Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2014 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
Mathieu Chartier | b666f48 | 2015-02-18 14:33:14 -0800 | [diff] [blame] | 17 | #include "base/arena_containers.h" |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 18 | #include "bounds_check_elimination.h" |
| 19 | #include "nodes.h" |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 20 | |
| 21 | namespace art { |
| 22 | |
| 23 | class MonotonicValueRange; |
| 24 | |
| 25 | /** |
| 26 | * A value bound is represented as a pair of value and constant, |
| 27 | * e.g. array.length - 1. |
| 28 | */ |
| 29 | class ValueBound : public ValueObject { |
| 30 | public: |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 31 | ValueBound(HInstruction* instruction, int32_t constant) { |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 32 | if (instruction != nullptr && instruction->IsIntConstant()) { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 33 | // Normalize ValueBound with constant instruction. |
| 34 | int32_t instr_const = instruction->AsIntConstant()->GetValue(); |
Mingyao Yang | 8c8bad8 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 35 | if (!WouldAddOverflowOrUnderflow(instr_const, constant)) { |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 36 | instruction_ = nullptr; |
| 37 | constant_ = instr_const + constant; |
| 38 | return; |
| 39 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 40 | } |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 41 | instruction_ = instruction; |
| 42 | constant_ = constant; |
| 43 | } |
| 44 | |
Mingyao Yang | 8c8bad8 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 45 | // Return whether (left + right) overflows or underflows. |
| 46 | static bool WouldAddOverflowOrUnderflow(int32_t left, int32_t right) { |
| 47 | if (right == 0) { |
| 48 | return false; |
| 49 | } |
| 50 | if ((right > 0) && (left <= INT_MAX - right)) { |
| 51 | // No overflow. |
| 52 | return false; |
| 53 | } |
| 54 | if ((right < 0) && (left >= INT_MIN - right)) { |
| 55 | // No underflow. |
| 56 | return false; |
| 57 | } |
| 58 | return true; |
| 59 | } |
| 60 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 61 | static bool IsAddOrSubAConstant(HInstruction* instruction, |
| 62 | HInstruction** left_instruction, |
| 63 | int* right_constant) { |
| 64 | if (instruction->IsAdd() || instruction->IsSub()) { |
| 65 | HBinaryOperation* bin_op = instruction->AsBinaryOperation(); |
| 66 | HInstruction* left = bin_op->GetLeft(); |
| 67 | HInstruction* right = bin_op->GetRight(); |
| 68 | if (right->IsIntConstant()) { |
| 69 | *left_instruction = left; |
| 70 | int32_t c = right->AsIntConstant()->GetValue(); |
| 71 | *right_constant = instruction->IsAdd() ? c : -c; |
| 72 | return true; |
| 73 | } |
| 74 | } |
| 75 | *left_instruction = nullptr; |
| 76 | *right_constant = 0; |
| 77 | return false; |
| 78 | } |
| 79 | |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 80 | // Try to detect useful value bound format from an instruction, e.g. |
| 81 | // a constant or array length related value. |
| 82 | static ValueBound DetectValueBoundFromValue(HInstruction* instruction, bool* found) { |
| 83 | DCHECK(instruction != nullptr); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 84 | if (instruction->IsIntConstant()) { |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 85 | *found = true; |
| 86 | return ValueBound(nullptr, instruction->AsIntConstant()->GetValue()); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 87 | } |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 88 | |
| 89 | if (instruction->IsArrayLength()) { |
| 90 | *found = true; |
| 91 | return ValueBound(instruction, 0); |
| 92 | } |
| 93 | // Try to detect (array.length + c) format. |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 94 | HInstruction *left; |
| 95 | int32_t right; |
| 96 | if (IsAddOrSubAConstant(instruction, &left, &right)) { |
| 97 | if (left->IsArrayLength()) { |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 98 | *found = true; |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 99 | return ValueBound(left, right); |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 100 | } |
| 101 | } |
| 102 | |
| 103 | // No useful bound detected. |
| 104 | *found = false; |
| 105 | return ValueBound::Max(); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 106 | } |
| 107 | |
| 108 | HInstruction* GetInstruction() const { return instruction_; } |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 109 | int32_t GetConstant() const { return constant_; } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 110 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 111 | bool IsRelatedToArrayLength() const { |
| 112 | // Some bounds are created with HNewArray* as the instruction instead |
| 113 | // of HArrayLength*. They are treated the same. |
| 114 | return (instruction_ != nullptr) && |
| 115 | (instruction_->IsArrayLength() || instruction_->IsNewArray()); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 116 | } |
| 117 | |
| 118 | bool IsConstant() const { |
| 119 | return instruction_ == nullptr; |
| 120 | } |
| 121 | |
| 122 | static ValueBound Min() { return ValueBound(nullptr, INT_MIN); } |
| 123 | static ValueBound Max() { return ValueBound(nullptr, INT_MAX); } |
| 124 | |
| 125 | bool Equals(ValueBound bound) const { |
| 126 | return instruction_ == bound.instruction_ && constant_ == bound.constant_; |
| 127 | } |
| 128 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 129 | static HInstruction* FromArrayLengthToNewArrayIfPossible(HInstruction* instruction) { |
| 130 | // Null check on the NewArray should have been eliminated by instruction |
| 131 | // simplifier already. |
| 132 | if (instruction->IsArrayLength() && instruction->InputAt(0)->IsNewArray()) { |
| 133 | return instruction->InputAt(0)->AsNewArray(); |
| 134 | } |
| 135 | return instruction; |
| 136 | } |
| 137 | |
| 138 | static bool Equal(HInstruction* instruction1, HInstruction* instruction2) { |
| 139 | if (instruction1 == instruction2) { |
| 140 | return true; |
| 141 | } |
| 142 | |
| 143 | if (instruction1 == nullptr || instruction2 == nullptr) { |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 144 | return false; |
| 145 | } |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 146 | |
| 147 | // Some bounds are created with HNewArray* as the instruction instead |
| 148 | // of HArrayLength*. They are treated the same. |
| 149 | instruction1 = FromArrayLengthToNewArrayIfPossible(instruction1); |
| 150 | instruction2 = FromArrayLengthToNewArrayIfPossible(instruction2); |
| 151 | return instruction1 == instruction2; |
| 152 | } |
| 153 | |
| 154 | // Returns if it's certain this->bound >= `bound`. |
| 155 | bool GreaterThanOrEqualTo(ValueBound bound) const { |
| 156 | if (Equal(instruction_, bound.instruction_)) { |
| 157 | return constant_ >= bound.constant_; |
| 158 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 159 | // Not comparable. Just return false. |
| 160 | return false; |
| 161 | } |
| 162 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 163 | // Returns if it's certain this->bound <= `bound`. |
| 164 | bool LessThanOrEqualTo(ValueBound bound) const { |
| 165 | if (Equal(instruction_, bound.instruction_)) { |
| 166 | return constant_ <= bound.constant_; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 167 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 168 | // Not comparable. Just return false. |
| 169 | return false; |
| 170 | } |
| 171 | |
| 172 | // Try to narrow lower bound. Returns the greatest of the two if possible. |
| 173 | // Pick one if they are not comparable. |
| 174 | static ValueBound NarrowLowerBound(ValueBound bound1, ValueBound bound2) { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 175 | if (bound1.GreaterThanOrEqualTo(bound2)) { |
| 176 | return bound1; |
| 177 | } |
| 178 | if (bound2.GreaterThanOrEqualTo(bound1)) { |
| 179 | return bound2; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 180 | } |
| 181 | |
| 182 | // Not comparable. Just pick one. We may lose some info, but that's ok. |
| 183 | // Favor constant as lower bound. |
| 184 | return bound1.IsConstant() ? bound1 : bound2; |
| 185 | } |
| 186 | |
| 187 | // Try to narrow upper bound. Returns the lowest of the two if possible. |
| 188 | // Pick one if they are not comparable. |
| 189 | static ValueBound NarrowUpperBound(ValueBound bound1, ValueBound bound2) { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 190 | if (bound1.LessThanOrEqualTo(bound2)) { |
| 191 | return bound1; |
| 192 | } |
| 193 | if (bound2.LessThanOrEqualTo(bound1)) { |
| 194 | return bound2; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 195 | } |
| 196 | |
| 197 | // Not comparable. Just pick one. We may lose some info, but that's ok. |
| 198 | // Favor array length as upper bound. |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 199 | return bound1.IsRelatedToArrayLength() ? bound1 : bound2; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 200 | } |
| 201 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 202 | // Add a constant to a ValueBound. |
| 203 | // `overflow` or `underflow` will return whether the resulting bound may |
| 204 | // overflow or underflow an int. |
| 205 | ValueBound Add(int32_t c, bool* overflow, bool* underflow) const { |
| 206 | *overflow = *underflow = false; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 207 | if (c == 0) { |
| 208 | return *this; |
| 209 | } |
| 210 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 211 | int32_t new_constant; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 212 | if (c > 0) { |
