vtk-m2/vtkm/internal/Assume.h
Kenneth Moreland 3dd66e852a Do not use __assume for icc in gcc compatability mode
When using the GNU header files on a system, the icc compiler emulates
the behavior of the gcc compiler on the system. (See https://
software.intel.com/en-us/node/522750) This appears to mean that icc
features that are not available in gcc could get turned off. In
particular, we found that the __assume feature stopped working.

To get around this problem, do not use __assume when compiling with icc
and __GNUC__ is defined. Instead, use the available gcc features.
2018-04-04 15:00:03 -06:00

75 lines
3.6 KiB
C

//============================================================================
// Copyright (c) Kitware, Inc.
// All rights reserved.
// See LICENSE.txt for details.
// This software is distributed WITHOUT ANY WARRANTY; without even
// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
// PURPOSE. See the above copyright notice for more information.
//
// Copyright 2014 National Technology & Engineering Solutions of Sandia, LLC (NTESS).
// Copyright 2014 UT-Battelle, LLC.
// Copyright 2014 Los Alamos National Security.
//
// Under the terms of Contract DE-NA0003525 with NTESS,
// the U.S. Government retains certain rights in this software.
//
// Under the terms of Contract DE-AC52-06NA25396 with Los Alamos National
// Laboratory (LANL), the U.S. Government retains certain rights in
// this software.
//============================================================================
#ifndef vtk_m_internal_Assume_h
#define vtk_m_internal_Assume_h
#include <vtkm/Assert.h>
// Description:
// VTKM_ASSUME instructs the compiler that a certain non-obvious condition will
// *always* be true. Beware that if cond is false at runtime, the results are
// unpredictable (and likely catastrophic). A runtime assertion is added so
// that debugging builds may easily catch violations of the condition.
//
// A useful application of this macro is when a method is passed in a
// vtkm::Vec that is uninitialized and conditional fills the vtkm::Vec
// based on other runtime information such as cell type. This allows you to
// assert that only valid cell types will be used, producing more efficient
// code.
//
#define VTKM_ASSUME(cond) \
VTKM_SWALLOW_SEMICOLON_PRE_BLOCK \
{ \
const bool c = cond; \
VTKM_ASSERT("Bad assumption in VTKM_ASSUME: " #cond&& c); \
VTKM_ASSUME_IMPL(c); \
(void)c; /* Prevents unused var warnings */ \
} \
VTKM_SWALLOW_SEMICOLON_POST_BLOCK
// VTKM_ASSUME_IMPL is compiler-specific:
#if defined(__CUDA_ARCH__)
//For all versions of CUDA this is a no-op while we look
//for a CUDA asm snippet that replicates this kind of behavior
#define VTKM_ASSUME_IMPL(cond) (void)0 /* no-op */
#else
#if defined(VTKM_MSVC)
#define VTKM_ASSUME_IMPL(cond) __assume(cond)
#elif defined(VTKM_ICC) && !defined(__GNUC__)
#define VTKM_ASSUME_IMPL(cond) __assume(cond)
#elif (defined(VTKM_GCC) || defined(VTKM_ICC)) && \
(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5))
// Added in 4.5.0:
#define VTKM_ASSUME_IMPL(cond) \
if (!(cond)) \
__builtin_unreachable()
#elif defined(VTKM_CLANG)
#define VTKM_ASSUME_IMPL(cond) \
if (!(cond)) \
__builtin_unreachable()
#else
#define VTKM_ASSUME_IMPL(cond) (void)0 /* no-op */
#endif
#endif
#endif // vtk_m_internal_Assume_h