[mlir][dataflow] disallow outside use of propagateIfChanged for DataFlowSolver

mlir/include/mlir/Analysis/DataFlowFramework.h

@@ -401,6 +401,8 @@ class DataFlowSolver {
 
   /// Propagate an update to an analysis state if it changed by pushing
   /// dependent work items to the back of the queue.
+  /// This should only be used when DataFlowSolver is running.
+  /// Otherwise, the solver won't process the work items.
   void propagateIfChanged(AnalysisState *state, ChangeResult changed);
 
   /// Get the configuration of the solver.
@@ -410,6 +412,9 @@ class DataFlowSolver {
   /// Configuration of the dataflow solver.
   DataFlowConfig config;
 
+  /// The solver is working on the worklist.
+  bool isRunning = false;
+
   /// The solver's work queue. Work items can be inserted to the front of the
   /// queue to be processed greedily, speeding up computations that otherwise
   /// quickly degenerate to quadratic due to propagation of state updates.

mlir/lib/Analysis/DataFlowFramework.cpp

@@ -10,6 +10,7 @@
 #include "mlir/IR/Location.h"
 #include "mlir/IR/Operation.h"
 #include "mlir/IR/Value.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/Config/abi-breaking.h"
 #include "llvm/Support/Casting.h"
@@ -104,6 +105,10 @@ Location LatticeAnchor::getLoc() const {
 //===----------------------------------------------------------------------===//
 
 LogicalResult DataFlowSolver::initializeAndRun(Operation *top) {
+  // Enable enqueue to the worklist.
+  isRunning = true;
+  auto guard = llvm::make_scope_exit([&]() { isRunning = false; });
+
   // Initialize the analyses.
   for (DataFlowAnalysis &analysis : llvm::make_pointee_range(childAnalyses)) {
     DATAFLOW_DEBUG(llvm::dbgs()
@@ -134,6 +139,8 @@ LogicalResult DataFlowSolver::initializeAndRun(Operation *top) {
 
 void DataFlowSolver::propagateIfChanged(AnalysisState *state,
                                         ChangeResult changed) {
+  assert(isRunning &&
+         "DataFlowSolver is not running, should not use propagateIfChanged");
   if (changed == ChangeResult::Change) {
     DATAFLOW_DEBUG(llvm::dbgs() << "Propagating update to " << state->debugName
                                 << " of " << state->anchor << "\n"