[modules] Initial support for explicitly loading .pcm files.

Implicit module builds are not well-suited to a lot of build systems. In
particular, they fare badly in distributed build systems, and they lead to
build artifacts that are not tracked as part of the usual dependency management
process. This change allows explicitly-built module files (which are already
supported through the -emit-module flag) to be explicitly loaded into a build,
allowing build systems to opt to manage module builds and dependencies
themselves.

This is only the first step in supporting such configurations, and it should
be considered experimental and subject to change or removal for now.

llvm-svn: 220359

3 files changed, 41 insertions, 24 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 3a6e6551dbf..f3181546320 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -389,14 +389,14 @@ bool PCHValidator::ReadDiagnosticOptions(
   // If the original import came from a file explicitly generated by the user,
   // don't check the diagnostic mappings.
   // FIXME: currently this is approximated by checking whether this is not a
-  // module import.
+  // module import of an implicitly-loaded module file.
   // Note: ModuleMgr.rbegin() may not be the current module, but it must be in
   // the transitive closure of its imports, since unrelated modules cannot be
   // imported until after this module finishes validation.
   ModuleFile *TopImport = *ModuleMgr.rbegin();
   while (!TopImport->ImportedBy.empty())
     TopImport = TopImport->ImportedBy[0];
-  if (TopImport->Kind != MK_Module)
+  if (TopImport->Kind != MK_ImplicitModule)
     return false;
 
   StringRef ModuleName = TopImport->ModuleName;
@@ -781,7 +781,7 @@ IdentifierInfo *ASTIdentifierLookupTrait::ReadData(const internal_key_type& k,
       }
     }
 
-    if (F.Kind == MK_Module) {
+    if (F.Kind == MK_ImplicitModule || F.Kind == MK_ExplicitModule) {
       // Macro definitions are stored from newest to oldest, so reverse them
       // before registering them.
       llvm::SmallVector<unsigned, 8> MacroSizes;
@@ -1238,7 +1238,8 @@ bool ASTReader::ReadSLocEntry(int ID) {
     SrcMgr::CharacteristicKind
       FileCharacter = (SrcMgr::CharacteristicKind)Record[2];
     SourceLocation IncludeLoc = ReadSourceLocation(*F, Record[1]);
-    if (IncludeLoc.isInvalid() && F->Kind == MK_Module) {
+    if (IncludeLoc.isInvalid() &&
+        (F->Kind == MK_ImplicitModule || F->Kind == MK_ExplicitModule)) {
       IncludeLoc = getImportLocation(F);
     }
     unsigned Code = SLocEntryCursor.ReadCode();
@@ -1284,7 +1285,7 @@ std::pair<SourceLocation, StringRef> ASTReader::getModuleImportLoc(int ID) {
 
   // Find which module file this entry lands in.
   ModuleFile *M = GlobalSLocEntryMap.find(-ID)->second;
-  if (M->Kind != MK_Module)
+  if (M->Kind != MK_ImplicitModule && M->Kind != MK_ExplicitModule)
     return std::make_pair(SourceLocation(), "");
 
   // FIXME: Can we map this down to a particular submodule? That would be
@@ -1773,7 +1774,8 @@ void ASTReader::resolvePendingMacro(IdentifierInfo *II,
                                     const PendingMacroInfo &PMInfo) {
   assert(II);
 
-  if (PMInfo.M->Kind != MK_Module) {
+  if (PMInfo.M->Kind != MK_ImplicitModule &&
+      PMInfo.M->Kind != MK_ExplicitModule) {
     installPCHMacroDirectives(II, *PMInfo.M,
                               PMInfo.PCHMacroData.MacroDirectivesOffset);
     return;
@@ -1797,7 +1799,7 @@ void ASTReader::resolvePendingMacro(IdentifierInfo *II,
 
 void ASTReader::installPCHMacroDirectives(IdentifierInfo *II,
                                           ModuleFile &M, uint64_t Offset) {
-  assert(M.Kind != MK_Module);
+  assert(M.Kind != MK_ImplicitModule && M.Kind != MK_ExplicitModule);
 
   BitstreamCursor &Cursor = M.MacroCursor;
   SavedStreamPosition SavedPosition(Cursor);
@@ -2279,7 +2281,8 @@ ASTReader::ReadControlBlock(ModuleFile &F,
 
         unsigned N = NumUserInputs;
         if (ValidateSystemInputs ||
-            (HSOpts.ModulesValidateOncePerBuildSession && F.Kind == MK_Module))
+            (HSOpts.ModulesValidateOncePerBuildSession &&
+             F.Kind == MK_ImplicitModule))
           N = NumInputs;
 
         for (unsigned I = 0; I < N; ++I) {
@@ -3191,7 +3194,7 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       break;
 
     case IMPORTED_MODULES: {
-      if (F.Kind != MK_Module) {
+      if (F.Kind != MK_ImplicitModule && F.Kind != MK_ExplicitModule) {
         // If we aren't loading a module (which has its own exports), make
         // all of the imported modules visible.
         // FIXME: Deal with macros-only imports.
@@ -3289,29 +3292,40 @@ ASTReader::ReadModuleMapFileBlock(RecordData &Record, ModuleFile &F,
   unsigned Idx = 0;
   F.ModuleMapPath = ReadString(Record, Idx);
 
