[NFC][OpenMP] Update description of OMPGridValues enums

[saiislam]

Summary

Update comments describing how OMPGridValues enums will be used in
clang, deviceRTLs, and hsa and cuda plugins.

[JonChesterfield]

This can't be used in the libomptarget plugins or in the deviceRTL, as both are required to compile without the llvm sources available.

Current preferences appears to be to copy and paste the numbers between the two files. At the least, we should have a test outside of llvm & openmp trees that verifies the numbers are the same in each.

@jdoerfert can you remember who was strongly against #include between openmp and llvm? I'm failing to find the discussion, and the mail "Sharing enums between llvm and openmp" didn't reach a conclusion

[saiislam]

In D86232#2226668, @JonChesterfield wrote:

This can't be used in the libomptarget plugins or in the deviceRTL, as both are required to compile without the llvm sources available.

Current preferences appears to be to copy and paste the numbers between the two files. At the least, we should have a test outside of llvm & openmp trees that verifies the numbers are the same in each.

@jdoerfert can you remember who was strongly against #include between openmp and llvm? I'm failing to find the discussion, and the mail "Sharing enums between llvm and openmp" didn't reach a conclusion

What about if we put these gridvalues in OMPKinds.def (or OMP.td)?
Ultimately we need a common place to share content with clang, RTLs, and plugins.

[jdoerfert]

Ultimately we need a common place to share content with clang, RTLs, and plugins.

That was my hope.

[saiislam]

Ping.
Merged patch D87841 uses the Gridvalue as described here.

[jdoerfert]

LGTM

llvm/include/llvm/Frontend/OpenMP/OMPGridValues.h

 ///        We can change grid values for a "fat" binary so that different
 ///        passes get the correct values when generating code for a
 ///        multi-target binary. Both amdgcn and nvptx values are stored in
 ///        this file. In the future, should there be differences between GPUs
 ///        of the same architecture, then simply make a different array and
 ///        use the new array name.
 ///
 /// Example usage in clang:
-///   const unsigned slot_size = ctx.GetTargetInfo().getGridValue(GV_Warp_Size);
+///   const unsigned slot_size =
+///   ctx.GetTargetInfo().getGridValue(llvm::omp::GVIDX::GV_Warp_Size);
 ///
 /// Example usage in libomptarget/deviceRTLs:
-///   #include "OMPGridValues.h"
+///   #include "llvm/Frontend/OpenMP/OMPGridValues.h"
 ///   #ifdef __AMDGPU__
 ///     #define GRIDVAL AMDGPUGpuGridValues
 ///   #else
 ///     #define GRIDVAL NVPTXGpuGridValues
 ///   #endif
 ///   ... Then use this reference for GV_Warp_Size in the deviceRTL source.
-///   GRIDVAL[GV_Warp_Size]
+///   llvm::omp::GRIDVAL[llvm::omp::GVIDX::GV_Warp_Size]
 ///
 /// Example usage in libomptarget hsa plugin:
-///   #include "OMPGridValues.h"
+///   #include "llvm/Frontend/OpenMP/OMPGridValues.h"
 ///   #define GRIDVAL AMDGPUGpuGridValues
 ///   ... Then use this reference to access GV_Warp_Size in the hsa plugin.
-///   GRIDVAL[GV_Warp_Size]
+///   llvm::omp::GRIDVAL[llvm::omp::GVIDX::GV_Warp_Size]
 ///
 /// Example usage in libomptarget cuda plugin:
-///    #include "OMPGridValues.h"
+///    #include "llvm/Frontend/OpenMP/OMPGridValues.h"
 ///    #define GRIDVAL NVPTXGpuGridValues
 ///   ... Then use this reference to access GV_Warp_Size in the cuda plugin.
-///    GRIDVAL[GV_Warp_Size]
+///    llvm::omp::GRIDVAL[llvm::omp::GVIDX::GV_Warp_Size]
 ///
 enum GVIDX {
   /// The maximum number of workers in a kernel.
   /// (THREAD_ABSOLUTE_LIMIT) - (GV_Warp_Size), might be issue for blockDim.z
   GV_Threads,
   /// The size reserved for data in a shared memory slot.
   GV_Slot_Size,
   /// The default value of maximum number of threads in a worker warp.