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/* $OpenBSD: s_rintl.c,v 1.2 2016/09/12 19:47:02 guenther Exp $ */ |
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/*- |
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* Copyright (c) 2008 David Schultz <das@FreeBSD.ORG> |
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* All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in the |
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* documentation and/or other materials provided with the distribution. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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* SUCH DAMAGE. |
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*/ |
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#include <sys/types.h> |
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#include <machine/ieee.h> |
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#include <float.h> |
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#include <math.h> |
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#if LDBL_MAX_EXP != 0x4000 |
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/* We also require the usual bias, min exp and expsign packing. */ |
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#error "Unsupported long double format" |
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#endif |
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#define BIAS (LDBL_MAX_EXP - 1) |
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static const float |
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shift[2] = { |
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#if LDBL_MANT_DIG == 64 |
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0x1.0p63, -0x1.0p63 |
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#elif LDBL_MANT_DIG == 113 |
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0x1.0p112, -0x1.0p112 |
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#else |
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#error "Unsupported long double format" |
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#endif |
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}; |
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static const float zero[2] = { 0.0, -0.0 }; |
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long double |
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rintl(long double x) |
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{ |
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union { |
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long double e; |
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struct ieee_ext bits; |
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} u; |
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uint32_t expsign; |
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int ex, sign; |
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u.e = x; |
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expsign = (u.bits.ext_sign << 15) | u.bits.ext_exp; |
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ex = expsign & 0x7fff; |
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✗✓ |
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if (ex >= BIAS + LDBL_MANT_DIG - 1) { |
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if (ex == BIAS + LDBL_MAX_EXP) |
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return (x + x); /* Inf, NaN, or unsupported format */ |
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return (x); /* finite and already an integer */ |
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} |
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sign = expsign >> 15; |
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/* |
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* The following code assumes that intermediate results are |
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* evaluated in long double precision. If they are evaluated in |
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* greater precision, double rounding may occur, and if they are |
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* evaluated in less precision (as on i386), results will be |
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* wildly incorrect. |
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*/ |
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x += shift[sign]; |
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x -= shift[sign]; |
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/* |
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* If the result is +-0, then it must have the same sign as x, but |
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* the above calculation doesn't always give this. Fix up the sign. |
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*/ |
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✗✓ |
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if (ex < BIAS && x == 0.0L) |
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return (zero[sign]); |
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return (x); |
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} |
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DEF_NONSTD(rintl); |