From aed44ecee39e66d19c0f9788992c0578a3742ec3 Mon Sep 17 00:00:00 2001
From: "bmeurer@chromium.org" <bmeurer@chromium.org>
Date: Fri, 5 Sep 2014 11:10:28 +0000
Subject: [PATCH] [turbofan] Nodes are killed by resetting all their inputs to
 zero.

TEST=compiler-unittests,mjsunit/numops-fuzz
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/540253003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23725 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 src/compiler/graph-reducer-unittest.cc        | 27 ++++++++++---------
 src/compiler/node.cc                          |  1 -
 src/compiler/node.h                           |  2 ++
 .../value-numbering-reducer-unittest.cc       |  8 +++---
 src/compiler/value-numbering-reducer.cc       |  2 +-
 5 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/src/compiler/graph-reducer-unittest.cc b/src/compiler/graph-reducer-unittest.cc
index 9dbc9ea2ad..6567203e88 100644
--- a/src/compiler/graph-reducer-unittest.cc
+++ b/src/compiler/graph-reducer-unittest.cc
@@ -20,7 +20,8 @@ namespace compiler {
 
 namespace {
 
-SimpleOperator OP0(0, Operator::kNoWrite, 0, 0, "op0");
+SimpleOperator OP0(0, Operator::kNoWrite, 0, 1, "op0");
+SimpleOperator OP1(1, Operator::kNoProperties, 1, 1, "op1");
 
 
 struct MockReducer : public Reducer {
@@ -73,6 +74,19 @@ class GraphReducerTest : public TestWithZone {
 };
 
 
+TEST_F(GraphReducerTest, NodeIsDeadAfterReplace) {
+  StrictMock<MockReducer> r;
+  Node* node0 = graph()->NewNode(&OP0);
+  Node* node1 = graph()->NewNode(&OP1, node0);
+  Node* node2 = graph()->NewNode(&OP1, node0);
+  EXPECT_CALL(r, Reduce(node1)).WillOnce(Return(Reducer::Replace(node2)));
+  ReduceNode(node1, &r);
+  EXPECT_FALSE(node0->IsDead());
+  EXPECT_TRUE(node1->IsDead());
+  EXPECT_FALSE(node2->IsDead());
+}
+
+
 TEST_F(GraphReducerTest, ReduceOnceForEveryReducer) {
   StrictMock<MockReducer> r1, r2;
   Node* node0 = graph()->NewNode(&OP0);
@@ -95,17 +109,6 @@ TEST_F(GraphReducerTest, ReduceAgainAfterChanged) {
   ReduceNode(node0, &r1, &r2, &r3);
 }
 
-
-TEST_F(GraphReducerTest, OperatorIsNullAfterReplace) {
-  StrictMock<MockReducer> r;
-  Node* node0 = graph()->NewNode(&OP0);
-  Node* node1 = graph()->NewNode(&OP0);
-  EXPECT_CALL(r, Reduce(node0)).WillOnce(Return(Reducer::Replace(node1)));
-  ReduceNode(node0, &r);
-  EXPECT_EQ(NULL, node0->op());
-  EXPECT_EQ(&OP0, node1->op());
-}
-
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
diff --git a/src/compiler/node.cc b/src/compiler/node.cc
index 8e5c0df215..66294bd180 100644
--- a/src/compiler/node.cc
+++ b/src/compiler/node.cc
@@ -14,7 +14,6 @@ void Node::Kill() {
   DCHECK_NOT_NULL(op());
   RemoveAllInputs();
   DCHECK(uses().empty());
-  set_op(NULL);
 }
 
 
diff --git a/src/compiler/node.h b/src/compiler/node.h
index d8a44939f3..ac2f332210 100644
--- a/src/compiler/node.h
+++ b/src/compiler/node.h
@@ -53,6 +53,8 @@ class Node FINAL : public GenericNode<NodeData, Node> {
       : GenericNode<NodeData, Node>(graph, input_count) {}
 
   void Initialize(const Operator* op) { set_op(op); }
+
+  bool IsDead() const { return InputCount() > 0 && InputAt(0) == NULL; }
   void Kill();
 
   void CollectProjections(ZoneVector<Node*>* projections);
diff --git a/src/compiler/value-numbering-reducer-unittest.cc b/src/compiler/value-numbering-reducer-unittest.cc
index 28a9856059..8db6458031 100644
--- a/src/compiler/value-numbering-reducer-unittest.cc
+++ b/src/compiler/value-numbering-reducer-unittest.cc
@@ -15,6 +15,7 @@ namespace compiler {
 namespace {
 
 const SimpleOperator kOp0(0, Operator::kNoProperties, 0, 1, "op0");
+const SimpleOperator kOp1(1, Operator::kNoProperties, 1, 1, "op1");
 
 }  // namespace
 
@@ -44,11 +45,12 @@ TEST_F(ValueNumberingReducerTest, AllInputsAreChecked) {
 }
 
 
-TEST_F(ValueNumberingReducerTest, KilledNodesAreNeverReturned) {
-  Node* n1 = graph()->NewNode(&kOp0);
+TEST_F(ValueNumberingReducerTest, DeadNodesAreNeverReturned) {
+  Node* n0 = graph()->NewNode(&kOp0);
+  Node* n1 = graph()->NewNode(&kOp1, n0);
   EXPECT_FALSE(Reduce(n1).Changed());
   n1->Kill();
-  EXPECT_FALSE(Reduce(graph()->NewNode(&kOp0)).Changed());
+  EXPECT_FALSE(Reduce(graph()->NewNode(&kOp1, n0)).Changed());
 }
 
 
diff --git a/src/compiler/value-numbering-reducer.cc b/src/compiler/value-numbering-reducer.cc
index bdc9a52017..595a4f3017 100644
--- a/src/compiler/value-numbering-reducer.cc
+++ b/src/compiler/value-numbering-reducer.cc
@@ -59,7 +59,7 @@ ValueNumberingReducer::~ValueNumberingReducer() {}
 Reduction ValueNumberingReducer::Reduce(Node* node) {
   Entry** head = &buckets_[HashCode(node) % arraysize(buckets_)];
   for (Entry* entry = *head; entry; entry = entry->next()) {
-    if (entry->node()->op() == NULL) continue;
+    if (entry->node()->IsDead()) continue;
     if (entry->node() == node) return NoChange();
     if (Equals(node, entry->node())) {
       return Replace(entry->node());