Index: include/llvm/Support/FileSystem.h
===================================================================
--- include/llvm/Support/FileSystem.h
+++ include/llvm/Support/FileSystem.h
@@ -181,7 +181,7 @@
 
   file_status(file_type Type) : Type(Type) {}
 
-  file_status(file_type Type, uint32_t LastAccessTimeHigh,
+  file_status(file_type Type, perms Perms, uint32_t LastAccessTimeHigh,
               uint32_t LastAccessTimeLow, uint32_t LastWriteTimeHigh,
               uint32_t LastWriteTimeLow, uint32_t VolumeSerialNumber,
               uint32_t FileSizeHigh, uint32_t FileSizeLow,
@@ -191,7 +191,7 @@
         LastWriteTimeLow(LastWriteTimeLow),
         VolumeSerialNumber(VolumeSerialNumber), FileSizeHigh(FileSizeHigh),
         FileSizeLow(FileSizeLow), FileIndexHigh(FileIndexHigh),
-        FileIndexLow(FileIndexLow), Type(Type) {}
+        FileIndexLow(FileIndexLow), Type(Type), Perms(Perms) {}
   #endif
 
   // getters
@@ -562,6 +562,16 @@
 /// @brief A version for when a file descriptor is already available.
 std::error_code status(int FD, file_status &Result);
 
+/// @brief Set file permissions.
+///
+/// @param Permissions New file permissions.
+/// @returns errc::success if the permissions were successfully set, otherwise
+///          a platform-specific erroc_code.
+/// @note On Windows, all permissions except *_write are ignored. Using any of
+///       owner_write, group_write, or all_write will make the file writable.
+///       Otherwise, the file will be marked as read-only.
+std::error_code permissions(const Twine &Path, perms Permissions);
+
 /// @brief Get file size.
 ///
 /// @param Path Input path.
Index: lib/Support/Unix/Path.inc
===================================================================
--- lib/Support/Unix/Path.inc
+++ lib/Support/Unix/Path.inc
@@ -527,6 +527,15 @@
   return fillStatus(StatRet, Status, Result);
 }
 
+std::error_code permissions(const Twine &Path, sys::fs::perms Permissions) {
+  SmallString<128> PathStorage;
+  StringRef P = Path.toNullTerminatedStringRef(PathStorage);
+
+  if (::chmod(P.begin(), Permissions))
+    return std::error_code(errno, std::generic_category());
+  return std::error_code();
+}
+
 std::error_code setLastModificationAndAccessTime(int FD, TimePoint<> Time) {
 #if defined(HAVE_FUTIMENS)
   timespec Times[2];
Index: lib/Support/Windows/Path.inc
===================================================================
--- lib/Support/Windows/Path.inc
+++ lib/Support/Windows/Path.inc
@@ -529,13 +529,15 @@
     file_type Type = (Info.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
                          ? file_type::directory_file
                          : file_type::regular_file;
-    Result =
-        file_status(Type, Info.ftLastAccessTime.dwHighDateTime,
-                    Info.ftLastAccessTime.dwLowDateTime,
-                    Info.ftLastWriteTime.dwHighDateTime,
-                    Info.ftLastWriteTime.dwLowDateTime,
-                    Info.dwVolumeSerialNumber, Info.nFileSizeHigh,
-                    Info.nFileSizeLow, Info.nFileIndexHigh, Info.nFileIndexLow);
+    perms Permissions = (Info.dwFileAttributes & FILE_ATTRIBUTE_READONLY)
+                            ? (all_read | all_exe)
+                            : all_all;
+    Result = file_status(
+        Type, Permissions, Info.ftLastAccessTime.dwHighDateTime,
+        Info.ftLastAccessTime.dwLowDateTime,
+        Info.ftLastWriteTime.dwHighDateTime, Info.ftLastWriteTime.dwLowDateTime,
+        Info.dwVolumeSerialNumber, Info.nFileSizeHigh, Info.nFileSizeLow,
+        Info.nFileIndexHigh, Info.nFileIndexLow);
     return std::error_code();
   }
 
