[Mlir-commits] [mlir] [mlir][scf] Add simple LICM pattern for `scf.while` (PR #76370)

[Mehdi Amini]

joker-eph wrote:

> Now, back to this PR, I agree with @joker-eph here: LICM, even a simplified version, isn't canonicalization, it's a transformation.

Actually you're saying the opposite of me :)

I'm saying that:

```
for (auto value : vector) {
  int a = f(x, y, z); // loop invariant
  g(value, a);
}
```

and:

```
int a = f(x, y, z); // loop invariant
for (auto value : vector) {
  g(value, a);
}
```

Are equivalent programs, and the argument that the second one "may increase register pressure" (for example, use any kind of target-specific optimization) is not a valid objection to canonicalization.


https://github.com/llvm/llvm-project/pull/76370