Index: lib/Basic/FileManager.cpp
===================================================================
--- lib/Basic/FileManager.cpp
+++ lib/Basic/FileManager.cpp
@@ -497,8 +497,22 @@
   StringRef CanonicalName(Dir->getName());
 
   SmallString<4096> CanonicalNameBuf;
+#ifdef _WIN32
+  CanonicalNameBuf = CanonicalName;
+  llvm::sys::fs::make_absolute(CanonicalNameBuf);
+  llvm::sys::path::native(CanonicalNameBuf);
+  // We've run into needing to remove '..' here in the wild though, so
+  // remove it.
+  // On Windows, symlinks are significantly less prevalent, so removing
+  // '..' is pretty safe.
+  // Ideally we'd have an equivalent of `realpath` and could implement
+  // sys::fs::canonical across all the platforms.
+  llvm::sys::path::remove_dots(CanonicalNameBuf, /* remove_dot_dot */ true);
+  CanonicalName = StringRef(CanonicalNameBuf).copy(CanonicalNameStorage);
+#else
   if (!FS->getRealPath(Dir->getName(), CanonicalNameBuf))
     CanonicalName = StringRef(CanonicalNameBuf).copy(CanonicalNameStorage);
+#endif
 
   CanonicalDirNames.insert({Dir, CanonicalName});
   return CanonicalName;
Index: test/Frontend/absolute-paths-windows.test
===================================================================
--- /dev/null
+++ test/Frontend/absolute-paths-windows.test
@@ -0,0 +1,9 @@
+// REQUIRES: system-windows
+// RUN: rm -rf %t.dir
+// RUN: mkdir -p %t.dir\real
+// RUN: cmd /c mklink /j %t.dir\junc %t.dir\real
+// RUN: echo "wrong code" > %t.dir\real\foo.cpp
+// RUN: not %clang_cc1 -fsyntax-only -fdiagnostics-absolute-paths %t.dir\junc\foo.cpp 2>&1 | FileCheck %s
+
+// CHECK-NOT: .dir\real\foo.cpp
+// CHECK: .dir\junc\foo.cpp
Index: test/Frontend/lit.local.cfg
===================================================================
--- test/Frontend/lit.local.cfg
+++ test/Frontend/lit.local.cfg
@@ -1 +1 @@
-config.suffixes = ['.c', '.cpp', '.m', '.mm', '.ll', '.cl']
+config.suffixes = ['.c', '.cpp', '.m', '.mm', '.ll', '.cl', '.test']