Cache visible Clang modules for interface printing in 'ModuleDecl'

Instead of caching the collection of visible Clang modules in the 'TypePrinter', compute and cache them in the 'ModuleDecl'. When printing a textual interface, the compiler will instantiate many new instances of 'TypePrinter', which means caching them there is not useful.

Author: artemcm

include/swift/AST/Module.h

@@ -39,6 +39,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MD5.h"
 #include <optional>
+#include <unordered_map>
 #include <set>
 
 namespace clang {
@@ -537,6 +538,11 @@ class ModuleDecl
   std::optional<std::pair<ModuleDecl *, Identifier>>
       declaringModuleAndBystander;
 
+  /// A cache of this module's visible Clang modules
+  /// parameterized by the Swift interface print mode.
+  using VisibleClangModuleSet = llvm::DenseMap<const clang::Module *, ModuleDecl *>;
+  std::unordered_map<PrintOptions::InterfaceMode, VisibleClangModuleSet> CachedVisibleClangModuleSet;
+
   /// If this module is an underscored cross import overlay, gets the underlying
   /// module that declared it (which may itself be a cross-import overlay),
   /// along with the name of the required bystander module. Used by tooling to
@@ -578,6 +584,14 @@ class ModuleDecl
   bool getRequiredBystandersIfCrossImportOverlay(
       ModuleDecl *declaring, SmallVectorImpl<Identifier> &bystanderNames);
 
+  /// Computes all Clang modules that are visible from this moule.
+  /// This includes any modules that are imported transitively through public
+  /// (`@_exported`) imports.
+  ///
+  /// The computed map associates each visible Clang module with the
+  /// corresponding Swift module.
+  const VisibleClangModuleSet &
+  getVisibleClangModules(PrintOptions::InterfaceMode contentMode);
 
   /// Walks and loads the declared, underscored cross-import overlays of this
   /// module and its underlying clang module, transitively, to find all cross

lib/AST/ASTPrinter.cpp

@@ -5725,8 +5725,6 @@ class TypePrinter : public TypeVisitor<TypePrinter> {
 
   ASTPrinter &Printer;
   const PrintOptions &Options;
-  std::optional<llvm::DenseMap<const clang::Module *, ModuleDecl *>>
-      VisibleClangModules;
 
   void printGenericArgs(ArrayRef<Type> flatArgs) {
     Printer << "<";
@@ -5800,56 +5798,6 @@ class TypePrinter : public TypeVisitor<TypePrinter> {
     return T->hasSimpleTypeRepr();
   }
 
-  /// Computes the map that is cached by `getVisibleClangModules()`.
-  /// Do not call directly.
-  llvm::DenseMap<const clang::Module *, ModuleDecl *>
-  computeVisibleClangModules() {
-    assert(Options.CurrentModule &&
-           "CurrentModule needs to be set to determine imported Clang modules");
-
-    llvm::DenseMap<const clang::Module *, ModuleDecl *> Result;
-
-    // For the current module, consider both private and public imports.
-    ModuleDecl::ImportFilter Filter = ModuleDecl::ImportFilterKind::Exported;
-    Filter |= ModuleDecl::ImportFilterKind::Default;
-
-    // For private or package swiftinterfaces, also look through @_spiOnly imports.
-    if (!Options.printPublicInterface())
-      Filter |= ModuleDecl::ImportFilterKind::SPIOnly;
-    // Consider package import for package interface
-    if (Options.printPackageInterface())
-      Filter |= ModuleDecl::ImportFilterKind::PackageOnly;
-
-    SmallVector<ImportedModule, 4> Imports;
-    Options.CurrentModule->getImportedModules(Imports, Filter);
-
-    SmallVector<ModuleDecl *, 4> ModulesToProcess;
-    for (const auto &Import : Imports) {
-      ModulesToProcess.push_back(Import.importedModule);
-    }
-
-    SmallPtrSet<ModuleDecl *, 4> Processed;
-    while (!ModulesToProcess.empty()) {
-      ModuleDecl *Mod = ModulesToProcess.back();
-      ModulesToProcess.pop_back();
-
-      if (!Processed.insert(Mod).second)
-        continue;
-
-      if (const clang::Module *ClangModule = Mod->findUnderlyingClangModule())
-        Result[ClangModule] = Mod;
-
-      // For transitive imports, consider only public imports.
-      Imports.clear();
-      Mod->getImportedModules(Imports, ModuleDecl::ImportFilterKind::Exported);
-      for (const auto &Import : Imports) {
-        ModulesToProcess.push_back(Import.importedModule);
-      }
-    }
-
-    return Result;
-  }
-
   /// Returns all Clang modules that are visible from `Options.CurrentModule`.
   /// This includes any modules that are imported transitively through public
   /// (`@_exported`) imports.
@@ -5858,10 +5806,7 @@ class TypePrinter : public TypeVisitor<TypePrinter> {
   /// corresponding Swift module.
   const llvm::DenseMap<const clang::Module *, ModuleDecl *> &
   getVisibleClangModules() {
-    if (!VisibleClangModules) {
-      VisibleClangModules = computeVisibleClangModules();
-    }
-    return *VisibleClangModules;
+    return Options.CurrentModule->getVisibleClangModules(Options.InterfaceContentKind);
   }
 
