text: // 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/codegen.h"
  #include "src/compiler/all-nodes.h"
  #include "src/compiler/common-operator.h"
  #include "src/compiler/diamond.h"
  #include "src/compiler/graph.h"
  #include "src/compiler/js-graph.h"
  #include "src/compiler/js-operator.h"
  #include "src/compiler/operator.h"
  #include "src/compiler/osr.h"
  #include "test/cctest/cctest.h"
  
  using namespace v8::internal;
  using namespace v8::internal::compiler;
  
  // TODO(titzer): move this method to a common testing place.
  
  static int CheckInputs(Node* node, Node* i0 = NULL, Node* i1 = NULL,
                         Node* i2 = NULL, Node* i3 = NULL) {
    int count = 4;
    if (i3 == NULL) count = 3;
    if (i2 == NULL) count = 2;
    if (i1 == NULL) count = 1;
    if (i0 == NULL) count = 0;
    CHECK_EQ(count, node->InputCount());
    if (i0 != NULL) CHECK_EQ(i0, node->InputAt(0));
    if (i1 != NULL) CHECK_EQ(i1, node->InputAt(1));
    if (i2 != NULL) CHECK_EQ(i2, node->InputAt(2));
    if (i3 != NULL) CHECK_EQ(i3, node->InputAt(3));
    return count;
  }
  
  
  static Operator kIntLt(IrOpcode::kInt32LessThan, Operator::kPure,
                         "Int32LessThan", 2, 0, 0, 1, 0, 0);
  static Operator kIntAdd(IrOpcode::kInt32Add, Operator::kPure, "Int32Add", 2, 0,
                          0, 1, 0, 0);
  
  
  static const int kMaxOsrValues = 10;
  
  class OsrDeconstructorTester : public HandleAndZoneScope {
   public:
    explicit OsrDeconstructorTester(int num_values)
        : isolate(main_isolate()),
          common(main_zone()),
          graph(main_zone()),
          jsgraph(main_isolate(), &graph, &common, NULL, NULL),
          start(graph.NewNode(common.Start(1))),
          p0(graph.NewNode(common.Parameter(0), start)),
          end(graph.NewNode(common.End(), start)),
          osr_normal_entry(graph.NewNode(common.OsrNormalEntry(), start, start)),
          osr_loop_entry(graph.NewNode(common.OsrLoopEntry(), start, start)),
          self(graph.NewNode(common.Int32Constant(0xaabbccdd))) {
      CHECK(num_values <= kMaxOsrValues);
      graph.SetStart(start);
      for (int i = 0; i < num_values; i++) {
        osr_values[i] = graph.NewNode(common.OsrValue(i), osr_loop_entry);
      }
    }
  
    Isolate* isolate;
    CommonOperatorBuilder common;
    Graph graph;
    JSGraph jsgraph;
    Node* start;
    Node* p0;
    Node* end;
    Node* osr_normal_entry;
    Node* osr_loop_entry;
    Node* self;
    Node* osr_values[kMaxOsrValues];
  
    Node* NewOsrPhi(Node* loop, Node* incoming, int osr_value, Node* back1 = NULL,
                    Node* back2 = NULL, Node* back3 = NULL) {
      int count = 5;
      if (back3 == NULL) count = 4;
      if (back2 == NULL) count = 3;
      if (back1 == NULL) count = 2;
      CHECK_EQ(loop->InputCount(), count);
      CHECK_EQ(osr_loop_entry, loop->InputAt(1));
  
      Node* inputs[6];
      inputs[0] = incoming;
      inputs[1] = osr_values[osr_value];
      if (count > 2) inputs[2] = back1;
      if (count > 3) inputs[3] = back2;
      if (count > 4) inputs[4] = back3;
      inputs[count] = loop;
      return graph.NewNode(common.Phi(kMachAnyTagged, count), count + 1, inputs);
    }
  
    Node* NewLoop(bool is_osr, int num_backedges, Node* entry = NULL) {
      CHECK_LT(num_backedges, 4);
      CHECK_GE(num_backedges, 0);
      int count = 1 + num_backedges;
      if (entry == NULL) entry = osr_normal_entry;
      Node* inputs[5] = {entry, self, self, self, self};
      if (is_osr) {
        count = 2 + num_backedges;
        inputs[1] = osr_loop_entry;
      }
  
