[LLVMdev] Is it an opt bug ?

[Seb]

Hi Duncan,

I included original email in BUG description which described original issue
with store being removed.

BR
Seb

2012/2/29 Duncan Sands <baldrick at free.fr>

> Hi Seb,
>
>
>  Already done here : http://llvm.org/bugs/show_bug.**cgi?id=12130<http://llvm.org/bugs/show_bug.cgi?id=12130>
>>
>
> that doesn't describe the original issue (second store removed), it is
> talking
> about a different issue that appeared at -O1 (and it first seemed to
> explain
> your original problem; but now I think the -O1 transform was correct and
> does
> not explain your original problem).
>
> Ciao, Duncan.
>
>
>> Thanks for your answers
>> Best Regards
>> Seb
>>
>> 2012/2/29 Duncan Sands <baldrick at free.fr <mailto:baldrick at free.fr>>
>>
>>
>>    Hi Seb,
>>
>>
>>        If I remove datalayout definition, code is not optimized and work
>> as
>>        expected.
>>        So my question is:
>>
>>        What attribute/value/interpretation of data-layout would cause
>> this type
>>        of bug?
>>
>>
>>    all kinds of optimizers use datalayout (and are disabled if there is
>> none).  For
>>    example, alias analysis, anything that needs to understand
>> getelementptr
>>    offsets, the list is endless.
>>
>>    I suggest you open a bug report, describing your original problem as
>> in your
>>    first email.
>>
>>    Ciao, Duncan.
>>
>>        Thanks for your answers
>>        Seb
>>
>>        2012/2/28 Duncan Sands <baldrick at free.fr <mailto:baldrick at free.fr>
>>        <mailto:baldrick at free.fr <mailto:baldrick at free.fr>>>
>>
>>
>>
>>            On 28/02/12 17:48, John Regehr wrote:
>>         >> void t2(double *x)
>>         >> {
>>         >>       long long a[2];
>>         >>       a[0] = 3;
>>         >>       a[1] = 5;
>>         >>       *x = * ((double *) a);
>>         >>       *(x+1) = * ((double *) &a[a[0]-2]);
>>         >> }
>>         >
>>         > Doesn't this code violate the strict aliasing rules?
>>
>>            Maybe, but the LLVM IR he showed seems perfectly well defined.
>>
>>            Ciao, Duncan.
>>            ______________________________ _________________
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>>
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>> >
>>
>>
>>
>>
>>
>
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