Nonvirtual pointer visitor in GCs

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index 488739cfbf2f115848aa9a7b095500405043f7be..2d557b5110886e8987e9dfdd3e800ae9a516834a 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -453,9 +453,49 @@ class RawObject {
   }
 
   void Validate(Isolate* isolate) const;
-  intptr_t VisitPointers(ObjectPointerVisitor* visitor);
   bool FindObject(FindObjectVisitor* visitor);
 
+  intptr_t VisitPointers(ObjectPointerVisitor* visitor) {

[erikcorry, 2017/05/31 10:40:42]

I think instead of duplicating the code you can just call
VisitPointersNonvirtual(visitor) here.  In that case perhaps you should move
this to a .cc file to stop the inliner getting overly eager for things where it
does not matter.

+    // Fall back to virtual variant for predefined classes
+    intptr_t class_id = GetClassId();
+    if (class_id < kNumPredefinedCids) {
+      return VisitPointersPredefined(visitor, class_id);
+    }
+
+    // Calculate the first and last raw object pointer fields.
+    intptr_t instance_size = Size();
+    uword obj_addr = ToAddr(this);
+    uword from = obj_addr + sizeof(RawObject);
+    uword to = obj_addr + instance_size - kWordSize;
+
+    // Call visitor function non-virtually
+    visitor->VisitPointers(reinterpret_cast<RawObject**>(from),
+                           reinterpret_cast<RawObject**>(to));
+
+    return instance_size;
+  }
+
+  template <class V>

[erikcorry, 2017/05/31 10:40:42]

template <class V, bool call_virtually = false>

This way you can avoid the code duplication.

+  intptr_t VisitPointersNonvirtual(V* visitor) {

[erikcorry, 2017/05/31 10:40:42]

Perhaps it should be called VisitPointersTemplatized if it is also used for the
virtual version.

+    // Fall back to virtual variant for predefined classes
+    intptr_t class_id = GetClassId();
+    if (class_id < kNumPredefinedCids) {
+      return VisitPointersPredefined(visitor, class_id);
+    }
+
+    // Calculate the first and last raw object pointer fields.
+    intptr_t instance_size = Size();
+    uword obj_addr = ToAddr(this);
+    uword from = obj_addr + sizeof(RawObject);
+    uword to = obj_addr + instance_size - kWordSize;
+
+    // Call visitor function non-virtually
+    visitor->V::VisitPointers(reinterpret_cast<RawObject**>(from),
+                              reinterpret_cast<RawObject**>(to));
+
+    return instance_size;
+  }
+
   static RawObject* FromAddr(uword addr) {
     // We expect the untagged address here.
     ASSERT((addr & kSmiTagMask) != kHeapObjectTag);
@@ -513,6 +553,9 @@ class RawObject {
                                         kHeapObjectTag);
   }
 
+  intptr_t VisitPointersPredefined(ObjectPointerVisitor* visitor,
+                                   intptr_t class_id);
+
   intptr_t SizeFromClass() const;
 
   intptr_t GetClassId() const {