Add no-unused-but-set-parameter to skip verbose warning

CMakeLists.txt

@@ -41,6 +41,16 @@ set(GC_LIB_SOURCES CACHE INTERNAL "The graph_compiler library source paths")
 set(GC_LIB_INCLUDES CACHE INTERNAL "The graph_compiler library include paths")
 
 add_definitions(${LLVM_DEFINITIONS})
+
+set(GC_MLIR_CXX_FLAGS "")
+# Silence a false positive GCC -Wunused-but-set-parameter warning in constexpr
+# cases, by marking SelectedCase as used. See
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85827 for details. The issue is
+# fixed in GCC 10.
+if(CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "10.0")
+  check_cxx_compiler_flag("-Wno-unused-but-set-parameter" CXX_SUPPORTS_WNO_UNUSED_BUT_SET_PARAMETER)
+  append_if(CXX_SUPPORTS_WNO_UNUSED_BUT_SET_PARAMETER "-Wno-unused-but-set-parameter" GC_MLIR_CXX_FLAGS)
+endif()
 include("cmake/version.cmake")
 
 add_subdirectory(include)

lib/gc/CMakeLists.txt

@@ -1,2 +1,6 @@
+if(GC_MLIR_CXX_FLAGS)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${GC_MLIR_CXX_FLAGS}")
+endif()
+
 add_subdirectory(Dialect)
 add_subdirectory(Transforms)

unittests/CMakeLists.txt

@@ -3,6 +3,9 @@ if (NOT GC_TEST_ENABLE)
     return()
 endif ()
 
+if(GC_MLIR_CXX_FLAGS)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${GC_MLIR_CXX_FLAGS}")
+endif()
 add_definitions(-DMLIR_INCLUDE_TESTS)
 add_custom_target(GCUnitTests)
 set_target_properties(GCUnitTests PROPERTIES FOLDER "MLIR GC Tests")