Index: clang/lib/Frontend/CompilerInstance.cpp
===================================================================
--- clang/lib/Frontend/CompilerInstance.cpp
+++ clang/lib/Frontend/CompilerInstance.cpp
@@ -661,11 +661,7 @@
     if (OF.TempFilename.empty())
       continue;
 
-    // If '-working-directory' was passed, the output filename should be
-    // relative to that.
-    SmallString<128> NewOutFile(OF.Filename);
-    FileMgr->FixupRelativePath(NewOutFile);
-    std::error_code EC = llvm::sys::fs::rename(OF.TempFilename, NewOutFile);
+    std::error_code EC = llvm::sys::fs::rename(OF.TempFilename, OF.Filename);
     if (!EC)
       continue;
     getDiagnostics().Report(diag::err_unable_to_rename_temp)
@@ -730,6 +726,15 @@
   assert((!CreateMissingDirectories || UseTemporary) &&
          "CreateMissingDirectories is only allowed when using temporary files");
 
+  // If '-working-directory' was passed, the output filename should be
+  // relative to that.
+  Optional<SmallString<128>> AbsPath;
+  if (!llvm::sys::path::is_absolute(OutputPath)) {
+    AbsPath.emplace(OutputPath);
+    FileMgr->FixupRelativePath(*AbsPath);
+    OutputPath = *AbsPath;
+  }
+
   std::unique_ptr<llvm::raw_fd_ostream> OS;
   Optional<StringRef> OSFile;
 
Index: clang/test/Frontend/output-paths.c
===================================================================
--- clang/test/Frontend/output-paths.c
+++ clang/test/Frontend/output-paths.c
@@ -2,3 +2,9 @@
 // RUN: FileCheck -check-prefix=OUTPUTFAIL -DMSG=%errc_ENOENT -input-file=%t %s
 
 // OUTPUTFAIL: error: unable to open output file '{{.*}}doesnotexist{{.}}somename': '[[MSG]]'
+
+// Check that -working-directory is respected when diagnosing output failures.
+//
+// RUN: rm -rf %t.d && mkdir -p %t.d/%basename_t-inner.d
+// RUN: %clang_cc1 -emit-llvm -working-directory %t.d -E -o %basename_t-inner.d/somename %s -verify
+// expected-no-diagnostics