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/StringRef.h"
18 #include "llvm/IR/DiagnosticInfo.h"
19 #include "llvm/IR/Function.h"
20 #include "llvm/IR/GlobalAlias.h"
21 #include "llvm/IR/GlobalValue.h"
22 #include "llvm/IR/GlobalVariable.h"
23 #include "llvm/IR/InlineAsm.h"
24 #include "llvm/IR/Module.h"
25 #include "llvm/MC/MCAsmInfo.h"
26 #include "llvm/MC/MCContext.h"
27 #include "llvm/MC/MCInstrInfo.h"
28 #include "llvm/MC/MCObjectFileInfo.h"
29 #include "llvm/MC/MCParser/MCAsmParser.h"
30 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
31 #include "llvm/MC/MCRegisterInfo.h"
32 #include "llvm/MC/MCSubtargetInfo.h"
33 #include "llvm/MC/MCSymbol.h"
34 #include "llvm/MC/MCTargetOptions.h"
35 #include "llvm/MC/TargetRegistry.h"
36 #include "llvm/Object/SymbolicFile.h"
37 #include "llvm/Support/Casting.h"
38 #include "llvm/Support/ErrorHandling.h"
39 #include "llvm/Support/MemoryBuffer.h"
40 #include "llvm/Support/SMLoc.h"
41 #include "llvm/Support/SourceMgr.h"
42 #include "llvm/Support/raw_ostream.h"
43 #include "llvm/TargetParser/Triple.h"
44 #include <cassert>
45 #include <cstdint>
46 #include <memory>
47 #include <string>
48
49 using namespace llvm;
50 using namespace object;
51
addModule(Module * M)52 void ModuleSymbolTable::addModule(Module *M) {
53 if (FirstMod)
54 assert(FirstMod->getTargetTriple() == M->getTargetTriple());
55 else
56 FirstMod = M;
57
58 for (GlobalValue &GV : M->global_values())
59 SymTab.push_back(&GV);
60
61 CollectAsmSymbols(*M, [this](StringRef Name, BasicSymbolRef::Flags Flags) {
62 SymTab.push_back(new (AsmSymbols.Allocate())
63 AsmSymbol(std::string(Name), Flags));
64 });
65 }
66
67 static void
initializeRecordStreamer(const Module & M,function_ref<void (RecordStreamer &)> Init)68 initializeRecordStreamer(const Module &M,
69 function_ref<void(RecordStreamer &)> Init) {
70 // This function may be called twice, once for ModuleSummaryIndexAnalysis and
71 // the other when writing the IR symbol table. If parsing inline assembly has
72 // caused errors in the first run, suppress the second run.
73 if (M.getContext().getDiagHandlerPtr()->HasErrors)
74 return;
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, 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(
103 MemoryBuffer::getMemBuffer(InlineAsm, "<inline asm>"));
104 SourceMgr SrcMgr;
105 SrcMgr.AddNewSourceBuffer(std::move(Buffer), SMLoc());
106
107 MCContext MCCtx(TT, MAI.get(), MRI.get(), STI.get(), &SrcMgr);
108 std::unique_ptr<MCObjectFileInfo> MOFI(
109 T->createMCObjectFileInfo(MCCtx, /*PIC=*/false));
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 MCCtx.setDiagnosticHandler([&](const SMDiagnostic &SMD, bool IsInlineAsm,
123 const SourceMgr &SrcMgr,
124 std::vector<const MDNode *> &LocInfos) {
125 M.getContext().diagnose(
126 DiagnosticInfoSrcMgr(SMD, M.getName(), IsInlineAsm, /*LocCookie=*/0));
127 });
128
129 // Module-level inline asm is assumed to use At&t syntax (see
130 // AsmPrinter::doInitialization()).
131 Parser->setAssemblerDialect(InlineAsm::AD_ATT);
132
133 Parser->setTargetParser(*TAP);
134 if (Parser->Run(false))
135 return;
136
137 Init(Streamer);
138 }
139
CollectAsmSymbols(const Module & M,function_ref<void (StringRef,BasicSymbolRef::Flags)> AsmSymbol)140 void ModuleSymbolTable::CollectAsmSymbols(
141 const Module &M,
142 function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmSymbol) {
143 initializeRecordStreamer(M, [&](RecordStreamer &Streamer) {
144 Streamer.flushSymverDirectives();
145
146 for (auto &KV : Streamer) {
147 StringRef Key = KV.first();
148 RecordStreamer::State Value = KV.second;
149 // FIXME: For now we just assume that all asm symbols are executable.
