| The Android Open Source Project | 1dc9e47 | 2009-03-03 19:28:35 -0800 | [diff] [blame] | 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 <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 |