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 using namespace llvm;
58
59 #define DEBUG_TYPE "ctrloops"
60
61 #ifndef NDEBUG
62 static cl::opt<int> CTRLoopLimit("ppc-max-ctrloop", cl::Hidden, cl::init(-1));
63 #endif
64
65 STATISTIC(NumCTRLoops, "Number of loops converted to CTR loops");
66
67 namespace llvm {
68 void initializePPCCTRLoopsPass(PassRegistry&);
69 #ifndef NDEBUG
70 void initializePPCCTRLoopsVerifyPass(PassRegistry&);
71 #endif
72 }
73
74 namespace {
75 struct PPCCTRLoops : public FunctionPass {
76
77 #ifndef NDEBUG
78 static int Counter;
79 #endif
80
81 public:
82 static char ID;
83
PPCCTRLoops__anon2edf53350111::PPCCTRLoops84 PPCCTRLoops() : FunctionPass(ID), TM(nullptr) {
85 initializePPCCTRLoopsPass(*PassRegistry::getPassRegistry());
86 }
PPCCTRLoops__anon2edf53350111::PPCCTRLoops87 PPCCTRLoops(PPCTargetMachine &TM) : FunctionPass(ID), TM(&TM) {
88 initializePPCCTRLoopsPass(*PassRegistry::getPassRegistry());
89 }
90
91 bool runOnFunction(Function &F) override;
92
getAnalysisUsage__anon2edf53350111::PPCCTRLoops93 void getAnalysisUsage(AnalysisUsage &AU) const override {
94 AU.addRequired<LoopInfoWrapperPass>();
95 AU.addPreserved<LoopInfoWrapperPass>();
96 AU.addRequired<DominatorTreeWrapperPass>();
97 AU.addPreserved<DominatorTreeWrapperPass>();
98 AU.addRequired<ScalarEvolutionWrapperPass>();
99 }
100
101 private:
102 bool mightUseCTR(const Triple &TT, BasicBlock *BB);
103 bool convertToCTRLoop(Loop *L);
104
105 private:
106 PPCTargetMachine *TM;
107 LoopInfo *LI;
108 ScalarEvolution *SE;
109 const DataLayout *DL;
110 DominatorTree *DT;
111 const TargetLibraryInfo *LibInfo;
112 bool PreserveLCSSA;
113 };
114
115 char PPCCTRLoops::ID = 0;
116 #ifndef NDEBUG
117 int PPCCTRLoops::Counter = 0;
118 #endif
119
120 #ifndef NDEBUG
121 struct PPCCTRLoopsVerify : public MachineFunctionPass {
122 public:
123 static char ID;
124
PPCCTRLoopsVerify__anon2edf53350111::PPCCTRLoopsVerify125 PPCCTRLoopsVerify() : MachineFunctionPass(ID) {
126 initializePPCCTRLoopsVerifyPass(*PassRegistry::getPassRegistry());
127 }
128
getAnalysisUsage__anon2edf53350111::PPCCTRLoopsVerify129 void getAnalysisUsage(AnalysisUsage &AU) const override {
130 AU.addRequired<MachineDominatorTree>();
131 MachineFunctionPass::getAnalysisUsage(AU);
132 }
133
134 bool runOnMachineFunction(MachineFunction &MF) override;
135
136 private:
137 MachineDominatorTree *MDT;
138 };
139
140 char PPCCTRLoopsVerify::ID = 0;
141 #endif // NDEBUG
142 } // end anonymous namespace
143
144 INITIALIZE_PASS_BEGIN(PPCCTRLoops, "ppc-ctr-loops", "PowerPC CTR Loops",
145 false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)146 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
147 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
148 INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
149 INITIALIZE_PASS_END(PPCCTRLoops, "ppc-ctr-loops", "PowerPC CTR Loops",
150 false, false)
151
152 FunctionPass *llvm::createPPCCTRLoops(PPCTargetMachine &TM) {
153 return new PPCCTRLoops(TM);
154 }
155
156 #ifndef NDEBUG
157 INITIALIZE_PASS_BEGIN(PPCCTRLoopsVerify, "ppc-ctr-loops-verify",
