1 //===-- Bitcode/Reader/ValueList.h - Number values --------------*- 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 class gives values and types Unique ID's.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_LIB_BITCODE_READER_VALUELIST_H
14 #define LLVM_LIB_BITCODE_READER_VALUELIST_H
15 
16 #include "llvm/IR/ValueHandle.h"
17 #include <cassert>
18 #include <utility>
19 #include <vector>
20 
21 namespace llvm {
22 
23 class Constant;
24 class Error;
25 class LLVMContext;
26 class Type;
27 class Value;
28 
29 class BitcodeReaderValueList {
30   /// Maps Value ID to pair of Value* and Type ID.
31   std::vector<std::pair<WeakTrackingVH, unsigned>> ValuePtrs;
32 
33   /// As we resolve forward-referenced constants, we add information about them
34   /// to this vector.  This allows us to resolve them in bulk instead of
35   /// resolving each reference at a time.  See the code in
36   /// ResolveConstantForwardRefs for more information about this.
37   ///
38   /// The key of this vector is the placeholder constant, the value is the slot
39   /// number that holds the resolved value.
40   using ResolveConstantsTy = std::vector<std::pair<Constant *, unsigned>>;
41   ResolveConstantsTy ResolveConstants;
42   LLVMContext &Context;
43 
44   /// Maximum number of valid references. Forward references exceeding the
45   /// maximum must be invalid.
46   unsigned RefsUpperBound;
47 
48 public:
49   BitcodeReaderValueList(LLVMContext &C, size_t RefsUpperBound)
50       : Context(C),
51         RefsUpperBound(std::min((size_t)std::numeric_limits<unsigned>::max(),
52                                 RefsUpperBound)) {}
53 
54   ~BitcodeReaderValueList() {
55     assert(ResolveConstants.empty() && "Constants not resolved?");
56   }
57 
58   // vector compatibility methods
59   unsigned size() const { return ValuePtrs.size(); }
60   void resize(unsigned N) {
61     ValuePtrs.resize(N);
62   }
63   void push_back(Value *V, unsigned TypeID) {
64     ValuePtrs.emplace_back(V, TypeID);
65   }
66 
67   void clear() {
68     assert(ResolveConstants.empty() && "Constants not resolved?");
69     ValuePtrs.clear();
70   }
71 
72   Value *operator[](unsigned i) const {
73     assert(i < ValuePtrs.size());
74     return ValuePtrs[i].first;
75   }
76 
77   unsigned getTypeID(unsigned ValNo) const {
78     assert(ValNo < ValuePtrs.size());
79     return ValuePtrs[ValNo].second;
80   }
81 
82   Value *back() const { return ValuePtrs.back().first; }
83   void pop_back() {
84     ValuePtrs.pop_back();
85   }
86   bool empty() const { return ValuePtrs.empty(); }
87 
88   void shrinkTo(unsigned N) {
89     assert(N <= size() && "Invalid shrinkTo request!");
90     ValuePtrs.resize(N);
91   }
92 
93   Constant *getConstantFwdRef(unsigned Idx, Type *Ty, unsigned TyID);
94   Value *getValueFwdRef(unsigned Idx, Type *Ty, unsigned TyID);
95 
96   Error assignValue(unsigned Idx, Value *V, unsigned TypeID);
97 
98   /// Once all constants are read, this method bulk resolves any forward
99   /// references.
100   void resolveConstantForwardRefs();
101 };
102 
103 } // end namespace llvm
104 
105 #endif // LLVM_LIB_BITCODE_READER_VALUELIST_H
106