linux-kernel - [PATCH 2/2] bitops.h: Add sign

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Message-Id: <1421757055-8234-3-git-send-email-martink@posteo.de>
Date:	Tue, 20 Jan 2015 13:30:55 +0100
From:	Martin Kepplinger <martink@...teo.de>
To:	torvalds@...ux-foundation.org, jsrhbz@...argh.force9.co.uk,
	christoph.muellner@...obroma-systems.com, linux@...ck-us.net,
	linux@...musvillemoes.dk, paulmck@...ux.vnet.ibm.com,
	tglx@...utronix.de, mingo@...nel.org, akpm@...ux-foundation.org,
	hpa@...or.com, maxime.coquelin@...com,
	linux-kernel@...r.kernel.org, peterz@...radead.org, tytso@....edu
Cc:	linux-tip-commits@...r.kernel.org,
	Martin Kepplinger <martink@...teo.de>
Subject: [PATCH 2/2] bitops.h: Add sign_extend64() API

Add sign_extend64() for sign extending any (hardware-)given signed value
greater than 32 bits to s64.

Suggested-by: Christoph Muellner <christoph.muellner@...obroma-systems.com>
Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Martin Kepplinger <martink@...teo.de>
---
 include/linux/bitops.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 336f22b..2fd47c8 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -173,6 +173,17 @@ static inline __s32 sign_extend32(__u32 value, int index)
 	return (__s32)(value << shift) >> shift;
 }
 
+/**
+ * sign_extend64 - sign extend a 64-bit value using specified bit as sign-bit
+ * @value: value to sign extend
+ * @index: 0 based bit index (0<=index<64) to sign bit
+ */
+static inline __s64 sign_extend64(__u64 value, int index)
+{
+	__u8 shift = 63 - index;
+	return (__s64)(value << shift) >> shift;
+}
+
 static inline unsigned fls_long(unsigned long l)
 {
 	if (sizeof(l) == 4)
-- 
2.1.4

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