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Re: Incorrect bitfield aliasing with Tree SSA


On 6/18/07, Adam Nemet <anemet@caviumnetworks.com> wrote:
Richard Kenner writes:
> > Not a new type just a new alias set.  As you return the parent alias
> > set of the field right now you might as well return a separate alias
> > set different from the type's alias set.
>
> OK, same question: why do you need a new alias set?  The one for the
> parent works fine.

Yes it works (or worked more precisely) but it does not fully describe
the situation, it rather works around it.  It equates two aliases that
are really not.  One is what the structure can alias and the other
what a field can.  The two are obviously not the same but I agree if
you make them the same, things more or less work.  The problem is that
it is not the complete reality.

Exactly.

With inventing a new alias set we can hopefully *precisely* describe the situation for the rest of the compiler. This might give us not just better means to argue about this issue but as far as I can see more accurate aliasing information.

Exactly.



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