Re: Loop jamming!?

"Stanley Chow" <>
9 Aug 1997 20:14:43 -0400

          From comp.compilers

Related articles
[9 earlier articles]
Re: Loop jamming!? (1997-07-28)
Re: Loop jamming!? (Steve Simmons) (1997-07-29)
Re: Loop jamming!? (Stanley Chow) (1997-07-31)
Re: Loop jamming!? (Jan Vorbrueggen) (1997-07-31)
Re: Loop jamming!? (cliffc) (1997-08-07)
Re: Loop jamming!? (Mike Kent) (1997-08-07)
Re: Loop jamming!? (Stanley Chow) (1997-08-09)
| List of all articles for this month |

From: "Stanley Chow" <>
Newsgroups: comp.compilers
Date: 9 Aug 1997 20:14:43 -0400
Organization: Bell-Northern Research Ltd.
References: 97-07-130 97-08-010
Keywords: optimize

Stanley Chow wrote:
>> Loop jamming will result in a loop that is, in general, slower than
>> each of the original loops. The time penalty will depend on many
>> factors (including cache size, serial dependency, multiple ALU) and
>> in the extreme case, the time penalty can be zero wrt the slower loop.

  <> wrote:
>Actually, it's pretty easy for the jammed loop to run faster than the
>slowest loop, if the cache locality is right.

Then the compiler was not doing a good job for the slow loop - it should
have managed the cache better. In the extreme :-), it could invent
the "extra" loop and use loop jamming to speed up the slow loop.

Stanley Chow;, (613) 763-2831
Nortel/BNR, PO Box 3511 Station C, Ottawa, Ontario

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