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 LLVMContext;
25 class Type;
26 class Value;
27 
28 class BitcodeReaderValueList {
29   std::vector<WeakTrackingVH> ValuePtrs;
30 
31   /// Struct containing fully-specified copies of the type of each
32   /// value. When pointers are opaque, this will be contain non-opaque
33   /// variants so that restructuring instructions can determine their
34   /// type correctly even if being loaded from old bitcode where some
35   /// types are implicit.
36   std::vector<Type *> FullTypes;
37 
38   /// As we resolve forward-referenced constants, we add information about them
39   /// to this vector.  This allows us to resolve them in bulk instead of
40   /// resolving each reference at a time.  See the code in
41   /// ResolveConstantForwardRefs for more information about this.
42   ///
43   /// The key of this vector is the placeholder constant, the value is the slot
44   /// number that holds the resolved value.
45   using ResolveConstantsTy = std::vector<std::pair<Constant *, unsigned>>;
46   ResolveConstantsTy ResolveConstants;
47   LLVMContext &Context;
48 
49 public:
50   BitcodeReaderValueList(LLVMContext &C) : Context(C) {}
51 
52   ~BitcodeReaderValueList() {
53     assert(ResolveConstants.empty() && "Constants not resolved?");
54   }
55 
56   // vector compatibility methods
57   unsigned size() const { return ValuePtrs.size(); }
58   void resize(unsigned N) {
59     ValuePtrs.resize(N);
60     FullTypes.resize(N);
61   }
62   void push_back(Value *V, Type *Ty) {
63     ValuePtrs.emplace_back(V);
64     FullTypes.emplace_back(Ty);
65   }
66 
67   void clear() {
68     assert(ResolveConstants.empty() && "Constants not resolved?");
69     ValuePtrs.clear();
70     FullTypes.clear();
71   }
72 
73   Value *operator[](unsigned i) const {
74     assert(i < ValuePtrs.size());
75     return ValuePtrs[i];
76   }
77 
78   Value *back() const { return ValuePtrs.back(); }
79   void pop_back() {
80     ValuePtrs.pop_back();
81     FullTypes.pop_back();
82   }
83   bool empty() const { return ValuePtrs.empty(); }
84 
85   void shrinkTo(unsigned N) {
86     assert(N <= size() && "Invalid shrinkTo request!");
87     ValuePtrs.resize(N);
88     FullTypes.resize(N);
89   }
90 
91   Constant *getConstantFwdRef(unsigned Idx, Type *Ty);
92   Value *getValueFwdRef(unsigned Idx, Type *Ty, Type **FullTy = nullptr);
93 
94   void assignValue(Value *V, unsigned Idx, Type *FullTy);
95 
96   /// Once all constants are read, this method bulk resolves any forward
97   /// references.
98   void resolveConstantForwardRefs();
99 };
100 
101 } // end namespace llvm
102 
103 #endif // LLVM_LIB_BITCODE_READER_VALUELIST_H
104