[turbofan] Fix GVN of projections and add verification for projection uniqueness.

src/compiler/verifier.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 "src/compiler/verifier.h"
 
 #include <algorithm>
 #include <deque>
 #include <queue>
 #include <sstream>
@@ skipping 807 matching lines @@
       break;
   }
 }  // NOLINT(readability/fn_size)
 
 
 void Verifier::Run(Graph* graph, Typing typing) {
   CHECK_NOT_NULL(graph->start());
   CHECK_NOT_NULL(graph->end());
   Zone zone;
   Visitor visitor(&zone, typing);
-  for (Node* node : AllNodes(&zone, graph).live) visitor.Check(node);
+  AllNodes all(&zone, graph);
+  for (Node* node : all.live) visitor.Check(node);
+
+  // Check the uniqueness of projections.
+  for (Node* proj : all.live) {
+    if (proj->opcode() != IrOpcode::kProjection) continue;
+    Node* node = proj->InputAt(0);
+    for (Node* other : node->uses()) {
+      if (all.IsLive(other) && other != proj &&
+          other->opcode() == IrOpcode::kProjection &&
+          ProjectionIndexOf(other->op()) == ProjectionIndexOf(proj->op())) {
+        V8_Fatal(__FILE__, __LINE__,
+                 "Node #%d:%s has duplicate projections #%d and #%d",
+                 node->id(), node->op()->mnemonic(), proj->id(), other->id());
+      }
+    }
+  }
 }
 
 
 // -----------------------------------------------------------------------------
 
 static bool HasDominatingDef(Schedule* schedule, Node* node,
                              BasicBlock* container, BasicBlock* use_block,
                              int use_pos) {
   BasicBlock* block = use_block;
   while (true) {
@@ skipping 220 matching lines @@
     // Check inputs for all nodes in the block.
     for (size_t i = 0; i < block->NodeCount(); i++) {
       Node* node = block->NodeAt(i);
       CheckInputsDominate(schedule, block, node, static_cast<int>(i) - 1);
     }
   }
 }
 }
 }
 }  // namespace v8::internal::compiler