Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757891AbYHSTCV (ORCPT ); Tue, 19 Aug 2008 15:02:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754177AbYHSTCG (ORCPT ); Tue, 19 Aug 2008 15:02:06 -0400 Received: from el-out-1112.google.com ([209.85.162.183]:13492 "EHLO el-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756168AbYHSTCD (ORCPT ); Tue, 19 Aug 2008 15:02:03 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=QVNKQJlW9smBIuNzQNv/LV3RosbNE2JrAxjJu6fLgKEZ3SLQo1cmaFZOqIvwSV6cH1 9fn+RQ/l1qPpfrZuXzAKaLMdH/Mrl417dq0wWNPy0Ptqcr8jCr5se20ALZzU74KHFLlS 2tRpcV6YI/i/iPb1AX8Egsy/avtGs0fbqB28g= Subject: Re: [PATCH 18/23] sparc: use the new byteorder headers From: Harvey Harrison To: David Miller Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org In-Reply-To: <20080819.014350.79505195.davem@davemloft.net> References: <1219106897.17033.71.camel@brick> <20080819.014350.79505195.davem@davemloft.net> Content-Type: text/plain Date: Tue, 19 Aug 2008 12:02:00 -0700 Message-Id: <1219172520.17033.85.camel@brick> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3489 Lines: 113 On Tue, 2008-08-19 at 01:43 -0700, David Miller wrote: > From: Harvey Harrison > Date: Mon, 18 Aug 2008 17:48:17 -0700 > > > Signed-off-by: Harvey Harrison > > I'm not so sure about this. > > If I understand the ___swab*() inlines in linux/swab.h, > it has the following priority of swapping methods: > > 1) If arch defines __arch_swab*(), this is used. > > 2) If arch defines __arch_swab*p(), variable is popped onto > the stack and we do the pointer based operation. 2a) If defined(__SWAB_64_THRU_32__) swab64 uses swab32 internally. > > 3) Else normal C version is used. > Your above understanding is correct. > Case #2 is totally disagree with. > > Especially for small swaps such as 16-bit the inline expansion > of the portable C code is going to be much better than popping > the variable onto and then back off the stack. > I thought gcc wasn't too bad for this case these days for attribute_const inlines? But without evidence to back it up, you're right that the generic C version should just be used if an arch hasn't provided an override. > Sparc 64-bit only provides the __arch_swab*p() routines so > #2 is what will in fact be used here. > > So NACK based upon that analysis. From: Harvey Harrison Subject: [PATCH] byteorder: use generic C version for value byteswapping David Miller noted that popping the variable on and back off the stack will probably be more expensive than just using the generic C byteswapping code. Remove the fallback to the swap-from-pointer helper when no arch override for the value byteswap has been defined. Signed-off-by: Harvey Harrison --- include/linux/swab.h | 10 ---------- 1 files changed, 0 insertions(+), 10 deletions(-) diff --git a/include/linux/swab.h b/include/linux/swab.h index 270d5c2..bbed279 100644 --- a/include/linux/swab.h +++ b/include/linux/swab.h @@ -47,8 +47,6 @@ static inline __attribute_const__ __u16 ___swab16(__u16 val) { #ifdef __arch_swab16 return __arch_swab16(val); -#elif defined(__arch_swab16p) - return __arch_swab16p(&val); #else return __const_swab16(val); #endif @@ -58,8 +56,6 @@ static inline __attribute_const__ __u32 ___swab32(__u32 val) { #ifdef __arch_swab32 return __arch_swab32(val); -#elif defined(__arch_swab32p) - return __arch_swab32p(&val); #else return __const_swab32(val); #endif @@ -69,8 +65,6 @@ static inline __attribute_const__ __u64 ___swab64(__u64 val) { #ifdef __arch_swab64 return __arch_swab64(val); -#elif defined(__arch_swab64p) - return __arch_swab64p(&val); #elif defined(__SWAB_64_THRU_32__) __u32 h = val >> 32; __u32 l = val & ((1ULL << 32) - 1); @@ -84,8 +78,6 @@ static inline __attribute_const__ __u32 ___swahw32(__u32 val) { #ifdef __arch_swahw32 return __arch_swahw32(val); -#elif defined(__arch_swahw32p) - return __arch_swahw32p(&val); #else return __const_swahw32(val); #endif @@ -95,8 +87,6 @@ static inline __attribute_const__ __u32 ___swahb32(__u32 val) { #ifdef __arch_swahb32 return __arch_swahb32(val); -#elif defined(__arch_swahb32p) - return __arch_swahb32p(&val); #else return __const_swahb32(val); #endif -- 1.6.0.274.g8aacc -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/