Phabricator D49466

[dankm]

Summary

path prefix mapping: enforce path matching

Force the prefix string to match a complete prefix in the
path to remap, and strip any trailing path separators from
the resulting path.

Allows -ffile-prefix-map=/a=b /a/test.c to be remapped to b/test.c
and -ffile-prefix-map==/fake_prefix /a/test.c to become
/fake_prefix/a/test.c.

Likewise, -ffile-prefix-map=/a= /a/test.c becomes test.c instead of
/test.c. For the latter you'd use -ffile-prefix-map=/a=/.

Merge remote-tracking branch 'llvm/master' into D49466

Do not remap MainFileName twice.

Merge remote-tracking branch 'llvm/master' into D49466

Path: enhance prefix mapping

Return true when a path is remapped, and allow replacing the
original path entirely.

Break on first match.

Merge remote-tracking branch 'llvm/master' into D49466

Style fix

Unit test updates

Clean up path handling some more

Rewrite path prefix replacement

Add a bunch of tests for odd corner cases.

Merge remote-tracking branch 'llvm/master' into D49466

Address path feedback

Use new flag in clang

Get contract in order

[lebedev.ri]

Please fix patch title and description

[dankm]

In D65556#1610001, @lebedev.ri wrote:

Please fix patch title and description

Sorry, I'm going to delete this. It was supposed to be a new patchset on D49466.

clang/include/clang/Basic/DiagnosticDriverKinds.td

 def err_drv_invalid_mfloat_abi : Error<
   "invalid float ABI '%0'">;
 def err_drv_invalid_mtp : Error<
   "invalid thread pointer reading mode '%0'">;
 def err_drv_missing_arg_mtp : Error<
   "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<
   "no more than one option '--config' is allowed">;
 def err_drv_config_file_not_exist : Error<
   "configuration file '%0' does not exist">;
 def err_drv_config_file_not_found : Error<
   "configuration file '%0' cannot be found">;

clang/include/clang/Driver/Options.td

 def fdebug_ranges_base_address: Flag <["-"], "fdebug-ranges-base-address">, Group<f_Group>,
   Flags<[CC1Option]>, HelpText<"Use DWARF base address selection entries in debug_ranges">;
 def fno_debug_ranges_base_address: Flag <["-"], "fno-debug-ranges-base-address">, Group<f_Group>,
   Flags<[CC1Option]>;
 def fsplit_dwarf_inlining: Flag <["-"], "fsplit-dwarf-inlining">, Group<f_Group>,
   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>,
   Flags<[CoreOption]>, HelpText<"Emit debug line number tables only">;
 def gline_directives_only : Flag<["-"], "gline-directives-only">, Group<gN_Group>,
   Flags<[CoreOption]>, HelpText<"Emit debug line info directives only">;
 def gmlt : Flag<["-"], "gmlt">, Alias<gline_tables_only>;
 def g0 : Flag<["-"], "g0">, Group<gN_Group>;

clang/include/clang/Lex/PreprocessorOptions.h

public:
   /// The set of modules that failed to build.
   ///
   /// This pointer will be shared among all of the compiler instances created
   /// to (re)build modules, so that once a module fails to build anywhere,
   /// other instances will see that the module has failed and won't try to
   /// 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) {}
 
   void addMacroDef(StringRef Name) { Macros.emplace_back(Name, false); }
   void addMacroUndef(StringRef Name) { Macros.emplace_back(Name, true); }
 
   void addRemappedFile(StringRef From, StringRef To) {
     RemappedFiles.emplace_back(From, To);

clang/lib/CodeGen/CGDebugInfo.h

#include "clang/Basic/OpenCLImageTypes.def"
   llvm::DIType *OCLReserveIDDITy = nullptr;
 #define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
   llvm::DIType *Id##Ty = nullptr;
 #include "clang/Basic/OpenCLExtensionTypes.def"
 
   /// 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.
   llvm::SmallDenseMap<QualType, llvm::Metadata *> SizeExprCache;
 
   struct ObjCInterfaceCacheEntry {
     const ObjCInterfaceType *Type;
     llvm::DIType *Decl;

clang/lib/CodeGen/CGDebugInfo.cpp

if (llvm::sys::path::is_absolute(RemappedFile)) {
     File = RemappedFile;
   }
   llvm::DIFile *F = DBuilder.createFile(File, Dir, CSInfo, Source);
   DIFileCache[FileName.data()].reset(F);
   return F;
 }
 
