llvm dev - Mar 2021 - [RFC] Adding range metadata to array subscripts.

Am Do., 25. März 2021 um 09:42 Uhr schrieb Clement Courbet via
llvm-dev <llvm-dev at lists.llvm.org>:
> So I tried implementing this on top of `inrange`, and I found out that you
can only have one `inrange` index, which doesn't allow us to represent
access into multidimensional arrays : https://reviews.llvm.org/D99341
I think this is only for the internal representation. According to the
reference (https://llvm.org/docs/LangRef.html#id230), it is allowed
for each dimension.

Michael

On Thu, Mar 25, 2021 at 5:33 PM Michael Kruse <llvmdev at meinersbur.de>
wrote:
> Am Do., 25. März 2021 um 09:42 Uhr schrieb Clement Courbet via
> llvm-dev <llvm-dev at lists.llvm.org>:
> > So I tried implementing this on top of `inrange`, and I found out that
> you can only have one `inrange` index, which doesn't allow us to
represent
> access into multidimensional arrays : https://reviews.llvm.org/D99341
>
> I think this is only for the internal representation. According to the
> reference (https://llvm.org/docs/LangRef.html#id230), it is allowed
> for each dimension.
>
>
This means that we would have to store one bit per index instead of a
single index (right now the implementation is limiting the number of
indices to 64). That means that we can support at most 6 indices with
SubclassOptionalData. That might be sufficient for the most common cases
(not representing the inrange data is not a correctness issue), but we have
to be aware of that limitation.
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