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<ScalarEvolutionWrapperPass>(); 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(ScalarEvolutionWrapperPass) 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<ScalarEvolutionWrapperPass>().getSE(); 173 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 174 DL = &F.getParent()->getDataLayout(); 175 auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>(); 176 LibInfo = TLIP ? &TLIP->getTLI() : nullptr; 177 178 bool MadeChange = false; 179 180 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); 181 I != E; ++I) { 182 Loop *L = *I; 183 if (!L->getParentLoop()) 184 MadeChange |= convertToCTRLoop(L); 185 } 186 187 return MadeChange; 188 } 189 190 static bool isLargeIntegerTy(bool Is32Bit, Type *Ty) { 191 if (IntegerType *ITy = dyn_cast<IntegerType>(Ty)) 192 return ITy->getBitWidth() > (Is32Bit ? 32U : 64U); 193 194 return false; 195 } 196 197 // Determining the address of a TLS variable results in a function call in 198 // certain TLS models. 199 static bool memAddrUsesCTR(const PPCTargetMachine *TM, 200 const llvm::Value *MemAddr) { 201 const auto *GV = dyn_cast<GlobalValue>(MemAddr); 202 if (!GV) 203 return false; 204 if (!GV->isThreadLocal()) 205 return false; 206 if (!TM) 207 return true; 208 TLSModel::Model Model = TM->getTLSModel(GV); 209 return Model == TLSModel::GeneralDynamic || Model == TLSModel::LocalDynamic; 210 } 211 212 bool PPCCTRLoops::mightUseCTR(const Triple &TT, BasicBlock *BB) { 213 for (BasicBlock::iterator J = BB->begin(), JE = BB->end(); 214 J != JE; ++J) { 215 if (CallInst *CI = dyn_cast<CallInst>(J)) { 216 if (InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue())) { 217 // Inline ASM is okay, unless it clobbers the ctr register. 218 InlineAsm::ConstraintInfoVector CIV = IA->ParseConstraints(); 219 for (unsigned i = 0, ie = CIV.size(); i < ie; ++i) { 220 InlineAsm::ConstraintInfo &C = CIV[i]; 221 if (C.Type != InlineAsm::isInput) 222 for (unsigned j = 0, je = C.Codes.size(); j < je; ++j) 223 if (StringRef(C.Codes[j]).equals_lower("{ctr}")) 224 return true; 225 } 226 227 continue; 228 } 229 230 if (!TM) 231 return true; 232 const TargetLowering *TLI = 233 TM->getSubtargetImpl(*BB->getParent())->getTargetLowering(); 234 235 if (Function *F = CI->getCalledFunction()) { 236 // Most intrinsics don't become function calls, but some might. 237 // sin, cos, exp and log are always calls. 238 unsigned Opcode; 239 if (F->getIntrinsicID() != Intrinsic::not_intrinsic) { 240 switch (F->getIntrinsicID()) { 241 default: continue; 242 243 // VisualStudio defines setjmp as _setjmp 244 #if defined(_MSC_VER) && defined(setjmp) && \ 245 !defined(setjmp_undefined_for_msvc) 246 # pragma push_macro("setjmp") 247 # undef setjmp 248 # define setjmp_undefined_for_msvc 249 #endif 250 251 case Intrinsic::setjmp: 252 253 #if defined(_MSC_VER) && defined(setjmp_undefined_for_msvc) 254 // let's return it to _setjmp state 255 # pragma pop_macro("setjmp") 256 # undef setjmp_undefined_for_msvc 257 #endif 258 259 case Intrinsic::longjmp: 260 261 // Exclude eh_sjlj_setjmp; we don't need to exclude eh_sjlj_longjmp 262 // because, although it does clobber the counter register, the 263 // control can't then return to inside the loop unless there is also 264 // an eh_sjlj_setjmp. 