Reduce complexity of searching circular function calls

Author: mscuttari

mlir/lib/Dialect/Bufferization/Transforms/OneShotModuleBufferize.cpp

@@ -343,15 +343,25 @@ static LogicalResult getFuncOpsOrderedByCalls(
 
   // Iteratively remove function operations that do not call any of the
   // functions remaining in the callCounter map and add them to ordered list.
-  while (!numberCallOpsContainedInFuncOp.empty()) {
-    auto it = llvm::find_if(numberCallOpsContainedInFuncOp,
-                            [](auto entry) { return entry.getSecond() == 0; });
-    if (it == numberCallOpsContainedInFuncOp.end())
-      break;
-    orderedFuncOps.push_back(it->getFirst());
-    for (auto callee : calledBy[it->getFirst()])
-      numberCallOpsContainedInFuncOp[callee]--;
-    numberCallOpsContainedInFuncOp.erase(it);
+  SmallVector<func::FuncOp> worklist;
+
+  for (const auto &entry : numberCallOpsContainedInFuncOp) {
+    if (entry.second == 0)
+      worklist.push_back(entry.first);
+  }
+
+  while (!worklist.empty()) {
+    func::FuncOp func = worklist.pop_back_val();
+    orderedFuncOps.push_back(func);
+
+    for (func::FuncOp caller : calledBy[func]) {
+      auto &count = numberCallOpsContainedInFuncOp[caller];
+
+      if (--count == 0)
+        worklist.push_back(caller);
+    }
+
+    numberCallOpsContainedInFuncOp.erase(func);
   }
 
   // Put all other functions in the list of remaining functions. These are