150 uint32_t Res = BasicSymbolRef::SF_Executable;
151 switch (Value) {
152 case RecordStreamer::NeverSeen:
153 llvm_unreachable("NeverSeen should have been replaced earlier");
154 case RecordStreamer::DefinedGlobal:
155 Res |= BasicSymbolRef::SF_Global;
156 break;
157 case RecordStreamer::Defined:
158 break;
159 case RecordStreamer::Global:
160 case RecordStreamer::Used:
161 Res |= BasicSymbolRef::SF_Undefined;
162 Res |= BasicSymbolRef::SF_Global;
163 break;
164 case RecordStreamer::DefinedWeak:
165 Res |= BasicSymbolRef::SF_Weak;
166 Res |= BasicSymbolRef::SF_Global;
167 break;
168 case RecordStreamer::UndefinedWeak:
169 Res |= BasicSymbolRef::SF_Weak;
170 Res |= BasicSymbolRef::SF_Undefined;
171 }
172 AsmSymbol(Key, BasicSymbolRef::Flags(Res));
173 }
174 });
175
176 // In ELF, object code generated for x86-32 and some code models of x86-64 may
177 // reference the special symbol _GLOBAL_OFFSET_TABLE_ that is not used in the
178 // IR. Record it like inline asm symbols.
179 Triple TT(M.getTargetTriple());
180 if (!TT.isOSBinFormatELF() || !TT.isX86())
181 return;
182 auto CM = M.getCodeModel();
183 if (TT.getArch() == Triple::x86 || CM == CodeModel::Medium ||
184 CM == CodeModel::Large) {
185 AsmSymbol("_GLOBAL_OFFSET_TABLE_",
186 BasicSymbolRef::Flags(BasicSymbolRef::SF_Undefined |
187 BasicSymbolRef::SF_Global));
188 }
189 }
190
CollectAsmSymvers(const Module & M,function_ref<void (StringRef,StringRef)> AsmSymver)191 void ModuleSymbolTable::CollectAsmSymvers(
192 const Module &M, function_ref<void(StringRef, StringRef)> AsmSymver) {
193 initializeRecordStreamer(M, [&](RecordStreamer &Streamer) {
194 for (auto &KV : Streamer.symverAliases())
195 for (auto &Alias : KV.second)
196 AsmSymver(KV.first->getName(), Alias);
197 });
198 }
199
printSymbolName(raw_ostream & OS,Symbol S) const200 void ModuleSymbolTable::printSymbolName(raw_ostream &OS, Symbol S) const {
201 if (isa<AsmSymbol *>(S)) {
202 OS << cast<AsmSymbol *>(S)->first;
203 return;
204 }
205
206 auto *GV = cast<GlobalValue *>(S);
207 if (GV->hasDLLImportStorageClass())
208 OS << "__imp_";
209
210 Mang.getNameWithPrefix(OS, GV, false);
211 }
212
getSymbolFlags(Symbol S) const213 uint32_t ModuleSymbolTable::getSymbolFlags(Symbol S) const {
214 if (isa<AsmSymbol *>(S))
215 return cast<AsmSymbol *>(S)->second;
216
217 auto *GV = cast<GlobalValue *>(S);
218
219 uint32_t Res = BasicSymbolRef::SF_None;
220 if (GV->isDeclarationForLinker())
221 Res |= BasicSymbolRef::SF_Undefined;
222 else if (GV->hasHiddenVisibility() && !GV->hasLocalLinkage())
223 Res |= BasicSymbolRef::SF_Hidden;
224 if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
225 if (GVar->isConstant())
226 Res |= BasicSymbolRef::SF_Const;
227 }
228 if (const GlobalObject *GO = GV->getAliaseeObject())
229 if (isa<Function>(GO) || isa<GlobalIFunc>(GO))
230 Res |= BasicSymbolRef::SF_Executable;
231 if (isa<GlobalAlias>(GV))
232 Res |= BasicSymbolRef::SF_Indirect;
233 if (GV->hasPrivateLinkage())
234 Res |= BasicSymbolRef::SF_FormatSpecific;
235 if (!GV->hasLocalLinkage())
236 Res |= BasicSymbolRef::SF_Global;
237 if (GV->hasCommonLinkage())
238 Res |= BasicSymbolRef::SF_Common;
239 if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
240 GV->hasExternalWeakLinkage())
241 Res |= BasicSymbolRef::SF_Weak;
242
243 if (GV->getName().starts_with("llvm."))
244 Res |= BasicSymbolRef::SF_FormatSpecific;
245 else if (auto *Var = dyn_cast<GlobalVariable>(GV)) {
246 if (Var->getSection() == "llvm.metadata")
247 Res |= BasicSymbolRef::SF_FormatSpecific;
248 }
249
250 return Res;
251 }
252