Revert "Allow searching for prebuilt implicit modules."

This reverts commit 71e108c.

This change caused a build failure on Windows:
http://lab.llvm.org:8011/#/builders/83/builds/570

Author: sstamenova

clang/docs/Modules.rst

@@ -225,11 +225,6 @@ Command-line parameters
 ``-fprebuilt-module-path=<directory>``
   Specify the path to the prebuilt modules. If specified, we will look for modules in this directory for a given top-level module name. We don't need a module map for loading prebuilt modules in this directory and the compiler will not try to rebuild these modules. This can be specified multiple times.
 
-``-fprebuilt-implicit-modules``
-  Enable prebuilt implicit modules. If a prebuilt module is not found in the
-  prebuilt modules paths (specified via ``-fprebuilt-module-path``), we will
-  look for a matching implicit module in the prebuilt modules paths.
-
 -cc1 Options
 ~~~~~~~~~~~~
 
@@ -240,123 +235,6 @@ Command-line parameters
   being built if the command line arguments are not homogeneous across your
   build.
 
-Using Prebuilt Modules
-----------------------
-
-Below are a few examples illustrating uses of prebuilt modules via the different options.
-
-First, let's set up files for our examples.
-
-.. code-block:: c
-
-  /* A.h */
-  #ifdef ENABLE_A
-  void a() {}
-  #endif
-
-.. code-block:: c
-
-  /* B.h */
-  #include "A.h"
-
-.. code-block:: c
-
-  /* use.c */
-  #include "B.h"
-  void use() {
-  #ifdef ENABLE_A
-    a();
-  #endif
-  }
-
-.. code-block:: c
-
-  /* module.modulemap */
-  module A {
-    header "A.h"
-  }
-  module B {
-    header "B.h"
-    export *
-  }
-
-In the examples below, the compilation of ``use.c`` can be done without ``-cc1``, but the commands used to prebuild the modules would need to be updated to take into account the default options passed to ``clang -cc1``. (See ``clang use.c -v``)
-Note also that, since we use ``-cc1``, we specify the ``-fmodule-map-file=`` or ``-fimplicit-module-maps`` options explicitly. When using the clang driver, ``-fimplicit-module-maps`` is implied by ``-fmodules``.
-
-First let us use an explicit mapping from modules to files.
-
-.. code-block:: sh
-
-  rm -rf prebuilt ; mkdir prebuilt
-  clang -cc1 -emit-module -o prebuilt/A.pcm -fmodules module.modulemap -fmodule-name=A
-  clang -cc1 -emit-module -o prebuilt/B.pcm -fmodules module.modulemap -fmodule-name=B -fmodule-file=A=prebuilt/A.pcm
-  clang -cc1 -emit-obj use.c -fmodules -fmodule-map-file=module.modulemap -fmodule-file=A=prebuilt/A.pcm -fmodule-file=B=prebuilt/B.pcm
-
-Instead of of specifying the mappings manually, it can be convenient to use the ``-fprebuilt-module-path`` option. Let's also use ``-fimplicit-module-maps`` instead of manually pointing to our module map.
-
-.. code-block:: sh
-
-  rm -rf prebuilt; mkdir prebuilt
-  clang -cc1 -emit-module -o prebuilt/A.pcm -fmodules module.modulemap -fmodule-name=A
-  clang -cc1 -emit-module -o prebuilt/B.pcm -fmodules module.modulemap -fmodule-name=B -fprebuilt-module-path=prebuilt
-  clang -cc1 -emit-obj use.c -fmodules -fimplicit-module-maps -fprebuilt-module-path=prebuilt
-
-A trick to prebuild all modules required for our source file in one command is to generate implicit modules while using the ``-fdisable-module-hash`` option.
-
-.. code-block:: sh
-
-  rm -rf prebuilt ; mkdir prebuilt
-  clang -cc1 -emit-obj use.c -fmodules -fimplicit-module-maps -fmodules-cache-path=prebuilt -fdisable-module-hash
-  ls prebuilt/*.pcm
-  # prebuilt/A.pcm  prebuilt/B.pcm
-
-Note that with explicit or prebuilt modules, we are responsible for, and should be particularly careful about the compatibility of our modules.
