[mlir][transform] Improve error message of tracking listener. (#66987)

This PR extends the error message of the tracking listener when
replacement ops cannot be found. That may happen if the applied patterns
replace an op by an op of a different kind or by block arguments.
However, this only matters if there are alive handles to the replaced
op. The new error message mentions that explicitly and reports the alive
handles.

Author: ingomueller-net

mlir/include/mlir/Dialect/Transform/IR/TransformInterfaces.h

@@ -774,7 +774,8 @@ class TransformResults {
   /// corresponds to the given list of payload IR ops. Each result must be set
   /// by the transformation exactly once in case of transformation succeeding.
   /// The value must have a type implementing TransformHandleTypeInterface.
-  template <typename Range> void set(OpResult value, Range &&ops) {
+  template <typename Range>
+  void set(OpResult value, Range &&ops) {
     int64_t position = value.getResultNumber();
     assert(position < static_cast<int64_t>(operations.size()) &&
            "setting results for a non-existent handle");
@@ -929,8 +930,9 @@ class TrackingListener : public RewriterBase::Listener,
   ///
   /// Derived classes may override `findReplacementOp` to specify custom
   /// replacement rules.
-  virtual FailureOr<Operation *> findReplacementOp(Operation *op,
-                                                   ValueRange newValues) const;
+  virtual DiagnosedSilenceableFailure
+  findReplacementOp(Operation *&result, Operation *op,
+                    ValueRange newValues) const;
 
   /// Notify the listener that the pattern failed to match the given operation,
   /// and provide a callback to populate a diagnostic with the reason why the
@@ -942,8 +944,9 @@ class TrackingListener : public RewriterBase::Listener,
   /// This function is called when a tracked payload op is dropped because no
   /// replacement op was found. Derived classes can implement this function for
   /// custom error handling.
-  virtual void notifyPayloadReplacementNotFound(Operation *op,
-                                                ValueRange values) {}
+  virtual void
+  notifyPayloadReplacementNotFound(Operation *op, ValueRange values,
+                                   DiagnosedSilenceableFailure &&diag) {}
 
   /// Return the single op that defines all given values (if any).
   static Operation *getCommonDefiningOp(ValueRange values);
@@ -983,8 +986,9 @@ class ErrorCheckingTrackingListener : public TrackingListener {
   bool failed() const;
 
 protected:
-  void notifyPayloadReplacementNotFound(Operation *op,
-                                        ValueRange values) override;
+  void
+  notifyPayloadReplacementNotFound(Operation *op, ValueRange values,
+                                   DiagnosedSilenceableFailure &&diag) override;
 
 private:
   /// The error state of this listener. "Success" indicates that no error

mlir/lib/Dialect/Transform/IR/TransformInterfaces.cpp

@@ -1289,45 +1289,59 @@ Operation *transform::TrackingListener::getCommonDefiningOp(ValueRange values) {
   return defOp;
 }
 
-FailureOr<Operation *>
-transform::TrackingListener::findReplacementOp(Operation *op,
-                                               ValueRange newValues) const {
+DiagnosedSilenceableFailure transform::TrackingListener::findReplacementOp(
+    Operation *&result, Operation *op, ValueRange newValues) const {
   assert(op->getNumResults() == newValues.size() &&
          "invalid number of replacement values");
   SmallVector<Value> values(newValues.begin(), newValues.end());
 
+  DiagnosedSilenceableFailure diag = emitSilenceableFailure(
+      getTransformOp(), "tracking listener failed to find replacement op "
+                        "during application of this transform op");
+
   do {
     // If the replacement values belong to different ops, drop the mapping.
     Operation *defOp = getCommonDefiningOp(values);
-    if (!defOp)
-      return failure();
+    if (!defOp) {
+      diag.attachNote() << "replacement values belong to different ops";
+      return diag;
+    }
 
     // If the defining op has the same type, we take it as a replacement.
-    if (op->getName() == defOp->getName())
-      return defOp;
+    if (op->getName() == defOp->getName()) {
+      result = defOp;
+      return DiagnosedSilenceableFailure::success();
+    }
 
