[turbofan] First version of loop peeling.

test/unittests/compiler/loop-peeling-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/access-builder.h"
+#include "src/compiler/graph.h"
+#include "src/compiler/graph-visualizer.h"
+#include "src/compiler/js-graph.h"
+#include "src/compiler/loop-peeling.h"
+#include "src/compiler/machine-operator.h"
+#include "src/compiler/node.h"
+#include "src/compiler/node-properties-inl.h"
+#include "test/unittests/compiler/compiler-test-utils.h"
+#include "test/unittests/compiler/graph-unittest.h"
+#include "test/unittests/compiler/node-test-utils.h"
+#include "testing/gmock-support.h"
+
+using testing::AllOf;
+using testing::BitEq;
+using testing::Capture;
+using testing::CaptureEq;
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+struct While {
+  Node* loop;
+  Node* branch;
+  Node* if_true;
+  Node* exit;
+};
+
+
+// A helper for building branches.
+struct Branch {
+  Node* branch;
+  Node* if_true;
+  Node* if_false;
+};
+
+
+// A helper for building counters attached to loops.
+struct Counter {
+  Node* base;
+  Node* inc;
+  Node* phi;
+  Node* add;
+};
+
+
+class LoopPeelingTest : public GraphTest {
+ public:
+  LoopPeelingTest() : GraphTest(1), machine_(zone()) {}
+  ~LoopPeelingTest() OVERRIDE {}
+
+ protected:
+  MachineOperatorBuilder machine_;
+
+  MachineOperatorBuilder* machine() { return &machine_; }
+
+  LoopTree* GetLoopTree() {
+    if (FLAG_trace_turbo_graph) {
+      OFStream os(stdout);
+      os << AsRPO(*graph());
+    }
+    Zone zone(isolate());
+    return LoopFinder::BuildLoopTree(graph(), &zone);
+  }
+
+
+  PeeledIteration* PeelOne() {
+    LoopTree* loop_tree = GetLoopTree();
+    return Peel(loop_tree, loop_tree->outer_loops()[0]);
+  }
+
+  PeeledIteration* Peel(LoopTree* loop_tree, LoopTree::Loop* loop) {
+    PeeledIteration* peeled =
+        LoopPeeler::Peel(graph(), common(), loop_tree, loop, zone());
+    if (FLAG_trace_turbo_graph) {
+      OFStream os(stdout);
+      os << AsRPO(*graph());
+    }
+    return peeled;
+  }
+
+  Node* InsertReturn(Node* val, Node* effect, Node* control) {
+    Node* r = graph()->NewNode(common()->Return(), val, effect, control);
+    graph()->SetEnd(r);
+    return r;
+  }
+
+  Node* ExpectPeeled(Node* node, PeeledIteration* iter) {
+    Node* p = iter->map(node);
+    EXPECT_NE(node, p);
+    return p;
+  }
+
+  void ExpectNotPeeled(Node* node, PeeledIteration* iter) {
+    EXPECT_EQ(node, iter->map(node));
+  }
+
+  While NewWhile(Node* cond, Node* control = nullptr) {
+    if (control == nullptr) control = start();
+    Node* loop = graph()->NewNode(common()->Loop(2), control, control);
+    Node* branch = graph()->NewNode(common()->Branch(), cond, loop);
+    Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
+    Node* exit = graph()->NewNode(common()->IfFalse(), branch);
+    loop->ReplaceInput(1, if_true);
