[Polly][CMake] Use object library to build two flavours of Polly.

[Meinersbur]

Summary

Polly comes in two library flavors: One loadable module to use the LLVM framework -load mechanism, and another one that host applications can link to. These have very different requirements for Polly's own dependencies.

The loadable module assumes that all its LLVM dependencies are already available in the address space of the host application, and is not allowed to bring in its own copy of any LLVM library (including the NVPTX backend in case of Polly-ACC).

The non-module library is intended to be linked to using target_link_libraries. CMake would then resolve all of its dependencies, including NVPTX and ensure that only a single instance of each library will be used.

This is a less invasive alternative to D32392.

I did not manage to make LLVM_LINK_LLVM_DYLIB=ON build work entirely. check-polly works, but trying to install it gives an error

CMake Error at tools/polly/lib/cmake_install.cmake:40 (file):
  file INSTALL cannot find
  "/root/build/llvm/release_loadpolly_dylib/tools/polly/lib/CMakeFiles/CMakeRelink.dir/LLVMPolly.so".
Call Stack (most recent call first):
  tools/polly/cmake_install.cmake:46 (include)
  tools/cmake_install.cmake:37 (include)
  cmake_install.cmake:62 (include)

According to http://public.kitware.com/pipermail/cmake/2016-July/063992.html this has might not be Polly's fault. It occures with lld as well.

[Meinersbur]

Properly handle dylibs (e.g. if LLVM_LINK_LLVM_DYLIB=ON, do not link any LLVM component since it should be already in the libLLVM.so)

[singam-sanjay]

lib/CMakeLists.txt

89

Why can't we just add PollyCore as a dependency ?

153

We need all these libraries and not just those that might be returned by llvm_map_components_to_libnames(nvptx_libs NVPTX) (I'm assuming that you mean nvptx_libs might turn out to be a subset of all possible NVPTX libraries).

Nevertheless, won't all LLVMNVPTX* libraries be included in nvptx_libs since they are all a part of the NVPTX backend ?

unittests/CMakeLists.txt

12

patch failed to update this file because it couldn't find these comments. At which commit did you create the diff ?

[singam-sanjay]

This patch works on my system.

[Meinersbur]

lib/CMakeLists.txt

89

That should work as well, if PollyCore was a static library. For OBJECT libraries, this is the only way to do. See https://cmake.org/cmake/help/v3.8/command/add_library.html#object-libraries

Here are the reasons:

• LLVM also creates OBJECT libraries when it creates static and shared libraries in one build.
• There is one less library that could be either a shared or static library.
• Without it, the Polly and LLVM library would be empty. This could cause symbols of PollyCore to not get pulled-in by the linker, which gets us into trouble.
• CMake might order PollyCore behind PollyISL and PollyPPCG in the linker command linker, meaning it would not pull anything from them because theirs symbols were not required then.

153

There are two separate cases:

• We are building inside the LLVM tree: Then cmake knowns which libraries NVPTX* depend on and adjust the linker command line accordingly. This is exactly how LLVM's CMakeLists.txt do this (using LLVM_LINK_COMPONENTS)

• We are building out-of-tree: Then we don't know the NVPTX* dependencies. however, we link against all the libraries (using LLVM_LIBS), so all its dependencies are already available (including NVPTX*, so the second case is kind-of redundant, I might remove them).

I think I don't actually understood your question. What are "all" libraries? llvm_map_components_to_libnames returns: LLVMNVPTXCodeGen LLVMNVPTXInfo LLVMNVPTXDesc LLVMNVPTXAsmPrinter.

unittests/CMakeLists.txt

12

The comments were added in r301095 ([CMake] Fix unittests in out-of-LLVM-tree builds.)

[Meinersbur]

Pre-commit update.

• Don't redundantly call target_link_libraries on Polly.

