Fix for bug 245480. Calling new Array(a) with a single argument could

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 431643f24bf84705ba5fdaf8adcf676616807e93..1dd27ac9bd7c7cdde01f51f4ac63778fcd9c187e 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -3923,8 +3923,26 @@ void LCodeGen::DoCallNewArray(LCallNewArray* instr) {
     ArrayNoArgumentConstructorStub stub(kind, disable_allocation_sites);
     CallCode(stub.GetCode(isolate()), RelocInfo::CONSTRUCT_CALL, instr);
   } else if (instr->arity() == 1) {
+    Label done;
+    if (IsFastPackedElementsKind(kind)) {
+      Label packed_case;
+      // We might need a change here
+      // look at the first argument
+      __ movq(rcx, Operand(rsp, 0));
+      __ testq(rcx, rcx);
+      __ j(zero, &packed_case);
+
+      ElementsKind holey_kind = GetHoleyElementsKind(kind);
+      ArraySingleArgumentConstructorStub stub(holey_kind,
+                                              disable_allocation_sites);
+      CallCode(stub.GetCode(isolate()), RelocInfo::CONSTRUCT_CALL, instr);
+      __ jmp(&done);
+      __ bind(&packed_case);
+    }
+
     ArraySingleArgumentConstructorStub stub(kind, disable_allocation_sites);
     CallCode(stub.GetCode(isolate()), RelocInfo::CONSTRUCT_CALL, instr);
+    __ bind(&done);
   } else {
     ArrayNArgumentsConstructorStub stub(kind, disable_allocation_sites);
     CallCode(stub.GetCode(isolate()), RelocInfo::CONSTRUCT_CALL, instr);