Lazily declare default constructors. We now delay the construction of

declarations for implicit default constructors, copy constructors,
copy assignment operators, and destructors. On a "simple" translation
unit that includes a bunch of C++ standard library headers, we
generate relatively few of these implicit declarations now:

  4/159 implicit default constructors created
  18/236 implicit copy constructors created
  70/241 implicit copy assignment operators created
  0/173 implicit destructors created

And, on this translation unit, this optimization doesn't really
provide any benefit. I'll do some more performance measurements soon,
but this completes the implementation work for <rdar://problem/8151045>.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@107551 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 18 insertions, 6 deletions

diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index b13deec19a..c11e3b371d 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -466,6 +466,10 @@ static bool CanDeclareSpecialMemberFunction(ASTContext &Context,
 void Sema::ForceDeclarationOfImplicitMembers(CXXRecordDecl *Class) {
   if (!CanDeclareSpecialMemberFunction(Context, Class))
     return;
+
+  // If the default constructor has not yet been declared, do so now.
+  if (!Class->hasDeclaredDefaultConstructor())
+    DeclareImplicitDefaultConstructor(Class);
   
   // If the copy constructor has not yet been declared, do so now.
   if (!Class->hasDeclaredCopyConstructor())
@@ -509,9 +513,14 @@ static void DeclareImplicitMemberFunctionsWithName(Sema &S,
   switch (Name.getNameKind()) {
   case DeclarationName::CXXConstructorName:
     if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(DC))
-      if (Record->getDefinition() && !Record->hasDeclaredCopyConstructor() &&
-          CanDeclareSpecialMemberFunction(S.Context, Record))
-        S.DeclareImplicitCopyConstructor(const_cast<CXXRecordDecl *>(Record));
+      if (Record->getDefinition() &&
+          CanDeclareSpecialMemberFunction(S.Context, Record)) {
+        if (!Record->hasDeclaredDefaultConstructor())
+          S.DeclareImplicitDefaultConstructor(
+                                           const_cast<CXXRecordDecl *>(Record));
+        if (!Record->hasDeclaredCopyConstructor())
+          S.DeclareImplicitCopyConstructor(const_cast<CXXRecordDecl *>(Record));
+      }
     break;
       
   case DeclarationName::CXXDestructorName:
@@ -2005,9 +2014,12 @@ void Sema::LookupOverloadedOperatorName(OverloadedOperatorKind Op, Scope *S,
 /// \brief Look up the constructors for the given class.
 DeclContext::lookup_result Sema::LookupConstructors(CXXRecordDecl *Class) {
   // If the copy constructor has not yet been declared, do so now.
-  if (CanDeclareSpecialMemberFunction(Context, Class) &&
-      !Class->hasDeclaredCopyConstructor())
-    DeclareImplicitCopyConstructor(Class);
+  if (CanDeclareSpecialMemberFunction(Context, Class)) {
+    if (!Class->hasDeclaredDefaultConstructor())
+      DeclareImplicitDefaultConstructor(Class);
+    if (!Class->hasDeclaredCopyConstructor())
+      DeclareImplicitCopyConstructor(Class);
+  }
   
   CanQualType T = Context.getCanonicalType(Context.getTypeDeclType(Class));
   DeclarationName Name = Context.DeclarationNames.getCXXConstructorName(T);