     // Replacing an op with a constant-like equivalent is a common
     // canonicalization.
-    if (defOp->hasTrait<OpTrait::ConstantLike>())
-      return defOp;
+    if (defOp->hasTrait<OpTrait::ConstantLike>()) {
+      result = defOp;
+      return DiagnosedSilenceableFailure::success();
+    }
 
     values.clear();
 
     // Skip through ops that implement FindPayloadReplacementOpInterface.
     if (auto findReplacementOpInterface =
             dyn_cast<FindPayloadReplacementOpInterface>(defOp)) {
       values.assign(findReplacementOpInterface.getNextOperands());
+      diag.attachNote(defOp->getLoc()) << "using operands provided by "
+                                          "'FindPayloadReplacementOpInterface'";
       continue;
     }
 
     // Skip through ops that implement CastOpInterface.
     if (isa<CastOpInterface>(defOp)) {
       values.assign(defOp->getOperands().begin(), defOp->getOperands().end());
+      diag.attachNote(defOp->getLoc())
+          << "using output of 'CastOpInterface' op";
       continue;
     }
   } while (!values.empty());
 
-  return failure();
+  diag.attachNote() << "ran out of suitable replacement values";
+  return diag;
 }
 
 LogicalResult transform::TrackingListener::notifyMatchFailure(
@@ -1396,32 +1410,39 @@ void transform::TrackingListener::notifyOperationReplaced(
   };
 
   // Helper function to check if the handle is alive.
-  auto hasAliveUser = [&]() {
+  auto firstAliveUser = [&]() -> std::optional<OpOperand *> {
     for (Value v : opHandles) {
-      for (Operation *user : v.getUsers())
-        if (user != transformOp && !happensBefore(user, transformOp))
-          return true;
+      for (OpOperand &use : v.getUses())
+        if (use.getOwner() != transformOp &&
+            !happensBefore(use.getOwner(), transformOp))
+          return &use;
     }
-    return false;
-  };
+    return std::nullopt;
+  }();
 
-  if (!hasAliveUser() || handleWasConsumed()) {
+  if (!firstAliveUser.has_value() || handleWasConsumed()) {
     // The op is tracked but the corresponding handles are dead or were
     // consumed. Drop the op form the mapping.
     (void)replacePayloadOp(op, nullptr);
     return;
   }
 
-  FailureOr<Operation *> replacement = findReplacementOp(op, newValues);
+  Operation *replacement;
+  DiagnosedSilenceableFailure diag =
+      findReplacementOp(replacement, op, newValues);
   // If the op is tracked but no replacement op was found, send a
   // notification.
-  if (failed(replacement)) {
-    notifyPayloadReplacementNotFound(op, newValues);
+  if (!diag.succeeded()) {
+    diag.attachNote((*firstAliveUser)->getOwner()->getLoc())
+        << "replacement is required because alive handle(s) exist "
+        << "(first use in this op as operand number "
+        << (*firstAliveUser)->getOperandNumber() << ")";
+    notifyPayloadReplacementNotFound(op, newValues, std::move(diag));
     (void)replacePayloadOp(op, nullptr);
     return;
   }
 
-  (void)replacePayloadOp(op, *replacement);
+  (void)replacePayloadOp(op, replacement);
 }
 
 transform::ErrorCheckingTrackingListener::~ErrorCheckingTrackingListener() {
@@ -1444,17 +1465,20 @@ bool transform::ErrorCheckingTrackingListener::failed() const {
 }
 
 void transform::ErrorCheckingTrackingListener::notifyPayloadReplacementNotFound(
-    Operation *op, ValueRange values) {
-  if (status.succeeded()) {
-    status = emitSilenceableFailure(
-        getTransformOp(), "tracking listener failed to find replacement op");
-  }
+    Operation *op, ValueRange values, DiagnosedSilenceableFailure &&diag) {
+
+  // Merge potentially existing diags and store the result in the listener.
+  SmallVector<Diagnostic> diags;
+  diag.takeDiagnostics(diags);
+  if (!status.succeeded())
+    status.takeDiagnostics(diags);
+  status = DiagnosedSilenceableFailure::silenceableFailure(std::move(diags));
 
