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/ADT/SetVector.h"
  35 #include "llvm/IR/Instruction.h"
  36 #include "llvm/IR/Operator.h"
  37 #include "llvm/IR/User.h"
  38
  39 namespace llvm {
  40 class Function;
  41 template <typename T, typename... TArgs> class AnalysisManager;
  42 template <class T> class ArrayRef;
  43 class AssumptionCache;
  44 class CallBase;
  45 class DominatorTree;
  46 class DataLayout;
  47 class FastMathFlags;
  48 struct LoopStandardAnalysisResults;
  49 class OptimizationRemarkEmitter;
  50 class Pass;
  51 class TargetLibraryInfo;
  52 class Type;
  53 class Value;
  54 class MDNode;
  55 class BinaryOperator;
  56
  57 /// InstrInfoQuery provides an interface to query additional information for
  58 /// instructions like metadata or keywords like nsw, which provides conservative
  59 /// results if the users specified it is safe to use.
  60 struct InstrInfoQuery {
  61   InstrInfoQuery(bool UMD) : UseInstrInfo(UMD) {}
  62   InstrInfoQuery() : UseInstrInfo(true) {}
  63   bool UseInstrInfo = true;
  64
  65   MDNode *getMetadata(const Instruction *I, unsigned KindID) const {
  66     if (UseInstrInfo)
  67       return I->getMetadata(KindID);
  68     return nullptr;
  69   }
  70
  71   template <class InstT> bool hasNoUnsignedWrap(const InstT *Op) const {
  72     if (UseInstrInfo)
  73       return Op->hasNoUnsignedWrap();
  74     return false;
  75   }
  76
  77   template <class InstT> bool hasNoSignedWrap(const InstT *Op) const {
  78     if (UseInstrInfo)
  79       return Op->hasNoSignedWrap();
  80     return false;
  81   }
  82
  83   bool isExact(const BinaryOperator *Op) const {
  84     if (UseInstrInfo && isa<PossiblyExactOperator>(Op))
  85       return cast<PossiblyExactOperator>(Op)->isExact();
  86     return false;
  87   }
  88 };
  89
  90 struct SimplifyQuery {
  91   const DataLayout &DL;
  92   const TargetLibraryInfo *TLI = nullptr;
  93   const DominatorTree *DT = nullptr;
  94   AssumptionCache *AC = nullptr;
  95   const Instruction *CxtI = nullptr;
  96
  97   // Wrapper to query additional information for instructions like metadata or
  98   // keywords like nsw, which provides conservative results if those cannot
  99   // be safely used.
 100   const InstrInfoQuery IIQ;
 101
 102   SimplifyQuery(const DataLayout &DL, const Instruction *CXTI = nullptr)
 103       : DL(DL), CxtI(CXTI) {}
 104
 105   SimplifyQuery(const DataLayout &DL, const TargetLibraryInfo *TLI,
 106                 const DominatorTree *DT = nullptr,
 107                 AssumptionCache *AC = nullptr,
 108                 const Instruction *CXTI = nullptr, bool UseInstrInfo = true)
 109       : DL(DL), TLI(TLI), DT(DT), AC(AC), CxtI(CXTI), IIQ(UseInstrInfo) {}
 110   SimplifyQuery getWithInstruction(Instruction *I) const {
 111     SimplifyQuery Copy(*this);
 112     Copy.CxtI = I;
 113     return Copy;
 114   }
 115 };
 116
 117 // NOTE: the explicit multiple argument versions of these functions are
 118 // deprecated.
 119 // Please use the SimplifyQuery versions in new code.
 120
 121 /// Given operand for an FNeg, fold the result or return null.
 122 Value *SimplifyFNegInst(Value *Op, FastMathFlags FMF,
 123                         const SimplifyQuery &Q);
 124
 125 /// Given operands for an Add, fold the result or return null.
 126 Value *SimplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
 127                        const SimplifyQuery &Q);
 128
 129 /// Given operands for a Sub, fold the result or return null.
 130 Value *SimplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
 131                        const SimplifyQuery &Q);
 132
 133 /// Given operands for an FAdd, fold the result or return null.
 134 Value *SimplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 135                         const SimplifyQuery &Q);
 136
 137 /// Given operands for an FSub, fold the result or return null.
 138 Value *SimplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 139                         const SimplifyQuery &Q);
 140
 141 /// Given operands for an FMul, fold the result or return null.
 142 Value *SimplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 143                         const SimplifyQuery &Q);
 144
 145 /// Given operands for a Mul, fold the result or return null.
 146 Value *SimplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 147
 148 /// Given operands for an SDiv, fold the result or return null.
 149 Value *SimplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 150
 151 /// Given operands for a UDiv, fold the result or return null.
 152 Value *SimplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 153
 154 /// Given operands for an FDiv, fold the result or return null.
 155 Value *SimplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 156                         const SimplifyQuery &Q);
 157
 158 /// Given operands for an SRem, fold the result or return null.
 159 Value *SimplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 160
 161 /// Given operands for a URem, fold the result or return null.
 162 Value *SimplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 163
 164 /// Given operands for an FRem, fold the result or return null.
 165 Value *SimplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 166                         const SimplifyQuery &Q);
 167
 168 /// Given operands for a Shl, fold the result or return null.
