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glibc  2.9
s_ceil.c
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00001 /* Copyright (C) 1998, 2000, 2006, 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 #include <math_ldbl_opt.h>
00022 
00023 /* Use the -inf rounding mode conversion instructions to implement
00024    ceil, via something akin to -floor(-x).  This is much faster than
00025    playing with the fpcr to achieve +inf rounding mode.  */
00026 
00027 double
00028 __ceil (double x)
00029 {
00030   double two52 = copysign (0x1.0p52, x);
00031   double r, tmp;
00032   
00033   __asm (
00034 #ifdef _IEEE_FP_INEXACT
00035         "addt/suim %2, %3, %1\n\tsubt/suim %1, %3, %0"
00036 #else
00037         "addt/sum %2, %3, %1\n\tsubt/sum %1, %3, %0"
00038 #endif
00039         : "=&f"(r), "=&f"(tmp)
00040         : "f"(-x), "f"(-two52));
00041 
00042   /* Fix up the negation we did above, as well as handling -0 properly. */
00043   return copysign (r, x);
00044 }
00045 
00046 weak_alias (__ceil, ceil)
00047 #ifdef NO_LONG_DOUBLE
00048 strong_alias (__ceil, __ceill)
00049 weak_alias (__ceil, ceill)
00050 #endif
00051 #if LONG_DOUBLE_COMPAT(libm, GLIBC_2_0)
00052 compat_symbol (libm, __ceil, ceill, GLIBC_2_0);
00053 #endif