1 //===- ConstantFolder.h - Constant folding helper ---------------*- 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 defines the ConstantFolder class, a helper for IRBuilder.
10 // It provides IRBuilder with a set of methods for creating constants
11 // with minimal folding.  For general constant creation and folding,
12 // use ConstantExpr and the routines in llvm/Analysis/ConstantFolding.h.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_IR_CONSTANTFOLDER_H
17 #define LLVM_IR_CONSTANTFOLDER_H
18 
19 #include "llvm/ADT/ArrayRef.h"
20 #include "llvm/ADT/STLExtras.h"
21 #include "llvm/IR/Constants.h"
22 #include "llvm/IR/ConstantFold.h"
23 #include "llvm/IR/IRBuilderFolder.h"
24 #include "llvm/IR/Instruction.h"
25 #include "llvm/IR/Operator.h"
26 
27 namespace llvm {
28 
29 /// ConstantFolder - Create constants with minimum, target independent, folding.
30 class ConstantFolder final : public IRBuilderFolder {
31   virtual void anchor();
32 
33 public:
34   explicit ConstantFolder() = default;
35 
36   //===--------------------------------------------------------------------===//
37   // Value-based folders.
38   //
39   // Return an existing value or a constant if the operation can be simplified.
40   // Otherwise return nullptr.
41   //===--------------------------------------------------------------------===//
42 
43   Value *FoldBinOp(Instruction::BinaryOps Opc, Value *LHS,
44                    Value *RHS) const override {
45     auto *LC = dyn_cast<Constant>(LHS);
46     auto *RC = dyn_cast<Constant>(RHS);
47     if (LC && RC) {
48       if (ConstantExpr::isDesirableBinOp(Opc))
49         return ConstantExpr::get(Opc, LC, RC);
50       return ConstantFoldBinaryInstruction(Opc, LC, RC);
51     }
52     return nullptr;
53   }
54 
55   Value *FoldExactBinOp(Instruction::BinaryOps Opc, Value *LHS, Value *RHS,
56                         bool IsExact) const override {
57     auto *LC = dyn_cast<Constant>(LHS);
58     auto *RC = dyn_cast<Constant>(RHS);
59     if (LC && RC) {
60       if (ConstantExpr::isDesirableBinOp(Opc))
61         return ConstantExpr::get(Opc, LC, RC,
62                                  IsExact ? PossiblyExactOperator::IsExact : 0);
63       return ConstantFoldBinaryInstruction(Opc, LC, RC);
64     }
65     return nullptr;
66   }
67 
68   Value *FoldNoWrapBinOp(Instruction::BinaryOps Opc, Value *LHS, Value *RHS,
69                          bool HasNUW, bool HasNSW) const override {
70     auto *LC = dyn_cast<Constant>(LHS);
71     auto *RC = dyn_cast<Constant>(RHS);
72     if (LC && RC) {
73       if (ConstantExpr::isDesirableBinOp(Opc)) {
74         unsigned Flags = 0;
75         if (HasNUW)
76           Flags |= OverflowingBinaryOperator::NoUnsignedWrap;
77         if (HasNSW)
78           Flags |= OverflowingBinaryOperator::NoSignedWrap;
79         return ConstantExpr::get(Opc, LC, RC, Flags);
80       }
81       return ConstantFoldBinaryInstruction(Opc, LC, RC);
82     }
83     return nullptr;
84   }
85 
86   Value *FoldBinOpFMF(Instruction::BinaryOps Opc, Value *LHS, Value *RHS,
87                       FastMathFlags FMF) const override {
88     return FoldBinOp(Opc, LHS, RHS);
89   }
90 
91   Value *FoldUnOpFMF(Instruction::UnaryOps Opc, Value *V,
92                       FastMathFlags FMF) const override {
93     if (Constant *C = dyn_cast<Constant>(V))
94       return ConstantFoldUnaryInstruction(Opc, C);
95     return nullptr;
96   }
97 
98   Value *FoldICmp(CmpInst::Predicate P, Value *LHS, Value *RHS) const override {
99     auto *LC = dyn_cast<Constant>(LHS);
100     auto *RC = dyn_cast<Constant>(RHS);
101     if (LC && RC)
102       return ConstantExpr::getCompare(P, LC, RC);
103     return nullptr;
104   }
105 
106   Value *FoldGEP(Type *Ty, Value *Ptr, ArrayRef<Value *> IdxList,
107                  bool IsInBounds = false) const override {
108     if (!ConstantExpr::isSupportedGetElementPtr(Ty))
109       return nullptr;
110 
111     if (auto *PC = dyn_cast<Constant>(Ptr)) {
112       // Every index must be constant.
