Index: llvm/test/tools/llvm-config/booleans.test
===================================================================
--- llvm/test/tools/llvm-config/booleans.test
+++ llvm/test/tools/llvm-config/booleans.test
@@ -18,7 +18,7 @@
 CHECK-BUILD-MODE-NOT: warning
 
 RUN: llvm-config --build-system 2>&1 | FileCheck --check-prefix=CHECK-BUILD-SYSTEM %s
-CHECK-BUILD-SYSTEM: cmake
+CHECK-BUILD-SYSTEM: {{cmake|gn}}
 CHECK-BUILD-SYSTEM-NOT: error:
 CHECK-BUILD-SYSTEM-NOT: warning
 
Index: llvm/utils/gn/build/libs/edit/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/build/libs/edit/BUILD.gn
@@ -0,0 +1,12 @@
+import("//llvm/utils/gn/build/libs/edit/enable.gni")
+
+config("edit_config") {
+  visibility = [ ":edit" ]
+  libs = [ "edit" ]
+}
+
+group("edit") {
+  if (llvm_enable_libedit) {
+    public_configs = [ ":edit_config" ]
+  }
+}
Index: llvm/utils/gn/build/libs/edit/enable.gni
===================================================================
--- /dev/null
+++ llvm/utils/gn/build/libs/edit/enable.gni
@@ -0,0 +1,3 @@
+declare_args() {
+  llvm_enable_libedit = host_os == "mac"
+}
Index: llvm/utils/gn/build/write_cmake_config.py
===================================================================
--- llvm/utils/gn/build/write_cmake_config.py
+++ llvm/utils/gn/build/write_cmake_config.py
@@ -53,6 +53,9 @@
     values = {}
     for value in args.values:
         key, val = value.split('=', 1)
+        if key in values:
+            print('duplicate key "%s" in args' % key, file=sys.stderr)
+            return 1
         values[key] = val.replace('\\n', '\n')
     unused_values = set(values.keys())
 
Index: llvm/utils/gn/secondary/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/BUILD.gn
+++ llvm/utils/gn/secondary/BUILD.gn
@@ -5,60 +5,8 @@
   deps = [
     "//clang/test",
     "//lld/test",
-    "//llvm/tools/bugpoint",
-    "//llvm/tools/dsymutil",
-    "//llvm/tools/lli",
-    "//llvm/tools/lli/ChildTarget:lli-child-target",
-    "//llvm/tools/llvm-c-test",
-    "//llvm/tools/llvm-cfi-verify",
-    "//llvm/tools/llvm-cov",
-    "//llvm/tools/llvm-cvtres",
-    "//llvm/tools/llvm-cxxdump",
-    "//llvm/tools/llvm-cxxfilt",
-    "//llvm/tools/llvm-cxxmap",
-    "//llvm/tools/llvm-diff",
-    "//llvm/tools/llvm-dwp",
-    "//llvm/tools/llvm-exegesis",
-    "//llvm/tools/llvm-extract",
-    "//llvm/tools/llvm-isel-fuzzer",
-    "//llvm/tools/llvm-link",
-    "//llvm/tools/llvm-mca",
-    "//llvm/tools/llvm-mt",
-    "//llvm/tools/llvm-opt-fuzzer",
-    "//llvm/tools/llvm-opt-report",
-    "//llvm/tools/llvm-rc",
-    "//llvm/tools/llvm-rtdyld",
-    "//llvm/tools/llvm-size",
-    "//llvm/tools/llvm-split",
-    "//llvm/tools/llvm-strings",
-    "//llvm/tools/llvm-undname",
-    "//llvm/tools/llvm-xray",
-    "//llvm/tools/sancov",
-    "//llvm/tools/sanstats",
-    "//llvm/tools/verify-uselistorder",
-    "//llvm/utils/yaml-bench",
+    "//llvm/test",
   ]
-  if (clang_enable_arcmt) {
-    deps += [
-      "//clang/tools/arcmt-test",
-      "//clang/tools/c-arcmt-test",
-    ]
-  }
-  if (clang_enable_static_analyzer) {
-    deps += [
-      "//clang/tools/clang-check",
-      "//clang/tools/clang-func-mapping",
-    ]
-  }
-  if (host_os != "win") {
-    # loadable_modules don't work on Windows.