| 213 | if (constant_ > INT_MAX - c) { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 214 | *overflow = true; |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 215 | return Max(); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 216 | } |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 217 | |
| 218 | new_constant = constant_ + c; |
| 219 | // (array.length + non-positive-constant) won't overflow an int. |
| 220 | if (IsConstant() || (IsRelatedToArrayLength() && new_constant <= 0)) { |
| 221 | return ValueBound(instruction_, new_constant); |
| 222 | } |
| 223 | // Be conservative. |
| 224 | *overflow = true; |
| 225 | return Max(); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 226 | } else { |
| 227 | if (constant_ < INT_MIN - c) { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 228 | *underflow = true; |
| 229 | return Min(); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 230 | } |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 231 | |
| 232 | new_constant = constant_ + c; |
| 233 | // Regardless of the value new_constant, (array.length+new_constant) will |
| 234 | // never underflow since array.length is no less than 0. |
| 235 | if (IsConstant() || IsRelatedToArrayLength()) { |
| 236 | return ValueBound(instruction_, new_constant); |
| 237 | } |
| 238 | // Be conservative. |
| 239 | *underflow = true; |
| 240 | return Min(); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 241 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 242 | } |
| 243 | |
| 244 | private: |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 245 | HInstruction* instruction_; |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 246 | int32_t constant_; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 247 | }; |
| 248 | |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 249 | // Collect array access data for a loop. |
| 250 | // TODO: make it work for multiple arrays inside the loop. |
| 251 | class ArrayAccessInsideLoopFinder : public ValueObject { |
| 252 | public: |
| 253 | explicit ArrayAccessInsideLoopFinder(HInstruction* induction_variable) |
| 254 | : induction_variable_(induction_variable), |
| 255 | found_array_length_(nullptr), |
| 256 | offset_low_(INT_MAX), |
| 257 | offset_high_(INT_MIN) { |
| 258 | Run(); |
| 259 | } |
| 260 | |
| 261 | HArrayLength* GetFoundArrayLength() const { return found_array_length_; } |
| 262 | bool HasFoundArrayLength() const { return found_array_length_ != nullptr; } |
| 263 | int32_t GetOffsetLow() const { return offset_low_; } |
| 264 | int32_t GetOffsetHigh() const { return offset_high_; } |
| 265 | |
Mingyao Yang | 9d750ef | 2015-04-26 18:15:30 -0700 | [diff] [blame] | 266 | // Returns if `block` that is in loop_info may exit the loop, unless it's |
| 267 | // the loop header for loop_info. |
| 268 | static bool EarlyExit(HBasicBlock* block, HLoopInformation* loop_info) { |
| 269 | DCHECK(loop_info->Contains(*block)); |
| 270 | if (block == loop_info->GetHeader()) { |
| 271 | // Loop header of loop_info. Exiting loop is normal. |
| 272 | return false; |
| 273 | } |
| 274 | const GrowableArray<HBasicBlock*> successors = block->GetSuccessors(); |
| 275 | for (size_t i = 0; i < successors.Size(); i++) { |
| 276 | if (!loop_info->Contains(*successors.Get(i))) { |
| 277 | // One of the successors exits the loop. |
| 278 | return true; |
| 279 | } |
| 280 | } |
| 281 | return false; |
| 282 | } |
| 283 | |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 284 | void Run() { |
| 285 | HLoopInformation* loop_info = induction_variable_->GetBlock()->GetLoopInformation(); |
| 286 | // Must be simplified loop. |
| 287 | DCHECK_EQ(loop_info->GetBackEdges().Size(), 1U); |
Mingyao Yang | 9d750ef | 2015-04-26 18:15:30 -0700 | [diff] [blame] | 288 | for (HBlocksInLoopIterator it_loop(*loop_info); !it_loop.Done(); it_loop.Advance()) { |
| 289 | HBasicBlock* block = it_loop.Current(); |
| 290 | DCHECK(block->IsInLoop()); |
| 291 | HBasicBlock* back_edge = loop_info->GetBackEdges().Get(0); |
| 292 | if (!block->Dominates(back_edge)) { |
| 293 | // In order not to trigger deoptimization unnecessarily, make sure |
| 294 | // that all array accesses collected are really executed in the loop. |
| 295 | // For array accesses in a branch inside the loop, don't collect the |
| 296 | // access. The bounds check in that branch might not be eliminated. |
| 297 | continue; |
| 298 | } |
| 299 | if (EarlyExit(block, loop_info)) { |
| 300 | // If the loop body can exit loop (like break, return, etc.), it's not guaranteed |
| 301 | // that the loop will loop through the full monotonic value range from |
| 302 | // initial_ to end_. So adding deoptimization might be too aggressive and can |
| 303 | // trigger deoptimization unnecessarily even if the loop won't actually throw |
| 304 | // AIOOBE. Otherwise, the loop induction variable is going to cover the full |
| 305 | // monotonic value range from initial_ to end_, and deoptimizations are added |
| 306 | // iff the loop will throw AIOOBE. |
| 307 | found_array_length_ = nullptr; |
| 308 | return; |
| 309 | } |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 310 | for (HInstruction* instruction = block->GetFirstInstruction(); |
| 311 | instruction != nullptr; |
| 312 | instruction = instruction->GetNext()) { |
| 313 | if (!instruction->IsArrayGet() && !instruction->IsArraySet()) { |
| 314 | continue; |
| 315 | } |
| 316 | HInstruction* index = instruction->InputAt(1); |
| 317 | if (!index->IsBoundsCheck()) { |
| 318 | continue; |
| 319 | } |
| 320 | |
| 321 | HArrayLength* array_length = index->InputAt(1)->AsArrayLength(); |
| 322 | if (array_length == nullptr) { |
| 323 | DCHECK(index->InputAt(1)->IsIntConstant()); |
| 324 | // TODO: may optimize for constant case. |
| 325 | continue; |
| 326 | } |
| 327 | |
| 328 | HInstruction* array = array_length->InputAt(0); |
| 329 | if (array->IsNullCheck()) { |
| 330 | array = array->AsNullCheck()->InputAt(0); |
| 331 | } |
| 332 | if (loop_info->Contains(*array->GetBlock())) { |
| 333 | // Array is defined inside the loop. Skip. |
| 334 | continue; |
| 335 | } |
| 336 | |
| 337 | if (found_array_length_ != nullptr && found_array_length_ != array_length) { |
| 338 | // There is already access for another array recorded for the loop. |
| 339 | // TODO: handle multiple arrays. |
| 340 | continue; |
| 341 | } |
| 342 | |
| 343 | index = index->AsBoundsCheck()->InputAt(0); |
| 344 | HInstruction* left = index; |
| 345 | int32_t right = 0; |
| 346 | if (left == induction_variable_ || |
| 347 | (ValueBound::IsAddOrSubAConstant(index, &left, &right) && |
| 348 | left == induction_variable_)) { |
| 349 | // For patterns like array[i] or array[i + 2]. |
| 350 | if (right < offset_low_) { |
| 351 | offset_low_ = right; |
| 352 | } |
| 353 | if (right > offset_high_) { |
| 354 | offset_high_ = right; |
| 355 | } |
| 356 | } else { |
| 357 | // Access not in induction_variable/(induction_variable_ + constant) |
| 358 | // format. Skip. |
| 359 | continue; |
| 360 | } |
| 361 | // Record this array. |
| 362 | found_array_length_ = array_length; |
| 363 | } |
| 364 | } |
| 365 | } |
| 366 | |
| 367 | private: |
| 368 | // The instruction that corresponds to a MonotonicValueRange. |
| 369 | HInstruction* induction_variable_; |
| 370 | |
| 371 | // The array length of the array that's accessed inside the loop. |
| 372 | HArrayLength* found_array_length_; |
| 373 | |
| 374 | // The lowest and highest constant offsets relative to induction variable |
| 375 | // instruction_ in all array accesses. |
| 376 | // If array access are: array[i-1], array[i], array[i+1], |
| 377 | // offset_low_ is -1 and offset_high is 1. |
| 378 | int32_t offset_low_; |
| 379 | int32_t offset_high_; |
| 380 | |
| 381 | DISALLOW_COPY_AND_ASSIGN(ArrayAccessInsideLoopFinder); |
| 382 | }; |
| 383 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 384 | /** |
| 385 | * Represent a range of lower bound and upper bound, both being inclusive. |
| 386 | * Currently a ValueRange may be generated as a result of the following: |
| 387 | * comparisons related to array bounds, array bounds check, add/sub on top |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 388 | * of an existing value range, NewArray or a loop phi corresponding to an |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 389 | * incrementing/decrementing array index (MonotonicValueRange). |
| 390 | */ |
| 391 | class ValueRange : public ArenaObject<kArenaAllocMisc> { |
| 392 | public: |
| 393 | ValueRange(ArenaAllocator* allocator, ValueBound lower, ValueBound upper) |
| 394 | : allocator_(allocator), lower_(lower), upper_(upper) {} |
| 395 | |
| 396 | virtual ~ValueRange() {} |
| 397 | |
Mingyao Yang | 57e0475 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 398 | virtual MonotonicValueRange* AsMonotonicValueRange() { return nullptr; } |
| 399 | bool IsMonotonicValueRange() { |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 400 | return AsMonotonicValueRange() != nullptr; |
| 401 | } |
| 402 | |
| 403 | ArenaAllocator* GetAllocator() const { return allocator_; } |
| 404 | ValueBound GetLower() const { return lower_; } |
| 405 | ValueBound GetUpper() const { return upper_; } |
| 406 | |
| 407 | // If it's certain that this value range fits in other_range. |
| 408 | virtual bool FitsIn(ValueRange* other_range) const { |
| 409 | if (other_range == nullptr) { |
| 410 | return true; |
| 411 | } |
| 412 | DCHECK(!other_range->IsMonotonicValueRange()); |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 413 | return lower_.GreaterThanOrEqualTo(other_range->lower_) && |
