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<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
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(ScalarEvolution)initializeScalarEvolutionPass(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(); AnnotateIgnoreWritesBegin("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 152); AnnotateHappensBefore("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 152, &initialized); initialized = 2; AnnotateIgnoreWritesEnd
("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 152); } else { sys::cas_flag tmp = initialized; sys::MemoryFence
(); while (tmp != 2) { tmp = initialized; sys::MemoryFence();
} } AnnotateHappensAfter("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 152, &initialized); }
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(); AnnotateIgnoreWritesBegin("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 152); AnnotateHappensBefore("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 152, &initialized); initialized = 2; AnnotateIgnoreWritesEnd
("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 152); } else { sys::cas_flag tmp = initialized; sys::MemoryFence
(); while (tmp != 2) { tmp = initialized; sys::MemoryFence();
} } AnnotateHappensAfter("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 152, &initialized); }
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(); AnnotateIgnoreWritesBegin("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 163); AnnotateHappensBefore("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 163, &initialized); initialized = 2; AnnotateIgnoreWritesEnd
("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 163); } else { sys::cas_flag tmp = initialized; sys::MemoryFence
(); while (tmp != 2) { tmp = initialized; sys::MemoryFence();
} } AnnotateHappensAfter("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 163, &initialized); }
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(); AnnotateIgnoreWritesBegin("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 163); AnnotateHappensBefore("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 163, &initialized); initialized = 2; AnnotateIgnoreWritesEnd
("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 163); } else { sys::cas_flag tmp = initialized; sys::MemoryFence
(); while (tmp != 2) { tmp = initialized; sys::MemoryFence();
} } AnnotateHappensAfter("/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 163, &initialized); }
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<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
191static 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.
200static 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
213bool 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 = TM->getSubtargetImpl()->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 MVT VTy =
355 TLI->getSimpleValueType(CI->getArgOperand(0)->getType(), true);
356 if (VTy == MVT::Other)
357 return true;
358
359 if (TLI->isOperationLegalOrCustom(Opcode, VTy))
360 continue;
361 else if (VTy.isVector() &&
362 TLI->isOperationLegalOrCustom(Opcode, VTy.getScalarType()))
363 continue;
364
365 return true;
366 }
367 }
368
369 return true;
370 } else if (isa<BinaryOperator>(J) &&
371 J->getType()->getScalarType()->isPPC_FP128Ty()) {
372 // Most operations on ppc_f128 values become calls.
373 return true;
374 } else if (isa<UIToFPInst>(J) || isa<SIToFPInst>(J) ||
375 isa<FPToUIInst>(J) || isa<FPToSIInst>(J)) {
376 CastInst *CI = cast<CastInst>(J);
377 if (CI->getSrcTy()->getScalarType()->isPPC_FP128Ty() ||
378 CI->getDestTy()->getScalarType()->isPPC_FP128Ty() ||
379 isLargeIntegerTy(TT.isArch32Bit(), CI->getSrcTy()->getScalarType()) ||
380 isLargeIntegerTy(TT.isArch32Bit(), CI->getDestTy()->getScalarType()))
381 return true;
382 } else if (isLargeIntegerTy(TT.isArch32Bit(),
383 J->getType()->getScalarType()) &&
384 (J->getOpcode() == Instruction::UDiv ||
385 J->getOpcode() == Instruction::SDiv ||
386 J->getOpcode() == Instruction::URem ||
387 J->getOpcode() == Instruction::SRem)) {
388 return true;
389 } else if (TT.isArch32Bit() &&
390 isLargeIntegerTy(false, J->getType()->getScalarType()) &&
391 (J->getOpcode() == Instruction::Shl ||
392 J->getOpcode() == Instruction::AShr ||
393 J->getOpcode() == Instruction::LShr)) {
394 // Only on PPC32, for 128-bit integers (specifically not 64-bit
395 // integers), these might be runtime calls.
396 return true;
397 } else if (isa<IndirectBrInst>(J) || isa<InvokeInst>(J)) {
398 // On PowerPC, indirect jumps use the counter register.
399 return true;
400 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(J)) {
401 if (!TM)
402 return true;
403 const TargetLowering *TLI = TM->getSubtargetImpl()->getTargetLowering();
404
405 if (SI->getNumCases() + 1 >= (unsigned)TLI->getMinimumJumpTableEntries())
406 return true;
407 }
408 for (Value *Operand : J->operands())
409 if (memAddrUsesCTR(TM, Operand))
410 return true;
411 }
412
413 return false;
414}
415
416bool PPCCTRLoops::convertToCTRLoop(Loop *L) {
417 bool MadeChange = false;
418
419 Triple TT = Triple(L->getHeader()->getParent()->getParent()->
420 getTargetTriple());
421 if (!TT.isArch32Bit() && !TT.isArch64Bit())
422 return MadeChange; // Unknown arch. type.
