LiveInterval.cpp revision 4ee451de366474b9c228b4e5fa573795a715216d
1//===-- LiveInterval.cpp - Live Interval Representation -------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the LiveRange and LiveInterval classes. Given some 11// numbering of each the machine instructions an interval [i, j) is said to be a 12// live interval for register v if there is no instruction with number j' > j 13// such that v is live at j' abd there is no instruction with number i' < i such 14// that v is live at i'. In this implementation intervals can have holes, 15// i.e. an interval might look like [1,20), [50,65), [1000,1001). Each 16// individual range is represented as an instance of LiveRange, and the whole 17// interval is represented as an instance of LiveInterval. 18// 19//===----------------------------------------------------------------------===// 20 21#include "llvm/CodeGen/LiveInterval.h" 22#include "llvm/ADT/SmallSet.h" 23#include "llvm/ADT/STLExtras.h" 24#include "llvm/Support/Streams.h" 25#include "llvm/Target/MRegisterInfo.h" 26#include <algorithm> 27#include <map> 28#include <ostream> 29using namespace llvm; 30 31// An example for liveAt(): 32// 33// this = [1,4), liveAt(0) will return false. The instruction defining this 34// spans slots [0,3]. The interval belongs to an spilled definition of the 35// variable it represents. This is because slot 1 is used (def slot) and spans 36// up to slot 3 (store slot). 37// 38bool LiveInterval::liveAt(unsigned I) const { 39 Ranges::const_iterator r = std::upper_bound(ranges.begin(), ranges.end(), I); 40 41 if (r == ranges.begin()) 42 return false; 43 44 --r; 45 return r->contains(I); 46} 47 48// overlaps - Return true if the intersection of the two live intervals is 49// not empty. 50// 51// An example for overlaps(): 52// 53// 0: A = ... 54// 4: B = ... 55// 8: C = A + B ;; last use of A 56// 57// The live intervals should look like: 58// 59// A = [3, 11) 60// B = [7, x) 61// C = [11, y) 62// 63// A->overlaps(C) should return false since we want to be able to join 64// A and C. 65// 66bool LiveInterval::overlapsFrom(const LiveInterval& other, 67 const_iterator StartPos) const { 68 const_iterator i = begin(); 69 const_iterator ie = end(); 70 const_iterator j = StartPos; 71 const_iterator je = other.end(); 72 73 assert((StartPos->start <= i->start || StartPos == other.begin()) && 74 StartPos != other.end() && "Bogus start position hint!"); 75 76 if (i->start < j->start) { 77 i = std::upper_bound(i, ie, j->start); 78 if (i != ranges.begin()) --i; 79 } else if (j->start < i->start) { 80 ++StartPos; 81 if (StartPos != other.end() && StartPos->start <= i->start) { 82 assert(StartPos < other.end() && i < end()); 83 j = std::upper_bound(j, je, i->start); 84 if (j != other.ranges.begin()) --j; 85 } 86 } else { 87 return true; 88 } 89 90 if (j == je) return false; 91 92 while (i != ie) { 93 if (i->start > j->start) { 94 std::swap(i, j); 95 std::swap(ie, je); 96 } 97 98 if (i->end > j->start) 99 return true; 100 ++i; 101 } 102 103 return false; 104} 105 106/// extendIntervalEndTo - This method is used when we want to extend the range 107/// specified by I to end at the specified endpoint. To do this, we should 108/// merge and eliminate all ranges that this will overlap with. The iterator is 109/// not invalidated. 