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/mips/lithium-gap-resolver-mips.h" 6 7#include "src/crankshaft/mips/lithium-codegen-mips.h" 8 9namespace v8 { 10namespace internal { 11 12LGapResolver::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 20void 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 51void 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 65void 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 123void 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 137void 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 __ lw(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 162void 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 __ sw(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 186void 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 __ sw(source_register, cgen_->ToMemOperand(destination)); 200 } 201 } else if (source->IsStackSlot()) { 202 MemOperand source_operand = cgen_->ToMemOperand(source); 203 if (destination->IsRegister()) { 204 __ lw(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 __ lwc1(kLithiumScratchDouble, source_operand); 215 __ swc1(kLithiumScratchDouble, destination_operand); 216 } else { 217 __ lw(at, source_operand); 218 __ sw(at, destination_operand); 219 } 220 } else { 221 __ lw(kLithiumScratchReg, source_operand); 222 __ sw(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 Representation r = cgen_->IsSmi(constant_source) 231 ? Representation::Smi() : Representation::Integer32(); 232 if (cgen_->IsInteger32(constant_source)) { 233 __ li(dst, Operand(cgen_->ToRepresentation(constant_source, r))); 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 Representation r = cgen_->IsSmi(constant_source) 245 ? Representation::Smi() : Representation::Integer32(); 246 if (cgen_->IsInteger32(constant_source)) { 247 __ li(kLithiumScratchReg, 248 Operand(cgen_->ToRepresentation(constant_source, r))); 249 } else { 250 __ li(kLithiumScratchReg, cgen_->ToHandle(constant_source)); 251 } 252 __ sw(kLithiumScratchReg, cgen_->ToMemOperand(destination)); 253 } 254 255 } else if (source->IsDoubleRegister()) { 256 DoubleRegister source_register = cgen_->ToDoubleRegister(source); 257 if (destination->IsDoubleRegister()) { 258 __ mov_d(cgen_->ToDoubleRegister(destination), source_register); 259 } else { 260 DCHECK(destination->IsDoubleStackSlot()); 261 MemOperand destination_operand = cgen_->ToMemOperand(destination); 262 __ sdc1(source_register, destination_operand); 263 } 264 265 } else if (source->IsDoubleStackSlot()) { 266 MemOperand source_operand = cgen_->ToMemOperand(source); 267 if (destination->IsDoubleRegister()) { 268 __ ldc1(cgen_->ToDoubleRegister(destination), source_operand); 269 } else { 270 DCHECK(destination->IsDoubleStackSlot()); 271 MemOperand destination_operand = cgen_->ToMemOperand(destination); 272 if (in_cycle_) { 273 // kLithiumScratchDouble was used to break the cycle, 274 // but kLithiumScratchReg is free. 275 MemOperand source_high_operand = 276 cgen_->ToHighMemOperand(source); 277 MemOperand destination_high_operand = 278 cgen_->ToHighMemOperand(destination); 279 __ lw(kLithiumScratchReg, source_operand); 280 __ sw(kLithiumScratchReg, destination_operand); 281 __ lw(kLithiumScratchReg, source_high_operand); 282 __ sw(kLithiumScratchReg, destination_high_operand); 283 } else { 284 __ ldc1(kLithiumScratchDouble, source_operand); 285 __ sdc1(kLithiumScratchDouble, destination_operand); 286 } 287 } 288 } else { 289 UNREACHABLE(); 290 } 291 292 moves_[index].Eliminate(); 293} 294 295 296#undef __ 297 298} // namespace internal 299} // namespace v8 300