include/llvm/ExecutionEngine/Orc/LazyEmittingLayer.h

   1 //===- LazyEmittingLayer.h - Lazily emit IR to lower JIT layers -*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Contains the definition for a lazy-emitting layer for the JIT.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_EXECUTIONENGINE_ORC_LAZYEMITTINGLAYER_H
  14 #define LLVM_EXECUTIONENGINE_ORC_LAZYEMITTINGLAYER_H
  15
  16 #include "llvm/ADT/STLExtras.h"
  17 #include "llvm/ADT/StringMap.h"
  18 #include "llvm/ADT/StringRef.h"
  19 #include "llvm/ExecutionEngine/JITSymbol.h"
  20 #include "llvm/ExecutionEngine/Orc/Core.h"
  21 #include "llvm/IR/GlobalValue.h"
  22 #include "llvm/IR/Mangler.h"
  23 #include "llvm/IR/Module.h"
  24 #include "llvm/Support/ErrorHandling.h"
  25 #include "llvm/Support/raw_ostream.h"
  26 #include <algorithm>
  27 #include <cassert>
  28 #include <list>
  29 #include <memory>
  30 #include <string>
  31
  32 namespace llvm {
  33 namespace orc {
  34
  35 /// Lazy-emitting IR layer.
  36 ///
  37 ///   This layer accepts LLVM IR Modules (via addModule) but does not
  38 /// immediately emit them the layer below. Instead, emission to the base layer
  39 /// is deferred until the first time the client requests the address (via
  40 /// JITSymbol::getAddress) for a symbol contained in this layer.
  41 template <typename BaseLayerT> class LazyEmittingLayer {
  42 private:
  43   class EmissionDeferredModule {
  44   public:
  45     EmissionDeferredModule(VModuleKey K, std::unique_ptr<Module> M)
  46         : K(std::move(K)), M(std::move(M)) {}
  47
  48     JITSymbol find(StringRef Name, bool ExportedSymbolsOnly, BaseLayerT &B) {
  49       switch (EmitState) {
  50       case NotEmitted:
  51         if (auto GV = searchGVs(Name, ExportedSymbolsOnly)) {
  52           JITSymbolFlags Flags = JITSymbolFlags::fromGlobalValue(*GV);
  53           auto GetAddress = [this, ExportedSymbolsOnly, Name = Name.str(),
  54                              &B]() -> Expected<JITTargetAddress> {
  55             if (this->EmitState == Emitting)
  56               return 0;
  57             else if (this->EmitState == NotEmitted) {
  58               this->EmitState = Emitting;
  59               if (auto Err = this->emitToBaseLayer(B))
  60                 return std::move(Err);
  61               this->EmitState = Emitted;
  62             }
  63             if (auto Sym = B.findSymbolIn(K, Name, ExportedSymbolsOnly))
  64               return Sym.getAddress();
  65             else if (auto Err = Sym.takeError())
  66               return std::move(Err);
  67             else
  68               llvm_unreachable("Successful symbol lookup should return "
  69                                "definition address here");
  70           };
  71           return JITSymbol(std::move(GetAddress), Flags);
  72         } else
  73           return nullptr;
  74       case Emitting:
  75         // Calling "emit" can trigger a recursive call to 'find' (e.g. to check
  76         // for pre-existing definitions of common-symbol), but any symbol in
  77         // this module would already have been found internally (in the
  78         // RuntimeDyld that did the lookup), so just return a nullptr here.
