[llvm] c027553 - [cmake] Disable GCC 9's -Wpessimizing-move

[Martin Storsjö via llvm-commits]

Author: Martin Storsjö
Date: 2021-03-22T15:14:46+02:00
New Revision: c027553d95fa481e873d47186e761bddc6f12d92

URL: https://github.com/llvm/llvm-project/commit/c027553d95fa481e873d47186e761bddc6f12d92
DIFF: https://github.com/llvm/llvm-project/commit/c027553d95fa481e873d47186e761bddc6f12d92.diff

LOG: [cmake] Disable GCC 9's -Wpessimizing-move

Similar to the existing code for disabling GCC's -Wredudant-move,
also check for the -Wpessimizing-move option and disable it if
possible.

This silences another bunch of noisy warnings when building LLVM
with GCC 9.

As noted for -Wredundant-move, the code can't be fixed to silence the
warnings while retaining support for older compilers.

Differential Revision: https://reviews.llvm.org/D98942

Added: 
    

Modified: 
    llvm/cmake/modules/HandleLLVMOptions.cmake

Removed: 
    


################################################################################
diff  --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
index 0c575b6608b0..8b64694757e9 100644
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -690,14 +690,17 @@ if (LLVM_ENABLE_WARNINGS AND (LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
   check_cxx_compiler_flag("-Wclass-memaccess" CXX_SUPPORTS_CLASS_MEMACCESS_FLAG)
   append_if(CXX_SUPPORTS_CLASS_MEMACCESS_FLAG "-Wno-class-memaccess" CMAKE_CXX_FLAGS)
 
-  # Disable -Wredundant-move on GCC>=9. GCC wants to remove std::move in code
-  # like "A foo(ConvertibleToA a) { return std::move(a); }", but this code does
-  # not compile (or uses the copy constructor instead) on clang<=3.8. Clang also
-  # has a -Wredundant-move, but it only fires when the types match exactly, so
-  # we can keep it here.
+  # Disable -Wredundant-move and -Wpessimizing-move on GCC>=9. GCC wants to
+  # remove std::move in code like "A foo(ConvertibleToA a) {
+  # return std::move(a); }", but this code does not compile (or uses the copy
+  # constructor instead) on clang<=3.8. Clang also has a -Wredundant-move and
+  # -Wpessimizing-move, but they only fire when the types match exactly, so we
+  # can keep them here.
   if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     check_cxx_compiler_flag("-Wredundant-move" CXX_SUPPORTS_REDUNDANT_MOVE_FLAG)
     append_if(CXX_SUPPORTS_REDUNDANT_MOVE_FLAG "-Wno-redundant-move" CMAKE_CXX_FLAGS)
+    check_cxx_compiler_flag("-Wpessimizing-move" CXX_SUPPORTS_PESSIMIZING_MOVE_FLAG)
+    append_if(CXX_SUPPORTS_PESSIMIZING_MOVE_FLAG "-Wno-pessimizing-move" CMAKE_CXX_FLAGS)
   endif()
 
   # The LLVM libraries have no stable C++ API, so -Wnoexcept-type is not useful.