-Using mismatching compilation options and modules may lead to issues.
-
-.. code-block:: sh
-
-  clang -cc1 -emit-obj use.c -fmodules -fimplicit-module-maps -fprebuilt-module-path=prebuilt -DENABLE_A
-  # use.c:4:10: warning: implicit declaration of function 'a' is invalid in C99 [-Wimplicit-function-declaration]
-  #   return a(x);
-  #          ^
-  # 1 warning generated.
-
-So we need to maintain multiple versions of prebuilt modules. We can do so using a manual module mapping, or pointing to a different prebuilt module cache path. For example:
-
-.. code-block:: sh
-
-  rm -rf prebuilt ; mkdir prebuilt ; rm -rf prebuilt_a ; mkdir prebuilt_a
-  clang -cc1 -emit-obj use.c -fmodules -fimplicit-module-maps -fmodules-cache-path=prebuilt -fdisable-module-hash
-  clang -cc1 -emit-obj use.c -fmodules -fimplicit-module-maps -fmodules-cache-path=prebuilt_a -fdisable-module-hash -DENABLE_A
-  clang -cc1 -emit-obj use.c -fmodules -fimplicit-module-maps -fprebuilt-module-path=prebuilt
-  clang -cc1 -emit-obj use.c -fmodules -fimplicit-module-maps -fprebuilt-module-path=prebuilt_a -DENABLE_A
-
-
-Instead of managing the different module versions manually, we can build implicit modules in a given cache path (using ``-fmodules-cache-path``), and reuse them as prebuilt implicit modules by passing ``-fprebuilt-module-path`` and ``-fprebuilt-implicit-modules``.
-
-.. code-block:: sh
-
-  rm -rf prebuilt; mkdir prebuilt
-  clang -cc1 -emit-obj -o use.o use.c -fmodules -fimplicit-module-maps -fmodules-cache-path=prebuilt
-  clang -cc1 -emit-obj -o use.o use.c -fmodules -fimplicit-module-maps -fmodules-cache-path=prebuilt -DENABLE_A
-  find prebuilt -name "*.pcm"
-  # prebuilt/1AYBIGPM8R2GA/A-3L1K4LUA6O31.pcm
-  # prebuilt/1AYBIGPM8R2GA/B-3L1K4LUA6O31.pcm
-  # prebuilt/VH0YZMF1OIRK/A-3L1K4LUA6O31.pcm
-  # prebuilt/VH0YZMF1OIRK/B-3L1K4LUA6O31.pcm
-  clang -cc1 -emit-obj -o use.o use.c -fmodules -fimplicit-module-maps -fprebuilt-module-path=prebuilt -fprebuilt-implicit-modules
-  clang -cc1 -emit-obj -o use.o use.c -fmodules -fimplicit-module-maps -fprebuilt-module-path=prebuilt -fprebuilt-implicit-modules -DENABLE_A
-
-Finally we want to allow implicit modules for configurations that were not prebuilt. When using the clang driver a module cache path is implicitly selected. Using ``-cc1``, we simply add use the ``-fmodules-cache-path`` option.
-
-.. code-block:: sh
-
-  clang -cc1 -emit-obj -o use.o use.c -fmodules -fimplicit-module-maps -fprebuilt-module-path=prebuilt -fprebuilt-implicit-modules -fmodules-cache-path=cache
-  clang -cc1 -emit-obj -o use.o use.c -fmodules -fimplicit-module-maps -fprebuilt-module-path=prebuilt -fprebuilt-implicit-modules -fmodules-cache-path=cache -DENABLE_A
-  clang -cc1 -emit-obj -o use.o use.c -fmodules -fimplicit-module-maps -fprebuilt-module-path=prebuilt -fprebuilt-implicit-modules -fmodules-cache-path=cache -DENABLE_A -DOTHER_OPTIONS
-
-This way, a single directory containing multiple variants of modules can be prepared and reused. The options configuring the module cache are independent of other options.
