[mlir][Hoisting] Hoisting vector.extract/vector.broadcast pairs (#86108)

This transformation, inspired by what is done in
hoist_redundant_transfers, hoists pairs of extract/broadcast operations
out of scf.for loops.

It changes a loop of the form:

```
%res = scf.for _ = _ to _ step _ iter_args(%iarg = %v) -> (t1) {
  %e = vector.extract %iarg : t1 to t2
  %u = "some_use"(%e) : (t2) -> t2
  %b = vector.broadcast %u : t2 to t1
  scf.yield %b : t1
}
```

into the following:

```
%e = vector.extract %v: t1 to t2
%res' = scf.for _ = _ to _ step _ iter_args(%iarg = %e) -> (t2) {
  %u' = "some_use"(%iarg) : (t2) -> t2
  scf.yield %u' : t2
}
%res = vector.broadcast %res' : t2 to t1
```

0 files changed, 0 insertions, 0 deletions