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SubjectRe: linux/bitops.h
On 05/04/16 15:06, John Denker wrote:
> On 05/04/2016 02:56 PM, H. Peter Anvin wrote:
>>> Beware that shifting by an amount >= the number of bits in the
>>> word remains Undefined Behavior.
>> This construct has been supported as a rotate since at least gcc2.
> How then should we understand the story told in commit d7e35dfa?
> Is the story wrong?
> At the very least, something inconsistent is going on. There
> are 8 functions. Why did d7e35dfa change one of them but
> not the other 7?

Yes. d7e35dfa is baloney IMNSHO. All it does is produce worse code, and
the description even says so.

As I said, gcc has treated the former code as idiomatic since gcc 2, so
that support is beyond ancient.


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