[Beignet] [PATCH] GBE: refine the llvm multi-thread related code.

[Zhigang Gong]

This path works well. Just pushed, thanks.

It seems that the LLVM/CLANG 3.5 is the best ever version we have now.
We are going to change our ReadMe to recommend 3.5 rather than the one year
old 3.3 after the official relase of LLVM 3.5.

Thanks,
Zhigang Gong.

On Tue, Aug 26, 2014 at 03:39:24PM +0800, Ruiling Song wrote:
> LLVM 3.5 remove llvm_start/stop_multithreaded() API, instead multi-thread
> support is determined when build llvm(build option LLVM_ENABLE_THREADS).
> llvm_is_multithreaded() is used to check whether llvm is built with
> muti-thread support.
> 
> If multi-thread is not support(LLVM3.3/3.4 or 3.5 built with LLVM_ENABLE_THREADS off),
> we simply add a mutex when calling clang/llvm related API.
> 
> Signed-off-by: Ruiling Song <ruiling.song at intel.com>
> ---
>  backend/src/backend/program.cpp |   14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/backend/src/backend/program.cpp b/backend/src/backend/program.cpp
> index 50396c8..d992f7b 100644
> --- a/backend/src/backend/program.cpp
> +++ b/backend/src/backend/program.cpp
> @@ -846,11 +846,14 @@ namespace gbe {
>      // will delete the module and act in GenProgram::CleanLlvmResource().
>      llvm::Module * out_module;
>      llvm::LLVMContext* llvm_ctx = new llvm::LLVMContext;
> +
> +    static std::mutex llvm_mutex;
> +    if (!llvm::llvm_is_multithreaded())
> +      llvm_mutex.lock();
> +
>      if (buildModuleFromSource(clName.c_str(), &out_module, llvm_ctx, clOpt.c_str(),
>                                stringSize, err, errSize)) {
>      // Now build the program from llvm
> -      static std::mutex gbe_mutex;
> -      gbe_mutex.lock();
>        size_t clangErrSize = 0;
>        if (err != NULL) {
>          GBE_ASSERT(errSize != NULL);
> @@ -863,11 +866,14 @@ namespace gbe {
>                                      err, errSize, optLevel);
>        if (err != NULL)
>          *errSize += clangErrSize;
> -      gbe_mutex.unlock();
>        if (OCL_OUTPUT_BUILD_LOG && options)
>          llvm::errs() << options;
>      } else
>        p = NULL;
> +
> +    if (!llvm::llvm_is_multithreaded())
> +      llvm_mutex.unlock();
> +
>      remove(clName.c_str());
>      return p;
>    }
> @@ -1261,11 +1267,9 @@ namespace gbe
>        gbe_release_printf_info = gbe::kernelReleasePrintfSet;
>        gbe_output_printf = gbe::kernelOutputPrintf;
>        genSetupCallBacks();
> -      llvm::llvm_start_multithreaded();
>      }
>  
>      ~CallBackInitializer() {
> -      llvm::llvm_stop_multithreaded();
>  #if (LLVM_VERSION_MAJOR == 3) && (LLVM_VERSION_MINOR > 3)
>        llvm::llvm_shutdown();
>  #endif
> -- 
> 1.7.10.4
> 
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