[Mlir-commits] [mlir] [MLIR] Refactor the walkAndApplyPatterns driver to remove the recursion (PR #154037)

[Jakub Kuderski]

================
@@ -88,20 +90,97 @@ void walkAndApplyPatterns(Operation *op,
   PatternApplicator applicator(patterns);
   applicator.applyDefaultCostModel();
 
+  // Iterator on all reachable operations in the region.
+  // Also keep track if we visited the nested regions of the current op
+  // already to drive the post-order traversal.
+  struct RegionReachableOpIterator {
+    RegionReachableOpIterator(Region *region) : region(region) {
+      regionIt = region->begin();
+      if (regionIt != region->end())
+        blockIt = regionIt->begin();
+    }
+    // Advance the iterator to the next reachable operation.
+    void advance() {
+      assert(regionIt != region->end());
+      hasVisitedRegions = false;
+      if (blockIt == regionIt->end()) {
+        regionIt++;
+        if (regionIt != region->end())
+          blockIt = regionIt->begin();
+        return;
+      }
+      blockIt++;
----------------
kuhar wrote:

```suggestion
      ++blockIt;
```

https://github.com/llvm/llvm-project/pull/154037