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

R=bmeurer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1020873002

Cr-Commit-Position: refs/heads/master@{#27304}

src/compiler/common-operator.cc

@@ -294,7 +294,7 @@ struct CommonOperatorGlobalCache FINAL {
     ProjectionOperator()
         : Operator1<size_t>(          // --
               IrOpcode::kProjection,  // opcode
-              Operator::kFoldable | Operator::kNoThrow,  // flags
+              Operator::kPure,        // flags
               "Projection",           // name
               1, 0, 0, 1, 0, 0,       // counts,
               kIndex) {}              // parameter

src/compiler/scheduler.cc

@@ -1401,6 +1401,8 @@ class ScheduleLateNodeVisitor {
   BasicBlock* SplitNode(BasicBlock* block, Node* node) {
     // For now, we limit splitting to pure nodes.
     if (!node->op()->HasProperty(Operator::kPure)) return block;
+    // TODO(titzer): fix the special case of splitting of projections.
+    if (node->opcode() == IrOpcode::kProjection) return block;
 
     // The {block} is common dominator of all uses of {node}, so we cannot
     // split anything unless the {block} has at least two successors.
@@ -1573,6 +1575,8 @@ class ScheduleLateNodeVisitor {
       inputs[index] = input;
     }
     Node* copy = scheduler_->graph_->NewNode(node->op(), input_count, inputs);
+    TRACE(("clone #%d:%s -> #%d\n"), node->id(), node->op()->mnemonic(),
+          copy->id());
     scheduler_->node_data_.resize(copy->id() + 1,
                                   scheduler_->DefaultSchedulerData());
     scheduler_->node_data_[copy->id()] = scheduler_->node_data_[node->id()];

src/compiler/verifier.cc

@@ -825,7 +825,23 @@ void Verifier::Run(Graph* graph, Typing typing) {
   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());
+      }
+    }
+  }
 }