1 /* 2 * Copyright (C) 2015 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 17 #include "induction_var_range.h" 18 19 #include <limits> 20 21 namespace art { 22 23 /** Returns true if 64-bit constant fits in 32-bit constant. */ 24 static bool CanLongValueFitIntoInt(int64_t c) { 25 return std::numeric_limits<int32_t>::min() <= c && c <= std::numeric_limits<int32_t>::max(); 26 } 27 28 /** Returns true if 32-bit addition can be done safely. */ 29 static bool IsSafeAdd(int32_t c1, int32_t c2) { 30 return CanLongValueFitIntoInt(static_cast<int64_t>(c1) + static_cast<int64_t>(c2)); 31 } 32 33 /** Returns true if 32-bit subtraction can be done safely. */ 34 static bool IsSafeSub(int32_t c1, int32_t c2) { 35 return CanLongValueFitIntoInt(static_cast<int64_t>(c1) - static_cast<int64_t>(c2)); 36 } 37 38 /** Returns true if 32-bit multiplication can be done safely. */ 39 static bool IsSafeMul(int32_t c1, int32_t c2) { 40 return CanLongValueFitIntoInt(static_cast<int64_t>(c1) * static_cast<int64_t>(c2)); 41 } 42 43 /** Returns true if 32-bit division can be done safely. */ 44 static bool IsSafeDiv(int32_t c1, int32_t c2) { 45 return c2 != 0 && CanLongValueFitIntoInt(static_cast<int64_t>(c1) / static_cast<int64_t>(c2)); 46 } 47 48 /** Returns true for 32/64-bit constant instruction. */ 49 static bool IsIntAndGet(HInstruction* instruction, int64_t* value) { 50 if (instruction->IsIntConstant()) { 51 *value = instruction->AsIntConstant()->GetValue(); 52 return true; 53 } else if (instruction->IsLongConstant()) { 54 *value = instruction->AsLongConstant()->GetValue(); 55 return true; 56 } 57 return false; 58 } 59 60 /** 61 * An upper bound a * (length / a) + b, where a >= 1, can be conservatively rewritten as length + b 62 * because length >= 0 is true. This makes it more likely the bound is useful to clients. 63 */ 64 static InductionVarRange::Value SimplifyMax(InductionVarRange::Value v) { 65 int64_t value; 66 if (v.is_known && 67 v.a_constant >= 1 && 68 v.instruction->IsDiv() && 69 v.instruction->InputAt(0)->IsArrayLength() && 70 IsIntAndGet(v.instruction->InputAt(1), &value) && v.a_constant == value) { 71 return InductionVarRange::Value(v.instruction->InputAt(0), 1, v.b_constant); 72 } 73 return v; 74 } 75 76 /** 77 * Corrects a value for type to account for arithmetic wrap-around in lower precision. 78 */ 79 static InductionVarRange::Value CorrectForType(InductionVarRange::Value v, Primitive::Type type) { 80 switch (type) { 81 case Primitive::kPrimShort: 82 case Primitive::kPrimChar: 83 case Primitive::kPrimByte: { 84 // Constants within range only. 85 // TODO: maybe some room for improvement, like allowing widening conversions 86 const int32_t min = Primitive::MinValueOfIntegralType(type); 87 const int32_t max = Primitive::MaxValueOfIntegralType(type); 88 return (v.is_known && v.a_constant == 0 && min <= v.b_constant && v.b_constant <= max) 89 ? v 90 : InductionVarRange::Value(); 91 } 92 default: 93 // At int or higher. 94 return v; 95 } 96 } 97 98 /** Helper method to test for a constant value. */ 99 static bool IsConstantValue(InductionVarRange::Value v) { 100 return v.is_known && v.a_constant == 0; 101 } 102 103 /** Helper method to test for same constant value. */ 104 static bool IsSameConstantValue(InductionVarRange::Value v1, InductionVarRange::Value v2) { 105 return IsConstantValue(v1) && IsConstantValue(v2) && v1.b_constant == v2.b_constant; 106 } 107 108 /** Helper method to insert an instruction. */ 109 static HInstruction* Insert(HBasicBlock* block, HInstruction* instruction) { 110 DCHECK(block != nullptr); 111 DCHECK(block->GetLastInstruction() != nullptr) << block->GetBlockId(); 112 DCHECK(instruction != nullptr); 113 block->InsertInstructionBefore(instruction, block->GetLastInstruction()); 114 return instruction; 115 } 116 117 // 118 // Public class methods. 