Bug Summary

File:lib/Target/PowerPC/PPCCTRLoops.cpp
Location:line 286, column 38
Description:Value stored to 'Opcode' is never read

Annotated Source Code

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
60using namespace llvm;
61
62#define DEBUG_TYPE"ctrloops" "ctrloops"
63
64#ifndef NDEBUG
65static cl::opt<int> CTRLoopLimit("ppc-max-ctrloop", cl::Hidden, cl::init(-1));
66#endif
67
68STATISTIC(NumCTRLoops, "Number of loops converted to CTR loops")static llvm::Statistic NumCTRLoops = { "ctrloops", "Number of loops converted to CTR loops"
, 0, 0 };
69
70namespace llvm {
71 void initializePPCCTRLoopsPass(PassRegistry&);
72#ifndef NDEBUG
73 void initializePPCCTRLoopsVerifyPass(PassRegistry&);
74#endif
75}
76
77namespace {
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
146INITIALIZE_PASS_BEGIN(PPCCTRLoops, "ppc-ctr-loops", "PowerPC CTR Loops",static void* initializePPCCTRLoopsPassOnce(PassRegistry &
Registry) {
147 false, false)static void* initializePPCCTRLoopsPassOnce(PassRegistry &
Registry) {
148INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
149INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry);
150INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)initializeScalarEvolutionWrapperPassPass(Registry);
151INITIALIZE_PASS_END(PPCCTRLoops, "ppc-ctr-loops", "PowerPC CTR Loops",PassInfo *PI = new PassInfo("PowerPC CTR Loops", "ppc-ctr-loops"
, & PPCCTRLoops ::ID, PassInfo::NormalCtor_t(callDefaultCtor
< PPCCTRLoops >), false, false); Registry.registerPass(
*PI, true); return PI; } void llvm::initializePPCCTRLoopsPass
(PassRegistry &Registry) { static volatile sys::cas_flag initialized
= 0; sys::cas_flag old_val = sys::CompareAndSwap(&initialized
, 1, 0); if (old_val == 0) { initializePPCCTRLoopsPassOnce(Registry
); sys::MemoryFence(); ; ; initialized = 2; ; } else { sys::cas_flag
tmp = initialized; sys::MemoryFence(); while (tmp != 2) { tmp
= initialized; sys::MemoryFence(); } } ; }
152 false, false)PassInfo *PI = new PassInfo("PowerPC CTR Loops", "ppc-ctr-loops"
, & PPCCTRLoops ::ID, PassInfo::NormalCtor_t(callDefaultCtor
< PPCCTRLoops >), false, false); Registry.registerPass(
*PI, true); return PI; } void llvm::initializePPCCTRLoopsPass
(PassRegistry &Registry) { static volatile sys::cas_flag initialized
= 0; sys::cas_flag old_val = sys::CompareAndSwap(&initialized
, 1, 0); if (old_val == 0) { initializePPCCTRLoopsPassOnce(Registry
); sys::MemoryFence(); ; ; initialized = 2; ; } else { sys::cas_flag
tmp = initialized; sys::MemoryFence(); while (tmp != 2) { tmp
= initialized; sys::MemoryFence(); } } ; }
153
154FunctionPass *llvm::createPPCCTRLoops(PPCTargetMachine &TM) {
155 return new PPCCTRLoops(TM);
156}
157
158#ifndef NDEBUG
159INITIALIZE_PASS_BEGIN(PPCCTRLoopsVerify, "ppc-ctr-loops-verify",static void* initializePPCCTRLoopsVerifyPassOnce(PassRegistry
&Registry) {
160 "PowerPC CTR Loops Verify", false, false)static void* initializePPCCTRLoopsVerifyPassOnce(PassRegistry
&Registry) {
161INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)initializeMachineDominatorTreePass(Registry);
162INITIALIZE_PASS_END(PPCCTRLoopsVerify, "ppc-ctr-loops-verify",PassInfo *PI = new PassInfo("PowerPC CTR Loops Verify", "ppc-ctr-loops-verify"
, & PPCCTRLoopsVerify ::ID, PassInfo::NormalCtor_t(callDefaultCtor
< PPCCTRLoopsVerify >), false, false); Registry.registerPass
(*PI, true); return PI; } void llvm::initializePPCCTRLoopsVerifyPass
(PassRegistry &Registry) { static volatile sys::cas_flag initialized
= 0; sys::cas_flag old_val = sys::CompareAndSwap(&initialized
, 1, 0); if (old_val == 0) { initializePPCCTRLoopsVerifyPassOnce
(Registry); sys::MemoryFence(); ; ; initialized = 2; ; } else
{ sys::cas_flag tmp = initialized; sys::MemoryFence(); while
(tmp != 2) { tmp = initialized; sys::MemoryFence(); } } ; }
163 "PowerPC CTR Loops Verify", false, false)PassInfo *PI = new PassInfo("PowerPC CTR Loops Verify", "ppc-ctr-loops-verify"
, & PPCCTRLoopsVerify ::ID, PassInfo::NormalCtor_t(callDefaultCtor
< PPCCTRLoopsVerify >), false, false); Registry.registerPass
(*PI, true); return PI; } void llvm::initializePPCCTRLoopsVerifyPass
(PassRegistry &Registry) { static volatile sys::cas_flag initialized
= 0; sys::cas_flag old_val = sys::CompareAndSwap(&initialized
, 1, 0); if (old_val == 0) { initializePPCCTRLoopsVerifyPassOnce
(Registry); sys::MemoryFence(); ; ; initialized = 2; ; } else
{ sys::cas_flag tmp = initialized; sys::MemoryFence(); while
(tmp != 2) { tmp = initialized; sys::MemoryFence(); } } ; }
164
165FunctionPass *llvm::createPPCCTRLoopsVerify() {
166 return new PPCCTRLoopsVerify();
167}
168#endif // NDEBUG
169
170bool 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
