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;
34 class ImmutableCallSite;
35 class TargetLibraryInfo;
38 /// If this constant is a constant offset from a global, return the global and
39 /// the constant. Because of constantexprs, this function is recursive.
40 bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, APInt &Offset,
41 const DataLayout &DL);
43 /// ConstantFoldInstruction - Try to constant fold the specified instruction.
44 /// If successful, the constant result is returned, if not, null is returned.
45 /// Note that this fails if not all of the operands are constant. Otherwise,
46 /// this function can only fail when attempting to fold instructions like loads
47 /// and stores, which have no constant expression form.
48 Constant *ConstantFoldInstruction(Instruction *I, const DataLayout &DL,
49 const TargetLibraryInfo *TLI = nullptr);
51 /// ConstantFoldConstant - Attempt to fold the constant using the
52 /// specified DataLayout.
53 /// If successful, the constant result is returned, if not, null is returned.
54 Constant *ConstantFoldConstant(const Constant *C, const DataLayout &DL,
55 const TargetLibraryInfo *TLI = nullptr);
57 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
58 /// specified operands. If successful, the constant result is returned, if not,
59 /// null is returned. Note that this function can fail when attempting to
60 /// fold instructions like loads and stores, which have no constant expression
63 Constant *ConstantFoldInstOperands(Instruction *I, ArrayRef<Constant *> Ops,
65 const TargetLibraryInfo *TLI = nullptr);
67 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
68 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
69 /// returns a constant expression of the specified operands.
72 ConstantFoldCompareInstOperands(unsigned Predicate, Constant *LHS,
73 Constant *RHS, const DataLayout &DL,
74 const TargetLibraryInfo *TLI = nullptr);
76 /// \brief Attempt to constant fold a binary operation with the specified
77 /// operands. If it fails, it returns a constant expression of the specified
79 Constant *ConstantFoldBinaryOpOperands(unsigned Opcode, Constant *LHS,
80 Constant *RHS, const DataLayout &DL);
82 /// \brief Attempt to constant fold a cast with the specified operand. If it
83 /// fails, it returns a constant expression of the specified operand.
84 Constant *ConstantFoldCastOperand(unsigned Opcode, Constant *C, Type *DestTy,
85 const DataLayout &DL);
87 /// ConstantFoldInsertValueInstruction - Attempt to constant fold an insertvalue
88 /// instruction with the specified operands and indices. The constant result is
89 /// returned if successful; if not, null is returned.
90 Constant *ConstantFoldInsertValueInstruction(Constant *Agg, Constant *Val,
91 ArrayRef<unsigned> Idxs);
93 /// \brief Attempt to constant fold an extractvalue instruction with the
94 /// specified operands and indices. The constant result is returned if
95 /// successful; if not, null is returned.
96 Constant *ConstantFoldExtractValueInstruction(Constant *Agg,
97 ArrayRef<unsigned> Idxs);
99 /// \brief Attempt to constant fold an extractelement instruction with the
100 /// specified operands and indices. The constant result is returned if
101 /// successful; if not, null is returned.
102 Constant *ConstantFoldExtractElementInstruction(Constant *Val, Constant *Idx);
104 /// \brief Attempt to constant fold a shufflevector instruction with the
105 /// specified operands and indices. The constant result is returned if
106 /// successful; if not, null is returned.
107 Constant *ConstantFoldShuffleVectorInstruction(Constant *V1, Constant *V2,
110 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would
111 /// produce if it is constant and determinable. If this is not determinable,
113 Constant *ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty, const DataLayout &DL);
115 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
116 /// getelementptr constantexpr, return the constant value being addressed by the
117 /// constant expression, or null if something is funny and we can't decide.
118 Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE);
120 /// ConstantFoldLoadThroughGEPIndices - Given a constant and getelementptr
121 /// indices (with an *implied* zero pointer index that is not in the list),
122 /// return the constant value being addressed by a virtual load, or null if
123 /// something is funny and we can't decide.
124 Constant *ConstantFoldLoadThroughGEPIndices(Constant *C,
125 ArrayRef<Constant *> Indices);
127 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
128 /// the specified function.
129 bool canConstantFoldCallTo(ImmutableCallSite CS, const Function *F);
131 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
132 /// with the specified arguments, returning null if unsuccessful.
133 Constant *ConstantFoldCall(ImmutableCallSite CS, Function *F,
134 ArrayRef<Constant *> Operands,
135 const TargetLibraryInfo *TLI = nullptr);
137 /// \brief Check whether the given call has no side-effects.
138 /// Specifically checks for math routimes which sometimes set errno.
139 bool isMathLibCallNoop(CallSite CS, const TargetLibraryInfo *TLI);