Add LLVM_ENABLE_LLD option to use LLD as C/C++ linker.

Differential revision: https://reviews.llvm.org/D22896


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277093 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -317,6 +317,7 @@ endif()
 option(LLVM_ENABLE_CXX1Y "Compile with C++1y enabled." OFF)
 option(LLVM_ENABLE_LIBCXX "Use libc++ if available." OFF)
 option(LLVM_ENABLE_LIBCXXABI "Use libc++abi when using libc++." OFF)
+option(LLVM_ENABLE_LLD "Use lld as C and C++ linker." OFF)
 option(LLVM_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
 option(LLVM_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
 

cmake/modules/HandleLLVMOptions.cmake

@@ -144,6 +144,12 @@ function(add_flag_or_print_warning flag name)
   endif()
 endfunction()
 
+if(LLVM_ENABLE_LLD)
+  check_cxx_compiler_flag("-fuse-ld=lld" CXX_SUPPORTS_LLD)
+  append_if(CXX_SUPPORTS_LLD "-fuse-ld=lld"
+    CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
+endif()
+
 if( LLVM_ENABLE_PIC )
   if( XCODE )
     # Xcode has -mdynamic-no-pic on by default, which overrides -fPIC. I don't