c2a0ee5886
gcc/fortran/ChangeLog: * arith.cc (arith_power): Handle modular arithmetic for BT_UNSIGNED. (eval_intrinsic): Error for unsigned exponentiation with -pedantic. * expr.cc (gfc_type_convert_binary): Use type of first argument for unsigned exponentiation. * gfortran.texi: Mention arithmetic exponentiation. * resolve.cc (resolve_operator): Allow unsigned exponentiation. * trans-decl.cc (gfc_build_intrinsic_function_decls): Build declarations for unsigned exponentiation. * trans-expr.cc (gfc_conv_cst_uint_power): New function. (gfc_conv_power_op): Call it. Handle unsigned exponentiation. * trans.h (gfor_fndecl_unsigned_pow_list): Add declaration. libgfortran/ChangeLog: * Makefile.am: Add files for unsigned exponentiation. * Makefile.in: Regenerate. * gfortran.map: Add functions for unsigned exponentiation. * generated/pow_m16_m1.c: New file. * generated/pow_m16_m16.c: New file. * generated/pow_m16_m2.c: New file. * generated/pow_m16_m4.c: New file. * generated/pow_m16_m8.c: New file. * generated/pow_m1_m1.c: New file. * generated/pow_m1_m16.c: New file. * generated/pow_m1_m2.c: New file. * generated/pow_m1_m4.c: New file. * generated/pow_m1_m8.c: New file. * generated/pow_m2_m1.c: New file. * generated/pow_m2_m16.c: New file. * generated/pow_m2_m2.c: New file. * generated/pow_m2_m4.c: New file. * generated/pow_m2_m8.c: New file. * generated/pow_m4_m1.c: New file. * generated/pow_m4_m16.c: New file. * generated/pow_m4_m2.c: New file. * generated/pow_m4_m4.c: New file. * generated/pow_m4_m8.c: New file. * generated/pow_m8_m1.c: New file. * generated/pow_m8_m16.c: New file. * generated/pow_m8_m2.c: New file. * generated/pow_m8_m4.c: New file. * generated/pow_m8_m8.c: New file. * m4/powu.m4: New file. gcc/testsuite/ChangeLog: * gfortran.dg/unsigned_15.f90: Adjust error messages. * gfortran.dg/unsigned_43.f90: New test. * gfortran.dg/unsigned_44.f90: New test.
79 lines
2.3 KiB
C
79 lines
2.3 KiB
C
/* Support routines for the intrinsic power (**) operator
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for UNSIGNED, using modulo arithmetic.
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Copyright (C) 2025 Free Software Foundation, Inc.
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Contributed by Thomas Koenig.
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This file is part of the GNU Fortran 95 runtime library (libgfortran).
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Libgfortran is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public
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License as published by the Free Software Foundation; either
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version 3 of the License, or (at your option) any later version.
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Libgfortran is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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#include "libgfortran.h"
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/* Use Binary Method to calculate the powi. This is not an optimal but
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a simple and reasonable arithmetic. See section 4.6.3, "Evaluation of
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Powers" of Donald E. Knuth, "Seminumerical Algorithms", Vol. 2, "The Art
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of Computer Programming", 3rd Edition, 1998. */
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#if defined (HAVE_GFC_UINTEGER_16) && defined (HAVE_GFC_UINTEGER_4)
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GFC_UINTEGER_16 pow_m16_m4 (GFC_UINTEGER_16 x, GFC_UINTEGER_4 n);
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export_proto(pow_m16_m4);
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inline static GFC_UINTEGER_16
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power_simple_m16_m4 (GFC_UINTEGER_16 x, GFC_UINTEGER_4 n)
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{
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GFC_UINTEGER_16 pow = 1;
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for (;;)
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{
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if (n & 1)
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pow *= x;
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n >>= 1;
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if (n)
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x *= x;
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else
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break;
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}
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return pow;
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}
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/* For odd x, Euler's theorem tells us that x**(2^(m-1)) = 1 mod 2^m.
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For even x, we use the fact that (2*x)^m = 0 mod 2^m. */
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GFC_UINTEGER_16
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pow_m16_m4 (GFC_UINTEGER_16 x, GFC_UINTEGER_4 n)
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{
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const GFC_UINTEGER_16 mask = (GFC_UINTEGER_16) (-1) / 2;
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if (n == 0)
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return 1;
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if (x == 0)
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return 0;
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if (x & 1)
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return power_simple_m16_m4 (x, n & mask);
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if (n > sizeof (x) * 8)
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return 0;
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return power_simple_m16_m4 (x, n);
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}
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#endif
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