[vm, gc] Remove the evacuating compactor.

This was a temporary measure to verify the VM could handle moving old-space objects before we had the sliding compactor.

Bug: https://github.com/dart-lang/sdk/issues/30978
Change-Id: I4ffec413918481c0af4828d126930455f620935d
Reviewed-on: https://dart-review.googlesource.com/22663
Reviewed-by: Siva Annamalai <asiva@google.com>
Reviewed-by: Erik Corry <erikcorry@google.com>

runtime/observatory/tests/service/dominator_tree_user_test.dart

@@ -2,8 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // VMOptions=--error_on_bad_type --error_on_bad_override
-// VMOptions=--use_compactor_evacuating
-// VMOptions=--use_compactor_sliding
+// VMOptions=--use_compactor
 
 import 'package:observatory/heap_snapshot.dart';
 import 'package:observatory/models.dart' as M;

runtime/observatory/tests/service/dominator_tree_vm_test.dart

@@ -2,8 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // VMOptions=--error_on_bad_type --error_on_bad_override
-// VMOptions=--use_compactor_evacuating
-// VMOptions=--use_compactor_sliding
+// VMOptions=--use_compactor
 
 import 'package:observatory/heap_snapshot.dart';
 import 'package:observatory/models.dart' as M;

runtime/vm/flag_list.h

@@ -175,10 +175,7 @@
   D(trace_zones, bool, false, "Traces allocation sizes in the zone.")          \
   P(truncating_left_shift, bool, true,                                         \
     "Optimize left shift to truncate if possible")                             \
-  R(use_compactor_evacuating, false, bool, false,                              \
-    "Compact the heap during old-space GC.")                                   \
-  R(use_compactor_sliding, false, bool, false,                                 \
-    "Compact the heap during old-space GC.")                                   \
+  P(use_compactor, bool, false, "Compact the heap during old-space GC.")       \
   P(use_cha_deopt, bool, true,                                                 \
     "Use class hierarchy analysis even if it can cause deoptimization.")       \
   P(use_field_guards, bool, !USING_DBC,                                        \

runtime/vm/gc_compactor.cc

@@ -414,44 +414,4 @@ void GCCompactor::ForwardPointersForSliding() {
   heap_->ForwardWeakTables(this);
 }
 
-// Moves live objects to fresh pages. Returns the number of bytes moved.
-intptr_t GCCompactor::EvacuatePages(HeapPage* pages) {
-  TIMELINE_FUNCTION_GC_DURATION(thread(), "EvacuatePages");
-
-  intptr_t moved_bytes = 0;
-  for (HeapPage* page = pages; page != NULL; page = page->next()) {
-    uword old_addr = page->object_start();
-    uword end = page->object_end();
-    while (old_addr < end) {
-      RawObject* old_obj = RawObject::FromAddr(old_addr);
-      const intptr_t size = old_obj->Size();
-      if (old_obj->IsMarked()) {
-        ASSERT(!old_obj->IsFreeListElement());
-        ASSERT(!old_obj->IsForwardingCorpse());
-        uword new_addr = heap_->old_space()->TryAllocateDataBumpLocked(
-            size, PageSpace::kForceGrowth);
-        if (new_addr == 0) {
-          OUT_OF_MEMORY();
-        }
-
-        memmove(reinterpret_cast<void*>(new_addr),
-                reinterpret_cast<void*>(old_addr), size);
-
-        RawObject* new_obj = RawObject::FromAddr(new_addr);
-        new_obj->ClearMarkBit();
-
-        ForwardingCorpse* forwarder =
-            ForwardingCorpse::AsForwarder(old_addr, size);
-        forwarder->set_target(new_obj);
-        heap_->ForwardWeakEntries(old_obj, new_obj);
-
-        moved_bytes += size;
-      }
-      old_addr += size;
-    }
-  }
-
-  return moved_bytes;
-}
-
 }  // namespace dart

runtime/vm/gc_compactor.h

@@ -18,7 +18,7 @@ class Heap;
 class HeapPage;
 class RawObject;
 
-// Implements an evacuating compactor and a sliding compactor.
+// Implements a sliding compactor.
 class GCCompactor : public ValueObject,
                     private HandleVisitor,
                     private ObjectPointerVisitor {
@@ -31,8 +31,6 @@ class GCCompactor : public ValueObject,
 
   void CompactBySliding(HeapPage* pages, FreeList* freelist, Mutex* mutex);
 
-  intptr_t EvacuatePages(HeapPage* page);
-
  private:
   void SlidePage(HeapPage* page);
   uword SlideBlock(uword first_object, ForwardingPage* forwarding_page);

runtime/vm/pages.cc

@@ -984,10 +984,8 @@ void PageSpace::MarkSweep() {
 
       mid3 = OS::GetCurrentMonotonicMicros();
 
-      if (FLAG_use_compactor_evacuating) {
-        EvacuatingCompact(thread);
-      } else if (FLAG_use_compactor_sliding) {
-        SlidingCompact(thread);
+      if (FLAG_use_compactor) {
+        Compact(thread);
       } else if (FLAG_concurrent_sweep) {
         ConcurrentSweep(isolate);
       } else {
@@ -1041,7 +1039,7 @@ void PageSpace::MarkSweep() {
     ml.NotifyAll();
   }
 
-  if (FLAG_use_compactor_evacuating || FLAG_use_compactor_sliding) {
+  if (FLAG_use_compactor) {
     // Const object tables are hashed by address: rehash.
     SafepointOperationScope safepoint(thread);
     thread->isolate()->RehashConstants();
@@ -1078,37 +1076,7 @@ void PageSpace::ConcurrentSweep(Isolate* isolate) {
                              &freelist_[HeapPage::kData]);
 }
 
-void PageSpace::EvacuatingCompact(Thread* thread) {
-  thread->isolate()->set_compaction_in_progress(true);
-  HeapPage* pages_to_evacuate = pages_;
-  pages_ = pages_tail_ = NULL;
-
-  GCCompactor compactor(thread, heap_);
-  intptr_t moved_bytes = compactor.EvacuatePages(pages_to_evacuate);
-  usage_.used_in_words -= (moved_bytes / kWordSize);
-
-  Become::FollowForwardingPointers(thread);
-
-  {
-    MutexLocker ml(pages_lock_);
-    HeapPage* page = pages_to_evacuate;
-    while (page != NULL) {
-      HeapPage* next = page->next();
-      IncreaseCapacityInWordsLocked(-(page->memory_->size() >> kWordSizeLog2));
-      page->Deallocate();
-      page = next;
-    }
-  }
-  thread->isolate()->set_compaction_in_progress(false);
-
-  if (FLAG_verify_after_gc) {
-    OS::PrintErr("Verifying after compacting...");
-    heap_->VerifyGC(kForbidMarked);
-    OS::PrintErr(" done.\n");
-  }
-}
-
-void PageSpace::SlidingCompact(Thread* thread) {
+void PageSpace::Compact(Thread* thread) {
   thread->isolate()->set_compaction_in_progress(true);
   GCCompactor compactor(thread, heap_);
   compactor.CompactBySliding(pages_, &freelist_[HeapPage::kData], pages_lock_);

runtime/vm/pages.h

@@ -389,8 +389,7 @@ class PageSpace {
 
   void BlockingSweep();
   void ConcurrentSweep(Isolate* isolate);
-  void EvacuatingCompact(Thread* thread);
-  void SlidingCompact(Thread* thread);
+  void Compact(Thread* thread);
 
   static intptr_t LargePageSizeInWordsFor(intptr_t size);