CMakeLists.txt

target_include_directories(gtest
       PUBLIC
       "${UNITTEST_DIR}/googletest/include"
       "${UNITTEST_DIR}/googlemock/include"
 
       PRIVATE
       "${UNITTEST_DIR}/googletest"
       "${UNITTEST_DIR}/googlemock"
     )
-    target_link_libraries(gtest ${LLVM_SYSTEM_LIBS})
+    target_link_libraries(gtest -lpthread)
 
     add_library(gtest_main ${UNITTEST_DIR}/UnitTestMain/TestMain.cpp)
     target_link_libraries(gtest_main gtest)
 
     set(POLLY_GTEST_AVAIL 1)
   endif()
 
   # Make sure the isl c files are built as fPIC

lib/CMakeLists.txt

 # Compile ISL into a separate library.
 add_subdirectory(External)
 
 set(POLLY_HEADER_FILES)
 if (MSVC_IDE OR XCODE)
   file(GLOB_RECURSE POLLY_HEADER_FILES "${POLLY_SOURCE_DIR}/include/polly/*.h")
 endif ()
 
-add_polly_library(Polly
+# 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_library(PollyCore OBJECT
   Analysis/DependenceInfo.cpp
   Analysis/PolyhedralInfo.cpp
   Analysis/ScopDetection.cpp
   Analysis/ScopDetectionDiagnostic.cpp
   Analysis/ScopInfo.cpp
   Analysis/ScopBuilder.cpp
   Analysis/ScopGraphPrinter.cpp
   Analysis/ScopPass.cpp
add_library(PollyCore OBJECT
   Transform/ScheduleOptimizer.cpp
   Transform/FlattenSchedule.cpp
   Transform/FlattenAlgo.cpp
   Transform/DeLICM.cpp
   Transform/Simplify.cpp
   ${POLLY_HEADER_FILES}
   )
 
+# Create the library that can be linked into LLVM's tools and Polly's unittests.
+# It depends on all library it needs, such that with
+# LLVM_POLLY_LINK_INTO_TOOLS=ON, its dependencies like PollyISL are linked as
+# well.
+add_polly_library(Polly $<TARGET_OBJECTS:PollyCore>)
+target_link_libraries(Polly
+  ${ISL_TARGET}
+)
+
+# Additional dependencies for Polly-ACC.
 if (GPU_CODEGEN)
   target_link_libraries(Polly PollyPPCG)
-endif (GPU_CODEGEN)
+endif ()
+
+# Add Polly's LLVM dependencies.
+# When built inside the LLVM source tree, these are CMake targets that will
+# depend on their dependencies and CMake ensures they are added in the right
+# order.
+# If Polly is built independently, just add all LLVM libraries. LLVM_ROOT_DIR
+# might have been configured to compile to individual libraries or a single
+# libLLVM.so (called dylib), reported by llvm-config, so there is no fixed list
+# of required libraries.
+if (DEFINED LLVM_MAIN_SRC_DIR)
 
-target_link_libraries(Polly ${ISL_TARGET})
+  # Polly-ACC requires the NVPTX backend to work. Ask LLVM about its libraries.
+  set(nvptx_libs)
+  if (GPU_CODEGEN)
+    # This call emits an error if they NVPTX backend is not enable.
+    llvm_map_components_to_libnames(nvptx_libs NVPTX)
+  endif ()
 
-if (BUILD_SHARED_LIBS)
+  if (LLVM_LINK_LLVM_DYLIB)
+    # The shlib/dylib contains all the LLVM components
+    # (including NVPTX is enabled) already. Adding them to target_link_libraries
+    # would cause them being twice in the address space
+    # (their LLVM*.a/so and their copies in libLLVM.so)
+    # which results in errors when the two instances try to register the same
+    # command-line switches.
+    target_link_libraries(Polly LLVM)
+  else ()
     target_link_libraries(Polly
       LLVMSupport
       LLVMCore
       LLVMScalarOpts
       LLVMInstCombine
       LLVMTransformUtils
       LLVMAnalysis
       LLVMipo
       LLVMMC
+      ${nvptx_libs}
 # The libraries below are required for darwin: http://PR26392
       LLVMBitReader
       LLVMMCParser
       LLVMObject
       LLVMProfileData
       LLVMTarget
       LLVMVectorize
     )
-  link_directories(
-    ${LLVM_LIBRARY_DIR}
-  )
-elseif (LLVM_LINK_LLVM_DYLIB)
+  endif ()
+else ()
+  # When Polly-ACC is enabled, we assume that the host LLVM was also built with
+  # the NVPTX target enabled.
   target_link_libraries(Polly
-    LLVM
-  )
-  link_directories(
-    ${LLVM_LIBRARY_DIR}
+    ${LLVM_LIBS}
+    ${LLVM_SYSTEM_LIBS}
   )
-endif()
+endif ()
 
