Fix occasional crash when lithium goes out of vregs.

src/x64/lithium-x64.cc

 // Copyright 2012 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 667 matching lines @@
   return instr;
 }
 
 
 LUnallocated* LChunkBuilder::TempRegister() {
   LUnallocated* operand =
       new(zone()) LUnallocated(LUnallocated::MUST_HAVE_REGISTER);
   int vreg = allocator_->GetVirtualRegister();
   if (!allocator_->AllocationOk()) {
     Abort("Out of virtual registers while trying to allocate temp register.");
-    return NULL;
+    vreg = 0;
   }
   operand->set_virtual_register(vreg);
   return operand;
 }
 
 
 LOperand* LChunkBuilder::FixedTemp(Register reg) {
   LUnallocated* operand = ToUnallocated(reg);
   ASSERT(operand->HasFixedPolicy());
   return operand;
@@ skipping 1857 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64