Index: include/llvm/Support/VirtualFileSystem.h
===================================================================
--- include/llvm/Support/VirtualFileSystem.h
+++ include/llvm/Support/VirtualFileSystem.h
@@ -67,6 +67,7 @@
   static Status copyWithNewName(const Status &In, StringRef NewName);
   static Status copyWithNewName(const llvm::sys::fs::file_status &In,
                                 StringRef NewName);
+  static Status copyWithNewSize(const Status &In, uint64_t Size);
 
   /// Returns the name that should be used for this file or directory.
   StringRef getName() const { return Name; }
Index: lib/Support/VirtualFileSystem.cpp
===================================================================
--- lib/Support/VirtualFileSystem.cpp
+++ lib/Support/VirtualFileSystem.cpp
@@ -85,6 +85,12 @@
                 In.permissions());
 }
 
+Status Status::copyWithNewSize(const Status &In, uint64_t Size) {
+  return Status(In.getName(), In.getUniqueID(), In.getLastModificationTime(),
+                In.getUser(), In.getGroup(), Size, In.getType(),
+                In.getPermissions());
+}
+
 bool Status::equivalent(const Status &Other) const {
   assert(isStatusKnown() && Other.isStatusKnown());
   return getUniqueID() == Other.getUniqueID();
Index: unittests/Support/VirtualFileSystemTest.cpp
===================================================================
--- unittests/Support/VirtualFileSystemTest.cpp
+++ unittests/Support/VirtualFileSystemTest.cpp
@@ -1775,3 +1775,14 @@
   checkContents(FS->dir_begin("//root/foo", EC),
                 {"//root/foo/a", "//root/foo/b"});
 }
+
+TEST_F(InMemoryFileSystemTest, CopyStatusWithSize) {
+  FS.addFile("/a", 0, MemoryBuffer::getMemBuffer("a"));
+  auto Stat = FS.status("/a");
+  ASSERT_TRUE(Stat);
+  auto CopyStat = vfs::Status::copyWithNewSize(*Stat, 2);
+  ASSERT_EQ(CopyStat.getSize(), 2u);
+  ASSERT_NE(CopyStat.getSize(), Stat->getSize());
+  ASSERT_EQ(CopyStat.getName(), Stat->getName());
+  ASSERT_EQ(CopyStat.getUniqueID(), Stat->getUniqueID());
+}