[Mlir-commits] [mlir] [mlir][DialectUtils] Fix 0 step handling in `constantTripCount` (PR #177329)

[Matthias Springer]

================
@@ -357,9 +357,15 @@ func.func @regression(%arg0: memref<i64>, %arg1: index) {
 // -----
 
 // Regression test: Make sure that we do not crash.
-// The step is 0, the loop will be eliminated.
+
 // CHECK-LABEL: func @zero_step(
-//       CHECK-NOT:   scf.for
+//       CHECK:   %[[c0:.*]] = arith.constant 0
+//       CHECK:   %[[c1:.*]] = arith.constant 1
+//       CHECK:   %[[poison:.*]] = ub.poison
----------------
matthias-springer wrote:

This feels like a problem of the loop peeling transformation to me. Loop peeling is not well-defined when you have a step size of 0.

```
/// Rewrite a for loop with bounds/step that potentially do not divide evenly
/// into a for loop where the step divides the iteration space evenly, followed
/// by an scf.if for the last (partial) iteration (if any).
```

This part: **`step divides the iteration space evenly`**


https://github.com/llvm/llvm-project/pull/177329