+  // Report more details.
   status.attachNote(op->getLoc()) << "[" << errorCounter << "] replaced op";
   for (auto &&[index, value] : llvm::enumerate(values))
     status.attachNote(value.getLoc())
         << "[" << errorCounter << "] replacement value " << index;
-
   ++errorCounter;
 }
 

mlir/test/Dialect/Transform/test-pattern-application.mlir

@@ -37,12 +37,14 @@ transform.sequence failures(propagate) {
 ^bb1(%arg1: !transform.any_op):
   %0 = transform.structured.match ops{["test.container"]} in %arg1 : (!transform.any_op) -> !transform.any_op
   %1 = transform.structured.match ops{["test.foo"]} in %arg1 : (!transform.any_op) -> !transform.any_op
-  // expected-error @below {{tracking listener failed to find replacement op}}
+  // expected-error @below {{tracking listener failed to find replacement op during application of this transform op}}
+  // expected-note @below {{ran out of suitable replacement values}}
   transform.apply_patterns to %0 {
     transform.apply_patterns.transform.test_patterns
   } : !transform.any_op
   // %1 must be used in some way. If no replacement payload op could be found,
   // an error is thrown only if the handle is not dead.
+  // expected-note @below {{replacement is required because alive handle(s) exist (first use in this op as operand number 0)}}
   transform.annotate %1 "annotated" : !transform.any_op
 }
 

mlir/test/lib/Dialect/Tensor/TestTensorTransforms.cpp

@@ -32,8 +32,8 @@ struct TestTensorTransforms
   TestTensorTransforms(const TestTensorTransforms &pass) : PassWrapper(pass) {}
 
   void getDependentDialects(DialectRegistry &registry) const override {
-    registry
-        .insert<arith::ArithDialect, scf::SCFDialect, linalg::LinalgDialect>();
+    registry.insert<arith::ArithDialect, scf::SCFDialect, linalg::LinalgDialect,
+                    transform::TransformDialect>();
   }
 
   StringRef getArgument() const final {
@@ -292,10 +292,10 @@ class DummyTrackingListener : public transform::TrackingListener {
 
   // Expose `findReplacementOp` as a public function, so that it can be tested.
   Operation *getReplacementOp(Operation *op, ValueRange newValues) const {
-    FailureOr<Operation *> replacementOp = findReplacementOp(op, newValues);
-    if (failed(replacementOp))
+    Operation *replacementOp;
+    if (!findReplacementOp(replacementOp, op, newValues).succeeded())
       return nullptr;
-    return *replacementOp;
+    return replacementOp;
   }
 };
 } // namespace
@@ -352,8 +352,17 @@ static LogicalResult testTrackingListenerReplacements(Operation *rootOp) {
   transform::TransformState transformState =
       transform::detail::makeTransformStateForTesting(/*region=*/nullptr,
                                                       /*payloadRoot=*/nullptr);
-  DummyTrackingListener listener(transformState,
-                                 transform::TransformOpInterface());
+  MLIRContext *context = rootOp->getContext();
+  OpBuilder builder(context);
+  auto transformOp = builder.create<transform::NamedSequenceOp>(
+      rootOp->getLoc(),
+      /*sym_name=*/"test_sequence",
+      /*function_type=*/
+      TypeAttr::get(FunctionType::get(context, TypeRange{}, TypeRange{})),
+      /*sym_visibility*/ StringAttr::get(context, "public"),
+      /*arg_attrs=*/ArrayAttr::get(context, ArrayRef<Attribute>()),
+      /*res_attrs=*/ArrayAttr::get(context, ArrayRef<Attribute>()));
+  DummyTrackingListener listener(transformState, transformOp);
   Operation *replacement = listener.getReplacementOp(replaced, replacements);
   if (!replacement) {
     replaced->emitError("listener could not find replacement op");