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.
5 #include "src/hydrogen-representation-changes.h"
10 void HRepresentationChangesPhase::InsertRepresentationChangeForUse(
11 HValue* value, HValue* use_value, int use_index, Representation to) {
12 // Insert the representation change right before its use. For phi-uses we
13 // insert at the end of the corresponding predecessor.
14 HInstruction* next = NULL;
15 if (use_value->IsPhi()) {
16 next = use_value->block()->predecessors()->at(use_index)->end();
18 next = HInstruction::cast(use_value);
20 // For constants we try to make the representation change at compile
21 // time. When a representation change is not possible without loss of
22 // information we treat constants like normal instructions and insert the
23 // change instructions for them.
24 HInstruction* new_value = NULL;
25 bool is_truncating_to_smi = use_value->CheckFlag(HValue::kTruncatingToSmi);
26 bool is_truncating_to_int = use_value->CheckFlag(HValue::kTruncatingToInt32);
27 if (value->IsConstant()) {
28 HConstant* constant = HConstant::cast(value);
29 // Try to create a new copy of the constant with the new representation.
30 if (is_truncating_to_int && to.IsInteger32()) {
31 Maybe<HConstant*> res = constant->CopyToTruncatedInt32(graph()->zone());
32 if (res.has_value) new_value = res.value;
34 new_value = constant->CopyToRepresentation(to, graph()->zone());
38 if (new_value == NULL) {
39 if (((to.IsFloat32x4() || to.IsFloat64x2() || to.IsInt32x4()) &&
40 !value->representation().IsTagged()) ||
41 ((value->representation().IsFloat32x4() ||
42 value->representation().IsFloat64x2() ||
43 value->representation().IsInt32x4()) &&
45 new_value = HUnarySIMDOperation::New(graph()->zone(),
46 graph()->entry_block()->last_environment()->context(),
47 value, kSIMD128Change, to);
49 new_value = new(graph()->zone()) HChange(
50 value, to, is_truncating_to_smi, is_truncating_to_int);
52 if (!use_value->operand_position(use_index).IsUnknown()) {
53 new_value->set_position(use_value->operand_position(use_index));
55 DCHECK(!FLAG_hydrogen_track_positions ||
56 !graph()->info()->IsOptimizing());
60 new_value->InsertBefore(next);
61 use_value->SetOperandAt(use_index, new_value);
65 static bool IsNonDeoptingIntToSmiChange(HChange* change) {
66 Representation from_rep = change->from();
67 Representation to_rep = change->to();
68 // Flags indicating Uint32 operations are set in a later Hydrogen phase.
69 DCHECK(!change->CheckFlag(HValue::kUint32));
70 return from_rep.IsInteger32() && to_rep.IsSmi() && SmiValuesAre32Bits();
74 void HRepresentationChangesPhase::InsertRepresentationChangesForValue(
76 Representation r = value->representation();
77 if (r.IsNone()) return;
78 if (value->HasNoUses()) {
79 if (value->IsForceRepresentation()) value->DeleteAndReplaceWith(NULL);
83 for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) {
84 HValue* use_value = it.value();
85 int use_index = it.index();
86 Representation req = use_value->RequiredInputRepresentation(use_index);
87 if (req.IsNone() || req.Equals(r)) continue;
89 // If this is an HForceRepresentation instruction, and an HChange has been
90 // inserted above it, examine the input representation of the HChange. If
91 // that's int32, and this HForceRepresentation use is int32, and int32 to
92 // smi changes can't cause deoptimisation, set the input of the use to the
93 // input of the HChange.
94 if (value->IsForceRepresentation()) {
95 HValue* input = HForceRepresentation::cast(value)->value();
96 if (input->IsChange()) {
97 HChange* change = HChange::cast(input);
98 if (change->from().Equals(req) && IsNonDeoptingIntToSmiChange(change)) {
99 use_value->SetOperandAt(use_index, change->value());
104 InsertRepresentationChangeForUse(value, use_value, use_index, req);
106 if (value->HasNoUses()) {
107 DCHECK(value->IsConstant() || value->IsForceRepresentation());
108 value->DeleteAndReplaceWith(NULL);
110 // The only purpose of a HForceRepresentation is to represent the value
111 // after the (possible) HChange instruction. We make it disappear.