265 case Intrinsic::eh_sjlj_setjmp: 266 267 case Intrinsic::memcpy: 268 case Intrinsic::memmove: 269 case Intrinsic::memset: 270 case Intrinsic::powi: 271 case Intrinsic::log: 272 case Intrinsic::log2: 273 case Intrinsic::log10: 274 case Intrinsic::exp: 275 case Intrinsic::exp2: 276 case Intrinsic::pow: 277 case Intrinsic::sin: 278 case Intrinsic::cos: 279 return true; 280 case Intrinsic::copysign: 281 if (CI->getArgOperand(0)->getType()->getScalarType()-> 282 isPPC_FP128Ty()) 283 return true; 284 else 285 continue; // ISD::FCOPYSIGN is never a library call. 286 case Intrinsic::sqrt: Opcode = ISD::FSQRT; break; 287 case Intrinsic::floor: Opcode = ISD::FFLOOR; break; 288 case Intrinsic::ceil: Opcode = ISD::FCEIL; break; 289 case Intrinsic::trunc: Opcode = ISD::FTRUNC; break; 290 case Intrinsic::rint: Opcode = ISD::FRINT; break; 291 case Intrinsic::nearbyint: Opcode = ISD::FNEARBYINT; break; 292 case Intrinsic::round: Opcode = ISD::FROUND; break; 293 } 294 } 295 296 // PowerPC does not use [US]DIVREM or other library calls for 297 // operations on regular types which are not otherwise library calls 298 // (i.e. soft float or atomics). If adapting for targets that do, 299 // additional care is required here. 300 301 LibFunc::Func Func; 302 if (!F->hasLocalLinkage() && F->hasName() && LibInfo && 303 LibInfo->getLibFunc(F->getName(), Func) && 304 LibInfo->hasOptimizedCodeGen(Func)) { 305 // Non-read-only functions are never treated as intrinsics. 306 if (!CI->onlyReadsMemory()) 307 return true; 308 309 // Conversion happens only for FP calls. 310 if (!CI->getArgOperand(0)->getType()->isFloatingPointTy()) 311 return true; 312 313 switch (Func) { 314 default: return true; 315 case LibFunc::copysign: 316 case LibFunc::copysignf: 317 continue; // ISD::FCOPYSIGN is never a library call. 318 case LibFunc::copysignl: 319 return true; 320 case LibFunc::fabs: 321 case LibFunc::fabsf: 322 case LibFunc::fabsl: 323 continue; // ISD::FABS is never a library call. 324 case LibFunc::sqrt: 325 case LibFunc::sqrtf: 326 case LibFunc::sqrtl: 327 Opcode = ISD::FSQRT; break; 328 case LibFunc::floor: 329 case LibFunc::floorf: 330 case LibFunc::floorl: 331 Opcode = ISD::FFLOOR; break; 332 case LibFunc::nearbyint: 333 case LibFunc::nearbyintf: 334 case LibFunc::nearbyintl: 335 Opcode = ISD::FNEARBYINT; break; 336 case LibFunc::ceil: 337 case LibFunc::ceilf: 338 case LibFunc::ceill: 339 Opcode = ISD::FCEIL; break; 340 case LibFunc::rint: 341 case LibFunc::rintf: 342 case LibFunc::rintl: 343 Opcode = ISD::FRINT; break; 344 case LibFunc::round: 345 case LibFunc::roundf: 346 case LibFunc::roundl: 347 Opcode = ISD::FROUND; break; 348 case LibFunc::trunc: 349 case LibFunc::truncf: 350 case LibFunc::truncl: 351 Opcode = ISD::FTRUNC; break; 352 } 353 354 auto &DL = CI->getModule()->getDataLayout(); 355 MVT VTy = TLI->getSimpleValueType(DL, CI->getArgOperand(0)->getType(), 356 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 = 405 TM->getSubtargetImpl(*BB->getParent())->getTargetLowering(); 406 407 if (SI->getNumCases() + 1 >= (unsigned)TLI->getMinimumJumpTableEntries()) 408 return true; 409 } 410 for (Value *Operand : J->operands()) 411 if (memAddrUsesCTR(TM, Operand)) 412 return true; 413 } 414 415 return false; 416 } 417 418 bool PPCCTRLoops::convertToCTRLoop(Loop *L) { 419 bool MadeChange = false; 420 421 const Triple TT = 422 Triple(L->getHeader()->getParent()->getParent()->getTargetTriple()); 423 if (!TT.isArch32Bit() && !TT.isArch64Bit()) 424 return MadeChange; // Unknown arch. type. 425 426 // Process nested loops first. 427 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) { 428 MadeChange |= convertToCTRLoop(*I); 429 } 430 431 // If a nested loop has been converted, then we can't convert this loop. 432 if (MadeChange) 433 return MadeChange; 434 435 #ifndef NDEBUG 436 // Stop trying after reaching the limit (if any). 437 int Limit = CTRLoopLimit; 438 if (Limit >= 0) { 439 if (Counter >= CTRLoopLimit) 440 return false; 441 Counter++; 442 } 443 #endif 444 445 // We don't want to spill/restore the counter register, and so we don't 446 // want to use the counter register if the loop contains calls. 