  79         return nullptr;
  80       case Emitted:
  81         return B.findSymbolIn(K, Name, ExportedSymbolsOnly);
  82       }
  83       llvm_unreachable("Invalid emit-state.");
  84     }
  85
  86     Error removeModuleFromBaseLayer(BaseLayerT& BaseLayer) {
  87       return EmitState != NotEmitted ? BaseLayer.removeModule(K)
  88                                      : Error::success();
  89     }
  90
  91     void emitAndFinalize(BaseLayerT &BaseLayer) {
  92       assert(EmitState != Emitting &&
  93              "Cannot emitAndFinalize while already emitting");
  94       if (EmitState == NotEmitted) {
  95         EmitState = Emitting;
  96         emitToBaseLayer(BaseLayer);
  97         EmitState = Emitted;
  98       }
  99       BaseLayer.emitAndFinalize(K);
 100     }
 101
 102   private:
 103
 104     const GlobalValue* searchGVs(StringRef Name,
 105                                  bool ExportedSymbolsOnly) const {
 106       // FIXME: We could clean all this up if we had a way to reliably demangle
 107       //        names: We could just demangle name and search, rather than
 108       //        mangling everything else.
 109
 110       // If we have already built the mangled name set then just search it.
 111       if (MangledSymbols) {
 112         auto VI = MangledSymbols->find(Name);
 113         if (VI == MangledSymbols->end())
 114           return nullptr;
 115         auto GV = VI->second;
 116         if (!ExportedSymbolsOnly || GV->hasDefaultVisibility())
 117           return GV;
 118         return nullptr;
 119       }
 120
 121       // If we haven't built the mangled name set yet, try to build it. As an
 122       // optimization this will leave MangledNames set to nullptr if we find
 123       // Name in the process of building the set.
 124       return buildMangledSymbols(Name, ExportedSymbolsOnly);
 125     }
 126
 127     Error emitToBaseLayer(BaseLayerT &BaseLayer) {
 128       // We don't need the mangled names set any more: Once we've emitted this
 129       // to the base layer we'll just look for symbols there.
 130       MangledSymbols.reset();
 131       return BaseLayer.addModule(std::move(K), std::move(M));
 132     }
 133
 134     // If the mangled name of the given GlobalValue matches the given search
 135     // name (and its visibility conforms to the ExportedSymbolsOnly flag) then
 136     // return the symbol. Otherwise, add the mangled name to the Names map and
 137     // return nullptr.
 138     const GlobalValue* addGlobalValue(StringMap<const GlobalValue*> &Names,
 139                                       const GlobalValue &GV,
 140                                       const Mangler &Mang, StringRef SearchName,
 141                                       bool ExportedSymbolsOnly) const {
 142       // Modules don't "provide" decls or common symbols.
 143       if (GV.isDeclaration() || GV.hasCommonLinkage())
 144         return nullptr;
 145
 146       // Mangle the GV name.
 147       std::string MangledName;
 148       {
 149         raw_string_ostream MangledNameStream(MangledName);
 150         Mang.getNameWithPrefix(MangledNameStream, &GV, false);
 151       }
 152
 153       // Check whether this is the name we were searching for, and if it is then
 154       // bail out early.
 155       if (MangledName == SearchName)
 156         if (!ExportedSymbolsOnly || GV.hasDefaultVisibility())
 157           return &GV;
 158
 159       // Otherwise add this to the map for later.
 160       Names[MangledName] = &GV;
 161       return nullptr;
 162     }
 163
 164     // Build the MangledSymbols map. Bails out early (with MangledSymbols left set
 165     // to nullptr) if the given SearchName is found while building the map.
 166     const GlobalValue* buildMangledSymbols(StringRef SearchName,
 167                                            bool ExportedSymbolsOnly) const {
 168       assert(!MangledSymbols && "Mangled symbols map already exists?");
 169
 170       auto Symbols = std::make_unique<StringMap<const GlobalValue*>>();
 171
 172       Mangler Mang;
 173
 174       for (const auto &GO : M->global_objects())
 175           if (auto GV = addGlobalValue(*Symbols, GO, Mang, SearchName,
 176                                        ExportedSymbolsOnly))
 177             return GV;
 178
 179       MangledSymbols = std::move(Symbols);
 180       return nullptr;
 181     }
 182
 183     enum { NotEmitted, Emitting, Emitted } EmitState = NotEmitted;
 184     VModuleKey K;
 185     std::unique_ptr<Module> M;
 186     mutable std::unique_ptr<StringMap<const GlobalValue*>> MangledSymbols;
 187   };
 188
 189   BaseLayerT &BaseLayer;
 190   std::map<VModuleKey, std::unique_ptr<EmissionDeferredModule>> ModuleMap;
 191
 192 public:
 193
 194   /// Construct a lazy emitting layer.
