Avoid uninitialized member warning on gcc 4.3.4

src/ia32/lithium-codegen-ia32.cc

 // Copyright 2011 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 1441 matching lines @@
         // Smis: 0 -> false, all other -> true.
         __ test(reg, Operand(reg));
         __ j(equal, false_label);
         __ JumpIfSmi(reg, true_label);
       } else if (expected.NeedsMap()) {
         // If we need a map later and have a Smi -> deopt.
         __ test(reg, Immediate(kSmiTagMask));
         DeoptimizeIf(zero, instr->environment());
       }
 
-      Register map;
+      Register map = no_reg;
       if (expected.NeedsMap()) {
         map = ToRegister(instr->TempAt(0));
         ASSERT(!map.is(reg));
         __ mov(map, FieldOperand(reg, HeapObject::kMapOffset));
         // Everything with a map could be undetectable, so check this now.
         __ test_b(FieldOperand(map, Map::kBitFieldOffset),
                   1 << Map::kIsUndetectable);
         // Undetectable -> false.
         __ j(not_zero, false_label);
       }
@@ skipping 2926 matching lines @@
                                          env->deoptimization_index());
   __ InvokeBuiltin(Builtins::IN, CALL_FUNCTION, safepoint_generator);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32