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[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
This commit is contained in:
Martin Storsjö 2021-03-19 13:45:52 +02:00
parent 972b6a3a34
commit c027553d95
1 changed files with 8 additions and 5 deletions
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13
llvm/cmake/modules/HandleLLVMOptions.cmake
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@ -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.