   template <typename T>

lib/AST/Module.cpp

@@ -1718,6 +1718,54 @@ void ModuleDecl::getMissingImportedModules(
   FORWARD(getMissingImportedModules, (imports));
 }
 
+const llvm::DenseMap<const clang::Module *, ModuleDecl *> &
+ModuleDecl::getVisibleClangModules(PrintOptions::InterfaceMode contentMode) {
+  if (CachedVisibleClangModuleSet.find(contentMode) != CachedVisibleClangModuleSet.end())
+    return CachedVisibleClangModuleSet[contentMode];
+  else
+    CachedVisibleClangModuleSet.emplace(contentMode, VisibleClangModuleSet{});
+  VisibleClangModuleSet &result = CachedVisibleClangModuleSet[contentMode];
+
+  // For the current module, consider both private and public imports.
+  ModuleDecl::ImportFilter Filter = ModuleDecl::ImportFilterKind::Exported;
+  Filter |= ModuleDecl::ImportFilterKind::Default;
+
+  // For private or package swiftinterfaces, also look through @_spiOnly imports.
+  if (contentMode != PrintOptions::InterfaceMode::Public)
+    Filter |= ModuleDecl::ImportFilterKind::SPIOnly;
+  // Consider package import for package interface
+  if (contentMode == PrintOptions::InterfaceMode::Package)
+    Filter |= ModuleDecl::ImportFilterKind::PackageOnly;
+
+  SmallVector<ImportedModule, 32> Imports;
+  getImportedModules(Imports, Filter);
+
+  SmallVector<ModuleDecl *, 32> ModulesToProcess;
+  for (const auto &Import : Imports)
+    ModulesToProcess.push_back(Import.importedModule);
+
+  SmallPtrSet<ModuleDecl *, 32> Processed;
+  while (!ModulesToProcess.empty()) {
+    ModuleDecl *Mod = ModulesToProcess.back();
+    ModulesToProcess.pop_back();
+
+    if (!Processed.insert(Mod).second)
+      continue;
+
+    if (const clang::Module *ClangModule = Mod->findUnderlyingClangModule())
+      result[ClangModule] = Mod;
+
+    // For transitive imports, consider only public imports.
+    Imports.clear();
+    Mod->getImportedModules(Imports, ModuleDecl::ImportFilterKind::Exported);
+    for (const auto &Import : Imports) {
+      ModulesToProcess.push_back(Import.importedModule);
+    }
+  }
+
+  return result;
+}
+
 void
 SourceFile::getImportedModules(SmallVectorImpl<ImportedModule> &modules,
                                ModuleDecl::ImportFilter filter) const {