Disable asserts for CUDA architecture builds

`assert` is supported on recent CUDA cards, but compiling it appears to be
very slow. By default, the `VTKM_ASSERT` macro has been disabled whenever
compiling for a CUDA device (i.e. when `__CUDA_ARCH__` is defined).

Asserts for CUDA devices can be turned back on by turning the
`VTKm_NO_ASSERT_CUDA` CMake variable off. Turning this CMake variable off
will enable assertions in CUDA kernels unless there is another reason
turning off all asserts (such as a release build).

CMakeLists.txt

@@ -108,6 +108,11 @@ vtkm_option(VTKm_ENABLE_LOGGING "Enable VTKm Logging" ON)
 # performance.
 vtkm_option(VTKm_NO_ASSERT "Disable assertions in debugging builds." OFF)
 
+# The CUDA compiler (as of CUDA 11) takes a surprising long time to compile
+# kernels with assert in them. By default we turn off asserts when compiling
+# for CUDA devices.
+vtkm_option(VTKm_NO_ASSERT_CUDA "Disable assertions for CUDA devices." ON)
+
 # When VTK-m is embedded into larger projects that wish to make end user
 # applications they want to only install libraries and don't want CMake/headers
 # installed.
@@ -135,6 +140,7 @@ vtkm_option(VTKm_NO_INSTALL_README_LICENSE "disable the installation of README a
 mark_as_advanced(
   VTKm_ENABLE_LOGGING
   VTKm_NO_ASSERT
+  VTKm_NO_ASSERT_CUDA
   VTKm_INSTALL_ONLY_LIBRARIES
   VTKm_HIDE_PRIVATE_SYMBOLS
   VTKm_ENABLE_DEVELOPER_FLAGS

docs/changelog/cuda-no-assert.md

@@ -0,0 +1,10 @@
+# Disable asserts for CUDA architecture builds
+
+`assert` is supported on recent CUDA cards, but compiling it appears to be
+very slow. By default, the `VTKM_ASSERT` macro has been disabled whenever
+compiling for a CUDA device (i.e. when `__CUDA_ARCH__` is defined).
+
+Asserts for CUDA devices can be turned back on by turning the
+`VTKm_NO_ASSERT_CUDA` CMake variable off. Turning this CMake variable off
+will enable assertions in CUDA kernels unless there is another reason
+turning off all asserts (such as a release build).

vtkm/Assert.h

@@ -15,6 +15,15 @@
 
 #include <cassert>
 
+// Pick up conditions where we want to turn on/off assert.
+#ifndef VTKM_NO_ASSERT
+#if defined(NDEBUG)
+#define VTKM_NO_ASSERT
+#elif defined(__CUDA_ARCH__) && defined(VTKM_NO_ASSERT_CUDA)
+#define VTKM_NO_ASSERT
+#endif
+#endif // VTKM_NO_ASSERT
+
 /// \def VTKM_ASSERT(condition)
 ///
 /// Asserts that \a condition resolves to true.  If \a condition is false,
@@ -28,11 +37,7 @@
 ///
 /// The VTKM_NO_ASSERT cmake and preprocessor option allows debugging builds
 /// to remove assertions for performance reasons.
-#if defined(VTKM_CUDA_VERSION_MAJOR) && (VTKM_CUDA_VERSION_MAJOR == 7)
-//CUDA 7.5 doesn't support assert in device code
-#define VTKM_ASSERT(condition) (void)(condition)
-#elif !defined(NDEBUG) && !defined(VTKM_NO_ASSERT)
-//Only assert if we are in debug mode and don't have VTKM_NO_ASSERT defined
+#ifndef VTKM_NO_ASSERT
 #define VTKM_ASSERT(condition) assert(condition)
 #define VTKM_ASSERTS_CHECKED
 #else

vtkm/internal/CMakeLists.txt

@@ -14,6 +14,7 @@
 # that we expect for our C++ defines.
 
 set(VTKM_NO_ASSERT ${VTKm_NO_ASSERT})
+set(VTKM_NO_ASSERT_CUDA ${VTKm_NO_ASSERT_CUDA})
 set(VTKM_USE_DOUBLE_PRECISION ${VTKm_USE_DOUBLE_PRECISION})
 set(VTKM_USE_64BIT_IDS ${VTKm_USE_64BIT_IDS})
 

vtkm/internal/Configure.h.in

@@ -62,6 +62,10 @@
 #cmakedefine VTKM_NO_ASSERT
 #endif
 
+#if !defined(VTKM_NO_ASSERT_CUDA)
+#cmakedefine VTKM_NO_ASSERT_CUDA
+#endif
+
 #if !defined(VTKM_USE_DOUBLE_PRECISION) && !defined(VTKM_NO_DOUBLE_PRECISION)
 #cmakedefine VTKM_USE_DOUBLE_PRECISION
 #endif