Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760712AbcLARFI (ORCPT ); Thu, 1 Dec 2016 12:05:08 -0500 Received: from mail-pg0-f66.google.com ([74.125.83.66]:35028 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760589AbcLARFE (ORCPT ); Thu, 1 Dec 2016 12:05:04 -0500 From: Joshua Clayton To: Alan Tull , Moritz Fischer , Rob Herring , Mark Rutland , Russell King Cc: Joshua Clayton , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v4 1/3] lib: add bitrev8x4() Date: Thu, 1 Dec 2016 09:04:50 -0800 Message-Id: X-Mailer: git-send-email 2.9.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2423 Lines: 88 Add a function to reverse bytes within a 32 bit word. This function is more efficient than using the 8 bit version when iterating over an array Signed-off-by: Joshua Clayton --- Looking for an ACK from Russell King on this patch (or at least the arm specific implementation) arch/arm/include/asm/bitrev.h | 5 +++++ include/linux/bitrev.h | 26 ++++++++++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/arch/arm/include/asm/bitrev.h b/arch/arm/include/asm/bitrev.h index ec291c3..6d2e9ca 100644 --- a/arch/arm/include/asm/bitrev.h +++ b/arch/arm/include/asm/bitrev.h @@ -17,4 +17,9 @@ static __always_inline __attribute_const__ u8 __arch_bitrev8(u8 x) return __arch_bitrev32((u32)x) >> 24; } +static __always_inline __attribute_const__ u32 __arch_bitrev8x4(u32 x) +{ + __asm__ ("rbit %0, %1; rev %0, %0" : "=r" (x) : "r" (x)); +} + #endif diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h index fb790b8..b1cfa1a 100644 --- a/include/linux/bitrev.h +++ b/include/linux/bitrev.h @@ -9,6 +9,7 @@ #define __bitrev32 __arch_bitrev32 #define __bitrev16 __arch_bitrev16 #define __bitrev8 __arch_bitrev8 +#define __bitrev8x4 __arch_bitrev8x4 #else extern u8 const byte_rev_table[256]; @@ -27,6 +28,14 @@ static inline u32 __bitrev32(u32 x) return (__bitrev16(x & 0xffff) << 16) | __bitrev16(x >> 16); } +static inline u32 __bitrev8x4(u32 x) +{ + return(__bitrev8(x & 0xff) | + (__bitrev8((x >> 8) & 0xff) << 8) | + (__bitrev8((x >> 16) & 0xff) << 16) | + (__bitrev8((x >> 24) & 0xff) << 24)); +} + #endif /* CONFIG_HAVE_ARCH_BITREVERSE */ #define __constant_bitrev32(x) \ @@ -50,6 +59,15 @@ static inline u32 __bitrev32(u32 x) __x; \ }) +#define __constant_bitrev8x4(x) \ +({ \ + u32 __x = x; \ + __x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 4); \ + __x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 2); \ + __x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 1); \ + __x; \ +}) + #define __constant_bitrev8(x) \ ({ \ u8 __x = x; \ @@ -75,6 +93,14 @@ static inline u32 __bitrev32(u32 x) __bitrev16(__x); \ }) +#define bitrev8x4(x) \ +({ \ + u32 __x = x; \ + __builtin_constant_p(__x) ? \ + __constant_bitrev8x4(__x) : \ + __bitrev8x4(__x); \ +}) + #define bitrev8(x) \ ({ \ u8 __x = x; \ -- 2.9.3