447 for (Loop::block_iterator I = L->block_begin(), IE = L->block_end(); 448 I != IE; ++I) 449 if (mightUseCTR(TT, *I)) 450 return MadeChange; 451 452 SmallVector<BasicBlock*, 4> ExitingBlocks; 453 L->getExitingBlocks(ExitingBlocks); 454 455 BasicBlock *CountedExitBlock = nullptr; 456 const SCEV *ExitCount = nullptr; 457 BranchInst *CountedExitBranch = nullptr; 458 for (SmallVectorImpl<BasicBlock *>::iterator I = ExitingBlocks.begin(), 459 IE = ExitingBlocks.end(); I != IE; ++I) { 460 const SCEV *EC = SE->getExitCount(L, *I); 461 DEBUG(dbgs() << "Exit Count for " << *L << " from block " << 462 (*I)->getName() << ": " << *EC << "\n"); 463 if (isa<SCEVCouldNotCompute>(EC)) 464 continue; 465 if (const SCEVConstant *ConstEC = dyn_cast<SCEVConstant>(EC)) { 466 if (ConstEC->getValue()->isZero()) 467 continue; 468 } else if (!SE->isLoopInvariant(EC, L)) 469 continue; 470 471 if (SE->getTypeSizeInBits(EC->getType()) > (TT.isArch64Bit() ? 64 : 32)) 472 continue; 473 474 // We now have a loop-invariant count of loop iterations (which is not the 475 // constant zero) for which we know that this loop will not exit via this 476 // exisiting block. 477 478 // We need to make sure that this block will run on every loop iteration. 479 // For this to be true, we must dominate all blocks with backedges. Such 480 // blocks are in-loop predecessors to the header block. 481 bool NotAlways = false; 482 for (pred_iterator PI = pred_begin(L->getHeader()), 483 PIE = pred_end(L->getHeader()); PI != PIE; ++PI) { 484 if (!L->contains(*PI)) 485 continue; 486 487 if (!DT->dominates(*I, *PI)) { 488 NotAlways = true; 489 break; 490 } 491 } 492 493 if (NotAlways) 494 continue; 495 496 // Make sure this blocks ends with a conditional branch. 497 Instruction *TI = (*I)->getTerminator(); 498 if (!TI) 499 continue; 500 501 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { 502 if (!BI->isConditional()) 503 continue; 504 505 CountedExitBranch = BI; 506 } else 507 continue; 508 509 // Note that this block may not be the loop latch block, even if the loop 510 // has a latch block. 511 CountedExitBlock = *I; 512 ExitCount = EC; 513 break; 514 } 515 516 if (!CountedExitBlock) 517 return MadeChange; 518 519 BasicBlock *Preheader = L->getLoopPreheader(); 520 521 // If we don't have a preheader, then insert one. If we already have a 522 // preheader, then we can use it (except if the preheader contains a use of 523 // the CTR register because some such uses might be reordered by the 524 // selection DAG after the mtctr instruction). 525 if (!Preheader || mightUseCTR(TT, Preheader)) 526 Preheader = InsertPreheaderForLoop(L, this); 527 if (!Preheader) 528 return MadeChange; 529 530 DEBUG(dbgs() << "Preheader for exit count: " << Preheader->getName() << "\n"); 531 532 // Insert the count into the preheader and replace the condition used by the 533 // selected branch. 534 MadeChange = true; 535 536 SCEVExpander SCEVE(*SE, Preheader->getModule()->getDataLayout(), "loopcnt"); 537 LLVMContext &C = SE->getContext(); 538 Type *CountType = TT.isArch64Bit() ? Type::getInt64Ty(C) : 539 Type::getInt32Ty(C); 540 if (!ExitCount->getType()->isPointerTy() && 541 ExitCount->getType() != CountType) 542 ExitCount = SE->getZeroExtendExpr(ExitCount, CountType); 543 ExitCount = SE->getAddExpr(ExitCount, 544 SE->getConstant(CountType, 1)); 545 Value *ECValue = SCEVE.expandCodeFor(ExitCount, CountType, 546 Preheader->getTerminator()); 547 548 IRBuilder<> CountBuilder(Preheader->getTerminator()); 549 Module *M = Preheader->getParent()->getParent(); 550 Value *MTCTRFunc = Intrinsic::getDeclaration(M, Intrinsic::ppc_mtctr, 551 CountType); 552 CountBuilder.CreateCall(MTCTRFunc, ECValue); 553 554 IRBuilder<> CondBuilder(CountedExitBranch); 555 Value *DecFunc = 556 Intrinsic::getDeclaration(M, Intrinsic::ppc_is_decremented_ctr_nonzero); 557 Value *NewCond = CondBuilder.CreateCall(DecFunc, {}); 558 Value *OldCond = CountedExitBranch->getCondition(); 559 CountedExitBranch->setCondition(NewCond); 560 561 // The false branch must exit the loop. 562 if (!L->contains(CountedExitBranch->getSuccessor(0))) 563 CountedExitBranch->swapSuccessors(); 564 565 // The old condition may be dead now, and may have even created a dead PHI 566 // (the original induction variable). 