IfConversion.cpp revision 5412d06e9c352c9795f4a71b91c4f869585866eb
1//===-- IfConversion.cpp - Machine code if conversion pass. ---------------===// 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 machine instruction level if-conversion pass. 11// 12//===----------------------------------------------------------------------===// 13 14#define DEBUG_TYPE "ifcvt" 15#include "llvm/Function.h" 16#include "llvm/CodeGen/Passes.h" 17#include "llvm/CodeGen/MachineModuleInfo.h" 18#include "llvm/CodeGen/MachineFunctionPass.h" 19#include "llvm/Target/TargetInstrInfo.h" 20#include "llvm/Target/TargetLowering.h" 21#include "llvm/Target/TargetMachine.h" 22#include "llvm/Support/CommandLine.h" 23#include "llvm/Support/Debug.h" 24#include "llvm/ADT/DepthFirstIterator.h" 25#include "llvm/ADT/Statistic.h" 26#include "llvm/ADT/STLExtras.h" 27using namespace llvm; 28 29// Hidden options for help debugging. 30static cl::opt<int> IfCvtFnStart("ifcvt-fn-start", cl::init(-1), cl::Hidden); 31static cl::opt<int> IfCvtFnStop("ifcvt-fn-stop", cl::init(-1), cl::Hidden); 32static cl::opt<int> IfCvtLimit("ifcvt-limit", cl::init(-1), cl::Hidden); 33static cl::opt<bool> DisableSimple("disable-ifcvt-simple", 34 cl::init(false), cl::Hidden); 35static cl::opt<bool> DisableSimpleF("disable-ifcvt-simple-false", 36 cl::init(false), cl::Hidden); 37static cl::opt<bool> DisableTriangle("disable-ifcvt-triangle", 38 cl::init(false), cl::Hidden); 39static cl::opt<bool> DisableTriangleR("disable-ifcvt-triangle-rev", 40 cl::init(false), cl::Hidden); 41static cl::opt<bool> DisableTriangleF("disable-ifcvt-triangle-false", 42 cl::init(false), cl::Hidden); 43static cl::opt<bool> DisableTriangleFR("disable-ifcvt-triangle-false-rev", 44 cl::init(false), cl::Hidden); 45static cl::opt<bool> DisableDiamond("disable-ifcvt-diamond", 46 cl::init(false), cl::Hidden); 47 48STATISTIC(NumSimple, "Number of simple if-conversions performed"); 49STATISTIC(NumSimpleFalse, "Number of simple (F) if-conversions performed"); 50STATISTIC(NumTriangle, "Number of triangle if-conversions performed"); 51STATISTIC(NumTriangleRev, "Number of triangle (R) if-conversions performed"); 52STATISTIC(NumTriangleFalse,"Number of triangle (F) if-conversions performed"); 53STATISTIC(NumTriangleFRev, "Number of triangle (F/R) if-conversions performed"); 54STATISTIC(NumDiamonds, "Number of diamond if-conversions performed"); 55STATISTIC(NumIfConvBBs, "Number of if-converted blocks"); 56STATISTIC(NumDupBBs, "Number of duplicated blocks"); 57 58namespace { 59 class VISIBILITY_HIDDEN IfConverter : public MachineFunctionPass { 60 enum IfcvtKind { 61 ICNotClassfied, // BB data valid, but not classified. 62 ICSimpleFalse, // Same as ICSimple, but on the false path. 63 ICSimple, // BB is entry of an one split, no rejoin sub-CFG. 64 ICTriangleFRev, // Same as ICTriangleFalse, but false path rev condition. 65 ICTriangleRev, // Same as ICTriangle, but true path rev condition. 66 ICTriangleFalse, // Same as ICTriangle, but on the false path. 67 ICTriangle, // BB is entry of a triangle sub-CFG. 68 ICDiamond // BB is entry of a diamond sub-CFG. 69 }; 70 71 /// BBInfo - One per MachineBasicBlock, this is used to cache the result 72 /// if-conversion feasibility analysis. This includes results from 73 /// TargetInstrInfo::AnalyzeBranch() (i.e. TBB, FBB, and Cond), and its 74 /// classification, and common tail block of its successors (if it's a 75 /// diamond shape), its size, whether it's predicable, and whether any 76 /// instruction can clobber the 'would-be' predicate. 77 /// 78 /// IsDone - True if BB is not to be considered for ifcvt. 79 /// IsBeingAnalyzed - True if BB is currently being analyzed. 80 /// IsAnalyzed - True if BB has been analyzed (info is still valid). 81 /// IsEnqueued - True if BB has been enqueued to be ifcvt'ed. 82 /// IsBrAnalyzable - True if AnalyzeBranch() returns false. 83 /// HasFallThrough - True if BB may fallthrough to the following BB. 84 /// IsUnpredicable - True if BB is known to be unpredicable. 85 /// ClobbersPred - True if BB could modify predicates (e.g. has 86 /// cmp, call, etc.) 87 /// NonPredSize - Number of non-predicated instructions. 88 /// BB - Corresponding MachineBasicBlock. 89 /// TrueBB / FalseBB- See AnalyzeBranch(). 90 /// BrCond - Conditions for end of block conditional branches. 91 /// Predicate - Predicate used in the BB. 92 struct BBInfo { 93 bool IsDone : 1; 94 bool IsBeingAnalyzed : 1; 95 bool IsAnalyzed : 1; 96 bool IsEnqueued : 1; 97 bool IsBrAnalyzable : 1; 98 bool HasFallThrough : 1; 99 bool IsUnpredicable : 1; 100 bool CannotBeCopied : 1; 101 bool ClobbersPred : 1; 102 unsigned NonPredSize; 103 MachineBasicBlock *BB; 104 MachineBasicBlock *TrueBB; 105 MachineBasicBlock *FalseBB; 106 SmallVector<MachineOperand, 4> BrCond; 107 SmallVector<MachineOperand, 4> Predicate; 108 BBInfo() : IsDone(false), IsBeingAnalyzed(false), 109 IsAnalyzed(false), IsEnqueued(false), IsBrAnalyzable(false), 110 HasFallThrough(false), IsUnpredicable(false), 111 CannotBeCopied(false), ClobbersPred(false), NonPredSize(0), 112 BB(0), TrueBB(0), FalseBB(0) {} 113 }; 114 115 /// IfcvtToken - Record information about pending if-conversions to attemp: 116 /// BBI - Corresponding BBInfo. 117 /// Kind - Type of block. See IfcvtKind. 118 /// NeedSubsumsion - True if the to be predicated BB has already been 119 /// predicated. 