+    return {loop, branch, if_true, exit};
+  }
+
+  void Chain(While* a, Node* control) { a->loop->ReplaceInput(0, control); }
+  void Nest(While* a, While* b) {
+    b->loop->ReplaceInput(1, a->exit);
+    a->loop->ReplaceInput(0, b->if_true);
+  }
+  Node* NewPhi(While* w, Node* a, Node* b) {
+    return graph()->NewNode(common()->Phi(kMachAnyTagged, 2), a, b, w->loop);
+  }
+
+  Branch NewBranch(Node* cond, Node* control = nullptr) {
+    if (control == nullptr) control = start();
+    Node* branch = graph()->NewNode(common()->Branch(), cond, control);
+    Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
+    Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
+    return {branch, if_true, if_false};
+  }
+
+  Counter NewCounter(While* w, int32_t b, int32_t k) {
+    Node* base = Int32Constant(b);
+    Node* inc = Int32Constant(k);
+    Node* phi =
+        graph()->NewNode(common()->Phi(kMachAnyTagged, 2), base, base, w->loop);
+    Node* add = graph()->NewNode(machine()->Int32Add(), phi, inc);
+    phi->ReplaceInput(1, add);
+    return {base, inc, phi, add};
+  }
+};
+
+
+TEST_F(LoopPeelingTest, SimpleLoop) {
+  Node* p0 = Parameter(0);
+  While w = NewWhile(p0);
+  Node* r = InsertReturn(p0, start(), w.exit);
+
+  PeeledIteration* peeled = PeelOne();
+
+  Node* br1 = ExpectPeeled(w.branch, peeled);
+  Node* if_true1 = ExpectPeeled(w.if_true, peeled);
+  Node* if_false1 = ExpectPeeled(w.exit, peeled);
+
+  EXPECT_THAT(br1, IsBranch(p0, start()));
+  EXPECT_THAT(if_true1, IsIfTrue(br1));
+  EXPECT_THAT(if_false1, IsIfFalse(br1));
+
+  EXPECT_THAT(w.loop, IsLoop(if_true1, w.if_true));
+  EXPECT_THAT(r, IsReturn(p0, start(), IsMerge(w.exit, if_false1)));
+}
+
+
+TEST_F(LoopPeelingTest, SimpleLoopWithCounter) {
+  Node* p0 = Parameter(0);
+  While w = NewWhile(p0);
+  Counter c = NewCounter(&w, 0, 1);
+  Node* r = InsertReturn(c.phi, start(), w.exit);
+
+  PeeledIteration* peeled = PeelOne();
+
+  Node* br1 = ExpectPeeled(w.branch, peeled);
+  Node* if_true1 = ExpectPeeled(w.if_true, peeled);
+  Node* if_false1 = ExpectPeeled(w.exit, peeled);
+
+  EXPECT_THAT(br1, IsBranch(p0, start()));
+  EXPECT_THAT(if_true1, IsIfTrue(br1));
+  EXPECT_THAT(if_false1, IsIfFalse(br1));
+  EXPECT_THAT(w.loop, IsLoop(if_true1, w.if_true));
+
+  EXPECT_THAT(peeled->map(c.add), IsInt32Add(c.base, c.inc));
+
+  Capture<Node*> merge;
+  EXPECT_THAT(
+      r, IsReturn(IsPhi(kMachAnyTagged, c.phi, c.base,
+                        AllOf(CaptureEq(&merge), IsMerge(w.exit, if_false1))),
+                  start(), CaptureEq(&merge)));
+}
+
+
+TEST_F(LoopPeelingTest, SimpleNestedLoopWithCounter_peel_outer) {
+  Node* p0 = Parameter(0);
+  While outer = NewWhile(p0);
+  While inner = NewWhile(p0);
+  Nest(&inner, &outer);
+
+  Counter c = NewCounter(&outer, 0, 1);
+  Node* r = InsertReturn(c.phi, start(), outer.exit);
+
+  PeeledIteration* peeled = PeelOne();
+
