1 // Copyright 2011 the V8 project authors. All rights reserved. 2 // Redistribution and use in source and binary forms, with or without 3 // modification, are permitted provided that the following conditions are 4 // met: 5 // 6 // * Redistributions of source code must retain the above copyright 7 // notice, this list of conditions and the following disclaimer. 8 // * Redistributions in binary form must reproduce the above 9 // copyright notice, this list of conditions and the following 10 // disclaimer in the documentation and/or other materials provided 11 // with the distribution. 12 // * Neither the name of Google Inc. nor the names of its 13 // contributors may be used to endorse or promote products derived 14 // from this software without specific prior written permission. 15 // 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28 #include "v8.h" 29 30 #include "arm/lithium-gap-resolver-arm.h" 31 #include "arm/lithium-codegen-arm.h" 32 33 namespace v8 { 34 namespace internal { 35 36 static const Register kSavedValueRegister = { 9 }; 37 static const DoubleRegister kSavedDoubleValueRegister = { 0 }; 38 39 LGapResolver::LGapResolver(LCodeGen* owner) 40 : cgen_(owner), moves_(32), root_index_(0), in_cycle_(false), 41 saved_destination_(NULL) { } 42 43 44 void LGapResolver::Resolve(LParallelMove* parallel_move) { 45 ASSERT(moves_.is_empty()); 46 // Build up a worklist of moves. 47 BuildInitialMoveList(parallel_move); 48 49 for (int i = 0; i < moves_.length(); ++i) { 50 LMoveOperands move = moves_[i]; 51 // Skip constants to perform them last. They don't block other moves 52 // and skipping such moves with register destinations keeps those 53 // registers free for the whole algorithm. 54 if (!move.IsEliminated() && !move.source()->IsConstantOperand()) { 55 root_index_ = i; // Any cycle is found when by reaching this move again. 56 PerformMove(i); 57 if (in_cycle_) { 58 RestoreValue(); 59 } 60 } 61 } 62 63 // Perform the moves with constant sources. 64 for (int i = 0; i < moves_.length(); ++i) { 65 if (!moves_[i].IsEliminated()) { 66 ASSERT(moves_[i].source()->IsConstantOperand()); 67 EmitMove(i); 68 } 69 } 70 71 moves_.Rewind(0); 72 } 73 74 75 void LGapResolver::BuildInitialMoveList(LParallelMove* parallel_move) { 76 // Perform a linear sweep of the moves to add them to the initial list of 77 // moves to perform, ignoring any move that is redundant (the source is 78 // the same as the destination, the destination is ignored and 79 // unallocated, or the move was already eliminated). 80 const ZoneList<LMoveOperands>* moves = parallel_move->move_operands(); 81 for (int i = 0; i < moves->length(); ++i) { 82 LMoveOperands move = moves->at(i); 83 if (!move.IsRedundant()) moves_.Add(move); 84 } 85 Verify(); 86 } 87 88 89 void LGapResolver::PerformMove(int index) { 90 // Each call to this function performs a move and deletes it from the move 91 // graph. We first recursively perform any move blocking this one. We 92 // mark a move as "pending" on entry to PerformMove in order to detect 93 // cycles in the move graph. 94 95 // We can only find a cycle, when doing a depth-first traversal of moves, 96 // be encountering the starting move again. So by spilling the source of 97 // the starting move, we break the cycle. All moves are then unblocked, 98 // and the starting move is completed by writing the spilled value to 99 // its destination. All other moves from the spilled source have been 100 // completed prior to breaking the cycle. 101 // An additional complication is that moves to MemOperands with large 102 // offsets (more than 1K or 4K) require us to spill this spilled value to 103 // the stack, to free up the register. 