[llvm] ADT/Matrix: two-dimensional Container with View (PR #98893)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> > Besides, std::mdspan is only available from C++26
> 
> My point was that we could implement something like mdspan in LLVM.

Yes, and that's what I've implemented in MatrixView. The storage class is essentially SmallVector with an additional field for tracking the number of columns.
 
> > This is related to adding constexpr to ArrayRef, because otherwise, I can't mark anything that depends on ArrayRef functions as constexpr.
> 
> What are constexpr functions do you need that depend on ArrayRef?

The constructors, drop_back, drop_front, slice, for instance.


https://github.com/llvm/llvm-project/pull/98893