1 //===-- PPCCTRLoops.cpp - Identify and generate CTR loops -----------------===// 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 pass identifies loops where we can generate the PPC branch instructions 11 // that decrement and test the count register (CTR) (bdnz and friends). 12 // 13 // The pattern that defines the induction variable can changed depending on 14 // prior optimizations. For example, the IndVarSimplify phase run by 'opt' 15 // normalizes induction variables, and the Loop Strength Reduction pass 16 // run by 'llc' may also make changes to the induction variable. 17 // 18 // Criteria for CTR loops: 19 // - Countable loops (w/ ind. var for a trip count) 20 // - Try inner-most loops first 21 // - No nested CTR loops. 22 // - No function calls in loops. 23 // 24 //===----------------------------------------------------------------------===// 25 26 #include "llvm/Transforms/Scalar.h" 27 #include "PPC.h" 28 #include "PPCTargetMachine.h" 29 #include "llvm/ADT/STLExtras.h" 30 #include "llvm/ADT/Statistic.h" 31 #include "llvm/Analysis/LoopInfo.h" 32 #include "llvm/Analysis/ScalarEvolutionExpander.h" 33 #include "llvm/Analysis/TargetLibraryInfo.h" 34 #include "llvm/IR/Constants.h" 35 #include "llvm/IR/DerivedTypes.h" 36 #include "llvm/IR/Dominators.h" 37 #include "llvm/IR/InlineAsm.h" 38 #include "llvm/IR/Instructions.h" 39 #include "llvm/IR/IntrinsicInst.h" 40 #include "llvm/IR/Module.h" 41 #include "llvm/IR/ValueHandle.h" 42 #include "llvm/PassSupport.h" 43 #include "llvm/Support/CommandLine.h" 44 #include "llvm/Support/Debug.h" 45 #include "llvm/Support/raw_ostream.h" 46 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 47 #include "llvm/Transforms/Utils/Local.h" 48 #include "llvm/Transforms/Utils/LoopUtils.h" 49 50 #ifndef NDEBUG 51 #include "llvm/CodeGen/MachineDominators.h" 52 #include "llvm/CodeGen/MachineFunction.h" 53 #include "llvm/CodeGen/MachineFunctionPass.h" 54 #include "llvm/CodeGen/MachineRegisterInfo.h" 55 #endif 56 57 #include <algorithm> 58 #include <vector> 59 60 using namespace llvm; 61 62 #define DEBUG_TYPE "ctrloops" 63 64 #ifndef NDEBUG 65 static cl::opt<int> CTRLoopLimit("ppc-max-ctrloop", cl::Hidden, cl::init(-1)); 66 #endif 67 68 STATISTIC(NumCTRLoops, "Number of loops converted to CTR loops"); 69 70 namespace llvm { 71 void initializePPCCTRLoopsPass(PassRegistry&); 72 #ifndef NDEBUG 73 void initializePPCCTRLoopsVerifyPass(PassRegistry&); 74 #endif 75 } 76 77 namespace { 78 struct PPCCTRLoops : public FunctionPass { 79 80 #ifndef NDEBUG 81 static int Counter; 82 #endif 83 84 public: 85 static char ID; 86 87 PPCCTRLoops() : FunctionPass(ID), TM(nullptr) { 88 initializePPCCTRLoopsPass(*PassRegistry::getPassRegistry()); 89 } 90 PPCCTRLoops(PPCTargetMachine &TM) : FunctionPass(ID), TM(&TM) { 91 initializePPCCTRLoopsPass(*PassRegistry::getPassRegistry()); 92 } 93 94 bool runOnFunction(Function &F) override; 95 96 void getAnalysisUsage(AnalysisUsage &AU) const override { 97 AU.addRequired<LoopInfoWrapperPass>(); 98 AU.addPreserved<LoopInfoWrapperPass>(); 99 AU.addRequired<DominatorTreeWrapperPass>(); 