120 /// NumDups - Number of instructions that would be duplicated due 121 /// to this if-conversion. (For diamonds, the number of 122 /// identical instructions at the beginnings of both 123 /// paths). 124 /// NumDups2 - For diamonds, the number of identical instructions 125 /// at the ends of both paths. 126 struct IfcvtToken { 127 BBInfo &BBI; 128 IfcvtKind Kind; 129 bool NeedSubsumsion; 130 unsigned NumDups; 131 unsigned NumDups2; 132 IfcvtToken(BBInfo &b, IfcvtKind k, bool s, unsigned d, unsigned d2 = 0) 133 : BBI(b), Kind(k), NeedSubsumsion(s), NumDups(d), NumDups2(d2) {} 134 }; 135 136 /// Roots - Basic blocks that do not have successors. These are the starting 137 /// points of Graph traversal. 138 std::vector<MachineBasicBlock*> Roots; 139 140 /// BBAnalysis - Results of if-conversion feasibility analysis indexed by 141 /// basic block number. 142 std::vector<BBInfo> BBAnalysis; 143 144 const TargetLowering *TLI; 145 const TargetInstrInfo *TII; 146 bool MadeChange; 147 public: 148 static char ID; 149 IfConverter() : MachineFunctionPass(&ID) {} 150 151 virtual bool runOnMachineFunction(MachineFunction &MF); 152 virtual const char *getPassName() const { return "If Converter"; } 153 154 private: 155 bool ReverseBranchCondition(BBInfo &BBI); 156 bool ValidSimple(BBInfo &TrueBBI, unsigned &Dups) const; 157 bool ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI, 158 bool FalseBranch, unsigned &Dups) const; 159 bool ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI, 160 unsigned &Dups1, unsigned &Dups2) const; 161 void ScanInstructions(BBInfo &BBI); 162 BBInfo &AnalyzeBlock(MachineBasicBlock *BB, 163 std::vector<IfcvtToken*> &Tokens); 164 bool FeasibilityAnalysis(BBInfo &BBI, SmallVectorImpl<MachineOperand> &Cond, 165 bool isTriangle = false, bool RevBranch = false); 166 bool AnalyzeBlocks(MachineFunction &MF, 167 std::vector<IfcvtToken*> &Tokens); 168 void InvalidatePreds(MachineBasicBlock *BB); 169 void RemoveExtraEdges(BBInfo &BBI); 170 bool IfConvertSimple(BBInfo &BBI, IfcvtKind Kind); 171 bool IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind); 172 bool IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, 173 unsigned NumDups1, unsigned NumDups2); 174 void PredicateBlock(BBInfo &BBI, 175 MachineBasicBlock::iterator E, 176 SmallVectorImpl<MachineOperand> &Cond); 177 void CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI, 178 SmallVectorImpl<MachineOperand> &Cond, 179 bool IgnoreBr = false); 180 void MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI); 181 182 bool MeetIfcvtSizeLimit(unsigned Size) const { 183 return Size > 0 && Size <= TLI->getIfCvtBlockSizeLimit(); 184 } 185 186 // blockAlwaysFallThrough - Block ends without a terminator. 187 bool blockAlwaysFallThrough(BBInfo &BBI) const { 188 return BBI.IsBrAnalyzable && BBI.TrueBB == NULL; 189 } 190 191 // IfcvtTokenCmp - Used to sort if-conversion candidates. 192 static bool IfcvtTokenCmp(IfcvtToken *C1, IfcvtToken *C2) { 193 int Incr1 = (C1->Kind == ICDiamond) 194 ? -(int)(C1->NumDups + C1->NumDups2) : (int)C1->NumDups; 195 int Incr2 = (C2->Kind == ICDiamond) 196 ? -(int)(C2->NumDups + C2->NumDups2) : (int)C2->NumDups; 197 if (Incr1 > Incr2) 198 return true; 199 else if (Incr1 == Incr2) { 200 // Favors subsumsion. 201 if (C1->NeedSubsumsion == false && C2->NeedSubsumsion == true) 202 return true; 203 else if (C1->NeedSubsumsion == C2->NeedSubsumsion) { 204 // Favors diamond over triangle, etc. 205 if ((unsigned)C1->Kind < (unsigned)C2->Kind) 206 return true; 207 else if (C1->Kind == C2->Kind) 208 return C1->BBI.BB->getNumber() < C2->BBI.BB->getNumber(); 209 } 210 } 211 return false; 212 } 213 }; 214 215 char IfConverter::ID = 0; 216} 217 218static RegisterPass<IfConverter> 219X("if-converter", "If Converter"); 220 221FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); } 222 223bool IfConverter::runOnMachineFunction(MachineFunction &MF) { 224 TLI = MF.getTarget().getTargetLowering(); 225 TII = MF.getTarget().getInstrInfo(); 226 if (!TII) return false; 227 228 static int FnNum = -1; 229 DOUT << "\nIfcvt: function (" << ++FnNum << ") \'" 230 << MF.getFunction()->getName() << "\'"; 231 232 if (FnNum < IfCvtFnStart || (IfCvtFnStop != -1 && FnNum > IfCvtFnStop)) { 233 DOUT << " skipped\n"; 234 return false; 235 } 236 DOUT << "\n"; 237 238 MF.RenumberBlocks(); 239 BBAnalysis.resize(MF.getNumBlockIDs()); 240 241 // Look for root nodes, i.e. blocks without successors. 242 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) 243 if (I->succ_empty()) 244 Roots.push_back(I); 245 246 std::vector<IfcvtToken*> Tokens; 247 MadeChange = false; 248 unsigned NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle + 249 NumTriangleRev + NumTriangleFalse + NumTriangleFRev + NumDiamonds; 250 while (IfCvtLimit == -1 || (int)NumIfCvts < IfCvtLimit) { 251 // Do an intial analysis for each basic block and finding all the potential 252 // candidates to perform if-convesion. 