[LLVMdev] Is it an opt bug ?

[Duncan Sands]

Hi Seb,

> Already done here : 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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>