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v8/test/unittests/compiler/dead-code-elimination-unittest.cc
bmeurer 733a246386 [turbofan] Proper dead code elimination as regular reducer. 
The three different concerns that the ControlReducer used to deal with
are now properly separated into

  a.) DeadCodeElimination, which is a regular AdvancedReducer, that
      propagates Dead via control edges,
  b.) CommonOperatorReducer, which does strength reduction on common
      operators (i.e. Branch, Phi, and friends), and
  c.) GraphTrimming, which removes dead->live edges from the graph.

This will make it possible to run the DeadCodeElimination together with
other passes that actually introduce Dead nodes, i.e. typed lowering;
and it opens the door for general inlining without two stage fix point
iteration.

To make the DeadCodeElimination easier and more uniform, we basically
reverted the introduction of DeadValue and DeadEffect, and changed the
Dead operator to produce control, value and effect. Note however that
this is not a requirement, but merely a way to make dead propagation
easier and more uniform. We could always go back and decide to have
different Dead operators if some other change requires that.

Note that there are several additional opportunities for cleanup now,
i.e. OSR deconstruction could be a regular reducer now, and we don't
need to use TheHole as dead value marker in the GraphReducer. And we can
actually run the dead code elimination together with the other passes
instead of using separate passes over the graph.  We will do this in
follow up CLs.

R=jarin@chromium.org, mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/1193833002

