LiveInterval.cpp revision d4e4937b79a7da789379a09117cc74f20cd60623
1//===-- LiveInterval.cpp - Live Interval Representation -------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source 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/STLExtras.h" 23#include "llvm/Support/Streams.h" 24#include "llvm/Target/MRegisterInfo.h" 25#include <algorithm> 26#include <map> 27#include <ostream> 28using namespace llvm; 29 30// An example for liveAt(): 31// 32// this = [1,4), liveAt(0) will return false. The instruction defining this 33// spans slots [0,3]. The interval belongs to an spilled definition of the 34// variable it represents. This is because slot 1 is used (def slot) and spans 35// up to slot 3 (store slot). 36// 37bool LiveInterval::liveAt(unsigned I) const { 38 Ranges::const_iterator r = std::upper_bound(ranges.begin(), ranges.end(), I); 39 40 if (r == ranges.begin()) 41 return false; 42 43 --r; 44 return r->contains(I); 45} 46 47// overlaps - Return true if the intersection of the two live intervals is 48// not empty. 49// 50// An example for overlaps(): 51// 52// 0: A = ... 53// 4: B = ... 54// 8: C = A + B ;; last use of A 55// 56// The live intervals should look like: 57// 58// A = [3, 11) 59// B = [7, x) 60// C = [11, y) 61// 62// A->overlaps(C) should return false since we want to be able to join 63// A and C. 64// 65bool LiveInterval::overlapsFrom(const LiveInterval& other, 66 const_iterator StartPos) const { 67 const_iterator i = begin(); 68 const_iterator ie = end(); 69 const_iterator j = StartPos; 70 const_iterator je = other.end(); 71 72 assert((StartPos->start <= i->start || StartPos == other.begin()) && 73 StartPos != other.end() && "Bogus start position hint!"); 74 75 if (i->start < j->start) { 76 i = std::upper_bound(i, ie, j->start); 77 if (i != ranges.begin()) --i; 78 } else if (j->start < i->start) { 79 ++StartPos; 80 if (StartPos != other.end() && StartPos->start <= i->start) { 81 assert(StartPos < other.end() && i < end()); 82 j = std::upper_bound(j, je, i->start); 83 if (j != other.ranges.begin()) --j; 84 } 85 } else { 86 return true; 87 } 88 89 if (j == je) return false; 90 91 while (i != ie) { 92 if (i->start > j->start) { 93 std::swap(i, j); 94 std::swap(ie, je); 95 } 96 97 if (i->end > j->start) 98 return true; 99 ++i; 100 } 101 102 return false; 103} 104 105/// extendIntervalEndTo - This method is used when we want to extend the range 106/// specified by I to end at the specified endpoint. To do this, we should 107/// merge and eliminate all ranges that this will overlap with. The iterator is 108/// not invalidated. 109void LiveInterval::extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd) { 110 assert(I != ranges.end() && "Not a valid interval!"); 111 VNInfo *ValNo = I->valno; 112 unsigned OldEnd = I->end; 113 114 // Search for the first interval that we can't merge with. 115 Ranges::iterator MergeTo = next(I); 116 for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) { 117 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!"); 118 } 119 120 // If NewEnd was in the middle of an interval, make sure to get its endpoint. 121 I->end = std::max(NewEnd, prior(MergeTo)->end); 122 123 // Erase any dead ranges. 124 ranges.erase(next(I), MergeTo); 125 126 // Update kill info. 127 removeKills(*ValNo, OldEnd, I->end-1); 128 129 // If the newly formed range now touches the range after it and if they have 130 // the same value number, merge the two ranges into one range. 131 Ranges::iterator Next = next(I); 132 if (Next != ranges.end() && Next->start <= I->end && Next->valno == ValNo) { 133 I->end = Next->end; 134 ranges.erase(Next); 135 } 136} 137 138 139/// extendIntervalStartTo - This method is used when we want to extend the range 140/// specified by I to start at the specified endpoint. To do this, we should 141/// merge and eliminate all ranges that this will overlap with. 142LiveInterval::Ranges::iterator 143LiveInterval::extendIntervalStartTo(Ranges::iterator I, unsigned NewStart) { 144 assert(I != ranges.end() && "Not a valid interval!"); 145 VNInfo *ValNo = I->valno; 146 147 // Search for the first interval that we can't merge with. 148 Ranges::iterator MergeTo = I; 149 do { 150 if (MergeTo == ranges.begin()) { 151 I->start = NewStart; 152 ranges.erase(MergeTo, I); 153 return I; 154 } 155 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!"); 156 --MergeTo; 157 } while (NewStart <= MergeTo->start); 158 159 // If we start in the middle of another interval, just delete a range and 160 // extend that interval. 