-    # FIXME: In the CMake build, ENABLE_SHARED makes them work somehow
-    # (but they're off by default there too).
-    deps += [
-      "//llvm/lib/Transforms/Hello",
-      "//llvm/tools/bugpoint-passes",
-    ]
-  }
   testonly = true
 }
 
Index: llvm/utils/gn/secondary/clang/tools/libclang/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/clang/tools/libclang/BUILD.gn
+++ llvm/utils/gn/secondary/clang/tools/libclang/BUILD.gn
@@ -6,7 +6,7 @@
 # - linking in clangTidyPlugin and clangIncludeFixerPlugin from
 #   clang-tools-extra (which doesn't have any GN build files yet)
 # - using libclang.exports
-# - an build target copying the Python bindings
+# - a build target copying the Python bindings
 # - the GN linux build always builds without -fPIC (as if LLVM_ENABLE_PIC=OFF
 #   in the CMake build), so libclang is always a static library on linux
 # - the GN build doesn't have LIBCLANG_BUILD_STATIC
@@ -78,7 +78,12 @@
     ldflags = [
       "-Wl,-compatibility_version,1",
       "-Wl,-current_version,$llvm_version",
+
+      # See llvm_setup_rpath() in CMake.
       "-Wl,-install_name,@rpath/libclang.dylib",
+      "-Wl,-rpath,@loader_path/../lib",
     ]
   }
+
+  # FIXME: Use libclang.exports
 }
Index: llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
+++ llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
@@ -1,6 +1,7 @@
 import("//llvm/lib/Target/targets.gni")
 import("//llvm/triples.gni")
 import("//llvm/utils/gn/build/buildflags.gni")
+import("//llvm/utils/gn/build/libs/edit/enable.gni")
 import("//llvm/utils/gn/build/libs/pthread/enable.gni")
 import("//llvm/utils/gn/build/libs/terminfo/enable.gni")
 import("//llvm/utils/gn/build/libs/xar/enable.gni")
@@ -178,7 +179,6 @@
       "HAVE_CRASHREPORTER_INFO=1",
       "HAVE_DECL_ARC4RANDOM=1",
       "HAVE_DLADDR=1",
-      "HAVE_LIBEDIT=1",
       "HAVE_MALLOC_H=",
       "HAVE_MACH_MACH_H=1",
       "HAVE_MALLOC_MALLOC_H=1",
@@ -190,7 +190,6 @@
       "HAVE_CRASHREPORTER_INFO=",
       "HAVE_DECL_ARC4RANDOM=",
       "HAVE_DLADDR=",
-      "HAVE_LIBEDIT=",
       "HAVE_MACH_MACH_H=",
       "HAVE_MALLOC_H=1",
       "HAVE_MALLOC_MALLOC_H=",
@@ -292,6 +291,12 @@
     args += [ "LTDL_SHLIB_EXT=.dll" ]
   }
 
+  if (llvm_enable_libedit) {
+    args += [ "HAVE_LIBEDIT=1" ]
+  } else {
+    args += [ "HAVE_LIBEDIT=" ]
+  }
+
   if (llvm_enable_libxar) {
     args += [ "HAVE_LIBXAR=1" ]
   } else {
Index: llvm/utils/gn/secondary/llvm/lib/LineEditor/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/llvm/lib/LineEditor/BUILD.gn
@@ -0,0 +1,12 @@
+static_library("LineEditor") {
+  output_name = "LLVMLineEditor"
+  deps = [
+    "//llvm/utils/gn/build/libs/edit",
+    "//llvm/lib/Support",
+    "//llvm/include/llvm/Config:config",
+  ]
+
+  sources = [
+    "LineEditor.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/llvm/lib/Target/targets_string.gni
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/llvm/lib/Target/targets_string.gni
@@ -0,0 +1,11 @@
+import("//llvm/lib/Target/targets.gni")
+
+# A single string with all built targets, separated by spaces.
