[clang][scan-deps] Report a scanned TU's visible modules #147969

cyndyishida · 2025-07-10T14:03:15Z

Clients of the dependency scanning service may need to add dependencies based on the visibility of importing modules, for example, when determining whether a Swift overlay dependency should be brought in based on whether there's a corresponding visible clang module for it.
This patch introduces a new field VisibleModules that contains all the visible top-level modules in a given TU.
Because visibility is determined by which headers or (sub)modules were imported, and not top-level module dependencies, the scanner now performs a separate DFS starting from what was directly imported for this computation.

In my local performance testing, there was no observable performance impact.

resolves: rdar://151416358

llvmbot · 2025-07-10T14:03:50Z

@llvm/pr-subscribers-clang

Author: Cyndy Ishida (cyndyishida)

Changes

Clients of the dependency scanning service may need to add dependencies based on the visibility of top-level modules, for example, when determining whether a Swift overlay dependency should be brought in based on whether there's a corresponding visible clang module for it.
This patch introduces a new field VisibleModules that contains all the visible top-level modules in a given TU.
Because visibility is determined by which headers or (sub)modules were imported, and not top-level module dependencies, the scanner now performs a separate DFS starting from what was directly imported for this computation.

In my local performance testing, there was no observable performance impact.

resolves: rdar://151416358

Patch is 36.60 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/147969.diff

33 Files Affected:

(modified) clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h (+9)
(modified) clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h (+2)
(modified) clang/include/clang/Tooling/DependencyScanning/ModuleDepCollector.h (+8)
(modified) clang/lib/Tooling/DependencyScanning/DependencyScanningTool.cpp (+2)
(modified) clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp (+30-1)
(modified) clang/test/ClangScanDeps/diagnostics.c (+3)
(modified) clang/test/ClangScanDeps/header-search-pruning-transitive.c (+8)
(modified) clang/test/ClangScanDeps/modules-context-hash-ignore-macros.c (+9)
(modified) clang/test/ClangScanDeps/modules-context-hash-outputs.c (+6)
(modified) clang/test/ClangScanDeps/modules-context-hash-warnings.c (+6)
(modified) clang/test/ClangScanDeps/modules-context-hash.c (+6)
(modified) clang/test/ClangScanDeps/modules-dep-args.c (+4)
(modified) clang/test/ClangScanDeps/modules-extern-submodule.c (+4)
(modified) clang/test/ClangScanDeps/modules-extern-unrelated.m (+5)
(modified) clang/test/ClangScanDeps/modules-fmodule-name-no-module-built.m (+4)
(modified) clang/test/ClangScanDeps/modules-full-output-tu-order.c (+2)
(modified) clang/test/ClangScanDeps/modules-full.cpp (+13)
(modified) clang/test/ClangScanDeps/modules-has-include-umbrella-header.c (+6)
(modified) clang/test/ClangScanDeps/modules-implementation-private.m (+4)
(modified) clang/test/ClangScanDeps/modules-implicit-dot-private.m (+3)
(modified) clang/test/ClangScanDeps/modules-incomplete-umbrella.c (+8)
(modified) clang/test/ClangScanDeps/modules-inferred.m (+3)
(modified) clang/test/ClangScanDeps/modules-no-undeclared-includes.c (+3)
(modified) clang/test/ClangScanDeps/modules-pch-common-stale.c (+9)
(modified) clang/test/ClangScanDeps/modules-pch-common-submodule.c (+7)
(modified) clang/test/ClangScanDeps/modules-pch-common-via-submodule.c (+6)
(modified) clang/test/ClangScanDeps/modules-pch.c (+12)
(modified) clang/test/ClangScanDeps/modules-priv-fw-from-pub.m (+4)
(modified) clang/test/ClangScanDeps/multiple-commands.c (+14)
(modified) clang/test/ClangScanDeps/removed-args.c (+4)
(modified) clang/test/ClangScanDeps/tu-buffer.c (+4)
(added) clang/test/ClangScanDeps/visible-modules.c (+72)
(modified) clang/tools/clang-scan-deps/ClangScanDeps.cpp (+14)

diff --git a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h
index ee24e5d1543d3..14de81a5ff2b6 100644
--- a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h
+++ b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h
@@ -57,6 +57,10 @@ struct TranslationUnitDeps {
   /// determined that the differences are benign for this compilation.
   std::vector<ModuleID> ClangModuleDeps;
 
