CMakeLists: Don't set LLVM_MAIN_SRC_DIR when building stand-alone clang

[tstellar]

Summary

clang was using LLVM_MAIN_SRC_DIR to search for lit.py to use for
running clang's lit tests. This was dangerous though, because
LLVM_MAIN_SRC_DIR was determined by using llvm-config --src-root
and this directory may have been modified since llvm-config was
built (e.g. User builds and install llvm trunk and then checks out the
release_40 branch in their source tree).

[chapuni]

Let me know steps for testing that you suppose.
I guess;

• Use installed version of lit via virtualenv.
• Use out-of-tree version of gtest.
• Use another build tree to use FileCheck &c.

I know the clause CLANG_BUILT_STANDALONE would be made simpler if we could abandon testing in standalone build.

[tstellar]

In D32595#740222, @chapuni wrote:

Let me know steps for testing that you suppose.
I guess;

• Use installed version of lit via virtualenv.

Not necessarily via virtualenv, either by installing the lit pypi package or using a distro package: https://admin.fedoraproject.org/pkgdb/package/rpms/python-lit/

• Use out-of-tree version of gtest.

I don't really have a plan for gtest, but this already doesn't work for out of tree builds (unless you have the source tree on your system, but I don't think we should be relying on this).

• Use another build tree to use FileCheck &c.

These could come from a build tree or could be installed on this system.

I know the clause CLANG_BUILT_STANDALONE would be made simpler if we could abandon testing in standalone build.

[beanz]

Is this really something we should be supporting? Building and testing clang with potentially out-of-sync lit or gtest seems undesirable to me.

It is worth noting that we do have mods to gtest, so supporting any standard distribution of it seems like a not great idea. The general approach in the past for standalone builds has been to disable testing unless an LLVM source tree is available, and I think that might be the right approach.

Also, this all kinda becomes moot if LLVM moves to a mono-repo (really not trying to troll here), because people actively developing LLVM projects will basically be forced to have LLVM source trees anyways.

Thoughts?

[mgorny]

This is going to break Gentoo. We're relying on the ability to specify LLVM_MAIN_SRC_DIR to provide unpacked LLVM sources with gtest. Without that, I don't see how we can use tests.

[mgorny]

(note that I don't mind removing the llvm-config bit for it; but we need the cache variable to stay)

[tstellar]

In D32595#769044, @beanz wrote:

Is this really something we should be supporting? Building and testing clang with potentially out-of-sync lit or gtest seems undesirable to me.

This is actually what this patch is trying to avoid. For example prior to this patch, if you build and install llvm trunk to /usr/local, and then checkout an older stable branch in your llvm tree, when you try and build clang from trunk using the llvm install from /usr/local, it will pull lit and gtest from the LLVM source tree which is now much older than the checkout of clang you are using.

It is worth noting that we do have mods to gtest, so supporting any standard distribution of it seems like a not great idea. The general approach in the past for standalone builds has been to disable testing unless an LLVM source tree is available, and I think that might be the right approach.

Also, this all kinda becomes moot if LLVM moves to a mono-repo (really not trying to troll here), because people actively developing LLVM projects will basically be forced to have LLVM source trees anyways.

Thoughts?

[beanz]

Ah. I see what you're saying. I was thinking of the mismatch in a different way, but your solution makes sense. LGTM.

[chapuni]

I don't think this would be ready to land.

[mgorny]

Could you please rebase? I'm pretty sure this breaks our use but I can't test since it no longer applies cleanly.

CMakeLists.txt

set(LLVM_ENABLE_ASSERTIONS ${ENABLE_ASSERTIONS}
       CACHE BOOL "Enable assertions")
     # Assertions should follow llvm-config's.
     mark_as_advanced(LLVM_ENABLE_ASSERTIONS)
   endif()
 
   set(LLVM_TOOLS_BINARY_DIR ${TOOLS_BINARY_DIR} CACHE PATH "Path to llvm/bin")
   set(LLVM_LIBRARY_DIR ${LIBRARY_DIR} CACHE PATH "Path to llvm/lib")
   set(LLVM_BINARY_DIR ${LLVM_OBJ_ROOT} CACHE PATH "Path to LLVM build tree")
-  set(LLVM_MAIN_SRC_DIR ${MAIN_SRC_DIR} CACHE PATH "Path to LLVM source tree")
 
   # Normalize LLVM_CMAKE_PATH. --cmakedir might contain backslashes.
   # CMake assumes slashes as PATH.
   file(TO_CMAKE_PATH ${LLVM_CONFIG_CMAKE_PATH} LLVM_CMAKE_PATH)
 
   find_program(LLVM_TABLEGEN_EXE "llvm-tblgen" ${LLVM_TOOLS_BINARY_DIR}
     NO_DEFAULT_PATH)
 
Please install Python or specify the PYTHON_EXECUTABLE CMake variable.")
 