+llvm_targets_to_build_string = ""
+foreach(target, llvm_targets_to_build) {
+  if (llvm_targets_to_build_string != "") {
+    llvm_targets_to_build_string += " "
+  }
+  llvm_targets_to_build_string += target
+}
+
Index: llvm/utils/gn/secondary/llvm/lib/Testing/Support/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/llvm/lib/Testing/Support/BUILD.gn
@@ -0,0 +1,12 @@
+static_library("Support") {
+  output_name = "LLVMTestingSupport"
+  deps = [
+    "//llvm/lib/Support",
+    "//llvm/utils/unittest:gtest",
+  ]
+  sources = [
+    "Error.cpp",
+    "SupportHelpers.cpp",
+  ]
+  testonly = true
+}
Index: llvm/utils/gn/secondary/llvm/lib/TextAPI/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/llvm/lib/TextAPI/BUILD.gn
@@ -0,0 +1,12 @@
+static_library("TextAPI") {
+  output_name = "LLVMTextAPI"
+  deps = [
+    "//llvm/lib/BinaryFormat",
+    "//llvm/lib/Support",
+  ]
+  include_dirs = [ "." ]
+  sources = [
+    "ELF/ELFStub.cpp",
+    "ELF/TBEHandler.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/llvm/test/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/llvm/test/BUILD.gn
@@ -0,0 +1,299 @@
+import("//llvm/lib/DebugInfo/PDB/enable_dia.gni")
+import("//llvm/lib/Target/targets_string.gni")
+import("//llvm/triples.gni")
+import("//llvm/utils/gn/build/buildflags.gni")
+import("//llvm/utils/gn/build/libs/pthread/enable.gni")
+import("//llvm/utils/gn/build/libs/xar/enable.gni")
+import("//llvm/utils/gn/build/libs/xml/enable.gni")
+import("//llvm/utils/gn/build/libs/zlib/enable.gni")
+import("llvm_lit_site_cfg_files.gni")
+
+template("write_lit_config") {
+  action(target_name) {
+    script = "//llvm/utils/gn/build/write_cmake_config.py"
+
+    sources = [
+      invoker.input,
+    ]
+    outputs = [
+      invoker.output,
+    ]
+    args = [
+      "-o",
+      rebase_path(outputs[0], root_out_dir),
+      rebase_path(sources[0], root_out_dir),
+
+      "LIT_SITE_CFG_IN_HEADER=## Autogenerated from ${sources[0]}, do not edit",
+      "ENABLE_SHARED=0",
+      "LLVM_BINARY_DIR=" +
+          rebase_path(get_label_info("//llvm", "target_out_dir")),
+      "LLVM_SOURCE_DIR=" + rebase_path("//llvm"),
+      "LLVM_TOOLS_DIR=" + rebase_path("$root_out_dir/bin"),
+    ]
+    if (host_os == "win") {
+      # See comment for Windows solink in llvm/utils/gn/build/toolchain/BUILD.gn
+      args += [ "SHLIBDIR=" + rebase_path("$root_out_dir/bin") ]
+    } else {
+      args += [ "SHLIBDIR=" + rebase_path("$root_out_dir/lib") ]
+    }
+    args += invoker.extra_args
+  }
+}
+
+write_lit_config("lit_site_cfg") {
+  input = "//llvm/test/lit.site.cfg.py.in"
+  output = llvm_lit_site_cfg_file
+  extra_args = [
+    "BUILD_SHARED_LIBS=0",
+
+    # Only used by the Go bindings tests, or if LLVM_USE_SANITIZER includes
+    # asan and the host OS is macOS. The GN build currently never uses
+    # LLVM_USE_SANITIZER.  (See also CMAKE_CXX_COMPILER in clang/test/BUILD.gn.)
+    "HOST_CC=cc",
+
+    # Only used by the Go bindings tests, or if LLVM_USE_SANITIZER includes
+    # lsan and the host OS is macOS. The GN build currently never uses
+    # LLVM_USE_SANITIZER.  (See also CMAKE_CXX_COMPILER in clang/test/BUILD.gn.)