190static 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.
199static 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
212bool 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;
Value stored to 'Opcode' is never read
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
418bool 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 " <<do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "Exit Count for " << *L
<< " from block " << (*I)->getName() <<
": " << *EC << "\n"; } } while (0)
462 (*I)->getName() << ": " << *EC << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "Exit Count for " << *L
<< " from block " << (*I)->getName() <<
": " << *EC << "\n"; } } while (0);
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")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "Preheader for exit count: " <<
Preheader->getName() << "\n"; } } while (0);
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
575static 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
590static 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
603check_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() << " (" <<do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "BB#" << MBB->getNumber
() << " (" << MBB->getFullName() << ") instruction "
<< *I << " clobbers CTR, invalidating " <<
"BB#" << BI->getParent()->getNumber() << " ("
<< BI->getParent()->getFullName() << ") instruction "
<< *BI << "\n"; } } while (0)
618 MBB->getFullName() << ") instruction " << *I <<do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "BB#" << MBB->getNumber
() << " (" << MBB->getFullName() << ") instruction "
<< *I << " clobbers CTR, invalidating " <<
"BB#" << BI->getParent()->getNumber() << " ("
<< BI->getParent()->getFullName() << ") instruction "
<< *BI << "\n"; } } while (0)
619 " clobbers CTR, invalidating " << "BB#" <<do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "BB#" << MBB->getNumber
() << " (" << MBB->getFullName() << ") instruction "
<< *I << " clobbers CTR, invalidating " <<
"BB#" << BI->getParent()->getNumber() << " ("
<< BI->getParent()->getFullName() << ") instruction "
<< *BI << "\n"; } } while (0)
620 BI->getParent()->getNumber() << " (" <<do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "BB#" << MBB->getNumber
() << " (" << MBB->getFullName() << ") instruction "
<< *I << " clobbers CTR, invalidating " <<
"BB#" << BI->getParent()->getNumber() << " ("
<< BI->getParent()->getFullName() << ") instruction "
<< *BI << "\n"; } } while (0)
621 BI->getParent()->getFullName() << ") instruction " <<do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "BB#" << MBB->getNumber
() << " (" << MBB->getFullName() << ") instruction "
<< *I << " clobbers CTR, invalidating " <<
"BB#" << BI->getParent()->getNumber() << " ("
<< BI->getParent()->getFullName() << ") instruction "
<< *BI << "\n"; } } while (0)
622 *BI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "BB#" << MBB->getNumber
() << " (" << MBB->getFullName() << ") instruction "
<< *I << " clobbers CTR, invalidating " <<
"BB#" << BI->getParent()->getNumber() << " ("
<< BI->getParent()->getFullName() << ") instruction "
<< *BI << "\n"; } } while (0);
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) {
634queue_preds:
635 if (MachineFunction::iterator(MBB) == MBB->getParent()->begin()) {
636 DEBUG(dbgs() << "Unable to find a MTCTR instruction for BB#" <<do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "Unable to find a MTCTR instruction for BB#"
<< BI->getParent()->getNumber() << " (" <<
BI->getParent()->getFullName() << ") instruction "
<< *BI << "\n"; } } while (0)
637 BI->getParent()->getNumber() << " (" <<do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "Unable to find a MTCTR instruction for BB#"
<< BI->getParent()->getNumber() << " (" <<
BI->getParent()->getFullName() << ") instruction "
<< *BI << "\n"; } } while (0)
638 BI->getParent()->getFullName() << ") instruction " <<do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "Unable to find a MTCTR instruction for BB#"
<< BI->getParent()->getNumber() << " (" <<
BI->getParent()->getFullName() << ") instruction "
<< *BI << "\n"; } } while (0)
639 *BI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "Unable to find a MTCTR instruction for BB#"
<< BI->getParent()->getNumber() << " (" <<
BI->getParent()->getFullName() << ") instruction "
<< *BI << "\n"; } } while (0);
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
659bool 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!")::llvm::llvm_unreachable_internal("Invalid PPC CTR loop!", "/tmp/buildd/llvm-toolchain-snapshot-3.8~svn246424/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 676);
677 }
678 }
679
680 return false;
681}
682#endif // NDEBUG
683