[LLVMdev] LLVM for heterogenous platforms

[Jeffrey Yasskin]

Does your C code ever use the 'long' type? If so, the LLVM IR will be
different depending on whether it's targeting linux-32 or linux-64. Do
you ever use size_t? Same problem. Do you ever use a union containing
both pointers and integers? See above. In principle, it's possible to
write platform-independent IR, or even C code that compiles to
platform-independent IR. In practice, especially if you include any
system headers, it's remarkably hard.

On Wed, Mar 3, 2010 at 7:42 AM, Olaf Krzikalla <krzikalla at gmx.net> wrote:
> Hi llvm,
>
> it's for sure an obvious idea to use llvm as IR for heterogenous
> platforms (e.g. CPU+GPU).
> In theory someone could write plain C/C++ code, which by clang is
> translated to llvm-IL and then
> together with JIT-backends packed in an appropriate executable. Thus all
> the limitations
> and hassles of openCL or CUDA could be avoided. I wonder if there
> already is a related project?
>
> Of course in practice this gets much more complicated mainly due to
> memory access problems.
> But this issues can be adressed later. For the moment I'm just
> interested in the reasonability of the general idea.
>
>
> Best
> Olaf
>
>
> PS: I strongly disagree with the llvm FAQ entry, where sizeof is used to
> reason C and C++ as platform-dependent languages. Indeed sizeof is there
> to abstract from platform-specifics. Of course you can (ab)use it (e.g.
> specialize a template which take int's as template parameters and then
> pass a sizeof result). But in general I think that neither C(++) is
> platform-dependent nor the llvm-IR needs to be platform-dependent.