[clang][modules] Report module maps affecting `no_undeclared_includes…

…` modules

Since D106876, PCM files don't report module maps as input files unless they contributed to the compilation.

Reporting only module maps of (transitively) imported modules is not enough, though. For modules marked with `[no_undeclared_includes]`, other module maps affect the compilation by introducing anti-dependencies.

This patch makes sure such module maps are being reported as input files.

Depends on D120463.

Reviewed By: dexonsmith

Differential Revision: https://reviews.llvm.org/D120464

clang/include/clang/Basic/Module.h

@@ -371,6 +371,10 @@ class Module {
   /// The set of use declarations that have yet to be resolved.
   SmallVector<ModuleId, 2> UnresolvedDirectUses;
 
+  /// When \c NoUndeclaredIncludes is true, the set of modules this module tried
+  /// to import but didn't because they are not direct uses.
+  llvm::SmallSetVector<const Module *, 2> UndeclaredUses;
+
   /// A library or framework to link against when an entity from this
   /// module is used.
   struct LinkLibrary {
@@ -601,7 +605,7 @@ class Module {
 
   /// Determine whether this module has declared its intention to
   /// directly use another module.
-  bool directlyUses(const Module *Requested) const;
+  bool directlyUses(const Module *Requested);
 
   /// Add the given feature requirement to the list of features
   /// required by this module.

clang/lib/Basic/Module.cpp

@@ -267,7 +267,7 @@ ArrayRef<const FileEntry *> Module::getTopHeaders(FileManager &FileMgr) {
   return llvm::makeArrayRef(TopHeaders.begin(), TopHeaders.end());
 }
 
-bool Module::directlyUses(const Module *Requested) const {
+bool Module::directlyUses(const Module *Requested) {
   auto *Top = getTopLevelModule();
 
   // A top-level module implicitly uses itself.
@@ -282,6 +282,9 @@ bool Module::directlyUses(const Module *Requested) const {
   if (!Requested->Parent && Requested->Name == "_Builtin_stddef_max_align_t")
     return true;
 
+  if (NoUndeclaredIncludes)
+    UndeclaredUses.insert(Requested);
+
   return false;
 }
 

clang/lib/Serialization/ASTWriter.cpp

@@ -164,8 +164,8 @@ namespace {
 std::set<const FileEntry *> GetAllModuleMaps(const HeaderSearch &HS,
                                              Module *RootModule) {
   std::set<const FileEntry *> ModuleMaps{};
-  std::set<Module *> ProcessedModules;
-  SmallVector<Module *> ModulesToProcess{RootModule};
+  std::set<const Module *> ProcessedModules;
+  SmallVector<const Module *> ModulesToProcess{RootModule};
 
   SmallVector<const FileEntry *, 16> FilesByUID;
   HS.getFileMgr().GetUniqueIDMapping(FilesByUID);
@@ -209,6 +209,11 @@ std::set<const FileEntry *> GetAllModuleMaps(const HeaderSearch &HS,
       }
       ModulesToProcess.push_back(ImportedModule);
     }
+
+    for (const Module *UndeclaredModule : CurrentModule->UndeclaredUses)
+      if (UndeclaredModule &&
+          ProcessedModules.find(UndeclaredModule) == ProcessedModules.end())
+        ModulesToProcess.push_back(UndeclaredModule);
   }
 
   return ModuleMaps;
@@ -2861,6 +2866,8 @@ void ASTWriter::WriteSubmodules(Module *WritingModule) {
     // Might be unnecessary as use declarations are only used to build the
     // module itself.
 
+    // TODO: Consider serializing undeclared uses of modules.
+
     // Emit the link libraries.
     for (const auto &LL : Mod->LinkLibraries) {
       RecordData::value_type Record[] = {SUBMODULE_LINK_LIBRARY,

clang/test/Modules/add-remove-irrelevant-module-map.m

@@ -25,6 +25,34 @@
 
 // Neither PCM file considers 'b.modulemap' an input:
 //
-// RUN: %clang_cc1 -module-file-info %t/cache-without-b/a.pcm | FileCheck %s
-// RUN: %clang_cc1 -module-file-info %t/cache-with-b/a.pcm | FileCheck %s
-// CHECK-NOT: Input file: {{.*}}/b.modulemap
+// RUN: %clang_cc1 -module-file-info %t/cache-without-b/a.pcm | FileCheck %s --check-prefix=CHECK-B
+// RUN: %clang_cc1 -module-file-info %t/cache-with-b/a.pcm | FileCheck %s --check-prefix=CHECK-B
+// CHECK-B-NOT: Input file: {{.*}}/b.modulemap
+
+//--- c.modulemap
+module c [no_undeclared_includes] { header "c.h" }
+
+//--- c.h
+#if __has_include("d.h") // This should use 'd.modulemap' in order to determine that 'd.h'
+                         // doesn't exist for 'c' because of its '[no_undeclared_includes]'.
+#endif
+
+//--- d.modulemap
+module d { header "d.h" }
+
+//--- d.h
+// empty
+
+//--- test-no-undeclared-includes.m
+// expected-no-diagnostics
+@import c;
+
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t/cache -fdisable-module-hash \
+// RUN:   -fmodule-map-file=%t/c.modulemap -fmodule-map-file=%t/d.modulemap \
+// RUN:   %t/test-no-undeclared-includes.m -verify
+
+// The PCM file considers 'd.modulemap' an input because it affects the compilation,
+// although it doesn't describe the built module or its imports.
+//
+// RUN: %clang_cc1 -module-file-info %t/cache/c.pcm | FileCheck %s --check-prefix=CHECK-D -DDIR=%t
+// CHECK-D: Input file: [[DIR]]/d.modulemap