| 414 | upper_.LessThanOrEqualTo(other_range->upper_); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 415 | } |
| 416 | |
| 417 | // Returns the intersection of this and range. |
| 418 | // If it's not possible to do intersection because some |
| 419 | // bounds are not comparable, it's ok to pick either bound. |
| 420 | virtual ValueRange* Narrow(ValueRange* range) { |
| 421 | if (range == nullptr) { |
| 422 | return this; |
| 423 | } |
| 424 | |
| 425 | if (range->IsMonotonicValueRange()) { |
| 426 | return this; |
| 427 | } |
| 428 | |
| 429 | return new (allocator_) ValueRange( |
| 430 | allocator_, |
| 431 | ValueBound::NarrowLowerBound(lower_, range->lower_), |
| 432 | ValueBound::NarrowUpperBound(upper_, range->upper_)); |
| 433 | } |
| 434 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 435 | // Shift a range by a constant. |
| 436 | ValueRange* Add(int32_t constant) const { |
| 437 | bool overflow, underflow; |
| 438 | ValueBound lower = lower_.Add(constant, &overflow, &underflow); |
| 439 | if (underflow) { |
| 440 | // Lower bound underflow will wrap around to positive values |
| 441 | // and invalidate the upper bound. |
| 442 | return nullptr; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 443 | } |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 444 | ValueBound upper = upper_.Add(constant, &overflow, &underflow); |
| 445 | if (overflow) { |
| 446 | // Upper bound overflow will wrap around to negative values |
| 447 | // and invalidate the lower bound. |
| 448 | return nullptr; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 449 | } |
| 450 | return new (allocator_) ValueRange(allocator_, lower, upper); |
| 451 | } |
| 452 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 453 | private: |
| 454 | ArenaAllocator* const allocator_; |
| 455 | const ValueBound lower_; // inclusive |
| 456 | const ValueBound upper_; // inclusive |
| 457 | |
| 458 | DISALLOW_COPY_AND_ASSIGN(ValueRange); |
| 459 | }; |
| 460 | |
| 461 | /** |
| 462 | * A monotonically incrementing/decrementing value range, e.g. |
| 463 | * the variable i in "for (int i=0; i<array.length; i++)". |
| 464 | * Special care needs to be taken to account for overflow/underflow |
| 465 | * of such value ranges. |
| 466 | */ |
| 467 | class MonotonicValueRange : public ValueRange { |
| 468 | public: |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 469 | MonotonicValueRange(ArenaAllocator* allocator, |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 470 | HPhi* induction_variable, |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 471 | HInstruction* initial, |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 472 | int32_t increment, |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 473 | ValueBound bound) |
| 474 | // To be conservative, give it full range [INT_MIN, INT_MAX] in case it's |
| 475 | // used as a regular value range, due to possible overflow/underflow. |
| 476 | : ValueRange(allocator, ValueBound::Min(), ValueBound::Max()), |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 477 | induction_variable_(induction_variable), |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 478 | initial_(initial), |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 479 | end_(nullptr), |
| 480 | inclusive_(false), |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 481 | increment_(increment), |
| 482 | bound_(bound) {} |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 483 | |
| 484 | virtual ~MonotonicValueRange() {} |
| 485 | |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 486 | HInstruction* GetInductionVariable() const { return induction_variable_; } |
Mingyao Yang | 57e0475 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 487 | int32_t GetIncrement() const { return increment_; } |
Mingyao Yang | 57e0475 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 488 | ValueBound GetBound() const { return bound_; } |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 489 | void SetEnd(HInstruction* end) { end_ = end; } |
| 490 | void SetInclusive(bool inclusive) { inclusive_ = inclusive; } |
| 491 | HBasicBlock* GetLoopHead() const { |
| 492 | DCHECK(induction_variable_->GetBlock()->IsLoopHeader()); |
| 493 | return induction_variable_->GetBlock(); |
| 494 | } |
Mingyao Yang | 57e0475 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 495 | |
| 496 | MonotonicValueRange* AsMonotonicValueRange() OVERRIDE { return this; } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 497 | |
| 498 | // If it's certain that this value range fits in other_range. |
| 499 | bool FitsIn(ValueRange* other_range) const OVERRIDE { |
| 500 | if (other_range == nullptr) { |
| 501 | return true; |
| 502 | } |
| 503 | DCHECK(!other_range->IsMonotonicValueRange()); |
| 504 | return false; |
| 505 | } |
| 506 | |
| 507 | // Try to narrow this MonotonicValueRange given another range. |
| 508 | // Ideally it will return a normal ValueRange. But due to |
| 509 | // possible overflow/underflow, that may not be possible. |
| 510 | ValueRange* Narrow(ValueRange* range) OVERRIDE { |
| 511 | if (range == nullptr) { |
| 512 | return this; |
| 513 | } |
| 514 | DCHECK(!range->IsMonotonicValueRange()); |
| 515 | |
| 516 | if (increment_ > 0) { |
| 517 | // Monotonically increasing. |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 518 | ValueBound lower = ValueBound::NarrowLowerBound(bound_, range->GetLower()); |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 519 | if (!lower.IsConstant() || lower.GetConstant() == INT_MIN) { |
| 520 | // Lower bound isn't useful. Leave it to deoptimization. |
| 521 | return this; |
| 522 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 523 | |
| 524 | // We currently conservatively assume max array length is INT_MAX. If we can |
| 525 | // make assumptions about the max array length, e.g. due to the max heap size, |
| 526 | // divided by the element size (such as 4 bytes for each integer array), we can |
| 527 | // lower this number and rule out some possible overflows. |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 528 | int32_t max_array_len = INT_MAX; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 529 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 530 | // max possible integer value of range's upper value. |
| 531 | int32_t upper = INT_MAX; |
| 532 | // Try to lower upper. |
| 533 | ValueBound upper_bound = range->GetUpper(); |
| 534 | if (upper_bound.IsConstant()) { |
| 535 | upper = upper_bound.GetConstant(); |
| 536 | } else if (upper_bound.IsRelatedToArrayLength() && upper_bound.GetConstant() <= 0) { |
| 537 | // Normal case. e.g. <= array.length - 1. |
| 538 | upper = max_array_len + upper_bound.GetConstant(); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 539 | } |
| 540 | |
| 541 | // If we can prove for the last number in sequence of initial_, |
| 542 | // initial_ + increment_, initial_ + 2 x increment_, ... |
| 543 | // that's <= upper, (last_num_in_sequence + increment_) doesn't trigger overflow, |
| 544 | // then this MonoticValueRange is narrowed to a normal value range. |
| 545 | |
| 546 | // Be conservative first, assume last number in the sequence hits upper. |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 547 | int32_t last_num_in_sequence = upper; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 548 | if (initial_->IsIntConstant()) { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 549 | int32_t initial_constant = initial_->AsIntConstant()->GetValue(); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 550 | if (upper <= initial_constant) { |
| 551 | last_num_in_sequence = upper; |
| 552 | } else { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 553 | // Cast to int64_t for the substraction part to avoid int32_t overflow. |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 554 | last_num_in_sequence = initial_constant + |
| 555 | ((int64_t)upper - (int64_t)initial_constant) / increment_ * increment_; |
| 556 | } |
| 557 | } |
| 558 | if (last_num_in_sequence <= INT_MAX - increment_) { |
| 559 | // No overflow. The sequence will be stopped by the upper bound test as expected. |
| 560 | return new (GetAllocator()) ValueRange(GetAllocator(), lower, range->GetUpper()); |
| 561 | } |
| 562 | |
| 563 | // There might be overflow. Give up narrowing. |
| 564 | return this; |
| 565 | } else { |
| 566 | DCHECK_NE(increment_, 0); |
| 567 | // Monotonically decreasing. |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 568 | ValueBound upper = ValueBound::NarrowUpperBound(bound_, range->GetUpper()); |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 569 | if ((!upper.IsConstant() || upper.GetConstant() == INT_MAX) && |
| 570 | !upper.IsRelatedToArrayLength()) { |
| 571 | // Upper bound isn't useful. Leave it to deoptimization. |
| 572 | return this; |
| 573 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 574 | |
| 575 | // Need to take care of underflow. Try to prove underflow won't happen |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 576 | // for common cases. |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 577 | if (range->GetLower().IsConstant()) { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 578 | int32_t constant = range->GetLower().GetConstant(); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 579 | if (constant >= INT_MIN - increment_) { |
| 580 | return new (GetAllocator()) ValueRange(GetAllocator(), range->GetLower(), upper); |
| 581 | } |
| 582 | } |
