Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 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/arm/lithium-codegen-arm.h" |
| 6 | #include "src/crankshaft/arm/lithium-gap-resolver-arm.h" |
| 7 | |
| 8 | namespace v8 { |
| 9 | namespace internal { |
| 10 | |
| 11 | // We use the root register to spill a value while breaking a cycle in parallel |
| 12 | // moves. We don't need access to roots while resolving the move list and using |
| 13 | // the root register has two advantages: |
| 14 | // - It is not in crankshaft allocatable registers list, so it can't interfere |
| 15 | // with any of the moves we are resolving. |
| 16 | // - We don't need to push it on the stack, as we can reload it with its value |
| 17 | // once we have resolved a cycle. |
| 18 | #define kSavedValueRegister kRootRegister |
| 19 | |
| 20 | |
| 21 | LGapResolver::LGapResolver(LCodeGen* owner) |
| 22 | : cgen_(owner), moves_(32, owner->zone()), root_index_(0), in_cycle_(false), |
| 23 | saved_destination_(NULL), need_to_restore_root_(false) { } |
| 24 | |
| 25 | |
| 26 | #define __ ACCESS_MASM(cgen_->masm()) |
| 27 | |
| 28 | |
| 29 | void LGapResolver::Resolve(LParallelMove* parallel_move) { |
| 30 | DCHECK(moves_.is_empty()); |
| 31 | // Build up a worklist of moves. |
| 32 | BuildInitialMoveList(parallel_move); |
| 33 | |
| 34 | for (int i = 0; i < moves_.length(); ++i) { |
| 35 | LMoveOperands move = moves_[i]; |
| 36 | // Skip constants to perform them last. They don't block other moves |
| 37 | // and skipping such moves with register destinations keeps those |
| 38 | // registers free for the whole algorithm. |
| 39 | if (!move.IsEliminated() && !move.source()->IsConstantOperand()) { |
| 40 | root_index_ = i; // Any cycle is found when by reaching this move again. |
| 41 | PerformMove(i); |
| 42 | if (in_cycle_) { |
| 43 | RestoreValue(); |
| 44 | } |
| 45 | } |
| 46 | } |
| 47 | |
| 48 | // Perform the moves with constant sources. |
| 49 | for (int i = 0; i < moves_.length(); ++i) { |
| 50 | if (!moves_[i].IsEliminated()) { |
| 51 | DCHECK(moves_[i].source()->IsConstantOperand()); |
| 52 | EmitMove(i); |
| 53 | } |
| 54 | } |
| 55 | |
| 56 | if (need_to_restore_root_) { |
| 57 | DCHECK(kSavedValueRegister.is(kRootRegister)); |
| 58 | __ InitializeRootRegister(); |
| 59 | need_to_restore_root_ = false; |
| 60 | } |
| 61 | |
| 62 | moves_.Rewind(0); |
| 63 | } |
| 64 | |
| 65 | |
| 66 | void LGapResolver::BuildInitialMoveList(LParallelMove* parallel_move) { |
| 67 | // Perform a linear sweep of the moves to add them to the initial list of |
| 68 | // moves to perform, ignoring any move that is redundant (the source is |
| 69 | // the same as the destination, the destination is ignored and |
| 70 | // unallocated, or the move was already eliminated). |
| 71 | const ZoneList<LMoveOperands>* moves = parallel_move->move_operands(); |
| 72 | for (int i = 0; i < moves->length(); ++i) { |
| 73 | LMoveOperands move = moves->at(i); |
| 74 | if (!move.IsRedundant()) moves_.Add(move, cgen_->zone()); |
| 75 | } |
| 76 | Verify(); |
| 77 | } |
| 78 | |
| 79 | |
| 80 | void LGapResolver::PerformMove(int index) { |
| 81 | // Each call to this function performs a move and deletes it from the move |
| 82 | // graph. We first recursively perform any move blocking this one. We |