119 // 120 121 InductionVarRange::InductionVarRange(HInductionVarAnalysis* induction_analysis) 122 : induction_analysis_(induction_analysis) { 123 DCHECK(induction_analysis != nullptr); 124 } 125 126 bool InductionVarRange::GetInductionRange(HInstruction* context, 127 HInstruction* instruction, 128 /*out*/Value* min_val, 129 /*out*/Value* max_val, 130 /*out*/bool* needs_finite_test) { 131 HLoopInformation* loop = context->GetBlock()->GetLoopInformation(); // closest enveloping loop 132 if (loop == nullptr) { 133 return false; // no loop 134 } 135 HInductionVarAnalysis::InductionInfo* info = induction_analysis_->LookupInfo(loop, instruction); 136 if (info == nullptr) { 137 return false; // no induction information 138 } 139 // Type int or lower (this is not too restrictive since intended clients, like 140 // bounds check elimination, will have truncated higher precision induction 141 // at their use point already). 142 switch (info->type) { 143 case Primitive::kPrimInt: 144 case Primitive::kPrimShort: 145 case Primitive::kPrimChar: 146 case Primitive::kPrimByte: 147 break; 148 default: 149 return false; 150 } 151 // Set up loop information. 152 HBasicBlock* header = loop->GetHeader(); 153 bool in_body = context->GetBlock() != header; 154 HInductionVarAnalysis::InductionInfo* trip = 155 induction_analysis_->LookupInfo(loop, header->GetLastInstruction()); 156 // Find range. 157 *min_val = GetVal(info, trip, in_body, /* is_min */ true); 158 *max_val = SimplifyMax(GetVal(info, trip, in_body, /* is_min */ false)); 159 *needs_finite_test = NeedsTripCount(info) && IsUnsafeTripCount(trip); 160 return true; 161 } 162 163 bool InductionVarRange::RefineOuter(/*in-out*/ Value* min_val, 164 /*in-out*/ Value* max_val) const { 165 if (min_val->instruction != nullptr || max_val->instruction != nullptr) { 166 Value v1_min = RefineOuter(*min_val, /* is_min */ true); 167 Value v2_max = RefineOuter(*max_val, /* is_min */ false); 168 // The refined range is safe if both sides refine the same instruction. Otherwise, since two 169 // different ranges are combined, the new refined range is safe to pass back to the client if 170 // the extremes of the computed ranges ensure no arithmetic wrap-around anomalies occur. 171 if (min_val->instruction != max_val->instruction) { 172 Value v1_max = RefineOuter(*min_val, /* is_min */ false); 173 Value v2_min = RefineOuter(*max_val, /* is_min */ true); 174 if (!IsConstantValue(v1_max) || 175 !IsConstantValue(v2_min) || 176 v1_max.b_constant > v2_min.b_constant) { 177 return false; 178 } 179 } 180 // Did something change? 181 if (v1_min.instruction != min_val->instruction || v2_max.instruction != max_val->instruction) { 182 *min_val = v1_min; 183 *max_val = v2_max; 184 return true; 185 } 186 } 187 return false; 188 } 189 190 bool InductionVarRange::CanGenerateCode(HInstruction* context, 191 HInstruction* instruction, 192 /*out*/bool* needs_finite_test, 193 /*out*/bool* needs_taken_test) { 194 return GenerateCode(context, 195 instruction, 196 nullptr, nullptr, nullptr, nullptr, nullptr, // nothing generated yet 197 needs_finite_test, 198 needs_taken_test); 199 } 200 201 void InductionVarRange::GenerateRangeCode(HInstruction* context, 202 HInstruction* instruction, 203 HGraph* graph, 204 HBasicBlock* block, 205 /*out*/HInstruction** lower, 206 /*out*/HInstruction** upper) { 207 bool b1, b2; // unused 208 if (!GenerateCode(context, instruction, graph, block, lower, upper, nullptr, &b1, &b2)) { 209 LOG(FATAL) << "Failed precondition: GenerateCode()"; 210 } 211 } 212 213 void InductionVarRange::GenerateTakenTest(HInstruction* context, 214 HGraph* graph, 215 HBasicBlock* block, 216 /*out*/HInstruction** taken_test) { 217 bool b1, b2; // unused 218 if (!GenerateCode(context, context, graph, block, nullptr, nullptr, taken_test, &b1, &b2)) { 219 LOG(FATAL) << "Failed precondition: GenerateCode()"; 220 } 221 } 222 223 // 224 // Private class methods. 