Summary: This removes the use of OpenMP offloading to build the device runtime. The main benefit here is that we no longer need to rely on offloading semantics to build a device only runtime. Things like variants are now no longer needed and can just be simple if-defs. In the future, I will remove most of the special handling here and fold it into calls to the `<gpuintrin.h>` functions instead. Additionally I will rework the compilation to make this a separate runtime. The current plan is to have this, but make including OpenMP and offloading either automatically add it, or print a warning if it's missing. This will allow us to use a normal CMake workflow and delete all the weird 'lets pull the clang binary out of the build' business. ``` -DRUNTIMES_amdgcn-amd-amdhsa_LLVM_ENABLE_RUNTIMES=offload -DLLVM_RUNTIME_TARGETS=amdgcn-amd-amdhsa ``` After that, linking the OpenMP device runtime will be `-Xoffload-linker -lomp`. I.e. no more fat binary business. Only look at the most recent commit since this includes the two dependencies (fix to AMDGPUEmitPrintfBinding and the PointerToMember bug).
Summary: We used to avoid a lot of this stuff because we didn't properly handle variadics in device code. That's been solved for now, so we can just make an internal printf handler that forwards to the external `vprintf` function. This is either provided by NVIDIA's SDK or by the GPU libc implementation. The main reason for doing this is because it prevents the stupid AMDGPU printf pass from mangling our beautiful printfs!
This reverts commit fea5914c926e2f013a8b5e27eaa74c7047fb2c71.
This reverts commit 069e8bcd82c4420239f95c7e6a09e1f756317cfc. Summary: Some tests failing, revert this for now.
Summary: Currently there are several layers to handle `printf`. Since we now have varargs and an implementation of `printf` this can be heavily simplified. 1. The frontend renames `printf` into `omp_vprintf` and gives it an argument buffer. Removing 1. triggered some code in the AMDGPU backend menat for HIP / OpenCL, so I hadded an exception to it. 2. Forward this to CUDA vprintf or ignore it. We no longer need special handling for it since we have varargs. So now we just forward this to CUDA vprintf if we have libc, otherwise just leave `printf` as an external function and expect that `libc` will be linked in.
Summary: These functions provide special-case implementations internal to the OpenMP device runtime. This can potentially conflict with the symbols pulled in from the actual GPU `libc`. This patch makes these weak, so in the case that the GPU libc functions exist they will be overridden. This should not impact performance in the average case because the old `-mlink-builtin-bitcode` version does internalization, deleting weak, and the new LTO path will resolve to the strong reference and then internalize it.
In a nutshell, this moves our libomptarget code to populate the offload subproject. With this commit, users need to enable the new LLVM/Offload subproject as a runtime in their cmake configuration. No further changes are expected for downstream code. Tests and other components still depend on OpenMP and have also not been renamed. The results below are for a build in which OpenMP and Offload are enabled runtimes. In addition to the pure `git mv`, we needed to adjust some CMake files. Nothing is intended to change semantics. ``` ninja check-offload ``` Works with the X86 and AMDGPU offload tests ``` ninja check-openmp ``` Still works but doesn't build offload tests anymore. ``` ls install/lib ``` Shows all expected libraries, incl. - `libomptarget.devicertl.a` - `libomptarget-nvptx-sm_90.bc` - `libomptarget.rtl.amdgpu.so` -> `libomptarget.rtl.amdgpu.so.18git` - `libomptarget.so` -> `libomptarget.so.18git` Fixes: https://github.com/llvm/llvm-project/issues/75124 --------- Co-authored-by: Saiyedul Islam <Saiyedul.Islam@amd.com>