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 (at) wimsey.com), Winning Strategies, Inc. 34 */ 35 36 #include <machine/asm.h> 37 38 RCSID("$FreeBSD: src/lib/msun/i387/e_exp.S,v 1.11 2005/10/30 12:21:02 bde Exp $") 39 40 /* e^x = 2^(x * log2(e)) */ 41 ENTRY(exp) 42 /* 43 * If x is +-Inf, then the subtraction would give Inf-Inf = NaN. 44 * Avoid this. Also avoid it if x is NaN for convenience. 45 */ 46 movl 8(%esp),%eax 47 andl $0x7fffffff,%eax 48 cmpl $0x7ff00000,%eax 49 jae x_Inf_or_NaN 50 51 fldl 4(%esp) 52 53 /* 54 * Extended precision is needed to reduce the maximum error from 55 * hundreds of ulps to less than 1 ulp. Switch to it if necessary. 56 * We may as well set the rounding mode to to-nearest and mask traps 57 * if we switch. 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) 66 1: 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) 80 1: 81 ret 82 83 x_Inf_or_NaN: 84 /* 85 * Return 0 if x is -Inf. Otherwise just return x; when x is Inf 86 * this gives Inf, and when x is a NaN this gives the same result 87 * as (x + x) (x quieted). 88 */ 89 cmpl $0xfff00000,8(%esp) 90 jne x_not_minus_Inf 91 cmpl $0,4(%esp) 92 jne x_not_minus_Inf 93 fldz 94 ret 95 96 x_not_minus_Inf: 97 fldl 4(%esp) 98 ret 99
