8335147: Serial: Refactor TenuredGeneration::promote

Reviewed-by: tschatzl, iwalulya

src/hotspot/share/gc/serial/defNewGeneration.cpp

@@ -768,25 +768,25 @@ oop DefNewGeneration::copy_to_survivor_space(oop old) {
   bool new_obj_is_tenured = false;
   // Otherwise try allocating obj tenured
   if (obj == nullptr) {
-    obj = _old_gen->promote(old, s);
+    obj = _old_gen->allocate_for_promotion(old, s);
     if (obj == nullptr) {
       handle_promotion_failure(old);
       return old;
     }
 
-    ContinuationGCSupport::transform_stack_chunk(obj);
-
     new_obj_is_tenured = true;
-  } else {
-    // Prefetch beyond obj
-    const intx interval = PrefetchCopyIntervalInBytes;
-    Prefetch::write(obj, interval);
+  }
 
-    // Copy obj
-    Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
+  // Prefetch beyond obj
+  const intx interval = PrefetchCopyIntervalInBytes;
+  Prefetch::write(obj, interval);
 
-    ContinuationGCSupport::transform_stack_chunk(obj);
+  // Copy obj
+  Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
 
+  ContinuationGCSupport::transform_stack_chunk(obj);
+
+  if (!new_obj_is_tenured) {
     // Increment age if obj still in new generation
     obj->incr_age();
     age_table()->add(obj, s);

src/hotspot/share/gc/serial/tenuredGeneration.cpp

@@ -387,7 +387,7 @@ bool TenuredGeneration::promotion_attempt_is_safe(size_t max_promotion_in_bytes)
   return res;
 }
 
-oop TenuredGeneration::promote(oop obj, size_t obj_size) {
+oop TenuredGeneration::allocate_for_promotion(oop obj, size_t obj_size) {
   assert(obj_size == obj->size(), "bad obj_size passed in");
 
 #ifndef PRODUCT
@@ -401,15 +401,9 @@ oop TenuredGeneration::promote(oop obj, size_t obj_size) {
   if (result == nullptr) {
     // Promotion of obj into gen failed.  Try to expand and allocate.
     result = expand_and_allocate(obj_size, false);
-    if (result == nullptr) {
-      return nullptr;
-    }
   }
 
-  // Copy to new location.
-  Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(obj), result, obj_size);
-  oop new_obj = cast_to_oop<HeapWord*>(result);
-  return new_obj;
+  return cast_to_oop<HeapWord*>(result);
 }
 
 HeapWord*

src/hotspot/share/gc/serial/tenuredGeneration.hpp

@@ -163,12 +163,11 @@ public:
   bool promotion_attempt_is_safe(size_t max_promoted_in_bytes) const;
 
   // "obj" is the address of an object in young-gen.  Allocate space for "obj"
-  // in the old-gen, and copy "obj" into the newly allocated space, if
-  // possible, returning the result (or null if the allocation failed).
+  // in the old-gen, returning the result (or null if the allocation failed).
   //
   // The "obj_size" argument is just obj->size(), passed along so the caller can
   // avoid repeating the virtual call to retrieve it.
-  oop promote(oop obj, size_t obj_size);
+  oop allocate_for_promotion(oop obj, size_t obj_size);
 
   virtual void verify();
   virtual void print_on(outputStream* st) const;