423
424 // Process nested loops first.
425 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) {
426 MadeChange |= convertToCTRLoop(*I);
427 }
428
429 // If a nested loop has been converted, then we can't convert this loop.
430 if (MadeChange)
431 return MadeChange;
432
433#ifndef NDEBUG
434 // Stop trying after reaching the limit (if any).
435 int Limit = CTRLoopLimit;
436 if (Limit >= 0) {
437 if (Counter >= CTRLoopLimit)
438 return false;
439 Counter++;
440 }
441#endif
442
443 // We don't want to spill/restore the counter register, and so we don't
444 // want to use the counter register if the loop contains calls.
445 for (Loop::block_iterator I = L->block_begin(), IE = L->block_end();
446 I != IE; ++I)
447 if (mightUseCTR(TT, *I))
448 return MadeChange;
449
450 SmallVector<BasicBlock*, 4> ExitingBlocks;
451 L->getExitingBlocks(ExitingBlocks);
452
453 BasicBlock *CountedExitBlock = nullptr;
454 const SCEV *ExitCount = nullptr;
455 BranchInst *CountedExitBranch = nullptr;
456 for (SmallVectorImpl<BasicBlock *>::iterator I = ExitingBlocks.begin(),
457 IE = ExitingBlocks.end(); I != IE; ++I) {
458 const SCEV *EC = SE->getExitCount(L, *I);
459 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)
460 (*I)->getName() << ": " << *EC << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("ctrloops")) { dbgs() << "Exit Count for " << *L
<< " from block " << (*I)->getName() <<
": " << *EC << "\n"; } } while (0);
461 if (isa<SCEVCouldNotCompute>(EC))
462 continue;
463 if (const SCEVConstant *ConstEC = dyn_cast<SCEVConstant>(EC)) {
464 if (ConstEC->getValue()->isZero())
465 continue;
466 } else if (!SE->isLoopInvariant(EC, L))
467 continue;
468
469 if (SE->getTypeSizeInBits(EC->getType()) > (TT.isArch64Bit() ? 64 : 32))
470 continue;
471
472 // We now have a loop-invariant count of loop iterations (which is not the
473 // constant zero) for which we know that this loop will not exit via this
474 // exisiting block.
475
476 // We need to make sure that this block will run on every loop iteration.
477 // For this to be true, we must dominate all blocks with backedges. Such
478 // blocks are in-loop predecessors to the header block.
479 bool NotAlways = false;
480 for (pred_iterator PI = pred_begin(L->getHeader()),
481 PIE = pred_end(L->getHeader()); PI != PIE; ++PI) {
482 if (!L->contains(*PI))
483 continue;
484
485 if (!DT->dominates(*I, *PI)) {
486 NotAlways = true;
487 break;
488 }
489 }
490
491 if (NotAlways)
492 continue;
493
494 // Make sure this blocks ends with a conditional branch.
495 Instruction *TI = (*I)->getTerminator();
496 if (!TI)
497 continue;
498
499 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
500 if (!BI->isConditional())
501 continue;
502
503 CountedExitBranch = BI;
504 } else
505 continue;
506
507 // Note that this block may not be the loop latch block, even if the loop
508 // has a latch block.
509 CountedExitBlock = *I;
510 ExitCount = EC;
511 break;
512 }
513
514 if (!CountedExitBlock)
515 return MadeChange;
516
517 BasicBlock *Preheader = L->getLoopPreheader();
518
519 // If we don't have a preheader, then insert one. If we already have a
520 // preheader, then we can use it (except if the preheader contains a use of
521 // the CTR register because some such uses might be reordered by the
522 // selection DAG after the mtctr instruction).
523 if (!Preheader || mightUseCTR(TT, Preheader))
524 Preheader = InsertPreheaderForLoop(L, this);
525 if (!Preheader)
526 return MadeChange;
527
528 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);
529
530 // Insert the count into the preheader and replace the condition used by the
531 // selected branch.
532 MadeChange = true;
533
534 SCEVExpander SCEVE(*SE, "loopcnt");
535 LLVMContext &C = SE->getContext();
536 Type *CountType = TT.isArch64Bit() ? Type::getInt64Ty(C) :
537 Type::getInt32Ty(C);
538 if (!ExitCount->getType()->isPointerTy() &&
539 ExitCount->getType() != CountType)
540 ExitCount = SE->getZeroExtendExpr(ExitCount, CountType);
541 ExitCount = SE->getAddExpr(ExitCount,
542 SE->getConstant(CountType, 1));
543 Value *ECValue = SCEVE.expandCodeFor(ExitCount, CountType,
544 Preheader->getTerminator());
545
546 IRBuilder<> CountBuilder(Preheader->getTerminator());
547 Module *M = Preheader->getParent()->getParent();
548 Value *MTCTRFunc = Intrinsic::getDeclaration(M, Intrinsic::ppc_mtctr,
549 CountType);
550 CountBuilder.CreateCall(MTCTRFunc, ECValue);
551
552 IRBuilder<> CondBuilder(CountedExitBranch);
553 Value *DecFunc =
554 Intrinsic::getDeclaration(M, Intrinsic::ppc_is_decremented_ctr_nonzero);
555 Value *NewCond = CondBuilder.CreateCall(DecFunc);
556 Value *OldCond = CountedExitBranch->getCondition();
557 CountedExitBranch->setCondition(NewCond);
558
559 // The false branch must exit the loop.
