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Issue 1405363003: Move Hydrogen and Lithium to src/crankshaft/ (Closed) Base URL: https://chromium.googlesource.com/v8/v8.git@master
Patch Set: rebased Created 5 years, 2 months ago
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1 // Copyright 2013 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/hydrogen-infer-representation.h"
6
7 namespace v8 {
8 namespace internal {
9
10 void HInferRepresentationPhase::AddToWorklist(HValue* current) {
11 if (current->representation().IsTagged()) return;
12 if (!current->CheckFlag(HValue::kFlexibleRepresentation)) return;
13 if (in_worklist_.Contains(current->id())) return;
14 worklist_.Add(current, zone());
15 in_worklist_.Add(current->id());
16 }
17
18
19 void HInferRepresentationPhase::Run() {
20 // (1) Initialize bit vectors and count real uses. Each phi gets a
21 // bit-vector of length <number of phis>.
22 const ZoneList<HPhi*>* phi_list = graph()->phi_list();
23 int phi_count = phi_list->length();
24 ZoneList<BitVector*> connected_phis(phi_count, zone());
25 for (int i = 0; i < phi_count; ++i) {
26 phi_list->at(i)->InitRealUses(i);
27 BitVector* connected_set = new(zone()) BitVector(phi_count, zone());
28 connected_set->Add(i);
29 connected_phis.Add(connected_set, zone());
30 }
31
32 // (2) Do a fixed point iteration to find the set of connected phis. A
33 // phi is connected to another phi if its value is used either directly or
34 // indirectly through a transitive closure of the def-use relation.
35 bool change = true;
36 while (change) {
37 change = false;
38 // We normally have far more "forward edges" than "backward edges",
39 // so we terminate faster when we walk backwards.
40 for (int i = phi_count - 1; i >= 0; --i) {
41 HPhi* phi = phi_list->at(i);
42 for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
43 HValue* use = it.value();
44 if (use->IsPhi()) {
45 int id = HPhi::cast(use)->phi_id();
46 if (connected_phis[i]->UnionIsChanged(*connected_phis[id]))
47 change = true;
48 }
49 }
50 }
51 }
52
53 // Set truncation flags for groups of connected phis. This is a conservative
54 // approximation; the flag will be properly re-computed after representations
55 // have been determined.
56 if (phi_count > 0) {
57 BitVector done(phi_count, zone());
58 for (int i = 0; i < phi_count; ++i) {
59 if (done.Contains(i)) continue;
60
61 // Check if all uses of all connected phis in this group are truncating.
62 bool all_uses_everywhere_truncating_int32 = true;
63 bool all_uses_everywhere_truncating_smi = true;
64 for (BitVector::Iterator it(connected_phis[i]);
65 !it.Done();
66 it.Advance()) {
67 int index = it.Current();
68 all_uses_everywhere_truncating_int32 &=
69 phi_list->at(index)->CheckFlag(HInstruction::kTruncatingToInt32);
70 all_uses_everywhere_truncating_smi &=
71 phi_list->at(index)->CheckFlag(HInstruction::kTruncatingToSmi);
72 done.Add(index);
73 }
74
75 if (!all_uses_everywhere_truncating_int32) {
76 // Clear truncation flag of this group of connected phis.
77 for (BitVector::Iterator it(connected_phis[i]);
78 !it.Done();
79 it.Advance()) {
80 int index = it.Current();
81 phi_list->at(index)->ClearFlag(HInstruction::kTruncatingToInt32);
82 }
83 }
84 if (!all_uses_everywhere_truncating_smi) {
85 // Clear truncation flag of this group of connected phis.
86 for (BitVector::Iterator it(connected_phis[i]);
87 !it.Done();
88 it.Advance()) {
89 int index = it.Current();
90 phi_list->at(index)->ClearFlag(HInstruction::kTruncatingToSmi);
91 }
92 }
93 }
94 }
95
96 // Simplify constant phi inputs where possible.
97 // This step uses kTruncatingToInt32 flags of phis.
98 for (int i = 0; i < phi_count; ++i) {
99 phi_list->at(i)->SimplifyConstantInputs();
100 }
101
102 // Use the phi reachability information from step 2 to
103 // sum up the non-phi use counts of all connected phis.
104 for (int i = 0; i < phi_count; ++i) {
105 HPhi* phi = phi_list->at(i);
106 for (BitVector::Iterator it(connected_phis[i]);
107 !it.Done();
108 it.Advance()) {
109 int index = it.Current();
110 HPhi* it_use = phi_list->at(index);
111 if (index != i) phi->AddNonPhiUsesFrom(it_use); // Don't count twice.
112 }
113 }
114
115 // Initialize work list
116 for (int i = 0; i < graph()->blocks()->length(); ++i) {
117 HBasicBlock* block = graph()->blocks()->at(i);
118 const ZoneList<HPhi*>* phis = block->phis();
119 for (int j = 0; j < phis->length(); ++j) {
120 AddToWorklist(phis->at(j));
121 }
122
123 for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
124 HInstruction* current = it.Current();
125 AddToWorklist(current);
126 }
127 }
128
129 // Do a fixed point iteration, trying to improve representations
130 while (!worklist_.is_empty()) {
131 HValue* current = worklist_.RemoveLast();
132 current->InferRepresentation(this);
133 in_worklist_.Remove(current->id());
134 }
135
136 // Lastly: any instruction that we don't have representation information
137 // for defaults to Tagged.
138 for (int i = 0; i < graph()->blocks()->length(); ++i) {
139 HBasicBlock* block = graph()->blocks()->at(i);
140 const ZoneList<HPhi*>* phis = block->phis();
141 for (int j = 0; j < phis->length(); ++j) {
142 HPhi* phi = phis->at(j);
143 if (phi->representation().IsNone()) {
144 phi->ChangeRepresentation(Representation::Tagged());
145 }
146 }
147 for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
148 HInstruction* current = it.Current();
149 if (current->representation().IsNone() &&
150 current->CheckFlag(HInstruction::kFlexibleRepresentation)) {
151 if (current->CheckFlag(HInstruction::kCannotBeTagged)) {
152 current->ChangeRepresentation(Representation::Double());
153 } else {
154 current->ChangeRepresentation(Representation::Tagged());
155 }
156 }
157 }
158 }
159 }
160
161 } // namespace internal
162 } // namespace v8
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