Merge pull request #7 from gottesmm/add-support-for-enable-lto

Add support for -DLLVM_ENABLE_LTO

Author: gottesmm

cmake/modules/HandleLLVMOptions.cmake

@@ -635,6 +635,19 @@ append_if(LLVM_BUILD_INSTRUMENTED "-fprofile-instr-generate"
   CMAKE_EXE_LINKER_FLAGS
   CMAKE_SHARED_LINKER_FLAGS)
 
+set(LLVM_ENABLE_LTO OFF CACHE STRING "Build LLVM with LTO. May be specified as Thin or Full to use a particular kind of LTO")
+string(TOUPPER "${LLVM_ENABLE_LTO}" uppercase_LLVM_ENABLE_LTO)
+if(uppercase_LLVM_ENABLE_LTO STREQUAL "THIN")
+  append("-flto=thin" CMAKE_CXX_FLAGS CMAKE_C_FLAGS
+                      CMAKE_EXE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
+elseif(uppercase_LLVM_ENABLE_LTO STREQUAL "FULL")
+  append("-flto=full" CMAKE_CXX_FLAGS CMAKE_C_FLAGS
+                 CMAKE_EXE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
+elseif(LLVM_ENABLE_LTO)
+  append("-flto" CMAKE_CXX_FLAGS CMAKE_C_FLAGS
+                 CMAKE_EXE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
+endif()
+
 # Plugin support
 # FIXME: Make this configurable.
 if(WIN32 OR CYGWIN)

docs/CMake.rst

@@ -347,6 +347,11 @@ LLVM-specific variables
   are ``Address``, ``Memory``, ``MemoryWithOrigins``, ``Undefined``, ``Thread``,
   and ``Address;Undefined``. Defaults to empty string.
 
+**LLVM_ENABLE_LTO**:STRING
+  Add ``-flto`` or ``-flto=`` flags to the compile and link command
+  lines, enabling link-time optimization. Possible values are ``Off``,
+  ``On``, ``Thin`` and ``Full``. Defaults to OFF.
+
 **LLVM_PARALLEL_COMPILE_JOBS**:STRING
   Define the maximum number of concurrent compilation jobs.