LLVM  6.0.0svn
CodeGenPrepare.cpp
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1 //===- CodeGenPrepare.cpp - Prepare a function for code generation --------===//
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 munges the code in the input function to better prepare it for
11 // SelectionDAG-based code generation. This works around limitations in it's
12 // basic-block-at-a-time approach. It should eventually be removed.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/SetVector.h"
18 #include "llvm/ADT/SmallSet.h"
19 #include "llvm/ADT/Statistic.h"
22 #include "llvm/Analysis/CFG.h"
24 #include "llvm/Analysis/LoopInfo.h"
30 #include "llvm/CodeGen/Analysis.h"
31 #include "llvm/CodeGen/Passes.h"
33 #include "llvm/IR/CallSite.h"
34 #include "llvm/IR/Constants.h"
35 #include "llvm/IR/DataLayout.h"
36 #include "llvm/IR/DerivedTypes.h"
37 #include "llvm/IR/Dominators.h"
38 #include "llvm/IR/Function.h"
40 #include "llvm/IR/IRBuilder.h"
41 #include "llvm/IR/InlineAsm.h"
42 #include "llvm/IR/Instructions.h"
43 #include "llvm/IR/IntrinsicInst.h"
44 #include "llvm/IR/MDBuilder.h"
45 #include "llvm/IR/PatternMatch.h"
46 #include "llvm/IR/Statepoint.h"
47 #include "llvm/IR/ValueHandle.h"
48 #include "llvm/IR/ValueMap.h"
49 #include "llvm/Pass.h"
52 #include "llvm/Support/Debug.h"
63 
64 using namespace llvm;
65 using namespace llvm::PatternMatch;
66 
67 #define DEBUG_TYPE "codegenprepare"
68 
69 STATISTIC(NumBlocksElim, "Number of blocks eliminated");
70 STATISTIC(NumPHIsElim, "Number of trivial PHIs eliminated");
71 STATISTIC(NumGEPsElim, "Number of GEPs converted to casts");
72 STATISTIC(NumCmpUses, "Number of uses of Cmp expressions replaced with uses of "
73  "sunken Cmps");
74 STATISTIC(NumCastUses, "Number of uses of Cast expressions replaced with uses "
75  "of sunken Casts");
76 STATISTIC(NumMemoryInsts, "Number of memory instructions whose address "
77  "computations were sunk");
78 STATISTIC(NumExtsMoved, "Number of [s|z]ext instructions combined with loads");
79 STATISTIC(NumExtUses, "Number of uses of [s|z]ext instructions optimized");
80 STATISTIC(NumAndsAdded,
81  "Number of and mask instructions added to form ext loads");
82 STATISTIC(NumAndUses, "Number of uses of and mask instructions optimized");
83 STATISTIC(NumRetsDup, "Number of return instructions duplicated");
84 STATISTIC(NumDbgValueMoved, "Number of debug value instructions moved");
85 STATISTIC(NumSelectsExpanded, "Number of selects turned into branches");
86 STATISTIC(NumStoreExtractExposed, "Number of store(extractelement) exposed");
87 
88 STATISTIC(NumMemCmpCalls, "Number of memcmp calls");
89 STATISTIC(NumMemCmpNotConstant, "Number of memcmp calls without constant size");
90 STATISTIC(NumMemCmpGreaterThanMax,
91  "Number of memcmp calls with size greater than max size");
92 STATISTIC(NumMemCmpInlined, "Number of inlined memcmp calls");
93 
95  "disable-cgp-branch-opts", cl::Hidden, cl::init(false),
96  cl::desc("Disable branch optimizations in CodeGenPrepare"));
97 
98 static cl::opt<bool>
99  DisableGCOpts("disable-cgp-gc-opts", cl::Hidden, cl::init(false),
100  cl::desc("Disable GC optimizations in CodeGenPrepare"));
101 
103  "disable-cgp-select2branch", cl::Hidden, cl::init(false),
104  cl::desc("Disable select to branch conversion."));
105 
107  "addr-sink-using-gep", cl::Hidden, cl::init(true),
108  cl::desc("Address sinking in CGP using GEPs."));
109 
111  "enable-andcmp-sinking", cl::Hidden, cl::init(true),
112  cl::desc("Enable sinkinig and/cmp into branches."));
113 
115  "disable-cgp-store-extract", cl::Hidden, cl::init(false),
116  cl::desc("Disable store(extract) optimizations in CodeGenPrepare"));
117 
119  "stress-cgp-store-extract", cl::Hidden, cl::init(false),
120  cl::desc("Stress test store(extract) optimizations in CodeGenPrepare"));
121 
123  "disable-cgp-ext-ld-promotion", cl::Hidden, cl::init(false),
124  cl::desc("Disable ext(promotable(ld)) -> promoted(ext(ld)) optimization in "
125  "CodeGenPrepare"));
126 
128  "stress-cgp-ext-ld-promotion", cl::Hidden, cl::init(false),
129  cl::desc("Stress test ext(promotable(ld)) -> promoted(ext(ld)) "
130  "optimization in CodeGenPrepare"));
131 
133  "disable-preheader-prot", cl::Hidden, cl::init(false),
134  cl::desc("Disable protection against removing loop preheaders"));
135 
137  "profile-guided-section-prefix", cl::Hidden, cl::init(true), cl::ZeroOrMore,
138  cl::desc("Use profile info to add section prefix for hot/cold functions"));
139 
141  "cgp-freq-ratio-to-skip-merge", cl::Hidden, cl::init(2),
142  cl::desc("Skip merging empty blocks if (frequency of empty block) / "
143  "(frequency of destination block) is greater than this ratio"));
144 
146  "force-split-store", cl::Hidden, cl::init(false),
147  cl::desc("Force store splitting no matter what the target query says."));
148 
149 static cl::opt<bool>
150 EnableTypePromotionMerge("cgp-type-promotion-merge", cl::Hidden,
151  cl::desc("Enable merging of redundant sexts when one is dominating"
152  " the other."), cl::init(true));
153 
155  "memcmp-num-loads-per-block", cl::Hidden, cl::init(1),
156  cl::desc("The number of loads per basic block for inline expansion of "
157  "memcmp that is only being compared against zero."));
158 
159 namespace {
160 typedef SmallPtrSet<Instruction *, 16> SetOfInstrs;
161 typedef PointerIntPair<Type *, 1, bool> TypeIsSExt;
162 typedef DenseMap<Instruction *, TypeIsSExt> InstrToOrigTy;
163 typedef SmallVector<Instruction *, 16> SExts;
164 typedef DenseMap<Value *, SExts> ValueToSExts;
165 class TypePromotionTransaction;
166 
167  class CodeGenPrepare : public FunctionPass {
168  const TargetMachine *TM;
169  const TargetSubtargetInfo *SubtargetInfo;
170  const TargetLowering *TLI;
171  const TargetRegisterInfo *TRI;
172  const TargetTransformInfo *TTI;
173  const TargetLibraryInfo *TLInfo;
174  const LoopInfo *LI;
175  std::unique_ptr<BlockFrequencyInfo> BFI;
176  std::unique_ptr<BranchProbabilityInfo> BPI;
177 
178  /// As we scan instructions optimizing them, this is the next instruction
179  /// to optimize. Transforms that can invalidate this should update it.
180  BasicBlock::iterator CurInstIterator;
181 
182  /// Keeps track of non-local addresses that have been sunk into a block.
183  /// This allows us to avoid inserting duplicate code for blocks with
184  /// multiple load/stores of the same address.
185  ValueMap<Value*, Value*> SunkAddrs;
186 
187  /// Keeps track of all instructions inserted for the current function.
188  SetOfInstrs InsertedInsts;
189  /// Keeps track of the type of the related instruction before their
190  /// promotion for the current function.
191  InstrToOrigTy PromotedInsts;
192 
193  /// Keep track of instructions removed during promotion.
194  SetOfInstrs RemovedInsts;
195 
196  /// Keep track of sext chains based on their initial value.
197  DenseMap<Value *, Instruction *> SeenChainsForSExt;
198 
199  /// Keep track of SExt promoted.
200  ValueToSExts ValToSExtendedUses;
201 
202  /// True if CFG is modified in any way.
203  bool ModifiedDT;
204 
205  /// True if optimizing for size.
206  bool OptSize;
207 
208  /// DataLayout for the Function being processed.
209  const DataLayout *DL;
210 
211  public:
212  static char ID; // Pass identification, replacement for typeid
213  CodeGenPrepare()
214  : FunctionPass(ID), TM(nullptr), TLI(nullptr), TTI(nullptr),
215  DL(nullptr) {
217  }
218  bool runOnFunction(Function &F) override;
219 
220  StringRef getPassName() const override { return "CodeGen Prepare"; }
221 
222  void getAnalysisUsage(AnalysisUsage &AU) const override {
223  // FIXME: When we can selectively preserve passes, preserve the domtree.
228  }
229 
230  private:
231  bool eliminateFallThrough(Function &F);
232  bool eliminateMostlyEmptyBlocks(Function &F);
233  BasicBlock *findDestBlockOfMergeableEmptyBlock(BasicBlock *BB);
234  bool canMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
235  void eliminateMostlyEmptyBlock(BasicBlock *BB);
236  bool isMergingEmptyBlockProfitable(BasicBlock *BB, BasicBlock *DestBB,
237  bool isPreheader);
238  bool optimizeBlock(BasicBlock &BB, bool &ModifiedDT);
239  bool optimizeInst(Instruction *I, bool &ModifiedDT);
240  bool optimizeMemoryInst(Instruction *I, Value *Addr,
241  Type *AccessTy, unsigned AS);
242  bool optimizeInlineAsmInst(CallInst *CS);
243  bool optimizeCallInst(CallInst *CI, bool &ModifiedDT);
244  bool optimizeExt(Instruction *&I);
245  bool optimizeExtUses(Instruction *I);
246  bool optimizeLoadExt(LoadInst *I);
247  bool optimizeSelectInst(SelectInst *SI);
248  bool optimizeShuffleVectorInst(ShuffleVectorInst *SI);
249  bool optimizeSwitchInst(SwitchInst *CI);
250  bool optimizeExtractElementInst(Instruction *Inst);
251  bool dupRetToEnableTailCallOpts(BasicBlock *BB);
252  bool placeDbgValues(Function &F);
253  bool canFormExtLd(const SmallVectorImpl<Instruction *> &MovedExts,
254  LoadInst *&LI, Instruction *&Inst, bool HasPromoted);
255  bool tryToPromoteExts(TypePromotionTransaction &TPT,
256  const SmallVectorImpl<Instruction *> &Exts,
257  SmallVectorImpl<Instruction *> &ProfitablyMovedExts,
258  unsigned CreatedInstsCost = 0);
259  bool mergeSExts(Function &F);
260  bool performAddressTypePromotion(
261  Instruction *&Inst,
262  bool AllowPromotionWithoutCommonHeader,
263  bool HasPromoted, TypePromotionTransaction &TPT,
264  SmallVectorImpl<Instruction *> &SpeculativelyMovedExts);
265  bool splitBranchCondition(Function &F);
266  bool simplifyOffsetableRelocate(Instruction &I);
267  bool splitIndirectCriticalEdges(Function &F);
268  };
269 }
270 
271 char CodeGenPrepare::ID = 0;
272 INITIALIZE_PASS_BEGIN(CodeGenPrepare, DEBUG_TYPE,
273  "Optimize for code generation", false, false)
276  "Optimize for code generation", false, false)
277 
278 FunctionPass *llvm::createCodeGenPreparePass() { return new CodeGenPrepare(); }
279 
280 bool CodeGenPrepare::runOnFunction(Function &F) {
281  if (skipFunction(F))
282  return false;
283 
284  DL = &F.getParent()->getDataLayout();
285 
286  bool EverMadeChange = false;
287  // Clear per function information.
288  InsertedInsts.clear();
289  PromotedInsts.clear();
290  BFI.reset();
291  BPI.reset();
292 
293  ModifiedDT = false;
294  if (auto *TPC = getAnalysisIfAvailable<TargetPassConfig>()) {
295  TM = &TPC->getTM<TargetMachine>();
296  SubtargetInfo = TM->getSubtargetImpl(F);
297  TLI = SubtargetInfo->getTargetLowering();
298  TRI = SubtargetInfo->getRegisterInfo();
299  }
300  TLInfo = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
301  TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
302  LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
303  OptSize = F.optForSize();
304 
306  ProfileSummaryInfo *PSI =
307  getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
308  if (PSI->isFunctionHotInCallGraph(&F))
309  F.setSectionPrefix(".hot");
310  else if (PSI->isFunctionColdInCallGraph(&F))
311  F.setSectionPrefix(".unlikely");
312  }
313 
314  /// This optimization identifies DIV instructions that can be
315  /// profitably bypassed and carried out with a shorter, faster divide.
316  if (!OptSize && TLI && TLI->isSlowDivBypassed()) {
317  const DenseMap<unsigned int, unsigned int> &BypassWidths =
318  TLI->getBypassSlowDivWidths();
319  BasicBlock* BB = &*F.begin();
320  while (BB != nullptr) {
321  // bypassSlowDivision may create new BBs, but we don't want to reapply the
322  // optimization to those blocks.
323  BasicBlock* Next = BB->getNextNode();
324  EverMadeChange |= bypassSlowDivision(BB, BypassWidths);
325  BB = Next;
326  }
327  }
328 
329  // Eliminate blocks that contain only PHI nodes and an
330  // unconditional branch.
331  EverMadeChange |= eliminateMostlyEmptyBlocks(F);
332 
333  // llvm.dbg.value is far away from the value then iSel may not be able
334  // handle it properly. iSel will drop llvm.dbg.value if it can not
335  // find a node corresponding to the value.
336  EverMadeChange |= placeDbgValues(F);
337 
338  if (!DisableBranchOpts)
339  EverMadeChange |= splitBranchCondition(F);
340 
341  // Split some critical edges where one of the sources is an indirect branch,
342  // to help generate sane code for PHIs involving such edges.
343  EverMadeChange |= splitIndirectCriticalEdges(F);
344 
345  bool MadeChange = true;
346  while (MadeChange) {
347  MadeChange = false;
348  SeenChainsForSExt.clear();
349  ValToSExtendedUses.clear();
350  RemovedInsts.clear();
351  for (Function::iterator I = F.begin(); I != F.end(); ) {
352  BasicBlock *BB = &*I++;
353  bool ModifiedDTOnIteration = false;
354  MadeChange |= optimizeBlock(*BB, ModifiedDTOnIteration);
355 
356  // Restart BB iteration if the dominator tree of the Function was changed
357  if (ModifiedDTOnIteration)
358  break;
359  }
360  if (EnableTypePromotionMerge && !ValToSExtendedUses.empty())
361  MadeChange |= mergeSExts(F);
362 
363  // Really free removed instructions during promotion.
364  for (Instruction *I : RemovedInsts)
365  I->deleteValue();
366 
367  EverMadeChange |= MadeChange;
368  }
369 
370  SunkAddrs.clear();
371 
372  if (!DisableBranchOpts) {
373  MadeChange = false;
375  for (BasicBlock &BB : F) {
376  SmallVector<BasicBlock *, 2> Successors(succ_begin(&BB), succ_end(&BB));
377  MadeChange |= ConstantFoldTerminator(&BB, true);
378  if (!MadeChange) continue;
379 
381  II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
382  if (pred_begin(*II) == pred_end(*II))
383  WorkList.insert(*II);
384  }
385 
386  // Delete the dead blocks and any of their dead successors.
387  MadeChange |= !WorkList.empty();
388  while (!WorkList.empty()) {
389  BasicBlock *BB = *WorkList.begin();
390  WorkList.erase(BB);
391  SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
392 
393  DeleteDeadBlock(BB);
394 
396  II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
397  if (pred_begin(*II) == pred_end(*II))
398  WorkList.insert(*II);
399  }
400 
401  // Merge pairs of basic blocks with unconditional branches, connected by
402  // a single edge.
403  if (EverMadeChange || MadeChange)
404  MadeChange |= eliminateFallThrough(F);
405 
406  EverMadeChange |= MadeChange;
407  }
408 
409  if (!DisableGCOpts) {
410  SmallVector<Instruction *, 2> Statepoints;
411  for (BasicBlock &BB : F)
412  for (Instruction &I : BB)
413  if (isStatepoint(I))
414  Statepoints.push_back(&I);
415  for (auto &I : Statepoints)
416  EverMadeChange |= simplifyOffsetableRelocate(*I);
417  }
418 
419  return EverMadeChange;
420 }
421 
422 /// Merge basic blocks which are connected by a single edge, where one of the
423 /// basic blocks has a single successor pointing to the other basic block,
424 /// which has a single predecessor.
425 bool CodeGenPrepare::eliminateFallThrough(Function &F) {
426  bool Changed = false;
427  // Scan all of the blocks in the function, except for the entry block.
428  for (Function::iterator I = std::next(F.begin()), E = F.end(); I != E;) {
429  BasicBlock *BB = &*I++;
430  // If the destination block has a single pred, then this is a trivial
431  // edge, just collapse it.
432  BasicBlock *SinglePred = BB->getSinglePredecessor();
433 
434  // Don't merge if BB's address is taken.
435  if (!SinglePred || SinglePred == BB || BB->hasAddressTaken()) continue;
436 
437  BranchInst *Term = dyn_cast<BranchInst>(SinglePred->getTerminator());
438  if (Term && !Term->isConditional()) {
439  Changed = true;
440  DEBUG(dbgs() << "To merge:\n"<< *SinglePred << "\n\n\n");
441  // Remember if SinglePred was the entry block of the function.
442  // If so, we will need to move BB back to the entry position.
443  bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
444  MergeBasicBlockIntoOnlyPred(BB, nullptr);
445 
446  if (isEntry && BB != &BB->getParent()->getEntryBlock())
447  BB->moveBefore(&BB->getParent()->getEntryBlock());
448 
449  // We have erased a block. Update the iterator.
450  I = BB->getIterator();
451  }
452  }
453  return Changed;
454 }
455 
456 /// Find a destination block from BB if BB is mergeable empty block.
457 BasicBlock *CodeGenPrepare::findDestBlockOfMergeableEmptyBlock(BasicBlock *BB) {
458  // If this block doesn't end with an uncond branch, ignore it.
460  if (!BI || !BI->isUnconditional())
461  return nullptr;
462 
463  // If the instruction before the branch (skipping debug info) isn't a phi
464  // node, then other stuff is happening here.
465  BasicBlock::iterator BBI = BI->getIterator();
466  if (BBI != BB->begin()) {
467  --BBI;
468  while (isa<DbgInfoIntrinsic>(BBI)) {
469  if (BBI == BB->begin())
470  break;
471  --BBI;
472  }
473  if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI))
474  return nullptr;
475  }
476 
477  // Do not break infinite loops.
478  BasicBlock *DestBB = BI->getSuccessor(0);
479  if (DestBB == BB)
480  return nullptr;
481 
482  if (!canMergeBlocks(BB, DestBB))
483  DestBB = nullptr;
484 
485  return DestBB;
486 }
487 
488 // Return the unique indirectbr predecessor of a block. This may return null
489 // even if such a predecessor exists, if it's not useful for splitting.
490 // If a predecessor is found, OtherPreds will contain all other (non-indirectbr)
491 // predecessors of BB.
492 static BasicBlock *
494  // If the block doesn't have any PHIs, we don't care about it, since there's
495  // no point in splitting it.
496  PHINode *PN = dyn_cast<PHINode>(BB->begin());
497  if (!PN)
498  return nullptr;
499 
500  // Verify we have exactly one IBR predecessor.
501  // Conservatively bail out if one of the other predecessors is not a "regular"
502  // terminator (that is, not a switch or a br).
503  BasicBlock *IBB = nullptr;
504  for (unsigned Pred = 0, E = PN->getNumIncomingValues(); Pred != E; ++Pred) {
505  BasicBlock *PredBB = PN->getIncomingBlock(Pred);
506  TerminatorInst *PredTerm = PredBB->getTerminator();
507  switch (PredTerm->getOpcode()) {
508  case Instruction::IndirectBr:
509  if (IBB)
510  return nullptr;
511  IBB = PredBB;
512  break;
513  case Instruction::Br:
514  case Instruction::Switch:
515  OtherPreds.push_back(PredBB);
516  continue;
517  default:
518  return nullptr;
519  }
520  }
521 
522  return IBB;
523 }
524 
525 // Split critical edges where the source of the edge is an indirectbr
526 // instruction. This isn't always possible, but we can handle some easy cases.
527 // This is useful because MI is unable to split such critical edges,
528 // which means it will not be able to sink instructions along those edges.
529 // This is especially painful for indirect branches with many successors, where
530 // we end up having to prepare all outgoing values in the origin block.
531 //
532 // Our normal algorithm for splitting critical edges requires us to update
533 // the outgoing edges of the edge origin block, but for an indirectbr this
534 // is hard, since it would require finding and updating the block addresses
535 // the indirect branch uses. But if a block only has a single indirectbr
536 // predecessor, with the others being regular branches, we can do it in a
537 // different way.
538 // Say we have A -> D, B -> D, I -> D where only I -> D is an indirectbr.
539 // We can split D into D0 and D1, where D0 contains only the PHIs from D,
540 // and D1 is the D block body. We can then duplicate D0 as D0A and D0B, and
541 // create the following structure:
542 // A -> D0A, B -> D0A, I -> D0B, D0A -> D1, D0B -> D1
543 bool CodeGenPrepare::splitIndirectCriticalEdges(Function &F) {
544  // Check whether the function has any indirectbrs, and collect which blocks
545  // they may jump to. Since most functions don't have indirect branches,
546  // this lowers the common case's overhead to O(Blocks) instead of O(Edges).
548  for (auto &BB : F) {
549  auto *IBI = dyn_cast<IndirectBrInst>(BB.getTerminator());
550  if (!IBI)
551  continue;
552 
553  for (unsigned Succ = 0, E = IBI->getNumSuccessors(); Succ != E; ++Succ)
554  Targets.insert(IBI->getSuccessor(Succ));
555  }
556 
557  if (Targets.empty())
558  return false;
559 
560  bool Changed = false;
561  for (BasicBlock *Target : Targets) {
563  BasicBlock *IBRPred = findIBRPredecessor(Target, OtherPreds);
564  // If we did not found an indirectbr, or the indirectbr is the only
565  // incoming edge, this isn't the kind of edge we're looking for.
566  if (!IBRPred || OtherPreds.empty())
567  continue;
568 
569  // Don't even think about ehpads/landingpads.
570  Instruction *FirstNonPHI = Target->getFirstNonPHI();
571  if (FirstNonPHI->isEHPad() || Target->isLandingPad())
572  continue;
573 
574  BasicBlock *BodyBlock = Target->splitBasicBlock(FirstNonPHI, ".split");
575  // It's possible Target was its own successor through an indirectbr.
576  // In this case, the indirectbr now comes from BodyBlock.
577  if (IBRPred == Target)
578  IBRPred = BodyBlock;
579 
580  // At this point Target only has PHIs, and BodyBlock has the rest of the
581  // block's body. Create a copy of Target that will be used by the "direct"
582  // preds.
583  ValueToValueMapTy VMap;
584  BasicBlock *DirectSucc = CloneBasicBlock(Target, VMap, ".clone", &F);
585 
586  for (BasicBlock *Pred : OtherPreds) {
587  // If the target is a loop to itself, then the terminator of the split
588  // block needs to be updated.
589  if (Pred == Target)
590  BodyBlock->getTerminator()->replaceUsesOfWith(Target, DirectSucc);
591  else
592  Pred->getTerminator()->replaceUsesOfWith(Target, DirectSucc);
593  }
594 
595  // Ok, now fix up the PHIs. We know the two blocks only have PHIs, and that
596  // they are clones, so the number of PHIs are the same.
597  // (a) Remove the edge coming from IBRPred from the "Direct" PHI
598  // (b) Leave that as the only edge in the "Indirect" PHI.
599  // (c) Merge the two in the body block.
600  BasicBlock::iterator Indirect = Target->begin(),
601  End = Target->getFirstNonPHI()->getIterator();
602  BasicBlock::iterator Direct = DirectSucc->begin();
603  BasicBlock::iterator MergeInsert = BodyBlock->getFirstInsertionPt();
604 
605  assert(&*End == Target->getTerminator() &&
606  "Block was expected to only contain PHIs");
607 
608  while (Indirect != End) {
609  PHINode *DirPHI = cast<PHINode>(Direct);
610  PHINode *IndPHI = cast<PHINode>(Indirect);
611 
612  // Now, clean up - the direct block shouldn't get the indirect value,
613  // and vice versa.
614  DirPHI->removeIncomingValue(IBRPred);
615  Direct++;
616 
617  // Advance the pointer here, to avoid invalidation issues when the old
618  // PHI is erased.
619  Indirect++;
620 
621  PHINode *NewIndPHI = PHINode::Create(IndPHI->getType(), 1, "ind", IndPHI);
622  NewIndPHI->addIncoming(IndPHI->getIncomingValueForBlock(IBRPred),
623  IBRPred);
624 
625  // Create a PHI in the body block, to merge the direct and indirect
626  // predecessors.
627  PHINode *MergePHI =
628  PHINode::Create(IndPHI->getType(), 2, "merge", &*MergeInsert);
629  MergePHI->addIncoming(NewIndPHI, Target);
630  MergePHI->addIncoming(DirPHI, DirectSucc);
631 
632  IndPHI->replaceAllUsesWith(MergePHI);
633  IndPHI->eraseFromParent();
634  }
635 
636  Changed = true;
637  }
638 
639  return Changed;
640 }
641 
642 /// Eliminate blocks that contain only PHI nodes, debug info directives, and an
643 /// unconditional branch. Passes before isel (e.g. LSR/loopsimplify) often split
644 /// edges in ways that are non-optimal for isel. Start by eliminating these
645 /// blocks so we can split them the way we want them.
646 bool CodeGenPrepare::eliminateMostlyEmptyBlocks(Function &F) {
648  SmallVector<Loop *, 16> LoopList(LI->begin(), LI->end());
649  while (!LoopList.empty()) {
650  Loop *L = LoopList.pop_back_val();
651  LoopList.insert(LoopList.end(), L->begin(), L->end());
652  if (BasicBlock *Preheader = L->getLoopPreheader())
653  Preheaders.insert(Preheader);
654  }
655 
656  bool MadeChange = false;
657  // Note that this intentionally skips the entry block.
658  for (Function::iterator I = std::next(F.begin()), E = F.end(); I != E;) {
659  BasicBlock *BB = &*I++;
660  BasicBlock *DestBB = findDestBlockOfMergeableEmptyBlock(BB);
661  if (!DestBB ||
662  !isMergingEmptyBlockProfitable(BB, DestBB, Preheaders.count(BB)))
663  continue;
664 
665  eliminateMostlyEmptyBlock(BB);
666  MadeChange = true;
667  }
668  return MadeChange;
669 }
670 
671 bool CodeGenPrepare::isMergingEmptyBlockProfitable(BasicBlock *BB,
672  BasicBlock *DestBB,
673  bool isPreheader) {
674  // Do not delete loop preheaders if doing so would create a critical edge.
675  // Loop preheaders can be good locations to spill registers. If the
676  // preheader is deleted and we create a critical edge, registers may be
677  // spilled in the loop body instead.
678  if (!DisablePreheaderProtect && isPreheader &&
679  !(BB->getSinglePredecessor() &&
681  return false;
682 
683  // Try to skip merging if the unique predecessor of BB is terminated by a
684  // switch or indirect branch instruction, and BB is used as an incoming block
685  // of PHIs in DestBB. In such case, merging BB and DestBB would cause ISel to
686  // add COPY instructions in the predecessor of BB instead of BB (if it is not
687  // merged). Note that the critical edge created by merging such blocks wont be
688  // split in MachineSink because the jump table is not analyzable. By keeping
689  // such empty block (BB), ISel will place COPY instructions in BB, not in the
690  // predecessor of BB.
691  BasicBlock *Pred = BB->getUniquePredecessor();
692  if (!Pred ||
693  !(isa<SwitchInst>(Pred->getTerminator()) ||
694  isa<IndirectBrInst>(Pred->getTerminator())))
695  return true;
696 
697  if (BB->getTerminator() != BB->getFirstNonPHI())
698  return true;
699 
700  // We use a simple cost heuristic which determine skipping merging is
701  // profitable if the cost of skipping merging is less than the cost of
702  // merging : Cost(skipping merging) < Cost(merging BB), where the
703  // Cost(skipping merging) is Freq(BB) * (Cost(Copy) + Cost(Branch)), and
704  // the Cost(merging BB) is Freq(Pred) * Cost(Copy).
705  // Assuming Cost(Copy) == Cost(Branch), we could simplify it to :
706  // Freq(Pred) / Freq(BB) > 2.
707  // Note that if there are multiple empty blocks sharing the same incoming
708  // value for the PHIs in the DestBB, we consider them together. In such
709  // case, Cost(merging BB) will be the sum of their frequencies.
710 
711  if (!isa<PHINode>(DestBB->begin()))
712  return true;
713 
714  SmallPtrSet<BasicBlock *, 16> SameIncomingValueBBs;
715 
716  // Find all other incoming blocks from which incoming values of all PHIs in
717  // DestBB are the same as the ones from BB.
718  for (pred_iterator PI = pred_begin(DestBB), E = pred_end(DestBB); PI != E;
719  ++PI) {
720  BasicBlock *DestBBPred = *PI;
721  if (DestBBPred == BB)
722  continue;
723 
724  bool HasAllSameValue = true;
725  BasicBlock::const_iterator DestBBI = DestBB->begin();
726  while (const PHINode *DestPN = dyn_cast<PHINode>(DestBBI++)) {
727  if (DestPN->getIncomingValueForBlock(BB) !=
728  DestPN->getIncomingValueForBlock(DestBBPred)) {
729  HasAllSameValue = false;
730  break;
731  }
732  }
733  if (HasAllSameValue)
734  SameIncomingValueBBs.insert(DestBBPred);
735  }
736 
737  // See if all BB's incoming values are same as the value from Pred. In this
738  // case, no reason to skip merging because COPYs are expected to be place in
739  // Pred already.
740  if (SameIncomingValueBBs.count(Pred))
741  return true;
742 
743  if (!BFI) {
744  Function &F = *BB->getParent();
745  LoopInfo LI{DominatorTree(F)};
746  BPI.reset(new BranchProbabilityInfo(F, LI));
747  BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
748  }
749 
750  BlockFrequency PredFreq = BFI->getBlockFreq(Pred);
751  BlockFrequency BBFreq = BFI->getBlockFreq(BB);
752 
753  for (auto SameValueBB : SameIncomingValueBBs)
754  if (SameValueBB->getUniquePredecessor() == Pred &&
755  DestBB == findDestBlockOfMergeableEmptyBlock(SameValueBB))
756  BBFreq += BFI->getBlockFreq(SameValueBB);
757 
758  return PredFreq.getFrequency() <=
760 }
761 
762 /// Return true if we can merge BB into DestBB if there is a single
763 /// unconditional branch between them, and BB contains no other non-phi
764 /// instructions.
765 bool CodeGenPrepare::canMergeBlocks(const BasicBlock *BB,
766  const BasicBlock *DestBB) const {
767  // We only want to eliminate blocks whose phi nodes are used by phi nodes in
768  // the successor. If there are more complex condition (e.g. preheaders),
769  // don't mess around with them.
770  BasicBlock::const_iterator BBI = BB->begin();
771  while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
772  for (const User *U : PN->users()) {
773  const Instruction *UI = cast<Instruction>(U);
774  if (UI->getParent() != DestBB || !isa<PHINode>(UI))
775  return false;
776  // If User is inside DestBB block and it is a PHINode then check
777  // incoming value. If incoming value is not from BB then this is
778  // a complex condition (e.g. preheaders) we want to avoid here.
