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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/branch-elimination.h"
#include "src/codegen/tick-counter.h"
#include "src/compiler/js-graph.h"
#include "src/compiler/linkage.h"
#include "src/compiler/node-properties.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"
namespace v8 {
namespace internal {
namespace compiler {
class BranchEliminationTest : public GraphTest {
public:
BranchEliminationTest()
: machine_(zone(), MachineType::PointerRepresentation(),
MachineOperatorBuilder::kNoFlags) {}
MachineOperatorBuilder* machine() { return &machine_; }
void Reduce() {
JSOperatorBuilder javascript(zone());
JSGraph jsgraph(isolate(), graph(), common(), &javascript, nullptr,
machine());
GraphReducer graph_reducer(zone(), graph(), tick_counter(), broker(),
jsgraph.Dead());
BranchElimination branch_condition_elimination(&graph_reducer, &jsgraph,
zone());
graph_reducer.AddReducer(&branch_condition_elimination);
graph_reducer.ReduceGraph();
}
private:
MachineOperatorBuilder machine_;
};
TEST_F(BranchEliminationTest, NestedBranchSameTrue) {
// { return (x ? (x ? 1 : 2) : 3; }
// should be reduced to
// { return (x ? 1 : 3; }
Node* condition = Parameter(0);
Node* outer_branch =
graph()->NewNode(common()->Branch(), condition, graph()->start());
Node* outer_if_true = graph()->NewNode(common()->IfTrue(), outer_branch);
Node* inner_branch =
graph()->NewNode(common()->Branch(), condition, outer_if_true);
Node* inner_if_true = graph()->NewNode(common()->IfTrue(), inner_branch);
Node* inner_if_false = graph()->NewNode(common()->IfFalse(), inner_branch);
Node* inner_merge =
graph()->NewNode(common()->Merge(2), inner_if_true, inner_if_false);
Node* inner_phi =
graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
Int32Constant(1), Int32Constant(2), inner_merge);
Node* outer_if_false = graph()->NewNode(common()->IfFalse(), outer_branch);
Node* outer_merge =
graph()->NewNode(common()->Merge(2), inner_merge, outer_if_false);
Node* outer_phi =
graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
inner_phi, Int32Constant(3), outer_merge);
Node* zero = graph()->NewNode(common()->Int32Constant(0));
Node* ret = graph()->NewNode(common()->Return(), zero, outer_phi,
graph()->start(), outer_merge);
graph()->SetEnd(graph()->NewNode(common()->End(1), ret));
Reduce();
// Outer branch should not be rewritten, the inner branch should be discarded.
EXPECT_THAT(outer_branch, IsBranch(condition, graph()->start()));
EXPECT_THAT(inner_phi,
IsPhi(MachineRepresentation::kWord32, IsInt32Constant(1),
IsInt32Constant(2), IsMerge(outer_if_true, IsDead())));
}
TEST_F(BranchEliminationTest, NestedBranchSameFalse) {
// { return (x ? 1 : (x ? 2 : 3); }
// should be reduced to
// { return (x ? 1 : 3; }
Node* condition = Parameter(0);
Node* outer_branch =
graph()->NewNode(common()->Branch(), condition, graph()->start());
Node* outer_if_true = graph()->NewNode(common()->IfTrue(), outer_branch);
Node* outer_if_false = graph()->NewNode(common()->IfFalse(), outer_branch);
Node* inner_branch =
graph()->NewNode(common()->Branch(), condition, outer_if_false);
Node* inner_if_true = graph()->NewNode(common()->IfTrue(), inner_branch);
Node* inner_if_false = graph()->NewNode(common()->IfFalse(), inner_branch);
Node* inner_merge =
graph()->NewNode(common()->Merge(2), inner_if_true, inner_if_false);
Node* inner_phi =
graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
Int32Constant(2), Int32Constant(3), inner_merge);
Node* outer_merge =
graph()->NewNode(common()->Merge(2), outer_if_true, inner_merge);
Node* outer_phi =
graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
Int32Constant(1), inner_phi, outer_merge);
Node* zero = graph()->NewNode(common()->Int32Constant(0));
Node* ret = graph()->NewNode(common()->Return(), zero, outer_phi,
graph()->start(), outer_merge);
graph()->SetEnd(graph()->NewNode(common()->End(1), ret));
Reduce();
// Outer branch should not be rewritten, the inner branch should be discarded.