| 83 | // mark a move as "pending" on entry to PerformMove in order to detect |
| 84 | // cycles in the move graph. |
| 85 | |
| 86 | // We can only find a cycle, when doing a depth-first traversal of moves, |
| 87 | // be encountering the starting move again. So by spilling the source of |
| 88 | // the starting move, we break the cycle. All moves are then unblocked, |
| 89 | // and the starting move is completed by writing the spilled value to |
| 90 | // its destination. All other moves from the spilled source have been |
| 91 | // completed prior to breaking the cycle. |
| 92 | // An additional complication is that moves to MemOperands with large |
| 93 | // offsets (more than 1K or 4K) require us to spill this spilled value to |
| 94 | // the stack, to free up the register. |
| 95 | DCHECK(!moves_[index].IsPending()); |
| 96 | DCHECK(!moves_[index].IsRedundant()); |
| 97 | |
| 98 | // Clear this move's destination to indicate a pending move. The actual |
| 99 | // destination is saved in a stack allocated local. Multiple moves can |
| 100 | // be pending because this function is recursive. |
| 101 | DCHECK(moves_[index].source() != NULL); // Or else it will look eliminated. |
| 102 | LOperand* destination = moves_[index].destination(); |
| 103 | moves_[index].set_destination(NULL); |
| 104 | |
| 105 | // Perform a depth-first traversal of the move graph to resolve |
| 106 | // dependencies. Any unperformed, unpending move with a source the same |
| 107 | // as this one's destination blocks this one so recursively perform all |
| 108 | // such moves. |
| 109 | for (int i = 0; i < moves_.length(); ++i) { |
| 110 | LMoveOperands other_move = moves_[i]; |
| 111 | if (other_move.Blocks(destination) && !other_move.IsPending()) { |
| 112 | PerformMove(i); |
| 113 | // If there is a blocking, pending move it must be moves_[root_index_] |
| 114 | // and all other moves with the same source as moves_[root_index_] are |
| 115 | // sucessfully executed (because they are cycle-free) by this loop. |
| 116 | } |
| 117 | } |
| 118 | |
| 119 | // We are about to resolve this move and don't need it marked as |
| 120 | // pending, so restore its destination. |
| 121 | moves_[index].set_destination(destination); |
| 122 | |
| 123 | // The move may be blocked on a pending move, which must be the starting move. |
| 124 | // In this case, we have a cycle, and we save the source of this move to |
| 125 | // a scratch register to break it. |
| 126 | LMoveOperands other_move = moves_[root_index_]; |
| 127 | if (other_move.Blocks(destination)) { |
| 128 | DCHECK(other_move.IsPending()); |
| 129 | BreakCycle(index); |
| 130 | return; |
| 131 | } |
| 132 | |
| 133 | // This move is no longer blocked. |
| 134 | EmitMove(index); |
| 135 | } |
| 136 | |
| 137 | |
| 138 | void LGapResolver::Verify() { |
| 139 | #ifdef ENABLE_SLOW_DCHECKS |
| 140 | // No operand should be the destination for more than one move. |
| 141 | for (int i = 0; i < moves_.length(); ++i) { |
| 142 | LOperand* destination = moves_[i].destination(); |
| 143 | for (int j = i + 1; j < moves_.length(); ++j) { |
| 144 | SLOW_DCHECK(!destination->Equals(moves_[j].destination())); |
| 145 | } |
| 146 | } |
| 147 | #endif |
| 148 | } |
| 149 | |
| 150 | |