+    "HOST_CXX=c++",
+
+    # Only used by the Go bindings tests, and for detecting a 32-bit build
+    # and in a belt-and-suspenders check for detecting 32-bit host builds.
+    # (That check also checks LLVM_HOST_TRIPLE.)
+    "HOST_LDFLAGS=",
+
+    "LLVM_ENABLE_FFI=0",
+    "LLVM_HAVE_OPT_VIEWER_MODULES=0",
+    "LLVM_HOST_TRIPLE=$llvm_host_triple",
+    "LLVM_LIBRARY_DIR=" + rebase_path("$root_out_dir/lib"),
+    "LLVM_LINK_LLVM_DYLIB=0",
+    "LLVM_LIT_TOOLS_DIR=",  # Intentionally empty, matches cmake build.
+    "LLVM_NATIVE_ARCH=$native_target",
+    "LLVM_TOOL_LTO_BUILD=1",
+    "LLVM_USE_INTEL_JITEVENTS=0",
+    "LLVM_USE_SANITIZER=",
+    "PYTHON_EXECUTABLE=$python_path",
+    "TARGETS_TO_BUILD=$llvm_targets_to_build_string",
+    "TARGET_TRIPLE=$llvm_target_triple",
+
+    # No bindings are implemented in the GN build.
+    "LLVM_BINDINGS=",
+
+    "GO_EXECUTABLE=",
+    "LLVM_INCLUDE_GO_TESTS=0",
+
+    "HAVE_OCAMLOPT=0",
+    "HAVE_OCAML_OUNIT=0",
+    "OCAMLFIND=OCAMLFIND-NOTFOUND",
+    "OCAMLFLAGS=",
+  ]
+
+  if (host_cpu == "x64") {
+    extra_args += [ "HOST_ARCH=x86_64" ]
+  } else {
+    assert(false, "unimplemented host_cpu " + host_cpu)
+  }
+
+  if (host_os == "mac") {
+    extra_args += [
+      "EXEEXT=",
+      "HOST_OS=Darwin",
+      "SHLIBEXT=.dylib",
+    ]
+  } else if (host_os == "linux") {
+    extra_args += [
+      "EXEEXT=",
+      "HOST_OS=Linux",
+      "SHLIBEXT=.so",
+    ]
+  } else if (host_os == "win") {
+    extra_args += [
+      "EXEEXT=.exe",
+      "HOST_OS=Windows",
+      "SHLIBEXT=.dll",
+    ]
+  } else {
+    assert(false, "unsupported host_os " + host_os)
+  }
+  if (host_os == "linux") {
+    # lit.cfg.py's have_ld_plugin_support() checks for "gold" in --version,
+    # so just claim that ld is gold on Linux.  The function also checks if
+    # LLVMgold.so exists, but since that target isn't hooked up yet in the GN
+    # build the LLVMgold.so tests currently don't run anywhere in the GN build.
+    extra_args += [ "GOLD_EXECUTABLE=ld" ]
+  } else {
+    extra_args += [ "GOLD_EXECUTABLE=" ]
+  }
+  if (host_os == "mac") {
+    extra_args += [ "LD64_EXECUTABLE=ld" ]
+  } else {
+    extra_args += [ "LD64_EXECUTABLE=" ]
+  }
+
+  if (llvm_enable_assertions) {
+    extra_args += [ "ENABLE_ASSERTIONS=1" ]
+  } else {
+    extra_args += [ "ENABLE_ASSERTIONS=0" ]  # Must be 0.
+  }
+
+  if (llvm_enable_libxar) {
+    extra_args += [ "HAVE_LIBXAR=1" ]
+  } else {
+    extra_args += [ "HAVE_LIBXAR=0" ]  # Must be 0.
+  }
+
+  if (llvm_enable_dia_sdk) {
+    extra_args += [ "LLVM_ENABLE_DIA_SDK=1" ]
+  } else {
+    extra_args += [ "LLVM_ENABLE_DIA_SDK=0" ]  # Must be 0.