+  /// A list of module names that are visible to this translation unit. This
+  /// includes both direct and transitive module dependencies.
+  std::vector<std::string> VisibleModules;
+
   /// A list of the C++20 named modules this translation unit depends on.
   std::vector<std::string> NamedModuleDeps;
 
@@ -188,6 +192,10 @@ class FullDependencyConsumer : public DependencyConsumer {
     DirectModuleDeps.push_back(ID);
   }
 
+  void handleVisibleModule(std::string ModuleName) override {
+    VisibleModules.push_back(ModuleName);
+  }
+
   void handleContextHash(std::string Hash) override {
     ContextHash = std::move(Hash);
   }
@@ -210,6 +218,7 @@ class FullDependencyConsumer : public DependencyConsumer {
   std::string ModuleName;
   std::vector<std::string> NamedModuleDeps;
   std::vector<ModuleID> DirectModuleDeps;
+  std::vector<std::string> VisibleModules;
   std::vector<Command> Commands;
   std::string ContextHash;
   std::vector<std::string> OutputPaths;
diff --git a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h
index 3e232c79397ce..6060e4b43312e 100644
--- a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h
+++ b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h
@@ -59,6 +59,8 @@ class DependencyConsumer {
 
   virtual void handleDirectModuleDependency(ModuleID MD) = 0;
 
+  virtual void handleVisibleModule(std::string ModuleName) = 0;
+
   virtual void handleContextHash(std::string Hash) = 0;
 };
 
diff --git a/clang/include/clang/Tooling/DependencyScanning/ModuleDepCollector.h b/clang/include/clang/Tooling/DependencyScanning/ModuleDepCollector.h
index e96c49883d3c6..4136cb73f7043 100644
--- a/clang/include/clang/Tooling/DependencyScanning/ModuleDepCollector.h
+++ b/clang/include/clang/Tooling/DependencyScanning/ModuleDepCollector.h
@@ -323,6 +323,11 @@ class ModuleDepCollector final : public DependencyCollector {
   llvm::MapVector<const Module *, PrebuiltModuleDep> DirectPrebuiltModularDeps;
   /// Working set of direct modular dependencies.
   llvm::SetVector<const Module *> DirectModularDeps;
+  /// Working set of direct modular dependencies, as they were imported.
+  llvm::SmallPtrSet<const Module *, 32> DirectImports;
+  /// All direct and transitive visible modules.
+  llvm::StringSet<> VisibleModules;
+
   /// Options that control the dependency output generation.
   std::unique_ptr<DependencyOutputOptions> Opts;
   /// A Clang invocation that's based on the original TU invocation and that has
@@ -337,6 +342,9 @@ class ModuleDepCollector final : public DependencyCollector {
   /// Checks whether the module is known as being prebuilt.
   bool isPrebuiltModule(const Module *M);
 
+  /// Computes all visible modules resolved from direct imports.
+  void addVisibleModules();
+
   /// Adds \p Path to \c FileDeps, making it absolute if necessary.
   void addFileDep(StringRef Path);
   /// Adds \p Path to \c MD.FileDeps, making it absolute if necessary.
diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningTool.cpp b/clang/lib/Tooling/DependencyScanning/DependencyScanningTool.cpp
index 515211d47b348..d3d7641b83d48 100644
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningTool.cpp
+++ b/clang/lib/Tooling/DependencyScanning/DependencyScanningTool.cpp
@@ -40,6 +40,7 @@ class MakeDependencyPrinterConsumer : public DependencyConsumer {
   void handlePrebuiltModuleDependency(PrebuiltModuleDep PMD) override {}
   void handleModuleDependency(ModuleDeps MD) override {}
   void handleDirectModuleDependency(ModuleID ID) override {}
+  void handleVisibleModule(std::string ModuleName) override {}
   void handleContextHash(std::string Hash) override {}
 