110void LiveInterval::extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd) { 111 assert(I != ranges.end() && "Not a valid interval!"); 112 VNInfo *ValNo = I->valno; 113 unsigned OldEnd = I->end; 114 115 // Search for the first interval that we can't merge with. 116 Ranges::iterator MergeTo = next(I); 117 for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) { 118 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!"); 119 } 120 121 // If NewEnd was in the middle of an interval, make sure to get its endpoint. 122 I->end = std::max(NewEnd, prior(MergeTo)->end); 123 124 // Erase any dead ranges. 125 ranges.erase(next(I), MergeTo); 126 127 // Update kill info. 128 removeKills(ValNo, OldEnd, I->end-1); 129 130 // If the newly formed range now touches the range after it and if they have 131 // the same value number, merge the two ranges into one range. 132 Ranges::iterator Next = next(I); 133 if (Next != ranges.end() && Next->start <= I->end && Next->valno == ValNo) { 134 I->end = Next->end; 135 ranges.erase(Next); 136 } 137} 138 139 140/// extendIntervalStartTo - This method is used when we want to extend the range 141/// specified by I to start at the specified endpoint. To do this, we should 142/// merge and eliminate all ranges that this will overlap with. 143LiveInterval::Ranges::iterator 144LiveInterval::extendIntervalStartTo(Ranges::iterator I, unsigned NewStart) { 145 assert(I != ranges.end() && "Not a valid interval!"); 146 VNInfo *ValNo = I->valno; 147 148 // Search for the first interval that we can't merge with. 149 Ranges::iterator MergeTo = I; 150 do { 151 if (MergeTo == ranges.begin()) { 152 I->start = NewStart; 153 ranges.erase(MergeTo, I); 154 return I; 155 } 156 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!"); 157 --MergeTo; 158 } while (NewStart <= MergeTo->start); 159 160 // If we start in the middle of another interval, just delete a range and 161 // extend that interval. 162 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) { 163 MergeTo->end = I->end; 164 } else { 165 // Otherwise, extend the interval right after. 166 ++MergeTo; 167 MergeTo->start = NewStart; 168 MergeTo->end = I->end; 169 } 170 171 ranges.erase(next(MergeTo), next(I)); 172 return MergeTo; 173} 174 175LiveInterval::iterator 176LiveInterval::addRangeFrom(LiveRange LR, iterator From) { 177 unsigned Start = LR.start, End = LR.end; 178 iterator it = std::upper_bound(From, ranges.end(), Start); 179 180 // If the inserted interval starts in the middle or right at the end of 181 // another interval, just extend that interval to contain the range of LR. 182 if (it != ranges.begin()) { 183 iterator B = prior(it); 184 if (LR.valno == B->valno) { 185 if (B->start <= Start && B->end >= Start) { 186 extendIntervalEndTo(B, End); 187 return B; 188 } 189 } else { 190 // Check to make sure that we are not overlapping two live ranges with 191 // different valno's. 192 assert(B->end <= Start && 193 "Cannot overlap two LiveRanges with differing ValID's" 194 " (did you def the same reg twice in a MachineInstr?)"); 195 } 196 } 197 198 // Otherwise, if this range ends in the middle of, or right next to, another 199 // interval, merge it into that interval. 200 if (it != ranges.end()) 201 if (LR.valno == it->valno) { 202 if (it->start <= End) { 203 it = extendIntervalStartTo(it, Start); 204 205 // If LR is a complete superset of an interval, we may need to grow its 206 // endpoint as well. 207 if (End > it->end) 208 extendIntervalEndTo(it, End); 209 else if (End < it->end) 210 // Overlapping intervals, there might have been a kill here. 211 removeKill(it->valno, End); 212 return it; 213 } 214 } else { 215 // Check to make sure that we are not overlapping two live ranges with 216 // different valno's. 217 assert(it->start >= End && 218 "Cannot overlap two LiveRanges with differing ValID's"); 219 } 220 221 // Otherwise, this is just a new range that doesn't interact with anything. 