+  }
+
+  if (llvm_enable_libxml2) {
+    extra_args += [ "LLVM_LIBXML2_ENABLED=1" ]
+  } else {
+    extra_args += [ "LLVM_LIBXML2_ENABLED=" ]  # Must be empty.
+  }
+
+  if (llvm_enable_threads) {
+    extra_args += [ "LLVM_ENABLE_THREADS=1" ]
+  } else {
+    extra_args += [ "LLVM_ENABLE_THREADS=0" ]  # Must be 0.
+  }
+
+  if (llvm_enable_zlib) {
+    extra_args += [ "HAVE_LIBZ=1" ]
+  } else {
+    extra_args += [ "HAVE_LIBZ=0" ]  # Must be 0.
+  }
+}
+
+write_lit_config("lit_unit_site_cfg") {
+  input = "//llvm/test/Unit/lit.site.cfg.py.in"
+  output = llvm_lit_unit_site_cfg_file
+  extra_args = [ "LLVM_BUILD_MODE=." ]
+}
+
+# This target should contain all dependencies of check-llvm.
+# //:default depends on it, so that ninja's default target builds all
+# prerequisites for check-llvm but doesn't run check-llvm itself.
+group("test") {
+  deps = [
+    ":lit_site_cfg",
+    ":lit_unit_site_cfg",
+
+    # Because llvm/tools/llvm-config/BUILD.gn calls llvm-build to generate
+    # LibraryDependencies.inc, llvm-config expects these libraries to exist
+    # even though nothing but unittests depends on them.  Add explicit
+    # dependencies to make sure the libaries exist on disk when llvm-config's
+    # lit tests run.
+    "//llvm/lib/LineEditor",
+    "//llvm/lib/Testing/Support",
+    "//llvm/lib/TextAPI",
+    "//llvm/tools/bugpoint",
+    "//llvm/tools/dsymutil",
+    "//llvm/tools/llc",
+    "//llvm/tools/lli",
+    "//llvm/tools/lli/ChildTarget:lli-child-target",
+    "//llvm/tools/llvm-ar:symlinks",
+    "//llvm/tools/llvm-as",
+    "//llvm/tools/llvm-bcanalyzer",
+    "//llvm/tools/llvm-c-test",
+    "//llvm/tools/llvm-cat",
+    "//llvm/tools/llvm-cfi-verify",
+    "//llvm/tools/llvm-cov",
+    "//llvm/tools/llvm-cvtres",
+    "//llvm/tools/llvm-cxxdump",
+    "//llvm/tools/llvm-cxxfilt",
+    "//llvm/tools/llvm-cxxmap",
+    "//llvm/tools/llvm-diff",
+    "//llvm/tools/llvm-dis",
+    "//llvm/tools/llvm-dwarfdump",
+    "//llvm/tools/llvm-dwp",
+    "//llvm/tools/llvm-extract",
+    "//llvm/tools/llvm-isel-fuzzer",
+    "//llvm/tools/llvm-link",
+    "//llvm/tools/llvm-lto",
+    "//llvm/tools/llvm-lto2",
+    "//llvm/tools/llvm-mc",
+    "//llvm/tools/llvm-mca",
+    "//llvm/tools/llvm-modextract",
+    "//llvm/tools/llvm-mt",
+    "//llvm/tools/llvm-nm",
+    "//llvm/tools/llvm-objcopy:symlinks",
+    "//llvm/tools/llvm-objdump",
+    "//llvm/tools/llvm-opt-fuzzer",
+    "//llvm/tools/llvm-opt-report",
+    "//llvm/tools/llvm-pdbutil",
+    "//llvm/tools/llvm-profdata",
+    "//llvm/tools/llvm-rc",
+    "//llvm/tools/llvm-readobj:symlinks",
+    "//llvm/tools/llvm-rtdyld",
+    "//llvm/tools/llvm-size",
+    "//llvm/tools/llvm-split",
+    "//llvm/tools/llvm-strings",
+    "//llvm/tools/llvm-symbolizer",
+    "//llvm/tools/llvm-undname",
+    "//llvm/tools/llvm-xray",
+    "//llvm/tools/lto",
+    "//llvm/tools/obj2yaml",
+    "//llvm/tools/opt",
+    "//llvm/tools/sancov",
+    "//llvm/tools/sanstats",
+    "//llvm/tools/verify-uselistorder",
+    "//llvm/tools/yaml2obj",
+    "//llvm/utils/FileCheck",
+    "//llvm/utils/TableGen:llvm-tblgen",
+    "//llvm/utils/count",
+    "//llvm/utils/not",
+
+    # llvm-config wants libgtest_main.a to exist at runtime when run as in
+    # its tests, but nothing in the tree depends on them.