-
 Module Semantics
 ================
 

clang/include/clang/Driver/Options.td

@@ -1439,9 +1439,6 @@ def fmodules_user_build_path : Separate<["-"], "fmodules-user-build-path">, Grou
 def fprebuilt_module_path : Joined<["-"], "fprebuilt-module-path=">, Group<i_Group>,
   Flags<[NoXarchOption, CC1Option]>, MetaVarName<"<directory>">,
   HelpText<"Specify the prebuilt module path">;
-def fprebuilt_implicit_modules : Flag <["-"], "fprebuilt-implicit-modules">, Group<f_Group>,
-  Flags<[NoXarchOption, CC1Option]>,
-  HelpText<"Look up implicit modules in the prebuilt module 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">;

clang/include/clang/Frontend/CompilerInstance.h

@@ -649,10 +649,7 @@ class CompilerInstance : public ModuleLoader {
   /// and replace any existing one with it.
   void createPreprocessor(TranslationUnitKind TUKind);
 
-  std::string getSpecificModuleCachePath(StringRef ModuleHash);
-  std::string getSpecificModuleCachePath() {
-    return getSpecificModuleCachePath(getInvocation().getModuleHash());
-  }
+  std::string getSpecificModuleCachePath();
 
   /// Create the AST context.
   void createASTContext();

clang/include/clang/Lex/HeaderSearch.h

@@ -183,9 +183,6 @@ class HeaderSearch {
   /// a system header.
   std::vector<std::pair<std::string, bool>> SystemHeaderPrefixes;
 
-  /// The hash used for module cache paths.
-  std::string ModuleHash;
-
   /// The path to the module cache.
   std::string ModuleCachePath;
 
@@ -322,17 +319,11 @@ class HeaderSearch {
     return {};
   }
 
-  /// Set the hash to use for module cache paths.
-  void setModuleHash(StringRef Hash) { ModuleHash = std::string(Hash); }
-
   /// Set the path to the module cache.
   void setModuleCachePath(StringRef CachePath) {
     ModuleCachePath = std::string(CachePath);
   }
 
-  /// Retrieve the module hash.
-  StringRef getModuleHash() const { return ModuleHash; }
-
   /// Retrieve the path to the module cache.
   StringRef getModuleCachePath() const { return ModuleCachePath; }
 
@@ -521,15 +512,6 @@ class HeaderSearch {
   std::string getPrebuiltModuleFileName(StringRef ModuleName,
                                         bool FileMapOnly = false);
 
-  /// Retrieve the name of the prebuilt module file that should be used
-  /// to load the given module.
-  ///
-  /// \param Module The module whose module file name will be returned.
-  ///
-  /// \returns The name of the module file that corresponds to this module,
-  /// or an empty string if this module does not correspond to any module file.
-  std::string getPrebuiltImplicitModuleFileName(Module *Module);
-
   /// Retrieve the name of the (to-be-)cached module file that should
   /// be used to load a module with the given name.
   ///
@@ -632,22 +614,6 @@ class HeaderSearch {
   Module *lookupModule(StringRef ModuleName, StringRef SearchName,
                        bool AllowExtraModuleMapSearch = false);
 
-  /// Retrieve the name of the (to-be-)cached module file that should
-  /// be used to load a module with the given name.
-  ///
-  /// \param ModuleName The module whose module file name will be returned.
-  ///
-  /// \param ModuleMapPath A path that when combined with \c ModuleName
-  /// uniquely identifies this module. See Module::ModuleMap.
-  ///
-  /// \param CachePath A path to the module cache.
-  ///
-  /// \returns The name of the module file that corresponds to this module,
-  /// or an empty string if this module does not correspond to any module file.
-  std::string getCachedModuleFileNameImpl(StringRef ModuleName,
-                                          StringRef ModuleMapPath,
-                                          StringRef CachePath);
-
   /// Retrieve a module with the given name, which may be part of the
   /// given framework.
   ///

clang/include/clang/Lex/HeaderSearchOptions.h

@@ -142,10 +142,6 @@ class HeaderSearchOptions {
   /// file.
   unsigned ModuleMapFileHomeIsCwd : 1;
 
-  /// Also search for prebuilt implicit modules in the prebuilt module cache
-  /// path.
