1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
|
// Copyright 2013 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/crankshaft/hydrogen-representation-changes.h"
namespace v8 {
namespace internal {
void HRepresentationChangesPhase::InsertRepresentationChangeForUse(
HValue* value, HValue* use_value, int use_index, Representation to) {
// Insert the representation change right before its use. For phi-uses we
// insert at the end of the corresponding predecessor.
HInstruction* next = NULL;
if (use_value->IsPhi()) {
next = use_value->block()->predecessors()->at(use_index)->end();
} else {
next = HInstruction::cast(use_value);
}
// For constants we try to make the representation change at compile
// time. When a representation change is not possible without loss of
// information we treat constants like normal instructions and insert the
// change instructions for them.
HInstruction* new_value = NULL;
bool is_truncating_to_smi = use_value->CheckFlag(HValue::kTruncatingToSmi);
bool is_truncating_to_int = use_value->CheckFlag(HValue::kTruncatingToInt32);
bool is_truncating_to_number =
use_value->CheckFlag(HValue::kTruncatingToNumber);
if (value->IsConstant()) {
HConstant* constant = HConstant::cast(value);
// Try to create a new copy of the constant with the new representation.
if (is_truncating_to_int && to.IsInteger32()) {
Maybe<HConstant*> res = constant->CopyToTruncatedInt32(graph()->zone());
if (res.IsJust()) new_value = res.FromJust();
} else {
new_value = constant->CopyToRepresentation(to, graph()->zone());
}
}
if (new_value == NULL) {
new_value = new (graph()->zone())
HChange(value, to, is_truncating_to_smi, is_truncating_to_int,
is_truncating_to_number);
}
new_value->InsertBefore(next);
use_value->SetOperandAt(use_index, new_value);
}
static bool IsNonDeoptingIntToSmiChange(HChange* change) {
Representation from_rep = change->from();
Representation to_rep = change->to();
// Flags indicating Uint32 operations are set in a later Hydrogen phase.
DCHECK(!change->CheckFlag(HValue::kUint32));
return from_rep.IsInteger32() && to_rep.IsSmi() && SmiValuesAre32Bits();
}
void HRepresentationChangesPhase::InsertRepresentationChangesForValue(
HValue* value) {
Representation r = value->representation();
if (r.IsNone()) {
#ifdef DEBUG
for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) {
HValue* use_value = it.value();
int use_index = it.index();
Representation req = use_value->RequiredInputRepresentation(use_index);
DCHECK(req.IsNone());
}
#endif
return;
}
if (value->HasNoUses()) {
if (value->IsForceRepresentation()) value->DeleteAndReplaceWith(NULL);
return;
}
for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) {
HValue* use_value = it.value();
int use_index = it.index();
Representation req = use_value->RequiredInputRepresentation(use_index);
if (req.IsNone() || req.Equals(r)) continue;
// If this is an HForceRepresentation instruction, and an HChange has been
// inserted above it, examine the input representation of the HChange. If
// that's int32, and this HForceRepresentation use is int32, and int32 to
// smi changes can't cause deoptimisation, set the input of the use to the
// input of the HChange.
if (value->IsForceRepresentation()) {
HValue* input = HForceRepresentation::cast(value)->value();
if (input->IsChange()) {
HChange* change = HChange::cast(input);
if (change->from().Equals(req) && IsNonDeoptingIntToSmiChange(change)) {
use_value->SetOperandAt(use_index, change->value());
continue;
}
}
}
InsertRepresentationChangeForUse(value, use_value, use_index, req);
}
if (value->HasNoUses()) {
DCHECK(value->IsConstant() || value->IsForceRepresentation());
value->DeleteAndReplaceWith(NULL);
} else {
// The only purpose of a HForceRepresentation is to represent the value
// after the (possible) HChange instruction. We make it disappear.
if (value->IsForceRepresentation()) {
value->DeleteAndReplaceWith(HForceRepresentation::cast(value)->value());
}
}
}
void HRepresentationChangesPhase::Run() {
// Compute truncation flag for phis:
//
// - Initially assume that all phis allow truncation to number and iteratively
// remove the ones that are used in an operation that not do an implicit
// ToNumber conversion.
// - Also assume that all Integer32 phis allow ToInt32 truncation and all
// Smi phis allow truncation to Smi.
