1 //===-------------------- Layer.cpp - Layer interfaces --------------------===//
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 #include "llvm/ExecutionEngine/Orc/Layer.h"
10 
11 #include "llvm/ExecutionEngine/Orc/DebugUtils.h"
12 #include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
13 #include "llvm/ExecutionEngine/Orc/ObjectFileInterface.h"
14 #include "llvm/IR/Constants.h"
15 #include "llvm/Support/Debug.h"
16 
17 #define DEBUG_TYPE "orc"
18 
19 namespace llvm {
20 namespace orc {
21 
22 IRLayer::~IRLayer() = default;
23 
24 Error IRLayer::add(ResourceTrackerSP RT, ThreadSafeModule TSM) {
25   assert(RT && "RT can not be null");
26   auto &JD = RT->getJITDylib();
27   return JD.define(std::make_unique<BasicIRLayerMaterializationUnit>(
28                        *this, *getManglingOptions(), std::move(TSM)),
29                    std::move(RT));
30 }
31 
32 IRMaterializationUnit::IRMaterializationUnit(
33     ExecutionSession &ES, const IRSymbolMapper::ManglingOptions &MO,
34     ThreadSafeModule TSM)
35     : MaterializationUnit(Interface()), TSM(std::move(TSM)) {
36 
37   assert(this->TSM && "Module must not be null");
38 
39   MangleAndInterner Mangle(ES, this->TSM.getModuleUnlocked()->getDataLayout());
40   this->TSM.withModuleDo([&](Module &M) {
41     for (auto &G : M.global_values()) {
42       // Skip globals that don't generate symbols.
43 
44       if (!G.hasName() || G.isDeclaration() || G.hasLocalLinkage() ||
45           G.hasAvailableExternallyLinkage() || G.hasAppendingLinkage())
46         continue;
47 
48       // thread locals generate different symbols depending on whether or not
49       // emulated TLS is enabled.
50       if (G.isThreadLocal() && MO.EmulatedTLS) {
51         auto &GV = cast<GlobalVariable>(G);
52 
53         auto Flags = JITSymbolFlags::fromGlobalValue(GV);
54 
55         auto EmuTLSV = Mangle(("__emutls_v." + GV.getName()).str());
56         SymbolFlags[EmuTLSV] = Flags;
57         SymbolToDefinition[EmuTLSV] = &GV;
58 
59         // If this GV has a non-zero initializer we'll need to emit an
60         // __emutls.t symbol too.
61         if (GV.hasInitializer()) {
62           const auto *InitVal = GV.getInitializer();
63 
64           // Skip zero-initializers.
65           if (isa<ConstantAggregateZero>(InitVal))
66             continue;
67           const auto *InitIntValue = dyn_cast<ConstantInt>(InitVal);
68           if (InitIntValue && InitIntValue->isZero())
69             continue;
70 
71           auto EmuTLST = Mangle(("__emutls_t." + GV.getName()).str());
72           SymbolFlags[EmuTLST] = Flags;
73         }
74         continue;
75       }
76 
77       // Otherwise we just need a normal linker mangling.
78       auto MangledName = Mangle(G.getName());
79       SymbolFlags[MangledName] = JITSymbolFlags::fromGlobalValue(G);
80       if (G.getComdat() &&
81           G.getComdat()->getSelectionKind() != Comdat::NoDeduplicate)
82         SymbolFlags[MangledName] |= JITSymbolFlags::Weak;
83       SymbolToDefinition[MangledName] = &G;
84     }
85 
86     // If we need an init symbol for this module then create one.
87     if (!getStaticInitGVs(M).empty()) {
88       size_t Counter = 0;
89 
90       do {
91         std::string InitSymbolName;
92         raw_string_ostream(InitSymbolName)
93             << "$." << M.getModuleIdentifier() << ".__inits." << Counter++;
94         InitSymbol = ES.intern(InitSymbolName);
95       } while (SymbolFlags.count(InitSymbol));
96 
97       SymbolFlags[InitSymbol] = JITSymbolFlags::MaterializationSideEffectsOnly;
98     }
99   });
100 }
101 
102 IRMaterializationUnit::IRMaterializationUnit(
103     ThreadSafeModule TSM, Interface I,
104     SymbolNameToDefinitionMap SymbolToDefinition)
105     : MaterializationUnit(std::move(I)), TSM(std::move(TSM)),
106       SymbolToDefinition(std::move(SymbolToDefinition)) {}
107 
108 StringRef IRMaterializationUnit::getName() const {
109   if (TSM)
110     return TSM.withModuleDo(
111         [](const Module &M) -> StringRef { return M.getModuleIdentifier(); });
112   return "<null module>";
113 }
114 
115 void IRMaterializationUnit::discard(const JITDylib &JD,
116                                     const SymbolStringPtr &Name) {
117   LLVM_DEBUG(JD.getExecutionSession().runSessionLocked([&]() {
118     dbgs() << "In " << JD.getName() << " discarding " << *Name << " from MU@"
119            << this << " (" << getName() << ")\n";
120   }););
121 
122   auto I = SymbolToDefinition.find(Name);
123   assert(I != SymbolToDefinition.end() &&
124          "Symbol not provided by this MU, or previously discarded");
125   assert(!I->second->isDeclaration() &&
126          "Discard should only apply to definitions");
127   I->second->setLinkage(GlobalValue::AvailableExternallyLinkage);
128   // According to the IR verifier, "Declaration[s] may not be in a Comdat!"
