Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2015 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #include "src/compiler/branch-elimination.h" |
| 6 | #include "src/compiler/js-graph.h" |
| 7 | #include "src/compiler/linkage.h" |
| 8 | #include "src/compiler/node-properties.h" |
| 9 | #include "test/unittests/compiler/compiler-test-utils.h" |
| 10 | #include "test/unittests/compiler/graph-unittest.h" |
| 11 | #include "test/unittests/compiler/node-test-utils.h" |
| 12 | #include "testing/gmock-support.h" |
| 13 | |
| 14 | namespace v8 { |
| 15 | namespace internal { |
| 16 | namespace compiler { |
| 17 | |
| 18 | class BranchEliminationTest : public TypedGraphTest { |
| 19 | public: |
| 20 | BranchEliminationTest() |
| 21 | : machine_(zone(), MachineType::PointerRepresentation(), |
| 22 | MachineOperatorBuilder::kNoFlags) {} |
| 23 | |
| 24 | MachineOperatorBuilder* machine() { return &machine_; } |
| 25 | |
| 26 | void Reduce() { |
| 27 | JSOperatorBuilder javascript(zone()); |
| 28 | JSGraph jsgraph(isolate(), graph(), common(), &javascript, nullptr, |
| 29 | machine()); |
| 30 | GraphReducer graph_reducer(zone(), graph(), jsgraph.Dead()); |
| 31 | BranchElimination branch_condition_elimination(&graph_reducer, &jsgraph, |
| 32 | zone()); |
| 33 | graph_reducer.AddReducer(&branch_condition_elimination); |
| 34 | graph_reducer.ReduceGraph(); |
| 35 | } |
| 36 | |
| 37 | private: |
| 38 | MachineOperatorBuilder machine_; |
| 39 | }; |
| 40 | |
| 41 | |
| 42 | TEST_F(BranchEliminationTest, NestedBranchSameTrue) { |
| 43 | // { return (x ? (x ? 1 : 2) : 3; } |
| 44 | // should be reduced to |
| 45 | // { return (x ? 1 : 3; } |
| 46 | Node* condition = Parameter(0); |
| 47 | Node* outer_branch = |
| 48 | graph()->NewNode(common()->Branch(), condition, graph()->start()); |
| 49 | |
| 50 | Node* outer_if_true = graph()->NewNode(common()->IfTrue(), outer_branch); |
| 51 | Node* inner_branch = |
| 52 | graph()->NewNode(common()->Branch(), condition, outer_if_true); |
| 53 | Node* inner_if_true = graph()->NewNode(common()->IfTrue(), inner_branch); |
| 54 | Node* inner_if_false = graph()->NewNode(common()->IfFalse(), inner_branch); |
| 55 | Node* inner_merge = |
| 56 | graph()->NewNode(common()->Merge(2), inner_if_true, inner_if_false); |
| 57 | Node* inner_phi = |
| 58 | graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2), |
| 59 | Int32Constant(1), Int32Constant(2), inner_merge); |
| 60 | |
| 61 | Node* outer_if_false = graph()->NewNode(common()->IfFalse(), outer_branch); |
| 62 | Node* outer_merge = |
| 63 | graph()->NewNode(common()->Merge(2), inner_merge, outer_if_false); |
| 64 | Node* outer_phi = |
| 65 | graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2), |
| 66 | inner_phi, Int32Constant(3), outer_merge); |
| 67 | |
| 68 | Node* ret = graph()->NewNode(common()->Return(), outer_phi, graph()->start(), |
| 69 | outer_merge); |
| 70 | graph()->SetEnd(graph()->NewNode(common()->End(1), ret)); |
| 71 | |
| 72 | Reduce(); |
| 73 | |
| 74 | // Outer branch should not be rewritten, the inner branch should be discarded. |