      Node* loop = graph.NewNode(common.Loop(count), count, inputs);
      for (int i = 0; i < loop->InputCount(); i++) {
        if (loop->InputAt(i) == self) loop->ReplaceInput(i, loop);
      }
  
      return loop;
    }
  
    Node* NewOsrLoop(int num_backedges, Node* entry = NULL) {
      return NewLoop(true, num_backedges, entry);
    }
  
    void DeconstructOsr() {
      OsrHelper helper(0, 0);
      helper.Deconstruct(&jsgraph, &common, main_zone());
      AllNodes nodes(main_zone(), &graph);
      // Should be edited out.
      CHECK(!nodes.IsLive(osr_normal_entry));
      CHECK(!nodes.IsLive(osr_loop_entry));
      // No dangling nodes should be left over.
      for (Node* const node : nodes.live) {
        for (Node* const use : node->uses()) {
          CHECK(std::find(nodes.live.begin(), nodes.live.end(), use) !=
                nodes.live.end());
        }
      }
    }
  };
  
  
  TEST(Deconstruct_osr0) {
    OsrDeconstructorTester T(0);
  
    Node* loop = T.NewOsrLoop(1);
  
    T.graph.SetEnd(loop);
  
    T.DeconstructOsr();
  
    CheckInputs(loop, T.start, loop);
  }
  
  
  TEST(Deconstruct_osr1) {
    OsrDeconstructorTester T(1);
  
    Node* loop = T.NewOsrLoop(1);
    Node* osr_phi =
        T.NewOsrPhi(loop, T.jsgraph.OneConstant(), 0, T.jsgraph.ZeroConstant());
  
    Node* ret = T.graph.NewNode(T.common.Return(), osr_phi, T.start, loop);
    T.graph.SetEnd(ret);
  
    T.DeconstructOsr();
  
    CheckInputs(loop, T.start, loop);
    CheckInputs(osr_phi, T.osr_values[0], T.jsgraph.ZeroConstant(), loop);
    CheckInputs(ret, osr_phi, T.start, loop);
  }
  
  
  TEST(Deconstruct_osr1_type) {
    OsrDeconstructorTester T(1);
  
    Node* loop = T.NewOsrLoop(1);
    Node* osr_phi =
        T.NewOsrPhi(loop, T.jsgraph.OneConstant(), 0, T.jsgraph.ZeroConstant());
    Type* type = Type::Signed32();
    NodeProperties::SetBounds(osr_phi, Bounds(type, type));
  
    Node* ret = T.graph.NewNode(T.common.Return(), osr_phi, T.start, loop);
    T.graph.SetEnd(ret);
  
    OsrHelper helper(0, 0);
    helper.Deconstruct(&T.jsgraph, &T.common, T.main_zone());
  
    CHECK_EQ(type, NodeProperties::GetBounds(T.osr_values[0]).lower);
    CHECK_EQ(type, NodeProperties::GetBounds(T.osr_values[0]).upper);
  
    CheckInputs(loop, T.start, loop);
    CheckInputs(osr_phi, T.osr_values[0], T.jsgraph.ZeroConstant(), loop);
    CheckInputs(ret, osr_phi, T.start, loop);
  }
  
  
  TEST(Deconstruct_osr_remove_prologue) {
    OsrDeconstructorTester T(1);
    Diamond d(&T.graph, &T.common, T.p0);
    d.Chain(T.osr_normal_entry);
  
    Node* loop = T.NewOsrLoop(1, d.merge);
    Node* osr_phi =
        T.NewOsrPhi(loop, T.jsgraph.OneConstant(), 0, T.jsgraph.ZeroConstant());
  
    Node* ret = T.graph.NewNode(T.common.Return(), osr_phi, T.start, loop);
    T.graph.SetEnd(ret);
  
    T.DeconstructOsr();
  
    CheckInputs(loop, T.start, loop);
    CheckInputs(osr_phi, T.osr_values[0], T.jsgraph.ZeroConstant(), loop);
    CheckInputs(ret, osr_phi, T.start, loop);
  
    // The control before the loop should have been removed.
    AllNodes nodes(T.main_zone(), &T.graph);
    CHECK(!nodes.IsLive(d.branch));
    CHECK(!nodes.IsLive(d.if_true));
    CHECK(!nodes.IsLive(d.if_false));
    CHECK(!nodes.IsLive(d.merge));
  }
  
  
  TEST(Deconstruct_osr_with_body1) {
    OsrDeconstructorTester T(1);
  
    Node* loop = T.NewOsrLoop(1);
  
    Node* branch = T.graph.NewNode(T.common.Branch(), T.p0, loop);
    Node* if_true = T.graph.NewNode(T.common.IfTrue(), branch);
    Node* if_false = T.graph.NewNode(T.common.IfFalse(), branch);
    loop->ReplaceInput(2, if_true);
  