   void printDependencies(std::string &S) {
@@ -175,6 +176,7 @@ TranslationUnitDeps FullDependencyConsumer::takeTranslationUnitDeps() {
   TU.NamedModuleDeps = std::move(NamedModuleDeps);
   TU.FileDeps = std::move(Dependencies);
   TU.PrebuiltModuleDeps = std::move(PrebuiltModuleDeps);
+  TU.VisibleModules = std::move(VisibleModules);
   TU.Commands = std::move(Commands);
 
   for (auto &&M : ClangModuleDeps) {
diff --git a/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp b/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
index fa86d714ff69a..1a36171b0d483 100644
--- a/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
+++ b/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
@@ -673,8 +673,10 @@ void ModuleDepCollectorPP::handleImport(const Module *Imported) {
   if (MDC.isPrebuiltModule(TopLevelModule))
     MDC.DirectPrebuiltModularDeps.insert(
         {TopLevelModule, PrebuiltModuleDep{TopLevelModule}});
-  else
+  else {
     MDC.DirectModularDeps.insert(TopLevelModule);
+    MDC.DirectImports.insert(Imported);
+  }
 }
 
 void ModuleDepCollectorPP::EndOfMainFile() {
@@ -706,6 +708,8 @@ void ModuleDepCollectorPP::EndOfMainFile() {
     if (!MDC.isPrebuiltModule(M))
       MDC.DirectModularDeps.insert(M);
 
+  MDC.addVisibleModules();
+
   for (const Module *M : MDC.DirectModularDeps)
     handleTopLevelModule(M);
 
@@ -727,6 +731,9 @@ void ModuleDepCollectorPP::EndOfMainFile() {
       MDC.Consumer.handleDirectModuleDependency(It->second->ID);
   }
 
+  for (auto &&I : MDC.VisibleModules)
+    MDC.Consumer.handleVisibleModule(std::string(I.getKey()));
+
   for (auto &&I : MDC.FileDeps)
     MDC.Consumer.handleFileDependency(I);
 
@@ -993,6 +1000,28 @@ bool ModuleDepCollector::isPrebuiltModule(const Module *M) {
   return true;
 }
 