112 if (value->IsForceRepresentation()) {
113 value->DeleteAndReplaceWith(HForceRepresentation::cast(value)->value());
119 void HRepresentationChangesPhase::Run() {
120 // Compute truncation flag for phis: Initially assume that all
121 // int32-phis allow truncation and iteratively remove the ones that
122 // are used in an operation that does not allow a truncating
124 ZoneList<HPhi*> int_worklist(8, zone());
125 ZoneList<HPhi*> smi_worklist(8, zone());
127 const ZoneList<HPhi*>* phi_list(graph()->phi_list());
128 for (int i = 0; i < phi_list->length(); i++) {
129 HPhi* phi = phi_list->at(i);
130 if (phi->representation().IsInteger32()) {
131 phi->SetFlag(HValue::kTruncatingToInt32);
132 } else if (phi->representation().IsSmi()) {
133 phi->SetFlag(HValue::kTruncatingToSmi);
134 phi->SetFlag(HValue::kTruncatingToInt32);
138 for (int i = 0; i < phi_list->length(); i++) {
139 HPhi* phi = phi_list->at(i);
140 HValue* value = NULL;
141 if (phi->representation().IsSmiOrInteger32() &&
142 !phi->CheckUsesForFlag(HValue::kTruncatingToInt32, &value)) {
143 int_worklist.Add(phi, zone());
144 phi->ClearFlag(HValue::kTruncatingToInt32);
145 if (FLAG_trace_representation) {
146 PrintF("#%d Phi is not truncating Int32 because of #%d %s\n",
147 phi->id(), value->id(), value->Mnemonic());
151 if (phi->representation().IsSmi() &&
152 !phi->CheckUsesForFlag(HValue::kTruncatingToSmi, &value)) {
153 smi_worklist.Add(phi, zone());
154 phi->ClearFlag(HValue::kTruncatingToSmi);
155 if (FLAG_trace_representation) {
156 PrintF("#%d Phi is not truncating Smi because of #%d %s\n",
157 phi->id(), value->id(), value->Mnemonic());
162 while (!int_worklist.is_empty()) {
163 HPhi* current = int_worklist.RemoveLast();
164 for (int i = 0; i < current->OperandCount(); ++i) {
165 HValue* input = current->OperandAt(i);
166 if (input->IsPhi() &&
167 input->representation().IsSmiOrInteger32() &&
168 input->CheckFlag(HValue::kTruncatingToInt32)) {
169 if (FLAG_trace_representation) {
170 PrintF("#%d Phi is not truncating Int32 because of #%d %s\n",
171 input->id(), current->id(), current->Mnemonic());
173 input->ClearFlag(HValue::kTruncatingToInt32);
174 int_worklist.Add(HPhi::cast(input), zone());
179 while (!smi_worklist.is_empty()) {
180 HPhi* current = smi_worklist.RemoveLast();
181 for (int i = 0; i < current->OperandCount(); ++i) {
182 HValue* input = current->OperandAt(i);
183 if (input->IsPhi() &&
184 input->representation().IsSmi() &&
185 input->CheckFlag(HValue::kTruncatingToSmi)) {
186 if (FLAG_trace_representation) {
187 PrintF("#%d Phi is not truncating Smi because of #%d %s\n",
188 input->id(), current->id(), current->Mnemonic());
190 input->ClearFlag(HValue::kTruncatingToSmi);
191 smi_worklist.Add(HPhi::cast(input), zone());
196 const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
197 for (int i = 0; i < blocks->length(); ++i) {
198 // Process phi instructions first.
199 const HBasicBlock* block(blocks->at(i));
200 const ZoneList<HPhi*>* phis = block->phis();
201 for (int j = 0; j < phis->length(); j++) {
202 InsertRepresentationChangesForValue(phis->at(j));
205 // Process normal instructions.
206 for (HInstruction* current = block->first(); current != NULL; ) {
207 HInstruction* next = current->next();
208 InsertRepresentationChangesForValue(current);
214 } } // namespace v8::internal