lkml.org 
[lkml]   [2016]   [May]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: linux/bitops.h
From
Date
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




\
 
 \ /
  Last update: 2016-05-05 03:01    [W:0.099 / U:2.804 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site