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Date: Sat, 11 Aug 2007 08:43:22 +0800 From: Herbert Xu <herbert@...dor.apana.org.au> To: Segher Boessenkool <segher@...nel.crashing.org> Cc: paulmck@...ux.vnet.ibm.com, heiko.carstens@...ibm.com, horms@...ge.net.au, linux-kernel@...r.kernel.org, csnook@...hat.com, rpjday@...dspring.com, netdev@...r.kernel.org, ak@...e.de, cfriesen@...tel.com, akpm@...ux-foundation.org, torvalds@...ux-foundation.org, jesper.juhl@...il.com, linux-arch@...r.kernel.org, zlynx@....org, schwidefsky@...ibm.com, davem@...emloft.net, wensong@...ux-vs.org, wjiang@...ilience.com Subject: Re: [PATCH 1/24] make atomic_read() behave consistently on alpha On Sat, Aug 11, 2007 at 02:38:40AM +0200, Segher Boessenkool wrote: > >>That means GCC cannot compile Linux; it already optimises > >>some accesses to scalars to smaller accesses when it knows > >>it is allowed to. Not often though, since it hardly ever > >>helps in the cost model it employs. > > > >Please give an example code snippet + gcc version + arch > >to back this up. > > unsigned char f(unsigned long *p) > { > return *p & 1; > } This doesn't really matter since we only care about the LSB. Do you have an example where gcc reads it non-atmoically and we care about all parts? Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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