| 583 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 584 | // For non-constant lower bound, just assume might be underflow. Give up narrowing. |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 585 | return this; |
| 586 | } |
| 587 | } |
| 588 | |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 589 | // Returns true if adding a (constant >= value) check for deoptimization |
| 590 | // is allowed and will benefit compiled code. |
| 591 | bool CanAddDeoptimizationConstant(HInstruction* value, |
| 592 | int32_t constant, |
| 593 | bool* is_proven) { |
| 594 | *is_proven = false; |
| 595 | // See if we can prove the relationship first. |
| 596 | if (value->IsIntConstant()) { |
| 597 | if (value->AsIntConstant()->GetValue() >= constant) { |
| 598 | // Already true. |
| 599 | *is_proven = true; |
| 600 | return true; |
| 601 | } else { |
| 602 | // May throw exception. Don't add deoptimization. |
| 603 | // Keep bounds checks in the loops. |
| 604 | return false; |
| 605 | } |
| 606 | } |
| 607 | // Can benefit from deoptimization. |
| 608 | return true; |
| 609 | } |
| 610 | |
| 611 | // Adds a check that (value >= constant), and HDeoptimize otherwise. |
| 612 | void AddDeoptimizationConstant(HInstruction* value, |
| 613 | int32_t constant) { |
| 614 | HBasicBlock* block = induction_variable_->GetBlock(); |
| 615 | DCHECK(block->IsLoopHeader()); |
| 616 | HGraph* graph = block->GetGraph(); |
| 617 | HBasicBlock* pre_header = block->GetLoopInformation()->GetPreHeader(); |
| 618 | HSuspendCheck* suspend_check = block->GetLoopInformation()->GetSuspendCheck(); |
| 619 | HIntConstant* const_instr = graph->GetIntConstant(constant); |
| 620 | HCondition* cond = new (graph->GetArena()) HLessThan(value, const_instr); |
| 621 | HDeoptimize* deoptimize = new (graph->GetArena()) |
| 622 | HDeoptimize(cond, suspend_check->GetDexPc()); |
| 623 | pre_header->InsertInstructionBefore(cond, pre_header->GetLastInstruction()); |
| 624 | pre_header->InsertInstructionBefore(deoptimize, pre_header->GetLastInstruction()); |
| 625 | deoptimize->CopyEnvironmentFromWithLoopPhiAdjustment( |
| 626 | suspend_check->GetEnvironment(), block); |
| 627 | } |
| 628 | |
| 629 | // Returns true if adding a (value <= array_length + offset) check for deoptimization |
| 630 | // is allowed and will benefit compiled code. |
| 631 | bool CanAddDeoptimizationArrayLength(HInstruction* value, |
| 632 | HArrayLength* array_length, |
| 633 | int32_t offset, |
| 634 | bool* is_proven) { |
| 635 | *is_proven = false; |
| 636 | if (offset > 0) { |
| 637 | // There might be overflow issue. |
| 638 | // TODO: handle this, possibly with some distance relationship between |
| 639 | // offset_low and offset_high, or using another deoptimization to make |
| 640 | // sure (array_length + offset) doesn't overflow. |
| 641 | return false; |
| 642 | } |
| 643 | |
| 644 | // See if we can prove the relationship first. |
| 645 | if (value == array_length) { |
| 646 | if (offset >= 0) { |
| 647 | // Already true. |
| 648 | *is_proven = true; |
| 649 | return true; |
| 650 | } else { |
| 651 | // May throw exception. Don't add deoptimization. |
| 652 | // Keep bounds checks in the loops. |
| 653 | return false; |
| 654 | } |
| 655 | } |
| 656 | // Can benefit from deoptimization. |
| 657 | return true; |
| 658 | } |
| 659 | |
| 660 | // Adds a check that (value <= array_length + offset), and HDeoptimize otherwise. |
| 661 | void AddDeoptimizationArrayLength(HInstruction* value, |
| 662 | HArrayLength* array_length, |
| 663 | int32_t offset) { |
| 664 | HBasicBlock* block = induction_variable_->GetBlock(); |
| 665 | DCHECK(block->IsLoopHeader()); |
| 666 | HGraph* graph = block->GetGraph(); |
| 667 | HBasicBlock* pre_header = block->GetLoopInformation()->GetPreHeader(); |
| 668 | HSuspendCheck* suspend_check = block->GetLoopInformation()->GetSuspendCheck(); |
| 669 | |
| 670 | // We may need to hoist null-check and array_length out of loop first. |
| 671 | if (!array_length->GetBlock()->Dominates(pre_header)) { |
| 672 | HInstruction* array = array_length->InputAt(0); |
| 673 | HNullCheck* null_check = array->AsNullCheck(); |
| 674 | if (null_check != nullptr) { |
| 675 | array = null_check->InputAt(0); |
| 676 | } |
| 677 | // We've already made sure array is defined before the loop when collecting |
| 678 | // array accesses for the loop. |
| 679 | DCHECK(array->GetBlock()->Dominates(pre_header)); |
| 680 | if (null_check != nullptr && !null_check->GetBlock()->Dominates(pre_header)) { |
| 681 | // Hoist null check out of loop with a deoptimization. |
| 682 | HNullConstant* null_constant = graph->GetNullConstant(); |
| 683 | HCondition* null_check_cond = new (graph->GetArena()) HEqual(array, null_constant); |
| 684 | // TODO: for one dex_pc, share the same deoptimization slow path. |
| 685 | HDeoptimize* null_check_deoptimize = new (graph->GetArena()) |
| 686 | HDeoptimize(null_check_cond, suspend_check->GetDexPc()); |
| 687 | pre_header->InsertInstructionBefore(null_check_cond, pre_header->GetLastInstruction()); |
| 688 | pre_header->InsertInstructionBefore( |
| 689 | null_check_deoptimize, pre_header->GetLastInstruction()); |
| 690 | // Eliminate null check in the loop. |
| 691 | null_check->ReplaceWith(array); |
| 692 | null_check->GetBlock()->RemoveInstruction(null_check); |
| 693 | null_check_deoptimize->CopyEnvironmentFromWithLoopPhiAdjustment( |
| 694 | suspend_check->GetEnvironment(), block); |
| 695 | } |
| 696 | // Hoist array_length out of loop. |
| 697 | array_length->MoveBefore(pre_header->GetLastInstruction()); |
| 698 | } |
| 699 | |
| 700 | HIntConstant* offset_instr = graph->GetIntConstant(offset); |
| 701 | HAdd* add = new (graph->GetArena()) HAdd(Primitive::kPrimInt, array_length, offset_instr); |
| 702 | HCondition* cond = new (graph->GetArena()) HGreaterThan(value, add); |
| 703 | HDeoptimize* deoptimize = new (graph->GetArena()) |
| 704 | HDeoptimize(cond, suspend_check->GetDexPc()); |
| 705 | pre_header->InsertInstructionBefore(add, pre_header->GetLastInstruction()); |
| 706 | pre_header->InsertInstructionBefore(cond, pre_header->GetLastInstruction()); |
| 707 | pre_header->InsertInstructionBefore(deoptimize, pre_header->GetLastInstruction()); |
| 708 | deoptimize->CopyEnvironmentFromWithLoopPhiAdjustment( |
| 709 | suspend_check->GetEnvironment(), block); |
| 710 | } |
| 711 | |
| 712 | // Add deoptimizations in loop pre-header with the collected array access |
| 713 | // data so that value ranges can be established in loop body. |
| 714 | // Returns true if deoptimizations are successfully added, or if it's proven |
| 715 | // it's not necessary. |
| 716 | bool AddDeoptimization(const ArrayAccessInsideLoopFinder& finder) { |
| 717 | int32_t offset_low = finder.GetOffsetLow(); |
| 718 | int32_t offset_high = finder.GetOffsetHigh(); |
| 719 | HArrayLength* array_length = finder.GetFoundArrayLength(); |
| 720 | |
| 721 | HBasicBlock* pre_header = |
| 722 | induction_variable_->GetBlock()->GetLoopInformation()->GetPreHeader(); |
| 723 | if (!initial_->GetBlock()->Dominates(pre_header) || |
| 724 | !end_->GetBlock()->Dominates(pre_header)) { |
| 725 | // Can't move initial_ or end_ into pre_header for comparisons. |
| 726 | return false; |
| 727 | } |
| 728 | |
| 729 | bool is_constant_proven, is_length_proven; |
| 730 | if (increment_ == 1) { |
| 731 | // Increasing from initial_ to end_. |
| 732 | int32_t offset = inclusive_ ? -offset_high - 1 : -offset_high; |
| 733 | if (CanAddDeoptimizationConstant(initial_, -offset_low, &is_constant_proven) && |
| 734 | CanAddDeoptimizationArrayLength(end_, array_length, offset, &is_length_proven)) { |
| 735 | if (!is_constant_proven) { |
| 736 | AddDeoptimizationConstant(initial_, -offset_low); |
| 737 | } |
| 738 | if (!is_length_proven) { |
| 739 | AddDeoptimizationArrayLength(end_, array_length, offset); |
| 740 | } |
| 741 | return true; |
| 742 | } |
| 743 | } else if (increment_ == -1) { |
| 744 | // Decreasing from initial_ to end_. |
| 745 | int32_t constant = inclusive_ ? -offset_low : -offset_low - 1; |
| 746 | if (CanAddDeoptimizationConstant(end_, constant, &is_constant_proven) && |
| 747 | CanAddDeoptimizationArrayLength( |
| 748 | initial_, array_length, -offset_high - 1, &is_length_proven)) { |
| 749 | if (!is_constant_proven) { |
| 750 | AddDeoptimizationConstant(end_, constant); |
| 751 | } |
| 752 | if (!is_length_proven) { |
| 753 | AddDeoptimizationArrayLength(initial_, array_length, -offset_high - 1); |
| 754 | } |
| 755 | return true; |
| 756 | } |
| 757 | } |
| 758 | return false; |
| 759 | } |
| 760 | |
| 761 | // Try to add HDeoptimize's in the loop pre-header first to narrow this range. |
| 762 | ValueRange* NarrowWithDeoptimization() { |
| 763 | if (increment_ != 1 && increment_ != -1) { |
| 764 | // TODO: possibly handle overflow/underflow issues with deoptimization. |
| 765 | return this; |
| 766 | } |
| 767 | |
| 768 | if (end_ == nullptr) { |
| 769 | // No full info to add deoptimization. |
| 770 | return this; |
| 771 | } |
| 772 | |
| 773 | ArrayAccessInsideLoopFinder finder(induction_variable_); |
| 774 | |
| 775 | if (!finder.HasFoundArrayLength()) { |
Mingyao Yang | 9d750ef | 2015-04-26 18:15:30 -0700 | [diff] [blame] | 776 | // No array access was found inside the loop that can benefit |
| 777 | // from deoptimization. |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 778 | return this; |
| 779 | } |
| 780 | |
| 781 | if (!AddDeoptimization(finder)) { |
| 782 | return this; |
| 783 | } |
| 784 | |
| 785 | // After added deoptimizations, induction variable fits in |
| 786 | // [-offset_low, array.length-1-offset_high], adjusted with collected offsets. |
| 787 | ValueBound lower = ValueBound(0, -finder.GetOffsetLow()); |
