Re: alignment of data-types

anton@mips.complang.tuwien.ac.at (Anton Ertl)
11 Feb 2003 01:43:57 -0500

          From comp.compilers
Related articles
Re: alignment of data-types gah@ugcs.caltech.edu (Glen Herrmannsfeldt) (2003-02-06)
Re: alignment of data-types anton@mips.complang.tuwien.ac.at (2003-02-11)
Re: alignment of data-types markmcintyre@spamcop.net (Mark McIntyre) (2003-02-11)
Re: alignment of data-types gah@ugcs.caltech.edu (Glen Herrmannsfeldt) (2003-02-12)
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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.lang.c,comp.compilers
Followup-To: comp.compilers
Date: 11 Feb 2003 01:43:57 -0500
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
References: <3e3fbe78$0$49117$e4fe514c@news.xs4all.nl> <u6i04vgrps4ar212a1s8knie78jm193e63@4ax.com> 03-02-033
Keywords: architecture, practice
Posted-Date: 11 Feb 2003 01:43:57 EST

"Glen Herrmannsfeldt" <gah@ugcs.caltech.edu> writes:
>It is common for x86 compilers to allocate double variables on 4 byte
>boundaries. This was optimal on the 386 and 486, but not on pentium
>and later processors. The difference can be large.


In many cases (e.g., structure members, function parameters) this is
required by Intel's ABI. This is particularly nasty because it is
incompatible with the hardware alignment checking of the 486 and later
CPUs (AC flag). I hope AMD fixed this in the x86-64 ABI.


Followups to comp.compilers.


- anton
--
M. Anton Ertl
anton@mips.complang.tuwien.ac.at
http://www.complang.tuwien.ac.at/anton/home.html


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