[turbofan] In GraphReducer::Replace, check uses to not misuse the replacement.

src/compiler/graph-reducer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <functional>
 #include <limits>
 
 #include "src/compiler/graph.h"
 #include "src/compiler/graph-reducer.h"
 #include "src/compiler/node.h"
@@ skipping 141 matching lines @@
     }
   }
 }
 
 
 void GraphReducer::Replace(Node* node, Node* replacement) {
   Replace(node, replacement, std::numeric_limits<NodeId>::max());
 }
 
 
+namespace {
+
+
+void VerifyUseReplacement(const Edge& edge, const Node* replacement) {

[Michael Starzinger, 2015/09/25 10:54:18]

suggestion: We could move this verification methods into the verifier.[h|cc]
file (maybe static methods on Verifier or even a separate NodeVerifier with
static methods). Same applies for the NodeProperties::ChangeOp verification. Not
sure it's worth it, up to you.

+  // Check that the user does not misuse the replacement.
+  DCHECK(!NodeProperties::IsControlEdge(edge) ||
+         replacement->op()->ControlOutputCount() > 0);
+  DCHECK(!NodeProperties::IsEffectEdge(edge) ||
+         replacement->op()->EffectOutputCount() > 0);
+  DCHECK(!NodeProperties::IsFrameStateEdge(edge) ||
+         replacement->opcode() == IrOpcode::kFrameState);
+}
+
+}  // namespace
+
+
 void GraphReducer::Replace(Node* node, Node* replacement, NodeId max_id) {
   if (node == graph()->start()) graph()->SetStart(replacement);
   if (node == graph()->end()) graph()->SetEnd(replacement);
   if (replacement->id() <= max_id) {
     // {replacement} is an old node, so unlink {node} and assume that
     // {replacement} was already reduced and finish.
     for (Edge edge : node->use_edges()) {
       Node* const user = edge.from();
+      VerifyUseReplacement(edge, replacement);
       edge.UpdateTo(replacement);
       // Don't revisit this node if it refers to itself.
       if (user != node) Revisit(user);
     }
     node->Kill();
   } else {
     // Replace all old uses of {node} with {replacement}, but allow new nodes
     // created by this reduction to use {node}.
     for (Edge edge : node->use_edges()) {
       Node* const user = edge.from();
@@ skipping 72 matching lines @@
 void GraphReducer::Revisit(Node* node) {
   if (state_.Get(node) == State::kVisited) {
     state_.Set(node, State::kRevisit);
     revisit_.push(node);
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8