     # Check prebuilt llvm/utils.
     if(EXISTS ${LLVM_TOOLS_BINARY_DIR}/FileCheck${CMAKE_EXECUTABLE_SUFFIX}
         AND EXISTS ${LLVM_TOOLS_BINARY_DIR}/count${CMAKE_EXECUTABLE_SUFFIX}
         AND EXISTS ${LLVM_TOOLS_BINARY_DIR}/not${CMAKE_EXECUTABLE_SUFFIX})
       set(LLVM_UTILS_PROVIDED ON)
     endif()
 
-    if(EXISTS ${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py)
-      # Note: path not really used, except for checking if lit was found
-      set(LLVM_LIT ${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py)
-      if(NOT LLVM_UTILS_PROVIDED)
-        add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/FileCheck utils/FileCheck)
-        add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/count utils/count)
-        add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/not utils/not)
-        set(LLVM_UTILS_PROVIDED ON)
-        set(CLANG_TEST_DEPS FileCheck count not)
-      endif()
-      set(UNITTEST_DIR ${LLVM_MAIN_SRC_DIR}/utils/unittest)
-      if(EXISTS ${UNITTEST_DIR}/googletest/include/gtest/gtest.h
-          AND NOT EXISTS ${LLVM_LIBRARY_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}gtest${CMAKE_STATIC_LIBRARY_SUFFIX}
-          AND EXISTS ${UNITTEST_DIR}/CMakeLists.txt)
-        add_subdirectory(${UNITTEST_DIR} utils/unittest)
-      endif()
-    else()
-      # Seek installed Lit.
-      find_program(LLVM_LIT
-                   NAMES llvm-lit lit.py lit
-                   PATHS "${LLVM_MAIN_SRC_DIR}/utils/lit"
-                   DOC "Path to lit.py")
-    endif()
+                 PATHS "${LLVM_TOOLS_BINARY_DIR}"
 
     if(LLVM_LIT)
       # Define the default arguments to use with 'lit', and an option for the user
       # to override.
       set(LIT_ARGS_DEFAULT "-sv")
       if (MSVC OR XCODE)
         set(LIT_ARGS_DEFAULT "${LIT_ARGS_DEFAULT} --no-progress-bar")
       endif()
if(NOT EXISTS ${CLANG_ORDER_FILE})
     else()
       message(FATAL_ERROR "Specified order file '${CLANG_ORDER_FILE}' does not exist.")
     endif()
   endif()
 endif()
 
 
 if( CLANG_INCLUDE_TESTS )
-  if(EXISTS ${LLVM_MAIN_SRC_DIR}/utils/unittest/googletest/include/gtest/gtest.h)
-    add_subdirectory(unittests)
-    list(APPEND CLANG_TEST_DEPS ClangUnitTests)
-    list(APPEND CLANG_TEST_PARAMS
-      clang_unit_site_config=${CMAKE_CURRENT_BINARY_DIR}/test/Unit/lit.site.cfg
-      )
-  endif()
+
   add_subdirectory(test)
 
   if(CLANG_BUILT_STANDALONE)
     # Add a global check rule now that all subdirectories have been traversed
     # and we know the total set of lit testsuites.
     get_property(LLVM_LIT_TESTSUITES GLOBAL PROPERTY LLVM_LIT_TESTSUITES)
     get_property(LLVM_LIT_PARAMS GLOBAL PROPERTY LLVM_LIT_PARAMS)
     get_property(LLVM_LIT_DEPENDS GLOBAL PROPERTY LLVM_LIT_DEPENDS)
     get_property(LLVM_LIT_EXTRA_ARGS GLOBAL PROPERTY LLVM_LIT_EXTRA_ARGS)
     add_lit_target(check-all
       "Running all regression tests"
       ${LLVM_LIT_TESTSUITES}
       PARAMS ${LLVM_LIT_PARAMS}
       DEPENDS ${LLVM_LIT_DEPENDS}
       ARGS ${LLVM_LIT_EXTRA_ARGS}
       )
+  else()
+    if(EXISTS ${LLVM_MAIN_SRC_DIR}/utils/unittest/googletest/include/gtest/gtest.h)
+      add_subdirectory(unittests)
+      list(APPEND CLANG_TEST_DEPS ClangUnitTests)
+      list(APPEND CLANG_TEST_PARAMS
+        clang_unit_site_config=${CMAKE_CURRENT_BINARY_DIR}/test/Unit/lit.site.cfg
+        )
+    endif()
   endif()
   add_subdirectory(utils/perf-training)
 endif()
 
 option(CLANG_INCLUDE_DOCS "Generate build targets for the Clang docs."
   ${LLVM_INCLUDE_DOCS})
 if( CLANG_INCLUDE_DOCS )
   add_subdirectory(docs)