1 // Copyright 2012 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/crankshaft/mips64/lithium-gap-resolver-mips64.h"
6
7 #include "src/crankshaft/mips64/lithium-codegen-mips64.h"
8
9 namespace v8 {
10 namespace internal {
11
LGapResolver(LCodeGen * owner)12 LGapResolver::LGapResolver(LCodeGen* owner)
13 : cgen_(owner),
14 moves_(32, owner->zone()),
15 root_index_(0),
16 in_cycle_(false),
17 saved_destination_(NULL) {}
18
19
Resolve(LParallelMove * parallel_move)20 void LGapResolver::Resolve(LParallelMove* parallel_move) {
21 DCHECK(moves_.is_empty());
22 // Build up a worklist of moves.
23 BuildInitialMoveList(parallel_move);
24
25 for (int i = 0; i < moves_.length(); ++i) {
26 LMoveOperands move = moves_[i];
27 // Skip constants to perform them last. They don't block other moves
28 // and skipping such moves with register destinations keeps those
29 // registers free for the whole algorithm.
30 if (!move.IsEliminated() && !move.source()->IsConstantOperand()) {
31 root_index_ = i; // Any cycle is found when by reaching this move again.
32 PerformMove(i);
33 if (in_cycle_) {
34 RestoreValue();
35 }
36 }
37 }
38
39 // Perform the moves with constant sources.
40 for (int i = 0; i < moves_.length(); ++i) {
41 if (!moves_[i].IsEliminated()) {
42 DCHECK(moves_[i].source()->IsConstantOperand());
43 EmitMove(i);
44 }
45 }
46
47 moves_.Rewind(0);
48 }
49
50
BuildInitialMoveList(LParallelMove * parallel_move)51 void LGapResolver::BuildInitialMoveList(LParallelMove* parallel_move) {
52 // Perform a linear sweep of the moves to add them to the initial list of
53 // moves to perform, ignoring any move that is redundant (the source is
54 // the same as the destination, the destination is ignored and
55 // unallocated, or the move was already eliminated).
56 const ZoneList<LMoveOperands>* moves = parallel_move->move_operands();
57 for (int i = 0; i < moves->length(); ++i) {
58 LMoveOperands move = moves->at(i);
59 if (!move.IsRedundant()) moves_.Add(move, cgen_->zone());
60 }
61 Verify();
62 }
63
64
PerformMove(int index)65 void LGapResolver::PerformMove(int index) {
66 // Each call to this function performs a move and deletes it from the move
67 // graph. We first recursively perform any move blocking this one. We
68 // mark a move as "pending" on entry to PerformMove in order to detect
69 // cycles in the move graph.
70
71 // We can only find a cycle, when doing a depth-first traversal of moves,
72 // be encountering the starting move again. So by spilling the source of
73 // the starting move, we break the cycle. All moves are then unblocked,
74 // and the starting move is completed by writing the spilled value to
75 // its destination. All other moves from the spilled source have been
76 // completed prior to breaking the cycle.
77 // An additional complication is that moves to MemOperands with large
78 // offsets (more than 1K or 4K) require us to spill this spilled value to
79 // the stack, to free up the register.
80 DCHECK(!moves_[index].IsPending());
81 DCHECK(!moves_[index].IsRedundant());
82
83 // Clear this move's destination to indicate a pending move. The actual
84 // destination is saved in a stack allocated local. Multiple moves can
85 // be pending because this function is recursive.
86 DCHECK(moves_[index].source() != NULL); // Or else it will look eliminated.
87 LOperand* destination = moves_[index].destination();
88 moves_[index].set_destination(NULL);
89
90 // Perform a depth-first traversal of the move graph to resolve
91 // dependencies. Any unperformed, unpending move with a source the same
92 // as this one's destination blocks this one so recursively perform all
93 // such moves.
94 for (int i = 0; i < moves_.length(); ++i) {
95 LMoveOperands other_move = moves_[i];
96 if (other_move.Blocks(destination) && !other_move.IsPending()) {
97 PerformMove(i);
98 // If there is a blocking, pending move it must be moves_[root_index_]
99 // and all other moves with the same source as moves_[root_index_] are
100 // sucessfully executed (because they are cycle-free) by this loop.
101 }
102 }
103
104 // We are about to resolve this move and don't need it marked as
105 // pending, so restore its destination.
