1//===- InstCombine.h - Main InstCombine pass definition ---------*- C++ -*-===//
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#ifndef INSTCOMBINE_INSTCOMBINE_H
11#define INSTCOMBINE_INSTCOMBINE_H
12
13#include "InstCombineWorklist.h"
14#include "llvm/Analysis/TargetFolder.h"
15#include "llvm/Analysis/ValueTracking.h"
16#include "llvm/IR/IRBuilder.h"
17#include "llvm/IR/InstVisitor.h"
18#include "llvm/IR/IntrinsicInst.h"
19#include "llvm/IR/Operator.h"
20#include "llvm/Pass.h"
21#include "llvm/Transforms/Utils/SimplifyLibCalls.h"
22
23#define DEBUG_TYPE "instcombine"
24
25namespace llvm {
26class CallSite;
27class DataLayout;
28class TargetLibraryInfo;
29class DbgDeclareInst;
30class MemIntrinsic;
31class MemSetInst;
32
33/// SelectPatternFlavor - We can match a variety of different patterns for
34/// select operations.
35enum SelectPatternFlavor {
36  SPF_UNKNOWN = 0,
37  SPF_SMIN,
38  SPF_UMIN,
39  SPF_SMAX,
40  SPF_UMAX,
41  SPF_ABS,
42  SPF_NABS
43};
44
45/// getComplexity:  Assign a complexity or rank value to LLVM Values...
46///   0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
47static inline unsigned getComplexity(Value *V) {
48  if (isa<Instruction>(V)) {
49    if (BinaryOperator::isNeg(V) || BinaryOperator::isFNeg(V) ||
50        BinaryOperator::isNot(V))
51      return 3;
52    return 4;
53  }
54  if (isa<Argument>(V))
55    return 3;
56  return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
57}
58
59/// AddOne - Add one to a Constant
60static inline Constant *AddOne(Constant *C) {
61  return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1));
62}
63/// SubOne - Subtract one from a Constant
64static inline Constant *SubOne(Constant *C) {
65  return ConstantExpr::getSub(C, ConstantInt::get(C->getType(), 1));
66}
67
68/// InstCombineIRInserter - This is an IRBuilder insertion helper that works
69/// just like the normal insertion helper, but also adds any new instructions
70/// to the instcombine worklist.
71class LLVM_LIBRARY_VISIBILITY InstCombineIRInserter
72    : public IRBuilderDefaultInserter<true> {
73  InstCombineWorklist &Worklist;
74
75public:
76  InstCombineIRInserter(InstCombineWorklist &WL) : Worklist(WL) {}
77
78  void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB,
79                    BasicBlock::iterator InsertPt) const {
80    IRBuilderDefaultInserter<true>::InsertHelper(I, Name, BB, InsertPt);
81    Worklist.Add(I);
82  }
83};
84
85/// InstCombiner - The -instcombine pass.
86class LLVM_LIBRARY_VISIBILITY InstCombiner
87    : public FunctionPass,
88      public InstVisitor<InstCombiner, Instruction *> {
89  const DataLayout *DL;
90  TargetLibraryInfo *TLI;
91  bool MadeIRChange;
92  LibCallSimplifier *Simplifier;
93  bool MinimizeSize;
94
95public:
96  /// Worklist - All of the instructions that need to be simplified.
97  InstCombineWorklist Worklist;
98
99  /// Builder - This is an IRBuilder that automatically inserts new
100  /// instructions into the worklist when they are created.