 169 Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
 170                        const SimplifyQuery &Q);
 171
 172 /// Given operands for a LShr, fold the result or return null.
 173 Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
 174                         const SimplifyQuery &Q);
 175
 176 /// Given operands for a AShr, fold the result or return nulll.
 177 Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
 178                         const SimplifyQuery &Q);
 179
 180 /// Given operands for an And, fold the result or return null.
 181 Value *SimplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 182
 183 /// Given operands for an Or, fold the result or return null.
 184 Value *SimplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 185
 186 /// Given operands for an Xor, fold the result or return null.
 187 Value *SimplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 188
 189 /// Given operands for an ICmpInst, fold the result or return null.
 190 Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
 191                         const SimplifyQuery &Q);
 192
 193 /// Given operands for an FCmpInst, fold the result or return null.
 194 Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
 195                         FastMathFlags FMF, const SimplifyQuery &Q);
 196
 197 /// Given operands for a SelectInst, fold the result or return null.
 198 Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
 199                           const SimplifyQuery &Q);
 200
 201 /// Given operands for a GetElementPtrInst, fold the result or return null.
 202 Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
 203                        const SimplifyQuery &Q);
 204
 205 /// Given operands for an InsertValueInst, fold the result or return null.
 206 Value *SimplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs,
 207                                const SimplifyQuery &Q);
 208
 209 /// Given operands for an InsertElement, fold the result or return null.
 210 Value *SimplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx,
 211                                  const SimplifyQuery &Q);
 212
 213 /// Given operands for an ExtractValueInst, fold the result or return null.
 214 Value *SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
 215                                 const SimplifyQuery &Q);
 216
 217 /// Given operands for an ExtractElementInst, fold the result or return null.
 218 Value *SimplifyExtractElementInst(Value *Vec, Value *Idx,
 219                                   const SimplifyQuery &Q);
 220
 221 /// Given operands for a CastInst, fold the result or return null.
 222 Value *SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
 223                         const SimplifyQuery &Q);
 224
 225 /// Given operands for a ShuffleVectorInst, fold the result or return null.
 226 Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, Constant *Mask,
 227                                  Type *RetTy, const SimplifyQuery &Q);
 228
 229 //=== Helper functions for higher up the class hierarchy.
 230
 231 /// Given operands for a CmpInst, fold the result or return null.
 232 Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
 233                        const SimplifyQuery &Q);
 234
 235 /// Given operand for a UnaryOperator, fold the result or return null.
 236 Value *SimplifyUnOp(unsigned Opcode, Value *Op, const SimplifyQuery &Q);
 237
 238 /// Given operand for a UnaryOperator, fold the result or return null.
 239 /// Try to use FastMathFlags when folding the result.
 240 Value *SimplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF,
 241                     const SimplifyQuery &Q);
 242
 243 /// Given operands for a BinaryOperator, fold the result or return null.
 244 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
 245                      const SimplifyQuery &Q);
 246
 247 /// Given operands for a BinaryOperator, fold the result or return null.
 248 /// Try to use FastMathFlags when folding the result.
 249 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
 250                      FastMathFlags FMF, const SimplifyQuery &Q);
 251
 252 /// Given a callsite, fold the result or return null.
 253 Value *SimplifyCall(CallBase *Call, const SimplifyQuery &Q);
 254
 255 /// See if we can compute a simplified version of this instruction. If not,
 256 /// return null.
 257 Value *SimplifyInstruction(Instruction *I, const SimplifyQuery &Q,
 258                            OptimizationRemarkEmitter *ORE = nullptr);
 259
 260 /// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively.
 261 ///
 262 /// This first performs a normal RAUW of I with SimpleV. It then recursively
 263 /// attempts to simplify those users updated by the operation. The 'I'
 264 /// instruction must not be equal to the simplified value 'SimpleV'.
 265 /// If UnsimplifiedUsers is provided, instructions that could not be simplified
 266 /// are added to it.
 267 ///
 268 /// The function returns true if any simplifications were performed.
 269 bool replaceAndRecursivelySimplify(
 270     Instruction *I, Value *SimpleV, const TargetLibraryInfo *TLI = nullptr,
 271     const DominatorTree *DT = nullptr, AssumptionCache *AC = nullptr,
 272     SmallSetVector<Instruction *, 8> *UnsimplifiedUsers = nullptr);
 273
 274 /// Recursively attempt to simplify an instruction.
 275 ///
 276 /// This routine uses SimplifyInstruction to simplify 'I', and if successful
 277 /// replaces uses of 'I' with the simplified value. It then recurses on each
 278 /// of the users impacted. It returns true if any simplifications were
 279 /// performed.
 280 bool recursivelySimplifyInstruction(Instruction *I,
 281                                     const TargetLibraryInfo *TLI = nullptr,
 282                                     const DominatorTree *DT = nullptr,
 283                                     AssumptionCache *AC = nullptr);
 284
 285 // These helper functions return a SimplifyQuery structure that contains as
 286 // many of the optional analysis we use as are currently valid.  This is the
 287 // strongly preferred way of constructing SimplifyQuery in passes.
 288 const SimplifyQuery getBestSimplifyQuery(Pass &, Function &);
 289 template <class T, class... TArgs>
 290 const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &,
 291                                          Function &);
 292 const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &,
 293                                          const DataLayout &);
 294 } // end namespace llvm
 295
 296 #endif
 297