/*
 * Copyright (c) 1993,94 Winning Strategies, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Winning Strategies, Inc.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Written by:
 *      J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
 */

#include <machine/asm.h>
/* e^x = 2^(x * log2(e)) */
ENTRY(exp)
        /*
         * If x is +-Inf, then the subtraction would give Inf-Inf = NaN.
         * Avoid this.  Also avoid it if x is NaN for convenience.
         */
        movl    8(%esp),%eax
        andl    $0x7fffffff,%eax
        cmpl    $0x7ff00000,%eax
        jae     x_Inf_or_NaN

        fldl    4(%esp)

        /*
         * Extended precision is needed to reduce the maximum error from
         * hundreds of ulps to less than 1 ulp.  Switch to it if necessary.
         * We may as well set the rounding mode to to-nearest and mask traps
         * if we switch.
         */
        fstcw   4(%esp)
        movl    4(%esp),%eax
        andl    $0x0300,%eax
        cmpl    $0x0300,%eax            /* RC == 0 && PC == 3? */
        je      1f                      /* jump if mode is good */
        movl    $0x137f,8(%esp)
        fldcw   8(%esp)
1:
        fldl2e
        fmulp                           /* x * log2(e) */
        fst     %st(1)
        frndint                         /* int(x * log2(e)) */
        fst     %st(2)
        fsubrp                          /* fract(x * log2(e)) */
        f2xm1                           /* 2^(fract(x * log2(e))) - 1 */ 
        fld1
        faddp                           /* 2^(fract(x * log2(e))) */
        fscale                          /* e^x */
        fstp    %st(1)
        je      1f
        fldcw   4(%esp)
1:
        ret

x_Inf_or_NaN:
        /*
         * Return 0 if x is -Inf.  Otherwise just return x; when x is Inf
         * this gives Inf, and when x is a NaN this gives the same result
         * as (x + x) (x quieted).
         */
        cmpl    $0xfff00000,8(%esp)
        jne     x_not_minus_Inf
        cmpl    $0,4(%esp)
        jne     x_not_minus_Inf
        fldz
        ret

x_not_minus_Inf:
        fldl    4(%esp)
        ret
END(exp)

        .section .note.GNU-stack,"",%progbits