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Re: powerpc & unaligned block moves with fp registers
- To: mrs at windriver dot com
- Subject: Re: powerpc & unaligned block moves with fp registers
- From: degger at fhm dot edu
- Date: Sun, 11 Nov 2001 00:23:15 +0100 (CET)
- Cc: gcc at gcc dot gnu dot org
- Reply-To: degger at fhm dot edu
On 10 Nov, mike stump wrote:
>> Pessimistic or not, we should try to avoid misaligned accesses on any
>> cost since they are in a lucky case at least magnitude slower.
> I reject the notion that we should at any cost. What if it costs are
> 10% on the SPEC2000 performance benchmark? What if we are using -Os,
> and it makes code 6% larger? A good change, will be backed up by size
> and time numbers from a variety of benchmarks.
Ok, I take my "on any cost" back. -Os is of course a different picture,
when optimising for size alignment doesn't play such a big role. Anyway
the mentioned cases are pretty rare (at least I haven't seen much
wrongly aligned structures here in the past) and thusly I also think
that aligning them properly would make such a big different in code