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bitops.h: add sign_extend64() 

Months back, this was discussed, see https://lkml.org/lkml/2015/1/18/289
The result was the 64-bit version being "likely fine", "valuable" and
"correct".  The discussion fell asleep but since there are possible users,
let's add it.

Signed-off-by: Martin Kepplinger <martin.kepplinger@theobroma-systems.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: George Spelvin <linux@horizon.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Maxime Coquelin <maxime.coquelin@st.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Martin Kepplinger 2015-11-06 16:31:02 -08:00 committed by Linus Torvalds
parent e2eb53aa96
commit 48e203e21b
1 changed files with 11 additions and 0 deletions
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11
include/linux/bitops.h
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@ -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)