113       if (any_of(IdxList, [](Value *V) { return !isa<Constant>(V); }))
114         return nullptr;
115 
116       if (IsInBounds)
117         return ConstantExpr::getInBoundsGetElementPtr(Ty, PC, IdxList);
118       else
119         return ConstantExpr::getGetElementPtr(Ty, PC, IdxList);
120     }
121     return nullptr;
122   }
123 
124   Value *FoldSelect(Value *C, Value *True, Value *False) const override {
125     auto *CC = dyn_cast<Constant>(C);
126     auto *TC = dyn_cast<Constant>(True);
127     auto *FC = dyn_cast<Constant>(False);
128     if (CC && TC && FC)
129       return ConstantFoldSelectInstruction(CC, TC, FC);
130     return nullptr;
131   }
132 
133   Value *FoldExtractValue(Value *Agg,
134                           ArrayRef<unsigned> IdxList) const override {
135     if (auto *CAgg = dyn_cast<Constant>(Agg))
136       return ConstantFoldExtractValueInstruction(CAgg, IdxList);
137     return nullptr;
138   };
139 
140   Value *FoldInsertValue(Value *Agg, Value *Val,
141                          ArrayRef<unsigned> IdxList) const override {
142     auto *CAgg = dyn_cast<Constant>(Agg);
143     auto *CVal = dyn_cast<Constant>(Val);
144     if (CAgg && CVal)
145       return ConstantFoldInsertValueInstruction(CAgg, CVal, IdxList);
146     return nullptr;
147   }
148 
149   Value *FoldExtractElement(Value *Vec, Value *Idx) const override {
150     auto *CVec = dyn_cast<Constant>(Vec);
151     auto *CIdx = dyn_cast<Constant>(Idx);
152     if (CVec && CIdx)
153       return ConstantExpr::getExtractElement(CVec, CIdx);
154     return nullptr;
155   }
156 
157   Value *FoldInsertElement(Value *Vec, Value *NewElt,
158                            Value *Idx) const override {
159     auto *CVec = dyn_cast<Constant>(Vec);
160     auto *CNewElt = dyn_cast<Constant>(NewElt);
161     auto *CIdx = dyn_cast<Constant>(Idx);
162     if (CVec && CNewElt && CIdx)
163       return ConstantExpr::getInsertElement(CVec, CNewElt, CIdx);
164     return nullptr;
165   }
166 
167   Value *FoldShuffleVector(Value *V1, Value *V2,
168                            ArrayRef<int> Mask) const override {
169     auto *C1 = dyn_cast<Constant>(V1);
170     auto *C2 = dyn_cast<Constant>(V2);
171     if (C1 && C2)
172       return ConstantExpr::getShuffleVector(C1, C2, Mask);
173     return nullptr;
174   }
175 
176   //===--------------------------------------------------------------------===//
177   // Cast/Conversion Operators
178   //===--------------------------------------------------------------------===//
179 
180   Constant *CreateCast(Instruction::CastOps Op, Constant *C,
181                        Type *DestTy) const override {
182     return ConstantExpr::getCast(Op, C, DestTy);
183   }
184 
185   Constant *CreatePointerCast(Constant *C, Type *DestTy) const override {
186     return ConstantExpr::getPointerCast(C, DestTy);
187   }
188 
189   Constant *CreatePointerBitCastOrAddrSpaceCast(Constant *C,
190                                                 Type *DestTy) const override {
191     return ConstantExpr::getPointerBitCastOrAddrSpaceCast(C, DestTy);
192   }
193 
194   Constant *CreateIntCast(Constant *C, Type *DestTy,
195                           bool isSigned) const override {
196     return ConstantExpr::getIntegerCast(C, DestTy, isSigned);
197   }
198 
199   Constant *CreateFPCast(Constant *C, Type *DestTy) const override {
200     return ConstantExpr::getFPCast(C, DestTy);
201   }
202 
203   Constant *CreateBitCast(Constant *C, Type *DestTy) const override {
204     return CreateCast(Instruction::BitCast, C, DestTy);
205   }
206 
207   Constant *CreateIntToPtr(Constant *C, Type *DestTy) const override {
208     return CreateCast(Instruction::IntToPtr, C, DestTy);
209   }
210 
211   Constant *CreatePtrToInt(Constant *C, Type *DestTy) const override {
212     return CreateCast(Instruction::PtrToInt, C, DestTy);
213   }
214 
215   Constant *CreateZExtOrBitCast(Constant *C, Type *DestTy) const override {
216     return ConstantExpr::getZExtOrBitCast(C, DestTy);
217   }
218 
219   Constant *CreateSExtOrBitCast(Constant *C, Type *DestTy) const override {
220     return ConstantExpr::getSExtOrBitCast(C, DestTy);
221   }
222 
223   Constant *CreateTruncOrBitCast(Constant *C, Type *DestTy) const override {
224     return ConstantExpr::getTruncOrBitCast(C, DestTy);
225   }
226 
227   //===--------------------------------------------------------------------===//
228   // Compare Instructions
229   //===--------------------------------------------------------------------===//
230 
231   Constant *CreateFCmp(CmpInst::Predicate P, Constant *LHS,
232                        Constant *RHS) const override {
233     return ConstantExpr::getCompare(P, LHS, RHS);
234   }
235 };
236 
237 } // end namespace llvm
238 
239 #endif // LLVM_IR_CONSTANTFOLDER_H
240