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 the multiplication of a FMA, fold the result or return
 146 /// null. In contrast to SimplifyFMulInst, this function will not perform
 147 /// simplifications whose unrounded results differ when rounded to the argument
 148 /// type.
 149 Value *SimplifyFMAFMul(Value *LHS, Value *RHS, FastMathFlags FMF,
 150                        const SimplifyQuery &Q);
 151
 152 /// Given operands for a Mul, fold the result or return null.
 153 Value *SimplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 154
 155 /// Given operands for an SDiv, fold the result or return null.
 156 Value *SimplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 157
 158 /// Given operands for a UDiv, fold the result or return null.
 159 Value *SimplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 160
 161 /// Given operands for an FDiv, fold the result or return null.
 162 Value *SimplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 163                         const SimplifyQuery &Q);
 164
 165 /// Given operands for an SRem, fold the result or return null.
 166 Value *SimplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 167
 168 /// Given operands for a URem, fold the result or return null.
 169 Value *SimplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 170
 171 /// Given operands for an FRem, fold the result or return null.
 172 Value *SimplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF,
 173                         const SimplifyQuery &Q);
 174
 175 /// Given operands for a Shl, fold the result or return null.
 176 Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
 177                        const SimplifyQuery &Q);
 178
 179 /// Given operands for a LShr, fold the result or return null.
 180 Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
 181                         const SimplifyQuery &Q);
 182
 183 /// Given operands for a AShr, fold the result or return nulll.
 184 Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
 185                         const SimplifyQuery &Q);
 186
 187 /// Given operands for an And, fold the result or return null.
 188 Value *SimplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 189
 190 /// Given operands for an Or, fold the result or return null.
 191 Value *SimplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 192
 193 /// Given operands for an Xor, fold the result or return null.
 194 Value *SimplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
 195
 196 /// Given operands for an ICmpInst, fold the result or return null.
 197 Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
 198                         const SimplifyQuery &Q);
 199
 200 /// Given operands for an FCmpInst, fold the result or return null.
 201 Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
 202                         FastMathFlags FMF, const SimplifyQuery &Q);
 203
 204 /// Given operands for a SelectInst, fold the result or return null.
 205 Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
 206                           const SimplifyQuery &Q);
 207
 208 /// Given operands for a GetElementPtrInst, fold the result or return null.
 209 Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
 210                        const SimplifyQuery &Q);
 211
 212 /// Given operands for an InsertValueInst, fold the result or return null.
 213 Value *SimplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs,
 214                                const SimplifyQuery &Q);
 215
 216 /// Given operands for an InsertElement, fold the result or return null.
 217 Value *SimplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx,
 218                                  const SimplifyQuery &Q);
 219
 220 /// Given operands for an ExtractValueInst, fold the result or return null.
 221 Value *SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
 222                                 const SimplifyQuery &Q);
 223
 224 /// Given operands for an ExtractElementInst, fold the result or return null.
 225 Value *SimplifyExtractElementInst(Value *Vec, Value *Idx,
 226                                   const SimplifyQuery &Q);
 227
 228 /// Given operands for a CastInst, fold the result or return null.
 229 Value *SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
 230                         const SimplifyQuery &Q);
 231
 232 /// Given operands for a ShuffleVectorInst, fold the result or return null.
 233 Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, Constant *Mask,
 234                                  Type *RetTy, const SimplifyQuery &Q);
 235
 236 //=== Helper functions for higher up the class hierarchy.
 237
 238 /// Given operands for a CmpInst, fold the result or return null.
 239 Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
 240                        const SimplifyQuery &Q);
 241
 242 /// Given operand for a UnaryOperator, fold the result or return null.
 243 Value *SimplifyUnOp(unsigned Opcode, Value *Op, const SimplifyQuery &Q);
 244
 245 /// Given operand for a UnaryOperator, fold the result or return null.
 246 /// Try to use FastMathFlags when folding the result.
 247 Value *SimplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF,
 248                     const SimplifyQuery &Q);
 249
 250 /// Given operands for a BinaryOperator, fold the result or return null.
 251 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
 252                      const SimplifyQuery &Q);
 253
 254 /// Given operands for a BinaryOperator, fold the result or return null.
 255 /// Try to use FastMathFlags when folding the result.
 256 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
 257                      FastMathFlags FMF, const SimplifyQuery &Q);
 258
 259 /// Given a callsite, fold the result or return null.
 260 Value *SimplifyCall(CallBase *Call, const SimplifyQuery &Q);
 261
 262 /// See if we can compute a simplified version of this instruction. If not,
 263 /// return null.
 264 Value *SimplifyInstruction(Instruction *I, const SimplifyQuery &Q,
 265                            OptimizationRemarkEmitter *ORE = nullptr);
 266
 267 /// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively.
 268 ///
 269 /// This first performs a normal RAUW of I with SimpleV. It then recursively
 270 /// attempts to simplify those users updated by the operation. The 'I'
 271 /// instruction must not be equal to the simplified value 'SimpleV'.
 272 /// If UnsimplifiedUsers is provided, instructions that could not be simplified
 273 /// are added to it.
 274 ///
 275 /// The function returns true if any simplifications were performed.
 276 bool replaceAndRecursivelySimplify(
 277     Instruction *I, Value *SimpleV, const TargetLibraryInfo *TLI = nullptr,
 278     const DominatorTree *DT = nullptr, AssumptionCache *AC = nullptr,
 279     SmallSetVector<Instruction *, 8> *UnsimplifiedUsers = nullptr);
 280
 281 /// Recursively attempt to simplify an instruction.
 282 ///
 283 /// This routine uses SimplifyInstruction to simplify 'I', and if successful
 284 /// replaces uses of 'I' with the simplified value. It then recurses on each
 285 /// of the users impacted. It returns true if any simplifications were
 286 /// performed.
 287 bool recursivelySimplifyInstruction(Instruction *I,
 288                                     const TargetLibraryInfo *TLI = nullptr,
 289                                     const DominatorTree *DT = nullptr,
 290                                     AssumptionCache *AC = nullptr);
 291
 292 // These helper functions return a SimplifyQuery structure that contains as
 293 // many of the optional analysis we use as are currently valid.  This is the
 294 // strongly preferred way of constructing SimplifyQuery in passes.
 295 const SimplifyQuery getBestSimplifyQuery(Pass &, Function &);
 296 template <class T, class... TArgs>
 297 const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &,
 298                                          Function &);
 299 const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &,
 300                                          const DataLayout &);
 301 } // end namespace llvm
 302
 303 #endif
 304