[tip:core/types] bitops: Add sign_extend8(), 16 and 64 functions

[tip-bot for Martin Kepplinger <tipbot@zytor.com>]

Commit-ID:  7e9358073d3f0ed0a028c48aa54009b3296dffc9
Gitweb:     http://git.kernel.org/tip/7e9358073d3f0ed0a028c48aa54009b3296dffc9
Author:     Martin Kepplinger <martink@posteo.de>
AuthorDate: Mon, 12 Jan 2015 18:22:50 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 18 Jan 2015 20:03:51 +0100

bitops: Add sign_extend8(), 16 and 64 functions

This adds helper functions for sign-extending signed values of any
lower (hardware-)given size to s8, s16 or s64 respectively, just like
sign_extend32() for s32.

This completes the sign_extend*() API family to work on all bit sizes
like most other bitops APIs do.

Suggested-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
Signed-off-by: Martin Kepplinger <martink@posteo.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: John Sullivan <jsrhbz@kanargh.force9.co.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maxime COQUELIN <maxime.coquelin@st.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1421083370-24924-1-git-send-email-martink@posteo.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/bitops.h | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 5d858e0..9c31680 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -161,6 +161,28 @@ static inline __u8 ror8(__u8 word, unsigned int shift)
 }
 
 /**
+ * sign_extend8 - sign extend a 8-bit value using specified bit as sign-bit
+ * @value: value to sign extend
+ * @index: 0 based bit index (0<=index<8) to sign bit
+ */
+static inline __s8 sign_extend8(__u8 value, int index)
+{
+	__u8 shift = 7 - index;
+	return (__s8)(value << shift) >> shift;
+}
+
+/**
+ * sign_extend16 - sign extend a 16-bit value using specified bit as sign-bit
+ * @value: value to sign extend
+ * @index: 0 based bit index (0<=index<16) to sign bit
+ */
+static inline __s16 sign_extend16(__u16 value, int index)
+{
+	__u8 shift = 15 - index;
+	return (__s16)(value << shift) >> shift;
+}
+
+/**
  * sign_extend32 - sign extend a 32-bit value using specified bit as sign-bit
  * @value: value to sign extend
  * @index: 0 based bit index (0<=index<32) to sign bit
@@ -171,6 +193,17 @@ 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)