Index: llvm/utils/gn/build/BUILDCONFIG.gn
===================================================================
--- llvm/utils/gn/build/BUILDCONFIG.gn
+++ llvm/utils/gn/build/BUILDCONFIG.gn
@@ -2,7 +2,7 @@
 # Targets can opt out of a config by removing it from their local configs list.
 # If you're adding global flags and don't need targets to be able to opt out,
 # add the flags to compiler_defaults, not to a new config.
-_shared_binary_target_configs = [
+shared_binary_target_configs = [
   "//llvm/utils/gn/build:compiler_defaults",
   "//llvm/utils/gn/build:llvm_code",
   "//llvm/utils/gn/build:warn_covered_switch_default",
@@ -10,19 +10,19 @@
 
 # Apply that default list to the binary target types.
 set_defaults("executable") {
-  configs = _shared_binary_target_configs
+  configs = shared_binary_target_configs
 }
 set_defaults("loadable_module") {
-  configs = _shared_binary_target_configs
+  configs = shared_binary_target_configs
 }
 set_defaults("static_library") {
-  configs = _shared_binary_target_configs
+  configs = shared_binary_target_configs
 }
 set_defaults("shared_library") {
-  configs = _shared_binary_target_configs
+  configs = shared_binary_target_configs
 }
 set_defaults("source_set") {
-  configs = _shared_binary_target_configs
+  configs = shared_binary_target_configs
 }
 
 if (host_os == "win") {
Index: llvm/utils/gn/build/sync_source_lists_from_cmake.py
===================================================================
--- llvm/utils/gn/build/sync_source_lists_from_cmake.py
+++ llvm/utils/gn/build/sync_source_lists_from_cmake.py
@@ -4,7 +4,11 @@
 
 For each BUILD.gn file in the tree, checks if the list of cpp files in
 it is identical to the list of cpp files in the corresponding CMakeLists.txt
-file, and prints the difference if not."""
+file, and prints the difference if not.
+
+Also checks that each CMakeLists.txt file below unittests/ folders that define
+binaries have corresponding BUILD.gn files.
+"""
 
 from __future__ import print_function
 
@@ -12,7 +16,8 @@
 import re
 import subprocess
 
-def main():
+
+def sync_source_lists():
     gn_files = subprocess.check_output(
             ['git', 'ls-files', '*BUILD.gn']).splitlines()
 
@@ -50,5 +55,24 @@
             print('remove:\n' + '\n'.join(remove))
         print()
 
+
+def sync_unittests():
+    checked = [ 'clang', 'lld' ]
+    for c in checked:
+        for root, _, _ in os.walk(os.path.join(c, 'unittests')):
+            cmake_file = os.path.join(root, 'CMakeLists.txt')
+            if not os.path.exists(cmake_file):
+                continue
+            gn_file = os.path.join('llvm/utils/gn/secondary', root, 'BUILD.gn')
+            if not os.path.exists(gn_file):
+                print('missing GN file %s for unittest CMake file %s' %
+                      (gn_file, cmake_file))
+
+
+def main():
+    sync_source_lists()
+    sync_unittests()
+
+
 if __name__ == '__main__':
     main()
Index: llvm/utils/gn/secondary/clang/lib/ASTMatchers/Dynamic/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/lib/ASTMatchers/Dynamic/BUILD.gn
@@ -0,0 +1,16 @@
+static_library("Dynamic") {
+  output_name = "clangDynamicASTMatchers"
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/ASTMatchers",
+    "//clang/lib/Basic",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "Diagnostics.cpp",
+    "Parser.cpp",
+    "Registry.cpp",
+    "VariantValue.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/test/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/clang/test/BUILD.gn
+++ llvm/utils/gn/secondary/clang/test/BUILD.gn
@@ -125,6 +125,7 @@
     "//clang/tools/clang-rename",
     "//clang/tools/diagtool",
     "//clang/tools/driver:symlinks",
+    "//clang/unittests",
     "//clang/utils/TableGen:clang-tblgen",
     "//clang/utils/hmaptool",
     "//llvm/tools/llc",
@@ -159,7 +160,6 @@
     ]
   }
 
