1 //===-- ConstantFolding.h - Fold instructions into constants ----*- 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 // This file declares routines for folding instructions into constants when all 11 // operands are constants, for example "sub i32 1, 0" -> "1". 12 // 13 // Also, to supplement the basic VMCore ConstantExpr simplifications, 14 // this file declares some additional folding routines that can make use of 15 // DataLayout information. These functions cannot go in VMCore due to library 16 // dependency issues. 17 // 18 //===----------------------------------------------------------------------===// 19 20 #ifndef LLVM_ANALYSIS_CONSTANTFOLDING_H 21 #define LLVM_ANALYSIS_CONSTANTFOLDING_H 22 23 namespace llvm { 24 class Constant; 25 class ConstantExpr; 26 class Instruction; 27 class DataLayout; 28 class TargetLibraryInfo; 29 class Function; 30 class Type; 31 template<typename T> 32 class ArrayRef; 33 34 /// ConstantFoldInstruction - Try to constant fold the specified instruction. 35 /// If successful, the constant result is returned, if not, null is returned. 36 /// Note that this fails if not all of the operands are constant. Otherwise, 37 /// this function can only fail when attempting to fold instructions like loads 38 /// and stores, which have no constant expression form. 39 Constant *ConstantFoldInstruction(Instruction *I, 40 const DataLayout *TD = nullptr, 41 const TargetLibraryInfo *TLI = nullptr); 42 43 /// ConstantFoldConstantExpression - Attempt to fold the constant expression 44 /// using the specified DataLayout. If successful, the constant result is 45 /// result is returned, if not, null is returned. 46 Constant *ConstantFoldConstantExpression(const ConstantExpr *CE, 47 const DataLayout *TD = nullptr, 48 const TargetLibraryInfo *TLI =nullptr); 49 50 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 51 /// specified operands. If successful, the constant result is returned, if not, 52 /// null is returned. Note that this function can fail when attempting to 53 /// fold instructions like loads and stores, which have no constant expression 54 /// form. 55 /// 56 Constant *ConstantFoldInstOperands(unsigned Opcode, Type *DestTy, 57 ArrayRef<Constant *> Ops, 58 const DataLayout *TD = nullptr, 59 const TargetLibraryInfo *TLI = nullptr); 60 61 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare 62 /// instruction (icmp/fcmp) with the specified operands. If it fails, it 63 /// returns a constant expression of the specified operands. 64 /// 65 Constant *ConstantFoldCompareInstOperands(unsigned Predicate, 66 Constant *LHS, Constant *RHS, 67 const DataLayout *TD = nullptr, 68 const TargetLibraryInfo *TLI=nullptr); 69 70 /// ConstantFoldInsertValueInstruction - Attempt to constant fold an insertvalue 71 /// instruction with the specified operands and indices. The constant result is 72 /// returned if successful; if not, null is returned. 73 Constant *ConstantFoldInsertValueInstruction(Constant *Agg, Constant *Val, 74 ArrayRef<unsigned> Idxs); 75 76 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would 77 /// produce if it is constant and determinable. If this is not determinable, 78 /// return null. 79 Constant *ConstantFoldLoadFromConstPtr(Constant *C, 80 const DataLayout *TD = nullptr); 81 82 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 83 /// getelementptr constantexpr, return the constant value being addressed by the 84 /// constant expression, or null if something is funny and we can't decide. 85 Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE); 86 87 /// ConstantFoldLoadThroughGEPIndices - Given a constant and getelementptr 88 /// indices (with an *implied* zero pointer index that is not in the list), 89 /// return the constant value being addressed by a virtual load, or null if 90 /// something is funny and we can't decide. 91 Constant *ConstantFoldLoadThroughGEPIndices(Constant *C, 92 ArrayRef<Constant*> Indices); 93 94 /// canConstantFoldCallTo - Return true if its even possible to fold a call to 95 /// the specified function. 96 bool canConstantFoldCallTo(const Function *F); 97 98 /// ConstantFoldCall - Attempt to constant fold a call to the specified function 99 /// with the specified arguments, returning null if unsuccessful. 100 Constant *ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands, 101 const TargetLibraryInfo *TLI = nullptr); 102 } 103 104 #endif 105