Fix compiler extension builds

[serge-sans-paille]

Summary

• Update documentation now that the move to monorepo has been made
• Fix validation issue when building examples
• Add NO_MODULE option to match Polly specific requirements (i.e. building the module *and* linking it statically)

[serge-sans-paille]

I've tested that with LLVM_BYE_LINK_INTO_TOOLS ON/OFF, LLVM_BUILD_EXAMPLES ON/OFF LLVM_POLLY_LINK_INTO_TOOLS ON/OFF and it seems okay.

[serge-sans-paille]

• Test and handle the combination of LLVM_BUILD_EXAMPLE=OFF + LLVM_BYE_LINK_INTO_TOOLS=ON

[Meinersbur]

llvm/cmake/modules/AddLLVM.cmake

850–856

[doc] Document the NO_MODULE option

868

[nit] indention

llvm/examples/Bye/CMakeLists.txt

0–1

[serious] Whether example targets are generated is controlled by LLVM_INCLUDE_EXAMPLES. LLVM_BUILD_EXAMPLES should control EXCLUDE_FROM_ALL or similar. Is there a corresponding option for pass plugins, especially if LLVM_BYE_LINK_INTO_TOOLS is off?

I'd assume that if LLVM_BUILD_EXAMPLES is off, but LLVM_BYE_LINK_INTO_TOOLS is on, that latter would effectively override EXCLUDE_FROM_ALL since the plugin is needed to built opt,bugpoint,etc.

Btw, what is the "Fix validation issue when building examples"?

[fhahn]

Does this fix llvm/test/Feature/load_extension.ll on macOS by any chance?

[serge-sans-paille]

In D72327#1808263, @fhahn wrote:

Does this fix llvm/test/Feature/load_extension.ll on macOS by any chance?

Now it should, but I'm waiting for my pre-commit validation to state if that's actually the case.

llvm/examples/Bye/CMakeLists.txt

0–1

I'd assume that if LLVM_BUILD_EXAMPLES is off, but LLVM_BYE_LINK_INTO_TOOLS is on, that latter would effectively override EXCLUDE_FROM_ALL since the plugin is needed to built opt,bugpoint,etc.

The problem I wanted to solve here is having LLVM_BYE_LINK_INTO_TOOLS=ON in release build, because Bye is just an example library. But it's nice to be able to test it. Maybe I should just issue a warning in that case?

Btw, what is the "Fix validation issue when building examples"?

There was a mismatch between the lit feature « requires build_example » and « LLVM_BUILD_EXAMPLES » I've updated the patch in that aspect, taking into account your remark.

[Meinersbur]

LGTM

llvm/cmake/modules/AddLLVM.cmake

897

[nit] accidental whitespace change

llvm/examples/Bye/CMakeLists.txt

2

The message could be more specific about this is not good, something like "Release build contains example code for development".

Recently we had a discussion about adding tutorial pass code to the repository, and how to include it into the build system, where D61446 came up as well. We should at some point agree how to handle example/tutorial code in release builds.

[suggestion] Only print the warning in release builds, maybe by checking CMAKE_BUILD_TYPE or LLVM_ENABLE_ASSERTIONS.

[serge-sans-paille]

• Fix OSX build.

The problem was deeper than expected and arise when the pass extension mechanism is used from plugin *and* static library, e.g. when Polly is linked in and a plugin is loaded.

In that case, the pass extension registry may be initialized before the first shared library is opened, and thus upon llvm_shutdown, the library ar dlclosed *before* the pass extension registered is deleted. At that moment the callback registered in the pass extension registry points to a function from the dlclosed library, and bad thing happens (namely the std::function destructor segfaults).

The patch consists in forcing the init order through a call to a function that triggers the construction of the managedstatic holding thedlopened library handles.