-  # FIXME: dep on "//clang/unittests" once it exists
   # FIXME: clang_build_examples
   testonly = true
 }
Index: llvm/utils/gn/secondary/clang/unittests/AST/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/AST/BUILD.gn
@@ -0,0 +1,33 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("ASTTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/ASTMatchers",
+    "//clang/lib/Analysis",
+    "//clang/lib/Basic",
+    "//clang/lib/Frontend",
+    "//clang/lib/Tooling",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "ASTContextParentMapTest.cpp",
+    "ASTImporterTest.cpp",
+    "ASTTypeTraitsTest.cpp",
+    "ASTVectorTest.cpp",
+    "CommentLexer.cpp",
+    "CommentParser.cpp",
+    "CommentTextTest.cpp",
+    "DataCollectionTest.cpp",
+    "DeclPrinterTest.cpp",
+    "DeclTest.cpp",
+    "EvaluateAsRValueTest.cpp",
+    "ExternalASTSourceTest.cpp",
+    "Language.cpp",
+    "NamedDeclPrinterTest.cpp",
+    "SourceLocationTest.cpp",
+    "StmtPrinterTest.cpp",
+    "StructuralEquivalenceTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/ASTMatchers/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/ASTMatchers/BUILD.gn
@@ -0,0 +1,19 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("ASTMatchersTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/ASTMatchers",
+    "//clang/lib/Basic",
+    "//clang/lib/Frontend",
+    "//clang/lib/Tooling",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "ASTMatchersInternalTest.cpp",
+    "ASTMatchersNarrowingTest.cpp",
+    "ASTMatchersNodeTest.cpp",
+    "ASTMatchersTraversalTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/ASTMatchers/Dynamic/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/ASTMatchers/Dynamic/BUILD.gn
@@ -0,0 +1,19 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("DynamicASTMatchersTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/ASTMatchers",
+    "//clang/lib/ASTMatchers/Dynamic",
+    "//clang/lib/Basic",
+    "//clang/lib/Frontend",
+    "//clang/lib/Tooling",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "ParserTest.cpp",
+    "RegistryTest.cpp",
+    "VariantValueTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/Analysis/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Analysis/BUILD.gn
@@ -0,0 +1,19 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("ClangAnalysisTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/ASTMatchers",
+    "//clang/lib/Analysis",
+    "//clang/lib/Basic",
+    "//clang/lib/Frontend",
+    "//clang/lib/Tooling",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "CFGTest.cpp",
+    "CloneDetectionTest.cpp",
+    "ExprMutationAnalyzerTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/BUILD.gn
@@ -0,0 +1,35 @@
+import("//clang/lib/StaticAnalyzer/Frontend/enable.gni")
+
+group("unittests") {
+  deps = [
+    "AST:ASTTests",
+    "ASTMatchers:ASTMatchersTests",
+    "ASTMatchers/Dynamic:DynamicASTMatchersTests",
+    "Basic:BasicTests",
+    "CodeGen:ClangCodeGenTests",
+    "CrossTU:CrossTUTests",
+    "Driver:ClangDriverTests",
+    "Format:FormatTests",
+    "Index:IndexTests",
+    "Lex:LexTests",
+    "Rename:ClangRenameTests",
+    "Rewrite:RewriteTests",
+    "Sema:SemaTests",
+    "Tooling:ToolingTests",
+  ]
+  if (clang_enable_static_analyzer) {
+    deps += [
+      "Analysis:ClangAnalysisTests",
+      "Frontend:FrontendTests",
+      "StaticAnalyzer:StaticAnalysisTests",
+    ]
+  }
+  if (host_os != "win") {
+    # FIXME: libclang unit tests are disabled on Windows due
+    # to failures, mostly in libclang.VirtualFileOverlay_*.
+    # FIXME: Also, the executable can't find libclang.dll since that's
+    # in a different directory.
+    deps += [ "libclang:libclangTests" ]
+  }
+  testonly = true
+}
Index: llvm/utils/gn/secondary/clang/unittests/Basic/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Basic/BUILD.gn
@@ -0,0 +1,18 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("BasicTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/Basic",
+    "//clang/lib/Lex",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "CharInfoTest.cpp",
+    "DiagnosticTest.cpp",
+    "FileManagerTest.cpp",
+    "FixedPointTest.cpp",
+    "MemoryBufferCacheTest.cpp",
+    "SourceManagerTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/CodeGen/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/CodeGen/BUILD.gn
@@ -0,0 +1,21 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("ClangCodeGenTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/Basic",
+    "//clang/lib/CodeGen",
+    "//clang/lib/Frontend",
+    "//clang/lib/Lex",
+    "//clang/lib/Parse",
