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Date: Mon, 16 May 2016 19:06:08 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Zhaoxiu Zeng <zengzhaoxiu@....com> Cc: linux-kernel@...r.kernel.org, bp@...e.de, gnomes@...rguk.ukuu.org.uk, andi@...stfloor.org, dvyukov@...gle.com, Zhaoxiu Zeng <zhaoxiu.zeng@...il.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org, Denys Vlasenko <dvlasenk@...hat.com> Subject: Re: [patch V4 09/31] bitops: Add x86-specific parity functions On Mon, May 16, 2016 at 11:49:05PM +0800, Zhaoxiu Zeng wrote: > On 2016/5/11 17:31, Peter Zijlstra wrote: > > Please use the GEN_*_RMWcc() stuff to avoid the setpo where possible. > > Setpo is better. > In most cases, we need to store the parity, or compare it with other variables. > > For example, in drivers/net/ethernet/broadcom/tg3.c, > > static int tg3_test_nvram(struct tg3 *tp) > { > ...... > if (parity8(data[i]) == !!parity[i]) > goto out; > ...... > } > > If use GEN_BINARY_RMWcc stuff, > > static inline unsigned int __arch_parity8(unsigned int w) > { > GEN_BINARY_RMWcc("testb", w, "er", 0xff, "%0", "po"); > } blergh; GCC does indeed make a mess of that. It looks we'll need the cc-output stuff for this in order for GCC to generates sane code for that :/
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