-# Build a monolithic Polly.a and a thin module LLVMPolly.moduleext that links to
-# that static library.
+# Create a loadable module Polly.so that can be loaded using
+# LLVM's/clang's "-load" option.
 if (MSVC)
   # Add dummy target, because loadable modules are not supported on Windows
   add_custom_target(LLVMPolly)
   set_target_properties(LLVMPolly PROPERTIES FOLDER "Polly")
 else ()
   add_polly_loadable_module(LLVMPolly
     Polly.cpp
+    $<TARGET_OBJECTS:PollyCore>
   )
 
-  target_link_libraries(LLVMPolly Polly)
+  # Only add the dependencies that are not part of LLVM. The latter are assumed
+  # to be already available in the address space the module is loaded into.
+  # Adding them once more would have the effect that both copies try to register
+  # the same command line options, to which LLVM reacts with an error.
+  # If Polly-ACC is enabled, the NVPTX target is also expected to reside in the
+  # hosts. This is not the case for bugpoint. Use LLVM_POLLY_LINK_INTO_TOOLS=ON
+  # instead which will automatically resolve the additional dependencies by
+  # Polly.
+  target_link_libraries(LLVMPolly ${ISL_TARGET})
+  if (GPU_CODEGEN)
+    target_link_libraries(LLVMPolly PollyPPCG)
+  endif ()
 
   set_target_properties(LLVMPolly
     PROPERTIES
     LINKER_LANGUAGE CXX
     PREFIX "")
 endif ()
 
 if (TARGET intrinsics_gen)
   # Check if we are building as part of an LLVM build
   add_dependencies(Polly intrinsics_gen)
 endif()
 

unittests/CMakeLists.txt

 add_custom_target(PollyUnitTests)
 set_target_properties(PollyUnitTests PROPERTIES FOLDER "Polly")
 
 # add_polly_unittest(test_dirname file1.cpp file2.cpp)
 #
 # Will compile the list of files together and link against Polly and its dependences.
 function(add_polly_unittest test_name)
   if(COMMAND add_unittest)
     add_unittest(PollyUnitTests ${test_name} ${ARGN})
-    target_link_libraries(${test_name} Polly)
-
-    # The Polly target does not depend on its required libraries, except:
-    # - BUILD_SHARED_LIBS=ON
-    #     in which case calling target_link_libraries again is redundant.
-    # - LLVM_LINK_LLVM_DYLIB=ON
-    #     in which case it depends on libLLVM.so, so no additional libs needed.
-    #     We are also not allowed to link against the plain LLVM* libraries,
-    #     which would result in multiple instances of these to be loaded.
-    if (NOT LLVM_LINK_LLVM_DYLIB)
-      target_link_libraries(${test_name} LLVMCore LLVMSupport LLVMDemangle LLVMipo)
-    endif ()
   else()
     add_executable(${test_name} EXCLUDE_FROM_ALL ${ARGN})
     set_target_properties(${test_name} PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
 
-    target_link_libraries(${test_name} gtest_main gtest Polly ${LLVM_LIBS})
+    target_link_libraries(${test_name} gtest_main gtest)
     add_dependencies(PollyUnitTests ${test_name})
 
     set_property(TARGET ${test_name} PROPERTY FOLDER "Polly")
   endif()
+  target_link_libraries(${test_name} Polly)
 endfunction()
 
 add_subdirectory(Isl)
 add_subdirectory(Flatten)
 add_subdirectory(DeLICM)