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/StringRef.h"
19 #include "llvm/IR/DiagnosticInfo.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/IR/GlobalAlias.h"
22 #include "llvm/IR/GlobalValue.h"
23 #include "llvm/IR/GlobalVariable.h"
24 #include "llvm/IR/InlineAsm.h"
25 #include "llvm/IR/Module.h"
26 #include "llvm/MC/MCAsmInfo.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCInstrInfo.h"
29 #include "llvm/MC/MCObjectFileInfo.h"
30 #include "llvm/MC/MCParser/MCAsmParser.h"
31 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
32 #include "llvm/MC/MCRegisterInfo.h"
33 #include "llvm/MC/MCSubtargetInfo.h"
34 #include "llvm/MC/MCSymbol.h"
35 #include "llvm/MC/MCTargetOptions.h"
36 #include "llvm/MC/TargetRegistry.h"
37 #include "llvm/Object/SymbolicFile.h"
38 #include "llvm/Support/Casting.h"
39 #include "llvm/Support/ErrorHandling.h"
40 #include "llvm/Support/MemoryBuffer.h"
41 #include "llvm/Support/SMLoc.h"
42 #include "llvm/Support/SourceMgr.h"
43 #include "llvm/Support/raw_ostream.h"
44 #include "llvm/TargetParser/Triple.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 
addModule(Module * M)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
initializeRecordStreamer(const Module & M,function_ref<void (RecordStreamer &)> Init)70 initializeRecordStreamer(const Module &M,
71                          function_ref<void(RecordStreamer &)> Init) {
72   // This function may be called twice, once for ModuleSummaryIndexAnalysis and
73   // the other when writing the IR symbol table. If parsing inline assembly has
74   // caused errors in the first run, suppress the second run.
75   if (M.getContext().getDiagHandlerPtr()->HasErrors)
76     return;
77   StringRef InlineAsm = M.getModuleInlineAsm();
78   if (InlineAsm.empty())
79     return;
80 
81   std::string Err;
82   const Triple TT(M.getTargetTriple());
83   const Target *T = TargetRegistry::lookupTarget(TT.str(), Err);
84   assert(T && T->hasMCAsmParser());
85 
86   std::unique_ptr<MCRegisterInfo> MRI(T->createMCRegInfo(TT.str()));
87   if (!MRI)
88     return;
89 
90   MCTargetOptions MCOptions;
91   std::unique_ptr<MCAsmInfo> MAI(T->createMCAsmInfo(*MRI, TT.str(), MCOptions));
92   if (!MAI)
93     return;
94 
95   std::unique_ptr<MCSubtargetInfo> STI(
96       T->createMCSubtargetInfo(TT.str(), "", ""));
97   if (!STI)
98     return;
99 
100   std::unique_ptr<MCInstrInfo> MCII(T->createMCInstrInfo());
101   if (!MCII)
102     return;
103 
104   std::unique_ptr<MemoryBuffer> Buffer(
105       MemoryBuffer::getMemBuffer(InlineAsm, "<inline asm>"));
106   SourceMgr SrcMgr;
107   SrcMgr.AddNewSourceBuffer(std::move(Buffer), SMLoc());
108 
109   MCContext MCCtx(TT, MAI.get(), MRI.get(), STI.get(), &SrcMgr);
110   std::unique_ptr<MCObjectFileInfo> MOFI(
111       T->createMCObjectFileInfo(MCCtx, /*PIC=*/false));
112   MOFI->setSDKVersion(M.getSDKVersion());
113   MCCtx.setObjectFileInfo(MOFI.get());
114   RecordStreamer Streamer(MCCtx, M);
115   T->createNullTargetStreamer(Streamer);
116 
117   std::unique_ptr<MCAsmParser> Parser(
118       createMCAsmParser(SrcMgr, MCCtx, Streamer, *MAI));
119 
120   std::unique_ptr<MCTargetAsmParser> TAP(
121       T->createMCAsmParser(*STI, *Parser, *MCII, MCOptions));
122   if (!TAP)
123     return;
124 
125   MCCtx.setDiagnosticHandler([&](const SMDiagnostic &SMD, bool IsInlineAsm,
126                                  const SourceMgr &SrcMgr,
127                                  std::vector<const MDNode *> &LocInfos) {
128     M.getContext().diagnose(
129         DiagnosticInfoSrcMgr(SMD, M.getName(), IsInlineAsm, /*LocCookie=*/0));
130   });
131 
132   // Module-level inline asm is assumed to use At&t syntax (see
133   // AsmPrinter::doInitialization()).