+  Node* bro = ExpectPeeled(outer.branch, peeled);
+  Node* if_trueo = ExpectPeeled(outer.if_true, peeled);
+  Node* if_falseo = ExpectPeeled(outer.exit, peeled);
+
+  EXPECT_THAT(bro, IsBranch(p0, start()));
+  EXPECT_THAT(if_trueo, IsIfTrue(bro));
+  EXPECT_THAT(if_falseo, IsIfFalse(bro));
+
+  Node* bri = ExpectPeeled(inner.branch, peeled);
+  Node* if_truei = ExpectPeeled(inner.if_true, peeled);
+  Node* if_falsei = ExpectPeeled(inner.exit, peeled);
+
+  EXPECT_THAT(bri, IsBranch(p0, ExpectPeeled(inner.loop, peeled)));
+  EXPECT_THAT(if_truei, IsIfTrue(bri));
+  EXPECT_THAT(if_falsei, IsIfFalse(bri));
+
+  EXPECT_THAT(outer.loop, IsLoop(if_falsei, inner.exit));
+  EXPECT_THAT(peeled->map(c.add), IsInt32Add(c.base, c.inc));
+
+  Capture<Node*> merge;
+  EXPECT_THAT(
+      r,
+      IsReturn(IsPhi(kMachAnyTagged, c.phi, c.base,
+                     AllOf(CaptureEq(&merge), IsMerge(outer.exit, if_falseo))),
+               start(), CaptureEq(&merge)));
+}
+
+
+TEST_F(LoopPeelingTest, SimpleNestedLoopWithCounter_peel_inner) {
+  Node* p0 = Parameter(0);
+  While outer = NewWhile(p0);
+  While inner = NewWhile(p0);
+  Nest(&inner, &outer);
+
+  Counter c = NewCounter(&outer, 0, 1);
+  Node* r = InsertReturn(c.phi, start(), outer.exit);
+
+  LoopTree* loop_tree = GetLoopTree();
+  LoopTree::Loop* loop = loop_tree->ContainingLoop(inner.loop);
+  EXPECT_NE(nullptr, loop);
+  EXPECT_EQ(1u, loop->depth());
+
+  PeeledIteration* peeled = Peel(loop_tree, loop);
+
+  ExpectNotPeeled(outer.loop, peeled);
+  ExpectNotPeeled(outer.branch, peeled);
+  ExpectNotPeeled(outer.if_true, peeled);
+  ExpectNotPeeled(outer.exit, peeled);
+
+  Node* bri = ExpectPeeled(inner.branch, peeled);
+  Node* if_truei = ExpectPeeled(inner.if_true, peeled);
+  Node* if_falsei = ExpectPeeled(inner.exit, peeled);
+
+  EXPECT_THAT(bri, IsBranch(p0, ExpectPeeled(inner.loop, peeled)));
+  EXPECT_THAT(if_truei, IsIfTrue(bri));
+  EXPECT_THAT(if_falsei, IsIfFalse(bri));
+
+  EXPECT_THAT(outer.loop, IsLoop(start(), IsMerge(inner.exit, if_falsei)));
+  ExpectNotPeeled(c.add, peeled);
+
+  EXPECT_THAT(r, IsReturn(c.phi, start(), outer.exit));
+}
+
+
+TEST_F(LoopPeelingTest, SimpleInnerCounter_peel_inner) {
+  Node* p0 = Parameter(0);
+  While outer = NewWhile(p0);
+  While inner = NewWhile(p0);
+  Nest(&inner, &outer);
+  Counter c = NewCounter(&inner, 0, 1);
+  Node* phi = NewPhi(&outer, Int32Constant(11), c.phi);
+
+  Node* r = InsertReturn(phi, start(), outer.exit);
+
+  LoopTree* loop_tree = GetLoopTree();
+  LoopTree::Loop* loop = loop_tree->ContainingLoop(inner.loop);
+  EXPECT_NE(nullptr, loop);
+  EXPECT_EQ(1u, loop->depth());
+
+  PeeledIteration* peeled = Peel(loop_tree, loop);
+
+  ExpectNotPeeled(outer.loop, peeled);
+  ExpectNotPeeled(outer.branch, peeled);
+  ExpectNotPeeled(outer.if_true, peeled);
+  ExpectNotPeeled(outer.exit, peeled);
+
+  Node* bri = ExpectPeeled(inner.branch, peeled);