222 // Insert it. 223 return ranges.insert(it, LR); 224} 225 226 227/// removeRange - Remove the specified range from this interval. Note that 228/// the range must already be in this interval in its entirety. 229void LiveInterval::removeRange(unsigned Start, unsigned End) { 230 // Find the LiveRange containing this span. 231 Ranges::iterator I = std::upper_bound(ranges.begin(), ranges.end(), Start); 232 assert(I != ranges.begin() && "Range is not in interval!"); 233 --I; 234 assert(I->contains(Start) && I->contains(End-1) && 235 "Range is not entirely in interval!"); 236 237 // If the span we are removing is at the start of the LiveRange, adjust it. 238 if (I->start == Start) { 239 if (I->end == End) { 240 removeKills(I->valno, Start, End); 241 ranges.erase(I); // Removed the whole LiveRange. 242 } else 243 I->start = End; 244 return; 245 } 246 247 // Otherwise if the span we are removing is at the end of the LiveRange, 248 // adjust the other way. 249 if (I->end == End) { 250 removeKills(I->valno, Start, End); 251 I->end = Start; 252 return; 253 } 254 255 // Otherwise, we are splitting the LiveRange into two pieces. 256 unsigned OldEnd = I->end; 257 I->end = Start; // Trim the old interval. 258 259 // Insert the new one. 260 ranges.insert(next(I), LiveRange(End, OldEnd, I->valno)); 261} 262 263/// getLiveRangeContaining - Return the live range that contains the 264/// specified index, or null if there is none. 265LiveInterval::const_iterator 266LiveInterval::FindLiveRangeContaining(unsigned Idx) const { 267 const_iterator It = std::upper_bound(begin(), end(), Idx); 268 if (It != ranges.begin()) { 269 --It; 270 if (It->contains(Idx)) 271 return It; 272 } 273 274 return end(); 275} 276 277LiveInterval::iterator 278LiveInterval::FindLiveRangeContaining(unsigned Idx) { 279 iterator It = std::upper_bound(begin(), end(), Idx); 280 if (It != begin()) { 281 --It; 282 if (It->contains(Idx)) 283 return It; 284 } 285 286 return end(); 287} 288 289/// join - Join two live intervals (this, and other) together. This applies 290/// mappings to the value numbers in the LHS/RHS intervals as specified. If 291/// the intervals are not joinable, this aborts. 292void LiveInterval::join(LiveInterval &Other, const int *LHSValNoAssignments, 293 const int *RHSValNoAssignments, 294 SmallVector<VNInfo*, 16> &NewVNInfo) { 295 // Determine if any of our live range values are mapped. This is uncommon, so 296 // we want to avoid the interval scan if not. 297 bool MustMapCurValNos = false; 298 unsigned NumVals = getNumValNums(); 299 unsigned NumNewVals = NewVNInfo.size(); 300 for (unsigned i = 0; i != NumVals; ++i) { 301 unsigned LHSValID = LHSValNoAssignments[i]; 302 if (i != LHSValID || 303 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) 304 MustMapCurValNos = true; 305 } 306 307 // If we have to apply a mapping to our base interval assignment, rewrite it 308 // now. 309 if (MustMapCurValNos) { 310 // Map the first live range. 311 iterator OutIt = begin(); 312 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]]; 313 ++OutIt; 314 for (iterator I = OutIt, E = end(); I != E; ++I) { 315 OutIt->valno = NewVNInfo[LHSValNoAssignments[I->valno->id]]; 316 317 // If this live range has the same value # as its immediate predecessor, 318 // and if they are neighbors, remove one LiveRange. This happens when we 319 // have [0,3:0)[4,7:1) and map 0/1 onto the same value #. 