161 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) { 162 MergeTo->end = I->end; 163 } else { 164 // Otherwise, extend the interval right after. 165 ++MergeTo; 166 MergeTo->start = NewStart; 167 MergeTo->end = I->end; 168 } 169 170 ranges.erase(next(MergeTo), next(I)); 171 return MergeTo; 172} 173 174LiveInterval::iterator 175LiveInterval::addRangeFrom(LiveRange LR, iterator From) { 176 unsigned Start = LR.start, End = LR.end; 177 iterator it = std::upper_bound(From, ranges.end(), Start); 178 179 // If the inserted interval starts in the middle or right at the end of 180 // another interval, just extend that interval to contain the range of LR. 181 if (it != ranges.begin()) { 182 iterator B = prior(it); 183 if (LR.valno == B->valno) { 184 if (B->start <= Start && B->end >= Start) { 185 extendIntervalEndTo(B, End); 186 return B; 187 } 188 } else { 189 // Check to make sure that we are not overlapping two live ranges with 190 // different valno's. 191 assert(B->end <= Start && 192 "Cannot overlap two LiveRanges with differing ValID's" 193 " (did you def the same reg twice in a MachineInstr?)"); 194 } 195 } 196 197 // Otherwise, if this range ends in the middle of, or right next to, another 198 // interval, merge it into that interval. 199 if (it != ranges.end()) 200 if (LR.valno == it->valno) { 201 if (it->start <= End) { 202 it = extendIntervalStartTo(it, Start); 203 204 // If LR is a complete superset of an interval, we may need to grow its 205 // endpoint as well. 206 if (End > it->end) 207 extendIntervalEndTo(it, End); 208 return it; 209 } 210 } else { 211 // Check to make sure that we are not overlapping two live ranges with 212 // different valno's. 213 assert(it->start >= End && 214 "Cannot overlap two LiveRanges with differing ValID's"); 215 } 216 217 // Otherwise, this is just a new range that doesn't interact with anything. 218 // Insert it. 219 return ranges.insert(it, LR); 220} 221 222 223/// removeRange - Remove the specified range from this interval. Note that 224/// the range must already be in this interval in its entirety. 225void LiveInterval::removeRange(unsigned Start, unsigned End) { 226 // Find the LiveRange containing this span. 227 Ranges::iterator I = std::upper_bound(ranges.begin(), ranges.end(), Start); 228 assert(I != ranges.begin() && "Range is not in interval!"); 229 --I; 230 assert(I->contains(Start) && I->contains(End-1) && 231 "Range is not entirely in interval!"); 232 233 // If the span we are removing is at the start of the LiveRange, adjust it. 234 if (I->start == Start) { 235 if (I->end == End) { 236 removeKills(*I->valno, Start, End); 237 ranges.erase(I); // Removed the whole LiveRange. 238 } else 239 I->start = End; 240 return; 241 } 242 243 // Otherwise if the span we are removing is at the end of the LiveRange, 244 // adjust the other way. 245 if (I->end == End) { 246 removeKills(*I->valno, Start, End); 247 I->end = Start; 248 return; 249 } 250 251 // Otherwise, we are splitting the LiveRange into two pieces. 252 unsigned OldEnd = I->end; 253 I->end = Start; // Trim the old interval. 254 255 // Insert the new one. 256 ranges.insert(next(I), LiveRange(End, OldEnd, I->valno)); 257} 258 259/// getLiveRangeContaining - Return the live range that contains the 260/// specified index, or null if there is none. 261LiveInterval::const_iterator 262LiveInterval::FindLiveRangeContaining(unsigned Idx) const { 263 const_iterator It = std::upper_bound(begin(), end(), Idx); 264 if (It != ranges.begin()) { 265 --It; 266 if (It->contains(Idx)) 267 return It; 268 } 269 270 return end(); 271} 272 273LiveInterval::iterator 274LiveInterval::FindLiveRangeContaining(unsigned Idx) { 275 iterator It = std::upper_bound(begin(), end(), Idx); 276 if (It != begin()) { 277 --It; 278 if (It->contains(Idx)) 279 return It; 280 } 281 282 return end(); 283} 284 285/// join - Join two live intervals (this, and other) together. This applies 286/// mappings to the value numbers in the LHS/RHS intervals as specified. If 287/// the intervals are not joinable, this aborts. 