llvm/llvm/include/llvm/DebugInfo/CodeView/TypeHashing.h

//===- TypeHashing.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_DEBUGINFO_CODEVIEW_TYPEHASHING_H
#define LLVM_DEBUGINFO_CODEVIEW_TYPEHASHING_H

#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/StringRef.h"

#include "llvm/DebugInfo/CodeView/CVRecord.h"
#include "llvm/DebugInfo/CodeView/TypeCollection.h"
#include "llvm/DebugInfo/CodeView/TypeIndex.h"

#include "llvm/Support/FormatProviders.h"

#include <type_traits>

namespace llvm {
class raw_ostream;
namespace codeview {

/// A locally hashed type represents a straightforward hash code of a serialized
/// record.  The record is simply serialized, and then the bytes are hashed by
/// a standard algorithm.  This is sufficient for the case of de-duplicating
/// records within a single sequence of types, because if two records both have
/// a back-reference to the same type in the same stream, they will both have
/// the same numeric value for the TypeIndex of the back reference.
struct LocallyHashedType { … };

enum class GlobalTypeHashAlg : uint16_t { … };

/// A globally hashed type represents a hash value that is sufficient to
/// uniquely identify a record across multiple type streams or type sequences.
/// This works by, for any given record A which references B, replacing the
/// TypeIndex that refers to B with a previously-computed global hash for B.  As
/// this is a recursive algorithm (e.g. the global hash of B also depends on the
/// global hashes of the types that B refers to), a global hash can uniquely
/// identify that A occurs in another stream that has a completely
/// different graph structure.  Although the hash itself is slower to compute,
/// probing is much faster with a globally hashed type, because the hash itself
/// is considered "as good as" the original type.  Since type records can be
/// quite large, this makes the equality comparison of the hash much faster than
/// equality comparison of a full record.
struct GloballyHashedType { … };
static_assert …;
} // namespace codeview

template <> struct DenseMapInfo<codeview::LocallyHashedType> { … };

template <> struct DenseMapInfo<codeview::GloballyHashedType> { … };

template <> struct format_provider<codeview::LocallyHashedType> { … };

template <> struct format_provider<codeview::GloballyHashedType> { … };

} // namespace llvm

#endif