+    "//llvm/lib/IR",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "BufferSourceTest.cpp",
+    "CodeGenExternalTest.cpp",
+    "IncrementalProcessingTest.cpp",
+    "TBAAMetadataTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/CrossTU/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/CrossTU/BUILD.gn
@@ -0,0 +1,17 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("CrossTUTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/Basic",
+    "//clang/lib/CrossTU",
+    "//clang/lib/Frontend",
+    "//clang/lib/Tooling",
+    "//llvm/lib/Support",
+    "//llvm/lib/Target:TargetsToBuild",
+  ]
+  sources = [
+    "CrossTranslationUnitTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/Driver/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Driver/BUILD.gn
@@ -0,0 +1,18 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("ClangDriverTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/Basic",
+    "//clang/lib/Driver",
+    "//llvm/lib/Option",
+    "//llvm/lib/Support",
+    "//llvm/lib/Target:TargetsToBuild",
+  ]
+  sources = [
+    "DistroTest.cpp",
+    "ModuleCacheTest.cpp",
+    "MultilibTest.cpp",
+    "ToolChainTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/Format/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Format/BUILD.gn
@@ -0,0 +1,31 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("FormatTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/Basic",
+    "//clang/lib/Format",
+    "//clang/lib/Frontend",
+    "//clang/lib/Rewrite",
+    "//clang/lib/Tooling/Core",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "CleanupTest.cpp",
+    "FormatTest.cpp",
+    "FormatTestComments.cpp",
+    "FormatTestJS.cpp",
+    "FormatTestJava.cpp",
+    "FormatTestObjC.cpp",
+    "FormatTestProto.cpp",
+    "FormatTestRawStrings.cpp",
+    "FormatTestSelective.cpp",
+    "FormatTestTableGen.cpp",
+    "FormatTestTextProto.cpp",
+    "NamespaceEndCommentsFixerTest.cpp",
+    "SortImportsTestJS.cpp",
+    "SortImportsTestJava.cpp",
+    "SortIncludesTest.cpp",
+    "UsingDeclarationsSorterTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/Frontend/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Frontend/BUILD.gn
@@ -0,0 +1,25 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("FrontendTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/Basic",
+    "//clang/lib/CodeGen",
+    "//clang/lib/Frontend",
+    "//clang/lib/FrontendTool",
+    "//clang/lib/Lex",
+    "//clang/lib/Sema",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "ASTUnitTest.cpp",
+    "CodeGenActionTest.cpp",
+    "CompilerInstanceTest.cpp",
+    "FixedPointString.cpp",
+    "FrontendActionTest.cpp",
+    "OutputStreamTest.cpp",
+    "PCHPreambleTest.cpp",
+    "ParsedSourceLocationTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/Index/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Index/BUILD.gn
@@ -0,0 +1,18 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("IndexTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/Basic",
+    "//clang/lib/Frontend",
+    "//clang/lib/Index",
+    "//clang/lib/Lex",
+    "//clang/lib/Serialization",
+    "//clang/lib/Tooling",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "IndexTests.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/Lex/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Lex/BUILD.gn
@@ -0,0 +1,20 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("LexTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/Basic",
+    "//clang/lib/Lex",
+    "//clang/lib/Parse",
+    "//clang/lib/Sema",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "HeaderMapTest.cpp",
+    "HeaderSearchTest.cpp",
+    "LexerTest.cpp",
+    "PPCallbacksTest.cpp",
+    "PPConditionalDirectiveRecordTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/Rename/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Rename/BUILD.gn
@@ -0,0 +1,28 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("ClangRenameTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+
+  # We'd like clang/unittests/Tooling/RewriterTestContext.h in the test.
+  include_dirs = [ "../.." ]
+
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/ASTMatchers",
+    "//clang/lib/Basic",
+    "//clang/lib/Format",
+    "//clang/lib/Frontend",
+    "//clang/lib/Rewrite",
+    "//clang/lib/Tooling",
+    "//clang/lib/Tooling/Core",
+    "//clang/lib/Tooling/Refactoring",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "RenameAliasTest.cpp",
+    "RenameClassTest.cpp",
+    "RenameEnumTest.cpp",
+    "RenameFunctionTest.cpp",
