1 files changed, 27 insertions, 14 deletions
diff --git a/clang/lib/Frontend/ModuleDependencyCollector.cpp b/clang/lib/Frontend/ModuleDependencyCollector.cpp
index 578910a..9b34d42 100644
--- a/clang/lib/Frontend/ModuleDependencyCollector.cpp
+++ b/clang/lib/Frontend/ModuleDependencyCollector.cpp
@@ -201,7 +201,8 @@ bool ModuleDependencyCollector::getRealPath(StringRef SrcPath,
   return true;
 }
 
-std::error_code ModuleDependencyCollector::copyToRoot(StringRef Src) {
+std::error_code ModuleDependencyCollector::copyToRoot(StringRef Src,
+                                                      StringRef Dst) {
   using namespace llvm::sys;
 
   // We need an absolute src path to append to the root.
@@ -213,23 +214,35 @@ std::error_code ModuleDependencyCollector::copyToRoot(StringRef Src) {
   AbsoluteSrc = path::remove_leading_dotslash(AbsoluteSrc);
 
   // Canonicalize the source path by removing "..", "." components.
-  SmallString<256> CanonicalPath = AbsoluteSrc;
-  path::remove_dots(CanonicalPath, /*remove_dot_dot=*/true);
+  SmallString<256> VirtualPath = AbsoluteSrc;
+  path::remove_dots(VirtualPath, /*remove_dot_dot=*/true);
 
   // If a ".." component is present after a symlink component, remove_dots may
   // lead to the wrong real destination path. Let the source be canonicalized
   // like that but make sure we always use the real path for the destination.
-  SmallString<256> RealPath;
-  if (!getRealPath(AbsoluteSrc, RealPath))
-    RealPath = CanonicalPath;
-  SmallString<256> Dest = getDest();
-  path::append(Dest, path::relative_path(RealPath));
+  SmallString<256> CopyFrom;
+  if (!getRealPath(AbsoluteSrc, CopyFrom))
+    CopyFrom = VirtualPath;
+  SmallString<256> CacheDst = getDest();
+
+  if (Dst.empty()) {
+    // The common case is to map the virtual path to the same path inside the
+    // cache.
+    path::append(CacheDst, path::relative_path(CopyFrom));
+  } else {
+    // When collecting entries from input vfsoverlays, copy the external
+    // contents into the cache but still map from the source.
+    if (!fs::exists(Dst))
+      return std::error_code();
+    path::append(CacheDst, Dst);
+    CopyFrom = Dst;
+  }
 
   // Copy the file into place.
-  if (std::error_code EC = fs::create_directories(path::parent_path(Dest),
-                                                   /*IgnoreExisting=*/true))
+  if (std::error_code EC = fs::create_directories(path::parent_path(CacheDst),
+                                                  /*IgnoreExisting=*/true))
     return EC;
-  if (std::error_code EC = fs::copy_file(RealPath, Dest))
+  if (std::error_code EC = fs::copy_file(CopyFrom, CacheDst))
     return EC;
 
   // Always map a canonical src path to its real path into the YAML, by doing
@@ -237,12 +250,12 @@ std::error_code ModuleDependencyCollector::copyToRoot(StringRef Src) {
   // overlay, which is a way to emulate symlink inside the VFS; this is also
   // needed for correctness, not doing that can lead to module redifinition
   // errors.
-  addFileMapping(CanonicalPath, Dest);
+  addFileMapping(VirtualPath, CacheDst);
   return std::error_code();
 }
 
-void ModuleDependencyCollector::addFile(StringRef Filename) {
+void ModuleDependencyCollector::addFile(StringRef Filename, StringRef FileDst) {
   if (insertSeen(Filename))
-    if (copyToRoot(Filename))
+    if (copyToRoot(Filename, FileDst))
       HasErrors = true;
 }