clang/lib/AST/ByteCode/Source.h

//===--- Source.h - Source location provider 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 a program which organises and links multiple bytecode functions.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_AST_INTERP_SOURCE_H
#define LLVM_CLANG_AST_INTERP_SOURCE_H

#include "PrimType.h"
#include "clang/AST/DeclBase.h"
#include "clang/AST/Stmt.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/Endian.h"

namespace clang {
class Expr;
class SourceLocation;
class SourceRange;
namespace interp {
class Function;

/// Pointer into the code segment.
class CodePtr final {
public:
  CodePtr() = default;

  CodePtr &operator+=(int32_t Offset) {
    Ptr += Offset;
    return *this;
  }

  CodePtr operator+(int32_t Offset) { return CodePtr(Ptr + Offset); }

  int32_t operator-(const CodePtr &RHS) const {
    assert(Ptr != nullptr && RHS.Ptr != nullptr && "Invalid code pointer");
    return Ptr - RHS.Ptr;
  }

  CodePtr operator-(size_t RHS) const {
    assert(Ptr != nullptr && "Invalid code pointer");
    return CodePtr(Ptr - RHS);
  }

  bool operator!=(const CodePtr &RHS) const { return Ptr != RHS.Ptr; }
  const std::byte *operator*() const { return Ptr; }
  explicit operator bool() const { return Ptr; }
  bool operator<=(const CodePtr &RHS) const { return Ptr <= RHS.Ptr; }
  bool operator>=(const CodePtr &RHS) const { return Ptr >= RHS.Ptr; }
  bool operator==(const CodePtr RHS) const { return Ptr == RHS.Ptr; }

  /// Reads data and advances the pointer.
  template <typename T> std::enable_if_t<!std::is_pointer<T>::value, T> read() {
    assert(aligned(Ptr));
    using namespace llvm::support;
    T Value = endian::read<T, llvm::endianness::native>(Ptr);
    Ptr += align(sizeof(T));
    return Value;
  }

private:
  friend class Function;
  /// Constructor used by Function to generate pointers.
  CodePtr(const std::byte *Ptr) : Ptr(Ptr) {}
  /// Pointer into the code owned by a function.
  const std::byte *Ptr = nullptr;
};

/// Describes the statement/declaration an opcode was generated from.
class SourceInfo final {
public:
  SourceInfo() : Source(nullptr) {}
  SourceInfo(const Stmt *E) : Source(E) {}
  SourceInfo(const Decl *D) : Source(D) {}

  SourceLocation getLoc() const;
  SourceRange getRange() const;

  const Stmt *asStmt() const {
    return dyn_cast_if_present<const Stmt *>(Source);
  }
  const Decl *asDecl() const {
    return dyn_cast_if_present<const Decl *>(Source);
  }
  const Expr *asExpr() const { return dyn_cast_if_present<Expr>(asStmt()); }

  explicit operator bool() const { return !Source.isNull(); }

  bool operator!=(SourceInfo O) { return Source != O.Source; }

private:
  llvm::PointerUnion<const Decl *, const Stmt *> Source;
};
static_assert(sizeof(SourceInfo) == sizeof(void *));

// A map from byte code offset to source information.
// This is used to get the location in the input source file for diagnostics.
class SourceMap final {
private:
  llvm::SmallVector<uint32_t> Offsets;
  llvm::SmallVector<SourceInfo> Infos;

public:
  SourceMap() = default;
  void push(uint32_t Offset, SourceInfo Info) {
    Offsets.push_back(Offset);
    Infos.push_back(Info);
  }

  bool empty() const { return Offsets.empty(); }
  SourceInfo back() const { return Infos.back(); }

  SourceInfo findSourceForOffset(uint32_t Offset) const {
    assert(!Offsets.empty());
    assert(Offsets.size() == Infos.size());
#ifndef NDEBUG
    assert(llvm::is_sorted(Offsets));
#endif

    // Find the last offset <= Offset.
    auto *It = llvm::upper_bound(Offsets, Offset);
    if (It == Offsets.begin())
      return Infos[0];

    --It;
    return Infos[It - Offsets.begin()];
  }
};

/// Interface for classes which map locations to sources.
class SourceMapper {
public:
  virtual ~SourceMapper() {}
  /// Returns source information for a given PC in a function.
  virtual SourceInfo getSource(CodePtr PC) const = 0;
};

} // namespace interp
} // namespace clang

#endif