1 //===--- Context.h - Context for the constexpr 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 // Defines the constexpr execution context.
10 //
11 // The execution context manages cached bytecode and the global context.
12 // It invokes the compiler and interpreter, propagating errors.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_CLANG_AST_INTERP_CONTEXT_H
17 #define LLVM_CLANG_AST_INTERP_CONTEXT_H
18 
19 #include "InterpStack.h"
20 #include "clang/AST/APValue.h"
21 
22 namespace clang {
23 class ASTContext;
24 class LangOptions;
25 class FunctionDecl;
26 class VarDecl;
27 
28 namespace interp {
29 class Function;
30 class Program;
31 class State;
32 enum PrimType : unsigned;
33 
34 /// Holds all information required to evaluate constexpr code in a module.
35 class Context final {
36 public:
37   /// Initialises the constexpr VM.
38   Context(ASTContext &Ctx);
39 
40   /// Cleans up the constexpr VM.
41   ~Context();
42 
43   /// Checks if a function is a potential constant expression.
44   bool isPotentialConstantExpr(State &Parent, const FunctionDecl *FnDecl);
45 
46   /// Evaluates a toplevel expression as an rvalue.
47   bool evaluateAsRValue(State &Parent, const Expr *E, APValue &Result);
48 
49   /// Evaluates a toplevel initializer.
50   bool evaluateAsInitializer(State &Parent, const VarDecl *VD, APValue &Result);
51 
52   /// Returns the AST context.
53   ASTContext &getASTContext() const { return Ctx; }
54   /// Returns the language options.
55   const LangOptions &getLangOpts() const;
56   /// Returns the interpreter stack.
57   InterpStack &getStack() { return Stk; }
58   /// Returns CHAR_BIT.
59   unsigned getCharBit() const;
60 
61   /// Classifies an expression.
62   std::optional<PrimType> classify(QualType T) const;
63 
64 private:
65   /// Runs a function.
66   bool Run(State &Parent, Function *Func, APValue &Result);
67 
68   /// Checks a result from the interpreter.
69   bool Check(State &Parent, llvm::Expected<bool> &&R);
70 
71   /// Current compilation context.
72   ASTContext &Ctx;
73   /// Interpreter stack, shared across invocations.
74   InterpStack Stk;
75   /// Constexpr program.
76   std::unique_ptr<Program> P;
77 };
78 
79 } // namespace interp
80 } // namespace clang
81 
82 #endif
83