Function.h

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//===--- Function.h - Bytecode function for the 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 the Function class which holds all bytecode function-specific data.
//
// The scope class which describes local variables is also defined here.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CLANG_AST_INTERP_FUNCTION_H
#define LLVM_CLANG_AST_INTERP_FUNCTION_H
 
#include "Descriptor.h"
#include "Source.h"
#include "clang/AST/ASTLambda.h"
#include "clang/AST/Attr.h"
#include "clang/AST/Decl.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/Support/raw_ostream.h"
 
namespace clang {
namespace interp {
class Program;
class ByteCodeEmitter;
class Pointer;
enum PrimType : uint32_t;
 
/// Describes a scope block.
///
/// The block gathers all the descriptors of the locals defined in this block.
class Scope final {
public:
  /// Information about a local's storage.
  struct Local {
    /// Offset of the local in frame.
    unsigned Offset;
    /// Descriptor of the local.
    Descriptor *Desc;
  };
 
  using LocalVectorTy = llvm::SmallVector<Local, 8>;
 
  Scope(LocalVectorTy &&Descriptors) : Descriptors(std::move(Descriptors)) {}
 
  llvm::iterator_range<LocalVectorTy::const_iterator> locals() const {
    return llvm::make_range(Descriptors.begin(), Descriptors.end());
  }
 
private:
  /// Object descriptors in this block.
  LocalVectorTy Descriptors;
};
 
using FunctionDeclTy =
    llvm::PointerUnion<const FunctionDecl *, const BlockExpr *>;
 
/// Bytecode function.
///
/// Contains links to the bytecode of the function, as well as metadata
/// describing all arguments and stack-local variables.
///
/// # Calling Convention
///
/// When calling a function, all argument values must be on the stack.
///
/// If the function has a This pointer (i.e. hasThisPointer() returns true,
/// the argument values need to be preceeded by a Pointer for the This object.
///
/// If the function uses Return Value Optimization, the arguments (and
/// potentially the This pointer) need to be preceeded by a Pointer pointing
/// to the location to construct the returned value.
///
/// After the function has been called, it will remove all arguments,
/// including RVO and This pointer, from the stack.
///
class Function final {
public:
  using ParamDescriptor = std::pair<PrimType, Descriptor *>;
 
  /// Returns the size of the function's local stack.
  unsigned getFrameSize() const { return FrameSize; }
  /// Returns the size of the argument stack.
  unsigned getArgSize() const { return ArgSize; }
 
  /// Returns a pointer to the start of the code.
  CodePtr getCodeBegin() const { return Code.data(); }
  /// Returns a pointer to the end of the code.
  CodePtr getCodeEnd() const { return Code.data() + Code.size(); }
 
  /// Returns the original FunctionDecl.
  const FunctionDecl *getDecl() const {
    return dyn_cast<const FunctionDecl *>(Source);
  }
  const BlockExpr *getExpr() const {
    return dyn_cast<const BlockExpr *>(Source);
  }
 
  /// Returns the name of the function decl this code
  /// was generated for.
  const std::string getName() const {
    if (!Source || !getDecl())
      return "<<expr>>";
 
    return getDecl()->getQualifiedNameAsString();
  }
 
  /// Returns a parameter descriptor.
  ParamDescriptor getParamDescriptor(unsigned Offset) const;
 
  /// Checks if the first argument is a RVO pointer.
  bool hasRVO() const { return HasRVO; }
 
  bool hasNonNullAttr() const { return getDecl()->hasAttr<NonNullAttr>(); }
 
  /// Range over the scope blocks.
  llvm::iterator_range<llvm::SmallVector<Scope, 2>::const_iterator>
  scopes() const {
    return llvm::make_range(Scopes.begin(), Scopes.end());
  }
 
  /// Range over argument types.
  using arg_reverse_iterator =
      SmallVectorImpl<PrimType>::const_reverse_iterator;
  llvm::iterator_range<arg_reverse_iterator> args_reverse() const {
    return llvm::reverse(ParamTypes);
  }
 
  /// Returns a specific scope.