1 //====- TargetFolder.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 TargetFolder class, a helper for IRBuilder.
10 // It provides IRBuilder with a set of methods for creating constants with
11 // target dependent folding, in addition to the same target-independent
12 // folding that the ConstantFolder class provides.  For general constant
13 // creation and folding, use ConstantExpr and the routines in
14 // llvm/Analysis/ConstantFolding.h.
15 //
16 //===----------------------------------------------------------------------===//
17 
18 #ifndef LLVM_ANALYSIS_TARGETFOLDER_H
19 #define LLVM_ANALYSIS_TARGETFOLDER_H
20 
21 #include "llvm/ADT/ArrayRef.h"
22 #include "llvm/Analysis/ConstantFolding.h"
23 #include "llvm/IR/Constants.h"
24 #include "llvm/IR/IRBuilderFolder.h"
25 #include "llvm/IR/Operator.h"
26 
27 namespace llvm {
28 
29 class Constant;
30 class DataLayout;
31 class Type;
32 
33 /// TargetFolder - Create constants with target dependent folding.
34 class TargetFolder final : public IRBuilderFolder {
35   const DataLayout &DL;
36 
37   /// Fold - Fold the constant using target specific information.
38   Constant *Fold(Constant *C) const {
39     return ConstantFoldConstant(C, DL);
40   }
41 
42   virtual void anchor();
43 
44 public:
45   explicit TargetFolder(const DataLayout &DL) : DL(DL) {}
46 
47   //===--------------------------------------------------------------------===//
48   // Value-based folders.
49   //
50   // Return an existing value or a constant if the operation can be simplified.
51   // Otherwise return nullptr.
52   //===--------------------------------------------------------------------===//
53 
54   Value *FoldBinOp(Instruction::BinaryOps Opc, Value *LHS,
55                    Value *RHS) const override {
56     auto *LC = dyn_cast<Constant>(LHS);
57     auto *RC = dyn_cast<Constant>(RHS);
58     if (LC && RC) {
59       if (ConstantExpr::isDesirableBinOp(Opc))
60         return Fold(ConstantExpr::get(Opc, LC, RC));
61       return ConstantFoldBinaryOpOperands(Opc, LC, RC, DL);
62     }
63     return nullptr;
64   }
65 
66   Value *FoldExactBinOp(Instruction::BinaryOps Opc, Value *LHS, Value *RHS,
67                         bool IsExact) const override {
68     auto *LC = dyn_cast<Constant>(LHS);
69     auto *RC = dyn_cast<Constant>(RHS);
70     if (LC && RC) {
71       if (ConstantExpr::isDesirableBinOp(Opc))
72         return Fold(ConstantExpr::get(
73             Opc, LC, RC, IsExact ? PossiblyExactOperator::IsExact : 0));
74       return ConstantFoldBinaryOpOperands(Opc, LC, RC, DL);
75     }
76     return nullptr;
77   }
78 
79   Value *FoldNoWrapBinOp(Instruction::BinaryOps Opc, Value *LHS, Value *RHS,
80                          bool HasNUW, bool HasNSW) const override {
81     auto *LC = dyn_cast<Constant>(LHS);
82     auto *RC = dyn_cast<Constant>(RHS);
83     if (LC && RC) {
84       if (ConstantExpr::isDesirableBinOp(Opc)) {
85         unsigned Flags = 0;
86         if (HasNUW)
87           Flags |= OverflowingBinaryOperator::NoUnsignedWrap;
88         if (HasNSW)
89           Flags |= OverflowingBinaryOperator::NoSignedWrap;
90         return Fold(ConstantExpr::get(Opc, LC, RC, Flags));
91       }
92       return ConstantFoldBinaryOpOperands(Opc, LC, RC, DL);
93     }
94     return nullptr;
95   }
96 
97   Value *FoldBinOpFMF(Instruction::BinaryOps Opc, Value *LHS, Value *RHS,
98                       FastMathFlags FMF) const override {
99     return FoldBinOp(Opc, LHS, RHS);
100   }
101 
102   Value *FoldICmp(CmpInst::Predicate P, Value *LHS, Value *RHS) const override {
103     auto *LC = dyn_cast<Constant>(LHS);
104     auto *RC = dyn_cast<Constant>(RHS);
105     if (LC && RC)
106       return Fold(ConstantExpr::getCompare(P, LC, RC));
107     return nullptr;
108   }
109 
110   Value *FoldUnOpFMF(Instruction::UnaryOps Opc, Value *V,
111                       FastMathFlags FMF) const override {
112     if (Constant *C = dyn_cast<Constant>(V))
113       return Fold(ConstantExpr::get(Opc, C));
114     return nullptr;
115   }
116 
117   Value *FoldGEP(Type *Ty, Value *Ptr, ArrayRef<Value *> IdxList,
118                  bool IsInBounds = false) const override {
119     if (auto *PC = dyn_cast<Constant>(Ptr)) {
120       // Every index must be constant.
