[turbofan] Remove last_use_ field from Node.

test/unittests/compiler/node-unittest.cc

 // Copyright 2015 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/node.h"
 #include "src/compiler/operator.h"
 #include "test/unittests/test-utils.h"
 #include "testing/gmock-support.h"
 
 using testing::ElementsAre;
@@ skipping 30 matching lines @@
   EXPECT_EQ(kOpcode0, node->opcode());
 }
 
 
 TEST_F(NodeTest, NewWithInputs) {
   Node* n0 = Node::New(zone(), 0, &kOp0, 0, nullptr, false);
   EXPECT_EQ(0, n0->UseCount());
   EXPECT_EQ(0, n0->InputCount());
   Node* n1 = Node::New(zone(), 1, &kOp1, 1, &n0, false);
   EXPECT_EQ(1, n0->UseCount());
-  EXPECT_EQ(n1, n0->UseAt(0));
+  EXPECT_THAT(n0->uses(), UnorderedElementsAre(n1));
   EXPECT_EQ(0, n1->UseCount());
   EXPECT_EQ(1, n1->InputCount());
   EXPECT_EQ(n0, n1->InputAt(0));
   Node* n0_n1[] = {n0, n1};
   Node* n2 = Node::New(zone(), 2, &kOp2, 2, n0_n1, false);
   EXPECT_EQ(2, n0->UseCount());
-  EXPECT_EQ(n1, n0->UseAt(0));
-  EXPECT_EQ(n2, n0->UseAt(1));
+  EXPECT_THAT(n0->uses(), UnorderedElementsAre(n1, n2));
+  EXPECT_THAT(n1->uses(), UnorderedElementsAre(n2));
   EXPECT_EQ(2, n2->InputCount());
   EXPECT_EQ(n0, n2->InputAt(0));
   EXPECT_EQ(n1, n2->InputAt(1));
 }
 
 
 TEST_F(NodeTest, InputIteratorEmpty) {
   Node* node = Node::New(zone(), 0, &kOp0, 0, nullptr, false);
   EXPECT_EQ(node->inputs().begin(), node->inputs().end());
 }
@@ skipping 91 matching lines @@
   EXPECT_THAT(node->inputs(), ElementsAre(n0, n1, n0));
   node->AppendInput(zone(), n0);
   EXPECT_THAT(node->inputs(), ElementsAre(n0, n1, n0, n0));
   node->AppendInput(zone(), n1);
   EXPECT_THAT(node->inputs(), ElementsAre(n0, n1, n0, n0, n1));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8