1/* $OpenBSD: e_exp.S,v 1.8 2008/09/07 20:36:08 martynas Exp $ */ 2/* $NetBSD: e_exp.S,v 1.12 2002/02/27 16:32:46 christos Exp $ */ 3 4/* 5 * Copyright (c) 1993,94 Winning Strategies, Inc. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by Winning Strategies, Inc. 19 * 4. The name of the author may not be used to endorse or promote products 20 * derived from this software without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 */ 33 34/* 35 * Written by: 36 * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc. 37 */ 38 39#include <machine/asm.h> 40 41/* e^x = 2^(x * log2(e)) */ 42ENTRY(exp) 43 /* 44 * If x is +-Inf, then the subtraction would give Inf-Inf = NaN. 45 * Avoid this. Also avoid it if x is NaN for convenience. 46 */ 47 movl 8(%esp),%eax 48 andl $0x7fffffff,%eax 49 cmpl $0x7ff00000,%eax 50 jae x_Inf_or_NaN 51 52 fldl 4(%esp) 53 54 /* 55 * Ensure that the rounding mode is to nearest (to give the smallest 56 * possible fraction) and that the precision is as high as possible. 57 * We may as well mask interrupts if we switch the mode. 58 */ 59 fstcw 4(%esp) 60 movl 4(%esp),%eax 61 andl $0x0300,%eax 62 cmpl $0x0300,%eax /* RC == 0 && PC == 3? */ 63 je 1f /* jump if mode is good */ 64 movl $0x137f,8(%esp) 65 fldcw 8(%esp) 661: 67 fldl2e 68 fmulp /* x * log2(e) */ 69 fst %st(1) 70 frndint /* int(x * log2(e)) */ 71 fst %st(2) 72 fsubrp /* fract(x * log2(e)) */ 73 f2xm1 /* 2^(fract(x * log2(e))) - 1 */ 74 fld1 75 faddp /* 2^(fract(x * log2(e))) */ 76 fscale /* e^x */ 77 fstp %st(1) 78 je 1f 79 fldcw 4(%esp) 801: 81 ret 82 83x_Inf_or_NaN: 84 /* 85 * Return 0 if x is -Inf. Otherwise just return x, although the 86 * C version would return (x + x) (Real Indefinite) if x is a NaN. 87 */ 88 cmpl $0xfff00000,8(%esp) 89 jne x_not_minus_Inf 90 cmpl $0,4(%esp) 91 jne x_not_minus_Inf 92 fldz 93 ret 94 95x_not_minus_Inf: 96 fldl 4(%esp) 97 ret 98