101  typedef IRBuilder<true, TargetFolder, InstCombineIRInserter> BuilderTy;
102  BuilderTy *Builder;
103
104  static char ID; // Pass identification, replacement for typeid
105  InstCombiner() : FunctionPass(ID), DL(nullptr), Builder(nullptr) {
106    MinimizeSize = false;
107    initializeInstCombinerPass(*PassRegistry::getPassRegistry());
108  }
109
110public:
111  bool runOnFunction(Function &F) override;
112
113  bool DoOneIteration(Function &F, unsigned ItNum);
114
115  void getAnalysisUsage(AnalysisUsage &AU) const override;
116
117  const DataLayout *getDataLayout() const { return DL; }
118
119  TargetLibraryInfo *getTargetLibraryInfo() const { return TLI; }
120
121  // Visitation implementation - Implement instruction combining for different
122  // instruction types.  The semantics are as follows:
123  // Return Value:
124  //    null        - No change was made
125  //     I          - Change was made, I is still valid, I may be dead though
126  //   otherwise    - Change was made, replace I with returned instruction
127  //
128  Instruction *visitAdd(BinaryOperator &I);
129  Instruction *visitFAdd(BinaryOperator &I);
130  Value *OptimizePointerDifference(Value *LHS, Value *RHS, Type *Ty);
131  Instruction *visitSub(BinaryOperator &I);
132  Instruction *visitFSub(BinaryOperator &I);
133  Instruction *visitMul(BinaryOperator &I);
134  Value *foldFMulConst(Instruction *FMulOrDiv, Constant *C,
135                       Instruction *InsertBefore);
136  Instruction *visitFMul(BinaryOperator &I);
137  Instruction *visitURem(BinaryOperator &I);
138  Instruction *visitSRem(BinaryOperator &I);
139  Instruction *visitFRem(BinaryOperator &I);
140  bool SimplifyDivRemOfSelect(BinaryOperator &I);
141  Instruction *commonRemTransforms(BinaryOperator &I);
142  Instruction *commonIRemTransforms(BinaryOperator &I);
143  Instruction *commonDivTransforms(BinaryOperator &I);
144  Instruction *commonIDivTransforms(BinaryOperator &I);
145  Instruction *visitUDiv(BinaryOperator &I);
146  Instruction *visitSDiv(BinaryOperator &I);
147  Instruction *visitFDiv(BinaryOperator &I);
148  Value *FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS);
149  Value *FoldAndOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
150  Instruction *visitAnd(BinaryOperator &I);
151  Value *FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS);
152  Value *FoldOrOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
153  Instruction *FoldOrWithConstants(BinaryOperator &I, Value *Op, Value *A,
154                                   Value *B, Value *C);
155  Instruction *visitOr(BinaryOperator &I);
156  Instruction *visitXor(BinaryOperator &I);
157  Instruction *visitShl(BinaryOperator &I);
158  Instruction *visitAShr(BinaryOperator &I);
159  Instruction *visitLShr(BinaryOperator &I);
160  Instruction *commonShiftTransforms(BinaryOperator &I);
161  Instruction *FoldFCmp_IntToFP_Cst(FCmpInst &I, Instruction *LHSI,
162                                    Constant *RHSC);
163  Instruction *FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
164                                            GlobalVariable *GV, CmpInst &ICI,
165                                            ConstantInt *AndCst = nullptr);
166  Instruction *visitFCmpInst(FCmpInst &I);
167  Instruction *visitICmpInst(ICmpInst &I);
168  Instruction *visitICmpInstWithCastAndCast(ICmpInst &ICI);
169  Instruction *visitICmpInstWithInstAndIntCst(ICmpInst &ICI, Instruction *LHS,
170                                              ConstantInt *RHS);
171  Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
172                              ConstantInt *DivRHS);
173  Instruction *FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *DivI,
174                              ConstantInt *DivRHS);
175  Instruction *FoldICmpAddOpCst(Instruction &ICI, Value *X, ConstantInt *CI,
176                                ICmpInst::Predicate Pred);
177  Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
178                           ICmpInst::Predicate Cond, Instruction &I);
179  Instruction *FoldShiftByConstant(Value *Op0, Constant *Op1,
180                                   BinaryOperator &I);
181  Instruction *commonCastTransforms(CastInst &CI);
182  Instruction *commonPointerCastTransforms(CastInst &CI);
183  Instruction *visitTrunc(TruncInst &CI);
184  Instruction *visitZExt(ZExtInst &CI);
185  Instruction *visitSExt(SExtInst &CI);
186  Instruction *visitFPTrunc(FPTruncInst &CI);
187  Instruction *visitFPExt(CastInst &CI);
188  Instruction *visitFPToUI(FPToUIInst &FI);
189  Instruction *visitFPToSI(FPToSIInst &FI);
190  Instruction *visitUIToFP(CastInst &CI);
191  Instruction *visitSIToFP(CastInst &CI);
192  Instruction *visitPtrToInt(PtrToIntInst &CI);
193  Instruction *visitIntToPtr(IntToPtrInst &CI);
194  Instruction *visitBitCast(BitCastInst &CI);
195  Instruction *visitAddrSpaceCast(AddrSpaceCastInst &CI);
196  Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI, Instruction *FI);
197  Instruction *FoldSelectIntoOp(SelectInst &SI, Value *, Value *);
198  Instruction *FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1,
199                            Value *A, Value *B, Instruction &Outer,
200                            SelectPatternFlavor SPF2, Value *C);
201  Instruction *visitSelectInst(SelectInst &SI);
202  Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
203  Instruction *visitCallInst(CallInst &CI);
204  Instruction *visitInvokeInst(InvokeInst &II);
205
206  Instruction *SliceUpIllegalIntegerPHI(PHINode &PN);
207  Instruction *visitPHINode(PHINode &PN);
208  Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
209  Instruction *visitAllocaInst(AllocaInst &AI);
210  Instruction *visitAllocSite(Instruction &FI);
211  Instruction *visitFree(CallInst &FI);
212  Instruction *visitLoadInst(LoadInst &LI);
213  Instruction *visitStoreInst(StoreInst &SI);
214  Instruction *visitBranchInst(BranchInst &BI);
215  Instruction *visitSwitchInst(SwitchInst &SI);
216  Instruction *visitInsertValueInst(InsertValueInst &IV);
217  Instruction *visitInsertElementInst(InsertElementInst &IE);
218  Instruction *visitExtractElementInst(ExtractElementInst &EI);
219  Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
220  Instruction *visitExtractValueInst(ExtractValueInst &EV);
221  Instruction *visitLandingPadInst(LandingPadInst &LI);
222
223  // visitInstruction - Specify what to return for unhandled instructions...
