1 //===-- ConstantFolding.h - Fold instructions into constants ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file declares routines for folding instructions into constants when all
11 // operands are constants, for example "sub i32 1, 0" -> "1".
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
18 //===----------------------------------------------------------------------===//
20 #ifndef LLVM_ANALYSIS_CONSTANTFOLDING_H
21 #define LLVM_ANALYSIS_CONSTANTFOLDING_H
25 template <typename T> class ArrayRef;
32 class TargetLibraryInfo;
35 /// If this constant is a constant offset from a global, return the global and
36 /// the constant. Because of constantexprs, this function is recursive.
37 bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, APInt &Offset,
38 const DataLayout &DL);
40 /// ConstantFoldInstruction - Try to constant fold the specified instruction.
41 /// If successful, the constant result is returned, if not, null is returned.
42 /// Note that this fails if not all of the operands are constant. Otherwise,
43 /// this function can only fail when attempting to fold instructions like loads
44 /// and stores, which have no constant expression form.
45 Constant *ConstantFoldInstruction(Instruction *I, const DataLayout &DL,
46 const TargetLibraryInfo *TLI = nullptr);
48 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
49 /// using the specified DataLayout. If successful, the constant result is
50 /// result is returned, if not, null is returned.
52 ConstantFoldConstantExpression(const ConstantExpr *CE, const DataLayout &DL,
53 const TargetLibraryInfo *TLI = nullptr);
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
61 Constant *ConstantFoldInstOperands(Instruction *I, ArrayRef<Constant *> Ops,
63 const TargetLibraryInfo *TLI = nullptr);
65 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
66 /// specified operands. If successful, the constant result is returned, if not,
67 /// null is returned. Note that this function can fail when attempting to
68 /// fold instructions like loads and stores, which have no constant expression
71 /// This function doesn't work for compares (use ConstantFoldCompareInstOperands
72 /// for this) and GEPs.
73 Constant *ConstantFoldInstOperands(unsigned Opcode, Type *DestTy,
74 ArrayRef<Constant *> Ops,
76 const TargetLibraryInfo *TLI = nullptr);
78 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
79 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
80 /// returns a constant expression of the specified operands.
83 ConstantFoldCompareInstOperands(unsigned Predicate, Constant *LHS,
84 Constant *RHS, const DataLayout &DL,
85 const TargetLibraryInfo *TLI = nullptr);
87 /// \brief Attempt to constant fold a binary operation with the specified
88 /// operands. If it fails, it returns a constant expression of the specified
90 Constant *ConstantFoldBinaryOpOperands(unsigned Opcode, Constant *LHS,
91 Constant *RHS, const DataLayout &DL);
93 /// \brief Attempt to constant fold a cast with the specified operand. If it
94 /// fails, it returns a constant expression of the specified operand.
95 Constant *ConstantFoldCastOperand(unsigned Opcode, Constant *C, Type *DestTy,
96 const DataLayout &DL);
98 /// ConstantFoldInsertValueInstruction - Attempt to constant fold an insertvalue
99 /// instruction with the specified operands and indices. The constant result is
100 /// returned if successful; if not, null is returned.
101 Constant *ConstantFoldInsertValueInstruction(Constant *Agg, Constant *Val,
102 ArrayRef<unsigned> Idxs);
104 /// \brief Attempt to constant fold an extractvalue instruction with the
105 /// specified operands and indices. The constant result is returned if
106 /// successful; if not, null is returned.
107 Constant *ConstantFoldExtractValueInstruction(Constant *Agg,
108 ArrayRef<unsigned> Idxs);
110 /// \brief Attempt to constant fold an extractelement instruction with the
111 /// specified operands and indices. The constant result is returned if
112 /// successful; if not, null is returned.
113 Constant *ConstantFoldExtractElementInstruction(Constant *Val, Constant *Idx);
115 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would
116 /// produce if it is constant and determinable. If this is not determinable,
118 Constant *ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty, const DataLayout &DL);
120 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
121 /// getelementptr constantexpr, return the constant value being addressed by the
122 /// constant expression, or null if something is funny and we can't decide.
123 Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE);
125 /// ConstantFoldLoadThroughGEPIndices - Given a constant and getelementptr
126 /// indices (with an *implied* zero pointer index that is not in the list),
127 /// return the constant value being addressed by a virtual load, or null if
128 /// something is funny and we can't decide.
129 Constant *ConstantFoldLoadThroughGEPIndices(Constant *C,
130 ArrayRef<Constant *> Indices);
132 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
133 /// the specified function.
134 bool canConstantFoldCallTo(const Function *F);
136 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
137 /// with the specified arguments, returning null if unsuccessful.
138 Constant *ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands,
139 const TargetLibraryInfo *TLI = nullptr);