[TurboFan] Diagnostic code to track down bug in representation selection

We need to characterize the types of dead (IrOpcode::kDead) nodes
introduced in compilation phases prior to representation selection.
Normally, a dead node isn't expected at the start of this phase. The
question is, which phase introduced the dead node and failed to
deal with it properly?

Bug: chromium:780658
Change-Id: Ief5b45480bb7d704a2d09dafd60b5d389e0fd42e
Reviewed-on: https://chromium-review.googlesource.com/765968Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49328}

src/compiler/bytecode-graph-builder.cc

@@ -3191,7 +3191,7 @@ Node* BytecodeGraphBuilder::MakeNode(const Operator* op, int value_input_count,
       // The frame state will be inserted later. Here we misuse the {Dead} node
       // as a sentinel to be later overwritten with the real frame state by the
       // calls to {PrepareFrameState} within individual visitor methods.
-      *current_input++ = jsgraph()->Dead();
+      *current_input++ = jsgraph()->Dead(JSGraph::DeadCustomer::GraphBuilding);
     }
     if (has_effect) {
       *current_input++ = environment()->GetEffectDependency();

src/compiler/effect-control-linearizer.cc

@@ -390,7 +390,9 @@ void EffectControlLinearizer::Run() {
           // The input blocks do not have the same effect. We have
           // to create an effect phi node.
           inputs_buffer.clear();
-          inputs_buffer.resize(block->PredecessorCount(), jsgraph()->Dead());
+          inputs_buffer.resize(
+              block->PredecessorCount(),
+              jsgraph()->Dead(JSGraph::DeadCustomer::Unspecified));
           inputs_buffer.push_back(control);
           effect = graph()->NewNode(
               common()->EffectPhi(static_cast<int>(block->PredecessorCount())),

src/compiler/escape-analysis-reducer.cc

@@ -74,7 +74,7 @@ Reduction EscapeAnalysisReducer::Reduce(Node* node) {
     DCHECK(node->opcode() != IrOpcode::kAllocate &&
            node->opcode() != IrOpcode::kFinishRegion);
     DCHECK_NE(replacement, node);
-    if (replacement != jsgraph()->Dead()) {
+    if (replacement != jsgraph()->Dead(JSGraph::DeadCustomer::EscapeAnalysis)) {
       replacement = MaybeGuard(node, replacement);
     }
     RelaxEffectsAndControls(node);
@@ -178,7 +178,7 @@ Node* EscapeAnalysisReducer::ReduceDeoptState(Node* node, Node* effect,
         Node* field =
             analysis_result().GetVirtualObjectField(vobject, offset, effect);
         CHECK_NOT_NULL(field);
-        if (field != jsgraph()->Dead()) {
+        if (field != jsgraph()->Dead(JSGraph::DeadCustomer::EscapeAnalysis)) {
           inputs.push_back(ReduceDeoptState(field, effect, deduplicator));
         }
       }

src/compiler/escape-analysis.cc

@@ -216,7 +216,10 @@ class EscapeAnalysisTracker : public ZoneObject {
             replacement->id());
     }
 
-    void MarkForDeletion() { SetReplacement(tracker_->jsgraph_->Dead()); }
+    void MarkForDeletion() {
+      SetReplacement(
+          tracker_->jsgraph_->Dead(JSGraph::DeadCustomer::EscapeAnalysis));
+    }
 
     ~Scope() {
       if (replacement_ != tracker_->replacements_[current_node()] ||
@@ -430,7 +433,10 @@ VariableTracker::State VariableTracker::MergeInputs(Node* effect_phi) {
         // must have been created by a previous reduction of this [effect_phi].
         for (int i = 0; i < arity; ++i) {
           NodeProperties::ReplaceValueInput(
-              old_value, buffer_[i] ? buffer_[i] : graph_->Dead(), i);
+              old_value,
+              buffer_[i] ? buffer_[i]
+                         : graph_->Dead(JSGraph::DeadCustomer::EscapeAnalysis),
+              i);
           // This change cannot affect the rest of the reducer, so there is no
           // need to trigger additional revisitations.
         }
@@ -540,7 +546,8 @@ void ReduceNode(const Operator* op, EscapeAnalysisTracker::Scope* current,
       if (const VirtualObject* vobject = current->InitVirtualObject(size_int)) {
         // Initialize with dead nodes as a sentinel for uninitialized memory.
         for (Variable field : *vobject) {
-          current->Set(field, jsgraph->Dead());
+          current->Set(field,
+                       jsgraph->Dead(JSGraph::DeadCustomer::EscapeAnalysis));
         }
       }
       break;

src/compiler/js-graph.cc

@@ -301,10 +301,30 @@ Node* JSGraph::SingleDeadTypedStateValues() {
                     SparseInputMask(SparseInputMask::kEndMarker << 1))));
 }
 