EXPECT_THAT(outer_branch, IsBranch(condition, graph()->start()));
EXPECT_THAT(inner_phi,
IsPhi(MachineRepresentation::kWord32, IsInt32Constant(2),
IsInt32Constant(3), IsMerge(IsDead(), outer_if_false)));
}
TEST_F(BranchEliminationTest, BranchAfterDiamond) {
// { var y = x ? 1 : 2; return y + x ? 3 : 4; }
// second branch's condition should be replaced with a phi.
Node* condition = Parameter(0);
Node* branch1 =
graph()->NewNode(common()->Branch(), condition, graph()->start());
Node* if_true1 = graph()->NewNode(common()->IfTrue(), branch1);
Node* if_false1 = graph()->NewNode(common()->IfFalse(), branch1);
Node* merge1 = graph()->NewNode(common()->Merge(2), if_true1, if_false1);
Node* phi1 =
graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
Int32Constant(1), Int32Constant(2), merge1);
// Second branch use the same condition.
Node* branch2 = graph()->NewNode(common()->Branch(), condition, merge1);
Node* if_true2 = graph()->NewNode(common()->IfTrue(), branch2);
Node* if_false2 = graph()->NewNode(common()->IfFalse(), branch2);
Node* merge2 = graph()->NewNode(common()->Merge(2), if_true2, if_false2);
Node* phi2 =
graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
Int32Constant(3), Int32Constant(4), merge1);
Node* add = graph()->NewNode(machine()->Int32Add(), phi1, phi2);
Node* zero = graph()->NewNode(common()->Int32Constant(0));
Node* ret =
graph()->NewNode(common()->Return(), zero, add, graph()->start(), merge2);
graph()->SetEnd(graph()->NewNode(common()->End(1), ret));
Reduce();
// The branch condition for branch2 should be a phi with constants.
EXPECT_THAT(branch2,
IsBranch(IsPhi(MachineRepresentation::kWord32, IsInt32Constant(1),
IsInt32Constant(0), merge1),
merge1));
}
TEST_F(BranchEliminationTest, BranchInsideLoopSame) {
// if (x) while (x) { return 2; } else { return 1; }
// should be rewritten to
// if (x) while (true) { return 2; } else { return 1; }
Node* condition = Parameter(0);
Node* outer_branch =
graph()->NewNode(common()->Branch(), condition, graph()->start());
Node* outer_if_true = graph()->NewNode(common()->IfTrue(), outer_branch);
Node* loop = graph()->NewNode(common()->Loop(1), outer_if_true);
Node* effect =
graph()->NewNode(common()->EffectPhi(1), graph()->start(), loop);
Node* inner_branch = graph()->NewNode(common()->Branch(), condition, loop);
Node* inner_if_true = graph()->NewNode(common()->IfTrue(), inner_branch);
Node* zero = graph()->NewNode(common()->Int32Constant(0));
Node* ret1 = graph()->NewNode(common()->Return(), zero, Int32Constant(2),
effect, inner_if_true);
Node* inner_if_false = graph()->NewNode(common()->IfFalse(), inner_branch);
loop->AppendInput(zone(), inner_if_false);
NodeProperties::ChangeOp(loop, common()->Loop(2));
effect->InsertInput(zone(), 1, effect);
NodeProperties::ChangeOp(effect, common()->EffectPhi(2));
Node* outer_if_false = graph()->NewNode(common()->IfFalse(), outer_branch);
Node* outer_merge =
graph()->NewNode(common()->Merge(2), loop, outer_if_false);
Node* outer_ephi = graph()->NewNode(common()->EffectPhi(2), effect,
graph()->start(), outer_merge);
Node* ret2 = graph()->NewNode(common()->Return(), zero, Int32Constant(1),
outer_ephi, outer_merge);
Node* terminate = graph()->NewNode(common()->Terminate(), effect, loop);
graph()->SetEnd(graph()->NewNode(common()->End(3), ret1, ret2, terminate));
Reduce();
// Outer branch should not be rewritten, the inner branch should be discarded.
EXPECT_THAT(outer_branch, IsBranch(condition, graph()->start()));
EXPECT_THAT(ret1, IsReturn(IsInt32Constant(2), effect, loop));
}
} // namespace compiler
} // namespace internal
} // namespace v8