 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, true))
+      break;
+  while (llvm::sys::path::is_separator(p.back()))
+    p.set_size(p.size() - 1);
+  return p.str();
 }
 
 unsigned CGDebugInfo::getLineNumber(SourceLocation Loc) {
   if (Loc.isInvalid() && CurLoc.isInvalid())
     return 0;
   SourceManager &SM = CGM.getContext().getSourceManager();
   PresumedLoc PLoc = SM.getPresumedLoc(Loc.isValid() ? Loc : CurLoc);
   return PLoc.isValid() ? PLoc.getLine() : 0;
void CGDebugInfo::CreateCompileUnit() {
   auto &CGOpts = CGM.getCodeGenOpts();
   // The DIFile used by the CU is distinct from the main source
   // file. Its directory part specifies what becomes the
   // DW_AT_comp_dir (the compilation directory), even if the source
   // file was specified with an absolute path.
   if (CSKind)
     CSInfo.emplace(*CSKind, Checksum);
   llvm::DIFile *CUFile = DBuilder.createFile(
-      remapDIPath(MainFileName), remapDIPath(getCurrentDirname()), CSInfo,
+      MainFileName, remapDIPath(getCurrentDirname()), CSInfo,
       getSource(SM, SM.getMainFileID()));
 
   // Create new compile unit.
   TheCU = DBuilder.createCompileUnit(
       LangTag, CUFile, CGOpts.EmitVersionIdentMetadata ? Producer : "",
       LO.Optimize || CGOpts.PrepareForLTO || CGOpts.PrepareForThinLTO,
       CGOpts.DwarfDebugFlags, RuntimeVers, CGOpts.SplitDwarfFile, EmissionKind,
       DwoId, CGOpts.SplitDwarfInlining, CGOpts.DebugInfoForProfiling,

clang/lib/Driver/ToolChains/Clang.cpp

CmdArgs.push_back(A->getValue());
                  VFS.getCurrentWorkingDirectory()) {
     CmdArgs.push_back("-fdebug-compilation-dir");
     CmdArgs.push_back(Args.MakeArgString(*CWD));
   }
 }
 
 /// 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 disabled, while the slp vectorizer is
 /// enabled.
 static bool shouldEnableVectorizerAtOLevel(const ArgList &Args, bool isSlpVec) {
   if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {
     if (A->getOption().matches(options::OPT_O4) ||
         A->getOption().matches(options::OPT_Ofast))
       return true;
if (!IsIAMCU)
     forAllAssociatedToolChains(C, JA, getToolChain(),
                                [&Args, &CmdArgs](const ToolChain &TC) {
                                  TC.AddClangSystemIncludeArgs(Args, CmdArgs);
                                });
   else {
     // For IAMCU add special include arguments.
     getToolChain().AddIAMCUIncludeArgs(Args, CmdArgs);
   }
+
+  addMacroPrefixMapArg(D, Args, CmdArgs);
 }
 
 // FIXME: Move to target hook.
 static bool isSignedCharDefault(const llvm::Triple &Triple) {
   switch (Triple.getArch()) {
   default:
     return true;
 

clang/lib/Driver/ToolChains/FreeBSD.cpp

 //===--- FreeBSD.cpp - FreeBSD ToolChain Implementations --------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "FreeBSD.h"
 #include "Arch/ARM.h"
 #include "Arch/Mips.h"
 #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"
 #include "llvm/Support/VirtualFileSystem.h"
 
 using namespace clang::driver;
 using namespace clang::driver::tools;
 using namespace clang::driver::toolchains;
 using namespace clang;
 using namespace llvm::opt;
 
 void freebsd::Assembler::ConstructJob(Compilation &C, const JobAction &JA,
                                       const InputInfo &Output,
                                       const InputInfoList &Inputs,
                                       const ArgList &Args,
                                       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.
   switch (getToolChain().getArch()) {
   default:
     break;
   case llvm::Triple::x86:
     CmdArgs.push_back("--32");
void freebsd::Assembler::ConstructJob(Compilation &C, const JobAction &JA,
   case llvm::Triple::sparcv9: {
     std::string CPU = getCPUName(Args, getToolChain().getTriple());
     CmdArgs.push_back(sparc::getSparcAsmModeForCPU(CPU, getToolChain().getTriple()));
     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);
 