320 if (OutIt->valno == (OutIt-1)->valno && (OutIt-1)->end == OutIt->start) { 321 (OutIt-1)->end = OutIt->end; 322 } else { 323 if (I != OutIt) { 324 OutIt->start = I->start; 325 OutIt->end = I->end; 326 } 327 328 // Didn't merge, on to the next one. 329 ++OutIt; 330 } 331 } 332 333 // If we merge some live ranges, chop off the end. 334 ranges.erase(OutIt, end()); 335 } 336 337 // Remember assignements because val# ids are changing. 338 SmallVector<unsigned, 16> OtherAssignments; 339 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I) 340 OtherAssignments.push_back(RHSValNoAssignments[I->valno->id]); 341 342 // Update val# info. Renumber them and make sure they all belong to this 343 // LiveInterval now. Also remove dead val#'s. 344 unsigned NumValNos = 0; 345 for (unsigned i = 0; i < NumNewVals; ++i) { 346 VNInfo *VNI = NewVNInfo[i]; 347 if (VNI) { 348 if (i >= NumVals) 349 valnos.push_back(VNI); 350 else 351 valnos[NumValNos] = VNI; 352 VNI->id = NumValNos++; // Renumber val#. 353 } 354 } 355 if (NumNewVals < NumVals) 356 valnos.resize(NumNewVals); // shrinkify 357 358 // Okay, now insert the RHS live ranges into the LHS. 359 iterator InsertPos = begin(); 360 unsigned RangeNo = 0; 361 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I, ++RangeNo) { 362 // Map the valno in the other live range to the current live range. 363 I->valno = NewVNInfo[OtherAssignments[RangeNo]]; 364 assert(I->valno && "Adding a dead range?"); 365 InsertPos = addRangeFrom(*I, InsertPos); 366 } 367 368 weight += Other.weight; 369 if (Other.preference && !preference) 370 preference = Other.preference; 371} 372 373/// MergeRangesInAsValue - Merge all of the intervals in RHS into this live 374/// interval as the specified value number. The LiveRanges in RHS are 375/// allowed to overlap with LiveRanges in the current interval, but only if 376/// the overlapping LiveRanges have the specified value number. 377void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS, 378 VNInfo *LHSValNo) { 379 // TODO: Make this more efficient. 380 iterator InsertPos = begin(); 381 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) { 382 // Map the valno in the other live range to the current live range. 383 LiveRange Tmp = *I; 384 Tmp.valno = LHSValNo; 385 InsertPos = addRangeFrom(Tmp, InsertPos); 386 } 387} 388 389 390/// MergeValueInAsValue - Merge all of the live ranges of a specific val# 391/// in RHS into this live interval as the specified value number. 392/// The LiveRanges in RHS are allowed to overlap with LiveRanges in the 393/// current interval, it will replace the value numbers of the overlaped 394/// live ranges with the specified value number. 395void LiveInterval::MergeValueInAsValue(const LiveInterval &RHS, 396 const VNInfo *RHSValNo, VNInfo *LHSValNo) { 397 SmallVector<VNInfo*, 4> ReplacedValNos; 398 iterator IP = begin(); 399 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) { 400 if (I->valno != RHSValNo) 401 continue; 402 unsigned Start = I->start, End = I->end; 403 IP = std::upper_bound(IP, end(), Start); 404 // If the start of this range overlaps with an existing liverange, trim it. 405 if (IP != begin() && IP[-1].end > Start) { 406 if (IP->valno != LHSValNo) { 407 ReplacedValNos.push_back(IP->valno); 408 IP->valno = LHSValNo; // Update val#. 409 } 410 Start = IP[-1].end; 411 // Trimmed away the whole range? 