+  Node* if_truei = ExpectPeeled(inner.if_true, peeled);
+  Node* if_falsei = ExpectPeeled(inner.exit, peeled);
+
+  EXPECT_THAT(bri, IsBranch(p0, ExpectPeeled(inner.loop, peeled)));
+  EXPECT_THAT(if_truei, IsIfTrue(bri));
+  EXPECT_THAT(if_falsei, IsIfFalse(bri));
+
+  EXPECT_THAT(outer.loop, IsLoop(start(), IsMerge(inner.exit, if_falsei)));
+  EXPECT_THAT(peeled->map(c.add), IsInt32Add(c.base, c.inc));
+
+  Node* back = phi->InputAt(1);
+  EXPECT_THAT(back, IsPhi(kMachAnyTagged, c.phi, c.base,
+                          IsMerge(inner.exit, if_falsei)));
+
+  EXPECT_THAT(phi,
+              IsPhi(kMachAnyTagged, IsInt32Constant(11), back, outer.loop));
+
+  EXPECT_THAT(r, IsReturn(phi, start(), outer.exit));
+}
+
+
+TEST_F(LoopPeelingTest, TwoBackedgeLoop) {
+  Node* p0 = Parameter(0);
+  Node* loop = graph()->NewNode(common()->Loop(3), start(), start(), start());
+  Branch b1 = NewBranch(p0, loop);
+  Branch b2 = NewBranch(p0, b1.if_true);
+
+  loop->ReplaceInput(1, b2.if_true);
+  loop->ReplaceInput(2, b2.if_false);
+
+  Node* r = InsertReturn(p0, start(), b1.if_false);
+
+  PeeledIteration* peeled = PeelOne();
+
+  Node* b1b = ExpectPeeled(b1.branch, peeled);
+  Node* b1t = ExpectPeeled(b1.if_true, peeled);
+  Node* b1f = ExpectPeeled(b1.if_false, peeled);
+
+  EXPECT_THAT(b1b, IsBranch(p0, start()));
+  EXPECT_THAT(ExpectPeeled(b1.if_true, peeled), IsIfTrue(b1b));
+  EXPECT_THAT(b1f, IsIfFalse(b1b));
+
+  Node* b2b = ExpectPeeled(b2.branch, peeled);
+  Node* b2t = ExpectPeeled(b2.if_true, peeled);
+  Node* b2f = ExpectPeeled(b2.if_false, peeled);
+
+  EXPECT_THAT(b2b, IsBranch(p0, b1t));
+  EXPECT_THAT(b2t, IsIfTrue(b2b));
+  EXPECT_THAT(b2f, IsIfFalse(b2b));
+
+  EXPECT_THAT(loop, IsLoop(IsMerge(b2t, b2f), b2.if_true, b2.if_false));
+  EXPECT_THAT(r, IsReturn(p0, start(), IsMerge(b1.if_false, b1f)));
+}
+
+
+TEST_F(LoopPeelingTest, TwoBackedgeLoopWithPhi) {
+  Node* p0 = Parameter(0);
+  Node* loop = graph()->NewNode(common()->Loop(3), start(), start(), start());
+  Branch b1 = NewBranch(p0, loop);
+  Branch b2 = NewBranch(p0, b1.if_true);
+  Node* phi =
+      graph()->NewNode(common()->Phi(kMachAnyTagged, 3), Int32Constant(0),
+                       Int32Constant(1), Int32Constant(2), loop);
+
+  loop->ReplaceInput(1, b2.if_true);
+  loop->ReplaceInput(2, b2.if_false);
+
+  Node* r = InsertReturn(phi, start(), b1.if_false);
+
+  PeeledIteration* peeled = PeelOne();
+
+  Node* b1b = ExpectPeeled(b1.branch, peeled);
+  Node* b1t = ExpectPeeled(b1.if_true, peeled);
+  Node* b1f = ExpectPeeled(b1.if_false, peeled);
+
+  EXPECT_THAT(b1b, IsBranch(p0, start()));
+  EXPECT_THAT(ExpectPeeled(b1.if_true, peeled), IsIfTrue(b1b));
+  EXPECT_THAT(b1f, IsIfFalse(b1b));
+
+  Node* b2b = ExpectPeeled(b2.branch, peeled);
+  Node* b2t = ExpectPeeled(b2.if_true, peeled);
+  Node* b2f = ExpectPeeled(b2.if_false, peeled);
+
