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Diffstat (limited to 'libgfortran/m4/pow.m4')
| -rw-r--r-- | libgfortran/m4/pow.m4 | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/libgfortran/m4/pow.m4 b/libgfortran/m4/pow.m4 new file mode 100644 index 0000000000..0d8524165e --- /dev/null +++ b/libgfortran/m4/pow.m4 @@ -0,0 +1,83 @@ +`/* Support routines for the intrinsic power (**) operator. + Copyright (C) 2004-2017 Free Software Foundation, Inc. + Contributed by Paul Brook + +This file is part of the GNU Fortran 95 runtime library (libgfortran). + +Libgfortran is free software; you can redistribute it and/or +modify it under the terms of the GNU General Public +License as published by the Free Software Foundation; either +version 3 of the License, or (at your option) any later version. + +Libgfortran is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +Under Section 7 of GPL version 3, you are granted additional +permissions described in the GCC Runtime Library Exception, version +3.1, as published by the Free Software Foundation. + +You should have received a copy of the GNU General Public License and +a copy of the GCC Runtime Library Exception along with this program; +see the files COPYING3 and COPYING.RUNTIME respectively. If not, see +<http://www.gnu.org/licenses/>. */ + +#include "libgfortran.h"' + +include(iparm.m4)dnl + +/* Use Binary Method to calculate the powi. This is not an optimal but + a simple and reasonable arithmetic. See section 4.6.3, "Evaluation of + Powers" of Donald E. Knuth, "Seminumerical Algorithms", Vol. 2, "The Art + of Computer Programming", 3rd Edition, 1998. */ + +`#if defined (HAVE_'rtype_name`) && defined (HAVE_'atype_name`)' + +rtype_name `pow_'rtype_code`_'atype_code` ('rtype_name` a, 'atype_name` b); +export_proto(pow_'rtype_code`_'atype_code`); + +'rtype_name` +pow_'rtype_code`_'atype_code` ('rtype_name` a, 'atype_name` b) +{ + 'rtype_name` pow, x; + 'atype_name` n; + GFC_UINTEGER_'atype_kind` u; + + n = b; + x = a; + pow = 1; + if (n != 0) + { + if (n < 0) + { +'ifelse(rtype_letter,i,`dnl + if (x == 1) + return 1; + if (x == -1) + return (n & 1) ? -1 : 1; + return (x == 0) ? 1 / x : 0; +',` + u = -n; + x = pow / x; +')dnl +` } + else + { + u = n; + } + for (;;) + { + if (u & 1) + pow *= x; + u >>= 1; + if (u) + x *= x; + else + break; + } + } + return pow; +} + +#endif' |