Currently the `getTiledImplementation` and `generateResultTileValue`
return just `SmallVector<Operation *>` and `FailureOr<Value>`.
- For `getTiledImplementation` returning empty implies tiling wasnt
done. There is also an implicit assumption that the tiled operation
results correspond to the tiled values of the result of the original
operation. This cannot handle cases where the tiled implementation
might use multiple operations to compute the tiled value for the
results of the untiled operation. Sometimes, the tiled operation
might not directly give the tiled values, and might require casts,
etc to get a replacement.
- For `generateResultTileValue`, it is assumed that the op defining
the returned `Value` is the operation that represents the tiled
computation. Again presence of casts, etc violate this.
Instead make these methods return
```
struct TilingResult {
SmallVector<Operation *> tiledOps;
SmallVector<Value> tiledValues;
};
```
The `tiledOps` represent the operations generated that are relevant
for subsequent transformations. The `tiledValues` represent the tiled
values for the results of the original operation. This better
transmits the state of the transformed IR.
As a consequence the following methods also return `FailureOr<TilingResult>`
- `tensor::replaceExtractSliceWithTiledProducer`
- `tensor::bubbleUpPadSlice`
Differential Revision: https://reviews.llvm.org/D145133
std::optional::value() has undesired exception checking semantics and is
unavailable in older Xcode (see _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS). The
call sites block std::optional migration.