779  if (UI->getParent() == DestBB) {
780  if (const PHINode *UPN = dyn_cast<PHINode>(UI))
781  for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) {
782  Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I));
783  if (Insn && Insn->getParent() == BB &&
784  Insn->getParent() != UPN->getIncomingBlock(I))
785  return false;
786  }
787  }
788  }
789  }
790 
791  // If BB and DestBB contain any common predecessors, then the phi nodes in BB
792  // and DestBB may have conflicting incoming values for the block. If so, we
793  // can't merge the block.
794  const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin());
795  if (!DestBBPN) return true; // no conflict.
796 
797  // Collect the preds of BB.
799  if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
800  // It is faster to get preds from a PHI than with pred_iterator.
801  for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
802  BBPreds.insert(BBPN->getIncomingBlock(i));
803  } else {
804  BBPreds.insert(pred_begin(BB), pred_end(BB));
805  }
806 
807  // Walk the preds of DestBB.
808  for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) {
809  BasicBlock *Pred = DestBBPN->getIncomingBlock(i);
810  if (BBPreds.count(Pred)) { // Common predecessor?
811  BBI = DestBB->begin();
812  while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
813  const Value *V1 = PN->getIncomingValueForBlock(Pred);
814  const Value *V2 = PN->getIncomingValueForBlock(BB);
815 
816  // If V2 is a phi node in BB, look up what the mapped value will be.
817  if (const PHINode *V2PN = dyn_cast<PHINode>(V2))
818  if (V2PN->getParent() == BB)
819  V2 = V2PN->getIncomingValueForBlock(Pred);
820 
821  // If there is a conflict, bail out.
822  if (V1 != V2) return false;
823  }
824  }
825  }
826 
827  return true;
828 }
829 
830 
831 /// Eliminate a basic block that has only phi's and an unconditional branch in
832 /// it.
833 void CodeGenPrepare::eliminateMostlyEmptyBlock(BasicBlock *BB) {
834  BranchInst *BI = cast<BranchInst>(BB->getTerminator());
835  BasicBlock *DestBB = BI->getSuccessor(0);
836 
837  DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB);
838 
839  // If the destination block has a single pred, then this is a trivial edge,
840  // just collapse it.
841  if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
842  if (SinglePred != DestBB) {
843  // Remember if SinglePred was the entry block of the function. If so, we
844  // will need to move BB back to the entry position.
845  bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
846  MergeBasicBlockIntoOnlyPred(DestBB, nullptr);
847 
848  if (isEntry && BB != &BB->getParent()->getEntryBlock())
849  BB->moveBefore(&BB->getParent()->getEntryBlock());
850 
851  DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
852  return;
853  }
854  }
855 
856  // Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB
857  // to handle the new incoming edges it is about to have.
858  PHINode *PN;
859  for (BasicBlock::iterator BBI = DestBB->begin();
860  (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
861  // Remove the incoming value for BB, and remember it.
862  Value *InVal = PN->removeIncomingValue(BB, false);
863 
864  // Two options: either the InVal is a phi node defined in BB or it is some
865  // value that dominates BB.
866  PHINode *InValPhi = dyn_cast<PHINode>(InVal);
867  if (InValPhi && InValPhi->getParent() == BB) {
868  // Add all of the input values of the input PHI as inputs of this phi.
869  for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
870  PN->addIncoming(InValPhi->getIncomingValue(i),
871  InValPhi->getIncomingBlock(i));
872  } else {
873  // Otherwise, add one instance of the dominating value for each edge that
874  // we will be adding.
875  if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
876  for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
877  PN->addIncoming(InVal, BBPN->getIncomingBlock(i));
878  } else {
879  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
880  PN->addIncoming(InVal, *PI);
881  }
882  }
883  }
884 
885  // The PHIs are now updated, change everything that refers to BB to use
886  // DestBB and remove BB.
887  BB->replaceAllUsesWith(DestBB);
888  BB->eraseFromParent();
889  ++NumBlocksElim;
890 
891  DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
892 }
893 
894 // Computes a map of base pointer relocation instructions to corresponding
895 // derived pointer relocation instructions given a vector of all relocate calls
897  const SmallVectorImpl<GCRelocateInst *> &AllRelocateCalls,
899  &RelocateInstMap) {
900  // Collect information in two maps: one primarily for locating the base object
901  // while filling the second map; the second map is the final structure holding
902  // a mapping between Base and corresponding Derived relocate calls
904  for (auto *ThisRelocate : AllRelocateCalls) {
905  auto K = std::make_pair(ThisRelocate->getBasePtrIndex(),
906  ThisRelocate->getDerivedPtrIndex());
907  RelocateIdxMap.insert(std::make_pair(K, ThisRelocate));
908  }
909  for (auto &Item : RelocateIdxMap) {
910  std::pair<unsigned, unsigned> Key = Item.first;
911  if (Key.first == Key.second)
912  // Base relocation: nothing to insert
913  continue;
914 
915  GCRelocateInst *I = Item.second;
916  auto BaseKey = std::make_pair(Key.first, Key.first);
917 
918  // We're iterating over RelocateIdxMap so we cannot modify it.
919  auto MaybeBase = RelocateIdxMap.find(BaseKey);
920  if (MaybeBase == RelocateIdxMap.end())
921  // TODO: We might want to insert a new base object relocate and gep off
922  // that, if there are enough derived object relocates.
923  continue;
924 
925  RelocateInstMap[MaybeBase->second].push_back(I);
926  }
927 }
928 
929 // Accepts a GEP and extracts the operands into a vector provided they're all
930 // small integer constants
932  SmallVectorImpl<Value *> &OffsetV) {
933  for (unsigned i = 1; i < GEP->getNumOperands(); i++) {
934  // Only accept small constant integer operands
935  auto Op = dyn_cast<ConstantInt>(GEP->getOperand(i));
936  if (!Op || Op->getZExtValue() > 20)
937  return false;
938  }
939 
940  for (unsigned i = 1; i < GEP->getNumOperands(); i++)
941  OffsetV.push_back(GEP->getOperand(i));
942  return true;
943 }
944 
945 // Takes a RelocatedBase (base pointer relocation instruction) and Targets to
946 // replace, computes a replacement, and affects it.
947 static bool
949  const SmallVectorImpl<GCRelocateInst *> &Targets) {
950  bool MadeChange = false;
951  for (GCRelocateInst *ToReplace : Targets) {
952  assert(ToReplace->getBasePtrIndex() == RelocatedBase->getBasePtrIndex() &&
953  "Not relocating a derived object of the original base object");
954  if (ToReplace->getBasePtrIndex() == ToReplace->getDerivedPtrIndex()) {
955  // A duplicate relocate call. TODO: coalesce duplicates.
956  continue;
957  }
958 
959  if (RelocatedBase->getParent() != ToReplace->getParent()) {
960  // Base and derived relocates are in different basic blocks.
961  // In this case transform is only valid when base dominates derived
962  // relocate. However it would be too expensive to check dominance
963  // for each such relocate, so we skip the whole transformation.
964  continue;
965  }
966 
967  Value *Base = ToReplace->getBasePtr();
968  auto Derived = dyn_cast<GetElementPtrInst>(ToReplace->getDerivedPtr());
969  if (!Derived || Derived->getPointerOperand() != Base)
970  continue;
971 
972  SmallVector<Value *, 2> OffsetV;
973  if (!getGEPSmallConstantIntOffsetV(Derived, OffsetV))
974  continue;
975 
976  // Create a Builder and replace the target callsite with a gep
977  assert(RelocatedBase->getNextNode() &&
978  "Should always have one since it's not a terminator");
979 
980  // Insert after RelocatedBase
981  IRBuilder<> Builder(RelocatedBase->getNextNode());
982  Builder.SetCurrentDebugLocation(ToReplace->getDebugLoc());
983 
984  // If gc_relocate does not match the actual type, cast it to the right type.
985  // In theory, there must be a bitcast after gc_relocate if the type does not
986  // match, and we should reuse it to get the derived pointer. But it could be
987  // cases like this:
988  // bb1:
989  // ...
990  // %g1 = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(...)
991  // br label %merge
992  //
993  // bb2:
994  // ...
995  // %g2 = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(...)
996  // br label %merge
997  //
998  // merge:
999  // %p1 = phi i8 addrspace(1)* [ %g1, %bb1 ], [ %g2, %bb2 ]
1000  // %cast = bitcast i8 addrspace(1)* %p1 in to i32 addrspace(1)*
1001  //
1002  // In this case, we can not find the bitcast any more. So we insert a new bitcast
1003  // no matter there is already one or not. In this way, we can handle all cases, and
1004  // the extra bitcast should be optimized away in later passes.
1005  Value *ActualRelocatedBase = RelocatedBase;
1006  if (RelocatedBase->getType() != Base->getType()) {
1007  ActualRelocatedBase =
1008  Builder.CreateBitCast(RelocatedBase, Base->getType());
1009  }
1010  Value *Replacement = Builder.CreateGEP(
1011  Derived->getSourceElementType(), ActualRelocatedBase, makeArrayRef(OffsetV));
1012  Replacement->takeName(ToReplace);
1013  // If the newly generated derived pointer's type does not match the original derived
1014  // pointer's type, cast the new derived pointer to match it. Same reasoning as above.
1015  Value *ActualReplacement = Replacement;
1016  if (Replacement->getType() != ToReplace->getType()) {
1017  ActualReplacement =
1018  Builder.CreateBitCast(Replacement, ToReplace->getType());
1019  }
1020  ToReplace->replaceAllUsesWith(ActualReplacement);
1021  ToReplace->eraseFromParent();
1022 
1023  MadeChange = true;
1024  }
1025  return MadeChange;
1026 }
1027 
1028 // Turns this:
1029 //
1030 // %base = ...
1031 // %ptr = gep %base + 15
1032 // %tok = statepoint (%fun, i32 0, i32 0, i32 0, %base, %ptr)
1033 // %base' = relocate(%tok, i32 4, i32 4)
1034 // %ptr' = relocate(%tok, i32 4, i32 5)
1035 // %val = load %ptr'
1036 //
1037 // into this:
1038 //
1039 // %base = ...
1040 // %ptr = gep %base + 15
1041 // %tok = statepoint (%fun, i32 0, i32 0, i32 0, %base, %ptr)
1042 // %base' = gc.relocate(%tok, i32 4, i32 4)
1043 // %ptr' = gep %base' + 15
1044 // %val = load %ptr'
1045 bool CodeGenPrepare::simplifyOffsetableRelocate(Instruction &I) {
1046  bool MadeChange = false;
1047  SmallVector<GCRelocateInst *, 2> AllRelocateCalls;
1048 
1049  for (auto *U : I.users())
1050  if (GCRelocateInst *Relocate = dyn_cast<GCRelocateInst>(U))
1051  // Collect all the relocate calls associated with a statepoint
1052  AllRelocateCalls.push_back(Relocate);
1053 
1054  // We need atleast one base pointer relocation + one derived pointer
1055  // relocation to mangle
1056  if (AllRelocateCalls.size() < 2)
1057  return false;
1058 
1059  // RelocateInstMap is a mapping from the base relocate instruction to the
1060  // corresponding derived relocate instructions
1062  computeBaseDerivedRelocateMap(AllRelocateCalls, RelocateInstMap);
1063  if (RelocateInstMap.empty())
1064  return false;
1065 
1066  for (auto &Item : RelocateInstMap)
1067  // Item.first is the RelocatedBase to offset against
1068  // Item.second is the vector of Targets to replace
1069  MadeChange = simplifyRelocatesOffABase(Item.first, Item.second);
1070  return MadeChange;
1071 }
1072 
1073 /// SinkCast - Sink the specified cast instruction into its user blocks
1074 static bool SinkCast(CastInst *CI) {
1075  BasicBlock *DefBB = CI->getParent();
1076 
1077  /// InsertedCasts - Only insert a cast in each block once.
1078  DenseMap<BasicBlock*, CastInst*> InsertedCasts;
1079 
1080  bool MadeChange = false;
1081  for (Value::user_iterator UI = CI->user_begin(), E = CI->user_end();
1082  UI != E; ) {
1083  Use &TheUse = UI.getUse();
1084  Instruction *User = cast<Instruction>(*UI);
1085 
1086  // Figure out which BB this cast is used in. For PHI's this is the
1087  // appropriate predecessor block.
1088  BasicBlock *UserBB = User->getParent();
1089  if (PHINode *PN = dyn_cast<PHINode>(User)) {
1090  UserBB = PN->getIncomingBlock(TheUse);
1091  }
1092 
1093  // Preincrement use iterator so we don't invalidate it.
1094  ++UI;
1095 
1096  // The first insertion point of a block containing an EH pad is after the
1097  // pad. If the pad is the user, we cannot sink the cast past the pad.
1098  if (User->isEHPad())
1099  continue;
1100 
1101  // If the block selected to receive the cast is an EH pad that does not
1102  // allow non-PHI instructions before the terminator, we can't sink the
1103  // cast.
1104  if (UserBB->getTerminator()->isEHPad())
1105  continue;
1106 
1107  // If this user is in the same block as the cast, don't change the cast.
1108  if (UserBB == DefBB) continue;
1109 
1110  // If we have already inserted a cast into this block, use it.
1111  CastInst *&InsertedCast = InsertedCasts[UserBB];
1112 
1113  if (!InsertedCast) {
1114  BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
1115  assert(InsertPt != UserBB->end());
1116  InsertedCast = CastInst::Create(CI->getOpcode(), CI->getOperand(0),
1117  CI->getType(), "", &*InsertPt);
1118  }
1119 
1120  // Replace a use of the cast with a use of the new cast.
1121  TheUse = InsertedCast;
1122  MadeChange = true;
1123  ++NumCastUses;
1124  }
1125 
1126  // If we removed all uses, nuke the cast.
1127  if (CI->use_empty()) {
1128  CI->eraseFromParent();
1129  MadeChange = true;
1130  }
1131 
1132  return MadeChange;
1133 }
1134 
1135 /// If the specified cast instruction is a noop copy (e.g. it's casting from
1136 /// one pointer type to another, i32->i8 on PPC), sink it into user blocks to
1137 /// reduce the number of virtual registers that must be created and coalesced.
1138 ///
1139 /// Return true if any changes are made.
1140 ///
1142  const DataLayout &DL) {
1143  // Sink only "cheap" (or nop) address-space casts. This is a weaker condition
1144  // than sinking only nop casts, but is helpful on some platforms.
1145  if (auto *ASC = dyn_cast<AddrSpaceCastInst>(CI)) {
1146  if (!TLI.isCheapAddrSpaceCast(ASC->getSrcAddressSpace(),
1147  ASC->getDestAddressSpace()))
1148  return false;
1149  }
1150 
1151  // If this is a noop copy,
1152  EVT SrcVT = TLI.getValueType(DL, CI->getOperand(0)->getType());
1153  EVT DstVT = TLI.getValueType(DL, CI->getType());
1154 
1155  // This is an fp<->int conversion?
1156  if (SrcVT.isInteger() != DstVT.isInteger())
1157  return false;
1158 
1159  // If this is an extension, it will be a zero or sign extension, which
1160  // isn't a noop.
1161  if (SrcVT.bitsLT(DstVT)) return false;
1162 
1163  // If these values will be promoted, find out what they will be promoted
1164  // to. This helps us consider truncates on PPC as noop copies when they
1165  // are.
1166  if (TLI.getTypeAction(CI->getContext(), SrcVT) ==
1168  SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
1169  if (TLI.getTypeAction(CI->getContext(), DstVT) ==
1171  DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);
1172 
1173  // If, after promotion, these are the same types, this is a noop copy.
1174  if (SrcVT != DstVT)
1175  return false;
1176 
1177  return SinkCast(CI);
1178 }
1179 
1180 /// Try to combine CI into a call to the llvm.uadd.with.overflow intrinsic if
1181 /// possible.
1182 ///
1183 /// Return true if any changes were made.
1185  Value *A, *B;
1186  Instruction *AddI;
1187  if (!match(CI,
1189  return false;
1190 
1191  Type *Ty = AddI->getType();
1192  if (!isa<IntegerType>(Ty))
1193  return false;
1194 
1195  // We don't want to move around uses of condition values this late, so we we
1196  // check if it is legal to create the call to the intrinsic in the basic
1197  // block containing the icmp:
1198 
1199  if (AddI->getParent() != CI->getParent() && !AddI->hasOneUse())
1200  return false;
1201 
1202 #ifndef NDEBUG
1203  // Someday m_UAddWithOverflow may get smarter, but this is a safe assumption
1204  // for now:
1205  if (AddI->hasOneUse())
1206  assert(*AddI->user_begin() == CI && "expected!");
1207 #endif
1208 
1209  Module *M = CI->getModule();
1210  Value *F = Intrinsic::getDeclaration(M, Intrinsic::uadd_with_overflow, Ty);
1211 
1212  auto *InsertPt = AddI->hasOneUse() ? CI : AddI;
1213 
1214  auto *UAddWithOverflow =
1215  CallInst::Create(F, {A, B}, "uadd.overflow", InsertPt);
1216  auto *UAdd = ExtractValueInst::Create(UAddWithOverflow, 0, "uadd", InsertPt);
1217  auto *Overflow =
1218  ExtractValueInst::Create(UAddWithOverflow, 1, "overflow", InsertPt);
1219 
1220  CI->replaceAllUsesWith(Overflow);
1221  AddI->replaceAllUsesWith(UAdd);
1222  CI->eraseFromParent();
1223  AddI->eraseFromParent();
1224  return true;
1225 }
1226 
1227 /// Sink the given CmpInst into user blocks to reduce the number of virtual
1228 /// registers that must be created and coalesced. This is a clear win except on
1229 /// targets with multiple condition code registers (PowerPC), where it might
1230 /// lose; some adjustment may be wanted there.
1231 ///
1232 /// Return true if any changes are made.
1233 static bool SinkCmpExpression(CmpInst *CI, const TargetLowering *TLI) {
1234  BasicBlock *DefBB = CI->getParent();
1235 
1236  // Avoid sinking soft-FP comparisons, since this can move them into a loop.
1237  if (TLI && TLI->useSoftFloat() && isa<FCmpInst>(CI))
1238  return false;
1239 
1240  // Only insert a cmp in each block once.
1241  DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
1242 
1243  bool MadeChange = false;
1244  for (Value::user_iterator UI = CI->user_begin(), E = CI->user_end();
1245  UI != E; ) {
1246  Use &TheUse = UI.getUse();
1247  Instruction *User = cast<Instruction>(*UI);
1248 
1249  // Preincrement use iterator so we don't invalidate it.
1250  ++UI;
1251 
1252  // Don't bother for PHI nodes.
1253  if (isa<PHINode>(User))
1254  continue;
1255 
1256  // Figure out which BB this cmp is used in.
1257  BasicBlock *UserBB = User->getParent();
1258 
1259  // If this user is in the same block as the cmp, don't change the cmp.
1260  if (UserBB == DefBB) continue;
1261 
1262  // If we have already inserted a cmp into this block, use it.
1263  CmpInst *&InsertedCmp = InsertedCmps[UserBB];
1264 
1265  if (!InsertedCmp) {
1266  BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
1267  assert(InsertPt != UserBB->end());
1268  InsertedCmp =
1269  CmpInst::Create(CI->getOpcode(), CI->getPredicate(),
1270  CI->getOperand(0), CI->getOperand(1), "", &*InsertPt);
1271  // Propagate the debug info.
1272  InsertedCmp->setDebugLoc(CI->getDebugLoc());
1273  }
1274 
1275  // Replace a use of the cmp with a use of the new cmp.
1276  TheUse = InsertedCmp;
1277  MadeChange = true;
1278  ++NumCmpUses;
1279  }
1280 
1281  // If we removed all uses, nuke the cmp.
1282  if (CI->use_empty()) {
1283  CI->eraseFromParent();
1284  MadeChange = true;
1285  }
1286 
1287  return MadeChange;
1288 }
1289 
1290 static bool OptimizeCmpExpression(CmpInst *CI, const TargetLowering *TLI) {
1291  if (SinkCmpExpression(CI, TLI))
1292  return true;
1293 
1294  if (CombineUAddWithOverflow(CI))
1295  return true;
1296 
1297  return false;
1298 }
1299 
1300 /// Duplicate and sink the given 'and' instruction into user blocks where it is
1301 /// used in a compare to allow isel to generate better code for targets where
1302 /// this operation can be combined.
1303 ///
1304 /// Return true if any changes are made.
1306  const TargetLowering &TLI,
1307  SetOfInstrs &InsertedInsts) {
1308  // Double-check that we're not trying to optimize an instruction that was
1309  // already optimized by some other part of this pass.
1310  assert(!InsertedInsts.count(AndI) &&
1311  "Attempting to optimize already optimized and instruction");
1312  (void) InsertedInsts;
1313 
1314  // Nothing to do for single use in same basic block.
1315  if (AndI->hasOneUse() &&
1316  AndI->getParent() == cast<Instruction>(*AndI->user_begin())->getParent())
1317  return false;
1318 
1319  // Try to avoid cases where sinking/duplicating is likely to increase register
1320  // pressure.
1321  if (!isa<ConstantInt>(AndI->getOperand(0)) &&
1322  !isa<ConstantInt>(AndI->getOperand(1)) &&
1323  AndI->getOperand(0)->hasOneUse() && AndI->getOperand(1)->hasOneUse())
1324  return false;
1325 
1326  for (auto *U : AndI->users()) {
1327  Instruction *User = cast<Instruction>(U);
1328 
1329  // Only sink for and mask feeding icmp with 0.
1330  if (!isa<ICmpInst>(User))
1331  return false;
1332 
1333  auto *CmpC = dyn_cast<ConstantInt>(User->getOperand(1));
1334  if (!CmpC || !CmpC->isZero())
1335  return false;
1336  }
1337 
1338  if (!TLI.isMaskAndCmp0FoldingBeneficial(*AndI))
1339  return false;
1340 
1341  DEBUG(dbgs() << "found 'and' feeding only icmp 0;\n");
1342  DEBUG(AndI->getParent()->dump());
1343 
1344  // Push the 'and' into the same block as the icmp 0. There should only be
1345  // one (icmp (and, 0)) in each block, since CSE/GVN should have removed any
1346  // others, so we don't need to keep track of which BBs we insert into.
1347  for (Value::user_iterator UI = AndI->user_begin(), E = AndI->user_end();
1348  UI != E; ) {
1349  Use &TheUse = UI.getUse();
1350  Instruction *User = cast<Instruction>(*UI);
1351 
1352  // Preincrement use iterator so we don't invalidate it.
1353  ++UI;
1354 
1355  DEBUG(dbgs() << "sinking 'and' use: " << *User << "\n");
1356 
1357  // Keep the 'and' in the same place if the use is already in the same block.
1358  Instruction *InsertPt =
1359  User->getParent() == AndI->getParent() ? AndI : User;
1360  Instruction *InsertedAnd =
1361  BinaryOperator::Create(Instruction::And, AndI->getOperand(0),
1362  AndI->getOperand(1), "", InsertPt);
1363  // Propagate the debug info.
1364  InsertedAnd->setDebugLoc(AndI->getDebugLoc());
1365 
1366  // Replace a use of the 'and' with a use of the new 'and'.
1367  TheUse = InsertedAnd;
1368  ++NumAndUses;
1369  DEBUG(User->getParent()->dump());
1370  }
1371 
1372  // We removed all uses, nuke the and.
1373  AndI->eraseFromParent();
1374  return true;
1375 }
1376 
1377 /// Check if the candidates could be combined with a shift instruction, which
1378 /// includes:
1379 /// 1. Truncate instruction
1380 /// 2. And instruction and the imm is a mask of the low bits:
1381 /// imm & (imm+1) == 0
1383  if (!isa<TruncInst>(User)) {
1384  if (User->getOpcode() != Instruction::And ||
1385  !isa<ConstantInt>(User->getOperand(1)))
1386  return false;
1387 
1388  const APInt &Cimm = cast<ConstantInt>(User->getOperand(1))->getValue();
1389 
1390  if ((Cimm & (Cimm + 1)).getBoolValue())
1391  return false;
1392  }
1393  return true;
1394 }
1395 
1396 /// Sink both shift and truncate instruction to the use of truncate's BB.
1397 static bool
1400  const TargetLowering &TLI, const DataLayout &DL) {
1401  BasicBlock *UserBB = User->getParent();
1402  DenseMap<BasicBlock *, CastInst *> InsertedTruncs;
1403  TruncInst *TruncI = dyn_cast<TruncInst>(User);
1404  bool MadeChange = false;
1405 
1406  for (Value::user_iterator TruncUI = TruncI->user_begin(),
1407  TruncE = TruncI->user_end();
1408  TruncUI != TruncE;) {
1409 
1410  Use &TruncTheUse = TruncUI.getUse();
1411  Instruction *TruncUser = cast<Instruction>(*TruncUI);
1412  // Preincrement use iterator so we don't invalidate it.
1413 
1414  ++TruncUI;
1415 
1416  int ISDOpcode = TLI.InstructionOpcodeToISD(TruncUser->getOpcode());
1417  if (!ISDOpcode)
1418  continue;
1419 
1420  // If the use is actually a legal node, there will not be an
1421  // implicit truncate.
1422  // FIXME: always querying the result type is just an
1423  // approximation; some nodes' legality is determined by the
1424  // operand or other means. There's no good way to find out though.
1425  if (TLI.isOperationLegalOrCustom(
1426  ISDOpcode, TLI.getValueType(DL, TruncUser->getType(), true)))
1427  continue;
1428 
1429  // Don't bother for PHI nodes.
1430  if (isa<PHINode>(TruncUser))
1431  continue;
1432 
1433  BasicBlock *TruncUserBB = TruncUser->getParent();
1434 
1435  if (UserBB == TruncUserBB)
1436  continue;
1437 
1438  BinaryOperator *&InsertedShift = InsertedShifts[TruncUserBB];
1439  CastInst *&InsertedTrunc = InsertedTruncs[TruncUserBB];
1440 
1441  if (!InsertedShift && !InsertedTrunc) {
1442  BasicBlock::iterator InsertPt = TruncUserBB->getFirstInsertionPt();
1443  assert(InsertPt != TruncUserBB->end());
1444  // Sink the shift
1445  if (ShiftI->getOpcode() == Instruction::AShr)
1446  InsertedShift = BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI,
1447  "", &*InsertPt);
1448  else
1449  InsertedShift = BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI,
1450  "", &*InsertPt);
1451 
1452  // Sink the trunc
1453  BasicBlock::iterator TruncInsertPt = TruncUserBB->getFirstInsertionPt();
1454  TruncInsertPt++;
1455  assert(TruncInsertPt != TruncUserBB->end());
1456 
1457  InsertedTrunc = CastInst::Create(TruncI->getOpcode(), InsertedShift,
1458  TruncI->getType(), "", &*TruncInsertPt);
1459 
1460  MadeChange = true;
1461 
1462  TruncTheUse = InsertedTrunc;
1463  }
1464  }
1465  return MadeChange;
1466 }
1467 
1468 /// Sink the shift *right* instruction into user blocks if the uses could
1469 /// potentially be combined with this shift instruction and generate BitExtract
1470 /// instruction. It will only be applied if the architecture supports BitExtract
1471 /// instruction. Here is an example:
1472 /// BB1:
1473 /// %x.extract.shift = lshr i64 %arg1, 32
1474 /// BB2:
1475 /// %x.extract.trunc = trunc i64 %x.extract.shift to i16
1476 /// ==>
1477 ///
1478 /// BB2:
1479 /// %x.extract.shift.1 = lshr i64 %arg1, 32
1480 /// %x.extract.trunc = trunc i64 %x.extract.shift.1 to i16
1481 ///
1482 /// CodeGen will recoginze the pattern in BB2 and generate BitExtract
1483 /// instruction.
1484 /// Return true if any changes are made.
1486  const TargetLowering &TLI,
1487  const DataLayout &DL) {
1488  BasicBlock *DefBB = ShiftI->getParent();
1489 
1490  /// Only insert instructions in each block once.
1492 
1493  bool shiftIsLegal = TLI.isTypeLegal(TLI.getValueType(DL, ShiftI->getType()));
1494 
1495  bool MadeChange = false;
1496  for (Value::user_iterator UI = ShiftI->user_begin(), E = ShiftI->user_end();
1497  UI != E;) {
1498  Use &TheUse = UI.getUse();
1499  Instruction *User = cast<Instruction>(*UI);
1500  // Preincrement use iterator so we don't invalidate it.
1501  ++UI;
1502 
1503  // Don't bother for PHI nodes.
1504  if (isa<PHINode>(User))
1505  continue;
1506 
1507  if (!isExtractBitsCandidateUse(User))
1508  continue;
1509 
1510  BasicBlock *UserBB = User->getParent();
1511 
1512  if (UserBB == DefBB) {
1513  // If the shift and truncate instruction are in the same BB. The use of
1514  // the truncate(TruncUse) may still introduce another truncate if not
1515  // legal. In this case, we would like to sink both shift and truncate
1516  // instruction to the BB of TruncUse.
1517  // for example:
1518  // BB1:
1519  // i64 shift.result = lshr i64 opnd, imm
1520  // trunc.result = trunc shift.result to i16
1521  //
1522  // BB2:
1523  // ----> We will have an implicit truncate here if the architecture does
1524  // not have i16 compare.
1525  // cmp i16 trunc.result, opnd2
1526  //
1527  if (isa<TruncInst>(User) && shiftIsLegal
1528  // If the type of the truncate is legal, no trucate will be
1529  // introduced in other basic blocks.
1530  &&
1531  (!TLI.isTypeLegal(TLI.getValueType(DL, User->getType()))))
1532  MadeChange =
1533  SinkShiftAndTruncate(ShiftI, User, CI, InsertedShifts, TLI, DL);
1534 
1535  continue;
1536  }
1537  // If we have already inserted a shift into this block, use it.
1538  BinaryOperator *&InsertedShift = InsertedShifts[UserBB];
1539 
1540  if (!InsertedShift) {
1541  BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
1542  assert(InsertPt != UserBB->end());
1543 
1544  if (ShiftI->getOpcode() == Instruction::AShr)
1545  InsertedShift = BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI,
1546  "", &*InsertPt);
1547  else
1548  InsertedShift = BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI,
1549  "", &*InsertPt);
1550 
1551  MadeChange = true;
1552  }
1553 
1554  // Replace a use of the shift with a use of the new shift.
1555  TheUse = InsertedShift;
1556  }
1557 
1558  // If we removed all uses, nuke the shift.
1559  if (ShiftI->use_empty())
1560  ShiftI->eraseFromParent();
1561 
1562  return MadeChange;
1563 }
1564 
1565 /// If counting leading or trailing zeros is an expensive operation and a zero
1566 /// input is defined, add a check for zero to avoid calling the intrinsic.
1567 ///
1568 /// We want to transform:
1569 /// %z = call i64 @llvm.cttz.i64(i64 %A, i1 false)
1570 ///
1571 /// into:
1572 /// entry:
1573 /// %cmpz = icmp eq i64 %A, 0
1574 /// br i1 %cmpz, label %cond.end, label %cond.false
1575 /// cond.false:
1576 /// %z = call i64 @llvm.cttz.i64(i64 %A, i1 true)
1577 /// br label %cond.end
1578 /// cond.end:
1579 /// %ctz = phi i64 [ 64, %entry ], [ %z, %cond.false ]
1580 ///
1581 /// If the transform is performed, return true and set ModifiedDT to true.
1582 static bool despeculateCountZeros(IntrinsicInst *CountZeros,
1583  const TargetLowering *TLI,
1584  const DataLayout *DL,
1585  bool &ModifiedDT) {
1586  if (!TLI || !DL)
1587  return false;
1588 
1589  // If a zero input is undefined, it doesn't make sense to despeculate that.
1590  if (match(CountZeros->getOperand(1), m_One()))
1591  return false;
1592 
1593  // If it's cheap to speculate, there's nothing to do.
1594  auto IntrinsicID = CountZeros->getIntrinsicID();
1595  if ((IntrinsicID == Intrinsic::cttz && TLI->isCheapToSpeculateCttz()) ||
1596  (IntrinsicID == Intrinsic::ctlz && TLI->isCheapToSpeculateCtlz()))
1597  return false;
1598 
1599  // Only handle legal scalar cases. Anything else requires too much work.