253 bool Change = AnalyzeBlocks(MF, Tokens); 254 while (!Tokens.empty()) { 255 IfcvtToken *Token = Tokens.back(); 256 Tokens.pop_back(); 257 BBInfo &BBI = Token->BBI; 258 IfcvtKind Kind = Token->Kind; 259 unsigned NumDups = Token->NumDups; 260 unsigned NumDups2 = Token->NumDups2; 261 262 delete Token; 263 264 // If the block has been evicted out of the queue or it has already been 265 // marked dead (due to it being predicated), then skip it. 266 if (BBI.IsDone) 267 BBI.IsEnqueued = false; 268 if (!BBI.IsEnqueued) 269 continue; 270 271 BBI.IsEnqueued = false; 272 273 bool RetVal = false; 274 switch (Kind) { 275 default: assert(false && "Unexpected!"); 276 break; 277 case ICSimple: 278 case ICSimpleFalse: { 279 bool isFalse = Kind == ICSimpleFalse; 280 if ((isFalse && DisableSimpleF) || (!isFalse && DisableSimple)) break; 281 DOUT << "Ifcvt (Simple" << (Kind == ICSimpleFalse ? " false" :"") 282 << "): BB#" << BBI.BB->getNumber() << " (" 283 << ((Kind == ICSimpleFalse) 284 ? BBI.FalseBB->getNumber() 285 : BBI.TrueBB->getNumber()) << ") "; 286 RetVal = IfConvertSimple(BBI, Kind); 287 DOUT << (RetVal ? "succeeded!" : "failed!") << "\n"; 288 if (RetVal) { 289 if (isFalse) NumSimpleFalse++; 290 else NumSimple++; 291 } 292 break; 293 } 294 case ICTriangle: 295 case ICTriangleRev: 296 case ICTriangleFalse: 297 case ICTriangleFRev: { 298 bool isFalse = Kind == ICTriangleFalse; 299 bool isRev = (Kind == ICTriangleRev || Kind == ICTriangleFRev); 300 if (DisableTriangle && !isFalse && !isRev) break; 301 if (DisableTriangleR && !isFalse && isRev) break; 302 if (DisableTriangleF && isFalse && !isRev) break; 303 if (DisableTriangleFR && isFalse && isRev) break; 304 DOUT << "Ifcvt (Triangle"; 305 if (isFalse) 306 DOUT << " false"; 307 if (isRev) 308 DOUT << " rev"; 309 DOUT << "): BB#" << BBI.BB->getNumber() << " (T:" 310 << BBI.TrueBB->getNumber() << ",F:" 311 << BBI.FalseBB->getNumber() << ") "; 312 RetVal = IfConvertTriangle(BBI, Kind); 313 DOUT << (RetVal ? "succeeded!" : "failed!") << "\n"; 314 if (RetVal) { 315 if (isFalse) { 316 if (isRev) NumTriangleFRev++; 317 else NumTriangleFalse++; 318 } else { 319 if (isRev) NumTriangleRev++; 320 else NumTriangle++; 321 } 322 } 323 break; 324 } 325 case ICDiamond: { 326 if (DisableDiamond) break; 327 DOUT << "Ifcvt (Diamond): BB#" << BBI.BB->getNumber() << " (T:" 328 << BBI.TrueBB->getNumber() << ",F:" 329 << BBI.FalseBB->getNumber() << ") "; 330 RetVal = IfConvertDiamond(BBI, Kind, NumDups, NumDups2); 331 DOUT << (RetVal ? "succeeded!" : "failed!") << "\n"; 332 if (RetVal) NumDiamonds++; 333 break; 334 } 335 } 336 337 Change |= RetVal; 338 339 NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle + NumTriangleRev + 340 NumTriangleFalse + NumTriangleFRev + NumDiamonds; 341 if (IfCvtLimit != -1 && (int)NumIfCvts >= IfCvtLimit) 342 break; 343 } 344 345 if (!Change) 346 break; 347 MadeChange |= Change; 348 } 349 350 // Delete tokens in case of early exit. 351 while (!Tokens.empty()) { 352 IfcvtToken *Token = Tokens.back(); 353 Tokens.pop_back(); 354 delete Token; 355 } 356 357 Tokens.clear(); 358 Roots.clear(); 359 BBAnalysis.clear(); 360 361 return MadeChange; 362} 363 364/// findFalseBlock - BB has a fallthrough. Find its 'false' successor given 365/// its 'true' successor. 366static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB, 367 MachineBasicBlock *TrueBB) { 368 for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(), 369 E = BB->succ_end(); SI != E; ++SI) { 370 MachineBasicBlock *SuccBB = *SI; 371 if (SuccBB != TrueBB) 372 return SuccBB; 373 } 374 return NULL; 375} 376 377/// ReverseBranchCondition - Reverse the condition of the end of the block 378/// branchs. Swap block's 'true' and 'false' successors. 379bool IfConverter::ReverseBranchCondition(BBInfo &BBI) { 380 if (!TII->ReverseBranchCondition(BBI.BrCond)) { 381 TII->RemoveBranch(*BBI.BB); 382 TII->InsertBranch(*BBI.BB, BBI.FalseBB, BBI.TrueBB, BBI.BrCond); 383 std::swap(BBI.TrueBB, BBI.FalseBB); 384 return true; 385 } 386 return false; 387} 388 389/// getNextBlock - Returns the next block in the function blocks ordering. If 390/// it is the end, returns NULL. 391static inline MachineBasicBlock *getNextBlock(MachineBasicBlock *BB) { 392 MachineFunction::iterator I = BB; 393 MachineFunction::iterator E = BB->getParent()->end(); 394 if (++I == E) 395 return NULL; 396 return I; 397} 398 399/// ValidSimple - Returns true if the 'true' block (along with its 400/// predecessor) forms a valid simple shape for ifcvt. It also returns the 401/// number of instructions that the ifcvt would need to duplicate if performed 402/// in Dups. 403bool IfConverter::ValidSimple(BBInfo &TrueBBI, unsigned &Dups) const { 404 Dups = 0; 405 if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone) 406 return false; 407 408 if (TrueBBI.IsBrAnalyzable) 409 return false; 410 411 if (TrueBBI.BB->pred_size() > 1) { 412 if (TrueBBI.CannotBeCopied || 413 TrueBBI.NonPredSize > TLI->getIfCvtDupBlockSizeLimit()) 414 return false; 415 Dups = TrueBBI.NonPredSize; 416 } 417 418 return true; 419} 420 421/// ValidTriangle - Returns true if the 'true' and 'false' blocks (along 422/// with their common predecessor) forms a valid triangle shape for ifcvt. 423/// If 'FalseBranch' is true, it checks if 'true' block's false branch 424/// branches to the false branch rather than the other way around. It also 425/// returns the number of instructions that the ifcvt would need to duplicate 426/// if performed in 'Dups'. 427bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI, 428 bool FalseBranch, unsigned &Dups) const { 429 Dups = 0; 430 if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone) 431 return false; 432 433 if (TrueBBI.BB->pred_size() > 1) { 434 if (TrueBBI.CannotBeCopied) 435 return false; 436 437 unsigned Size = TrueBBI.NonPredSize; 438 if (TrueBBI.IsBrAnalyzable) { 439 if (TrueBBI.TrueBB && TrueBBI.BrCond.empty()) 440 // End with an unconditional branch. It will be removed. 