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 
addModule(Module * M)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
initializeRecordStreamer(const Module & M,function_ref<void (RecordStreamer &)> Init)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   MCContext MCCtx(TT, MAI.get(), MRI.get(), STI.get());
103   std::unique_ptr<MCObjectFileInfo> MOFI(
104       T->createMCObjectFileInfo(MCCtx, /*PIC=*/false));
105   MOFI->setSDKVersion(M.getSDKVersion());
106   MCCtx.setObjectFileInfo(MOFI.get());
107   RecordStreamer Streamer(MCCtx, M);
108   T->createNullTargetStreamer(Streamer);
109 
110   std::unique_ptr<MemoryBuffer> Buffer(MemoryBuffer::getMemBuffer(InlineAsm));
111   SourceMgr SrcMgr;
112   SrcMgr.AddNewSourceBuffer(std::move(Buffer), SMLoc());
113   std::unique_ptr<MCAsmParser> Parser(
114       createMCAsmParser(SrcMgr, MCCtx, Streamer, *MAI));
115 
116   std::unique_ptr<MCTargetAsmParser> TAP(
117       T->createMCAsmParser(*STI, *Parser, *MCII, MCOptions));
118   if (!TAP)
119     return;
120 
121   // Module-level inline asm is assumed to use At&t syntax (see
122   // AsmPrinter::doInitialization()).
123   Parser->setAssemblerDialect(InlineAsm::AD_ATT);
124 
125   Parser->setTargetParser(*TAP);
126   if (Parser->Run(false))
127     return;
128 
129   Init(Streamer);
130 }
131 
CollectAsmSymbols(const Module & M,function_ref<void (StringRef,BasicSymbolRef::Flags)> AsmSymbol)132 void ModuleSymbolTable::CollectAsmSymbols(
133     const Module &M,
134     function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmSymbol) {
135   initializeRecordStreamer(M, [&](RecordStreamer &Streamer) {
136     Streamer.flushSymverDirectives();
137 
138     for (auto &KV : Streamer) {
139       StringRef Key = KV.first();
140       RecordStreamer::State Value = KV.second;
141       // FIXME: For now we just assume that all asm symbols are executable.
142       uint32_t Res = BasicSymbolRef::SF_Executable;
143       switch (Value) {
144       case RecordStreamer::NeverSeen:
145         llvm_unreachable("NeverSeen should have been replaced earlier");
146       case RecordStreamer::DefinedGlobal:
147         Res |= BasicSymbolRef::SF_Global;
148         break;
149       case RecordStreamer::Defined:
150         break;
151       case RecordStreamer::Global:
152       case RecordStreamer::Used:
153         Res |= BasicSymbolRef::SF_Undefined;
154         Res |= BasicSymbolRef::SF_Global;
155         break;
156       case RecordStreamer::DefinedWeak:
157         Res |= BasicSymbolRef::SF_Weak;
158         Res |= BasicSymbolRef::SF_Global;
159         break;
160       case RecordStreamer::UndefinedWeak:
161         Res |= BasicSymbolRef::SF_Weak;
162         Res |= BasicSymbolRef::SF_Undefined;
163       }
164       AsmSymbol(Key, BasicSymbolRef::Flags(Res));
165     }
166   });
167 }
168 
CollectAsmSymvers(const Module & M,function_ref<void (StringRef,StringRef)> AsmSymver)169 void ModuleSymbolTable::CollectAsmSymvers(
170     const Module &M, function_ref<void(StringRef, StringRef)> AsmSymver) {
171   initializeRecordStreamer(M, [&](RecordStreamer &Streamer) {
172     for (auto &KV : Streamer.symverAliases())
173       for (auto &Alias : KV.second)
174         AsmSymver(KV.first->getName(), Alias);
175   });
176 }
177 
printSymbolName(raw_ostream & OS,Symbol S) const178 void ModuleSymbolTable::printSymbolName(raw_ostream &OS, Symbol S) const {
179   if (S.is<AsmSymbol *>()) {
180     OS << S.get<AsmSymbol *>()->first;
181     return;
182   }
183 
184   auto *GV = S.get<GlobalValue *>();
185   if (GV->hasDLLImportStorageClass())
186     OS << "__imp_";
187 
188   Mang.getNameWithPrefix(OS, GV, false);
189 }
190 
getSymbolFlags(Symbol S) const191 uint32_t ModuleSymbolTable::getSymbolFlags(Symbol S) const {
192   if (S.is<AsmSymbol *>())
193     return S.get<AsmSymbol *>()->second;
194 
195   auto *GV = S.get<GlobalValue *>();
196 
197   uint32_t Res = BasicSymbolRef::SF_None;
198   if (GV->isDeclarationForLinker())
199     Res |= BasicSymbolRef::SF_Undefined;
200   else if (GV->hasHiddenVisibility() && !GV->hasLocalLinkage())
201     Res |= BasicSymbolRef::SF_Hidden;
202   if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
203     if (GVar->isConstant())
204       Res |= BasicSymbolRef::SF_Const;
205   }
206   if (dyn_cast_or_null<Function>(GV->getBaseObject()))
207     Res |= BasicSymbolRef::SF_Executable;
208   if (isa<GlobalAlias>(GV))
209     Res |= BasicSymbolRef::SF_Indirect;
210   if (GV->hasPrivateLinkage())
211     Res |= BasicSymbolRef::SF_FormatSpecific;
212   if (!GV->hasLocalLinkage())
213     Res |= BasicSymbolRef::SF_Global;
214   if (GV->hasCommonLinkage())
215     Res |= BasicSymbolRef::SF_Common;
216   if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
217       GV->hasExternalWeakLinkage())
218     Res |= BasicSymbolRef::SF_Weak;
219 
220   if (GV->getName().startswith("llvm."))
221     Res |= BasicSymbolRef::SF_FormatSpecific;
222   else if (auto *Var = dyn_cast<GlobalVariable>(GV)) {
223     if (Var->getSection() == "llvm.metadata")
224       Res |= BasicSymbolRef::SF_FormatSpecific;
225   }
226 
227   return Res;
228 }
229