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

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3905 matching lines @@
   __ Set(rax, instr->arity());
   __ Move(rbx, instr->hydrogen()->property_cell());
   ElementsKind kind = instr->hydrogen()->elements_kind();
   bool disable_allocation_sites =
       (AllocationSiteInfo::GetMode(kind) == TRACK_ALLOCATION_SITE);
 
   if (instr->arity() == 0) {
     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);
   }
 }
 
 
 void LCodeGen::DoCallRuntime(LCallRuntime* instr) {
   CallRuntime(instr->function(), instr->arity(), instr);
 }
@@ skipping 1648 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64