[RFC][OpenMP][Offloading] dlopen plugins with version

[tianshilei1992]

Summary

Currently we open a plugin using its name such as libomptarget.rtl.cuda.so. We
don't verify its version, and always assume the backward compatibility, by
restricting changes of the plugin interfaces. Since LLVM 15, we made the plugin
a LLVM library, which means now it has version, because LLVM libraries are not
guaranteed backward compatible among major versions. Given that fact, in this
patch, we load a plugin w/ version in its name. This could at least prevent the
problem caused by incompatible LLVM components.

[jhuber6]

That can land now that we agreed on no major version compatibility right.

openmp/libomptarget/src/CMakeLists.txt

add_llvm_library(omptarget
 
   ADDITIONAL_HEADER_DIRS
   ${LIBOMPTARGET_INCLUDE_DIR}
 
   LINK_COMPONENTS
   Support
   Object
 
-  LINK_LIBS 
+  LINK_LIBS
   PRIVATE
   "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/exports"
   NO_INSTALL_RPATH
 )
 target_include_directories(omptarget PRIVATE ${LIBOMPTARGET_INCLUDE_DIR})
 
+target_compile_definitions(omptarget PRIVATE LLVM_VERSION=${LLVM_VERSION_MAJOR}${LLVM_VERSION_SUFFIX})
+
 # libomptarget.so needs to be aware of where the plugins live as they
 # are now separated in the build directory.
 set_target_properties(omptarget PROPERTIES INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/..")
 install(TARGETS omptarget LIBRARY COMPONENT omptarget DESTINATION "${OPENMP_INSTALL_LIBDIR}")

openmp/libomptarget/src/rtl.cpp

 #include <cstdlib>
 #include <cstring>
 #include <mutex>
 #include <string>
 
 using namespace llvm;
 using namespace llvm::sys;
 
+#ifndef LLVM_VERSION
+#define PLUGIN_VERSION ""
+#else
+#define VERSION_STR(X) #X
+#define PLUGIN_VERSION "." VERSION_STR(LLVM_VERSION)
+#endif
+
 // List of all plugins that can support offloading.
+
 static const char *RTLNames[] = {
-    /* PowerPC target       */ "libomptarget.rtl.ppc64.so",
-    /* x86_64 target        */ "libomptarget.rtl.x86_64.so",
-    /* CUDA target          */ "libomptarget.rtl.cuda.so",
-    /* AArch64 target       */ "libomptarget.rtl.aarch64.so",
-    /* SX-Aurora VE target  */ "libomptarget.rtl.ve.so",
-    /* AMDGPU target        */ "libomptarget.rtl.amdgpu.so",
-    /* Remote target        */ "libomptarget.rtl.rpc.so",
+    /* PowerPC target       */ "libomptarget.rtl.ppc64.so" PLUGIN_VERSION,
+    /* x86_64 target        */ "libomptarget.rtl.x86_64.so" PLUGIN_VERSION,
+    /* CUDA target          */ "libomptarget.rtl.cuda.so" PLUGIN_VERSION,
+    /* AArch64 target       */ "libomptarget.rtl.aarch64.so" PLUGIN_VERSION,
+    /* SX-Aurora VE target  */ "libomptarget.rtl.ve.so" PLUGIN_VERSION,
+    /* AMDGPU target        */ "libomptarget.rtl.amdgpu.so" PLUGIN_VERSION,
+    /* Remote target        */ "libomptarget.rtl.rpc.so" PLUGIN_VERSION,
 };
 
+#undef PLUGIN_VERSION
+#ifdef VERSION_STR
+#undef VERSION_STR
+#endif
+
 PluginManager *PM;
 
 static char *ProfileTraceFile = nullptr;
 
 __attribute__((constructor(101))) void init() {
   DP("Init target library!\n");
 
   bool UseEventsForAtomicTransfers = true;