New hydrogen instruction to reduce cost of growing an array on keyed stores.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index d9cef76afff441d592ad5a698aca53204f2868eb..ba724b6f05bb6eb5f3689e7b3845a30e57a785c6 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -2393,6 +2393,21 @@ LInstruction* LChunkBuilder::DoTrapAllocationMemento(
 }
 
 
+LInstruction* LChunkBuilder::DoMaybeGrowElements(HMaybeGrowElements* instr) {
+  info()->MarkAsDeferredCalling();
+  LOperand* context = UseFixed(instr->context(), esi);
+  LOperand* object = Use(instr->object());
+  LOperand* elements = UseAny(instr->elements());
+  LOperand* key = UseRegisterOrConstant(instr->key());
+  LOperand* current_capacity = UseRegisterOrConstant(instr->current_capacity());
+
+  LMaybeGrowElements* result = new (zone())
+      LMaybeGrowElements(context, object, elements, key, current_capacity);
+  DefineFixed(result, eax);
+  return AssignPointerMap(AssignEnvironment(result));
+}
+
+
 LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   bool is_in_object = instr->access().IsInobject();
   bool is_external_location = instr->access().IsExternalMemory() &&