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 ConstantExpr::get(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 (auto *PC = dyn_cast<Constant>(Ptr)) {
109       // Every index must be constant.
110       if (any_of(IdxList, [](Value *V) { return !isa<Constant>(V); }))
111         return nullptr;
112 
113       if (IsInBounds)
114         return ConstantExpr::getInBoundsGetElementPtr(Ty, PC, IdxList);
115       else
116         return ConstantExpr::getGetElementPtr(Ty, PC, IdxList);
117     }
118     return nullptr;
119   }
120 
121   Value *FoldSelect(Value *C, Value *True, Value *False) const override {
122     auto *CC = dyn_cast<Constant>(C);
123     auto *TC = dyn_cast<Constant>(True);
124     auto *FC = dyn_cast<Constant>(False);
125     if (CC && TC && FC)
126       return ConstantExpr::getSelect(CC, TC, FC);
127     return nullptr;
128   }
129 
130   Value *FoldExtractValue(Value *Agg,
131                           ArrayRef<unsigned> IdxList) const override {
132     if (auto *CAgg = dyn_cast<Constant>(Agg))
133       return ConstantFoldExtractValueInstruction(CAgg, IdxList);
134     return nullptr;
135   };
136 
137   Value *FoldInsertValue(Value *Agg, Value *Val,
138                          ArrayRef<unsigned> IdxList) const override {
139     auto *CAgg = dyn_cast<Constant>(Agg);
140     auto *CVal = dyn_cast<Constant>(Val);
141     if (CAgg && CVal)
142       return ConstantFoldInsertValueInstruction(CAgg, CVal, IdxList);
143     return nullptr;
144   }
145 
146   Value *FoldExtractElement(Value *Vec, Value *Idx) const override {
147     auto *CVec = dyn_cast<Constant>(Vec);
148     auto *CIdx = dyn_cast<Constant>(Idx);
149     if (CVec && CIdx)
150       return ConstantExpr::getExtractElement(CVec, CIdx);
151     return nullptr;
152   }
153 
154   Value *FoldInsertElement(Value *Vec, Value *NewElt,
155                            Value *Idx) const override {
156     auto *CVec = dyn_cast<Constant>(Vec);
157     auto *CNewElt = dyn_cast<Constant>(NewElt);
158     auto *CIdx = dyn_cast<Constant>(Idx);
159     if (CVec && CNewElt && CIdx)
160       return ConstantExpr::getInsertElement(CVec, CNewElt, CIdx);
161     return nullptr;
162   }
163 
164   Value *FoldShuffleVector(Value *V1, Value *V2,
165                            ArrayRef<int> Mask) const override {
166     auto *C1 = dyn_cast<Constant>(V1);
167     auto *C2 = dyn_cast<Constant>(V2);
168     if (C1 && C2)
169       return ConstantExpr::getShuffleVector(C1, C2, Mask);
170     return nullptr;
171   }
172 
173   //===--------------------------------------------------------------------===//
174   // Cast/Conversion Operators
175   //===--------------------------------------------------------------------===//
176 
177   Constant *CreateCast(Instruction::CastOps Op, Constant *C,
178                        Type *DestTy) const override {
179     return ConstantExpr::getCast(Op, C, DestTy);
180   }
181 
182   Constant *CreatePointerCast(Constant *C, Type *DestTy) const override {
183     return ConstantExpr::getPointerCast(C, DestTy);
184   }
185 
186   Constant *CreatePointerBitCastOrAddrSpaceCast(Constant *C,
187                                                 Type *DestTy) const override {
188     return ConstantExpr::getPointerBitCastOrAddrSpaceCast(C, DestTy);
189   }
190 
191   Constant *CreateIntCast(Constant *C, Type *DestTy,
192                           bool isSigned) const override {
193     return ConstantExpr::getIntegerCast(C, DestTy, isSigned);
194   }
195 
196   Constant *CreateFPCast(Constant *C, Type *DestTy) const override {
197     return ConstantExpr::getFPCast(C, DestTy);
198   }
199 
200   Constant *CreateBitCast(Constant *C, Type *DestTy) const override {
201     return CreateCast(Instruction::BitCast, C, DestTy);
202   }
203 
204   Constant *CreateIntToPtr(Constant *C, Type *DestTy) const override {
205     return CreateCast(Instruction::IntToPtr, C, DestTy);
206   }
207 
208   Constant *CreatePtrToInt(Constant *C, Type *DestTy) const override {
209     return CreateCast(Instruction::PtrToInt, C, DestTy);
210   }
211 
212   Constant *CreateZExtOrBitCast(Constant *C, Type *DestTy) const override {
213     return ConstantExpr::getZExtOrBitCast(C, DestTy);
214   }
215 
216   Constant *CreateSExtOrBitCast(Constant *C, Type *DestTy) const override {
217     return ConstantExpr::getSExtOrBitCast(C, DestTy);
218   }
219 
220   Constant *CreateTruncOrBitCast(Constant *C, Type *DestTy) const override {
221     return ConstantExpr::getTruncOrBitCast(C, DestTy);
222   }
223 
224   //===--------------------------------------------------------------------===//
225   // Compare Instructions
226   //===--------------------------------------------------------------------===//
227 
228   Constant *CreateFCmp(CmpInst::Predicate P, Constant *LHS,
229                        Constant *RHS) const override {
230     return ConstantExpr::getCompare(P, LHS, RHS);
231   }
232 };
233 
234 } // end namespace llvm
235 
236 #endif // LLVM_IR_CONSTANTFOLDER_H
237