6 files changed, 19 insertions, 0 deletions
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 6b7bfe77f1a..4b90e43754f 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -575,6 +575,9 @@ def fms_memptr_rep_EQ : Joined<["-"], "fms-memptr-rep=">, Group<f_Group>, Flags<
 def fmodules_cache_path : Joined<["-"], "fmodules-cache-path=">, Group<i_Group>,
   Flags<[DriverOption, CC1Option]>, MetaVarName<"<directory>">,
   HelpText<"Specify the module cache path">;
+def fmodules_user_build_path : Separate<["-"], "fmodules-user-build-path">, Group<i_Group>,
+  Flags<[DriverOption, CC1Option]>, MetaVarName<"<directory>">,
+  HelpText<"Specify the module user build path">;
 def fmodules_prune_interval : Joined<["-"], "fmodules-prune-interval=">, Group<i_Group>,
   Flags<[CC1Option]>, MetaVarName<"<seconds>">,
   HelpText<"Specify the interval (in seconds) between attempts to prune the module cache">;
diff --git a/clang/include/clang/Lex/HeaderSearchOptions.h b/clang/include/clang/Lex/HeaderSearchOptions.h
index 5abcdad2d57..53b4bdc4c9f 100644
--- a/clang/include/clang/Lex/HeaderSearchOptions.h
+++ b/clang/include/clang/Lex/HeaderSearchOptions.h
@@ -89,6 +89,9 @@ public:
   /// \brief The directory used for the module cache.
   std::string ModuleCachePath;
 
+  /// \brief The directory used for a user build.
+  std::string ModuleUserBuildPath;
+
   /// \brief Whether we should disable the use of the hash string within the
   /// module cache.
   ///
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 50ad7e65eb3..911b6a02aee 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3366,6 +3366,13 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back(Args.MakeArgString(DefaultModuleCache));
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_fmodules_user_build_path)) {
+    A->claim();
+    if (HaveModules) {
+      A->render(Args, CmdArgs);
+    }
+  }
+
   // Pass through all -fmodules-ignore-macro arguments.
   Args.AddAllArgs(CmdArgs, options::OPT_fmodules_ignore_macro);
   Args.AddLastArg(CmdArgs, options::OPT_fmodules_prune_interval);
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 85aae236b8a..f8cb9388661 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -918,6 +918,7 @@ static void ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args) {
     Opts.UseLibcxx = (strcmp(A->getValue(), "libc++") == 0);
   Opts.ResourceDir = Args.getLastArgValue(OPT_resource_dir);
   Opts.ModuleCachePath = Args.getLastArgValue(OPT_fmodules_cache_path);
+  Opts.ModuleUserBuildPath = Args.getLastArgValue(OPT_fmodules_user_build_path);
   Opts.DisableModuleHash = Args.hasArg(OPT_fdisable_module_hash);
   // -fmodules implies -fmodule-maps
   Opts.ModuleMaps = Args.hasArg(OPT_fmodule_maps) || Args.hasArg(OPT_fmodules);
@@ -1821,6 +1822,9 @@ std::string CompilerInvocation::getModuleHash() const {
                       hsOpts.UseStandardCXXIncludes,
                       hsOpts.UseLibcxx);
 
+  // Extend the signature with the user build path.
+  code = hash_combine(code, hsOpts.ModuleUserBuildPath);
+
   // Darwin-specific hack: if we have a sysroot, use the contents and
   // modification time of
   //   $sysroot/System/Library/CoreServices/SystemVersion.plist
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 458d9ec95cf..41c532ec274 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -4297,6 +4297,7 @@ bool ASTReader::ParseHeaderSearchOptions(const RecordData &Record,
 
   HSOpts.ResourceDir = ReadString(Record, Idx);
   HSOpts.ModuleCachePath = ReadString(Record, Idx);
+  HSOpts.ModuleUserBuildPath = ReadString(Record, Idx);
   HSOpts.DisableModuleHash = Record[Idx++];
   HSOpts.UseBuiltinIncludes = Record[Idx++];
   HSOpts.UseStandardSystemIncludes = Record[Idx++];
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index c9c339eaee8..3365d1ee0c5 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -1161,6 +1161,7 @@ void ASTWriter::WriteControlBlock(Preprocessor &PP, ASTContext &Context,
 
   AddString(HSOpts.ResourceDir, Record);
   AddString(HSOpts.ModuleCachePath, Record);
+  AddString(HSOpts.ModuleUserBuildPath, Record);
   Record.push_back(HSOpts.DisableModuleHash);
   Record.push_back(HSOpts.UseBuiltinIncludes);
   Record.push_back(HSOpts.UseStandardSystemIncludes);