224  Instruction *visitInstruction(Instruction &I) { return nullptr; }
225
226private:
227  bool ShouldChangeType(Type *From, Type *To) const;
228  Value *dyn_castNegVal(Value *V) const;
229  Value *dyn_castFNegVal(Value *V, bool NoSignedZero = false) const;
230  Type *FindElementAtOffset(Type *PtrTy, int64_t Offset,
231                            SmallVectorImpl<Value *> &NewIndices);
232  Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI);
233
234  /// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually
235  /// results in any code being generated and is interesting to optimize out. If
236  /// the cast can be eliminated by some other simple transformation, we prefer
237  /// to do the simplification first.
238  bool ShouldOptimizeCast(Instruction::CastOps opcode, const Value *V,
239                          Type *Ty);
240
241  Instruction *visitCallSite(CallSite CS);
242  Instruction *tryOptimizeCall(CallInst *CI, const DataLayout *DL);
243  bool transformConstExprCastCall(CallSite CS);
244  Instruction *transformCallThroughTrampoline(CallSite CS,
245                                              IntrinsicInst *Tramp);
246  Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
247                                 bool DoXform = true);
248  Instruction *transformSExtICmp(ICmpInst *ICI, Instruction &CI);
249  bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS);
250  bool WillNotOverflowUnsignedAdd(Value *LHS, Value *RHS);
251  Value *EmitGEPOffset(User *GEP);
252  Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN);
253  Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask);
254
255public:
256  // InsertNewInstBefore - insert an instruction New before instruction Old
257  // in the program.  Add the new instruction to the worklist.
258  //
259  Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
260    assert(New && !New->getParent() &&
261           "New instruction already inserted into a basic block!");
262    BasicBlock *BB = Old.getParent();
263    BB->getInstList().insert(&Old, New); // Insert inst
264    Worklist.Add(New);
265    return New;
266  }
267
268  // InsertNewInstWith - same as InsertNewInstBefore, but also sets the
269  // debug loc.
270  //
271  Instruction *InsertNewInstWith(Instruction *New, Instruction &Old) {
272    New->setDebugLoc(Old.getDebugLoc());
273    return InsertNewInstBefore(New, Old);
274  }
275
276  // ReplaceInstUsesWith - This method is to be used when an instruction is
277  // found to be dead, replacable with another preexisting expression.  Here
278  // we add all uses of I to the worklist, replace all uses of I with the new
279  // value, then return I, so that the inst combiner will know that I was
280  // modified.
281  //
282  Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
283    Worklist.AddUsersToWorkList(I); // Add all modified instrs to worklist.
284
285    // If we are replacing the instruction with itself, this must be in a
286    // segment of unreachable code, so just clobber the instruction.
287    if (&I == V)
288      V = UndefValue::get(I.getType());
289
290    DEBUG(dbgs() << "IC: Replacing " << I << "\n"
291                    "    with " << *V << '\n');
292
293    I.replaceAllUsesWith(V);
294    return &I;
295  }
296
297  // EraseInstFromFunction - When dealing with an instruction that has side
298  // effects or produces a void value, we can't rely on DCE to delete the
299  // instruction.  Instead, visit methods should return the value returned by
300  // this function.
301  Instruction *EraseInstFromFunction(Instruction &I) {
302    DEBUG(dbgs() << "IC: ERASE " << I << '\n');
303
304    assert(I.use_empty() && "Cannot erase instruction that is used!");
305    // Make sure that we reprocess all operands now that we reduced their
306    // use counts.
