diff --git a/include/clang/Basic/DiagnosticDriverKinds.td b/include/clang/Basic/DiagnosticDriverKinds.td
index 95d67b1..5ff03e1 100644
--- a/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/include/clang/Basic/DiagnosticDriverKinds.td
@@ -91,6 +91,8 @@
   "there is no external assembler that can be used on this platform">;
 def err_drv_unable_to_remove_file : Error<
   "unable to remove file: %0">;
+def err_drv_unable_to_set_working_directory : Error <
+  "unable to set working directory: %0">;
 def err_drv_command_failure : Error<
   "unable to execute command: %0">;
 def err_drv_invalid_darwin_version : Error<
diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index 222efd5..7a0defe 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -1012,6 +1012,11 @@
     }
   }
 
+  // Check for working directory option before accessing any files
+  if (Arg *WD = Args.getLastArg(options::OPT_working_directory))
+    if (VFS->setCurrentWorkingDirectory(WD->getValue()))
+      Diag(diag::err_drv_unable_to_set_working_directory) << WD->getValue();
+
   // FIXME: This stuff needs to go into the Compilation, not the driver.
   bool CCCPrintPhases;
 
@@ -1993,20 +1998,11 @@
   if (Value == "-")
     return true;
 
-  SmallString<64> Path(Value);
-  if (Arg *WorkDir = Args.getLastArg(options::OPT_working_directory)) {
-    if (!llvm::sys::path::is_absolute(Path)) {
-      SmallString<64> Directory(WorkDir->getValue());
-      llvm::sys::path::append(Directory, Value);
-      Path.assign(Directory);
-    }
-  }
-
-  if (getVFS().exists(Path))
+  if (getVFS().exists(Value))
     return true;
 
   if (IsCLMode()) {
-    if (!llvm::sys::path::is_absolute(Twine(Path)) &&
+    if (!llvm::sys::path::is_absolute(Twine(Value)) &&
         llvm::sys::Process::FindInEnvPath("LIB", Value))
       return true;
 
@@ -2032,12 +2028,12 @@
     if (getOpts().findNearest(Value, Nearest, IncludedFlagsBitmask,
                               ExcludedFlagsBitmask) <= 1) {
       Diag(clang::diag::err_drv_no_such_file_with_suggestion)
-          << Path << Nearest;
+          << Value << Nearest;
       return false;
     }
   }
 
-  Diag(clang::diag::err_drv_no_such_file) << Path;
+  Diag(clang::diag::err_drv_no_such_file) << Value;
   return false;
 }
 
diff --git a/lib/Driver/ToolChains/Clang.cpp b/lib/Driver/ToolChains/Clang.cpp
index ad3f181..711d353 100644
--- a/lib/Driver/ToolChains/Clang.cpp
+++ b/lib/Driver/ToolChains/Clang.cpp
@@ -519,16 +519,15 @@
 }
 
 /// Add a CC1 option to specify the debug compilation directory.
-static void addDebugCompDirArg(const ArgList &Args, ArgStringList &CmdArgs) {
+static void addDebugCompDirArg(const ArgList &Args, ArgStringList &CmdArgs,
+                               const llvm::vfs::FileSystem &VFS) {
   if (Arg *A = Args.getLastArg(options::OPT_fdebug_compilation_dir)) {
     CmdArgs.push_back("-fdebug-compilation-dir");
     CmdArgs.push_back(A->getValue());
-  } else {
-    SmallString<128> cwd;
-    if (!llvm::sys::fs::current_path(cwd)) {
-      CmdArgs.push_back("-fdebug-compilation-dir");
-      CmdArgs.push_back(Args.MakeArgString(cwd));
-    }
+  } else if (llvm::ErrorOr<std::string> CWD =
+                 VFS.getCurrentWorkingDirectory()) {
+    CmdArgs.push_back("-fdebug-compilation-dir");
+    CmdArgs.push_back(Args.MakeArgString(*CWD));
   }
 }
 
@@ -808,13 +807,8 @@
     else
       OutputFilename = llvm::sys::path::filename(Output.getBaseInput());
     SmallString<128> CoverageFilename = OutputFilename;
-    if (llvm::sys::path::is_relative(CoverageFilename)) {
-      SmallString<128> Pwd;
-      if (!llvm::sys::fs::current_path(Pwd)) {
-        llvm::sys::path::append(Pwd, CoverageFilename);
-        CoverageFilename.swap(Pwd);
-      }
-    }
+    if (llvm::sys::path::is_relative(CoverageFilename))
+      (void)D.getVFS().makeAbsolute(CoverageFilename);
     llvm::sys::path::replace_extension(CoverageFilename, "gcno");
 
