CMake: Set LLVM_MAIN_INCLUDE_DIR to LLVM_INCLUDE_DIR

[tstellar]

Summary

LLVM_INCLUDE_DIR comes from LLVMConfig.cmake, which is already available to
us, so we don't need to user llvm-config to query this value.

Also, the value returned by llvm-config is wrong if llvm-config is
installed to a different prefix than the includes.

[chapuni]

The changes themselves look good.
But I don't understand your issue. Did you happen to any cases that llvm-config or --includedir prevents something?

I think we may get rid of llvm-config there in near future. Instead, we should let CMake find LLVM as a package.

Possible steps;

1. Use llvm-config just to inform --cmakedir.
2. Add an option to use find_package(LLVM).
3. Nuke llvm-config stuff. (Then, we might miss consistency of llvm-config...)

[tstellar]

In D32578#739094, @chapuni wrote:

The changes themselves look good.
But I don't understand your issue. Did you happen to any cases that llvm-config or --includedir prevents something?

If you install llvm-config to /usr/libexec/llvm/bin, then llvm-config --includedir will ignore where the include files actually are and always return /usr/libexec/llvm/include

I think we may get rid of llvm-config there in near future. Instead, we should let CMake find LLVM as a package.

Possible steps;

1. Use llvm-config just to inform --cmakedir.
2. Add an option to use find_package(LLVM).
3. Nuke llvm-config stuff. (Then, we might miss consistency of llvm-config...)

This is what I'm looking at doing. This is just one of the preliminary cleanups.

[chapuni]

In D32578#739474, @tstellar wrote:

If you install llvm-config to /usr/libexec/llvm/bin, then llvm-config --includedir will ignore where the include files actually are and always return /usr/libexec/llvm/include

It's a problem in llvm-config, I think. llvm-config should know installed prefix(es).

[mgorny]

LGTM.

CMakeLists.txt

if(NOT MSVC_IDE)
     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_MAIN_INCLUDE_DIR ${INCLUDE_DIR} CACHE PATH "Path to llvm/include")
   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)
 
   find_package(LLVM REQUIRED HINTS "${LLVM_CMAKE_PATH}")
   list(APPEND CMAKE_MODULE_PATH ${LLVM_DIR})
 
+  set(LLVM_MAIN_INCLUDE_DIR ${LLVM_BINARY_DIR}/include)
+
   # They are used as destination of target generators.
   set(LLVM_RUNTIME_OUTPUT_INTDIR ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/bin)
   set(LLVM_LIBRARY_OUTPUT_INTDIR ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX})
   if(WIN32 OR CYGWIN)
     # DLL platform -- put DLLs into bin.
     set(LLVM_SHLIB_OUTPUT_INTDIR ${LLVM_RUNTIME_OUTPUT_INTDIR})
   else()
     set(LLVM_SHLIB_OUTPUT_INTDIR ${LLVM_LIBRARY_OUTPUT_INTDIR})
if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )
   include(VersionFromVCS)
 
   set(PACKAGE_VERSION "${LLVM_PACKAGE_VERSION}")
 
   if (NOT DEFINED LLVM_INCLUDE_TESTS)
     set(LLVM_INCLUDE_TESTS ON)
   endif()
 
-  include_directories("${LLVM_BINARY_DIR}/include" "${LLVM_MAIN_INCLUDE_DIR}")
+  include_directories("${LLVM_MAIN_INCLUDE_DIR}")
   link_directories("${LLVM_LIBRARY_DIR}")
 
   set( CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin )
   set( CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX} )
   set( CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX} )
 
   if(LLVM_INCLUDE_TESTS)
     set(Python_ADDITIONAL_VERSIONS 2.7)