1600  Type *Ty = CountZeros->getType();
1601  unsigned SizeInBits = Ty->getPrimitiveSizeInBits();
1602  if (Ty->isVectorTy() || SizeInBits > DL->getLargestLegalIntTypeSizeInBits())
1603  return false;
1604 
1605  // The intrinsic will be sunk behind a compare against zero and branch.
1606  BasicBlock *StartBlock = CountZeros->getParent();
1607  BasicBlock *CallBlock = StartBlock->splitBasicBlock(CountZeros, "cond.false");
1608 
1609  // Create another block after the count zero intrinsic. A PHI will be added
1610  // in this block to select the result of the intrinsic or the bit-width
1611  // constant if the input to the intrinsic is zero.
1612  BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(CountZeros));
1613  BasicBlock *EndBlock = CallBlock->splitBasicBlock(SplitPt, "cond.end");
1614 
1615  // Set up a builder to create a compare, conditional branch, and PHI.
1616  IRBuilder<> Builder(CountZeros->getContext());
1617  Builder.SetInsertPoint(StartBlock->getTerminator());
1618  Builder.SetCurrentDebugLocation(CountZeros->getDebugLoc());
1619 
1620  // Replace the unconditional branch that was created by the first split with
1621  // a compare against zero and a conditional branch.
1623  Value *Cmp = Builder.CreateICmpEQ(CountZeros->getOperand(0), Zero, "cmpz");
1624  Builder.CreateCondBr(Cmp, EndBlock, CallBlock);
1625  StartBlock->getTerminator()->eraseFromParent();
1626 
1627  // Create a PHI in the end block to select either the output of the intrinsic
1628  // or the bit width of the operand.
1629  Builder.SetInsertPoint(&EndBlock->front());
1630  PHINode *PN = Builder.CreatePHI(Ty, 2, "ctz");
1631  CountZeros->replaceAllUsesWith(PN);
1632  Value *BitWidth = Builder.getInt(APInt(SizeInBits, SizeInBits));
1633  PN->addIncoming(BitWidth, StartBlock);
1634  PN->addIncoming(CountZeros, CallBlock);
1635 
1636  // We are explicitly handling the zero case, so we can set the intrinsic's
1637  // undefined zero argument to 'true'. This will also prevent reprocessing the
1638  // intrinsic; we only despeculate when a zero input is defined.
1639  CountZeros->setArgOperand(1, Builder.getTrue());
1640  ModifiedDT = true;
1641  return true;
1642 }
1643 
1644 // This class provides helper functions to expand a memcmp library call into an
1645 // inline expansion.
1647  struct ResultBlock {
1648  BasicBlock *BB;
1649  PHINode *PhiSrc1;
1650  PHINode *PhiSrc2;
1651  ResultBlock();
1652  };
1653 
1654  CallInst *CI;
1655  ResultBlock ResBlock;
1656  unsigned MaxLoadSize;
1657  unsigned NumBlocks;
1658  unsigned NumBlocksNonOneByte;
1659  unsigned NumLoadsPerBlock;
1660  std::vector<BasicBlock *> LoadCmpBlocks;
1661  BasicBlock *EndBlock;
1662  PHINode *PhiRes;
1663  bool IsUsedForZeroCmp;
1664  const DataLayout &DL;
1665  IRBuilder<> Builder;
1666 
1667  unsigned calculateNumBlocks(unsigned Size);
1668  void createLoadCmpBlocks();
1669  void createResultBlock();
1670  void setupResultBlockPHINodes();
1671  void setupEndBlockPHINodes();
1672  void emitLoadCompareBlock(unsigned Index, unsigned LoadSize,
1673  unsigned GEPIndex);
1674  Value *getCompareLoadPairs(unsigned Index, unsigned Size,
1675  unsigned &NumBytesProcessed);
1676  void emitLoadCompareBlockMultipleLoads(unsigned Index, unsigned Size,
1677  unsigned &NumBytesProcessed);
1678  void emitLoadCompareByteBlock(unsigned Index, unsigned GEPIndex);
1679  void emitMemCmpResultBlock();
1680  Value *getMemCmpExpansionZeroCase(unsigned Size);
1681  Value *getMemCmpEqZeroOneBlock(unsigned Size);
1682  Value *getMemCmpOneBlock(unsigned Size);
1683  unsigned getLoadSize(unsigned Size);
1684  unsigned getNumLoads(unsigned Size);
1685 
1686 public:
1687  MemCmpExpansion(CallInst *CI, uint64_t Size, unsigned MaxLoadSize,
1688  unsigned NumLoadsPerBlock, const DataLayout &DL);
1689  Value *getMemCmpExpansion(uint64_t Size);
1690 };
1691 
1692 MemCmpExpansion::ResultBlock::ResultBlock()
1693  : BB(nullptr), PhiSrc1(nullptr), PhiSrc2(nullptr) {}
1694 
1695 // Initialize the basic block structure required for expansion of memcmp call
1696 // with given maximum load size and memcmp size parameter.
1697 // This structure includes:
1698 // 1. A list of load compare blocks - LoadCmpBlocks.
1699 // 2. An EndBlock, split from original instruction point, which is the block to
1700 // return from.
1701 // 3. ResultBlock, block to branch to for early exit when a
1702 // LoadCmpBlock finds a difference.
1704  unsigned MaxLoadSize, unsigned LoadsPerBlock,
1705  const DataLayout &TheDataLayout)
1706  : CI(CI), MaxLoadSize(MaxLoadSize), NumLoadsPerBlock(LoadsPerBlock),
1707  DL(TheDataLayout), Builder(CI) {
1708 
1709  // A memcmp with zero-comparison with only one block of load and compare does
1710  // not need to set up any extra blocks. This case could be handled in the DAG,
1711  // but since we have all of the machinery to flexibly expand any memcpy here,
1712  // we choose to handle this case too to avoid fragmented lowering.
1713  IsUsedForZeroCmp = isOnlyUsedInZeroEqualityComparison(CI);
1714  NumBlocks = calculateNumBlocks(Size);
1715  if ((!IsUsedForZeroCmp && NumLoadsPerBlock != 1) || NumBlocks != 1) {
1716  BasicBlock *StartBlock = CI->getParent();
1717  EndBlock = StartBlock->splitBasicBlock(CI, "endblock");
1718  setupEndBlockPHINodes();
1719  createResultBlock();
1720 
1721  // If return value of memcmp is not used in a zero equality, we need to
1722  // calculate which source was larger. The calculation requires the
1723  // two loaded source values of each load compare block.
1724  // These will be saved in the phi nodes created by setupResultBlockPHINodes.
1725  if (!IsUsedForZeroCmp)
1726  setupResultBlockPHINodes();
1727 
1728  // Create the number of required load compare basic blocks.
1729  createLoadCmpBlocks();
1730 
1731  // Update the terminator added by splitBasicBlock to branch to the first
1732  // LoadCmpBlock.
1733  StartBlock->getTerminator()->setSuccessor(0, LoadCmpBlocks[0]);
1734  }
1735 
1736  Builder.SetCurrentDebugLocation(CI->getDebugLoc());
1737 }
1738 
1739 void MemCmpExpansion::createLoadCmpBlocks() {
1740  for (unsigned i = 0; i < NumBlocks; i++) {
1741  BasicBlock *BB = BasicBlock::Create(CI->getContext(), "loadbb",
1742  EndBlock->getParent(), EndBlock);
1743  LoadCmpBlocks.push_back(BB);
1744  }
1745 }
1746 
1747 void MemCmpExpansion::createResultBlock() {
1748  ResBlock.BB = BasicBlock::Create(CI->getContext(), "res_block",
1749  EndBlock->getParent(), EndBlock);
1750 }
1751 
1752 // This function creates the IR instructions for loading and comparing 1 byte.
1753 // It loads 1 byte from each source of the memcmp parameters with the given
1754 // GEPIndex. It then subtracts the two loaded values and adds this result to the
1755 // final phi node for selecting the memcmp result.
1756 void MemCmpExpansion::emitLoadCompareByteBlock(unsigned Index,
1757  unsigned GEPIndex) {
1758  Value *Source1 = CI->getArgOperand(0);
1759  Value *Source2 = CI->getArgOperand(1);
1760 
1761  Builder.SetInsertPoint(LoadCmpBlocks[Index]);
1762  Type *LoadSizeType = Type::getInt8Ty(CI->getContext());
1763  // Cast source to LoadSizeType*.
1764  if (Source1->getType() != LoadSizeType)
1765  Source1 = Builder.CreateBitCast(Source1, LoadSizeType->getPointerTo());
1766  if (Source2->getType() != LoadSizeType)
1767  Source2 = Builder.CreateBitCast(Source2, LoadSizeType->getPointerTo());
1768 
1769  // Get the base address using the GEPIndex.
1770  if (GEPIndex != 0) {
1771  Source1 = Builder.CreateGEP(LoadSizeType, Source1,
1772  ConstantInt::get(LoadSizeType, GEPIndex));
1773  Source2 = Builder.CreateGEP(LoadSizeType, Source2,
1774  ConstantInt::get(LoadSizeType, GEPIndex));
1775  }
1776 
1777  Value *LoadSrc1 = Builder.CreateLoad(LoadSizeType, Source1);
1778  Value *LoadSrc2 = Builder.CreateLoad(LoadSizeType, Source2);
1779 
1780  LoadSrc1 = Builder.CreateZExt(LoadSrc1, Type::getInt32Ty(CI->getContext()));
1781  LoadSrc2 = Builder.CreateZExt(LoadSrc2, Type::getInt32Ty(CI->getContext()));
1782  Value *Diff = Builder.CreateSub(LoadSrc1, LoadSrc2);
1783 
1784  PhiRes->addIncoming(Diff, LoadCmpBlocks[Index]);
1785 
1786  if (Index < (LoadCmpBlocks.size() - 1)) {
1787  // Early exit branch if difference found to EndBlock. Otherwise, continue to
1788  // next LoadCmpBlock,
1789  Value *Cmp = Builder.CreateICmp(ICmpInst::ICMP_NE, Diff,
1790  ConstantInt::get(Diff->getType(), 0));
1791  BranchInst *CmpBr =
1792  BranchInst::Create(EndBlock, LoadCmpBlocks[Index + 1], Cmp);
1793  Builder.Insert(CmpBr);
1794  } else {
1795  // The last block has an unconditional branch to EndBlock.
1796  BranchInst *CmpBr = BranchInst::Create(EndBlock);
1797  Builder.Insert(CmpBr);
1798  }
1799 }
1800 
1801 unsigned MemCmpExpansion::getNumLoads(unsigned Size) {
1802  return (Size / MaxLoadSize) + countPopulation(Size % MaxLoadSize);
1803 }
1804 
1805 unsigned MemCmpExpansion::getLoadSize(unsigned Size) {
1806  return MinAlign(PowerOf2Floor(Size), MaxLoadSize);
1807 }
1808 
1809 /// Generate an equality comparison for one or more pairs of loaded values.
1810 /// This is used in the case where the memcmp() call is compared equal or not
1811 /// equal to zero.
1812 Value *MemCmpExpansion::getCompareLoadPairs(unsigned Index, unsigned Size,
1813  unsigned &NumBytesProcessed) {
1814  std::vector<Value *> XorList, OrList;
1815  Value *Diff;
1816 
1817  unsigned RemainingBytes = Size - NumBytesProcessed;
1818  unsigned NumLoadsRemaining = getNumLoads(RemainingBytes);
1819  unsigned NumLoads = std::min(NumLoadsRemaining, NumLoadsPerBlock);
1820 
1821  // For a single-block expansion, start inserting before the memcmp call.
1822  if (LoadCmpBlocks.empty())
1823  Builder.SetInsertPoint(CI);
1824  else
1825  Builder.SetInsertPoint(LoadCmpBlocks[Index]);
1826 
1827  Value *Cmp = nullptr;
1828  for (unsigned i = 0; i < NumLoads; ++i) {
1829  unsigned LoadSize = getLoadSize(RemainingBytes);
1830  unsigned GEPIndex = NumBytesProcessed / LoadSize;
1831  NumBytesProcessed += LoadSize;
1832  RemainingBytes -= LoadSize;
1833 
1834  Type *LoadSizeType = IntegerType::get(CI->getContext(), LoadSize * 8);
1835  Type *MaxLoadType = IntegerType::get(CI->getContext(), MaxLoadSize * 8);
1836  assert(LoadSize <= MaxLoadSize && "Unexpected load type");
1837 
1838  Value *Source1 = CI->getArgOperand(0);
1839  Value *Source2 = CI->getArgOperand(1);
1840 
1841  // Cast source to LoadSizeType*.
1842  if (Source1->getType() != LoadSizeType)
1843  Source1 = Builder.CreateBitCast(Source1, LoadSizeType->getPointerTo());
1844  if (Source2->getType() != LoadSizeType)
1845  Source2 = Builder.CreateBitCast(Source2, LoadSizeType->getPointerTo());
1846 
1847  // Get the base address using the GEPIndex.
1848  if (GEPIndex != 0) {
1849  Source1 = Builder.CreateGEP(LoadSizeType, Source1,
1850  ConstantInt::get(LoadSizeType, GEPIndex));
1851  Source2 = Builder.CreateGEP(LoadSizeType, Source2,
1852  ConstantInt::get(LoadSizeType, GEPIndex));
1853  }
1854 
1855  // Get a constant or load a value for each source address.
1856  Value *LoadSrc1 = nullptr;
1857  if (auto *Source1C = dyn_cast<Constant>(Source1))
1858  LoadSrc1 = ConstantFoldLoadFromConstPtr(Source1C, LoadSizeType, DL);
1859  if (!LoadSrc1)
1860  LoadSrc1 = Builder.CreateLoad(LoadSizeType, Source1);
1861 
1862  Value *LoadSrc2 = nullptr;
1863  if (auto *Source2C = dyn_cast<Constant>(Source2))
1864  LoadSrc2 = ConstantFoldLoadFromConstPtr(Source2C, LoadSizeType, DL);
1865  if (!LoadSrc2)
1866  LoadSrc2 = Builder.CreateLoad(LoadSizeType, Source2);
1867 
1868  if (NumLoads != 1) {
1869  if (LoadSizeType != MaxLoadType) {
1870  LoadSrc1 = Builder.CreateZExt(LoadSrc1, MaxLoadType);
1871  LoadSrc2 = Builder.CreateZExt(LoadSrc2, MaxLoadType);
1872  }
1873  // If we have multiple loads per block, we need to generate a composite
1874  // comparison using xor+or.
1875  Diff = Builder.CreateXor(LoadSrc1, LoadSrc2);
1876  Diff = Builder.CreateZExt(Diff, MaxLoadType);
1877  XorList.push_back(Diff);
1878  } else {
1879  // If there's only one load per block, we just compare the loaded values.
1880  Cmp = Builder.CreateICmpNE(LoadSrc1, LoadSrc2);
1881  }
1882  }
1883 
1884  auto pairWiseOr = [&](std::vector<Value *> &InList) -> std::vector<Value *> {
1885  std::vector<Value *> OutList;
1886  for (unsigned i = 0; i < InList.size() - 1; i = i + 2) {
1887  Value *Or = Builder.CreateOr(InList[i], InList[i + 1]);
1888  OutList.push_back(Or);
1889  }
1890  if (InList.size() % 2 != 0)
1891  OutList.push_back(InList.back());
1892  return OutList;
1893  };
1894 
1895  if (!Cmp) {
1896  // Pairwise OR the XOR results.
1897  OrList = pairWiseOr(XorList);
1898 
1899  // Pairwise OR the OR results until one result left.
1900  while (OrList.size() != 1) {
1901  OrList = pairWiseOr(OrList);
1902  }
1903  Cmp = Builder.CreateICmpNE(OrList[0], ConstantInt::get(Diff->getType(), 0));
1904  }
1905 
1906  return Cmp;
1907 }
1908 
1909 void MemCmpExpansion::emitLoadCompareBlockMultipleLoads(
1910  unsigned Index, unsigned Size, unsigned &NumBytesProcessed) {
1911  Value *Cmp = getCompareLoadPairs(Index, Size, NumBytesProcessed);
1912 
1913  BasicBlock *NextBB = (Index == (LoadCmpBlocks.size() - 1))
1914  ? EndBlock
1915  : LoadCmpBlocks[Index + 1];
1916  // Early exit branch if difference found to ResultBlock. Otherwise,
1917  // continue to next LoadCmpBlock or EndBlock.
1918  BranchInst *CmpBr = BranchInst::Create(ResBlock.BB, NextBB, Cmp);
1919  Builder.Insert(CmpBr);
1920 
1921  // Add a phi edge for the last LoadCmpBlock to Endblock with a value of 0
1922  // since early exit to ResultBlock was not taken (no difference was found in
1923  // any of the bytes).
1924  if (Index == LoadCmpBlocks.size() - 1) {
1925  Value *Zero = ConstantInt::get(Type::getInt32Ty(CI->getContext()), 0);
1926  PhiRes->addIncoming(Zero, LoadCmpBlocks[Index]);
1927  }
1928 }
1929 
1930 // This function creates the IR intructions for loading and comparing using the
1931 // given LoadSize. It loads the number of bytes specified by LoadSize from each
1932 // source of the memcmp parameters. It then does a subtract to see if there was
1933 // a difference in the loaded values. If a difference is found, it branches
1934 // with an early exit to the ResultBlock for calculating which source was
1935 // larger. Otherwise, it falls through to the either the next LoadCmpBlock or
1936 // the EndBlock if this is the last LoadCmpBlock. Loading 1 byte is handled with
1937 // a special case through emitLoadCompareByteBlock. The special handling can
1938 // simply subtract the loaded values and add it to the result phi node.
1939 void MemCmpExpansion::emitLoadCompareBlock(unsigned Index, unsigned LoadSize,
1940  unsigned GEPIndex) {
1941  if (LoadSize == 1) {
1942  MemCmpExpansion::emitLoadCompareByteBlock(Index, GEPIndex);
1943  return;
1944  }
1945 
1946  Type *LoadSizeType = IntegerType::get(CI->getContext(), LoadSize * 8);
1947  Type *MaxLoadType = IntegerType::get(CI->getContext(), MaxLoadSize * 8);
1948  assert(LoadSize <= MaxLoadSize && "Unexpected load type");
1949 
1950  Value *Source1 = CI->getArgOperand(0);
1951  Value *Source2 = CI->getArgOperand(1);
1952 
1953  Builder.SetInsertPoint(LoadCmpBlocks[Index]);
1954  // Cast source to LoadSizeType*.
1955  if (Source1->getType() != LoadSizeType)
1956  Source1 = Builder.CreateBitCast(Source1, LoadSizeType->getPointerTo());
1957  if (Source2->getType() != LoadSizeType)
1958  Source2 = Builder.CreateBitCast(Source2, LoadSizeType->getPointerTo());
1959 
1960  // Get the base address using the GEPIndex.
1961  if (GEPIndex != 0) {
1962  Source1 = Builder.CreateGEP(LoadSizeType, Source1,
1963  ConstantInt::get(LoadSizeType, GEPIndex));
1964  Source2 = Builder.CreateGEP(LoadSizeType, Source2,
1965  ConstantInt::get(LoadSizeType, GEPIndex));
1966  }
1967 
1968  // Load LoadSizeType from the base address.
1969  Value *LoadSrc1 = Builder.CreateLoad(LoadSizeType, Source1);
1970  Value *LoadSrc2 = Builder.CreateLoad(LoadSizeType, Source2);
1971 
1972  if (DL.isLittleEndian()) {
1974  Intrinsic::bswap, LoadSizeType);
1975  LoadSrc1 = Builder.CreateCall(Bswap, LoadSrc1);
1976  LoadSrc2 = Builder.CreateCall(Bswap, LoadSrc2);
1977  }
1978 
1979  if (LoadSizeType != MaxLoadType) {
1980  LoadSrc1 = Builder.CreateZExt(LoadSrc1, MaxLoadType);
1981  LoadSrc2 = Builder.CreateZExt(LoadSrc2, MaxLoadType);
1982  }
1983 
1984  // Add the loaded values to the phi nodes for calculating memcmp result only
1985  // if result is not used in a zero equality.
1986  if (!IsUsedForZeroCmp) {
1987  ResBlock.PhiSrc1->addIncoming(LoadSrc1, LoadCmpBlocks[Index]);
1988  ResBlock.PhiSrc2->addIncoming(LoadSrc2, LoadCmpBlocks[Index]);
1989  }
1990 
1991  Value *Cmp = Builder.CreateICmp(ICmpInst::ICMP_EQ, LoadSrc1, LoadSrc2);
1992  BasicBlock *NextBB = (Index == (LoadCmpBlocks.size() - 1))
1993  ? EndBlock
1994  : LoadCmpBlocks[Index + 1];
1995  // Early exit branch if difference found to ResultBlock. Otherwise, continue
1996  // to next LoadCmpBlock or EndBlock.
1997  BranchInst *CmpBr = BranchInst::Create(NextBB, ResBlock.BB, Cmp);
1998  Builder.Insert(CmpBr);
1999 
2000  // Add a phi edge for the last LoadCmpBlock to Endblock with a value of 0
2001  // since early exit to ResultBlock was not taken (no difference was found in
2002  // any of the bytes).
2003  if (Index == LoadCmpBlocks.size() - 1) {
2004  Value *Zero = ConstantInt::get(Type::getInt32Ty(CI->getContext()), 0);
2005  PhiRes->addIncoming(Zero, LoadCmpBlocks[Index]);
2006  }
2007 }
2008 
2009 // This function populates the ResultBlock with a sequence to calculate the
2010 // memcmp result. It compares the two loaded source values and returns -1 if
2011 // src1 < src2 and 1 if src1 > src2.
2012 void MemCmpExpansion::emitMemCmpResultBlock() {
2013  // Special case: if memcmp result is used in a zero equality, result does not
2014  // need to be calculated and can simply return 1.
2015  if (IsUsedForZeroCmp) {
2016  BasicBlock::iterator InsertPt = ResBlock.BB->getFirstInsertionPt();
2017  Builder.SetInsertPoint(ResBlock.BB, InsertPt);
2018  Value *Res = ConstantInt::get(Type::getInt32Ty(CI->getContext()), 1);
2019  PhiRes->addIncoming(Res, ResBlock.BB);
2020  BranchInst *NewBr = BranchInst::Create(EndBlock);
2021  Builder.Insert(NewBr);
2022  return;
2023  }
2024  BasicBlock::iterator InsertPt = ResBlock.BB->getFirstInsertionPt();
2025  Builder.SetInsertPoint(ResBlock.BB, InsertPt);
2026 
2027  Value *Cmp = Builder.CreateICmp(ICmpInst::ICMP_ULT, ResBlock.PhiSrc1,
2028  ResBlock.PhiSrc2);
2029 
2030  Value *Res =
2031  Builder.CreateSelect(Cmp, ConstantInt::get(Builder.getInt32Ty(), -1),
2032  ConstantInt::get(Builder.getInt32Ty(), 1));
2033 
2034  BranchInst *NewBr = BranchInst::Create(EndBlock);
2035  Builder.Insert(NewBr);
2036  PhiRes->addIncoming(Res, ResBlock.BB);
2037 }
2038 
2039 unsigned MemCmpExpansion::calculateNumBlocks(unsigned Size) {
2040  unsigned NumBlocks = 0;
2041  bool HaveOneByteLoad = false;
2042  unsigned RemainingSize = Size;
2043  unsigned LoadSize = MaxLoadSize;
2044  while (RemainingSize) {
2045  if (LoadSize == 1)
2046  HaveOneByteLoad = true;
2047  NumBlocks += RemainingSize / LoadSize;
2048  RemainingSize = RemainingSize % LoadSize;
2049  LoadSize = LoadSize / 2;
2050  }
2051  NumBlocksNonOneByte = HaveOneByteLoad ? (NumBlocks - 1) : NumBlocks;
2052 
2053  if (IsUsedForZeroCmp)
2054  NumBlocks = NumBlocks / NumLoadsPerBlock +
2055  (NumBlocks % NumLoadsPerBlock != 0 ? 1 : 0);
2056 
2057  return NumBlocks;
2058 }
2059 
2060 void MemCmpExpansion::setupResultBlockPHINodes() {
2061  Type *MaxLoadType = IntegerType::get(CI->getContext(), MaxLoadSize * 8);
2062  Builder.SetInsertPoint(ResBlock.BB);
2063  ResBlock.PhiSrc1 =
2064  Builder.CreatePHI(MaxLoadType, NumBlocksNonOneByte, "phi.src1");
2065  ResBlock.PhiSrc2 =
2066  Builder.CreatePHI(MaxLoadType, NumBlocksNonOneByte, "phi.src2");
2067 }
2068 
2069 void MemCmpExpansion::setupEndBlockPHINodes() {
2070  Builder.SetInsertPoint(&EndBlock->front());
2071  PhiRes = Builder.CreatePHI(Type::getInt32Ty(CI->getContext()), 2, "phi.res");
2072 }
2073 
2074 Value *MemCmpExpansion::getMemCmpExpansionZeroCase(unsigned Size) {
2075  unsigned NumBytesProcessed = 0;
2076  // This loop populates each of the LoadCmpBlocks with the IR sequence to
2077  // handle multiple loads per block.
2078  for (unsigned i = 0; i < NumBlocks; ++i)
2079  emitLoadCompareBlockMultipleLoads(i, Size, NumBytesProcessed);
2080 
2081  emitMemCmpResultBlock();
2082  return PhiRes;
2083 }
2084 
2085 /// A memcmp expansion that compares equality with 0 and only has one block of
2086 /// load and compare can bypass the compare, branch, and phi IR that is required
2087 /// in the general case.
2088 Value *MemCmpExpansion::getMemCmpEqZeroOneBlock(unsigned Size) {
2089  unsigned NumBytesProcessed = 0;
2090  Value *Cmp = getCompareLoadPairs(0, Size, NumBytesProcessed);
2091  return Builder.CreateZExt(Cmp, Type::getInt32Ty(CI->getContext()));
2092 }
2093 
2094 /// A memcmp expansion that only has one block of load and compare can bypass
2095 /// the compare, branch, and phi IR that is required in the general case.
2096 Value *MemCmpExpansion::getMemCmpOneBlock(unsigned Size) {
2097  assert(NumLoadsPerBlock == 1 && "Only handles one load pair per block");
2098 
2099  Type *LoadSizeType = IntegerType::get(CI->getContext(), Size * 8);
2100  Value *Source1 = CI->getArgOperand(0);
2101  Value *Source2 = CI->getArgOperand(1);
2102 
2103  // Cast source to LoadSizeType*.
2104  if (Source1->getType() != LoadSizeType)
2105  Source1 = Builder.CreateBitCast(Source1, LoadSizeType->getPointerTo());
2106  if (Source2->getType() != LoadSizeType)
2107  Source2 = Builder.CreateBitCast(Source2, LoadSizeType->getPointerTo());
2108 
2109  // Load LoadSizeType from the base address.
2110  Value *LoadSrc1 = Builder.CreateLoad(LoadSizeType, Source1);
2111  Value *LoadSrc2 = Builder.CreateLoad(LoadSizeType, Source2);
2112 
2113  if (DL.isLittleEndian() && Size != 1) {
2115  Intrinsic::bswap, LoadSizeType);
2116  LoadSrc1 = Builder.CreateCall(Bswap, LoadSrc1);
2117  LoadSrc2 = Builder.CreateCall(Bswap, LoadSrc2);
2118  }
2119 
2120  // TODO: Instead of comparing ULT, just subtract and return the difference?
2121  Value *CmpNE = Builder.CreateICmpNE(LoadSrc1, LoadSrc2);
2122  Value *CmpULT = Builder.CreateICmpULT(LoadSrc1, LoadSrc2);
2123  Type *I32 = Builder.getInt32Ty();
2124  Value *Sel1 = Builder.CreateSelect(CmpULT, ConstantInt::get(I32, -1),
2125  ConstantInt::get(I32, 1));
2126  return Builder.CreateSelect(CmpNE, Sel1, ConstantInt::get(I32, 0));
2127 }
2128 
2129 // This function expands the memcmp call into an inline expansion and returns
2130 // the memcmp result.
2132  if (IsUsedForZeroCmp)
2133  return NumBlocks == 1 ? getMemCmpEqZeroOneBlock(Size) :
2134  getMemCmpExpansionZeroCase(Size);
2135 
2136  // TODO: Handle more than one load pair per block in getMemCmpOneBlock().
2137  if (NumBlocks == 1 && NumLoadsPerBlock == 1)
2138  return getMemCmpOneBlock(Size);
2139 
2140  // This loop calls emitLoadCompareBlock for comparing Size bytes of the two
2141  // memcmp sources. It starts with loading using the maximum load size set by
2142  // the target. It processes any remaining bytes using a load size which is the
2143  // next smallest power of 2.
2144  unsigned LoadSize = MaxLoadSize;
2145  unsigned NumBytesToBeProcessed = Size;
2146  unsigned Index = 0;
2147  while (NumBytesToBeProcessed) {
2148  // Calculate how many blocks we can create with the current load size.
2149  unsigned NumBlocks = NumBytesToBeProcessed / LoadSize;
2150  unsigned GEPIndex = (Size - NumBytesToBeProcessed) / LoadSize;
2151  NumBytesToBeProcessed = NumBytesToBeProcessed % LoadSize;
2152 
2153  // For each NumBlocks, populate the instruction sequence for loading and
2154  // comparing LoadSize bytes.
2155  while (NumBlocks--) {
2156  emitLoadCompareBlock(Index, LoadSize, GEPIndex);
2157  Index++;
2158  GEPIndex++;
2159  }
2160  // Get the next LoadSize to use.
2161  LoadSize = LoadSize / 2;
2162  }
2163 
2164  emitMemCmpResultBlock();
2165  return PhiRes;
2166 }
2167 
2168 // This function checks to see if an expansion of memcmp can be generated.
2169 // It checks for constant compare size that is less than the max inline size.
2170 // If an expansion cannot occur, returns false to leave as a library call.
2171 // Otherwise, the library call is replaced with a new IR instruction sequence.