| 75 | EXPECT_THAT(outer_branch, IsBranch(condition, graph()->start())); |
| 76 | EXPECT_THAT(inner_phi, |
| 77 | IsPhi(MachineRepresentation::kWord32, IsInt32Constant(1), |
| 78 | IsInt32Constant(2), IsMerge(outer_if_true, IsDead()))); |
| 79 | } |
| 80 | |
| 81 | |
| 82 | TEST_F(BranchEliminationTest, NestedBranchSameFalse) { |
| 83 | // { return (x ? 1 : (x ? 2 : 3); } |
| 84 | // should be reduced to |
| 85 | // { return (x ? 1 : 3; } |
| 86 | Node* condition = Parameter(0); |
| 87 | Node* outer_branch = |
| 88 | graph()->NewNode(common()->Branch(), condition, graph()->start()); |
| 89 | |
| 90 | Node* outer_if_true = graph()->NewNode(common()->IfTrue(), outer_branch); |
| 91 | |
| 92 | Node* outer_if_false = graph()->NewNode(common()->IfFalse(), outer_branch); |
| 93 | Node* inner_branch = |
| 94 | graph()->NewNode(common()->Branch(), condition, outer_if_false); |
| 95 | Node* inner_if_true = graph()->NewNode(common()->IfTrue(), inner_branch); |
| 96 | Node* inner_if_false = graph()->NewNode(common()->IfFalse(), inner_branch); |
| 97 | Node* inner_merge = |
| 98 | graph()->NewNode(common()->Merge(2), inner_if_true, inner_if_false); |
| 99 | Node* inner_phi = |
| 100 | graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2), |
| 101 | Int32Constant(2), Int32Constant(3), inner_merge); |
| 102 | |
| 103 | Node* outer_merge = |
| 104 | graph()->NewNode(common()->Merge(2), outer_if_true, inner_merge); |
| 105 | Node* outer_phi = |
| 106 | graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2), |
| 107 | Int32Constant(1), inner_phi, outer_merge); |
| 108 | |
| 109 | Node* ret = graph()->NewNode(common()->Return(), outer_phi, graph()->start(), |
| 110 | outer_merge); |
| 111 | graph()->SetEnd(graph()->NewNode(common()->End(1), ret)); |
| 112 | |
| 113 | Reduce(); |
| 114 | |
| 115 | // Outer branch should not be rewritten, the inner branch should be discarded. |
| 116 | EXPECT_THAT(outer_branch, IsBranch(condition, graph()->start())); |
| 117 | EXPECT_THAT(inner_phi, |
| 118 | IsPhi(MachineRepresentation::kWord32, IsInt32Constant(2), |
| 119 | IsInt32Constant(3), IsMerge(IsDead(), outer_if_false))); |
| 120 | } |
| 121 | |
| 122 | |
| 123 | TEST_F(BranchEliminationTest, BranchAfterDiamond) { |
| 124 | // { var y = x ? 1 : 2; return y + x ? 3 : 4; } |
| 125 | // should not be reduced. |
| 126 | Node* condition = Parameter(0); |
| 127 | |
| 128 | Node* branch1 = |
| 129 | graph()->NewNode(common()->Branch(), condition, graph()->start()); |
| 130 | Node* if_true1 = graph()->NewNode(common()->IfTrue(), branch1); |
| 131 | Node* if_false1 = graph()->NewNode(common()->IfFalse(), branch1); |
| 132 | Node* merge1 = graph()->NewNode(common()->Merge(2), if_true1, if_false1); |
| 133 | Node* phi1 = |
| 134 | graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2), |
| 135 | Int32Constant(1), Int32Constant(2), merge1); |
| 136 | |
| 137 | Node* branch2 = graph()->NewNode(common()->Branch(), condition, merge1); |
| 138 | Node* if_true2 = graph()->NewNode(common()->IfTrue(), branch2); |
| 139 | Node* if_false2 = graph()->NewNode(common()->IfFalse(), branch2); |