225 // 226 227 bool InductionVarRange::IsConstant(HInductionVarAnalysis::InductionInfo* info, 228 ConstantRequest request, 229 /*out*/ int64_t *value) const { 230 if (info != nullptr) { 231 // A direct 32-bit or 64-bit constant fetch. This immediately satisfies 232 // any of the three requests (kExact, kAtMost, and KAtLeast). 233 if (info->induction_class == HInductionVarAnalysis::kInvariant && 234 info->operation == HInductionVarAnalysis::kFetch) { 235 if (IsIntAndGet(info->fetch, value)) { 236 return true; 237 } 238 } 239 // Try range analysis while traversing outward on loops. 240 bool in_body = true; // no known trip count 241 Value v_min = GetVal(info, nullptr, in_body, /* is_min */ true); 242 Value v_max = GetVal(info, nullptr, in_body, /* is_min */ false); 243 do { 244 // Make sure *both* extremes are known to avoid arithmetic wrap-around anomalies. 245 if (IsConstantValue(v_min) && IsConstantValue(v_max) && v_min.b_constant <= v_max.b_constant) { 246 if ((request == kExact && v_min.b_constant == v_max.b_constant) || request == kAtMost) { 247 *value = v_max.b_constant; 248 return true; 249 } else if (request == kAtLeast) { 250 *value = v_min.b_constant; 251 return true; 252 } 253 } 254 } while (RefineOuter(&v_min, &v_max)); 255 // Exploit array length + c >= c, with c <= 0 to avoid arithmetic wrap-around anomalies 256 // (e.g. array length == maxint and c == 1 would yield minint). 257 if (request == kAtLeast) { 258 if (v_min.a_constant == 1 && v_min.b_constant <= 0 && v_min.instruction->IsArrayLength()) { 259 *value = v_min.b_constant; 260 return true; 261 } 262 } 263 } 264 return false; 265 } 266 267 bool InductionVarRange::NeedsTripCount(HInductionVarAnalysis::InductionInfo* info) const { 268 if (info != nullptr) { 269 if (info->induction_class == HInductionVarAnalysis::kLinear) { 270 return true; 271 } else if (info->induction_class == HInductionVarAnalysis::kWrapAround) { 272 return NeedsTripCount(info->op_b); 273 } 274 } 275 return false; 276 } 277 278 bool InductionVarRange::IsBodyTripCount(HInductionVarAnalysis::InductionInfo* trip) const { 279 if (trip != nullptr) { 280 if (trip->induction_class == HInductionVarAnalysis::kInvariant) { 281 return trip->operation == HInductionVarAnalysis::kTripCountInBody || 282 trip->operation == HInductionVarAnalysis::kTripCountInBodyUnsafe; 283 } 284 } 285 return false; 286 } 287 288 bool InductionVarRange::IsUnsafeTripCount(HInductionVarAnalysis::InductionInfo* trip) const { 289 if (trip != nullptr) { 290 if (trip->induction_class == HInductionVarAnalysis::kInvariant) { 291 return trip->operation == HInductionVarAnalysis::kTripCountInBodyUnsafe || 292 trip->operation == HInductionVarAnalysis::kTripCountInLoopUnsafe; 293 } 294 } 295 return false; 296 } 297 298 InductionVarRange::Value InductionVarRange::GetLinear(HInductionVarAnalysis::InductionInfo* info, 299 HInductionVarAnalysis::InductionInfo* trip, 300 bool in_body, 301 bool is_min) const { 302 // Detect common situation where an offset inside the trip count cancels out during range 303 // analysis (finding max a * (TC - 1) + OFFSET for a == 1 and TC = UPPER - OFFSET or finding 304 // min a * (TC - 1) + OFFSET for a == -1 and TC = OFFSET - UPPER) to avoid losing information 305 // with intermediate results that only incorporate single instructions. 306 if (trip != nullptr) { 307 HInductionVarAnalysis::InductionInfo* trip_expr = trip->op_a; 308 if (trip_expr->operation == HInductionVarAnalysis::kSub) { 309 int64_t stride_value = 0; 310 if (IsConstant(info->op_a, kExact, &stride_value)) { 311 if (!is_min && stride_value == 1) { 312 // Test original trip's negative operand (trip_expr->op_b) against offset of induction. 313 if (HInductionVarAnalysis::InductionEqual(trip_expr->op_b, info->op_b)) { 314 // Analyze cancelled trip with just the positive operand (trip_expr->op_a). 