Re: linux/bitops.h

[H. Peter Anvin]

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.

	-hpa