441 --Size; 442 else { 443 MachineBasicBlock *FExit = FalseBranch 444 ? TrueBBI.TrueBB : TrueBBI.FalseBB; 445 if (FExit) 446 // Require a conditional branch 447 ++Size; 448 } 449 } 450 if (Size > TLI->getIfCvtDupBlockSizeLimit()) 451 return false; 452 Dups = Size; 453 } 454 455 MachineBasicBlock *TExit = FalseBranch ? TrueBBI.FalseBB : TrueBBI.TrueBB; 456 if (!TExit && blockAlwaysFallThrough(TrueBBI)) { 457 MachineFunction::iterator I = TrueBBI.BB; 458 if (++I == TrueBBI.BB->getParent()->end()) 459 return false; 460 TExit = I; 461 } 462 return TExit && TExit == FalseBBI.BB; 463} 464 465static 466MachineBasicBlock::iterator firstNonBranchInst(MachineBasicBlock *BB, 467 const TargetInstrInfo *TII) { 468 MachineBasicBlock::iterator I = BB->end(); 469 while (I != BB->begin()) { 470 --I; 471 if (!I->getDesc().isBranch()) 472 break; 473 } 474 return I; 475} 476 477/// ValidDiamond - Returns true if the 'true' and 'false' blocks (along 478/// with their common predecessor) forms a valid diamond shape for ifcvt. 479bool IfConverter::ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI, 480 unsigned &Dups1, unsigned &Dups2) const { 481 Dups1 = Dups2 = 0; 482 if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone || 483 FalseBBI.IsBeingAnalyzed || FalseBBI.IsDone) 484 return false; 485 486 MachineBasicBlock *TT = TrueBBI.TrueBB; 487 MachineBasicBlock *FT = FalseBBI.TrueBB; 488 489 if (!TT && blockAlwaysFallThrough(TrueBBI)) 490 TT = getNextBlock(TrueBBI.BB); 491 if (!FT && blockAlwaysFallThrough(FalseBBI)) 492 FT = getNextBlock(FalseBBI.BB); 493 if (TT != FT) 494 return false; 495 if (TT == NULL && (TrueBBI.IsBrAnalyzable || FalseBBI.IsBrAnalyzable)) 496 return false; 497 if (TrueBBI.BB->pred_size() > 1 || FalseBBI.BB->pred_size() > 1) 498 return false; 499 500 // FIXME: Allow true block to have an early exit? 501 if (TrueBBI.FalseBB || FalseBBI.FalseBB || 502 (TrueBBI.ClobbersPred && FalseBBI.ClobbersPred)) 503 return false; 504 505 MachineBasicBlock::iterator TI = TrueBBI.BB->begin(); 506 MachineBasicBlock::iterator FI = FalseBBI.BB->begin(); 507 while (TI != TrueBBI.BB->end() && FI != FalseBBI.BB->end()) { 508 if (!TI->isIdenticalTo(FI)) 509 break; 510 ++Dups1; 511 ++TI; 512 ++FI; 513 } 514 515 TI = firstNonBranchInst(TrueBBI.BB, TII); 516 FI = firstNonBranchInst(FalseBBI.BB, TII); 517 while (TI != TrueBBI.BB->begin() && FI != FalseBBI.BB->begin()) { 518 if (!TI->isIdenticalTo(FI)) 519 break; 520 ++Dups2; 521 --TI; 522 --FI; 523 } 524 525 return true; 526} 527 528/// ScanInstructions - Scan all the instructions in the block to determine if 529/// the block is predicable. In most cases, that means all the instructions 530/// in the block are isPredicable(). Also checks if the block contains any 531/// instruction which can clobber a predicate (e.g. condition code register). 532/// If so, the block is not predicable unless it's the last instruction. 533void IfConverter::ScanInstructions(BBInfo &BBI) { 534 if (BBI.IsDone) 535 return; 536 537 bool AlreadyPredicated = BBI.Predicate.size() > 0; 538 // First analyze the end of BB branches. 539 BBI.TrueBB = BBI.FalseBB = NULL; 540 BBI.BrCond.clear(); 541 BBI.IsBrAnalyzable = 542 !TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond); 543 BBI.HasFallThrough = BBI.IsBrAnalyzable && BBI.FalseBB == NULL; 544 545 if (BBI.BrCond.size()) { 546 // No false branch. This BB must end with a conditional branch and a 547 // fallthrough. 548 if (!BBI.FalseBB) 549 BBI.FalseBB = findFalseBlock(BBI.BB, BBI.TrueBB); 550 assert(BBI.FalseBB && "Expected to find the fallthrough block!"); 551 } 552 553 // Then scan all the instructions. 554 BBI.NonPredSize = 0; 555 BBI.ClobbersPred = false; 556 bool SeenCondBr = false; 557 for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end(); 558 I != E; ++I) { 559 const TargetInstrDesc &TID = I->getDesc(); 560 if (TID.isNotDuplicable()) 561 BBI.CannotBeCopied = true; 562 563 bool isPredicated = TII->isPredicated(I); 564 bool isCondBr = BBI.IsBrAnalyzable && TID.isConditionalBranch(); 565 566 if (!isCondBr) { 567 if (!isPredicated) 568 BBI.NonPredSize++; 569 else if (!AlreadyPredicated) { 570 // FIXME: This instruction is already predicated before the 571 // if-conversion pass. It's probably something like a conditional move. 572 // Mark this block unpredicable for now. 573 BBI.IsUnpredicable = true; 574 return; 575 } 576 577 } 578 579 if (BBI.ClobbersPred && !isPredicated) { 580 // Predicate modification instruction should end the block (except for 581 // already predicated instructions and end of block branches). 582 if (isCondBr) { 583 SeenCondBr = true; 584 585 // Conditional branches is not predicable. But it may be eliminated. 586 continue; 587 } 588 589 // Predicate may have been modified, the subsequent (currently) 590 // unpredicated instructions cannot be correctly predicated. 591 BBI.IsUnpredicable = true; 592 return; 593 } 594 595 // FIXME: Make use of PredDefs? e.g. ADDC, SUBC sets predicates but are 596 // still potentially predicable. 597 std::vector<MachineOperand> PredDefs; 598 if (TII->DefinesPredicate(I, PredDefs)) 599 BBI.ClobbersPred = true; 600 601 if (!TID.isPredicable()) { 602 BBI.IsUnpredicable = true; 603 return; 604 } 605 } 606} 607 608/// FeasibilityAnalysis - Determine if the block is a suitable candidate to be 609/// predicated by the specified predicate. 