  * 1. Redistributions of source code must retain the above copyright
            9  *    notice, this list of conditions and the following disclaimer.
           10  * 2. Redistributions in binary form must reproduce the above copyright
           11  *    notice, this list of conditions and the following disclaimer in the
           12  *    documentation and/or other materials provided with the distribution.
           13  * 3. All advertising materials mentioning features or use of this software
           14  *    must display the following acknowledgement:
           15  *      This product includes software developed by Winning Strategies, Inc.
           16  * 4. The name of the author may not be used to endorse or promote products
           17  *    derived from this software without specific prior written permission.
           18  *
           19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
           20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
           21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
           22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
           23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
           24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
           25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
           26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
           27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
           28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
           29  */
           30 
           31 /*
           32  * Written by:
           33  *        J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
           34  */
           35 
           36 #include <asm.h>
           37 
           38 /* e^x = 2^(x * log2(e)) */
           39 ENTRY(__ieee754_exp)
           40         /*
           41          * If x is +-Inf, then the subtraction would give Inf-Inf = NaN.
           42          * Avoid this.  Also avoid it if x is NaN for convenience.
           43          */
           44         movl        8(%esp),%eax
           45         andl        $0x7fffffff,%eax
           46         cmpl        $0x7ff00000,%eax
           47         jae        x_Inf_or_NaN
           48 
           49         fldl        4(%esp)
           50 
           51         /*
           52          * Ensure that the rounding mode is to nearest (to give the smallest
           53          * possible fraction) and that the precision is as high as possible.
           54          * We may as well mask interrupts if we switch the mode.
           55          */
           56         fstcw        4(%esp)
           57         movl        4(%esp),%eax
           58         andl        $0x0300,%eax
           59         cmpl        $0x0300,%eax                /* RC == 0 && PC == 3? */
           60         je        1f                        /* jump if mode is good */
           61         movl        $0x137f,8(%esp)
           62         fldcw        8(%esp)
           63 1:
           64         fldl2e
           65         fmulp                                /* x * log2(e) */
           66         fst        %st(1)
           67         frndint                                /* int(x * log2(e)) */
           68         fst        %st(2)
           69         fsubrp                                /* fract(x * log2(e)) */
           70         f2xm1                                /* 2^(fract(x * log2(e))) - 1 */ 
           71         fld1
           72         faddp                                /* 2^(fract(x * log2(e))) */
           73         fscale                                /* e^x */
           74         fstp        %st(1)
           75         je        1f
           76         fldcw        4(%esp)
           77 1:
           78         ret
           79 
           80 x_Inf_or_NaN:
           81         /*
           82          * Return 0 if x is -Inf.  Otherwise just return x, although the
           83          * C version would return (x + x) (Real Indefinite) if x is a NaN.
           84          */
           85         cmpl        $0xfff00000,8(%esp)
           86         jne        x_not_minus_Inf
           87         cmpl        $0,4(%esp)
           88         jne        x_not_minus_Inf
           89         fldz
           90         ret
           91 
           92 x_not_minus_Inf:
           93         fldl        4(%esp)
           94         ret