412 if (Start >= End) continue; 413 } 414 // If the end of this range overlaps with an existing liverange, trim it. 415 if (IP != end() && End > IP->start) { 416 if (IP->valno != LHSValNo) { 417 ReplacedValNos.push_back(IP->valno); 418 IP->valno = LHSValNo; // Update val#. 419 } 420 End = IP->start; 421 // If this trimmed away the whole range, ignore it. 422 if (Start == End) continue; 423 } 424 425 // Map the valno in the other live range to the current live range. 426 IP = addRangeFrom(LiveRange(Start, End, LHSValNo), IP); 427 } 428 429 430 SmallSet<VNInfo*, 4> Seen; 431 for (unsigned i = 0, e = ReplacedValNos.size(); i != e; ++i) { 432 VNInfo *V1 = ReplacedValNos[i]; 433 if (Seen.insert(V1)) { 434 bool isDead = true; 435 for (const_iterator I = begin(), E = end(); I != E; ++I) 436 if (I->valno == V1) { 437 isDead = false; 438 break; 439 } 440 if (isDead) { 441 // Now that V1 is dead, remove it. If it is the largest value number, 442 // just nuke it (and any other deleted values neighboring it), otherwise 443 // mark it as ~1U so it can be nuked later. 444 if (V1->id == getNumValNums()-1) { 445 do { 446 VNInfo *VNI = valnos.back(); 447 valnos.pop_back(); 448 VNI->~VNInfo(); 449 } while (valnos.back()->def == ~1U); 450 } else { 451 V1->def = ~1U; 452 } 453 } 454 } 455 } 456} 457 458 459/// MergeInClobberRanges - For any live ranges that are not defined in the 460/// current interval, but are defined in the Clobbers interval, mark them 461/// used with an unknown definition value. 462void LiveInterval::MergeInClobberRanges(const LiveInterval &Clobbers, 463 BumpPtrAllocator &VNInfoAllocator) { 464 if (Clobbers.begin() == Clobbers.end()) return; 465 466 // Find a value # to use for the clobber ranges. If there is already a value# 467 // for unknown values, use it. 468 // FIXME: Use a single sentinal number for these! 469 VNInfo *ClobberValNo = getNextValue(~0U, 0, VNInfoAllocator); 470 471 iterator IP = begin(); 472 for (const_iterator I = Clobbers.begin(), E = Clobbers.end(); I != E; ++I) { 473 unsigned Start = I->start, End = I->end; 474 IP = std::upper_bound(IP, end(), Start); 475 476 // If the start of this range overlaps with an existing liverange, trim it. 477 if (IP != begin() && IP[-1].end > Start) { 478 Start = IP[-1].end; 479 // Trimmed away the whole range? 480 if (Start >= End) continue; 481 } 482 // If the end of this range overlaps with an existing liverange, trim it. 483 if (IP != end() && End > IP->start) { 484 End = IP->start; 485 // If this trimmed away the whole range, ignore it. 486 if (Start == End) continue; 487 } 488 489 // Insert the clobber interval. 490 IP = addRangeFrom(LiveRange(Start, End, ClobberValNo), IP); 491 } 492} 493 494/// MergeValueNumberInto - This method is called when two value nubmers 495/// are found to be equivalent. This eliminates V1, replacing all 496/// LiveRanges with the V1 value number with the V2 value number. This can 497/// cause merging of V1/V2 values numbers and compaction of the value space. 498void LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) { 499 assert(V1 != V2 && "Identical value#'s are always equivalent!"); 500 501 // This code actually merges the (numerically) larger value number into the 502 // smaller value number, which is likely to allow us to compactify the value 503 // space. The only thing we have to be careful of is to preserve the 504 // instruction that defines the result value. 505 506 // Make sure V2 is smaller than V1. 507 if (V1->id < V2->id) { 508 copyValNumInfo(V1, V2); 509 std::swap(V1, V2); 510 } 511 512 // Merge V1 live ranges into V2. 