1 //===- ModuleSymbolTable.cpp - symbol table for in-memory IR --------------===//
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 // This class represents a symbol table built from in-memory IR. It provides
10 // access to GlobalValues and should only be used if such access is required
11 // (e.g. in the LTO implementation).
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/Object/ModuleSymbolTable.h"
16 #include "RecordStreamer.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/ADT/SmallString.h"
19 #include "llvm/ADT/StringMap.h"
20 #include "llvm/ADT/StringRef.h"
21 #include "llvm/ADT/Triple.h"
22 #include "llvm/IR/Function.h"
23 #include "llvm/IR/GlobalAlias.h"
24 #include "llvm/IR/GlobalValue.h"
25 #include "llvm/IR/GlobalVariable.h"
26 #include "llvm/IR/InlineAsm.h"
27 #include "llvm/IR/Module.h"
28 #include "llvm/MC/MCAsmInfo.h"
29 #include "llvm/MC/MCContext.h"
30 #include "llvm/MC/MCDirectives.h"
31 #include "llvm/MC/MCInstrInfo.h"
32 #include "llvm/MC/MCObjectFileInfo.h"
33 #include "llvm/MC/MCParser/MCAsmParser.h"
34 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
35 #include "llvm/MC/MCRegisterInfo.h"
36 #include "llvm/MC/MCSubtargetInfo.h"
37 #include "llvm/MC/MCSymbol.h"
38 #include "llvm/MC/MCTargetOptions.h"
39 #include "llvm/Object/SymbolicFile.h"
40 #include "llvm/Support/Casting.h"
41 #include "llvm/Support/CodeGen.h"
42 #include "llvm/Support/ErrorHandling.h"
43 #include "llvm/Support/MemoryBuffer.h"
44 #include "llvm/Support/SMLoc.h"
45 #include "llvm/Support/SourceMgr.h"
46 #include "llvm/Support/TargetRegistry.h"
47 #include "llvm/Support/raw_ostream.h"
48 #include <algorithm>
49 #include <cassert>
50 #include <cstdint>
51 #include <memory>
52 #include <string>
53 
54 using namespace llvm;
55 using namespace object;
56 
57 void ModuleSymbolTable::addModule(Module *M) {
58   if (FirstMod)
59     assert(FirstMod->getTargetTriple() == M->getTargetTriple());
60   else
61     FirstMod = M;
62 
63   for (GlobalValue &GV : M->global_values())
64     SymTab.push_back(&GV);
65 
66   CollectAsmSymbols(*M, [this](StringRef Name, BasicSymbolRef::Flags Flags) {
67     SymTab.push_back(new (AsmSymbols.Allocate())
68                          AsmSymbol(std::string(Name), Flags));
69   });
70 }
71 
72 static void
73 initializeRecordStreamer(const Module &M,
74                          function_ref<void(RecordStreamer &)> Init) {
75   StringRef InlineAsm = M.getModuleInlineAsm();
76   if (InlineAsm.empty())
77     return;
78 
79   std::string Err;
80   const Triple TT(M.getTargetTriple());
81   const Target *T = TargetRegistry::lookupTarget(TT.str(), Err);
82   assert(T && T->hasMCAsmParser());
83 
84   std::unique_ptr<MCRegisterInfo> MRI(T->createMCRegInfo(TT.str()));
85   if (!MRI)
86     return;
87 
88   MCTargetOptions MCOptions;
89   std::unique_ptr<MCAsmInfo> MAI(T->createMCAsmInfo(*MRI, TT.str(), MCOptions));
90   if (!MAI)
91     return;
92 
93   std::unique_ptr<MCSubtargetInfo> STI(
94       T->createMCSubtargetInfo(TT.str(), "", ""));
95   if (!STI)
96     return;
97 
98   std::unique_ptr<MCInstrInfo> MCII(T->createMCInstrInfo());
99   if (!MCII)
100     return;
101 
102   std::unique_ptr<MemoryBuffer> Buffer(MemoryBuffer::getMemBuffer(InlineAsm));
103   SourceMgr SrcMgr;
104   SrcMgr.AddNewSourceBuffer(std::move(Buffer), SMLoc());
105 
106   MCContext MCCtx(TT, MAI.get(), MRI.get(), STI.get(), &SrcMgr);
107   std::unique_ptr<MCObjectFileInfo> MOFI(
108       T->createMCObjectFileInfo(MCCtx, /*PIC=*/false));
109   MOFI->setSDKVersion(M.getSDKVersion());
110   MCCtx.setObjectFileInfo(MOFI.get());
111   RecordStreamer Streamer(MCCtx, M);
112   T->createNullTargetStreamer(Streamer);
113 
114   std::unique_ptr<MCAsmParser> Parser(
115       createMCAsmParser(SrcMgr, MCCtx, Streamer, *MAI));
116 
117   std::unique_ptr<MCTargetAsmParser> TAP(
118       T->createMCAsmParser(*STI, *Parser, *MCII, MCOptions));
119   if (!TAP)
120     return;
121 
122   // Module-level inline asm is assumed to use At&t syntax (see
123   // AsmPrinter::doInitialization()).
