[clang] Add API to iterate already loaded specializations

This avoids deserialization if necessary, for example in DeclUnloader.

See also https://reviews.llvm.org/D154328

Author: hahnjo

interpreter/cling/lib/Interpreter/DeclUnloader.cpp

@@ -941,8 +941,8 @@ bool DeclUnloader::VisitRedeclarable(clang::Redeclarable<T>* R, DeclContext* DC)
     bool Successful = true;
 
     // Remove specializations:
-    for (FunctionTemplateDecl::spec_iterator I = FTD->spec_begin(),
-           E = FTD->spec_end(); I != E; ++I)
+    for (FunctionTemplateDecl::spec_iterator I = FTD->loaded_spec_begin(),
+           E = FTD->loaded_spec_end(); I != E; ++I)
       Successful &= Visit(*I);
 
     Successful &= VisitRedeclarableTemplateDecl(FTD);
@@ -954,8 +954,8 @@ bool DeclUnloader::VisitRedeclarable(clang::Redeclarable<T>* R, DeclContext* DC)
     // ClassTemplateDecl: TemplateDecl, Redeclarable
     bool Successful = true;
     // Remove specializations:
-    for (ClassTemplateDecl::spec_iterator I = CTD->spec_begin(),
-           E = CTD->spec_end(); I != E; ++I)
+    for (ClassTemplateDecl::spec_iterator I = CTD->loaded_spec_begin(),
+           E = CTD->loaded_spec_end(); I != E; ++I)
       Successful &= Visit(*I);
 
     Successful &= VisitRedeclarableTemplateDecl(CTD);

interpreter/llvm-project/clang/include/clang/AST/DeclTemplate.h

@@ -1119,6 +1119,20 @@ class FunctionTemplateDecl : public RedeclarableTemplateDecl {
     return makeSpecIterator(getSpecializations(), true);
   }
 
+  /// All specializations that that have already been loaded, ie avoiding
+  /// deserialization of lazily registered specializations.
+  spec_range loaded_specializations() const {
+    return spec_range(loaded_spec_begin(), loaded_spec_end());
+  }
+
+  spec_iterator loaded_spec_begin() const {
+    return makeSpecIterator(getCommonPtr()->Specializations, false);
+  }
+
+  spec_iterator loaded_spec_end() const {
+    return makeSpecIterator(getCommonPtr()->Specializations, true);
+  }
+
   /// Retrieve the "injected" template arguments that correspond to the
   /// template parameters of this function template.
   ///
@@ -2448,6 +2462,20 @@ class ClassTemplateDecl : public RedeclarableTemplateDecl {
     return makeSpecIterator(getSpecializations(), true);
   }
 
+  /// All specializations that that have already been loaded, ie avoiding
+  /// deserialization of lazily registered specializations.
+  spec_range loaded_specializations() const {
+    return spec_range(loaded_spec_begin(), loaded_spec_end());
+  }
+
+  spec_iterator loaded_spec_begin() const {
+    return makeSpecIterator(getCommonPtr()->Specializations, false);
+  }
+
+  spec_iterator loaded_spec_end() const {
+    return makeSpecIterator(getCommonPtr()->Specializations, true);
+  }
+
   // Implement isa/cast/dyncast support
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
   static bool classofKind(Kind K) { return K == ClassTemplate; }
@@ -3251,6 +3279,20 @@ class VarTemplateDecl : public RedeclarableTemplateDecl {
     return makeSpecIterator(getSpecializations(), true);
   }
 
+  /// All specializations that that have already been loaded, ie avoiding
+  /// deserialization of lazily registered specializations.
+  spec_range loaded_specializations() const {
+    return spec_range(loaded_spec_begin(), loaded_spec_end());
+  }
+
+  spec_iterator loaded_spec_begin() const {
+    return makeSpecIterator(getCommonPtr()->Specializations, false);
+  }
+
+  spec_iterator loaded_spec_end() const {
+    return makeSpecIterator(getCommonPtr()->Specializations, true);
+  }
+
   // Implement isa/cast/dyncast support
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
   static bool classofKind(Kind K) { return K == VarTemplate; }