Prefill pre-allocated memory of folded allocation with one pointer fillers when heap verifier is on.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 16f502ddaf7b11f3d9600ecd40b025dc899e38d1..930e991379c158706bfe586db5d958d62186b517 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -3237,35 +3237,9 @@ void HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
   dominator_allocate_instr->UpdateSize(new_dominator_size);
 
 #ifdef VERIFY_HEAP
-  HInstruction* free_space_instr =
-      new(zone) HInnerAllocatedObject(dominator_allocate_instr,
-                                      dominator_size_constant,
-                                      type());
-  free_space_instr->InsertAfter(dominator_allocate_instr);
-  HConstant* filler_map = new(zone) HConstant(
-      isolate()->factory()->free_space_map(),
-      UniqueValueId(isolate()->heap()->free_space_map()),
-      Representation::Tagged(),
-      HType::Tagged(),
-      false,
-      true,
-      false,
-      false);
-  filler_map->InsertAfter(free_space_instr);
-
-  HInstruction* store_map = new(zone) HStoreNamedField(
-      free_space_instr, HObjectAccess::ForMap(), filler_map);
-  store_map->SetFlag(HValue::kHasNoObservableSideEffects);
-  store_map->InsertAfter(filler_map);
-
-  HInstruction* free_space_size = new(zone) HConstant(current_size_constant);
-  free_space_size->InsertAfter(store_map);
-  HObjectAccess access =
-      HObjectAccess::ForJSObjectOffset(FreeSpace::kSizeOffset);
-  HInstruction* store_size = new(zone) HStoreNamedField(
-      free_space_instr, access, free_space_size);
-  store_size->SetFlag(HValue::kHasNoObservableSideEffects);
-  store_size->InsertAfter(free_space_size);
+  if (FLAG_verify_heap) {
+    dominator_allocate_instr->SetFlags(HAllocate::PREFILL_WITH_FILLER);
+  }
 #endif
 
   // After that replace the dominated allocate instruction.