| 788 | ValueBound upper = ValueBound(finder.GetFoundArrayLength(), -1 - finder.GetOffsetHigh()); |
| 789 | // We've narrowed the range after added deoptimizations. |
| 790 | return new (GetAllocator()) ValueRange(GetAllocator(), lower, upper); |
| 791 | } |
| 792 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 793 | private: |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 794 | HPhi* const induction_variable_; // Induction variable for this monotonic value range. |
| 795 | HInstruction* const initial_; // Initial value. |
| 796 | HInstruction* end_; // End value. |
| 797 | bool inclusive_; // Whether end value is inclusive. |
| 798 | const int32_t increment_; // Increment for each loop iteration. |
| 799 | const ValueBound bound_; // Additional value bound info for initial_. |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 800 | |
| 801 | DISALLOW_COPY_AND_ASSIGN(MonotonicValueRange); |
| 802 | }; |
| 803 | |
| 804 | class BCEVisitor : public HGraphVisitor { |
| 805 | public: |
Mingyao Yang | d43b3ac | 2015-04-01 14:03:04 -0700 | [diff] [blame] | 806 | // The least number of bounds checks that should be eliminated by triggering |
| 807 | // the deoptimization technique. |
| 808 | static constexpr size_t kThresholdForAddingDeoptimize = 2; |
| 809 | |
| 810 | // Very large constant index is considered as an anomaly. This is a threshold |
| 811 | // beyond which we don't bother to apply the deoptimization technique since |
| 812 | // it's likely some AIOOBE will be thrown. |
| 813 | static constexpr int32_t kMaxConstantForAddingDeoptimize = INT_MAX - 1024 * 1024; |
| 814 | |
Andreas Gampe | 0418b5b | 2014-12-04 17:24:50 -0800 | [diff] [blame] | 815 | explicit BCEVisitor(HGraph* graph) |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 816 | : HGraphVisitor(graph), |
Mingyao Yang | d43b3ac | 2015-04-01 14:03:04 -0700 | [diff] [blame] | 817 | maps_(graph->GetBlocks().Size()), |
| 818 | need_to_revisit_block_(false) {} |
| 819 | |
| 820 | void VisitBasicBlock(HBasicBlock* block) OVERRIDE { |
| 821 | first_constant_index_bounds_check_map_.clear(); |
| 822 | HGraphVisitor::VisitBasicBlock(block); |
| 823 | if (need_to_revisit_block_) { |
| 824 | AddComparesWithDeoptimization(block); |
| 825 | need_to_revisit_block_ = false; |
| 826 | first_constant_index_bounds_check_map_.clear(); |
| 827 | GetValueRangeMap(block)->clear(); |
| 828 | HGraphVisitor::VisitBasicBlock(block); |
| 829 | } |
| 830 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 831 | |
| 832 | private: |
| 833 | // Return the map of proven value ranges at the beginning of a basic block. |
| 834 | ArenaSafeMap<int, ValueRange*>* GetValueRangeMap(HBasicBlock* basic_block) { |
| 835 | int block_id = basic_block->GetBlockId(); |
| 836 | if (maps_.at(block_id) == nullptr) { |
| 837 | std::unique_ptr<ArenaSafeMap<int, ValueRange*>> map( |
| 838 | new ArenaSafeMap<int, ValueRange*>( |
| 839 | std::less<int>(), GetGraph()->GetArena()->Adapter())); |
| 840 | maps_.at(block_id) = std::move(map); |
| 841 | } |
| 842 | return maps_.at(block_id).get(); |
| 843 | } |
| 844 | |
| 845 | // Traverse up the dominator tree to look for value range info. |
| 846 | ValueRange* LookupValueRange(HInstruction* instruction, HBasicBlock* basic_block) { |
| 847 | while (basic_block != nullptr) { |
| 848 | ArenaSafeMap<int, ValueRange*>* map = GetValueRangeMap(basic_block); |
| 849 | if (map->find(instruction->GetId()) != map->end()) { |
| 850 | return map->Get(instruction->GetId()); |
| 851 | } |
| 852 | basic_block = basic_block->GetDominator(); |
| 853 | } |
| 854 | // Didn't find any. |
| 855 | return nullptr; |
| 856 | } |
| 857 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 858 | // Narrow the value range of `instruction` at the end of `basic_block` with `range`, |
| 859 | // and push the narrowed value range to `successor`. |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 860 | void ApplyRangeFromComparison(HInstruction* instruction, HBasicBlock* basic_block, |
Mingyao Yang | 8c8bad8 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 861 | HBasicBlock* successor, ValueRange* range) { |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 862 | ValueRange* existing_range = LookupValueRange(instruction, basic_block); |
Mingyao Yang | 8c8bad8 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 863 | if (existing_range == nullptr) { |
| 864 | if (range != nullptr) { |
| 865 | GetValueRangeMap(successor)->Overwrite(instruction->GetId(), range); |
| 866 | } |
| 867 | return; |
| 868 | } |
| 869 | if (existing_range->IsMonotonicValueRange()) { |
| 870 | DCHECK(instruction->IsLoopHeaderPhi()); |
| 871 | // Make sure the comparison is in the loop header so each increment is |
| 872 | // checked with a comparison. |
| 873 | if (instruction->GetBlock() != basic_block) { |
| 874 | return; |
| 875 | } |
| 876 | } |
| 877 | ValueRange* narrowed_range = existing_range->Narrow(range); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 878 | if (narrowed_range != nullptr) { |
| 879 | GetValueRangeMap(successor)->Overwrite(instruction->GetId(), narrowed_range); |
| 880 | } |
| 881 | } |
| 882 | |
Mingyao Yang | 57e0475 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 883 | // Special case that we may simultaneously narrow two MonotonicValueRange's to |
| 884 | // regular value ranges. |
| 885 | void HandleIfBetweenTwoMonotonicValueRanges(HIf* instruction, |
| 886 | HInstruction* left, |
| 887 | HInstruction* right, |
| 888 | IfCondition cond, |
| 889 | MonotonicValueRange* left_range, |
| 890 | MonotonicValueRange* right_range) { |
| 891 | DCHECK(left->IsLoopHeaderPhi()); |
| 892 | DCHECK(right->IsLoopHeaderPhi()); |
| 893 | if (instruction->GetBlock() != left->GetBlock()) { |
| 894 | // Comparison needs to be in loop header to make sure it's done after each |
| 895 | // increment/decrement. |
| 896 | return; |
| 897 | } |
| 898 | |
| 899 | // Handle common cases which also don't have overflow/underflow concerns. |
| 900 | if (left_range->GetIncrement() == 1 && |
| 901 | left_range->GetBound().IsConstant() && |
| 902 | right_range->GetIncrement() == -1 && |
| 903 | right_range->GetBound().IsRelatedToArrayLength() && |
| 904 | right_range->GetBound().GetConstant() < 0) { |
Mingyao Yang | 57e0475 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 905 | HBasicBlock* successor = nullptr; |
| 906 | int32_t left_compensation = 0; |
| 907 | int32_t right_compensation = 0; |
| 908 | if (cond == kCondLT) { |
| 909 | left_compensation = -1; |
| 910 | right_compensation = 1; |
| 911 | successor = instruction->IfTrueSuccessor(); |
| 912 | } else if (cond == kCondLE) { |
| 913 | successor = instruction->IfTrueSuccessor(); |
| 914 | } else if (cond == kCondGT) { |
| 915 | successor = instruction->IfFalseSuccessor(); |
| 916 | } else if (cond == kCondGE) { |
| 917 | left_compensation = -1; |
| 918 | right_compensation = 1; |
| 919 | successor = instruction->IfFalseSuccessor(); |
| 920 | } else { |
| 921 | // We don't handle '=='/'!=' test in case left and right can cross and |
| 922 | // miss each other. |
| 923 | return; |
| 924 | } |
| 925 | |
| 926 | if (successor != nullptr) { |
| 927 | bool overflow; |
| 928 | bool underflow; |
| 929 | ValueRange* new_left_range = new (GetGraph()->GetArena()) ValueRange( |
| 930 | GetGraph()->GetArena(), |
| 931 | left_range->GetBound(), |
| 932 | right_range->GetBound().Add(left_compensation, &overflow, &underflow)); |
| 933 | if (!overflow && !underflow) { |
| 934 | ApplyRangeFromComparison(left, instruction->GetBlock(), successor, |
| 935 | new_left_range); |
| 936 | } |
| 937 | |
| 938 | ValueRange* new_right_range = new (GetGraph()->GetArena()) ValueRange( |
| 939 | GetGraph()->GetArena(), |
| 940 | left_range->GetBound().Add(right_compensation, &overflow, &underflow), |
| 941 | right_range->GetBound()); |
| 942 | if (!overflow && !underflow) { |
| 943 | ApplyRangeFromComparison(right, instruction->GetBlock(), successor, |
| 944 | new_right_range); |
| 945 | } |
| 946 | } |
| 947 | } |
| 948 | } |
| 949 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 950 | // Handle "if (left cmp_cond right)". |
| 951 | void HandleIf(HIf* instruction, HInstruction* left, HInstruction* right, IfCondition cond) { |
| 952 | HBasicBlock* block = instruction->GetBlock(); |
| 953 | |
| 954 | HBasicBlock* true_successor = instruction->IfTrueSuccessor(); |
| 955 | // There should be no critical edge at this point. |
| 956 | DCHECK_EQ(true_successor->GetPredecessors().Size(), 1u); |
| 957 | |
| 958 | HBasicBlock* false_successor = instruction->IfFalseSuccessor(); |
| 959 | // There should be no critical edge at this point. |
| 960 | DCHECK_EQ(false_successor->GetPredecessors().Size(), 1u); |
| 961 | |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 962 | ValueRange* left_range = LookupValueRange(left, block); |
| 963 | MonotonicValueRange* left_monotonic_range = nullptr; |
| 964 | if (left_range != nullptr) { |
| 965 | left_monotonic_range = left_range->AsMonotonicValueRange(); |
| 966 | if (left_monotonic_range != nullptr) { |
| 967 | HBasicBlock* loop_head = left_monotonic_range->GetLoopHead(); |
| 968 | if (instruction->GetBlock() != loop_head) { |
| 969 | // For monotonic value range, don't handle `instruction` |
| 970 | // if it's not defined in the loop header. |
| 971 | return; |
| 972 | } |
| 973 | } |
| 974 | } |
| 975 | |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 976 | bool found; |
| 977 | ValueBound bound = ValueBound::DetectValueBoundFromValue(right, &found); |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 978 | // Each comparison can establish a lower bound and an upper bound |