100 AU.addPreserved<DominatorTreeWrapperPass>(); 101 AU.addRequired<ScalarEvolution>(); 102 } 103 104 private: 105 bool mightUseCTR(const Triple &TT, BasicBlock *BB); 106 bool convertToCTRLoop(Loop *L); 107 108 private: 109 PPCTargetMachine *TM; 110 LoopInfo *LI; 111 ScalarEvolution *SE; 112 const DataLayout *DL; 113 DominatorTree *DT; 114 const TargetLibraryInfo *LibInfo; 115 }; 116 117 char PPCCTRLoops::ID = 0; 118 #ifndef NDEBUG 119 int PPCCTRLoops::Counter = 0; 120 #endif 121 122 #ifndef NDEBUG 123 struct PPCCTRLoopsVerify : public MachineFunctionPass { 124 public: 125 static char ID; 126 127 PPCCTRLoopsVerify() : MachineFunctionPass(ID) { 128 initializePPCCTRLoopsVerifyPass(*PassRegistry::getPassRegistry()); 129 } 130 131 void getAnalysisUsage(AnalysisUsage &AU) const override { 132 AU.addRequired<MachineDominatorTree>(); 133 MachineFunctionPass::getAnalysisUsage(AU); 134 } 135 136 bool runOnMachineFunction(MachineFunction &MF) override; 137 138 private: 139 MachineDominatorTree *MDT; 140 }; 141 142 char PPCCTRLoopsVerify::ID = 0; 143 #endif // NDEBUG 144 } // end anonymous namespace 145 146 INITIALIZE_PASS_BEGIN(PPCCTRLoops, "ppc-ctr-loops", "PowerPC CTR Loops", 147 false, false) 148 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 149 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) 150 INITIALIZE_PASS_DEPENDENCY(ScalarEvolution) 151 INITIALIZE_PASS_END(PPCCTRLoops, "ppc-ctr-loops", "PowerPC CTR Loops", 152 false, false) 153 154 FunctionPass *llvm::createPPCCTRLoops(PPCTargetMachine &TM) { 155 return new PPCCTRLoops(TM); 156 } 157 158 #ifndef NDEBUG 159 INITIALIZE_PASS_BEGIN(PPCCTRLoopsVerify, "ppc-ctr-loops-verify", 160 "PowerPC CTR Loops Verify", false, false) 161 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree) 162 INITIALIZE_PASS_END(PPCCTRLoopsVerify, "ppc-ctr-loops-verify", 163 "PowerPC CTR Loops Verify", false, false) 164 165 FunctionPass *llvm::createPPCCTRLoopsVerify() { 166 return new PPCCTRLoopsVerify(); 167 } 168 #endif // NDEBUG 169 170 bool PPCCTRLoops::runOnFunction(Function &F) { 171 LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); 172 SE = &getAnalysis<ScalarEvolution>(); 173 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 174 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>(); 175 DL = DLP ? &DLP->getDataLayout() : nullptr; 176 auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>(); 177 LibInfo = TLIP ? &TLIP->getTLI() : nullptr; 178 179 bool MadeChange = false; 180 181 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); 182 I != E; ++I) { 183 Loop *L = *I; 184 if (!L->getParentLoop()) 185 MadeChange |= convertToCTRLoop(L); 186 } 187 188 return MadeChange; 189 } 190 191 static bool isLargeIntegerTy(bool Is32Bit, Type *Ty) { 192 if (IntegerType *ITy = dyn_cast<IntegerType>(Ty)) 193 return ITy->getBitWidth() > (Is32Bit ? 32U : 64U); 194 195 return false; 196 } 197 198 // Determining the address of a TLS variable results in a function call in 199 // certain TLS models. 