307    if (I.getNumOperands() < 8) {
308      for (User::op_iterator i = I.op_begin(), e = I.op_end(); i != e; ++i)
309        if (Instruction *Op = dyn_cast<Instruction>(*i))
310          Worklist.Add(Op);
311    }
312    Worklist.Remove(&I);
313    I.eraseFromParent();
314    MadeIRChange = true;
315    return nullptr; // Don't do anything with FI
316  }
317
318  void computeKnownBits(Value *V, APInt &KnownZero, APInt &KnownOne,
319                        unsigned Depth = 0) const {
320    return llvm::computeKnownBits(V, KnownZero, KnownOne, DL, Depth);
321  }
322
323  bool MaskedValueIsZero(Value *V, const APInt &Mask,
324                         unsigned Depth = 0) const {
325    return llvm::MaskedValueIsZero(V, Mask, DL, Depth);
326  }
327  unsigned ComputeNumSignBits(Value *Op, unsigned Depth = 0) const {
328    return llvm::ComputeNumSignBits(Op, DL, Depth);
329  }
330
331private:
332  /// SimplifyAssociativeOrCommutative - This performs a few simplifications for
333  /// operators which are associative or commutative.
334  bool SimplifyAssociativeOrCommutative(BinaryOperator &I);
335
336  /// SimplifyUsingDistributiveLaws - This tries to simplify binary operations
337  /// which some other binary operation distributes over either by factorizing
338  /// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this
339  /// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is
340  /// a win).  Returns the simplified value, or null if it didn't simplify.
341  Value *SimplifyUsingDistributiveLaws(BinaryOperator &I);
342
343  /// SimplifyDemandedUseBits - Attempts to replace V with a simpler value
344  /// based on the demanded bits.
345  Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask, APInt &KnownZero,
346                                 APInt &KnownOne, unsigned Depth);
347  bool SimplifyDemandedBits(Use &U, APInt DemandedMask, APInt &KnownZero,
348                            APInt &KnownOne, unsigned Depth = 0);
349  /// Helper routine of SimplifyDemandedUseBits. It tries to simplify demanded
350  /// bit for "r1 = shr x, c1; r2 = shl r1, c2" instruction sequence.
351  Value *SimplifyShrShlDemandedBits(Instruction *Lsr, Instruction *Sftl,
352                                    APInt DemandedMask, APInt &KnownZero,
353                                    APInt &KnownOne);
354
355  /// SimplifyDemandedInstructionBits - Inst is an integer instruction that
356  /// SimplifyDemandedBits knows about.  See if the instruction has any
357  /// properties that allow us to simplify its operands.
358  bool SimplifyDemandedInstructionBits(Instruction &Inst);
359
360  Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
361                                    APInt &UndefElts, unsigned Depth = 0);
362
363  Value *SimplifyVectorOp(BinaryOperator &Inst);
364
365  // FoldOpIntoPhi - Given a binary operator, cast instruction, or select
366  // which has a PHI node as operand #0, see if we can fold the instruction
367  // into the PHI (which is only possible if all operands to the PHI are
368  // constants).
369  //
370  Instruction *FoldOpIntoPhi(Instruction &I);
371
372  // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
373  // operator and they all are only used by the PHI, PHI together their
374  // inputs, and do the operation once, to the result of the PHI.
375  Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
376  Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
377  Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
378  Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
379
380  Instruction *OptAndOp(Instruction *Op, ConstantInt *OpRHS,
381                        ConstantInt *AndRHS, BinaryOperator &TheAnd);
382
383  Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask,
384                            bool isSub, Instruction &I);
385  Value *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi, bool isSigned,
386                         bool Inside);
387  Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI);
388  Instruction *MatchBSwap(BinaryOperator &I);
389  bool SimplifyStoreAtEndOfBlock(StoreInst &SI);
390  Instruction *SimplifyMemTransfer(MemIntrinsic *MI);
391  Instruction *SimplifyMemSet(MemSetInst *MI);
392
393  Value *EvaluateInDifferentType(Value *V, Type *Ty, bool isSigned);
394
395  /// Descale - Return a value X such that Val = X * Scale, or null if none.  If
396  /// the multiplication is known not to overflow then NoSignedWrap is set.
397  Value *Descale(Value *Val, APInt Scale, bool &NoSignedWrap);
398};
399
400} // end namespace llvm.
401
402#undef DEBUG_TYPE
403
404#endif
405