106 moves_[index].set_destination(destination);
107
108 // The move may be blocked on a pending move, which must be the starting move.
109 // In this case, we have a cycle, and we save the source of this move to
110 // a scratch register to break it.
111 LMoveOperands other_move = moves_[root_index_];
112 if (other_move.Blocks(destination)) {
113 DCHECK(other_move.IsPending());
114 BreakCycle(index);
115 return;
116 }
117
118 // This move is no longer blocked.
119 EmitMove(index);
120 }
121
122
Verify()123 void LGapResolver::Verify() {
124 #ifdef ENABLE_SLOW_DCHECKS
125 // No operand should be the destination for more than one move.
126 for (int i = 0; i < moves_.length(); ++i) {
127 LOperand* destination = moves_[i].destination();
128 for (int j = i + 1; j < moves_.length(); ++j) {
129 SLOW_DCHECK(!destination->Equals(moves_[j].destination()));
130 }
131 }
132 #endif
133 }
134
135 #define __ ACCESS_MASM(cgen_->masm())
136
BreakCycle(int index)137 void LGapResolver::BreakCycle(int index) {
138 // We save in a register the value that should end up in the source of
139 // moves_[root_index]. After performing all moves in the tree rooted
140 // in that move, we save the value to that source.
141 DCHECK(moves_[index].destination()->Equals(moves_[root_index_].source()));
142 DCHECK(!in_cycle_);
143 in_cycle_ = true;
144 LOperand* source = moves_[index].source();
145 saved_destination_ = moves_[index].destination();
146 if (source->IsRegister()) {
147 __ mov(kLithiumScratchReg, cgen_->ToRegister(source));
148 } else if (source->IsStackSlot()) {
149 __ ld(kLithiumScratchReg, cgen_->ToMemOperand(source));
150 } else if (source->IsDoubleRegister()) {
151 __ mov_d(kLithiumScratchDouble, cgen_->ToDoubleRegister(source));
152 } else if (source->IsDoubleStackSlot()) {
153 __ ldc1(kLithiumScratchDouble, cgen_->ToMemOperand(source));
154 } else {
155 UNREACHABLE();
156 }
157 // This move will be done by restoring the saved value to the destination.
158 moves_[index].Eliminate();
159 }
160
161
RestoreValue()162 void LGapResolver::RestoreValue() {
163 DCHECK(in_cycle_);
164 DCHECK(saved_destination_ != NULL);
165
166 // Spilled value is in kLithiumScratchReg or kLithiumScratchDouble.
167 if (saved_destination_->IsRegister()) {
168 __ mov(cgen_->ToRegister(saved_destination_), kLithiumScratchReg);
169 } else if (saved_destination_->IsStackSlot()) {
170 __ sd(kLithiumScratchReg, cgen_->ToMemOperand(saved_destination_));
171 } else if (saved_destination_->IsDoubleRegister()) {
172 __ mov_d(cgen_->ToDoubleRegister(saved_destination_),
173 kLithiumScratchDouble);
174 } else if (saved_destination_->IsDoubleStackSlot()) {
175 __ sdc1(kLithiumScratchDouble,
176 cgen_->ToMemOperand(saved_destination_));
177 } else {
178 UNREACHABLE();
179 }
180
181 in_cycle_ = false;
182 saved_destination_ = NULL;
183 }
184
185
EmitMove(int index)186 void LGapResolver::EmitMove(int index) {
187 LOperand* source = moves_[index].source();
188 LOperand* destination = moves_[index].destination();
189
190 // Dispatch on the source and destination operand kinds. Not all
191 // combinations are possible.
192
193 if (source->IsRegister()) {
194 Register source_register = cgen_->ToRegister(source);
195 if (destination->IsRegister()) {
196 __ mov(cgen_->ToRegister(destination), source_register);
197 } else {
198 DCHECK(destination->IsStackSlot());
199 __ sd(source_register, cgen_->ToMemOperand(destination));
200 }
201 } else if (source->IsStackSlot()) {
202 MemOperand source_operand = cgen_->ToMemOperand(source);
203 if (destination->IsRegister()) {
204 __ ld(cgen_->ToRegister(destination), source_operand);
205 } else {
206 DCHECK(destination->IsStackSlot());
207 MemOperand destination_operand = cgen_->ToMemOperand(destination);
208 if (in_cycle_) {
209 if (!destination_operand.OffsetIsInt16Encodable()) {
210 // 'at' is overwritten while saving the value to the destination.
