Support/FileSystem: Add rename implementation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120818 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/Unix/PathV2.inc b/lib/Support/Unix/PathV2.inc
index e6972f8..8ecf2a4 100644
--- a/lib/Support/Unix/PathV2.inc
+++ b/lib/Support/Unix/PathV2.inc
@@ -200,6 +200,19 @@
   return make_error_code(errc::success);
 }
 
+error_code rename(const Twine &from, const Twine &to) {
+  // Get arguments.
+  SmallString<128> from_storage;
+  SmallString<128> to_storage;
+  StringRef f = from.toNullTerminatedStringRef(from_storage);
+  StringRef t = to.toNullTerminatedStringRef(to_storage);
+
+  if (::rename(f.begin(), t.begin()) == -1)
+    return error_code(errno, system_category());
+
+  return make_error_code(errc::success);
+}
+
 error_code exists(const Twine &path, bool &result) {
   SmallString<128> path_storage;
   StringRef p = path.toNullTerminatedStringRef(path_storage);