8379200: G1: Remove G1HeapRegion completion facility

Reviewed-by: ayang, iwalulya

Author: Thomas Schatzl

src/hotspot/share/gc/g1/g1CollectionSet.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -174,7 +174,6 @@ void G1CollectionSet::iterate(G1HeapRegionClosure* cl) const {
     G1HeapRegion* r = _g1h->region_at(_regions[i]);
     bool result = cl->do_heap_region(r);
     if (result) {
-      cl->set_incomplete();
       return;
     }
   }

src/hotspot/share/gc/g1/g1ConcurrentMark.cpp

@@ -817,10 +817,6 @@ class G1ClearBitMapTask : public WorkerTask {
     SuspendibleThreadSetJoiner sts_join(_suspendible);
     G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hr_claimer, worker_id);
   }
-
-  bool is_complete() {
-    return _cl.is_complete();
-  }
 };
 
 void G1ConcurrentMark::clear_bitmap(WorkerThreads* workers, bool may_yield) {
@@ -835,7 +831,6 @@ void G1ConcurrentMark::clear_bitmap(WorkerThreads* workers, bool may_yield) {
 
   log_debug(gc, ergo)("Running %s with %u workers for %zu work units.", cl.name(), num_workers, num_chunks);
   workers->run_task(&cl, num_workers);
-  guarantee(may_yield || cl.is_complete(), "Must have completed iteration when not yielding.");
 }
 
 void G1ConcurrentMark::cleanup_for_next_mark() {

src/hotspot/share/gc/g1/g1HeapRegion.hpp

@@ -567,41 +567,15 @@ class G1HeapRegion : public CHeapObj<mtGC> {
 // G1HeapRegionClosure is used for iterating over regions.
 // Terminates the iteration when the "do_heap_region" method returns "true".
 class G1HeapRegionClosure : public StackObj {
-  friend class G1HeapRegionManager;
-  friend class G1CollectionSet;
-  friend class G1CollectionSetCandidates;
-
-  bool _is_complete;
-  void set_incomplete() { _is_complete = false; }
-
 public:
-  G1HeapRegionClosure(): _is_complete(true) {}
-
   // Typically called on each region until it returns true.
   virtual bool do_heap_region(G1HeapRegion* r) = 0;
-
-  // True after iteration if the closure was applied to all heap regions
-  // and returned "false" in all cases.
-  bool is_complete() { return _is_complete; }
 };
 
 class G1HeapRegionIndexClosure : public StackObj {
-  friend class G1HeapRegionManager;
-  friend class G1CollectionSet;
-  friend class G1CollectionSetCandidates;
-
-  bool _is_complete;
-  void set_incomplete() { _is_complete = false; }
-
 public:
-  G1HeapRegionIndexClosure(): _is_complete(true) {}
-
   // Typically called on each region until it returns true.
   virtual bool do_heap_region_index(uint region_index) = 0;
-
-  // True after iteration if the closure was applied to all heap regions
-  // and returned "false" in all cases.
-  bool is_complete() { return _is_complete; }
 };
 
 #endif // SHARE_GC_G1_G1HEAPREGION_HPP

src/hotspot/share/gc/g1/g1HeapRegionManager.cpp

@@ -511,7 +511,6 @@ void G1HeapRegionManager::iterate(G1HeapRegionClosure* blk) const {
     guarantee(at(i) != nullptr, "Tried to access region %u that has a null G1HeapRegion*", i);
     bool res = blk->do_heap_region(at(i));
     if (res) {
-      blk->set_incomplete();
       return;
     }
   }
@@ -526,7 +525,6 @@ void G1HeapRegionManager::iterate(G1HeapRegionIndexClosure* blk) const {
     }
     bool res = blk->do_heap_region_index(i);
     if (res) {
-      blk->set_incomplete();
       return;
     }
   }