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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 . F L O A T _ C O N T R O L --
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6 -- --
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7 -- S p e c --
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8 -- --
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9 -- Copyright (C) 2000-2017, AdaCore --
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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 -- Control functions for floating-point unit
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33
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34 package System.Float_Control is
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35 pragma Pure;
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36 -- This is not fully correct, but this unit is with-ed by pure units
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37 -- (eg s-imgrea).
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38
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39 procedure Reset;
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40 pragma Inline (Reset);
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41 -- Reset the floating-point processor to the default state needed to get
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42 -- correct Ada semantics for the target. Some third party tools change
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43 -- the settings for the floating-point processor. Reset can be called
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44 -- to reset the floating-point processor into the mode required by GNAT
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45 -- for correct operation. Use this call after a call to foreign code if
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46 -- you suspect incorrect floating-point operation after the call.
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47 --
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48 -- For example under Windows NT some system DLL calls change the default
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49 -- FPU arithmetic to 64 bit precision mode. However, since in Ada 95 it
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50 -- is required to provide full access to the floating-point types of the
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51 -- architecture, GNAT requires full 80-bit precision mode, and Reset makes
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52 -- sure this mode is established.
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53 --
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54 -- Similarly on the PPC processor, it is important that overflow and
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55 -- underflow exceptions be disabled.
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56 --
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57 -- The call to Reset simply has no effect if the target environment
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58 -- does not give rise to such concerns.
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59 end System.Float_Control;
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