[llvm] [cmake] Provide split include paths in LLVMConfig

[mgorny]

Summary

Modify LLVMConfig to provide split variables for in-source and generated
include paths. Currently, it uses a single value for both
LLVM_INCLUDE_DIRS and LLVM_INCLUDE_DIR which works for install tree but
fails hard at build tree (where LLVM_INCLUDE_DIR incorrectly contains
multiple values).

Instead, put the generated directory in LLVM_INCLUDE_DIR, and the source
tree in LLVM_MAIN_INCLUDE_DIR which is consistent with in-LLVM builds.
For install tree, both variables will have the same value.

[sgraenitz]

Can't speak for all the subprojects, but with D57995 this should work for LLDB.

[mgorny]

Getting some more people for their opinion on this.

[rnk]

It seems like we could move clients of the single variable, LLVM_INCLUDE_DIR, to the LLVM_INCLUDE_DIRS list instead of doing this. Are there any reasons why that doesn't work for some clients?
This new arrangement bakes in the idea that LLVM has at most two include dirs, which is OK, I doubt we'll break that assumption.

[mgorny]

Yeah, I was thinking of doing that too (in particular making TableGen.cmake use it instead of LLVM_MAIN_INCLUDE_DIR) but I'm not sure if someone doesn't have some obscure use case I'd break this way. My main concern is that other packages had LLVM_MAIN_INCLUDE_DIR as cache variable for stand-alone builds, so people could've overrode it independently of LLVM_INCLUDE_DIRS.

[xiaobai]

Subscribing @compnerd so that he can properly rebase D58109 after this change (or a change like it) goes in.

[rnk]

lgtm

llvm/cmake/modules/CMakeLists.txt

 set(LLVM_BUILD_LIBRARY_DIR \"${LLVM_LIBRARY_DIR}\")
 set(LLVM_BUILD_MAIN_INCLUDE_DIR \"${LLVM_MAIN_INCLUDE_DIR}\")
 set(LLVM_BUILD_MAIN_SRC_DIR \"${LLVM_MAIN_SRC_DIR}\")
 ")
 set(LLVM_CONFIG_INCLUDE_DIRS
   "${LLVM_MAIN_INCLUDE_DIR}"
   "${LLVM_INCLUDE_DIR}"
   )
+set(LLVM_CONFIG_INCLUDE_DIR
+  "${LLVM_INCLUDE_DIR}"
+  )
+set(LLVM_CONFIG_MAIN_INCLUDE_DIR
+  "${LLVM_MAIN_INCLUDE_DIR}"
+  )
 set(LLVM_CONFIG_LIBRARY_DIRS
   "${LLVM_LIBRARY_DIR}"
   )
 set(LLVM_CONFIG_CMAKE_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
 set(LLVM_CONFIG_BINARY_DIR "${LLVM_BINARY_DIR}")
 set(LLVM_CONFIG_TOOLS_BINARY_DIR "${LLVM_TOOLS_BINARY_DIR}")
 
 if (LLVM_LINK_LLVM_DYLIB)

 # Construct the proper number of get_filename_component(... PATH)
 # calls to compute the installation prefix.
 string(REGEX REPLACE "/" ";" _count "${LLVM_INSTALL_PACKAGE_DIR}")
 foreach(p ${_count})
   set(LLVM_CONFIG_CODE "${LLVM_CONFIG_CODE}
 get_filename_component(LLVM_INSTALL_PREFIX \"\${LLVM_INSTALL_PREFIX}\" PATH)")
 endforeach(p)
 set(LLVM_CONFIG_INCLUDE_DIRS "\${LLVM_INSTALL_PREFIX}/include")
+set(LLVM_CONFIG_INCLUDE_DIR "${LLVM_CONFIG_INCLUDE_DIRS}")
+set(LLVM_CONFIG_MAIN_INCLUDE_DIR "${LLVM_CONFIG_INCLUDE_DIRS}")
 set(LLVM_CONFIG_LIBRARY_DIRS "\${LLVM_INSTALL_PREFIX}/lib\${LLVM_LIBDIR_SUFFIX}")
 set(LLVM_CONFIG_CMAKE_DIR "\${LLVM_INSTALL_PREFIX}/${LLVM_INSTALL_PACKAGE_DIR}")
 set(LLVM_CONFIG_BINARY_DIR "\${LLVM_INSTALL_PREFIX}")
 set(LLVM_CONFIG_TOOLS_BINARY_DIR "\${LLVM_INSTALL_PREFIX}/bin")
 set(LLVM_CONFIG_EXPORTS_FILE "\${LLVM_CMAKE_DIR}/LLVMExports.cmake")
 set(LLVM_CONFIG_EXPORTS "${LLVM_EXPORTS}")
 configure_file(
   LLVMConfig.cmake.in

llvm/cmake/modules/LLVMConfig.cmake.in

 
 set(LLVM_ON_UNIX @LLVM_ON_UNIX@)
 
 set(LLVM_LIBDIR_SUFFIX @LLVM_LIBDIR_SUFFIX@)
 
 set(LLVM_INCLUDE_DIRS "@LLVM_CONFIG_INCLUDE_DIRS@")
 set(LLVM_LIBRARY_DIRS "@LLVM_CONFIG_LIBRARY_DIRS@")
 
-# These variables are duplicated, but they must match the LLVM variables of the
-# same name. The variables ending in "S" could some day become lists, and are
-# preserved for convention and compatibility.
-set(LLVM_INCLUDE_DIR "@LLVM_CONFIG_INCLUDE_DIRS@")
+# These variables are duplicated for install tree but they have different
+# values for build tree.  LLVM_INCLUDE_DIRS contains both source
+# and generated include directories while the following variables have
+# them split.
+set(LLVM_INCLUDE_DIR "@LLVM_CONFIG_INCLUDE_DIR@")
+set(LLVM_MAIN_INCLUDE_DIR "@LLVM_CONFIG_MAIN_INCLUDE_DIR@")
 set(LLVM_LIBRARY_DIR "@LLVM_CONFIG_LIBRARY_DIRS@")
 
 set(LLVM_DEFINITIONS "@LLVM_DEFINITIONS@")
 set(LLVM_CMAKE_DIR "@LLVM_CONFIG_CMAKE_DIR@")
 set(LLVM_BINARY_DIR "@LLVM_CONFIG_BINARY_DIR@")
 set(LLVM_TOOLS_BINARY_DIR "@LLVM_CONFIG_TOOLS_BINARY_DIR@")
 set(LLVM_TOOLS_INSTALL_DIR "@LLVM_TOOLS_INSTALL_DIR@")
 set(LLVM_HAVE_OPT_VIEWER_MODULES @LLVM_HAVE_OPT_VIEWER_MODULES@)