Cr-Commit-Position: refs/heads/master@{#29146}
2015-06-19 12:07:26 +00:00

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// 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/common-operator.h"
#include "src/compiler/dead-code-elimination.h"
#include "test/unittests/compiler/graph-reducer-unittest.h"
#include "test/unittests/compiler/graph-unittest.h"
#include "test/unittests/compiler/node-test-utils.h"
#include "testing/gmock-support.h"
using testing::StrictMock;
namespace v8 {
namespace internal {
namespace compiler {
class DeadCodeEliminationTest : public GraphTest {
public:
explicit DeadCodeEliminationTest(int num_parameters = 4)
: GraphTest(num_parameters) {}
~DeadCodeEliminationTest() override {}
protected:
Reduction Reduce(AdvancedReducer::Editor* editor, Node* node) {
DeadCodeElimination reducer(editor, graph(), common());
return reducer.Reduce(node);
}
Reduction Reduce(Node* node) {
StrictMock<MockAdvancedReducerEditor> editor;
return Reduce(&editor, node);
}
};
namespace {
const MachineType kMachineTypes[] = {
kMachFloat32, kMachFloat64, kMachInt8, kMachUint8, kMachInt16,
kMachUint16, kMachInt32, kMachUint32, kMachInt64, kMachUint64,
kMachPtr, kMachAnyTagged, kRepBit, kRepWord8, kRepWord16,
kRepWord32, kRepWord64, kRepFloat32, kRepFloat64, kRepTagged};
const int kMaxInputs = 16;
const Operator kOp0(0, Operator::kNoProperties, "Op0", 1, 1, 1, 1, 1, 1);
} // namespace
// -----------------------------------------------------------------------------
// General dead propagation
TEST_F(DeadCodeEliminationTest, GeneralDeadPropagation) {
Node* const value = Parameter(0);
Node* const effect = graph()->start();
Node* const dead = graph()->NewNode(common()->Dead());
Node* const node = graph()->NewNode(&kOp0, value, effect, dead);
Reduction const r = Reduce(node);
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
// -----------------------------------------------------------------------------
// Branch
TEST_F(DeadCodeEliminationTest, BranchWithDeadControlInput) {
BranchHint const kHints[] = {BranchHint::kNone, BranchHint::kTrue,
BranchHint::kFalse};
TRACED_FOREACH(BranchHint, hint, kHints) {
Reduction const r =
Reduce(graph()->NewNode(common()->Branch(hint), Parameter(0),
graph()->NewNode(common()->Dead())));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
}
// -----------------------------------------------------------------------------
// IfTrue
TEST_F(DeadCodeEliminationTest, IfTrueWithDeadInput) {
Reduction const r = Reduce(
graph()->NewNode(common()->IfTrue(), graph()->NewNode(common()->Dead())));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
// -----------------------------------------------------------------------------
// IfFalse
TEST_F(DeadCodeEliminationTest, IfFalseWithDeadInput) {
Reduction const r = Reduce(graph()->NewNode(
common()->IfFalse(), graph()->NewNode(common()->Dead())));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
// -----------------------------------------------------------------------------
// IfSuccess
TEST_F(DeadCodeEliminationTest, IfSuccessWithDeadInput) {
Reduction const r = Reduce(graph()->NewNode(
common()->IfSuccess(), graph()->NewNode(common()->Dead())));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
// -----------------------------------------------------------------------------
// IfException
TEST_F(DeadCodeEliminationTest, IfExceptionWithDeadControlInput) {
IfExceptionHint const kHints[] = {IfExceptionHint::kLocallyCaught,
IfExceptionHint::kLocallyUncaught};
TRACED_FOREACH(IfExceptionHint, hint, kHints) {
Reduction const r =
Reduce(graph()->NewNode(common()->IfException(hint), graph()->start(),
graph()->NewNode(common()->Dead())));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
}
// -----------------------------------------------------------------------------
// End
TEST_F(DeadCodeEliminationTest, EndWithDeadAndStart) {
Node* const dead = graph()->NewNode(common()->Dead());
Node* const start = graph()->start();
Reduction const r = Reduce(graph()->NewNode(common()->End(2), dead, start));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsEnd(start));
}
TEST_F(DeadCodeEliminationTest, EndWithOnlyDeadInputs) {
Node* inputs[kMaxInputs];
TRACED_FORRANGE(int, input_count, 1, kMaxInputs - 1) {
for (int i = 0; i < input_count; ++i) {
inputs[i] = graph()->NewNode(common()->Dead());
}
Reduction const r = Reduce(
graph()->NewNode(common()->End(input_count), input_count, inputs));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
}
// -----------------------------------------------------------------------------
// Merge
TEST_F(DeadCodeEliminationTest, MergeWithOnlyDeadInputs) {
Node* inputs[kMaxInputs + 1];
TRACED_FORRANGE(int, input_count, 1, kMaxInputs - 1) {
for (int i = 0; i < input_count; ++i) {
inputs[i] = graph()->NewNode(common()->Dead());
}
Reduction const r = Reduce(
graph()->NewNode(common()->Merge(input_count), input_count, inputs));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
}
TEST_F(DeadCodeEliminationTest, MergeWithOneLiveAndOneDeadInput) {
Node* const v0 = Parameter(0);
Node* const v1 = Parameter(1);
Node* const c0 =
graph()->NewNode(&kOp0, v0, graph()->start(), graph()->start());
Node* const c1 = graph()->NewNode(common()->Dead());
Node* const e0 = graph()->NewNode(&kOp0, v0, graph()->start(), c0);
Node* const e1 = graph()->NewNode(&kOp0, v1, graph()->start(), c1);
Node* const merge = graph()->NewNode(common()->Merge(2), c0, c1);
Node* const phi =
graph()->NewNode(common()->Phi(kMachAnyTagged, 2), v0, v1, merge);
Node* const ephi = graph()->NewNode(common()->EffectPhi(2), e0, e1, merge);
StrictMock<MockAdvancedReducerEditor> editor;
EXPECT_CALL(editor, Replace(phi, v0));
EXPECT_CALL(editor, Replace(ephi, e0));
Reduction const r = Reduce(&editor, merge);
ASSERT_TRUE(r.Changed());
EXPECT_EQ(c0, r.replacement());
}
TEST_F(DeadCodeEliminationTest, MergeWithTwoLiveAndTwoDeadInputs) {
