Index: include/clang/Basic/DiagnosticDriverKinds.td
===================================================================
--- include/clang/Basic/DiagnosticDriverKinds.td
+++ include/clang/Basic/DiagnosticDriverKinds.td
@@ -115,8 +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_fdebug_prefix_map : Error<
-  "invalid argument '%0' to -fdebug-prefix-map">;
+def err_drv_invalid_argument_to_option : Error<
+  "invalid argument '%0' to -%1">;
 def err_drv_malformed_sanitizer_blacklist : Error<
   "malformed sanitizer blacklist: '%0'">;
 def err_drv_duplicate_config : Error<
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -1836,10 +1836,16 @@
   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/PreprocessorOptions.h
===================================================================
--- include/clang/Lex/PreprocessorOptions.h
+++ include/clang/Lex/PreprocessorOptions.h
@@ -170,6 +170,9 @@
   /// build it again.
   std::shared_ptr<FailedModulesSet> FailedModules;
 
+  /// A prefix map for __FILE__ and __BASE_FILE__
+  std::map<std::string, std::string, std::greater<std::string>> MacroPrefixMap;
+
 public:
   PreprocessorOptions() : PrecompiledPreambleBytes(0, false) {}
 
Index: lib/CodeGen/CGDebugInfo.h
===================================================================
--- lib/CodeGen/CGDebugInfo.h
+++ lib/CodeGen/CGDebugInfo.h
@@ -83,7 +83,7 @@
   /// Cache of previously constructed Types.
   llvm::DenseMap<const void *, llvm::TrackingMDRef> TypeCache;
 
-  llvm::SmallDenseMap<llvm::StringRef, llvm::StringRef> DebugPrefixMap;
+  std::map<llvm::StringRef, llvm::StringRef, std::greater<llvm::StringRef>> DebugPrefixMap;
 
   /// Cache that maps VLA types to size expressions for that type,
   /// represented by instantiated Metadata nodes.
Index: lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- lib/CodeGen/CGDebugInfo.cpp
+++ lib/CodeGen/CGDebugInfo.cpp
@@ -471,10 +471,13 @@
 }
 
 std::string CGDebugInfo::remapDIPath(StringRef Path) const {
+  SmallString<256> p = Path;
   for (const auto &Entry : DebugPrefixMap)
-    if (Path.startswith(Entry.first))
-      return (Twine(Entry.second) + Path.substr(Entry.first.size())).str();
-  return Path.str();
+    if (llvm::sys::path::replace_path_prefix(p, Entry.first, Entry.second))
+      break;
+  while (llvm::sys::path::is_separator(p.back()))
+    p.set_size(p.size() - 1);
+  return p.str();
 }
 
 unsigned CGDebugInfo::getLineNumber(SourceLocation Loc) {
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -613,16 +613,30 @@
 
 /// 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_fdebug_prefix_map_EQ)) {
+  for (const Arg *A : Args.filtered(options::OPT_ffile_prefix_map_EQ,
+                                    options::OPT_fdebug_prefix_map_EQ)) {
     StringRef Map = A->getValue();
     if (Map.find('=') == StringRef::npos)
-      D.Diag(diag::err_drv_invalid_argument_to_fdebug_prefix_map) << Map;
+      D.Diag(diag::err_drv_invalid_argument_to_option) << Map << A->getOption().getName();
     else
       CmdArgs.push_back(Args.MakeArgString("-fdebug-prefix-map=" + Map));
     A->claim();
   }
 }
 
+/// Add a CC1 and CC1AS 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,
+                                    options::OPT_fmacro_prefix_map_EQ)) {
+    StringRef Map = A->getValue();
+    if (Map.find('=') == StringRef::npos)
+      D.Diag(diag::err_drv_invalid_argument_to_option) << Map << A->getOption().getName();
+    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) {
@@ -1261,6 +1275,8 @@
     // For IAMCU add special include arguments.
     getToolChain().AddIAMCUIncludeArgs(Args, CmdArgs);
   }
+
+  addMacroPrefixMapArg(D, Args, CmdArgs);
 }
 
