[crankshaft] Fragmentation-free allocation folding.

src/crankshaft/hydrogen-instructions.cc

Index: src/crankshaft/hydrogen-instructions.cc
diff --git a/src/crankshaft/hydrogen-instructions.cc b/src/crankshaft/hydrogen-instructions.cc
index 3d48d8fb71862d1e486ac6f0cc68911a8759f8a0..7fa653b368efe2afa2b05d3ab2c45d57223a58a2 100644
--- a/src/crankshaft/hydrogen-instructions.cc
+++ b/src/crankshaft/hydrogen-instructions.cc
@@ -3253,103 +3253,33 @@ bool HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
     }
   }
 
-  bool keep_heap_iterable = FLAG_log_gc || FLAG_heap_stats;
-#ifdef VERIFY_HEAP
-  keep_heap_iterable = keep_heap_iterable || FLAG_verify_heap;
-#endif
-
-  if (keep_heap_iterable) {
-    dominator_allocate->MakePrefillWithFiller();
-  } else {
-    // TODO(hpayer): This is a short-term hack to make allocation mementos
-    // work again in new space.
-    dominator_allocate->ClearNextMapWord(original_object_size);
+  if (!dominator_allocate->IsAllocationFoldingDominator()) {
+    HAllocate* first_alloc = HAllocate::New(
+        isolate, zone, dominator_allocate->context(), dominator_size,
+        dominator_allocate->type(),
+        IsNewSpaceAllocation() ? NOT_TENURED : TENURED, JS_OBJECT_TYPE);
+    first_alloc->MakeAllocationFoldingDominated();
+    first_alloc->InsertAfter(dominator_allocate);
+    dominator_allocate->ReplaceAllUsesWith(first_alloc);
+    dominator_allocate->MakeAllocationFoldingDominator();
+    if (FLAG_trace_allocation_folding) {
+      PrintF("#%d (%s) inserted for dominator #%d (%s)\n", first_alloc->id(),
+             first_alloc->Mnemonic(), dominator_allocate->id(),
+             dominator_allocate->Mnemonic());
+    }
   }
 
-  dominator_allocate->UpdateClearNextMapWord(MustClearNextMapWord());
-
-  // After that replace the dominated allocate instruction.
-  HInstruction* inner_offset = HConstant::CreateAndInsertBefore(
-      isolate, zone, context(), dominator_size_constant, Representation::None(),
-      this);
+  MakeAllocationFoldingDominated();
 
-  HInstruction* dominated_allocate_instr = HInnerAllocatedObject::New(
-      isolate, zone, context(), dominator_allocate, inner_offset, type());
-  dominated_allocate_instr->InsertBefore(this);
-  DeleteAndReplaceWith(dominated_allocate_instr);
   if (FLAG_trace_allocation_folding) {
-    PrintF("#%d (%s) folded into #%d (%s)\n",
-        id(), Mnemonic(), dominator_allocate->id(),
-        dominator_allocate->Mnemonic());
+    PrintF("#%d (%s) folded into #%d (%s), new dominator size: %d\n", id(),
+           Mnemonic(), dominator_allocate->id(), dominator_allocate->Mnemonic(),
+           new_dominator_size);
   }
   return true;
 }
 
 
-void HAllocate::UpdateFreeSpaceFiller(int32_t free_space_size) {
-  DCHECK(filler_free_space_size_ != NULL);
-  Zone* zone = block()->zone();
-  // We must explicitly force Smi representation here because on x64 we
-  // would otherwise automatically choose int32, but the actual store
-  // requires a Smi-tagged value.
-  HConstant* new_free_space_size = HConstant::CreateAndInsertBefore(
-      block()->isolate(), zone, context(),
-      filler_free_space_size_->value()->GetInteger32Constant() +
-          free_space_size,
-      Representation::Smi(), filler_free_space_size_);
-  filler_free_space_size_->UpdateValue(new_free_space_size);
-}
-
-
-void HAllocate::CreateFreeSpaceFiller(int32_t free_space_size) {
-  DCHECK(filler_free_space_size_ == NULL);
-  Isolate* isolate = block()->isolate();
-  Zone* zone = block()->zone();
-  HInstruction* free_space_instr =
-      HInnerAllocatedObject::New(isolate, zone, context(), dominating_allocate_,
-                                 dominating_allocate_->size(), type());
-  free_space_instr->InsertBefore(this);
-  HConstant* filler_map = HConstant::CreateAndInsertAfter(
-      zone, Unique<Map>::CreateImmovable(isolate->factory()->free_space_map()),
-      true, free_space_instr);
-  HInstruction* store_map =
-      HStoreNamedField::New(isolate, zone, context(), free_space_instr,
-                            HObjectAccess::ForMap(), filler_map);
-  store_map->SetFlag(HValue::kHasNoObservableSideEffects);
-  store_map->InsertAfter(filler_map);
-
-  // We must explicitly force Smi representation here because on x64 we
-  // would otherwise automatically choose int32, but the actual store
-  // requires a Smi-tagged value.
-  HConstant* filler_size =
-      HConstant::CreateAndInsertAfter(isolate, zone, context(), free_space_size,
-                                      Representation::Smi(), store_map);
-  // Must force Smi representation for x64 (see comment above).
-  HObjectAccess access = HObjectAccess::ForMapAndOffset(
-      isolate->factory()->free_space_map(), FreeSpace::kSizeOffset,
-      Representation::Smi());
-  HStoreNamedField* store_size = HStoreNamedField::New(
-      isolate, zone, context(), free_space_instr, access, filler_size);
-  store_size->SetFlag(HValue::kHasNoObservableSideEffects);
-  store_size->InsertAfter(filler_size);
-  filler_free_space_size_ = store_size;
-}
-
-
-void HAllocate::ClearNextMapWord(int offset) {
-  if (MustClearNextMapWord()) {
-    Zone* zone = block()->zone();
-    HObjectAccess access =
-        HObjectAccess::ForObservableJSObjectOffset(offset);
-    HStoreNamedField* clear_next_map =
-        HStoreNamedField::New(block()->isolate(), zone, context(), this, access,
-                              block()->graph()->GetConstant0());
-    clear_next_map->ClearAllSideEffects();
-    clear_next_map->InsertAfter(this);
-  }
-}
-
-
 std::ostream& HAllocate::PrintDataTo(std::ostream& os) const {  // NOLINT
   os << NameOf(size()) << " (";
   if (IsNewSpaceAllocation()) os << "N";