200 static bool memAddrUsesCTR(const PPCTargetMachine *TM, 201 const llvm::Value *MemAddr) { 202 const auto *GV = dyn_cast<GlobalValue>(MemAddr); 203 if (!GV) 204 return false; 205 if (!GV->isThreadLocal()) 206 return false; 207 if (!TM) 208 return true; 209 TLSModel::Model Model = TM->getTLSModel(GV); 210 return Model == TLSModel::GeneralDynamic || Model == TLSModel::LocalDynamic; 211 } 212 213 bool PPCCTRLoops::mightUseCTR(const Triple &TT, BasicBlock *BB) { 214 for (BasicBlock::iterator J = BB->begin(), JE = BB->end(); 215 J != JE; ++J) { 216 if (CallInst *CI = dyn_cast<CallInst>(J)) { 217 if (InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue())) { 218 // Inline ASM is okay, unless it clobbers the ctr register. 219 InlineAsm::ConstraintInfoVector CIV = IA->ParseConstraints(); 220 for (unsigned i = 0, ie = CIV.size(); i < ie; ++i) { 221 InlineAsm::ConstraintInfo &C = CIV[i]; 222 if (C.Type != InlineAsm::isInput) 223 for (unsigned j = 0, je = C.Codes.size(); j < je; ++j) 224 if (StringRef(C.Codes[j]).equals_lower("{ctr}")) 225 return true; 226 } 227 228 continue; 229 } 230 231 if (!TM) 232 return true; 233 const TargetLowering *TLI = 234 TM->getSubtargetImpl(*BB->getParent())->getTargetLowering(); 235 236 if (Function *F = CI->getCalledFunction()) { 237 // Most intrinsics don't become function calls, but some might. 238 // sin, cos, exp and log are always calls. 239 unsigned Opcode; 240 if (F->getIntrinsicID() != Intrinsic::not_intrinsic) { 241 switch (F->getIntrinsicID()) { 242 default: continue; 243 244 // VisualStudio defines setjmp as _setjmp 245 #if defined(_MSC_VER) && defined(setjmp) && \ 246 !defined(setjmp_undefined_for_msvc) 247 # pragma push_macro("setjmp") 248 # undef setjmp 249 # define setjmp_undefined_for_msvc 250 #endif 251 252 case Intrinsic::setjmp: 253 254 #if defined(_MSC_VER) && defined(setjmp_undefined_for_msvc) 255 // let's return it to _setjmp state 256 # pragma pop_macro("setjmp") 257 # undef setjmp_undefined_for_msvc 258 #endif 259 260 case Intrinsic::longjmp: 261 262 // Exclude eh_sjlj_setjmp; we don't need to exclude eh_sjlj_longjmp 263 // because, although it does clobber the counter register, the 264 // control can't then return to inside the loop unless there is also 265 // an eh_sjlj_setjmp. 266 case Intrinsic::eh_sjlj_setjmp: 267 268 case Intrinsic::memcpy: 269 case Intrinsic::memmove: 270 case Intrinsic::memset: 271 case Intrinsic::powi: 272 case Intrinsic::log: 273 case Intrinsic::log2: 274 case Intrinsic::log10: 275 case Intrinsic::exp: 276 case Intrinsic::exp2: 277 case Intrinsic::pow: 278 case Intrinsic::sin: 279 case Intrinsic::cos: 280 return true; 281 case Intrinsic::copysign: 282 if (CI->getArgOperand(0)->getType()->getScalarType()-> 283 isPPC_FP128Ty()) 284 return true; 285 else 286 continue; // ISD::FCOPYSIGN is never a library call. 287 case Intrinsic::sqrt: Opcode = ISD::FSQRT; break; 288 case Intrinsic::floor: Opcode = ISD::FFLOOR; break; 289 case Intrinsic::ceil: Opcode = ISD::FCEIL; break; 290 case Intrinsic::trunc: Opcode = ISD::FTRUNC; break; 291 case Intrinsic::rint: Opcode = ISD::FRINT; break; 292 case Intrinsic::nearbyint: Opcode = ISD::FNEARBYINT; break; 293 