@@ -588,6 +590,24 @@
   return getStatus(FileHandle, Result);
 }
 
+std::error_code permissions(const Twine &Path, sys::fs::perms Permissions) {
+  SmallString<128> Storage;
+  SmallVector<wchar_t, 128> PathUTF16;
+
+  StringRef Path8 = Path.toStringRef(Storage);
+  if (std::error_code ec = widenPath(Path8, PathUTF16))
+    return ec;
+
+  DWORD NewAttributes = FILE_ATTRIBUTE_NORMAL;
+  if (!(Permissions &
+        (sys::fs::owner_write | sys::fs::group_write | sys::fs::all_write)))
+    NewAttributes = FILE_ATTRIBUTE_READONLY;
+  if (!::SetFileAttributesW(PathUTF16.begin(), NewAttributes))
+    return mapWindowsError(GetLastError());
+
+  return std::error_code();
+}
+
 std::error_code setLastModificationAndAccessTime(int FD, TimePoint<> Time) {
   FILETIME FT = toFILETIME(Time);
   HANDLE FileHandle = reinterpret_cast<HANDLE>(_get_osfhandle(FD));
Index: unittests/Support/Path.cpp
===================================================================
--- unittests/Support/Path.cpp
+++ unittests/Support/Path.cpp
@@ -1188,4 +1188,217 @@
   ASSERT_EQ(D1, D2) << "D1: " << TestDirectory << "\nD2: " << path;
 }
 
+TEST_F(FileSystemTest, permissions) {
+  int FD;
+  SmallString<64> TempPath;
+  ASSERT_NO_ERROR(fs::createTemporaryFile("prefix", "temp", FD, TempPath));
+  FileRemover Cleanup(TempPath);
+
+  // Make sure it exists.
+  ASSERT_TRUE(sys::fs::exists(Twine(TempPath)));
+
+  fs::file_status Status;
+  std::error_code NoError;
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_all), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_read | fs::all_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_read | fs::all_exe);
+
+#if defined(LLVM_ON_WIN32)
+  fs::perms ReadOnly = fs::all_read | fs::all_exe;
+  EXPECT_EQ(fs::permissions(TempPath, fs::no_perms), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::owner_read), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::owner_write), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::owner_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::owner_all), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::group_read), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::group_write), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::group_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::group_all), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::others_read), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::others_write), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::others_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::others_all), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_read), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_write), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::set_uid_on_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::set_gid_on_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::sticky_bit), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::set_uid_on_exe | fs::set_gid_on_exe |
+                                          fs::sticky_bit),
+            NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, ReadOnly | fs::set_uid_on_exe |
+                                          fs::set_gid_on_exe | fs::sticky_bit),
+            NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), ReadOnly);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_all | fs::set_uid_on_exe |
+                                          fs::set_gid_on_exe | fs::sticky_bit),
+            NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_all);
+#else
+  EXPECT_EQ(fs::permissions(TempPath, fs::no_perms), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::no_perms);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::owner_read), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::owner_read);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::owner_write), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::owner_write);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::owner_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::owner_exe);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::owner_all), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::owner_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::group_read), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::group_read);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::group_write), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::group_write);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::group_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::group_exe);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::group_all), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::group_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::others_read), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::others_read);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::others_write), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::others_write);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::others_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::others_exe);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::others_all), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::others_all);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_read), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_read);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_write), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_write);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_exe);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::set_uid_on_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::set_uid_on_exe);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::set_gid_on_exe), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::set_gid_on_exe);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::sticky_bit), NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::sticky_bit);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::set_uid_on_exe | fs::set_gid_on_exe |
+                                          fs::sticky_bit),
+            NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(),
+            fs::set_uid_on_exe | fs::set_gid_on_exe | fs::sticky_bit);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_read | fs::set_uid_on_exe |
+                                          fs::set_gid_on_exe | fs::sticky_bit),
+            NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_read | fs::set_uid_on_exe |
+                                      fs::set_gid_on_exe | fs::sticky_bit);
+
+  EXPECT_EQ(fs::permissions(TempPath, fs::all_all | fs::set_uid_on_exe |
+                                          fs::set_gid_on_exe | fs::sticky_bit),
+            NoError);
+  ASSERT_NO_ERROR(fs::status(FD, Status));
+  EXPECT_EQ(Status.permissions(), fs::all_all | fs::set_uid_on_exe |
+                                      fs::set_gid_on_exe | fs::sticky_bit);
+#endif
+}
 } // anonymous namespace