-Node* JSGraph::Dead() {
-  return CACHED(kDead, graph()->NewNode(common()->Dead()));
+Node* JSGraph::Dead(DeadCustomer which) {
+  switch (which) {
+#define RETURN_CUSTOMER_NODE(customer) \
+  case customer:                       \
+    return CACHED(kDead##customer, graph()->NewNode(common()->Dead()));
+
+    CUSTOMER_LIST(RETURN_CUSTOMER_NODE)
+#undef RETURN_CUSTOMER_NODE
+    default:
+      V8_Fatal(__FILE__, __LINE__, "Unexpected Which dead node detected");
+  }
+  return nullptr;
 }
 
+const char* JSGraph::WhichDeadNode(Node* node) {
+#define SEARCH_FOR_DEAD_CUSTOMER(name)      \
+  if (node == cached_nodes_[kDead##name]) { \
+    return #name;                           \
+  }
+
+  CUSTOMER_LIST(SEARCH_FOR_DEAD_CUSTOMER)
+#undef SEARCH_FOR_DEAD_CUSTOMER
+  return "Uncached dead node";
+}
 
 void JSGraph::GetCachedNodes(NodeVector* nodes) {
   cache_.GetCachedNodes(nodes);
@@ -315,6 +335,8 @@ void JSGraph::GetCachedNodes(NodeVector* nodes) {
   }
 }
 
+#undef CACHED
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8

src/compiler/js-graph.h

@@ -152,8 +152,26 @@ class V8_EXPORT_PRIVATE JSGraph : public NON_EXPORTED_BASE(ZoneObject) {
   // dead accumulator.
   Node* SingleDeadTypedStateValues();
 
-  // Create a control node that serves as dependency for dead nodes.
-  Node* Dead();
+// Create a control node that serves as dependency for dead nodes.
+// TODO(mvstanton): We distinguish between different types of dead nodes
+// to track down bug chromium:780658. After fixing this bug, the
+// enum can be removed.
+#define CUSTOMER_LIST(V)   \
+  V(GraphBuilding)         \
+  V(TypeHint)              \
+  V(Inlining)              \
+  V(ContextSpecialization) \
+  V(EscapeAnalysis)        \
+  V(GraphReducer)          \
+  V(Unspecified)
+
+  enum DeadCustomer {
+#define DEFINE_DEAD_CUSTOMER_ENUM(name) name,
+    CUSTOMER_LIST(DEFINE_DEAD_CUSTOMER_ENUM)
+#undef DEFINE_DEAD_CUSTOMER_ENUM
+  };
+  Node* Dead(DeadCustomer which);
+  const char* WhichDeadNode(Node* node);
 
   CommonOperatorBuilder* common() const { return common_; }
   JSOperatorBuilder* javascript() const { return javascript_; }
@@ -195,8 +213,10 @@ class V8_EXPORT_PRIVATE JSGraph : public NON_EXPORTED_BASE(ZoneObject) {
     kNaNConstant,
     kEmptyStateValues,
     kSingleDeadTypedStateValues,
-    kDead,
-    kNumCachedNodes  // Must remain last.
+#define DEFINE_CACHED_DEAD_CUSTOMER_ENUM(name) kDead##name,
+    CUSTOMER_LIST(DEFINE_CACHED_DEAD_CUSTOMER_ENUM)
+#undef DEFINE_CACHED_DEAD_CUSTOMER_ENUM
+        kNumCachedNodes  // Must remain last.
   };
 
   Isolate* isolate_;

src/compiler/js-inlining-heuristic.cc

@@ -540,11 +540,15 @@ bool JSInliningHeuristic::TryReuseDispatch(Node* node, Node* callee,
   }
 