//
ZoneList<HPhi*> number_worklist(8, zone());
ZoneList<HPhi*> int_worklist(8, zone());
ZoneList<HPhi*> smi_worklist(8, zone());
const ZoneList<HPhi*>* phi_list(graph()->phi_list());
for (int i = 0; i < phi_list->length(); i++) {
HPhi* phi = phi_list->at(i);
if (phi->representation().IsInteger32()) {
phi->SetFlag(HValue::kTruncatingToInt32);
} else if (phi->representation().IsSmi()) {
phi->SetFlag(HValue::kTruncatingToSmi);
phi->SetFlag(HValue::kTruncatingToInt32);
}
phi->SetFlag(HValue::kTruncatingToNumber);
}
for (int i = 0; i < phi_list->length(); i++) {
HPhi* phi = phi_list->at(i);
HValue* value = NULL;
if (phi->CheckFlag(HValue::kTruncatingToNumber) &&
!phi->CheckUsesForFlag(HValue::kTruncatingToNumber, &value)) {
number_worklist.Add(phi, zone());
phi->ClearFlag(HValue::kTruncatingToNumber);
phi->ClearFlag(HValue::kTruncatingToInt32);
phi->ClearFlag(HValue::kTruncatingToSmi);
if (FLAG_trace_representation) {
PrintF("#%d Phi is not truncating Number because of #%d %s\n",
phi->id(), value->id(), value->Mnemonic());
}
} else if (phi->representation().IsSmiOrInteger32() &&
!phi->CheckUsesForFlag(HValue::kTruncatingToInt32, &value)) {
int_worklist.Add(phi, zone());
phi->ClearFlag(HValue::kTruncatingToInt32);
phi->ClearFlag(HValue::kTruncatingToSmi);
if (FLAG_trace_representation) {
PrintF("#%d Phi is not truncating Int32 because of #%d %s\n",
phi->id(), value->id(), value->Mnemonic());
}
} else if (phi->representation().IsSmi() &&
!phi->CheckUsesForFlag(HValue::kTruncatingToSmi, &value)) {
smi_worklist.Add(phi, zone());
phi->ClearFlag(HValue::kTruncatingToSmi);
if (FLAG_trace_representation) {
PrintF("#%d Phi is not truncating Smi because of #%d %s\n",
phi->id(), value->id(), value->Mnemonic());
}
}
}
while (!number_worklist.is_empty()) {
HPhi* current = number_worklist.RemoveLast();
for (int i = current->OperandCount() - 1; i >= 0; --i) {
HValue* input = current->OperandAt(i);
if (input->IsPhi() && input->CheckFlag(HValue::kTruncatingToNumber)) {
if (FLAG_trace_representation) {
PrintF("#%d Phi is not truncating Number because of #%d %s\n",
input->id(), current->id(), current->Mnemonic());
}
input->ClearFlag(HValue::kTruncatingToNumber);
input->ClearFlag(HValue::kTruncatingToInt32);
input->ClearFlag(HValue::kTruncatingToSmi);
number_worklist.Add(HPhi::cast(input), zone());
}
}
}
while (!int_worklist.is_empty()) {
HPhi* current = int_worklist.RemoveLast();
for (int i = 0; i < current->OperandCount(); ++i) {
HValue* input = current->OperandAt(i);
if (input->IsPhi() &&
input->representation().IsSmiOrInteger32() &&
input->CheckFlag(HValue::kTruncatingToInt32)) {
if (FLAG_trace_representation) {
PrintF("#%d Phi is not truncating Int32 because of #%d %s\n",
input->id(), current->id(), current->Mnemonic());
}
input->ClearFlag(HValue::kTruncatingToInt32);
int_worklist.Add(HPhi::cast(input), zone());
}
}
}
while (!smi_worklist.is_empty()) {
HPhi* current = smi_worklist.RemoveLast();
for (int i = 0; i < current->OperandCount(); ++i) {
HValue* input = current->OperandAt(i);
if (input->IsPhi() &&
input->representation().IsSmi() &&
input->CheckFlag(HValue::kTruncatingToSmi)) {
if (FLAG_trace_representation) {
PrintF("#%d Phi is not truncating Smi because of #%d %s\n",
input->id(), current->id(), current->Mnemonic());
}
input->ClearFlag(HValue::kTruncatingToSmi);
smi_worklist.Add(HPhi::cast(input), zone());
}
}
}
const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
for (int i = 0; i < blocks->length(); ++i) {
// Process phi instructions first.
const HBasicBlock* block(blocks->at(i));
const ZoneList<HPhi*>* phis = block->phis();
for (int j = 0; j < phis->length(); j++) {
InsertRepresentationChangesForValue(phis->at(j));
}
// Process normal instructions.
for (HInstruction* current = block->first(); current != NULL; ) {
HInstruction* next = current->next();
InsertRepresentationChangesForValue(current);
current = next;
}
}
}
} // namespace internal
} // namespace v8
|