     CmdArgs.push_back("-coverage-notes-file");
@@ -1937,13 +1931,14 @@
     CompilationDatabase = std::move(File);
   }
   auto &CDB = *CompilationDatabase;
-  SmallString<128> Buf;
-  if (llvm::sys::fs::current_path(Buf))
-    Buf = ".";
-  CDB << "{ \"directory\": \"" << escape(Buf) << "\"";
+  auto CWD = D.getVFS().getCurrentWorkingDirectory();
+  if (!CWD)
+    CWD = ".";
+  CDB << "{ \"directory\": \"" << escape(*CWD) << "\"";
   CDB << ", \"file\": \"" << escape(Input.getFilename()) << "\"";
   CDB << ", \"output\": \"" << escape(Output.getFilename()) << "\"";
   CDB << ", \"arguments\": [\"" << escape(D.ClangExecutable) << "\"";
+  SmallString<128> Buf;
   Buf = "-x";
   Buf += types::getTypeName(Input.getType());
   CDB << ", \"" << escape(Buf) << "\"";
@@ -4377,7 +4372,7 @@
     CmdArgs.push_back("-fno-autolink");
 
   // Add in -fdebug-compilation-dir if necessary.
-  addDebugCompDirArg(Args, CmdArgs);
+  addDebugCompDirArg(Args, CmdArgs, D.getVFS());
 
   addDebugPrefixMapArg(D, Args, CmdArgs);
 
@@ -6138,7 +6133,7 @@
     DebugInfoKind = (WantDebug ? codegenoptions::LimitedDebugInfo
                                : codegenoptions::NoDebugInfo);
     // Add the -fdebug-compilation-dir flag if needed.
-    addDebugCompDirArg(Args, CmdArgs);
+    addDebugCompDirArg(Args, CmdArgs, C.getDriver().getVFS());
 
     addDebugPrefixMapArg(getToolChain().getDriver(), Args, CmdArgs);
 
diff --git a/test/Driver/gen-cdb-fragment.c b/test/Driver/gen-cdb-fragment.c
index f12a0e0..41d6989 100644
--- a/test/Driver/gen-cdb-fragment.c
+++ b/test/Driver/gen-cdb-fragment.c
@@ -15,6 +15,14 @@
 // RUN: %clang -target x86_64-apple-macos10.15 -S %s -o -  -gen-cdb-fragment-path %t.cdb
 // RUN: ls %t.cdb | FileCheck --check-prefix=CHECK-LS %s
 
+// Working directory arg is respected.
+// RUN: rm -rf %t.cdb
+// RUN: mkdir %t.cdb
+// RUN: %clang -target x86_64-apple-macos10.15 -working-directory %t.cdb -c %s -o -  -gen-cdb-fragment-path "."
+// RUN: ls %t.cdb | FileCheck --check-prefix=CHECK-LS %s
+// RUN: cat %t.cdb/*.json | FileCheck --check-prefix=CHECK-CWD %s
+// CHECK-CWD: "directory": "{{.*}}.cdb"
+
 // -### does not emit the CDB fragment
 // RUN: rm -rf %t.cdb
 // RUN: mkdir %t.cdb
diff --git a/test/Driver/working-directory.c b/test/Driver/working-directory.c
index 15ba8f0..7cfe22d 100644
--- a/test/Driver/working-directory.c
+++ b/test/Driver/working-directory.c
@@ -1,3 +1,12 @@
-// RUN: %clang -### -working-directory /no/such/dir/ input 2>&1 | FileCheck %s
+// RUN: %clang -### -coverage -working-directory /no/such/dir/ input 2>&1 | FileCheck %s
+// RUN: %clang -### -coverage -working-directory %p/Inputs no_such_file.cpp -c 2>&1 | FileCheck %s --check-prefix=CHECK_NO_FILE
+// RUN: %clang -### -coverage -working-directory %p/Inputs pchfile.cpp -c 2>&1 | FileCheck %s --check-prefix=CHECK_WORKS
+// RUN: fail please
 
-//CHECK: no such file or directory: '/no/such/dir/input'
+// CHECK: unable to set working directory: /no/such/dir/
+
+// CHECK_NO_FILE: no such file or directory: 'no_such_file.cpp'
+
+// CHECK_WORKS: "-coverage-notes-file" "{{[^"]+}}test{{/|\\\\}}Driver{{/|\\\\}}Inputs{{/|\\\\}}pchfile.gcno"
+// CHECK_WORKS: "-working-directory" "{{[^"]+}}test{{/|\\\\}}Driver{{/|\\\\}}Inputs"
+// CHECK_WORKS: "-fdebug-compilation-dir" "{{[^"]+}}test{{/|\\\\}}Driver{{/|\\\\}}Inputs"