158 "PowerPC CTR Loops Verify", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)159 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
160 INITIALIZE_PASS_END(PPCCTRLoopsVerify, "ppc-ctr-loops-verify",
161 "PowerPC CTR Loops Verify", false, false)
162
163 FunctionPass *llvm::createPPCCTRLoopsVerify() {
164 return new PPCCTRLoopsVerify();
165 }
166 #endif // NDEBUG
167
runOnFunction(Function & F)168 bool PPCCTRLoops::runOnFunction(Function &F) {
169 if (skipFunction(F))
170 return false;
171
172 LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
173 SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
174 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
175 DL = &F.getParent()->getDataLayout();
176 auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
177 LibInfo = TLIP ? &TLIP->getTLI() : nullptr;
178 PreserveLCSSA = mustPreserveAnalysisID(LCSSAID);
179
180 bool MadeChange = false;
181
182 for (LoopInfo::iterator I = LI->begin(), E = LI->end();
183 I != E; ++I) {
184 Loop *L = *I;
185 if (!L->getParentLoop())
186 MadeChange |= convertToCTRLoop(L);
187 }
188
189 return MadeChange;
190 }
191
isLargeIntegerTy(bool Is32Bit,Type * Ty)192 static bool isLargeIntegerTy(bool Is32Bit, Type *Ty) {
193 if (IntegerType *ITy = dyn_cast<IntegerType>(Ty))
194 return ITy->getBitWidth() > (Is32Bit ? 32U : 64U);
195
196 return false;
197 }
198
199 // Determining the address of a TLS variable results in a function call in
200 // certain TLS models.
memAddrUsesCTR(const PPCTargetMachine * TM,const Value * MemAddr)201 static bool memAddrUsesCTR(const PPCTargetMachine *TM,
202 const Value *MemAddr) {
203 const auto *GV = dyn_cast<GlobalValue>(MemAddr);
204 if (!GV) {
205 // Recurse to check for constants that refer to TLS global variables.
206 if (const auto *CV = dyn_cast<Constant>(MemAddr))
207 for (const auto &CO : CV->operands())
208 if (memAddrUsesCTR(TM, CO))
209 return true;
210
211 return false;
212 }
213
214 if (!GV->isThreadLocal())
215 return false;
216 if (!TM)
217 return true;
218 TLSModel::Model Model = TM->getTLSModel(GV);
219 return Model == TLSModel::GeneralDynamic || Model == TLSModel::LocalDynamic;
220 }
221
mightUseCTR(const Triple & TT,BasicBlock * BB)222 bool PPCCTRLoops::mightUseCTR(const Triple &TT, BasicBlock *BB) {
223 for (BasicBlock::iterator J = BB->begin(), JE = BB->end();
224 J != JE; ++J) {
225 if (CallInst *CI = dyn_cast<CallInst>(J)) {
226 if (InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue())) {
227 // Inline ASM is okay, unless it clobbers the ctr register.
228 InlineAsm::ConstraintInfoVector CIV = IA->ParseConstraints();
229 for (unsigned i = 0, ie = CIV.size(); i < ie; ++i) {
230 InlineAsm::ConstraintInfo &C = CIV[i];
231 if (C.Type != InlineAsm::isInput)
232 for (unsigned j = 0, je = C.Codes.size(); j < je; ++j)
233 if (StringRef(C.Codes[j]).equals_lower("{ctr}"))
234 return true;
235 }
236
237 continue;
238 }
239
240 if (!TM)
241 return true;
242 const TargetLowering *TLI =
243 TM->getSubtargetImpl(*BB->getParent())->getTargetLowering();
244
245 if (Function *F = CI->getCalledFunction()) {
246 // Most intrinsics don't become function calls, but some might.
