diff --git a/lib/Support/Unix/PathV2.inc b/lib/Support/Unix/PathV2.inc
index b18023c..d8575bf 100644
--- a/lib/Support/Unix/PathV2.inc
+++ b/lib/Support/Unix/PathV2.inc
@@ -263,6 +263,20 @@
   return make_error_code(errc::success);
 }
 
+error_code file_size(const Twine &path, uint64_t &result) {
+  SmallString<128> path_storage;
+  StringRef p = path.toNullTerminatedStringRef(path_storage);
+
+  struct stat status;
+  if (::stat(p.begin(), &status) == -1)
+    return error_code(errno, system_category());
+  if (!S_ISREG(status.st_mode))
+    return error_code(EPERM, system_category());
+
+  result = status.st_size;
+  return make_error_code(errc::success);
+}
+
 error_code unique_file(const Twine &model, int &result_fd,
                              SmallVectorImpl<char> &result_path) {
   SmallString<128> Model;
diff --git a/lib/Support/Windows/PathV2.inc b/lib/Support/Windows/PathV2.inc
index e7aa93b..dd7fefa 100644
--- a/lib/Support/Windows/PathV2.inc
+++ b/lib/Support/Windows/PathV2.inc
@@ -406,6 +406,27 @@
   return make_error_code(errc::success);
 }
 
+error_code file_size(const Twine &path, uint64_t &result) {
+  SmallString<128> path_storage;
+  SmallVector<wchar_t, 128> path_utf16;
+
+  if (error_code ec = UTF8ToUTF16(path.toStringRef(path_storage),
+                                  path_utf16))
+    return ec;
+
+  WIN32_FILE_ATTRIBUTE_DATA FileData;
+  if (!::GetFileAttributesExW(path_utf16.begin(),
+                              ::GetFileExInfoStandard,
+                              &FileData))
+    return make_error_code(windows_error(::GetLastError()));
+
+  result =
+    (uint64_t(FileData.nFileSizeHigh) << (sizeof(FileData.nFileSizeLow) * 8))
+    + FileData.nFileSizeLow;
+
+  return make_error_code(errc::success);
+}
+
 error_code unique_file(const Twine &model, int &result_fd,
                              SmallVectorImpl<char> &result_path) {
   // Use result_path as temp storage.