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());
 
   for (const auto &II : Inputs)
     CmdArgs.push_back(II.getFilename());
 

clang/lib/Driver/ToolChains/Gnu.cpp

case llvm::Triple::systemz: {
     // Always pass an -march option, since our default of z10 is later
     // than the GNU assembler's default.
     StringRef CPUName = systemz::getSystemZTargetCPU(Args);
     CmdArgs.push_back(Args.MakeArgString("-march=" + CPUName));
     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.AddAllArgs(CmdArgs, options::OPT_I);
   Args.AddAllArgValues(CmdArgs, options::OPT_Wa_COMMA, options::OPT_Xassembler);
 
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());
 
   for (const auto &II : Inputs)
     CmdArgs.push_back(II.getFilename());

clang/lib/Frontend/CompilerInvocation.cpp

static void ParsePreprocessorArgs(PreprocessorOptions &Opts, ArgList &Args,
   Opts.DetailedRecord = Args.hasArg(OPT_detailed_preprocessing_record);
   Opts.DisablePCHValidation = Args.hasArg(OPT_fno_validate_pch);
   Opts.AllowPCHWithCompilerErrors = Args.hasArg(OPT_fallow_pch_with_errors);
 
   Opts.DumpDeserializedPCHDecls = Args.hasArg(OPT_dump_deserialized_pch_decls);
   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(',');
     unsigned Bytes = 0;
     unsigned EndOfLine = 0;
 
     if (Comma == StringRef::npos ||
         Value.substr(0, Comma).getAsInteger(10, Bytes) ||

clang/lib/Lex/PPMacroExpansion.cpp

 #include "clang/Lex/DirectoryLookup.h"
 #include "clang/Lex/ExternalPreprocessorSource.h"
 #include "clang/Lex/HeaderSearch.h"
 #include "clang/Lex/LexDiagnostic.h"
 #include "clang/Lex/MacroArgs.h"
 #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"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallString.h"

 /// Implements the __is_target_environment builtin macro.
 static bool isTargetEnvironment(const TargetInfo &TI,
                                 const IdentifierInfo *II) {
   std::string EnvName = (llvm::Twine("---") + II->getName().lower()).str();
   llvm::Triple Env(EnvName);
   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, true))
+      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) {
   // Figure out which token this is.
   IdentifierInfo *II = Tok.getIdentifierInfo();
   assert(II && "Can't be a macro without id info!");
 
   // If this is an _Pragma or Microsoft __pragma directive, expand it,
if (II == Ident__BASE_FILE__ && PLoc.isValid()) {
         if (PLoc.isInvalid())
           break;
 
         NextLoc = PLoc.getIncludeLoc();
       }
     }
 
     // Escape this filename.  Turn '\' -> '\\' '"' -> '\"'
-    SmallString<128> FN;
+    SmallString<256> FN;
     if (PLoc.isValid()) {
       // __FILE_NAME__ is a Clang-specific extension that expands to the
       // the last part of __FILE__.
       if (II == Ident__FILE_NAME__) {
         // Try to get the last path component, failing that return the original
         // presumed location.
         StringRef PLFileName = llvm::sys::path::filename(PLoc.getFilename());
         if (PLFileName != "")
           FN += PLFileName;
         else
           FN += PLoc.getFilename();
       } else {
         FN += PLoc.getFilename();
       }
       Lexer::Stringify(FN);
+      remapMacroPath(FN, PPOpts->MacroPrefixMap);
       OS << '"' << FN << '"';
     }
     Tok.setKind(tok::string_literal);
   } else if (II == Ident__DATE__) {
     Diag(Tok.getLocation(), diag::warn_pp_date_time);
     if (!DATELoc.isValid())
       ComputeDATE_TIME(DATELoc, TIMELoc, *this);
     Tok.setKind(tok::string_literal);

clang/test/CodeGen/debug-prefix-map.c

 // RUN: %clang_cc1 -debug-info-kind=standalone -fdebug-prefix-map=%p=/UNLIKELY_PATH/empty %s -emit-llvm -o - | FileCheck %s -check-prefix CHECK-NO-MAIN-FILE-NAME
 // 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"
 
 int main(int argc, char **argv) {
   (void)argc;
   (void)argv;
   return 0;
 }

clang/test/Driver/debug-prefix-map.S

 // 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
 
 // More tests for this flag in debug-prefix-map.c.

