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glibc  2.9
w_sqrtf.c
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00001 /* Single-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.h"
00021 #include "math_private.h"
00022 #include <fenv_libc.h>
00023 
00024 #include <sysdep.h>
00025 #include <ldsodefs.h>
00026 
00027 #ifdef __STDC__
00028 float
00029 __sqrtf (float x)           /* wrapper sqrtf */
00030 #else
00031 float
00032 __sqrtf (x)                 /* wrapper sqrtf */
00033      float x;
00034 #endif
00035 {
00036 #ifdef _IEEE_LIBM
00037   return __ieee754_sqrtf (x);
00038 #else
00039   float z;
00040 /* Power4 (ISA V2.0) and above implement sqrtf in hardware.  */
00041    __asm __volatile (
00042        "      fsqrts %0,%1\n"
00043               : "=f" (z)
00044               : "f" (x));
00045 
00046   if (__builtin_expect (_LIB_VERSION == _IEEE_, 0))
00047     return z;
00048     
00049   if (__builtin_expect (x != x, 0))
00050     return z;
00051     
00052   if  (__builtin_expect (x < 0.0, 0))
00053     /* sqrtf(negative) */
00054     return (float) __kernel_standard ((double) x, (double) x, 126);
00055   else
00056     return z;
00057 #endif
00058 }
00059 
00060 weak_alias (__sqrtf, sqrtf)