[modules] Load the ModuleOffsetMap from the module header lazily.

If we never need to map any ID within the module to its global ID, we don't
need the module offset map. If a compilation transitively depends on lots of
unused module files, this can result in a modest performance improvement.

llvm-svn: 295517

1 files changed, 110 insertions, 81 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 452f5410a8c..985d68e348e 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -1107,7 +1107,7 @@ bool ASTReader::ReadVisibleDeclContextStorage(ModuleFile &M,
   return false;
 }
 
-void ASTReader::Error(StringRef Msg) {
+void ASTReader::Error(StringRef Msg) const {
   Error(diag::err_fe_pch_malformed, Msg);
   if (Context.getLangOpts().Modules && !Diags.isDiagnosticInFlight() &&
       !PP.getHeaderSearchInfo().getModuleCachePath().empty()) {
@@ -1117,7 +1117,7 @@ void ASTReader::Error(StringRef Msg) {
 }
 
 void ASTReader::Error(unsigned DiagID,
-                      StringRef Arg1, StringRef Arg2) {
+                      StringRef Arg1, StringRef Arg2) const {
   if (Diags.isDiagnosticInFlight())
     Diags.SetDelayedDiagnostic(DiagID, Arg1, Arg2);
   else
@@ -1584,7 +1584,11 @@ MacroInfo *ASTReader::ReadMacroRecord(ModuleFile &F, uint64_t Offset) {
 }
 
 PreprocessedEntityID
-ASTReader::getGlobalPreprocessedEntityID(ModuleFile &M, unsigned LocalID) const {
+ASTReader::getGlobalPreprocessedEntityID(ModuleFile &M,
+                                         unsigned LocalID) const {
+  if (!M.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(M);
+
   ContinuousRangeMap<uint32_t, int, 2>::const_iterator
     I = M.PreprocessedEntityRemap.find(LocalID - NUM_PREDEF_PP_ENTITY_IDS);
   assert(I != M.PreprocessedEntityRemap.end()
@@ -2935,83 +2939,9 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       break;
     }
 
-    case MODULE_OFFSET_MAP: {
-      // Additional remapping information.
-      const unsigned char *Data = (const unsigned char*)Blob.data();
-      const unsigned char *DataEnd = Data + Blob.size();
-
-      // If we see this entry before SOURCE_LOCATION_OFFSETS, add placeholders.
-      if (F.SLocRemap.find(0) == F.SLocRemap.end()) {
-        F.SLocRemap.insert(std::make_pair(0U, 0));
-        F.SLocRemap.insert(std::make_pair(2U, 1));
-      }
-
-      // Continuous range maps we may be updating in our module.
-      typedef ContinuousRangeMap<uint32_t, int, 2>::Builder
-          RemapBuilder;
-      RemapBuilder SLocRemap(F.SLocRemap);
-      RemapBuilder IdentifierRemap(F.IdentifierRemap);
-      RemapBuilder MacroRemap(F.MacroRemap);
-      RemapBuilder PreprocessedEntityRemap(F.PreprocessedEntityRemap);
-      RemapBuilder SubmoduleRemap(F.SubmoduleRemap);
-      RemapBuilder SelectorRemap(F.SelectorRemap);
-      RemapBuilder DeclRemap(F.DeclRemap);
-      RemapBuilder TypeRemap(F.TypeRemap);
-
-      while (Data < DataEnd) {
-        using namespace llvm::support;
-        uint16_t Len = endian::readNext<uint16_t, little, unaligned>(Data);
-        StringRef Name = StringRef((const char*)Data, Len);
-        Data += Len;
-        ModuleFile *OM = ModuleMgr.lookup(Name);
-        if (!OM) {
-          std::string Msg =
-              "SourceLocation remap refers to unknown module, cannot find ";
-          Msg.append(Name);
-          Error(Msg);
-          return Failure;
-        }
-
-        uint32_t SLocOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t IdentifierIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t MacroIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t PreprocessedEntityIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t SubmoduleIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t SelectorIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t DeclIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t TypeIndexOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-
-        uint32_t None = std::numeric_limits<uint32_t>::max();
-
-        auto mapOffset = [&](uint32_t Offset, uint32_t BaseOffset,
-                             RemapBuilder &Remap) {
-          if (Offset != None)
-            Remap.insert(std::make_pair(Offset,
-                                        static_cast<int>(BaseOffset - Offset)));
-        };
-        mapOffset(SLocOffset, OM->SLocEntryBaseOffset, SLocRemap);
-        mapOffset(IdentifierIDOffset, OM->BaseIdentifierID, IdentifierRemap);
-        mapOffset(MacroIDOffset, OM->BaseMacroID, MacroRemap);
-        mapOffset(PreprocessedEntityIDOffset, OM->BasePreprocessedEntityID,
-                  PreprocessedEntityRemap);
-        mapOffset(SubmoduleIDOffset, OM->BaseSubmoduleID, SubmoduleRemap);
-        mapOffset(SelectorIDOffset, OM->BaseSelectorID, SelectorRemap);
-        mapOffset(DeclIDOffset, OM->BaseDeclID, DeclRemap);
-        mapOffset(TypeIndexOffset, OM->BaseTypeIndex, TypeRemap);
-
-        // Global -> local mappings.
-        F.GlobalToLocalDeclIDs[OM] = DeclIDOffset;
-      }
+    case MODULE_OFFSET_MAP:
+      F.ModuleOffsetMap = Blob;
       break;
-    }
 