247 // sin, cos, exp and log are always calls.
248 unsigned Opcode = 0;
249 if (F->getIntrinsicID() != Intrinsic::not_intrinsic) {
250 switch (F->getIntrinsicID()) {
251 default: continue;
252 // If we have a call to ppc_is_decremented_ctr_nonzero, or ppc_mtctr
253 // we're definitely using CTR.
254 case Intrinsic::ppc_is_decremented_ctr_nonzero:
255 case Intrinsic::ppc_mtctr:
256 return true;
257
258 // VisualStudio defines setjmp as _setjmp
259 #if defined(_MSC_VER) && defined(setjmp) && \
260 !defined(setjmp_undefined_for_msvc)
261 # pragma push_macro("setjmp")
262 # undef setjmp
263 # define setjmp_undefined_for_msvc
264 #endif
265
266 case Intrinsic::setjmp:
267
268 #if defined(_MSC_VER) && defined(setjmp_undefined_for_msvc)
269 // let's return it to _setjmp state
270 # pragma pop_macro("setjmp")
271 # undef setjmp_undefined_for_msvc
272 #endif
273
274 case Intrinsic::longjmp:
275
276 // Exclude eh_sjlj_setjmp; we don't need to exclude eh_sjlj_longjmp
277 // because, although it does clobber the counter register, the
278 // control can't then return to inside the loop unless there is also
279 // an eh_sjlj_setjmp.
280 case Intrinsic::eh_sjlj_setjmp:
281
282 case Intrinsic::memcpy:
283 case Intrinsic::memmove:
284 case Intrinsic::memset:
285 case Intrinsic::powi:
286 case Intrinsic::log:
287 case Intrinsic::log2:
288 case Intrinsic::log10:
289 case Intrinsic::exp:
290 case Intrinsic::exp2:
291 case Intrinsic::pow:
292 case Intrinsic::sin:
293 case Intrinsic::cos:
294 return true;
295 case Intrinsic::copysign:
296 if (CI->getArgOperand(0)->getType()->getScalarType()->
297 isPPC_FP128Ty())
298 return true;
299 else
300 continue; // ISD::FCOPYSIGN is never a library call.
301 case Intrinsic::sqrt: Opcode = ISD::FSQRT; break;
302 case Intrinsic::floor: Opcode = ISD::FFLOOR; break;
303 case Intrinsic::ceil: Opcode = ISD::FCEIL; break;
304 case Intrinsic::trunc: Opcode = ISD::FTRUNC; break;
305 case Intrinsic::rint: Opcode = ISD::FRINT; break;
306 case Intrinsic::nearbyint: Opcode = ISD::FNEARBYINT; break;
307 case Intrinsic::round: Opcode = ISD::FROUND; break;
308 case Intrinsic::minnum: Opcode = ISD::FMINNUM; break;
309 case Intrinsic::maxnum: Opcode = ISD::FMAXNUM; break;
310 }
311 }
312
313 // PowerPC does not use [US]DIVREM or other library calls for
314 // operations on regular types which are not otherwise library calls
315 // (i.e. soft float or atomics). If adapting for targets that do,
316 // additional care is required here.
317
318 LibFunc::Func Func;
319 if (!F->hasLocalLinkage() && F->hasName() && LibInfo &&
320 LibInfo->getLibFunc(F->getName(), Func) &&
321 LibInfo->hasOptimizedCodeGen(Func)) {
322 // Non-read-only functions are never treated as intrinsics.
323 if (!CI->onlyReadsMemory())
324 return true;
325
326 // Conversion happens only for FP calls.
327 if (!CI->getArgOperand(0)->getType()->isFloatingPointTy())
328 return true;
329
330 switch (Func) {
331 default: return true;
332 case LibFunc::copysign:
333 case LibFunc::copysignf:
334 continue; // ISD::FCOPYSIGN is never a library call.
