[llvm] [mlir] [MLIR][Analysis] Consolidate topological sort utilities (PR #92563)

[Tobias Gysi via llvm-commits]

================
@@ -146,3 +151,135 @@ bool mlir::computeTopologicalSorting(
 
   return allOpsScheduled;
 }
+
+SetVector<Block *> mlir::getBlocksSortedByDominance(Region &region) {
+  // For each block that has not been visited yet (i.e. that has no
+  // predecessors), add it to the list as well as its successors.
+  SetVector<Block *> blocks;
+  for (Block &b : region) {
+    if (blocks.count(&b) == 0) {
+      llvm::ReversePostOrderTraversal<Block *> traversal(&b);
+      blocks.insert(traversal.begin(), traversal.end());
+    }
+  }
+  assert(blocks.size() == region.getBlocks().size() &&
+         "some blocks are not sorted");
+
+  return blocks;
+}
+
+namespace {
+class TopoSortHelper {
+public:
+  explicit TopoSortHelper(const SetVector<Operation *> &toSort)
+      : toSort(toSort) {}
+
+  /// Executes the topological sort of the operations this instance was
+  /// constructed with. This function will destroy the internal state of the
+  /// instance.
+  SetVector<Operation *> sort() {
+    if (toSort.size() <= 1)
+      // Note: Creates a copy on purpose.
+      return toSort;
+
+    // First, find the root region to start the traversal through the IR. This
+    // additionally enriches the internal caches with all relevant ancestor
+    // regions and blocks.
+    Region *rootRegion = findCommonAncestorRegion();
+    assert(rootRegion && "expected all ops to have a common ancestor");
+
+    // Sort all element in `toSort` by traversing the IR in the appropriate
+    // order.
+    SetVector<Operation *> result = topoSortRegion(*rootRegion);
+    assert(result.size() == toSort.size() &&
+           "expected all operations to be present in the result");
+    return result;
+  }
+
+private:
+  /// Computes the closest common ancestor region of all operations in `toSort`.
+  /// Remembers all the traversed regions in `ancestorRegions`.
----------------
gysit wrote:

```suggestion
```
Since it is not a function parameter anymore and mentioned in other places, I would drop this sentence. If not, then the ancestor blocks should be mentioned as well.

https://github.com/llvm/llvm-project/pull/92563