Node* const v0 = Parameter(0);
Node* const v1 = Parameter(1);
Node* const v2 = Parameter(2);
Node* const v3 = Parameter(3);
Node* const c0 =
graph()->NewNode(&kOp0, v0, graph()->start(), graph()->start());
Node* const c1 = graph()->NewNode(common()->Dead());
Node* const c2 = graph()->NewNode(common()->Dead());
Node* const c3 = graph()->NewNode(&kOp0, v3, graph()->start(), c0);
Node* const e0 = graph()->start();
Node* const e1 = graph()->NewNode(&kOp0, v1, e0, c0);
Node* const e2 = graph()->NewNode(&kOp0, v2, e1, c0);
Node* const e3 = graph()->NewNode(&kOp0, v3, graph()->start(), c3);
Node* const merge = graph()->NewNode(common()->Merge(4), c0, c1, c2, c3);
Node* const phi =
graph()->NewNode(common()->Phi(kMachAnyTagged, 4), v0, v1, v2, v3, merge);
Node* const ephi =
graph()->NewNode(common()->EffectPhi(4), e0, e1, e2, e3, merge);
StrictMock<MockAdvancedReducerEditor> editor;
EXPECT_CALL(editor, Revisit(phi));
EXPECT_CALL(editor, Revisit(ephi));
Reduction const r = Reduce(&editor, merge);
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsMerge(c0, c3));
EXPECT_THAT(phi, IsPhi(kMachAnyTagged, v0, v3, r.replacement()));
EXPECT_THAT(ephi, IsEffectPhi(e0, e3, r.replacement()));
}
// -----------------------------------------------------------------------------
// Loop
TEST_F(DeadCodeEliminationTest, LoopWithDeadFirstInput) {
Node* inputs[kMaxInputs + 1];
TRACED_FORRANGE(int, input_count, 1, kMaxInputs - 1) {
inputs[0] = graph()->NewNode(common()->Dead());
for (int i = 1; i < input_count; ++i) {
inputs[i] = graph()->start();
}
Reduction const r = Reduce(
graph()->NewNode(common()->Loop(input_count), input_count, inputs));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
}
TEST_F(DeadCodeEliminationTest, LoopWithOnlyDeadInputs) {
Node* inputs[kMaxInputs + 1];
TRACED_FORRANGE(int, input_count, 1, kMaxInputs - 1) {
for (int i = 0; i < input_count; ++i) {
inputs[i] = graph()->NewNode(common()->Dead());
}
Reduction const r = Reduce(
graph()->NewNode(common()->Loop(input_count), input_count, inputs));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
}
TEST_F(DeadCodeEliminationTest, LoopWithOneLiveAndOneDeadInput) {
Node* const v0 = Parameter(0);
Node* const v1 = Parameter(1);
Node* const c0 =
graph()->NewNode(&kOp0, v0, graph()->start(), graph()->start());
Node* const c1 = graph()->NewNode(common()->Dead());
Node* const e0 = graph()->NewNode(&kOp0, v0, graph()->start(), c0);
Node* const e1 = graph()->NewNode(&kOp0, v1, graph()->start(), c1);
Node* const loop = graph()->NewNode(common()->Loop(2), c0, c1);
Node* const phi =
graph()->NewNode(common()->Phi(kMachAnyTagged, 2), v0, v1, loop);
Node* const ephi = graph()->NewNode(common()->EffectPhi(2), e0, e1, loop);
Node* const terminate = graph()->NewNode(common()->Terminate(), ephi, loop);
StrictMock<MockAdvancedReducerEditor> editor;
EXPECT_CALL(editor, Replace(phi, v0));
EXPECT_CALL(editor, Replace(ephi, e0));
EXPECT_CALL(editor, Replace(terminate, IsDead()));
Reduction const r = Reduce(&editor, loop);
ASSERT_TRUE(r.Changed());
EXPECT_EQ(c0, r.replacement());
}
TEST_F(DeadCodeEliminationTest, LoopWithTwoLiveAndTwoDeadInputs) {
Node* const v0 = Parameter(0);
Node* const v1 = Parameter(1);
Node* const v2 = Parameter(2);
Node* const v3 = Parameter(3);
Node* const c0 =
graph()->NewNode(&kOp0, v0, graph()->start(), graph()->start());
Node* const c1 = graph()->NewNode(common()->Dead());
Node* const c2 = graph()->NewNode(common()->Dead());
Node* const c3 = graph()->NewNode(&kOp0, v3, graph()->start(), c0);
Node* const e0 = graph()->start();
Node* const e1 = graph()->NewNode(&kOp0, v1, e0, c0);
Node* const e2 = graph()->NewNode(&kOp0, v2, e1, c0);
Node* const e3 = graph()->NewNode(&kOp0, v3, graph()->start(), c3);
Node* const loop = graph()->NewNode(common()->Loop(4), c0, c1, c2, c3);
Node* const phi =
graph()->NewNode(common()->Phi(kMachAnyTagged, 4), v0, v1, v2, v3, loop);
Node* const ephi =
graph()->NewNode(common()->EffectPhi(4), e0, e1, e2, e3, loop);
StrictMock<MockAdvancedReducerEditor> editor;
EXPECT_CALL(editor, Revisit(phi));
EXPECT_CALL(editor, Revisit(ephi));
Reduction const r = Reduce(&editor, loop);
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsLoop(c0, c3));
EXPECT_THAT(phi, IsPhi(kMachAnyTagged, v0, v3, r.replacement()));
EXPECT_THAT(ephi, IsEffectPhi(e0, e3, r.replacement()));
}
// -----------------------------------------------------------------------------
// Phi
TEST_F(DeadCodeEliminationTest, PhiWithDeadControlInput) {
Node* inputs[kMaxInputs + 1];
TRACED_FOREACH(MachineType, type, kMachineTypes) {
TRACED_FORRANGE(int, input_count, 1, kMaxInputs) {
for (int i = 0; i < input_count; ++i) {
inputs[i] = Parameter(i);
}
inputs[input_count] = graph()->NewNode(common()->Dead());
Reduction const r = Reduce(graph()->NewNode(
common()->Phi(type, input_count), input_count + 1, inputs));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
}
}
// -----------------------------------------------------------------------------
// EffectPhi
TEST_F(DeadCodeEliminationTest, EffectPhiWithDeadControlInput) {
Node* inputs[kMaxInputs + 1];
TRACED_FORRANGE(int, input_count, 1, kMaxInputs) {
for (int i = 0; i < input_count; ++i) {
inputs[i] = graph()->start();
}
inputs[input_count] = graph()->NewNode(common()->Dead());
Reduction const r = Reduce(graph()->NewNode(
common()->EffectPhi(input_count), input_count + 1, inputs));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
}
// -----------------------------------------------------------------------------
// Terminate
TEST_F(DeadCodeEliminationTest, TerminateWithDeadControlInput) {
Reduction const r =
Reduce(graph()->NewNode(common()->Terminate(), graph()->start(),
graph()->NewNode(common()->Dead())));
ASSERT_TRUE(r.Changed());
EXPECT_THAT(r.replacement(), IsDead());
}
} // namespace compiler
} // namespace internal
} // namespace v8
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