   // Mark the control inputs dead, so that we can kill the merge.
-  node->ReplaceInput(input_count - 1, jsgraph()->Dead());
-  callee->ReplaceInput(num_calls, jsgraph()->Dead());
-  effect_phi->ReplaceInput(num_calls, jsgraph()->Dead());
+  node->ReplaceInput(input_count - 1,
+                     jsgraph()->Dead(JSGraph::DeadCustomer::Inlining));
+  callee->ReplaceInput(num_calls,
+                       jsgraph()->Dead(JSGraph::DeadCustomer::Inlining));
+  effect_phi->ReplaceInput(num_calls,
+                           jsgraph()->Dead(JSGraph::DeadCustomer::Inlining));
   if (checkpoint) {
-    checkpoint->ReplaceInput(2, jsgraph()->Dead());
+    checkpoint->ReplaceInput(2,
+                             jsgraph()->Dead(JSGraph::DeadCustomer::Inlining));
   }
 
   merge->Kill();

src/compiler/js-inlining.cc

@@ -179,7 +179,7 @@ Reduction JSInliner::InlineCall(Node* call, Node* new_target, Node* context,
                        control_output);
     } else {
       ReplaceWithValue(exception_target, exception_target, exception_target,
-                       jsgraph()->Dead());
+                       jsgraph()->Dead(JSGraph::DeadCustomer::Inlining));
     }
   }
 
@@ -224,8 +224,9 @@ Reduction JSInliner::InlineCall(Node* call, Node* new_target, Node* context,
     ReplaceWithValue(call, value_output, effect_output, control_output);
     return Changed(value_output);
   } else {
-    ReplaceWithValue(call, jsgraph()->Dead(), jsgraph()->Dead(),
-                     jsgraph()->Dead());
+    ReplaceWithValue(call, jsgraph()->Dead(JSGraph::DeadCustomer::Inlining),
+                     jsgraph()->Dead(JSGraph::DeadCustomer::Inlining),
+                     jsgraph()->Dead(JSGraph::DeadCustomer::Inlining));
     return Changed(call);
   }
 }

src/compiler/js-native-context-specialization.cc

@@ -890,7 +890,8 @@ Reduction JSNativeContextSpecialization::ReduceNamedAccess(
     // Generate the final merge point for all (polymorphic) branches.
     int const control_count = static_cast<int>(controls.size());
     if (control_count == 0) {
-      value = effect = control = jsgraph()->Dead();
+      value = effect = control =
+          jsgraph()->Dead(JSGraph::DeadCustomer::ContextSpecialization);
     } else if (control_count == 1) {
       value = values.front();
       effect = effects.front();
@@ -976,7 +977,8 @@ Reduction JSNativeContextSpecialization::ReduceJSLoadNamed(Node* node) {
   DCHECK_EQ(IrOpcode::kJSLoadNamed, node->opcode());
   NamedAccess const& p = NamedAccessOf(node->op());
   Node* const receiver = NodeProperties::GetValueInput(node, 0);
-  Node* const value = jsgraph()->Dead();
+  Node* const value =
+      jsgraph()->Dead(JSGraph::DeadCustomer::ContextSpecialization);
 
   // Check if we have a constant receiver.
   HeapObjectMatcher m(receiver);
@@ -1243,7 +1245,8 @@ Reduction JSNativeContextSpecialization::ReduceElementAccess(
       // Generate the final merge point for all (polymorphic) branches.
       int const control_count = static_cast<int>(controls.size());
       if (control_count == 0) {
-        value = effect = control = jsgraph()->Dead();
+        value = effect = control =
+            jsgraph()->Dead(JSGraph::DeadCustomer::ContextSpecialization);
       } else if (control_count == 1) {
         value = values.front();
         effect = effects.front();
@@ -1442,7 +1445,7 @@ Reduction JSNativeContextSpecialization::ReduceJSLoadProperty(Node* node) {
   PropertyAccess const& p = PropertyAccessOf(node->op());
   Node* receiver = NodeProperties::GetValueInput(node, 0);
   Node* name = NodeProperties::GetValueInput(node, 1);
-  Node* value = jsgraph()->Dead();
+  Node* value = jsgraph()->Dead(JSGraph::DeadCustomer::ContextSpecialization);
   Node* effect = NodeProperties::GetEffectInput(node);
   Node* control = NodeProperties::GetControlInput(node);
 