315 HInductionVarAnalysis::InductionInfo cancelled_trip( 316 trip->induction_class, 317 trip->operation, 318 trip_expr->op_a, 319 trip->op_b, 320 nullptr, 321 trip->type); 322 return GetVal(&cancelled_trip, trip, in_body, is_min); 323 } 324 } else if (is_min && stride_value == -1) { 325 // Test original trip's positive operand (trip_expr->op_a) against offset of induction. 326 if (HInductionVarAnalysis::InductionEqual(trip_expr->op_a, info->op_b)) { 327 // Analyze cancelled trip with just the negative operand (trip_expr->op_b). 328 HInductionVarAnalysis::InductionInfo neg( 329 HInductionVarAnalysis::kInvariant, 330 HInductionVarAnalysis::kNeg, 331 nullptr, 332 trip_expr->op_b, 333 nullptr, 334 trip->type); 335 HInductionVarAnalysis::InductionInfo cancelled_trip( 336 trip->induction_class, trip->operation, &neg, trip->op_b, nullptr, trip->type); 337 return SubValue(Value(0), GetVal(&cancelled_trip, trip, in_body, !is_min)); 338 } 339 } 340 } 341 } 342 } 343 // General rule of linear induction a * i + b, for normalized 0 <= i < TC. 344 return AddValue(GetMul(info->op_a, trip, trip, in_body, is_min), 345 GetVal(info->op_b, trip, in_body, is_min)); 346 } 347 348 InductionVarRange::Value InductionVarRange::GetFetch(HInstruction* instruction, 349 HInductionVarAnalysis::InductionInfo* trip, 350 bool in_body, 351 bool is_min) const { 352 // Detect constants and chase the fetch a bit deeper into the HIR tree, so that it becomes 353 // more likely range analysis will compare the same instructions as terminal nodes. 354 int64_t value; 355 if (IsIntAndGet(instruction, &value) && CanLongValueFitIntoInt(value)) { 356 return Value(static_cast<int32_t>(value)); 357 } else if (instruction->IsAdd()) { 358 if (IsIntAndGet(instruction->InputAt(0), &value) && CanLongValueFitIntoInt(value)) { 359 return AddValue(Value(static_cast<int32_t>(value)), 360 GetFetch(instruction->InputAt(1), trip, in_body, is_min)); 361 } else if (IsIntAndGet(instruction->InputAt(1), &value) && CanLongValueFitIntoInt(value)) { 362 return AddValue(GetFetch(instruction->InputAt(0), trip, in_body, is_min), 363 Value(static_cast<int32_t>(value))); 364 } 365 } else if (instruction->IsArrayLength() && instruction->InputAt(0)->IsNewArray()) { 366 return GetFetch(instruction->InputAt(0)->InputAt(0), trip, in_body, is_min); 367 } else if (instruction->IsTypeConversion()) { 368 // Since analysis is 32-bit (or narrower) we allow a widening along the path. 369 if (instruction->AsTypeConversion()->GetInputType() == Primitive::kPrimInt && 370 instruction->AsTypeConversion()->GetResultType() == Primitive::kPrimLong) { 371 return GetFetch(instruction->InputAt(0), trip, in_body, is_min); 372 } 373 } else if (is_min) { 374 // Special case for finding minimum: minimum of trip-count in loop-body is 1. 375 if (trip != nullptr && in_body && instruction == trip->op_a->fetch) { 376 return Value(1); 377 } 378 } 379 return Value(instruction, 1, 0); 380 } 381 382 InductionVarRange::Value InductionVarRange::GetVal(HInductionVarAnalysis::InductionInfo* info, 383 HInductionVarAnalysis::InductionInfo* trip, 384 bool in_body, 385 bool is_min) const { 386 if (info != nullptr) { 387 switch (info->induction_class) { 388 case HInductionVarAnalysis::kInvariant: 389 // Invariants. 390 switch (info->operation) { 391 case HInductionVarAnalysis::kAdd: 392 return AddValue(GetVal(info->op_a, trip, in_body, is_min), 393 GetVal(info->op_b, trip, in_body, is_min)); 394 case HInductionVarAnalysis::kSub: // second reversed! 395 return SubValue(GetVal(info->op_a, trip, in_body, is_min), 396 GetVal(info->op_b, trip, in_body, !is_min)); 397 case HInductionVarAnalysis::kNeg: // second reversed! 