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

src/arm64/lithium-arm64.cc

Index: src/arm64/lithium-arm64.cc
diff --git a/src/arm64/lithium-arm64.cc b/src/arm64/lithium-arm64.cc
index a4a36bfa153613668b659fdf27e10ed4b7f19a19..76b41ec1ff6d0e2836298ea92b5e0a7b865da1be 100644
--- a/src/arm64/lithium-arm64.cc
+++ b/src/arm64/lithium-arm64.cc
@@ -2567,6 +2567,21 @@ LInstruction* LChunkBuilder::DoTrapAllocationMemento(
 }
 
 
+LInstruction* LChunkBuilder::DoMaybeGrowElements(HMaybeGrowElements* instr) {
+  info()->MarkAsDeferredCalling();
+  LOperand* context = UseFixed(instr->context(), cp);
+  LOperand* object = UseRegister(instr->object());
+  LOperand* elements = UseRegister(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, x0);
+  return AssignPointerMap(AssignEnvironment(result));
+}
+
+
 LInstruction* LChunkBuilder::DoTypeof(HTypeof* instr) {
   LOperand* context = UseFixed(instr->context(), cp);
   LOperand* value = UseFixed(instr->value(), x3);