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.
Fold(Constant * C)38   Constant *Fold(Constant *C) const {
39     return ConstantFoldConstant(C, DL);
40   }
41 
42   virtual void anchor();
43 
44 public:
TargetFolder(const DataLayout & DL)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 
FoldBinOp(Instruction::BinaryOps Opc,Value * LHS,Value * RHS)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 
FoldExactBinOp(Instruction::BinaryOps Opc,Value * LHS,Value * RHS,bool IsExact)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 
FoldNoWrapBinOp(Instruction::BinaryOps Opc,Value * LHS,Value * RHS,bool HasNUW,bool HasNSW)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 
FoldBinOpFMF(Instruction::BinaryOps Opc,Value * LHS,Value * RHS,FastMathFlags FMF)97   Value *FoldBinOpFMF(Instruction::BinaryOps Opc, Value *LHS, Value *RHS,
98                       FastMathFlags FMF) const override {
99     return FoldBinOp(Opc, LHS, RHS);
100   }
101 
FoldICmp(CmpInst::Predicate P,Value * LHS,Value * RHS)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 
FoldUnOpFMF(Instruction::UnaryOps Opc,Value * V,FastMathFlags FMF)110   Value *FoldUnOpFMF(Instruction::UnaryOps Opc, Value *V,
111                       FastMathFlags FMF) const override {
112     if (Constant *C = dyn_cast<Constant>(V))
113       return ConstantFoldUnaryOpOperand(Opc, C, DL);
114     return nullptr;
115   }
116 
117   Value *FoldGEP(Type *Ty, Value *Ptr, ArrayRef<Value *> IdxList,
118                  bool IsInBounds = false) const override {
119     if (!ConstantExpr::isSupportedGetElementPtr(Ty))
120       return nullptr;
121 
122     if (auto *PC = dyn_cast<Constant>(Ptr)) {
123       // Every index must be constant.
124       if (any_of(IdxList, [](Value *V) { return !isa<Constant>(V); }))
125         return nullptr;
126       if (IsInBounds)
127         return Fold(ConstantExpr::getInBoundsGetElementPtr(Ty, PC, IdxList));
128       else
129         return Fold(ConstantExpr::getGetElementPtr(Ty, PC, IdxList));
130     }
131     return nullptr;
132   }
133 
FoldSelect(Value * C,Value * True,Value * False)134   Value *FoldSelect(Value *C, Value *True, Value *False) const override {
135     auto *CC = dyn_cast<Constant>(C);
136     auto *TC = dyn_cast<Constant>(True);
137     auto *FC = dyn_cast<Constant>(False);
138     if (CC && TC && FC)
139       return ConstantFoldSelectInstruction(CC, TC, FC);
140 
141     return nullptr;
142   }
143 
FoldExtractValue(Value * Agg,ArrayRef<unsigned> IdxList)144   Value *FoldExtractValue(Value *Agg,
145                           ArrayRef<unsigned> IdxList) const override {
146     if (auto *CAgg = dyn_cast<Constant>(Agg))
147       return ConstantFoldExtractValueInstruction(CAgg, IdxList);
148     return nullptr;
149   };
150 
FoldInsertValue(Value * Agg,Value * Val,ArrayRef<unsigned> IdxList)151   Value *FoldInsertValue(Value *Agg, Value *Val,
152                          ArrayRef<unsigned> IdxList) const override {
153     auto *CAgg = dyn_cast<Constant>(Agg);
154     auto *CVal = dyn_cast<Constant>(Val);
155     if (CAgg && CVal)
156       return ConstantFoldInsertValueInstruction(CAgg, CVal, IdxList);
157     return nullptr;
158   }
159 
FoldExtractElement(Value * Vec,Value * Idx)160   Value *FoldExtractElement(Value *Vec, Value *Idx) const override {
161     auto *CVec = dyn_cast<Constant>(Vec);
162     auto *CIdx = dyn_cast<Constant>(Idx);
163     if (CVec && CIdx)
164       return Fold(ConstantExpr::getExtractElement(CVec, CIdx));
165     return nullptr;
166   }
167 
FoldInsertElement(Value * Vec,Value * NewElt,Value * Idx)168   Value *FoldInsertElement(Value *Vec, Value *NewElt,
169                            Value *Idx) const override {
170     auto *CVec = dyn_cast<Constant>(Vec);
171     auto *CNewElt = dyn_cast<Constant>(NewElt);
172     auto *CIdx = dyn_cast<Constant>(Idx);
173     if (CVec && CNewElt && CIdx)
174       return Fold(ConstantExpr::getInsertElement(CVec, CNewElt, CIdx));
175     return nullptr;
176   }
177 
FoldShuffleVector(Value * V1,Value * V2,ArrayRef<int> Mask)178   Value *FoldShuffleVector(Value *V1, Value *V2,
179                            ArrayRef<int> Mask) const override {
180     auto *C1 = dyn_cast<Constant>(V1);
181     auto *C2 = dyn_cast<Constant>(V2);
182     if (C1 && C2)
183       return Fold(ConstantExpr::getShuffleVector(C1, C2, Mask));
184     return nullptr;
185   }
186 
FoldCast(Instruction::CastOps Op,Value * V,Type * DestTy)187   Value *FoldCast(Instruction::CastOps Op, Value *V,
188                   Type *DestTy) const override {
189     if (auto *C = dyn_cast<Constant>(V))
190       return ConstantFoldCastOperand(Op, C, DestTy, DL);
191     return nullptr;
192   }
193 
194   //===--------------------------------------------------------------------===//
195   // Cast/Conversion Operators
196   //===--------------------------------------------------------------------===//
197 
CreatePointerCast(Constant * C,Type * DestTy)198   Constant *CreatePointerCast(Constant *C, Type *DestTy) const override {
199     if (C->getType() == DestTy)
200       return C; // avoid calling Fold
201     return Fold(ConstantExpr::getPointerCast(C, DestTy));
202   }
203 
CreatePointerBitCastOrAddrSpaceCast(Constant * C,Type * DestTy)204   Constant *CreatePointerBitCastOrAddrSpaceCast(Constant *C,
205                                                 Type *DestTy) const override {
206     if (C->getType() == DestTy)
207       return C; // avoid calling Fold
208     return Fold(ConstantExpr::getPointerBitCastOrAddrSpaceCast(C, DestTy));
209   }
210 
211   //===--------------------------------------------------------------------===//
212   // Compare Instructions
213   //===--------------------------------------------------------------------===//
214 
CreateFCmp(CmpInst::Predicate P,Constant * LHS,Constant * RHS)215   Constant *CreateFCmp(CmpInst::Predicate P, Constant *LHS,
216                        Constant *RHS) const override {
217     return Fold(ConstantExpr::getCompare(P, LHS, RHS));
218   }
219 };
220 
221 }
222 
223 #endif
224