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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- S Y S T E M . X P _ B M L --
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6 -- --
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7 -- B o d y --
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8 -- --
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145
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9 -- Copyright (C) 1992-2019, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 with System.Unsigned_Types; use System.Unsigned_Types;
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33
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34 package body System.Exp_LLU is
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35
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36 ----------------------------
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37 -- Exp_Long_Long_Unsigned --
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38 ----------------------------
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39
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40 function Exp_Long_Long_Unsigned
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41 (Left : Long_Long_Unsigned;
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42 Right : Natural)
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43 return Long_Long_Unsigned
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44 is
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45 Result : Long_Long_Unsigned := 1;
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46 Factor : Long_Long_Unsigned := Left;
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47 Exp : Natural := Right;
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48
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49 begin
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50 -- We use the standard logarithmic approach, Exp gets shifted right
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51 -- testing successive low order bits and Factor is the value of the
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52 -- base raised to the next power of 2.
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53
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54 -- Note: it is not worth special casing the cases of base values -1,0,+1
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55 -- since the expander does this when the base is a literal, and other
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56 -- cases will be extremely rare.
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57
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58 if Exp /= 0 then
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59 loop
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60 if Exp rem 2 /= 0 then
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61 Result := Result * Factor;
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62 end if;
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63
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64 Exp := Exp / 2;
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65 exit when Exp = 0;
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66 Factor := Factor * Factor;
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67 end loop;
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68 end if;
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69
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70 return Result;
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71
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72 end Exp_Long_Long_Unsigned;
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73
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74 end System.Exp_LLU;
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