Index: include/clang/Basic/DiagnosticDriverKinds.td
===================================================================
--- include/clang/Basic/DiagnosticDriverKinds.td
+++ include/clang/Basic/DiagnosticDriverKinds.td
@@ -115,6 +115,8 @@
   "missing argument to '%0'">;
 def err_drv_invalid_libcxx_deployment : Error<
   "invalid deployment target for -stdlib=libc++ (requires %0 or later)">;
+def err_drv_invalid_argument_to_fmacro_prefix_map : Error<
+  "invalid argument '%0' to -fmacro-prefix-map">;
 def err_drv_invalid_argument_to_fdebug_prefix_map : Error<
   "invalid argument '%0' to -fdebug-prefix-map">;
 def err_drv_malformed_sanitizer_blacklist : Error<
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -1748,10 +1748,16 @@
   Flags<[CC1Option]>, HelpText<"Provide minimal debug info in the object/executable to facilitate online symbolication/stack traces in the absence of .dwo/.dwp files when using Split DWARF">;
 def fno_split_dwarf_inlining: Flag<["-"], "fno-split-dwarf-inlining">, Group<f_Group>,
   Flags<[CC1Option]>;
+def ffile_prefix_map_EQ
+  : Joined<["-"], "ffile-prefix-map=">, Group<f_Group>, Flags<[CC1Option]>,
+    HelpText<"remap file source paths in debug info and predefined preprocessor macros">;
 def fdebug_prefix_map_EQ
   : Joined<["-"], "fdebug-prefix-map=">, Group<f_Group>,
     Flags<[CC1Option,CC1AsOption]>,
     HelpText<"remap file source paths in debug info">;
+def fmacro_prefix_map_EQ
+  : Joined<["-"], "fmacro-prefix-map=">, Group<Preprocessor_Group>, Flags<[CC1Option]>,
+    HelpText<"remap file source paths in predefined preprocessor macros">;
 def g_Flag : Flag<["-"], "g">, Group<g_Group>,
   HelpText<"Generate source-level debug information">;
 def gline_tables_only : Flag<["-"], "gline-tables-only">, Group<gN_Group>,
Index: include/clang/Lex/Preprocessor.h
===================================================================
--- include/clang/Lex/Preprocessor.h
+++ include/clang/Lex/Preprocessor.h
@@ -151,6 +151,9 @@
   /// objects internal to the Preprocessor.
   llvm::BumpPtrAllocator BP;
 
+  /// A prefix map for __FILE__ and __BASEFILE__
+  llvm::SmallDenseMap<llvm::StringRef, llvm::StringRef> MacroPrefixMap;
+
   /// Identifiers for builtin macros and other builtins.
   IdentifierInfo *Ident__LINE__, *Ident__FILE__;   // __LINE__, __FILE__
   IdentifierInfo *Ident__DATE__, *Ident__TIME__;   // __DATE__, __TIME__
Index: include/clang/Lex/PreprocessorOptions.h
===================================================================
--- include/clang/Lex/PreprocessorOptions.h
+++ include/clang/Lex/PreprocessorOptions.h
@@ -167,6 +167,9 @@
   /// build it again.
   std::shared_ptr<FailedModulesSet> FailedModules;
 
+  /// A prefix map for __FILE__ and __BASEFILE__
+  std::map<std::string, std::string> MacroPrefixMap;
+
 public:
   PreprocessorOptions() : PrecompiledPreambleBytes(0, false) {}
 
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -606,6 +606,14 @@
 
 /// Add a CC1 and CC1AS option to specify the debug file path prefix map.
 static void addDebugPrefixMapArg(const Driver &D, const ArgList &Args, ArgStringList &CmdArgs) {
+  for (const Arg *A : Args.filtered(options::OPT_ffile_prefix_map_EQ)) {
+    StringRef Map = A->getValue();
+    if (Map.find('=') == StringRef::npos)
+      D.Diag(diag::err_drv_invalid_argument_to_fdebug_prefix_map) << Map;
+    else
+      CmdArgs.push_back(Args.MakeArgString("-fdebug-prefix-map=" + Map));
+    A->claim();
+  }
   for (const Arg *A : Args.filtered(options::OPT_fdebug_prefix_map_EQ)) {
     StringRef Map = A->getValue();
     if (Map.find('=') == StringRef::npos)
@@ -616,6 +624,26 @@
   }
 }
 