335 case LibFunc::copysignl:
336 return true;
337 case LibFunc::fabs:
338 case LibFunc::fabsf:
339 case LibFunc::fabsl:
340 continue; // ISD::FABS is never a library call.
341 case LibFunc::sqrt:
342 case LibFunc::sqrtf:
343 case LibFunc::sqrtl:
344 Opcode = ISD::FSQRT; break;
345 case LibFunc::floor:
346 case LibFunc::floorf:
347 case LibFunc::floorl:
348 Opcode = ISD::FFLOOR; break;
349 case LibFunc::nearbyint:
350 case LibFunc::nearbyintf:
351 case LibFunc::nearbyintl:
352 Opcode = ISD::FNEARBYINT; break;
353 case LibFunc::ceil:
354 case LibFunc::ceilf:
355 case LibFunc::ceill:
356 Opcode = ISD::FCEIL; break;
357 case LibFunc::rint:
358 case LibFunc::rintf:
359 case LibFunc::rintl:
360 Opcode = ISD::FRINT; break;
361 case LibFunc::round:
362 case LibFunc::roundf:
363 case LibFunc::roundl:
364 Opcode = ISD::FROUND; break;
365 case LibFunc::trunc:
366 case LibFunc::truncf:
367 case LibFunc::truncl:
368 Opcode = ISD::FTRUNC; break;
369 case LibFunc::fmin:
370 case LibFunc::fminf:
371 case LibFunc::fminl:
372 Opcode = ISD::FMINNUM; break;
373 case LibFunc::fmax:
374 case LibFunc::fmaxf:
375 case LibFunc::fmaxl:
376 Opcode = ISD::FMAXNUM; break;
377 }
378 }
379
380 if (Opcode) {
381 auto &DL = CI->getModule()->getDataLayout();
382 MVT VTy = TLI->getSimpleValueType(DL, CI->getArgOperand(0)->getType(),
383 true);
384 if (VTy == MVT::Other)
385 return true;
386
387 if (TLI->isOperationLegalOrCustom(Opcode, VTy))
388 continue;
389 else if (VTy.isVector() &&
390 TLI->isOperationLegalOrCustom(Opcode, VTy.getScalarType()))
391 continue;
392
393 return true;
394 }
395 }
396
397 return true;
398 } else if (isa<BinaryOperator>(J) &&
399 J->getType()->getScalarType()->isPPC_FP128Ty()) {
400 // Most operations on ppc_f128 values become calls.
401 return true;
402 } else if (isa<UIToFPInst>(J) || isa<SIToFPInst>(J) ||
403 isa<FPToUIInst>(J) || isa<FPToSIInst>(J)) {
404 CastInst *CI = cast<CastInst>(J);
405 if (CI->getSrcTy()->getScalarType()->isPPC_FP128Ty() ||
406 CI->getDestTy()->getScalarType()->isPPC_FP128Ty() ||
407 isLargeIntegerTy(TT.isArch32Bit(), CI->getSrcTy()->getScalarType()) ||
408 isLargeIntegerTy(TT.isArch32Bit(), CI->getDestTy()->getScalarType()))
409 return true;
410 } else if (isLargeIntegerTy(TT.isArch32Bit(),
411 J->getType()->getScalarType()) &&
412 (J->getOpcode() == Instruction::UDiv ||
413 J->getOpcode() == Instruction::SDiv ||
414 J->getOpcode() == Instruction::URem ||
415 J->getOpcode() == Instruction::SRem)) {
416 return true;
417 } else if (TT.isArch32Bit() &&
418 isLargeIntegerTy(false, J->getType()->getScalarType()) &&
419 (J->getOpcode() == Instruction::Shl ||
420 J->getOpcode() == Instruction::AShr ||
421 J->getOpcode() == Instruction::LShr)) {
422 // Only on PPC32, for 128-bit integers (specifically not 64-bit
423 // integers), these might be runtime calls.
424 return true;
425 } else if (isa<IndirectBrInst>(J) || isa<InvokeInst>(J)) {
426 // On PowerPC, indirect jumps use the counter register.
