Index: llvm/trunk/include/llvm/Support/FileSystem.h
===================================================================
--- llvm/trunk/include/llvm/Support/FileSystem.h
+++ llvm/trunk/include/llvm/Support/FileSystem.h
@@ -720,9 +720,11 @@
                                  unsigned Mode = all_read | all_write,
                                  sys::fs::OpenFlags Flags = sys::fs::F_RW);
 
-/// @brief Simpler version for clients that don't want an open file.
+/// @brief Simpler version for clients that don't want an open file. An empty
+/// file will still be created.
 std::error_code createUniqueFile(const Twine &Model,
-                                 SmallVectorImpl<char> &ResultPath);
+                                 SmallVectorImpl<char> &ResultPath,
+                                 unsigned Mode = all_read | all_write);
 
 /// Represents a temporary file.
 ///
@@ -775,13 +777,36 @@
                                     SmallVectorImpl<char> &ResultPath,
                                     sys::fs::OpenFlags Flags = sys::fs::F_RW);
 
-/// @brief Simpler version for clients that don't want an open file.
+/// @brief Simpler version for clients that don't want an open file. An empty
+/// file will still be created.
 std::error_code createTemporaryFile(const Twine &Prefix, StringRef Suffix,
                                     SmallVectorImpl<char> &ResultPath);
 
 std::error_code createUniqueDirectory(const Twine &Prefix,
                                       SmallVectorImpl<char> &ResultPath);
 
+/// @brief Get a unique name, not currently exisiting in the filesystem. Subject
+/// to race conditions, prefer to use createUniqueFile instead.
+///
+/// Similar to createUniqueFile, but instead of creating a file only
+/// checks if it exists. This function is subject to race conditions, if you
+/// want to use the returned name to actually create a file, use
+/// createUniqueFile instead.
+std::error_code getPotentiallyUniqueFileName(const Twine &Model,
+                                             SmallVectorImpl<char> &ResultPath);
+
+/// @brief Get a unique temporary file name, not currently exisiting in the
+/// filesystem. Subject to race conditions, prefer to use createTemporaryFile
+/// instead.
+///
+/// Similar to createTemporaryFile, but instead of creating a file only
+/// checks if it exists. This function is subject to race conditions, if you
+/// want to use the returned name to actually create a file, use
+/// createTemporaryFile instead.
+std::error_code
+getPotentiallyUniqueTempFileName(const Twine &Prefix, StringRef Suffix,
+                                 SmallVectorImpl<char> &ResultPath);
+
 inline OpenFlags operator|(OpenFlags A, OpenFlags B) {
   return OpenFlags(unsigned(A) | unsigned(B));
 }
Index: llvm/trunk/lib/Support/Path.cpp
===================================================================
--- llvm/trunk/lib/Support/Path.cpp
+++ llvm/trunk/lib/Support/Path.cpp
@@ -757,9 +757,15 @@
 }
 
 std::error_code createUniqueFile(const Twine &Model,
-                                 SmallVectorImpl<char> &ResultPath) {
-  int Dummy;
-  return createUniqueEntity(Model, Dummy, ResultPath, false, 0, FS_Name);
+                                 SmallVectorImpl<char> &ResultPath,
+                                 unsigned Mode) {
+  int FD;
+  auto EC = createUniqueFile(Model, FD, ResultPath, Mode);
+  if (EC)
+    return EC;
+  // FD is only needed to avoid race conditions. Close it right away.
+  close(FD);
+  return EC;
 }
 
 static std::error_code
@@ -794,8 +800,13 @@
 
 std::error_code createTemporaryFile(const Twine &Prefix, StringRef Suffix,
                                     SmallVectorImpl<char> &ResultPath) {
-  int Dummy;
-  return createTemporaryFile(Prefix, Suffix, Dummy, ResultPath, FS_Name);
+  int FD;
+  auto EC = createTemporaryFile(Prefix, Suffix, FD, ResultPath);
+  if (EC)
+    return EC;
+  // FD is only needed to avoid race conditions. Close it right away.
+  close(FD);
+  return EC;
 }
 
 
@@ -804,8 +815,22 @@
 std::error_code createUniqueDirectory(const Twine &Prefix,
                                       SmallVectorImpl<char> &ResultPath) {
   int Dummy;
-  return createUniqueEntity(Prefix + "-%%%%%%", Dummy, ResultPath,
-                            true, 0, FS_Dir);
+  return createUniqueEntity(Prefix + "-%%%%%%", Dummy, ResultPath, true, 0,
+                            FS_Dir);
+}
+
+std::error_code
+getPotentiallyUniqueFileName(const Twine &Model,
+                             SmallVectorImpl<char> &ResultPath) {
+  int Dummy;
+  return createUniqueEntity(Model, Dummy, ResultPath, false, 0, FS_Name);
+}
+
+std::error_code
+getPotentiallyUniqueTempFileName(const Twine &Prefix, StringRef Suffix,
+                                 SmallVectorImpl<char> &ResultPath) {
+  int Dummy;
+  return createTemporaryFile(Prefix, Suffix, Dummy, ResultPath, FS_Name);
 }
 
 static std::error_code make_absolute(const Twine &current_directory,