    Node* osr_phi =
        T.NewOsrPhi(loop, T.jsgraph.OneConstant(), 0, T.jsgraph.ZeroConstant());
  
    Node* ret = T.graph.NewNode(T.common.Return(), osr_phi, T.start, if_false);
    T.graph.SetEnd(ret);
  
    T.DeconstructOsr();
  
    CheckInputs(loop, T.start, if_true);
    CheckInputs(branch, T.p0, loop);
    CheckInputs(if_true, branch);
    CheckInputs(if_false, branch);
    CheckInputs(osr_phi, T.osr_values[0], T.jsgraph.ZeroConstant(), loop);
    CheckInputs(ret, osr_phi, T.start, if_false);
  }
  
  
  TEST(Deconstruct_osr_with_body2) {
    OsrDeconstructorTester T(1);
  
    Node* loop = T.NewOsrLoop(1);
  
    // Two chained branches in the the body of the loop.
    Node* branch1 = T.graph.NewNode(T.common.Branch(), T.p0, loop);
    Node* if_true1 = T.graph.NewNode(T.common.IfTrue(), branch1);
    Node* if_false1 = T.graph.NewNode(T.common.IfFalse(), branch1);
  
    Node* branch2 = T.graph.NewNode(T.common.Branch(), T.p0, if_true1);
    Node* if_true2 = T.graph.NewNode(T.common.IfTrue(), branch2);
    Node* if_false2 = T.graph.NewNode(T.common.IfFalse(), branch2);
    loop->ReplaceInput(2, if_true2);
  
    Node* osr_phi =
        T.NewOsrPhi(loop, T.jsgraph.OneConstant(), 0, T.jsgraph.ZeroConstant());
  
    Node* merge = T.graph.NewNode(T.common.Merge(2), if_false1, if_false2);
    Node* ret = T.graph.NewNode(T.common.Return(), osr_phi, T.start, merge);
    T.graph.SetEnd(ret);
  
    T.DeconstructOsr();
  
    CheckInputs(loop, T.start, if_true2);
    CheckInputs(branch1, T.p0, loop);
    CheckInputs(branch2, T.p0, if_true1);
    CheckInputs(if_true1, branch1);
    CheckInputs(if_false1, branch1);
    CheckInputs(if_true2, branch2);
    CheckInputs(if_false2, branch2);
  
    CheckInputs(osr_phi, T.osr_values[0], T.jsgraph.ZeroConstant(), loop);
    CheckInputs(ret, osr_phi, T.start, merge);
    CheckInputs(merge, if_false1, if_false2);
  }
  
  
  TEST(Deconstruct_osr_with_body3) {
    OsrDeconstructorTester T(1);
  
    Node* loop = T.NewOsrLoop(2);
  
    // Two branches that create two different backedges.
    Node* branch1 = T.graph.NewNode(T.common.Branch(), T.p0, loop);
    Node* if_true1 = T.graph.NewNode(T.common.IfTrue(), branch1);
    Node* if_false1 = T.graph.NewNode(T.common.IfFalse(), branch1);
  
    Node* branch2 = T.graph.NewNode(T.common.Branch(), T.p0, if_true1);
    Node* if_true2 = T.graph.NewNode(T.common.IfTrue(), branch2);
    Node* if_false2 = T.graph.NewNode(T.common.IfFalse(), branch2);
    loop->ReplaceInput(2, if_false1);
    loop->ReplaceInput(3, if_true2);
  
    Node* osr_phi =
        T.NewOsrPhi(loop, T.jsgraph.OneConstant(), 0, T.jsgraph.ZeroConstant(),
                    T.jsgraph.ZeroConstant());
  
    Node* ret = T.graph.NewNode(T.common.Return(), osr_phi, T.start, if_false2);
    T.graph.SetEnd(ret);
  
    T.DeconstructOsr();
  
    CheckInputs(loop, T.start, if_false1, if_true2);
    CheckInputs(branch1, T.p0, loop);
    CheckInputs(branch2, T.p0, if_true1);
    CheckInputs(if_true1, branch1);
    CheckInputs(if_false1, branch1);
    CheckInputs(if_true2, branch2);
    CheckInputs(if_false2, branch2);
  
