diff options
Diffstat (limited to 'libgfortran/generated/pow_i4_i8.c')
-rw-r--r-- | libgfortran/generated/pow_i4_i8.c | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/libgfortran/generated/pow_i4_i8.c b/libgfortran/generated/pow_i4_i8.c new file mode 100644 index 00000000000..72e8837912c --- /dev/null +++ b/libgfortran/generated/pow_i4_i8.c @@ -0,0 +1,62 @@ +/* Support routines for the intrinsic power (**) operator. + Copyright 2004 Free Software Foundation, Inc. + Contributed by Paul Brook + +This file is part of the GNU Fortran 95 runtime library (libgfor). + +Libgfor is free software; you can redistribute it and/or +modify it under the terms of the GNU Lesser General Public +License as published by the Free Software Foundation; either +version 2.1 of the License, or (at your option) any later version. + +Ligbfor 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 Lesser General Public License for more details. + +You should have received a copy of the GNU Lesser General Public +License along with libgfor; see the file COPYING.LIB. If not, +write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, +Boston, MA 02111-1307, USA. */ + +#include "config.h" +#include "libgfortran.h" + +/* Uuse 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. */ + +GFC_INTEGER_4 +prefix(pow_i4_i8) (GFC_INTEGER_4 a, GFC_INTEGER_8 b) +{ + GFC_INTEGER_4 pow, x; + GFC_INTEGER_8 n, 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; + } + u = n; + for (;;) + { + if (u & 1) + pow *= x; + u >>= 1; + if (u) + x *= x; + else + break; + } + } + return pow; +} |