427 return true;
428 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(J)) {
429 if (!TM)
430 return true;
431 const TargetLowering *TLI =
432 TM->getSubtargetImpl(*BB->getParent())->getTargetLowering();
433
434 if (SI->getNumCases() + 1 >= (unsigned)TLI->getMinimumJumpTableEntries())
435 return true;
436 }
437
438 if (TM->getSubtargetImpl(*BB->getParent())->getTargetLowering()->useSoftFloat()) {
439 switch(J->getOpcode()) {
440 case Instruction::FAdd:
441 case Instruction::FSub:
442 case Instruction::FMul:
443 case Instruction::FDiv:
444 case Instruction::FRem:
445 case Instruction::FPTrunc:
446 case Instruction::FPExt:
447 case Instruction::FPToUI:
448 case Instruction::FPToSI:
449 case Instruction::UIToFP:
450 case Instruction::SIToFP:
451 case Instruction::FCmp:
452 return true;
453 }
454 }
455
456 for (Value *Operand : J->operands())
457 if (memAddrUsesCTR(TM, Operand))
458 return true;
459 }
460
461 return false;
462 }
463
convertToCTRLoop(Loop * L)464 bool PPCCTRLoops::convertToCTRLoop(Loop *L) {
465 bool MadeChange = false;
466
467 const Triple TT =
468 Triple(L->getHeader()->getParent()->getParent()->getTargetTriple());
469 if (!TT.isArch32Bit() && !TT.isArch64Bit())
470 return MadeChange; // Unknown arch. type.
471
472 // Process nested loops first.
473 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) {
474 MadeChange |= convertToCTRLoop(*I);
475 DEBUG(dbgs() << "Nested loop converted\n");
476 }
477
478 // If a nested loop has been converted, then we can't convert this loop.
479 if (MadeChange)
480 return MadeChange;
481
482 #ifndef NDEBUG
483 // Stop trying after reaching the limit (if any).
484 int Limit = CTRLoopLimit;
485 if (Limit >= 0) {
486 if (Counter >= CTRLoopLimit)
487 return false;
488 Counter++;
489 }
490 #endif
491
492 // We don't want to spill/restore the counter register, and so we don't
493 // want to use the counter register if the loop contains calls.
494 for (Loop::block_iterator I = L->block_begin(), IE = L->block_end();
495 I != IE; ++I)
496 if (mightUseCTR(TT, *I))
497 return MadeChange;
498
499 SmallVector<BasicBlock*, 4> ExitingBlocks;
500 L->getExitingBlocks(ExitingBlocks);
501
502 BasicBlock *CountedExitBlock = nullptr;
503 const SCEV *ExitCount = nullptr;
504 BranchInst *CountedExitBranch = nullptr;
505 for (SmallVectorImpl<BasicBlock *>::iterator I = ExitingBlocks.begin(),
506 IE = ExitingBlocks.end(); I != IE; ++I) {
507 const SCEV *EC = SE->getExitCount(L, *I);
508 DEBUG(dbgs() << "Exit Count for " << *L << " from block " <<
509 (*I)->getName() << ": " << *EC << "\n");
510 if (isa<SCEVCouldNotCompute>(EC))
511 continue;
512 if (const SCEVConstant *ConstEC = dyn_cast<SCEVConstant>(EC)) {
513 if (ConstEC->getValue()->isZero())
514 continue;
515 } else if (!SE->isLoopInvariant(EC, L))
516 continue;
517
518 if (SE->getTypeSizeInBits(EC->getType()) > (TT.isArch64Bit() ? 64 : 32))
519 continue;
520
521 // We now have a loop-invariant count of loop iterations (which is not the
522 // constant zero) for which we know that this loop will not exit via this
523 // exisiting block.
524
525 // We need to make sure that this block will run on every loop iteration.
526 // For this to be true, we must dominate all blocks with backedges. Such
527 // blocks are in-loop predecessors to the header block.
