[Libomptarget] Build plugins with protected visibility by default

[jhuber6]

Summary

The plugins all define the same interface symbols. This is generally not
a problem when calling the plugin directly from the dynamic library's
handle. However, when calling from within the plugin itself it is
possible for another plugin's symbols to preempt the symbols. This was
observed with the __tgt_rtl_is_valid_binary call in the
__tgt_rtl_is_valid_binary_info function being mapped to the x86_64
plugin.

This patch changes the default visibility to protected intead. This
visibility ensures that these symbols are all externally visible from
the plugin, but ensures their definitions are fixed within the shared
library. Having protected visiiblity makes such symbol preemption
impossible.

[tianshilei1992]

LGTM

openmp/libomptarget/plugins/CMakeLists.txt

add_llvm_library("omptarget.rtl.${tmachine_libname}"
 
       NO_INSTALL_RPATH
     )
 
     # Install plugin under the lib destination folder.
     install(TARGETS "omptarget.rtl.${tmachine_libname}"
       LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
     set_target_properties("omptarget.rtl.${tmachine_libname}" PROPERTIES
-      INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/..")
+      INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
+      CXX_VISIBILITY_PRESET protected)
 
     target_include_directories( "omptarget.rtl.${tmachine_libname}" PRIVATE
       ${LIBOMPTARGET_INCLUDE_DIR}
       ${LIBOMPTARGET_DEP_LIBFFI_INCLUDE_DIR})
 
     list(APPEND LIBOMPTARGET_TESTED_PLUGINS
       "omptarget.rtl.${tmachine_libname}")
 

openmp/libomptarget/plugins/amdgpu/CMakeLists.txt

target_include_directories(
   ${LIBOMPTARGET_INCLUDE_DIR}
   ${CMAKE_CURRENT_SOURCE_DIR}/impl
 )
 
 
 # Install plugin under the lib destination folder.
 install(TARGETS omptarget.rtl.amdgpu LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
 set_target_properties(omptarget.rtl.amdgpu PROPERTIES 
-  INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/..")
+  INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
+  CXX_VISIBILITY_PRESET protected)
 
 # Report to the parent scope that we are building a plugin for hsa.
 # This controls whether tests are run for the nvptx offloading target
 # Run them if libhsa is available, or if the user explicitly asked for dlopen
 # Otherwise this plugin is being built speculatively and there may be no hsa available
 if (${hsa-runtime64_FOUND} OR LIBOMPTARGET_FORCE_DLOPEN_LIBHSA)
   # Report to the parent scope that we are building a plugin for amdgpu
   set(LIBOMPTARGET_SYSTEM_TARGETS "${LIBOMPTARGET_SYSTEM_TARGETS} amdgcn-amd-amdhsa amdgcn-amd-amdhsa-oldDriver" PARENT_SCOPE)
   set(LIBOMPTARGET_SYSTEM_TARGETS "${LIBOMPTARGET_SYSTEM_TARGETS} amdgcn-amd-amdhsa amdgcn-amd-amdhsa-LTO" PARENT_SCOPE)
   list(APPEND LIBOMPTARGET_TESTED_PLUGINS "omptarget.rtl.amdgpu")
   set(LIBOMPTARGET_TESTED_PLUGINS "${LIBOMPTARGET_TESTED_PLUGINS}" PARENT_SCOPE)
 else()
   libomptarget_say("Not generating amdgcn test targets as libhsa is not linkable")
   return()
 endif()
 

openmp/libomptarget/plugins/cuda/CMakeLists.txt

add_llvm_library(omptarget.rtl.cuda
     NO_INSTALL_RPATH
   )
 endif()
 add_dependencies(omptarget.rtl.cuda omptarget.devicertl.nvptx)
 
 # Install plugin under the lib destination folder.
 install(TARGETS omptarget.rtl.cuda LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
 set_target_properties(omptarget.rtl.cuda PROPERTIES 
-  INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/..")
+  INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
+  CXX_VISIBILITY_PRESET protected)
 
 target_include_directories(omptarget.rtl.cuda PRIVATE
   ${LIBOMPTARGET_INCLUDE_DIR}
 )
 
 # Report to the parent scope that we are building a plugin for CUDA.
 # This controls whether tests are run for the nvptx offloading target
 # Run them if libcuda is available, or if the user explicitly asked for dlopen

openmp/libomptarget/plugins/ve/CMakeLists.txt

add_llvm_library("omptarget.rtl.${tmachine_libname}"
     "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports -Wl,-z,defs"
 
     NO_INSTALL_RPATH
   )
 
   # Install plugin under the lib destination folder.
   install(TARGETS  "omptarget.rtl.${tmachine_libname}" LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
   set_target_properties("omptarget.rtl.${tmachine_libname}" PROPERTIES 
-    INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/..")
+    INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
+    CXX_VISIBILITY_PRESET protected)
 
   target_include_directories("omptarget.rtl.${tmachine_libname}" PRIVATE
     ${LIBOMPTARGET_INCLUDE_DIR}
     ${LIBOMPTARGET_DEP_VEO_INCLUDE_DIR})
 
   target_link_libraries(
     "omptarget.rtl.${tmachine_libname}"
     elf_common