2172 /// We want to transform:
2173 /// %call = call signext i32 @memcmp(i8* %0, i8* %1, i64 15)
2174 /// To:
2175 /// loadbb:
2176 /// %0 = bitcast i32* %buffer2 to i8*
2177 /// %1 = bitcast i32* %buffer1 to i8*
2178 /// %2 = bitcast i8* %1 to i64*
2179 /// %3 = bitcast i8* %0 to i64*
2180 /// %4 = load i64, i64* %2
2181 /// %5 = load i64, i64* %3
2182 /// %6 = call i64 @llvm.bswap.i64(i64 %4)
2183 /// %7 = call i64 @llvm.bswap.i64(i64 %5)
2184 /// %8 = sub i64 %6, %7
2185 /// %9 = icmp ne i64 %8, 0
2186 /// br i1 %9, label %res_block, label %loadbb1
2187 /// res_block: ; preds = %loadbb2,
2188 /// %loadbb1, %loadbb
2189 /// %phi.src1 = phi i64 [ %6, %loadbb ], [ %22, %loadbb1 ], [ %36, %loadbb2 ]
2190 /// %phi.src2 = phi i64 [ %7, %loadbb ], [ %23, %loadbb1 ], [ %37, %loadbb2 ]
2191 /// %10 = icmp ult i64 %phi.src1, %phi.src2
2192 /// %11 = select i1 %10, i32 -1, i32 1
2193 /// br label %endblock
2194 /// loadbb1: ; preds = %loadbb
2195 /// %12 = bitcast i32* %buffer2 to i8*
2196 /// %13 = bitcast i32* %buffer1 to i8*
2197 /// %14 = bitcast i8* %13 to i32*
2198 /// %15 = bitcast i8* %12 to i32*
2199 /// %16 = getelementptr i32, i32* %14, i32 2
2200 /// %17 = getelementptr i32, i32* %15, i32 2
2201 /// %18 = load i32, i32* %16
2202 /// %19 = load i32, i32* %17
2203 /// %20 = call i32 @llvm.bswap.i32(i32 %18)
2204 /// %21 = call i32 @llvm.bswap.i32(i32 %19)
2205 /// %22 = zext i32 %20 to i64
2206 /// %23 = zext i32 %21 to i64
2207 /// %24 = sub i64 %22, %23
2208 /// %25 = icmp ne i64 %24, 0
2209 /// br i1 %25, label %res_block, label %loadbb2
2210 /// loadbb2: ; preds = %loadbb1
2211 /// %26 = bitcast i32* %buffer2 to i8*
2212 /// %27 = bitcast i32* %buffer1 to i8*
2213 /// %28 = bitcast i8* %27 to i16*
2214 /// %29 = bitcast i8* %26 to i16*
2215 /// %30 = getelementptr i16, i16* %28, i16 6
2216 /// %31 = getelementptr i16, i16* %29, i16 6
2217 /// %32 = load i16, i16* %30
2218 /// %33 = load i16, i16* %31
2219 /// %34 = call i16 @llvm.bswap.i16(i16 %32)
2220 /// %35 = call i16 @llvm.bswap.i16(i16 %33)
2221 /// %36 = zext i16 %34 to i64
2222 /// %37 = zext i16 %35 to i64
2223 /// %38 = sub i64 %36, %37
2224 /// %39 = icmp ne i64 %38, 0
2225 /// br i1 %39, label %res_block, label %loadbb3
2226 /// loadbb3: ; preds = %loadbb2
2227 /// %40 = bitcast i32* %buffer2 to i8*
2228 /// %41 = bitcast i32* %buffer1 to i8*
2229 /// %42 = getelementptr i8, i8* %41, i8 14
2230 /// %43 = getelementptr i8, i8* %40, i8 14
2231 /// %44 = load i8, i8* %42
2232 /// %45 = load i8, i8* %43
2233 /// %46 = zext i8 %44 to i32
2234 /// %47 = zext i8 %45 to i32
2235 /// %48 = sub i32 %46, %47
2236 /// br label %endblock
2237 /// endblock: ; preds = %res_block,
2238 /// %loadbb3
2239 /// %phi.res = phi i32 [ %48, %loadbb3 ], [ %11, %res_block ]
2240 /// ret i32 %phi.res
2241 static bool expandMemCmp(CallInst *CI, const TargetTransformInfo *TTI,
2242  const TargetLowering *TLI, const DataLayout *DL) {
2243  NumMemCmpCalls++;
2244 
2245  // TTI call to check if target would like to expand memcmp. Also, get the
2246  // MaxLoadSize.
2247  unsigned MaxLoadSize;
2248  if (!TTI->expandMemCmp(CI, MaxLoadSize))
2249  return false;
2250 
2251  // Early exit from expansion if -Oz.
2252  if (CI->getFunction()->optForMinSize())
2253  return false;
2254 
2255  // Early exit from expansion if size is not a constant.
2256  ConstantInt *SizeCast = dyn_cast<ConstantInt>(CI->getArgOperand(2));
2257  if (!SizeCast) {
2258  NumMemCmpNotConstant++;
2259  return false;
2260  }
2261 
2262  // Early exit from expansion if size greater than max bytes to load.
2263  uint64_t SizeVal = SizeCast->getZExtValue();
2264  unsigned NumLoads = 0;
2265  unsigned RemainingSize = SizeVal;
2266  unsigned LoadSize = MaxLoadSize;
2267  while (RemainingSize) {
2268  NumLoads += RemainingSize / LoadSize;
2269  RemainingSize = RemainingSize % LoadSize;
2270  LoadSize = LoadSize / 2;
2271  }
2272 
2273  if (NumLoads > TLI->getMaxExpandSizeMemcmp(CI->getFunction()->optForSize())) {
2274  NumMemCmpGreaterThanMax++;
2275  return false;
2276  }
2277 
2278  NumMemCmpInlined++;
2279 
2280  // MemCmpHelper object creates and sets up basic blocks required for
2281  // expanding memcmp with size SizeVal.
2282  unsigned NumLoadsPerBlock = MemCmpNumLoadsPerBlock;
2283  MemCmpExpansion MemCmpHelper(CI, SizeVal, MaxLoadSize, NumLoadsPerBlock, *DL);
2284 
2285  Value *Res = MemCmpHelper.getMemCmpExpansion(SizeVal);
2286 
2287  // Replace call with result of expansion and erase call.
2288  CI->replaceAllUsesWith(Res);
2289  CI->eraseFromParent();
2290 
2291  return true;
2292 }
2293 
2294 bool CodeGenPrepare::optimizeCallInst(CallInst *CI, bool &ModifiedDT) {
2295  BasicBlock *BB = CI->getParent();
2296 
2297  // Lower inline assembly if we can.
2298  // If we found an inline asm expession, and if the target knows how to
2299  // lower it to normal LLVM code, do so now.
2300  if (TLI && isa<InlineAsm>(CI->getCalledValue())) {
2301  if (TLI->ExpandInlineAsm(CI)) {
2302  // Avoid invalidating the iterator.
2303  CurInstIterator = BB->begin();
2304  // Avoid processing instructions out of order, which could cause
2305  // reuse before a value is defined.
2306  SunkAddrs.clear();
2307  return true;
2308  }
2309  // Sink address computing for memory operands into the block.
2310  if (optimizeInlineAsmInst(CI))
2311  return true;
2312  }
2313 
2314  // Align the pointer arguments to this call if the target thinks it's a good
2315  // idea
2316  unsigned MinSize, PrefAlign;
2317  if (TLI && TLI->shouldAlignPointerArgs(CI, MinSize, PrefAlign)) {
2318  for (auto &Arg : CI->arg_operands()) {
2319  // We want to align both objects whose address is used directly and
2320  // objects whose address is used in casts and GEPs, though it only makes
2321  // sense for GEPs if the offset is a multiple of the desired alignment and
2322  // if size - offset meets the size threshold.
2323  if (!Arg->getType()->isPointerTy())
2324  continue;
2326  cast<PointerType>(Arg->getType())->getAddressSpace()),
2327  0);
2328  Value *Val = Arg->stripAndAccumulateInBoundsConstantOffsets(*DL, Offset);
2329  uint64_t Offset2 = Offset.getLimitedValue();
2330  if ((Offset2 & (PrefAlign-1)) != 0)
2331  continue;
2332  AllocaInst *AI;
2333  if ((AI = dyn_cast<AllocaInst>(Val)) && AI->getAlignment() < PrefAlign &&
2334  DL->getTypeAllocSize(AI->getAllocatedType()) >= MinSize + Offset2)
2335  AI->setAlignment(PrefAlign);
2336  // Global variables can only be aligned if they are defined in this
2337  // object (i.e. they are uniquely initialized in this object), and
2338  // over-aligning global variables that have an explicit section is
2339  // forbidden.
2340  GlobalVariable *GV;
2341  if ((GV = dyn_cast<GlobalVariable>(Val)) && GV->canIncreaseAlignment() &&
2342  GV->getPointerAlignment(*DL) < PrefAlign &&
2343  DL->getTypeAllocSize(GV->getValueType()) >=
2344  MinSize + Offset2)
2345  GV->setAlignment(PrefAlign);
2346  }
2347  // If this is a memcpy (or similar) then we may be able to improve the
2348  // alignment
2349  if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(CI)) {
2350  unsigned Align = getKnownAlignment(MI->getDest(), *DL);
2351  if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
2352  Align = std::min(Align, getKnownAlignment(MTI->getSource(), *DL));
2353  if (Align > MI->getAlignment())
2354  MI->setAlignment(ConstantInt::get(MI->getAlignmentType(), Align));
2355  }
2356  }
2357 
2358  // If we have a cold call site, try to sink addressing computation into the
2359  // cold block. This interacts with our handling for loads and stores to
2360  // ensure that we can fold all uses of a potential addressing computation
2361  // into their uses. TODO: generalize this to work over profiling data
2362  if (!OptSize && CI->hasFnAttr(Attribute::Cold))
2363  for (auto &Arg : CI->arg_operands()) {
2364  if (!Arg->getType()->isPointerTy())
2365  continue;
2366  unsigned AS = Arg->getType()->getPointerAddressSpace();
2367  return optimizeMemoryInst(CI, Arg, Arg->getType(), AS);
2368  }
2369 
2371  if (II) {
2372  switch (II->getIntrinsicID()) {
2373  default: break;
2374  case Intrinsic::objectsize: {
2375  // Lower all uses of llvm.objectsize.*
2376  ConstantInt *RetVal =
2377  lowerObjectSizeCall(II, *DL, TLInfo, /*MustSucceed=*/true);
2378  // Substituting this can cause recursive simplifications, which can
2379  // invalidate our iterator. Use a WeakTrackingVH to hold onto it in case
2380  // this
2381  // happens.
2382  Value *CurValue = &*CurInstIterator;
2383  WeakTrackingVH IterHandle(CurValue);
2384 
2385  replaceAndRecursivelySimplify(CI, RetVal, TLInfo, nullptr);
2386 
2387  // If the iterator instruction was recursively deleted, start over at the
2388  // start of the block.
2389  if (IterHandle != CurValue) {
2390  CurInstIterator = BB->begin();
2391  SunkAddrs.clear();
2392  }
2393  return true;
2394  }
2395  case Intrinsic::aarch64_stlxr:
2396  case Intrinsic::aarch64_stxr: {
2397  ZExtInst *ExtVal = dyn_cast<ZExtInst>(CI->getArgOperand(0));
2398  if (!ExtVal || !ExtVal->hasOneUse() ||
2399  ExtVal->getParent() == CI->getParent())
2400  return false;
2401  // Sink a zext feeding stlxr/stxr before it, so it can be folded into it.
2402  ExtVal->moveBefore(CI);
2403  // Mark this instruction as "inserted by CGP", so that other
2404  // optimizations don't touch it.
2405  InsertedInsts.insert(ExtVal);
2406  return true;
2407  }
2408  case Intrinsic::invariant_group_barrier:
2409  II->replaceAllUsesWith(II->getArgOperand(0));
2410  II->eraseFromParent();
2411  return true;
2412 
2413  case Intrinsic::cttz:
2414  case Intrinsic::ctlz:
2415  // If counting zeros is expensive, try to avoid it.
2416  return despeculateCountZeros(II, TLI, DL, ModifiedDT);
2417  }
2418 
2419  if (TLI) {
2420  SmallVector<Value*, 2> PtrOps;
2421  Type *AccessTy;
2422  if (TLI->getAddrModeArguments(II, PtrOps, AccessTy))
2423  while (!PtrOps.empty()) {
2424  Value *PtrVal = PtrOps.pop_back_val();
2425  unsigned AS = PtrVal->getType()->getPointerAddressSpace();
2426  if (optimizeMemoryInst(II, PtrVal, AccessTy, AS))
2427  return true;
2428  }
2429  }
2430  }
2431 
2432  // From here on out we're working with named functions.
2433  if (!CI->getCalledFunction()) return false;
2434 
2435  // Lower all default uses of _chk calls. This is very similar
2436  // to what InstCombineCalls does, but here we are only lowering calls
2437  // to fortified library functions (e.g. __memcpy_chk) that have the default
2438  // "don't know" as the objectsize. Anything else should be left alone.
2439  FortifiedLibCallSimplifier Simplifier(TLInfo, true);
2440  if (Value *V = Simplifier.optimizeCall(CI)) {
2441  CI->replaceAllUsesWith(V);
2442  CI->eraseFromParent();
2443  return true;
2444  }
2445 
2446  LibFunc Func;
2447  if (TLInfo->getLibFunc(ImmutableCallSite(CI), Func) &&
2448  Func == LibFunc_memcmp && expandMemCmp(CI, TTI, TLI, DL)) {
2449  ModifiedDT = true;
2450  return true;
2451  }
2452  return false;
2453 }
2454 
2455 /// Look for opportunities to duplicate return instructions to the predecessor
2456 /// to enable tail call optimizations. The case it is currently looking for is:
2457 /// @code
2458 /// bb0:
2459 /// %tmp0 = tail call i32 @f0()
2460 /// br label %return
2461 /// bb1:
2462 /// %tmp1 = tail call i32 @f1()
2463 /// br label %return
2464 /// bb2:
2465 /// %tmp2 = tail call i32 @f2()
2466 /// br label %return
2467 /// return:
2468 /// %retval = phi i32 [ %tmp0, %bb0 ], [ %tmp1, %bb1 ], [ %tmp2, %bb2 ]
2469 /// ret i32 %retval
2470 /// @endcode
2471 ///
2472 /// =>
2473 ///
2474 /// @code
2475 /// bb0:
2476 /// %tmp0 = tail call i32 @f0()
2477 /// ret i32 %tmp0
2478 /// bb1:
2479 /// %tmp1 = tail call i32 @f1()
2480 /// ret i32 %tmp1
2481 /// bb2:
2482 /// %tmp2 = tail call i32 @f2()
2483 /// ret i32 %tmp2
2484 /// @endcode
2485 bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB) {
2486  if (!TLI)
2487  return false;
2488 
2489  ReturnInst *RetI = dyn_cast<ReturnInst>(BB->getTerminator());
2490  if (!RetI)
2491  return false;
2492 
2493  PHINode *PN = nullptr;
2494  BitCastInst *BCI = nullptr;
2495  Value *V = RetI->getReturnValue();
2496  if (V) {
2497  BCI = dyn_cast<BitCastInst>(V);
2498  if (BCI)
2499  V = BCI->getOperand(0);
2500 
2501  PN = dyn_cast<PHINode>(V);
2502  if (!PN)
2503  return false;
2504  }
2505 
2506  if (PN && PN->getParent() != BB)
2507  return false;
2508 
2509  // Make sure there are no instructions between the PHI and return, or that the
2510  // return is the first instruction in the block.
2511  if (PN) {
2512  BasicBlock::iterator BI = BB->begin();
2513  do { ++BI; } while (isa<DbgInfoIntrinsic>(BI));
2514  if (&*BI == BCI)
2515  // Also skip over the bitcast.
2516  ++BI;
2517  if (&*BI != RetI)
2518  return false;
2519  } else {
2520  BasicBlock::iterator BI = BB->begin();
2521  while (isa<DbgInfoIntrinsic>(BI)) ++BI;
2522  if (&*BI != RetI)
2523  return false;
2524  }
2525 
2526  /// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
2527  /// call.
2528  const Function *F = BB->getParent();
2529  SmallVector<CallInst*, 4> TailCalls;
2530  if (PN) {
2531  for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
2532  CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I));
2533  // Make sure the phi value is indeed produced by the tail call.
2534  if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
2535  TLI->mayBeEmittedAsTailCall(CI) &&
2536  attributesPermitTailCall(F, CI, RetI, *TLI))
2537  TailCalls.push_back(CI);
2538  }
2539  } else {
2540  SmallPtrSet<BasicBlock*, 4> VisitedBBs;
2541  for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
2542  if (!VisitedBBs.insert(*PI).second)
2543  continue;
2544 
2545  BasicBlock::InstListType &InstList = (*PI)->getInstList();
2546  BasicBlock::InstListType::reverse_iterator RI = InstList.rbegin();
2547  BasicBlock::InstListType::reverse_iterator RE = InstList.rend();
2548  do { ++RI; } while (RI != RE && isa<DbgInfoIntrinsic>(&*RI));
2549  if (RI == RE)
2550  continue;
2551 
2552  CallInst *CI = dyn_cast<CallInst>(&*RI);
2553  if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI) &&
2554  attributesPermitTailCall(F, CI, RetI, *TLI))
2555  TailCalls.push_back(CI);
2556  }
2557  }
2558 
2559  bool Changed = false;
2560  for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) {
2561  CallInst *CI = TailCalls[i];
2562  CallSite CS(CI);
2563 
2564  // Conservatively require the attributes of the call to match those of the
2565  // return. Ignore noalias because it doesn't affect the call sequence.
2566  AttributeList CalleeAttrs = CS.getAttributes();
2567  if (AttrBuilder(CalleeAttrs, AttributeList::ReturnIndex)
2568  .removeAttribute(Attribute::NoAlias) !=
2569  AttrBuilder(CalleeAttrs, AttributeList::ReturnIndex)
2570  .removeAttribute(Attribute::NoAlias))
2571  continue;
2572 
2573  // Make sure the call instruction is followed by an unconditional branch to
2574  // the return block.
2575  BasicBlock *CallBB = CI->getParent();
2576  BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator());
2577  if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB)
2578  continue;
2579 
2580  // Duplicate the return into CallBB.
2581  (void)FoldReturnIntoUncondBranch(RetI, BB, CallBB);
2582  ModifiedDT = Changed = true;
2583  ++NumRetsDup;
2584  }
2585 
2586  // If we eliminated all predecessors of the block, delete the block now.
2587  if (Changed && !BB->hasAddressTaken() && pred_begin(BB) == pred_end(BB))
2588  BB->eraseFromParent();
2589 
2590  return Changed;
2591 }
2592 
2593 //===----------------------------------------------------------------------===//
2594 // Memory Optimization
2595 //===----------------------------------------------------------------------===//
2596 
2597 namespace {
2598 
2599 /// This is an extended version of TargetLowering::AddrMode
2600 /// which holds actual Value*'s for register values.
2601 struct ExtAddrMode : public TargetLowering::AddrMode {
2602  Value *BaseReg;
2603  Value *ScaledReg;
2604  ExtAddrMode() : BaseReg(nullptr), ScaledReg(nullptr) {}
2605  void print(raw_ostream &OS) const;
2606  void dump() const;
2607 
2608  bool operator==(const ExtAddrMode& O) const {
2609  return (BaseReg == O.BaseReg) && (ScaledReg == O.ScaledReg) &&
2610  (BaseGV == O.BaseGV) && (BaseOffs == O.BaseOffs) &&
2611  (HasBaseReg == O.HasBaseReg) && (Scale == O.Scale);
2612  }
2613 };
2614 
2615 #ifndef NDEBUG
2616 static inline raw_ostream &operator<<(raw_ostream &OS, const ExtAddrMode &AM) {
2617  AM.print(OS);
2618  return OS;
2619 }
2620 #endif
2621 
2622 void ExtAddrMode::print(raw_ostream &OS) const {
2623  bool NeedPlus = false;
2624  OS << "[";
2625  if (BaseGV) {
2626  OS << (NeedPlus ? " + " : "")
2627  << "GV:";
2628  BaseGV->printAsOperand(OS, /*PrintType=*/false);
2629  NeedPlus = true;
2630  }
2631 
2632  if (BaseOffs) {
2633  OS << (NeedPlus ? " + " : "")
2634  << BaseOffs;
2635  NeedPlus = true;
2636  }
2637 
2638  if (BaseReg) {
2639  OS << (NeedPlus ? " + " : "")
2640  << "Base:";
2641  BaseReg->printAsOperand(OS, /*PrintType=*/false);
2642  NeedPlus = true;
2643  }
2644  if (Scale) {
2645  OS << (NeedPlus ? " + " : "")
2646  << Scale << "*";
2647  ScaledReg->printAsOperand(OS, /*PrintType=*/false);
2648  }
2649 
2650  OS << ']';
2651 }
2652 
2653 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
2654 LLVM_DUMP_METHOD void ExtAddrMode::dump() const {
2655  print(dbgs());
2656  dbgs() << '\n';
2657 }
2658 #endif
2659 
2660 /// \brief This class provides transaction based operation on the IR.
2661 /// Every change made through this class is recorded in the internal state and
2662 /// can be undone (rollback) until commit is called.
2663 class TypePromotionTransaction {
2664 
2665  /// \brief This represents the common interface of the individual transaction.
2666  /// Each class implements the logic for doing one specific modification on
2667  /// the IR via the TypePromotionTransaction.
2668  class TypePromotionAction {
2669  protected:
2670  /// The Instruction modified.
2671  Instruction *Inst;
2672 
2673  public:
2674  /// \brief Constructor of the action.
2675  /// The constructor performs the related action on the IR.
2676  TypePromotionAction(Instruction *Inst) : Inst(Inst) {}
2677 
2678  virtual ~TypePromotionAction() {}
2679 
2680  /// \brief Undo the modification done by this action.
2681  /// When this method is called, the IR must be in the same state as it was
2682  /// before this action was applied.
2683  /// \pre Undoing the action works if and only if the IR is in the exact same
2684  /// state as it was directly after this action was applied.
2685  virtual void undo() = 0;
2686 
2687  /// \brief Advocate every change made by this action.
2688  /// When the results on the IR of the action are to be kept, it is important
2689  /// to call this function, otherwise hidden information may be kept forever.
2690  virtual void commit() {
2691  // Nothing to be done, this action is not doing anything.
2692  }
2693  };
2694 
2695  /// \brief Utility to remember the position of an instruction.
2696  class InsertionHandler {
2697  /// Position of an instruction.
2698  /// Either an instruction:
2699  /// - Is the first in a basic block: BB is used.
2700  /// - Has a previous instructon: PrevInst is used.
2701  union {
2702  Instruction *PrevInst;
2703  BasicBlock *BB;
2704  } Point;
2705  /// Remember whether or not the instruction had a previous instruction.
2706  bool HasPrevInstruction;
2707 
2708  public:
2709  /// \brief Record the position of \p Inst.
2710  InsertionHandler(Instruction *Inst) {
2711  BasicBlock::iterator It = Inst->getIterator();
2712  HasPrevInstruction = (It != (Inst->getParent()->begin()));
2713  if (HasPrevInstruction)
2714  Point.PrevInst = &*--It;
2715  else
2716  Point.BB = Inst->getParent();
2717  }
2718 
2719  /// \brief Insert \p Inst at the recorded position.
2720  void insert(Instruction *Inst) {
2721  if (HasPrevInstruction) {
2722  if (Inst->getParent())
2723  Inst->removeFromParent();
2724  Inst->insertAfter(Point.PrevInst);
2725  } else {
2726  Instruction *Position = &*Point.BB->getFirstInsertionPt();
2727  if (Inst->getParent())
2728  Inst->moveBefore(Position);
2729  else
2730  Inst->insertBefore(Position);
2731  }
2732  }
2733  };
2734 
2735  /// \brief Move an instruction before another.
2736  class InstructionMoveBefore : public TypePromotionAction {
2737  /// Original position of the instruction.
2738  InsertionHandler Position;
2739 
2740  public:
2741  /// \brief Move \p Inst before \p Before.
2742  InstructionMoveBefore(Instruction *Inst, Instruction *Before)
2743  : TypePromotionAction(Inst), Position(Inst) {
2744  DEBUG(dbgs() << "Do: move: " << *Inst << "\nbefore: " << *Before << "\n");
2745  Inst->moveBefore(Before);
2746  }
2747 
2748  /// \brief Move the instruction back to its original position.
2749  void undo() override {
2750  DEBUG(dbgs() << "Undo: moveBefore: " << *Inst << "\n");
2751  Position.insert(Inst);
2752  }
2753  };
2754 
2755  /// \brief Set the operand of an instruction with a new value.
2756  class OperandSetter : public TypePromotionAction {
2757  /// Original operand of the instruction.
2758  Value *Origin;
2759  /// Index of the modified instruction.
2760  unsigned Idx;
2761 
2762  public:
2763  /// \brief Set \p Idx operand of \p Inst with \p NewVal.
2764  OperandSetter(Instruction *Inst, unsigned Idx, Value *NewVal)
2765  : TypePromotionAction(Inst), Idx(Idx) {
2766  DEBUG(dbgs() << "Do: setOperand: " << Idx << "\n"
2767  << "for:" << *Inst << "\n"
2768  << "with:" << *NewVal << "\n");
2769  Origin = Inst->getOperand(Idx);
2770  Inst->setOperand(Idx, NewVal);
2771  }
2772 
2773  /// \brief Restore the original value of the instruction.
2774  void undo() override {
2775  DEBUG(dbgs() << "Undo: setOperand:" << Idx << "\n"
2776  << "for: " << *Inst << "\n"
2777  << "with: " << *Origin << "\n");
2778  Inst->setOperand(Idx, Origin);
2779  }
2780  };
2781 
2782  /// \brief Hide the operands of an instruction.
2783  /// Do as if this instruction was not using any of its operands.
2784  class OperandsHider : public TypePromotionAction {
2785  /// The list of original operands.
2786  SmallVector<Value *, 4> OriginalValues;
2787 
2788  public:
2789  /// \brief Remove \p Inst from the uses of the operands of \p Inst.
2790  OperandsHider(Instruction *Inst) : TypePromotionAction(Inst) {
2791  DEBUG(dbgs() << "Do: OperandsHider: " << *Inst << "\n");
2792  unsigned NumOpnds = Inst->getNumOperands();
2793  OriginalValues.reserve(NumOpnds);
2794  for (unsigned It = 0; It < NumOpnds; ++It) {
2795  // Save the current operand.
2796  Value *Val = Inst->getOperand(It);
2797  OriginalValues.push_back(Val);
2798  // Set a dummy one.
2799  // We could use OperandSetter here, but that would imply an overhead
2800  // that we are not willing to pay.
2801  Inst->setOperand(It, UndefValue::get(Val->getType()));
2802  }
2803  }
2804 
2805  /// \brief Restore the original list of uses.
2806  void undo() override {
2807  DEBUG(dbgs() << "Undo: OperandsHider: " << *Inst << "\n");
2808  for (unsigned It = 0, EndIt = OriginalValues.size(); It != EndIt; ++It)
2809  Inst->setOperand(It, OriginalValues[It]);
2810  }
2811  };
2812 
2813  /// \brief Build a truncate instruction.
2814  class TruncBuilder : public TypePromotionAction {
2815  Value *Val;
2816  public:
2817  /// \brief Build a truncate instruction of \p Opnd producing a \p Ty
2818  /// result.
2819  /// trunc Opnd to Ty.
2820  TruncBuilder(Instruction *Opnd, Type *Ty) : TypePromotionAction(Opnd) {
2821  IRBuilder<> Builder(Opnd);
2822  Val = Builder.CreateTrunc(Opnd, Ty, "promoted");
2823  DEBUG(dbgs() << "Do: TruncBuilder: " << *Val << "\n");
2824  }
2825 
2826  /// \brief Get the built value.
2827  Value *getBuiltValue() { return Val; }
2828 
2829  /// \brief Remove the built instruction.
2830  void undo() override {
2831  DEBUG(dbgs() << "Undo: TruncBuilder: " << *Val << "\n");
2832  if (Instruction *IVal = dyn_cast<Instruction>(Val))
2833  IVal->eraseFromParent();
2834  }
2835  };
2836 
2837  /// \brief Build a sign extension instruction.
2838  class SExtBuilder : public TypePromotionAction {
2839  Value *Val;
2840  public:
2841  /// \brief Build a sign extension instruction of \p Opnd producing a \p Ty
2842  /// result.
2843  /// sext Opnd to Ty.
2844  SExtBuilder(Instruction *InsertPt, Value *Opnd, Type *Ty)
2845  : TypePromotionAction(InsertPt) {
2846  IRBuilder<> Builder(InsertPt);
2847  Val = Builder.CreateSExt(Opnd, Ty, "promoted");
2848  DEBUG(dbgs() << "Do: SExtBuilder: " << *Val << "\n");
2849  }
2850 
2851  /// \brief Get the built value.
2852  Value *getBuiltValue() { return Val; }
2853 
2854  /// \brief Remove the built instruction.
2855  void undo() override {
2856  DEBUG(dbgs() << "Undo: SExtBuilder: " << *Val << "\n");
2857  if (Instruction *IVal = dyn_cast<Instruction>(Val))
2858  IVal->eraseFromParent();
2859  }
2860  };
2861 
2862  /// \brief Build a zero extension instruction.
2863  class ZExtBuilder : public TypePromotionAction {
2864  Value *Val;
2865  public:
2866  /// \brief Build a zero extension instruction of \p Opnd producing a \p Ty
2867  /// result.
2868  /// zext Opnd to Ty.
2869  ZExtBuilder(Instruction *InsertPt, Value *Opnd, Type *Ty)
2870  : TypePromotionAction(InsertPt) {
2871  IRBuilder<> Builder(InsertPt);
2872  Val = Builder.CreateZExt(Opnd, Ty, "promoted");
2873  DEBUG(dbgs() << "Do: ZExtBuilder: " << *Val << "\n");
2874  }
2875 
2876  /// \brief Get the built value.
2877  Value *getBuiltValue() { return Val; }
2878 
2879  /// \brief Remove the built instruction.
2880  void undo() override {
2881  DEBUG(dbgs() << "Undo: ZExtBuilder: " << *Val << "\n");
2882  if (Instruction *IVal = dyn_cast<Instruction>(Val))
2883  IVal->eraseFromParent();
2884  }
2885  };
2886 
2887  /// \brief Mutate an instruction to another type.
2888  class TypeMutator : public TypePromotionAction {
2889  /// Record the original type.
2890  Type *OrigTy;
2891 
2892  public:
2893  /// \brief Mutate the type of \p Inst into \p NewTy.
2894  TypeMutator(Instruction *Inst, Type *NewTy)
2895  : TypePromotionAction(Inst), OrigTy(Inst->getType()) {
2896  DEBUG(dbgs() << "Do: MutateType: " << *Inst << " with " << *NewTy
2897  << "\n");
2898  Inst->mutateType(NewTy);
2899  }
2900 
2901  /// \brief Mutate the instruction back to its original type.
2902  void undo() override {
2903  DEBUG(dbgs() << "Undo: MutateType: " << *Inst << " with " << *OrigTy
2904  << "\n");
2905  Inst->mutateType(OrigTy);
2906  }
2907  };
2908 
2909  /// \brief Replace the uses of an instruction by another instruction.
2910  class UsesReplacer : public TypePromotionAction {
2911  /// Helper structure to keep track of the replaced uses.
2912  struct InstructionAndIdx {
2913  /// The instruction using the instruction.
2914  Instruction *Inst;
2915  /// The index where this instruction is used for Inst.
2916  unsigned Idx;
2917  InstructionAndIdx(Instruction *Inst, unsigned Idx)
2918  : Inst(Inst), Idx(Idx) {}
2919  };
2920 
2921  /// Keep track of the original uses (pair Instruction, Index).
2922  SmallVector<InstructionAndIdx, 4> OriginalUses;
2923  typedef SmallVectorImpl<InstructionAndIdx>::iterator use_iterator;
2924 
2925  public:
2926  /// \brief Replace all the use of \p Inst by \p New.
2927  UsesReplacer(Instruction *Inst, Value *New) : TypePromotionAction(Inst) {
2928  DEBUG(dbgs() << "Do: UsersReplacer: " << *Inst << " with " << *New
2929  << "\n");
2930  // Record the original uses.
2931  for (Use &U : Inst->uses()) {
2932  Instruction *UserI = cast<Instruction>(U.getUser());
2933  OriginalUses.push_back(InstructionAndIdx(UserI, U.getOperandNo()));
2934  }
2935  // Now, we can replace the uses.
2936  Inst->replaceAllUsesWith(New);
2937  }
2938 
2939  /// \brief Reassign the original uses of Inst to Inst.
2940  void undo() override {
2941  DEBUG(dbgs() << "Undo: UsersReplacer: " << *Inst << "\n");
2942  for (use_iterator UseIt = OriginalUses.begin(),
2943  EndIt = OriginalUses.end();
2944  UseIt != EndIt; ++UseIt) {
2945  UseIt->Inst->setOperand(UseIt->Idx, Inst);
2946  }
2947  }
2948  };
2949 
2950  /// \brief Remove an instruction from the IR.
2951  class InstructionRemover : public TypePromotionAction {
2952  /// Original position of the instruction.
2953  InsertionHandler Inserter;
2954  /// Helper structure to hide all the link to the instruction. In other
2955  /// words, this helps to do as if the instruction was removed.
2956  OperandsHider Hider;
2957  /// Keep track of the uses replaced, if any.
2958  UsesReplacer *Replacer;
2959  /// Keep track of instructions removed.