| 979 | // for the left hand side. |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 980 | ValueBound lower = bound; |
| 981 | ValueBound upper = bound; |
| 982 | if (!found) { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 983 | // No constant or array.length+c format bound found. |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 984 | // For i<j, we can still use j's upper bound as i's upper bound. Same for lower. |
Mingyao Yang | 57e0475 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 985 | ValueRange* right_range = LookupValueRange(right, block); |
| 986 | if (right_range != nullptr) { |
| 987 | if (right_range->IsMonotonicValueRange()) { |
Mingyao Yang | 57e0475 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 988 | if (left_range != nullptr && left_range->IsMonotonicValueRange()) { |
| 989 | HandleIfBetweenTwoMonotonicValueRanges(instruction, left, right, cond, |
| 990 | left_range->AsMonotonicValueRange(), |
| 991 | right_range->AsMonotonicValueRange()); |
| 992 | return; |
| 993 | } |
| 994 | } |
| 995 | lower = right_range->GetLower(); |
| 996 | upper = right_range->GetUpper(); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 997 | } else { |
| 998 | lower = ValueBound::Min(); |
| 999 | upper = ValueBound::Max(); |
| 1000 | } |
| 1001 | } |
| 1002 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1003 | bool overflow, underflow; |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1004 | if (cond == kCondLT || cond == kCondLE) { |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 1005 | if (left_monotonic_range != nullptr) { |
| 1006 | // Update the info for monotonic value range. |
| 1007 | if (left_monotonic_range->GetInductionVariable() == left && |
| 1008 | left_monotonic_range->GetIncrement() < 0 && |
| 1009 | block == left_monotonic_range->GetLoopHead() && |
| 1010 | instruction->IfFalseSuccessor()->GetLoopInformation() == block->GetLoopInformation()) { |
| 1011 | left_monotonic_range->SetEnd(right); |
| 1012 | left_monotonic_range->SetInclusive(cond == kCondLT); |
| 1013 | } |
| 1014 | } |
| 1015 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1016 | if (!upper.Equals(ValueBound::Max())) { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1017 | int32_t compensation = (cond == kCondLT) ? -1 : 0; // upper bound is inclusive |
| 1018 | ValueBound new_upper = upper.Add(compensation, &overflow, &underflow); |
| 1019 | if (overflow || underflow) { |
| 1020 | return; |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 1021 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1022 | ValueRange* new_range = new (GetGraph()->GetArena()) |
| 1023 | ValueRange(GetGraph()->GetArena(), ValueBound::Min(), new_upper); |
| 1024 | ApplyRangeFromComparison(left, block, true_successor, new_range); |
| 1025 | } |
| 1026 | |
| 1027 | // array.length as a lower bound isn't considered useful. |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1028 | if (!lower.Equals(ValueBound::Min()) && !lower.IsRelatedToArrayLength()) { |
| 1029 | int32_t compensation = (cond == kCondLE) ? 1 : 0; // lower bound is inclusive |
| 1030 | ValueBound new_lower = lower.Add(compensation, &overflow, &underflow); |
| 1031 | if (overflow || underflow) { |
| 1032 | return; |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 1033 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1034 | ValueRange* new_range = new (GetGraph()->GetArena()) |
| 1035 | ValueRange(GetGraph()->GetArena(), new_lower, ValueBound::Max()); |
| 1036 | ApplyRangeFromComparison(left, block, false_successor, new_range); |
| 1037 | } |
| 1038 | } else if (cond == kCondGT || cond == kCondGE) { |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 1039 | if (left_monotonic_range != nullptr) { |
| 1040 | // Update the info for monotonic value range. |
| 1041 | if (left_monotonic_range->GetInductionVariable() == left && |
| 1042 | left_monotonic_range->GetIncrement() > 0 && |
| 1043 | block == left_monotonic_range->GetLoopHead() && |
| 1044 | instruction->IfFalseSuccessor()->GetLoopInformation() == block->GetLoopInformation()) { |
| 1045 | left_monotonic_range->SetEnd(right); |
| 1046 | left_monotonic_range->SetInclusive(cond == kCondGT); |
| 1047 | } |
| 1048 | } |
| 1049 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1050 | // array.length as a lower bound isn't considered useful. |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1051 | if (!lower.Equals(ValueBound::Min()) && !lower.IsRelatedToArrayLength()) { |
| 1052 | int32_t compensation = (cond == kCondGT) ? 1 : 0; // lower bound is inclusive |
| 1053 | ValueBound new_lower = lower.Add(compensation, &overflow, &underflow); |
| 1054 | if (overflow || underflow) { |
| 1055 | return; |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 1056 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1057 | ValueRange* new_range = new (GetGraph()->GetArena()) |
| 1058 | ValueRange(GetGraph()->GetArena(), new_lower, ValueBound::Max()); |
| 1059 | ApplyRangeFromComparison(left, block, true_successor, new_range); |
| 1060 | } |
| 1061 | |
| 1062 | if (!upper.Equals(ValueBound::Max())) { |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1063 | int32_t compensation = (cond == kCondGE) ? -1 : 0; // upper bound is inclusive |
| 1064 | ValueBound new_upper = upper.Add(compensation, &overflow, &underflow); |
| 1065 | if (overflow || underflow) { |
| 1066 | return; |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 1067 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1068 | ValueRange* new_range = new (GetGraph()->GetArena()) |
| 1069 | ValueRange(GetGraph()->GetArena(), ValueBound::Min(), new_upper); |
| 1070 | ApplyRangeFromComparison(left, block, false_successor, new_range); |
| 1071 | } |
| 1072 | } |
| 1073 | } |
| 1074 | |
| 1075 | void VisitBoundsCheck(HBoundsCheck* bounds_check) { |
| 1076 | HBasicBlock* block = bounds_check->GetBlock(); |
| 1077 | HInstruction* index = bounds_check->InputAt(0); |
| 1078 | HInstruction* array_length = bounds_check->InputAt(1); |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1079 | DCHECK(array_length->IsIntConstant() || array_length->IsArrayLength()); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1080 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1081 | if (!index->IsIntConstant()) { |
| 1082 | ValueRange* index_range = LookupValueRange(index, block); |
| 1083 | if (index_range != nullptr) { |
| 1084 | ValueBound lower = ValueBound(nullptr, 0); // constant 0 |
| 1085 | ValueBound upper = ValueBound(array_length, -1); // array_length - 1 |
| 1086 | ValueRange* array_range = new (GetGraph()->GetArena()) |
| 1087 | ValueRange(GetGraph()->GetArena(), lower, upper); |
| 1088 | if (index_range->FitsIn(array_range)) { |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1089 | ReplaceBoundsCheck(bounds_check, index); |
| 1090 | return; |
| 1091 | } |
| 1092 | } |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1093 | } else { |
| 1094 | int32_t constant = index->AsIntConstant()->GetValue(); |
| 1095 | if (constant < 0) { |
| 1096 | // Will always throw exception. |
| 1097 | return; |
| 1098 | } |
| 1099 | if (array_length->IsIntConstant()) { |
| 1100 | if (constant < array_length->AsIntConstant()->GetValue()) { |
| 1101 | ReplaceBoundsCheck(bounds_check, index); |
| 1102 | } |
| 1103 | return; |
| 1104 | } |
| 1105 | |
| 1106 | DCHECK(array_length->IsArrayLength()); |
| 1107 | ValueRange* existing_range = LookupValueRange(array_length, block); |
| 1108 | if (existing_range != nullptr) { |
| 1109 | ValueBound lower = existing_range->GetLower(); |
| 1110 | DCHECK(lower.IsConstant()); |
| 1111 | if (constant < lower.GetConstant()) { |
| 1112 | ReplaceBoundsCheck(bounds_check, index); |
| 1113 | return; |
| 1114 | } else { |
| 1115 | // Existing range isn't strong enough to eliminate the bounds check. |
| 1116 | // Fall through to update the array_length range with info from this |
| 1117 | // bounds check. |
| 1118 | } |
| 1119 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1120 | |
Mingyao Yang | d43b3ac | 2015-04-01 14:03:04 -0700 | [diff] [blame] | 1121 | if (first_constant_index_bounds_check_map_.find(array_length->GetId()) == |
| 1122 | first_constant_index_bounds_check_map_.end()) { |
| 1123 | // Remember the first bounds check against array_length of a constant index. |
| 1124 | // That bounds check instruction has an associated HEnvironment where we |
| 1125 | // may add an HDeoptimize to eliminate bounds checks of constant indices |
| 1126 | // against array_length. |
| 1127 | first_constant_index_bounds_check_map_.Put(array_length->GetId(), bounds_check); |
| 1128 | } else { |
| 1129 | // We've seen it at least twice. It's beneficial to introduce a compare with |
| 1130 | // deoptimization fallback to eliminate the bounds checks. |
| 1131 | need_to_revisit_block_ = true; |
| 1132 | } |
| 1133 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1134 | // Once we have an array access like 'array[5] = 1', we record array.length >= 6. |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1135 | // We currently don't do it for non-constant index since a valid array[i] can't prove |
| 1136 | // a valid array[i-1] yet due to the lower bound side. |
Mingyao Yang | d43b3ac | 2015-04-01 14:03:04 -0700 | [diff] [blame] | 1137 | if (constant == INT_MAX) { |
| 1138 | // INT_MAX as an index will definitely throw AIOOBE. |
| 1139 | return; |
| 1140 | } |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 1141 | ValueBound lower = ValueBound(nullptr, constant + 1); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1142 | ValueBound upper = ValueBound::Max(); |
