1  /* Truncate argument to nearest integral value not larger than the argument.
       2     Copyright (C) 1997-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #define NO_MATH_REDIRECT
      20  #include <math.h>
      21  
      22  #include <math_private.h>
      23  #include <libm-alias-double.h>
      24  #include <math-use-builtins.h>
      25  
      26  
      27  double
      28  __trunc (double x)
      29  {
      30  #if USE_TRUNC_BUILTIN
      31    return __builtin_trunc (x);
      32  #else
      33    /* Use generic implementation.  */
      34    int64_t i0, j0;
      35    int64_t sx;
      36  
      37    EXTRACT_WORDS64 (i0, x);
      38    sx = i0 & UINT64_C (0x8000000000000000);
      39    j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
      40    if (j0 < 52)
      41      {
      42        if (j0 < 0)
      43  	/* The magnitude of the number is < 1 so the result is +-0.  */
      44  	INSERT_WORDS64 (x, sx);
      45        else
      46  	INSERT_WORDS64 (x, sx | (i0 & ~(UINT64_C (0x000fffffffffffff) >> j0)));
      47      }
      48    else
      49      {
      50        if (j0 == 0x400)
      51  	/* x is inf or NaN.  */
      52  	return x + x;
      53      }
      54  
      55    return x;
      56  #endif /* ! USE_TRUNC_BUILTIN  */
      57  }
      58  #ifndef __trunc
      59  libm_alias_double (__trunc, trunc)
      60  #endif