Matthias Springer cf9b77a636 [mlir][bufferization] Fix bug in bufferization of elementwise ops (#97209) ...

There is an optimization in One-Shot Bufferize wrt. ops that bufferize
to elementwise access. A copy can sometimes be avoided. E.g.:
```
%0 = tensor.empty()
%1 = tensor.fill ...
%2 = linalg.map ins(%1, ...) outs(%1)
```

In the above example, a buffer copy is not needed for %1, even though
the same buffer is read/written by two different operands (of the same
op). That's because the op bufferizes to elementwise access.

```c++
// Two equivalent operands of the same op are not conflicting if the op
// bufferizes to element-wise access. I.e., all loads at a position
// happen before all stores to the same position.
```

This optimization cannot be applied when op dominance cannot be used to
rule out conflicts. E.g., when the `linalg.map` is inside of a loop. In
such a case, the reads/writes happen multiple times and it is not
guaranteed that "all loads at a position happen before all stores to the
same position."

Fixes #90019.

2024-07-01 19:00:21 +02:00

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