+    "RenameMemberTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/Rewrite/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Rewrite/BUILD.gn
@@ -0,0 +1,12 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("RewriteTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/Rewrite",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "RewriteBufferTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/Sema/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Sema/BUILD.gn
@@ -0,0 +1,18 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("SemaTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/Basic",
+    "//clang/lib/Frontend",
+    "//clang/lib/Parse",
+    "//clang/lib/Sema",
+    "//clang/lib/Tooling",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "CodeCompleteTest.cpp",
+    "ExternalSemaSourceTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/StaticAnalyzer/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/StaticAnalyzer/BUILD.gn
@@ -0,0 +1,17 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("StaticAnalysisTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/lib/Analysis",
+    "//clang/lib/Basic",
+    "//clang/lib/StaticAnalyzer/Core",
+    "//clang/lib/StaticAnalyzer/Frontend",
+    "//clang/lib/Tooling",
+    "//llvm/lib/Support",
+  ]
+  sources = [
+    "AnalyzerOptionsTest.cpp",
+    "RegisterCustomCheckersTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/Tooling/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/Tooling/BUILD.gn
@@ -0,0 +1,61 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("ToolingTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  include_dirs = [ "." ]
+  deps = [
+    "//clang/lib/AST",
+    "//clang/lib/ASTMatchers",
+    "//clang/lib/Basic",
+    "//clang/lib/Format",
+    "//clang/lib/Frontend",
+    "//clang/lib/Lex",
+    "//clang/lib/Rewrite",
+    "//clang/lib/Tooling",
+    "//clang/lib/Tooling/Core",
+    "//clang/lib/Tooling/Refactoring",
+    "//llvm/lib/Support",
+    "//llvm/lib/Target:TargetsToBuild",
+  ]
+  sources = [
+    "ASTSelectionTest.cpp",
+    "CastExprTest.cpp",
+    "CommentHandlerTest.cpp",
+    "CompilationDatabaseTest.cpp",
+    "DiagnosticsYamlTest.cpp",
+    "ExecutionTest.cpp",
+    "FixItTest.cpp",
+    "HeaderIncludesTest.cpp",
+    "LexicallyOrderedRecursiveASTVisitorTest.cpp",
+    "LookupTest.cpp",
+    "QualTypeNamesTest.cpp",
+    "RecursiveASTVisitorTestDeclVisitor.cpp",
+    "RecursiveASTVisitorTestPostOrderVisitor.cpp",
+    "RecursiveASTVisitorTestTypeLocVisitor.cpp",
+    "RecursiveASTVisitorTests/Attr.cpp",
+    "RecursiveASTVisitorTests/CXXBoolLiteralExpr.cpp",
+    "RecursiveASTVisitorTests/CXXMemberCall.cpp",
+    "RecursiveASTVisitorTests/CXXOperatorCallExprTraverser.cpp",
+    "RecursiveASTVisitorTests/Class.cpp",
+    "RecursiveASTVisitorTests/ConstructExpr.cpp",
+    "RecursiveASTVisitorTests/DeclRefExpr.cpp",
+    "RecursiveASTVisitorTests/ImplicitCtor.cpp",
+    "RecursiveASTVisitorTests/InitListExprPostOrder.cpp",
+    "RecursiveASTVisitorTests/InitListExprPostOrderNoQueue.cpp",
+    "RecursiveASTVisitorTests/InitListExprPreOrder.cpp",
+    "RecursiveASTVisitorTests/InitListExprPreOrderNoQueue.cpp",
+    "RecursiveASTVisitorTests/IntegerLiteral.cpp",
+    "RecursiveASTVisitorTests/LambdaDefaultCapture.cpp",
+    "RecursiveASTVisitorTests/LambdaExpr.cpp",
+    "RecursiveASTVisitorTests/NestedNameSpecifiers.cpp",
+    "RecursiveASTVisitorTests/ParenExpr.cpp",
+    "RecursiveASTVisitorTests/TemplateArgumentLocTraverser.cpp",
+    "RecursiveASTVisitorTests/TraversalScope.cpp",
+    "RefactoringActionRulesTest.cpp",
+    "RefactoringCallbacksTest.cpp",
+    "RefactoringTest.cpp",
+    "ReplacementsYamlTest.cpp",
+    "RewriterTest.cpp",
+    "ToolingTest.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/clang/unittests/libclang/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/clang/unittests/libclang/BUILD.gn
@@ -0,0 +1,14 @@
+import("//llvm/utils/unittest/unittest.gni")
+
+unittest("libclangTests") {
+  configs += [ "//llvm/utils/gn/build:clang_code" ]
+  deps = [
+    "//clang/tools/libclang",
+  ]
+  sources = [
+    "LibclangTest.cpp",
+  ]
+  if (host_os == "mac") {
+    ldflags = [ "-Wl,-rpath," + rebase_path("$root_out_dir/lib") ]
+  }
+}
Index: llvm/utils/gn/secondary/lld/unittests/DriverTests/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/lld/unittests/DriverTests/BUILD.gn
+++ llvm/utils/gn/secondary/lld/unittests/DriverTests/BUILD.gn
@@ -1,15 +1,12 @@
-executable("DriverTests") {
-  # test/Unit/lit.cfg expects unittests in LLD_BINARY_DIR/unittest
-  output_dir = target_out_dir
+import("//llvm/utils/unittest/unittest.gni")
 
