Subject: Re: powerpc gcc alignment problem
To: None <firstname.lastname@example.org>
From: David Edelsohn <email@example.com>
Date: 12/29/1999 01:53:48
I think that you are confusing alignment requirements with
performance optimizations. PowerPC implementations operating in
big-endian mode do not require strict alignment.
Any programmer who designs a data structure with small objects
first probably never took a course on data layout, probably does not
understand CPU architectures, and probably does not care about
performance. There is a limit to how much a compiler should try to cover
up bad programming.
GCC currently does not seem to have fine-enough granularity for
choosing optimal data movement instructions. This current discussion
falls under the SLOW_UNALIGNED_ACCESS performance optimization heuristics,
not STRICT_ALIGNMENT correctness requirement. This GCC heuristic needs
more flexibility to properly represent architectures like PowerPC.