1 /*- 2 * Copyright (c) 2008 David Schultz <das@FreeBSD.ORG> 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 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 #include "cdefs-compat.h" 28 //__FBSDID("$FreeBSD: src/lib/msun/src/s_rintl.c,v 1.5 2008/02/22 11:59:05 bde Exp $"); 29 30 #include <float.h> 31 #include <openlibm_fenv.h> 32 #include <openlibm_math.h> 33 34 #include "fpmath.h" 35 36 //VBS 37 #include "math_private.h" 38 39 40 #if LDBL_MAX_EXP != 0x4000 41 /* We also require the usual bias, min exp and expsign packing. */ 42 #error "Unsupported long double format" 43 #endif 44 45 #define BIAS (LDBL_MAX_EXP - 1) 46 47 static const float 48 shift[2] = { 49 #if LDBL_MANT_DIG == 64 50 0x1.0p63, -0x1.0p63 51 #elif LDBL_MANT_DIG == 113 52 0x1.0p112, -0x1.0p112 53 #else 54 #error "Unsupported long double format" 55 #endif 56 }; 57 static const float zero[2] = { 0.0, -0.0 }; 58 59 DLLEXPORT long double 60 rintl(long double x) 61 { 62 union IEEEl2bits u; 63 u_int32_t expsign; 64 int ex, sign; 65 66 u.e = x; 67 expsign = u.xbits.expsign; 68 ex = expsign & 0x7fff; 69 70 if (ex >= BIAS + LDBL_MANT_DIG - 1) { 71 if (ex == BIAS + LDBL_MAX_EXP) 72 return (x + x); /* Inf, NaN, or unsupported format */ 73 return (x); /* finite and already an integer */ 74 } 75 sign = expsign >> 15; 76 77 /* 78 * The following code assumes that intermediate results are 79 * evaluated in long double precision. If they are evaluated in 80 * greater precision, double rounding may occur, and if they are 81 * evaluated in less precision (as on i386), results will be 82 * wildly incorrect. 83 */ 84 x += shift[sign]; 85 x -= shift[sign]; 86 87 /* 88 * If the result is +-0, then it must have the same sign as x, but 89 * the above calculation doesn't always give this. Fix up the sign. 90 */ 91 if (ex < BIAS && x == 0.0L) 92 return (zero[sign]); 93 94 return (x); 95 } 96 97 /* 98 * We save and restore the floating-point environment to avoid raising 99 * an inexact exception. We can get away with using fesetenv() 100 * instead of feclearexcept()/feupdateenv() to restore the environment 101 * because the only exception defined for rint() is overflow, and 102 * rounding can't overflow as long as emax >= p. 103 */ 104 #define DECL(type, fn, rint) \ 105 DLLEXPORT type \ 106 fn(type x) \ 107 { \ 108 type ret; \ 109 fenv_t env; \ 110 \ 111 fegetenv(&env); \ 112 ret = rint(x); \ 113 fesetenv(&env); \ 114 return (ret); \ 115 } 116 DECL(long double, nearbyintl, rintl) 117