From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: aliased & packed?
Date: 1997/05/13
Date: 1997-05-13T00:00:00+00:00 [thread overview]
Message-ID: <dewar.863545022@merv> (raw)
In-Reply-To: 1997May13.065907.1@eisner
Larry said
<<The original machines uses the 21064 chip, with Loads and Stores being
at a minimum of 32 bit granularity. Having loaded the desired 32 bits
it takes a couple of instructions to shift and mask the desired byte
into having a register all to itself. Storing requires reading the
old value first, combining, and writing.>>
One further comment on this issue. If you use 8-bit characters, it is not
so bad to load and store 8-bits. What is truly horrible is guaranteeing
independence. That is very expensive.
BUT, the pragma Pack, even if it does not make any difference from a storage
representation point of view, does mean that you no longer have to provide
independence -- so this is the very valuable function of pragma Pack on
things like char_array and string.
next prev parent reply other threads:[~1997-05-13 0:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-05-11 0:00 aliased & packed? tmoran
1997-05-11 0:00 ` Robert Dewar
1997-05-11 0:00 ` Tom Moran
1997-05-12 0:00 ` Robert Dewar
1997-05-12 0:00 ` Robert A Duff
[not found] ` <1997May13.065907.1@eisner>
1997-05-13 0:00 ` Robert A Duff
1997-05-13 0:00 ` Larry Kilgallen
1997-05-14 0:00 ` Richard Kenner
1997-05-13 0:00 ` Robert Dewar [this message]
-- strict thread matches above, loose matches on Subject: below --
1997-05-09 0:00 Tom Moran
1997-05-09 0:00 ` Stephen Leake
1997-05-09 0:00 ` Tom Moran
1997-05-10 0:00 ` Robert Dewar
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