include/llvm/Analysis/InstructionSimplify.h

   1 //===-- InstructionSimplify.h - Fold instrs into simpler forms --*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file declares routines for folding instructions into simpler forms
  10 // that do not require creating new instructions.  This does constant folding
  11 // ("add i32 1, 1" -> "2") but can also handle non-constant operands, either
  12 // returning a constant ("and i32 %x, 0" -> "0") or an already existing value
  13 // ("and i32 %x, %x" -> "%x").  If the simplification is also an instruction
  14 // then it dominates the original instruction.
  15 //
  16 // These routines implicitly resolve undef uses. The easiest way to be safe when
  17 // using these routines to obtain simplified values for existing instructions is
  18 // to always replace all uses of the instructions with the resulting simplified
  19 // values. This will prevent other code from seeing the same undef uses and
  20 // resolving them to different values.
  21 //
  22 // These routines are designed to tolerate moderately incomplete IR, such as
  23 // instructions that are not connected to basic blocks yet. However, they do
  24 // require that all the IR that they encounter be valid. In particular, they
  25 // require that all non-constant values be defined in the same function, and the
  26 // same call context of that function (and not split between caller and callee
  27 // contexts of a directly recursive call, for example).
  28 //
  29 //===----------------------------------------------------------------------===//
  30
  31 #ifndef LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H
  32 #define LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H
  33
  34 #include "llvm/IR/Instruction.h"
  35 #include "llvm/IR/Operator.h"
  36 #include "llvm/IR/User.h"
  37
  38 namespace llvm {
  39 class Function;
  40 template <typename T, typename... TArgs> class AnalysisManager;
  41 template <class T> class ArrayRef;
  42 class AssumptionCache;
  43 class CallBase;
  44 class DominatorTree;
  45 class DataLayout;
  46 class FastMathFlags;
  47 struct LoopStandardAnalysisResults;
  48 class OptimizationRemarkEmitter;
  49 class Pass;
  50 class TargetLibraryInfo;
  51 class Type;
  52 class Value;
  53 class MDNode;
  54 class BinaryOperator;
  55
  56 /// InstrInfoQuery provides an interface to query additional information for
  57 /// instructions like metadata or keywords like nsw, which provides conservative
  58 /// results if the users specified it is safe to use.
  59 struct InstrInfoQuery {
  60   InstrInfoQuery(bool UMD) : UseInstrInfo(UMD) {}
  61   InstrInfoQuery() : UseInstrInfo(true) {}
  62   bool UseInstrInfo = true;
  63
  64   MDNode *getMetadata(const Instruction *I, unsigned KindID) const {
  65     if (UseInstrInfo)
  66       return I->getMetadata(KindID);
  67     return nullptr;
  68   }
  69
  70   template <class InstT> bool hasNoUnsignedWrap(const InstT *Op) const {
  71     if (UseInstrInfo)
  72       return Op->hasNoUnsignedWrap();
  73     return false;
  74   }
  75
  76   template <class InstT> bool hasNoSignedWrap(const InstT *Op) const {
  77     if (UseInstrInfo)
  78       return Op->hasNoSignedWrap();
  79     return false;
  80   }
  81
  82   bool isExact(const BinaryOperator *Op) const {
  83     if (UseInstrInfo && isa<PossiblyExactOperator>(Op))
  84       return cast<PossiblyExactOperator>(Op)->isExact();
  85     return false;
  86   }
  87 };
  88
  89 struct SimplifyQuery {
  90   const DataLayout &DL;
  91   const TargetLibraryInfo *TLI = nullptr;
  92   const DominatorTree *DT = nullptr;
  93   AssumptionCache *AC = nullptr;
  94   const Instruction *CxtI = nullptr;
  95
  96   // Wrapper to query additional information for instructions like metadata or
  97   // keywords like nsw, which provides conservative results if those cannot
  98   // be safely used.