288void LiveInterval::join(LiveInterval &Other, int *LHSValNoAssignments, 289 int *RHSValNoAssignments, 290 SmallVector<VNInfo*, 16> &NewVNInfo) { 291 292 // There might be some dead val#, create VNInfo for them. 293 for (unsigned i = 0, e = NewVNInfo.size(); i != e; ++i) { 294 VNInfo *VNI = NewVNInfo[i]; 295 if (!VNI) { 296 VNI = new VNInfo(this, i, ~1U, 0); 297 NewVNInfo[i] = VNI; 298 } 299 } 300 301 // Determine if any of our live range values are mapped. This is uncommon, so 302 // we want to avoid the interval scan if not. 303 bool MustMapCurValNos = false; 304 for (vni_iterator i = vni_begin(), e = vni_end(); i != e; ++i) { 305 VNInfo *VNI = *i; 306 unsigned VN = VNI->id; 307 if (VNI->def == ~1U) continue; // tombstone value # 308 if (VNI != NewVNInfo[LHSValNoAssignments[VN]]) { 309 MustMapCurValNos = true; 310 break; 311 } 312 } 313 314 // If we have to apply a mapping to our base interval assignment, rewrite it 315 // now. 316 if (MustMapCurValNos) { 317 // Map the first live range. 318 iterator OutIt = begin(); 319 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]]; 320 ++OutIt; 321 for (iterator I = OutIt, E = end(); I != E; ++I) { 322 OutIt->valno = NewVNInfo[LHSValNoAssignments[I->valno->id]]; 323 324 // If this live range has the same value # as its immediate predecessor, 325 // and if they are neighbors, remove one LiveRange. This happens when we 326 // have [0,3:0)[4,7:1) and map 0/1 onto the same value #. 327 if (OutIt->valno == (OutIt-1)->valno && (OutIt-1)->end == OutIt->start) { 328 (OutIt-1)->end = OutIt->end; 329 } else { 330 if (I != OutIt) { 331 OutIt->start = I->start; 332 OutIt->end = I->end; 333 } 334 335 // Didn't merge, on to the next one. 336 ++OutIt; 337 } 338 } 339 340 // If we merge some live ranges, chop off the end. 341 ranges.erase(OutIt, end()); 342 } 343 344 // Remember assignements because val# ids are changing. 345 std::vector<unsigned> OtherAssignments; 346 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I) 347 OtherAssignments.push_back(RHSValNoAssignments[I->valno->id]); 348 349 // Update val# info. Renumber them and make sure they all belong to this 350 // LiveInterval now. 351 valnos.clear(); 352 for (unsigned i = 0, e = NewVNInfo.size(); i != e; ++i) { 353 VNInfo *VNI = NewVNInfo[i]; 354 VNI->parent = this; 355 VNI->id = i; // Renumber val#. 356 valnos.push_back(VNI); 357 } 358 359 // Okay, now insert the RHS live ranges into the LHS. 360 iterator InsertPos = begin(); 361 unsigned RangeNo = 0; 362 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I, ++RangeNo) { 363 // Map the valno in the other live range to the current live range. 364 I->valno = NewVNInfo[OtherAssignments[RangeNo]]; 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/// MergeInClobberRanges - For any live ranges that are not defined in the 391/// current interval, but are defined in the Clobbers interval, mark them 392/// used with an unknown definition value. 393void LiveInterval::MergeInClobberRanges(const LiveInterval &Clobbers) { 394 if (Clobbers.begin() == Clobbers.end()) return; 395 396 // Find a value # to use for the clobber ranges. If there is already a value# 397 // for unknown values, use it. 398 // FIXME: Use a single sentinal number for these! 399 VNInfo *ClobberValNo = getNextValue(~0U, 0); 400 401 iterator IP = begin(); 402 for (const_iterator I = Clobbers.begin(), E = Clobbers.end(); I != E; ++I) { 403 unsigned Start = I->start, End = I->end; 404 IP = std::upper_bound(IP, end(), Start); 405 406 // If the start of this range overlaps with an existing liverange, trim it. 407 if (IP != begin() && IP[-1].end > Start) { 408 Start = IP[-1].end; 409 // Trimmed away the whole range? 