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glibc  2.9
s_truncf.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 /* Use the chopped rounding mode conversion instructions to implement trunc. */
00024 
00025 float
00026 __truncf (float x)
00027 {
00028   float two23 = copysignf (0x1.0p23, x);
00029   float r, tmp;
00030   
00031   __asm (
00032 #ifdef _IEEE_FP_INEXACT
00033         "adds/suic %2, %3, %1\n\tsubs/suic %1, %3, %0"
00034 #else
00035         "adds/suc %2, %3, %1\n\tsubs/suc %1, %3, %0"
00036 #endif
00037         : "=&f"(r), "=&f"(tmp)
00038         : "f"(x), "f"(two23));
00039 
00040   /* trunc(-0) == -0, and in general we'll always have the same
00041      sign as our input.  */
00042   return copysignf (r, x);
00043 }
00044 
00045 weak_alias (__truncf, truncf)