+void ModuleDepCollector::addVisibleModules() {
+  llvm::DenseSet<Module *> ImportedModules;
+  auto InsertVisibleModules = [&](const Module *M) {
+    if (ImportedModules.contains(M))
+      return;
+
+    VisibleModules.insert(M->getTopLevelModuleName());
+    SmallVector<Module *> Stack(M->Imports.begin(), M->Imports.end());
+    while (!Stack.empty()) {
+      Module *CurrModule = Stack.pop_back_val();
+      if (ImportedModules.contains(CurrModule))
+        continue;
+      ImportedModules.insert(CurrModule);
+      VisibleModules.insert(CurrModule->getTopLevelModuleName());
+      CurrModule->getExportedModules(Stack);
+    }
+  };
+
+  for (const Module *Import : DirectImports)
+    InsertVisibleModules(Import);
+}
+
 static StringRef makeAbsoluteAndPreferred(CompilerInstance &CI, StringRef Path,
                                           SmallVectorImpl<char> &Storage) {
   if (llvm::sys::path::is_absolute(Path) &&
diff --git a/clang/test/ClangScanDeps/diagnostics.c b/clang/test/ClangScanDeps/diagnostics.c
index 8e3cf4c9f9fa6..4d09740d7b5ae 100644
--- a/clang/test/ClangScanDeps/diagnostics.c
+++ b/clang/test/ClangScanDeps/diagnostics.c
@@ -50,6 +50,9 @@ module mod { header "mod.h" }
 // CHECK-NEXT:           "module-name": "mod"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ],
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "mod"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK-NOT:          "-fimplicit-modules"
 // CHECK-NOT:          "-fimplicit-module-maps"
diff --git a/clang/test/ClangScanDeps/header-search-pruning-transitive.c b/clang/test/ClangScanDeps/header-search-pruning-transitive.c
index 1e829bb02ddc4..680228d51a181 100644
--- a/clang/test/ClangScanDeps/header-search-pruning-transitive.c
+++ b/clang/test/ClangScanDeps/header-search-pruning-transitive.c
@@ -104,6 +104,10 @@ module X { header "X.h" }
 // CHECK-NEXT:           "module-name": "X"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ],
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "X",
+// CHECK-NEXT:          "Y"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK:            ],
 // CHECK:            "file-deps": [
@@ -159,6 +163,10 @@ module X { header "X.h" }
 // CHECK-NEXT:           "module-name": "X"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ],
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "X",
+// CHECK-NEXT:          "Y"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK:            ],
 // CHECK:            "file-deps": [
diff --git a/clang/test/ClangScanDeps/modules-context-hash-ignore-macros.c b/clang/test/ClangScanDeps/modules-context-hash-ignore-macros.c
index 9f7a62fb9eb74..065a10dfb4841 100644
--- a/clang/test/ClangScanDeps/modules-context-hash-ignore-macros.c
+++ b/clang/test/ClangScanDeps/modules-context-hash-ignore-macros.c
@@ -36,6 +36,9 @@
 // CHECK-NEXT:            "module-name": "Mod"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ]
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "Mod"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK-NOT:          "-DFOO"
 // CHECK-NOT:          "FOO"
@@ -49,6 +52,9 @@
 // CHECK-NEXT:            "module-name": "Mod"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ]
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "Mod"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK:              "-D"
 // CHECK-NEXT:         "FOO"
@@ -62,6 +68,9 @@
 // CHECK-NEXT:            "module-name": "Mod"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ]
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "Mod"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK:              "-fmodules-ignore-macro=FOO"
 // CHECK:              "-D"
diff --git a/clang/test/ClangScanDeps/modules-context-hash-outputs.c b/clang/test/ClangScanDeps/modules-context-hash-outputs.c
index 5e63e60a70370..75f8f1c583d92 100644
--- a/clang/test/ClangScanDeps/modules-context-hash-outputs.c
+++ b/clang/test/ClangScanDeps/modules-context-hash-outputs.c
@@ -34,6 +34,9 @@
 // CHECK-NEXT:            "module-name": "Mod"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ]
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "Mod"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK:              "-dependency-file"
 // CHECK:            ]
@@ -46,6 +49,9 @@
 // CHECK-NEXT:            "module-name": "Mod"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ]
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "Mod"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK-NOT:          "-MF"
 // CHECK-NOT:          "-dependency-file"
diff --git a/clang/test/ClangScanDeps/modules-context-hash-warnings.c b/clang/test/ClangScanDeps/modules-context-hash-warnings.c