case Intrinsic::round: Opcode = ISD::FROUND; break; 294 } 295 } 296 297 // PowerPC does not use [US]DIVREM or other library calls for 298 // operations on regular types which are not otherwise library calls 299 // (i.e. soft float or atomics). If adapting for targets that do, 300 // additional care is required here. 301 302 LibFunc::Func Func; 303 if (!F->hasLocalLinkage() && F->hasName() && LibInfo && 304 LibInfo->getLibFunc(F->getName(), Func) && 305 LibInfo->hasOptimizedCodeGen(Func)) { 306 // Non-read-only functions are never treated as intrinsics. 307 if (!CI->onlyReadsMemory()) 308 return true; 309 310 // Conversion happens only for FP calls. 311 if (!CI->getArgOperand(0)->getType()->isFloatingPointTy()) 312 return true; 313 314 switch (Func) { 315 default: return true; 316 case LibFunc::copysign: 317 case LibFunc::copysignf: 318 continue; // ISD::FCOPYSIGN is never a library call. 319 case LibFunc::copysignl: 320 return true; 321 case LibFunc::fabs: 322 case LibFunc::fabsf: 323 case LibFunc::fabsl: 324 continue; // ISD::FABS is never a library call. 325 case LibFunc::sqrt: 326 case LibFunc::sqrtf: 327 case LibFunc::sqrtl: 328 Opcode = ISD::FSQRT; break; 329 case LibFunc::floor: 330 case LibFunc::floorf: 331 case LibFunc::floorl: 332 Opcode = ISD::FFLOOR; break; 333 case LibFunc::nearbyint: 334 case LibFunc::nearbyintf: 335 case LibFunc::nearbyintl: 336 Opcode = ISD::FNEARBYINT; break; 337 case LibFunc::ceil: 338 case LibFunc::ceilf: 339 case LibFunc::ceill: 340 Opcode = ISD::FCEIL; break; 341 case LibFunc::rint: 342 case LibFunc::rintf: 343 case LibFunc::rintl: 344 Opcode = ISD::FRINT; break; 345 case LibFunc::round: 346 case LibFunc::roundf: 347 case LibFunc::roundl: 348 Opcode = ISD::FROUND; break; 349 case LibFunc::trunc: 350 case LibFunc::truncf: 351 case LibFunc::truncl: 352 Opcode = ISD::FTRUNC; break; 353 } 354 355 MVT VTy = 356 TLI->getSimpleValueType(CI->getArgOperand(0)->getType(), true); 357 if (VTy == MVT::Other) 358 return true; 359 360 if (TLI->isOperationLegalOrCustom(Opcode, VTy)) 361 continue; 362 else if (VTy.isVector() && 363 TLI->isOperationLegalOrCustom(Opcode, VTy.getScalarType())) 364 continue; 365 366 return true; 367 } 368 } 369 370 return true; 371 } else if (isa<BinaryOperator>(J) && 372 J->getType()->getScalarType()->isPPC_FP128Ty()) { 373 // Most operations on ppc_f128 values become calls. 374 return true; 375 } else if (isa<UIToFPInst>(J) || isa<SIToFPInst>(J) || 376 isa<FPToUIInst>(J) || isa<FPToSIInst>(J)) { 377 CastInst *CI = cast<CastInst>(J); 378 if (CI->getSrcTy()->getScalarType()->isPPC_FP128Ty() || 379 CI->getDestTy()->getScalarType()->isPPC_FP128Ty() || 380 isLargeIntegerTy(TT.isArch32Bit(), CI->getSrcTy()->getScalarType()) || 381 isLargeIntegerTy(TT.isArch32Bit(), CI->getDestTy()->getScalarType())) 382 return true; 383 } else if (isLargeIntegerTy(TT.isArch32Bit(), 384 J->getType()->getScalarType()) && 385 (J->getOpcode() == Instruction::UDiv || 386 J->getOpcode() == Instruction::SDiv || 387 J->getOpcode() == Instruction::URem || 388 J->getOpcode() == Instruction::SRem)) { 389 return true; 390 } else if (TT.isArch32Bit() && 391 isLargeIntegerTy(false, J->getType()->getScalarType()) && 392 (J->getOpcode() == Instruction::Shl || 393 J->getOpcode() == Instruction::AShr || 394 J->getOpcode() == Instruction::LShr)) { 395 // Only on PPC32, for 128-bit integers (specifically not 64-bit 396 // integers), these might be runtime calls. 