+  EXPECT_THAT(b2b, IsBranch(p0, b1t));
+  EXPECT_THAT(b2t, IsIfTrue(b2b));
+  EXPECT_THAT(b2f, IsIfFalse(b2b));
+
+  EXPECT_THAT(loop, IsLoop(IsMerge(b2t, b2f), b2.if_true, b2.if_false));
+
+  EXPECT_THAT(
+      phi, IsPhi(kMachAnyTagged, IsPhi(kMachAnyTagged, IsInt32Constant(1),
+                                       IsInt32Constant(2), IsMerge(b2t, b2f)),
+                 IsInt32Constant(1), IsInt32Constant(2), loop));
+
+  Capture<Node*> merge;
+  EXPECT_THAT(
+      r, IsReturn(IsPhi(kMachAnyTagged, phi, IsInt32Constant(0),
+                        AllOf(CaptureEq(&merge), IsMerge(b1.if_false, b1f))),
+                  start(), CaptureEq(&merge)));
+}
+
+
+TEST_F(LoopPeelingTest, TwoBackedgeLoopWithCounter) {
+  Node* p0 = Parameter(0);
+  Node* loop = graph()->NewNode(common()->Loop(3), start(), start(), start());
+  Branch b1 = NewBranch(p0, loop);
+  Branch b2 = NewBranch(p0, b1.if_true);
+  Node* phi =
+      graph()->NewNode(common()->Phi(kMachAnyTagged, 3), Int32Constant(0),
+                       Int32Constant(1), Int32Constant(2), loop);
+
+  phi->ReplaceInput(
+      1, graph()->NewNode(machine()->Int32Add(), phi, Int32Constant(1)));
+  phi->ReplaceInput(
+      2, graph()->NewNode(machine()->Int32Add(), phi, Int32Constant(2)));
+
+  loop->ReplaceInput(1, b2.if_true);
+  loop->ReplaceInput(2, b2.if_false);
+
+  Node* r = InsertReturn(phi, start(), b1.if_false);
+
+  PeeledIteration* peeled = PeelOne();
+
+  Node* b1b = ExpectPeeled(b1.branch, peeled);
+  Node* b1t = ExpectPeeled(b1.if_true, peeled);
+  Node* b1f = ExpectPeeled(b1.if_false, peeled);
+
+  EXPECT_THAT(b1b, IsBranch(p0, start()));
+  EXPECT_THAT(ExpectPeeled(b1.if_true, peeled), IsIfTrue(b1b));
+  EXPECT_THAT(b1f, IsIfFalse(b1b));
+
+  Node* b2b = ExpectPeeled(b2.branch, peeled);
+  Node* b2t = ExpectPeeled(b2.if_true, peeled);
+  Node* b2f = ExpectPeeled(b2.if_false, peeled);
+
+  EXPECT_THAT(b2b, IsBranch(p0, b1t));
+  EXPECT_THAT(b2t, IsIfTrue(b2b));
+  EXPECT_THAT(b2f, IsIfFalse(b2b));
+
+  Capture<Node*> entry;
+  EXPECT_THAT(loop, IsLoop(AllOf(CaptureEq(&entry), IsMerge(b2t, b2f)),
+                           b2.if_true, b2.if_false));
+
+  Node* eval = phi->InputAt(0);
+
+  EXPECT_THAT(eval, IsPhi(kMachAnyTagged,
+                          IsInt32Add(IsInt32Constant(0), IsInt32Constant(1)),
+                          IsInt32Add(IsInt32Constant(0), IsInt32Constant(2)),
+                          CaptureEq(&entry)));
+
+  EXPECT_THAT(phi,
+              IsPhi(kMachAnyTagged, eval, IsInt32Add(phi, IsInt32Constant(1)),
+                    IsInt32Add(phi, IsInt32Constant(2)), loop));
+
+  Capture<Node*> merge;
+  EXPECT_THAT(
+      r, IsReturn(IsPhi(kMachAnyTagged, phi, IsInt32Constant(0),
+                        AllOf(CaptureEq(&merge), IsMerge(b1.if_false, b1f))),
+                  start(), CaptureEq(&merge)));
+}
+
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8