index 09d2f20b329e3..5a3d76e158c98 100644
--- a/clang/test/ClangScanDeps/modules-context-hash-warnings.c
+++ b/clang/test/ClangScanDeps/modules-context-hash-warnings.c
@@ -34,6 +34,9 @@
 // CHECK-NEXT:            "module-name": "Mod"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ]
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "Mod"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK:              "-Wall"
 // CHECK:            ]
@@ -46,6 +49,9 @@
 // CHECK-NEXT:            "module-name": "Mod"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ]
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "Mod"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK-NOT:          "-Wall"
 // CHECK:            ]
diff --git a/clang/test/ClangScanDeps/modules-context-hash.c b/clang/test/ClangScanDeps/modules-context-hash.c
index 9489563576d3b..6ea831f7aed08 100644
--- a/clang/test/ClangScanDeps/modules-context-hash.c
+++ b/clang/test/ClangScanDeps/modules-context-hash.c
@@ -51,6 +51,9 @@
 // CHECK-NEXT:           "module-name": "mod"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ],
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:       "mod"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK:            ],
 // CHECK:            "file-deps": [
@@ -89,6 +92,9 @@
 // CHECK:                "module-name": "mod"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ],
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:       "mod"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK:            ],
 // CHECK:            "file-deps": [
diff --git a/clang/test/ClangScanDeps/modules-dep-args.c b/clang/test/ClangScanDeps/modules-dep-args.c
index 19f915923b84c..310a33e9533cf 100644
--- a/clang/test/ClangScanDeps/modules-dep-args.c
+++ b/clang/test/ClangScanDeps/modules-dep-args.c
@@ -87,6 +87,10 @@ module Direct { header "direct.h" }
 // CHECK-NEXT:           "module-name": "Direct"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ],
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "Direct",
+// CHECK-NEXT:          "Transitive"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK_CACHE:        "-fmodule-file={{.*}}/cache/{{.*}}/Direct-{{.*}}.pcm"
 // CHECK_BUILD:        "-fmodule-file={{.*}}/build/{{.*}}/Direct-{{.*}}.pcm"
diff --git a/clang/test/ClangScanDeps/modules-extern-submodule.c b/clang/test/ClangScanDeps/modules-extern-submodule.c
index 01d3d6ba5e0d3..7a2b49879b97b 100644
--- a/clang/test/ClangScanDeps/modules-extern-submodule.c
+++ b/clang/test/ClangScanDeps/modules-extern-submodule.c
@@ -107,6 +107,10 @@ module third {}
 // CHECK-NEXT:               "module-name": "first"
 // CHECK-NEXT:             }
 // CHECK-NEXT:           ],
+// CHECK-NEXT:           "visible-clang-modules": [
+// CHECK-NEXT:              "first",
+// CHECK-NEXT:              "second"
+// CHECK-NEXT:           ],
 // CHECK-NEXT:           "command-line": [
 // CHECK-NEXT:             "-cc1",
 // CHECK:                  "-fmodule-map-file=[[PREFIX]]/first/first/module.modulemap",
diff --git a/clang/test/ClangScanDeps/modules-extern-unrelated.m b/clang/test/ClangScanDeps/modules-extern-unrelated.m
index c003f0d9a2ee8..50ee7464419f7 100644
--- a/clang/test/ClangScanDeps/modules-extern-unrelated.m
+++ b/clang/test/ClangScanDeps/modules-extern-unrelated.m
@@ -113,6 +113,11 @@
 // CHECK-NEXT:               "module-name": "zeroth"
 // CHECK-NEXT:             }
 // CHECK-NEXT:           ],
+// CHECK-NEXT:           "visible-clang-modules": [
+// CHECK-NEXT:              "first",
+// CHECK-NEXT:              "second",
+// CHECK-NEXT:              "zeroth"
+// CHECK-NEXT:           ],
 // CHECK-NEXT:           "command-line": [
 // CHECK:                ],
 // CHECK-NEXT:           "executable": "{{.*}}",
diff --git a/clang/test/ClangScanDeps/modules-fmodule-name-no-module-built.m b/clang/test/ClangScanDeps/modules-fmodule-name-no-module-built.m
index cfe29c2bf7cdb..0d91808e2bc04 100644
--- a/clang/test/ClangScanDeps/modules-fmodule-name-no-module-built.m
+++ b/clang/test/ClangScanDeps/modules-fmodule-name-no-module-built.m
@@ -41,6 +41,10 @@
 // CHECK-NEXT:           "module-name": "header2"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ],
+// CHECK-NEXT:       "visible-clang-modules": [
+// CHECK-NEXT:          "header2",
+// CHECK-NEXT:          "header3"
+// CHECK-NEXT:       ],
 // CHECK-NEXT:       "command-line": [
 // CHECK:            ],
 // CHECK:            "file-deps": [
diff --git a/clang/test/ClangScanDeps/modules-full-output-tu-order.c b/clang/test/ClangScanDeps/modules-full-output-tu-order.c
