diff --git a/llvm/include/llvm/Support/CommandLine.h b/llvm/include/llvm/Support/CommandLine.h
--- a/llvm/include/llvm/Support/CommandLine.h
+++ b/llvm/include/llvm/Support/CommandLine.h
@@ -20,6 +20,7 @@
 #define LLVM_SUPPORT_COMMANDLINE_H
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
@@ -40,6 +41,12 @@
 #include <vector>
 
 namespace llvm {
+namespace vfs {
+
+class FileSystem;
+IntrusiveRefCntPtr<FileSystem> getRealFileSystem();
+
+} // namespace vfs
 
 class StringSaver;
 class raw_ostream;
@@ -1964,10 +1971,13 @@
 /// with nullptrs in the Argv vector.
 /// \param [in] RelativeNames true if names of nested response files must be
 /// resolved relative to including file.
+/// \param [in] FS File system used for all file access when running the tool.
 /// \return true if all @files were expanded successfully or there were none.
-bool ExpandResponseFiles(StringSaver &Saver, TokenizerCallback Tokenizer,
-                         SmallVectorImpl<const char *> &Argv,
-                         bool MarkEOLs = false, bool RelativeNames = false);
+bool ExpandResponseFiles(
+    StringSaver &Saver, TokenizerCallback Tokenizer,
+    SmallVectorImpl<const char *> &Argv, bool MarkEOLs = false,
+    bool RelativeNames = false,
+    llvm::vfs::FileSystem &FS = *llvm::vfs::getRealFileSystem());
 
 /// Mark all options not part of this category as cl::ReallyHidden.
 ///
diff --git a/llvm/lib/Support/CommandLine.cpp b/llvm/lib/Support/CommandLine.cpp
--- a/llvm/lib/Support/CommandLine.cpp
+++ b/llvm/lib/Support/CommandLine.cpp
@@ -37,6 +37,7 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Process.h"
 #include "llvm/Support/StringSaver.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstdlib>
 #include <map>
@@ -1046,9 +1047,10 @@
 static bool ExpandResponseFile(StringRef FName, StringSaver &Saver,
                                TokenizerCallback Tokenizer,
                                SmallVectorImpl<const char *> &NewArgv,
-                               bool MarkEOLs, bool RelativeNames) {
+                               bool MarkEOLs, bool RelativeNames,
+                               llvm::vfs::FileSystem &FS) {
   ErrorOr<std::unique_ptr<MemoryBuffer>> MemBufOrErr =
-      MemoryBuffer::getFile(FName);
+      FS.getBufferForFile(FName);
   if (!MemBufOrErr)
     return false;
   MemoryBuffer &MemBuf = *MemBufOrErr.get();
@@ -1068,6 +1070,9 @@
   else if (hasUTF8ByteOrderMark(BufRef))
     Str = StringRef(BufRef.data() + 3, BufRef.size() - 3);
 
+  llvm::ErrorOr<std::string> CurrDir = FS.getCurrentWorkingDirectory();
+  if (!CurrDir)
+    return false;
   // Tokenize the contents into NewArgv.
   Tokenizer(Str, Saver, NewArgv, MarkEOLs);
 
@@ -1084,9 +1089,7 @@
             SmallString<128> ResponseFile;
             ResponseFile.append(1, '@');
             if (llvm::sys::path::is_relative(FName)) {
-              SmallString<128> curr_dir;
-              llvm::sys::fs::current_path(curr_dir);
-              ResponseFile.append(curr_dir.str());
+              ResponseFile.append(CurrDir.get());
             }
             llvm::sys::path::append(
                 ResponseFile, llvm::sys::path::parent_path(FName), FileName);
@@ -1101,8 +1104,8 @@
 /// Expand response files on a command line recursively using the given
 /// StringSaver and tokenization strategy.
 bool cl::ExpandResponseFiles(StringSaver &Saver, TokenizerCallback Tokenizer,
-                             SmallVectorImpl<const char *> &Argv,
-                             bool MarkEOLs, bool RelativeNames) {
+                             SmallVectorImpl<const char *> &Argv, bool MarkEOLs,
+                             bool RelativeNames, llvm::vfs::FileSystem &FS) {
   bool AllExpanded = true;
   struct ResponseFileRecord {
     const char *File;
@@ -1139,8 +1142,13 @@
     }
 
     const char *FName = Arg + 1;
-    auto IsEquivalent = [FName](const ResponseFileRecord &RFile) {
-      return sys::fs::equivalent(RFile.File, FName);
+    auto IsEquivalent = [FName, &FS](const ResponseFileRecord &RFile) {
+      SmallVector<char, 128> LHSPath;
+      SmallVector<char, 128> RHSPath;
+      if (FS.getRealPath(FName, LHSPath) || FS.getRealPath(RFile.File, RHSPath)) {
+        return false;
+      }
+      return LHSPath == RHSPath;
     };
 
     // Check for recursive response files.
@@ -1156,7 +1164,7 @@
     // contents.  Nested response files are expanded in subsequent iterations.
     SmallVector<const char *, 0> ExpandedArgv;
     if (!ExpandResponseFile(FName, Saver, Tokenizer, ExpandedArgv, MarkEOLs,
-                            RelativeNames)) {
+                            RelativeNames, FS)) {
       // We couldn't read this file, so we leave it in the argument stream and
       // move on.
       AllExpanded = false;
@@ -1187,7 +1195,8 @@
 bool cl::readConfigFile(StringRef CfgFile, StringSaver &Saver,
                         SmallVectorImpl<const char *> &Argv) {
   if (!ExpandResponseFile(CfgFile, Saver, cl::tokenizeConfigFile, Argv,
-                          /*MarkEOLs*/ false, /*RelativeNames*/ true))
+                          /*MarkEOLs*/ false, /*RelativeNames*/ true,
+                          *llvm::vfs::getRealFileSystem()))
     return false;
   return ExpandResponseFiles(Saver, cl::tokenizeConfigFile, Argv,
                              /*MarkEOLs*/ false, /*RelativeNames*/ true);