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
27namespace llvm {
28
29/// ConstantFolder - Create constants with minimum, target independent, folding.
30class ConstantFolder final : public IRBuilderFolder {
31  virtual void anchor();
32
33public:
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  Value *FoldCast(Instruction::CastOps Op, Value *V,
177                  Type *DestTy) const override {
178    if (auto *C = dyn_cast<Constant>(V)) {
179      if (ConstantExpr::isDesirableCastOp(Op))
180        return ConstantExpr::getCast(Op, C, DestTy);
181      return ConstantFoldCastInstruction(Op, C, DestTy);
182    }
183    return nullptr;
184  }
185
186  //===--------------------------------------------------------------------===//
187  // Cast/Conversion Operators
188  //===--------------------------------------------------------------------===//
189
190  Constant *CreatePointerCast(Constant *C, Type *DestTy) const override {
191    return ConstantExpr::getPointerCast(C, DestTy);
192  }
193
194  Constant *CreatePointerBitCastOrAddrSpaceCast(Constant *C,
195                                                Type *DestTy) const override {
196    return ConstantExpr::getPointerBitCastOrAddrSpaceCast(C, DestTy);
197  }
198
199  //===--------------------------------------------------------------------===//
200  // Compare Instructions
201  //===--------------------------------------------------------------------===//
202
203  Constant *CreateFCmp(CmpInst::Predicate P, Constant *LHS,
204                       Constant *RHS) const override {
205    return ConstantExpr::getCompare(P, LHS, RHS);
206  }
207};
208
209} // end namespace llvm
210
211#endif // LLVM_IR_CONSTANTFOLDER_H
212