 // FIXME: Move to target hook.
Index: lib/Driver/ToolChains/FreeBSD.cpp
===================================================================
--- lib/Driver/ToolChains/FreeBSD.cpp
+++ lib/Driver/ToolChains/FreeBSD.cpp
@@ -13,6 +13,7 @@
 #include "Arch/Sparc.h"
 #include "CommonArgs.h"
 #include "clang/Driver/Compilation.h"
+#include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/Options.h"
 #include "clang/Driver/SanitizerArgs.h"
 #include "llvm/Option/ArgList.h"
@@ -31,6 +32,7 @@
                                       const char *LinkingOutput) const {
   claimNoWarnArgs(Args);
   ArgStringList CmdArgs;
+  const auto &D = getToolChain().getDriver();
 
   // When building 32-bit code on FreeBSD/amd64, we have to explicitly
   // instruct as in the base system to assemble 32-bit code.
@@ -102,6 +104,18 @@
     AddAssemblerKPIC(getToolChain(), Args, CmdArgs);
     break;
   }
+  }
+
+  for (const Arg *A : Args.filtered(options::OPT_ffile_prefix_map_EQ,
+                                    options::OPT_fdebug_prefix_map_EQ)) {
+    StringRef Map = A->getValue();
+    if (Map.find('=') == StringRef::npos)
+      D.Diag(diag::err_drv_invalid_argument_to_option) << Map << A->getOption().getName();
+    else {
+      CmdArgs.push_back(Args.MakeArgString("--debug-prefix-map"));
+      CmdArgs.push_back(Args.MakeArgString(Map));
+    }
+    A->claim();
   }
 
   Args.AddAllArgValues(CmdArgs, options::OPT_Wa_COMMA, options::OPT_Xassembler);
Index: lib/Driver/ToolChains/Gnu.cpp
===================================================================
--- lib/Driver/ToolChains/Gnu.cpp
+++ lib/Driver/ToolChains/Gnu.cpp
@@ -799,6 +799,18 @@
   }
   }
 
+  for (const Arg *A : Args.filtered(options::OPT_ffile_prefix_map_EQ,
+                                    options::OPT_fdebug_prefix_map_EQ)) {
+    StringRef Map = A->getValue();
+    if (Map.find('=') == StringRef::npos)
+      D.Diag(diag::err_drv_invalid_argument_to_option) << Map << A->getOption().getName();
+    else {
+      CmdArgs.push_back(Args.MakeArgString("--debug-prefix-map"));
+      CmdArgs.push_back(Args.MakeArgString(Map));
+    }
+    A->claim();
+  }
+
   Args.AddAllArgs(CmdArgs, options::OPT_I);
   Args.AddAllArgValues(CmdArgs, options::OPT_Wa_COMMA, options::OPT_Xassembler);
 
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -3091,6 +3091,9 @@
   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
@@ -29,6 +29,7 @@
 #include "clang/Lex/MacroInfo.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Lex/PreprocessorLexer.h"
+#include "clang/Lex/PreprocessorOptions.h"
 #include "clang/Lex/Token.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
@@ -44,6 +45,7 @@
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Format.h"
+#include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
@@ -1456,6 +1458,15 @@
   return TI.getTriple().getEnvironment() == Env.getEnvironment();
 }
 
+static void remapMacroPath(
+    SmallString<256> &Path,
+    const std::map<std::string, std::string, std::greater<std::string>>
+        &MacroPrefixMap) {
+  for (const auto &Entry : MacroPrefixMap)
+    if (llvm::sys::path::replace_path_prefix(Path, Entry.first, Entry.second))
+      break;
+}
+
 /// 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) {
@@ -1519,10 +1530,11 @@
     }
 
