29 Jan 1996 17:48:21 -0500

Related articles |
---|

[3 earlier articles] |

Re: Compiler optimization of division and remainder richard@atheist.tamu.edu (1996-01-28) |

Re: Compiler optimization of division and remainder prener@watson.ibm.com (1996-01-29) |

Re: Compiler optimization of division and remainder hbaker@netcom.com (1996-01-29) |

Re: Compiler optimization of division and remainder Peter-Lawrence.Montgomery@cwi.nl (1996-01-29) |

Re: Compiler optimization of division and remainder johnmce@world.std.com (1996-01-29) |

Re: Compiler optimization of division and remainder michael.williams@armltd.co.uk (1996-01-29) |

Re: Compiler optimization of division and remainder jgj@ssd.hcsc.com (1996-01-29) |

Re: Compiler optimization of division and remainder dave@occl-cam.demon.co.uk (Dave Lloyd) (1996-01-29) |

Re: Compiler optimization of division and remainder dave@occl-cam.demon.co.uk (Dave Lloyd) (1996-02-02) |

From: | jgj@ssd.hcsc.com (Jeff Jackson) |

Newsgroups: | comp.compilers |

Date: | 29 Jan 1996 17:48:21 -0500 |

Organization: | I would rather be windsurfing. |

References: | 96-01-088 |

Keywords: | optimize, arithmetic |

*> On another newsgroup, a poster claimed that some compilers could*

*> optimize a program which used both a/b and a%b (both quotient and*

*> remainder with the _same_ arguments) in such a way that the compiler*

*> would perform only a single hardware division operation and arrange to*

*> use both the quotient and remainder from this single operation.*

Our compilers here at Harris Computer Systems Corporation do this. On

the PowerPC, we just expand the 'mod' operator in our trees into the

low level operations, including a divide, to do it. CSE elimination

should then pick up the divides and do them only once.

On previous architectures, where a single instruction gave both the

quotient and the remainder, we expanded both the divide and mod

operator into extract_quotient and extract_remainder operators of a

divmod operator.

Peter-Lawrence.Montgomery@cwi.nl (Peter L. Montgomery) suggests a

similar thing for comparisons. We get that one too with a method like

the divmod method described above.

--

Jeffrey Glen Jackson

jgj@ssd.csd.harris.com

--

Post a followup to this message

Return to the
comp.compilers page.

Search the
comp.compilers archives again.