[llvm-dev] extra loads in nested for-loop

Phil Tomson via llvm-dev llvm-dev at lists.llvm.org
Mon Jul 11 16:21:53 PDT 2016


On Mon, Jul 11, 2016 at 2:20 PM, Krzysztof Parzyszek via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> On 7/11/2016 3:27 PM, Phil Tomson via llvm-dev wrote:
>
>>
>> I guess I'm a bit surprised that -O3 wouldn't automatically do what I've
>> done in the second version of the C code when generating code from the
>> first version?
>>
>
> This is most likely because a, b, and c are assumed to be aliased.
>

In the context of this particular function wouldn't alias analysis be able
to figure out that there is no alias to a? Although, I guess considering
the possibility of multi-threading it might be difficult to make that
determination in all other parts of the program.

Phil

>
> -Krzysztof
>
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