[OpenMP][NFC] Flatten plugin-nextgen/common folder sturcture (#73725)

For historic reasons we had it setup that there was
`  plugin-nextgen/common/PluginInterface/<sources + headers>`
which is not what we do anywhere else.
Now it looks like the rest:
```
  plugin-nextgen/common/include/<headers>
  plugin-nextgen/common/src/<sources>
```
As part of this, `dlwrap.h` was moved into common/include (as
`DLWrap.h`)
since it is exclusively used by the plugins.

Author: jdoerfert

openmp/libomptarget/plugins-nextgen/CMakeLists.txt

@@ -47,7 +47,7 @@ if(CMAKE_SYSTEM_PROCESSOR MATCHES "${tmachine}$")
 
         LINK_LIBS
         PRIVATE
-        PluginInterface
+        PluginCommon
         ${LIBOMPTARGET_DEP_LIBFFI_LIBRARIES}
         ${OPENMP_PTHREAD_LIB}
 

openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt

@@ -80,7 +80,7 @@ add_llvm_library(omptarget.rtl.amdgpu SHARED
 
   LINK_LIBS
   PRIVATE
-  PluginInterface
+  PluginCommon
   ${LIBOMPTARGET_DEP_LIBRARIES}
   ${OPENMP_PTHREAD_LIB}
   ${LDFLAGS_UNDEFINED}

openmp/libomptarget/plugins-nextgen/amdgpu/dynamic_hsa/hsa.cpp

@@ -15,7 +15,7 @@
 
 #include "Shared/Debug.h"
 
-#include "dlwrap.h"
+#include "DLWrap.h"
 #include "hsa.h"
 #include "hsa_ext_amd.h"
 #include <memory>

openmp/libomptarget/plugins-nextgen/common/CMakeLists.txt

@@ -10,5 +10,94 @@
 #
 ##===----------------------------------------------------------------------===##
 
+# NOTE: Don't try to build `PluginInterface` using `add_llvm_library` because we
+# don't want to export `PluginInterface` while `add_llvm_library` requires that.
+add_library(PluginCommon OBJECT
+  src/PluginInterface.cpp
+  src/GlobalHandler.cpp
+  src/JIT.cpp
+  src/RPC.cpp
+  src/Utils/ELF.cpp
+)
+
+# Only enable JIT for those targets that LLVM can support.
+string(TOUPPER "${LLVM_TARGETS_TO_BUILD}" TargetsSupported)
+foreach(Target ${TargetsSupported})
+	target_compile_definitions(PluginCommon PRIVATE "LIBOMPTARGET_JIT_${Target}")
+endforeach()
+
+# This is required when using LLVM libraries.
+llvm_update_compile_flags(PluginCommon)
+
+if (LLVM_LINK_LLVM_DYLIB)
+  set(llvm_libs LLVM)
+else()
+  llvm_map_components_to_libnames(llvm_libs
+    ${LLVM_TARGETS_TO_BUILD}
+    AggressiveInstCombine
+    Analysis
+    BinaryFormat
+    BitReader
+    BitWriter
+    CodeGen
+    Core
+    Extensions
+    InstCombine
+    Instrumentation
+    IPO
+    IRReader
+    Linker
+    MC
+    Object
+    Passes
+    Remarks
+    ScalarOpts
+    Support
+    Target
+    TargetParser
+    TransformUtils
+    Vectorize
+  )
+endif()
+
+target_link_libraries(PluginCommon
+  PUBLIC
+    ${llvm_libs}
+)
+
+# Include the RPC server from the `libc` project if availible.
+if(TARGET llvmlibc_rpc_server AND ${LIBOMPTARGET_GPU_LIBC_SUPPORT})
+	target_link_libraries(PluginCommon PRIVATE llvmlibc_rpc_server)
+	target_compile_definitions(PluginCommon PRIVATE LIBOMPTARGET_RPC_SUPPORT)
+elseif(${LIBOMPTARGET_GPU_LIBC_SUPPORT})
+  find_library(llvmlibc_rpc_server NAMES llvmlibc_rpc_server
+               PATHS ${LIBOMPTARGET_LLVM_LIBRARY_DIR} NO_DEFAULT_PATH)
+  if(llvmlibc_rpc_server)
+		target_link_libraries(PluginCommon PRIVATE llvmlibc_rpc_server)
+		target_compile_definitions(PluginCommon PRIVATE LIBOMPTARGET_RPC_SUPPORT)
+  endif()
+endif()
+
+if ((OMPT_TARGET_DEFAULT) AND (LIBOMPTARGET_OMPT_SUPPORT))
+	target_link_libraries(PluginCommon PUBLIC OMPT)
+endif()
+
+# Define the TARGET_NAME and DEBUG_PREFIX.
+target_compile_definitions(PluginCommon PRIVATE
+  TARGET_NAME="PluginInterface"
+  DEBUG_PREFIX="PluginInterface"
+)
+
+target_include_directories(PluginCommon
+  PRIVATE
+  ${LIBOMPTARGET_INCLUDE_DIR}
+  PUBLIC
+  ${CMAKE_CURRENT_SOURCE_DIR}/include
+)
+
+set_target_properties(PluginCommon PROPERTIES
+  POSITION_INDEPENDENT_CODE ON
+  CXX_VISIBILITY_PRESET protected)
+
 add_subdirectory(OMPT)
-add_subdirectory(PluginInterface)
+

openmp/libomptarget/plugins-nextgen/common/PluginInterface/CMakeLists.txt

@@ -1,4 +1,4 @@
-//===------- dlwrap.h - Convenience wrapper around dlopen/dlsym  -- C++ -*-===//
+//===-- Shared/DLWrap.h - Convenience wrapper for dlopen/dlsym --*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -38,8 +38,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef DLWRAP_H_INCLUDED
-#define DLWRAP_H_INCLUDED
+#ifndef OMPTARGET_SHARED_DLWRAP_H
+#define OMPTARGET_SHARED_DLWRAP_H
 
 #include <array>
 #include <cstddef>
@@ -283,4 +283,4 @@ template <size_t Requested, size_t Required> constexpr void verboseAssert() {
                                           x9, x10);                            \
   }
 
-#endif
+#endif // OMPTARGET_SHARED_DLWRAP_H

openmp/libomptarget/include/dlwrap.h renamed to openmp/libomptarget/plugins-nextgen/common/include/DLWrap.h

@@ -34,7 +34,7 @@ add_llvm_library(omptarget.rtl.cuda SHARED
   Object
 
   LINK_LIBS PRIVATE
-  PluginInterface
+  PluginCommon
   ${OPENMP_PTHREAD_LIB}
 
   NO_INSTALL_RPATH

openmp/libomptarget/plugins-nextgen/common/PluginInterface/GlobalHandler.h renamed to openmp/libomptarget/plugins-nextgen/common/include/GlobalHandler.h

@@ -15,8 +15,8 @@
 
 #include "Shared/Debug.h"
 
+#include "DLWrap.h"
 #include "cuda.h"
-#include "dlwrap.h"
 
 #include <memory>
 #include <string>