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Subject: Re: [boost] [Endian] Performance
From: Tim Moore (tim_at_[hidden])
Date: 2011-09-07 09:28:18

On 9/7/11 1:49 AM, Mathias Gaunard wrote:
> On 09/07/2011 01:54 AM, Phil Endecott wrote:
>> Unfortunately not, no; in my tests the gcc built-ins were the
>> worse-performing on one platform.
> Then it's a bug that should be fixed in the compiler.
> (But then it could also be that your benchmark is imperfect)

There have been reports that some gcc builtins (especially for ARM) do not generate very good code. One description of gcc's
bswap builtin for ARM is here:

My own personal work has found that gcc's implemenation of the popcount builtin is very inefficient on IA-64 archs compared to
other well known (and easy to implement) bit-twiddling algorithms. (Of course, this is for cases where the popcount instruction
is not available in the target processor.)



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