     // Escape this filename.  Turn '\' -> '\\' '"' -> '\"'
-    SmallString<128> FN;
+    SmallString<256> FN;
     if (PLoc.isValid()) {
       FN += PLoc.getFilename();
       Lexer::Stringify(FN);
+      remapMacroPath(FN, PPOpts->MacroPrefixMap);
       OS << '"' << FN << '"';
     }
     Tok.setKind(tok::string_literal);
Index: test/CodeGen/debug-prefix-map.c
===================================================================
--- test/CodeGen/debug-prefix-map.c
+++ test/CodeGen/debug-prefix-map.c
@@ -2,6 +2,8 @@
 // RUN: %clang_cc1 -debug-info-kind=standalone -fdebug-prefix-map=%p=/UNLIKELY_PATH=empty %s -emit-llvm -o - | FileCheck %s -check-prefix CHECK-EVIL
 // RUN: %clang_cc1 -debug-info-kind=standalone -fdebug-prefix-map=%p=/UNLIKELY_PATH/empty %s -emit-llvm -o - -main-file-name debug-prefix-map.c | FileCheck %s
 // RUN: %clang_cc1 -debug-info-kind=standalone -fdebug-prefix-map=%p=/UNLIKELY_PATH/empty %s -emit-llvm -o - -fdebug-compilation-dir %p | FileCheck %s -check-prefix CHECK-COMPILATION-DIR
+// RUN: %clang -g -fdebug-prefix-map=%p=/UNLIKELY_PATH/empty -S -c %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang -g -ffile-prefix-map=%p=/UNLIKELY_PATH/empty -S -c %s -emit-llvm -o - | FileCheck %s
 
 #include "Inputs/stdio.h"
 
Index: test/Driver/debug-prefix-map.S
===================================================================
--- test/Driver/debug-prefix-map.S
+++ test/Driver/debug-prefix-map.S
@@ -1,4 +1,5 @@
 // RUN: %clang -### -g -fdebug-prefix-map=old=new %s 2>&1 | FileCheck %s
+// RUN: %clang -### -g -ffile-prefix-map=old=new %s 2>&1 | FileCheck %s
 
 // CHECK: cc1as
 // CHECK-SAME: -fdebug-prefix-map=old=new
Index: test/Driver/debug-prefix-map.c
===================================================================
--- test/Driver/debug-prefix-map.c
+++ test/Driver/debug-prefix-map.c
@@ -1,9 +1,28 @@
-// RUN: %clang -### -fdebug-prefix-map=old %s 2>&1 | FileCheck %s -check-prefix CHECK-INVALID
-// RUN: %clang -### -fdebug-prefix-map=old=new %s 2>&1 | FileCheck %s -check-prefix CHECK-SIMPLE
-// RUN: %clang -### -fdebug-prefix-map=old=n=ew %s 2>&1 | FileCheck %s -check-prefix CHECK-COMPLEX
-// RUN: %clang -### -fdebug-prefix-map=old= %s 2>&1 | FileCheck %s -check-prefix CHECK-EMPTY
+// RUN: %clang -### -fdebug-prefix-map=old %s 2>&1 | FileCheck %s -check-prefix CHECK-DEBUG-INVALID
+// RUN: %clang -### -fmacro-prefix-map=old %s 2>&1 | FileCheck %s -check-prefix CHECK-MACRO-INVALID
+// RUN: %clang -### -ffile-prefix-map=old %s 2>&1 | FileCheck %s -check-prefix CHECK-FILE-INVALID
 
