Wed, 21 Oct 1992 06:29:44 GMT

Related articles |
---|

Strength reduction of constant multipliers cliffc@cs.rice.edu (1992-10-13) |

Re: Strength reduction of constant multipliers davidm@voltaire.rational.com (1992-10-14) |

multiplication by constant - quick comparison of algorithms wu@sequent.com (Youfeng Wu) (1992-10-21) |

Re: multiplication by constant - quick comparison of algorithms preston@helena.cs.rice.edu (1992-10-21) |

Re: multiplication by constant - quick comparison of algorithms bgb@iexist.att.com (1992-10-25) |

Re: multiplication by constant - quick comparison of algorithms chased@rbbb.Eng.Sun.COM (1992-10-27) |

Re: multiplication by constant - quick comparison of algorithms joe@babel.ho.att.com (1992-10-28) |

Newsgroups: | comp.compilers |

From: | Youfeng Wu <wu@sequent.com> |

Organization: | Compilers Central |

Date: | Wed, 21 Oct 1992 06:29:44 GMT |

Keywords: | arithmetic, optimize |

References: | 92-10-057 92-10-069 |

For all numbers in [2, 10000], there is a total number of 64612 one's in

their binary represenations, and the following compares the total number

of add/sub/shift instructions used to perform all of the multiplications.

Cliff's Bernstein (Preston Briggs)

==========================================================

#insts 81751 70616

#insts/

Note: Cliff's algorithm generates many "shift by zero" and "add by zero"

instructions. The above numbers have already removed these nop

instructions.

It should be interesting to compare them when LEA instruction is allowed.

By allowing the following LEA instructions:

LEA( b, i, s ) = b + i << s, where s = 1, 2, or 3

I have an algorithm that achieves:

#insts 53670

#insts/

The question is how we can push the ratio of #insts/

Youfeng Wu

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