[Openmp-commits] [PATCH] D139287: [WIP][OpenMP] Introduce basic JIT support to OpenMP target offloading

[Joseph Huber via Phabricator via Openmp-commits]

jhuber6 added a comment.

Why do we have the JIT in the nextgen plugins? I figured that JIT would be handled by `libomptarget` proper rather than the plugins. I guess this is needed for per-kernel specialization? My idea of the rough pseudocode would be like this and we wouldn't need a complex class heirarchy. Also I don't know if we can skip `ptxas` by giving CUDA the ptx directly, we probably will need to invoke `lld` on the command line however right.

  for each image:
    if image is bitcode
      image = compile(image)
   register(image)



================
Comment at: clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp:879
                                "Cannot embed bitcode with multiple files.");
-    OutputFiles.push_back(static_cast<std::string>(BitcodeOutput.front()));
+    OutputFiles.push_back(Args.MakeArgString(BitcodeOutput.front()));
     return Error::success();
----------------
tianshilei1992 wrote:
> This will be pushed by Joseph in another patch.
Did that this morning.


================
Comment at: openmp/libomptarget/plugins-nextgen/common/PluginInterface/CMakeLists.txt:24
 # Plugin Interface library.
-add_library(PluginInterface OBJECT PluginInterface.cpp GlobalHandler.cpp)
+add_llvm_library(PluginInterface OBJECT PluginInterface.cpp GlobalHandler.cpp JIT.cpp)
 
----------------
tianshilei1992 wrote:
> I guess this might cause the issue of non-protected global symbols.
Should we be able to put all this in the `add_llvm_library`?


================
Comment at: openmp/libomptarget/plugins-nextgen/common/PluginInterface/JIT.cpp:47-51
+  InitializeAllTargetInfos();
+  InitializeAllTargets();
+  InitializeAllTargetMCs();
+  InitializeAllAsmParsers();
+  InitializeAllAsmPrinters();
----------------
We could probably limit these to the ones we actually care about since we know the triples. Not sure if it would save us much runtime.


================
Comment at: openmp/libomptarget/plugins-nextgen/common/PluginInterface/JIT.cpp:184
+
+  auto AddStream =
+      [&](size_t Task,
----------------
tianshilei1992 wrote:
> Is there any way that we don't write it to a file here?
Why do we need to invoke LTO here? I figured that we could call the backend directly since we have no need to actually link any filies, and we may not have a need to run more expensive optimizations when the bitcode is already optimized. If you do that then you should be able to just use a `raw_svector_ostream` as your output stream and get the compiled output written to that buffer.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D139287/new/

https://reviews.llvm.org/D139287