[Mlir-commits] [mlir] [mlir][dataflow] Update dataflow tutorial doc and add dataflow example code (PR #149296)

[lonely eagle]

================
@@ -237,60 +228,91 @@ function for the operation, that is specific to our analysis. A simple
 implementation for our example is shown below:
 
 ```c++
-class MetadataAnalysis : public ForwardDataFlowAnalysis<MetadataLatticeValue> {
+class MetadataAnalysis
+    : public SparseForwardDataFlowAnalysis<MetadataLatticeValueLattice> {
 public:
-  using ForwardDataFlowAnalysis<MetadataLatticeValue>::ForwardDataFlowAnalysis;
-
-  ChangeResult visitOperation(
-      Operation *op, ArrayRef<LatticeElement<ValueT> *> operands) override {
-    DictionaryAttr metadata = op->getAttrOfType<DictionaryAttr>("metadata");
-
-    // If we have no metadata for this operation, we will conservatively mark
-    // all of the results as having reached a pessimistic fixpoint.
-    if (!metadata)
-      return markAllPessimisticFixPoint(op->getResults());
-
-    // Otherwise, we will compute a lattice value for the metadata and join it
-    // into the current lattice element for all of our results.
-    MetadataLatticeValue latticeValue(metadata);
-    ChangeResult result = ChangeResult::NoChange;
-    for (Value value : op->getResults()) {
-      // We grab the lattice element for `value` via `getLatticeElement` and
-      // then join it with the lattice value for this operation's metadata. Note
-      // that during the analysis phase, it is fine to freely create a new
-      // lattice element for a value. This is why we don't use the
-      // `lookupLatticeElement` method here.
-      result |= getLatticeElement(value).join(latticeValue);
+  using SparseForwardDataFlowAnalysis::SparseForwardDataFlowAnalysis;
+  LogicalResult
+  visitOperation(Operation *op,
+                 ArrayRef<const MetadataLatticeValueLattice *> operands,
+                 ArrayRef<MetadataLatticeValueLattice *> results) override {
+  DictionaryAttr metadata = op->getAttrOfType<DictionaryAttr>("metadata");
+  // If we have no metadata for this operation and the operands is empty, we
+  // will conservatively mark all of the results as having reached a pessimistic
+  // fixpoint.
+  if (!metadata && operands.empty()) {
+    setAllToEntryStates(results);
+    return success();
+  }
+
+  MetadataLatticeValue latticeValue;
+  if (metadata)
+    latticeValue = MetadataLatticeValue(metadata);
+
+  // Otherwise, we will compute a lattice value for the metadata and join it
+  // into the current lattice element for all of our results.`results` stores
+  // the lattices corresponding to the results of op, We use a loop to traverse
+  // them.
+  for (int i = 0, e = results.size(); i < e; ++i) {
----------------
linuxlonelyeagle wrote:

I will make changes tomorrow when I have time.

https://github.com/llvm/llvm-project/pull/149296