2960  SetOfInstrs &RemovedInsts;
2961 
2962  public:
2963  /// \brief Remove all reference of \p Inst and optinally replace all its
2964  /// uses with New.
2965  /// \p RemovedInsts Keep track of the instructions removed by this Action.
2966  /// \pre If !Inst->use_empty(), then New != nullptr
2967  InstructionRemover(Instruction *Inst, SetOfInstrs &RemovedInsts,
2968  Value *New = nullptr)
2969  : TypePromotionAction(Inst), Inserter(Inst), Hider(Inst),
2970  Replacer(nullptr), RemovedInsts(RemovedInsts) {
2971  if (New)
2972  Replacer = new UsesReplacer(Inst, New);
2973  DEBUG(dbgs() << "Do: InstructionRemover: " << *Inst << "\n");
2974  RemovedInsts.insert(Inst);
2975  /// The instructions removed here will be freed after completing
2976  /// optimizeBlock() for all blocks as we need to keep track of the
2977  /// removed instructions during promotion.
2978  Inst->removeFromParent();
2979  }
2980 
2981  ~InstructionRemover() override { delete Replacer; }
2982 
2983  /// \brief Resurrect the instruction and reassign it to the proper uses if
2984  /// new value was provided when build this action.
2985  void undo() override {
2986  DEBUG(dbgs() << "Undo: InstructionRemover: " << *Inst << "\n");
2987  Inserter.insert(Inst);
2988  if (Replacer)
2989  Replacer->undo();
2990  Hider.undo();
2991  RemovedInsts.erase(Inst);
2992  }
2993  };
2994 
2995 public:
2996  /// Restoration point.
2997  /// The restoration point is a pointer to an action instead of an iterator
2998  /// because the iterator may be invalidated but not the pointer.
2999  typedef const TypePromotionAction *ConstRestorationPt;
3000 
3001  TypePromotionTransaction(SetOfInstrs &RemovedInsts)
3002  : RemovedInsts(RemovedInsts) {}
3003 
3004  /// Advocate every changes made in that transaction.
3005  void commit();
3006  /// Undo all the changes made after the given point.
3007  void rollback(ConstRestorationPt Point);
3008  /// Get the current restoration point.
3009  ConstRestorationPt getRestorationPoint() const;
3010 
3011  /// \name API for IR modification with state keeping to support rollback.
3012  /// @{
3013  /// Same as Instruction::setOperand.
3014  void setOperand(Instruction *Inst, unsigned Idx, Value *NewVal);
3015  /// Same as Instruction::eraseFromParent.
3016  void eraseInstruction(Instruction *Inst, Value *NewVal = nullptr);
3017  /// Same as Value::replaceAllUsesWith.
3018  void replaceAllUsesWith(Instruction *Inst, Value *New);
3019  /// Same as Value::mutateType.
3020  void mutateType(Instruction *Inst, Type *NewTy);
3021  /// Same as IRBuilder::createTrunc.
3022  Value *createTrunc(Instruction *Opnd, Type *Ty);
3023  /// Same as IRBuilder::createSExt.
3024  Value *createSExt(Instruction *Inst, Value *Opnd, Type *Ty);
3025  /// Same as IRBuilder::createZExt.
3026  Value *createZExt(Instruction *Inst, Value *Opnd, Type *Ty);
3027  /// Same as Instruction::moveBefore.
3028  void moveBefore(Instruction *Inst, Instruction *Before);
3029  /// @}
3030 
3031 private:
3032  /// The ordered list of actions made so far.
3034  typedef SmallVectorImpl<std::unique_ptr<TypePromotionAction>>::iterator CommitPt;
3035  SetOfInstrs &RemovedInsts;
3036 };
3037 
3038 void TypePromotionTransaction::setOperand(Instruction *Inst, unsigned Idx,
3039  Value *NewVal) {
3040  Actions.push_back(
3041  make_unique<TypePromotionTransaction::OperandSetter>(Inst, Idx, NewVal));
3042 }
3043 
3044 void TypePromotionTransaction::eraseInstruction(Instruction *Inst,
3045  Value *NewVal) {
3046  Actions.push_back(
3047  make_unique<TypePromotionTransaction::InstructionRemover>(Inst,
3048  RemovedInsts, NewVal));
3049 }
3050 
3051 void TypePromotionTransaction::replaceAllUsesWith(Instruction *Inst,
3052  Value *New) {
3053  Actions.push_back(make_unique<TypePromotionTransaction::UsesReplacer>(Inst, New));
3054 }
3055 
3056 void TypePromotionTransaction::mutateType(Instruction *Inst, Type *NewTy) {
3057  Actions.push_back(make_unique<TypePromotionTransaction::TypeMutator>(Inst, NewTy));
3058 }
3059 
3060 Value *TypePromotionTransaction::createTrunc(Instruction *Opnd,
3061  Type *Ty) {
3062  std::unique_ptr<TruncBuilder> Ptr(new TruncBuilder(Opnd, Ty));
3063  Value *Val = Ptr->getBuiltValue();
3064  Actions.push_back(std::move(Ptr));
3065  return Val;
3066 }
3067 
3068 Value *TypePromotionTransaction::createSExt(Instruction *Inst,
3069  Value *Opnd, Type *Ty) {
3070  std::unique_ptr<SExtBuilder> Ptr(new SExtBuilder(Inst, Opnd, Ty));
3071  Value *Val = Ptr->getBuiltValue();
3072  Actions.push_back(std::move(Ptr));
3073  return Val;
3074 }
3075 
3076 Value *TypePromotionTransaction::createZExt(Instruction *Inst,
3077  Value *Opnd, Type *Ty) {
3078  std::unique_ptr<ZExtBuilder> Ptr(new ZExtBuilder(Inst, Opnd, Ty));
3079  Value *Val = Ptr->getBuiltValue();
3080  Actions.push_back(std::move(Ptr));
3081  return Val;
3082 }
3083 
3084 void TypePromotionTransaction::moveBefore(Instruction *Inst,
3085  Instruction *Before) {
3086  Actions.push_back(
3087  make_unique<TypePromotionTransaction::InstructionMoveBefore>(Inst, Before));
3088 }
3089 
3090 TypePromotionTransaction::ConstRestorationPt
3091 TypePromotionTransaction::getRestorationPoint() const {
3092  return !Actions.empty() ? Actions.back().get() : nullptr;
3093 }
3094 
3095 void TypePromotionTransaction::commit() {
3096  for (CommitPt It = Actions.begin(), EndIt = Actions.end(); It != EndIt;
3097  ++It)
3098  (*It)->commit();
3099  Actions.clear();
3100 }
3101 
3102 void TypePromotionTransaction::rollback(
3103  TypePromotionTransaction::ConstRestorationPt Point) {
3104  while (!Actions.empty() && Point != Actions.back().get()) {
3105  std::unique_ptr<TypePromotionAction> Curr = Actions.pop_back_val();
3106  Curr->undo();
3107  }
3108 }
3109 
3110 /// \brief A helper class for matching addressing modes.
3111 ///
3112 /// This encapsulates the logic for matching the target-legal addressing modes.
3113 class AddressingModeMatcher {
3114  SmallVectorImpl<Instruction*> &AddrModeInsts;
3115  const TargetLowering &TLI;
3116  const TargetRegisterInfo &TRI;
3117  const DataLayout &DL;
3118 
3119  /// AccessTy/MemoryInst - This is the type for the access (e.g. double) and
3120  /// the memory instruction that we're computing this address for.
3121  Type *AccessTy;
3122  unsigned AddrSpace;
3123  Instruction *MemoryInst;
3124 
3125  /// This is the addressing mode that we're building up. This is
3126  /// part of the return value of this addressing mode matching stuff.
3127  ExtAddrMode &AddrMode;
3128 
3129  /// The instructions inserted by other CodeGenPrepare optimizations.
3130  const SetOfInstrs &InsertedInsts;
3131  /// A map from the instructions to their type before promotion.
3132  InstrToOrigTy &PromotedInsts;
3133  /// The ongoing transaction where every action should be registered.
3134  TypePromotionTransaction &TPT;
3135 
3136  /// This is set to true when we should not do profitability checks.
3137  /// When true, IsProfitableToFoldIntoAddressingMode always returns true.
3138  bool IgnoreProfitability;
3139 
3140  AddressingModeMatcher(SmallVectorImpl<Instruction *> &AMI,
3141  const TargetLowering &TLI,
3142  const TargetRegisterInfo &TRI,
3143  Type *AT, unsigned AS,
3144  Instruction *MI, ExtAddrMode &AM,
3145  const SetOfInstrs &InsertedInsts,
3146  InstrToOrigTy &PromotedInsts,
3147  TypePromotionTransaction &TPT)
3148  : AddrModeInsts(AMI), TLI(TLI), TRI(TRI),
3149  DL(MI->getModule()->getDataLayout()), AccessTy(AT), AddrSpace(AS),
3150  MemoryInst(MI), AddrMode(AM), InsertedInsts(InsertedInsts),
3151  PromotedInsts(PromotedInsts), TPT(TPT) {
3152  IgnoreProfitability = false;
3153  }
3154 public:
3155 
3156  /// Find the maximal addressing mode that a load/store of V can fold,
3157  /// give an access type of AccessTy. This returns a list of involved
3158  /// instructions in AddrModeInsts.
3159  /// \p InsertedInsts The instructions inserted by other CodeGenPrepare
3160  /// optimizations.
3161  /// \p PromotedInsts maps the instructions to their type before promotion.
3162  /// \p The ongoing transaction where every action should be registered.
3163  static ExtAddrMode Match(Value *V, Type *AccessTy, unsigned AS,
3164  Instruction *MemoryInst,
3165  SmallVectorImpl<Instruction*> &AddrModeInsts,
3166  const TargetLowering &TLI,
3167  const TargetRegisterInfo &TRI,
3168  const SetOfInstrs &InsertedInsts,
3169  InstrToOrigTy &PromotedInsts,
3170  TypePromotionTransaction &TPT) {
3171  ExtAddrMode Result;
3172 
3173  bool Success = AddressingModeMatcher(AddrModeInsts, TLI, TRI,
3174  AccessTy, AS,
3175  MemoryInst, Result, InsertedInsts,
3176  PromotedInsts, TPT).matchAddr(V, 0);
3177  (void)Success; assert(Success && "Couldn't select *anything*?");
3178  return Result;
3179  }
3180 private:
3181  bool matchScaledValue(Value *ScaleReg, int64_t Scale, unsigned Depth);
3182  bool matchAddr(Value *V, unsigned Depth);
3183  bool matchOperationAddr(User *Operation, unsigned Opcode, unsigned Depth,
3184  bool *MovedAway = nullptr);
3185  bool isProfitableToFoldIntoAddressingMode(Instruction *I,
3186  ExtAddrMode &AMBefore,
3187  ExtAddrMode &AMAfter);
3188  bool valueAlreadyLiveAtInst(Value *Val, Value *KnownLive1, Value *KnownLive2);
3189  bool isPromotionProfitable(unsigned NewCost, unsigned OldCost,
3190  Value *PromotedOperand) const;
3191 };
3192 
3193 /// Try adding ScaleReg*Scale to the current addressing mode.
3194 /// Return true and update AddrMode if this addr mode is legal for the target,
3195 /// false if not.
3196 bool AddressingModeMatcher::matchScaledValue(Value *ScaleReg, int64_t Scale,
3197  unsigned Depth) {
3198  // If Scale is 1, then this is the same as adding ScaleReg to the addressing
3199  // mode. Just process that directly.
3200  if (Scale == 1)
3201  return matchAddr(ScaleReg, Depth);
3202 
3203  // If the scale is 0, it takes nothing to add this.
3204  if (Scale == 0)
3205  return true;
3206 
3207  // If we already have a scale of this value, we can add to it, otherwise, we
3208  // need an available scale field.
3209  if (AddrMode.Scale != 0 && AddrMode.ScaledReg != ScaleReg)
3210  return false;
3211 
3212  ExtAddrMode TestAddrMode = AddrMode;
3213 
3214  // Add scale to turn X*4+X*3 -> X*7. This could also do things like
3215  // [A+B + A*7] -> [B+A*8].
3216  TestAddrMode.Scale += Scale;
3217  TestAddrMode.ScaledReg = ScaleReg;
3218 
3219  // If the new address isn't legal, bail out.
3220  if (!TLI.isLegalAddressingMode(DL, TestAddrMode, AccessTy, AddrSpace))
3221  return false;
3222 
3223  // It was legal, so commit it.
3224  AddrMode = TestAddrMode;
3225 
3226  // Okay, we decided that we can add ScaleReg+Scale to AddrMode. Check now
3227  // to see if ScaleReg is actually X+C. If so, we can turn this into adding
3228  // X*Scale + C*Scale to addr mode.
3229  ConstantInt *CI = nullptr; Value *AddLHS = nullptr;
3230  if (isa<Instruction>(ScaleReg) && // not a constant expr.
3231  match(ScaleReg, m_Add(m_Value(AddLHS), m_ConstantInt(CI)))) {
3232  TestAddrMode.ScaledReg = AddLHS;
3233  TestAddrMode.BaseOffs += CI->getSExtValue()*TestAddrMode.Scale;
3234 
3235  // If this addressing mode is legal, commit it and remember that we folded
3236  // this instruction.
3237  if (TLI.isLegalAddressingMode(DL, TestAddrMode, AccessTy, AddrSpace)) {
3238  AddrModeInsts.push_back(cast<Instruction>(ScaleReg));
3239  AddrMode = TestAddrMode;
3240  return true;
3241  }
3242  }
3243 
3244  // Otherwise, not (x+c)*scale, just return what we have.
3245  return true;
3246 }
3247 
3248 /// This is a little filter, which returns true if an addressing computation
3249 /// involving I might be folded into a load/store accessing it.
3250 /// This doesn't need to be perfect, but needs to accept at least
3251 /// the set of instructions that MatchOperationAddr can.
3252 static bool MightBeFoldableInst(Instruction *I) {
3253  switch (I->getOpcode()) {
3254  case Instruction::BitCast:
3255  case Instruction::AddrSpaceCast:
3256  // Don't touch identity bitcasts.
3257  if (I->getType() == I->getOperand(0)->getType())
3258  return false;
3259  return I->getType()->isPointerTy() || I->getType()->isIntegerTy();
3260  case Instruction::PtrToInt:
3261  // PtrToInt is always a noop, as we know that the int type is pointer sized.
3262  return true;
3263  case Instruction::IntToPtr:
3264  // We know the input is intptr_t, so this is foldable.
3265  return true;
3266  case Instruction::Add:
3267  return true;
3268  case Instruction::Mul:
3269  case Instruction::Shl:
3270  // Can only handle X*C and X << C.
3271  return isa<ConstantInt>(I->getOperand(1));
3272  case Instruction::GetElementPtr:
3273  return true;
3274  default:
3275  return false;
3276  }
3277 }
3278 
3279 /// \brief Check whether or not \p Val is a legal instruction for \p TLI.
3280 /// \note \p Val is assumed to be the product of some type promotion.
3281 /// Therefore if \p Val has an undefined state in \p TLI, this is assumed
3282 /// to be legal, as the non-promoted value would have had the same state.
3283 static bool isPromotedInstructionLegal(const TargetLowering &TLI,
3284  const DataLayout &DL, Value *Val) {
3285  Instruction *PromotedInst = dyn_cast<Instruction>(Val);
3286  if (!PromotedInst)
3287  return false;
3288  int ISDOpcode = TLI.InstructionOpcodeToISD(PromotedInst->getOpcode());
3289  // If the ISDOpcode is undefined, it was undefined before the promotion.
3290  if (!ISDOpcode)
3291  return true;
3292  // Otherwise, check if the promoted instruction is legal or not.
3293  return TLI.isOperationLegalOrCustom(
3294  ISDOpcode, TLI.getValueType(DL, PromotedInst->getType()));
3295 }
3296 
3297 /// \brief Hepler class to perform type promotion.
3298 class TypePromotionHelper {
3299  /// \brief Utility function to check whether or not a sign or zero extension
3300  /// of \p Inst with \p ConsideredExtType can be moved through \p Inst by
3301  /// either using the operands of \p Inst or promoting \p Inst.
3302  /// The type of the extension is defined by \p IsSExt.
3303  /// In other words, check if:
3304  /// ext (Ty Inst opnd1 opnd2 ... opndN) to ConsideredExtType.
3305  /// #1 Promotion applies:
3306  /// ConsideredExtType Inst (ext opnd1 to ConsideredExtType, ...).
3307  /// #2 Operand reuses:
3308  /// ext opnd1 to ConsideredExtType.
3309  /// \p PromotedInsts maps the instructions to their type before promotion.
3310  static bool canGetThrough(const Instruction *Inst, Type *ConsideredExtType,
3311  const InstrToOrigTy &PromotedInsts, bool IsSExt);
3312 
3313  /// \brief Utility function to determine if \p OpIdx should be promoted when
3314  /// promoting \p Inst.
3315  static bool shouldExtOperand(const Instruction *Inst, int OpIdx) {
3316  return !(isa<SelectInst>(Inst) && OpIdx == 0);
3317  }
3318 
3319  /// \brief Utility function to promote the operand of \p Ext when this
3320  /// operand is a promotable trunc or sext or zext.
3321  /// \p PromotedInsts maps the instructions to their type before promotion.
3322  /// \p CreatedInstsCost[out] contains the cost of all instructions
3323  /// created to promote the operand of Ext.
3324  /// Newly added extensions are inserted in \p Exts.
3325  /// Newly added truncates are inserted in \p Truncs.
3326  /// Should never be called directly.
3327  /// \return The promoted value which is used instead of Ext.
3328  static Value *promoteOperandForTruncAndAnyExt(
3329  Instruction *Ext, TypePromotionTransaction &TPT,
3330  InstrToOrigTy &PromotedInsts, unsigned &CreatedInstsCost,
3332  SmallVectorImpl<Instruction *> *Truncs, const TargetLowering &TLI);
3333 
3334  /// \brief Utility function to promote the operand of \p Ext when this
3335  /// operand is promotable and is not a supported trunc or sext.
3336  /// \p PromotedInsts maps the instructions to their type before promotion.
3337  /// \p CreatedInstsCost[out] contains the cost of all the instructions
3338  /// created to promote the operand of Ext.
3339  /// Newly added extensions are inserted in \p Exts.
3340  /// Newly added truncates are inserted in \p Truncs.
3341  /// Should never be called directly.
3342  /// \return The promoted value which is used instead of Ext.
3343  static Value *promoteOperandForOther(Instruction *Ext,
3344  TypePromotionTransaction &TPT,
3345  InstrToOrigTy &PromotedInsts,
3346  unsigned &CreatedInstsCost,
3349  const TargetLowering &TLI, bool IsSExt);
3350 
3351  /// \see promoteOperandForOther.
3352  static Value *signExtendOperandForOther(
3353  Instruction *Ext, TypePromotionTransaction &TPT,
3354  InstrToOrigTy &PromotedInsts, unsigned &CreatedInstsCost,
3356  SmallVectorImpl<Instruction *> *Truncs, const TargetLowering &TLI) {
3357  return promoteOperandForOther(Ext, TPT, PromotedInsts, CreatedInstsCost,
3358  Exts, Truncs, TLI, true);
3359  }
3360 
3361  /// \see promoteOperandForOther.
3362  static Value *zeroExtendOperandForOther(
3363  Instruction *Ext, TypePromotionTransaction &TPT,
3364  InstrToOrigTy &PromotedInsts, unsigned &CreatedInstsCost,
3366  SmallVectorImpl<Instruction *> *Truncs, const TargetLowering &TLI) {
3367  return promoteOperandForOther(Ext, TPT, PromotedInsts, CreatedInstsCost,
3368  Exts, Truncs, TLI, false);
3369  }
3370 
3371 public:
3372  /// Type for the utility function that promotes the operand of Ext.
3373  typedef Value *(*Action)(Instruction *Ext, TypePromotionTransaction &TPT,
3374  InstrToOrigTy &PromotedInsts,
3375  unsigned &CreatedInstsCost,
3378  const TargetLowering &TLI);
3379  /// \brief Given a sign/zero extend instruction \p Ext, return the approriate
3380  /// action to promote the operand of \p Ext instead of using Ext.
3381  /// \return NULL if no promotable action is possible with the current
3382  /// sign extension.
3383  /// \p InsertedInsts keeps track of all the instructions inserted by the
3384  /// other CodeGenPrepare optimizations. This information is important
3385  /// because we do not want to promote these instructions as CodeGenPrepare
3386  /// will reinsert them later. Thus creating an infinite loop: create/remove.
3387  /// \p PromotedInsts maps the instructions to their type before promotion.
3388  static Action getAction(Instruction *Ext, const SetOfInstrs &InsertedInsts,
3389  const TargetLowering &TLI,
3390  const InstrToOrigTy &PromotedInsts);
3391 };
3392 
3393 bool TypePromotionHelper::canGetThrough(const Instruction *Inst,
3394  Type *ConsideredExtType,
3395  const InstrToOrigTy &PromotedInsts,
3396  bool IsSExt) {
3397  // The promotion helper does not know how to deal with vector types yet.
3398  // To be able to fix that, we would need to fix the places where we
3399  // statically extend, e.g., constants and such.
3400  if (Inst->getType()->isVectorTy())
3401  return false;
3402 
3403  // We can always get through zext.
3404  if (isa<ZExtInst>(Inst))
3405  return true;
3406 
3407  // sext(sext) is ok too.
3408  if (IsSExt && isa<SExtInst>(Inst))
3409  return true;
3410 
3411  // We can get through binary operator, if it is legal. In other words, the
3412  // binary operator must have a nuw or nsw flag.
3413  const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(Inst);
3414  if (BinOp && isa<OverflowingBinaryOperator>(BinOp) &&
3415  ((!IsSExt && BinOp->hasNoUnsignedWrap()) ||
3416  (IsSExt && BinOp->hasNoSignedWrap())))
3417  return true;
3418 
3419  // Check if we can do the following simplification.
3420  // ext(trunc(opnd)) --> ext(opnd)
3421  if (!isa<TruncInst>(Inst))
3422  return false;
3423 
3424  Value *OpndVal = Inst->getOperand(0);
3425  // Check if we can use this operand in the extension.
3426  // If the type is larger than the result type of the extension, we cannot.
3427  if (!OpndVal->getType()->isIntegerTy() ||
3428  OpndVal->getType()->getIntegerBitWidth() >
3429  ConsideredExtType->getIntegerBitWidth())
3430  return false;
3431 
3432  // If the operand of the truncate is not an instruction, we will not have
3433  // any information on the dropped bits.
3434  // (Actually we could for constant but it is not worth the extra logic).
3435  Instruction *Opnd = dyn_cast<Instruction>(OpndVal);
3436  if (!Opnd)
3437  return false;
3438 
3439  // Check if the source of the type is narrow enough.
3440  // I.e., check that trunc just drops extended bits of the same kind of
3441  // the extension.
3442  // #1 get the type of the operand and check the kind of the extended bits.
3443  const Type *OpndType;
3444  InstrToOrigTy::const_iterator It = PromotedInsts.find(Opnd);
3445  if (It != PromotedInsts.end() && It->second.getInt() == IsSExt)
3446  OpndType = It->second.getPointer();
3447  else if ((IsSExt && isa<SExtInst>(Opnd)) || (!IsSExt && isa<ZExtInst>(Opnd)))
3448  OpndType = Opnd->getOperand(0)->getType();
3449  else
3450  return false;
3451 
3452  // #2 check that the truncate just drops extended bits.
3453  return Inst->getType()->getIntegerBitWidth() >=
3454  OpndType->getIntegerBitWidth();
3455 }
3456 
3457 TypePromotionHelper::Action TypePromotionHelper::getAction(
3458  Instruction *Ext, const SetOfInstrs &InsertedInsts,
3459  const TargetLowering &TLI, const InstrToOrigTy &PromotedInsts) {
3460  assert((isa<SExtInst>(Ext) || isa<ZExtInst>(Ext)) &&
3461  "Unexpected instruction type");
3462  Instruction *ExtOpnd = dyn_cast<Instruction>(Ext->getOperand(0));
3463  Type *ExtTy = Ext->getType();
3464  bool IsSExt = isa<SExtInst>(Ext);
3465  // If the operand of the extension is not an instruction, we cannot
3466  // get through.
3467  // If it, check we can get through.
3468  if (!ExtOpnd || !canGetThrough(ExtOpnd, ExtTy, PromotedInsts, IsSExt))
3469  return nullptr;
3470 
3471  // Do not promote if the operand has been added by codegenprepare.
3472  // Otherwise, it means we are undoing an optimization that is likely to be
3473  // redone, thus causing potential infinite loop.
3474  if (isa<TruncInst>(ExtOpnd) && InsertedInsts.count(ExtOpnd))
3475  return nullptr;
3476 
3477  // SExt or Trunc instructions.
3478  // Return the related handler.
3479  if (isa<SExtInst>(ExtOpnd) || isa<TruncInst>(ExtOpnd) ||
3480  isa<ZExtInst>(ExtOpnd))
3481  return promoteOperandForTruncAndAnyExt;
3482 
3483  // Regular instruction.
3484  // Abort early if we will have to insert non-free instructions.
3485  if (!ExtOpnd->hasOneUse() && !TLI.isTruncateFree(ExtTy, ExtOpnd->getType()))
3486  return nullptr;
3487  return IsSExt ? signExtendOperandForOther : zeroExtendOperandForOther;
3488 }
3489 
3490 Value *TypePromotionHelper::promoteOperandForTruncAndAnyExt(
3491  llvm::Instruction *SExt, TypePromotionTransaction &TPT,
3492  InstrToOrigTy &PromotedInsts, unsigned &CreatedInstsCost,
3494  SmallVectorImpl<Instruction *> *Truncs, const TargetLowering &TLI) {
3495  // By construction, the operand of SExt is an instruction. Otherwise we cannot
3496  // get through it and this method should not be called.
3497  Instruction *SExtOpnd = cast<Instruction>(SExt->getOperand(0));
3498  Value *ExtVal = SExt;
3499  bool HasMergedNonFreeExt = false;
3500  if (isa<ZExtInst>(SExtOpnd)) {
3501  // Replace s|zext(zext(opnd))
3502  // => zext(opnd).
3503  HasMergedNonFreeExt = !TLI.isExtFree(SExtOpnd);
3504  Value *ZExt =
3505  TPT.createZExt(SExt, SExtOpnd->getOperand(0), SExt->getType());
3506  TPT.replaceAllUsesWith(SExt, ZExt);
3507  TPT.eraseInstruction(SExt);
3508  ExtVal = ZExt;
3509  } else {
3510  // Replace z|sext(trunc(opnd)) or sext(sext(opnd))
3511  // => z|sext(opnd).
3512  TPT.setOperand(SExt, 0, SExtOpnd->getOperand(0));
3513  }
3514  CreatedInstsCost = 0;
3515 
3516  // Remove dead code.
3517  if (SExtOpnd->use_empty())
3518  TPT.eraseInstruction(SExtOpnd);
3519 
3520  // Check if the extension is still needed.
3521  Instruction *ExtInst = dyn_cast<Instruction>(ExtVal);
3522  if (!ExtInst || ExtInst->getType() != ExtInst->getOperand(0)->getType()) {
3523  if (ExtInst) {
3524  if (Exts)
3525  Exts->push_back(ExtInst);
3526  CreatedInstsCost = !TLI.isExtFree(ExtInst) && !HasMergedNonFreeExt;
3527  }
3528  return ExtVal;
3529  }
3530 
3531  // At this point we have: ext ty opnd to ty.
3532  // Reassign the uses of ExtInst to the opnd and remove ExtInst.
3533  Value *NextVal = ExtInst->getOperand(0);
3534  TPT.eraseInstruction(ExtInst, NextVal);
3535  return NextVal;
3536 }
3537 
3538 Value *TypePromotionHelper::promoteOperandForOther(
3539  Instruction *Ext, TypePromotionTransaction &TPT,
3540  InstrToOrigTy &PromotedInsts, unsigned &CreatedInstsCost,
3542  SmallVectorImpl<Instruction *> *Truncs, const TargetLowering &TLI,
3543  bool IsSExt) {
3544  // By construction, the operand of Ext is an instruction. Otherwise we cannot
3545  // get through it and this method should not be called.
3546  Instruction *ExtOpnd = cast<Instruction>(Ext->getOperand(0));
3547  CreatedInstsCost = 0;
3548  if (!ExtOpnd->hasOneUse()) {
3549  // ExtOpnd will be promoted.
3550  // All its uses, but Ext, will need to use a truncated value of the
3551  // promoted version.
3552  // Create the truncate now.
3553  Value *Trunc = TPT.createTrunc(Ext, ExtOpnd->getType());
3554  if (Instruction *ITrunc = dyn_cast<Instruction>(Trunc)) {
3555  ITrunc->removeFromParent();
3556  // Insert it just after the definition.
3557  ITrunc->insertAfter(ExtOpnd);
3558  if (Truncs)
3559  Truncs->push_back(ITrunc);
3560  }
3561 
3562  TPT.replaceAllUsesWith(ExtOpnd, Trunc);
3563  // Restore the operand of Ext (which has been replaced by the previous call
3564  // to replaceAllUsesWith) to avoid creating a cycle trunc <-> sext.
3565  TPT.setOperand(Ext, 0, ExtOpnd);
3566  }
3567 
3568  // Get through the Instruction:
3569  // 1. Update its type.
3570  // 2. Replace the uses of Ext by Inst.
3571  // 3. Extend each operand that needs to be extended.
3572 
3573  // Remember the original type of the instruction before promotion.
3574  // This is useful to know that the high bits are sign extended bits.
3575  PromotedInsts.insert(std::pair<Instruction *, TypeIsSExt>(
3576  ExtOpnd, TypeIsSExt(ExtOpnd->getType(), IsSExt)));
3577  // Step #1.
3578  TPT.mutateType(ExtOpnd, Ext->getType());
3579  // Step #2.
3580  TPT.replaceAllUsesWith(Ext, ExtOpnd);
3581  // Step #3.
3582  Instruction *ExtForOpnd = Ext;
3583 
3584  DEBUG(dbgs() << "Propagate Ext to operands\n");
3585  for (int OpIdx = 0, EndOpIdx = ExtOpnd->getNumOperands(); OpIdx != EndOpIdx;
3586  ++OpIdx) {
3587  DEBUG(dbgs() << "Operand:\n" << *(ExtOpnd->getOperand(OpIdx)) << '\n');
3588  if (ExtOpnd->getOperand(OpIdx)->getType() == Ext->getType() ||
3589  !shouldExtOperand(ExtOpnd, OpIdx)) {
3590  DEBUG(dbgs() << "No need to propagate\n");
3591  continue;
3592  }
3593  // Check if we can statically extend the operand.
3594  Value *Opnd = ExtOpnd->getOperand(OpIdx);
3595  if (const ConstantInt *Cst = dyn_cast<ConstantInt>(Opnd)) {
3596  DEBUG(dbgs() << "Statically extend\n");
3597  unsigned BitWidth = Ext->getType()->getIntegerBitWidth();
3598  APInt CstVal = IsSExt ? Cst->getValue().sext(BitWidth)
3599  : Cst->getValue().zext(BitWidth);
3600  TPT.setOperand(ExtOpnd, OpIdx, ConstantInt::get(Ext->getType(), CstVal));
3601  continue;
3602  }
3603  // UndefValue are typed, so we have to statically sign extend them.
3604  if (isa<UndefValue>(Opnd)) {
3605  DEBUG(dbgs() << "Statically extend\n");
3606  TPT.setOperand(ExtOpnd, OpIdx, UndefValue::get(Ext->getType()));
3607  continue;
3608  }
3609 
3610  // Otherwise we have to explicity sign extend the operand.
3611  // Check if Ext was reused to extend an operand.
3612  if (!ExtForOpnd) {
3613  // If yes, create a new one.