134   Parser->setAssemblerDialect(InlineAsm::AD_ATT);
135 
136   Parser->setTargetParser(*TAP);
137   if (Parser->Run(false))
138     return;
139 
140   Init(Streamer);
141 }
142 
CollectAsmSymbols(const Module & M,function_ref<void (StringRef,BasicSymbolRef::Flags)> AsmSymbol)143 void ModuleSymbolTable::CollectAsmSymbols(
144     const Module &M,
145     function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmSymbol) {
146   initializeRecordStreamer(M, [&](RecordStreamer &Streamer) {
147     Streamer.flushSymverDirectives();
148 
149     for (auto &KV : Streamer) {
150       StringRef Key = KV.first();
151       RecordStreamer::State Value = KV.second;
152       // FIXME: For now we just assume that all asm symbols are executable.
153       uint32_t Res = BasicSymbolRef::SF_Executable;
154       switch (Value) {
155       case RecordStreamer::NeverSeen:
156         llvm_unreachable("NeverSeen should have been replaced earlier");
157       case RecordStreamer::DefinedGlobal:
158         Res |= BasicSymbolRef::SF_Global;
159         break;
160       case RecordStreamer::Defined:
161         break;
162       case RecordStreamer::Global:
163       case RecordStreamer::Used:
164         Res |= BasicSymbolRef::SF_Undefined;
165         Res |= BasicSymbolRef::SF_Global;
166         break;
167       case RecordStreamer::DefinedWeak:
168         Res |= BasicSymbolRef::SF_Weak;
169         Res |= BasicSymbolRef::SF_Global;
170         break;
171       case RecordStreamer::UndefinedWeak:
172         Res |= BasicSymbolRef::SF_Weak;
173         Res |= BasicSymbolRef::SF_Undefined;
174       }
175       AsmSymbol(Key, BasicSymbolRef::Flags(Res));
176     }
177   });
178 }
179 
CollectAsmSymvers(const Module & M,function_ref<void (StringRef,StringRef)> AsmSymver)180 void ModuleSymbolTable::CollectAsmSymvers(
181     const Module &M, function_ref<void(StringRef, StringRef)> AsmSymver) {
182   initializeRecordStreamer(M, [&](RecordStreamer &Streamer) {
183     for (auto &KV : Streamer.symverAliases())
184       for (auto &Alias : KV.second)
185         AsmSymver(KV.first->getName(), Alias);
186   });
187 }
188 
printSymbolName(raw_ostream & OS,Symbol S) const189 void ModuleSymbolTable::printSymbolName(raw_ostream &OS, Symbol S) const {
190   if (isa<AsmSymbol *>(S)) {
191     OS << cast<AsmSymbol *>(S)->first;
192     return;
193   }
194 
195   auto *GV = cast<GlobalValue *>(S);
196   if (GV->hasDLLImportStorageClass())
197     OS << "__imp_";
198 
199   Mang.getNameWithPrefix(OS, GV, false);
200 }
201 
getSymbolFlags(Symbol S) const202 uint32_t ModuleSymbolTable::getSymbolFlags(Symbol S) const {
203   if (isa<AsmSymbol *>(S))
204     return cast<AsmSymbol *>(S)->second;
205 
206   auto *GV = cast<GlobalValue *>(S);
207 
208   uint32_t Res = BasicSymbolRef::SF_None;
209   if (GV->isDeclarationForLinker())
210     Res |= BasicSymbolRef::SF_Undefined;
211   else if (GV->hasHiddenVisibility() && !GV->hasLocalLinkage())
212     Res |= BasicSymbolRef::SF_Hidden;
213   if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
214     if (GVar->isConstant())
215       Res |= BasicSymbolRef::SF_Const;
216   }
217   if (const GlobalObject *GO = GV->getAliaseeObject())
218     if (isa<Function>(GO) || isa<GlobalIFunc>(GO))
219       Res |= BasicSymbolRef::SF_Executable;
220   if (isa<GlobalAlias>(GV))
221     Res |= BasicSymbolRef::SF_Indirect;
222   if (GV->hasPrivateLinkage())
223     Res |= BasicSymbolRef::SF_FormatSpecific;
224   if (!GV->hasLocalLinkage())
225     Res |= BasicSymbolRef::SF_Global;
226   if (GV->hasCommonLinkage())
227     Res |= BasicSymbolRef::SF_Common;
228   if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
229       GV->hasExternalWeakLinkage())
230     Res |= BasicSymbolRef::SF_Weak;
231 
232   if (GV->getName().starts_with("llvm."))
233     Res |= BasicSymbolRef::SF_FormatSpecific;
234   else if (auto *Var = dyn_cast<GlobalVariable>(GV)) {
235     if (Var->getSection() == "llvm.metadata")
236       Res |= BasicSymbolRef::SF_FormatSpecific;
237   }
238 
239   return Res;
240 }
241