121       if (any_of(IdxList, [](Value *V) { return !isa<Constant>(V); }))
122         return nullptr;
123       if (IsInBounds)
124         return Fold(ConstantExpr::getInBoundsGetElementPtr(Ty, PC, IdxList));
125       else
126         return Fold(ConstantExpr::getGetElementPtr(Ty, PC, IdxList));
127     }
128     return nullptr;
129   }
130 
131   Value *FoldSelect(Value *C, Value *True, Value *False) const override {
132     auto *CC = dyn_cast<Constant>(C);
133     auto *TC = dyn_cast<Constant>(True);
134     auto *FC = dyn_cast<Constant>(False);
135     if (CC && TC && FC)
136       return Fold(ConstantExpr::getSelect(CC, TC, FC));
137 
138     return nullptr;
139   }
140 
141   Value *FoldExtractValue(Value *Agg,
142                           ArrayRef<unsigned> IdxList) const override {
143     if (auto *CAgg = dyn_cast<Constant>(Agg))
144       return ConstantFoldExtractValueInstruction(CAgg, IdxList);
145     return nullptr;
146   };
147 
148   Value *FoldInsertValue(Value *Agg, Value *Val,
149                          ArrayRef<unsigned> IdxList) const override {
150     auto *CAgg = dyn_cast<Constant>(Agg);
151     auto *CVal = dyn_cast<Constant>(Val);
152     if (CAgg && CVal)
153       return ConstantFoldInsertValueInstruction(CAgg, CVal, IdxList);
154     return nullptr;
155   }
156 
157   Value *FoldExtractElement(Value *Vec, Value *Idx) const override {
158     auto *CVec = dyn_cast<Constant>(Vec);
159     auto *CIdx = dyn_cast<Constant>(Idx);
160     if (CVec && CIdx)
161       return Fold(ConstantExpr::getExtractElement(CVec, CIdx));
162     return nullptr;
163   }
164 
165   Value *FoldInsertElement(Value *Vec, Value *NewElt,
166                            Value *Idx) const override {
167     auto *CVec = dyn_cast<Constant>(Vec);
168     auto *CNewElt = dyn_cast<Constant>(NewElt);
169     auto *CIdx = dyn_cast<Constant>(Idx);
170     if (CVec && CNewElt && CIdx)
171       return Fold(ConstantExpr::getInsertElement(CVec, CNewElt, CIdx));
172     return nullptr;
173   }
174 
175   Value *FoldShuffleVector(Value *V1, Value *V2,
176                            ArrayRef<int> Mask) const override {
177     auto *C1 = dyn_cast<Constant>(V1);
178     auto *C2 = dyn_cast<Constant>(V2);
179     if (C1 && C2)
180       return Fold(ConstantExpr::getShuffleVector(C1, C2, Mask));
181     return nullptr;
182   }
183 
184   //===--------------------------------------------------------------------===//
185   // Cast/Conversion Operators
186   //===--------------------------------------------------------------------===//
187 
188   Constant *CreateCast(Instruction::CastOps Op, Constant *C,
189                        Type *DestTy) const override {
190     if (C->getType() == DestTy)
191       return C; // avoid calling Fold
192     return Fold(ConstantExpr::getCast(Op, C, DestTy));
193   }
194   Constant *CreateIntCast(Constant *C, Type *DestTy,
195                           bool isSigned) const override {
196     if (C->getType() == DestTy)
197       return C; // avoid calling Fold
198     return Fold(ConstantExpr::getIntegerCast(C, DestTy, isSigned));
199   }
200   Constant *CreatePointerCast(Constant *C, Type *DestTy) const override {
201     if (C->getType() == DestTy)
202       return C; // avoid calling Fold
203     return Fold(ConstantExpr::getPointerCast(C, DestTy));
204   }
205   Constant *CreateFPCast(Constant *C, Type *DestTy) const override {
206     if (C->getType() == DestTy)
207       return C; // avoid calling Fold
208     return Fold(ConstantExpr::getFPCast(C, DestTy));
209   }
210   Constant *CreateBitCast(Constant *C, Type *DestTy) const override {
211     return CreateCast(Instruction::BitCast, C, DestTy);
212   }
213   Constant *CreateIntToPtr(Constant *C, Type *DestTy) const override {
214     return CreateCast(Instruction::IntToPtr, C, DestTy);
215   }
216   Constant *CreatePtrToInt(Constant *C, Type *DestTy) const override {
217     return CreateCast(Instruction::PtrToInt, C, DestTy);
218   }
219   Constant *CreateZExtOrBitCast(Constant *C, Type *DestTy) const override {
220     if (C->getType() == DestTy)
221       return C; // avoid calling Fold
222     return Fold(ConstantExpr::getZExtOrBitCast(C, DestTy));
223   }
224   Constant *CreateSExtOrBitCast(Constant *C, Type *DestTy) const override {
225     if (C->getType() == DestTy)
226       return C; // avoid calling Fold
227     return Fold(ConstantExpr::getSExtOrBitCast(C, DestTy));
228   }
229   Constant *CreateTruncOrBitCast(Constant *C, Type *DestTy) const override {
230     if (C->getType() == DestTy)
231       return C; // avoid calling Fold
232     return Fold(ConstantExpr::getTruncOrBitCast(C, DestTy));
233   }
234 
235   Constant *CreatePointerBitCastOrAddrSpaceCast(Constant *C,
236                                                 Type *DestTy) const override {
237     if (C->getType() == DestTy)
238       return C; // avoid calling Fold
239     return Fold(ConstantExpr::getPointerBitCastOrAddrSpaceCast(C, DestTy));
240   }
241 
242   //===--------------------------------------------------------------------===//
243   // Compare Instructions
244   //===--------------------------------------------------------------------===//
245 
246   Constant *CreateFCmp(CmpInst::Predicate P, Constant *LHS,
247                        Constant *RHS) const override {
248     return Fold(ConstantExpr::getCompare(P, LHS, RHS));
249   }
250 };
251 
252 }
253 
254 #endif
255