Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Subject | Re: better patch for linux/bitops.h | From | John Denker <> | Date | Wed, 4 May 2016 14:52:28 -0700 |
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On 05/04/2016 02:42 PM, I wrote:
> I find it very odd that the other seven functions were not > upgraded. I suggest the attached fix-others.diff would make > things more consistent.
Here's a replacement patch. Same idea, less brain damage. Sorry for the confusion.
commit ba83b16d8430ee6104aa1feeed4ff7a82b02747a Author: John Denker <jsd@av8n.com> Date: Wed May 4 13:55:51 2016 -0700
Make ror64, rol64, ror32, ror16, rol16, ror8, and rol8 consistent with rol32 in their handling of shifting by a zero amount.
Same overall rationale as in d7e35dfa, just more consistently applied.
Beware that shifting by an amount >= the number of bits in the word remains Undefined Behavior. This should be either documented or fixed. It could be fixed easily enough.
diff --git a/include/linux/bitops.h b/include/linux/bitops.h index defeaac..90f389b 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -87,7 +87,7 @@ static __always_inline unsigned long hweight_long(unsigned long w) */ static inline __u64 rol64(__u64 word, unsigned int shift) { - return (word << shift) | (word >> (64 - shift)); + return (word << shift) | (word >> ((-shift) & 63)); } /** @@ -97,7 +97,7 @@ static inline __u64 rol64(__u64 word, unsigned int shift) */ static inline __u64 ror64(__u64 word, unsigned int shift) { - return (word >> shift) | (word << (64 - shift)); + return (word >> shift) | (word << ((-shift) & 63)); } /** @@ -117,7 +117,7 @@ static inline __u32 rol32(__u32 word, unsigned int shift) */ static inline __u32 ror32(__u32 word, unsigned int shift) { - return (word >> shift) | (word << (32 - shift)); + return (word >> shift) | (word << ((-shift) & 31)); } /** @@ -127,7 +127,7 @@ static inline __u32 ror32(__u32 word, unsigned int shift) */ static inline __u16 rol16(__u16 word, unsigned int shift) { - return (word << shift) | (word >> (16 - shift)); + return (word << shift) | (word >> ((-shift) & 15)); } /** @@ -137,7 +137,7 @@ static inline __u16 rol16(__u16 word, unsigned int shift) */ static inline __u16 ror16(__u16 word, unsigned int shift) { - return (word >> shift) | (word << (16 - shift)); + return (word >> shift) | (word << ((-shift) & 15)); } /** @@ -147,7 +147,7 @@ static inline __u16 ror16(__u16 word, unsigned int shift) */ static inline __u8 rol8(__u8 word, unsigned int shift) { - return (word << shift) | (word >> (8 - shift)); + return (word << shift) | (word >> ((-shift) & 7)); } /** @@ -157,7 +157,7 @@ static inline __u8 rol8(__u8 word, unsigned int shift) */ static inline __u8 ror8(__u8 word, unsigned int shift) { - return (word >> shift) | (word << (8 - shift)); + return (word >> shift) | (word << ((-shift) & 7)); } /** | ![\](/images/icornerr.gif) |