[Mlir-commits] [mlir] [MLIR][Affine] Fix fusion in the presence of cyclic deps in source nests (PR #128397)

[llvmlistbot at llvm.org]

================
@@ -28,10 +28,138 @@
 #include <optional>
 #include <type_traits>
 
+#define DEBUG_TYPE "affine-loop-analysis"
+
 using namespace mlir;
 using namespace mlir::affine;
 
-#define DEBUG_TYPE "affine-loop-analysis"
+namespace {
+
+/// A directed graph to model relationships between MLIR Operations.
+class DirectedOpGraph {
+public:
+  /// Add a node to
+  void addNode(Operation *op) {
+    assert(!hasNode(op) && "node already added");
+    nodes.emplace_back(op);
+    edges[op] = {};
+  }
+
+  /// Add an edge between `src` and `dest`.
+  void addEdge(Operation *src, Operation *dest) {
+    // This is a multi-graph.
+    assert(hasNode(src) && "src node does not exist in graph");
+    assert(hasNode(dest) && "dest node does not exist in graph");
+    edges[src].push_back(getNode(dest));
+  }
+
+  /// Returns true if there is a (directed) cycle in the graph.
+  bool hasCycle() { return dfsImpl(/*cycleCheck=*/true); }
+
+  void printEdges() {
+    for (auto &en : edges) {
+      llvm::dbgs() << *en.first << " (" << en.first << ")"
+                   << " has " << en.second.size() << " edges:\n";
+      for (auto *node : en.second) {
+        llvm::dbgs() << '\t' << *node->op << '\n';
+      }
+    }
+  }
+
+private:
+  /// A node of a directed graph between MLIR Operations to model various
+  /// relationships. This is meant to be used internally.
+  struct DGNode {
+    DGNode(Operation *op) : op(op) {};
+    Operation *op;
+
+    // Start and finish visit numbers are standard in DFS to implement things
+    // strongly connected components. These numbers are modified during analyses
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patel-vimal wrote:

typo in this phrase -> `implement things strongly connected components`.

https://github.com/llvm/llvm-project/pull/128397