llvm/llvm/include/llvm/DWARFLinker/Classic/DWARFLinkerDeclContext.h

//===- DWARFLinkerDeclContext.h ---------------------------------*- 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
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_DWARFLINKER_CLASSIC_DWARFLINKERDECLCONTEXT_H
#define LLVM_DWARFLINKER_CLASSIC_DWARFLINKERDECLCONTEXT_H

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/NonRelocatableStringpool.h"
#include "llvm/DebugInfo/DWARF/DWARFDebugLine.h"
#include "llvm/DebugInfo/DWARF/DWARFDie.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Path.h"
#include <atomic>

namespace llvm {
namespace dwarf_linker {
namespace classic {

class CompileUnit;
struct DeclMapInfo;

/// Small helper that resolves and caches file paths. This helps reduce the
/// number of calls to realpath which is expensive. We assume the input are
/// files, and cache the realpath of their parent. This way we can quickly
/// resolve different files under the same path.
class CachedPathResolver { … };

/// A DeclContext is a named program scope that is used for ODR uniquing of
/// types.
///
/// The set of DeclContext for the ODR-subject parts of a Dwarf link is
/// expanded (and uniqued) with each new object file processed. We need to
/// determine the context of each DIE in an linked object file to see if the
/// corresponding type has already been emitted.
///
/// The contexts are conceptually organized as a tree (eg. a function scope is
/// contained in a namespace scope that contains other scopes), but
/// storing/accessing them in an actual tree is too inefficient: we need to be
/// able to very quickly query a context for a given child context by name.
/// Storing a StringMap in each DeclContext would be too space inefficient.
///
/// The solution here is to give each DeclContext a link to its parent (this
/// allows to walk up the tree), but to query the existence of a specific
/// DeclContext using a separate DenseMap keyed on the hash of the fully
/// qualified name of the context.
class DeclContext { … };

/// This class gives a tree-like API to the DenseMap that stores the
/// DeclContext objects. It holds the BumpPtrAllocator where these objects will
/// be allocated.
class DeclContextTree { … };

/// Info type for the DenseMap storing the DeclContext pointers.
struct DeclMapInfo : private DenseMapInfo<DeclContext *> { … };

} // end of namespace classic
} // end of namespace dwarf_linker
} // end of namespace llvm

#endif // LLVM_DWARFLINKER_CLASSIC_DWARFLINKERDECLCONTEXT_H