397 return true; 398 } else if (isa<IndirectBrInst>(J) || isa<InvokeInst>(J)) { 399 // On PowerPC, indirect jumps use the counter register. 400 return true; 401 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(J)) { 402 if (!TM) 403 return true; 404 const TargetLowering *TLI = TM->getSubtargetImpl()->getTargetLowering(); 405 406 if (SI->getNumCases() + 1 >= (unsigned)TLI->getMinimumJumpTableEntries()) 407 return true; 408 } 409 for (Value *Operand : J->operands()) 410 if (memAddrUsesCTR(TM, Operand)) 411 return true; 412 } 413 414 return false; 415 } 416 417 bool PPCCTRLoops::convertToCTRLoop(Loop *L) { 418 bool MadeChange = false; 419 420 Triple TT = Triple(L->getHeader()->getParent()->getParent()-> 421 getTargetTriple()); 422 if (!TT.isArch32Bit() && !TT.isArch64Bit()) 423 return MadeChange; // Unknown arch. type. 424 425 // Process nested loops first. 426 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) { 427 MadeChange |= convertToCTRLoop(*I); 428 } 429 430 // If a nested loop has been converted, then we can't convert this loop. 431 if (MadeChange) 432 return MadeChange; 433 434 #ifndef NDEBUG 435 // Stop trying after reaching the limit (if any). 436 int Limit = CTRLoopLimit; 437 if (Limit >= 0) { 438 if (Counter >= CTRLoopLimit) 439 return false; 440 Counter++; 441 } 442 #endif 443 444 // We don't want to spill/restore the counter register, and so we don't 445 // want to use the counter register if the loop contains calls. 446 for (Loop::block_iterator I = L->block_begin(), IE = L->block_end(); 447 I != IE; ++I) 448 if (mightUseCTR(TT, *I)) 449 return MadeChange; 450 451 SmallVector<BasicBlock*, 4> ExitingBlocks; 452 L->getExitingBlocks(ExitingBlocks); 453 454 BasicBlock *CountedExitBlock = nullptr; 455 const SCEV *ExitCount = nullptr; 456 BranchInst *CountedExitBranch = nullptr; 457 for (SmallVectorImpl<BasicBlock *>::iterator I = ExitingBlocks.begin(), 458 IE = ExitingBlocks.end(); I != IE; ++I) { 459 const SCEV *EC = SE->getExitCount(L, *I); 460 DEBUG(dbgs() << "Exit Count for " << *L << " from block " << 461 (*I)->getName() << ": " << *EC << "\n"); 462 if (isa<SCEVCouldNotCompute>(EC)) 463 continue; 464 if (const SCEVConstant *ConstEC = dyn_cast<SCEVConstant>(EC)) { 465 if (ConstEC->getValue()->isZero()) 466 continue; 467 } else if (!SE->isLoopInvariant(EC, L)) 468 continue; 469 470 if (SE->getTypeSizeInBits(EC->getType()) > (TT.isArch64Bit() ? 64 : 32)) 471 continue; 472 473 // We now have a loop-invariant count of loop iterations (which is not the 474 // constant zero) for which we know that this loop will not exit via this 475 // exisiting block. 476 477 // We need to make sure that this block will run on every loop iteration. 