[all-commits] [llvm/llvm-project] 6e714c: [MLIR][SCF] Fix upliftWhileToForLoop post-loop IV ...

[Nick Riasanovsky via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6e714c8d91116794cb699cdf80c26afe9cda3ef3
      https://github.com/llvm/llvm-project/commit/6e714c8d91116794cb699cdf80c26afe9cda3ef3
  Author: Nick Riasanovsky <njriasan at meta.com>
  Date:   2026-09-22 (Tue, 22 Sep 2026)

  Changed paths:
    M mlir/lib/Dialect/SCF/Transforms/UpliftWhileToFor.cpp
    M mlir/test/Dialect/SCF/uplift-while.mlir

  Log Message:
  -----------
  [MLIR][SCF] Fix upliftWhileToForLoop post-loop IV value (#225476)

scf::upliftWhileToForLoop transforms a while loop that can be expressed
as a for loop into that for loop. For example in pseudocode:

```
var = init_val
while var < bound:
  ...
  var += step
```

into 

```
for (var=lb; var < bound; var += step) {
  ...
}
```

In this process the post-loop induction value is reconstructed as `lb +
(tripCount - 1) * step`. This is incorrect as there is a off by 1 error.

Here we reconstruct lb + max(ceilDiv(ub-lb, step), 0) * step instead:
drop the spurious -1 and clamp the trip count at zero for loops that
never execute. Adds a zero-trip regression test that folds to lb.



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