src/compiler/js-type-hint-lowering.cc

@@ -428,7 +428,7 @@ Node* JSTypeHintLowering::TryBuildSoftDeopt(FeedbackNexus& nexus, Node* effect,
   if ((flags() & kBailoutOnUninitialized) && nexus.IsUninitialized()) {
     Node* deoptimize = jsgraph()->graph()->NewNode(
         jsgraph()->common()->Deoptimize(DeoptimizeKind::kSoft, reason),
-        jsgraph()->Dead(), effect, control);
+        jsgraph()->Dead(JSGraph::DeadCustomer::TypeHint), effect, control);
     Node* frame_state = NodeProperties::FindFrameStateBefore(deoptimize);
     deoptimize->ReplaceInput(0, frame_state);
     return deoptimize;

src/compiler/pipeline.cc

@@ -664,7 +664,8 @@ class SourcePositionWrapper final : public Reducer {
 class JSGraphReducer final : public GraphReducer {
  public:
   JSGraphReducer(JSGraph* jsgraph, Zone* zone)
-      : GraphReducer(zone, jsgraph->graph(), jsgraph->Dead()) {}
+      : GraphReducer(zone, jsgraph->graph(),
+                     jsgraph->Dead(JSGraph::DeadCustomer::GraphReducer)) {}
   ~JSGraphReducer() final {}
 };
 

src/compiler/simplified-lowering.cc

@@ -206,6 +206,16 @@ class InputUseInfos {
 
 #endif  // DEBUG
 
+// TODO(mvstanton): Remove after fixing chromium:780658.
+static void UnexpectedDeadOpcode(const char* file, int line,
+                                 const char* deadCode, Node* node) {
+  // Record the deadcode in the stack to ease minidump debugging.
+  const char* format_string = "Unexpected dead opcode %s, node #%i\n.";
+  char buffer[256];
+  snprintf(buffer, sizeof(buffer), format_string, deadCode, node->id());
+  V8_Fatal(file, line, format_string, deadCode, node->id());
+}
+
 bool CanOverflowSigned32(const Operator* op, Type* left, Type* right,
                          Zone* type_zone) {
   // We assume the inputs are checked Signed32 (or known statically
@@ -3047,6 +3057,11 @@ class RepresentationSelector {
         // Assume the output is tagged.
         return SetOutput(node, MachineRepresentation::kTagged);
 
+      case IrOpcode::kDead: {
+        const char* deadVersion = jsgraph_->WhichDeadNode(node);
+        UnexpectedDeadOpcode(__FILE__, __LINE__, deadVersion, node);
+        break;
+      }
       default:
         V8_Fatal(
             __FILE__, __LINE__,
@@ -3092,7 +3107,7 @@ class RepresentationSelector {
       DCHECK_EQ(0, node->op()->EffectOutputCount());
     }
 
-    node->ReplaceUses(jsgraph_->Dead());
+    node->ReplaceUses(jsgraph_->Dead(JSGraph::DeadCustomer::Unspecified));
 
     node->NullAllInputs();  // The {node} is now dead.
   }

src/compiler/wasm-compiler.cc

@@ -94,7 +94,9 @@ WasmGraphBuilder::WasmGraphBuilder(
   DCHECK_NOT_NULL(jsgraph_);
 }
 
-Node* WasmGraphBuilder::Error() { return jsgraph()->Dead(); }
+Node* WasmGraphBuilder::Error() {
+  return jsgraph()->Dead(JSGraph::DeadCustomer::Unspecified);
+}
 
 Node* WasmGraphBuilder::Start(unsigned params) {
   Node* start = graph()->NewNode(jsgraph()->common()->Start(params));

test/unittests/compiler/branch-elimination-unittest.cc

@@ -27,7 +27,8 @@ class BranchEliminationTest : public GraphTest {
     JSOperatorBuilder javascript(zone());
     JSGraph jsgraph(isolate(), graph(), common(), &javascript, nullptr,
                     machine());
-    GraphReducer graph_reducer(zone(), graph(), jsgraph.Dead());
+    GraphReducer graph_reducer(
+        zone(), graph(), jsgraph.Dead(JSGraph::DeadCustomer::Unspecified));
     BranchElimination branch_condition_elimination(&graph_reducer, &jsgraph,
                                                    zone());
     graph_reducer.AddReducer(&branch_condition_elimination);