410 if (Start >= End) continue; 411 } 412 // If the end of this range overlaps with an existing liverange, trim it. 413 if (IP != end() && End > IP->start) { 414 End = IP->start; 415 // If this trimmed away the whole range, ignore it. 416 if (Start == End) continue; 417 } 418 419 // Insert the clobber interval. 420 IP = addRangeFrom(LiveRange(Start, End, ClobberValNo), IP); 421 } 422} 423 424/// MergeValueNumberInto - This method is called when two value nubmers 425/// are found to be equivalent. This eliminates V1, replacing all 426/// LiveRanges with the V1 value number with the V2 value number. This can 427/// cause merging of V1/V2 values numbers and compaction of the value space. 428void LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) { 429 assert(V1 != V2 && "Identical value#'s are always equivalent!"); 430 431 // This code actually merges the (numerically) larger value number into the 432 // smaller value number, which is likely to allow us to compactify the value 433 // space. The only thing we have to be careful of is to preserve the 434 // instruction that defines the result value. 435 436 // Make sure V2 is smaller than V1. 437 if (V1->id < V2->id) { 438 copyValNumInfo(*V1, *V2); 439 std::swap(V1, V2); 440 } 441 442 // Merge V1 live ranges into V2. 443 for (iterator I = begin(); I != end(); ) { 444 iterator LR = I++; 445 if (LR->valno != V1) continue; // Not a V1 LiveRange. 446 447 // Okay, we found a V1 live range. If it had a previous, touching, V2 live 448 // range, extend it. 449 if (LR != begin()) { 450 iterator Prev = LR-1; 451 if (Prev->valno == V2 && Prev->end == LR->start) { 452 Prev->end = LR->end; 453 454 // Erase this live-range. 455 ranges.erase(LR); 456 I = Prev+1; 457 LR = Prev; 458 } 459 } 460 461 // Okay, now we have a V1 or V2 live range that is maximally merged forward. 462 // Ensure that it is a V2 live-range. 463 LR->valno = V2; 464 465 // If we can merge it into later V2 live ranges, do so now. We ignore any 466 // following V1 live ranges, as they will be merged in subsequent iterations 467 // of the loop. 468 if (I != end()) { 469 if (I->start == LR->end && I->valno == V2) { 470 LR->end = I->end; 471 ranges.erase(I); 472 I = LR+1; 473 } 474 } 475 } 476 477 // Now that V1 is dead, remove it. If it is the largest value number, just 478 // nuke it (and any other deleted values neighboring it), otherwise mark it as 479 // ~1U so it can be nuked later. 480 if (V1->id == getNumValNums()-1) { 481 do { 482 VNInfo *VNI = valnos.back(); 483 valnos.pop_back(); 484 delete VNI; 485 } while (valnos.back()->def == ~1U); 486 } else { 487 V1->def = ~1U; 488 } 489} 490 491unsigned LiveInterval::getSize() const { 492 unsigned Sum = 0; 493 for (const_iterator I = begin(), E = end(); I != E; ++I) 494 Sum += I->end - I->start; 495 return Sum; 496} 497 498std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) { 499 return os << '[' << LR.start << ',' << LR.end << ':' << LR.valno->id << ")"; 500} 501 502void LiveRange::dump() const { 503 cerr << *this << "\n"; 504} 505 506void LiveInterval::print(std::ostream &OS, const MRegisterInfo *MRI) const { 507 if (MRI && MRegisterInfo::isPhysicalRegister(reg)) 508 OS << MRI->getName(reg); 509 else 510 OS << "%reg" << reg; 511 512 OS << ',' << weight; 513 514 if (empty()) 515 OS << "EMPTY"; 516 else { 517 OS << " = "; 518 for (LiveInterval::Ranges::const_iterator I = ranges.begin(), 519 E = ranges.end(); I != E; ++I) 520 OS << *I; 521 } 522 523 // Print value number info. 524 if (getNumValNums()) { 525 OS << " "; 526 unsigned vnum = 0; 527 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e; 528 ++i, ++vnum) { 529 const VNInfo *vni = *i; 530 if (vnum) OS << " "; 531 OS << vnum << "@"; 532 if (vni->def == ~1U) { 533 OS << "x"; 534 } else { 535 if (vni->def == ~0U) 536 OS << "?"; 537 else 538 OS << vni->def; 539 unsigned ee = vni->kills.size(); 540 if (ee) { 541 OS << "-("; 542 for (unsigned j = 0; j != ee; ++j) { 543 OS << vni->kills[j]; 544 if (j != ee-1) 545 OS << " "; 546 } 547 OS << ")"; 548 } 549 } 550 } 551 } 552} 553 554void LiveInterval::dump() const { 555 cerr << *this << "\n"; 556} 557 558 559void LiveRange::print(std::ostream &os) const { 560 os << *this; 561} 562