610bool IfConverter::FeasibilityAnalysis(BBInfo &BBI, 611 SmallVectorImpl<MachineOperand> &Pred, 612 bool isTriangle, bool RevBranch) { 613 // If the block is dead or unpredicable, then it cannot be predicated. 614 if (BBI.IsDone || BBI.IsUnpredicable) 615 return false; 616 617 // If it is already predicated, check if its predicate subsumes the new 618 // predicate. 619 if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Pred)) 620 return false; 621 622 if (BBI.BrCond.size()) { 623 if (!isTriangle) 624 return false; 625 626 // Test predicate subsumsion. 627 SmallVector<MachineOperand, 4> RevPred(Pred.begin(), Pred.end()); 628 SmallVector<MachineOperand, 4> Cond(BBI.BrCond.begin(), BBI.BrCond.end()); 629 if (RevBranch) { 630 if (TII->ReverseBranchCondition(Cond)) 631 return false; 632 } 633 if (TII->ReverseBranchCondition(RevPred) || 634 !TII->SubsumesPredicate(Cond, RevPred)) 635 return false; 636 } 637 638 return true; 639} 640 641/// AnalyzeBlock - Analyze the structure of the sub-CFG starting from 642/// the specified block. Record its successors and whether it looks like an 643/// if-conversion candidate. 644IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB, 645 std::vector<IfcvtToken*> &Tokens) { 646 BBInfo &BBI = BBAnalysis[BB->getNumber()]; 647 648 if (BBI.IsAnalyzed || BBI.IsBeingAnalyzed) 649 return BBI; 650 651 BBI.BB = BB; 652 BBI.IsBeingAnalyzed = true; 653 654 ScanInstructions(BBI); 655 656 // Unanalyable or ends with fallthrough or unconditional branch. 657 if (!BBI.IsBrAnalyzable || BBI.BrCond.empty()) { 658 BBI.IsBeingAnalyzed = false; 659 BBI.IsAnalyzed = true; 660 return BBI; 661 } 662 663 // Do not ifcvt if either path is a back edge to the entry block. 664 if (BBI.TrueBB == BB || BBI.FalseBB == BB) { 665 BBI.IsBeingAnalyzed = false; 666 BBI.IsAnalyzed = true; 667 return BBI; 668 } 669 670 BBInfo &TrueBBI = AnalyzeBlock(BBI.TrueBB, Tokens); 671 BBInfo &FalseBBI = AnalyzeBlock(BBI.FalseBB, Tokens); 672 673 if (TrueBBI.IsDone && FalseBBI.IsDone) { 674 BBI.IsBeingAnalyzed = false; 675 BBI.IsAnalyzed = true; 676 return BBI; 677 } 678 679 SmallVector<MachineOperand, 4> RevCond(BBI.BrCond.begin(), BBI.BrCond.end()); 680 bool CanRevCond = !TII->ReverseBranchCondition(RevCond); 681 682 unsigned Dups = 0; 683 unsigned Dups2 = 0; 684 bool TNeedSub = TrueBBI.Predicate.size() > 0; 685 bool FNeedSub = FalseBBI.Predicate.size() > 0; 686 bool Enqueued = false; 687 if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) && 688 MeetIfcvtSizeLimit(TrueBBI.NonPredSize - (Dups + Dups2)) && 689 MeetIfcvtSizeLimit(FalseBBI.NonPredSize - (Dups + Dups2)) && 690 FeasibilityAnalysis(TrueBBI, BBI.BrCond) && 691 FeasibilityAnalysis(FalseBBI, RevCond)) { 692 // Diamond: 693 // EBB 694 // / \_ 695 // | | 696 // TBB FBB 697 // \ / 698 // TailBB 699 // Note TailBB can be empty. 700 Tokens.push_back(new IfcvtToken(BBI, ICDiamond, TNeedSub|FNeedSub, Dups, 701 Dups2)); 702 Enqueued = true; 703 } 704 705 if (ValidTriangle(TrueBBI, FalseBBI, false, Dups) && 706 MeetIfcvtSizeLimit(TrueBBI.NonPredSize) && 707 FeasibilityAnalysis(TrueBBI, BBI.BrCond, true)) { 708 // Triangle: 709 // EBB 710 // | \_ 711 // | | 712 // | TBB 713 // | / 714 // FBB 715 Tokens.push_back(new IfcvtToken(BBI, ICTriangle, TNeedSub, Dups)); 716 Enqueued = true; 717 } 718 719 if (ValidTriangle(TrueBBI, FalseBBI, true, Dups) && 720 MeetIfcvtSizeLimit(TrueBBI.NonPredSize) && 721 FeasibilityAnalysis(TrueBBI, BBI.BrCond, true, true)) { 722 Tokens.push_back(new IfcvtToken(BBI, ICTriangleRev, TNeedSub, Dups)); 723 Enqueued = true; 724 } 725 726 if (ValidSimple(TrueBBI, Dups) && 727 MeetIfcvtSizeLimit(TrueBBI.NonPredSize) && 728 FeasibilityAnalysis(TrueBBI, BBI.BrCond)) { 729 // Simple (split, no rejoin): 730 // EBB 731 // | \_ 732 // | | 733 // | TBB---> exit 734 // | 735 // FBB 736 Tokens.push_back(new IfcvtToken(BBI, ICSimple, TNeedSub, Dups)); 737 Enqueued = true; 738 } 739 740 if (CanRevCond) { 741 // Try the other path... 742 if (ValidTriangle(FalseBBI, TrueBBI, false, Dups) && 743 MeetIfcvtSizeLimit(FalseBBI.NonPredSize) && 744 FeasibilityAnalysis(FalseBBI, RevCond, true)) { 745 Tokens.push_back(new IfcvtToken(BBI, ICTriangleFalse, FNeedSub, Dups)); 746 Enqueued = true; 747 } 748 749 if (ValidTriangle(FalseBBI, TrueBBI, true, Dups) && 750 MeetIfcvtSizeLimit(FalseBBI.NonPredSize) && 751 FeasibilityAnalysis(FalseBBI, RevCond, true, true)) { 752 Tokens.push_back(new IfcvtToken(BBI, ICTriangleFRev, FNeedSub, Dups)); 753 Enqueued = true; 754 } 755 756 if (ValidSimple(FalseBBI, Dups) && 757 MeetIfcvtSizeLimit(FalseBBI.NonPredSize) && 758 FeasibilityAnalysis(FalseBBI, RevCond)) { 759 Tokens.push_back(new IfcvtToken(BBI, ICSimpleFalse, FNeedSub, Dups)); 760 Enqueued = true; 761 } 762 } 763 764 BBI.IsEnqueued = Enqueued; 765 BBI.IsBeingAnalyzed = false; 766 BBI.IsAnalyzed = true; 767 return BBI; 768} 769 770/// AnalyzeBlocks - Analyze all blocks and find entries for all if-conversion 771/// candidates. It returns true if any CFG restructuring is done to expose more 772/// if-conversion opportunities. 