    CheckInputs(osr_phi, T.osr_values[0], T.jsgraph.ZeroConstant(),
                T.jsgraph.ZeroConstant(), loop);
    CheckInputs(ret, osr_phi, T.start, if_false2);
  }
  
  
  struct While {
    OsrDeconstructorTester& t;
    Node* branch;
    Node* if_true;
    Node* exit;
    Node* loop;
  
    While(OsrDeconstructorTester& R, Node* cond, bool is_osr, int backedges = 1)
        : t(R) {
      loop = t.NewLoop(is_osr, backedges);
      branch = t.graph.NewNode(t.common.Branch(), cond, loop);
      if_true = t.graph.NewNode(t.common.IfTrue(), branch);
      exit = t.graph.NewNode(t.common.IfFalse(), branch);
      loop->ReplaceInput(loop->InputCount() - 1, if_true);
    }
  
    void Nest(While& that) {
      that.loop->ReplaceInput(that.loop->InputCount() - 1, exit);
      this->loop->ReplaceInput(0, that.if_true);
    }
  
    Node* Phi(Node* i1, Node* i2, Node* i3) {
      if (loop->InputCount() == 2) {
        return t.graph.NewNode(t.common.Phi(kMachAnyTagged, 2), i1, i2, loop);
      } else {
        return t.graph.NewNode(t.common.Phi(kMachAnyTagged, 3), i1, i2, i3, loop);
      }
    }
  };
  
  
  static Node* FindSuccessor(Node* node, IrOpcode::Value opcode) {
    for (Node* use : node->uses()) {
      if (use->opcode() == opcode) return use;
    }
    UNREACHABLE();  // should have been found.
    return nullptr;
  }
  
  
  TEST(Deconstruct_osr_nested1) {
    OsrDeconstructorTester T(1);
  
    While outer(T, T.p0, false);
    While inner(T, T.p0, true);
    inner.Nest(outer);
  
    Node* outer_phi = outer.Phi(T.p0, T.p0, nullptr);
    outer.branch->ReplaceInput(0, outer_phi);
  
    Node* osr_phi = inner.Phi(T.jsgraph.OneConstant(), T.osr_values[0],
                              T.jsgraph.ZeroConstant());
    inner.branch->ReplaceInput(0, osr_phi);
    outer_phi->ReplaceInput(1, osr_phi);
  
    Node* ret =
        T.graph.NewNode(T.common.Return(), outer_phi, T.start, outer.exit);
    Node* end = T.graph.NewNode(T.common.End(), ret);
    T.graph.SetEnd(end);
  
    T.DeconstructOsr();
  
    // Check structure of deconstructed graph.
    // Check inner OSR loop is directly connected to start.
    CheckInputs(inner.loop, T.start, inner.if_true);
    CheckInputs(osr_phi, T.osr_values[0], T.jsgraph.ZeroConstant(), inner.loop);
  
    // Check control transfer to copy of outer loop.
    Node* new_outer_loop = FindSuccessor(inner.exit, IrOpcode::kLoop);
    Node* new_outer_phi = FindSuccessor(new_outer_loop, IrOpcode::kPhi);
    CHECK_NE(new_outer_loop, outer.loop);
    CHECK_NE(new_outer_phi, outer_phi);
  
    CheckInputs(new_outer_loop, inner.exit, new_outer_loop->InputAt(1));
  
    // Check structure of outer loop.
    Node* new_outer_branch = FindSuccessor(new_outer_loop, IrOpcode::kBranch);
    CHECK_NE(new_outer_branch, outer.branch);
    CheckInputs(new_outer_branch, new_outer_phi, new_outer_loop);
    Node* new_outer_exit = FindSuccessor(new_outer_branch, IrOpcode::kIfFalse);
    Node* new_outer_if_true = FindSuccessor(new_outer_branch, IrOpcode::kIfTrue);
  
    // Check structure of return.
    end = T.graph.end();
    Node* new_ret = end->InputAt(0);
    CHECK_EQ(IrOpcode::kReturn, new_ret->opcode());
    CheckInputs(new_ret, new_outer_phi, T.start, new_outer_exit);
  
    // Check structure of inner loop.
    Node* new_inner_loop = FindSuccessor(new_outer_if_true, IrOpcode::kLoop);
    Node* new_inner_phi = FindSuccessor(new_inner_loop, IrOpcode::kPhi);
  
    CheckInputs(new_inner_phi, T.jsgraph.OneConstant(), T.jsgraph.ZeroConstant(),
                new_inner_loop);
    CheckInputs(new_outer_phi, osr_phi, new_inner_phi, new_outer_loop);
  }
  
