From 48e203e21b29cd4b2c58403fe8bca68e2e854895 Mon Sep 17 00:00:00 2001 From: Martin Kepplinger Date: Fri, 6 Nov 2015 16:31:02 -0800 Subject: 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 Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Thomas Gleixner Cc: "H. Peter Anvin" Cc: George Spelvin Cc: Rasmus Villemoes Cc: Maxime Coquelin Cc: Denys Vlasenko Cc: Yury Norov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/bitops.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'include/linux/bitops.h') diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 5629923a8701..2b8ed123ad36 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) -- cgit v1.2.3