1 //===------ EvaluationResult.h - Result class  for the VM -------*- 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 #ifndef LLVM_CLANG_AST_INTERP_EVALUATION_RESULT_H
10 #define LLVM_CLANG_AST_INTERP_EVALUATION_RESULT_H
11 
12 #include "FunctionPointer.h"
13 #include "Pointer.h"
14 #include "clang/AST/APValue.h"
15 #include "clang/AST/Decl.h"
16 #include "clang/AST/Expr.h"
17 #include <optional>
18 #include <variant>
19 
20 namespace clang {
21 namespace interp {
22 class EvalEmitter;
23 class Context;
24 
25 /// Defines the result of an evaluation.
26 ///
27 /// The result might be in different forms--one of the pointer types,
28 /// an APValue, or nothing.
29 ///
30 /// We use this class to inspect and diagnose the result, as well as
31 /// convert it to the requested form.
32 class EvaluationResult final {
33 public:
34   enum ResultKind {
35     Empty,   // Initial state.
36     LValue,  // Result is an lvalue/pointer.
37     RValue,  // Result is an rvalue.
38     Invalid, // Result is invalid.
39     Valid,   // Result is valid and empty.
40   };
41 
42   using DeclTy = llvm::PointerUnion<const Decl *, const Expr *>;
43 
44 private:
45   const Context *Ctx = nullptr;
46   std::variant<std::monostate, Pointer, FunctionPointer, APValue> Value;
47   ResultKind Kind = Empty;
48   DeclTy Source = nullptr; // Currently only needed for dump().
49 
50   EvaluationResult(ResultKind Kind) : Kind(Kind) {
51     // Leave everything empty. Can be used as an
52     // error marker or for void return values.
53     assert(Kind == Valid || Kind == Invalid);
54   }
55 
56   void setSource(DeclTy D) { Source = D; }
57 
58   void setValue(const APValue &V) {
59     assert(empty());
60     assert(!V.isLValue());
61     Value = std::move(V);
62     Kind = RValue;
63   }
64   void setPointer(const Pointer P) {
65     assert(empty());
66     Value = P;
67     Kind = LValue;
68   }
69   void setFunctionPointer(const FunctionPointer &P) {
70     assert(empty());
71     Value = P;
72     Kind = LValue;
73   }
74   void setInvalid() {
75     assert(empty());
76     Kind = Invalid;
77   }
78   void setValid() {
79     assert(empty());
80     Kind = Valid;
81   }
82 
83 public:
84   EvaluationResult(const Context *Ctx) : Ctx(Ctx) {}
85 
86   bool empty() const { return Kind == Empty; }
87   bool isInvalid() const { return Kind == Invalid; }
88   bool isLValue() const { return Kind == LValue; }
89   bool isRValue() const { return Kind == RValue; }
90 
91   /// Returns an APValue for the evaluation result. The returned
92   /// APValue might be an LValue or RValue.
93   APValue toAPValue() const;
94 
95   /// If the result is an LValue, convert that to an RValue
96   /// and return it. This may fail, e.g. if the result is an
97   /// LValue and we can't read from it.
98   std::optional<APValue> toRValue() const;
99 
100   bool checkFullyInitialized(InterpState &S) const;
101 
102   /// Dump to stderr.
103   void dump() const;
104 
105   friend class EvalEmitter;
106 };
107 
108 } // namespace interp
109 } // namespace clang
110 
111 #endif
112