528 bool NotAlways = false;
529 for (pred_iterator PI = pred_begin(L->getHeader()),
530 PIE = pred_end(L->getHeader()); PI != PIE; ++PI) {
531 if (!L->contains(*PI))
532 continue;
533
534 if (!DT->dominates(*I, *PI)) {
535 NotAlways = true;
536 break;
537 }
538 }
539
540 if (NotAlways)
541 continue;
542
543 // Make sure this blocks ends with a conditional branch.
544 Instruction *TI = (*I)->getTerminator();
545 if (!TI)
546 continue;
547
548 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
549 if (!BI->isConditional())
550 continue;
551
552 CountedExitBranch = BI;
553 } else
554 continue;
555
556 // Note that this block may not be the loop latch block, even if the loop
557 // has a latch block.
558 CountedExitBlock = *I;
559 ExitCount = EC;
560 break;
561 }
562
563 if (!CountedExitBlock)
564 return MadeChange;
565
566 BasicBlock *Preheader = L->getLoopPreheader();
567
568 // If we don't have a preheader, then insert one. If we already have a
569 // preheader, then we can use it (except if the preheader contains a use of
570 // the CTR register because some such uses might be reordered by the
571 // selection DAG after the mtctr instruction).
572 if (!Preheader || mightUseCTR(TT, Preheader))
573 Preheader = InsertPreheaderForLoop(L, DT, LI, PreserveLCSSA);
574 if (!Preheader)
575 return MadeChange;
576
577 DEBUG(dbgs() << "Preheader for exit count: " << Preheader->getName() << "\n");
578
579 // Insert the count into the preheader and replace the condition used by the
580 // selected branch.
581 MadeChange = true;
582
583 SCEVExpander SCEVE(*SE, Preheader->getModule()->getDataLayout(), "loopcnt");
584 LLVMContext &C = SE->getContext();
585 Type *CountType = TT.isArch64Bit() ? Type::getInt64Ty(C) :
586 Type::getInt32Ty(C);
587 if (!ExitCount->getType()->isPointerTy() &&
588 ExitCount->getType() != CountType)
589 ExitCount = SE->getZeroExtendExpr(ExitCount, CountType);
590 ExitCount = SE->getAddExpr(ExitCount, SE->getOne(CountType));
591 Value *ECValue =
592 SCEVE.expandCodeFor(ExitCount, CountType, Preheader->getTerminator());
593
594 IRBuilder<> CountBuilder(Preheader->getTerminator());
595 Module *M = Preheader->getParent()->getParent();
596 Value *MTCTRFunc = Intrinsic::getDeclaration(M, Intrinsic::ppc_mtctr,
597 CountType);
598 CountBuilder.CreateCall(MTCTRFunc, ECValue);
599
600 IRBuilder<> CondBuilder(CountedExitBranch);
601 Value *DecFunc =
602 Intrinsic::getDeclaration(M, Intrinsic::ppc_is_decremented_ctr_nonzero);
603 Value *NewCond = CondBuilder.CreateCall(DecFunc, {});
604 Value *OldCond = CountedExitBranch->getCondition();
605 CountedExitBranch->setCondition(NewCond);
606
607 // The false branch must exit the loop.
608 if (!L->contains(CountedExitBranch->getSuccessor(0)))
609 CountedExitBranch->swapSuccessors();
610
611 // The old condition may be dead now, and may have even created a dead PHI
612 // (the original induction variable).