3614  DEBUG(dbgs() << "More operands to ext\n");
3615  Value *ValForExtOpnd = IsSExt ? TPT.createSExt(Ext, Opnd, Ext->getType())
3616  : TPT.createZExt(Ext, Opnd, Ext->getType());
3617  if (!isa<Instruction>(ValForExtOpnd)) {
3618  TPT.setOperand(ExtOpnd, OpIdx, ValForExtOpnd);
3619  continue;
3620  }
3621  ExtForOpnd = cast<Instruction>(ValForExtOpnd);
3622  }
3623  if (Exts)
3624  Exts->push_back(ExtForOpnd);
3625  TPT.setOperand(ExtForOpnd, 0, Opnd);
3626 
3627  // Move the sign extension before the insertion point.
3628  TPT.moveBefore(ExtForOpnd, ExtOpnd);
3629  TPT.setOperand(ExtOpnd, OpIdx, ExtForOpnd);
3630  CreatedInstsCost += !TLI.isExtFree(ExtForOpnd);
3631  // If more sext are required, new instructions will have to be created.
3632  ExtForOpnd = nullptr;
3633  }
3634  if (ExtForOpnd == Ext) {
3635  DEBUG(dbgs() << "Extension is useless now\n");
3636  TPT.eraseInstruction(Ext);
3637  }
3638  return ExtOpnd;
3639 }
3640 
3641 /// Check whether or not promoting an instruction to a wider type is profitable.
3642 /// \p NewCost gives the cost of extension instructions created by the
3643 /// promotion.
3644 /// \p OldCost gives the cost of extension instructions before the promotion
3645 /// plus the number of instructions that have been
3646 /// matched in the addressing mode the promotion.
3647 /// \p PromotedOperand is the value that has been promoted.
3648 /// \return True if the promotion is profitable, false otherwise.
3649 bool AddressingModeMatcher::isPromotionProfitable(
3650  unsigned NewCost, unsigned OldCost, Value *PromotedOperand) const {
3651  DEBUG(dbgs() << "OldCost: " << OldCost << "\tNewCost: " << NewCost << '\n');
3652  // The cost of the new extensions is greater than the cost of the
3653  // old extension plus what we folded.
3654  // This is not profitable.
3655  if (NewCost > OldCost)
3656  return false;
3657  if (NewCost < OldCost)
3658  return true;
3659  // The promotion is neutral but it may help folding the sign extension in
3660  // loads for instance.
3661  // Check that we did not create an illegal instruction.
3662  return isPromotedInstructionLegal(TLI, DL, PromotedOperand);
3663 }
3664 
3665 /// Given an instruction or constant expr, see if we can fold the operation
3666 /// into the addressing mode. If so, update the addressing mode and return
3667 /// true, otherwise return false without modifying AddrMode.
3668 /// If \p MovedAway is not NULL, it contains the information of whether or
3669 /// not AddrInst has to be folded into the addressing mode on success.
3670 /// If \p MovedAway == true, \p AddrInst will not be part of the addressing
3671 /// because it has been moved away.
3672 /// Thus AddrInst must not be added in the matched instructions.
3673 /// This state can happen when AddrInst is a sext, since it may be moved away.
3674 /// Therefore, AddrInst may not be valid when MovedAway is true and it must
3675 /// not be referenced anymore.
3676 bool AddressingModeMatcher::matchOperationAddr(User *AddrInst, unsigned Opcode,
3677  unsigned Depth,
3678  bool *MovedAway) {
3679  // Avoid exponential behavior on extremely deep expression trees.
3680  if (Depth >= 5) return false;
3681 
3682  // By default, all matched instructions stay in place.
3683  if (MovedAway)
3684  *MovedAway = false;
3685 
3686  switch (Opcode) {
3687  case Instruction::PtrToInt:
3688  // PtrToInt is always a noop, as we know that the int type is pointer sized.
3689  return matchAddr(AddrInst->getOperand(0), Depth);
3690  case Instruction::IntToPtr: {
3691  auto AS = AddrInst->getType()->getPointerAddressSpace();
3692  auto PtrTy = MVT::getIntegerVT(DL.getPointerSizeInBits(AS));
3693  // This inttoptr is a no-op if the integer type is pointer sized.
3694  if (TLI.getValueType(DL, AddrInst->getOperand(0)->getType()) == PtrTy)
3695  return matchAddr(AddrInst->getOperand(0), Depth);
3696  return false;
3697  }
3698  case Instruction::BitCast:
3699  // BitCast is always a noop, and we can handle it as long as it is
3700  // int->int or pointer->pointer (we don't want int<->fp or something).
3701  if ((AddrInst->getOperand(0)->getType()->isPointerTy() ||
3702  AddrInst->getOperand(0)->getType()->isIntegerTy()) &&
3703  // Don't touch identity bitcasts. These were probably put here by LSR,
3704  // and we don't want to mess around with them. Assume it knows what it
3705  // is doing.
3706  AddrInst->getOperand(0)->getType() != AddrInst->getType())
3707  return matchAddr(AddrInst->getOperand(0), Depth);
3708  return false;
3709  case Instruction::AddrSpaceCast: {
3710  unsigned SrcAS
3711  = AddrInst->getOperand(0)->getType()->getPointerAddressSpace();
3712  unsigned DestAS = AddrInst->getType()->getPointerAddressSpace();
3713  if (TLI.isNoopAddrSpaceCast(SrcAS, DestAS))
3714  return matchAddr(AddrInst->getOperand(0), Depth);
3715  return false;
3716  }
3717  case Instruction::Add: {
3718  // Check to see if we can merge in the RHS then the LHS. If so, we win.
3719  ExtAddrMode BackupAddrMode = AddrMode;
3720  unsigned OldSize = AddrModeInsts.size();
3721  // Start a transaction at this point.
3722  // The LHS may match but not the RHS.
3723  // Therefore, we need a higher level restoration point to undo partially
3724  // matched operation.
3725  TypePromotionTransaction::ConstRestorationPt LastKnownGood =
3726  TPT.getRestorationPoint();
3727 
3728  if (matchAddr(AddrInst->getOperand(1), Depth+1) &&
3729  matchAddr(AddrInst->getOperand(0), Depth+1))
3730  return true;
3731 
3732  // Restore the old addr mode info.
3733  AddrMode = BackupAddrMode;
3734  AddrModeInsts.resize(OldSize);
3735  TPT.rollback(LastKnownGood);
3736 
3737  // Otherwise this was over-aggressive. Try merging in the LHS then the RHS.
3738  if (matchAddr(AddrInst->getOperand(0), Depth+1) &&
3739  matchAddr(AddrInst->getOperand(1), Depth+1))
3740  return true;
3741 
3742  // Otherwise we definitely can't merge the ADD in.
3743  AddrMode = BackupAddrMode;
3744  AddrModeInsts.resize(OldSize);
3745  TPT.rollback(LastKnownGood);
3746  break;
3747  }
3748  //case Instruction::Or:
3749  // TODO: We can handle "Or Val, Imm" iff this OR is equivalent to an ADD.
3750  //break;
3751  case Instruction::Mul:
3752  case Instruction::Shl: {
3753  // Can only handle X*C and X << C.
3754  ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1));
3755  if (!RHS)
3756  return false;
3757  int64_t Scale = RHS->getSExtValue();
3758  if (Opcode == Instruction::Shl)
3759  Scale = 1LL << Scale;
3760 
3761  return matchScaledValue(AddrInst->getOperand(0), Scale, Depth);
3762  }
3763  case Instruction::GetElementPtr: {
3764  // Scan the GEP. We check it if it contains constant offsets and at most
3765  // one variable offset.
3766  int VariableOperand = -1;
3767  unsigned VariableScale = 0;
3768 
3769  int64_t ConstantOffset = 0;
3770  gep_type_iterator GTI = gep_type_begin(AddrInst);
3771  for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) {
3772  if (StructType *STy = GTI.getStructTypeOrNull()) {
3773  const StructLayout *SL = DL.getStructLayout(STy);
3774  unsigned Idx =
3775  cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue();
3776  ConstantOffset += SL->getElementOffset(Idx);
3777  } else {
3778  uint64_t TypeSize = DL.getTypeAllocSize(GTI.getIndexedType());
3779  if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
3780  ConstantOffset += CI->getSExtValue()*TypeSize;
3781  } else if (TypeSize) { // Scales of zero don't do anything.
3782  // We only allow one variable index at the moment.
3783  if (VariableOperand != -1)
3784  return false;
3785 
3786  // Remember the variable index.
3787  VariableOperand = i;
3788  VariableScale = TypeSize;
3789  }
3790  }
3791  }
3792 
3793  // A common case is for the GEP to only do a constant offset. In this case,
3794  // just add it to the disp field and check validity.
3795  if (VariableOperand == -1) {
3796  AddrMode.BaseOffs += ConstantOffset;
3797  if (ConstantOffset == 0 ||
3798  TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace)) {
3799  // Check to see if we can fold the base pointer in too.
3800  if (matchAddr(AddrInst->getOperand(0), Depth+1))
3801  return true;
3802  }
3803  AddrMode.BaseOffs -= ConstantOffset;
3804  return false;
3805  }
3806 
3807  // Save the valid addressing mode in case we can't match.
3808  ExtAddrMode BackupAddrMode = AddrMode;
3809  unsigned OldSize = AddrModeInsts.size();
3810 
3811  // See if the scale and offset amount is valid for this target.
3812  AddrMode.BaseOffs += ConstantOffset;
3813 
3814  // Match the base operand of the GEP.
3815  if (!matchAddr(AddrInst->getOperand(0), Depth+1)) {
3816  // If it couldn't be matched, just stuff the value in a register.
3817  if (AddrMode.HasBaseReg) {
3818  AddrMode = BackupAddrMode;
3819  AddrModeInsts.resize(OldSize);
3820  return false;
3821  }
3822  AddrMode.HasBaseReg = true;
3823  AddrMode.BaseReg = AddrInst->getOperand(0);
3824  }
3825 
3826  // Match the remaining variable portion of the GEP.
3827  if (!matchScaledValue(AddrInst->getOperand(VariableOperand), VariableScale,
3828  Depth)) {
3829  // If it couldn't be matched, try stuffing the base into a register
3830  // instead of matching it, and retrying the match of the scale.
3831  AddrMode = BackupAddrMode;
3832  AddrModeInsts.resize(OldSize);
3833  if (AddrMode.HasBaseReg)
3834  return false;
3835  AddrMode.HasBaseReg = true;
3836  AddrMode.BaseReg = AddrInst->getOperand(0);
3837  AddrMode.BaseOffs += ConstantOffset;
3838  if (!matchScaledValue(AddrInst->getOperand(VariableOperand),
3839  VariableScale, Depth)) {
3840  // If even that didn't work, bail.
3841  AddrMode = BackupAddrMode;
3842  AddrModeInsts.resize(OldSize);
3843  return false;
3844  }
3845  }
3846 
3847  return true;
3848  }
3849  case Instruction::SExt:
3850  case Instruction::ZExt: {
3851  Instruction *Ext = dyn_cast<Instruction>(AddrInst);
3852  if (!Ext)
3853  return false;
3854 
3855  // Try to move this ext out of the way of the addressing mode.
3856  // Ask for a method for doing so.
3857  TypePromotionHelper::Action TPH =
3858  TypePromotionHelper::getAction(Ext, InsertedInsts, TLI, PromotedInsts);
3859  if (!TPH)
3860  return false;
3861 
3862  TypePromotionTransaction::ConstRestorationPt LastKnownGood =
3863  TPT.getRestorationPoint();
3864  unsigned CreatedInstsCost = 0;
3865  unsigned ExtCost = !TLI.isExtFree(Ext);
3866  Value *PromotedOperand =
3867  TPH(Ext, TPT, PromotedInsts, CreatedInstsCost, nullptr, nullptr, TLI);
3868  // SExt has been moved away.
3869  // Thus either it will be rematched later in the recursive calls or it is
3870  // gone. Anyway, we must not fold it into the addressing mode at this point.
3871  // E.g.,
3872  // op = add opnd, 1
3873  // idx = ext op
3874  // addr = gep base, idx
3875  // is now:
3876  // promotedOpnd = ext opnd <- no match here
3877  // op = promoted_add promotedOpnd, 1 <- match (later in recursive calls)
3878  // addr = gep base, op <- match
3879  if (MovedAway)
3880  *MovedAway = true;
3881 
3882  assert(PromotedOperand &&
3883  "TypePromotionHelper should have filtered out those cases");
3884 
3885  ExtAddrMode BackupAddrMode = AddrMode;
3886  unsigned OldSize = AddrModeInsts.size();
3887 
3888  if (!matchAddr(PromotedOperand, Depth) ||
3889  // The total of the new cost is equal to the cost of the created
3890  // instructions.
3891  // The total of the old cost is equal to the cost of the extension plus
3892  // what we have saved in the addressing mode.
3893  !isPromotionProfitable(CreatedInstsCost,
3894  ExtCost + (AddrModeInsts.size() - OldSize),
3895  PromotedOperand)) {
3896  AddrMode = BackupAddrMode;
3897  AddrModeInsts.resize(OldSize);
3898  DEBUG(dbgs() << "Sign extension does not pay off: rollback\n");
3899  TPT.rollback(LastKnownGood);
3900  return false;
3901  }
3902  return true;
3903  }
3904  }
3905  return false;
3906 }
3907 
3908 /// If we can, try to add the value of 'Addr' into the current addressing mode.
3909 /// If Addr can't be added to AddrMode this returns false and leaves AddrMode
3910 /// unmodified. This assumes that Addr is either a pointer type or intptr_t
3911 /// for the target.
3912 ///
3913 bool AddressingModeMatcher::matchAddr(Value *Addr, unsigned Depth) {
3914  // Start a transaction at this point that we will rollback if the matching
3915  // fails.
3916  TypePromotionTransaction::ConstRestorationPt LastKnownGood =
3917  TPT.getRestorationPoint();
3918  if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) {
3919  // Fold in immediates if legal for the target.
3920  AddrMode.BaseOffs += CI->getSExtValue();
3921  if (TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace))
3922  return true;
3923  AddrMode.BaseOffs -= CI->getSExtValue();
3924  } else if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) {
3925  // If this is a global variable, try to fold it into the addressing mode.
3926  if (!AddrMode.BaseGV) {
3927  AddrMode.BaseGV = GV;
3928  if (TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace))
3929  return true;
3930  AddrMode.BaseGV = nullptr;
3931  }
3932  } else if (Instruction *I = dyn_cast<Instruction>(Addr)) {
3933  ExtAddrMode BackupAddrMode = AddrMode;
3934  unsigned OldSize = AddrModeInsts.size();
3935 
3936  // Check to see if it is possible to fold this operation.
3937  bool MovedAway = false;
3938  if (matchOperationAddr(I, I->getOpcode(), Depth, &MovedAway)) {
3939  // This instruction may have been moved away. If so, there is nothing
3940  // to check here.
3941  if (MovedAway)
3942  return true;
3943  // Okay, it's possible to fold this. Check to see if it is actually
3944  // *profitable* to do so. We use a simple cost model to avoid increasing
3945  // register pressure too much.
3946  if (I->hasOneUse() ||
3947  isProfitableToFoldIntoAddressingMode(I, BackupAddrMode, AddrMode)) {
3948  AddrModeInsts.push_back(I);
3949  return true;
3950  }
3951 
3952  // It isn't profitable to do this, roll back.
3953  //cerr << "NOT FOLDING: " << *I;
3954  AddrMode = BackupAddrMode;
3955  AddrModeInsts.resize(OldSize);
3956  TPT.rollback(LastKnownGood);
3957  }
3958  } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) {
3959  if (matchOperationAddr(CE, CE->getOpcode(), Depth))
3960  return true;
3961  TPT.rollback(LastKnownGood);
3962  } else if (isa<ConstantPointerNull>(Addr)) {
3963  // Null pointer gets folded without affecting the addressing mode.
3964  return true;
3965  }
3966 
3967  // Worse case, the target should support [reg] addressing modes. :)
3968  if (!AddrMode.HasBaseReg) {
3969  AddrMode.HasBaseReg = true;
3970  AddrMode.BaseReg = Addr;
3971  // Still check for legality in case the target supports [imm] but not [i+r].
3972  if (TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace))
3973  return true;
3974  AddrMode.HasBaseReg = false;
3975  AddrMode.BaseReg = nullptr;
3976  }
3977 
3978  // If the base register is already taken, see if we can do [r+r].
3979  if (AddrMode.Scale == 0) {
3980  AddrMode.Scale = 1;
3981  AddrMode.ScaledReg = Addr;
3982  if (TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace))
3983  return true;
3984  AddrMode.Scale = 0;
3985  AddrMode.ScaledReg = nullptr;
3986  }
3987  // Couldn't match.
3988  TPT.rollback(LastKnownGood);
3989  return false;
3990 }
3991 
3992 /// Check to see if all uses of OpVal by the specified inline asm call are due
3993 /// to memory operands. If so, return true, otherwise return false.
3994 static bool IsOperandAMemoryOperand(CallInst *CI, InlineAsm *IA, Value *OpVal,
3995  const TargetLowering &TLI,
3996  const TargetRegisterInfo &TRI) {
3997  const Function *F = CI->getFunction();
3998  TargetLowering::AsmOperandInfoVector TargetConstraints =
3999  TLI.ParseConstraints(F->getParent()->getDataLayout(), &TRI,
4000  ImmutableCallSite(CI));
4001 
4002  for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
4003  TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
4004 
4005  // Compute the constraint code and ConstraintType to use.
4006  TLI.ComputeConstraintToUse(OpInfo, SDValue());
4007 
4008  // If this asm operand is our Value*, and if it isn't an indirect memory
4009  // operand, we can't fold it!
4010  if (OpInfo.CallOperandVal == OpVal &&
4011  (OpInfo.ConstraintType != TargetLowering::C_Memory ||
4012  !OpInfo.isIndirect))
4013  return false;
4014  }
4015 
4016  return true;
4017 }
4018 
4019 // Max number of memory uses to look at before aborting the search to conserve
4020 // compile time.
4021 static constexpr int MaxMemoryUsesToScan = 20;
4022 
4023 /// Recursively walk all the uses of I until we find a memory use.
4024 /// If we find an obviously non-foldable instruction, return true.
4025 /// Add the ultimately found memory instructions to MemoryUses.
4026 static bool FindAllMemoryUses(
4027  Instruction *I,
4028  SmallVectorImpl<std::pair<Instruction *, unsigned>> &MemoryUses,
4029  SmallPtrSetImpl<Instruction *> &ConsideredInsts, const TargetLowering &TLI,
4030  const TargetRegisterInfo &TRI, int SeenInsts = 0) {
4031  // If we already considered this instruction, we're done.
4032  if (!ConsideredInsts.insert(I).second)
4033  return false;
4034 
4035  // If this is an obviously unfoldable instruction, bail out.
4036  if (!MightBeFoldableInst(I))
4037  return true;
4038 
4039  const bool OptSize = I->getFunction()->optForSize();
4040 
4041  // Loop over all the uses, recursively processing them.
4042  for (Use &U : I->uses()) {
4043  // Conservatively return true if we're seeing a large number or a deep chain
4044  // of users. This avoids excessive compilation times in pathological cases.
4045  if (SeenInsts++ >= MaxMemoryUsesToScan)
4046  return true;
4047 
4048  Instruction *UserI = cast<Instruction>(U.getUser());
4049  if (LoadInst *LI = dyn_cast<LoadInst>(UserI)) {
4050  MemoryUses.push_back(std::make_pair(LI, U.getOperandNo()));
4051  continue;
4052  }
4053 
4054  if (StoreInst *SI = dyn_cast<StoreInst>(UserI)) {
4055  unsigned opNo = U.getOperandNo();
4056  if (opNo != StoreInst::getPointerOperandIndex())
4057  return true; // Storing addr, not into addr.
4058  MemoryUses.push_back(std::make_pair(SI, opNo));
4059  continue;
4060  }
4061 
4062  if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(UserI)) {
4063  unsigned opNo = U.getOperandNo();
4064  if (opNo != AtomicRMWInst::getPointerOperandIndex())
4065  return true; // Storing addr, not into addr.
4066  MemoryUses.push_back(std::make_pair(RMW, opNo));
4067  continue;
4068  }
4069 
4070  if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(UserI)) {
4071  unsigned opNo = U.getOperandNo();
4072  if (opNo != AtomicCmpXchgInst::getPointerOperandIndex())
4073  return true; // Storing addr, not into addr.
4074  MemoryUses.push_back(std::make_pair(CmpX, opNo));
4075  continue;
4076  }
4077 
4078  if (CallInst *CI = dyn_cast<CallInst>(UserI)) {
4079  // If this is a cold call, we can sink the addressing calculation into
4080  // the cold path. See optimizeCallInst
4081  if (!OptSize && CI->hasFnAttr(Attribute::Cold))
4082  continue;
4083 
4085  if (!IA) return true;
4086 
4087  // If this is a memory operand, we're cool, otherwise bail out.
4088  if (!IsOperandAMemoryOperand(CI, IA, I, TLI, TRI))
4089  return true;
4090  continue;
4091  }
4092 
4093  if (FindAllMemoryUses(UserI, MemoryUses, ConsideredInsts, TLI, TRI,
4094  SeenInsts))
4095  return true;
4096  }
4097 
4098  return false;
4099 }
4100 
4101 /// Return true if Val is already known to be live at the use site that we're
4102 /// folding it into. If so, there is no cost to include it in the addressing
4103 /// mode. KnownLive1 and KnownLive2 are two values that we know are live at the
4104 /// instruction already.
4105 bool AddressingModeMatcher::valueAlreadyLiveAtInst(Value *Val,Value *KnownLive1,
4106  Value *KnownLive2) {
4107  // If Val is either of the known-live values, we know it is live!
4108  if (Val == nullptr || Val == KnownLive1 || Val == KnownLive2)
4109  return true;
4110 
4111  // All values other than instructions and arguments (e.g. constants) are live.
4112  if (!isa<Instruction>(Val) && !isa<Argument>(Val)) return true;
4113 
4114  // If Val is a constant sized alloca in the entry block, it is live, this is
4115  // true because it is just a reference to the stack/frame pointer, which is
4116  // live for the whole function.
4117  if (AllocaInst *AI = dyn_cast<AllocaInst>(Val))
4118  if (AI->isStaticAlloca())
4119  return true;
4120 
4121  // Check to see if this value is already used in the memory instruction's
4122  // block. If so, it's already live into the block at the very least, so we
4123  // can reasonably fold it.
4124  return Val->isUsedInBasicBlock(MemoryInst->getParent());
4125 }
4126 
4127 /// It is possible for the addressing mode of the machine to fold the specified
4128 /// instruction into a load or store that ultimately uses it.
4129 /// However, the specified instruction has multiple uses.
4130 /// Given this, it may actually increase register pressure to fold it
4131 /// into the load. For example, consider this code:
4132 ///
4133 /// X = ...
4134 /// Y = X+1
4135 /// use(Y) -> nonload/store
4136 /// Z = Y+1
4137 /// load Z
4138 ///
4139 /// In this case, Y has multiple uses, and can be folded into the load of Z
4140 /// (yielding load [X+2]). However, doing this will cause both "X" and "X+1" to
4141 /// be live at the use(Y) line. If we don't fold Y into load Z, we use one
4142 /// fewer register. Since Y can't be folded into "use(Y)" we don't increase the
4143 /// number of computations either.
4144 ///
4145 /// Note that this (like most of CodeGenPrepare) is just a rough heuristic. If
4146 /// X was live across 'load Z' for other reasons, we actually *would* want to
4147 /// fold the addressing mode in the Z case. This would make Y die earlier.
4148 bool AddressingModeMatcher::
4149 isProfitableToFoldIntoAddressingMode(Instruction *I, ExtAddrMode &AMBefore,
4150  ExtAddrMode &AMAfter) {
4151  if (IgnoreProfitability) return true;
4152 
4153  // AMBefore is the addressing mode before this instruction was folded into it,
4154  // and AMAfter is the addressing mode after the instruction was folded. Get
4155  // the set of registers referenced by AMAfter and subtract out those
4156  // referenced by AMBefore: this is the set of values which folding in this
4157  // address extends the lifetime of.
4158  //
4159  // Note that there are only two potential values being referenced here,
4160  // BaseReg and ScaleReg (global addresses are always available, as are any
4161  // folded immediates).
4162  Value *BaseReg = AMAfter.BaseReg, *ScaledReg = AMAfter.ScaledReg;
4163 
4164  // If the BaseReg or ScaledReg was referenced by the previous addrmode, their
4165  // lifetime wasn't extended by adding this instruction.
4166  if (valueAlreadyLiveAtInst(BaseReg, AMBefore.BaseReg, AMBefore.ScaledReg))
4167  BaseReg = nullptr;
4168  if (valueAlreadyLiveAtInst(ScaledReg, AMBefore.BaseReg, AMBefore.ScaledReg))
4169  ScaledReg = nullptr;
4170 
4171  // If folding this instruction (and it's subexprs) didn't extend any live
4172  // ranges, we're ok with it.
4173  if (!BaseReg && !ScaledReg)
4174  return true;
4175 
4176  // If all uses of this instruction can have the address mode sunk into them,
4177  // we can remove the addressing mode and effectively trade one live register
4178  // for another (at worst.) In this context, folding an addressing mode into
4179  // the use is just a particularly nice way of sinking it.
4181  SmallPtrSet<Instruction*, 16> ConsideredInsts;
4182  if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI, TRI))
4183  return false; // Has a non-memory, non-foldable use!
4184 
4185  // Now that we know that all uses of this instruction are part of a chain of
4186  // computation involving only operations that could theoretically be folded
4187  // into a memory use, loop over each of these memory operation uses and see
4188  // if they could *actually* fold the instruction. The assumption is that
4189  // addressing modes are cheap and that duplicating the computation involved
4190  // many times is worthwhile, even on a fastpath. For sinking candidates
4191  // (i.e. cold call sites), this serves as a way to prevent excessive code
4192  // growth since most architectures have some reasonable small and fast way to
4193  // compute an effective address. (i.e LEA on x86)
4194  SmallVector<Instruction*, 32> MatchedAddrModeInsts;
4195  for (unsigned i = 0, e = MemoryUses.size(); i != e; ++i) {
4196  Instruction *User = MemoryUses[i].first;
4197  unsigned OpNo = MemoryUses[i].second;
4198 
4199  // Get the access type of this use. If the use isn't a pointer, we don't
4200  // know what it accesses.
4201  Value *Address = User->getOperand(OpNo);
4202  PointerType *AddrTy = dyn_cast<PointerType>(Address->getType());
4203  if (!AddrTy)
4204  return false;
4205  Type *AddressAccessTy = AddrTy->getElementType();
4206  unsigned AS = AddrTy->getAddressSpace();
4207 
4208  // Do a match against the root of this address, ignoring profitability. This
4209  // will tell us if the addressing mode for the memory operation will
4210  // *actually* cover the shared instruction.
4211  ExtAddrMode Result;
4212  TypePromotionTransaction::ConstRestorationPt LastKnownGood =
4213  TPT.getRestorationPoint();
4214  AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, TRI,
4215  AddressAccessTy, AS,
4216  MemoryInst, Result, InsertedInsts,
4217  PromotedInsts, TPT);
4218  Matcher.IgnoreProfitability = true;
4219  bool Success = Matcher.matchAddr(Address, 0);
4220  (void)Success; assert(Success && "Couldn't select *anything*?");
4221 
4222  // The match was to check the profitability, the changes made are not
4223  // part of the original matcher. Therefore, they should be dropped
4224  // otherwise the original matcher will not present the right state.
4225  TPT.rollback(LastKnownGood);
4226 
4227  // If the match didn't cover I, then it won't be shared by it.
4228  if (!is_contained(MatchedAddrModeInsts, I))
4229  return false;
4230 
4231  MatchedAddrModeInsts.clear();
4232  }
4233 
4234  return true;
4235 }
4236 
4237 } // end anonymous namespace
4238 
4239 /// Return true if the specified values are defined in a
4240 /// different basic block than BB.
4241 static bool IsNonLocalValue(Value *V, BasicBlock *BB) {
4242  if (Instruction *I = dyn_cast<Instruction>(V))
4243  return I->getParent() != BB;
4244  return false;
4245 }
4246 
4247 /// Sink addressing mode computation immediate before MemoryInst if doing so
4248 /// can be done without increasing register pressure. The need for the
4249 /// register pressure constraint means this can end up being an all or nothing
4250 /// decision for all uses of the same addressing computation.
4251 ///
4252 /// Load and Store Instructions often have addressing modes that can do
4253 /// significant amounts of computation. As such, instruction selection will try
4254 /// to get the load or store to do as much computation as possible for the
4255 /// program. The problem is that isel can only see within a single block. As
4256 /// such, we sink as much legal addressing mode work into the block as possible.
4257 ///
4258 /// This method is used to optimize both load/store and inline asms with memory
4259 /// operands. It's also used to sink addressing computations feeding into cold
4260 /// call sites into their (cold) basic block.
4261 ///
4262 /// The motivation for handling sinking into cold blocks is that doing so can
4263 /// both enable other address mode sinking (by satisfying the register pressure
4264 /// constraint above), and reduce register pressure globally (by removing the
4265 /// addressing mode computation from the fast path entirely.).
4266 bool CodeGenPrepare::optimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
4267  Type *AccessTy, unsigned AddrSpace) {
4268  Value *Repl = Addr;
4269 
4270  // Try to collapse single-value PHI nodes. This is necessary to undo
4271  // unprofitable PRE transformations.
4272  SmallVector<Value*, 8> worklist;
4273  SmallPtrSet<Value*, 16> Visited;
4274  worklist.push_back(Addr);
4275 
4276  // Use a worklist to iteratively look through PHI nodes, and ensure that
4277  // the addressing mode obtained from the non-PHI roots of the graph
4278  // are equivalent.
4279  bool AddrModeFound = false;
4280  bool PhiSeen = false;
4281  SmallVector<Instruction*, 16> AddrModeInsts;
4282  ExtAddrMode AddrMode;
4283  TypePromotionTransaction TPT(RemovedInsts);
4284  TypePromotionTransaction::ConstRestorationPt LastKnownGood =
4285  TPT.getRestorationPoint();
4286  while (!worklist.empty()) {
4287  Value *V = worklist.back();
4288  worklist.pop_back();
4289 
4290  // We allow traversing cyclic Phi nodes.
4291  // In case of success after this loop we ensure that traversing through
4292  // Phi nodes ends up with all cases to compute address of the form
4293  // BaseGV + Base + Scale * Index + Offset
4294  // where Scale and Offset are constans and BaseGV, Base and Index
4295  // are exactly the same Values in all cases.
4296  // It means that BaseGV, Scale and Offset dominate our memory instruction
4297  // and have the same value as they had in address computation represented
4298  // as Phi. So we can safely sink address computation to memory instruction.
4299  if (!Visited.insert(V).second)
4300  continue;
4301 
4302  // For a PHI node, push all of its incoming values.
4303  if (PHINode *P = dyn_cast<PHINode>(V)) {
4304  for (Value *IncValue : P->incoming_values())
4305  worklist.push_back(IncValue);
4306  PhiSeen = true;
4307  continue;
4308  }
4309 
4310  // For non-PHIs, determine the addressing mode being computed. Note that
4311  // the result may differ depending on what other uses our candidate
4312  // addressing instructions might have.
4313  AddrModeInsts.clear();
4314  ExtAddrMode NewAddrMode = AddressingModeMatcher::Match(
4315  V, AccessTy, AddrSpace, MemoryInst, AddrModeInsts, *TLI, *TRI,
4316  InsertedInsts, PromotedInsts, TPT);
4317 
4318  if (!AddrModeFound) {
4319  AddrModeFound = true;
4320  AddrMode = NewAddrMode;
4321  continue;
4322  }
4323  if (NewAddrMode == AddrMode)
4324  continue;
4325 
4326  AddrModeFound = false;
4327  break;
4328  }
4329 
4330  // If the addressing mode couldn't be determined, or if multiple different
4331  // ones were determined, bail out now.
