[CUDA] Update README.CUDA with additional information
@@ -3,17 +3,28 @@ features may be missing or incomplete.
# Compiling pocl with CUDA support
-Add -DENABLE_CUDA=ON to the CMake command-line.
+Add `-DENABLE_CUDA=ON` to the CMake command-line.
-Assumes libcuda.so is on library search path. (TODO: Get CMake to sort
+Assumes `libcuda.so` is on library search path. (TODO: Get CMake to sort
this out).
Currently only tested with LLVM 3.8, and CUDA 7.0/7.5.
# Running on a CUDA device
-Requires CUDA_PATH environment variable to be set to root of CUDA
-installation.
+Use `POCL_DEVICES=CUDA` to select only CUDA devices.
+
+Requires `CUDA_PATH` environment variable to be set to the root of the
+CUDA installation (containing the `nvvm` directory).
+
+The `POCL_CUDA_GPU_ARCH` environment variable can be set to override
+the target GPU architecture (e.g. `POCL_CUDA_GPU_ARCH=sm_35`), which
+may be necessary in casees where LLVM doesn't yet support the
+architecture (currently an issue for `sm_32` and `sm_53`).
+
+The `POCL_NO_PTX_CACHE` environment variable can be set to `1` to
+force pocl to always regenerate the PTX module instead of using a
+cached version.
# Known issues
