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//===------ LazyReexports.h -- Utilities for lazy reexports -----*- C++ -*-===//
// 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
// Lazy re-exports are similar to normal re-exports, except that for callable
// symbols the definitions are replaced with trampolines that will look up and
// call through to the re-exported symbol at runtime. This can be used to
// enable lazy compilation.
#include "llvm/ExecutionEngine/Orc/Core.h"
#include "llvm/ExecutionEngine/Orc/IndirectionUtils.h"
#include "llvm/ExecutionEngine/Orc/Speculation.h"
namespace llvm {
class Triple;
namespace orc {
/// Manages a set of 'lazy call-through' trampolines. These are compiler
/// re-entry trampolines that are pre-bound to look up a given symbol in a given
/// JITDylib, then jump to that address. Since compilation of symbols is
/// triggered on first lookup, these call-through trampolines can be used to
/// implement lazy compilation.
/// The easiest way to construct these call-throughs is using the lazyReexport
/// function.
class LazyCallThroughManager {
/// Clients will want to take some action on first resolution, e.g. updating
/// a stub pointer. Instances of this class can be used to implement this.
class NotifyResolvedFunction {
virtual ~NotifyResolvedFunction() {}
/// Called the first time a lazy call through is executed and the target
/// symbol resolved.
virtual Error operator()(JITDylib &SourceJD,
const SymbolStringPtr &SymbolName,
JITTargetAddress ResolvedAddr) = 0;
virtual void anchor();
template <typename NotifyResolvedImpl>
class NotifyResolvedFunctionImpl : public NotifyResolvedFunction {
NotifyResolvedFunctionImpl(NotifyResolvedImpl NotifyResolved)
: NotifyResolved(std::move(NotifyResolved)) {}
Error operator()(JITDylib &SourceJD, const SymbolStringPtr &SymbolName,
JITTargetAddress ResolvedAddr) {
return NotifyResolved(SourceJD, SymbolName, ResolvedAddr);
NotifyResolvedImpl NotifyResolved;
/// Create a shared NotifyResolvedFunction from a given type that is
/// callable with the correct signature.
template <typename NotifyResolvedImpl>
static std::unique_ptr<NotifyResolvedFunction>
createNotifyResolvedFunction(NotifyResolvedImpl NotifyResolved) {
return std::make_unique<NotifyResolvedFunctionImpl<NotifyResolvedImpl>>(
// Return a free call-through trampoline and bind it to look up and call
// through to the given symbol.
Expected<JITTargetAddress> getCallThroughTrampoline(
JITDylib &SourceJD, SymbolStringPtr SymbolName,
std::shared_ptr<NotifyResolvedFunction> NotifyResolved);
LazyCallThroughManager(ExecutionSession &ES,
JITTargetAddress ErrorHandlerAddr,
std::unique_ptr<TrampolinePool> TP);
JITTargetAddress callThroughToSymbol(JITTargetAddress TrampolineAddr);
void setTrampolinePool(std::unique_ptr<TrampolinePool> TP) {
this->TP = std::move(TP);
using ReexportsMap =
std::map<JITTargetAddress, std::pair<JITDylib *, SymbolStringPtr>>;
using NotifiersMap =
std::map<JITTargetAddress, std::shared_ptr<NotifyResolvedFunction>>;
std::mutex LCTMMutex;
ExecutionSession &ES;
JITTargetAddress ErrorHandlerAddr;
std::unique_ptr<TrampolinePool> TP;
ReexportsMap Reexports;
NotifiersMap Notifiers;
/// A lazy call-through manager that builds trampolines in the current process.
class LocalLazyCallThroughManager : public LazyCallThroughManager {
LocalLazyCallThroughManager(ExecutionSession &ES,
JITTargetAddress ErrorHandlerAddr)
: LazyCallThroughManager(ES, ErrorHandlerAddr, nullptr) {}
template <typename ORCABI> Error init() {
auto TP = LocalTrampolinePool<ORCABI>::Create(
[this](JITTargetAddress TrampolineAddr) {
return callThroughToSymbol(TrampolineAddr);
if (!TP)
return TP.takeError();
return Error::success();
/// Create a LocalLazyCallThroughManager using the given ABI. See
/// createLocalLazyCallThroughManager.
template <typename ORCABI>
static Expected<std::unique_ptr<LocalLazyCallThroughManager>>
Create(ExecutionSession &ES, JITTargetAddress ErrorHandlerAddr) {
auto LLCTM = std::unique_ptr<LocalLazyCallThroughManager>(
new LocalLazyCallThroughManager(ES, ErrorHandlerAddr));
if (auto Err = LLCTM->init<ORCABI>())
return std::move(Err);
return std::move(LLCTM);
/// Create a LocalLazyCallThroughManager from the given triple and execution
/// session.
createLocalLazyCallThroughManager(const Triple &T, ExecutionSession &ES,
JITTargetAddress ErrorHandlerAddr);
/// A materialization unit that builds lazy re-exports. These are callable
/// entry points that call through to the given symbols.
/// Unlike a 'true' re-export, the address of the lazy re-export will not
/// match the address of the re-exported symbol, but calling it will behave
/// the same as calling the re-exported symbol.
class LazyReexportsMaterializationUnit : public MaterializationUnit {
LazyReexportsMaterializationUnit(LazyCallThroughManager &LCTManager,
IndirectStubsManager &ISManager,
JITDylib &SourceJD,
SymbolAliasMap CallableAliases,
ImplSymbolMap *SrcJDLoc, VModuleKey K);
StringRef getName() const override;
void materialize(MaterializationResponsibility R) override;
void discard(const JITDylib &JD, const SymbolStringPtr &Name) override;
static SymbolFlagsMap extractFlags(const SymbolAliasMap &Aliases);
LazyCallThroughManager &LCTManager;
IndirectStubsManager &ISManager;
JITDylib &SourceJD;
SymbolAliasMap CallableAliases;
ImplSymbolMap *AliaseeTable;
/// Define lazy-reexports based on the given SymbolAliasMap. Each lazy re-export
/// is a callable symbol that will look up and dispatch to the given aliasee on
/// first call. All subsequent calls will go directly to the aliasee.
inline std::unique_ptr<LazyReexportsMaterializationUnit>
lazyReexports(LazyCallThroughManager &LCTManager,
IndirectStubsManager &ISManager, JITDylib &SourceJD,
SymbolAliasMap CallableAliases, ImplSymbolMap *SrcJDLoc = nullptr,
VModuleKey K = VModuleKey()) {
return std::make_unique<LazyReexportsMaterializationUnit>(
LCTManager, ISManager, SourceJD, std::move(CallableAliases), SrcJDLoc,
} // End namespace orc
} // End namespace llvm