773bool IfConverter::AnalyzeBlocks(MachineFunction &MF, 774 std::vector<IfcvtToken*> &Tokens) { 775 bool Change = false; 776 std::set<MachineBasicBlock*> Visited; 777 for (unsigned i = 0, e = Roots.size(); i != e; ++i) { 778 for (idf_ext_iterator<MachineBasicBlock*> I=idf_ext_begin(Roots[i],Visited), 779 E = idf_ext_end(Roots[i], Visited); I != E; ++I) { 780 MachineBasicBlock *BB = *I; 781 AnalyzeBlock(BB, Tokens); 782 } 783 } 784 785 // Sort to favor more complex ifcvt scheme. 786 std::stable_sort(Tokens.begin(), Tokens.end(), IfcvtTokenCmp); 787 788 return Change; 789} 790 791/// canFallThroughTo - Returns true either if ToBB is the next block after BB or 792/// that all the intervening blocks are empty (given BB can fall through to its 793/// next block). 794static bool canFallThroughTo(MachineBasicBlock *BB, MachineBasicBlock *ToBB) { 795 MachineFunction::iterator I = BB; 796 MachineFunction::iterator TI = ToBB; 797 MachineFunction::iterator E = BB->getParent()->end(); 798 while (++I != TI) 799 if (I == E || !I->empty()) 800 return false; 801 return true; 802} 803 804/// InvalidatePreds - Invalidate predecessor BB info so it would be re-analyzed 805/// to determine if it can be if-converted. If predecessor is already enqueued, 806/// dequeue it! 807void IfConverter::InvalidatePreds(MachineBasicBlock *BB) { 808 for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(), 809 E = BB->pred_end(); PI != E; ++PI) { 810 BBInfo &PBBI = BBAnalysis[(*PI)->getNumber()]; 811 if (PBBI.IsDone || PBBI.BB == BB) 812 continue; 813 PBBI.IsAnalyzed = false; 814 PBBI.IsEnqueued = false; 815 } 816} 817 818/// InsertUncondBranch - Inserts an unconditional branch from BB to ToBB. 819/// 820static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB, 821 const TargetInstrInfo *TII) { 822 SmallVector<MachineOperand, 0> NoCond; 823 TII->InsertBranch(*BB, ToBB, NULL, NoCond); 824} 825 826/// RemoveExtraEdges - Remove true / false edges if either / both are no longer 827/// successors. 828void IfConverter::RemoveExtraEdges(BBInfo &BBI) { 829 MachineBasicBlock *TBB = NULL, *FBB = NULL; 830 SmallVector<MachineOperand, 4> Cond; 831 if (!TII->AnalyzeBranch(*BBI.BB, TBB, FBB, Cond)) 832 BBI.BB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty()); 833} 834 835/// IfConvertSimple - If convert a simple (split, no rejoin) sub-CFG. 836/// 837bool IfConverter::IfConvertSimple(BBInfo &BBI, IfcvtKind Kind) { 838 BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; 839 BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; 840 BBInfo *CvtBBI = &TrueBBI; 841 BBInfo *NextBBI = &FalseBBI; 842 843 SmallVector<MachineOperand, 4> Cond(BBI.BrCond.begin(), BBI.BrCond.end()); 844 if (Kind == ICSimpleFalse) 845 std::swap(CvtBBI, NextBBI); 846 847 if (CvtBBI->IsDone || 848 (CvtBBI->CannotBeCopied && CvtBBI->BB->pred_size() > 1)) { 849 // Something has changed. It's no longer safe to predicate this block. 850 BBI.IsAnalyzed = false; 851 CvtBBI->IsAnalyzed = false; 852 return false; 853 } 854 855 if (Kind == ICSimpleFalse) 856 if (TII->ReverseBranchCondition(Cond)) 857 assert(false && "Unable to reverse branch condition!"); 858 859 if (CvtBBI->BB->pred_size() > 1) { 860 BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); 861 // Copy instructions in the true block, predicate them add them to 862 // the entry block. 863 CopyAndPredicateBlock(BBI, *CvtBBI, Cond); 864 } else { 865 PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond); 866 867 // Merge converted block into entry block. 868 BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); 869 MergeBlocks(BBI, *CvtBBI); 870 } 871 872 bool IterIfcvt = true; 873 if (!canFallThroughTo(BBI.BB, NextBBI->BB)) { 874 InsertUncondBranch(BBI.BB, NextBBI->BB, TII); 875 BBI.HasFallThrough = false; 876 // Now ifcvt'd block will look like this: 877 // BB: 878 // ... 879 // t, f = cmp 880 // if t op 881 // b BBf 882 // 883 // We cannot further ifcvt this block because the unconditional branch 884 // will have to be predicated on the new condition, that will not be 885 // available if cmp executes. 886 IterIfcvt = false; 887 } 888 889 RemoveExtraEdges(BBI); 890 891 // Update block info. BB can be iteratively if-converted. 892 if (!IterIfcvt) 893 BBI.IsDone = true; 894 InvalidatePreds(BBI.BB); 895 CvtBBI->IsDone = true; 896 897 // FIXME: Must maintain LiveIns. 898 return true; 899} 900 901/// IfConvertTriangle - If convert a triangle sub-CFG. 902/// 903bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) { 904 BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; 905 BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; 906 BBInfo *CvtBBI = &TrueBBI; 907 BBInfo *NextBBI = &FalseBBI; 908 909 SmallVector<MachineOperand, 4> Cond(BBI.BrCond.begin(), BBI.BrCond.end()); 910 if (Kind == ICTriangleFalse || Kind == ICTriangleFRev) 911 std::swap(CvtBBI, NextBBI); 912 913 if (CvtBBI->IsDone || 914 (CvtBBI->CannotBeCopied && CvtBBI->BB->pred_size() > 1)) { 915 // Something has changed. It's no longer safe to predicate this block. 916 BBI.IsAnalyzed = false; 917 CvtBBI->IsAnalyzed = false; 918 return false; 919 } 920 921 if (Kind == ICTriangleFalse || Kind == ICTriangleFRev) 922 if (TII->ReverseBranchCondition(Cond)) 923 assert(false && "Unable to reverse branch condition!"); 924 925 if (Kind == ICTriangleRev || Kind == ICTriangleFRev) { 926 if (ReverseBranchCondition(*CvtBBI)) { 927 // BB has been changed, modify its predecessors (except for this 928 // one) so they don't get ifcvt'ed based on bad intel. 