RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-11-25 20:23:11 +01:00
Code Issues Projects Releases Wiki Activity

[CUDA] Add documentation explaining how to detect clang vs nvcc.

Browse Source 
llvm-svn: 264002
This commit is contained in:
Justin Lebar 2016-03-21 23:05:15 +00:00
parent 5096eeb640
commit c038c5cb7c
1 changed files with 28 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
docs/CompileCudaWithLLVM.rst
View File

@ -119,6 +119,34 @@ your GPU <https://developer.nvidia.com/cuda-gpus>`_. For example, if you want
to run your program on a GPU with compute capability of 3.5, you should specify
``--cuda-gpu-arch=sm_35``.
Detecting clang vs NVCC
=======================
Although clang's CUDA implementation is largely compatible with NVCC's, you may
still want to detect when you're compiling CUDA code specifically with clang.
This is tricky, because clang defines the ``__NVCC__`` macro, and because NVCC
may invoke clang as part of its own compilation process! For example, NVCC
uses the host compiler's preprocessor when compiling for device code, and that
host compiler may in fact be clang.
When clang is actually compiling CUDA code -- rather than being used as a
subtool of NVCC's -- it defines the ``__CUDA__`` macro. ``__CUDA_ARCH__`` is
defined only in device mode (but will be defined if NVCC is using clang as a
preprocessor). So you can use the following incantations to detect clang CUDA
compilation, in host and device modes:
.. code-block:: c++
#if defined(__clang__) && defined(__CUDA__) && !defined(__CUDA_ARCH__)
// clang compiling CUDA code, host mode.
#endif
#if defined(__clang__) && defined(__CUDA__) && defined(__CUDA_ARCH__)
// clang compiling CUDA code, device mode.
#endif
Optimizations
=============