211 // Therefore we can't use 'at'. It is OK if the read from the source
212 // destroys 'at', since that happens before the value is read.
213 // This uses only a single reg of the double reg-pair.
214 __ ldc1(kLithiumScratchDouble, source_operand);
215 __ sdc1(kLithiumScratchDouble, destination_operand);
216 } else {
217 __ ld(at, source_operand);
218 __ sd(at, destination_operand);
219 }
220 } else {
221 __ ld(kLithiumScratchReg, source_operand);
222 __ sd(kLithiumScratchReg, destination_operand);
223 }
224 }
225
226 } else if (source->IsConstantOperand()) {
227 LConstantOperand* constant_source = LConstantOperand::cast(source);
228 if (destination->IsRegister()) {
229 Register dst = cgen_->ToRegister(destination);
230 if (cgen_->IsSmi(constant_source)) {
231 __ li(dst, Operand(cgen_->ToSmi(constant_source)));
232 } else if (cgen_->IsInteger32(constant_source)) {
233 __ li(dst, Operand(cgen_->ToInteger32(constant_source)));
234 } else {
235 __ li(dst, cgen_->ToHandle(constant_source));
236 }
237 } else if (destination->IsDoubleRegister()) {
238 DoubleRegister result = cgen_->ToDoubleRegister(destination);
239 double v = cgen_->ToDouble(constant_source);
240 __ Move(result, v);
241 } else {
242 DCHECK(destination->IsStackSlot());
243 DCHECK(!in_cycle_); // Constant moves happen after all cycles are gone.
244 if (cgen_->IsSmi(constant_source)) {
245 __ li(kLithiumScratchReg, Operand(cgen_->ToSmi(constant_source)));
246 __ sd(kLithiumScratchReg, cgen_->ToMemOperand(destination));
247 } else if (cgen_->IsInteger32(constant_source)) {
248 __ li(kLithiumScratchReg, Operand(cgen_->ToInteger32(constant_source)));
249 __ sd(kLithiumScratchReg, cgen_->ToMemOperand(destination));
250 } else {
251 __ li(kLithiumScratchReg, cgen_->ToHandle(constant_source));
252 __ sd(kLithiumScratchReg, cgen_->ToMemOperand(destination));
253 }
254 }
255
256 } else if (source->IsDoubleRegister()) {
257 DoubleRegister source_register = cgen_->ToDoubleRegister(source);
258 if (destination->IsDoubleRegister()) {
259 __ mov_d(cgen_->ToDoubleRegister(destination), source_register);
260 } else {
261 DCHECK(destination->IsDoubleStackSlot());
262 MemOperand destination_operand = cgen_->ToMemOperand(destination);
263 __ sdc1(source_register, destination_operand);
264 }
265
266 } else if (source->IsDoubleStackSlot()) {
267 MemOperand source_operand = cgen_->ToMemOperand(source);
268 if (destination->IsDoubleRegister()) {
269 __ ldc1(cgen_->ToDoubleRegister(destination), source_operand);
270 } else {
271 DCHECK(destination->IsDoubleStackSlot());
272 MemOperand destination_operand = cgen_->ToMemOperand(destination);
273 if (in_cycle_) {
274 // kLithiumScratchDouble was used to break the cycle,
275 // but kLithiumScratchReg is free.
276 MemOperand source_high_operand =
277 cgen_->ToHighMemOperand(source);
278 MemOperand destination_high_operand =
279 cgen_->ToHighMemOperand(destination);
280 __ lw(kLithiumScratchReg, source_operand);
281 __ sw(kLithiumScratchReg, destination_operand);
282 __ lw(kLithiumScratchReg, source_high_operand);
283 __ sw(kLithiumScratchReg, destination_high_operand);
284 } else {
285 __ ldc1(kLithiumScratchDouble, source_operand);
286 __ sdc1(kLithiumScratchDouble, destination_operand);
287 }
288 }
289 } else {
290 UNREACHABLE();
291 }
292
293 moves_[index].Eliminate();
294 }
295
296
297 #undef __
298
299 } // namespace internal
300 } // namespace v8
301