4332  if (!AddrModeFound) {
4333  TPT.rollback(LastKnownGood);
4334  return false;
4335  }
4336  TPT.commit();
4337 
4338  // If all the instructions matched are already in this BB, don't do anything.
4339  // If we saw Phi node then it is not local definitely.
4340  if (!PhiSeen && none_of(AddrModeInsts, [&](Value *V) {
4341  return IsNonLocalValue(V, MemoryInst->getParent());
4342  })) {
4343  DEBUG(dbgs() << "CGP: Found local addrmode: " << AddrMode << "\n");
4344  return false;
4345  }
4346 
4347  // Insert this computation right after this user. Since our caller is
4348  // scanning from the top of the BB to the bottom, reuse of the expr are
4349  // guaranteed to happen later.
4350  IRBuilder<> Builder(MemoryInst);
4351 
4352  // Now that we determined the addressing expression we want to use and know
4353  // that we have to sink it into this block. Check to see if we have already
4354  // done this for some other load/store instr in this block. If so, reuse the
4355  // computation.
4356  Value *&SunkAddr = SunkAddrs[Addr];
4357  if (SunkAddr) {
4358  DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for "
4359  << *MemoryInst << "\n");
4360  if (SunkAddr->getType() != Addr->getType())
4361  SunkAddr = Builder.CreatePointerCast(SunkAddr, Addr->getType());
4362  } else if (AddrSinkUsingGEPs ||
4363  (!AddrSinkUsingGEPs.getNumOccurrences() && TM &&
4364  SubtargetInfo->useAA())) {
4365  // By default, we use the GEP-based method when AA is used later. This
4366  // prevents new inttoptr/ptrtoint pairs from degrading AA capabilities.
4367  DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
4368  << *MemoryInst << "\n");
4369  Type *IntPtrTy = DL->getIntPtrType(Addr->getType());
4370  Value *ResultPtr = nullptr, *ResultIndex = nullptr;
4371 
4372  // First, find the pointer.
4373  if (AddrMode.BaseReg && AddrMode.BaseReg->getType()->isPointerTy()) {
4374  ResultPtr = AddrMode.BaseReg;
4375  AddrMode.BaseReg = nullptr;
4376  }
4377 
4378  if (AddrMode.Scale && AddrMode.ScaledReg->getType()->isPointerTy()) {
4379  // We can't add more than one pointer together, nor can we scale a
4380  // pointer (both of which seem meaningless).
4381  if (ResultPtr || AddrMode.Scale != 1)
4382  return false;
4383 
4384  ResultPtr = AddrMode.ScaledReg;
4385  AddrMode.Scale = 0;
4386  }
4387 
4388  // It is only safe to sign extend the BaseReg if we know that the math
4389  // required to create it did not overflow before we extend it. Since
4390  // the original IR value was tossed in favor of a constant back when
4391  // the AddrMode was created we need to bail out gracefully if widths
4392  // do not match instead of extending it.
4393  //
4394  // (See below for code to add the scale.)
4395  if (AddrMode.Scale) {
4396  Type *ScaledRegTy = AddrMode.ScaledReg->getType();
4397  if (cast<IntegerType>(IntPtrTy)->getBitWidth() >
4398  cast<IntegerType>(ScaledRegTy)->getBitWidth())
4399  return false;
4400  }
4401 
4402  if (AddrMode.BaseGV) {
4403  if (ResultPtr)
4404  return false;
4405 
4406  ResultPtr = AddrMode.BaseGV;
4407  }
4408 
4409  // If the real base value actually came from an inttoptr, then the matcher
4410  // will look through it and provide only the integer value. In that case,
4411  // use it here.
4412  if (!DL->isNonIntegralPointerType(Addr->getType())) {
4413  if (!ResultPtr && AddrMode.BaseReg) {
4414  ResultPtr = Builder.CreateIntToPtr(AddrMode.BaseReg, Addr->getType(),
4415  "sunkaddr");
4416  AddrMode.BaseReg = nullptr;
4417  } else if (!ResultPtr && AddrMode.Scale == 1) {
4418  ResultPtr = Builder.CreateIntToPtr(AddrMode.ScaledReg, Addr->getType(),
4419  "sunkaddr");
4420  AddrMode.Scale = 0;
4421  }
4422  }
4423 
4424  if (!ResultPtr &&
4425  !AddrMode.BaseReg && !AddrMode.Scale && !AddrMode.BaseOffs) {
4426  SunkAddr = Constant::getNullValue(Addr->getType());
4427  } else if (!ResultPtr) {
4428  return false;
4429  } else {
4430  Type *I8PtrTy =
4431  Builder.getInt8PtrTy(Addr->getType()->getPointerAddressSpace());
4432  Type *I8Ty = Builder.getInt8Ty();
4433 
4434  // Start with the base register. Do this first so that subsequent address
4435  // matching finds it last, which will prevent it from trying to match it
4436  // as the scaled value in case it happens to be a mul. That would be
4437  // problematic if we've sunk a different mul for the scale, because then
4438  // we'd end up sinking both muls.
4439  if (AddrMode.BaseReg) {
4440  Value *V = AddrMode.BaseReg;
4441  if (V->getType() != IntPtrTy)
4442  V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr");
4443 
4444  ResultIndex = V;
4445  }
4446 
4447  // Add the scale value.
4448  if (AddrMode.Scale) {
4449  Value *V = AddrMode.ScaledReg;
4450  if (V->getType() == IntPtrTy) {
4451  // done.
4452  } else {
4453  assert(cast<IntegerType>(IntPtrTy)->getBitWidth() <
4454  cast<IntegerType>(V->getType())->getBitWidth() &&
4455  "We can't transform if ScaledReg is too narrow");
4456  V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
4457  }
4458 
4459  if (AddrMode.Scale != 1)
4460  V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale),
4461  "sunkaddr");
4462  if (ResultIndex)
4463  ResultIndex = Builder.CreateAdd(ResultIndex, V, "sunkaddr");
4464  else
4465  ResultIndex = V;
4466  }
4467 
4468  // Add in the Base Offset if present.
4469  if (AddrMode.BaseOffs) {
4470  Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
4471  if (ResultIndex) {
4472  // We need to add this separately from the scale above to help with
4473  // SDAG consecutive load/store merging.
4474  if (ResultPtr->getType() != I8PtrTy)
4475  ResultPtr = Builder.CreatePointerCast(ResultPtr, I8PtrTy);
4476  ResultPtr = Builder.CreateGEP(I8Ty, ResultPtr, ResultIndex, "sunkaddr");
4477  }
4478 
4479  ResultIndex = V;
4480  }
4481 
4482  if (!ResultIndex) {
4483  SunkAddr = ResultPtr;
4484  } else {
4485  if (ResultPtr->getType() != I8PtrTy)
4486  ResultPtr = Builder.CreatePointerCast(ResultPtr, I8PtrTy);
4487  SunkAddr = Builder.CreateGEP(I8Ty, ResultPtr, ResultIndex, "sunkaddr");
4488  }
4489 
4490  if (SunkAddr->getType() != Addr->getType())
4491  SunkAddr = Builder.CreatePointerCast(SunkAddr, Addr->getType());
4492  }
4493  } else {
4494  // We'd require a ptrtoint/inttoptr down the line, which we can't do for
4495  // non-integral pointers, so in that case bail out now.
4496  Type *BaseTy = AddrMode.BaseReg ? AddrMode.BaseReg->getType() : nullptr;
4497  Type *ScaleTy = AddrMode.Scale ? AddrMode.ScaledReg->getType() : nullptr;
4498  PointerType *BasePtrTy = dyn_cast_or_null<PointerType>(BaseTy);
4499  PointerType *ScalePtrTy = dyn_cast_or_null<PointerType>(ScaleTy);
4500  if (DL->isNonIntegralPointerType(Addr->getType()) ||
4501  (BasePtrTy && DL->isNonIntegralPointerType(BasePtrTy)) ||
4502  (ScalePtrTy && DL->isNonIntegralPointerType(ScalePtrTy)) ||
4503  (AddrMode.BaseGV &&
4504  DL->isNonIntegralPointerType(AddrMode.BaseGV->getType())))
4505  return false;
4506 
4507  DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
4508  << *MemoryInst << "\n");
4509  Type *IntPtrTy = DL->getIntPtrType(Addr->getType());
4510  Value *Result = nullptr;
4511 
4512  // Start with the base register. Do this first so that subsequent address
4513  // matching finds it last, which will prevent it from trying to match it
4514  // as the scaled value in case it happens to be a mul. That would be
4515  // problematic if we've sunk a different mul for the scale, because then
4516  // we'd end up sinking both muls.
4517  if (AddrMode.BaseReg) {
4518  Value *V = AddrMode.BaseReg;
4519  if (V->getType()->isPointerTy())
4520  V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr");
4521  if (V->getType() != IntPtrTy)
4522  V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr");
4523  Result = V;
4524  }
4525 
4526  // Add the scale value.
4527  if (AddrMode.Scale) {
4528  Value *V = AddrMode.ScaledReg;
4529  if (V->getType() == IntPtrTy) {
4530  // done.
4531  } else if (V->getType()->isPointerTy()) {
4532  V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr");
4533  } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
4534  cast<IntegerType>(V->getType())->getBitWidth()) {
4535  V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
4536  } else {
4537  // It is only safe to sign extend the BaseReg if we know that the math
4538  // required to create it did not overflow before we extend it. Since
4539  // the original IR value was tossed in favor of a constant back when
4540  // the AddrMode was created we need to bail out gracefully if widths
4541  // do not match instead of extending it.
4542  Instruction *I = dyn_cast_or_null<Instruction>(Result);
4543  if (I && (Result != AddrMode.BaseReg))
4544  I->eraseFromParent();
4545  return false;
4546  }
4547  if (AddrMode.Scale != 1)
4548  V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale),
4549  "sunkaddr");
4550  if (Result)
4551  Result = Builder.CreateAdd(Result, V, "sunkaddr");
4552  else
4553  Result = V;
4554  }
4555 
4556  // Add in the BaseGV if present.
4557  if (AddrMode.BaseGV) {
4558  Value *V = Builder.CreatePtrToInt(AddrMode.BaseGV, IntPtrTy, "sunkaddr");
4559  if (Result)
4560  Result = Builder.CreateAdd(Result, V, "sunkaddr");
4561  else
4562  Result = V;
4563  }
4564 
4565  // Add in the Base Offset if present.
4566  if (AddrMode.BaseOffs) {
4567  Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
4568  if (Result)
4569  Result = Builder.CreateAdd(Result, V, "sunkaddr");
4570  else
4571  Result = V;
4572  }
4573 
4574  if (!Result)
4575  SunkAddr = Constant::getNullValue(Addr->getType());
4576  else
4577  SunkAddr = Builder.CreateIntToPtr(Result, Addr->getType(), "sunkaddr");
4578  }
4579 
4580  MemoryInst->replaceUsesOfWith(Repl, SunkAddr);
4581 
4582  // If we have no uses, recursively delete the value and all dead instructions
4583  // using it.
4584  if (Repl->use_empty()) {
4585  // This can cause recursive deletion, which can invalidate our iterator.
4586  // Use a WeakTrackingVH to hold onto it in case this happens.
4587  Value *CurValue = &*CurInstIterator;
4588  WeakTrackingVH IterHandle(CurValue);
4589  BasicBlock *BB = CurInstIterator->getParent();
4590 
4592 
4593  if (IterHandle != CurValue) {
4594  // If the iterator instruction was recursively deleted, start over at the
4595  // start of the block.
4596  CurInstIterator = BB->begin();
4597  SunkAddrs.clear();
4598  }
4599  }
4600  ++NumMemoryInsts;
4601  return true;
4602 }
4603 
4604 /// If there are any memory operands, use OptimizeMemoryInst to sink their
4605 /// address computing into the block when possible / profitable.
4606 bool CodeGenPrepare::optimizeInlineAsmInst(CallInst *CS) {
4607  bool MadeChange = false;
4608 
4609  const TargetRegisterInfo *TRI =
4610  TM->getSubtargetImpl(*CS->getFunction())->getRegisterInfo();
4611  TargetLowering::AsmOperandInfoVector TargetConstraints =
4612  TLI->ParseConstraints(*DL, TRI, CS);
4613  unsigned ArgNo = 0;
4614  for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
4615  TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
4616 
4617  // Compute the constraint code and ConstraintType to use.
4618  TLI->ComputeConstraintToUse(OpInfo, SDValue());
4619 
4620  if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
4621  OpInfo.isIndirect) {
4622  Value *OpVal = CS->getArgOperand(ArgNo++);
4623  MadeChange |= optimizeMemoryInst(CS, OpVal, OpVal->getType(), ~0u);
4624  } else if (OpInfo.Type == InlineAsm::isInput)
4625  ArgNo++;
4626  }
4627 
4628  return MadeChange;
4629 }
4630 
4631 /// \brief Check if all the uses of \p Val are equivalent (or free) zero or
4632 /// sign extensions.
4633 static bool hasSameExtUse(Value *Val, const TargetLowering &TLI) {
4634  assert(!Val->use_empty() && "Input must have at least one use");
4635  const Instruction *FirstUser = cast<Instruction>(*Val->user_begin());
4636  bool IsSExt = isa<SExtInst>(FirstUser);
4637  Type *ExtTy = FirstUser->getType();
4638  for (const User *U : Val->users()) {
4639  const Instruction *UI = cast<Instruction>(U);
4640  if ((IsSExt && !isa<SExtInst>(UI)) || (!IsSExt && !isa<ZExtInst>(UI)))
4641  return false;
4642  Type *CurTy = UI->getType();
4643  // Same input and output types: Same instruction after CSE.
4644  if (CurTy == ExtTy)
4645  continue;
4646 
4647  // If IsSExt is true, we are in this situation:
4648  // a = Val
4649  // b = sext ty1 a to ty2
4650  // c = sext ty1 a to ty3
4651  // Assuming ty2 is shorter than ty3, this could be turned into:
4652  // a = Val
4653  // b = sext ty1 a to ty2
4654  // c = sext ty2 b to ty3
4655  // However, the last sext is not free.
4656  if (IsSExt)
4657  return false;
4658 
4659  // This is a ZExt, maybe this is free to extend from one type to another.
4660  // In that case, we would not account for a different use.
4661  Type *NarrowTy;
4662  Type *LargeTy;
4663  if (ExtTy->getScalarType()->getIntegerBitWidth() >
4664  CurTy->getScalarType()->getIntegerBitWidth()) {
4665  NarrowTy = CurTy;
4666  LargeTy = ExtTy;
4667  } else {
4668  NarrowTy = ExtTy;
4669  LargeTy = CurTy;
4670  }
4671 
4672  if (!TLI.isZExtFree(NarrowTy, LargeTy))
4673  return false;
4674  }
4675  // All uses are the same or can be derived from one another for free.
4676  return true;
4677 }
4678 
4679 /// \brief Try to speculatively promote extensions in \p Exts and continue
4680 /// promoting through newly promoted operands recursively as far as doing so is
4681 /// profitable. Save extensions profitably moved up, in \p ProfitablyMovedExts.
4682 /// When some promotion happened, \p TPT contains the proper state to revert
4683 /// them.
4684 ///
4685 /// \return true if some promotion happened, false otherwise.
4686 bool CodeGenPrepare::tryToPromoteExts(
4687  TypePromotionTransaction &TPT, const SmallVectorImpl<Instruction *> &Exts,
4688  SmallVectorImpl<Instruction *> &ProfitablyMovedExts,
4689  unsigned CreatedInstsCost) {
4690  bool Promoted = false;
4691 
4692  // Iterate over all the extensions to try to promote them.
4693  for (auto I : Exts) {
4694  // Early check if we directly have ext(load).
4695  if (isa<LoadInst>(I->getOperand(0))) {
4696  ProfitablyMovedExts.push_back(I);
4697  continue;
4698  }
4699 
4700  // Check whether or not we want to do any promotion. The reason we have
4701  // this check inside the for loop is to catch the case where an extension
4702  // is directly fed by a load because in such case the extension can be moved
4703  // up without any promotion on its operands.
4704  if (!TLI || !TLI->enableExtLdPromotion() || DisableExtLdPromotion)
4705  return false;
4706 
4707  // Get the action to perform the promotion.
4708  TypePromotionHelper::Action TPH =
4709  TypePromotionHelper::getAction(I, InsertedInsts, *TLI, PromotedInsts);
4710  // Check if we can promote.
4711  if (!TPH) {
4712  // Save the current extension as we cannot move up through its operand.
4713  ProfitablyMovedExts.push_back(I);
4714  continue;
4715  }
4716 
4717  // Save the current state.
4718  TypePromotionTransaction::ConstRestorationPt LastKnownGood =
4719  TPT.getRestorationPoint();
4721  unsigned NewCreatedInstsCost = 0;
4722  unsigned ExtCost = !TLI->isExtFree(I);
4723  // Promote.
4724  Value *PromotedVal = TPH(I, TPT, PromotedInsts, NewCreatedInstsCost,
4725  &NewExts, nullptr, *TLI);
4726  assert(PromotedVal &&
4727  "TypePromotionHelper should have filtered out those cases");
4728 
4729  // We would be able to merge only one extension in a load.
4730  // Therefore, if we have more than 1 new extension we heuristically
4731  // cut this search path, because it means we degrade the code quality.
4732  // With exactly 2, the transformation is neutral, because we will merge
4733  // one extension but leave one. However, we optimistically keep going,
4734  // because the new extension may be removed too.
4735  long long TotalCreatedInstsCost = CreatedInstsCost + NewCreatedInstsCost;
4736  // FIXME: It would be possible to propagate a negative value instead of
4737  // conservatively ceiling it to 0.
4738  TotalCreatedInstsCost =
4739  std::max((long long)0, (TotalCreatedInstsCost - ExtCost));
4740  if (!StressExtLdPromotion &&
4741  (TotalCreatedInstsCost > 1 ||
4742  !isPromotedInstructionLegal(*TLI, *DL, PromotedVal))) {
4743  // This promotion is not profitable, rollback to the previous state, and
4744  // save the current extension in ProfitablyMovedExts as the latest
4745  // speculative promotion turned out to be unprofitable.
4746  TPT.rollback(LastKnownGood);
4747  ProfitablyMovedExts.push_back(I);
4748  continue;
4749  }
4750  // Continue promoting NewExts as far as doing so is profitable.
4751  SmallVector<Instruction *, 2> NewlyMovedExts;
4752  (void)tryToPromoteExts(TPT, NewExts, NewlyMovedExts, TotalCreatedInstsCost);
4753  bool NewPromoted = false;
4754  for (auto ExtInst : NewlyMovedExts) {
4755  Instruction *MovedExt = cast<Instruction>(ExtInst);
4756  Value *ExtOperand = MovedExt->getOperand(0);
4757  // If we have reached to a load, we need this extra profitability check
4758  // as it could potentially be merged into an ext(load).
4759  if (isa<LoadInst>(ExtOperand) &&
4760  !(StressExtLdPromotion || NewCreatedInstsCost <= ExtCost ||
4761  (ExtOperand->hasOneUse() || hasSameExtUse(ExtOperand, *TLI))))
4762  continue;
4763 
4764  ProfitablyMovedExts.push_back(MovedExt);
4765  NewPromoted = true;
4766  }
4767 
4768  // If none of speculative promotions for NewExts is profitable, rollback
4769  // and save the current extension (I) as the last profitable extension.
4770  if (!NewPromoted) {
4771  TPT.rollback(LastKnownGood);
4772  ProfitablyMovedExts.push_back(I);
4773  continue;
4774  }
4775  // The promotion is profitable.
4776  Promoted = true;
4777  }
4778  return Promoted;
4779 }
4780 
4781 /// Merging redundant sexts when one is dominating the other.
4782 bool CodeGenPrepare::mergeSExts(Function &F) {
4783  DominatorTree DT(F);
4784  bool Changed = false;
4785  for (auto &Entry : ValToSExtendedUses) {
4786  SExts &Insts = Entry.second;
4787  SExts CurPts;
4788  for (Instruction *Inst : Insts) {
4789  if (RemovedInsts.count(Inst) || !isa<SExtInst>(Inst) ||
4790  Inst->getOperand(0) != Entry.first)
4791  continue;
4792  bool inserted = false;
4793  for (auto &Pt : CurPts) {
4794  if (DT.dominates(Inst, Pt)) {
4795  Pt->replaceAllUsesWith(Inst);
4796  RemovedInsts.insert(Pt);
4797  Pt->removeFromParent();
4798  Pt = Inst;
4799  inserted = true;
4800  Changed = true;
4801  break;
4802  }
4803  if (!DT.dominates(Pt, Inst))
4804  // Give up if we need to merge in a common dominator as the
4805  // expermients show it is not profitable.
4806  continue;
4807  Inst->replaceAllUsesWith(Pt);
4808  RemovedInsts.insert(Inst);
4809  Inst->removeFromParent();
4810  inserted = true;
4811  Changed = true;
4812  break;
4813  }
4814  if (!inserted)
4815  CurPts.push_back(Inst);
4816  }
4817  }
4818  return Changed;
4819 }
4820 
4821 /// Return true, if an ext(load) can be formed from an extension in
4822 /// \p MovedExts.
4823 bool CodeGenPrepare::canFormExtLd(
4824  const SmallVectorImpl<Instruction *> &MovedExts, LoadInst *&LI,
4825  Instruction *&Inst, bool HasPromoted) {
4826  for (auto *MovedExtInst : MovedExts) {
4827  if (isa<LoadInst>(MovedExtInst->getOperand(0))) {
4828  LI = cast<LoadInst>(MovedExtInst->getOperand(0));
4829  Inst = MovedExtInst;
4830  break;
4831  }
4832  }
4833  if (!LI)
4834  return false;
4835 
4836  // If they're already in the same block, there's nothing to do.
4837  // Make the cheap checks first if we did not promote.
4838  // If we promoted, we need to check if it is indeed profitable.
4839  if (!HasPromoted && LI->getParent() == Inst->getParent())
4840  return false;
4841 
4842  return TLI->isExtLoad(LI, Inst, *DL);
4843 }
4844 
4845 /// Move a zext or sext fed by a load into the same basic block as the load,
4846 /// unless conditions are unfavorable. This allows SelectionDAG to fold the
4847 /// extend into the load.
4848 ///
4849 /// E.g.,
4850 /// \code
4851 /// %ld = load i32* %addr
4852 /// %add = add nuw i32 %ld, 4
4853 /// %zext = zext i32 %add to i64
4854 // \endcode
4855 /// =>
4856 /// \code
4857 /// %ld = load i32* %addr
4858 /// %zext = zext i32 %ld to i64
4859 /// %add = add nuw i64 %zext, 4
4860 /// \encode
4861 /// Note that the promotion in %add to i64 is done in tryToPromoteExts(), which
4862 /// allow us to match zext(load i32*) to i64.
4863 ///
4864 /// Also, try to promote the computations used to obtain a sign extended
4865 /// value used into memory accesses.
4866 /// E.g.,
4867 /// \code
4868 /// a = add nsw i32 b, 3
4869 /// d = sext i32 a to i64
4870 /// e = getelementptr ..., i64 d
4871 /// \endcode
4872 /// =>
4873 /// \code
4874 /// f = sext i32 b to i64
4875 /// a = add nsw i64 f, 3
4876 /// e = getelementptr ..., i64 a
4877 /// \endcode
4878 ///
4879 /// \p Inst[in/out] the extension may be modified during the process if some
4880 /// promotions apply.
4881 bool CodeGenPrepare::optimizeExt(Instruction *&Inst) {
4882  // ExtLoad formation and address type promotion infrastructure requires TLI to
4883  // be effective.
4884  if (!TLI)
4885  return false;
4886 
4887  bool AllowPromotionWithoutCommonHeader = false;
4888  /// See if it is an interesting sext operations for the address type
4889  /// promotion before trying to promote it, e.g., the ones with the right
4890  /// type and used in memory accesses.
4891  bool ATPConsiderable = TTI->shouldConsiderAddressTypePromotion(
4892  *Inst, AllowPromotionWithoutCommonHeader);
4893  TypePromotionTransaction TPT(RemovedInsts);
4894  TypePromotionTransaction::ConstRestorationPt LastKnownGood =
4895  TPT.getRestorationPoint();
4897  SmallVector<Instruction *, 2> SpeculativelyMovedExts;
4898  Exts.push_back(Inst);
4899 
4900  bool HasPromoted = tryToPromoteExts(TPT, Exts, SpeculativelyMovedExts);
4901 
4902  // Look for a load being extended.
4903  LoadInst *LI = nullptr;
4904  Instruction *ExtFedByLoad;
4905 
4906  // Try to promote a chain of computation if it allows to form an extended
4907  // load.
4908  if (canFormExtLd(SpeculativelyMovedExts, LI, ExtFedByLoad, HasPromoted)) {
4909  assert(LI && ExtFedByLoad && "Expect a valid load and extension");
4910  TPT.commit();
4911  // Move the extend into the same block as the load
4912  ExtFedByLoad->removeFromParent();
4913  ExtFedByLoad->insertAfter(LI);
4914  // CGP does not check if the zext would be speculatively executed when moved
4915  // to the same basic block as the load. Preserving its original location
4916  // would pessimize the debugging experience, as well as negatively impact
4917  // the quality of sample pgo. We don't want to use "line 0" as that has a
4918  // size cost in the line-table section and logically the zext can be seen as
4919  // part of the load. Therefore we conservatively reuse the same debug
4920  // location for the load and the zext.
4921  ExtFedByLoad->setDebugLoc(LI->getDebugLoc());
4922  ++NumExtsMoved;
4923  Inst = ExtFedByLoad;
4924  return true;
4925  }
4926 
4927  // Continue promoting SExts if known as considerable depending on targets.
4928  if (ATPConsiderable &&
4929  performAddressTypePromotion(Inst, AllowPromotionWithoutCommonHeader,
4930  HasPromoted, TPT, SpeculativelyMovedExts))
4931  return true;
4932 
4933  TPT.rollback(LastKnownGood);
4934  return false;
4935 }
4936 
4937 // Perform address type promotion if doing so is profitable.
4938 // If AllowPromotionWithoutCommonHeader == false, we should find other sext
4939 // instructions that sign extended the same initial value. However, if
4940 // AllowPromotionWithoutCommonHeader == true, we expect promoting the
4941 // extension is just profitable.
4942 bool CodeGenPrepare::performAddressTypePromotion(
4943  Instruction *&Inst, bool AllowPromotionWithoutCommonHeader,
4944  bool HasPromoted, TypePromotionTransaction &TPT,
4945  SmallVectorImpl<Instruction *> &SpeculativelyMovedExts) {
4946  bool Promoted = false;
4947  SmallPtrSet<Instruction *, 1> UnhandledExts;
4948  bool AllSeenFirst = true;
4949  for (auto I : SpeculativelyMovedExts) {
4950  Value *HeadOfChain = I->getOperand(0);
4952  SeenChainsForSExt.find(HeadOfChain);
4953  // If there is an unhandled SExt which has the same header, try to promote
4954  // it as well.
4955  if (AlreadySeen != SeenChainsForSExt.end()) {
4956  if (AlreadySeen->second != nullptr)
4957  UnhandledExts.insert(AlreadySeen->second);
4958  AllSeenFirst = false;
4959  }
4960  }
4961 
4962  if (!AllSeenFirst || (AllowPromotionWithoutCommonHeader &&
4963  SpeculativelyMovedExts.size() == 1)) {
4964  TPT.commit();
4965  if (HasPromoted)
4966  Promoted = true;
4967  for (auto I : SpeculativelyMovedExts) {
4968  Value *HeadOfChain = I->getOperand(0);
4969  SeenChainsForSExt[HeadOfChain] = nullptr;
4970  ValToSExtendedUses[HeadOfChain].push_back(I);
4971  }
4972  // Update Inst as promotion happen.
4973  Inst = SpeculativelyMovedExts.pop_back_val();
4974  } else {
4975  // This is the first chain visited from the header, keep the current chain
4976  // as unhandled. Defer to promote this until we encounter another SExt
4977  // chain derived from the same header.
4978  for (auto I : SpeculativelyMovedExts) {
4979  Value *HeadOfChain = I->getOperand(0);
4980  SeenChainsForSExt[HeadOfChain] = Inst;
4981  }
4982  return false;
4983  }
4984 
4985  if (!AllSeenFirst && !UnhandledExts.empty())
4986  for (auto VisitedSExt : UnhandledExts) {
4987  if (RemovedInsts.count(VisitedSExt))
4988  continue;
4989  TypePromotionTransaction TPT(RemovedInsts);
4992  Exts.push_back(VisitedSExt);
4993  bool HasPromoted = tryToPromoteExts(TPT, Exts, Chains);
4994  TPT.commit();
4995  if (HasPromoted)
4996  Promoted = true;
4997  for (auto I : Chains) {
4998  Value *HeadOfChain = I->getOperand(0);
4999  // Mark this as handled.
5000  SeenChainsForSExt[HeadOfChain] = nullptr;
5001  ValToSExtendedUses[HeadOfChain].push_back(I);
5002  }
5003  }
5004  return Promoted;
5005 }
5006 
5007 bool CodeGenPrepare::optimizeExtUses(Instruction *I) {
5008  BasicBlock *DefBB = I->getParent();
5009 
5010  // If the result of a {s|z}ext and its source are both live out, rewrite all
5011  // other uses of the source with result of extension.
5012  Value *Src = I->getOperand(0);
5013  if (Src->hasOneUse())
5014  return false;
5015 
5016  // Only do this xform if truncating is free.
5017  if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType()))
5018  return false;
5019 
5020  // Only safe to perform the optimization if the source is also defined in
5021  // this block.
5022  if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
5023  return false;
5024 
5025  bool DefIsLiveOut = false;
5026  for (User *U : I->users()) {
5027  Instruction *UI = cast<Instruction>(U);
5028 
5029  // Figure out which BB this ext is used in.
5030  BasicBlock *UserBB = UI->getParent();
5031  if (UserBB == DefBB) continue;
5032  DefIsLiveOut = true;
5033  break;
5034  }
5035  if (!DefIsLiveOut)
5036  return false;
5037 
5038  // Make sure none of the uses are PHI nodes.
5039  for (User *U : Src->users()) {
5040  Instruction *UI = cast<Instruction>(U);
5041  BasicBlock *UserBB = UI->getParent();
5042  if (UserBB == DefBB) continue;
5043  // Be conservative. We don't want this xform to end up introducing
5044  // reloads just before load / store instructions.
5045  if (isa<PHINode>(UI) || isa<LoadInst>(UI) || isa<StoreInst>(UI))
5046  return false;
5047  }
5048 
5049  // InsertedTruncs - Only insert one trunc in each block once.
5050  DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
5051 
5052  bool MadeChange = false;
5053  for (Use &U : Src->uses()) {
5054  Instruction *User = cast<Instruction>(U.getUser());
5055 
5056  // Figure out which BB this ext is used in.
5057  BasicBlock *UserBB = User->getParent();
5058  if (UserBB == DefBB) continue;
5059 
5060  // Both src and def are live in this block. Rewrite the use.
5061  Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
5062 
5063  if (!InsertedTrunc) {
5064  BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
5065  assert(InsertPt != UserBB->end());
5066  InsertedTrunc = new TruncInst(I, Src->getType(), "", &*InsertPt);
5067  InsertedInsts.insert(InsertedTrunc);
5068  }
5069 
5070  // Replace a use of the {s|z}ext source with a use of the result.
5071  U = InsertedTrunc;
5072  ++NumExtUses;
5073  MadeChange = true;
5074  }
5075 
5076  return MadeChange;
5077 }
5078 
5079 // Find loads whose uses only use some of the loaded value's bits. Add an "and"
5080 // just after the load if the target can fold this into one extload instruction,
5081 // with the hope of eliminating some of the other later "and" instructions using
5082 // the loaded value. "and"s that are made trivially redundant by the insertion
5083 // of the new "and" are removed by this function, while others (e.g. those whose
5084 // path from the load goes through a phi) are left for isel to potentially
5085 // remove.
5086 //
5087 // For example:
5088 //
5089 // b0:
5090 // x = load i32
5091 // ...
