[CMake] Unify llvm_check_linker_flag and llvm_check_compiler_linker_flag

These have the same purposes but two different implementations.
llvm_check_compiler_linker_flag uses CMAKE_REQUIRED_FLAGS which affects
flags used both for compilation and linking which is problematic because
some flags may be link-only and trigger unused argument warning when set
during compilation. llvm_check_linker_flag does not have this issue so
we chose it as the prevailaing implementation.

Differential Revision: https://reviews.llvm.org/D143052

cmake/Modules/LLVMCheckCompilerLinkerFlag.cmake

@@ -1,35 +0,0 @@
-include(CMakePushCheckState)
-
-include(CheckCompilerFlag OPTIONAL)
-
-if(NOT COMMAND check_compiler_flag)
-  include(CheckCCompilerFlag)
-  include(CheckCXXCompilerFlag)
-endif()
-
-function(llvm_check_compiler_linker_flag lang flag out_var)
-  # If testing a flag with check_c_compiler_flag, it gets added to the compile
-  # command only, but not to the linker command in that test. If the flag
-  # is vital for linking to succeed, the test would fail even if it would
-  # have succeeded if it was included on both commands.
-  #
-  # Therefore, try adding the flag to CMAKE_REQUIRED_FLAGS, which gets
-  # added to both compiling and linking commands in the tests.
-
-  cmake_push_check_state()
-  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${flag}")
-  if(COMMAND check_compiler_flag)
-    check_compiler_flag("${lang}" "" ${out_var})
-  else()
-    # Until the minimum CMAKE version is 3.19
-    # cmake builtin compatible, except we assume lang is C or CXX
-    if("${lang}" STREQUAL "C")
-      check_c_compiler_flag("" ${out_var})
-    elseif("${lang}" STREQUAL "CXX")
-      check_cxx_compiler_flag("" ${out_var})
-    else()
-      message(FATAL_ERROR "\"${lang}\" is not C or CXX")
-    endif()
-  endif()
-  cmake_pop_check_state()
-endfunction()

compiler-rt/cmake/config-ix.cmake

@@ -1,10 +1,10 @@
 include(CMakePushCheckState)
-include(LLVMCheckCompilerLinkerFlag)
+include(LLVMCheckLinkerFlag)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 include(CheckIncludeFiles)
 include(CheckLibraryExists)
-include(LLVMCheckCompilerLinkerFlag)
+include(LLVMCheckLinkerFlag)
 include(CheckSymbolExists)
 include(TestBigEndian)
 
@@ -15,7 +15,7 @@ include(TestBigEndian)
 # libunwind (and the compiler implicit -lunwind wouldn't succeed as the newly
 # built libunwind isn't installed yet). For those cases, it'd be good to
 # link with --uwnindlib=none. Check if that option works.
-llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
+llvm_check_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
 
 check_library_exists(c fopen "" COMPILER_RT_HAS_LIBC)
 if (COMPILER_RT_USE_BUILTINS_LIBRARY)
@@ -195,12 +195,12 @@ check_library_exists(c++ __cxa_throw "" COMPILER_RT_HAS_LIBCXX)
 check_library_exists(stdc++ __cxa_throw "" COMPILER_RT_HAS_LIBSTDCXX)
 
 # Linker flags.
-llvm_check_compiler_linker_flag(C "-Wl,-z,text" COMPILER_RT_HAS_Z_TEXT)
-llvm_check_compiler_linker_flag(C "-fuse-ld=lld" COMPILER_RT_HAS_FUSE_LD_LLD_FLAG)
+llvm_check_linker_flag(C "-Wl,-z,text" COMPILER_RT_HAS_Z_TEXT)
+llvm_check_linker_flag(C "-fuse-ld=lld" COMPILER_RT_HAS_FUSE_LD_LLD_FLAG)
 
 if(${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
   set(VERS_COMPAT_OPTION "-Wl,-z,gnu-version-script-compat")
-  llvm_check_compiler_linker_flag(C "${VERS_COMPAT_OPTION}" COMPILER_RT_HAS_GNU_VERSION_SCRIPT_COMPAT)
+  llvm_check_linker_flag(C "${VERS_COMPAT_OPTION}" COMPILER_RT_HAS_GNU_VERSION_SCRIPT_COMPAT)
 endif()
 
 set(DUMMY_VERS ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/dummy.vers)
@@ -211,10 +211,10 @@ if(COMPILER_RT_HAS_GNU_VERSION_SCRIPT_COMPAT)
   # -z gnu-version-script-compat.
   string(APPEND VERS_OPTION " ${VERS_COMPAT_OPTION}")
 endif()
-llvm_check_compiler_linker_flag(C "${VERS_OPTION}" COMPILER_RT_HAS_VERSION_SCRIPT)
+llvm_check_linker_flag(C "${VERS_OPTION}" COMPILER_RT_HAS_VERSION_SCRIPT)
 
 if(ANDROID)
-  llvm_check_compiler_linker_flag(C "-Wl,-z,global" COMPILER_RT_HAS_Z_GLOBAL)
+  llvm_check_linker_flag(C "-Wl,-z,global" COMPILER_RT_HAS_Z_GLOBAL)
   check_library_exists(log __android_log_write "" COMPILER_RT_HAS_LIBLOG)
 endif()
 