[Meinersbur]

It would be nicer if you would commit (and upload for review) the three changes separately. You might just commit the first two changes since I think they are ok, but I am not sure about the ensureValid change, which needs some expertise from someone knowing sys::DynamicLibrary and llvm::ManagedStatic.

llvm/lib/Support/DynamicLibrary.cpp

152 ↗

(On Diff #237161)

[nit] clang-format would collapse double empty lines into one.

llvm/cmake/modules/AddLLVM.cmake

macro(add_llvm_executable name)
   endif()
   if(ARG_ENABLE_PLUGINS)
     set_property(GLOBAL APPEND PROPERTY LLVM_PLUGIN_TARGETS ${name})
   endif()
 
   llvm_codesign(${name} ENTITLEMENTS ${ARG_ENTITLEMENTS} BUNDLE_PATH ${ARG_BUNDLE_PATH})
 endmacro(add_llvm_executable name)
 
-# add_llvm_pass_plugin(name)
+# add_llvm_pass_plugin(name [NO_MODULE] ...)
 #   Add ${name} as an llvm plugin.
 #   If option LLVM_${name_upper}_LINK_INTO_TOOLS is set to ON, the plugin is registered statically.
 #   Otherwise a pluggable shared library is registered.
+#
+#   If NO_MODULE is specified, when option LLVM_${name_upper}_LINK_INTO_TOOLS is set to OFF,
+#   only an object library is built, and no module is built. This is specific to the Polly use case.
 function(add_llvm_pass_plugin name)
+  cmake_parse_arguments(ARG
+    "NO_MODULE" "" ""
+    ${ARGN})
 
   string(TOUPPER ${name} name_upper)
 
   option(LLVM_${name_upper}_LINK_INTO_TOOLS "Statically link ${name} into tools (if available)" OFF)
 
+  if(LLVM_${name_upper}_LINK_INTO_TOOLS)
+    list(REMOVE_ITEM ARG_UNPARSED_ARGUMENTS BUILDTREE_ONLY)
     # process_llvm_pass_plugins takes care of the actual linking, just create an
     # object library as of now
-  add_llvm_library(${name} OBJECT ${ARGN})
-
-  if(LLVM_${name_upper}_LINK_INTO_TOOLS)
-      target_compile_definitions(${name} PRIVATE LLVM_${name_upper}_LINK_INTO_TOOLS)
-      set_property(TARGET ${name} APPEND PROPERTY COMPILE_DEFINITIONS LLVM_LINK_INTO_TOOLS)
-      if (TARGET intrinsics_gen)
-        add_dependencies(obj.${name} intrinsics_gen)
-      endif()
-  endif()
-
+    add_llvm_library(${name} OBJECT ${ARG_UNPARSED_ARGUMENTS})
     message(STATUS "Registering ${name} as a pass plugin (static build: ${LLVM_${name_upper}_LINK_INTO_TOOLS})")
-  if(LLVM_${name_upper}_LINK_INTO_TOOLS)
     set_property(GLOBAL APPEND PROPERTY LLVM_COMPILE_EXTENSIONS ${name})
+  elseif(NOT ARG_NO_MODULE)
+    add_llvm_library(${name} MODULE ${ARG_UNPARSED_ARGUMENTS})
+  else()
+    add_llvm_library(${name} OBJECT ${ARG_UNPARSED_ARGUMENTS})
   endif()
+
 endfunction(add_llvm_pass_plugin)
 
 # Generate X Macro file for extension handling. It provides a
 # HANDLE_EXTENSION(extension_namespace, ExtensionProject) call for each extension
 # allowing client code to define HANDLE_EXTENSION to have a specific code be run for
 # each extension.
 #
 # Also correctly set lib dependencies between plugins and tools.
 function(process_llvm_pass_plugins)
   get_property(LLVM_EXTENSIONS GLOBAL PROPERTY LLVM_COMPILE_EXTENSIONS)
   file(WRITE "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "//extension handlers\n")
   foreach(llvm_extension ${LLVM_EXTENSIONS})
     string(TOLOWER ${llvm_extension} llvm_extension_lower)
 