  99   const InstrInfoQuery IIQ;
 100
 101   SimplifyQuery(const DataLayout &DL, const Instruction *CXTI = nullptr)
 102       : DL(DL), CxtI(CXTI) {}
 103
 104   SimplifyQuery(const DataLayout &DL, const TargetLibraryInfo *TLI,
 105                 const DominatorTree *DT = nullptr,
 106                 AssumptionCache *AC = nullptr,
 107                 const Instruction *CXTI = nullptr, bool UseInstrInfo = true)
 108       : DL(DL), TLI(TLI), DT(DT), AC(AC), CxtI(CXTI), IIQ(UseInstrInfo) {}
 109   SimplifyQuery getWithInstruction(Instruction *I) const {
 110     SimplifyQuery Copy(*this);
 111     Copy.CxtI = I;
 112     return Copy;
 113   }
 114 };
 115
 116 // NOTE: the explicit multiple argument versions of these functions are
 117 // deprecated.
 118 // Please use the SimplifyQuery versions in new code.
 119
 120 /// Given operands for an Add, fold the result or return null.
 121 Value *SimplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
 122                        const SimplifyQuery &Q);
 123
 124 /// Given operands for a Sub, fold the result or return null.
 125 Value *SimplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
 126                        const SimplifyQuery &Q);
 127
 128 /// Given operands for an FAdd, fold the result or return null.
 129 Value *SimplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 130                         const SimplifyQuery &Q);
 131
 132 /// Given operands for an FSub, fold the result or return null.
 133 Value *SimplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 134                         const SimplifyQuery &Q);
 135
 136 /// Given operands for an FMul, fold the result or return null.
 137 Value *SimplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 138                         const SimplifyQuery &Q);
 139
 140 /// Given operands for a Mul, fold the result or return null.
 141 Value *SimplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 142
 143 /// Given operands for an SDiv, fold the result or return null.
 144 Value *SimplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 145
 146 /// Given operands for a UDiv, fold the result or return null.
 147 Value *SimplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 148
 149 /// Given operands for an FDiv, fold the result or return null.
 150 Value *SimplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 151                         const SimplifyQuery &Q);
 152
 153 /// Given operands for an SRem, fold the result or return null.
 154 Value *SimplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 155
 156 /// Given operands for a URem, fold the result or return null.
 157 Value *SimplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 158
 159 /// Given operands for an FRem, fold the result or return null.
 160 Value *SimplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 161                         const SimplifyQuery &Q);
 162
 163 /// Given operands for a Shl, fold the result or return null.
 164 Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
 165                        const SimplifyQuery &Q);
 166
 167 /// Given operands for a LShr, fold the result or return null.
 168 Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
 169                         const SimplifyQuery &Q);
 170
 171 /// Given operands for a AShr, fold the result or return nulll.
 172 Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
 173                         const SimplifyQuery &Q);
 174
 175 /// Given operands for an And, fold the result or return null.
 176 Value *SimplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 177
 178 /// Given operands for an Or, fold the result or return null.
 179 Value *SimplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 180
 181 /// Given operands for an Xor, fold the result or return null.
 182 Value *SimplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 183
 184 /// Given operands for an ICmpInst, fold the result or return null.
 185 Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
 186                         const SimplifyQuery &Q);
 187
 188 /// Given operands for an FCmpInst, fold the result or return null.
 189 Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
 190                         FastMathFlags FMF, const SimplifyQuery &Q);
 191
 192 /// Given operands for a SelectInst, fold the result or return null.
 193 Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
 194                           const SimplifyQuery &Q);
 195
 196 /// Given operands for a GetElementPtrInst, fold the result or return null.
 197 Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
 198                        const SimplifyQuery &Q);
 199
 200 /// Given operands for an InsertValueInst, fold the result or return null.
 201 Value *SimplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs,
 202                                const SimplifyQuery &Q);
 203
 204 /// Given operands for an InsertElement, fold the result or return null.
 205 Value *SimplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx,
 206                                  const SimplifyQuery &Q);
 207
 208 /// Given operands for an ExtractValueInst, fold the result or return null.
