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 #include "llvm/ADT/PointerIntPair.h"
22 
23 namespace clang {
24 class ASTContext;
25 class LangOptions;
26 class Stmt;
27 class FunctionDecl;
28 class VarDecl;
29 
30 namespace interp {
31 class Function;
32 class Program;
33 class State;
34 enum PrimType : unsigned;
35 
36 /// Holds all information required to evaluate constexpr code in a module.
37 class Context {
38 public:
39   /// Initialises the constexpr VM.
40   Context(ASTContext &Ctx);
41 
42   /// Cleans up the constexpr VM.
43   ~Context();
44 
45   /// Checks if a function is a potential constant expression.
46   bool isPotentialConstantExpr(State &Parent, const FunctionDecl *FnDecl);
47 
48   /// Evaluates a toplevel expression as an rvalue.
49   bool evaluateAsRValue(State &Parent, const Expr *E, APValue &Result);
50 
51   /// Evaluates a toplevel initializer.
52   bool evaluateAsInitializer(State &Parent, const VarDecl *VD, APValue &Result);
53 
54   /// Returns the AST context.
55   ASTContext &getASTContext() const { return Ctx; }
56   /// Returns the language options.
57   const LangOptions &getLangOpts() const;
58   /// Returns the interpreter stack.
59   InterpStack &getStack() { return Stk; }
60   /// Returns CHAR_BIT.
61   unsigned getCharBit() const;
62 
63   /// Classifies an expression.
64   llvm::Optional<PrimType> classify(QualType T);
65 
66 private:
67   /// Runs a function.
68   bool Run(State &Parent, Function *Func, APValue &Result);
69 
70   /// Checks a result fromt the interpreter.
71   bool Check(State &Parent, llvm::Expected<bool> &&R);
72 
73 private:
74   /// Current compilation context.
75   ASTContext &Ctx;
76   /// Interpreter stack, shared across invocations.
77   InterpStack Stk;
78   /// Constexpr program.
79   std::unique_ptr<Program> P;
80 };
81 
82 } // namespace interp
83 } // namespace clang
84 
85 #endif
86