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//===- LazyEmittingLayer.h - Lazily emit IR to lower JIT layers -*- 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
// Contains the definition for a lazy-emitting layer for the JIT.
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ExecutionEngine/JITSymbol.h"
#include "llvm/ExecutionEngine/Orc/Core.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <list>
#include <memory>
#include <string>
namespace llvm {
namespace orc {
/// Lazy-emitting IR layer.
/// This layer accepts LLVM IR Modules (via addModule) but does not
/// immediately emit them the layer below. Instead, emission to the base layer
/// is deferred until the first time the client requests the address (via
/// JITSymbol::getAddress) for a symbol contained in this layer.
template <typename BaseLayerT> class LazyEmittingLayer {
class EmissionDeferredModule {
EmissionDeferredModule(VModuleKey K, std::unique_ptr<Module> M)
: K(std::move(K)), M(std::move(M)) {}
JITSymbol find(StringRef Name, bool ExportedSymbolsOnly, BaseLayerT &B) {
switch (EmitState) {
case NotEmitted:
if (auto GV = searchGVs(Name, ExportedSymbolsOnly)) {
JITSymbolFlags Flags = JITSymbolFlags::fromGlobalValue(*GV);
auto GetAddress = [this, ExportedSymbolsOnly, Name = Name.str(),
&B]() -> Expected<JITTargetAddress> {
if (this->EmitState == Emitting)
return 0;
else if (this->EmitState == NotEmitted) {
this->EmitState = Emitting;
if (auto Err = this->emitToBaseLayer(B))
return std::move(Err);
this->EmitState = Emitted;
if (auto Sym = B.findSymbolIn(K, Name, ExportedSymbolsOnly))
return Sym.getAddress();
else if (auto Err = Sym.takeError())
return std::move(Err);
llvm_unreachable("Successful symbol lookup should return "
"definition address here");
return JITSymbol(std::move(GetAddress), Flags);
} else
return nullptr;
case Emitting:
// Calling "emit" can trigger a recursive call to 'find' (e.g. to check
// for pre-existing definitions of common-symbol), but any symbol in
// this module would already have been found internally (in the
// RuntimeDyld that did the lookup), so just return a nullptr here.
return nullptr;
case Emitted:
return B.findSymbolIn(K, Name, ExportedSymbolsOnly);
llvm_unreachable("Invalid emit-state.");
Error removeModuleFromBaseLayer(BaseLayerT& BaseLayer) {
return EmitState != NotEmitted ? BaseLayer.removeModule(K)
: Error::success();
void emitAndFinalize(BaseLayerT &BaseLayer) {
assert(EmitState != Emitting &&
"Cannot emitAndFinalize while already emitting");
if (EmitState == NotEmitted) {
EmitState = Emitting;
EmitState = Emitted;
const GlobalValue* searchGVs(StringRef Name,
bool ExportedSymbolsOnly) const {
// FIXME: We could clean all this up if we had a way to reliably demangle
// names: We could just demangle name and search, rather than
// mangling everything else.
// If we have already built the mangled name set then just search it.
if (MangledSymbols) {
auto VI = MangledSymbols->find(Name);
if (VI == MangledSymbols->end())
return nullptr;
auto GV = VI->second;
if (!ExportedSymbolsOnly || GV->hasDefaultVisibility())
return GV;
return nullptr;
// If we haven't built the mangled name set yet, try to build it. As an
// optimization this will leave MangledNames set to nullptr if we find
// Name in the process of building the set.
return buildMangledSymbols(Name, ExportedSymbolsOnly);
Error emitToBaseLayer(BaseLayerT &BaseLayer) {
// We don't need the mangled names set any more: Once we've emitted this
// to the base layer we'll just look for symbols there.
return BaseLayer.addModule(std::move(K), std::move(M));
// If the mangled name of the given GlobalValue matches the given search
// name (and its visibility conforms to the ExportedSymbolsOnly flag) then
// return the symbol. Otherwise, add the mangled name to the Names map and
// return nullptr.
const GlobalValue* addGlobalValue(StringMap<const GlobalValue*> &Names,
const GlobalValue &GV,
const Mangler &Mang, StringRef SearchName,
bool ExportedSymbolsOnly) const {
// Modules don't "provide" decls or common symbols.
if (GV.isDeclaration() || GV.hasCommonLinkage())
return nullptr;
// Mangle the GV name.
std::string MangledName;
raw_string_ostream MangledNameStream(MangledName);
Mang.getNameWithPrefix(MangledNameStream, &GV, false);
// Check whether this is the name we were searching for, and if it is then
// bail out early.
if (MangledName == SearchName)
if (!ExportedSymbolsOnly || GV.hasDefaultVisibility())
return &GV;
// Otherwise add this to the map for later.