513 for (iterator I = begin(); I != end(); ) { 514 iterator LR = I++; 515 if (LR->valno != V1) continue; // Not a V1 LiveRange. 516 517 // Okay, we found a V1 live range. If it had a previous, touching, V2 live 518 // range, extend it. 519 if (LR != begin()) { 520 iterator Prev = LR-1; 521 if (Prev->valno == V2 && Prev->end == LR->start) { 522 Prev->end = LR->end; 523 524 // Erase this live-range. 525 ranges.erase(LR); 526 I = Prev+1; 527 LR = Prev; 528 } 529 } 530 531 // Okay, now we have a V1 or V2 live range that is maximally merged forward. 532 // Ensure that it is a V2 live-range. 533 LR->valno = V2; 534 535 // If we can merge it into later V2 live ranges, do so now. We ignore any 536 // following V1 live ranges, as they will be merged in subsequent iterations 537 // of the loop. 538 if (I != end()) { 539 if (I->start == LR->end && I->valno == V2) { 540 LR->end = I->end; 541 ranges.erase(I); 542 I = LR+1; 543 } 544 } 545 } 546 547 // Now that V1 is dead, remove it. If it is the largest value number, just 548 // nuke it (and any other deleted values neighboring it), otherwise mark it as 549 // ~1U so it can be nuked later. 550 if (V1->id == getNumValNums()-1) { 551 do { 552 VNInfo *VNI = valnos.back(); 553 valnos.pop_back(); 554 VNI->~VNInfo(); 555 } while (valnos.back()->def == ~1U); 556 } else { 557 V1->def = ~1U; 558 } 559} 560 561void LiveInterval::Copy(const LiveInterval &RHS, 562 BumpPtrAllocator &VNInfoAllocator) { 563 ranges.clear(); 564 valnos.clear(); 565 preference = RHS.preference; 566 weight = RHS.weight; 567 for (unsigned i = 0, e = RHS.getNumValNums(); i != e; ++i) { 568 const VNInfo *VNI = RHS.getValNumInfo(i); 569 VNInfo *NewVNI = getNextValue(~0U, 0, VNInfoAllocator); 570 copyValNumInfo(NewVNI, VNI); 571 } 572 for (unsigned i = 0, e = RHS.ranges.size(); i != e; ++i) { 573 const LiveRange &LR = RHS.ranges[i]; 574 addRange(LiveRange(LR.start, LR.end, getValNumInfo(LR.valno->id))); 575 } 576} 577 578unsigned LiveInterval::getSize() const { 579 unsigned Sum = 0; 580 for (const_iterator I = begin(), E = end(); I != E; ++I) 581 Sum += I->end - I->start; 582 return Sum; 583} 584 585std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) { 586 return os << '[' << LR.start << ',' << LR.end << ':' << LR.valno->id << ")"; 587} 588 589void LiveRange::dump() const { 590 cerr << *this << "\n"; 591} 592 593void LiveInterval::print(std::ostream &OS, const MRegisterInfo *MRI) const { 594 if (MRI && MRegisterInfo::isPhysicalRegister(reg)) 595 OS << MRI->getName(reg); 596 else 597 OS << "%reg" << reg; 598 599 OS << ',' << weight; 600 601 if (empty()) 602 OS << "EMPTY"; 603 else { 604 OS << " = "; 605 for (LiveInterval::Ranges::const_iterator I = ranges.begin(), 606 E = ranges.end(); I != E; ++I) 607 OS << *I; 608 } 609 610 // Print value number info. 611 if (getNumValNums()) { 612 OS << " "; 613 unsigned vnum = 0; 614 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e; 615 ++i, ++vnum) { 616 const VNInfo *vni = *i; 617 if (vnum) OS << " "; 618 OS << vnum << "@"; 619 if (vni->def == ~1U) { 620 OS << "x"; 621 } else { 622 if (vni->def == ~0U) 623 OS << "?"; 624 else 625 OS << vni->def; 626 unsigned ee = vni->kills.size(); 627 if (ee) { 628 OS << "-("; 629 for (unsigned j = 0; j != ee; ++j) { 630 OS << vni->kills[j]; 631 if (j != ee-1) 632 OS << " "; 633 } 634 if (vni->hasPHIKill) 635 OS << " phi"; 636 OS << ")"; 637 } 638 } 639 } 640 } 641} 642 643void LiveInterval::dump() const { 644 cerr << *this << "\n"; 645} 646 647 648void LiveRange::print(std::ostream &os) const { 649 os << *this; 650} 651