| 151 | void LGapResolver::BreakCycle(int index) { |
| 152 | // We save in a register the source of that move and we remember its |
| 153 | // destination. Then we mark this move as resolved so the cycle is |
| 154 | // broken and we can perform the other moves. |
| 155 | DCHECK(moves_[index].destination()->Equals(moves_[root_index_].source())); |
| 156 | DCHECK(!in_cycle_); |
| 157 | in_cycle_ = true; |
| 158 | LOperand* source = moves_[index].source(); |
| 159 | saved_destination_ = moves_[index].destination(); |
| 160 | if (source->IsRegister()) { |
| 161 | need_to_restore_root_ = true; |
| 162 | __ mov(kSavedValueRegister, cgen_->ToRegister(source)); |
| 163 | } else if (source->IsStackSlot()) { |
| 164 | need_to_restore_root_ = true; |
| 165 | __ ldr(kSavedValueRegister, cgen_->ToMemOperand(source)); |
| 166 | } else if (source->IsDoubleRegister()) { |
| 167 | __ vmov(kScratchDoubleReg, cgen_->ToDoubleRegister(source)); |
| 168 | } else if (source->IsDoubleStackSlot()) { |
| 169 | __ vldr(kScratchDoubleReg, cgen_->ToMemOperand(source)); |
| 170 | } else { |
| 171 | UNREACHABLE(); |
| 172 | } |
| 173 | // This move will be done by restoring the saved value to the destination. |
| 174 | moves_[index].Eliminate(); |
| 175 | } |
| 176 | |
| 177 | |
| 178 | void LGapResolver::RestoreValue() { |
| 179 | DCHECK(in_cycle_); |
| 180 | DCHECK(saved_destination_ != NULL); |
| 181 | |
| 182 | if (saved_destination_->IsRegister()) { |
| 183 | __ mov(cgen_->ToRegister(saved_destination_), kSavedValueRegister); |
| 184 | } else if (saved_destination_->IsStackSlot()) { |
| 185 | __ str(kSavedValueRegister, cgen_->ToMemOperand(saved_destination_)); |
| 186 | } else if (saved_destination_->IsDoubleRegister()) { |
| 187 | __ vmov(cgen_->ToDoubleRegister(saved_destination_), kScratchDoubleReg); |
| 188 | } else if (saved_destination_->IsDoubleStackSlot()) { |
| 189 | __ vstr(kScratchDoubleReg, cgen_->ToMemOperand(saved_destination_)); |
| 190 | } else { |
| 191 | UNREACHABLE(); |
| 192 | } |
| 193 | |
| 194 | in_cycle_ = false; |
| 195 | saved_destination_ = NULL; |
| 196 | } |
| 197 | |
| 198 | |
| 199 | void LGapResolver::EmitMove(int index) { |
| 200 | LOperand* source = moves_[index].source(); |
| 201 | LOperand* destination = moves_[index].destination(); |
| 202 | |
| 203 | // Dispatch on the source and destination operand kinds. Not all |
| 204 | // combinations are possible. |
| 205 | |
| 206 | if (source->IsRegister()) { |
| 207 | Register source_register = cgen_->ToRegister(source); |
| 208 | if (destination->IsRegister()) { |
| 209 | __ mov(cgen_->ToRegister(destination), source_register); |
| 210 | } else { |
| 211 | DCHECK(destination->IsStackSlot()); |
| 212 | __ str(source_register, cgen_->ToMemOperand(destination)); |
| 213 | } |
| 214 | } else if (source->IsStackSlot()) { |
| 215 | MemOperand source_operand = cgen_->ToMemOperand(source); |
| 216 | if (destination->IsRegister()) { |
| 217 | __ ldr(cgen_->ToRegister(destination), source_operand); |
| 218 | } else { |
| 219 | DCHECK(destination->IsStackSlot()); |
| 220 | MemOperand destination_operand = cgen_->ToMemOperand(destination); |
| 221 | if (!destination_operand.OffsetIsUint12Encodable()) { |
| 222 | // ip is overwritten while saving the value to the destination. |