Names[MangledName] = &GV;
return nullptr;
// Build the MangledSymbols map. Bails out early (with MangledSymbols left set
// to nullptr) if the given SearchName is found while building the map.
const GlobalValue* buildMangledSymbols(StringRef SearchName,
bool ExportedSymbolsOnly) const {
assert(!MangledSymbols && "Mangled symbols map already exists?");
auto Symbols = std::make_unique<StringMap<const GlobalValue*>>();
Mangler Mang;
for (const auto &GO : M->global_objects())
if (auto GV = addGlobalValue(*Symbols, GO, Mang, SearchName,
return GV;
MangledSymbols = std::move(Symbols);
return nullptr;
enum { NotEmitted, Emitting, Emitted } EmitState = NotEmitted;
VModuleKey K;
std::unique_ptr<Module> M;
mutable std::unique_ptr<StringMap<const GlobalValue*>> MangledSymbols;
BaseLayerT &BaseLayer;
std::map<VModuleKey, std::unique_ptr<EmissionDeferredModule>> ModuleMap;
/// Construct a lazy emitting layer.
LazyEmittingLayer(BaseLayerT &BaseLayer),
"ORCv1 layers (including LazyEmittingLayer) are deprecated. Please use "
"ORCv2, where lazy emission is the default");
/// Construct a lazy emitting layer.
LazyEmittingLayer(ORCv1DeprecationAcknowledgement, BaseLayerT &BaseLayer)
: BaseLayer(BaseLayer) {}
/// Add the given module to the lazy emitting layer.
Error addModule(VModuleKey K, std::unique_ptr<Module> M) {
assert(!ModuleMap.count(K) && "VModuleKey K already in use");
ModuleMap[K] =
std::make_unique<EmissionDeferredModule>(std::move(K), std::move(M));
return Error::success();
/// Remove the module represented by the given handle.
/// This method will free the memory associated with the given module, both
/// in this layer, and the base layer.
Error removeModule(VModuleKey K) {
auto I = ModuleMap.find(K);
assert(I != ModuleMap.end() && "VModuleKey K not valid here");
auto EDM = std::move(I.second);
return EDM->removeModuleFromBaseLayer(BaseLayer);
/// Search for the given named symbol.
/// @param Name The name of the symbol to search for.
/// @param ExportedSymbolsOnly If true, search only for exported symbols.
/// @return A handle for the given named symbol, if it exists.
JITSymbol findSymbol(const std::string &Name, bool ExportedSymbolsOnly) {
// Look for the symbol among existing definitions.
if (auto Symbol = BaseLayer.findSymbol(Name, ExportedSymbolsOnly))
return Symbol;
// If not found then search the deferred modules. If any of these contain a
// definition of 'Name' then they will return a JITSymbol that will emit
// the corresponding module when the symbol address is requested.
for (auto &KV : ModuleMap)
if (auto Symbol = KV.second->find(Name, ExportedSymbolsOnly, BaseLayer))
return Symbol;
// If no definition found anywhere return a null symbol.
return nullptr;
/// Get the address of the given symbol in the context of the of
/// compiled modules represented by the key K.
JITSymbol findSymbolIn(VModuleKey K, const std::string &Name,
bool ExportedSymbolsOnly) {
assert(ModuleMap.count(K) && "VModuleKey K not valid here");
return ModuleMap[K]->find(Name, ExportedSymbolsOnly, BaseLayer);
/// Immediately emit and finalize the module represented by the given
/// key.
Error emitAndFinalize(VModuleKey K) {
assert(ModuleMap.count(K) && "VModuleKey K not valid here");
return ModuleMap[K]->emitAndFinalize(BaseLayer);
template <typename BaseLayerT>
LazyEmittingLayer<BaseLayerT>::LazyEmittingLayer(BaseLayerT &BaseLayer)
: BaseLayer(BaseLayer) {}
} // end namespace orc
} // end namespace llvm