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145
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1 /* "True" vs "False" vs "Unknown".
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2 Copyright (C) 2019-2020 Free Software Foundation, Inc.
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3 Contributed by David Malcolm <dmalcolm@redhat.com>.
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4
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5 This file is part of GCC.
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6
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7 GCC is free software; you can redistribute it and/or modify it
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8 under the terms of the GNU General Public License as published by
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9 the Free Software Foundation; either version 3, or (at your option)
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10 any later version.
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11
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12 GCC is distributed in the hope that it will be useful, but
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13 WITHOUT ANY WARRANTY; without even the implied warranty of
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14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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15 General Public License for more details.
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16
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17 You should have received a copy of the GNU General Public License
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18 along with GCC; see the file COPYING3. If not see
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19 <http://www.gnu.org/licenses/>. */
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20
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21 #ifndef GCC_TRISTATE_H
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22 #define GCC_TRISTATE_H
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23
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24 /* "True" vs "False" vs "Unknown". */
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25
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26 class tristate {
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27 public:
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28 enum value {
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29 TS_UNKNOWN,
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30 TS_TRUE,
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31 TS_FALSE
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32 };
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33
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34 tristate (enum value val) : m_value (val) {}
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35 tristate (bool val) : m_value (val ? TS_TRUE : TS_FALSE) {}
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36 static tristate unknown () { return tristate (TS_UNKNOWN); }
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37
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38 const char *as_string () const;
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39
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40 bool is_known () const { return m_value != TS_UNKNOWN; }
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41 bool is_true () const { return m_value == TS_TRUE; }
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42 bool is_false () const { return m_value == TS_FALSE; }
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43
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44 tristate not_ () const;
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45 tristate or_ (tristate other) const;
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46 tristate and_ (tristate other) const;
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47
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48 bool operator== (const tristate &other) const
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49 {
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50 return m_value == other.m_value;
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51 }
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52
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53 bool operator!= (const tristate &other) const
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54 {
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55 return m_value != other.m_value;
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56 }
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57
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58 private:
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59 enum value m_value;
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60 };
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61
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62 /* Overloaded boolean operators on tristates. */
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63
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64 inline tristate
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65 operator ! (tristate t)
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66 {
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67 return t.not_ ();
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68 }
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69
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70 inline tristate
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71 operator || (tristate a, tristate b)
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72 {
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73 return a.or_ (b);
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74 }
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75
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76 inline tristate
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77 operator && (tristate a, tristate b)
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78 {
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79 return a.and_ (b);
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80 }
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81
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82 #endif /* GCC_TRISTATE_H */
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