398 return SubValue(Value(0), 399 GetVal(info->op_b, trip, in_body, !is_min)); 400 case HInductionVarAnalysis::kMul: 401 return GetMul(info->op_a, info->op_b, trip, in_body, is_min); 402 case HInductionVarAnalysis::kDiv: 403 return GetDiv(info->op_a, info->op_b, trip, in_body, is_min); 404 case HInductionVarAnalysis::kFetch: 405 return GetFetch(info->fetch, trip, in_body, is_min); 406 case HInductionVarAnalysis::kTripCountInLoop: 407 case HInductionVarAnalysis::kTripCountInLoopUnsafe: 408 if (!in_body && !is_min) { // one extra! 409 return GetVal(info->op_a, trip, in_body, is_min); 410 } 411 FALLTHROUGH_INTENDED; 412 case HInductionVarAnalysis::kTripCountInBody: 413 case HInductionVarAnalysis::kTripCountInBodyUnsafe: 414 if (is_min) { 415 return Value(0); 416 } else if (in_body) { 417 return SubValue(GetVal(info->op_a, trip, in_body, is_min), Value(1)); 418 } 419 break; 420 default: 421 break; 422 } 423 break; 424 case HInductionVarAnalysis::kLinear: { 425 return CorrectForType(GetLinear(info, trip, in_body, is_min), info->type); 426 } 427 case HInductionVarAnalysis::kWrapAround: 428 case HInductionVarAnalysis::kPeriodic: 429 return MergeVal(GetVal(info->op_a, trip, in_body, is_min), 430 GetVal(info->op_b, trip, in_body, is_min), is_min); 431 } 432 } 433 return Value(); 434 } 435 436 InductionVarRange::Value InductionVarRange::GetMul(HInductionVarAnalysis::InductionInfo* info1, 437 HInductionVarAnalysis::InductionInfo* info2, 438 HInductionVarAnalysis::InductionInfo* trip, 439 bool in_body, 440 bool is_min) const { 441 Value v1_min = GetVal(info1, trip, in_body, /* is_min */ true); 442 Value v1_max = GetVal(info1, trip, in_body, /* is_min */ false); 443 Value v2_min = GetVal(info2, trip, in_body, /* is_min */ true); 444 Value v2_max = GetVal(info2, trip, in_body, /* is_min */ false); 445 // Try to refine first operand. 446 if (!IsConstantValue(v1_min) && !IsConstantValue(v1_max)) { 447 RefineOuter(&v1_min, &v1_max); 448 } 449 // Constant times range. 450 if (IsSameConstantValue(v1_min, v1_max)) { 451 return MulRangeAndConstant(v2_min, v2_max, v1_min, is_min); 452 } else if (IsSameConstantValue(v2_min, v2_max)) { 453 return MulRangeAndConstant(v1_min, v1_max, v2_min, is_min); 454 } 455 // Positive range vs. positive or negative range. 456 if (IsConstantValue(v1_min) && v1_min.b_constant >= 0) { 457 if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) { 458 return is_min ? MulValue(v1_min, v2_min) : MulValue(v1_max, v2_max); 459 } else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) { 460 return is_min ? MulValue(v1_max, v2_min) : MulValue(v1_min, v2_max); 461 } 462 } 463 // Negative range vs. positive or negative range. 464 if (IsConstantValue(v1_max) && v1_max.b_constant <= 0) { 465 if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) { 466 return is_min ? MulValue(v1_min, v2_max) : MulValue(v1_max, v2_min); 467 } else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) { 468 return is_min ? MulValue(v1_max, v2_max) : MulValue(v1_min, v2_min); 469 } 470 } 471 return Value(); 472 } 473 474 InductionVarRange::Value InductionVarRange::GetDiv(HInductionVarAnalysis::InductionInfo* info1, 475 HInductionVarAnalysis::InductionInfo* info2, 476 HInductionVarAnalysis::InductionInfo* trip, 477 bool in_body, 478 bool is_min) const { 479 Value v1_min = GetVal(info1, trip, in_body, /* is_min */ true); 480 Value v1_max = GetVal(info1, trip, in_body, /* is_min */ false); 481 Value v2_min = GetVal(info2, trip, in_body, /* is_min */ true); 482 Value v2_max = GetVal(info2, trip, in_body, /* is_min */ false); 483 // Range divided by constant. 484 if (IsSameConstantValue(v2_min, v2_max)) { 485 return DivRangeAndConstant(v1_min, v1_max, v2_min, is_min); 486 } 487 // Positive range vs. positive or negative range. 488 if (IsConstantValue(v1_min) && v1_min.b_constant >= 0) { 489 if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) { 490 return is_min ? DivValue(v1_min, v2_max) : DivValue(v1_max, v2_min); 491 } else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) { 492 return is_min ? DivValue(v1_max, v2_max) : DivValue(v1_min, v2_min); 493 } 494 } 495 // Negative range vs. positive or negative range. 