[Clang Interpreter] Initial patch for the constexpr interpreter
Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.
Reviewers: Bigcheese, jfb, rsmith
Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D64146
llvm-svn: 371834
diff --git a/clang/lib/AST/Interp/Program.h b/clang/lib/AST/Interp/Program.h
new file mode 100644
index 0000000..5f0012d
--- /dev/null
+++ b/clang/lib/AST/Interp/Program.h
@@ -0,0 +1,220 @@
+//===--- Program.h - Bytecode for the constexpr VM --------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Defines a program which organises and links multiple bytecode functions.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_AST_INTERP_PROGRAM_H
+#define LLVM_CLANG_AST_INTERP_PROGRAM_H
+
+#include <map>
+#include <vector>
+#include "Function.h"
+#include "Pointer.h"
+#include "PrimType.h"
+#include "Record.h"
+#include "Source.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PointerUnion.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Allocator.h"
+
+namespace clang {
+class RecordDecl;
+class Expr;
+class FunctionDecl;
+class Stmt;
+class StringLiteral;
+class VarDecl;
+
+namespace interp {
+class Context;
+class State;
+class Record;
+class Scope;
+
+/// The program contains and links the bytecode for all functions.
+class Program {
+public:
+ Program(Context &Ctx) : Ctx(Ctx) {}
+
+ /// Emits a string literal among global data.
+ unsigned createGlobalString(const StringLiteral *S);
+
+ /// Returns a pointer to a global.
+ Pointer getPtrGlobal(unsigned Idx);
+
+ /// Returns the value of a global.
+ Block *getGlobal(unsigned Idx) {
+ assert(Idx < Globals.size());
+ return Globals[Idx]->block();
+ }
+
+ /// Finds a global's index.
+ llvm::Optional<unsigned> getGlobal(const ValueDecl *VD);
+
+ /// Returns or creates a global an creates an index to it.
+ llvm::Optional<unsigned> getOrCreateGlobal(const ValueDecl *VD);
+
+ /// Returns or creates a dummy value for parameters.
+ llvm::Optional<unsigned> getOrCreateDummy(const ParmVarDecl *PD);
+
+ /// Creates a global and returns its index.
+ llvm::Optional<unsigned> createGlobal(const ValueDecl *VD);
+
+ /// Creates a global from a lifetime-extended temporary.
+ llvm::Optional<unsigned> createGlobal(const Expr *E);
+
+ /// Creates a new function from a code range.
+ template <typename... Ts>
+ Function *createFunction(const FunctionDecl *Def, Ts &&... Args) {
+ auto *Func = new Function(*this, Def, std::forward<Ts>(Args)...);
+ Funcs.insert({Def, std::unique_ptr<Function>(Func)});
+ return Func;
+ }
+ /// Creates an anonymous function.
+ template <typename... Ts>
+ Function *createFunction(Ts &&... Args) {
+ auto *Func = new Function(*this, std::forward<Ts>(Args)...);
+ AnonFuncs.emplace_back(Func);
+ return Func;
+ }
+
+ /// Returns a function.
+ Function *getFunction(const FunctionDecl *F);
+
+ /// Returns a pointer to a function if it exists and can be compiled.
+ /// If a function couldn't be compiled, an error is returned.
+ /// If a function was not yet defined, a null pointer is returned.
+ llvm::Expected<Function *> getOrCreateFunction(const FunctionDecl *F);
+
+ /// Returns a record or creates one if it does not exist.
+ Record *getOrCreateRecord(const RecordDecl *RD);
+
+ /// Creates a descriptor for a primitive type.
+ Descriptor *createDescriptor(const DeclTy &D, PrimType Type,
+ bool IsConst = false,
+ bool IsTemporary = false,
+ bool IsMutable = false) {
+ return allocateDescriptor(D, Type, IsConst, IsTemporary, IsMutable);
+ }
+
+ /// Creates a descriptor for a composite type.