5092 // b1:
5093 // y = and x, 0xff
5094 // z = use y
5095 //
5096 // becomes:
5097 //
5098 // b0:
5099 // x = load i32
5100 // x' = and x, 0xff
5101 // ...
5102 // b1:
5103 // z = use x'
5104 //
5105 // whereas:
5106 //
5107 // b0:
5108 // x1 = load i32
5109 // ...
5110 // b1:
5111 // x2 = load i32
5112 // ...
5113 // b2:
5114 // x = phi x1, x2
5115 // y = and x, 0xff
5116 //
5117 // becomes (after a call to optimizeLoadExt for each load):
5118 //
5119 // b0:
5120 // x1 = load i32
5121 // x1' = and x1, 0xff
5122 // ...
5123 // b1:
5124 // x2 = load i32
5125 // x2' = and x2, 0xff
5126 // ...
5127 // b2:
5128 // x = phi x1', x2'
5129 // y = and x, 0xff
5130 //
5131 
5132 bool CodeGenPrepare::optimizeLoadExt(LoadInst *Load) {
5133 
5134  if (!Load->isSimple() ||
5135  !(Load->getType()->isIntegerTy() || Load->getType()->isPointerTy()))
5136  return false;
5137 
5138  // Skip loads we've already transformed.
5139  if (Load->hasOneUse() &&
5140  InsertedInsts.count(cast<Instruction>(*Load->user_begin())))
5141  return false;
5142 
5143  // Look at all uses of Load, looking through phis, to determine how many bits
5144  // of the loaded value are needed.
5147  SmallVector<Instruction *, 8> AndsToMaybeRemove;
5148  for (auto *U : Load->users())
5149  WorkList.push_back(cast<Instruction>(U));
5150 
5151  EVT LoadResultVT = TLI->getValueType(*DL, Load->getType());
5152  unsigned BitWidth = LoadResultVT.getSizeInBits();
5153  APInt DemandBits(BitWidth, 0);
5154  APInt WidestAndBits(BitWidth, 0);
5155 
5156  while (!WorkList.empty()) {
5157  Instruction *I = WorkList.back();
5158  WorkList.pop_back();
5159 
5160  // Break use-def graph loops.
5161  if (!Visited.insert(I).second)
5162  continue;
5163 
5164  // For a PHI node, push all of its users.
5165  if (auto *Phi = dyn_cast<PHINode>(I)) {
5166  for (auto *U : Phi->users())
5167  WorkList.push_back(cast<Instruction>(U));
5168  continue;
5169  }
5170 
5171  switch (I->getOpcode()) {
5172  case llvm::Instruction::And: {
5173  auto *AndC = dyn_cast<ConstantInt>(I->getOperand(1));
5174  if (!AndC)
5175  return false;
5176  APInt AndBits = AndC->getValue();
5177  DemandBits |= AndBits;
5178  // Keep track of the widest and mask we see.
5179  if (AndBits.ugt(WidestAndBits))
5180  WidestAndBits = AndBits;
5181  if (AndBits == WidestAndBits && I->getOperand(0) == Load)
5182  AndsToMaybeRemove.push_back(I);
5183  break;
5184  }
5185 
5186  case llvm::Instruction::Shl: {
5187  auto *ShlC = dyn_cast<ConstantInt>(I->getOperand(1));
5188  if (!ShlC)
5189  return false;
5190  uint64_t ShiftAmt = ShlC->getLimitedValue(BitWidth - 1);
5191  DemandBits.setLowBits(BitWidth - ShiftAmt);
5192  break;
5193  }
5194 
5195  case llvm::Instruction::Trunc: {
5196  EVT TruncVT = TLI->getValueType(*DL, I->getType());
5197  unsigned TruncBitWidth = TruncVT.getSizeInBits();
5198  DemandBits.setLowBits(TruncBitWidth);
5199  break;
5200  }
5201 
5202  default:
5203  return false;
5204  }
5205  }
5206 
5207  uint32_t ActiveBits = DemandBits.getActiveBits();
5208  // Avoid hoisting (and (load x) 1) since it is unlikely to be folded by the
5209  // target even if isLoadExtLegal says an i1 EXTLOAD is valid. For example,
5210  // for the AArch64 target isLoadExtLegal(ZEXTLOAD, i32, i1) returns true, but
5211  // (and (load x) 1) is not matched as a single instruction, rather as a LDR
5212  // followed by an AND.
5213  // TODO: Look into removing this restriction by fixing backends to either
5214  // return false for isLoadExtLegal for i1 or have them select this pattern to
5215  // a single instruction.
5216  //
5217  // Also avoid hoisting if we didn't see any ands with the exact DemandBits
5218  // mask, since these are the only ands that will be removed by isel.
5219  if (ActiveBits <= 1 || !DemandBits.isMask(ActiveBits) ||
5220  WidestAndBits != DemandBits)
5221  return false;
5222 
5223  LLVMContext &Ctx = Load->getType()->getContext();
5224  Type *TruncTy = Type::getIntNTy(Ctx, ActiveBits);
5225  EVT TruncVT = TLI->getValueType(*DL, TruncTy);
5226 
5227  // Reject cases that won't be matched as extloads.
5228  if (!LoadResultVT.bitsGT(TruncVT) || !TruncVT.isRound() ||
5229  !TLI->isLoadExtLegal(ISD::ZEXTLOAD, LoadResultVT, TruncVT))
5230  return false;
5231 
5232  IRBuilder<> Builder(Load->getNextNode());
5233  auto *NewAnd = dyn_cast<Instruction>(
5234  Builder.CreateAnd(Load, ConstantInt::get(Ctx, DemandBits)));
5235  // Mark this instruction as "inserted by CGP", so that other
5236  // optimizations don't touch it.
5237  InsertedInsts.insert(NewAnd);
5238 
5239  // Replace all uses of load with new and (except for the use of load in the
5240  // new and itself).
5241  Load->replaceAllUsesWith(NewAnd);
5242  NewAnd->setOperand(0, Load);
5243 
5244  // Remove any and instructions that are now redundant.
5245  for (auto *And : AndsToMaybeRemove)
5246  // Check that the and mask is the same as the one we decided to put on the
5247  // new and.
5248  if (cast<ConstantInt>(And->getOperand(1))->getValue() == DemandBits) {
5249  And->replaceAllUsesWith(NewAnd);
5250  if (&*CurInstIterator == And)
5251  CurInstIterator = std::next(And->getIterator());
5252  And->eraseFromParent();
5253  ++NumAndUses;
5254  }
5255 
5256  ++NumAndsAdded;
5257  return true;
5258 }
5259 
5260 /// Check if V (an operand of a select instruction) is an expensive instruction
5261 /// that is only used once.
5262 static bool sinkSelectOperand(const TargetTransformInfo *TTI, Value *V) {
5263  auto *I = dyn_cast<Instruction>(V);
5264  // If it's safe to speculatively execute, then it should not have side
5265  // effects; therefore, it's safe to sink and possibly *not* execute.
5266  return I && I->hasOneUse() && isSafeToSpeculativelyExecute(I) &&
5267  TTI->getUserCost(I) >= TargetTransformInfo::TCC_Expensive;
5268 }
5269 
5270 /// Returns true if a SelectInst should be turned into an explicit branch.
5272  const TargetLowering *TLI,
5273  SelectInst *SI) {
5274  // If even a predictable select is cheap, then a branch can't be cheaper.
5275  if (!TLI->isPredictableSelectExpensive())
5276  return false;
5277 
5278  // FIXME: This should use the same heuristics as IfConversion to determine
5279  // whether a select is better represented as a branch.
5280 
5281  // If metadata tells us that the select condition is obviously predictable,
5282  // then we want to replace the select with a branch.
5283  uint64_t TrueWeight, FalseWeight;
5284  if (SI->extractProfMetadata(TrueWeight, FalseWeight)) {
5285  uint64_t Max = std::max(TrueWeight, FalseWeight);
5286  uint64_t Sum = TrueWeight + FalseWeight;
5287  if (Sum != 0) {
5288  auto Probability = BranchProbability::getBranchProbability(Max, Sum);
5289  if (Probability > TLI->getPredictableBranchThreshold())
5290  return true;
5291  }
5292  }
5293 
5294  CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition());
5295 
5296  // If a branch is predictable, an out-of-order CPU can avoid blocking on its
5297  // comparison condition. If the compare has more than one use, there's
5298  // probably another cmov or setcc around, so it's not worth emitting a branch.
5299  if (!Cmp || !Cmp->hasOneUse())
5300  return false;
5301 
5302  // If either operand of the select is expensive and only needed on one side
5303  // of the select, we should form a branch.
5304  if (sinkSelectOperand(TTI, SI->getTrueValue()) ||
5305  sinkSelectOperand(TTI, SI->getFalseValue()))
5306  return true;
5307 
5308  return false;
5309 }
5310 
5311 /// If \p isTrue is true, return the true value of \p SI, otherwise return
5312 /// false value of \p SI. If the true/false value of \p SI is defined by any
5313 /// select instructions in \p Selects, look through the defining select
5314 /// instruction until the true/false value is not defined in \p Selects.
5316  SelectInst *SI, bool isTrue,
5317  const SmallPtrSet<const Instruction *, 2> &Selects) {
5318  Value *V;
5319 
5320  for (SelectInst *DefSI = SI; DefSI != nullptr && Selects.count(DefSI);
5321  DefSI = dyn_cast<SelectInst>(V)) {
5322  assert(DefSI->getCondition() == SI->getCondition() &&
5323  "The condition of DefSI does not match with SI");
5324  V = (isTrue ? DefSI->getTrueValue() : DefSI->getFalseValue());
5325  }
5326  return V;
5327 }
5328 
5329 /// If we have a SelectInst that will likely profit from branch prediction,
5330 /// turn it into a branch.
5331 bool CodeGenPrepare::optimizeSelectInst(SelectInst *SI) {
5332  // Find all consecutive select instructions that share the same condition.
5334  ASI.push_back(SI);
5336  It != SI->getParent()->end(); ++It) {
5337  SelectInst *I = dyn_cast<SelectInst>(&*It);
5338  if (I && SI->getCondition() == I->getCondition()) {
5339  ASI.push_back(I);
5340  } else {
5341  break;
5342  }
5343  }
5344 
5345  SelectInst *LastSI = ASI.back();
5346  // Increment the current iterator to skip all the rest of select instructions
5347  // because they will be either "not lowered" or "all lowered" to branch.
5348  CurInstIterator = std::next(LastSI->getIterator());
5349 
5350  bool VectorCond = !SI->getCondition()->getType()->isIntegerTy(1);
5351 
5352  // Can we convert the 'select' to CF ?
5353  if (DisableSelectToBranch || OptSize || !TLI || VectorCond ||
5354  SI->getMetadata(LLVMContext::MD_unpredictable))
5355  return false;
5356 
5357  TargetLowering::SelectSupportKind SelectKind;
5358  if (VectorCond)
5359  SelectKind = TargetLowering::VectorMaskSelect;
5360  else if (SI->getType()->isVectorTy())
5361  SelectKind = TargetLowering::ScalarCondVectorVal;
5362  else
5363  SelectKind = TargetLowering::ScalarValSelect;
5364 
5365  if (TLI->isSelectSupported(SelectKind) &&
5366  !isFormingBranchFromSelectProfitable(TTI, TLI, SI))
5367  return false;
5368 
5369  ModifiedDT = true;
5370 
5371  // Transform a sequence like this:
5372  // start:
5373  // %cmp = cmp uge i32 %a, %b
5374  // %sel = select i1 %cmp, i32 %c, i32 %d
5375  //
5376  // Into:
5377  // start:
5378  // %cmp = cmp uge i32 %a, %b
5379  // br i1 %cmp, label %select.true, label %select.false
5380  // select.true:
5381  // br label %select.end
5382  // select.false:
5383  // br label %select.end
5384  // select.end:
5385  // %sel = phi i32 [ %c, %select.true ], [ %d, %select.false ]
5386  //
5387  // In addition, we may sink instructions that produce %c or %d from
5388  // the entry block into the destination(s) of the new branch.
5389  // If the true or false blocks do not contain a sunken instruction, that
5390  // block and its branch may be optimized away. In that case, one side of the
5391  // first branch will point directly to select.end, and the corresponding PHI
5392  // predecessor block will be the start block.
5393 
5394  // First, we split the block containing the select into 2 blocks.
5395  BasicBlock *StartBlock = SI->getParent();
5396  BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(LastSI));
5397  BasicBlock *EndBlock = StartBlock->splitBasicBlock(SplitPt, "select.end");
5398 
5399  // Delete the unconditional branch that was just created by the split.
5400  StartBlock->getTerminator()->eraseFromParent();
5401 
5402  // These are the new basic blocks for the conditional branch.
5403  // At least one will become an actual new basic block.
5404  BasicBlock *TrueBlock = nullptr;
5405  BasicBlock *FalseBlock = nullptr;
5406  BranchInst *TrueBranch = nullptr;
5407  BranchInst *FalseBranch = nullptr;
5408 
5409  // Sink expensive instructions into the conditional blocks to avoid executing
5410  // them speculatively.
5411  for (SelectInst *SI : ASI) {
5412  if (sinkSelectOperand(TTI, SI->getTrueValue())) {
5413  if (TrueBlock == nullptr) {
5414  TrueBlock = BasicBlock::Create(SI->getContext(), "select.true.sink",
5415  EndBlock->getParent(), EndBlock);
5416  TrueBranch = BranchInst::Create(EndBlock, TrueBlock);
5417  }
5418  auto *TrueInst = cast<Instruction>(SI->getTrueValue());
5419  TrueInst->moveBefore(TrueBranch);
5420  }
5421  if (sinkSelectOperand(TTI, SI->getFalseValue())) {
5422  if (FalseBlock == nullptr) {
5423  FalseBlock = BasicBlock::Create(SI->getContext(), "select.false.sink",
5424  EndBlock->getParent(), EndBlock);
5425  FalseBranch = BranchInst::Create(EndBlock, FalseBlock);
5426  }
5427  auto *FalseInst = cast<Instruction>(SI->getFalseValue());
5428  FalseInst->moveBefore(FalseBranch);
5429  }
5430  }
5431 
5432  // If there was nothing to sink, then arbitrarily choose the 'false' side
5433  // for a new input value to the PHI.
5434  if (TrueBlock == FalseBlock) {
5435  assert(TrueBlock == nullptr &&
5436  "Unexpected basic block transform while optimizing select");
5437 
5438  FalseBlock = BasicBlock::Create(SI->getContext(), "select.false",
5439  EndBlock->getParent(), EndBlock);
5440  BranchInst::Create(EndBlock, FalseBlock);
5441  }
5442 
5443  // Insert the real conditional branch based on the original condition.
5444  // If we did not create a new block for one of the 'true' or 'false' paths
5445  // of the condition, it means that side of the branch goes to the end block
5446  // directly and the path originates from the start block from the point of
5447  // view of the new PHI.
5448  BasicBlock *TT, *FT;
5449  if (TrueBlock == nullptr) {
5450  TT = EndBlock;
5451  FT = FalseBlock;
5452  TrueBlock = StartBlock;
5453  } else if (FalseBlock == nullptr) {
5454  TT = TrueBlock;
5455  FT = EndBlock;
5456  FalseBlock = StartBlock;
5457  } else {
5458  TT = TrueBlock;
5459  FT = FalseBlock;
5460  }
5461  IRBuilder<>(SI).CreateCondBr(SI->getCondition(), TT, FT, SI);
5462 
5464  INS.insert(ASI.begin(), ASI.end());
5465  // Use reverse iterator because later select may use the value of the
5466  // earlier select, and we need to propagate value through earlier select
5467  // to get the PHI operand.
5468  for (auto It = ASI.rbegin(); It != ASI.rend(); ++It) {
5469  SelectInst *SI = *It;
5470  // The select itself is replaced with a PHI Node.
5471  PHINode *PN = PHINode::Create(SI->getType(), 2, "", &EndBlock->front());
5472  PN->takeName(SI);
5473  PN->addIncoming(getTrueOrFalseValue(SI, true, INS), TrueBlock);
5474  PN->addIncoming(getTrueOrFalseValue(SI, false, INS), FalseBlock);
5475 
5476  SI->replaceAllUsesWith(PN);
5477  SI->eraseFromParent();
5478  INS.erase(SI);
5479  ++NumSelectsExpanded;
5480  }
5481 
5482  // Instruct OptimizeBlock to skip to the next block.
5483  CurInstIterator = StartBlock->end();
5484  return true;
5485 }
5486 
5489  int SplatElem = -1;
5490  for (unsigned i = 0; i < Mask.size(); ++i) {
5491  if (SplatElem != -1 && Mask[i] != -1 && Mask[i] != SplatElem)
5492  return false;
5493  SplatElem = Mask[i];
5494  }
5495 
5496  return true;
5497 }
5498 
5499 /// Some targets have expensive vector shifts if the lanes aren't all the same
5500 /// (e.g. x86 only introduced "vpsllvd" and friends with AVX2). In these cases
5501 /// it's often worth sinking a shufflevector splat down to its use so that
5502 /// codegen can spot all lanes are identical.
5503 bool CodeGenPrepare::optimizeShuffleVectorInst(ShuffleVectorInst *SVI) {
5504  BasicBlock *DefBB = SVI->getParent();
5505 
5506  // Only do this xform if variable vector shifts are particularly expensive.
5507  if (!TLI || !TLI->isVectorShiftByScalarCheap(SVI->getType()))
5508  return false;
5509 
5510  // We only expect better codegen by sinking a shuffle if we can recognise a
5511  // constant splat.
5512  if (!isBroadcastShuffle(SVI))
5513  return false;
5514 
5515  // InsertedShuffles - Only insert a shuffle in each block once.
5516  DenseMap<BasicBlock*, Instruction*> InsertedShuffles;
5517 
5518  bool MadeChange = false;
5519  for (User *U : SVI->users()) {
5520  Instruction *UI = cast<Instruction>(U);
5521 
5522  // Figure out which BB this ext is used in.
5523  BasicBlock *UserBB = UI->getParent();
5524  if (UserBB == DefBB) continue;
5525 
5526  // For now only apply this when the splat is used by a shift instruction.
5527  if (!UI->isShift()) continue;
5528 
5529  // Everything checks out, sink the shuffle if the user's block doesn't
5530  // already have a copy.
5531  Instruction *&InsertedShuffle = InsertedShuffles[UserBB];
5532 
5533  if (!InsertedShuffle) {
5534  BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
5535  assert(InsertPt != UserBB->end());
5536  InsertedShuffle =
5537  new ShuffleVectorInst(SVI->getOperand(0), SVI->getOperand(1),
5538  SVI->getOperand(2), "", &*InsertPt);
5539  }
5540 
5541  UI->replaceUsesOfWith(SVI, InsertedShuffle);
5542  MadeChange = true;
5543  }
5544 
5545  // If we removed all uses, nuke the shuffle.
5546  if (SVI->use_empty()) {
5547  SVI->eraseFromParent();
5548  MadeChange = true;
5549  }
5550 
5551  return MadeChange;
5552 }
5553 
5554 bool CodeGenPrepare::optimizeSwitchInst(SwitchInst *SI) {
5555  if (!TLI || !DL)
5556  return false;
5557 
5558  Value *Cond = SI->getCondition();
5559  Type *OldType = Cond->getType();
5560  LLVMContext &Context = Cond->getContext();
5561  MVT RegType = TLI->getRegisterType(Context, TLI->getValueType(*DL, OldType));
5562  unsigned RegWidth = RegType.getSizeInBits();
5563 
5564  if (RegWidth <= cast<IntegerType>(OldType)->getBitWidth())
5565  return false;
5566 
5567  // If the register width is greater than the type width, expand the condition
5568  // of the switch instruction and each case constant to the width of the
5569  // register. By widening the type of the switch condition, subsequent
5570  // comparisons (for case comparisons) will not need to be extended to the
5571  // preferred register width, so we will potentially eliminate N-1 extends,
5572  // where N is the number of cases in the switch.
5573  auto *NewType = Type::getIntNTy(Context, RegWidth);
5574 
5575  // Zero-extend the switch condition and case constants unless the switch
5576  // condition is a function argument that is already being sign-extended.
5577  // In that case, we can avoid an unnecessary mask/extension by sign-extending
5578  // everything instead.
5579  Instruction::CastOps ExtType = Instruction::ZExt;
5580  if (auto *Arg = dyn_cast<Argument>(Cond))
5581  if (Arg->hasSExtAttr())
5582  ExtType = Instruction::SExt;
5583 
5584  auto *ExtInst = CastInst::Create(ExtType, Cond, NewType);
5585  ExtInst->insertBefore(SI);
5586  SI->setCondition(ExtInst);
5587  for (auto Case : SI->cases()) {
5588  APInt NarrowConst = Case.getCaseValue()->getValue();
5589  APInt WideConst = (ExtType == Instruction::ZExt) ?
5590  NarrowConst.zext(RegWidth) : NarrowConst.sext(RegWidth);
5591  Case.setValue(ConstantInt::get(Context, WideConst));
5592  }
5593 
5594  return true;
5595 }
5596 
5597 
5598 namespace {
5599 /// \brief Helper class to promote a scalar operation to a vector one.
5600 /// This class is used to move downward extractelement transition.
5601 /// E.g.,
5602 /// a = vector_op <2 x i32>
5603 /// b = extractelement <2 x i32> a, i32 0
5604 /// c = scalar_op b
5605 /// store c
5606 ///
5607 /// =>
5608 /// a = vector_op <2 x i32>
5609 /// c = vector_op a (equivalent to scalar_op on the related lane)
5610 /// * d = extractelement <2 x i32> c, i32 0
5611 /// * store d
5612 /// Assuming both extractelement and store can be combine, we get rid of the
5613 /// transition.
5614 class VectorPromoteHelper {
5615  /// DataLayout associated with the current module.
5616  const DataLayout &DL;
5617 
5618  /// Used to perform some checks on the legality of vector operations.
5619  const TargetLowering &TLI;
5620 
5621  /// Used to estimated the cost of the promoted chain.
5622  const TargetTransformInfo &TTI;
5623 
5624  /// The transition being moved downwards.
5625  Instruction *Transition;
5626  /// The sequence of instructions to be promoted.
5627  SmallVector<Instruction *, 4> InstsToBePromoted;
5628  /// Cost of combining a store and an extract.
5629  unsigned StoreExtractCombineCost;
5630  /// Instruction that will be combined with the transition.
5631  Instruction *CombineInst;
5632 
5633  /// \brief The instruction that represents the current end of the transition.
5634  /// Since we are faking the promotion until we reach the end of the chain
5635  /// of computation, we need a way to get the current end of the transition.
5636  Instruction *getEndOfTransition() const {
5637  if (InstsToBePromoted.empty())
5638  return Transition;
5639  return InstsToBePromoted.back();
5640  }
5641 
5642  /// \brief Return the index of the original value in the transition.
5643  /// E.g., for "extractelement <2 x i32> c, i32 1" the original value,
5644  /// c, is at index 0.
5645  unsigned getTransitionOriginalValueIdx() const {
5646  assert(isa<ExtractElementInst>(Transition) &&
5647  "Other kind of transitions are not supported yet");
5648  return 0;
5649  }
5650 
5651  /// \brief Return the index of the index in the transition.
5652  /// E.g., for "extractelement <2 x i32> c, i32 0" the index
5653  /// is at index 1.
5654  unsigned getTransitionIdx() const {
5655  assert(isa<ExtractElementInst>(Transition) &&
5656  "Other kind of transitions are not supported yet");
5657  return 1;
5658  }
5659 
5660  /// \brief Get the type of the transition.
5661  /// This is the type of the original value.
5662  /// E.g., for "extractelement <2 x i32> c, i32 1" the type of the
5663  /// transition is <2 x i32>.
5664  Type *getTransitionType() const {
5665  return Transition->getOperand(getTransitionOriginalValueIdx())->getType();
5666  }
5667 
5668  /// \brief Promote \p ToBePromoted by moving \p Def downward through.
5669  /// I.e., we have the following sequence:
5670  /// Def = Transition <ty1> a to <ty2>
5671  /// b = ToBePromoted <ty2> Def, ...
5672  /// =>
5673  /// b = ToBePromoted <ty1> a, ...
5674  /// Def = Transition <ty1> ToBePromoted to <ty2>
5675  void promoteImpl(Instruction *ToBePromoted);
5676 
5677  /// \brief Check whether or not it is profitable to promote all the
5678  /// instructions enqueued to be promoted.
5679  bool isProfitableToPromote() {
5680  Value *ValIdx = Transition->getOperand(getTransitionOriginalValueIdx());
5681  unsigned Index = isa<ConstantInt>(ValIdx)
5682  ? cast<ConstantInt>(ValIdx)->getZExtValue()
5683  : -1;
5684  Type *PromotedType = getTransitionType();
5685 
5686  StoreInst *ST = cast<StoreInst>(CombineInst);
5687  unsigned AS = ST->getPointerAddressSpace();
5688  unsigned Align = ST->getAlignment();
5689  // Check if this store is supported.
5691  TLI.getValueType(DL, ST->getValueOperand()->getType()), AS,
5692  Align)) {
5693  // If this is not supported, there is no way we can combine
5694  // the extract with the store.
5695  return false;
5696  }
5697 
5698  // The scalar chain of computation has to pay for the transition
5699  // scalar to vector.
5700  // The vector chain has to account for the combining cost.
5701  uint64_t ScalarCost =
5702  TTI.getVectorInstrCost(Transition->getOpcode(), PromotedType, Index);
5703  uint64_t VectorCost = StoreExtractCombineCost;
5704  for (const auto &Inst : InstsToBePromoted) {
5705  // Compute the cost.
5706  // By construction, all instructions being promoted are arithmetic ones.
5707  // Moreover, one argument is a constant that can be viewed as a splat
5708  // constant.
5709  Value *Arg0 = Inst->getOperand(0);
5710  bool IsArg0Constant = isa<UndefValue>(Arg0) || isa<ConstantInt>(Arg0) ||
5711  isa<ConstantFP>(Arg0);
5713  IsArg0Constant ? TargetTransformInfo::OK_UniformConstantValue
5714  : TargetTransformInfo::OK_AnyValue;
5716  !IsArg0Constant ? TargetTransformInfo::OK_UniformConstantValue
5717  : TargetTransformInfo::OK_AnyValue;
5718  ScalarCost += TTI.getArithmeticInstrCost(
5719  Inst->getOpcode(), Inst->getType(), Arg0OVK, Arg1OVK);
5720  VectorCost += TTI.getArithmeticInstrCost(Inst->getOpcode(), PromotedType,
5721  Arg0OVK, Arg1OVK);
5722  }
5723  DEBUG(dbgs() << "Estimated cost of computation to be promoted:\nScalar: "
5724  << ScalarCost << "\nVector: " << VectorCost << '\n');
5725  return ScalarCost > VectorCost;
5726  }
5727 
5728  /// \brief Generate a constant vector with \p Val with the same
5729  /// number of elements as the transition.
5730  /// \p UseSplat defines whether or not \p Val should be replicated
5731  /// across the whole vector.
5732  /// In other words, if UseSplat == true, we generate <Val, Val, ..., Val>,
5733  /// otherwise we generate a vector with as many undef as possible:
5734  /// <undef, ..., undef, Val, undef, ..., undef> where \p Val is only
5735  /// used at the index of the extract.
5736  Value *getConstantVector(Constant *Val, bool UseSplat) const {
5737  unsigned ExtractIdx = UINT_MAX;
5738  if (!UseSplat) {
5739  // If we cannot determine where the constant must be, we have to
5740  // use a splat constant.
5741  Value *ValExtractIdx = Transition->getOperand(getTransitionIdx());
5742  if (ConstantInt *CstVal = dyn_cast<ConstantInt>(ValExtractIdx))
5743  ExtractIdx = CstVal->getSExtValue();
5744  else
5745  UseSplat = true;
5746  }
5747 
5748  unsigned End = getTransitionType()->getVectorNumElements();
5749  if (UseSplat)
5750  return ConstantVector::getSplat(End, Val);
5751 
5752  SmallVector<Constant *, 4> ConstVec;
5753  UndefValue *UndefVal = UndefValue::get(Val->getType());
5754  for (unsigned Idx = 0; Idx != End; ++Idx) {
5755  if (Idx == ExtractIdx)
5756  ConstVec.push_back(Val);
5757  else
5758  ConstVec.push_back(UndefVal);
5759  }
5760  return ConstantVector::get(ConstVec);
5761  }
5762 
5763  /// \brief Check if promoting to a vector type an operand at \p OperandIdx
5764  /// in \p Use can trigger undefined behavior.
5765  static bool canCauseUndefinedBehavior(const Instruction *Use,
5766  unsigned OperandIdx) {
5767  // This is not safe to introduce undef when the operand is on
5768  // the right hand side of a division-like instruction.
5769  if (OperandIdx != 1)
5770  return false;
5771  switch (Use->getOpcode()) {
5772  default:
5773  return false;
5774  case Instruction::SDiv:
5775  case Instruction::UDiv:
5776  case Instruction::SRem:
5777  case Instruction::URem:
5778  return true;
5779  case Instruction::FDiv:
5780  case Instruction::FRem:
5781  return !Use->hasNoNaNs();
5782  }
5783  llvm_unreachable(nullptr);
5784  }
5785 
5786 public:
5787  VectorPromoteHelper(const DataLayout &DL, const TargetLowering &TLI,
5788  const TargetTransformInfo &TTI, Instruction *Transition,
5789  unsigned CombineCost)
5790  : DL(DL), TLI(TLI), TTI(TTI), Transition(Transition),
5791  StoreExtractCombineCost(CombineCost), CombineInst(nullptr) {
5792  assert(Transition && "Do not know how to promote null");
5793  }
5794 
5795  /// \brief Check if we can promote \p ToBePromoted to \p Type.
5796  bool canPromote(const Instruction *ToBePromoted) const {
5797  // We could support CastInst too.
5798  return isa<BinaryOperator>(ToBePromoted);
5799  }
5800 
5801  /// \brief Check if it is profitable to promote \p ToBePromoted
5802  /// by moving downward the transition through.
5803  bool shouldPromote(const Instruction *ToBePromoted) const {
5804  // Promote only if all the operands can be statically expanded.
5805  // Indeed, we do not want to introduce any new kind of transitions.
5806  for (const Use &U : ToBePromoted->operands()) {
5807  const Value *Val = U.get();
5808  if (Val == getEndOfTransition()) {
5809  // If the use is a division and the transition is on the rhs,
5810  // we cannot promote the operation, otherwise we may create a
5811  // division by zero.
5812  if (canCauseUndefinedBehavior(ToBePromoted, U.getOperandNo()))
5813  return false;
5814  continue;
5815  }
5816  if (!isa<ConstantInt>(Val) && !isa<UndefValue>(Val) &&
5817  !isa<ConstantFP>(Val))
5818  return false;
5819  }
5820  // Check that the resulting operation is legal.
5821  int ISDOpcode = TLI.InstructionOpcodeToISD(ToBePromoted->getOpcode());
5822  if (!ISDOpcode)
5823  return false;
5824  return StressStoreExtract ||
5826  ISDOpcode, TLI.getValueType(DL, getTransitionType(), true));
5827  }
5828 
5829  /// \brief Check whether or not \p Use can be combined
5830  /// with the transition.
5831  /// I.e., is it possible to do Use(Transition) => AnotherUse?
5832  bool canCombine(const Instruction *Use) { return isa<StoreInst>(Use); }
5833 
5834  /// \brief Record \p ToBePromoted as part of the chain to be promoted.
5835  void enqueueForPromotion(Instruction *ToBePromoted) {
5836  InstsToBePromoted.push_back(ToBePromoted);
5837  }
5838 
5839  /// \brief Set the instruction that will be combined with the transition.
5840  void recordCombineInstruction(Instruction *ToBeCombined) {
5841  assert(canCombine(ToBeCombined) && "Unsupported instruction to combine");
5842  CombineInst = ToBeCombined;