124   Parser->setAssemblerDialect(InlineAsm::AD_ATT);
125 
126   Parser->setTargetParser(*TAP);
127   if (Parser->Run(false))
128     return;
129 
130   Init(Streamer);
131 }
132 
133 void ModuleSymbolTable::CollectAsmSymbols(
134     const Module &M,
135     function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmSymbol) {
136   initializeRecordStreamer(M, [&](RecordStreamer &Streamer) {
137     Streamer.flushSymverDirectives();
138 
139     for (auto &KV : Streamer) {
140       StringRef Key = KV.first();
141       RecordStreamer::State Value = KV.second;
142       // FIXME: For now we just assume that all asm symbols are executable.
143       uint32_t Res = BasicSymbolRef::SF_Executable;
144       switch (Value) {
145       case RecordStreamer::NeverSeen:
146         llvm_unreachable("NeverSeen should have been replaced earlier");
147       case RecordStreamer::DefinedGlobal:
148         Res |= BasicSymbolRef::SF_Global;
149         break;
150       case RecordStreamer::Defined:
151         break;
152       case RecordStreamer::Global:
153       case RecordStreamer::Used:
154         Res |= BasicSymbolRef::SF_Undefined;
155         Res |= BasicSymbolRef::SF_Global;
156         break;
157       case RecordStreamer::DefinedWeak:
158         Res |= BasicSymbolRef::SF_Weak;
159         Res |= BasicSymbolRef::SF_Global;
160         break;
161       case RecordStreamer::UndefinedWeak:
162         Res |= BasicSymbolRef::SF_Weak;
163         Res |= BasicSymbolRef::SF_Undefined;
164       }
165       AsmSymbol(Key, BasicSymbolRef::Flags(Res));
166     }
167   });
168 }
169 
170 void ModuleSymbolTable::CollectAsmSymvers(
171     const Module &M, function_ref<void(StringRef, StringRef)> AsmSymver) {
172   initializeRecordStreamer(M, [&](RecordStreamer &Streamer) {
173     for (auto &KV : Streamer.symverAliases())
174       for (auto &Alias : KV.second)
175         AsmSymver(KV.first->getName(), Alias);
176   });
177 }
178 
179 void ModuleSymbolTable::printSymbolName(raw_ostream &OS, Symbol S) const {
180   if (S.is<AsmSymbol *>()) {
181     OS << S.get<AsmSymbol *>()->first;
182     return;
183   }
184 
185   auto *GV = S.get<GlobalValue *>();
186   if (GV->hasDLLImportStorageClass())
187     OS << "__imp_";
188 
189   Mang.getNameWithPrefix(OS, GV, false);
190 }
191 
192 uint32_t ModuleSymbolTable::getSymbolFlags(Symbol S) const {
193   if (S.is<AsmSymbol *>())
194     return S.get<AsmSymbol *>()->second;
195 
196   auto *GV = S.get<GlobalValue *>();
197 
198   uint32_t Res = BasicSymbolRef::SF_None;
199   if (GV->isDeclarationForLinker())
200     Res |= BasicSymbolRef::SF_Undefined;
201   else if (GV->hasHiddenVisibility() && !GV->hasLocalLinkage())
202     Res |= BasicSymbolRef::SF_Hidden;
203   if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
204     if (GVar->isConstant())
205       Res |= BasicSymbolRef::SF_Const;
206   }
207   if (dyn_cast_or_null<Function>(GV->getBaseObject()))
208     Res |= BasicSymbolRef::SF_Executable;
209   if (isa<GlobalAlias>(GV))
210     Res |= BasicSymbolRef::SF_Indirect;
211   if (GV->hasPrivateLinkage())
212     Res |= BasicSymbolRef::SF_FormatSpecific;
213   if (!GV->hasLocalLinkage())
214     Res |= BasicSymbolRef::SF_Global;
215   if (GV->hasCommonLinkage())
216     Res |= BasicSymbolRef::SF_Common;
217   if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
218       GV->hasExternalWeakLinkage())
219     Res |= BasicSymbolRef::SF_Weak;
220 
221   if (GV->getName().startswith("llvm."))
222     Res |= BasicSymbolRef::SF_FormatSpecific;
223   else if (auto *Var = dyn_cast<GlobalVariable>(GV)) {
224     if (Var->getSection() == "llvm.metadata")
225       Res |= BasicSymbolRef::SF_FormatSpecific;
226   }
227 
228   return Res;
229 }
230