diff --git a/llvm/utils/gn/secondary/BUILD.gn b/llvm/utils/gn/secondary/BUILD.gn
--- a/llvm/utils/gn/secondary/BUILD.gn
+++ b/llvm/utils/gn/secondary/BUILD.gn
@@ -9,6 +9,9 @@
     "//lld/test",
     "//llvm/test",
   ]
+  if (current_os == "linux") {
+    deps += [ "//compiler-rt" ]
+  }
   if (current_os == "linux" || current_os == "android") {
     deps += [ "//compiler-rt/test/hwasan" ]
   }
diff --git a/llvm/utils/gn/secondary/clang/runtimes.gni b/llvm/utils/gn/secondary/clang/runtimes.gni
new file mode 100644
--- /dev/null
+++ b/llvm/utils/gn/secondary/clang/runtimes.gni
@@ -0,0 +1,13 @@
+import("//clang/resource_dir.gni")
+import("//llvm/triples.gni")
+
+declare_args() {
+  # Enable per-target runtimes directory.
+  clang_enable_per_target_runtime_dir = false
+}
+
+if (clang_enable_per_target_runtime_dir) {
+  runtimes_dir = "$clang_resource_dir/$llvm_target_triple/lib"
+} else {
+  runtimes_dir = "$root_build_dir/lib"
+}
diff --git a/llvm/utils/gn/secondary/compiler-rt/BUILD.gn b/llvm/utils/gn/secondary/compiler-rt/BUILD.gn
new file mode 100644
--- /dev/null
+++ b/llvm/utils/gn/secondary/compiler-rt/BUILD.gn
@@ -0,0 +1,5 @@
+group("compiler-rt") {
+  deps = [
+    "lib(//llvm/utils/gn/build/toolchain:stage2_unix)",
+  ]
+}
diff --git a/llvm/utils/gn/secondary/compiler-rt/lib/BUILD.gn b/llvm/utils/gn/secondary/compiler-rt/lib/BUILD.gn
new file mode 100644
--- /dev/null
+++ b/llvm/utils/gn/secondary/compiler-rt/lib/BUILD.gn
@@ -0,0 +1,5 @@
+group("lib") {
+  deps = [
+    "builtins",
+  ]
+}
diff --git a/llvm/utils/gn/secondary/compiler-rt/lib/builtins/BUILD.gn b/llvm/utils/gn/secondary/compiler-rt/lib/builtins/BUILD.gn
new file mode 100644
--- /dev/null
+++ b/llvm/utils/gn/secondary/compiler-rt/lib/builtins/BUILD.gn
@@ -0,0 +1,269 @@
+import("//compiler-rt/target.gni")
+import("//llvm/utils/gn/build/buildflags.gni")
+
+declare_args() {
+  # Skip the atomic builtin (these should normally be provided by a shared library)
+  compiler_rt_exclude_atomic_builtin = true
+
+  # Compile builtins for baremetal.