560 if (!L->contains(CountedExitBranch->getSuccessor(0)))
561 CountedExitBranch->swapSuccessors();
562
563 // The old condition may be dead now, and may have even created a dead PHI
564 // (the original induction variable).
565 RecursivelyDeleteTriviallyDeadInstructions(OldCond);
566 DeleteDeadPHIs(CountedExitBlock);
567
568 ++NumCTRLoops;
569 return MadeChange;
570}
571
572#ifndef NDEBUG
573static bool clobbersCTR(const MachineInstr *MI) {
574 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
575 const MachineOperand &MO = MI->getOperand(i);
576 if (MO.isReg()) {
577 if (MO.isDef() && (MO.getReg() == PPC::CTR || MO.getReg() == PPC::CTR8))
578 return true;
579 } else if (MO.isRegMask()) {
580 if (MO.clobbersPhysReg(PPC::CTR) || MO.clobbersPhysReg(PPC::CTR8))
581 return true;
582 }
583 }
584
585 return false;
586}
587
588static bool verifyCTRBranch(MachineBasicBlock *MBB,
589 MachineBasicBlock::iterator I) {
590 MachineBasicBlock::iterator BI = I;
591 SmallSet<MachineBasicBlock *, 16> Visited;
592 SmallVector<MachineBasicBlock *, 8> Preds;
593 bool CheckPreds;
594
595 if (I == MBB->begin()) {
596 Visited.insert(MBB);
597 goto queue_preds;
598 } else
599 --I;
600
601check_block:
602 Visited.insert(MBB);
603 if (I == MBB->end())
604 goto queue_preds;
605
606 CheckPreds = true;
607 for (MachineBasicBlock::iterator IE = MBB->begin();; --I) {
608 unsigned Opc = I->getOpcode();
609 if (Opc == PPC::MTCTRloop || Opc == PPC::MTCTR8loop) {
610 CheckPreds = false;
611 break;
612 }
613
614 if (I != BI && clobbersCTR(I)) {
615 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)
616 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)
617 " 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)
618 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)
619 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)
620 *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);
621 return false;
622 }
623
624 if (I == IE)
625 break;
626 }
627
628 if (!CheckPreds && Preds.empty())
629 return true;
630
631 if (CheckPreds) {
632queue_preds:
633 if (MachineFunction::iterator(MBB) == MBB->getParent()->begin()) {
634 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)
635 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)
636 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)
637 *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);
638 return false;
639 }
640
641 for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
642 PIE = MBB->pred_end(); PI != PIE; ++PI)
643 Preds.push_back(*PI);
644 }
645
646 do {
647 MBB = Preds.pop_back_val();
648 if (!Visited.count(MBB)) {
649 I = MBB->getLastNonDebugInstr();
650 goto check_block;
651 }
652 } while (!Preds.empty());
653
654 return true;
655}
656
657bool PPCCTRLoopsVerify::runOnMachineFunction(MachineFunction &MF) {
658 MDT = &getAnalysis<MachineDominatorTree>();
659
660 // Verify that all bdnz/bdz instructions are dominated by a loop mtctr before
661 // any other instructions that might clobber the ctr register.
662 for (MachineFunction::iterator I = MF.begin(), IE = MF.end();
663 I != IE; ++I) {
664 MachineBasicBlock *MBB = I;
665 if (!MDT->isReachableFromEntry(MBB))
666 continue;
667
668 for (MachineBasicBlock::iterator MII = MBB->getFirstTerminator(),
669 MIIE = MBB->end(); MII != MIIE; ++MII) {
670 unsigned Opc = MII->getOpcode();
671 if (Opc == PPC::BDNZ8 || Opc == PPC::BDNZ ||
672 Opc == PPC::BDZ8 || Opc == PPC::BDZ)
673 if (!verifyCTRBranch(MBB, MII))
674 llvm_unreachable("Invalid PPC CTR loop!")::llvm::llvm_unreachable_internal("Invalid PPC CTR loop!", "/tmp/buildd/llvm-toolchain-snapshot-3.7~svn227492/lib/Target/PowerPC/PPCCTRLoops.cpp"
, 674);
675 }
676 }
677
678 return false;
679}
680#endif // NDEBUG
681