496 if (IsConstantValue(v1_max) && v1_max.b_constant <= 0) { 497 if (IsConstantValue(v2_min) && v2_min.b_constant >= 0) { 498 return is_min ? DivValue(v1_min, v2_min) : DivValue(v1_max, v2_max); 499 } else if (IsConstantValue(v2_max) && v2_max.b_constant <= 0) { 500 return is_min ? DivValue(v1_max, v2_min) : DivValue(v1_min, v2_max); 501 } 502 } 503 return Value(); 504 } 505 506 InductionVarRange::Value InductionVarRange::MulRangeAndConstant(Value v_min, 507 Value v_max, 508 Value c, 509 bool is_min) const { 510 return is_min == (c.b_constant >= 0) ? MulValue(v_min, c) : MulValue(v_max, c); 511 } 512 513 InductionVarRange::Value InductionVarRange::DivRangeAndConstant(Value v_min, 514 Value v_max, 515 Value c, 516 bool is_min) const { 517 return is_min == (c.b_constant >= 0) ? DivValue(v_min, c) : DivValue(v_max, c); 518 } 519 520 InductionVarRange::Value InductionVarRange::AddValue(Value v1, Value v2) const { 521 if (v1.is_known && v2.is_known && IsSafeAdd(v1.b_constant, v2.b_constant)) { 522 const int32_t b = v1.b_constant + v2.b_constant; 523 if (v1.a_constant == 0) { 524 return Value(v2.instruction, v2.a_constant, b); 525 } else if (v2.a_constant == 0) { 526 return Value(v1.instruction, v1.a_constant, b); 527 } else if (v1.instruction == v2.instruction && IsSafeAdd(v1.a_constant, v2.a_constant)) { 528 return Value(v1.instruction, v1.a_constant + v2.a_constant, b); 529 } 530 } 531 return Value(); 532 } 533 534 InductionVarRange::Value InductionVarRange::SubValue(Value v1, Value v2) const { 535 if (v1.is_known && v2.is_known && IsSafeSub(v1.b_constant, v2.b_constant)) { 536 const int32_t b = v1.b_constant - v2.b_constant; 537 if (v1.a_constant == 0 && IsSafeSub(0, v2.a_constant)) { 538 return Value(v2.instruction, -v2.a_constant, b); 539 } else if (v2.a_constant == 0) { 540 return Value(v1.instruction, v1.a_constant, b); 541 } else if (v1.instruction == v2.instruction && IsSafeSub(v1.a_constant, v2.a_constant)) { 542 return Value(v1.instruction, v1.a_constant - v2.a_constant, b); 543 } 544 } 545 return Value(); 546 } 547 548 InductionVarRange::Value InductionVarRange::MulValue(Value v1, Value v2) const { 549 if (v1.is_known && v2.is_known) { 550 if (v1.a_constant == 0) { 551 if (IsSafeMul(v1.b_constant, v2.a_constant) && IsSafeMul(v1.b_constant, v2.b_constant)) { 552 return Value(v2.instruction, v1.b_constant * v2.a_constant, v1.b_constant * v2.b_constant); 553 } 554 } else if (v2.a_constant == 0) { 555 if (IsSafeMul(v1.a_constant, v2.b_constant) && IsSafeMul(v1.b_constant, v2.b_constant)) { 556 return Value(v1.instruction, v1.a_constant * v2.b_constant, v1.b_constant * v2.b_constant); 557 } 558 } 559 } 560 return Value(); 561 } 562 563 InductionVarRange::Value InductionVarRange::DivValue(Value v1, Value v2) const { 564 if (v1.is_known && v2.is_known && v1.a_constant == 0 && v2.a_constant == 0) { 565 if (IsSafeDiv(v1.b_constant, v2.b_constant)) { 566 return Value(v1.b_constant / v2.b_constant); 567 } 568 } 569 return Value(); 570 } 571 572 InductionVarRange::Value InductionVarRange::MergeVal(Value v1, Value v2, bool is_min) const { 573 if (v1.is_known && v2.is_known) { 574 if (v1.instruction == v2.instruction && v1.a_constant == v2.a_constant) { 575 return Value(v1.instruction, v1.a_constant, 576 is_min ? std::min(v1.b_constant, v2.b_constant) 577 : std::max(v1.b_constant, v2.b_constant)); 578 } 579 } 580 return Value(); 581 } 582 583 InductionVarRange::Value InductionVarRange::RefineOuter(Value v, bool is_min) const { 584 if (v.instruction == nullptr) { 585 return v; // nothing to refine 586 } 587 HLoopInformation* loop = 588 v.instruction->GetBlock()->GetLoopInformation(); // closest enveloping loop 589 if (loop == nullptr) { 590 return v; // no loop 591 } 592 HInductionVarAnalysis::InductionInfo* info = induction_analysis_->LookupInfo(loop, v.instruction); 593 if (info == nullptr) { 594 return v; // no induction information 595 } 596 // Set up loop information. 