+  compiler_rt_baremetal_build = false
+}
+
+static_library("builtins") {
+  output_dir = crt_current_out_dir
+  output_name = "clang_rt.builtins-$crt_current_target"
+  complete_static_lib = true
+  cflags = [
+    "-fPIC",
+    "-fno-builtin",
+  ]
+  if (target_os != "android") {
+    cflags += [ "-fvisibility=hidden" ]
+  }
+  if (!is_debug) {
+    cflags += [ "-fomit-frame-pointer" ]
+  }
+  cflags_c = [ "-std=c11" ]
+  configs -= [ "//llvm/utils/gn/build:thin_archive" ]
+
+  sources = [
+    "absvdi2.c",
+    "absvsi2.c",
+    "absvti2.c",
+    "adddf3.c",
+    "addsf3.c",
+    "addtf3.c",
+    "addvdi3.c",
+    "addvsi3.c",
+    "addvti3.c",
+    "apple_versioning.c",
+    "ashldi3.c",
+    "ashlti3.c",
+    "ashrdi3.c",
+    "ashrti3.c",
+    "bswapdi2.c",
+    "bswapsi2.c",
+    "clzdi2.c",
+    "clzsi2.c",
+    "clzti2.c",
+    "cmpdi2.c",
+    "cmpti2.c",
+    "comparedf2.c",
+    "comparesf2.c",
+    "ctzdi2.c",
+    "ctzsi2.c",
+    "ctzti2.c",
+    "divdc3.c",
+    "divdf3.c",
+    "divdi3.c",
+    "divmoddi4.c",
+    "divmodsi4.c",
+    "divsc3.c",
+    "divsf3.c",
+    "divsi3.c",
+    "divtc3.c",
+    "divti3.c",
+    "divtf3.c",
+    "extendsfdf2.c",
+    "extendhfsf2.c",
+    "ffsdi2.c",
+    "ffssi2.c",
+    "ffsti2.c",
+    "fixdfdi.c",
+    "fixdfsi.c",
+    "fixdfti.c",
+    "fixsfdi.c",
+    "fixsfsi.c",
+    "fixsfti.c",
+    "fixunsdfdi.c",
+    "fixunsdfsi.c",
+    "fixunsdfti.c",
+    "fixunssfdi.c",
+    "fixunssfsi.c",
+    "fixunssfti.c",
+    "floatdidf.c",
+    "floatdisf.c",
+    "floatsidf.c",
+    "floatsisf.c",
+    "floattidf.c",
+    "floattisf.c",
+    "floatundidf.c",
+    "floatundisf.c",
+    "floatunsidf.c",
+    "floatunsisf.c",
+    "floatuntidf.c",
+    "floatuntisf.c",
+    "int_util.c",
+    "lshrdi3.c",
+    "lshrti3.c",
+    "moddi3.c",
+    "modsi3.c",
+    "modti3.c",
+    "muldc3.c",
+    "muldf3.c",
+    "muldi3.c",
+    "mulodi4.c",
+    "mulosi4.c",
+    "muloti4.c",
+    "mulsc3.c",
+    "mulsf3.c",
+    "multi3.c",
+    "multf3.c",
+    "mulvdi3.c",
+    "mulvsi3.c",
+    "mulvti3.c",
+    "negdf2.c",
+    "negdi2.c",
+    "negsf2.c",
+    "negti2.c",
+    "negvdi2.c",
+    "negvsi2.c",
+    "negvti2.c",
+    "os_version_check.c",
+    "paritydi2.c",
+    "paritysi2.c",
+    "parityti2.c",
+    "popcountdi2.c",
+    "popcountsi2.c",
+    "popcountti2.c",
+    "powidf2.c",
+    "powisf2.c",
+    "powitf2.c",
+    "subdf3.c",
+    "subsf3.c",
+    "subvdi3.c",
+    "subvsi3.c",
+    "subvti3.c",
+    "subtf3.c",
+    "trampoline_setup.c",
+    "truncdfhf2.c",
+    "truncdfsf2.c",
+    "truncsfhf2.c",
+    "ucmpdi2.c",
+    "ucmpti2.c",
+    "udivdi3.c",
+    "udivmoddi4.c",
+    "udivmodsi4.c",
+    "udivmodti4.c",
+    "udivsi3.c",
+    "udivti3.c",
+    "umoddi3.c",
+    "umodsi3.c",
+    "umodti3.c",
+  ]
+
+  if (target_os != "fuchsia") {
+    sources += [
+      "emutls.c ",
+      "enable_execute_stack.c",
+      "eprintf.c",
+    ]
+  }
+
+  if (target_os != "fuchsia" && !compiler_rt_baremetal_build) {
+    sources += [ "clear_cache.c" ]
+  }
+
+  if (target_os == "mac") {
+    sources += [
+      "atomic_flag_clear.c",
+      "atomic_flag_clear_explicit.c",
+      "atomic_flag_test_and_set.c",
+      "atomic_flag_test_and_set_explicit.c",
+      "atomic_signal_fence.c",
+      "atomic_thread_fence.c",
+    ]
+  }
+
+  if (target_cpu == "x86" || target_cpu == "x64") {
+    sources += [
+      "cpu_model.c",
+      "divxc3.c",
+      "fixxfdi.c",
+      "fixxfti.c",
+      "fixunsxfdi.c",
+      "fixunsxfsi.c",
+      "fixunsxfti.c",
+      "floatdixf.c",
+      "floattixf.c",
+      "floatundixf.c",
+      "floatuntixf.c",
+      "mulxc3.c",
+      "powixf2.c",
+    ]
+
+    if (target_os == "win") {
+      # Use C versions of functions when building on MSVC
+      # MSVC's assembler takes Intel syntax, not AT&T syntax.
