1 //===-- ConstantFolding.h - Fold instructions into constants ----*- 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 constants when all 10 // operands are constants, for example "sub i32 1, 0" -> "1". 11 // 12 // Also, to supplement the basic VMCore ConstantExpr simplifications, 13 // this file declares some additional folding routines that can make use of 14 // DataLayout information. These functions cannot go in VMCore due to library 15 // dependency issues. 16 // 17 //===----------------------------------------------------------------------===// 18 19 #ifndef LLVM_ANALYSIS_CONSTANTFOLDING_H 20 #define LLVM_ANALYSIS_CONSTANTFOLDING_H 21 22 namespace llvm { 23 class APInt; 24 template <typename T> class ArrayRef; 25 class CallBase; 26 class Constant; 27 class ConstantExpr; 28 class ConstantVector; 29 class DataLayout; 30 class Function; 31 class GlobalValue; 32 class Instruction; 33 class TargetLibraryInfo; 34 class Type; 35 36 /// If this constant is a constant offset from a global, return the global and 37 /// the constant. Because of constantexprs, this function is recursive. 38 bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, APInt &Offset, 39 const DataLayout &DL); 40 41 /// ConstantFoldInstruction - Try to constant fold the specified instruction. 42 /// If successful, the constant result is returned, if not, null is returned. 43 /// Note that this fails if not all of the operands are constant. Otherwise, 44 /// this function can only fail when attempting to fold instructions like loads 45 /// and stores, which have no constant expression form. 46 Constant *ConstantFoldInstruction(Instruction *I, const DataLayout &DL, 47 const TargetLibraryInfo *TLI = nullptr); 48 49 /// ConstantFoldConstant - Attempt to fold the constant using the 50 /// specified DataLayout. 51 /// If successful, the constant result is returned, if not, null is returned. 52 Constant *ConstantFoldConstant(const Constant *C, const DataLayout &DL, 53 const TargetLibraryInfo *TLI = nullptr); 54 55 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 56 /// specified operands. If successful, the constant result is returned, if not, 57 /// null is returned. Note that this function can fail when attempting to 58 /// fold instructions like loads and stores, which have no constant expression 59 /// form. 60 /// 61 Constant *ConstantFoldInstOperands(Instruction *I, ArrayRef<Constant *> Ops, 62 const DataLayout &DL, 63 const TargetLibraryInfo *TLI = nullptr); 64 65 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare 66 /// instruction (icmp/fcmp) with the specified operands. If it fails, it 67 /// returns a constant expression of the specified operands. 68 /// 69 Constant * 70 ConstantFoldCompareInstOperands(unsigned Predicate, Constant *LHS, 71 Constant *RHS, const DataLayout &DL, 72 const TargetLibraryInfo *TLI = nullptr); 73 74 /// Attempt to constant fold a unary operation with the specified 75 /// operand. If it fails, it returns a constant expression of the specified 76 /// operands. 77 Constant *ConstantFoldUnaryOpOperand(unsigned Opcode, Constant *Op, 78 const DataLayout &DL); 79 80 /// Attempt to constant fold a binary operation with the specified 81 /// operands. If it fails, it returns a constant expression of the specified 82 /// operands. 83 Constant *ConstantFoldBinaryOpOperands(unsigned Opcode, Constant *LHS, 84 Constant *RHS, const DataLayout &DL); 85 86 /// Attempt to constant fold a select instruction with the specified 87 /// operands. The constant result is returned if successful; if not, null is 88 /// returned. 89 Constant *ConstantFoldSelectInstruction(Constant *Cond, Constant *V1, 90 Constant *V2); 91 92 /// Attempt to constant fold a cast with the specified operand. If it 93 /// fails, it returns a constant expression of the specified operand. 94 Constant *ConstantFoldCastOperand(unsigned Opcode, Constant *C, Type *DestTy, 95 const DataLayout &DL); 96 97 /// ConstantFoldInsertValueInstruction - Attempt to constant fold an insertvalue 98 /// instruction with the specified operands and indices. The constant result is 99 /// returned if successful; if not, null is returned. 100 Constant *ConstantFoldInsertValueInstruction(Constant *Agg, Constant *Val, 101 ArrayRef<unsigned> Idxs); 102 103 /// Attempt to constant fold an extractvalue instruction with the 104 /// specified operands and indices. The constant result is returned if 105 /// successful; if not, null is returned. 106 Constant *ConstantFoldExtractValueInstruction(Constant *Agg, 107 ArrayRef<unsigned> Idxs); 108 109 /// Attempt to constant fold an insertelement instruction with the 110 /// specified operands and indices. The constant result is returned if 111 /// successful; if not, null is returned. 112 Constant *ConstantFoldInsertElementInstruction(Constant *Val, 113 Constant *Elt, 114 Constant *Idx); 115 116 /// Attempt to constant fold an extractelement instruction with the 117 /// specified operands and indices. The constant result is returned if 118 /// successful; if not, null is returned. 119 Constant *ConstantFoldExtractElementInstruction(Constant *Val, Constant *Idx); 120 121 /// Attempt to constant fold a shufflevector instruction with the 122 /// specified operands and indices. The constant result is returned if 123 /// successful; if not, null is returned. 124 Constant *ConstantFoldShuffleVectorInstruction(Constant *V1, Constant *V2, 125 Constant *Mask); 126 127 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would 128 /// produce if it is constant and determinable. If this is not determinable, 129 /// return null. 130 Constant *ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty, const DataLayout &DL); 131 132 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 133 /// getelementptr constantexpr, return the constant value being addressed by the 134 /// constant expression, or null if something is funny and we can't decide. 135 Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE); 136 137 /// ConstantFoldLoadThroughGEPIndices - Given a constant and getelementptr 138 /// indices (with an *implied* zero pointer index that is not in the list), 139 /// return the constant value being addressed by a virtual load, or null if 140 /// something is funny and we can't decide. 141 Constant *ConstantFoldLoadThroughGEPIndices(Constant *C, 142 ArrayRef<Constant *> Indices); 143 144 /// canConstantFoldCallTo - Return true if its even possible to fold a call to 145 /// the specified function. 146 bool canConstantFoldCallTo(const CallBase *Call, const Function *F); 147 148 /// ConstantFoldCall - Attempt to constant fold a call to the specified function 149 /// with the specified arguments, returning null if unsuccessful. 150 Constant *ConstantFoldCall(const CallBase *Call, Function *F, 151 ArrayRef<Constant *> Operands, 152 const TargetLibraryInfo *TLI = nullptr); 153 154 /// ConstantFoldLoadThroughBitcast - try to cast constant to destination type 155 /// returning null if unsuccessful. Can cast pointer to pointer or pointer to 156 /// integer and vice versa if their sizes are equal. 157 Constant *ConstantFoldLoadThroughBitcast(Constant *C, Type *DestTy, 158 const DataLayout &DL); 159 160 /// Check whether the given call has no side-effects. 161 /// Specifically checks for math routimes which sometimes set errno. 162 bool isMathLibCallNoop(const CallBase *Call, const TargetLibraryInfo *TLI); 163 } 164 165 #endif 166