597 HBasicBlock* header = loop->GetHeader(); 598 bool in_body = true; // inner always in more outer 599 HInductionVarAnalysis::InductionInfo* trip = 600 induction_analysis_->LookupInfo(loop, header->GetLastInstruction()); 601 // Try to refine "a x instruction + b" with outer loop range information on instruction. 602 return AddValue(MulValue(Value(v.a_constant), GetVal(info, trip, in_body, is_min)), Value(v.b_constant)); 603 } 604 605 bool InductionVarRange::GenerateCode(HInstruction* context, 606 HInstruction* instruction, 607 HGraph* graph, 608 HBasicBlock* block, 609 /*out*/HInstruction** lower, 610 /*out*/HInstruction** upper, 611 /*out*/HInstruction** taken_test, 612 /*out*/bool* needs_finite_test, 613 /*out*/bool* needs_taken_test) const { 614 HLoopInformation* loop = context->GetBlock()->GetLoopInformation(); // closest enveloping loop 615 if (loop == nullptr) { 616 return false; // no loop 617 } 618 HInductionVarAnalysis::InductionInfo* info = induction_analysis_->LookupInfo(loop, instruction); 619 if (info == nullptr) { 620 return false; // no induction information 621 } 622 // Set up loop information. 623 HBasicBlock* header = loop->GetHeader(); 624 bool in_body = context->GetBlock() != header; 625 HInductionVarAnalysis::InductionInfo* trip = 626 induction_analysis_->LookupInfo(loop, header->GetLastInstruction()); 627 if (trip == nullptr) { 628 return false; // codegen relies on trip count 629 } 630 // Determine what tests are needed. A finite test is needed if the evaluation code uses the 631 // trip-count and the loop maybe unsafe (because in such cases, the index could "overshoot" 632 // the computed range). A taken test is needed for any unknown trip-count, even if evaluation 633 // code does not use the trip-count explicitly (since there could be an implicit relation 634 // between e.g. an invariant subscript and a not-taken condition). 635 *needs_finite_test = NeedsTripCount(info) && IsUnsafeTripCount(trip); 636 *needs_taken_test = IsBodyTripCount(trip); 637 // Code generation for taken test: generate the code when requested or otherwise analyze 638 // if code generation is feasible when taken test is needed. 639 if (taken_test != nullptr) { 640 return GenerateCode(trip->op_b, nullptr, graph, block, taken_test, in_body, /* is_min */ false); 641 } else if (*needs_taken_test) { 642 if (!GenerateCode( 643 trip->op_b, nullptr, nullptr, nullptr, nullptr, in_body, /* is_min */ false)) { 644 return false; 645 } 646 } 647 // Code generation for lower and upper. 648 return 649 // Success on lower if invariant (not set), or code can be generated. 650 ((info->induction_class == HInductionVarAnalysis::kInvariant) || 651 GenerateCode(info, trip, graph, block, lower, in_body, /* is_min */ true)) && 652 // And success on upper. 653 GenerateCode(info, trip, graph, block, upper, in_body, /* is_min */ false); 654 } 655 656 bool InductionVarRange::GenerateCode(HInductionVarAnalysis::InductionInfo* info, 657 HInductionVarAnalysis::InductionInfo* trip, 658 HGraph* graph, // when set, code is generated 659 HBasicBlock* block, 660 /*out*/HInstruction** result, 661 bool in_body, 662 bool is_min) const { 663 if (info != nullptr) { 664 // Verify type safety. 665 Primitive::Type type = Primitive::kPrimInt; 666 if (info->type != type) { 667 return false; 668 } 669 // Handle current operation. 670 HInstruction* opa = nullptr; 671 HInstruction* opb = nullptr; 672 switch (info->induction_class) { 673 case HInductionVarAnalysis::kInvariant: 674 // Invariants. 