+      # Also use only MSVC compilable builtin implementations.
+      sources += [
+        "x86_64/floatdidf.c",
+        "x86_64/floatdisf.c",
+        "x86_64/floatdixf.c",
+      ]
+    }
+  }
+
+  if (target_cpu == "arm") {
+    sources += [
+      "arm/bswapdi2.S",
+      "arm/bswapsi2.S",
+      "arm/clzdi2.S",
+      "arm/clzsi2.S",
+      "arm/comparesf2.S",
+      "arm/divmodsi4.S",
+      "arm/divsi3.S",
+      "arm/modsi3.S",
+      "arm/sync_fetch_and_add_4.S",
+      "arm/sync_fetch_and_add_8.S",
+      "arm/sync_fetch_and_and_4.S",
+      "arm/sync_fetch_and_and_8.S",
+      "arm/sync_fetch_and_max_4.S",
+      "arm/sync_fetch_and_max_8.S",
+      "arm/sync_fetch_and_min_4.S",
+      "arm/sync_fetch_and_min_8.S",
+      "arm/sync_fetch_and_nand_4.S",
+      "arm/sync_fetch_and_nand_8.S",
+      "arm/sync_fetch_and_or_4.S",
+      "arm/sync_fetch_and_or_8.S",
+      "arm/sync_fetch_and_sub_4.S",
+      "arm/sync_fetch_and_sub_8.S",
+      "arm/sync_fetch_and_umax_4.S",
+      "arm/sync_fetch_and_umax_8.S",
+      "arm/sync_fetch_and_umin_4.S",
+      "arm/sync_fetch_and_umin_8.S",
+      "arm/sync_fetch_and_xor_4.S",
+      "arm/sync_fetch_and_xor_8.S",
+      "arm/udivmodsi4.S",
+      "arm/udivsi3.S",
+      "arm/umodsi3.S",
+    ]
+  }
+
+  if (target_cpu == "arm64") {
+    sources += [
+      "comparetf2.c",
+      "extenddftf2.c",
+      "extendsftf2.c",
+      "fixtfdi.c",
+      "fixtfsi.c",
+      "fixtfti.c",
+      "fixunstfdi.c",
+      "fixunstfsi.c",
+      "fixunstfti.c",
+      "floatditf.c",
+      "floatsitf.c",
+      "floattitf.c",
+      "floatunditf.c",
+      "floatunsitf.c",
+      "floatuntitf.c",
+      "multc3.c",
+      "trunctfdf2.c",
+      "trunctfsf2.c",
+    ]
+  }
+
+  if (!compiler_rt_exclude_atomic_builtin) {
+    sources += [ "atomic.c" ]
+  }
+}
diff --git a/llvm/utils/gn/secondary/compiler-rt/target.gni b/llvm/utils/gn/secondary/compiler-rt/target.gni
--- a/llvm/utils/gn/secondary/compiler-rt/target.gni
+++ b/llvm/utils/gn/secondary/compiler-rt/target.gni
@@ -1,6 +1,9 @@
 import("//clang/resource_dir.gni")
+import("//clang/runtimes.gni")
 
-if (current_os == "linux" || current_os == "android") {
+if (clang_enable_per_target_runtime_dir) {
+  crt_current_out_dir = runtimes_dir
+} else if (current_os == "linux" || current_os == "android") {
   crt_current_out_dir = "$clang_resource_dir/lib/linux"
 } else {
   assert(false, "unimplemented current_os " + current_os)