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From: | Adam Fedor |
Subject: | Re: Byte swapping for doubles |
Date: | Mon, 19 Mar 2007 16:34:44 -0600 |
VFP is a newer floating point architecture for ARM. With respect to endianess, the word endianess of doubles is always the same as the byte endianess of words. This contrast with the older and more common FPA architecture, which always uses big endian for doubles. In both architectures, the word endianness of 64-bit ints matches the word endianess of doubles.
After looking at NSByteOrder.h, it appears we do it correctly, as far as I can tell, swapping doubles the same ways as 64-bit int. Does Nikolaus (or anyone) have an actual bug report which shows the problem? I'm not sure I want to change anything without at least some one to verify it.
On Feb 6, 2007, at 9:00 AM, Fred Kiefer wrote:
I had an email discussion with Nikolaus Schaller about the code inNSByteOrder.h which does the byte swapping for GNUstep and he convincedme that we may not handle the case of swapping doubles correctly for certain ARM processors. Here the word order in doubles seems to differ from the general byte order.I had a quick search on the web and found ax_cv_c_float_words_bigendian(See http://autoconf-archive.cryp.to/ax_c_float_words_bigendian.html).Is there anybody out there, who understands word/byte order a bit betterand is able to fix this?
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