| 1143 | ValueRange* range = new (GetGraph()->GetArena()) |
| 1144 | ValueRange(GetGraph()->GetArena(), lower, upper); |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1145 | GetValueRangeMap(block)->Overwrite(array_length->GetId(), range); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1146 | } |
| 1147 | } |
| 1148 | |
| 1149 | void ReplaceBoundsCheck(HInstruction* bounds_check, HInstruction* index) { |
| 1150 | bounds_check->ReplaceWith(index); |
| 1151 | bounds_check->GetBlock()->RemoveInstruction(bounds_check); |
| 1152 | } |
| 1153 | |
| 1154 | void VisitPhi(HPhi* phi) { |
| 1155 | if (phi->IsLoopHeaderPhi() && phi->GetType() == Primitive::kPrimInt) { |
Andreas Gampe | 0418b5b | 2014-12-04 17:24:50 -0800 | [diff] [blame] | 1156 | DCHECK_EQ(phi->InputCount(), 2U); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1157 | HInstruction* instruction = phi->InputAt(1); |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1158 | HInstruction *left; |
| 1159 | int32_t increment; |
| 1160 | if (ValueBound::IsAddOrSubAConstant(instruction, &left, &increment)) { |
| 1161 | if (left == phi) { |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1162 | HInstruction* initial_value = phi->InputAt(0); |
| 1163 | ValueRange* range = nullptr; |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 1164 | if (increment == 0) { |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1165 | // Add constant 0. It's really a fixed value. |
| 1166 | range = new (GetGraph()->GetArena()) ValueRange( |
| 1167 | GetGraph()->GetArena(), |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 1168 | ValueBound(initial_value, 0), |
| 1169 | ValueBound(initial_value, 0)); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1170 | } else { |
| 1171 | // Monotonically increasing/decreasing. |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 1172 | bool found; |
| 1173 | ValueBound bound = ValueBound::DetectValueBoundFromValue( |
| 1174 | initial_value, &found); |
| 1175 | if (!found) { |
| 1176 | // No constant or array.length+c bound found. |
| 1177 | // For i=j, we can still use j's upper bound as i's upper bound. |
| 1178 | // Same for lower. |
| 1179 | ValueRange* initial_range = LookupValueRange(initial_value, phi->GetBlock()); |
| 1180 | if (initial_range != nullptr) { |
| 1181 | bound = increment > 0 ? initial_range->GetLower() : |
| 1182 | initial_range->GetUpper(); |
| 1183 | } else { |
| 1184 | bound = increment > 0 ? ValueBound::Min() : ValueBound::Max(); |
| 1185 | } |
| 1186 | } |
| 1187 | range = new (GetGraph()->GetArena()) MonotonicValueRange( |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1188 | GetGraph()->GetArena(), |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 1189 | phi, |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1190 | initial_value, |
Mingyao Yang | 6419752 | 2014-12-05 15:56:23 -0800 | [diff] [blame] | 1191 | increment, |
| 1192 | bound); |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1193 | } |
| 1194 | GetValueRangeMap(phi->GetBlock())->Overwrite(phi->GetId(), range); |
| 1195 | } |
| 1196 | } |
| 1197 | } |
| 1198 | } |
| 1199 | |
| 1200 | void VisitIf(HIf* instruction) { |
| 1201 | if (instruction->InputAt(0)->IsCondition()) { |
| 1202 | HCondition* cond = instruction->InputAt(0)->AsCondition(); |
| 1203 | IfCondition cmp = cond->GetCondition(); |
| 1204 | if (cmp == kCondGT || cmp == kCondGE || |
| 1205 | cmp == kCondLT || cmp == kCondLE) { |
| 1206 | HInstruction* left = cond->GetLeft(); |
| 1207 | HInstruction* right = cond->GetRight(); |
| 1208 | HandleIf(instruction, left, right, cmp); |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 1209 | |
| 1210 | HBasicBlock* block = instruction->GetBlock(); |
| 1211 | ValueRange* left_range = LookupValueRange(left, block); |
| 1212 | if (left_range == nullptr) { |
| 1213 | return; |
| 1214 | } |
| 1215 | |
| 1216 | if (left_range->IsMonotonicValueRange() && |
| 1217 | block == left_range->AsMonotonicValueRange()->GetLoopHead()) { |
| 1218 | // The comparison is for an induction variable in the loop header. |
| 1219 | DCHECK(left == left_range->AsMonotonicValueRange()->GetInductionVariable()); |
| 1220 | HBasicBlock* loop_body_successor; |
Mingyao Yang | 9d750ef | 2015-04-26 18:15:30 -0700 | [diff] [blame] | 1221 | if (LIKELY(block->GetLoopInformation()-> |
| 1222 | Contains(*instruction->IfFalseSuccessor()))) { |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 1223 | loop_body_successor = instruction->IfFalseSuccessor(); |
Mingyao Yang | 9d750ef | 2015-04-26 18:15:30 -0700 | [diff] [blame] | 1224 | } else { |
| 1225 | loop_body_successor = instruction->IfTrueSuccessor(); |
Mingyao Yang | 206d6fd | 2015-04-13 16:46:28 -0700 | [diff] [blame] | 1226 | } |
| 1227 | ValueRange* new_left_range = LookupValueRange(left, loop_body_successor); |
| 1228 | if (new_left_range == left_range) { |
| 1229 | // We are not successful in narrowing the monotonic value range to |
| 1230 | // a regular value range. Try using deoptimization. |
| 1231 | new_left_range = left_range->AsMonotonicValueRange()-> |
| 1232 | NarrowWithDeoptimization(); |
| 1233 | if (new_left_range != left_range) { |
| 1234 | GetValueRangeMap(instruction->IfFalseSuccessor())-> |
| 1235 | Overwrite(left->GetId(), new_left_range); |
| 1236 | } |
| 1237 | } |
| 1238 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1239 | } |
| 1240 | } |
| 1241 | } |
| 1242 | |
| 1243 | void VisitAdd(HAdd* add) { |
| 1244 | HInstruction* right = add->GetRight(); |
| 1245 | if (right->IsIntConstant()) { |
| 1246 | ValueRange* left_range = LookupValueRange(add->GetLeft(), add->GetBlock()); |
| 1247 | if (left_range == nullptr) { |
| 1248 | return; |
| 1249 | } |
| 1250 | ValueRange* range = left_range->Add(right->AsIntConstant()->GetValue()); |
| 1251 | if (range != nullptr) { |
| 1252 | GetValueRangeMap(add->GetBlock())->Overwrite(add->GetId(), range); |
| 1253 | } |
| 1254 | } |
| 1255 | } |
| 1256 | |
| 1257 | void VisitSub(HSub* sub) { |
| 1258 | HInstruction* left = sub->GetLeft(); |
| 1259 | HInstruction* right = sub->GetRight(); |
| 1260 | if (right->IsIntConstant()) { |
| 1261 | ValueRange* left_range = LookupValueRange(left, sub->GetBlock()); |
| 1262 | if (left_range == nullptr) { |
| 1263 | return; |
| 1264 | } |
| 1265 | ValueRange* range = left_range->Add(-right->AsIntConstant()->GetValue()); |
| 1266 | if (range != nullptr) { |
| 1267 | GetValueRangeMap(sub->GetBlock())->Overwrite(sub->GetId(), range); |
| 1268 | return; |
| 1269 | } |
| 1270 | } |
| 1271 | |
| 1272 | // Here we are interested in the typical triangular case of nested loops, |
| 1273 | // such as the inner loop 'for (int j=0; j<array.length-i; j++)' where i |
| 1274 | // is the index for outer loop. In this case, we know j is bounded by array.length-1. |
Mingyao Yang | 8c8bad8 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 1275 | |
| 1276 | // Try to handle (array.length - i) or (array.length + c - i) format. |
| 1277 | HInstruction* left_of_left; // left input of left. |
| 1278 | int32_t right_const = 0; |
| 1279 | if (ValueBound::IsAddOrSubAConstant(left, &left_of_left, &right_const)) { |
| 1280 | left = left_of_left; |
| 1281 | } |
| 1282 | // The value of left input of the sub equals (left + right_const). |
| 1283 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1284 | if (left->IsArrayLength()) { |
| 1285 | HInstruction* array_length = left->AsArrayLength(); |
| 1286 | ValueRange* right_range = LookupValueRange(right, sub->GetBlock()); |
| 1287 | if (right_range != nullptr) { |
| 1288 | ValueBound lower = right_range->GetLower(); |
| 1289 | ValueBound upper = right_range->GetUpper(); |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1290 | if (lower.IsConstant() && upper.IsRelatedToArrayLength()) { |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1291 | HInstruction* upper_inst = upper.GetInstruction(); |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1292 | // Make sure it's the same array. |
| 1293 | if (ValueBound::Equal(array_length, upper_inst)) { |
Mingyao Yang | 8c8bad8 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 1294 | int32_t c0 = right_const; |
| 1295 | int32_t c1 = lower.GetConstant(); |
| 1296 | int32_t c2 = upper.GetConstant(); |
| 1297 | // (array.length + c0 - v) where v is in [c1, array.length + c2] |
| 1298 | // gets [c0 - c2, array.length + c0 - c1] as its value range. |
| 1299 | if (!ValueBound::WouldAddOverflowOrUnderflow(c0, -c2) && |
| 1300 | !ValueBound::WouldAddOverflowOrUnderflow(c0, -c1)) { |
| 1301 | if ((c0 - c1) <= 0) { |
| 1302 | // array.length + (c0 - c1) won't overflow/underflow. |
| 1303 | ValueRange* range = new (GetGraph()->GetArena()) ValueRange( |
| 1304 | GetGraph()->GetArena(), |
| 1305 | ValueBound(nullptr, right_const - upper.GetConstant()), |
| 1306 | ValueBound(array_length, right_const - lower.GetConstant())); |
| 1307 | GetValueRangeMap(sub->GetBlock())->Overwrite(sub->GetId(), range); |
| 1308 | } |
| 1309 | } |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1310 | } |
| 1311 | } |
| 1312 | } |
| 1313 | } |
| 1314 | } |
| 1315 | |
Mingyao Yang | 8c8bad8 | 2015-02-09 18:13:26 -0800 | [diff] [blame] | 1316 | void FindAndHandlePartialArrayLength(HBinaryOperation* instruction) { |
| 1317 | DCHECK(instruction->IsDiv() || instruction->IsShr() || instruction->IsUShr()); |
| 1318 | HInstruction* right = instruction->GetRight(); |
| 1319 | int32_t right_const; |
| 1320 | if (right->IsIntConstant()) { |
| 1321 | right_const = right->AsIntConstant()->GetValue(); |
| 1322 | // Detect division by two or more. |
