Message-ID: <424FE1D3.9010805@osvik.no>
Date: Sun, 03 Apr 2005 14:30:11 +0200
From: Dag Arne Osvik <da@osvik.no>
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To: Stephen Rothwell <sfr@canb.auug.org.au>
CC: linux-kernel@vger.kernel.org
Subject: Re: Use of C99 int types
References: <424FD9BB.7040100@osvik.no> <20050403220508.712e14ec.sfr@canb.auug.org.au>
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Stephen Rothwell wrote:

>On Sun, 03 Apr 2005 13:55:39 +0200 Dag Arne Osvik <da@osvik.no> wrote:
>  
>
>>I've been working on a new DES implementation for Linux, and ran into
>>the problem of how to get access to C99 types like uint_fast32_t for
>>internal (not interface) use.  In my tests, key setup on Athlon 64 slows
>>down by 40% when using u32 instead of uint_fast32_t.
>>    
>>
>
>If you look in stdint.h you may find that uint_fast32_t is actually
>64 bits on Athlon 64 ... so does it help if you use u64?
>
>  
>

Yes, but wouldn't it be much better to avoid code like the following, 
which may also be wrong (in terms of speed)?

#ifdef CONFIG_64BIT  // or maybe CONFIG_X86_64?
  #define fast_u32 u64
#else
  #define fast_u32 u32
#endif

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