104 ASSERT(!moves_[index].IsPending()); 105 ASSERT(!moves_[index].IsRedundant()); 106 107 // Clear this move's destination to indicate a pending move. The actual 108 // destination is saved in a stack allocated local. Multiple moves can 109 // be pending because this function is recursive. 110 ASSERT(moves_[index].source() != NULL); // Or else it will look eliminated. 111 LOperand* destination = moves_[index].destination(); 112 moves_[index].set_destination(NULL); 113 114 // Perform a depth-first traversal of the move graph to resolve 115 // dependencies. Any unperformed, unpending move with a source the same 116 // as this one's destination blocks this one so recursively perform all 117 // such moves. 118 for (int i = 0; i < moves_.length(); ++i) { 119 LMoveOperands other_move = moves_[i]; 120 if (other_move.Blocks(destination) && !other_move.IsPending()) { 121 PerformMove(i); 122 // If there is a blocking, pending move it must be moves_[root_index_] 123 // and all other moves with the same source as moves_[root_index_] are 124 // sucessfully executed (because they are cycle-free) by this loop. 125 } 126 } 127 128 // We are about to resolve this move and don't need it marked as 129 // pending, so restore its destination. 130 moves_[index].set_destination(destination); 131 132 // The move may be blocked on a pending move, which must be the starting move. 133 // In this case, we have a cycle, and we save the source of this move to 134 // a scratch register to break it. 135 LMoveOperands other_move = moves_[root_index_]; 136 if (other_move.Blocks(destination)) { 137 ASSERT(other_move.IsPending()); 138 BreakCycle(index); 139 return; 140 } 141 142 // This move is no longer blocked. 143 EmitMove(index); 144 } 145 146 147 void LGapResolver::Verify() { 148 #ifdef ENABLE_SLOW_ASSERTS 149 // No operand should be the destination for more than one move. 150 for (int i = 0; i < moves_.length(); ++i) { 151 LOperand* destination = moves_[i].destination(); 152 for (int j = i + 1; j < moves_.length(); ++j) { 153 SLOW_ASSERT(!destination->Equals(moves_[j].destination())); 154 } 155 } 156 #endif 157 } 158 159 #define __ ACCESS_MASM(cgen_->masm()) 160 161 void LGapResolver::BreakCycle(int index) { 162 // We save in a register the value that should end up in the source of 163 // moves_[root_index]. After performing all moves in the tree rooted 164 // in that move, we save the value to that source. 165 ASSERT(moves_[index].destination()->Equals(moves_[root_index_].source())); 166 ASSERT(!in_cycle_); 167 in_cycle_ = true; 168 LOperand* source = moves_[index].source(); 169 saved_destination_ = moves_[index].destination(); 170 if (source->IsRegister()) { 171 __ mov(kSavedValueRegister, cgen_->ToRegister(source)); 172 } else if (source->IsStackSlot()) { 173 __ ldr(kSavedValueRegister, cgen_->ToMemOperand(source)); 174 } else if (source->IsDoubleRegister()) { 175 __ vmov(kSavedDoubleValueRegister, cgen_->ToDoubleRegister(source)); 176 } else if (source->IsDoubleStackSlot()) { 177 __ vldr(kSavedDoubleValueRegister, cgen_->ToMemOperand(source)); 178 } else { 179 UNREACHABLE(); 180 } 181 // This move will be done by restoring the saved value to the destination. 182 moves_[index].Eliminate(); 183 } 184 185 186 void LGapResolver::RestoreValue() { 187 ASSERT(in_cycle_); 188 ASSERT(saved_destination_ != NULL); 189 190 // Spilled value is in kSavedValueRegister or kSavedDoubleValueRegister. 