| 1323 | if ((instruction->IsDiv() && right_const <= 1) || |
| 1324 | (instruction->IsShr() && right_const < 1) || |
| 1325 | (instruction->IsUShr() && right_const < 1)) { |
| 1326 | return; |
| 1327 | } |
| 1328 | } else { |
| 1329 | return; |
| 1330 | } |
| 1331 | |
| 1332 | // Try to handle array.length/2 or (array.length-1)/2 format. |
| 1333 | HInstruction* left = instruction->GetLeft(); |
| 1334 | HInstruction* left_of_left; // left input of left. |
| 1335 | int32_t c = 0; |
| 1336 | if (ValueBound::IsAddOrSubAConstant(left, &left_of_left, &c)) { |
| 1337 | left = left_of_left; |
| 1338 | } |
| 1339 | // The value of left input of instruction equals (left + c). |
| 1340 | |
| 1341 | // (array_length + 1) or smaller divided by two or more |
| 1342 | // always generate a value in [INT_MIN, array_length]. |
| 1343 | // This is true even if array_length is INT_MAX. |
| 1344 | if (left->IsArrayLength() && c <= 1) { |
| 1345 | if (instruction->IsUShr() && c < 0) { |
| 1346 | // Make sure for unsigned shift, left side is not negative. |
| 1347 | // e.g. if array_length is 2, ((array_length - 3) >>> 2) is way bigger |
| 1348 | // than array_length. |
| 1349 | return; |
| 1350 | } |
| 1351 | ValueRange* range = new (GetGraph()->GetArena()) ValueRange( |
| 1352 | GetGraph()->GetArena(), |
| 1353 | ValueBound(nullptr, INT_MIN), |
| 1354 | ValueBound(left, 0)); |
| 1355 | GetValueRangeMap(instruction->GetBlock())->Overwrite(instruction->GetId(), range); |
| 1356 | } |
| 1357 | } |
| 1358 | |
| 1359 | void VisitDiv(HDiv* div) { |
| 1360 | FindAndHandlePartialArrayLength(div); |
| 1361 | } |
| 1362 | |
| 1363 | void VisitShr(HShr* shr) { |
| 1364 | FindAndHandlePartialArrayLength(shr); |
| 1365 | } |
| 1366 | |
| 1367 | void VisitUShr(HUShr* ushr) { |
| 1368 | FindAndHandlePartialArrayLength(ushr); |
| 1369 | } |
| 1370 | |
Mingyao Yang | 4559f00 | 2015-02-27 14:43:53 -0800 | [diff] [blame] | 1371 | void VisitAnd(HAnd* instruction) { |
| 1372 | if (instruction->GetRight()->IsIntConstant()) { |
| 1373 | int32_t constant = instruction->GetRight()->AsIntConstant()->GetValue(); |
| 1374 | if (constant > 0) { |
| 1375 | // constant serves as a mask so any number masked with it |
| 1376 | // gets a [0, constant] value range. |
| 1377 | ValueRange* range = new (GetGraph()->GetArena()) ValueRange( |
| 1378 | GetGraph()->GetArena(), |
| 1379 | ValueBound(nullptr, 0), |
| 1380 | ValueBound(nullptr, constant)); |
| 1381 | GetValueRangeMap(instruction->GetBlock())->Overwrite(instruction->GetId(), range); |
| 1382 | } |
| 1383 | } |
| 1384 | } |
| 1385 | |
Mingyao Yang | 0304e18 | 2015-01-30 16:41:29 -0800 | [diff] [blame] | 1386 | void VisitNewArray(HNewArray* new_array) { |
| 1387 | HInstruction* len = new_array->InputAt(0); |
| 1388 | if (!len->IsIntConstant()) { |
| 1389 | HInstruction *left; |
| 1390 | int32_t right_const; |
| 1391 | if (ValueBound::IsAddOrSubAConstant(len, &left, &right_const)) { |
| 1392 | // (left + right_const) is used as size to new the array. |
| 1393 | // We record "-right_const <= left <= new_array - right_const"; |
| 1394 | ValueBound lower = ValueBound(nullptr, -right_const); |
| 1395 | // We use new_array for the bound instead of new_array.length, |
| 1396 | // which isn't available as an instruction yet. new_array will |
| 1397 | // be treated the same as new_array.length when it's used in a ValueBound. |
| 1398 | ValueBound upper = ValueBound(new_array, -right_const); |
| 1399 | ValueRange* range = new (GetGraph()->GetArena()) |
| 1400 | ValueRange(GetGraph()->GetArena(), lower, upper); |
| 1401 | GetValueRangeMap(new_array->GetBlock())->Overwrite(left->GetId(), range); |
| 1402 | } |
| 1403 | } |
| 1404 | } |
| 1405 | |
Mingyao Yang | d43b3ac | 2015-04-01 14:03:04 -0700 | [diff] [blame] | 1406 | void VisitDeoptimize(HDeoptimize* deoptimize) { |
| 1407 | // Right now it's only HLessThanOrEqual. |
| 1408 | DCHECK(deoptimize->InputAt(0)->IsLessThanOrEqual()); |
| 1409 | HLessThanOrEqual* less_than_or_equal = deoptimize->InputAt(0)->AsLessThanOrEqual(); |
| 1410 | HInstruction* instruction = less_than_or_equal->InputAt(0); |
| 1411 | if (instruction->IsArrayLength()) { |
| 1412 | HInstruction* constant = less_than_or_equal->InputAt(1); |
| 1413 | DCHECK(constant->IsIntConstant()); |
| 1414 | DCHECK(constant->AsIntConstant()->GetValue() <= kMaxConstantForAddingDeoptimize); |
| 1415 | ValueBound lower = ValueBound(nullptr, constant->AsIntConstant()->GetValue() + 1); |
| 1416 | ValueRange* range = new (GetGraph()->GetArena()) |
| 1417 | ValueRange(GetGraph()->GetArena(), lower, ValueBound::Max()); |
| 1418 | GetValueRangeMap(deoptimize->GetBlock())->Overwrite(instruction->GetId(), range); |
| 1419 | } |
| 1420 | } |
| 1421 | |
| 1422 | void AddCompareWithDeoptimization(HInstruction* array_length, |
| 1423 | HIntConstant* const_instr, |
| 1424 | HBasicBlock* block) { |
| 1425 | DCHECK(array_length->IsArrayLength()); |
| 1426 | ValueRange* range = LookupValueRange(array_length, block); |
| 1427 | ValueBound lower_bound = range->GetLower(); |
| 1428 | DCHECK(lower_bound.IsConstant()); |
| 1429 | DCHECK(const_instr->GetValue() <= kMaxConstantForAddingDeoptimize); |
| 1430 | DCHECK_EQ(lower_bound.GetConstant(), const_instr->GetValue() + 1); |
| 1431 | |
| 1432 | // If array_length is less than lower_const, deoptimize. |
| 1433 | HBoundsCheck* bounds_check = first_constant_index_bounds_check_map_.Get( |
| 1434 | array_length->GetId())->AsBoundsCheck(); |
| 1435 | HCondition* cond = new (GetGraph()->GetArena()) HLessThanOrEqual(array_length, const_instr); |
| 1436 | HDeoptimize* deoptimize = new (GetGraph()->GetArena()) |
| 1437 | HDeoptimize(cond, bounds_check->GetDexPc()); |
| 1438 | block->InsertInstructionBefore(cond, bounds_check); |
| 1439 | block->InsertInstructionBefore(deoptimize, bounds_check); |
Nicolas Geoffray | 3dcd58c | 2015-04-03 11:02:38 +0100 | [diff] [blame] | 1440 | deoptimize->CopyEnvironmentFrom(bounds_check->GetEnvironment()); |
Mingyao Yang | d43b3ac | 2015-04-01 14:03:04 -0700 | [diff] [blame] | 1441 | } |
| 1442 | |
| 1443 | void AddComparesWithDeoptimization(HBasicBlock* block) { |
| 1444 | for (ArenaSafeMap<int, HBoundsCheck*>::iterator it = |
| 1445 | first_constant_index_bounds_check_map_.begin(); |
| 1446 | it != first_constant_index_bounds_check_map_.end(); |
| 1447 | ++it) { |
| 1448 | HBoundsCheck* bounds_check = it->second; |
| 1449 | HArrayLength* array_length = bounds_check->InputAt(1)->AsArrayLength(); |
| 1450 | HIntConstant* lower_bound_const_instr = nullptr; |
| 1451 | int32_t lower_bound_const = INT_MIN; |
| 1452 | size_t counter = 0; |
| 1453 | // Count the constant indexing for which bounds checks haven't |
| 1454 | // been removed yet. |
| 1455 | for (HUseIterator<HInstruction*> it2(array_length->GetUses()); |
| 1456 | !it2.Done(); |
| 1457 | it2.Advance()) { |
| 1458 | HInstruction* user = it2.Current()->GetUser(); |
| 1459 | if (user->GetBlock() == block && |
| 1460 | user->IsBoundsCheck() && |
| 1461 | user->AsBoundsCheck()->InputAt(0)->IsIntConstant()) { |
| 1462 | DCHECK_EQ(array_length, user->AsBoundsCheck()->InputAt(1)); |
| 1463 | HIntConstant* const_instr = user->AsBoundsCheck()->InputAt(0)->AsIntConstant(); |
| 1464 | if (const_instr->GetValue() > lower_bound_const) { |
| 1465 | lower_bound_const = const_instr->GetValue(); |
| 1466 | lower_bound_const_instr = const_instr; |
| 1467 | } |
| 1468 | counter++; |
| 1469 | } |
| 1470 | } |
| 1471 | if (counter >= kThresholdForAddingDeoptimize && |
| 1472 | lower_bound_const_instr->GetValue() <= kMaxConstantForAddingDeoptimize) { |
| 1473 | AddCompareWithDeoptimization(array_length, lower_bound_const_instr, block); |
| 1474 | } |
| 1475 | } |
| 1476 | } |
| 1477 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1478 | std::vector<std::unique_ptr<ArenaSafeMap<int, ValueRange*>>> maps_; |
| 1479 | |
Mingyao Yang | d43b3ac | 2015-04-01 14:03:04 -0700 | [diff] [blame] | 1480 | // Map an HArrayLength instruction's id to the first HBoundsCheck instruction in |
| 1481 | // a block that checks a constant index against that HArrayLength. |
| 1482 | SafeMap<int, HBoundsCheck*> first_constant_index_bounds_check_map_; |
| 1483 | |
| 1484 | // For the block, there is at least one HArrayLength instruction for which there |
| 1485 | // is more than one bounds check instruction with constant indexing. And it's |
| 1486 | // beneficial to add a compare instruction that has deoptimization fallback and |
| 1487 | // eliminate those bounds checks. |
| 1488 | bool need_to_revisit_block_; |
| 1489 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1490 | DISALLOW_COPY_AND_ASSIGN(BCEVisitor); |
| 1491 | }; |
| 1492 | |
| 1493 | void BoundsCheckElimination::Run() { |
Mark Mendell | 1152c92 | 2015-04-24 17:06:35 -0400 | [diff] [blame] | 1494 | if (!graph_->HasBoundsChecks()) { |
Mingyao Yang | e4335eb | 2015-03-02 15:14:13 -0800 | [diff] [blame] | 1495 | return; |
| 1496 | } |
| 1497 | |
Mingyao Yang | f384f88 | 2014-10-22 16:08:18 -0700 | [diff] [blame] | 1498 | BCEVisitor visitor(graph_); |
| 1499 | // Reverse post order guarantees a node's dominators are visited first. |
| 1500 | // We want to visit in the dominator-based order since if a value is known to |
| 1501 | // be bounded by a range at one instruction, it must be true that all uses of |
| 1502 | // that value dominated by that instruction fits in that range. Range of that |
| 1503 | // value can be narrowed further down in the dominator tree. |
| 1504 | // |
| 1505 | // TODO: only visit blocks that dominate some array accesses. |
| 1506 | visitor.VisitReversePostOrder(); |
| 1507 | } |
| 1508 | |
| 1509 | } // namespace art |