[CMake] Change -DENABLE_EXPERIMENTAL_NEW_PASS_MANAGER=off to -DLLVM_ENABLE_NEW_PASS_MANAGER=off

[MaskRay]

Summary

LLVM_ENABLE_NEW_PASS_MANAGER is set to ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER, so
-DLLVM_ENABLE_NEW_PASS_MANAGER=off has no effect.

Change the cache variable to LLVM_ENABLE_NEW_PASS_MANAGER instead.
An user opting out the new PM needs to switch from
-DENABLE_EXPERIMENTAL_NEW_PASS_MANAGER=off to
-DLLVM_ENABLE_NEW_PASS_MANAGER=off.

Also give a warning that -DLLVM_ENABLE_NEW_PASS_MANAGER=off is deprecated.

Intended for main and release/13.x

[aeubanks]

this is good, but IMO it's not clear enough in the description that this is a breaking change in terms of CMake flags (use -DLLVM_ENABLE_NEW_PASS_MANAGER instead of -DEXPERIMENTAL_NEW_PASS_MANAGER)

[aeubanks]

lg, thanks for doing this!

[MaskRay]

The Fuchsia change is quite obvious. Committing. If stable for some time, will push to release/13.x

[phosek]

LGTM

[MaskRay]

@aeubanks I have cherry picked this into release/13.x

clang/cmake/caches/Fuchsia-stage2.cmake

if(NOT APPLE)
   set(CLANG_DEFAULT_LINKER lld CACHE STRING "")
   set(CLANG_DEFAULT_OBJCOPY llvm-objcopy CACHE STRING "")
 endif()
 set(CLANG_DEFAULT_RTLIB compiler-rt CACHE STRING "")
 set(CLANG_ENABLE_ARCMT OFF CACHE BOOL "")
 set(CLANG_ENABLE_STATIC_ANALYZER ON CACHE BOOL "")
 set(CLANG_PLUGIN_SUPPORT OFF CACHE BOOL "")
 
-set(ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER ON CACHE BOOL "")
 set(ENABLE_LINKER_BUILD_ID ON CACHE BOOL "")
 set(ENABLE_X86_RELAX_RELOCATIONS ON CACHE BOOL "")
 
 set(CMAKE_BUILD_TYPE Release CACHE STRING "")
 if (APPLE)
   set(CMAKE_OSX_DEPLOYMENT_TARGET "10.13" CACHE STRING "")
 elseif(WIN32)
   set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded" CACHE STRING "")

clang/cmake/caches/Fuchsia.cmake

if(NOT APPLE)
   set(CLANG_DEFAULT_LINKER lld CACHE STRING "")
   set(CLANG_DEFAULT_OBJCOPY llvm-objcopy CACHE STRING "")
 endif()
 set(CLANG_DEFAULT_RTLIB compiler-rt CACHE STRING "")
 set(CLANG_ENABLE_ARCMT OFF CACHE BOOL "")
 set(CLANG_ENABLE_STATIC_ANALYZER ON CACHE BOOL "")
 set(CLANG_PLUGIN_SUPPORT OFF CACHE BOOL "")
 
-set(ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER ON CACHE BOOL "")
 set(ENABLE_LINKER_BUILD_ID ON CACHE BOOL "")
 set(ENABLE_X86_RELAX_RELOCATIONS ON CACHE BOOL "")
 
 set(LLVM_ENABLE_ASSERTIONS ON CACHE BOOL "")
 set(CMAKE_BUILD_TYPE Release CACHE STRING "")
 if(APPLE)
   set(CMAKE_OSX_DEPLOYMENT_TARGET "10.13" CACHE STRING "")
 elseif(WIN32)

llvm/CMakeLists.txt

if(WIN32 OR CYGWIN)
   else()
     set(LLVM_ENABLE_PLUGINS_default OFF)
   endif()
 else()
   set(LLVM_ENABLE_PLUGINS_default ${LLVM_ENABLE_PIC})
 endif()
 option(LLVM_ENABLE_PLUGINS "Enable plugin support" ${LLVM_ENABLE_PLUGINS_default})
 
-set(ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER TRUE CACHE BOOL
+set(LLVM_ENABLE_NEW_PASS_MANAGER TRUE CACHE BOOL
   "Enable the new pass manager by default.")
+if(NOT LLVM_ENABLE_NEW_PASS_MANAGER)
+  message(WARNING "Using the legacy pass manager for the optimization pipeline"
+                  " is deprecated. The functionality will degrade over time and"
+                  " be removed in a future release.")
+endif()
 
 include(HandleLLVMOptions)
 
 find_package(Python3 ${LLVM_MINIMUM_PYTHON_VERSION} REQUIRED
     COMPONENTS Interpreter)
 
 ######
 
if (NOT TENSORFLOW_AOT_PATH STREQUAL "")
   include_directories(${TENSORFLOW_AOT_PATH}/include)
   add_subdirectory(${TENSORFLOW_AOT_PATH}/xla_aot_runtime_src
     ${CMAKE_ARCHIVE_OUTPUT_DIRECTORY}/tf_runtime)
   install(TARGETS tf_xla_runtime EXPORT LLVMExports
     ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX} COMPONENT tf_xla_runtime)
   set_property(GLOBAL APPEND PROPERTY LLVM_EXPORTS tf_xla_runtime)
 endif()
 
-# Keep the legacy CMake flag ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER for
-# compatibility.
-set(LLVM_ENABLE_NEW_PASS_MANAGER ${ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER})
-
 # Configure the three LLVM configuration header files.
 configure_file(
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Config/config.h.cmake
   ${LLVM_INCLUDE_DIR}/llvm/Config/config.h)
 configure_file(
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Config/llvm-config.h.cmake
   ${LLVM_INCLUDE_DIR}/llvm/Config/llvm-config.h)
 configure_file(

llvm/docs/NewPassManager.rst

 
 LLVM currently contains two pass managers, the legacy PM and the new PM. The
 optimization pipeline (aka the middle-end) works with both the legacy PM and
 the new PM, whereas the backend target-dependent code generation only works
 with the legacy PM.
 
 For the optimization pipeline, the new PM is the default PM. The legacy PM is
 available for the optimization pipeline either by setting the CMake flag
-``-DENABLE_EXPERIMENTAL_NEW_PASS_MANAGER=OFF`` when building LLVM, or by
+``-DLLVM_ENABLE_NEW_PASS_MANAGER=OFF`` when building LLVM, or by
 various compiler/linker flags, e.g. ``-flegacy-pass-manager`` for ``clang``.
 
 There will be efforts to deprecate and remove the legacy PM for the
 optimization pipeline in the future.
 
 Some IR passes are considered part of the backend codegen pipeline even if
 they are LLVM IR passes (whereas all MIR passes are codegen passes). This
 includes anything added via ``TargetPassConfig`` hooks, e.g.
 ``TargetPassConfig::addCodeGenPrepare()``. As mentioned before, passes added
 in ``TargetMachine::adjustPassManager()`` are part of the optimization
 pipeline, and should have a corresponding line in
 ``TargetMachine::registerPassBuilderCallbacks()``.
 
 Currently there are efforts to make the codegen pipeline work with the new
 PM.