//===- 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_DWARFLINKERDECLCONTEXT_H
#define LLVM_DWARFLINKER_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 {
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 {
public:
/// Resolve a path by calling realpath and cache its result. The returned
/// StringRef is interned in the given \p StringPool.
StringRef resolve(const std::string &Path,
NonRelocatableStringpool &StringPool) {
StringRef FileName = sys::path::filename(Path);
StringRef ParentPath = sys::path::parent_path(Path);
// If the ParentPath has not yet been resolved, resolve and cache it for
// future look-ups.
if (!ResolvedPaths.count(ParentPath)) {
SmallString<256> RealPath;
sys::fs::real_path(ParentPath, RealPath);
ResolvedPaths.insert(
{ParentPath, std::string(RealPath.c_str(), RealPath.size())});
}
// Join the file name again with the resolved path.
SmallString<256> ResolvedPath(ResolvedPaths[ParentPath]);
sys::path::append(ResolvedPath, FileName);
return StringPool.internString(ResolvedPath);
}
private:
StringMap<std::string> ResolvedPaths;
};
/// 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 {
public:
using Map = DenseSet<DeclContext *, DeclMapInfo>;
DeclContext() : DefinedInClangModule(0), Parent(*this) {}
DeclContext(unsigned Hash, uint32_t Line, uint32_t ByteSize, uint16_t Tag,
StringRef Name, StringRef File, const DeclContext &Parent,
DWARFDie LastSeenDIE = DWARFDie(), unsigned CUId = 0)
: QualifiedNameHash(Hash), Line(Line), ByteSize(ByteSize), Tag(Tag),
DefinedInClangModule(0), Name(Name), File(File), Parent(Parent),
LastSeenDIE(LastSeenDIE), LastSeenCompileUnitID(CUId) {}
uint32_t getQualifiedNameHash() const { return QualifiedNameHash; }
bool setLastSeenDIE(CompileUnit &U, const DWARFDie &Die);
void setHasCanonicalDIE() { HasCanonicalDIE = true; }
bool hasCanonicalDIE() const { return HasCanonicalDIE; }
uint32_t getCanonicalDIEOffset() const { return CanonicalDIEOffset; }
void setCanonicalDIEOffset(uint32_t Offset) { CanonicalDIEOffset = Offset; }
bool isDefinedInClangModule() const { return DefinedInClangModule; }
void setDefinedInClangModule(bool Val) { DefinedInClangModule = Val; }
uint16_t getTag() const { return Tag; }
private:
friend DeclMapInfo;
unsigned QualifiedNameHash = 0;
uint32_t Line = 0;
uint32_t ByteSize = 0;
uint16_t Tag = dwarf::DW_TAG_compile_unit;
unsigned DefinedInClangModule : 1;
StringRef Name;
StringRef File;
const DeclContext &Parent;
DWARFDie LastSeenDIE;
uint32_t LastSeenCompileUnitID = 0;
std::atomic<uint32_t> CanonicalDIEOffset = {0};
bool HasCanonicalDIE = false;
};
/// 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 {
public:
/// Get the child of \a Context described by \a DIE in \a Unit. The
/// required strings will be interned in \a StringPool.
/// \returns The child DeclContext along with one bit that is set if
/// this context is invalid.
///
/// An invalid context means it shouldn't be considered for uniquing, but its
/// not returning null, because some children of that context might be
/// uniquing candidates.
///
/// FIXME: The invalid bit along the return value is to emulate some
/// dsymutil-classic functionality.
PointerIntPair<DeclContext *, 1> getChildDeclContext(DeclContext &Context,
const DWARFDie &DIE,
CompileUnit &Unit,
bool InClangModule);
DeclContext &getRoot() { return Root; }
private:
BumpPtrAllocator Allocator;
DeclContext Root;
DeclContext::Map Contexts;
/// Cached resolved paths from the line table.
/// The key is <UniqueUnitID, FileIdx>.
using ResolvedPathsMap = DenseMap<std::pair<unsigned, unsigned>, StringRef>;
ResolvedPathsMap ResolvedPaths;
/// Helper that resolves and caches fragments of file paths.
CachedPathResolver PathResolver;
/// String pool keeping real path bodies.
NonRelocatableStringpool StringPool;
StringRef getResolvedPath(CompileUnit &CU, unsigned FileNum,
const DWARFDebugLine::LineTable &LineTable);
};
/// Info type for the DenseMap storing the DeclContext pointers.
struct DeclMapInfo : private DenseMapInfo<DeclContext *> {
using DenseMapInfo<DeclContext *>::getEmptyKey;
using DenseMapInfo<DeclContext *>::getTombstoneKey;
static unsigned getHashValue(const DeclContext *Ctxt) {
return Ctxt->QualifiedNameHash;
}
static bool isEqual(const DeclContext *LHS, const DeclContext *RHS) {
if (RHS == getEmptyKey() || RHS == getTombstoneKey())
return RHS == LHS;
return LHS->QualifiedNameHash == RHS->QualifiedNameHash &&
LHS->Line == RHS->Line && LHS->ByteSize == RHS->ByteSize &&
LHS->Name.data() == RHS->Name.data() &&
LHS->File.data() == RHS->File.data() &&
LHS->Parent.QualifiedNameHash == RHS->Parent.QualifiedNameHash;
}
};
} // end namespace llvm
#endif // LLVM_DWARFLINKER_DWARFLINKERDECLCONTEXT_H