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