| 223 | // Therefore we can't use ip. It is OK if the read from the source |
| 224 | // destroys ip, since that happens before the value is read. |
| 225 | __ vldr(kScratchDoubleReg.low(), source_operand); |
| 226 | __ vstr(kScratchDoubleReg.low(), destination_operand); |
| 227 | } else { |
| 228 | __ ldr(ip, source_operand); |
| 229 | __ str(ip, destination_operand); |
| 230 | } |
| 231 | } |
| 232 | |
| 233 | } else if (source->IsConstantOperand()) { |
| 234 | LConstantOperand* constant_source = LConstantOperand::cast(source); |
| 235 | if (destination->IsRegister()) { |
| 236 | Register dst = cgen_->ToRegister(destination); |
| 237 | Representation r = cgen_->IsSmi(constant_source) |
| 238 | ? Representation::Smi() : Representation::Integer32(); |
| 239 | if (cgen_->IsInteger32(constant_source)) { |
| 240 | __ mov(dst, Operand(cgen_->ToRepresentation(constant_source, r))); |
| 241 | } else { |
| 242 | __ Move(dst, cgen_->ToHandle(constant_source)); |
| 243 | } |
| 244 | } else if (destination->IsDoubleRegister()) { |
| 245 | DwVfpRegister result = cgen_->ToDoubleRegister(destination); |
| 246 | double v = cgen_->ToDouble(constant_source); |
| 247 | __ Vmov(result, v, ip); |
| 248 | } else { |
| 249 | DCHECK(destination->IsStackSlot()); |
| 250 | DCHECK(!in_cycle_); // Constant moves happen after all cycles are gone. |
| 251 | need_to_restore_root_ = true; |
| 252 | Representation r = cgen_->IsSmi(constant_source) |
| 253 | ? Representation::Smi() : Representation::Integer32(); |
| 254 | if (cgen_->IsInteger32(constant_source)) { |
| 255 | __ mov(kSavedValueRegister, |
| 256 | Operand(cgen_->ToRepresentation(constant_source, r))); |
| 257 | } else { |
| 258 | __ Move(kSavedValueRegister, cgen_->ToHandle(constant_source)); |
| 259 | } |
| 260 | __ str(kSavedValueRegister, cgen_->ToMemOperand(destination)); |
| 261 | } |
| 262 | |
| 263 | } else if (source->IsDoubleRegister()) { |
| 264 | DwVfpRegister source_register = cgen_->ToDoubleRegister(source); |
| 265 | if (destination->IsDoubleRegister()) { |
| 266 | __ vmov(cgen_->ToDoubleRegister(destination), source_register); |
| 267 | } else { |
| 268 | DCHECK(destination->IsDoubleStackSlot()); |
| 269 | __ vstr(source_register, cgen_->ToMemOperand(destination)); |
| 270 | } |
| 271 | |
| 272 | } else if (source->IsDoubleStackSlot()) { |
| 273 | MemOperand source_operand = cgen_->ToMemOperand(source); |
| 274 | if (destination->IsDoubleRegister()) { |
| 275 | __ vldr(cgen_->ToDoubleRegister(destination), source_operand); |
| 276 | } else { |
| 277 | DCHECK(destination->IsDoubleStackSlot()); |
| 278 | MemOperand destination_operand = cgen_->ToMemOperand(destination); |
| 279 | if (in_cycle_) { |
| 280 | // kScratchDoubleReg was used to break the cycle. |
| 281 | __ vpush(kScratchDoubleReg); |
| 282 | __ vldr(kScratchDoubleReg, source_operand); |
| 283 | __ vstr(kScratchDoubleReg, destination_operand); |
| 284 | __ vpop(kScratchDoubleReg); |
| 285 | } else { |
| 286 | __ vldr(kScratchDoubleReg, source_operand); |
| 287 | __ vstr(kScratchDoubleReg, destination_operand); |
| 288 | } |
| 289 | } |
| 290 | } else { |
| 291 | UNREACHABLE(); |
| 292 | } |
| 293 | |
| 294 | moves_[index].Eliminate(); |
| 295 | } |
| 296 | |
| 297 | |
| 298 | #undef __ |
| 299 | |
| 300 | } // namespace internal |
| 301 | } // namespace v8 |