  
  TEST(Deconstruct_osr_nested2) {
    OsrDeconstructorTester T(1);
  
    // Test multiple backedge outer loop.
    While outer(T, T.p0, false, 2);
    While inner(T, T.p0, true);
    inner.Nest(outer);
  
    Node* outer_phi = outer.Phi(T.p0, T.p0, T.p0);
    outer.branch->ReplaceInput(0, outer_phi);
  
    Node* osr_phi = inner.Phi(T.jsgraph.OneConstant(), T.osr_values[0],
                              T.jsgraph.ZeroConstant());
    inner.branch->ReplaceInput(0, osr_phi);
    outer_phi->ReplaceInput(1, osr_phi);
    outer_phi->ReplaceInput(2, T.jsgraph.ZeroConstant());
  
    Node* x_branch = T.graph.NewNode(T.common.Branch(), osr_phi, inner.exit);
    Node* x_true = T.graph.NewNode(T.common.IfTrue(), x_branch);
    Node* x_false = T.graph.NewNode(T.common.IfFalse(), x_branch);
  
    outer.loop->ReplaceInput(1, x_true);
    outer.loop->ReplaceInput(2, x_false);
  
    Node* ret =
        T.graph.NewNode(T.common.Return(), outer_phi, T.start, outer.exit);
    Node* end = T.graph.NewNode(T.common.End(), ret);
    T.graph.SetEnd(end);
  
    T.DeconstructOsr();
  
    // Check structure of deconstructed graph.
    // Check inner OSR loop is directly connected to start.
    CheckInputs(inner.loop, T.start, inner.if_true);
    CheckInputs(osr_phi, T.osr_values[0], T.jsgraph.ZeroConstant(), inner.loop);
  
    // Check control transfer to copy of outer loop.
    Node* new_merge = FindSuccessor(x_true, IrOpcode::kMerge);
    CHECK_EQ(new_merge, FindSuccessor(x_false, IrOpcode::kMerge));
    CheckInputs(new_merge, x_true, x_false);
  
    Node* new_outer_loop = FindSuccessor(new_merge, IrOpcode::kLoop);
    Node* new_outer_phi = FindSuccessor(new_outer_loop, IrOpcode::kPhi);
    CHECK_NE(new_outer_loop, outer.loop);
    CHECK_NE(new_outer_phi, outer_phi);
  
    Node* new_entry_phi = FindSuccessor(new_merge, IrOpcode::kPhi);
    CheckInputs(new_entry_phi, osr_phi, T.jsgraph.ZeroConstant(), new_merge);
  
    CHECK_EQ(new_merge, new_outer_loop->InputAt(0));
  
    // Check structure of outer loop.
    Node* new_outer_branch = FindSuccessor(new_outer_loop, IrOpcode::kBranch);
    CHECK_NE(new_outer_branch, outer.branch);
    CheckInputs(new_outer_branch, new_outer_phi, new_outer_loop);
    Node* new_outer_exit = FindSuccessor(new_outer_branch, IrOpcode::kIfFalse);
    Node* new_outer_if_true = FindSuccessor(new_outer_branch, IrOpcode::kIfTrue);
  
    // Check structure of return.
    end = T.graph.end();
    Node* new_ret = end->InputAt(0);
    CHECK_EQ(IrOpcode::kReturn, new_ret->opcode());
    CheckInputs(new_ret, new_outer_phi, T.start, new_outer_exit);
  
    // Check structure of inner loop.
    Node* new_inner_loop = FindSuccessor(new_outer_if_true, IrOpcode::kLoop);
    Node* new_inner_phi = FindSuccessor(new_inner_loop, IrOpcode::kPhi);
  
    CheckInputs(new_inner_phi, T.jsgraph.OneConstant(), T.jsgraph.ZeroConstant(),
                new_inner_loop);
    CheckInputs(new_outer_phi, new_entry_phi, new_inner_phi,
                T.jsgraph.ZeroConstant(), new_outer_loop);
  }
  
  
  Node* MakeCounter(JSGraph* jsgraph, Node* start, Node* loop) {
    int count = loop->InputCount();
    NodeVector tmp_inputs(jsgraph->graph()->zone());
    for (int i = 0; i < count; i++) {
      tmp_inputs.push_back(start);
    }
    tmp_inputs.push_back(loop);
  
    Node* phi = jsgraph->graph()->NewNode(
        jsgraph->common()->Phi(kMachInt32, count), count + 1, &tmp_inputs[0]);
    Node* inc = jsgraph->graph()->NewNode(&kIntAdd, phi, jsgraph->OneConstant());
  
    for (int i = 1; i < count; i++) {
      phi->ReplaceInput(i, inc);
    }
    return phi;
  }
  