929 for (MachineBasicBlock::pred_iterator PI = CvtBBI->BB->pred_begin(), 930 E = CvtBBI->BB->pred_end(); PI != E; ++PI) { 931 MachineBasicBlock *PBB = *PI; 932 if (PBB == BBI.BB) 933 continue; 934 BBInfo &PBBI = BBAnalysis[PBB->getNumber()]; 935 if (PBBI.IsEnqueued) { 936 PBBI.IsAnalyzed = false; 937 PBBI.IsEnqueued = false; 938 } 939 } 940 } 941 } 942 943 bool HasEarlyExit = CvtBBI->FalseBB != NULL; 944 bool DupBB = CvtBBI->BB->pred_size() > 1; 945 if (DupBB) { 946 BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); 947 // Copy instructions in the true block, predicate them add them to 948 // the entry block. 949 CopyAndPredicateBlock(BBI, *CvtBBI, Cond, true); 950 } else { 951 // Predicate the 'true' block after removing its branch. 952 CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB); 953 PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond); 954 } 955 956 if (!DupBB) { 957 // Now merge the entry of the triangle with the true block. 958 BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); 959 MergeBlocks(BBI, *CvtBBI); 960 } 961 962 // If 'true' block has a 'false' successor, add an exit branch to it. 963 if (HasEarlyExit) { 964 SmallVector<MachineOperand, 4> RevCond(CvtBBI->BrCond.begin(), 965 CvtBBI->BrCond.end()); 966 if (TII->ReverseBranchCondition(RevCond)) 967 assert(false && "Unable to reverse branch condition!"); 968 TII->InsertBranch(*BBI.BB, CvtBBI->FalseBB, NULL, RevCond); 969 BBI.BB->addSuccessor(CvtBBI->FalseBB); 970 } 971 972 // Merge in the 'false' block if the 'false' block has no other 973 // predecessors. Otherwise, add a unconditional branch from to 'false'. 974 bool FalseBBDead = false; 975 bool IterIfcvt = true; 976 bool isFallThrough = canFallThroughTo(BBI.BB, NextBBI->BB); 977 if (!isFallThrough) { 978 // Only merge them if the true block does not fallthrough to the false 979 // block. By not merging them, we make it possible to iteratively 980 // ifcvt the blocks. 981 if (!HasEarlyExit && 982 NextBBI->BB->pred_size() == 1 && !NextBBI->HasFallThrough) { 983 MergeBlocks(BBI, *NextBBI); 984 FalseBBDead = true; 985 } else { 986 InsertUncondBranch(BBI.BB, NextBBI->BB, TII); 987 BBI.HasFallThrough = false; 988 } 989 // Mixed predicated and unpredicated code. This cannot be iteratively 990 // predicated. 991 IterIfcvt = false; 992 } 993 994 RemoveExtraEdges(BBI); 995 996 // Update block info. BB can be iteratively if-converted. 997 if (!IterIfcvt) 998 BBI.IsDone = true; 999 InvalidatePreds(BBI.BB); 1000 CvtBBI->IsDone = true; 1001 if (FalseBBDead) 1002 NextBBI->IsDone = true; 1003 1004 // FIXME: Must maintain LiveIns. 1005 return true; 1006} 1007 1008/// IfConvertDiamond - If convert a diamond sub-CFG. 1009/// 1010bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind, 1011 unsigned NumDups1, unsigned NumDups2) { 1012 BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; 1013 BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; 1014 MachineBasicBlock *TailBB = TrueBBI.TrueBB; 1015 // True block must fall through or ended with unanalyzable terminator. 1016 if (!TailBB) { 1017 if (blockAlwaysFallThrough(TrueBBI)) 1018 TailBB = FalseBBI.TrueBB; 1019 assert((TailBB || !TrueBBI.IsBrAnalyzable) && "Unexpected!"); 1020 } 1021 1022 if (TrueBBI.IsDone || FalseBBI.IsDone || 1023 TrueBBI.BB->pred_size() > 1 || 1024 FalseBBI.BB->pred_size() > 1) { 1025 // Something has changed. It's no longer safe to predicate these blocks. 1026 BBI.IsAnalyzed = false; 1027 TrueBBI.IsAnalyzed = false; 1028 FalseBBI.IsAnalyzed = false; 1029 return false; 1030 } 1031 1032 // Merge the 'true' and 'false' blocks by copying the instructions 1033 // from the 'false' block to the 'true' block. That is, unless the true 1034 // block would clobber the predicate, in that case, do the opposite. 1035 BBInfo *BBI1 = &TrueBBI; 1036 BBInfo *BBI2 = &FalseBBI; 1037 SmallVector<MachineOperand, 4> RevCond(BBI.BrCond.begin(), BBI.BrCond.end()); 1038 if (TII->ReverseBranchCondition(RevCond)) 1039 assert(false && "Unable to reverse branch condition!"); 1040 SmallVector<MachineOperand, 4> *Cond1 = &BBI.BrCond; 1041 SmallVector<MachineOperand, 4> *Cond2 = &RevCond; 1042 1043 // Figure out the more profitable ordering. 1044 bool DoSwap = false; 1045 if (TrueBBI.ClobbersPred && !FalseBBI.ClobbersPred) 1046 DoSwap = true; 1047 else if (TrueBBI.ClobbersPred == FalseBBI.ClobbersPred) { 1048 if (TrueBBI.NonPredSize > FalseBBI.NonPredSize) 1049 DoSwap = true; 1050 } 1051 if (DoSwap) { 1052 std::swap(BBI1, BBI2); 1053 std::swap(Cond1, Cond2); 1054 } 1055 1056 // Remove the conditional branch from entry to the blocks. 1057 BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); 1058 1059 // Remove the duplicated instructions at the beginnings of both paths. 1060 MachineBasicBlock::iterator DI1 = BBI1->BB->begin(); 1061 MachineBasicBlock::iterator DI2 = BBI2->BB->begin(); 1062 BBI1->NonPredSize -= NumDups1; 1063 BBI2->NonPredSize -= NumDups1; 1064 while (NumDups1 != 0) { 1065 ++DI1; 1066 ++DI2; 1067 --NumDups1; 1068 } 1069 BBI.BB->splice(BBI.BB->end(), BBI1->BB, BBI1->BB->begin(), DI1); 1070 BBI2->BB->erase(BBI2->BB->begin(), DI2); 1071 1072 // Predicate the 'true' block after removing its branch. 1073 BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB); 1074 DI1 = BBI1->BB->end(); 1075 for (unsigned i = 0; i != NumDups2; ++i) 1076 --DI1; 1077 BBI1->BB->erase(DI1, BBI1->BB->end()); 1078 PredicateBlock(*BBI1, BBI1->BB->end(), *Cond1); 1079 1080 // Predicate the 'false' block. 