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From: "Wang, Yalin" <Yalin.Wang@sonymobile.com>
To: "'Will Deacon'" <will.deacon@arm.com>
CC: "'Rob Herring'" <robherring2@gmail.com>, "'Joe Perches'" <joe@perches.com>,
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Date: Fri, 31 Oct 2014 10:03:27 +0800
Subject: RE: [RFC V5 3/3] arm64:add bitrev.h file to support rbit instruction
Thread-Topic: [RFC V5 3/3] arm64:add bitrev.h file to support rbit
 instruction
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> From: Will Deacon [mailto:will.deacon@arm.com]
> Sent: Thursday, October 30, 2014 8:01 PM
> To: Wang, Yalin
> Cc: 'Rob Herring'; 'Joe Perches'; 'Russell King - ARM Linux'; 'linux-
> kernel@vger.kernel.org'; 'akinobu.mita@gmail.com'; 'linux-mm@kvack.org';
> 'linux-arm-kernel@lists.infradead.org'
> Subject: Re: [RFC V5 3/3] arm64:add bitrev.h file to support rbit
> instruction
> 
> > +static __always_inline __attribute_const__ u32 __arch_bitrev32(u32 x)
> > +{
> > +	if (__builtin_constant_p(x)) {
> > +		x = (x >> 16) | (x << 16);
> > +		x = ((x & 0xFF00FF00) >> 8) | ((x & 0x00FF00FF) << 8);
> > +		x = ((x & 0xF0F0F0F0) >> 4) | ((x & 0x0F0F0F0F) << 4);
> > +		x = ((x & 0xCCCCCCCC) >> 2) | ((x & 0x33333333) << 2);
> > +		return ((x & 0xAAAAAAAA) >> 1) | ((x & 0x55555555) << 1);
> 
> Shouldn't this part be in the generic code?

Good  idea, I will change this part into linux/bitrev.h .
Thanks