| 140 | Node* merge2 = graph()->NewNode(common()->Merge(2), if_true2, if_false2); |
| 141 | Node* phi2 = |
| 142 | graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2), |
| 143 | Int32Constant(3), Int32Constant(4), merge1); |
| 144 | |
| 145 | |
| 146 | Node* add = graph()->NewNode(machine()->Int32Add(), phi1, phi2); |
| 147 | Node* ret = |
| 148 | graph()->NewNode(common()->Return(), add, graph()->start(), merge2); |
| 149 | graph()->SetEnd(graph()->NewNode(common()->End(1), ret)); |
| 150 | |
| 151 | Reduce(); |
| 152 | |
| 153 | // Outer branch should not be rewritten, the inner branch condition should |
| 154 | // be true. |
| 155 | EXPECT_THAT(branch1, IsBranch(condition, graph()->start())); |
| 156 | EXPECT_THAT(branch2, IsBranch(condition, merge1)); |
| 157 | } |
| 158 | |
| 159 | |
| 160 | TEST_F(BranchEliminationTest, BranchInsideLoopSame) { |
| 161 | // if (x) while (x) { return 2; } else { return 1; } |
| 162 | // should be rewritten to |
| 163 | // if (x) while (true) { return 2; } else { return 1; } |
| 164 | |
| 165 | Node* condition = Parameter(0); |
| 166 | |
| 167 | Node* outer_branch = |
| 168 | graph()->NewNode(common()->Branch(), condition, graph()->start()); |
| 169 | Node* outer_if_true = graph()->NewNode(common()->IfTrue(), outer_branch); |
| 170 | |
| 171 | |
| 172 | Node* loop = graph()->NewNode(common()->Loop(1), outer_if_true); |
| 173 | Node* effect = |
| 174 | graph()->NewNode(common()->EffectPhi(1), graph()->start(), loop); |
| 175 | |
| 176 | Node* inner_branch = graph()->NewNode(common()->Branch(), condition, loop); |
| 177 | |
| 178 | Node* inner_if_true = graph()->NewNode(common()->IfTrue(), inner_branch); |
| 179 | Node* ret1 = graph()->NewNode(common()->Return(), Int32Constant(2), effect, |
| 180 | inner_if_true); |
| 181 | |
| 182 | Node* inner_if_false = graph()->NewNode(common()->IfFalse(), inner_branch); |
| 183 | loop->AppendInput(zone(), inner_if_false); |
| 184 | NodeProperties::ChangeOp(loop, common()->Loop(2)); |
| 185 | effect->InsertInput(zone(), 1, effect); |
| 186 | NodeProperties::ChangeOp(effect, common()->EffectPhi(2)); |
| 187 | |
| 188 | Node* outer_if_false = graph()->NewNode(common()->IfFalse(), outer_branch); |
| 189 | Node* outer_merge = |
| 190 | graph()->NewNode(common()->Merge(2), loop, outer_if_false); |
| 191 | Node* outer_ephi = graph()->NewNode(common()->EffectPhi(2), effect, |
| 192 | graph()->start(), outer_merge); |
| 193 | |
| 194 | Node* ret2 = graph()->NewNode(common()->Return(), Int32Constant(1), |
| 195 | outer_ephi, outer_merge); |
| 196 | |
| 197 | Node* terminate = graph()->NewNode(common()->Terminate(), effect, loop); |
| 198 | graph()->SetEnd(graph()->NewNode(common()->End(3), ret1, ret2, terminate)); |
| 199 | |
| 200 | Reduce(); |
| 201 | |
| 202 | // Outer branch should not be rewritten, the inner branch should be discarded. |
| 203 | EXPECT_THAT(outer_branch, IsBranch(condition, graph()->start())); |
| 204 | EXPECT_THAT(ret1, IsReturn(IsInt32Constant(2), effect, loop)); |
| 205 | } |
| 206 | |
| 207 | } // namespace compiler |
| 208 | } // namespace internal |
| 209 | } // namespace v8 |