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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libgfortran/generated/pow_i16_i4.c
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+/* Support routines for the intrinsic power (**) operator.
+ Copyright 2004, 2007, 2009 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"
+
+
+/* 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_GFC_INTEGER_16) && defined (HAVE_GFC_INTEGER_4)
+
+GFC_INTEGER_16 pow_i16_i4 (GFC_INTEGER_16 a, GFC_INTEGER_4 b);
+export_proto(pow_i16_i4);
+
+GFC_INTEGER_16
+pow_i16_i4 (GFC_INTEGER_16 a, GFC_INTEGER_4 b)
+{
+ GFC_INTEGER_16 pow, x;
+ GFC_INTEGER_4 n;
+ GFC_UINTEGER_4 u;
+
+ n = b;
+ x = a;
+ pow = 1;
+ if (n != 0)
+ {
+ if (n < 0)
+ {
+ if (x == 1)
+ return 1;
+ if (x == -1)
+ return (n & 1) ? -1 : 1;
+ return (x == 0) ? 1 / x : 0;
+ }
+ else
+ {
+ u = n;
+ }
+ for (;;)
+ {
+ if (u & 1)
+ pow *= x;
+ u >>= 1;
+ if (u)
+ x *= x;
+ else
+ break;
+ }
+ }
+ return pow;
+}
+
+#endif