Index: llvm/trunk/include/llvm/Support/FileSystem.h
===================================================================
--- llvm/trunk/include/llvm/Support/FileSystem.h
+++ llvm/trunk/include/llvm/Support/FileSystem.h
@@ -648,16 +648,27 @@
 /// A version for when a file descriptor is already available.
 std::error_code status(int FD, file_status &Result);
 
+/// Get file creation mode mask of the process.
+///
+/// @returns Mask reported by umask(2)
+/// @note There is no umask on Windows. This function returns 0 always
+///       on Windows. This function does not return an error_code because
+///       umask(2) never fails. It is not thread safe.
+unsigned getUmask();
+
 /// Set file permissions.
 ///
 /// @param Path File to set permissions on.
 /// @param Permissions New file permissions.
+/// @param RespectUmask If true then Permissions will be changed to respect the
+///        umask of the current process.
 /// @returns errc::success if the permissions were successfully set, otherwise
 ///          a platform-specific error_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 setPermissions(const Twine &Path, perms Permissions);
+std::error_code setPermissions(const Twine &Path, perms Permissions,
+                               bool RespectUmask = false);
 
 /// Get file permissions.
 ///
Index: llvm/trunk/lib/Support/Unix/Path.inc
===================================================================
--- llvm/trunk/lib/Support/Unix/Path.inc
+++ llvm/trunk/lib/Support/Unix/Path.inc
@@ -694,10 +694,22 @@
   return fillStatus(StatRet, Status, Result);
 }
 
-std::error_code setPermissions(const Twine &Path, perms Permissions) {
+unsigned getUmask() {
+  // Chose arbitary new mask and reset the umask to the old mask.
+  // umask(2) never fails so ignore the return of the second call.
+  unsigned Mask = ::umask(0);
+  (void) ::umask(Mask);
+  return Mask;
+}
+
+std::error_code setPermissions(const Twine &Path, perms Permissions,
+                               bool RespectUmask) {
   SmallString<128> PathStorage;
   StringRef P = Path.toNullTerminatedStringRef(PathStorage);
 
+  if (RespectUmask)
+    Permissions = static_cast<perms>(Permissions & ~getUmask());
+
   if (::chmod(P.begin(), Permissions))
     return std::error_code(errno, std::generic_category());
   return std::error_code();
Index: llvm/trunk/lib/Support/Windows/Path.inc
===================================================================
--- llvm/trunk/lib/Support/Windows/Path.inc
+++ llvm/trunk/lib/Support/Windows/Path.inc
@@ -734,7 +734,12 @@
   return getStatus(FileHandle, Result);
 }
 
-std::error_code setPermissions(const Twine &Path, perms Permissions) {
+unsigned getUmask() {
+  return 0;
+}
+
+std::error_code setPermissions(const Twine &Path, perms Permissions,
+                               bool /*RespectUmask*/) {
   SmallVector<wchar_t, 128> PathUTF16;
   if (std::error_code EC = widenPath(Path, PathUTF16))
     return EC;
Index: llvm/trunk/unittests/Support/Path.cpp
===================================================================
--- llvm/trunk/unittests/Support/Path.cpp
+++ llvm/trunk/unittests/Support/Path.cpp
@@ -1526,6 +1526,59 @@
   EXPECT_EQ(TestDirectoryIsLocal, TempFileIsLocal);
 }
 
+TEST_F(FileSystemTest, getUmask) {
+#ifdef _WIN32
+  EXPECT_EQ(fs::getUmask(), 0U) << "Should always be 0 on Windows.";
+#else
+  unsigned OldMask = ::umask(0022);
+  unsigned CurrentMask = fs::getUmask();
+  EXPECT_EQ(CurrentMask, 0022U)
+      << "getUmask() didn't return previously set umask()";
+  EXPECT_EQ(::umask(OldMask), 0022) << "getUmask() may have changed umask()";
+#endif
+}
+
+TEST_F(FileSystemTest, RespectUmask) {
+#ifndef _WIN32
+  unsigned OldMask = ::umask(0022);
+
+  int FD;
+  SmallString<128> TempPath;
+  ASSERT_NO_ERROR(fs::createTemporaryFile("prefix", "temp", FD, TempPath));
+
+  fs::perms AllRWE = static_cast<fs::perms>(0777);
+
+  ASSERT_NO_ERROR(fs::setPermissions(TempPath, AllRWE /*RespectUmask=false*/));
+
+  ErrorOr<fs::perms> Perms = fs::getPermissions(TempPath);
+  ASSERT_TRUE(!!Perms);
+  EXPECT_EQ(Perms.get(), AllRWE) << "Should have ignored umask by default";
+
+  ASSERT_NO_ERROR(fs::setPermissions(TempPath, AllRWE, /*RespectUmask=*/false));
+
+  ErrorOr<fs::perms> Perms = fs::getPermissions(TempPath);
+  ASSERT_TRUE(!!Perms);
+  EXPECT_EQ(Perms.get(), AllRWE) << "Should have ignored umask";
+
+  ASSERT_NO_ERROR(fs::setPermissions(TempPath, AllRWE, /*RespectUmask=*/true));
+  Perms = fs::getPermissions(TempPath);
+  ASSERT_TRUE(!!Perms);
+  EXPECT_EQ(Perms.get(), static_cast<fs::perms>(0755))
+      << "Did not respect umask";
+
+  (void)::umask(0057);
+
+  ASSERT_NO_ERROR(fs::setPermissions(TempPath, AllRWE, /*RespectUmask=*/true));
+  Perms = fs::getPermissions(TempPath);
+  ASSERT_TRUE(!!Perms);
+  EXPECT_EQ(Perms.get(), static_cast<fs::perms>(0720))
+      << "Did not respect umask";
+
+  (void)::umask(OldMask);
+  (void)::close(FD);
+#endif
+}
+
 TEST_F(FileSystemTest, set_current_path) {
   SmallString<128> path;