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