22 Sep 1998 22:30:08 -0400

Related articles |
---|

Re: inlining + optimization = nuisance bugs luddy@concmp.com (Luddy Harrison) (1998-09-22) |

Re: floating point precision discussion jacob@jacob.remcomp.fr (1998-09-22) |

Re: floating point precision discussion chrisd@reservoir.com (Chris Dodd) (1998-09-22) |

From: | Chris Dodd <chrisd@reservoir.com> |

Newsgroups: | comp.compilers |

Date: | 22 Sep 1998 22:30:08 -0400 |

Organization: | Reservoir Labs |

References: | 98-09-093 98-09-112 |

Keywords: | arithmetic |

Our esteemed moderator wrote:

*> [Well, actually, there's are flag bits that lets you set the internal*

*> precision of the x86 to 32, 64, or 80 bits, so the forced store*

*> argument is a red herring.*

Actually, those flag bits only set the mantissa precision to 24, 53,

or 64 bits. They don't affect the exponent size, so even if you

restrict an x86 to double precision instead of extended, it can still

`fail' by not under/overflowing when it should. This makes these bits

essentially useless if you want strict IEEE semantics. The only way

to get that is to actually store each intermediate to memory and

reload it...

Chris Dodd

chrisd@reservoir.com

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