613 RecursivelyDeleteTriviallyDeadInstructions(OldCond);
614 DeleteDeadPHIs(CountedExitBlock);
615
616 ++NumCTRLoops;
617 return MadeChange;
618 }
619
620 #ifndef NDEBUG
clobbersCTR(const MachineInstr * MI)621 static bool clobbersCTR(const MachineInstr *MI) {
622 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
623 const MachineOperand &MO = MI->getOperand(i);
624 if (MO.isReg()) {
625 if (MO.isDef() && (MO.getReg() == PPC::CTR || MO.getReg() == PPC::CTR8))
626 return true;
627 } else if (MO.isRegMask()) {
628 if (MO.clobbersPhysReg(PPC::CTR) || MO.clobbersPhysReg(PPC::CTR8))
629 return true;
630 }
631 }
632
633 return false;
634 }
635
verifyCTRBranch(MachineBasicBlock * MBB,MachineBasicBlock::iterator I)636 static bool verifyCTRBranch(MachineBasicBlock *MBB,
637 MachineBasicBlock::iterator I) {
638 MachineBasicBlock::iterator BI = I;
639 SmallSet<MachineBasicBlock *, 16> Visited;
640 SmallVector<MachineBasicBlock *, 8> Preds;
641 bool CheckPreds;
642
643 if (I == MBB->begin()) {
644 Visited.insert(MBB);
645 goto queue_preds;
646 } else
647 --I;
648
649 check_block:
650 Visited.insert(MBB);
651 if (I == MBB->end())
652 goto queue_preds;
653
654 CheckPreds = true;
655 for (MachineBasicBlock::iterator IE = MBB->begin();; --I) {
656 unsigned Opc = I->getOpcode();
657 if (Opc == PPC::MTCTRloop || Opc == PPC::MTCTR8loop) {
658 CheckPreds = false;
659 break;
660 }
661
662 if (I != BI && clobbersCTR(I)) {
663 DEBUG(dbgs() << "BB#" << MBB->getNumber() << " (" <<
664 MBB->getFullName() << ") instruction " << *I <<
665 " clobbers CTR, invalidating " << "BB#" <<
666 BI->getParent()->getNumber() << " (" <<
667 BI->getParent()->getFullName() << ") instruction " <<
668 *BI << "\n");
669 return false;
670 }
671
672 if (I == IE)
673 break;
674 }
675
676 if (!CheckPreds && Preds.empty())
677 return true;
678
679 if (CheckPreds) {
680 queue_preds:
681 if (MachineFunction::iterator(MBB) == MBB->getParent()->begin()) {
682 DEBUG(dbgs() << "Unable to find a MTCTR instruction for BB#" <<
683 BI->getParent()->getNumber() << " (" <<
684 BI->getParent()->getFullName() << ") instruction " <<
685 *BI << "\n");
686 return false;
687 }
688
689 for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
690 PIE = MBB->pred_end(); PI != PIE; ++PI)
691 Preds.push_back(*PI);
692 }
693
694 do {
695 MBB = Preds.pop_back_val();
696 if (!Visited.count(MBB)) {
697 I = MBB->getLastNonDebugInstr();
698 goto check_block;
699 }
700 } while (!Preds.empty());
701
702 return true;
703 }
704
runOnMachineFunction(MachineFunction & MF)705 bool PPCCTRLoopsVerify::runOnMachineFunction(MachineFunction &MF) {
706 MDT = &getAnalysis<MachineDominatorTree>();
707
708 // Verify that all bdnz/bdz instructions are dominated by a loop mtctr before
709 // any other instructions that might clobber the ctr register.
710 for (MachineFunction::iterator I = MF.begin(), IE = MF.end();
711 I != IE; ++I) {
712 MachineBasicBlock *MBB = &*I;
713 if (!MDT->isReachableFromEntry(MBB))
714 continue;
715
716 for (MachineBasicBlock::iterator MII = MBB->getFirstTerminator(),
717 MIIE = MBB->end(); MII != MIIE; ++MII) {
718 unsigned Opc = MII->getOpcode();
719 if (Opc == PPC::BDNZ8 || Opc == PPC::BDNZ ||
720 Opc == PPC::BDZ8 || Opc == PPC::BDZ)
721 if (!verifyCTRBranch(MBB, MII))
722 llvm_unreachable("Invalid PPC CTR loop!");
723 }
724 }
725
726 return false;
727 }
728 #endif // NDEBUG
729