index 065b8ac8ae07f..79e2947c5f039 100644
--- a/clang/test/ClangScanDeps/modules-full-output-tu-order.c
+++ b/clang/test/ClangScanDeps/modules-full-output-tu-order.c
@@ -31,6 +31,7 @@
 // CHECK-NEXT:         {
 // CHECK-NEXT:           "clang-context-hash": "{{.*}}",
 // CHECK-NEXT:           "clang-module-deps": [],
+// CHECK-NEXT:           "visible-clang-modules": [],
 // CHECK-NEXT:           "command-line": [
 // CHECK:                  "-D"
 // CHECK-NEXT:             "ONE"
@@ -47,6 +48,7 @@
 // CHECK-NEXT:         {
 // CHECK-NEXT:           "clang-context-hash": "{{.*}}",
 // CHECK-NEXT:           "clang-module-deps": [],
+// CHECK-NEXT:           "visible-clang-modules": [],
 // CHECK-NEXT:           "command-line": [
 // CHECK:                  "-D"
 // CHECK-NEXT:             "TWO"
diff --git a/clang/test/ClangScanDeps/modules-full.cpp b/clang/test/ClangScanDeps/modules-full.cpp
index 38db3af4403bb..67da82eb35960 100644
--- a/clang/test/ClangScanDeps/modules-full.cpp
+++ b/clang/test/ClangScanDeps/modules-full.cpp
@@ -97,6 +97,10 @@
 // CHECK-NEXT:               "module-name": "header1"
 // CHECK-NEXT:             }
 // CHECK-NEXT:           ],
+// CHECK-NEXT:           "visible-clang-modules": [
+// CHECK-NEXT:              "header1",
+// CHECK-NEXT:              "header2"
+// CHECK-NEXT:           ],
 // CHECK-NEXT:           "command-line": [
 // CHECK-NOT:              "-fimplicit-modules"
 // CHECK-NOT:              "-fimplicit-module-maps"
@@ -120,6 +124,9 @@
 // CHECK-NEXT:               "module-name": "header1"
 // CHECK-NEXT:             }
 // CHECK-NEXT:           ],
+// CHECK-NEXT:           "visible-clang-modules": [
+// CHECK-NEXT:              "header1"
+// CHECK-NEXT:           ],
 // CHECK-NEXT:           "command-line": [
 // CHECK-NOT:              "-fimplicit-modules"
 // CHECK-NOT:              "-fimplicit-module-maps"
@@ -143,6 +150,9 @@
 // CHECK-NEXT:               "module-name": "header1"
 // CHECK-NEXT:             }
 // CHECK-NEXT:           ],
+// CHECK-NEXT:           "visible-clang-modules": [
+// CHECK-NEXT:              "header1"
+// CHECK-NEXT:           ],
 // CHECK-NEXT:           "command-line": [
 // CHECK-NOT:              "-fimplicit-modules"
 // CHECK-NOT:              "-fimplicit-module-maps"
@@ -166,6 +176,9 @@
 // CHECK-NEXT:               "module-name": "header1"
 // CHECK-NEXT:             }
 // CHECK-NEXT:           ],
+// CHECK-NEXT:           "visible-clang-modules": [
+// CHECK-NEXT:              "header1"
+// CHECK-NEXT:           ],
 // CHECK-NEXT:           "command-line": [
 // CHECK-NOT:              "-fimplicit-modules"
 // CHECK-NOT:              "-fimplicit-module-maps"
diff --git a/clang/test/ClangScanDeps/modules-has-include-umbrella-header.c b/clang/test/ClangScanDeps/modules-has-include-umbrella-header.c
index 022c59ca65db2..f27ea8e1ed2eb 100644
--- a/clang/test/ClangScanDeps/modules-has-include-umbrella-header.c
+++ b/clang/test/ClangScanDeps/modules-has-include-umbrella-header.c
@@ -62,6 +62,12 @@ module Dependency { header "dependency.h" }
 // CHECK-NEXT:               "module-name": "FW_Private"
 // CHECK-NEXT:             }
 // CHECK:                ],
+// CHECK:                "visible-clang-modules": [
+// CHECK-NEXT:              "Dependency",
+// CHECK-NEXT:              "FW_Private",
+// CHECK-NEXT:              "Import",
+// CHECK-NEXT:              "Poison"
+// CHECK-NEXT:           ],
 // CHECK-NEXT:           "command-line": [
 // CHECK:                ],
 // CHECK:                "file-deps": [
diff --git a/clang/test/ClangScanDeps/modules-implementation-private.m b/clang/test/ClangScanDeps/modules-implementation-private.m
index b376073f4b9ee..59e77b85b7967 100644
--- a/clang/test/ClangScanDeps/modules-implementation-private.m
+++ b/clang/test/ClangScanDeps/modules-implementation-private.m
@@ -60,6 +60,10 @@
 // CHECK-NEXT:               "module-name": "FW_Private"
 // CHECK-NEXT:             }
 // CHECK-NEXT:           ],
+// CHECK-NEXT:           "visible-clang-modules": [
+// CHECK-NEXT:           "FW",
+// CHECK-NEXT:           "FW_Private"
+// CHECK-NEXT:           ],
 // CHECK-NEXT:           "command-line": [
 // CHECK:                ],
 // CHECK:                "file-deps": [
diff --git a/clang/test/ClangScanDeps/modules-implicit-dot-private.m b/clang/test/ClangScanDeps/modules-implicit-dot-private.m
index aa8caf3451dc4..5dfac2b09b316 100644
--- a/clang/test/ClangScanDeps/modules-implicit-dot-private.m
+++ b/clang/test/ClangScanDeps/modules-implicit-dot-private.m
@@ -75,6 +75,9 @@
 // CHECK-NEXT:           "module-name": ...
[truncated]