     string(TOUPPER ${llvm_extension} llvm_extension_upper)
     string(SUBSTRING ${llvm_extension_upper} 0 1 llvm_extension_upper_first)
     string(SUBSTRING ${llvm_extension_lower} 1 -1 llvm_extension_lower_tail)
     string(CONCAT llvm_extension_project ${llvm_extension_upper_first} ${llvm_extension_lower_tail})
 
     if(LLVM_${llvm_extension_upper}_LINK_INTO_TOOLS)
       file(APPEND "${LLVM_BINARY_DIR}/include/llvm/Support/Extension.def.tmp" "HANDLE_EXTENSION(${llvm_extension_project})\n")
 
       get_property(llvm_plugin_targets GLOBAL PROPERTY LLVM_PLUGIN_TARGETS)
       foreach(llvm_plugin_target ${llvm_plugin_targets})
         set_property(TARGET ${llvm_plugin_target} APPEND PROPERTY LINK_LIBRARIES ${llvm_extension})
         set_property(TARGET ${llvm_plugin_target} APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${llvm_extension})
       endforeach()
     else()
       add_llvm_library(${llvm_extension_lower} MODULE obj.${llvm_extension_lower})
     endif()

llvm/examples/Bye/CMakeLists.txt

+if(LLVM_BYE_LINK_INTO_TOOLS)
+  message(WARNING "Setting LLVM_BYE_LINK_INTO_TOOLS=ON only makes sense for testing purpose")
+endif()
+
 add_llvm_pass_plugin(Bye
-    Bye.cpp
-    DEPENDS
-    intrinsics_gen
-    BUILDTREE_ONLY
-    )
 
-if (LLVM_LINK_LLVM_DYLIB)
-  target_link_libraries(Bye PUBLIC LLVM)
-else()
-  target_link_libraries(Bye
-    PUBLIC
-    LLVMSupport
-    LLVMCore
-    LLVMipo
-    LLVMPasses
-    )
-endif()
-
-if( LLVM_BUILD_EXAMPLES )
-  install(TARGETS ${name} RUNTIME DESTINATION examples)
-endif()
 set_target_properties(${name} PROPERTIES FOLDER "Examples")

llvm/test/lit.cfg.py

 
 # Loadable module
 if config.has_plugins:
     config.available_features.add('plugins')
 
 if config.build_examples:
     config.available_features.add('examples')
 
-if config.linked_bye_extension and config.build_examples:
+if config.linked_bye_extension:
     config.substitutions.append(('%llvmcheckext', 'CHECK-EXT'))
     config.substitutions.append(('%loadbye', ''))
 else:
     config.substitutions.append(('%llvmcheckext', 'CHECK-NOEXT'))
     config.substitutions.append(('%loadbye',
-                                 '-load={}/libBye{}'.format(config.llvm_shlib_dir,
+                                 '-load={}/Bye{}'.format(config.llvm_shlib_dir,
                                                                   config.llvm_shlib_ext)))
 
 # Static libraries are not built if BUILD_SHARED_LIBS is ON.
 if not config.build_shared_libs and not config.link_llvm_dylib:
     config.available_features.add('static-libs')
 
 def have_cxx_shared_library():
     readobj_exe = lit.util.which('llvm-readobj', config.llvm_tools_dir)

polly/lib/CMakeLists.txt

 set(POLLY_HEADER_FILES)
 if (MSVC_IDE OR XCODE)
   file(GLOB_RECURSE POLLY_HEADER_FILES "${POLLY_SOURCE_DIR}/include/polly/*.h")
 endif ()
 
 # Use an object-library to add the same files to multiple libs without requiring
 # the sources them to be recompiled for each of them.
 add_llvm_pass_plugin(Polly
+  NO_MODULE
   Analysis/DependenceInfo.cpp
   Analysis/PolyhedralInfo.cpp
   Analysis/ScopDetection.cpp
   Analysis/ScopDetectionDiagnostic.cpp
   Analysis/ScopInfo.cpp
   Analysis/ScopBuilder.cpp
   Analysis/ScopGraphPrinter.cpp
   Analysis/ScopPass.cpp