     case SOURCE_MANAGER_LINE_TABLE:
       if (ParseLineTable(F, Record))
@@ -3348,6 +3278,87 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
   }
 }
 
+void ASTReader::ReadModuleOffsetMap(ModuleFile &F) const {
+  assert(!F.ModuleOffsetMap.empty() && "no module offset map to read");
+
+  // Additional remapping information.
+  const unsigned char *Data = (const unsigned char*)F.ModuleOffsetMap.data();
+  const unsigned char *DataEnd = Data + F.ModuleOffsetMap.size();
+  F.ModuleOffsetMap = StringRef();
+
+  // If we see this entry before SOURCE_LOCATION_OFFSETS, add placeholders.
+  if (F.SLocRemap.find(0) == F.SLocRemap.end()) {
+    F.SLocRemap.insert(std::make_pair(0U, 0));
+    F.SLocRemap.insert(std::make_pair(2U, 1));
+  }
+
+  // Continuous range maps we may be updating in our module.
+  typedef ContinuousRangeMap<uint32_t, int, 2>::Builder
+      RemapBuilder;
+  RemapBuilder SLocRemap(F.SLocRemap);
+  RemapBuilder IdentifierRemap(F.IdentifierRemap);
+  RemapBuilder MacroRemap(F.MacroRemap);
+  RemapBuilder PreprocessedEntityRemap(F.PreprocessedEntityRemap);
+  RemapBuilder SubmoduleRemap(F.SubmoduleRemap);
+  RemapBuilder SelectorRemap(F.SelectorRemap);
+  RemapBuilder DeclRemap(F.DeclRemap);
+  RemapBuilder TypeRemap(F.TypeRemap);
+
+  while (Data < DataEnd) {
+    // FIXME: Looking up dependency modules by filename is horrible.
+    using namespace llvm::support;
+    uint16_t Len = endian::readNext<uint16_t, little, unaligned>(Data);
+    StringRef Name = StringRef((const char*)Data, Len);
+    Data += Len;
+    ModuleFile *OM = ModuleMgr.lookup(Name);
+    if (!OM) {
+      std::string Msg =
+          "SourceLocation remap refers to unknown module, cannot find ";
+      Msg.append(Name);
+      Error(Msg);
+      return;
+    }
+
+    uint32_t SLocOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t IdentifierIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t MacroIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t PreprocessedEntityIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t SubmoduleIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t SelectorIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t DeclIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t TypeIndexOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+
+    uint32_t None = std::numeric_limits<uint32_t>::max();
+
+    auto mapOffset = [&](uint32_t Offset, uint32_t BaseOffset,
+                         RemapBuilder &Remap) {
+      if (Offset != None)
+        Remap.insert(std::make_pair(Offset,
+                                    static_cast<int>(BaseOffset - Offset)));
+    };
+    mapOffset(SLocOffset, OM->SLocEntryBaseOffset, SLocRemap);
+    mapOffset(IdentifierIDOffset, OM->BaseIdentifierID, IdentifierRemap);
+    mapOffset(MacroIDOffset, OM->BaseMacroID, MacroRemap);
+    mapOffset(PreprocessedEntityIDOffset, OM->BasePreprocessedEntityID,
+              PreprocessedEntityRemap);
+    mapOffset(SubmoduleIDOffset, OM->BaseSubmoduleID, SubmoduleRemap);
+    mapOffset(SelectorIDOffset, OM->BaseSelectorID, SelectorRemap);
+    mapOffset(DeclIDOffset, OM->BaseDeclID, DeclRemap);
+    mapOffset(TypeIndexOffset, OM->BaseTypeIndex, TypeRemap);
+
+    // Global -> local mappings.
+    F.GlobalToLocalDeclIDs[OM] = DeclIDOffset;
+  }
+}
+
 ASTReader::ASTReadResult
 ASTReader::ReadModuleMapFileBlock(RecordData &Record, ModuleFile &F,
                                   const ModuleFile *ImportedBy,
@@ -6434,6 +6445,9 @@ ASTReader::getGlobalTypeID(ModuleFile &F, unsigned LocalID) const {
   if (LocalIndex < NUM_PREDEF_TYPE_IDS)
     return LocalID;
 