+  if (F.Kind == MK_ExplicitModule) {
+    // For an explicitly-loaded module, we don't care whether the original
+    // module map file exists or matches.
+    return Success;
+  }
+
   // Try to resolve ModuleName in the current header search context and
   // verify that it is found in the same module map file as we saved. If the
   // top-level AST file is a main file, skip this check because there is no
   // usable header search context.
   assert(!F.ModuleName.empty() &&
-         "MODULE_NAME should come before MOUDLE_MAP_FILE");
-  if (F.Kind == MK_Module && (*ModuleMgr.begin())->Kind != MK_MainFile) {
+         "MODULE_NAME should come before MODULE_MAP_FILE");
+  if (F.Kind == MK_ImplicitModule &&
+      (*ModuleMgr.begin())->Kind != MK_MainFile) {
+    // An implicitly-loaded module file should have its module listed in some
+    // module map file that we've already loaded.
     Module *M = PP.getHeaderSearchInfo().lookupModule(F.ModuleName);
-    if (!M) {
+    auto &Map = PP.getHeaderSearchInfo().getModuleMap();
+    const FileEntry *ModMap = M ? Map.getModuleMapFileForUniquing(M) : nullptr;
+    if (!ModMap) {
       assert(ImportedBy && "top-level import should be verified");
       if ((ClientLoadCapabilities & ARR_Missing) == 0)
-        Diag(diag::err_imported_module_not_found)
-          << F.ModuleName << ImportedBy->FileName;
+        Diag(diag::err_imported_module_not_found) << F.ModuleName << F.FileName
+                                                  << ImportedBy->FileName
+                                                  << F.ModuleMapPath;
       return Missing;
     }
 
+    assert(M->Name == F.ModuleName && "found module with different name");
+
     // Check the primary module map file.
-    auto &Map = PP.getHeaderSearchInfo().getModuleMap();
     const FileEntry *StoredModMap = FileMgr.getFile(F.ModuleMapPath);
-    const FileEntry *ModMap = Map.getModuleMapFileForUniquing(M);
     if (StoredModMap == nullptr || StoredModMap != ModMap) {
       assert(ModMap && "found module is missing module map file");
-      assert(M->Name == F.ModuleName && "found module with different name");
       assert(ImportedBy && "top-level import should be verified");
       if ((ClientLoadCapabilities & ARR_OutOfDate) == 0)
         Diag(diag::err_imported_module_modmap_changed)
@@ -3696,7 +3710,7 @@ ASTReader::ASTReadResult ASTReader::ReadAST(const std::string &FileName,
     // in the filesystem).
     for (unsigned I = 0, N = Loaded.size(); I != N; ++I) {
       ImportedModule &M = Loaded[I];
-      if (M.Mod->Kind == MK_Module) {
+      if (M.Mod->Kind == MK_ImplicitModule) {
         updateModuleTimestamp(*M.Mod);
       }
     }
@@ -3729,7 +3743,7 @@ ASTReader::ReadASTCore(StringRef FileName,
     break;
 
   case ModuleManager::Missing:
-    // The module file was missing; if the client handle handle, that, return
+    // The module file was missing; if the client can handle that, return
     // it.
     if (ClientLoadCapabilities & ARR_Missing)
       return Missing;
@@ -8196,14 +8210,16 @@ void ASTReader::finishPendingActions() {
       for (unsigned IDIdx = 0, NumIDs = GlobalIDs.size(); IDIdx != NumIDs;
            ++IDIdx) {
         const PendingMacroInfo &Info = GlobalIDs[IDIdx];
-        if (Info.M->Kind != MK_Module)
+        if (Info.M->Kind != MK_ImplicitModule &&
+            Info.M->Kind != MK_ExplicitModule)
           resolvePendingMacro(II, Info);
       }
       // Handle module imports.
       for (unsigned IDIdx = 0, NumIDs = GlobalIDs.size(); IDIdx != NumIDs;
            ++IDIdx) {
         const PendingMacroInfo &Info = GlobalIDs[IDIdx];
-        if (Info.M->Kind == MK_Module)
+        if (Info.M->Kind == MK_ImplicitModule ||
+            Info.M->Kind == MK_ExplicitModule)
           resolvePendingMacro(II, Info);
       }
     }
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index a3b773f6fc5..b5a447d197d 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -1194,7 +1194,7 @@ void ASTDeclReader::VisitNamespaceDecl(NamespaceDecl *D) {
     // any other module's anonymous namespaces, so don't attach the anonymous
     // namespace at all.
     NamespaceDecl *Anon = ReadDeclAs<NamespaceDecl>(Record, Idx);
-    if (F.Kind != MK_Module)
+    if (F.Kind != MK_ImplicitModule && F.Kind != MK_ExplicitModule)
       D->setAnonymousNamespace(Anon);
   } else {
     // Link this namespace back to the first declaration, which has already
@@ -3536,7 +3536,8 @@ void ASTDeclReader::UpdateDecl(Decl *D, ModuleFile &ModuleFile,
       // Each module has its own anonymous namespace, which is disjoint from
       // any other module's anonymous namespaces, so don't attach the anonymous
       // namespace at all.
-      if (ModuleFile.Kind != MK_Module) {
+      if (ModuleFile.Kind != MK_ImplicitModule &&
+          ModuleFile.Kind != MK_ExplicitModule) {
         if (TranslationUnitDecl *TU = dyn_cast<TranslationUnitDecl>(D))
           TU->setAnonymousNamespace(Anon);
         else
diff --git a/clang/lib/Serialization/ModuleManager.cpp b/clang/lib/Serialization/ModuleManager.cpp
index 18fe035456d..20249e0a7bd 100644
--- a/clang/lib/Serialization/ModuleManager.cpp
+++ b/clang/lib/Serialization/ModuleManager.cpp
@@ -89,7 +89,7 @@ ModuleManager::addModule(StringRef FileName, ModuleKind Type,
     ModuleEntry = New;
 
     New->InputFilesValidationTimestamp = 0;
-    if (New->Kind == MK_Module) {
+    if (New->Kind == MK_ImplicitModule) {
       std::string TimestampFilename = New->getTimestampFilename();
       vfs::Status Status;
       // A cached stat value would be fine as well.