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    SubjectRe: linux/bitops.h
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    On May 6, 2016 1:07:13 PM PDT, Sasha Levin <sasha.levin@oracle.com> wrote:
    >On 05/04/2016 08:30 PM, H. Peter Anvin wrote:
    >> 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.
    >
    >No, the description says that it produces worse code for *really
    >really* ancient
    >GCC versions.
    >
    >> As I said, gcc has treated the former code as idiomatic since gcc 2,
    >so that support is beyond ancient.
    >
    >Because something works in a specific way on one compiler isn't a
    >reason to
    >ignore this noncompliance with the standard.
    >
    >
    >Thanks,
    >Sasha

    4.6.2 is not "really, really ancient."
    --
    Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.

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