+  if (!F.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(F);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = F.TypeRemap.find(LocalIndex - NUM_PREDEF_TYPE_IDS);
   assert(I != F.TypeRemap.end() && "Invalid index into type index remap");
@@ -6614,6 +6628,9 @@ ASTReader::getGlobalDeclID(ModuleFile &F, LocalDeclID LocalID) const {
   if (LocalID < NUM_PREDEF_DECL_IDS)
     return LocalID;
 
+  if (!F.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(F);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = F.DeclRemap.find(LocalID - NUM_PREDEF_DECL_IDS);
   assert(I != F.DeclRemap.end() && "Invalid index into decl index remap");
@@ -7788,6 +7805,9 @@ IdentifierID ASTReader::getGlobalIdentifierID(ModuleFile &M, unsigned LocalID) {
   if (LocalID < NUM_PREDEF_IDENT_IDS)
     return LocalID;
 
+  if (!M.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(M);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = M.IdentifierRemap.find(LocalID - NUM_PREDEF_IDENT_IDS);
   assert(I != M.IdentifierRemap.end()
@@ -7826,6 +7846,9 @@ MacroID ASTReader::getGlobalMacroID(ModuleFile &M, unsigned LocalID) {
   if (LocalID < NUM_PREDEF_MACRO_IDS)
     return LocalID;
 
+  if (!M.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(M);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = M.MacroRemap.find(LocalID - NUM_PREDEF_MACRO_IDS);
   assert(I != M.MacroRemap.end() && "Invalid index into macro index remap");
@@ -7838,6 +7861,9 @@ ASTReader::getGlobalSubmoduleID(ModuleFile &M, unsigned LocalID) {
   if (LocalID < NUM_PREDEF_SUBMODULE_IDS)
     return LocalID;
 
+  if (!M.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(M);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = M.SubmoduleRemap.find(LocalID - NUM_PREDEF_SUBMODULE_IDS);
   assert(I != M.SubmoduleRemap.end()
@@ -7966,6 +7992,9 @@ ASTReader::getGlobalSelectorID(ModuleFile &M, unsigned LocalID) const {
   if (LocalID < NUM_PREDEF_SELECTOR_IDS)
     return LocalID;
 
+  if (!M.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(M);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = M.SelectorRemap.find(LocalID - NUM_PREDEF_SELECTOR_IDS);
   assert(I != M.SelectorRemap.end()
@@ -8491,11 +8520,11 @@ CXXTemporary *ASTReader::ReadCXXTemporary(ModuleFile &F,
   return CXXTemporary::Create(Context, Decl);
 }
 
-DiagnosticBuilder ASTReader::Diag(unsigned DiagID) {
+DiagnosticBuilder ASTReader::Diag(unsigned DiagID) const {
   return Diag(CurrentImportLoc, DiagID);
 }
 
-DiagnosticBuilder ASTReader::Diag(SourceLocation Loc, unsigned DiagID) {
+DiagnosticBuilder ASTReader::Diag(SourceLocation Loc, unsigned DiagID) const {
   return Diags.Report(Loc, DiagID);
 }