-  unsigned EnablePrebuiltImplicitModules : 1;
-
   /// The interval (in seconds) between pruning operations.
   ///
   /// This operation is expensive, because it requires Clang to walk through
@@ -221,9 +217,8 @@ class HeaderSearchOptions {
   HeaderSearchOptions(StringRef _Sysroot = "/")
       : Sysroot(_Sysroot), ModuleFormat("raw"), DisableModuleHash(false),
         ImplicitModuleMaps(false), ModuleMapFileHomeIsCwd(false),
-        EnablePrebuiltImplicitModules(false), UseBuiltinIncludes(true),
-        UseStandardSystemIncludes(true), UseStandardCXXIncludes(true),
-        UseLibcxx(false), Verbose(false),
+        UseBuiltinIncludes(true), UseStandardSystemIncludes(true),
+        UseStandardCXXIncludes(true), UseLibcxx(false), Verbose(false),
         ModulesValidateOncePerBuildSession(false),
         ModulesValidateSystemHeaders(false),
         ValidateASTInputFilesContent(false), UseDebugInfo(false),

clang/lib/Driver/ToolChains/Clang.cpp

@@ -3379,8 +3379,6 @@ static void RenderModulesOptions(Compilation &C, const Driver &D,
           std::string("-fprebuilt-module-path=") + A->getValue()));
       A->claim();
     }
-    if (Args.hasFlag(options::OPT_fprebuilt_implicit_modules, false))
-      CmdArgs.push_back("-fprebuilt-implicit-modules");
     if (Args.hasFlag(options::OPT_fmodules_validate_input_files_content,
                      options::OPT_fno_modules_validate_input_files_content,
                      false))

clang/lib/Frontend/CompilerInstance.cpp

@@ -428,12 +428,8 @@ void CompilerInstance::createPreprocessor(TranslationUnitKind TUKind) {
 
   PP->setPreprocessedOutput(getPreprocessorOutputOpts().ShowCPP);
 
-  if (PP->getLangOpts().Modules && PP->getLangOpts().ImplicitModules) {
-    std::string ModuleHash = getInvocation().getModuleHash();
-    PP->getHeaderSearchInfo().setModuleHash(ModuleHash);
-    PP->getHeaderSearchInfo().setModuleCachePath(
-        getSpecificModuleCachePath(ModuleHash));
-  }
+  if (PP->getLangOpts().Modules && PP->getLangOpts().ImplicitModules)
+    PP->getHeaderSearchInfo().setModuleCachePath(getSpecificModuleCachePath());
 
   // Handle generating dependencies, if requested.
   const DependencyOutputOptions &DepOpts = getDependencyOutputOpts();
@@ -481,11 +477,13 @@ void CompilerInstance::createPreprocessor(TranslationUnitKind TUKind) {
   }
 }
 
-std::string CompilerInstance::getSpecificModuleCachePath(StringRef ModuleHash) {
-  // Set up the module path, including the hash for the module-creation options.
+std::string CompilerInstance::getSpecificModuleCachePath() {
+  // Set up the module path, including the hash for the
+  // module-creation options.
