ARM: Improve code aging sequence.

src/arm/lithium-codegen-arm.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 143 matching lines @@
       __ stm(db_w, sp, cp.bit() | fp.bit() | lr.bit());
       __ Push(Smi::FromInt(StackFrame::STUB));
       // Adjust FP to point to saved FP.
       __ add(fp, sp, Operand(2 * kPointerSize));
     } else {
       PredictableCodeSizeScope predictible_code_size_scope(
           masm_, kNoCodeAgeSequenceLength * Assembler::kInstrSize);
       // The following three instructions must remain together and unmodified
       // for code aging to work properly.
       __ stm(db_w, sp, r1.bit() | cp.bit() | fp.bit() | lr.bit());
-      // Load undefined value here, so the value is ready for the loop
-      // below.
-      __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
+      __ nop(ip.code());
       // Adjust FP to point to saved FP.
       __ add(fp, sp, Operand(2 * kPointerSize));
     }
     frame_is_built_ = true;
     info_->AddNoFrameRange(0, masm_->pc_offset());
   }
 
   // Reserve space for the stack slots needed by the code.
   int slots = GetStackSlotCount();
   if (slots > 0) {
@@ skipping 5619 matching lines @@
   __ sub(scratch, result, Operand::PointerOffsetFromSmiKey(index));
   __ ldr(result, FieldMemOperand(scratch,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal