Bug Summary

File:lib/MC/WasmObjectWriter.cpp
Warning:line 1391, column 9
Value stored to 'Index' is never read

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name WasmObjectWriter.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-8/lib/clang/8.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-8~svn350071/build-llvm/lib/MC -I /build/llvm-toolchain-snapshot-8~svn350071/lib/MC -I /build/llvm-toolchain-snapshot-8~svn350071/build-llvm/include -I /build/llvm-toolchain-snapshot-8~svn350071/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/include/clang/8.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-8/lib/clang/8.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-8~svn350071/build-llvm/lib/MC -fdebug-prefix-map=/build/llvm-toolchain-snapshot-8~svn350071=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2018-12-27-042839-1215-1 -x c++ /build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp -faddrsig
1//===- lib/MC/WasmObjectWriter.cpp - Wasm File Writer ---------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements Wasm object file writer information.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/ADT/STLExtras.h"
15#include "llvm/ADT/SmallPtrSet.h"
16#include "llvm/BinaryFormat/Wasm.h"
17#include "llvm/Config/llvm-config.h"
18#include "llvm/MC/MCAsmBackend.h"
19#include "llvm/MC/MCAsmLayout.h"
20#include "llvm/MC/MCAssembler.h"
21#include "llvm/MC/MCContext.h"
22#include "llvm/MC/MCExpr.h"
23#include "llvm/MC/MCFixupKindInfo.h"
24#include "llvm/MC/MCObjectWriter.h"
25#include "llvm/MC/MCSectionWasm.h"
26#include "llvm/MC/MCSymbolWasm.h"
27#include "llvm/MC/MCValue.h"
28#include "llvm/MC/MCWasmObjectWriter.h"
29#include "llvm/Support/Casting.h"
30#include "llvm/Support/Debug.h"
31#include "llvm/Support/ErrorHandling.h"
32#include "llvm/Support/LEB128.h"
33#include "llvm/Support/StringSaver.h"
34#include <vector>
35
36using namespace llvm;
37
38#define DEBUG_TYPE"mc" "mc"
39
40namespace {
41
42// Went we ceate the indirect function table we start at 1, so that there is
43// and emtpy slot at 0 and therefore calling a null function pointer will trap.
44static const uint32_t kInitialTableOffset = 1;
45
46// For patching purposes, we need to remember where each section starts, both
47// for patching up the section size field, and for patching up references to
48// locations within the section.
49struct SectionBookkeeping {
50 // Where the size of the section is written.
51 uint64_t SizeOffset;
52 // Where the section header ends (without custom section name).
53 uint64_t PayloadOffset;
54 // Where the contents of the section starts.
55 uint64_t ContentsOffset;
56 uint32_t Index;
57};
58
59// The signature of a wasm function or event, in a struct capable of being used
60// as a DenseMap key.
61// TODO: Consider using wasm::WasmSignature directly instead.
62struct WasmSignature {
63 // Support empty and tombstone instances, needed by DenseMap.
64 enum { Plain, Empty, Tombstone } State;
65
66 // The return types of the function.
67 SmallVector<wasm::ValType, 1> Returns;
68
69 // The parameter types of the function.
70 SmallVector<wasm::ValType, 4> Params;
71
72 WasmSignature() : State(Plain) {}
73
74 bool operator==(const WasmSignature &Other) const {
75 return State == Other.State && Returns == Other.Returns &&
76 Params == Other.Params;
77 }
78};
79
80// Traits for using WasmSignature in a DenseMap.
81struct WasmSignatureDenseMapInfo {
82 static WasmSignature getEmptyKey() {
83 WasmSignature Sig;
84 Sig.State = WasmSignature::Empty;
85 return Sig;
86 }
87 static WasmSignature getTombstoneKey() {
88 WasmSignature Sig;
89 Sig.State = WasmSignature::Tombstone;
90 return Sig;
91 }
92 static unsigned getHashValue(const WasmSignature &Sig) {
93 uintptr_t Value = Sig.State;
94 for (wasm::ValType Ret : Sig.Returns)
95 Value += DenseMapInfo<uint32_t>::getHashValue(uint32_t(Ret));
96 for (wasm::ValType Param : Sig.Params)
97 Value += DenseMapInfo<uint32_t>::getHashValue(uint32_t(Param));
98 return Value;
99 }
100 static bool isEqual(const WasmSignature &LHS, const WasmSignature &RHS) {
101 return LHS == RHS;
102 }
103};
104
105// A wasm data segment. A wasm binary contains only a single data section
106// but that can contain many segments, each with their own virtual location
107// in memory. Each MCSection data created by llvm is modeled as its own
108// wasm data segment.
109struct WasmDataSegment {
110 MCSectionWasm *Section;
111 StringRef Name;
112 uint32_t Offset;
113 uint32_t Alignment;
114 uint32_t Flags;
115 SmallVector<char, 4> Data;
116};
117
118// A wasm function to be written into the function section.
119struct WasmFunction {
120 uint32_t SigIndex;
121 const MCSymbolWasm *Sym;
122};
123
124// A wasm global to be written into the global section.
125struct WasmGlobal {
126 wasm::WasmGlobalType Type;
127 uint64_t InitialValue;
128};
129
130// Information about a single item which is part of a COMDAT. For each data
131// segment or function which is in the COMDAT, there is a corresponding
132// WasmComdatEntry.
133struct WasmComdatEntry {
134 unsigned Kind;
135 uint32_t Index;
136};
137
138// Information about a single relocation.
139struct WasmRelocationEntry {
140 uint64_t Offset; // Where is the relocation.
141 const MCSymbolWasm *Symbol; // The symbol to relocate with.
142 int64_t Addend; // A value to add to the symbol.
143 unsigned Type; // The type of the relocation.
144 const MCSectionWasm *FixupSection; // The section the relocation is targeting.
145
146 WasmRelocationEntry(uint64_t Offset, const MCSymbolWasm *Symbol,
147 int64_t Addend, unsigned Type,
148 const MCSectionWasm *FixupSection)
149 : Offset(Offset), Symbol(Symbol), Addend(Addend), Type(Type),
150 FixupSection(FixupSection) {}
151
152 bool hasAddend() const {
153 switch (Type) {
154 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
155 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
156 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
157 case wasm::R_WEBASSEMBLY_FUNCTION_OFFSET_I32:
158 case wasm::R_WEBASSEMBLY_SECTION_OFFSET_I32:
159 return true;
160 default:
161 return false;
162 }
163 }
164
165 void print(raw_ostream &Out) const {
166 Out << wasm::relocTypetoString(Type) << " Off=" << Offset
167 << ", Sym=" << *Symbol << ", Addend=" << Addend
168 << ", FixupSection=" << FixupSection->getSectionName();
169 }
170
171#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
172 LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void dump() const { print(dbgs()); }
173#endif
174};
175
176static const uint32_t INVALID_INDEX = -1;
177
178struct WasmCustomSection {
179
180 StringRef Name;
181 MCSectionWasm *Section;
182
183 uint32_t OutputContentsOffset;
184 uint32_t OutputIndex;
185
186 WasmCustomSection(StringRef Name, MCSectionWasm *Section)
187 : Name(Name), Section(Section), OutputContentsOffset(0),
188 OutputIndex(INVALID_INDEX) {}
189};
190
191#if !defined(NDEBUG)
192raw_ostream &operator<<(raw_ostream &OS, const WasmRelocationEntry &Rel) {
193 Rel.print(OS);
194 return OS;
195}
196#endif
197
198class WasmObjectWriter : public MCObjectWriter {
199 support::endian::Writer W;
200
201 /// The target specific Wasm writer instance.
202 std::unique_ptr<MCWasmObjectTargetWriter> TargetObjectWriter;
203
204 // Relocations for fixing up references in the code section.
205 std::vector<WasmRelocationEntry> CodeRelocations;
206 uint32_t CodeSectionIndex;
207
208 // Relocations for fixing up references in the data section.
209 std::vector<WasmRelocationEntry> DataRelocations;
210 uint32_t DataSectionIndex;
211
212 // Index values to use for fixing up call_indirect type indices.
213 // Maps function symbols to the index of the type of the function
214 DenseMap<const MCSymbolWasm *, uint32_t> TypeIndices;
215 // Maps function symbols to the table element index space. Used
216 // for TABLE_INDEX relocation types (i.e. address taken functions).
217 DenseMap<const MCSymbolWasm *, uint32_t> TableIndices;
218 // Maps function/global symbols to the function/global/event/section index
219 // space.
220 DenseMap<const MCSymbolWasm *, uint32_t> WasmIndices;
221 // Maps data symbols to the Wasm segment and offset/size with the segment.
222 DenseMap<const MCSymbolWasm *, wasm::WasmDataReference> DataLocations;
223
224 // Stores output data (index, relocations, content offset) for custom
225 // section.
226 std::vector<WasmCustomSection> CustomSections;
227 // Relocations for fixing up references in the custom sections.
228 DenseMap<const MCSectionWasm *, std::vector<WasmRelocationEntry>>
229 CustomSectionsRelocations;
230
231 // Map from section to defining function symbol.
232 DenseMap<const MCSection *, const MCSymbol *> SectionFunctions;
233
234 DenseMap<WasmSignature, uint32_t, WasmSignatureDenseMapInfo> SignatureIndices;
235 SmallVector<WasmSignature, 4> Signatures;
236 SmallVector<WasmGlobal, 4> Globals;
237 SmallVector<WasmDataSegment, 4> DataSegments;
238 unsigned NumFunctionImports = 0;
239 unsigned NumGlobalImports = 0;
240 unsigned NumEventImports = 0;
241 uint32_t SectionCount = 0;
242
243 // TargetObjectWriter wrappers.
244 bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
245 unsigned getRelocType(const MCValue &Target, const MCFixup &Fixup) const {
246 return TargetObjectWriter->getRelocType(Target, Fixup);
247 }
248
249 void startSection(SectionBookkeeping &Section, unsigned SectionId);
250 void startCustomSection(SectionBookkeeping &Section, StringRef Name);
251 void endSection(SectionBookkeeping &Section);
252
253public:
254 WasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW,
255 raw_pwrite_stream &OS)
256 : W(OS, support::little), TargetObjectWriter(std::move(MOTW)) {}
257
258 ~WasmObjectWriter() override;
259
260private:
261 void reset() override {
262 CodeRelocations.clear();
263 DataRelocations.clear();
264 TypeIndices.clear();
265 WasmIndices.clear();
266 TableIndices.clear();
267 DataLocations.clear();
268 CustomSectionsRelocations.clear();
269 SignatureIndices.clear();
270 Signatures.clear();
271 Globals.clear();
272 DataSegments.clear();
273 SectionFunctions.clear();
274 NumFunctionImports = 0;
275 NumGlobalImports = 0;
276 MCObjectWriter::reset();
277 }
278
279 void writeHeader(const MCAssembler &Asm);
280
281 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
282 const MCFragment *Fragment, const MCFixup &Fixup,
283 MCValue Target, uint64_t &FixedValue) override;
284
285 void executePostLayoutBinding(MCAssembler &Asm,
286 const MCAsmLayout &Layout) override;
287
288 uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
289
290 void writeString(const StringRef Str) {
291 encodeULEB128(Str.size(), W.OS);
292 W.OS << Str;
293 }
294
295 void writeValueType(wasm::ValType Ty) { W.OS << static_cast<char>(Ty); }
296
297 void writeTypeSection(ArrayRef<WasmSignature> Signatures);
298 void writeImportSection(ArrayRef<wasm::WasmImport> Imports, uint32_t DataSize,
299 uint32_t NumElements);
300 void writeFunctionSection(ArrayRef<WasmFunction> Functions);
301 void writeGlobalSection();
302 void writeExportSection(ArrayRef<wasm::WasmExport> Exports);
303 void writeElemSection(ArrayRef<uint32_t> TableElems);
304 void writeCodeSection(const MCAssembler &Asm, const MCAsmLayout &Layout,
305 ArrayRef<WasmFunction> Functions);
306 void writeDataSection();
307 void writeEventSection(ArrayRef<wasm::WasmEventType> Events);
308 void writeRelocSection(uint32_t SectionIndex, StringRef Name,
309 std::vector<WasmRelocationEntry> &Relocations);
310 void writeLinkingMetaDataSection(
311 ArrayRef<wasm::WasmSymbolInfo> SymbolInfos,
312 ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs,
313 const std::map<StringRef, std::vector<WasmComdatEntry>> &Comdats);
314 void writeCustomSections(const MCAssembler &Asm, const MCAsmLayout &Layout);
315 void writeCustomRelocSections();
316 void
317 updateCustomSectionRelocations(const SmallVector<WasmFunction, 4> &Functions,
318 const MCAsmLayout &Layout);
319
320 uint32_t getProvisionalValue(const WasmRelocationEntry &RelEntry);
321 void applyRelocations(ArrayRef<WasmRelocationEntry> Relocations,
322 uint64_t ContentsOffset);
323
324 uint32_t getRelocationIndexValue(const WasmRelocationEntry &RelEntry);
325 uint32_t getFunctionType(const MCSymbolWasm &Symbol);
326 uint32_t getEventType(const MCSymbolWasm &Symbol);
327 void registerFunctionType(const MCSymbolWasm &Symbol);
328 void registerEventType(const MCSymbolWasm &Symbol);
329};
330
331} // end anonymous namespace
332
333WasmObjectWriter::~WasmObjectWriter() {}
334
335// Write out a section header and a patchable section size field.
336void WasmObjectWriter::startSection(SectionBookkeeping &Section,
337 unsigned SectionId) {
338 LLVM_DEBUG(dbgs() << "startSection " << SectionId << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "startSection " << SectionId <<
"\n"; } } while (false)
;
339 W.OS << char(SectionId);
340
341 Section.SizeOffset = W.OS.tell();
342
343 // The section size. We don't know the size yet, so reserve enough space
344 // for any 32-bit value; we'll patch it later.
345 encodeULEB128(UINT32_MAX(4294967295U), W.OS);
346
347 // The position where the section starts, for measuring its size.
348 Section.ContentsOffset = W.OS.tell();
349 Section.PayloadOffset = W.OS.tell();
350 Section.Index = SectionCount++;
351}
352
353void WasmObjectWriter::startCustomSection(SectionBookkeeping &Section,
354 StringRef Name) {
355 LLVM_DEBUG(dbgs() << "startCustomSection " << Name << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "startCustomSection " << Name
<< "\n"; } } while (false)
;
356 startSection(Section, wasm::WASM_SEC_CUSTOM);
357
358 // The position where the section header ends, for measuring its size.
359 Section.PayloadOffset = W.OS.tell();
360
361 // Custom sections in wasm also have a string identifier.
362 writeString(Name);
363
364 // The position where the custom section starts.
365 Section.ContentsOffset = W.OS.tell();
366}
367
368// Now that the section is complete and we know how big it is, patch up the
369// section size field at the start of the section.
370void WasmObjectWriter::endSection(SectionBookkeeping &Section) {
371 uint64_t Size = W.OS.tell() - Section.PayloadOffset;
372 if (uint32_t(Size) != Size)
373 report_fatal_error("section size does not fit in a uint32_t");
374
375 LLVM_DEBUG(dbgs() << "endSection size=" << Size << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "endSection size=" << Size <<
"\n"; } } while (false)
;
376
377 // Write the final section size to the payload_len field, which follows
378 // the section id byte.
379 uint8_t Buffer[16];
380 unsigned SizeLen = encodeULEB128(Size, Buffer, 5);
381 assert(SizeLen == 5)((SizeLen == 5) ? static_cast<void> (0) : __assert_fail
("SizeLen == 5", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 381, __PRETTY_FUNCTION__))
;
382 static_cast<raw_pwrite_stream &>(W.OS).pwrite((char *)Buffer, SizeLen,
383 Section.SizeOffset);
384}
385
386// Emit the Wasm header.
387void WasmObjectWriter::writeHeader(const MCAssembler &Asm) {
388 W.OS.write(wasm::WasmMagic, sizeof(wasm::WasmMagic));
389 W.write<uint32_t>(wasm::WasmVersion);
390}
391
392void WasmObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
393 const MCAsmLayout &Layout) {
394 // Build a map of sections to the function that defines them, for use
395 // in recordRelocation.
396 for (const MCSymbol &S : Asm.symbols()) {
397 const auto &WS = static_cast<const MCSymbolWasm &>(S);
398 if (WS.isDefined() && WS.isFunction() && !WS.isVariable()) {
399 const auto &Sec = static_cast<const MCSectionWasm &>(S.getSection());
400 auto Pair = SectionFunctions.insert(std::make_pair(&Sec, &S));
401 if (!Pair.second)
402 report_fatal_error("section already has a defining function: " +
403 Sec.getSectionName());
404 }
405 }
406}
407
408void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
409 const MCAsmLayout &Layout,
410 const MCFragment *Fragment,
411 const MCFixup &Fixup, MCValue Target,
412 uint64_t &FixedValue) {
413 MCAsmBackend &Backend = Asm.getBackend();
414 bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
415 MCFixupKindInfo::FKF_IsPCRel;
416 const auto &FixupSection = cast<MCSectionWasm>(*Fragment->getParent());
417 uint64_t C = Target.getConstant();
418 uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
419 MCContext &Ctx = Asm.getContext();
420
421 // The .init_array isn't translated as data, so don't do relocations in it.
422 if (FixupSection.getSectionName().startswith(".init_array"))
423 return;
424
425 if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
426 assert(RefB->getKind() == MCSymbolRefExpr::VK_None &&((RefB->getKind() == MCSymbolRefExpr::VK_None && "Should not have constructed this"
) ? static_cast<void> (0) : __assert_fail ("RefB->getKind() == MCSymbolRefExpr::VK_None && \"Should not have constructed this\""
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 427, __PRETTY_FUNCTION__))
427 "Should not have constructed this")((RefB->getKind() == MCSymbolRefExpr::VK_None && "Should not have constructed this"
) ? static_cast<void> (0) : __assert_fail ("RefB->getKind() == MCSymbolRefExpr::VK_None && \"Should not have constructed this\""
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 427, __PRETTY_FUNCTION__))
;
428
429 // Let A, B and C being the components of Target and R be the location of
430 // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
431 // If it is pcrel, we want to compute (A - B + C - R).
432
433 // In general, Wasm has no relocations for -B. It can only represent (A + C)
434 // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
435 // replace B to implement it: (A - R - K + C)
436 if (IsPCRel) {
437 Ctx.reportError(
438 Fixup.getLoc(),
439 "No relocation available to represent this relative expression");
440 return;
441 }
442
443 const auto &SymB = cast<MCSymbolWasm>(RefB->getSymbol());
444
445 if (SymB.isUndefined()) {
446 Ctx.reportError(Fixup.getLoc(),
447 Twine("symbol '") + SymB.getName() +
448 "' can not be undefined in a subtraction expression");
449 return;
450 }
451
452 assert(!SymB.isAbsolute() && "Should have been folded")((!SymB.isAbsolute() && "Should have been folded") ? static_cast
<void> (0) : __assert_fail ("!SymB.isAbsolute() && \"Should have been folded\""
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 452, __PRETTY_FUNCTION__))
;
453 const MCSection &SecB = SymB.getSection();
454 if (&SecB != &FixupSection) {
455 Ctx.reportError(Fixup.getLoc(),
456 "Cannot represent a difference across sections");
457 return;
458 }
459
460 uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
461 uint64_t K = SymBOffset - FixupOffset;
462 IsPCRel = true;
463 C -= K;
464 }
465
466 // We either rejected the fixup or folded B into C at this point.
467 const MCSymbolRefExpr *RefA = Target.getSymA();
468 const auto *SymA = RefA ? cast<MCSymbolWasm>(&RefA->getSymbol()) : nullptr;
469
470 if (SymA && SymA->isVariable()) {
471 const MCExpr *Expr = SymA->getVariableValue();
472 const auto *Inner = cast<MCSymbolRefExpr>(Expr);
473 if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
474 llvm_unreachable("weakref used in reloc not yet implemented")::llvm::llvm_unreachable_internal("weakref used in reloc not yet implemented"
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 474)
;
475 }
476
477 // Put any constant offset in an addend. Offsets can be negative, and
478 // LLVM expects wrapping, in contrast to wasm's immediates which can't
479 // be negative and don't wrap.
480 FixedValue = 0;
481
482 unsigned Type = getRelocType(Target, Fixup);
483 assert(!IsPCRel)((!IsPCRel) ? static_cast<void> (0) : __assert_fail ("!IsPCRel"
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 483, __PRETTY_FUNCTION__))
;
484 assert(SymA)((SymA) ? static_cast<void> (0) : __assert_fail ("SymA"
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 484, __PRETTY_FUNCTION__))
;
485
486 // Absolute offset within a section or a function.
487 // Currently only supported for for metadata sections.
488 // See: test/MC/WebAssembly/blockaddress.ll
489 if (Type == wasm::R_WEBASSEMBLY_FUNCTION_OFFSET_I32 ||
490 Type == wasm::R_WEBASSEMBLY_SECTION_OFFSET_I32) {
491 if (!FixupSection.getKind().isMetadata())
492 report_fatal_error("relocations for function or section offsets are "
493 "only supported in metadata sections");
494
495 const MCSymbol *SectionSymbol = nullptr;
496 const MCSection &SecA = SymA->getSection();
497 if (SecA.getKind().isText())
498 SectionSymbol = SectionFunctions.find(&SecA)->second;
499 else
500 SectionSymbol = SecA.getBeginSymbol();
501 if (!SectionSymbol)
502 report_fatal_error("section symbol is required for relocation");
503
504 C += Layout.getSymbolOffset(*SymA);
505 SymA = cast<MCSymbolWasm>(SectionSymbol);
506 }
507
508 // Relocation other than R_WEBASSEMBLY_TYPE_INDEX_LEB are required to be
509 // against a named symbol.
510 if (Type != wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB) {
511 if (SymA->getName().empty())
512 report_fatal_error("relocations against un-named temporaries are not yet "
513 "supported by wasm");
514
515 SymA->setUsedInReloc();
516 }
517
518 WasmRelocationEntry Rec(FixupOffset, SymA, C, Type, &FixupSection);
519 LLVM_DEBUG(dbgs() << "WasmReloc: " << Rec << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "WasmReloc: " << Rec <<
"\n"; } } while (false)
;
520
521 if (FixupSection.isWasmData()) {
522 DataRelocations.push_back(Rec);
523 } else if (FixupSection.getKind().isText()) {
524 CodeRelocations.push_back(Rec);
525 } else if (FixupSection.getKind().isMetadata()) {
526 CustomSectionsRelocations[&FixupSection].push_back(Rec);
527 } else {
528 llvm_unreachable("unexpected section type")::llvm::llvm_unreachable_internal("unexpected section type", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 528)
;
529 }
530}
531
532// Write X as an (unsigned) LEB value at offset Offset in Stream, padded
533// to allow patching.
534static void WritePatchableLEB(raw_pwrite_stream &Stream, uint32_t X,
535 uint64_t Offset) {
536 uint8_t Buffer[5];
537 unsigned SizeLen = encodeULEB128(X, Buffer, 5);
538 assert(SizeLen == 5)((SizeLen == 5) ? static_cast<void> (0) : __assert_fail
("SizeLen == 5", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 538, __PRETTY_FUNCTION__))
;
539 Stream.pwrite((char *)Buffer, SizeLen, Offset);
540}
541
542// Write X as an signed LEB value at offset Offset in Stream, padded
543// to allow patching.
544static void WritePatchableSLEB(raw_pwrite_stream &Stream, int32_t X,
545 uint64_t Offset) {
546 uint8_t Buffer[5];
547 unsigned SizeLen = encodeSLEB128(X, Buffer, 5);
548 assert(SizeLen == 5)((SizeLen == 5) ? static_cast<void> (0) : __assert_fail
("SizeLen == 5", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 548, __PRETTY_FUNCTION__))
;
549 Stream.pwrite((char *)Buffer, SizeLen, Offset);
550}
551
552// Write X as a plain integer value at offset Offset in Stream.
553static void WriteI32(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset) {
554 uint8_t Buffer[4];
555 support::endian::write32le(Buffer, X);
556 Stream.pwrite((char *)Buffer, sizeof(Buffer), Offset);
557}
558
559static const MCSymbolWasm *ResolveSymbol(const MCSymbolWasm &Symbol) {
560 if (Symbol.isVariable()) {
561 const MCExpr *Expr = Symbol.getVariableValue();
562 auto *Inner = cast<MCSymbolRefExpr>(Expr);
563 return cast<MCSymbolWasm>(&Inner->getSymbol());
564 }
565 return &Symbol;
566}
567
568// Compute a value to write into the code at the location covered
569// by RelEntry. This value isn't used by the static linker; it just serves
570// to make the object format more readable and more likely to be directly
571// useable.
572uint32_t
573WasmObjectWriter::getProvisionalValue(const WasmRelocationEntry &RelEntry) {
574 switch (RelEntry.Type) {
575 case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
576 case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32: {
577 // Provisional value is table address of the resolved symbol itself
578 const MCSymbolWasm *Sym = ResolveSymbol(*RelEntry.Symbol);
579 assert(Sym->isFunction())((Sym->isFunction()) ? static_cast<void> (0) : __assert_fail
("Sym->isFunction()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 579, __PRETTY_FUNCTION__))
;
580 return TableIndices[Sym];
581 }
582 case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
583 // Provisional value is same as the index
584 return getRelocationIndexValue(RelEntry);
585 case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
586 case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
587 case wasm::R_WEBASSEMBLY_EVENT_INDEX_LEB:
588 // Provisional value is function/global/event Wasm index
589 if (!WasmIndices.count(RelEntry.Symbol))
590 report_fatal_error("symbol not found in wasm index space: " +
591 RelEntry.Symbol->getName());
592 return WasmIndices[RelEntry.Symbol];
593 case wasm::R_WEBASSEMBLY_FUNCTION_OFFSET_I32:
594 case wasm::R_WEBASSEMBLY_SECTION_OFFSET_I32: {
595 const auto &Section =
596 static_cast<const MCSectionWasm &>(RelEntry.Symbol->getSection());
597 return Section.getSectionOffset() + RelEntry.Addend;
598 }
599 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
600 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
601 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB: {
602 // Provisional value is address of the global
603 const MCSymbolWasm *Sym = ResolveSymbol(*RelEntry.Symbol);
604 // For undefined symbols, use zero
605 if (!Sym->isDefined())
606 return 0;
607 const wasm::WasmDataReference &Ref = DataLocations[Sym];
608 const WasmDataSegment &Segment = DataSegments[Ref.Segment];
609 // Ignore overflow. LLVM allows address arithmetic to silently wrap.
610 return Segment.Offset + Ref.Offset + RelEntry.Addend;
611 }
612 default:
613 llvm_unreachable("invalid relocation type")::llvm::llvm_unreachable_internal("invalid relocation type", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 613)
;
614 }
615}
616
617static void addData(SmallVectorImpl<char> &DataBytes,
618 MCSectionWasm &DataSection) {
619 LLVM_DEBUG(errs() << "addData: " << DataSection.getSectionName() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { errs() << "addData: " << DataSection.getSectionName
() << "\n"; } } while (false)
;
620
621 DataBytes.resize(alignTo(DataBytes.size(), DataSection.getAlignment()));
622
623 for (const MCFragment &Frag : DataSection) {
624 if (Frag.hasInstructions())
625 report_fatal_error("only data supported in data sections");
626
627 if (auto *Align = dyn_cast<MCAlignFragment>(&Frag)) {
628 if (Align->getValueSize() != 1)
629 report_fatal_error("only byte values supported for alignment");
630 // If nops are requested, use zeros, as this is the data section.
631 uint8_t Value = Align->hasEmitNops() ? 0 : Align->getValue();
632 uint64_t Size =
633 std::min<uint64_t>(alignTo(DataBytes.size(), Align->getAlignment()),
634 DataBytes.size() + Align->getMaxBytesToEmit());
635 DataBytes.resize(Size, Value);
636 } else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) {
637 int64_t NumValues;
638 if (!Fill->getNumValues().evaluateAsAbsolute(NumValues))
639 llvm_unreachable("The fill should be an assembler constant")::llvm::llvm_unreachable_internal("The fill should be an assembler constant"
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 639)
;
640 DataBytes.insert(DataBytes.end(), Fill->getValueSize() * NumValues,
641 Fill->getValue());
642 } else if (auto *LEB = dyn_cast<MCLEBFragment>(&Frag)) {
643 const SmallVectorImpl<char> &Contents = LEB->getContents();
644 DataBytes.insert(DataBytes.end(), Contents.begin(), Contents.end());
645 } else {
646 const auto &DataFrag = cast<MCDataFragment>(Frag);
647 const SmallVectorImpl<char> &Contents = DataFrag.getContents();
648 DataBytes.insert(DataBytes.end(), Contents.begin(), Contents.end());
649 }
650 }
651
652 LLVM_DEBUG(dbgs() << "addData -> " << DataBytes.size() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "addData -> " << DataBytes
.size() << "\n"; } } while (false)
;
653}
654
655uint32_t
656WasmObjectWriter::getRelocationIndexValue(const WasmRelocationEntry &RelEntry) {
657 if (RelEntry.Type == wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB) {
658 if (!TypeIndices.count(RelEntry.Symbol))
659 report_fatal_error("symbol not found in type index space: " +
660 RelEntry.Symbol->getName());
661 return TypeIndices[RelEntry.Symbol];
662 }
663
664 return RelEntry.Symbol->getIndex();
665}
666
667// Apply the portions of the relocation records that we can handle ourselves
668// directly.
669void WasmObjectWriter::applyRelocations(
670 ArrayRef<WasmRelocationEntry> Relocations, uint64_t ContentsOffset) {
671 auto &Stream = static_cast<raw_pwrite_stream &>(W.OS);
672 for (const WasmRelocationEntry &RelEntry : Relocations) {
673 uint64_t Offset = ContentsOffset +
674 RelEntry.FixupSection->getSectionOffset() +
675 RelEntry.Offset;
676
677 LLVM_DEBUG(dbgs() << "applyRelocation: " << RelEntry << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "applyRelocation: " << RelEntry
<< "\n"; } } while (false)
;
678 uint32_t Value = getProvisionalValue(RelEntry);
679
680 switch (RelEntry.Type) {
681 case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
682 case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
683 case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
684 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
685 case wasm::R_WEBASSEMBLY_EVENT_INDEX_LEB:
686 WritePatchableLEB(Stream, Value, Offset);
687 break;
688 case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
689 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
690 case wasm::R_WEBASSEMBLY_FUNCTION_OFFSET_I32:
691 case wasm::R_WEBASSEMBLY_SECTION_OFFSET_I32:
692 WriteI32(Stream, Value, Offset);
693 break;
694 case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
695 case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
696 WritePatchableSLEB(Stream, Value, Offset);
697 break;
698 default:
699 llvm_unreachable("invalid relocation type")::llvm::llvm_unreachable_internal("invalid relocation type", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 699)
;
700 }
701 }
702}
703
704void WasmObjectWriter::writeTypeSection(ArrayRef<WasmSignature> Signatures) {
705 if (Signatures.empty())
706 return;
707
708 SectionBookkeeping Section;
709 startSection(Section, wasm::WASM_SEC_TYPE);
710
711 encodeULEB128(Signatures.size(), W.OS);
712
713 for (const WasmSignature &Sig : Signatures) {
714 W.OS << char(wasm::WASM_TYPE_FUNC);
715 encodeULEB128(Sig.Params.size(), W.OS);
716 for (wasm::ValType Ty : Sig.Params)
717 writeValueType(Ty);
718 encodeULEB128(Sig.Returns.size(), W.OS);
719 for (wasm::ValType Ty : Sig.Returns)
720 writeValueType(Ty);
721 }
722
723 endSection(Section);
724}
725
726void WasmObjectWriter::writeImportSection(ArrayRef<wasm::WasmImport> Imports,
727 uint32_t DataSize,
728 uint32_t NumElements) {
729 if (Imports.empty())
730 return;
731
732 uint32_t NumPages = (DataSize + wasm::WasmPageSize - 1) / wasm::WasmPageSize;
733
734 SectionBookkeeping Section;
735 startSection(Section, wasm::WASM_SEC_IMPORT);
736
737 encodeULEB128(Imports.size(), W.OS);
738 for (const wasm::WasmImport &Import : Imports) {
739 writeString(Import.Module);
740 writeString(Import.Field);
741 W.OS << char(Import.Kind);
742
743 switch (Import.Kind) {
744 case wasm::WASM_EXTERNAL_FUNCTION:
745 encodeULEB128(Import.SigIndex, W.OS);
746 break;
747 case wasm::WASM_EXTERNAL_GLOBAL:
748 W.OS << char(Import.Global.Type);
749 W.OS << char(Import.Global.Mutable ? 1 : 0);
750 break;
751 case wasm::WASM_EXTERNAL_MEMORY:
752 encodeULEB128(0, W.OS); // flags
753 encodeULEB128(NumPages, W.OS); // initial
754 break;
755 case wasm::WASM_EXTERNAL_TABLE:
756 W.OS << char(Import.Table.ElemType);
757 encodeULEB128(0, W.OS); // flags
758 encodeULEB128(NumElements, W.OS); // initial
759 break;
760 case wasm::WASM_EXTERNAL_EVENT:
761 encodeULEB128(Import.Event.Attribute, W.OS);
762 encodeULEB128(Import.Event.SigIndex, W.OS);
763 break;
764 default:
765 llvm_unreachable("unsupported import kind")::llvm::llvm_unreachable_internal("unsupported import kind", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 765)
;
766 }
767 }
768
769 endSection(Section);
770}
771
772void WasmObjectWriter::writeFunctionSection(ArrayRef<WasmFunction> Functions) {
773 if (Functions.empty())
774 return;
775
776 SectionBookkeeping Section;
777 startSection(Section, wasm::WASM_SEC_FUNCTION);
778
779 encodeULEB128(Functions.size(), W.OS);
780 for (const WasmFunction &Func : Functions)
781 encodeULEB128(Func.SigIndex, W.OS);
782
783 endSection(Section);
784}
785
786void WasmObjectWriter::writeGlobalSection() {
787 if (Globals.empty())
788 return;
789
790 SectionBookkeeping Section;
791 startSection(Section, wasm::WASM_SEC_GLOBAL);
792
793 encodeULEB128(Globals.size(), W.OS);
794 for (const WasmGlobal &Global : Globals) {
795 writeValueType(static_cast<wasm::ValType>(Global.Type.Type));
796 W.OS << char(Global.Type.Mutable);
797
798 W.OS << char(wasm::WASM_OPCODE_I32_CONST);
799 encodeSLEB128(Global.InitialValue, W.OS);
800 W.OS << char(wasm::WASM_OPCODE_END);
801 }
802
803 endSection(Section);
804}
805
806void WasmObjectWriter::writeEventSection(ArrayRef<wasm::WasmEventType> Events) {
807 if (Events.empty())
808 return;
809
810 SectionBookkeeping Section;
811 startSection(Section, wasm::WASM_SEC_EVENT);
812
813 encodeULEB128(Events.size(), W.OS);
814 for (const wasm::WasmEventType &Event : Events) {
815 encodeULEB128(Event.Attribute, W.OS);
816 encodeULEB128(Event.SigIndex, W.OS);
817 }
818
819 endSection(Section);
820}
821
822void WasmObjectWriter::writeExportSection(ArrayRef<wasm::WasmExport> Exports) {
823 if (Exports.empty())
824 return;
825
826 SectionBookkeeping Section;
827 startSection(Section, wasm::WASM_SEC_EXPORT);
828
829 encodeULEB128(Exports.size(), W.OS);
830 for (const wasm::WasmExport &Export : Exports) {
831 writeString(Export.Name);
832 W.OS << char(Export.Kind);
833 encodeULEB128(Export.Index, W.OS);
834 }
835
836 endSection(Section);
837}
838
839void WasmObjectWriter::writeElemSection(ArrayRef<uint32_t> TableElems) {
840 if (TableElems.empty())
841 return;
842
843 SectionBookkeeping Section;
844 startSection(Section, wasm::WASM_SEC_ELEM);
845
846 encodeULEB128(1, W.OS); // number of "segments"
847 encodeULEB128(0, W.OS); // the table index
848
849 // init expr for starting offset
850 W.OS << char(wasm::WASM_OPCODE_I32_CONST);
851 encodeSLEB128(kInitialTableOffset, W.OS);
852 W.OS << char(wasm::WASM_OPCODE_END);
853
854 encodeULEB128(TableElems.size(), W.OS);
855 for (uint32_t Elem : TableElems)
856 encodeULEB128(Elem, W.OS);
857
858 endSection(Section);
859}
860
861void WasmObjectWriter::writeCodeSection(const MCAssembler &Asm,
862 const MCAsmLayout &Layout,
863 ArrayRef<WasmFunction> Functions) {
864 if (Functions.empty())
865 return;
866
867 SectionBookkeeping Section;
868 startSection(Section, wasm::WASM_SEC_CODE);
869 CodeSectionIndex = Section.Index;
870
871 encodeULEB128(Functions.size(), W.OS);
872
873 for (const WasmFunction &Func : Functions) {
874 auto &FuncSection = static_cast<MCSectionWasm &>(Func.Sym->getSection());
875
876 int64_t Size = 0;
877 if (!Func.Sym->getSize()->evaluateAsAbsolute(Size, Layout))
878 report_fatal_error(".size expression must be evaluatable");
879
880 encodeULEB128(Size, W.OS);
881 FuncSection.setSectionOffset(W.OS.tell() - Section.ContentsOffset);
882 Asm.writeSectionData(W.OS, &FuncSection, Layout);
883 }
884
885 // Apply fixups.
886 applyRelocations(CodeRelocations, Section.ContentsOffset);
887
888 endSection(Section);
889}
890
891void WasmObjectWriter::writeDataSection() {
892 if (DataSegments.empty())
893 return;
894
895 SectionBookkeeping Section;
896 startSection(Section, wasm::WASM_SEC_DATA);
897 DataSectionIndex = Section.Index;
898
899 encodeULEB128(DataSegments.size(), W.OS); // count
900
901 for (const WasmDataSegment &Segment : DataSegments) {
902 encodeULEB128(0, W.OS); // memory index
903 W.OS << char(wasm::WASM_OPCODE_I32_CONST);
904 encodeSLEB128(Segment.Offset, W.OS); // offset
905 W.OS << char(wasm::WASM_OPCODE_END);
906 encodeULEB128(Segment.Data.size(), W.OS); // size
907 Segment.Section->setSectionOffset(W.OS.tell() - Section.ContentsOffset);
908 W.OS << Segment.Data; // data
909 }
910
911 // Apply fixups.
912 applyRelocations(DataRelocations, Section.ContentsOffset);
913
914 endSection(Section);
915}
916
917void WasmObjectWriter::writeRelocSection(
918 uint32_t SectionIndex, StringRef Name,
919 std::vector<WasmRelocationEntry> &Relocs) {
920 // See: https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md
921 // for descriptions of the reloc sections.
922
923 if (Relocs.empty())
924 return;
925
926 // First, ensure the relocations are sorted in offset order. In general they
927 // should already be sorted since `recordRelocation` is called in offset
928 // order, but for the code section we combine many MC sections into single
929 // wasm section, and this order is determined by the order of Asm.Symbols()
930 // not the sections order.
931 std::stable_sort(
932 Relocs.begin(), Relocs.end(),
933 [](const WasmRelocationEntry &A, const WasmRelocationEntry &B) {
934 return (A.Offset + A.FixupSection->getSectionOffset()) <
935 (B.Offset + B.FixupSection->getSectionOffset());
936 });
937
938 SectionBookkeeping Section;
939 startCustomSection(Section, std::string("reloc.") + Name.str());
940
941 encodeULEB128(SectionIndex, W.OS);
942 encodeULEB128(Relocs.size(), W.OS);
943 for (const WasmRelocationEntry &RelEntry : Relocs) {
944 uint64_t Offset =
945 RelEntry.Offset + RelEntry.FixupSection->getSectionOffset();
946 uint32_t Index = getRelocationIndexValue(RelEntry);
947
948 W.OS << char(RelEntry.Type);
949 encodeULEB128(Offset, W.OS);
950 encodeULEB128(Index, W.OS);
951 if (RelEntry.hasAddend())
952 encodeSLEB128(RelEntry.Addend, W.OS);
953 }
954
955 endSection(Section);
956}
957
958void WasmObjectWriter::writeCustomRelocSections() {
959 for (const auto &Sec : CustomSections) {
960 auto &Relocations = CustomSectionsRelocations[Sec.Section];
961 writeRelocSection(Sec.OutputIndex, Sec.Name, Relocations);
962 }
963}
964
965void WasmObjectWriter::writeLinkingMetaDataSection(
966 ArrayRef<wasm::WasmSymbolInfo> SymbolInfos,
967 ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs,
968 const std::map<StringRef, std::vector<WasmComdatEntry>> &Comdats) {
969 SectionBookkeeping Section;
970 startCustomSection(Section, "linking");
971 encodeULEB128(wasm::WasmMetadataVersion, W.OS);
972
973 SectionBookkeeping SubSection;
974 if (SymbolInfos.size() != 0) {
975 startSection(SubSection, wasm::WASM_SYMBOL_TABLE);
976 encodeULEB128(SymbolInfos.size(), W.OS);
977 for (const wasm::WasmSymbolInfo &Sym : SymbolInfos) {
978 encodeULEB128(Sym.Kind, W.OS);
979 encodeULEB128(Sym.Flags, W.OS);
980 switch (Sym.Kind) {
981 case wasm::WASM_SYMBOL_TYPE_FUNCTION:
982 case wasm::WASM_SYMBOL_TYPE_GLOBAL:
983 case wasm::WASM_SYMBOL_TYPE_EVENT:
984 encodeULEB128(Sym.ElementIndex, W.OS);
985 if ((Sym.Flags & wasm::WASM_SYMBOL_UNDEFINED) == 0)
986 writeString(Sym.Name);
987 break;
988 case wasm::WASM_SYMBOL_TYPE_DATA:
989 writeString(Sym.Name);
990 if ((Sym.Flags & wasm::WASM_SYMBOL_UNDEFINED) == 0) {
991 encodeULEB128(Sym.DataRef.Segment, W.OS);
992 encodeULEB128(Sym.DataRef.Offset, W.OS);
993 encodeULEB128(Sym.DataRef.Size, W.OS);
994 }
995 break;
996 case wasm::WASM_SYMBOL_TYPE_SECTION: {
997 const uint32_t SectionIndex =
998 CustomSections[Sym.ElementIndex].OutputIndex;
999 encodeULEB128(SectionIndex, W.OS);
1000 break;
1001 }
1002 default:
1003 llvm_unreachable("unexpected kind")::llvm::llvm_unreachable_internal("unexpected kind", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1003)
;
1004 }
1005 }
1006 endSection(SubSection);
1007 }
1008
1009 if (DataSegments.size()) {
1010 startSection(SubSection, wasm::WASM_SEGMENT_INFO);
1011 encodeULEB128(DataSegments.size(), W.OS);
1012 for (const WasmDataSegment &Segment : DataSegments) {
1013 writeString(Segment.Name);
1014 encodeULEB128(Segment.Alignment, W.OS);
1015 encodeULEB128(Segment.Flags, W.OS);
1016 }
1017 endSection(SubSection);
1018 }
1019
1020 if (!InitFuncs.empty()) {
1021 startSection(SubSection, wasm::WASM_INIT_FUNCS);
1022 encodeULEB128(InitFuncs.size(), W.OS);
1023 for (auto &StartFunc : InitFuncs) {
1024 encodeULEB128(StartFunc.first, W.OS); // priority
1025 encodeULEB128(StartFunc.second, W.OS); // function index
1026 }
1027 endSection(SubSection);
1028 }
1029
1030 if (Comdats.size()) {
1031 startSection(SubSection, wasm::WASM_COMDAT_INFO);
1032 encodeULEB128(Comdats.size(), W.OS);
1033 for (const auto &C : Comdats) {
1034 writeString(C.first);
1035 encodeULEB128(0, W.OS); // flags for future use
1036 encodeULEB128(C.second.size(), W.OS);
1037 for (const WasmComdatEntry &Entry : C.second) {
1038 encodeULEB128(Entry.Kind, W.OS);
1039 encodeULEB128(Entry.Index, W.OS);
1040 }
1041 }
1042 endSection(SubSection);
1043 }
1044
1045 endSection(Section);
1046}
1047
1048void WasmObjectWriter::writeCustomSections(const MCAssembler &Asm,
1049 const MCAsmLayout &Layout) {
1050 for (auto &CustomSection : CustomSections) {
1051 SectionBookkeeping Section;
1052 auto *Sec = CustomSection.Section;
1053 startCustomSection(Section, CustomSection.Name);
1054
1055 Sec->setSectionOffset(W.OS.tell() - Section.ContentsOffset);
1056 Asm.writeSectionData(W.OS, Sec, Layout);
1057
1058 CustomSection.OutputContentsOffset = Section.ContentsOffset;
1059 CustomSection.OutputIndex = Section.Index;
1060
1061 endSection(Section);
1062
1063 // Apply fixups.
1064 auto &Relocations = CustomSectionsRelocations[CustomSection.Section];
1065 applyRelocations(Relocations, CustomSection.OutputContentsOffset);
1066 }
1067}
1068
1069uint32_t WasmObjectWriter::getFunctionType(const MCSymbolWasm &Symbol) {
1070 assert(Symbol.isFunction())((Symbol.isFunction()) ? static_cast<void> (0) : __assert_fail
("Symbol.isFunction()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1070, __PRETTY_FUNCTION__))
;
1071 assert(TypeIndices.count(&Symbol))((TypeIndices.count(&Symbol)) ? static_cast<void> (
0) : __assert_fail ("TypeIndices.count(&Symbol)", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1071, __PRETTY_FUNCTION__))
;
1072 return TypeIndices[&Symbol];
1073}
1074
1075uint32_t WasmObjectWriter::getEventType(const MCSymbolWasm &Symbol) {
1076 assert(Symbol.isEvent())((Symbol.isEvent()) ? static_cast<void> (0) : __assert_fail
("Symbol.isEvent()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1076, __PRETTY_FUNCTION__))
;
1077 assert(TypeIndices.count(&Symbol))((TypeIndices.count(&Symbol)) ? static_cast<void> (
0) : __assert_fail ("TypeIndices.count(&Symbol)", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1077, __PRETTY_FUNCTION__))
;
1078 return TypeIndices[&Symbol];
1079}
1080
1081void WasmObjectWriter::registerFunctionType(const MCSymbolWasm &Symbol) {
1082 assert(Symbol.isFunction())((Symbol.isFunction()) ? static_cast<void> (0) : __assert_fail
("Symbol.isFunction()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1082, __PRETTY_FUNCTION__))
;
1083
1084 WasmSignature S;
1085 const MCSymbolWasm *ResolvedSym = ResolveSymbol(Symbol);
1086 if (auto *Sig = ResolvedSym->getSignature()) {
1087 S.Returns = Sig->Returns;
1088 S.Params = Sig->Params;
1089 }
1090
1091 auto Pair = SignatureIndices.insert(std::make_pair(S, Signatures.size()));
1092 if (Pair.second)
1093 Signatures.push_back(S);
1094 TypeIndices[&Symbol] = Pair.first->second;
1095
1096 LLVM_DEBUG(dbgs() << "registerFunctionType: " << Symboldo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "registerFunctionType: " << Symbol
<< " new:" << Pair.second << "\n"; } } while
(false)
1097 << " new:" << Pair.second << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "registerFunctionType: " << Symbol
<< " new:" << Pair.second << "\n"; } } while
(false)
;
1098 LLVM_DEBUG(dbgs() << " -> type index: " << Pair.first->second << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> type index: " << Pair
.first->second << "\n"; } } while (false)
;
1099}
1100
1101void WasmObjectWriter::registerEventType(const MCSymbolWasm &Symbol) {
1102 assert(Symbol.isEvent())((Symbol.isEvent()) ? static_cast<void> (0) : __assert_fail
("Symbol.isEvent()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1102, __PRETTY_FUNCTION__))
;
1103
1104 // TODO Currently we don't generate imported exceptions, but if we do, we
1105 // should have a way of infering types of imported exceptions.
1106 WasmSignature S;
1107 if (auto *Sig = Symbol.getSignature()) {
1108 S.Returns = Sig->Returns;
1109 S.Params = Sig->Params;
1110 }
1111
1112 auto Pair = SignatureIndices.insert(std::make_pair(S, Signatures.size()));
1113 if (Pair.second)
1114 Signatures.push_back(S);
1115 TypeIndices[&Symbol] = Pair.first->second;
1116
1117 LLVM_DEBUG(dbgs() << "registerEventType: " << Symbol << " new:" << Pair.seconddo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "registerEventType: " << Symbol
<< " new:" << Pair.second << "\n"; } } while
(false)
1118 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "registerEventType: " << Symbol
<< " new:" << Pair.second << "\n"; } } while
(false)
;
1119 LLVM_DEBUG(dbgs() << " -> type index: " << Pair.first->second << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> type index: " << Pair
.first->second << "\n"; } } while (false)
;
1120}
1121
1122static bool isInSymtab(const MCSymbolWasm &Sym) {
1123 if (Sym.isUsedInReloc())
1124 return true;
1125
1126 if (Sym.isComdat() && !Sym.isDefined())
1127 return false;
1128
1129 if (Sym.isTemporary() && Sym.getName().empty())
1130 return false;
1131
1132 if (Sym.isTemporary() && Sym.isData() && !Sym.getSize())
1133 return false;
1134
1135 if (Sym.isSection())
1136 return false;
1137
1138 return true;
1139}
1140
1141uint64_t WasmObjectWriter::writeObject(MCAssembler &Asm,
1142 const MCAsmLayout &Layout) {
1143 uint64_t StartOffset = W.OS.tell();
1144
1145 LLVM_DEBUG(dbgs() << "WasmObjectWriter::writeObject\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "WasmObjectWriter::writeObject\n"; }
} while (false)
;
1146 MCContext &Ctx = Asm.getContext();
1147
1148 // Collect information from the available symbols.
1149 SmallVector<WasmFunction, 4> Functions;
1150 SmallVector<uint32_t, 4> TableElems;
1151 SmallVector<wasm::WasmImport, 4> Imports;
1152 SmallVector<wasm::WasmExport, 4> Exports;
1153 SmallVector<wasm::WasmEventType, 1> Events;
1154 SmallVector<wasm::WasmSymbolInfo, 4> SymbolInfos;
1155 SmallVector<std::pair<uint16_t, uint32_t>, 2> InitFuncs;
1156 std::map<StringRef, std::vector<WasmComdatEntry>> Comdats;
1157 uint32_t DataSize = 0;
1158
1159 // For now, always emit the memory import, since loads and stores are not
1160 // valid without it. In the future, we could perhaps be more clever and omit
1161 // it if there are no loads or stores.
1162 MCSymbolWasm *MemorySym =
1163 cast<MCSymbolWasm>(Ctx.getOrCreateSymbol("__linear_memory"));
1164 wasm::WasmImport MemImport;
1165 MemImport.Module = MemorySym->getModuleName();
1166 MemImport.Field = MemorySym->getName();
1167 MemImport.Kind = wasm::WASM_EXTERNAL_MEMORY;
1168 Imports.push_back(MemImport);
1169
1170 // For now, always emit the table section, since indirect calls are not
1171 // valid without it. In the future, we could perhaps be more clever and omit
1172 // it if there are no indirect calls.
1173 MCSymbolWasm *TableSym =
1174 cast<MCSymbolWasm>(Ctx.getOrCreateSymbol("__indirect_function_table"));
1175 wasm::WasmImport TableImport;
1176 TableImport.Module = TableSym->getModuleName();
1177 TableImport.Field = TableSym->getName();
1178 TableImport.Kind = wasm::WASM_EXTERNAL_TABLE;
1179 TableImport.Table.ElemType = wasm::WASM_TYPE_ANYFUNC;
1180 Imports.push_back(TableImport);
1181
1182 // Populate SignatureIndices, and Imports and WasmIndices for undefined
1183 // symbols. This must be done before populating WasmIndices for defined
1184 // symbols.
1185 for (const MCSymbol &S : Asm.symbols()) {
1186 const auto &WS = static_cast<const MCSymbolWasm &>(S);
1187
1188 // Register types for all functions, including those with private linkage
1189 // (because wasm always needs a type signature).
1190 if (WS.isFunction())
1191 registerFunctionType(WS);
1192
1193 if (WS.isEvent())
1194 registerEventType(WS);
1195
1196 if (WS.isTemporary())
1197 continue;
1198
1199 // If the symbol is not defined in this translation unit, import it.
1200 if (!WS.isDefined() && !WS.isComdat()) {
1201 if (WS.isFunction()) {
1202 wasm::WasmImport Import;
1203 Import.Module = WS.getModuleName();
1204 Import.Field = WS.getName();
1205 Import.Kind = wasm::WASM_EXTERNAL_FUNCTION;
1206 Import.SigIndex = getFunctionType(WS);
1207 Imports.push_back(Import);
1208 WasmIndices[&WS] = NumFunctionImports++;
1209 } else if (WS.isGlobal()) {
1210 if (WS.isWeak())
1211 report_fatal_error("undefined global symbol cannot be weak");
1212
1213 wasm::WasmImport Import;
1214 Import.Module = WS.getModuleName();
1215 Import.Field = WS.getName();
1216 Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
1217 Import.Global = WS.getGlobalType();
1218 Imports.push_back(Import);
1219 WasmIndices[&WS] = NumGlobalImports++;
1220 } else if (WS.isEvent()) {
1221 if (WS.isWeak())
1222 report_fatal_error("undefined event symbol cannot be weak");
1223
1224 wasm::WasmImport Import;
1225 Import.Module = WS.getModuleName();
1226 Import.Field = WS.getName();
1227 Import.Kind = wasm::WASM_EXTERNAL_EVENT;
1228 Import.Event.Attribute = wasm::WASM_EVENT_ATTRIBUTE_EXCEPTION;
1229 Import.Event.SigIndex = getEventType(WS);
1230 Imports.push_back(Import);
1231 WasmIndices[&WS] = NumEventImports++;
1232 }
1233 }
1234 }
1235
1236 // Populate DataSegments and CustomSections, which must be done before
1237 // populating DataLocations.
1238 for (MCSection &Sec : Asm) {
1239 auto &Section = static_cast<MCSectionWasm &>(Sec);
1240 StringRef SectionName = Section.getSectionName();
1241
1242 // .init_array sections are handled specially elsewhere.
1243 if (SectionName.startswith(".init_array"))
1244 continue;
1245
1246 // Code is handled separately
1247 if (Section.getKind().isText())
1248 continue;
1249
1250 if (Section.isWasmData()) {
1251 uint32_t SegmentIndex = DataSegments.size();
1252 DataSize = alignTo(DataSize, Section.getAlignment());
1253 DataSegments.emplace_back();
1254 WasmDataSegment &Segment = DataSegments.back();
1255 Segment.Name = SectionName;
1256 Segment.Offset = DataSize;
1257 Segment.Section = &Section;
1258 addData(Segment.Data, Section);
1259 Segment.Alignment = Section.getAlignment();
1260 Segment.Flags = 0;
1261 DataSize += Segment.Data.size();
1262 Section.setSegmentIndex(SegmentIndex);
1263
1264 if (const MCSymbolWasm *C = Section.getGroup()) {
1265 Comdats[C->getName()].emplace_back(
1266 WasmComdatEntry{wasm::WASM_COMDAT_DATA, SegmentIndex});
1267 }
1268 } else {
1269 // Create custom sections
1270 assert(Sec.getKind().isMetadata())((Sec.getKind().isMetadata()) ? static_cast<void> (0) :
__assert_fail ("Sec.getKind().isMetadata()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1270, __PRETTY_FUNCTION__))
;
1271
1272 StringRef Name = SectionName;
1273
1274 // For user-defined custom sections, strip the prefix
1275 if (Name.startswith(".custom_section."))
1276 Name = Name.substr(strlen(".custom_section."));
1277
1278 MCSymbol *Begin = Sec.getBeginSymbol();
1279 if (Begin) {
1280 WasmIndices[cast<MCSymbolWasm>(Begin)] = CustomSections.size();
1281 if (SectionName != Begin->getName())
1282 report_fatal_error("section name and begin symbol should match: " +
1283 Twine(SectionName));
1284 }
1285 CustomSections.emplace_back(Name, &Section);
1286 }
1287 }
1288
1289 // Populate WasmIndices and DataLocations for defined symbols.
1290 for (const MCSymbol &S : Asm.symbols()) {
1291 // Ignore unnamed temporary symbols, which aren't ever exported, imported,
1292 // or used in relocations.
1293 if (S.isTemporary() && S.getName().empty())
1294 continue;
1295
1296 const auto &WS = static_cast<const MCSymbolWasm &>(S);
1297 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "MCSymbol: " << toString(WS.getType
()) << " '" << S << "'" << " isDefined="
<< S.isDefined() << " isExternal=" << S.isExternal
() << " isTemporary=" << S.isTemporary() <<
" isWeak=" << WS.isWeak() << " isHidden=" <<
WS.isHidden() << " isVariable=" << WS.isVariable
() << "\n"; } } while (false)
1298 dbgs() << "MCSymbol: " << toString(WS.getType()) << " '" << S << "'"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "MCSymbol: " << toString(WS.getType
()) << " '" << S << "'" << " isDefined="
<< S.isDefined() << " isExternal=" << S.isExternal
() << " isTemporary=" << S.isTemporary() <<
" isWeak=" << WS.isWeak() << " isHidden=" <<
WS.isHidden() << " isVariable=" << WS.isVariable
() << "\n"; } } while (false)
1299 << " isDefined=" << S.isDefined() << " isExternal="do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "MCSymbol: " << toString(WS.getType
()) << " '" << S << "'" << " isDefined="
<< S.isDefined() << " isExternal=" << S.isExternal
() << " isTemporary=" << S.isTemporary() <<
" isWeak=" << WS.isWeak() << " isHidden=" <<
WS.isHidden() << " isVariable=" << WS.isVariable
() << "\n"; } } while (false)
1300 << S.isExternal() << " isTemporary=" << S.isTemporary()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "MCSymbol: " << toString(WS.getType
()) << " '" << S << "'" << " isDefined="
<< S.isDefined() << " isExternal=" << S.isExternal
() << " isTemporary=" << S.isTemporary() <<
" isWeak=" << WS.isWeak() << " isHidden=" <<
WS.isHidden() << " isVariable=" << WS.isVariable
() << "\n"; } } while (false)
1301 << " isWeak=" << WS.isWeak() << " isHidden=" << WS.isHidden()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "MCSymbol: " << toString(WS.getType
()) << " '" << S << "'" << " isDefined="
<< S.isDefined() << " isExternal=" << S.isExternal
() << " isTemporary=" << S.isTemporary() <<
" isWeak=" << WS.isWeak() << " isHidden=" <<
WS.isHidden() << " isVariable=" << WS.isVariable
() << "\n"; } } while (false)
1302 << " isVariable=" << WS.isVariable() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "MCSymbol: " << toString(WS.getType
()) << " '" << S << "'" << " isDefined="
<< S.isDefined() << " isExternal=" << S.isExternal
() << " isTemporary=" << S.isTemporary() <<
" isWeak=" << WS.isWeak() << " isHidden=" <<
WS.isHidden() << " isVariable=" << WS.isVariable
() << "\n"; } } while (false)
;
1303
1304 if (WS.isVariable())
1305 continue;
1306 if (WS.isComdat() && !WS.isDefined())
1307 continue;
1308
1309 if (WS.isFunction()) {
1310 unsigned Index;
1311 if (WS.isDefined()) {
1312 if (WS.getOffset() != 0)
1313 report_fatal_error(
1314 "function sections must contain one function each");
1315
1316 if (WS.getSize() == 0)
1317 report_fatal_error(
1318 "function symbols must have a size set with .size");
1319
1320 // A definition. Write out the function body.
1321 Index = NumFunctionImports + Functions.size();
1322 WasmFunction Func;
1323 Func.SigIndex = getFunctionType(WS);
1324 Func.Sym = &WS;
1325 WasmIndices[&WS] = Index;
1326 Functions.push_back(Func);
1327
1328 auto &Section = static_cast<MCSectionWasm &>(WS.getSection());
1329 if (const MCSymbolWasm *C = Section.getGroup()) {
1330 Comdats[C->getName()].emplace_back(
1331 WasmComdatEntry{wasm::WASM_COMDAT_FUNCTION, Index});
1332 }
1333 } else {
1334 // An import; the index was assigned above.
1335 Index = WasmIndices.find(&WS)->second;
1336 }
1337
1338 LLVM_DEBUG(dbgs() << " -> function index: " << Index << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> function index: " <<
Index << "\n"; } } while (false)
;
1339
1340 } else if (WS.isData()) {
1341 if (WS.isTemporary() && !WS.getSize())
1342 continue;
1343
1344 if (!WS.isDefined()) {
1345 LLVM_DEBUG(dbgs() << " -> segment index: -1"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> segment index: -1" <<
"\n"; } } while (false)
1346 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> segment index: -1" <<
"\n"; } } while (false)
;
1347 continue;
1348 }
1349
1350 if (!WS.getSize())
1351 report_fatal_error("data symbols must have a size set with .size: " +
1352 WS.getName());
1353
1354 int64_t Size = 0;
1355 if (!WS.getSize()->evaluateAsAbsolute(Size, Layout))
1356 report_fatal_error(".size expression must be evaluatable");
1357
1358 auto &DataSection = static_cast<MCSectionWasm &>(WS.getSection());
1359 assert(DataSection.isWasmData())((DataSection.isWasmData()) ? static_cast<void> (0) : __assert_fail
("DataSection.isWasmData()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1359, __PRETTY_FUNCTION__))
;
1360
1361 // For each data symbol, export it in the symtab as a reference to the
1362 // corresponding Wasm data segment.
1363 wasm::WasmDataReference Ref = wasm::WasmDataReference{
1364 DataSection.getSegmentIndex(),
1365 static_cast<uint32_t>(Layout.getSymbolOffset(WS)),
1366 static_cast<uint32_t>(Size)};
1367 DataLocations[&WS] = Ref;
1368 LLVM_DEBUG(dbgs() << " -> segment index: " << Ref.Segment << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> segment index: " << Ref
.Segment << "\n"; } } while (false)
;
1369
1370 } else if (WS.isGlobal()) {
1371 // A "true" Wasm global (currently just __stack_pointer)
1372 if (WS.isDefined())
1373 report_fatal_error("don't yet support defined globals");
1374
1375 // An import; the index was assigned above
1376 LLVM_DEBUG(dbgs() << " -> global index: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> global index: " << WasmIndices
.find(&WS)->second << "\n"; } } while (false)
1377 << WasmIndices.find(&WS)->second << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> global index: " << WasmIndices
.find(&WS)->second << "\n"; } } while (false)
;
1378
1379 } else if (WS.isEvent()) {
1380 // C++ exception symbol (__cpp_exception)
1381 unsigned Index;
1382 if (WS.isDefined()) {
1383 Index = NumEventImports + Events.size();
1384 wasm::WasmEventType Event;
1385 Event.SigIndex = getEventType(WS);
1386 Event.Attribute = wasm::WASM_EVENT_ATTRIBUTE_EXCEPTION;
1387 WasmIndices[&WS] = Index;
1388 Events.push_back(Event);
1389 } else {
1390 // An import; the index was assigned above.
1391 Index = WasmIndices.find(&WS)->second;
Value stored to 'Index' is never read
1392 }
1393 LLVM_DEBUG(dbgs() << " -> event index: " << WasmIndices.find(&WS)->seconddo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> event index: " << WasmIndices
.find(&WS)->second << "\n"; } } while (false)
1394 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> event index: " << WasmIndices
.find(&WS)->second << "\n"; } } while (false)
;
1395
1396 } else {
1397 assert(WS.isSection())((WS.isSection()) ? static_cast<void> (0) : __assert_fail
("WS.isSection()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1397, __PRETTY_FUNCTION__))
;
1398 }
1399 }
1400
1401 // Populate WasmIndices and DataLocations for aliased symbols. We need to
1402 // process these in a separate pass because we need to have processed the
1403 // target of the alias before the alias itself and the symbols are not
1404 // necessarily ordered in this way.
1405 for (const MCSymbol &S : Asm.symbols()) {
1406 if (!S.isVariable())
1407 continue;
1408
1409 assert(S.isDefined())((S.isDefined()) ? static_cast<void> (0) : __assert_fail
("S.isDefined()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1409, __PRETTY_FUNCTION__))
;
1410
1411 // Find the target symbol of this weak alias and export that index
1412 const auto &WS = static_cast<const MCSymbolWasm &>(S);
1413 const MCSymbolWasm *ResolvedSym = ResolveSymbol(WS);
1414 LLVM_DEBUG(dbgs() << WS.getName() << ": weak alias of '" << *ResolvedSymdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << WS.getName() << ": weak alias of '"
<< *ResolvedSym << "'\n"; } } while (false)
1415 << "'\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << WS.getName() << ": weak alias of '"
<< *ResolvedSym << "'\n"; } } while (false)
;
1416
1417 if (WS.isFunction()) {
1418 assert(WasmIndices.count(ResolvedSym) > 0)((WasmIndices.count(ResolvedSym) > 0) ? static_cast<void
> (0) : __assert_fail ("WasmIndices.count(ResolvedSym) > 0"
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1418, __PRETTY_FUNCTION__))
;
1419 uint32_t WasmIndex = WasmIndices.find(ResolvedSym)->second;
1420 WasmIndices[&WS] = WasmIndex;
1421 LLVM_DEBUG(dbgs() << " -> index:" << WasmIndex << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> index:" << WasmIndex
<< "\n"; } } while (false)
;
1422 } else if (WS.isData()) {
1423 assert(DataLocations.count(ResolvedSym) > 0)((DataLocations.count(ResolvedSym) > 0) ? static_cast<void
> (0) : __assert_fail ("DataLocations.count(ResolvedSym) > 0"
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1423, __PRETTY_FUNCTION__))
;
1424 const wasm::WasmDataReference &Ref =
1425 DataLocations.find(ResolvedSym)->second;
1426 DataLocations[&WS] = Ref;
1427 LLVM_DEBUG(dbgs() << " -> index:" << Ref.Segment << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> index:" << Ref.Segment
<< "\n"; } } while (false)
;
1428 } else {
1429 report_fatal_error("don't yet support global/event aliases");
1430 }
1431 }
1432
1433 // Finally, populate the symbol table itself, in its "natural" order.
1434 for (const MCSymbol &S : Asm.symbols()) {
1435 const auto &WS = static_cast<const MCSymbolWasm &>(S);
1436 if (!isInSymtab(WS)) {
1437 WS.setIndex(INVALID_INDEX);
1438 continue;
1439 }
1440 LLVM_DEBUG(dbgs() << "adding to symtab: " << WS << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << "adding to symtab: " << WS <<
"\n"; } } while (false)
;
1441
1442 uint32_t Flags = 0;
1443 if (WS.isWeak())
1444 Flags |= wasm::WASM_SYMBOL_BINDING_WEAK;
1445 if (WS.isHidden())
1446 Flags |= wasm::WASM_SYMBOL_VISIBILITY_HIDDEN;
1447 if (!WS.isExternal() && WS.isDefined())
1448 Flags |= wasm::WASM_SYMBOL_BINDING_LOCAL;
1449 if (WS.isUndefined())
1450 Flags |= wasm::WASM_SYMBOL_UNDEFINED;
1451
1452 wasm::WasmSymbolInfo Info;
1453 Info.Name = WS.getName();
1454 Info.Kind = WS.getType();
1455 Info.Flags = Flags;
1456 if (!WS.isData()) {
1457 assert(WasmIndices.count(&WS) > 0)((WasmIndices.count(&WS) > 0) ? static_cast<void>
(0) : __assert_fail ("WasmIndices.count(&WS) > 0", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1457, __PRETTY_FUNCTION__))
;
1458 Info.ElementIndex = WasmIndices.find(&WS)->second;
1459 } else if (WS.isDefined()) {
1460 assert(DataLocations.count(&WS) > 0)((DataLocations.count(&WS) > 0) ? static_cast<void>
(0) : __assert_fail ("DataLocations.count(&WS) > 0", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1460, __PRETTY_FUNCTION__))
;
1461 Info.DataRef = DataLocations.find(&WS)->second;
1462 }
1463 WS.setIndex(SymbolInfos.size());
1464 SymbolInfos.emplace_back(Info);
1465 }
1466
1467 {
1468 auto HandleReloc = [&](const WasmRelocationEntry &Rel) {
1469 // Functions referenced by a relocation need to put in the table. This is
1470 // purely to make the object file's provisional values readable, and is
1471 // ignored by the linker, which re-calculates the relocations itself.
1472 if (Rel.Type != wasm::R_WEBASSEMBLY_TABLE_INDEX_I32 &&
1473 Rel.Type != wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB)
1474 return;
1475 assert(Rel.Symbol->isFunction())((Rel.Symbol->isFunction()) ? static_cast<void> (0) :
__assert_fail ("Rel.Symbol->isFunction()", "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1475, __PRETTY_FUNCTION__))
;
1476 const MCSymbolWasm &WS = *ResolveSymbol(*Rel.Symbol);
1477 uint32_t FunctionIndex = WasmIndices.find(&WS)->second;
1478 uint32_t TableIndex = TableElems.size() + kInitialTableOffset;
1479 if (TableIndices.try_emplace(&WS, TableIndex).second) {
1480 LLVM_DEBUG(dbgs() << " -> adding " << WS.getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> adding " << WS.getName
() << " to table: " << TableIndex << "\n"; }
} while (false)
1481 << " to table: " << TableIndex << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("mc")) { dbgs() << " -> adding " << WS.getName
() << " to table: " << TableIndex << "\n"; }
} while (false)
;
1482 TableElems.push_back(FunctionIndex);
1483 registerFunctionType(WS);
1484 }
1485 };
1486
1487 for (const WasmRelocationEntry &RelEntry : CodeRelocations)
1488 HandleReloc(RelEntry);
1489 for (const WasmRelocationEntry &RelEntry : DataRelocations)
1490 HandleReloc(RelEntry);
1491 }
1492
1493 // Translate .init_array section contents into start functions.
1494 for (const MCSection &S : Asm) {
1495 const auto &WS = static_cast<const MCSectionWasm &>(S);
1496 if (WS.getSectionName().startswith(".fini_array"))
1497 report_fatal_error(".fini_array sections are unsupported");
1498 if (!WS.getSectionName().startswith(".init_array"))
1499 continue;
1500 if (WS.getFragmentList().empty())
1501 continue;
1502
1503 // init_array is expected to contain a single non-empty data fragment
1504 if (WS.getFragmentList().size() != 3)
1505 report_fatal_error("only one .init_array section fragment supported");
1506
1507 auto IT = WS.begin();
1508 const MCFragment &EmptyFrag = *IT;
1509 if (EmptyFrag.getKind() != MCFragment::FT_Data)
1510 report_fatal_error(".init_array section should be aligned");
1511
1512 IT = std::next(IT);
1513 const MCFragment &AlignFrag = *IT;
1514 if (AlignFrag.getKind() != MCFragment::FT_Align)
1515 report_fatal_error(".init_array section should be aligned");
1516 if (cast<MCAlignFragment>(AlignFrag).getAlignment() != (is64Bit() ? 8 : 4))
1517 report_fatal_error(".init_array section should be aligned for pointers");
1518
1519 const MCFragment &Frag = *std::next(IT);
1520 if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data)
1521 report_fatal_error("only data supported in .init_array section");
1522
1523 uint16_t Priority = UINT16_MAX(65535);
1524 unsigned PrefixLength = strlen(".init_array");
1525 if (WS.getSectionName().size() > PrefixLength) {
1526 if (WS.getSectionName()[PrefixLength] != '.')
1527 report_fatal_error(
1528 ".init_array section priority should start with '.'");
1529 if (WS.getSectionName()
1530 .substr(PrefixLength + 1)
1531 .getAsInteger(10, Priority))
1532 report_fatal_error("invalid .init_array section priority");
1533 }
1534 const auto &DataFrag = cast<MCDataFragment>(Frag);
1535 const SmallVectorImpl<char> &Contents = DataFrag.getContents();
1536 for (const uint8_t *
1537 p = (const uint8_t *)Contents.data(),
1538 *end = (const uint8_t *)Contents.data() + Contents.size();
1539 p != end; ++p) {
1540 if (*p != 0)
1541 report_fatal_error("non-symbolic data in .init_array section");
1542 }
1543 for (const MCFixup &Fixup : DataFrag.getFixups()) {
1544 assert(Fixup.getKind() ==((Fixup.getKind() == MCFixup::getKindForSize(is64Bit() ? 8 : 4
, false)) ? static_cast<void> (0) : __assert_fail ("Fixup.getKind() == MCFixup::getKindForSize(is64Bit() ? 8 : 4, false)"
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1545, __PRETTY_FUNCTION__))
1545 MCFixup::getKindForSize(is64Bit() ? 8 : 4, false))((Fixup.getKind() == MCFixup::getKindForSize(is64Bit() ? 8 : 4
, false)) ? static_cast<void> (0) : __assert_fail ("Fixup.getKind() == MCFixup::getKindForSize(is64Bit() ? 8 : 4, false)"
, "/build/llvm-toolchain-snapshot-8~svn350071/lib/MC/WasmObjectWriter.cpp"
, 1545, __PRETTY_FUNCTION__))
;
1546 const MCExpr *Expr = Fixup.getValue();
1547 auto *Sym = dyn_cast<MCSymbolRefExpr>(Expr);
1548 if (!Sym)
1549 report_fatal_error("fixups in .init_array should be symbol references");
1550 if (Sym->getKind() != MCSymbolRefExpr::VK_WebAssembly_FUNCTION)
1551 report_fatal_error("symbols in .init_array should be for functions");
1552 if (Sym->getSymbol().getIndex() == INVALID_INDEX)
1553 report_fatal_error("symbols in .init_array should exist in symbtab");
1554 InitFuncs.push_back(
1555 std::make_pair(Priority, Sym->getSymbol().getIndex()));
1556 }
1557 }
1558
1559 // Write out the Wasm header.
1560 writeHeader(Asm);
1561
1562 writeTypeSection(Signatures);
1563 writeImportSection(Imports, DataSize, TableElems.size());
1564 writeFunctionSection(Functions);
1565 // Skip the "table" section; we import the table instead.
1566 // Skip the "memory" section; we import the memory instead.
1567 writeGlobalSection();
1568 writeEventSection(Events);
1569 writeExportSection(Exports);
1570 writeElemSection(TableElems);
1571 writeCodeSection(Asm, Layout, Functions);
1572 writeDataSection();
1573 writeCustomSections(Asm, Layout);
1574 writeLinkingMetaDataSection(SymbolInfos, InitFuncs, Comdats);
1575 writeRelocSection(CodeSectionIndex, "CODE", CodeRelocations);
1576 writeRelocSection(DataSectionIndex, "DATA", DataRelocations);
1577 writeCustomRelocSections();
1578
1579 // TODO: Translate the .comment section to the output.
1580 return W.OS.tell() - StartOffset;
1581}
1582
1583std::unique_ptr<MCObjectWriter>
1584llvm::createWasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW,
1585 raw_pwrite_stream &OS) {
1586 return llvm::make_unique<WasmObjectWriter>(std::move(MOTW), OS);
1587}