+unittest("DriverTests") {
   configs += [ "//llvm/utils/gn/build:lld_code" ]
   deps = [
     "//lld/lib/Driver",
     "//lld/lib/ReaderWriter/MachO",
-    "//llvm/utils/unittest/UnitTestMain",
   ]
   sources = [
     "DarwinLdDriverTest.cpp",
   ]
-  testonly = true
 }
Index: llvm/utils/gn/secondary/lld/unittests/MachOTests/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/lld/unittests/MachOTests/BUILD.gn
+++ llvm/utils/gn/secondary/lld/unittests/MachOTests/BUILD.gn
@@ -1,13 +1,11 @@
-executable("MachOTests") {
-  # test/Unit/lit.cfg expects unittests in LLD_BINARY_DIR/unittest
-  output_dir = target_out_dir
+import("//llvm/utils/unittest/unittest.gni")
 
+unittest("MachOTests") {
   configs += [ "//llvm/utils/gn/build:lld_code" ]
   deps = [
     "//lld/lib/Driver",
     "//lld/lib/ReaderWriter/MachO",
     "//lld/lib/ReaderWriter/YAML",
-    "//llvm/utils/unittest/UnitTestMain",
   ]
   sources = [
     "MachONormalizedFileBinaryReaderTests.cpp",
@@ -15,5 +13,4 @@
     "MachONormalizedFileToAtomsTests.cpp",
     "MachONormalizedFileYAMLTests.cpp",
   ]
-  testonly = true
 }
Index: llvm/utils/gn/secondary/llvm/utils/unittest/unittest.gni
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/llvm/utils/unittest/unittest.gni
@@ -0,0 +1,44 @@
+# This file defines a template for adding a unittest binary.
+#
+# It's a thin wrapper around GN's built-in executable() target type and
+# accepts the same parameters.
+#
+# Example use:
+#
+#   unittest("FormatTest") {
+#     sources = [ ... ]
+#     ...
+#   }
+
+template("unittest") {
+  executable(target_name) {
+    # Foward everything (configs, sources, deps, ...).
+    forward_variables_from(invoker, "*")
+
+    # Common settings for all unit tests.
+    # Unit test binaries shouldn't go right in out/gn/bin, for two reasons:
+    # 1. That's where production binaries go.
+    # 2. The CMake build doesn't put the unit tests of all projects (clang,
+    #    lld,...) in one directory, so it's not guaranteed that there won't
+    #    be name collisions between test binaries from separate projects.
+    # Each lit suite takes an foo_obj_root parameter and puts temporary files
+    # for lit tests at foo_obj_root/test and looks for unit test binaries
+    # below foo_obj_root/unittests. As long as the BUILD.gn files processing
+    # the lit.site.cfg.py.in files match the output dir here, it doesn't
+    # matter all that much where the unit test binaries go, with the weak
+    # constraints that test binaries of different projects should go in
+    # different folders, and that it's not too difficult to manually
+    # run the unit test binary if necessary. Using target_out_dir here
+    # means that //clang/unittests/Format gets its binary in
+    # out/gn/obj/clang/unittests/Format/FormatTests, which seems fine.
+    output_dir = target_out_dir
+    deps += [
+      "//llvm/utils/unittest/UnitTestMain",
+    ]
+    testonly = true
+  }
+}
+
+set_defaults("unittest") {
+  configs = shared_binary_target_configs
+}