478 // For this to be true, we must dominate all blocks with backedges. Such 479 // blocks are in-loop predecessors to the header block. 480 bool NotAlways = false; 481 for (pred_iterator PI = pred_begin(L->getHeader()), 482 PIE = pred_end(L->getHeader()); PI != PIE; ++PI) { 483 if (!L->contains(*PI)) 484 continue; 485 486 if (!DT->dominates(*I, *PI)) { 487 NotAlways = true; 488 break; 489 } 490 } 491 492 if (NotAlways) 493 continue; 494 495 // Make sure this blocks ends with a conditional branch. 496 Instruction *TI = (*I)->getTerminator(); 497 if (!TI) 498 continue; 499 500 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { 501 if (!BI->isConditional()) 502 continue; 503 504 CountedExitBranch = BI; 505 } else 506 continue; 507 508 // Note that this block may not be the loop latch block, even if the loop 509 // has a latch block. 510 CountedExitBlock = *I; 511 ExitCount = EC; 512 break; 513 } 514 515 if (!CountedExitBlock) 516 return MadeChange; 517 518 BasicBlock *Preheader = L->getLoopPreheader(); 519 520 // If we don't have a preheader, then insert one. If we already have a 521 // preheader, then we can use it (except if the preheader contains a use of 522 // the CTR register because some such uses might be reordered by the 523 // selection DAG after the mtctr instruction). 524 if (!Preheader || mightUseCTR(TT, Preheader)) 525 Preheader = InsertPreheaderForLoop(L, this); 526 if (!Preheader) 527 return MadeChange; 528 529 DEBUG(dbgs() << "Preheader for exit count: " << Preheader->getName() << "\n"); 530 531 // Insert the count into the preheader and replace the condition used by the 532 // selected branch. 533 MadeChange = true; 534 535 SCEVExpander SCEVE(*SE, "loopcnt"); 536 LLVMContext &C = SE->getContext(); 537 Type *CountType = TT.isArch64Bit() ? Type::getInt64Ty(C) : 538 Type::getInt32Ty(C); 539 if (!ExitCount->getType()->isPointerTy() && 540 ExitCount->getType() != CountType) 541 ExitCount = SE->getZeroExtendExpr(ExitCount, CountType); 542 ExitCount = SE->getAddExpr(ExitCount, 543 SE->getConstant(CountType, 1)); 544 Value *ECValue = SCEVE.expandCodeFor(ExitCount, CountType, 545 Preheader->getTerminator()); 546 547 IRBuilder<> CountBuilder(Preheader->getTerminator()); 548 Module *M = Preheader->getParent()->getParent(); 549 Value *MTCTRFunc = Intrinsic::getDeclaration(M, Intrinsic::ppc_mtctr, 550 CountType); 551 CountBuilder.CreateCall(MTCTRFunc, ECValue); 552 553 IRBuilder<> CondBuilder(CountedExitBranch); 554 Value *DecFunc = 555 Intrinsic::getDeclaration(M, Intrinsic::ppc_is_decremented_ctr_nonzero); 556 Value *NewCond = CondBuilder.CreateCall(DecFunc); 557 Value *OldCond = CountedExitBranch->getCondition(); 558 CountedExitBranch->setCondition(NewCond); 559 560 // The false branch must exit the loop. 561 if (!L->contains(CountedExitBranch->getSuccessor(0))) 562 CountedExitBranch->swapSuccessors(); 563 564 // The old condition may be dead now, and may have even created a dead PHI 565 // (the original induction variable). 