Automatically configure MLIR when flang is enabled

This is more friendly than the "Unknown CMake command “mlir_tablegen”."
that would be issued instead.

Differential Revision: https://reviews.llvm.org/D80359

diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index 06b8646..b224393 100644 (file)
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -81,6 +81,10 @@ set(LLVM_ENABLE_PROJECTS "" CACHE STRING
 if( LLVM_ENABLE_PROJECTS STREQUAL "all" )
   set( LLVM_ENABLE_PROJECTS ${LLVM_ALL_PROJECTS})
 endif()
+if ("flang" IN_LIST LLVM_ENABLE_PROJECTS AND NOT "mlir" IN_LIST LLVM_ENABLE_PROJECTS)
+  message(STATUS "Enabling MLIR as a dependency to flang")
+  list(APPEND LLVM_ENABLE_PROJECTS "mlir")
+endif()
 
 # LLVM_ENABLE_PROJECTS_USED is `ON` if the user has ever used the
 # `LLVM_ENABLE_PROJECTS` CMake cache variable.  This exists for