clang/test/Driver/debug-prefix-map.c

-// 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=

clang/test/Preprocessor/file_test.h

+filename: __FILE__
+basefile: __BASE_FILE__

clang/test/Preprocessor/file_test.c

+// 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:

llvm/include/llvm/Support/Path.h

 ///                  prepended.
 void replace_extension(SmallVectorImpl<char> &path, const Twine &extension,
                        Style style = Style::native);
 
 /// Replace matching path prefix with another path.
 ///
 /// @code
 ///   /foo, /old, /new => /foo
+///   /old, /old, /new => /new
+///   /old, /old/, /new, false => /old
+///   /old, /old/, /new, true => /new
 ///   /old/foo, /old, /new => /new/foo
+///   /old/foo, /old/, /new => /new/foo
+///   /old/foo, /old/, /new/ => /new/foo
+///   /oldfoo, /old, /new => /oldfoo
 ///   /foo, <empty>, /new => /new/foo
-///   /old/foo, /old, <empty> => /foo
+///   /foo, <empty>, new => new/foo
+///   /old/foo, /old, <empty>, false => /foo
+///   /old/foo, /old, <empty>, true => foo
 /// @endcode
 ///
 /// @param Path If \a Path starts with \a OldPrefix modify to instead
 ///        start with \a NewPrefix.
-/// @param OldPrefix The path prefix to strip from \a Path.
+/// @param OldPrefix The path prefix to strip from \a Path. Any trailing
+///        path separator is ignored if strict is true.
 /// @param NewPrefix The path prefix to replace \a NewPrefix with.
-void replace_path_prefix(SmallVectorImpl<char> &Path,
+/// @param style The path separator style
+/// @param strict Strict prefix path checking
+/// @result true if \a Path begins with OldPrefix
+bool replace_path_prefix(SmallVectorImpl<char> &Path,
                          const StringRef &OldPrefix, const StringRef &NewPrefix,
-                         Style style = Style::native);
+                         Style style = Style::native, bool strict = false);
+static inline bool replace_path_prefix(SmallVectorImpl<char> &Path,
+                         const StringRef &OldPrefix, const StringRef &NewPrefix,
+                         bool strict, Style style = Style::native) {
+  return replace_path_prefix(Path, OldPrefix, NewPrefix, style, strict);
+}
 
 /// Append to path.
 ///
 /// @code
 ///   /foo  + bar/f => /foo/bar/f
 ///   /foo/ + bar/f => /foo/bar/f
 ///   foo   + bar/f => foo/bar/f
 /// @endcode

llvm/lib/Support/Path.cpp

void replace_extension(SmallVectorImpl<char> &path, const Twine &extension,
   // Append '.' if needed.
   if (ext.size() > 0 && ext[0] != '.')
     path.push_back('.');
 
   // Append extension.
   path.append(ext.begin(), ext.end());
 }
 
-void replace_path_prefix(SmallVectorImpl<char> &Path,
+bool replace_path_prefix(SmallVectorImpl<char> &Path,
                          const StringRef &OldPrefix, const StringRef &NewPrefix,
-                         Style style) {
+                         Style style, bool strict) {
   if (OldPrefix.empty() && NewPrefix.empty())
-    return;
+    return false;
 
   StringRef OrigPath(Path.begin(), Path.size());
-  if (!OrigPath.startswith(OldPrefix))
-    return;
+  StringRef OldPrefixDir;
+
+  if (!strict && OldPrefix.size() > OrigPath.size())
+    return false;
+
+  if (!strict && OldPrefix.size() > OrigPath.size())
+    return false;
+
+  // Ensure OldPrefixDir does not have a trailing separator.
+  if (!OldPrefix.empty() && is_separator(OldPrefix.back()))
+    OldPrefixDir = parent_path(OldPrefix, style);
+  else
+    OldPrefixDir = OldPrefix;
+
+  if (!OrigPath.startswith(OldPrefixDir))
+    return false;
+
+  if (OrigPath.size() > OldPrefixDir.size())
+    if (!is_separator(OrigPath[OldPrefixDir.size()], style) && strict)
+      return false;
 
