[MLIR] Fix MLIR_MAIN_[SRC|INCLUDE]_DIR variables

[ekatz]

Summary

Define MLIR_MAIN_INCLUDE_DIR, as it was not set anywhere.
Set MLIR_MAIN_SRC_DIR to the actual "source directory", and not the "include directory" (as currently set).

[ekatz]

Note that MLIR_MAIN_INCLUDE_DIR is used in almost all (if not all) the CMakeLists.txt in the project.

mlir/CMakeLists.txt

 # MLIR project.
-set(MLIR_MAIN_SRC_DIR ${CMAKE_CURRENT_SOURCE_DIR}/include ) # --src-root
-set(MLIR_INCLUDE_DIR ${CMAKE_CURRENT_BINARY_DIR}/include ) # --includedir
+set(MLIR_MAIN_SRC_DIR     ${CMAKE_CURRENT_SOURCE_DIR}  )
+set(MLIR_MAIN_INCLUDE_DIR ${MLIR_MAIN_SRC_DIR}/include )
 
-set(MLIR_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
-set(MLIR_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
+set(MLIR_SOURCE_DIR  ${CMAKE_CURRENT_SOURCE_DIR})
+set(MLIR_BINARY_DIR  ${CMAKE_CURRENT_BINARY_DIR})
+set(MLIR_INCLUDE_DIR ${CMAKE_CURRENT_BINARY_DIR}/include)
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules")
 
 include(AddMLIR)
 
 # Installing the headers and docs needs to depend on generating any public
 # tablegen'd targets.
 add_custom_target(mlir-headers)

mlir/cmake/modules/AddMLIR.cmake

function(add_mlir_dialect dialect dialect_namespace)
   mlir_tablegen(${dialect}Dialect.h.inc -gen-dialect-decls -dialect=${dialect_namespace})
   add_public_tablegen_target(MLIR${dialect}IncGen)
   add_dependencies(mlir-headers MLIR${dialect}IncGen)
 endfunction()
 
 # Generate Documentation
 function(add_mlir_doc doc_filename command output_file output_directory)
   set(LLVM_TARGET_DEFINITIONS ${doc_filename}.td)
-  tablegen(MLIR ${output_file}.md ${command} "-I${MLIR_MAIN_SRC_DIR}" "-I${MLIR_INCLUDE_DIR}")
+  tablegen(MLIR ${output_file}.md ${command} "-I${MLIR_MAIN_INCLUDE_DIR}" "-I${MLIR_INCLUDE_DIR}")
   set(GEN_DOC_FILE ${MLIR_BINARY_DIR}/docs/${output_directory}${output_file}.md)
   add_custom_command(
           OUTPUT ${GEN_DOC_FILE}
           COMMAND ${CMAKE_COMMAND} -E copy
                   ${CMAKE_CURRENT_BINARY_DIR}/${output_file}.md
                   ${GEN_DOC_FILE}
           DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/${output_file}.md)
   add_custom_target(${output_file}DocGen DEPENDS ${GEN_DOC_FILE})