+    "//llvm/utils/unittest/UnitTestMain:gtest_main",
+    "//llvm/utils/yaml-bench",
+  ]
+  if (host_os == "mac") {
+    deps += [ ]
+  }
+  if (host_os != "win") {
+    # loadable_modules don't work on Windows.
+    # FIXME: In the CMake build, ENABLE_SHARED makes them work somehow
+    # (but they're off by default there too).
+    deps += [
+      "//llvm/lib/Transforms/Hello",
+      "//llvm/tools/bugpoint-passes",
+    ]
+  }
+
+  # FIXME: dep on "//llvm/unittests" once it exists
+  # FIXME: llvm_build_examples
+  testonly = true
+}
+
+action("check-llvm") {
+  script = "$root_out_dir/bin/llvm-lit"
+  if (host_os == "win") {
+    script += ".py"
+  }
+  args = [
+    "-sv",
+    "--param",
+    "llvm_site_config=" + rebase_path(llvm_lit_site_cfg_file, root_out_dir),
+    "--param",
+    "llvm_unit_site_config=" +
+        rebase_path(llvm_lit_unit_site_cfg_file, root_out_dir),
+    rebase_path(".", root_out_dir),
+  ]
+  outputs = [
+    "$target_gen_dir/run-lit",  # Non-existing, so that ninja runs it each time.
+  ]
+
+  # Since check-llvm is always dirty, //:default doesn't depend on it so that
+  # it's not part of the default ninja target.  Hence, check-llvm shouldn't
+  # have any deps except :test. so that the default target is sure to build
+  # all the deps.
+  deps = [
+    ":test",
+  ]
+  testonly = true
+
+  pool = "//:console"
+}
Index: llvm/utils/gn/secondary/llvm/test/llvm_lit_site_cfg_files.gni
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/llvm/test/llvm_lit_site_cfg_files.gni
@@ -0,0 +1,2 @@
+llvm_lit_site_cfg_file = "$root_gen_dir/llvm/test/lit.site.cfg.py"
+llvm_lit_unit_site_cfg_file = "$root_gen_dir/llvm/test/Unit/lit.site.cfg.py"
Index: llvm/utils/gn/secondary/llvm/tools/llvm-config/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/llvm/tools/llvm-config/BUILD.gn
+++ llvm/utils/gn/secondary/llvm/tools/llvm-config/BUILD.gn
@@ -1,4 +1,4 @@
-import("//llvm/lib/Target/targets.gni")
+import("//llvm/lib/Target/targets_string.gni")
 import("//llvm/utils/gn/build/buildflags.gni")
 import("//llvm/utils/gn/build/libs/pthread/enable.gni")
 import("//llvm/utils/gn/build/libs/terminfo/enable.gni")
@@ -6,14 +6,6 @@
 import("//llvm/utils/gn/build/libs/zlib/enable.gni")
 import("//llvm/version.gni")
 
-enable_targets = ""
-foreach(target, llvm_targets_to_build) {
-  if (enable_targets != "") {
-    enable_targets += " "
-  }
-  enable_targets += target
-}
-
 action("BuildVariables.inc") {
   script = "//llvm/utils/gn/build/write_cmake_config.py"
 
@@ -91,7 +83,7 @@
     "LLVM_CXXFLAGS=.",  # FIXME
     "LLVM_BUILDMODE=$build_mode",
     "LLVM_LIBDIR_SUFFIX=",
-    "LLVM_TARGETS_BUILT=$enable_targets",
+    "LLVM_TARGETS_BUILT=$llvm_targets_to_build_string",
     "LLVM_SYSTEM_LIBS=$system_libs",
     "LLVM_BUILD_SYSTEM=gn",
     "LLVM_HAS_RTTI=0",
@@ -108,12 +100,14 @@
 # FIXME: It'd be nice to not depend on llvm-build on this, Depending on all the
 # LLVMBuild.txt files just for this seems a bit overkill.  `gn desc` should
 # have all this information too and could be called at build time.
+# When this is removed, update llvm/test/BUILD.gn to no longer have unnecessary
+# deps on a couple llvm/lib/ targets.
