Better Clang LTO: install LLVMgold to bfd-plugins.

ar will automatically load any plugins that are installed to
../lib/bfd-plugins. Rather than needing to fix all of our build
systems, we can make LTO Just Work if we copy the gold plugin (and
its dependencies) into the binutils directory.

I've also added a test for cmake LTO.

Test: ./validate.py --filter flto
Bug: android/ndk#108
Change-Id: I1db61b8ef3405474c64ff20478daa86ca41ab3b3

build/core/build-binary.mk

@@ -616,12 +616,6 @@ ifeq (true,$(thin_archive))
     ar_flags := $(ar_flags)T
 endif
 
-ifeq (clang,$(NDK_TOOLCHAIN_VERSION))
-    ifneq ($(HOST_OS),windows)
-        ar_flags += --plugin $(TARGET_AR_PLUGIN)
-    endif
-endif
-
 $(LOCAL_BUILT_MODULE): PRIVATE_ABI := $(TARGET_ARCH_ABI)
 $(LOCAL_BUILT_MODULE): PRIVATE_AR := $(TARGET_AR) $(ar_flags) $(TARGET_AR_FLAGS)
 $(LOCAL_BUILT_MODULE): PRIVATE_AR_OBJECTS := $(ar_objects)

build/core/default-build-commands.mk

@@ -154,7 +154,6 @@ ifneq (clang,$(NDK_TOOLCHAIN_VERSION))
     TARGET_AR = $(TOOLCHAIN_PREFIX)gcc-ar
 else
     TARGET_AR = $(TOOLCHAIN_PREFIX)ar
-    TARGET_AR_PLUGIN = $(LLVM_TOOLCHAIN_PREBUILT_ROOT)/lib64/LLVMgold.so
 endif
 
 TARGET_ARFLAGS := crsD

checkbuild.py

@@ -297,6 +297,28 @@ def install_arch(self, out_dir, host, arch):
 
         ndk.builds.install_directory(toolchain_path, install_path)
 
+        if not host.startswith('windows'):
+            so = '.so'
+            if host == 'darwin':
+                so = '.dylib'
+
+            clang_libs = build_support.android_path(
+                'prebuilts/ndk/current/toolchains', host_tag, 'llvm/lib64')
+            llvmgold = os.path.join(clang_libs, 'LLVMgold.so')
+            libcxx = os.path.join(clang_libs, 'libc++' + so)
+            libllvm = os.path.join(clang_libs, 'libLLVM' + so)
+
+            bfd_plugins = os.path.join(install_path, 'lib/bfd-plugins')
+            os.makedirs(bfd_plugins)
+            shutil.copy2(llvmgold, bfd_plugins)
+
+            # The rpath on LLVMgold.so is ../lib64, so we have to install to
+            # lib/lib64 to have it be in the right place :(
+            lib_dir = os.path.join(install_path, 'lib/lib64')
+            os.makedirs(lib_dir)
+            shutil.copy2(libcxx, lib_dir)
+            shutil.copy2(libllvm, lib_dir)
+
 
 class ShaderTools(ndk.builds.InvokeBuildModule):
     name = 'shader-tools'

tests/build/flto/CMakeLists.txt

@@ -0,0 +1,10 @@
+cmake_minimum_required(VERSION 3.6.0)
+
+SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -flto")
+SET(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -flto")
+SET(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -fuse-ld=gold")
+
+add_library(bar STATIC jni/bar.c)
+
+add_executable(flto jni/flto.c)
+target_link_libraries(flto bar)