Define/guard MLIR_STANDALONE_BUILD LLVM_LIBRARY_OUTPUT_INTDIR var.

[stellaraccident]

Summary

It looks like MLIR is using the more modern CMAKE_LIBRARY_OUTPUT_DIRECTORY, but AddLLVM still uses this older LLVM specific alias.

In the specific case I was running into, the empty variable was causing -Wl,-rpath-link, on the command line, causing the following argument to be swallowed. This was maddening, because the following argument was the .o file containing main and I was getting main undefined errors when it was clearly there. This is egregious enough that I chose to guard it.

[mehdi_amini]

Oh wow, yet another fun debugging story :)

[jpienaar]

Thanks!

[tmatheson]

I don't think this is the right fix, as all the other uses of LLVM_LIBRARY_OUTPUT_INTDIR in AddLLVM are optional. See for example D13215.

Anyone building against an installed LLVM now has to define LLVM_LIBRARY_OUTPUT_INTDIR or their build will fail.

[stellaraccident]

In D153373#4437945, @tmatheson wrote:

I don't think this is the right fix, as all the other uses of LLVM_LIBRARY_OUTPUT_INTDIR in AddLLVM are optional. See for example D13215.

Anyone building against an installed LLVM now has to define LLVM_LIBRARY_OUTPUT_INTDIR or their build will fail.

Good point. Shall I patch this to only add the rpath-link flag if that is set.

TBH - I was looking at this locally and just saw that it was non optional in fact (it. It corrupts the liner command line) and didn't ask the question as to whether the entire check should be conditioned.

Let me do a revert because it sounds like it will break people. Then can roll forward a proper fix.

llvm/cmake/modules/AddLLVM.cmake

elseif(UNIX)
     set(_build_rpath "\$ORIGIN/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
     set(_install_rpath "\$ORIGIN/../lib${LLVM_LIBDIR_SUFFIX}")
     if(${CMAKE_SYSTEM_NAME} MATCHES "(FreeBSD|DragonFly)")
       set_property(TARGET ${name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,-z,origin ")
     endif()
     if(LLVM_LINKER_IS_GNULD)
       # $ORIGIN is not interpreted at link time by ld.bfd
+      if(NOT LLVM_LIBRARY_OUTPUT_INTDIR)
+        message(SEND_ERROR "Project does not define LLVM_LIBRARY_OUTPUT_INTDIR and it is required")
+      endif()
       set_property(TARGET ${name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,-rpath-link,${LLVM_LIBRARY_OUTPUT_INTDIR} ")
     endif()
   else()
     return()
   endif()
 
   # Enable BUILD_WITH_INSTALL_RPATH unless CMAKE_BUILD_RPATH is set and not

mlir/CMakeLists.txt

if(MLIR_STANDALONE_BUILD)
   if(EXISTS ${UNITTEST_DIR}/googletest/include/gtest/gtest.h)
     add_subdirectory(${UNITTEST_DIR} third-party/unittest)
   endif()
 
   set(CMAKE_LIBRARY_OUTPUT_DIRECTORY
     "${CMAKE_CURRENT_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}")
   set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/bin")
 
+  # Some LLVM CMake utilities use these aliases for the CMake builtin variables.
+  # We set them for compatibility.
+  set(LLVM_LIBRARY_OUTPUT_INTDIR ${CMAKE_LIBRARY_OUTPUT_DIRECTORY})
+  set(LLVM_RUNTIME_OUTPUT_INTDIR ${CMAKE_RUNTIME_OUTPUT_DIRECTORY})
+
   set(LLVM_LIT_ARGS "-sv" CACHE STRING "Default options for lit")
 endif()
 
 set(MLIR_TOOLS_INSTALL_DIR "${CMAKE_INSTALL_BINDIR}" CACHE PATH
     "Path for binary subdirectory (defaults to '${CMAKE_INSTALL_BINDIR}')")
 mark_as_advanced(MLIR_TOOLS_INSTALL_DIR)
 
 set(MLIR_MAIN_SRC_DIR     ${CMAKE_CURRENT_SOURCE_DIR}  )