+/// Add a CC1 option to specify the macro file path prefix map.
+static void addMacroPrefixMapArg(const Driver &D, const ArgList &Args, ArgStringList &CmdArgs) {
+  for (const Arg *A : Args.filtered(options::OPT_ffile_prefix_map_EQ)) {
+    StringRef Map = A->getValue();
+    if (Map.find('=') == StringRef::npos)
+      D.Diag(diag::err_drv_invalid_argument_to_fmacro_prefix_map) << Map;
+    else
+      CmdArgs.push_back(Args.MakeArgString("-fmacro-prefix-map=" + Map));
+    A->claim();
+  }
+  for (const Arg *A : Args.filtered(options::OPT_fmacro_prefix_map_EQ)) {
+    StringRef Map = A->getValue();
+    if (Map.find('=') == StringRef::npos)
+      D.Diag(diag::err_drv_invalid_argument_to_fmacro_prefix_map) << Map;
+    else
+      CmdArgs.push_back(Args.MakeArgString("-fmacro-prefix-map=" + Map));
+    A->claim();
+  }
+}
+
 /// Vectorize at all optimization levels greater than 1 except for -Oz.
 /// For -Oz the loop vectorizer is disable, while the slp vectorizer is enabled.
 static bool shouldEnableVectorizerAtOLevel(const ArgList &Args, bool isSlpVec) {
@@ -1223,6 +1251,8 @@
     // For IAMCU add special include arguments.
     getToolChain().AddIAMCUIncludeArgs(Args, CmdArgs);
   }
+
+  addMacroPrefixMapArg(D, Args, CmdArgs);
 }
 
 // FIXME: Move to target hook.
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -2845,6 +2845,11 @@
   for (const auto *A : Args.filtered(OPT_error_on_deserialized_pch_decl))
     Opts.DeserializedPCHDeclsToErrorOn.insert(A->getValue());
 
+  for (const auto &A : Args.getAllArgValues(OPT_fmacro_prefix_map_EQ))
+  {
+    Opts.MacroPrefixMap.insert(StringRef(A).split('='));
+  }
+
   if (const Arg *A = Args.getLastArg(OPT_preamble_bytes_EQ)) {
     StringRef Value(A->getValue());
     size_t Comma = Value.find(',');
Index: lib/Lex/PPMacroExpansion.cpp
===================================================================
--- lib/Lex/PPMacroExpansion.cpp
+++ lib/Lex/PPMacroExpansion.cpp
@@ -1453,6 +1453,15 @@
   return TI.getTriple().getEnvironment() == Env.getEnvironment();
 }
 
+static std::string remapMacroPath(StringRef Path,
+                           llvm::SmallDenseMap<StringRef,
+                           StringRef> &MacroPrefixMap) {
+  for (const auto &Entry : MacroPrefixMap)
+    if (Path.startswith(Entry.first))
+      return (Twine(Entry.second) + Path.substr(Entry.first.size())).str();
+  return Path.str();
+}
+
 /// ExpandBuiltinMacro - If an identifier token is read that is to be expanded
 /// as a builtin macro, handle it and return the next token as 'Tok'.
 void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
@@ -1516,9 +1525,11 @@
     }
 
     // Escape this filename.  Turn '\' -> '\\' '"' -> '\"'
-    SmallString<128> FN;
+    std::string FN;
     if (PLoc.isValid()) {
       FN += PLoc.getFilename();
+      // TODO remap macro prefix here
+      FN = remapMacroPath(FN, MacroPrefixMap);
       Lexer::Stringify(FN);
       OS << '"' << FN << '"';
     }
Index: lib/Lex/Preprocessor.cpp
===================================================================
--- lib/Lex/Preprocessor.cpp
+++ lib/Lex/Preprocessor.cpp
@@ -156,6 +156,9 @@
 
   if (this->PPOpts->GeneratePreamble)
     PreambleConditionalStack.startRecording();
+
+  for (const auto &KV : this->PPOpts->MacroPrefixMap)
+    MacroPrefixMap[KV.first] = KV.second;
 }
 
 Preprocessor::~Preprocessor() {