129   // Remove it, if this is a GlobalObject.
130   if (auto *GO = dyn_cast<GlobalObject>(I->second))
131     GO->setComdat(nullptr);
132   SymbolToDefinition.erase(I);
133 }
134 
135 BasicIRLayerMaterializationUnit::BasicIRLayerMaterializationUnit(
136     IRLayer &L, const IRSymbolMapper::ManglingOptions &MO, ThreadSafeModule TSM)
137     : IRMaterializationUnit(L.getExecutionSession(), MO, std::move(TSM)), L(L) {
138 }
139 
140 void BasicIRLayerMaterializationUnit::materialize(
141     std::unique_ptr<MaterializationResponsibility> R) {
142 
143   // Throw away the SymbolToDefinition map: it's not usable after we hand
144   // off the module.
145   SymbolToDefinition.clear();
146 
147   // If cloneToNewContextOnEmit is set, clone the module now.
148   if (L.getCloneToNewContextOnEmit())
149     TSM = cloneToNewContext(TSM);
150 
151 #ifndef NDEBUG
152   auto &ES = R->getTargetJITDylib().getExecutionSession();
153   auto &N = R->getTargetJITDylib().getName();
154 #endif // NDEBUG
155 
156   LLVM_DEBUG(ES.runSessionLocked(
157       [&]() { dbgs() << "Emitting, for " << N << ", " << *this << "\n"; }););
158   L.emit(std::move(R), std::move(TSM));
159   LLVM_DEBUG(ES.runSessionLocked([&]() {
160     dbgs() << "Finished emitting, for " << N << ", " << *this << "\n";
161   }););
162 }
163 
164 char ObjectLayer::ID;
165 
166 ObjectLayer::ObjectLayer(ExecutionSession &ES) : ES(ES) {}
167 
168 ObjectLayer::~ObjectLayer() = default;
169 
170 Error ObjectLayer::add(ResourceTrackerSP RT, std::unique_ptr<MemoryBuffer> O,
171                        MaterializationUnit::Interface I) {
172   assert(RT && "RT can not be null");
173   auto &JD = RT->getJITDylib();
174   return JD.define(std::make_unique<BasicObjectLayerMaterializationUnit>(
175                        *this, std::move(O), std::move(I)),
176                    std::move(RT));
177 }
178 
179 Error ObjectLayer::add(ResourceTrackerSP RT, std::unique_ptr<MemoryBuffer> O) {
180   auto I = getObjectFileInterface(getExecutionSession(), O->getMemBufferRef());
181   if (!I)
182     return I.takeError();
183   return add(std::move(RT), std::move(O), std::move(*I));
184 }
185 
186 Error ObjectLayer::add(JITDylib &JD, std::unique_ptr<MemoryBuffer> O) {
187   auto I = getObjectFileInterface(getExecutionSession(), O->getMemBufferRef());
188   if (!I)
189     return I.takeError();
190   return add(JD, std::move(O), std::move(*I));
191 }
192 
193 Expected<std::unique_ptr<BasicObjectLayerMaterializationUnit>>
194 BasicObjectLayerMaterializationUnit::Create(ObjectLayer &L,
195                                             std::unique_ptr<MemoryBuffer> O) {
196 
197   auto ObjInterface =
198       getObjectFileInterface(L.getExecutionSession(), O->getMemBufferRef());
199 
200   if (!ObjInterface)
201     return ObjInterface.takeError();
202 
203   return std::unique_ptr<BasicObjectLayerMaterializationUnit>(
204       new BasicObjectLayerMaterializationUnit(L, std::move(O),
205                                               std::move(*ObjInterface)));
206 }
207 
208 BasicObjectLayerMaterializationUnit::BasicObjectLayerMaterializationUnit(
209     ObjectLayer &L, std::unique_ptr<MemoryBuffer> O, Interface I)
210     : MaterializationUnit(std::move(I)), L(L), O(std::move(O)) {}
211 
212 StringRef BasicObjectLayerMaterializationUnit::getName() const {
213   if (O)
214     return O->getBufferIdentifier();
215   return "<null object>";
216 }
217 
218 void BasicObjectLayerMaterializationUnit::materialize(
219     std::unique_ptr<MaterializationResponsibility> R) {
220   L.emit(std::move(R), std::move(O));
221 }
222 
223 void BasicObjectLayerMaterializationUnit::discard(const JITDylib &JD,
224                                                   const SymbolStringPtr &Name) {
225   // This is a no-op for object files: Having removed 'Name' from SymbolFlags
226   // the symbol will be dead-stripped by the JIT linker.
227 }
228 
229 } // End namespace orc.
230 } // End namespace llvm.
231