+ Descriptor *createDescriptor(const DeclTy &D, const Type *Ty,
+ bool IsConst = false, bool IsTemporary = false,
+ bool IsMutable = false);
+
+ /// Context to manage declaration lifetimes.
+ class DeclScope {
+ public:
+ DeclScope(Program &P, const VarDecl *VD) : P(P) { P.startDeclaration(VD); }
+ ~DeclScope() { P.endDeclaration(); }
+
+ private:
+ Program &P;
+ };
+
+ /// Returns the current declaration ID.
+ llvm::Optional<unsigned> getCurrentDecl() const {
+ if (CurrentDeclaration == NoDeclaration)
+ return llvm::Optional<unsigned>{};
+ return LastDeclaration;
+ }
+
+private:
+ friend class DeclScope;
+
+ llvm::Optional<unsigned> createGlobal(const DeclTy &D, QualType Ty,
+ bool IsStatic, bool IsExtern);
+
+ /// Reference to the VM context.
+ Context &Ctx;
+ /// Mapping from decls to cached bytecode functions.
+ llvm::DenseMap<const FunctionDecl *, std::unique_ptr<Function>> Funcs;
+ /// List of anonymous functions.
+ std::vector<std::unique_ptr<Function>> AnonFuncs;
+
+ /// Function relocation locations.
+ llvm::DenseMap<const FunctionDecl *, std::vector<unsigned>> Relocs;
+
+ /// Custom allocator for global storage.
+ using PoolAllocTy = llvm::BumpPtrAllocatorImpl<llvm::MallocAllocator>;
+
+ /// Descriptor + storage for a global object.
+ ///
+ /// Global objects never go out of scope, thus they do not track pointers.
+ class Global {
+ public:
+ /// Create a global descriptor for string literals.
+ template <typename... Tys>
+ Global(Tys... Args) : B(std::forward<Tys>(Args)...) {}
+
+ /// Allocates the global in the pool, reserving storate for data.
+ void *operator new(size_t Meta, PoolAllocTy &Alloc, size_t Data) {
+ return Alloc.Allocate(Meta + Data, alignof(void *));
+ }
+
+ /// Return a pointer to the data.
+ char *data() { return B.data(); }
+ /// Return a pointer to the block.
+ Block *block() { return &B; }
+
+ private:
+ /// Required metadata - does not actually track pointers.
+ Block B;
+ };
+
+ /// Allocator for globals.
+ PoolAllocTy Allocator;
+
+ /// Global objects.
+ std::vector<Global *> Globals;
+ /// Cached global indices.
+ llvm::DenseMap<const void *, unsigned> GlobalIndices;
+
+ /// Mapping from decls to record metadata.
+ llvm::DenseMap<const RecordDecl *, Record *> Records;
+
+ /// Dummy parameter to generate pointers from.
+ llvm::DenseMap<const ParmVarDecl *, unsigned> DummyParams;
+
+ /// Creates a new descriptor.
+ template <typename... Ts>
+ Descriptor *allocateDescriptor(Ts &&... Args) {
+ return new (Allocator) Descriptor(std::forward<Ts>(Args)...);
+ }
+
+ /// No declaration ID.
+ static constexpr unsigned NoDeclaration = (unsigned)-1;
+ /// Last declaration ID.
+ unsigned LastDeclaration = 0;
+ /// Current declaration ID.
+ unsigned CurrentDeclaration = NoDeclaration;
+
+ /// Starts evaluating a declaration.
+ void startDeclaration(const VarDecl *Decl) {
+ LastDeclaration += 1;
+ CurrentDeclaration = LastDeclaration;
+ }
+
+ /// Ends a global declaration.
+ void endDeclaration() {
+ CurrentDeclaration = NoDeclaration;
+ }
+
+public:
+ /// Dumps the disassembled bytecode to \c llvm::errs().
+ void dump() const;
+ void dump(llvm::raw_ostream &OS) const;
+};
+
+} // namespace interp
+} // namespace clang
+
+#endif