Introduce a new data structure, LazyVector, which is a vector whose

contents are lazily loaded on demand from an external source (e.g., an
ExternalASTSource or ExternalSemaSource). The "loaded" entities are
kept separate from the "local" entities, so that the two can grow
independently.

Switch Sema::TentativeDefinitions from a normal vector that is eagerly
populated by the ASTReader into one of these LazyVectors, making the
ASTReader a bit more like me (i.e., lazy).



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@136262 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 28 insertions, 16 deletions

diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index c1d8fe03f1..cb240cc031 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -473,8 +473,12 @@ void Sema::ActOnEndOfTranslationUnit() {
   //   identifier, with the composite type as of the end of the
   //   translation unit, with an initializer equal to 0.
   llvm::SmallSet<VarDecl *, 32> Seen;
-  for (unsigned i = 0, e = TentativeDefinitions.size(); i != e; ++i) {
-    VarDecl *VD = TentativeDefinitions[i]->getActingDefinition();
+  for (TentativeDefinitionsType::iterator 
+            T = TentativeDefinitions.begin(ExternalSource),
+         TEnd = TentativeDefinitions.end();
+       T != TEnd; ++T) 
+  {
+    VarDecl *VD = (*T)->getActingDefinition();
 
     // If the tentative definition was completed, getActingDefinition() returns
     // null. If we've already seen this variable before, insert()'s second
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index b377be6267..9f8514f187 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -4328,13 +4328,6 @@ void ASTReader::InitializeSema(Sema &S) {
   }
   PreloadedDecls.clear();
 
-  // If there were any tentative definitions, deserialize them and add
-  // them to Sema's list of tentative definitions.
-  for (unsigned I = 0, N = TentativeDefinitions.size(); I != N; ++I) {
-    VarDecl *Var = cast<VarDecl>(GetDecl(TentativeDefinitions[I]));
-    SemaObj->TentativeDefinitions.push_back(Var);
-  }
-
   // If there were any unused file scoped decls, deserialize them and add to
   // Sema's list of unused file scoped decls.
   for (unsigned I = 0, N = UnusedFileScopedDecls.size(); I != N; ++I) {
@@ -4571,6 +4564,16 @@ void ASTReader::ReadKnownNamespaces(
   }
 }
 
+void ASTReader::ReadTentativeDefinitions(
+                  SmallVectorImpl<VarDecl *> &TentativeDefs) {
+  for (unsigned I = 0, N = TentativeDefinitions.size(); I != N; ++I) {
+    VarDecl *Var = dyn_cast_or_null<VarDecl>(GetDecl(TentativeDefinitions[I]));
+    if (Var)
+      TentativeDefs.push_back(Var);
+  }
+  TentativeDefinitions.clear();
+}
+
 void ASTReader::LoadSelector(Selector Sel) {
   // It would be complicated to avoid reading the methods anyway. So don't.
   ReadMethodPool(Sel);
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index 14824a0810..1acc140acd 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -2805,10 +2805,13 @@ void ASTWriter::WriteASTCore(Sema &SemaRef, MemorizeStatCalls *StatCalls,
   // TentativeDefinitions order.  Generally, this record will be empty for
   // headers.
   RecordData TentativeDefinitions;
-  for (unsigned i = 0, e = SemaRef.TentativeDefinitions.size(); i != e; ++i) {
-    AddDeclRef(SemaRef.TentativeDefinitions[i], TentativeDefinitions);
+  for (Sema::TentativeDefinitionsType::iterator 
+            T = SemaRef.TentativeDefinitions.begin(0, true),
+         TEnd = SemaRef.TentativeDefinitions.end();
+       T != TEnd; ++T) {
+    AddDeclRef(*T, TentativeDefinitions);
   }
-
+  
   // Build a record containing all of the file scoped decls in this file.
   RecordData UnusedFileScopedDecls;
   for (unsigned i=0, e = SemaRef.UnusedFileScopedDecls.size(); i !=e; ++i)
@@ -3072,11 +3075,13 @@ void ASTWriter::WriteASTChain(Sema &SemaRef, MemorizeStatCalls *StatCalls,
   // Build a record containing all of the new tentative definitions in this
   // file, in TentativeDefinitions order.
   RecordData TentativeDefinitions;
-  for (unsigned i = 0, e = SemaRef.TentativeDefinitions.size(); i != e; ++i) {
-    if (SemaRef.TentativeDefinitions[i]->getPCHLevel() == 0)
-      AddDeclRef(SemaRef.TentativeDefinitions[i], TentativeDefinitions);
+  for (Sema::TentativeDefinitionsType::iterator 
+       T = SemaRef.TentativeDefinitions.begin(0, true),
+       TEnd = SemaRef.TentativeDefinitions.end();
+       T != TEnd; ++T) {
+    AddDeclRef(*T, TentativeDefinitions);
   }
-
+  
   // Build a record containing all of the file scoped decls in this file.
   RecordData UnusedFileScopedDecls;
   for (unsigned i=0, e = SemaRef.UnusedFileScopedDecls.size(); i !=e; ++i) {