-// CHECK-INVALID: error: invalid argument 'old' to -fdebug-prefix-map
-// CHECK-SIMPLE: fdebug-prefix-map=old=new
-// CHECK-COMPLEX: fdebug-prefix-map=old=n=ew
-// CHECK-EMPTY: fdebug-prefix-map=old=
+// RUN: %clang -### -fdebug-prefix-map=old=new %s 2>&1 | FileCheck %s -check-prefix CHECK-DEBUG-SIMPLE
+// RUN: %clang -### -fmacro-prefix-map=old=new %s 2>&1 | FileCheck %s -check-prefix CHECK-MACRO-SIMPLE
+// RUN: %clang -### -ffile-prefix-map=old=new %s 2>&1 | FileCheck %s -check-prefix CHECK-DEBUG-SIMPLE
+// RUN: %clang -### -ffile-prefix-map=old=new %s 2>&1 | FileCheck %s -check-prefix CHECK-MACRO-SIMPLE
+
+// RUN: %clang -### -fdebug-prefix-map=old=n=ew %s 2>&1 | FileCheck %s -check-prefix CHECK-DEBUG-COMPLEX
+// RUN: %clang -### -fmacro-prefix-map=old=n=ew %s 2>&1 | FileCheck %s -check-prefix CHECK-MACRO-COMPLEX
+// RUN: %clang -### -ffile-prefix-map=old=n=ew %s 2>&1 | FileCheck %s -check-prefix CHECK-DEBUG-COMPLEX
+// RUN: %clang -### -ffile-prefix-map=old=n=ew %s 2>&1 | FileCheck %s -check-prefix CHECK-MACRO-COMPLEX
+
+// RUN: %clang -### -fdebug-prefix-map=old= %s 2>&1 | FileCheck %s -check-prefix CHECK-DEBUG-EMPTY
+// RUN: %clang -### -fmacro-prefix-map=old= %s 2>&1 | FileCheck %s -check-prefix CHECK-MACRO-EMPTY
+// RUN: %clang -### -ffile-prefix-map=old= %s 2>&1 | FileCheck %s -check-prefix CHECK-DEBUG-EMPTY
+// RUN: %clang -### -ffile-prefix-map=old= %s 2>&1 | FileCheck %s -check-prefix CHECK-MACRO-EMPTY
+
+// CHECK-DEBUG-INVALID: error: invalid argument 'old' to -fdebug-prefix-map
+// CHECK-MACRO-INVALID: error: invalid argument 'old' to -fmacro-prefix-map
+// CHECK-FILE-INVALID: error: invalid argument 'old' to -ffile-prefix-map
+// CHECK-DEBUG-SIMPLE: fdebug-prefix-map=old=new
+// CHECK-MACRO-SIMPLE: fmacro-prefix-map=old=new
+// CHECK-DEBUG-COMPLEX: fdebug-prefix-map=old=n=ew
+// CHECK-MACRO-COMPLEX: fmacro-prefix-map=old=n=ew
+// CHECK-DEBUG-EMPTY: fdebug-prefix-map=old=
+// CHECK-MACRO-EMPTY: fmacro-prefix-map=old=
Index: test/Preprocessor/file_test.h
===================================================================
--- /dev/null
+++ test/Preprocessor/file_test.h
@@ -0,0 +1,2 @@
+filename: __FILE__
+basefile: __BASE_FILE__
Index: test/Preprocessor/file_test.c
===================================================================
--- /dev/null
+++ test/Preprocessor/file_test.c
@@ -0,0 +1,22 @@
+// RUN: %clang -E -ffile-prefix-map=%p=/UNLIKELY_PATH/empty -c -o - %s | FileCheck %s
+// RUN: %clang -E -fmacro-prefix-map=%p=/UNLIKELY_PATH/empty -c -o - %s | FileCheck %s
+// RUN: %clang -E -fmacro-prefix-map=%p=/UNLIKELY_PATH=empty -c -o - %s | FileCheck %s -check-prefix CHECK-EVIL
+// RUN: %clang -E -fmacro-prefix-map=%p/= -c -o - %s | FileCheck %s --check-prefix CHECK-REMOVE
+
+filename: __FILE__
+#include "file_test.h"
+
+// CHECK: filename: "/UNLIKELY_PATH/empty{{[/\\]}}file_test.c"
+// CHECK: filename: "/UNLIKELY_PATH/empty{{[/\\]}}file_test.h"
+// CHECK: basefile: "/UNLIKELY_PATH/empty{{[/\\]}}file_test.c"
+// CHECK-NOT: filename:
+
+// CHECK-EVIL: filename: "/UNLIKELY_PATH=empty{{[/\\]}}file_test.c"
+// CHECK-EVIL: filename: "/UNLIKELY_PATH=empty{{[/\\]}}file_test.h"
+// CHECK-EVIL: basefile: "/UNLIKELY_PATH=empty{{[/\\]}}file_test.c"
+// CHECK-EVIL-NOT: filename:
+
+// CHECK-REMOVE: filename: "file_test.c"
+// CHECK-REMOVE: filename: "file_test.h"
+// CHECK-REMOVE: basefile: "file_test.c"
+// CHECK-REMOVE-NOT: filename: