[ASTWriter] Detect more non-affecting FileIDs to reduce source location duplication

clang/include/clang/Serialization/ASTWriter.h

@@ -491,6 +491,9 @@ class ASTWriter : public ASTDeserializationListener,
 
   /// Mapping from a source location entry to whether it is affecting or not.
   llvm::BitVector IsSLocAffecting;
+  /// Mapping from a source location entry to whether it must be included as
+  /// input file.
+  llvm::BitVector IsSLocFileEntryAffecting;
 
   /// Mapping from \c FileID to an index into the FileID adjustment table.
   std::vector<FileID> NonAffectingFileIDs;

clang/lib/Serialization/ASTReader.cpp

@@ -5862,6 +5862,12 @@ llvm::Error ASTReader::ReadSubmoduleBlock(ModuleFile &F,
       }
 
       CurrentModule->Kind = Kind;
+      // Note that we may be rewriting an existing location and it is important
+      // to keep doing that. In particular, we would like to prefer a
+      // `DefinitionLoc` loaded from the module file instead of the location
+      // created in the current source manager, because it allows the new
+      // location to be marked as "unaffecting" when writing and avoid creating
+      // duplicate locations for the same module map file.
       CurrentModule->DefinitionLoc = DefinitionLoc;
       CurrentModule->Signature = F.Signature;
       CurrentModule->IsFromModuleFile = true;

clang/lib/Serialization/ASTWriter.cpp

@@ -38,6 +38,7 @@
 #include "clang/AST/TypeLocVisitor.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/DiagnosticOptions.h"
+#include "clang/Basic/FileEntry.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/FileSystemOptions.h"
 #include "clang/Basic/IdentifierTable.h"
@@ -81,6 +82,7 @@
 #include "llvm/ADT/APSInt.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/ADT/STLExtras.h"
@@ -166,18 +168,25 @@ static TypeCode getTypeCodeForTypeClass(Type::TypeClass id) {
 
 namespace {
 
-std::optional<std::set<const FileEntry *>>
+struct AffectingModuleMaps {
+  llvm::DenseSet<FileID> DefinitionFileIDs;
+  llvm::DenseSet<const FileEntry *> DefinitionFiles;
+};
+
+std::optional<AffectingModuleMaps>
 GetAffectingModuleMaps(const Preprocessor &PP, Module *RootModule) {
   if (!PP.getHeaderSearchInfo()
            .getHeaderSearchOpts()
            .ModulesPruneNonAffectingModuleMaps)
     return std::nullopt;
 
   const HeaderSearch &HS = PP.getHeaderSearchInfo();
+  const SourceManager &SM = PP.getSourceManager();
   const ModuleMap &MM = HS.getModuleMap();
 
-  std::set<const FileEntry *> ModuleMaps;
-  std::set<const Module *> ProcessedModules;
+  llvm::DenseSet<FileID> ModuleMaps;
+
+  llvm::DenseSet<const Module *> ProcessedModules;
   auto CollectModuleMapsForHierarchy = [&](const Module *M) {
     M = M->getTopLevelModule();
 
@@ -192,13 +201,13 @@ GetAffectingModuleMaps(const Preprocessor &PP, Module *RootModule) {
 
       // The containing module map is affecting, because it's being pointed
       // into by Module::DefinitionLoc.
-      if (auto FE = MM.getContainingModuleMapFile(Mod))
-        ModuleMaps.insert(*FE);
+      if (auto F = MM.getContainingModuleMapFileID(Mod); F.isValid())
+        ModuleMaps.insert(F);
       // For inferred modules, the module map that allowed inferring is not
       // related to the virtual containing module map file. It did affect the
       // compilation, though.
-      if (auto FE = MM.getModuleMapFileForUniquing(Mod))
-        ModuleMaps.insert(*FE);
+      if (auto F = MM.getModuleMapFileIDForUniquing(Mod); F.isValid())
+        ModuleMaps.insert(F);
 
       for (auto *SubM : Mod->submodules())
         Q.push(SubM);
@@ -268,7 +277,16 @@ GetAffectingModuleMaps(const Preprocessor &PP, Module *RootModule) {
   // just ban module map hierarchies where module map defining a (sub)module X
   // includes a module map defining a module that's not a submodule of X.
 
-  return ModuleMaps;
+  llvm::DenseSet<const FileEntry *> ModuleFileEntries;
+  for (FileID MM : ModuleMaps) {
+    if (auto *FE = SM.getFileEntryForID(MM))
+      ModuleFileEntries.insert(FE);
+  }
+
+  AffectingModuleMaps R;
+  R.DefinitionFileIDs = std::move(ModuleMaps);
+  R.DefinitionFiles = std::move(ModuleFileEntries);
+  return std::move(R);
 }
 
 class ASTTypeWriter {
@@ -1772,7 +1790,7 @@ void ASTWriter::WriteInputFiles(SourceManager &SourceMgr,
       continue;
 
     // Do not emit input files that do not affect current module.
-    if (!IsSLocAffecting[I])
+    if (!IsSLocFileEntryAffecting[I])
       continue;
 
     InputFileEntry Entry(*Cache->OrigEntry);
@@ -4924,6 +4942,7 @@ void ASTWriter::computeNonAffectingInputFiles() {
   unsigned N = SrcMgr.local_sloc_entry_size();
 
   IsSLocAffecting.resize(N, true);
+  IsSLocFileEntryAffecting.resize(N, true);
 
   if (!WritingModule)
     return;
@@ -4960,10 +4979,12 @@ void ASTWriter::computeNonAffectingInputFiles() {
       continue;
 
