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glibc  2.9
s_roundf.c
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00001 /* Copyright (C) 2007 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003    Contributed by Richard Henderson.
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 
00022 
00023 float
00024 __roundf (float x)
00025 {
00026   const float almost_half = 0x1.fffffep-2;
00027   const float two23 = 0x1.0p23;
00028   float r, tmp;
00029   
00030   __asm (
00031 #ifdef _IEEE_FP_INEXACT
00032         "adds/suic %2, %3, %1\n\tsubs/suic %1, %3, %0"
00033 #else
00034         "adds/suc %2, %3, %1\n\tsubs/suc %1, %3, %0"
00035 #endif
00036         : "=&f"(r), "=&f"(tmp)
00037         : "f"(fabsf (x) + almost_half), "f"(two23));
00038 
00039   /* round(-0) == -0, and in general we'll always have the same
00040      sign as our input.  */
00041   return copysignf (r, x);
00042 }
00043 
00044 weak_alias (__roundf, roundf)