 action("LibraryDependencies.inc") {
   script = "//llvm/utils/llvm-build/llvm-build"
   output = "$target_gen_dir/LibraryDependencies.inc"
   args = [
     "--native-target=$native_target",
-    "--enable-targets=$enable_targets",
+    "--enable-targets=$llvm_targets_to_build_string",
     "--write-library-table=" + rebase_path(output, root_out_dir),
   ]
   outputs = [
Index: llvm/utils/gn/secondary/llvm/tools/lto/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/llvm/tools/lto/BUILD.gn
@@ -0,0 +1,39 @@
+import("//llvm/version.gni")
+
+lto_target_type = "loadable_module"
+if (host_os == "linux") {
+  # Linux needs -fPIC to build shared libs but they aren't on by default.
+  # For now, make libclang a static lib there.
+  lto_target_type = "static_library"
+}
+
+target(lto_target_type, "lto") {
+  output_name = "libLTO"
+  deps = [
+    "//llvm/lib/Bitcode/Reader",
+    "//llvm/lib/IR",
+    "//llvm/lib/LTO",
+    "//llvm/lib/MC",
+    "//llvm/lib/MC/MCDisassembler",
+    "//llvm/lib/Support",
+    "//llvm/lib/Target",
+    "//llvm/lib/Target:TargetsToBuild",
+  ]
+  sources = [
+    "LTODisassembler.cpp",
+    "lto.cpp",
+  ]
+
+  if (host_os == "mac") {
+    ldflags = [
+      "-Wl,-compatibility_version,1",
+      "-Wl,-current_version,$llvm_version",
+
+      # See llvm_setup_rpath() in CMake.
+      "-Wl,-install_name,@rpath/libLTO.dylib",
+      "-Wl,-rpath,@loader_path/../lib",
+    ]
+  }
+
+  # FIXME: Use lto.exports
+}
Index: llvm/utils/gn/secondary/llvm/utils/llvm-lit/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/llvm/utils/llvm-lit/BUILD.gn
+++ llvm/utils/gn/secondary/llvm/utils/llvm-lit/BUILD.gn
@@ -1,5 +1,6 @@
 import("//clang/test/clang_lit_site_cfg_files.gni")
 import("//lld/test/lld_lit_site_cfg_files.gni")
+import("//llvm/test/llvm_lit_site_cfg_files.gni")
 
 action("llvm-lit") {
   script = "//llvm/utils/gn/build/write_cmake_config.py"
@@ -32,6 +33,8 @@
     "//clang/test:lit_unit_site_cfg",
     "//lld/test:lit_site_cfg",
     "//lld/test:lit_unit_site_cfg",
+    "//llvm/test:lit_site_cfg",
+    "//llvm/test:lit_unit_site_cfg",
   ]
 
   # Note: \n is converted into a newline by write_cmake_config.py, not by gn.
@@ -43,6 +46,10 @@
                 rebase_path(lld_lit_site_cfg_file) + "')\n"
   config_map += "map_config('" + rebase_path("//lld/test/Unit/lit.cfg.py") +
                 "', '" + rebase_path(lld_lit_unit_site_cfg_file) + "')\n"
+  config_map += "map_config('" + rebase_path("//llvm/test/lit.cfg.py") +
+                "', '" + rebase_path(llvm_lit_site_cfg_file) + "')\n"
+  config_map += "map_config('" + rebase_path("//llvm/test/Unit/lit.cfg.py") +
+                "', '" + rebase_path(llvm_lit_unit_site_cfg_file) + "')\n"
 
   args = [
     "-o",