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//===----------------- ItaniumManglingCanonicalizer.cpp -------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/ProfileData/ItaniumManglingCanonicalizer.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Demangle/ItaniumDemangle.h"
#include "llvm/Support/Allocator.h"
using namespace llvm;
using llvm::itanium_demangle::ForwardTemplateReference;
using llvm::itanium_demangle::Node;
using llvm::itanium_demangle::NodeKind;
namespace {
struct FoldingSetNodeIDBuilder {
llvm::FoldingSetNodeID &ID;
void operator()(const Node *P) { ID.AddPointer(P); }
void operator()(std::string_view Str) {
if (Str.empty())
ID.AddString(llvm::StringRef(&*Str.begin(), Str.size()));
template <typename T>
std::enable_if_t<std::is_integral_v<T> || std::is_enum_v<T>> operator()(T V) {
ID.AddInteger((unsigned long long)V);
void operator()(itanium_demangle::NodeArray A) {
for (const Node *N : A)
template<typename ...T>
void profileCtor(llvm::FoldingSetNodeID &ID, Node::Kind K, T ...V) {
FoldingSetNodeIDBuilder Builder = {ID};
int VisitInOrder[] = {
(Builder(V), 0) ...,
0 // Avoid empty array if there are no arguments.
// FIXME: Convert this to a generic lambda when possible.
template<typename NodeT> struct ProfileSpecificNode {
FoldingSetNodeID &ID;
template<typename ...T> void operator()(T ...V) {
profileCtor(ID, NodeKind<NodeT>::Kind, V...);
struct ProfileNode {
FoldingSetNodeID &ID;
template<typename NodeT> void operator()(const NodeT *N) {
template<> void ProfileNode::operator()(const ForwardTemplateReference *N) {
llvm_unreachable("should never canonicalize a ForwardTemplateReference");
void profileNode(llvm::FoldingSetNodeID &ID, const Node *N) {
class FoldingNodeAllocator {
class alignas(alignof(Node *)) NodeHeader : public llvm::FoldingSetNode {
// 'Node' in this context names the injected-class-name of the base class.
itanium_demangle::Node *getNode() {
return reinterpret_cast<itanium_demangle::Node *>(this + 1);
void Profile(llvm::FoldingSetNodeID &ID) { profileNode(ID, getNode()); }
BumpPtrAllocator RawAlloc;
llvm::FoldingSet<NodeHeader> Nodes;
void reset() {}
template <typename T, typename... Args>
std::pair<Node *, bool> getOrCreateNode(bool CreateNewNodes, Args &&... As) {
// FIXME: Don't canonicalize forward template references for now, because
// they contain state (the resolved template node) that's not known at their
// point of creation.
if (std::is_same<T, ForwardTemplateReference>::value) {
// Note that we don't use if-constexpr here and so we must still write
// this code in a generic form.
return {new (RawAlloc.Allocate(sizeof(T), alignof(T)))
llvm::FoldingSetNodeID ID;
profileCtor(ID, NodeKind<T>::Kind, As...);
void *InsertPos;
if (NodeHeader *Existing = Nodes.FindNodeOrInsertPos(ID, InsertPos))
return {static_cast<T*>(Existing->getNode()), false};
if (!CreateNewNodes)
return {nullptr, true};
static_assert(alignof(T) <= alignof(NodeHeader),
"underaligned node header for specific node kind");
void *Storage =
RawAlloc.Allocate(sizeof(NodeHeader) + sizeof(T), alignof(NodeHeader));
NodeHeader *New = new (Storage) NodeHeader;
T *Result = new (New->getNode()) T(std::forward<Args>(As)...);
Nodes.InsertNode(New, InsertPos);
return {Result, true};
template<typename T, typename... Args>
Node *makeNode(Args &&...As) {
return getOrCreateNode<T>(true, std::forward<Args>(As)...).first;
void *allocateNodeArray(size_t sz) {
return RawAlloc.Allocate(sizeof(Node *) * sz, alignof(Node *));
class CanonicalizerAllocator : public FoldingNodeAllocator {
Node *MostRecentlyCreated = nullptr;
Node *TrackedNode = nullptr;
bool TrackedNodeIsUsed = false;
bool CreateNewNodes = true;
llvm::SmallDenseMap<Node*, Node*, 32> Remappings;
template<typename T, typename ...Args> Node *makeNodeSimple(Args &&...As) {
std::pair<Node *, bool> Result =
getOrCreateNode<T>(CreateNewNodes, std::forward<Args>(As)...);
if (Result.second) {
// Node is new. Make a note of that.