   SmallString<256> SpecificModuleCache(getHeaderSearchOpts().ModuleCachePath);
   if (!SpecificModuleCache.empty() && !getHeaderSearchOpts().DisableModuleHash)
-    llvm::sys::path::append(SpecificModuleCache, ModuleHash);
+    llvm::sys::path::append(SpecificModuleCache,
+                            getInvocation().getModuleHash());
   return std::string(SpecificModuleCache.str());
 }
 
@@ -1675,8 +1673,6 @@ static ModuleSource selectModuleSource(
   if (!HSOpts.PrebuiltModuleFiles.empty() ||
       !HSOpts.PrebuiltModulePaths.empty()) {
     ModuleFilename = HS.getPrebuiltModuleFileName(ModuleName);
-    if (HSOpts.EnablePrebuiltImplicitModules && ModuleFilename.empty())
-      ModuleFilename = HS.getPrebuiltImplicitModuleFileName(M);
     if (!ModuleFilename.empty())
       return MS_PrebuiltModulePath;
   }

clang/lib/Frontend/CompilerInvocation.cpp

@@ -2191,8 +2191,6 @@ static void ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args,
       !Args.hasArg(OPT_fmodules_disable_diagnostic_validation);
   Opts.ImplicitModuleMaps = Args.hasArg(OPT_fimplicit_module_maps);
   Opts.ModuleMapFileHomeIsCwd = Args.hasArg(OPT_fmodule_map_file_home_is_cwd);
-  Opts.EnablePrebuiltImplicitModules =
-      Args.hasArg(OPT_fprebuilt_implicit_modules);
   Opts.ModuleCachePruneInterval =
       getLastArgIntValue(Args, OPT_fmodules_prune_interval, 7 * 24 * 60 * 60);
   Opts.ModuleCachePruneAfter =

clang/lib/Lex/HeaderSearch.cpp

@@ -164,39 +164,14 @@ std::string HeaderSearch::getPrebuiltModuleFileName(StringRef ModuleName,
   return {};
 }
 
-std::string HeaderSearch::getPrebuiltImplicitModuleFileName(Module *Module) {
-  const FileEntry *ModuleMap =
-      getModuleMap().getModuleMapFileForUniquing(Module);
-  StringRef ModuleName = Module->Name;
-  StringRef ModuleMapPath = ModuleMap->getName();
-  StringRef ModuleCacheHash = HSOpts->DisableModuleHash ? "" : getModuleHash();
-  for (const std::string &Dir : HSOpts->PrebuiltModulePaths) {
-    SmallString<256> CachePath(Dir);
-    llvm::sys::fs::make_absolute(CachePath);
-    llvm::sys::path::append(CachePath, ModuleCacheHash);
-    std::string FileName =
-        getCachedModuleFileNameImpl(ModuleName, ModuleMapPath, CachePath);
-    if (!FileName.empty() && getFileMgr().getFile(FileName))
-      return FileName;
-  }
-  return {};
-}
-
 std::string HeaderSearch::getCachedModuleFileName(StringRef ModuleName,
                                                   StringRef ModuleMapPath) {
-  return getCachedModuleFileNameImpl(ModuleName, ModuleMapPath,
-                                     getModuleCachePath());
-}
-
-std::string HeaderSearch::getCachedModuleFileNameImpl(StringRef ModuleName,
-                                                      StringRef ModuleMapPath,
-                                                      StringRef CachePath) {
   // If we don't have a module cache path or aren't supposed to use one, we
   // can't do anything.
-  if (CachePath.empty())
+  if (getModuleCachePath().empty())
     return {};
 
-  SmallString<256> Result(CachePath);
+  SmallString<256> Result(getModuleCachePath());
   llvm::sys::fs::make_absolute(Result);
 
   if (HSOpts->DisableModuleHash) {

clang/lib/Serialization/ASTReader.cpp

@@ -5844,7 +5844,6 @@ bool ASTReader::ParseHeaderSearchOptions(const RecordData &Record,
   HSOpts.DisableModuleHash = Record[Idx++];
   HSOpts.ImplicitModuleMaps = Record[Idx++];
   HSOpts.ModuleMapFileHomeIsCwd = Record[Idx++];
-  HSOpts.EnablePrebuiltImplicitModules = Record[Idx++];
   HSOpts.UseBuiltinIncludes = Record[Idx++];
   HSOpts.UseStandardSystemIncludes = Record[Idx++];
   HSOpts.UseStandardCXXIncludes = Record[Idx++];

clang/lib/Serialization/ASTWriter.cpp

@@ -1320,7 +1320,6 @@ void ASTWriter::WriteControlBlock(Preprocessor &PP, ASTContext &Context,
   Record.push_back(HSOpts.DisableModuleHash);
   Record.push_back(HSOpts.ImplicitModuleMaps);
   Record.push_back(HSOpts.ModuleMapFileHomeIsCwd);
-  Record.push_back(HSOpts.EnablePrebuiltImplicitModules);
   Record.push_back(HSOpts.UseBuiltinIncludes);
   Record.push_back(HSOpts.UseStandardSystemIncludes);
   Record.push_back(HSOpts.UseStandardCXXIncludes);