566 RecursivelyDeleteTriviallyDeadInstructions(OldCond); 567 DeleteDeadPHIs(CountedExitBlock); 568 569 ++NumCTRLoops; 570 return MadeChange; 571 } 572 573 #ifndef NDEBUG 574 static bool clobbersCTR(const MachineInstr *MI) { 575 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 576 const MachineOperand &MO = MI->getOperand(i); 577 if (MO.isReg()) { 578 if (MO.isDef() && (MO.getReg() == PPC::CTR || MO.getReg() == PPC::CTR8)) 579 return true; 580 } else if (MO.isRegMask()) { 581 if (MO.clobbersPhysReg(PPC::CTR) || MO.clobbersPhysReg(PPC::CTR8)) 582 return true; 583 } 584 } 585 586 return false; 587 } 588 589 static bool verifyCTRBranch(MachineBasicBlock *MBB, 590 MachineBasicBlock::iterator I) { 591 MachineBasicBlock::iterator BI = I; 592 SmallSet<MachineBasicBlock *, 16> Visited; 593 SmallVector<MachineBasicBlock *, 8> Preds; 594 bool CheckPreds; 595 596 if (I == MBB->begin()) { 597 Visited.insert(MBB); 598 goto queue_preds; 599 } else 600 --I; 601 602 check_block: 603 Visited.insert(MBB); 604 if (I == MBB->end()) 605 goto queue_preds; 606 607 CheckPreds = true; 608 for (MachineBasicBlock::iterator IE = MBB->begin();; --I) { 609 unsigned Opc = I->getOpcode(); 610 if (Opc == PPC::MTCTRloop || Opc == PPC::MTCTR8loop) { 611 CheckPreds = false; 612 break; 613 } 614 615 if (I != BI && clobbersCTR(I)) { 616 DEBUG(dbgs() << "BB#" << MBB->getNumber() << " (" << 617 MBB->getFullName() << ") instruction " << *I << 618 " clobbers CTR, invalidating " << "BB#" << 619 BI->getParent()->getNumber() << " (" << 620 BI->getParent()->getFullName() << ") instruction " << 621 *BI << "\n"); 622 return false; 623 } 624 625 if (I == IE) 626 break; 627 } 628 629 if (!CheckPreds && Preds.empty()) 630 return true; 631 632 if (CheckPreds) { 633 queue_preds: 634 if (MachineFunction::iterator(MBB) == MBB->getParent()->begin()) { 635 DEBUG(dbgs() << "Unable to find a MTCTR instruction for BB#" << 636 BI->getParent()->getNumber() << " (" << 637 BI->getParent()->getFullName() << ") instruction " << 638 *BI << "\n"); 639 return false; 640 } 641 642 for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), 643 PIE = MBB->pred_end(); PI != PIE; ++PI) 644 Preds.push_back(*PI); 645 } 646 647 do { 648 MBB = Preds.pop_back_val(); 649 if (!Visited.count(MBB)) { 650 I = MBB->getLastNonDebugInstr(); 651 goto check_block; 652 } 653 } while (!Preds.empty()); 654 655 return true; 656 } 657 658 bool PPCCTRLoopsVerify::runOnMachineFunction(MachineFunction &MF) { 659 MDT = &getAnalysis<MachineDominatorTree>(); 660 661 // Verify that all bdnz/bdz instructions are dominated by a loop mtctr before 662 // any other instructions that might clobber the ctr register. 663 for (MachineFunction::iterator I = MF.begin(), IE = MF.end(); 664 I != IE; ++I) { 665 MachineBasicBlock *MBB = I; 666 if (!MDT->isReachableFromEntry(MBB)) 667 continue; 668 669 for (MachineBasicBlock::iterator MII = MBB->getFirstTerminator(), 670 MIIE = MBB->end(); MII != MIIE; ++MII) { 671 unsigned Opc = MII->getOpcode(); 672 if (Opc == PPC::BDNZ8 || Opc == PPC::BDNZ || 673 Opc == PPC::BDZ8 || Opc == PPC::BDZ) 674 if (!verifyCTRBranch(MBB, MII)) 675 llvm_unreachable("Invalid PPC CTR loop!"); 676 } 677 } 678 679 return false; 680 } 681 #endif // NDEBUG 682 683