     // Don't prune module maps that are affecting.
-    if (llvm::is_contained(*AffectingModuleMaps, *Cache->OrigEntry))
+    if (AffectingModuleMaps->DefinitionFileIDs.contains(FID))
       continue;
 
     IsSLocAffecting[I] = false;
+    IsSLocFileEntryAffecting[I] =
+        AffectingModuleMaps->DefinitionFiles.contains(*Cache->OrigEntry);
 
     FileIDAdjustment += 1;
     // Even empty files take up one element in the offset table.

clang/test/ClangScanDeps/modules-extern-submodule.c

@@ -43,7 +43,7 @@ module third {}
 // CHECK-NEXT:       "command-line": [
 // CHECK-NEXT:         "-cc1",
 // CHECK:              "-fmodule-map-file=[[PREFIX]]/second/second/module.modulemap"
-// CHECK-NOT:          "-fmodule-map-file=[[PREFIX]]/second/second/sub.modulemap"
+// CHECK-NEXT:         "-fmodule-map-file=[[PREFIX]]/second/second/sub.modulemap"
 // CHECK-NOT:          "-fmodule-map-file=[[PREFIX]]/third/module.modulemap"
 // CHECK:              "-fmodule-file=second=[[PREFIX]]/cache/{{.*}}/second-{{.*}}.pcm"
 // CHECK:            ],

clang/test/Modules/prune-non-affecting-module-map-repeated.cpp

@@ -0,0 +1,85 @@
+// Check that the same module map file passed to -fmodule-map-file *and*
+// available from one of the `-fmodule-file` does not allocate extra source
+// location space. This optimization is important for using module maps in
+// large codebases to avoid running out of source location space.
+
+// RUN: rm -rf %t && mkdir %t
+// RUN: split-file %s %t
+
+// RUN: %clang_cc1 -xc++ -fmodules -fno-implicit-modules -fmodule-map-file=%t/base.map -fmodule-name=base -emit-module %t/base.map -o %t/base.pcm
+// RUN: %clang_cc1 -xc++ -fmodules -fno-implicit-modules \
+// RUN:   -fmodule-map-file=%t/base.map -fmodule-map-file=%t/mod1.map \
+// RUN:   -fmodule-file=%t/base.pcm \
+// RUN:   -fmodule-name=mod1 -emit-module %t/mod1.map -o %t/mod1.pcm
+// RUN: %clang_cc1 -xc++ -fmodules -fno-implicit-modules \
+// RUN:   -fmodule-map-file=%t/base.map -fmodule-map-file=%t/mod1.map -fmodule-map-file=%t/mod2.map \
+// RUN:   -fmodule-file=%t/mod1.pcm \
+// RUN:   -fmodule-name=mod2 -emit-module %t/mod2.map -o %t/mod2.pcm
+// RUN: %clang_cc1 -xc++ -fmodules -fno-implicit-modules \
+// RUN:   -fmodule-map-file=%t/base.map -fmodule-map-file=%t/mod2.map -fmodule-map-file=%t/mod3.map \
+// RUN:   -fmodule-file=%t/mod2.pcm \
+// RUN:   -fmodule-name=mod3 -emit-module %t/mod3.map -o %t/mod3.pcm
+// RUN: %clang_cc1 -xc++ -fmodules -fno-implicit-modules \
+// RUN:   -fmodule-map-file=%t/base.map -fmodule-map-file=%t/mod3.map -fmodule-map-file=%t/mod4.map \
+// RUN:   -fmodule-file=%t/mod3.pcm \
+// RUN:   -fmodule-name=mod4 -emit-module %t/mod4.map -o %t/mod4.pcm
+// RUN: %clang_cc1 -xc++ -fmodules -fno-implicit-modules -fmodule-map-file=%t/base.map -fmodule-map-file=%t/mod4.map -fmodule-file=%t/mod4.pcm -fsyntax-only -verify %t/check_slocs.cc
+
+//--- base.map
+module base { header "vector.h" }
+//--- mod1.map
+module mod1 { header "mod1.h" }
+//--- mod2.map
+module mod2 { header "mod2.h" }
+//--- mod3.map
+module mod3 { header "mod3.h" }
+//--- mod4.map
+module mod4 { header "mod4.h" }
+//--- check_slocs.cc
+#include "mod4.h"
+#pragma clang __debug sloc_usage // expected-remark {{source manager location address space usage}}
+// expected-note@* {{% of available space}}
+
+// Module map files files that were specified on the command line are entered twice (once when parsing command-line, once loaded from the .pcm)
+// Those that  not specified on the command line must be entered once.
+
+// [email protected]:1 {{file entered 2 times}}
+// [email protected]:1 {{file entered 2 times}}
+// [email protected]:1 {{file entered 1 time}}
+// [email protected]:1 {{file entered 1 time}}
+// [email protected]:1 {{file entered 1 time}}
+// expected-note@* + {{file entered}}
+
+
+//--- vector.h
+#ifndef VECTOR_H
+#define VECTOR_H
+#endif
+
+//--- mod1.h
+#ifndef MOD1
+#define MOD1
+#include "vector.h"
+int mod1();
+#endif
+//--- mod2.h
+#ifndef MOD2
+#define MOD2
+#include "vector.h"
+#include "mod1.h"
+int mod2();
+#endif
+//--- mod3.h
+#ifndef MOD3
+#define MOD3
+#include "vector.h"
+#include "mod2.h"
+int mod3();
+#endif
+//--- mod4.h
+#ifndef MOD4
+#define MOD4
+#include "vector.h"
+#include "mod3.h"
+int mod4();
+#endif