567 RecursivelyDeleteTriviallyDeadInstructions(OldCond); 568 DeleteDeadPHIs(CountedExitBlock); 569 570 ++NumCTRLoops; 571 return MadeChange; 572 } 573 574 #ifndef NDEBUG 575 static bool clobbersCTR(const MachineInstr *MI) { 576 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 577 const MachineOperand &MO = MI->getOperand(i); 578 if (MO.isReg()) { 579 if (MO.isDef() && (MO.getReg() == PPC::CTR || MO.getReg() == PPC::CTR8)) 580 return true; 581 } else if (MO.isRegMask()) { 582 if (MO.clobbersPhysReg(PPC::CTR) || MO.clobbersPhysReg(PPC::CTR8)) 583 return true; 584 } 585 } 586 587 return false; 588 } 589 590 static bool verifyCTRBranch(MachineBasicBlock *MBB, 591 MachineBasicBlock::iterator I) { 592 MachineBasicBlock::iterator BI = I; 593 SmallSet<MachineBasicBlock *, 16> Visited; 594 SmallVector<MachineBasicBlock *, 8> Preds; 595 bool CheckPreds; 596 597 if (I == MBB->begin()) { 598 Visited.insert(MBB); 599 goto queue_preds; 600 } else 601 --I; 602 603 check_block: 604 Visited.insert(MBB); 605 if (I == MBB->end()) 606 goto queue_preds; 607 608 CheckPreds = true; 609 for (MachineBasicBlock::iterator IE = MBB->begin();; --I) { 610 unsigned Opc = I->getOpcode(); 611 if (Opc == PPC::MTCTRloop || Opc == PPC::MTCTR8loop) { 612 CheckPreds = false; 613 break; 614 } 615 616 if (I != BI && clobbersCTR(I)) { 617 DEBUG(dbgs() << "BB#" << MBB->getNumber() << " (" << 618 MBB->getFullName() << ") instruction " << *I << 619 " clobbers CTR, invalidating " << "BB#" << 620 BI->getParent()->getNumber() << " (" << 621 BI->getParent()->getFullName() << ") instruction " << 622 *BI << "\n"); 623 return false; 624 } 625 626 if (I == IE) 627 break; 628 } 629 630 if (!CheckPreds && Preds.empty()) 631 return true; 632 633 if (CheckPreds) { 634 queue_preds: 635 if (MachineFunction::iterator(MBB) == MBB->getParent()->begin()) { 636 DEBUG(dbgs() << "Unable to find a MTCTR instruction for BB#" << 637 BI->getParent()->getNumber() << " (" << 638 BI->getParent()->getFullName() << ") instruction " << 639 *BI << "\n"); 640 return false; 641 } 642 643 for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), 644 PIE = MBB->pred_end(); PI != PIE; ++PI) 645 Preds.push_back(*PI); 646 } 647 648 do { 649 MBB = Preds.pop_back_val(); 650 if (!Visited.count(MBB)) { 651 I = MBB->getLastNonDebugInstr(); 652 goto check_block; 653 } 654 } while (!Preds.empty()); 655 656 return true; 657 } 658 659 bool PPCCTRLoopsVerify::runOnMachineFunction(MachineFunction &MF) { 660 MDT = &getAnalysis<MachineDominatorTree>(); 661 662 // Verify that all bdnz/bdz instructions are dominated by a loop mtctr before 663 // any other instructions that might clobber the ctr register. 664 for (MachineFunction::iterator I = MF.begin(), IE = MF.end(); 665 I != IE; ++I) { 666 MachineBasicBlock *MBB = I; 667 if (!MDT->isReachableFromEntry(MBB)) 668 continue; 669 670 for (MachineBasicBlock::iterator MII = MBB->getFirstTerminator(), 671 MIIE = MBB->end(); MII != MIIE; ++MII) { 672 unsigned Opc = MII->getOpcode(); 673 if (Opc == PPC::BDNZ8 || Opc == PPC::BDNZ || 674 Opc == PPC::BDZ8 || Opc == PPC::BDZ) 675 if (!verifyCTRBranch(MBB, MII)) 676 llvm_unreachable("Invalid PPC CTR loop!"); 677 } 678 } 679 680 return false; 681 } 682 #endif // NDEBUG 683 684