Add small sandbox test for OMP offload in a python extension. (#584)

* Add small sandbox test for OMP offload in a python extension.

* Update omp target kernels to use is_device_ptr()

* Change target offload code to use is_device_ptr

Author: tskisner

etc/pyomptarget/Makefile

@@ -0,0 +1,27 @@
+
+# GCC 12.1.0 with offload support
+CXX := g++-12
+CXXFLAGS := -O0 -g -fPIC -pthread -std=c++11 -fcf-protection=none -fno-stack-protector
+CXX_OMP_FLAGS := -fopenmp -foffload=nvptx-none='-Wa,-m,sm_80 -misa=sm_80 -fPIC -lm -latomic'
+
+# NVHPC
+# CXX = nvc++
+# CXXFLAGS = -O0 -g -fPIC -pthread -std=c++11
+# CXX_OMP_FLAGS = -mp=gpu -Minfo=mp -gpu=cc86
+
+
+pybind := ../../src/toast/pybind11
+modext := $(shell python3-config --extension-suffix)
+pyincl := $(shell python3-config --includes)
+
+
+pyomptarget$(modext) : module.o
+	$(CXX) -shared -o pyomptarget$(modext) module.o $(CXX_OMP_FLAGS)
+
+module.o : module.cpp
+	$(CXX) $(CXXFLAGS) $(CXX_OMP_FLAGS) -I. -I$(pybind)/include $(pyincl) -c -o module.o module.cpp
+
+
+clean :
+	rm -f *.so *.o
+