MostRecentlyCreated = Result.first;
} else if (Result.first) {
// Node is pre-existing; check if it's in our remapping table.
if (auto *N = Remappings.lookup(Result.first)) {
Result.first = N;
assert(!Remappings.contains(Result.first) &&
"should never need multiple remap steps");
if (Result.first == TrackedNode)
TrackedNodeIsUsed = true;
return Result.first;
/// Helper to allow makeNode to be partially-specialized on T.
template<typename T> struct MakeNodeImpl {
CanonicalizerAllocator &Self;
template<typename ...Args> Node *make(Args &&...As) {
return Self.makeNodeSimple<T>(std::forward<Args>(As)...);
template<typename T, typename ...Args> Node *makeNode(Args &&...As) {
return MakeNodeImpl<T>{*this}.make(std::forward<Args>(As)...);
void reset() { MostRecentlyCreated = nullptr; }
void setCreateNewNodes(bool CNN) { CreateNewNodes = CNN; }
void addRemapping(Node *A, Node *B) {
// Note, we don't need to check whether B is also remapped, because if it
// was we would have already remapped it when building it.
Remappings.insert(std::make_pair(A, B));
bool isMostRecentlyCreated(Node *N) const { return MostRecentlyCreated == N; }
void trackUsesOf(Node *N) {
TrackedNode = N;
TrackedNodeIsUsed = false;
bool trackedNodeIsUsed() const { return TrackedNodeIsUsed; }
// FIXME: Also expand built-in substitutions?
using CanonicalizingDemangler =
} // namespace
struct ItaniumManglingCanonicalizer::Impl {
CanonicalizingDemangler Demangler = {nullptr, nullptr};
ItaniumManglingCanonicalizer::ItaniumManglingCanonicalizer() : P(new Impl) {}
ItaniumManglingCanonicalizer::~ItaniumManglingCanonicalizer() { delete P; }
ItaniumManglingCanonicalizer::addEquivalence(FragmentKind Kind, StringRef First,
StringRef Second) {
auto &Alloc = P->Demangler.ASTAllocator;
auto Parse = [&](StringRef Str) {
P->Demangler.reset(Str.begin(), Str.end());
Node *N = nullptr;
switch (Kind) {
// A <name>, with minor extensions to allow arbitrary namespace and
// template names that can't easily be written as <name>s.
case FragmentKind::Name:
// Very special case: allow "St" as a shorthand for "3std". It's not
// valid as a <name> mangling, but is nonetheless the most natural
// way to name the 'std' namespace.
if (Str.size() == 2 && P->Demangler.consumeIf("St"))
N = P->Demangler.make<itanium_demangle::NameType>("std");
// We permit substitutions to name templates without their template
// arguments. This mostly just falls out, as almost all template names
// are valid as <name>s, but we also want to parse <substitution>s as
// <name>s, even though they're not.
else if (Str.starts_with("S"))
// Parse the substitution and optional following template arguments.
N = P->Demangler.parseType();
N = P->Demangler.parseName();
// A <type>.
case FragmentKind::Type:
N = P->Demangler.parseType();
// An <encoding>.
case FragmentKind::Encoding:
N = P->Demangler.parseEncoding();
// If we have trailing junk, the mangling is invalid.
if (P->Demangler.numLeft() != 0)
N = nullptr;
// If any node was created after N, then we cannot safely remap it because
// it might already be in use by another node.
return std::make_pair(N, Alloc.isMostRecentlyCreated(N));
Node *FirstNode, *SecondNode;
bool FirstIsNew, SecondIsNew;
std::tie(FirstNode, FirstIsNew) = Parse(First);
if (!FirstNode)
return EquivalenceError::InvalidFirstMangling;
std::tie(SecondNode, SecondIsNew) = Parse(Second);
if (!SecondNode)
return EquivalenceError::InvalidSecondMangling;
// If they're already equivalent, there's nothing to do.
if (FirstNode == SecondNode)
return EquivalenceError::Success;
if (FirstIsNew && !Alloc.trackedNodeIsUsed())
Alloc.addRemapping(FirstNode, SecondNode);
else if (SecondIsNew)
Alloc.addRemapping(SecondNode, FirstNode);
return EquivalenceError::ManglingAlreadyUsed;
return EquivalenceError::Success;
static ItaniumManglingCanonicalizer::Key
parseMaybeMangledName(CanonicalizingDemangler &Demangler, StringRef Mangling,
bool CreateNewNodes) {
Demangler.reset(Mangling.begin(), Mangling.end());
// Attempt demangling only for names that look like C++ mangled names.
// Otherwise, treat them as extern "C" names. We permit the latter to
// be remapped by (eg)
// encoding 6memcpy 7memmove
// consistent with how they are encoded as local-names inside a C++ mangling.
Node *N;
if (Mangling.starts_with("_Z") || Mangling.starts_with("__Z") ||
Mangling.starts_with("___Z") || Mangling.starts_with("____Z"))
N = Demangler.parse();
N = Demangler.make<itanium_demangle::NameType>(
std::string_view(, Mangling.size()));
return reinterpret_cast<ItaniumManglingCanonicalizer::Key>(N);
ItaniumManglingCanonicalizer::canonicalize(StringRef Mangling) {
return parseMaybeMangledName(P->Demangler, Mangling, true);
ItaniumManglingCanonicalizer::lookup(StringRef Mangling) {
return parseMaybeMangledName(P->Demangler, Mangling, false);