[mlir][examples] Fix bugs in Standlone project's CMakeLists.txt

[christopherbate]

Fixes the following two issues from the Standalone project's
CMakeLists.txt:

• LLVM_DEFINITIONS is formatted as string by LLVMConfig.cmake in a
  manner which will cause unexpected results if the first definition
  in is of the form -Dkey=value. It must be preprocessed before passing
  it to add_definitions, see the recommendation in the LLVM CMake
  documentation.

• The HandleLLVMOptions script resets LLVM_DEFINITIONS to the definitions
  associated with the top-level source directory, so if the project is
  top level, using LLVM_DEFINITIONS after invoking HandleLLVMOptions
  is circular. Invoke HandleLLVMOptions only if the project is top-level
  and only after using LLVM_DEFINITIONS.

[llvmbot]

@llvm/pr-subscribers-mlir

Author: Christopher Bate (christopherbate)

Changes

Fixes the following two issues from the Standalone project's
CMakeLists.txt:

• LLVM_DEFINITIONS is formatted as string by LLVMConfig.cmake in a
  manner which will cause unexpected results if the first definition
  in is of the form -Dkey=value. It must be preprocessed before passing
  it to add_definitions, see the recommendation in the LLVM CMake
  documentation.

• The HandleLLVMOptions script resets LLVM_DEFINITIONS to the definitions
  associated with the top-level source directory, so if the project is
  top level, using LLVM_DEFINITIONS after invoking HandleLLVMOptions
  is circular. Invoke HandleLLVMOptions only if the project is top-level
  and only after using LLVM_DEFINITIONS.

---

Full diff: https://github.com/llvm/llvm-project/pull/127716.diff

1 Files Affected:

• (modified) mlir/examples/standalone/CMakeLists.txt (+6-1)

diff --git a/mlir/examples/standalone/CMakeLists.txt b/mlir/examples/standalone/CMakeLists.txt
index 038242ba1437a..34167dcc7985a 100644
--- a/mlir/examples/standalone/CMakeLists.txt
+++ b/mlir/examples/standalone/CMakeLists.txt
@@ -18,6 +18,12 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   list(APPEND CMAKE_MODULE_PATH "${MLIR_CMAKE_DIR}")
   list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
 
+  # This must go before 'HandleLLVMOptions', otherwise
+  # it has no effect. It shouldn't be required when
+  # building via the external projects mechanism.
+  separate_arguments(LLVM_DEFINITIONS_LIST NATIVE_COMMAND ${LLVM_DEFINITIONS})
+  add_definitions(${LLVM_DEFINITIONS_LIST})
+
   include(TableGen)
   include(AddLLVM)
   include(AddMLIR)
@@ -42,7 +48,6 @@ include_directories(${MLIR_INCLUDE_DIRS})
 include_directories(${STANDALONE_SOURCE_DIR}/include)
 include_directories(${STANDALONE_BINARY_DIR}/include)
 link_directories(${LLVM_BUILD_LIBRARY_DIR})
-add_definitions(${LLVM_DEFINITIONS})
 
 add_subdirectory(include)
 add_subdirectory(lib)