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
21namespace clang {
22class ASTContext;
23class LangOptions;
24class FunctionDecl;
25class VarDecl;
26class APValue;
27
28namespace interp {
29class Function;
30class Program;
31class State;
32enum PrimType : unsigned;
33
34struct ParamOffset {
35 unsigned Offset;
36 bool IsPtr;
37};
38
39/// Holds all information required to evaluate constexpr code in a module.
40class Context final {
41public:
42 /// Initialises the constexpr VM.
43 Context(ASTContext &Ctx);
44
45 /// Cleans up the constexpr VM.
46 ~Context();
47
48 /// Checks if a function is a potential constant expression.
49 bool isPotentialConstantExpr(State &Parent, const FunctionDecl *FnDecl);
50
51 /// Evaluates a toplevel expression as an rvalue.
52 bool evaluateAsRValue(State &Parent, const Expr *E, APValue &Result);
53
54 /// Like evaluateAsRvalue(), but does no implicit lvalue-to-rvalue conversion.
55 bool evaluate(State &Parent, const Expr *E, APValue &Result);
56
57 /// Evaluates a toplevel initializer.
58 bool evaluateAsInitializer(State &Parent, const VarDecl *VD, APValue &Result);
59
60 /// Returns the AST context.
61 ASTContext &getASTContext() const { return Ctx; }
62 /// Returns the language options.
63 const LangOptions &getLangOpts() const;
64 /// Returns the interpreter stack.
65 InterpStack &getStack() { return Stk; }
66 /// Returns CHAR_BIT.
67 unsigned getCharBit() const;
68 /// Return the floating-point semantics for T.
69 const llvm::fltSemantics &getFloatSemantics(QualType T) const;
70 /// Return the size of T in bits.
71 uint32_t getBitWidth(QualType T) const { return Ctx.getIntWidth(T); }
72
73 /// Classifies a type.
74 std::optional<PrimType> classify(QualType T) const;
75
76 /// Classifies an expression.
77 std::optional<PrimType> classify(const Expr *E) const {
78 assert(E);
79 if (E->isGLValue()) {
80 if (E->getType()->isFunctionType())
81 return PT_FnPtr;
82 return PT_Ptr;
83 }
84
85 return classify(T: E->getType());
86 }
87
88 const CXXMethodDecl *
89 getOverridingFunction(const CXXRecordDecl *DynamicDecl,
90 const CXXRecordDecl *StaticDecl,
91 const CXXMethodDecl *InitialFunction) const;
92
93 const Function *getOrCreateFunction(const FunctionDecl *FD);
94
95 /// Returns whether we should create a global variable for the
96 /// given ValueDecl.
97 static bool shouldBeGloballyIndexed(const ValueDecl *VD) {
98 if (const auto *V = dyn_cast<VarDecl>(Val: VD))
99 return V->hasGlobalStorage() || V->isConstexpr();
100
101 return false;
102 }
103
104 /// Returns the program. This is only needed for unittests.
105 Program &getProgram() const { return *P.get(); }
106
107 unsigned collectBaseOffset(const RecordDecl *BaseDecl,
108 const RecordDecl *DerivedDecl) const;
109
110 const Record *getRecord(const RecordDecl *D) const;
111
112 unsigned getEvalID() const { return EvalID; }
113
114private:
115 /// Runs a function.
116 bool Run(State &Parent, const Function *Func, APValue &Result);
117
118 /// Current compilation context.
119 ASTContext &Ctx;
120 /// Interpreter stack, shared across invocations.
121 InterpStack Stk;
122 /// Constexpr program.
123 std::unique_ptr<Program> P;
124 /// ID identifying an evaluation.
125 unsigned EvalID = 0;
126};
127
128} // namespace interp
129} // namespace clang
130
131#endif
132