[Spice-devel] [PATCH spice-gtk v3 1/5] Avoid clang warnings on casts with stricter alignment requirements
Christophe de Dinechin
christophe at dinechin.org
Wed May 17 10:20:35 UTC 2017
> On 17 May 2017, at 11:55, Christophe Fergeau <cfergeau at redhat.com> wrote:
>
> On Wed, May 17, 2017 at 11:45:50AM +0200, Christophe de Dinechin wrote:
>>> I'm really sure no architecture on hearth can do check and print in
>>> a single machine instruction.
>>
>> This is not what I said. I said that the cost in the likely case was one extra instruction.
>>
>>> Actually I don't know any architecture
>>> where a single check like this can be done in a single instruction.
>>
>> Reduced source code: https://pastebin.com/ibZEVThA.
>>
>> Machine code for x86 with clang: https://pastebin.com/Vmtwpkhf
>>
>> The test follows the call to malloc. It’s a single “testb” instruction
>> followed by a never-taken conditional jump to cold-code.
>
> NB: feel free to annotate such tests with G_LIKELY/G_UNLIKELY
Thanks. It’s already in my version, but I have not shared it yet.
Christophe
>
> Christophe
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