[flang-commits] [flang] [llvm] [mlir] [flang][OpenMP] Support the FULL clause on the UNROLL construct (PR #214115)

[Spencer Bryngelson via flang-commits]

================
@@ -557,6 +557,36 @@ def UnrollHeuristicOp : OpenMPTransform_Op<"unroll_heuristic", []> {
   let hasCustomAssemblyFormat = 1;
 }
 
+//===----------------------------------------------------------------------===//
+// OpenMP unroll_full operation
+//===----------------------------------------------------------------------===//
+
+def UnrollFullOp : OpenMPTransform_Op<"unroll_full", []> {
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sbryngelson wrote:

Added a verifier, but not the constant-bounds check, and I would like your read on it.

flang emits the trip count as a computed value even for a literal loop:

```mlir
%14 = arith.select %13, %c0_i32, %12 : i32
omp.canonical_loop(%canonloop) %iv : i32 in range(%14) { ... }
omp.unroll_full(%canonloop)
```

so `matchPattern(tripCount, m_Constant())` rejects flangs own output for `do i = 1, 100` -- it failed my two new tests. Verifiers run before folding, and `getConstantIntValue` only matches literal constants too, so I could not express "constant after folding" at that boundary. The verifier currently checks only that the applyee has a generator.

Options: leave it to semantics; fold the trip count in flang before emitting; or add a fold-aware check. Happy to do whichever you prefer.

https://github.com/llvm/llvm-project/pull/214115