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64 lines
2.3 KiB
C
64 lines
2.3 KiB
C
/*=========================================================================
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Program: Visualization Toolkit
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Module: vtkAssume.h
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Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
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All rights reserved.
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See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
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This software is distributed WITHOUT ANY WARRANTY; without even
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the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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PURPOSE. See the above copyright notice for more information.
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=========================================================================*/
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/**
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* @class VTK_ASSUME
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* @brief Provide compiler hints for non-obvious conditions.
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*/
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#ifndef vtkAssume_h
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#define vtkAssume_h
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#include "vtkConfigure.h"
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#include <cassert>
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/**
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* VTK_ASSUME instructs the compiler that a certain non-obvious condition will
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* *always* be true. Beware that if cond is false at runtime, the results are
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* unpredictable (and likely catastrophic). A runtime assertion is added so
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* that debugging builds may easily catch violations of the condition.
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* A useful application of this macro is when a vtkGenericDataArray subclass has
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* a known number of components at compile time. Adding, for example,
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* VTK_ASSUME(array->GetNumberOfComponents() == 3); allows the compiler to
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* provide faster access through the GetTypedComponent method, as the fixed data
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* stride in AOS arrays allows advanced optimization of the accesses.
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* A more detailed description of this class and related tools can be found
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* \ref VTK-7-1-ArrayDispatch "here".
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*/
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#define VTK_ASSUME(cond) \
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do { \
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const bool c = cond; \
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assert("Bad assumption in VTK_ASSUME: " #cond && c); \
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VTK_ASSUME_IMPL(c); \
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(void)c; /* Prevents unused var warnings */ \
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} while (false) /* do-while prevents extra semicolon warnings */
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// VTK_ASSUME_IMPL is compiler-specific:
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#if defined(VTK_COMPILER_MSVC) || defined(VTK_COMPILER_ICC)
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# define VTK_ASSUME_IMPL(cond) __assume(cond)
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#elif defined(VTK_COMPILER_GCC) && VTK_COMPILER_GCC_VERSION >= 40500
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// Added in 4.5.0:
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# define VTK_ASSUME_IMPL(cond) if (!(cond)) __builtin_unreachable()
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#elif defined(VTK_COMPILER_CLANG)
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# define VTK_ASSUME_IMPL(cond) if (!(cond)) __builtin_unreachable()
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#else
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# define VTK_ASSUME_IMPL(cond) do {} while (false) /* no-op */
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#endif
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#endif // vtkAssume_h
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// VTK-HeaderTest-Exclude: vtkAssume.h
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