[LLVMdev] ANN: libclc (OpenCL C library implementation)

[Peter Collingbourne]

Hi,

This is to announce the availability of libclc, an open source, BSD
licensed implementation of the library requirements of the OpenCL C
programming language, as specified by the OpenCL 1.1 Specification.
libclc is intended to be used with Clang's OpenCL frontend.

libclc website: http://www.pcc.me.uk/~peter/libclc/

libclc is designed to be portable and extensible. To this end,
it provides generic implementations of most library requirements,
allowing the target to override the generic implementation at the
granularity of individual functions.

libclc currently only supports the PTX target, but support for more
targets is welcome.

How does this project relate to the recently announced Portable OpenCL
(POCL) project?  Unlike POCL, this project is not intended to provide
an OpenCL host library (i.e. the OpenCL Platform Layer and OpenCL
Runtime specified in sections 4-5 of the OpenCL specification).
Instead, it provides only the requirements for the OpenCL C
Programming Language (section 6 et seq).  It is intended to be used
with an existing host library implementation, and comply with its
ABI requirements.

An example of such a host library is NVIDIA's OpenCL host library
for PTX -- the intention is to at some point provide a mechanism
for using the NVIDIA implementation of OpenCL with Clang, libclc
and LLVM's PTX backend instead of NVIDIA's own OpenCL compiler.
Another example would be POCL's host library, and the POCL developers
have expressed an interest in using libclc as their OpenCL C library
instead of developing their own.

I will hope to find time over the next few weeks to add libclc support
to the Clang driver.  The intention is that compiling OpenCL C programs
to PTX would be as easy as (something like this):

clang -target ptx32 -S file.cl

such that the driver would automatically locate the libclc headers,
add them to the include path and pre-include the main header file.
(The libclc support will of course be optional, and a -cl-stdlib=
flag will be provided to allow for switching between OpenCL standard
library implementations.)

Thanks,
-- 
Peter