675 switch (info->operation) { 676 case HInductionVarAnalysis::kAdd: 677 case HInductionVarAnalysis::kLT: 678 case HInductionVarAnalysis::kLE: 679 case HInductionVarAnalysis::kGT: 680 case HInductionVarAnalysis::kGE: 681 if (GenerateCode(info->op_a, trip, graph, block, &opa, in_body, is_min) && 682 GenerateCode(info->op_b, trip, graph, block, &opb, in_body, is_min)) { 683 if (graph != nullptr) { 684 HInstruction* operation = nullptr; 685 switch (info->operation) { 686 case HInductionVarAnalysis::kAdd: 687 operation = new (graph->GetArena()) HAdd(type, opa, opb); break; 688 case HInductionVarAnalysis::kLT: 689 operation = new (graph->GetArena()) HLessThan(opa, opb); break; 690 case HInductionVarAnalysis::kLE: 691 operation = new (graph->GetArena()) HLessThanOrEqual(opa, opb); break; 692 case HInductionVarAnalysis::kGT: 693 operation = new (graph->GetArena()) HGreaterThan(opa, opb); break; 694 case HInductionVarAnalysis::kGE: 695 operation = new (graph->GetArena()) HGreaterThanOrEqual(opa, opb); break; 696 default: 697 LOG(FATAL) << "unknown operation"; 698 } 699 *result = Insert(block, operation); 700 } 701 return true; 702 } 703 break; 704 case HInductionVarAnalysis::kSub: // second reversed! 705 if (GenerateCode(info->op_a, trip, graph, block, &opa, in_body, is_min) && 706 GenerateCode(info->op_b, trip, graph, block, &opb, in_body, !is_min)) { 707 if (graph != nullptr) { 708 *result = Insert(block, new (graph->GetArena()) HSub(type, opa, opb)); 709 } 710 return true; 711 } 712 break; 713 case HInductionVarAnalysis::kNeg: // reversed! 714 if (GenerateCode(info->op_b, trip, graph, block, &opb, in_body, !is_min)) { 715 if (graph != nullptr) { 716 *result = Insert(block, new (graph->GetArena()) HNeg(type, opb)); 717 } 718 return true; 719 } 720 break; 721 case HInductionVarAnalysis::kFetch: 722 if (graph != nullptr) { 723 *result = info->fetch; // already in HIR 724 } 725 return true; 726 case HInductionVarAnalysis::kTripCountInLoop: 727 case HInductionVarAnalysis::kTripCountInLoopUnsafe: 728 if (!in_body && !is_min) { // one extra! 729 return GenerateCode(info->op_a, trip, graph, block, result, in_body, is_min); 730 } 731 FALLTHROUGH_INTENDED; 732 case HInductionVarAnalysis::kTripCountInBody: 733 case HInductionVarAnalysis::kTripCountInBodyUnsafe: 734 if (is_min) { 735 if (graph != nullptr) { 736 *result = graph->GetIntConstant(0); 737 } 738 return true; 739 } else if (in_body) { 740 if (GenerateCode(info->op_a, trip, graph, block, &opb, in_body, is_min)) { 741 if (graph != nullptr) { 742 *result = Insert(block, 743 new (graph->GetArena()) 744 HSub(type, opb, graph->GetIntConstant(1))); 745 } 746 return true; 747 } 748 } 749 break; 750 default: 751 break; 752 } 753 break; 754 case HInductionVarAnalysis::kLinear: { 755 // Linear induction a * i + b, for normalized 0 <= i < TC. Restrict to unit stride only 756 // to avoid arithmetic wrap-around situations that are hard to guard against. 757 int64_t stride_value = 0; 758 if (IsConstant(info->op_a, kExact, &stride_value)) { 759 if (stride_value == 1 || stride_value == -1) { 760 const bool is_min_a = stride_value == 1 ? is_min : !is_min; 761 if (GenerateCode(trip, trip, graph, block, &opa, in_body, is_min_a) && 762 GenerateCode(info->op_b, trip, graph, block, &opb, in_body, is_min)) { 763 if (graph != nullptr) { 764 HInstruction* oper; 765 if (stride_value == 1) { 766 oper = new (graph->GetArena()) HAdd(type, opa, opb); 767 } else { 768 oper = new (graph->GetArena()) HSub(type, opb, opa); 769 } 770 *result = Insert(block, oper); 771 } 772 return true; 773 } 774 } 775 } 776 break; 777 } 778 case HInductionVarAnalysis::kWrapAround: 779 case HInductionVarAnalysis::kPeriodic: { 780 // Wrap-around and periodic inductions are restricted to constants only, so that extreme 781 // values are easy to test at runtime without complications of arithmetic wrap-around. 782 Value extreme = GetVal(info, trip, in_body, is_min); 783 if (IsConstantValue(extreme)) { 784 if (graph != nullptr) { 785 *result = graph->GetIntConstant(extreme.b_constant); 786 } 787 return true; 788 } 789 break; 790 } 791 default: 792 break; 793 } 794 } 795 return false; 796 } 797 798 } // namespace art 799
