Remove filler map when folding allocations and turn on allocation folding.

BUG=
R=titzer@chromium.org

Review URL: https://codereview.chromium.org/18384004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15631 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -215,7 +215,7 @@ DEFINE_bool(use_gvn, true, "use hydrogen global value numbering")
 DEFINE_bool(use_canonicalizing, true, "use hydrogen instruction canonicalizing")
 DEFINE_bool(use_inlining, true, "use function inlining")
 DEFINE_bool(use_escape_analysis, false, "use hydrogen escape analysis")
-DEFINE_bool(use_allocation_folding, false, "use allocation folding")
+DEFINE_bool(use_allocation_folding, true, "use allocation folding")
 DEFINE_int(max_inlined_source_size, 600,
            "maximum source size in bytes considered for a single inlining")
 DEFINE_int(max_inlined_nodes, 196,

src/hydrogen-instructions.cc

@@ -3216,37 +3216,6 @@ void HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
   new_dominator_size->InsertBefore(dominator_allocate_instr);
   dominator_allocate_instr->UpdateSize(new_dominator_size);
 
-  // TODO(hpayer): Remove filler map but make sure new space is valid.
-  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);
-
   // After that replace the dominated allocate instruction.
   HInstruction* dominated_allocate_instr =
       new(zone) HInnerAllocatedObject(dominator_allocate_instr,