1081 BBI2->NonPredSize -= TII->RemoveBranch(*BBI2->BB); 1082 DI2 = BBI2->BB->end(); 1083 while (NumDups2 != 0) { 1084 --DI2; 1085 --NumDups2; 1086 } 1087 PredicateBlock(*BBI2, DI2, *Cond2); 1088 1089 // Merge the true block into the entry of the diamond. 1090 MergeBlocks(BBI, *BBI1); 1091 MergeBlocks(BBI, *BBI2); 1092 1093 // If the if-converted block fallthrough or unconditionally branch into the 1094 // tail block, and the tail block does not have other predecessors, then 1095 // fold the tail block in as well. Otherwise, unless it falls through to the 1096 // tail, add a unconditional branch to it. 1097 if (TailBB) { 1098 BBInfo TailBBI = BBAnalysis[TailBB->getNumber()]; 1099 if (TailBB->pred_size() == 1 && !TailBBI.HasFallThrough) { 1100 BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); 1101 MergeBlocks(BBI, TailBBI); 1102 TailBBI.IsDone = true; 1103 } else { 1104 InsertUncondBranch(BBI.BB, TailBB, TII); 1105 BBI.HasFallThrough = false; 1106 } 1107 } 1108 1109 RemoveExtraEdges(BBI); 1110 1111 // Update block info. 1112 BBI.IsDone = TrueBBI.IsDone = FalseBBI.IsDone = true; 1113 InvalidatePreds(BBI.BB); 1114 1115 // FIXME: Must maintain LiveIns. 1116 return true; 1117} 1118 1119/// PredicateBlock - Predicate instructions from the start of the block to the 1120/// specified end with the specified condition. 1121void IfConverter::PredicateBlock(BBInfo &BBI, 1122 MachineBasicBlock::iterator E, 1123 SmallVectorImpl<MachineOperand> &Cond) { 1124 for (MachineBasicBlock::iterator I = BBI.BB->begin(); I != E; ++I) { 1125 if (TII->isPredicated(I)) 1126 continue; 1127 if (!TII->PredicateInstruction(I, Cond)) { 1128 cerr << "Unable to predicate " << *I << "!\n"; 1129 abort(); 1130 } 1131 } 1132 1133 std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate)); 1134 1135 BBI.IsAnalyzed = false; 1136 BBI.NonPredSize = 0; 1137 1138 NumIfConvBBs++; 1139} 1140 1141/// CopyAndPredicateBlock - Copy and predicate instructions from source BB to 1142/// the destination block. Skip end of block branches if IgnoreBr is true. 1143void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI, 1144 SmallVectorImpl<MachineOperand> &Cond, 1145 bool IgnoreBr) { 1146 MachineFunction &MF = *ToBBI.BB->getParent(); 1147 1148 for (MachineBasicBlock::iterator I = FromBBI.BB->begin(), 1149 E = FromBBI.BB->end(); I != E; ++I) { 1150 const TargetInstrDesc &TID = I->getDesc(); 1151 bool isPredicated = TII->isPredicated(I); 1152 // Do not copy the end of the block branches. 1153 if (IgnoreBr && !isPredicated && TID.isBranch()) 1154 break; 1155 1156 MachineInstr *MI = MF.CloneMachineInstr(I); 1157 ToBBI.BB->insert(ToBBI.BB->end(), MI); 1158 ToBBI.NonPredSize++; 1159 1160 if (!isPredicated) 1161 if (!TII->PredicateInstruction(MI, Cond)) { 1162 cerr << "Unable to predicate " << *MI << "!\n"; 1163 abort(); 1164 } 1165 } 1166 1167 std::vector<MachineBasicBlock *> Succs(FromBBI.BB->succ_begin(), 1168 FromBBI.BB->succ_end()); 1169 MachineBasicBlock *NBB = getNextBlock(FromBBI.BB); 1170 MachineBasicBlock *FallThrough = FromBBI.HasFallThrough ? NBB : NULL; 1171 1172 for (unsigned i = 0, e = Succs.size(); i != e; ++i) { 1173 MachineBasicBlock *Succ = Succs[i]; 1174 // Fallthrough edge can't be transferred. 1175 if (Succ == FallThrough) 1176 continue; 1177 ToBBI.BB->addSuccessor(Succ); 1178 } 1179 1180 std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(), 1181 std::back_inserter(ToBBI.Predicate)); 1182 std::copy(Cond.begin(), Cond.end(), std::back_inserter(ToBBI.Predicate)); 1183 1184 ToBBI.ClobbersPred |= FromBBI.ClobbersPred; 1185 ToBBI.IsAnalyzed = false; 1186 1187 NumDupBBs++; 1188} 1189 1190/// MergeBlocks - Move all instructions from FromBB to the end of ToBB. 1191/// 1192void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) { 1193 ToBBI.BB->splice(ToBBI.BB->end(), 1194 FromBBI.BB, FromBBI.BB->begin(), FromBBI.BB->end()); 1195 1196 // Redirect all branches to FromBB to ToBB. 1197 std::vector<MachineBasicBlock *> Preds(FromBBI.BB->pred_begin(), 1198 FromBBI.BB->pred_end()); 1199 for (unsigned i = 0, e = Preds.size(); i != e; ++i) { 1200 MachineBasicBlock *Pred = Preds[i]; 1201 if (Pred == ToBBI.BB) 1202 continue; 1203 Pred->ReplaceUsesOfBlockWith(FromBBI.BB, ToBBI.BB); 1204 } 1205 1206 std::vector<MachineBasicBlock *> Succs(FromBBI.BB->succ_begin(), 1207 FromBBI.BB->succ_end()); 1208 MachineBasicBlock *NBB = getNextBlock(FromBBI.BB); 1209 MachineBasicBlock *FallThrough = FromBBI.HasFallThrough ? NBB : NULL; 1210 1211 for (unsigned i = 0, e = Succs.size(); i != e; ++i) { 1212 MachineBasicBlock *Succ = Succs[i]; 1213 // Fallthrough edge can't be transferred. 1214 if (Succ == FallThrough) 1215 continue; 1216 FromBBI.BB->removeSuccessor(Succ); 1217 ToBBI.BB->addSuccessor(Succ); 1218 } 1219 1220 // Now FromBBI always fall through to the next block! 1221 if (NBB) 1222 FromBBI.BB->addSuccessor(NBB); 1223 1224 std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(), 1225 std::back_inserter(ToBBI.Predicate)); 1226 FromBBI.Predicate.clear(); 1227 1228 ToBBI.NonPredSize += FromBBI.NonPredSize; 1229 FromBBI.NonPredSize = 0; 1230 1231 ToBBI.ClobbersPred |= FromBBI.ClobbersPred; 1232 ToBBI.HasFallThrough = FromBBI.HasFallThrough; 1233 ToBBI.IsAnalyzed = false; 1234 FromBBI.IsAnalyzed = false; 1235} 1236