191 if (saved_destination_->IsRegister()) { 192 __ mov(cgen_->ToRegister(saved_destination_), kSavedValueRegister); 193 } else if (saved_destination_->IsStackSlot()) { 194 __ str(kSavedValueRegister, cgen_->ToMemOperand(saved_destination_)); 195 } else if (saved_destination_->IsDoubleRegister()) { 196 __ vmov(cgen_->ToDoubleRegister(saved_destination_), 197 kSavedDoubleValueRegister); 198 } else if (saved_destination_->IsDoubleStackSlot()) { 199 __ vstr(kSavedDoubleValueRegister, 200 cgen_->ToMemOperand(saved_destination_)); 201 } else { 202 UNREACHABLE(); 203 } 204 205 in_cycle_ = false; 206 saved_destination_ = NULL; 207 } 208 209 210 void LGapResolver::EmitMove(int index) { 211 LOperand* source = moves_[index].source(); 212 LOperand* destination = moves_[index].destination(); 213 214 // Dispatch on the source and destination operand kinds. Not all 215 // combinations are possible. 216 217 if (source->IsRegister()) { 218 Register source_register = cgen_->ToRegister(source); 219 if (destination->IsRegister()) { 220 __ mov(cgen_->ToRegister(destination), source_register); 221 } else { 222 ASSERT(destination->IsStackSlot()); 223 __ str(source_register, cgen_->ToMemOperand(destination)); 224 } 225 226 } else if (source->IsStackSlot()) { 227 MemOperand source_operand = cgen_->ToMemOperand(source); 228 if (destination->IsRegister()) { 229 __ ldr(cgen_->ToRegister(destination), source_operand); 230 } else { 231 ASSERT(destination->IsStackSlot()); 232 MemOperand destination_operand = cgen_->ToMemOperand(destination); 233 if (in_cycle_) { 234 if (!destination_operand.OffsetIsUint12Encodable()) { 235 // ip is overwritten while saving the value to the destination. 236 // Therefore we can't use ip. It is OK if the read from the source 237 // destroys ip, since that happens before the value is read. 238 __ vldr(kSavedDoubleValueRegister.low(), source_operand); 239 __ vstr(kSavedDoubleValueRegister.low(), destination_operand); 240 } else { 241 __ ldr(ip, source_operand); 242 __ str(ip, destination_operand); 243 } 244 } else { 245 __ ldr(kSavedValueRegister, source_operand); 246 __ str(kSavedValueRegister, destination_operand); 247 } 248 } 249 250 } else if (source->IsConstantOperand()) { 251 Operand source_operand = cgen_->ToOperand(source); 252 if (destination->IsRegister()) { 253 __ mov(cgen_->ToRegister(destination), source_operand); 254 } else { 255 ASSERT(destination->IsStackSlot()); 256 ASSERT(!in_cycle_); // Constant moves happen after all cycles are gone. 257 MemOperand destination_operand = cgen_->ToMemOperand(destination); 258 __ mov(kSavedValueRegister, source_operand); 259 __ str(kSavedValueRegister, cgen_->ToMemOperand(destination)); 260 } 261 262 } else if (source->IsDoubleRegister()) { 263 DoubleRegister source_register = cgen_->ToDoubleRegister(source); 264 if (destination->IsDoubleRegister()) { 265 __ vmov(cgen_->ToDoubleRegister(destination), source_register); 266 } else { 267 ASSERT(destination->IsDoubleStackSlot()); 268 MemOperand destination_operand = cgen_->ToMemOperand(destination); 269 __ vstr(source_register, destination_operand); 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 ASSERT(destination->IsDoubleStackSlot()); 278 MemOperand destination_operand = cgen_->ToMemOperand(destination); 279 if (in_cycle_) { 280 // kSavedDoubleValueRegister was used to break the cycle, 281 // but kSavedValueRegister is free. 282 MemOperand source_high_operand = 283 cgen_->ToHighMemOperand(source); 284 MemOperand destination_high_operand = 285 cgen_->ToHighMemOperand(destination); 286 __ ldr(kSavedValueRegister, source_operand); 287 __ str(kSavedValueRegister, destination_operand); 288 __ ldr(kSavedValueRegister, source_high_operand); 289 __ str(kSavedValueRegister, destination_high_operand); 290 } else { 291 __ vldr(kSavedDoubleValueRegister, source_operand); 292 __ vstr(kSavedDoubleValueRegister, destination_operand); 293 } 294 } 295 } else { 296 UNREACHABLE(); 297 } 298 299 moves_[index].Eliminate(); 300 } 301 302 303 #undef __ 304 305 } } // namespace v8::internal 306