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glibc  2.9
w_sqrt.c
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00001 /* Double-precision floating point square root wrapper.
00002    Copyright (C) 2004, 2007 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <math_ldbl_opt.h>
00021 #include "math.h"
00022 #include "math_private.h"
00023 #include <fenv_libc.h>
00024 
00025 #ifdef __STDC__
00026 double
00027 __sqrt (double x)           /* wrapper sqrt */
00028 #else
00029 double
00030 __sqrt (x)                  /* wrapper sqrt */
00031      double x;
00032 #endif
00033 {
00034   double z;
00035 /* Power4 (ISA V2.0) and above implement sqrt in hardware.  */
00036    __asm __volatile (
00037        "      fsqrt  %0,%1\n"
00038               : "=f" (z)
00039               : "f" (x));
00040 #ifdef _IEEE_LIBM
00041   return z;
00042 #else
00043   if (__builtin_expect (_LIB_VERSION == _IEEE_, 0))
00044     return z;
00045     
00046   if (__builtin_expect (x != x, 0))
00047     return z;
00048     
00049   if  (__builtin_expect (x < 0.0, 0))
00050     return __kernel_standard (x, x, 26);  /* sqrt(negative) */
00051   else
00052     return z;
00053 #endif
00054 }
00055 
00056 weak_alias (__sqrt, sqrt)
00057 #ifdef NO_LONG_DOUBLE
00058   strong_alias (__sqrt, __sqrtl) weak_alias (__sqrt, sqrtl)
00059 #endif
00060 #if LONG_DOUBLE_COMPAT(libm, GLIBC_2_0)
00061 compat_symbol (libm, __sqrt, sqrtl, GLIBC_2_0);
00062 #endif