   // If prefixes have the same size we can simply copy the new one over.
-  if (OldPrefix.size() == NewPrefix.size()) {
+  if (OldPrefixDir.size() == NewPrefix.size() && !strict) {
     llvm::copy(NewPrefix, Path.begin());
-    return;
+    return true;
   }
 
-  StringRef RelPath = OrigPath.substr(OldPrefix.size());
+  StringRef RelPath = OrigPath.substr(OldPrefixDir.size());
   SmallString<256> NewPath;
   path::append(NewPath, style, NewPrefix);
+  if (!RelPath.empty()) {
+    if (!is_separator(RelPath[0], style) || !strict)
       path::append(NewPath, style, RelPath);
+    else
+      path::append(NewPath, style, relative_path(RelPath, style));
+  }
+
   Path.swap(NewPath);
+
+  return true;
 }
 
 void native(const Twine &path, SmallVectorImpl<char> &result, Style style) {
   assert((!path.isSingleStringRef() ||
           path.getSingleStringRef().data() != result.data()) &&
          "path and result are not allowed to overlap!");
   // Clear result.
   result.clear();

llvm/unittests/Support/Path.cpp

TEST(Support, RemoveDots) {
   SmallString<64> Path2("././c");
   EXPECT_TRUE(path::remove_dots(Path2, true, path::Style::posix));
   EXPECT_EQ("c", Path2);
 }
 
 TEST(Support, ReplacePathPrefix) {
   SmallString<64> Path1("/foo");
   SmallString<64> Path2("/old/foo");
+  SmallString<64> Path3("/oldnew/foo");
   SmallString<64> OldPrefix("/old");
+  SmallString<64> OldPrefixSep("/old/");
   SmallString<64> NewPrefix("/new");
   SmallString<64> NewPrefix2("/longernew");
   SmallString<64> EmptyPrefix("");
 
   SmallString<64> Path = Path1;
   path::replace_path_prefix(Path, OldPrefix, NewPrefix);
   EXPECT_EQ(Path, "/foo");
   Path = Path2;
   path::replace_path_prefix(Path, OldPrefix, NewPrefix);
   EXPECT_EQ(Path, "/new/foo");
   Path = Path2;
   path::replace_path_prefix(Path, OldPrefix, NewPrefix2);
   EXPECT_EQ(Path, "/longernew/foo");
   Path = Path1;
   path::replace_path_prefix(Path, EmptyPrefix, NewPrefix);
   EXPECT_EQ(Path, "/new/foo");
   Path = Path2;
   path::replace_path_prefix(Path, OldPrefix, EmptyPrefix);
   EXPECT_EQ(Path, "/foo");
+  Path = Path2;
+  path::replace_path_prefix(Path, OldPrefix, EmptyPrefix, true);
+  EXPECT_EQ(Path, "foo");
+  Path = Path3;
+  path::replace_path_prefix(Path, OldPrefix, NewPrefix, false);
+  EXPECT_EQ(Path, "/newnew/foo");
+  Path = Path3;
+  path::replace_path_prefix(Path, OldPrefix, NewPrefix, true);
+  EXPECT_EQ(Path, "/oldnew/foo");
+  Path = Path3;
+  path::replace_path_prefix(Path, OldPrefixSep, NewPrefix, true);
+  EXPECT_EQ(Path, "/oldnew/foo");
+  Path = Path1;
+  path::replace_path_prefix(Path, EmptyPrefix, NewPrefix);
+  EXPECT_EQ(Path, "/new/foo");
+  Path = OldPrefix;
+  path::replace_path_prefix(Path, OldPrefix, NewPrefix);
+  EXPECT_EQ(Path, "/new");
+  Path = OldPrefixSep;
+  path::replace_path_prefix(Path, OldPrefix, NewPrefix);
+  EXPECT_EQ(Path, "/new/");
+  Path = OldPrefix;
+  path::replace_path_prefix(Path, OldPrefixSep, NewPrefix, false);
+  EXPECT_EQ(Path, "/old");
+  Path = OldPrefix;
+  path::replace_path_prefix(Path, OldPrefixSep, NewPrefix, true);
+  EXPECT_EQ(Path, "/new");
 }
 
 TEST_F(FileSystemTest, OpenFileForRead) {
   // Create a temp file.
   int FileDescriptor;
   SmallString<64> TempPath;
   ASSERT_NO_ERROR(
       fs::createTemporaryFile("prefix", "temp", FileDescriptor, TempPath));