 209 Value *SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
 210                                 const SimplifyQuery &Q);
 211
 212 /// Given operands for an ExtractElementInst, fold the result or return null.
 213 Value *SimplifyExtractElementInst(Value *Vec, Value *Idx,
 214                                   const SimplifyQuery &Q);
 215
 216 /// Given operands for a CastInst, fold the result or return null.
 217 Value *SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
 218                         const SimplifyQuery &Q);
 219
 220 /// Given operands for a ShuffleVectorInst, fold the result or return null.
 221 Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, Constant *Mask,
 222                                  Type *RetTy, const SimplifyQuery &Q);
 223
 224 //=== Helper functions for higher up the class hierarchy.
 225
 226 /// Given operands for a CmpInst, fold the result or return null.
 227 Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
 228                        const SimplifyQuery &Q);
 229
 230 /// Given operands for a BinaryOperator, fold the result or return null.
 231 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
 232                      const SimplifyQuery &Q);
 233
 234 /// Given operands for an FP BinaryOperator, fold the result or return null.
 235 /// In contrast to SimplifyBinOp, try to use FastMathFlag when folding the
 236 /// result. In case we don't need FastMathFlags, simply fall to SimplifyBinOp.
 237 Value *SimplifyFPBinOp(unsigned Opcode, Value *LHS, Value *RHS,
 238                        FastMathFlags FMF, const SimplifyQuery &Q);
 239
 240 /// Given a callsite, fold the result or return null.
 241 Value *SimplifyCall(CallBase *Call, const SimplifyQuery &Q);
 242
 243 /// Given a function and iterators over arguments, fold the result or return
 244 /// null.
 245 Value *SimplifyCall(CallBase *Call, Value *V, User::op_iterator ArgBegin,
 246                     User::op_iterator ArgEnd, const SimplifyQuery &Q);
 247
 248 /// Given a function and set of arguments, fold the result or return null.
 249 Value *SimplifyCall(CallBase *Call, Value *V, ArrayRef<Value *> Args,
 250                     const SimplifyQuery &Q);
 251
 252 /// See if we can compute a simplified version of this instruction. If not,
 253 /// return null.
 254 Value *SimplifyInstruction(Instruction *I, const SimplifyQuery &Q,
 255                            OptimizationRemarkEmitter *ORE = nullptr);
 256
 257 /// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively.
 258 ///
 259 /// This first performs a normal RAUW of I with SimpleV. It then recursively
 260 /// attempts to simplify those users updated by the operation. The 'I'
 261 /// instruction must not be equal to the simplified value 'SimpleV'.
 262 ///
 263 /// The function returns true if any simplifications were performed.
 264 bool replaceAndRecursivelySimplify(Instruction *I, Value *SimpleV,
 265                                    const TargetLibraryInfo *TLI = nullptr,
 266                                    const DominatorTree *DT = nullptr,
 267                                    AssumptionCache *AC = nullptr);
 268
 269 /// Recursively attempt to simplify an instruction.
 270 ///
 271 /// This routine uses SimplifyInstruction to simplify 'I', and if successful
 272 /// replaces uses of 'I' with the simplified value. It then recurses on each
 273 /// of the users impacted. It returns true if any simplifications were
 274 /// performed.
 275 bool recursivelySimplifyInstruction(Instruction *I,
 276                                     const TargetLibraryInfo *TLI = nullptr,
 277                                     const DominatorTree *DT = nullptr,
 278                                     AssumptionCache *AC = nullptr);
 279
 280 // These helper functions return a SimplifyQuery structure that contains as
 281 // many of the optional analysis we use as are currently valid.  This is the
 282 // strongly preferred way of constructing SimplifyQuery in passes.
 283 const SimplifyQuery getBestSimplifyQuery(Pass &, Function &);
 284 template <class T, class... TArgs>
 285 const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &,
 286                                          Function &);
 287 const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &,
 288                                          const DataLayout &);
 289 } // end namespace llvm
 290
 291 #endif
 292