cyndyishida · 2025-07-10T14:07:26Z

In my local performance testing, there was no observable performance impact.

To expand on what I tested, clang-scan-dep wall time for:

scanning a TU that includes every clang module under /S/L/F in the macOS 26 sdk.
scanning a real Objective-C-based project, that already took ~60 seconds to scan on my 10-core machine without my changes. There were 5222 compilation commands

All of these cases were tested 10 times with a clean & prepopulated module cache.

jansvoboda11

It seems like this is not actually returning the set of (what Clang calls) visible modules. Can you clarify what the desired semantics actually is?

clang/tools/clang-scan-deps/ClangScanDeps.cpp

clang/test/ClangScanDeps/visible-modules.c

clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h

jansvoboda11

LGTM

clang/test/ClangScanDeps/visible-modules.c

Co-authored-by: Jan Svoboda <[email protected]>

Clients of the dependency scanning service may need to add dependencies based on the visibility of importing modules, for example, when determining whether a Swift overlay dependency should be brought in based on whether there's a corresponding **visible** clang module for it. This patch introduces a new field `VisibleModules` that contains all the visible top-level modules in a given TU. Because visibility is determined by which headers or (sub)modules were imported, and not top-level module dependencies, the scanner now performs a separate DFS starting from what was directly imported for this computation. In my local performance testing, there was no observable performance impact. resolves: rdar://151416358 --------- Co-authored-by: Jan Svoboda <[email protected]> (cherry picked from commit 15c3793)

…g modules only Previously Swift overlay lookup was performed for every directly and transitively-imported Clang module. llvm/llvm-project#147969 introduced the concept of "visible" Clang modules from a given named Clang dependency scanner query which closely maps to the set of modules for which Swift will attempt to load a Swift overlay. This change switches overlay querying to apply only to the set of such visible modules. Resolves rdar://144797648

cyndyishida requested review from qiongsiwu, Bigcheese, benlangmuir and jansvoboda11 July 10, 2025 14:03

llvmbot added the clang Clang issues not falling into any other category label Jul 10, 2025

jansvoboda11 reviewed Jul 10, 2025

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clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp Show resolved Hide resolved

artemcm reviewed Jul 10, 2025

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cyndyishida force-pushed the eng/PR-151416358 branch from 52a1a71 to b72bf3e Compare July 11, 2025 02:25

[clang][scan-deps] Report a scanned TU's visible modules

87900ca

cyndyishida force-pushed the eng/PR-151416358 branch from b72bf3e to 87900ca Compare July 11, 2025 04:03

jansvoboda11 approved these changes Jul 11, 2025

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Update clang/test/ClangScanDeps/visible-modules.c

525f4ef

Co-authored-by: Jan Svoboda <[email protected]>

cyndyishida force-pushed the eng/PR-151416358 branch from d1b43ef to 525f4ef Compare July 11, 2025 15:08

cyndyishida merged commit 15c3793 into llvm:main Jul 11, 2025
9 checks passed

cyndyishida deleted the eng/PR-151416358 branch July 11, 2025 16:33

artemcm mentioned this pull request Jul 14, 2025

[Dependency Scanning] Restrict Swift overlay lookup to "visible" Clang modules only swiftlang/swift#83050

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[clang][scan-deps] Report a scanned TU's visible modules #147969

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cyndyishida commented Jul 10, 2025 •

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