Push/pop is just one peephole optimization. Puth them all...

src/arm/assembler-arm.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 958 matching lines @@
   void RecordComment(const char* msg);
 
   void RecordPosition(int pos);
   void RecordStatementPosition(int pos);
   void WriteRecordedPositions();
 
   int pc_offset() const { return pc_ - buffer_; }
   int current_position() const { return current_position_; }
   int current_statement_position() const { return current_statement_position_; }
 
+  bool can_peephole_optimize(int instructions) {
+    if (!FLAG_peephole_optimization) return false;
+    if (last_bound_pos_ > pc_offset() - instructions * kInstrSize) return false;
+    return reloc_info_writer.last_pc() <= pc_ - instructions * kInstrSize;
+  }
+
   // Read/patch instructions
   static Instr instr_at(byte* pc) { return *reinterpret_cast<Instr*>(pc); }
   static void instr_at_put(byte* pc, Instr instr) {
     *reinterpret_cast<Instr*>(pc) = instr;
   }
   static bool IsNop(Instr instr, int type = 0);
   static bool IsBranch(Instr instr);
   static int GetBranchOffset(Instr instr);
   static bool IsLdrRegisterImmediate(Instr instr);
   static int GetLdrRegisterImmediateOffset(Instr instr);
@@ skipping 139 matching lines @@
 
   friend class RegExpMacroAssemblerARM;
   friend class RelocInfo;
   friend class CodePatcher;
   friend class BlockConstPoolScope;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_ASSEMBLER_ARM_H_