 195   LLVM_ATTRIBUTE_DEPRECATED(
 196       LazyEmittingLayer(BaseLayerT &BaseLayer),
 197       "ORCv1 layers (including LazyEmittingLayer) are deprecated. Please use "
 198       "ORCv2, where lazy emission is the default");
 199
 200   /// Construct a lazy emitting layer.
 201   LazyEmittingLayer(ORCv1DeprecationAcknowledgement, BaseLayerT &BaseLayer)
 202       : BaseLayer(BaseLayer) {}
 203
 204   /// Add the given module to the lazy emitting layer.
 205   Error addModule(VModuleKey K, std::unique_ptr<Module> M) {
 206     assert(!ModuleMap.count(K) && "VModuleKey K already in use");
 207     ModuleMap[K] =
 208         std::make_unique<EmissionDeferredModule>(std::move(K), std::move(M));
 209     return Error::success();
 210   }
 211
 212   /// Remove the module represented by the given handle.
 213   ///
 214   ///   This method will free the memory associated with the given module, both
 215   /// in this layer, and the base layer.
 216   Error removeModule(VModuleKey K) {
 217     auto I = ModuleMap.find(K);
 218     assert(I != ModuleMap.end() && "VModuleKey K not valid here");
 219     auto EDM = std::move(I.second);
 220     ModuleMap.erase(I);
 221     return EDM->removeModuleFromBaseLayer(BaseLayer);
 222   }
 223
 224   /// Search for the given named symbol.
 225   /// @param Name The name of the symbol to search for.
 226   /// @param ExportedSymbolsOnly If true, search only for exported symbols.
 227   /// @return A handle for the given named symbol, if it exists.
 228   JITSymbol findSymbol(const std::string &Name, bool ExportedSymbolsOnly) {
 229     // Look for the symbol among existing definitions.
 230     if (auto Symbol = BaseLayer.findSymbol(Name, ExportedSymbolsOnly))
 231       return Symbol;
 232
 233     // If not found then search the deferred modules. If any of these contain a
 234     // definition of 'Name' then they will return a JITSymbol that will emit
 235     // the corresponding module when the symbol address is requested.
 236     for (auto &KV : ModuleMap)
 237       if (auto Symbol = KV.second->find(Name, ExportedSymbolsOnly, BaseLayer))
 238         return Symbol;
 239
 240     // If no definition found anywhere return a null symbol.
 241     return nullptr;
 242   }
 243
 244   /// Get the address of the given symbol in the context of the of
 245   ///        compiled modules represented by the key K.
 246   JITSymbol findSymbolIn(VModuleKey K, const std::string &Name,
 247                          bool ExportedSymbolsOnly) {
 248     assert(ModuleMap.count(K) && "VModuleKey K not valid here");
 249     return ModuleMap[K]->find(Name, ExportedSymbolsOnly, BaseLayer);
 250   }
 251
 252   /// Immediately emit and finalize the module represented by the given
 253   ///        key.
 254   Error emitAndFinalize(VModuleKey K) {
 255     assert(ModuleMap.count(K) && "VModuleKey K not valid here");
 256     return ModuleMap[K]->emitAndFinalize(BaseLayer);
 257   }
 258 };
 259
 260 template <typename BaseLayerT>
 261 LazyEmittingLayer<BaseLayerT>::LazyEmittingLayer(BaseLayerT &BaseLayer)
 262     : BaseLayer(BaseLayer) {}
 263
 264 } // end namespace orc
 265 } // end namespace llvm
 266
 267 #endif // LLVM_EXECUTIONENGINE_ORC_LAZYEMITTINGLAYER_H