@techreport{TR-IC-98-25,
  number = {IC-98-25},
  author = {Guido Araújo and Ricardo Pannain and Paulo Centoducatte and Mario Côrtes},
  title = {Code Compression Based on Operand Factorization},
  month = {July},
  year = {1998}, 
  institution = {Institute of Computing, University of Campinas},
  note = {In English, 22 pages.
    \par\selectlanguage{english}\textbf{Abstract}
      This paper proposes a code compression technique called {\em operand factorization}. 
      The key idea of operand factorization is the separation of program expression trees
      into sequences of {\em tree patterns} (opcodes) and {\em operand patterns} (registers
      and immediates). Using operand factorization we show that tree and operand patterns 
      have exponential frequency distributions. A set of experiments is performed to
      determine the best encoding technique that explores this feature. The experimental results 
      show an average compression ratio of 35$\%$ for SPEC CINT95 programs, when
      patterns are encoded using Huffman encoding. Another encoding method, that improves
      the performance of the decompression engine, results in an average compression ratio
      of 41$\%$. A decompression engine is proposed
      which assembles tree and operand patterns into uncompressed instruction sequences,
      using a combination of dictionaries and state machines.
  }
}