@@ -478,7 +478,7 @@ if(APPLE)
     -lc++
     -lc++abi)
 
-  llvm_check_compiler_linker_flag(C "-fapplication-extension" COMPILER_RT_HAS_APP_EXTENSION)
+  llvm_check_linker_flag(C "-fapplication-extension" COMPILER_RT_HAS_APP_EXTENSION)
   if(COMPILER_RT_HAS_APP_EXTENSION)
     list(APPEND DARWIN_COMMON_LINK_FLAGS "-fapplication-extension")
   endif()

libcxx/cmake/config-ix.cmake

@@ -1,6 +1,6 @@
 include(CMakePushCheckState)
 include(CheckLibraryExists)
-include(LLVMCheckCompilerLinkerFlag)
+include(LLVMCheckLinkerFlag)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 include(CheckCSourceCompiles)
@@ -12,7 +12,7 @@ include(CheckCSourceCompiles)
 # libunwind (and the compiler implicit -lunwind wouldn't succeed as the newly
 # built libunwind isn't installed yet). For those cases, it'd be good to
 # link with --uwnindlib=none. Check if that option works.
-llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)
+llvm_check_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)
 
 if(WIN32 AND NOT MINGW)
   # NOTE(compnerd) this is technically a lie, there is msvcrt, but for now, lets

libunwind/cmake/config-ix.cmake

@@ -2,14 +2,14 @@ include(CMakePushCheckState)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 include(CheckLibraryExists)
-include(LLVMCheckCompilerLinkerFlag)
+include(LLVMCheckLinkerFlag)
 include(CheckSymbolExists)
 include(CheckCSourceCompiles)
 
 # The compiler driver may be implicitly trying to link against libunwind, which
 # might not work if libunwind doesn't exist yet. Try to check if
 # --unwindlib=none is supported, and use that if possible.
-llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)
+llvm_check_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)
 
 check_library_exists(c fopen "" LIBUNWIND_HAS_C_LIB)
 
@@ -31,11 +31,11 @@ endif()
 # required for the link to go through. We remove sanitizers from the
 # configuration checks to avoid spurious link errors.
 
-llvm_check_compiler_linker_flag(CXX "-nostdlib++" CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+llvm_check_linker_flag(CXX "-nostdlib++" CXX_SUPPORTS_NOSTDLIBXX_FLAG)
 if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
   set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
 else()
-  llvm_check_compiler_linker_flag(C "-nodefaultlibs" C_SUPPORTS_NODEFAULTLIBS_FLAG)
+  llvm_check_linker_flag(C "-nodefaultlibs" C_SUPPORTS_NODEFAULTLIBS_FLAG)
   if (C_SUPPORTS_NODEFAULTLIBS_FLAG)
     set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
   endif()

runtimes/CMakeLists.txt

@@ -78,7 +78,7 @@ set(LLVM_CMAKE_DIR ${LLVM_MAIN_SRC_DIR}/cmake/modules)
 set(LLVM_PATH ${CMAKE_CURRENT_SOURCE_DIR}/../llvm)
 
 include(CheckLibraryExists)
-include(LLVMCheckCompilerLinkerFlag)
+include(LLVMCheckLinkerFlag)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 
@@ -110,7 +110,7 @@ if (NOT LLVM_RUNTIMES_LINKING_WORKS)
   # --unwindlib=none is supported, and use that if possible.
   # Don't add this if not necessary to fix linking, as it can break using
   # e.g. ASAN/TSAN.
-  llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)
+  llvm_check_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)
   if (CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)
     set(ORIG_CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")
     set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} --unwindlib=none")
@@ -140,7 +140,7 @@ endif()
 # Check for -nostdlib++ first; if there's no C++ standard library yet,
 # all check_cxx_compiler_flag commands will fail until we add -nostdlib++
 # (or -nodefaultlibs).
-llvm_check_compiler_linker_flag(CXX "-nostdlib++" CXX_SUPPORTS_NOSTDLIBXX_FLAG)
+llvm_check_linker_flag(CXX "-nostdlib++" CXX_SUPPORTS_NOSTDLIBXX_FLAG)
 if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
   set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
 endif()