  
  TEST(Deconstruct_osr_nested3) {
    OsrDeconstructorTester T(1);
  
    // outermost loop.
    While loop0(T, T.p0, false, 1);
    Node* loop0_cntr = MakeCounter(&T.jsgraph, T.p0, loop0.loop);
    loop0.branch->ReplaceInput(0, loop0_cntr);
  
    // middle loop.
    Node* loop1 = T.graph.NewNode(T.common.Loop(2), loop0.if_true, T.self);
    loop1->ReplaceInput(0, loop0.if_true);
    Node* loop1_phi =
        T.graph.NewNode(T.common.Phi(kMachAnyTagged, 2), loop0_cntr, loop0_cntr);
  
    // innermost (OSR) loop.
    While loop2(T, T.p0, true, 1);
    loop2.loop->ReplaceInput(0, loop1);
  
    Node* loop2_cntr = MakeCounter(&T.jsgraph, loop1_phi, loop2.loop);
    loop2_cntr->ReplaceInput(1, T.osr_values[0]);
    Node* osr_phi = loop2_cntr;
    Node* loop2_inc = loop2_cntr->InputAt(2);
    loop2.branch->ReplaceInput(0, loop2_cntr);
  
    loop1_phi->ReplaceInput(1, loop2_cntr);
    loop0_cntr->ReplaceInput(1, loop2_cntr);
  
    // Branch to either the outer or middle loop.
    Node* branch = T.graph.NewNode(T.common.Branch(), loop2_cntr, loop2.exit);
    Node* if_true = T.graph.NewNode(T.common.IfTrue(), branch);
    Node* if_false = T.graph.NewNode(T.common.IfFalse(), branch);
  
    loop0.loop->ReplaceInput(1, if_true);
    loop1->ReplaceInput(1, if_false);
  
    Node* ret =
        T.graph.NewNode(T.common.Return(), loop0_cntr, T.start, loop0.exit);
    Node* end = T.graph.NewNode(T.common.End(), ret);
    T.graph.SetEnd(end);
  
    T.DeconstructOsr();
  
    // Check structure of deconstructed graph.
    // Check loop2 (OSR loop) is directly connected to start.
    CheckInputs(loop2.loop, T.start, loop2.if_true);
    CheckInputs(osr_phi, T.osr_values[0], loop2_inc, loop2.loop);
    CheckInputs(loop2.branch, osr_phi, loop2.loop);
    CheckInputs(loop2.if_true, loop2.branch);
    CheckInputs(loop2.exit, loop2.branch);
    CheckInputs(branch, osr_phi, loop2.exit);
    CheckInputs(if_true, branch);
    CheckInputs(if_false, branch);
  
    // Check structure of new_loop1.
    Node* new_loop1_loop = FindSuccessor(if_false, IrOpcode::kLoop);
    // TODO(titzer): check the internal copy of loop2.
    USE(new_loop1_loop);
  
    // Check structure of new_loop0.
    Node* new_loop0_loop_entry = FindSuccessor(if_true, IrOpcode::kMerge);
    Node* new_loop0_loop = FindSuccessor(new_loop0_loop_entry, IrOpcode::kLoop);
    // TODO(titzer): check the internal copies of loop1 and loop2.
  
    Node* new_loop0_branch = FindSuccessor(new_loop0_loop, IrOpcode::kBranch);
    Node* new_loop0_if_true = FindSuccessor(new_loop0_branch, IrOpcode::kIfTrue);
    Node* new_loop0_exit = FindSuccessor(new_loop0_branch, IrOpcode::kIfFalse);
  
    USE(new_loop0_if_true);
  
    Node* new_ret = T.graph.end()->InputAt(0);
    CHECK_EQ(IrOpcode::kReturn, new_ret->opcode());
  
    Node* new_loop0_phi = new_ret->InputAt(0);
    CHECK_EQ(IrOpcode::kPhi, new_loop0_phi->opcode());
    CHECK_EQ(new_loop0_loop, NodeProperties::GetControlInput(new_loop0_phi));
    CHECK_EQ(new_loop0_phi, FindSuccessor(new_loop0_loop, IrOpcode::kPhi));
  
    // Check that the return returns the phi from the OSR loop and control
    // depends on the copy of the outer loop0.
    CheckInputs(new_ret, new_loop0_phi, T.graph.start(), new_loop0_exit);
  }
  