Re: [GIT PULL] x86/vdso changes for v3.16

[Andy Lutomirski]

On Fri, Jun 6, 2014 at 2:42 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 06/06/2014 02:39 PM, Andy Lutomirski wrote:
>>>
>>> For accessing memory members doing it via a pointer is pretty much TRT,
>>> but for things that might be in register it is undesirable to force it
>>> out to memory.
>>
>> Do you also believe in the folklore that GCC can optimize code
>> sequences like the things in that header?  Because I'm pretty sure
>> that no clang or gcc version I've ever seen can do it.
>>
>
> I have seen gcc do some pretty sophisticated memory elision lately.
> Don't know if that includes byte swaps.
>
>> On the other hand, even a factor of ten in the time it takes to run
>> vdso2c is completely irrelevant.
>
> Yep, as I noted in the patch I sent (which is broken - updated one
> included here.)

Acked-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>

The generated vdso-image-*.c files are identical.

--Andy

>
>         -hpa
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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