+
−/* signbit() macro: Determine the sign bit of a floating-point number.
+
−   Copyright (C) 2007, 2009-2011 Free Software Foundation, Inc.
+
−
+
−   This program is free software: you can redistribute it and/or modify
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−   it under the terms of the GNU General Public License as published by
+
−   the Free Software Foundation; either version 3 of the License, or
+
−   (at your option) any later version.
+
−
+
−   This program is distributed in the hope that it will be useful,
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−   but WITHOUT ANY WARRANTY; without even the implied warranty of
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−   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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−   GNU General Public License for more details.
+
−
+
−   You should have received a copy of the GNU General Public License
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−   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
−
+
−#include <config.h>
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−
+
−/* Specification.  */
+
−#include <math.h>
+
−
+
−#include <string.h>
+
−#include "isnanf-nolibm.h"
+
−#include "float+.h"
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−
+
−#ifdef gl_signbitf_OPTIMIZED_MACRO
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−# undef gl_signbitf
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−#endif
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−
+
−int
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−gl_signbitf (float arg)
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−{
+
−#if defined FLT_SIGNBIT_WORD && defined FLT_SIGNBIT_BIT
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−  /* The use of a union to extract the bits of the representation of a
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−     'long double' is safe in practice, despite of the "aliasing rules" of
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−     C99, because the GCC docs say
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−       "Even with '-fstrict-aliasing', type-punning is allowed, provided the
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−        memory is accessed through the union type."
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−     and similarly for other compilers.  */
+
−# define NWORDS \
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−    ((sizeof (float) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
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−  union { float value; unsigned int word[NWORDS]; } m;
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−  m.value = arg;
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−  return (m.word[FLT_SIGNBIT_WORD] >> FLT_SIGNBIT_BIT) & 1;
+
−#elif HAVE_COPYSIGNF_IN_LIBC
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−  return copysignf (1.0f, arg) < 0;
+
−#else
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−  /* This does not do the right thing for NaN, but this is irrelevant for
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−     most use cases.  */
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−  if (isnanf (arg))
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−    return 0;
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−  if (arg < 0.0f)
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−    return 1;
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−  else if (arg == 0.0f)
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−    {
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−      /* Distinguish 0.0f and -0.0f.  */
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−      static float plus_zero = 0.0f;
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−      float arg_mem = arg;
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−      return (memcmp (&plus_zero, &arg_mem, SIZEOF_FLT) != 0);
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−    }
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−  else
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−    return 0;
+
−#endif
+
−}