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llvm-project/lld/wasm/InputFiles.cpp

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//===- InputFiles.cpp -----------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "InputFiles.h"
#include "Config.h"
#include "InputChunks.h"
#include "InputElement.h"
#include "OutputSegment.h"
#include "SymbolTable.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Memory.h"
#include "lld/Common/Reproduce.h"
#include "llvm/Object/Binary.h"
#include "llvm/Object/Wasm.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/TarWriter.h"
#include "llvm/Support/raw_ostream.h"
#define DEBUG_TYPE "lld"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::wasm;
using namespace llvm::sys;
namespace lld {
// Returns a string in the format of "foo.o" or "foo.a(bar.o)".
std::string toString(const wasm::InputFile *file) {
if (!file)
return "<internal>";
if (file->archiveName.empty())
return std::string(file->getName());
return (file->archiveName + "(" + file->getName() + ")").str();
}
namespace wasm {
void InputFile::checkArch(Triple::ArchType arch) const {
bool is64 = arch == Triple::wasm64;
if (is64 && !config->is64.hasValue()) {
fatal(toString(this) +
": must specify -mwasm64 to process wasm64 object files");
} else if (config->is64.getValueOr(false) != is64) {
fatal(toString(this) +
": wasm32 object file can't be linked in wasm64 mode");
}
}
std::unique_ptr<llvm::TarWriter> tar;
Optional<MemoryBufferRef> readFile(StringRef path) {
log("Loading: " + path);
auto mbOrErr = MemoryBuffer::getFile(path);
if (auto ec = mbOrErr.getError()) {
error("cannot open " + path + ": " + ec.message());
return None;
}
std::unique_ptr<MemoryBuffer> &mb = *mbOrErr;
MemoryBufferRef mbref = mb->getMemBufferRef();
make<std::unique_ptr<MemoryBuffer>>(std::move(mb)); // take MB ownership
if (tar)
tar->append(relativeToRoot(path), mbref.getBuffer());
return mbref;
}
InputFile *createObjectFile(MemoryBufferRef mb, StringRef archiveName,
uint64_t offsetInArchive) {
file_magic magic = identify_magic(mb.getBuffer());
if (magic == file_magic::wasm_object) {
std::unique_ptr<Binary> bin =
CHECK(createBinary(mb), mb.getBufferIdentifier());
auto *obj = cast<WasmObjectFile>(bin.get());
if (obj->isSharedObject())
return make<SharedFile>(mb);
return make<ObjFile>(mb, archiveName);
}
if (magic == file_magic::bitcode)
return make<BitcodeFile>(mb, archiveName, offsetInArchive);
fatal("unknown file type: " + mb.getBufferIdentifier());
}
// Relocations contain either symbol or type indices. This function takes a
// relocation and returns relocated index (i.e. translates from the input
// symbol/type space to the output symbol/type space).
uint32_t ObjFile::calcNewIndex(const WasmRelocation &reloc) const {
if (reloc.Type == R_WASM_TYPE_INDEX_LEB) {
assert(typeIsUsed[reloc.Index]);
return typeMap[reloc.Index];
}
const Symbol *sym = symbols[reloc.Index];
if (auto *ss = dyn_cast<SectionSymbol>(sym))
sym = ss->getOutputSectionSymbol();
return sym->getOutputSymbolIndex();
}
// Relocations can contain addend for combined sections. This function takes a
// relocation and returns updated addend by offset in the output section.
uint64_t ObjFile::calcNewAddend(const WasmRelocation &reloc) const {
switch (reloc.Type) {
case R_WASM_MEMORY_ADDR_LEB:
case R_WASM_MEMORY_ADDR_LEB64:
case R_WASM_MEMORY_ADDR_SLEB64:
case R_WASM_MEMORY_ADDR_SLEB:
case R_WASM_MEMORY_ADDR_REL_SLEB:
case R_WASM_MEMORY_ADDR_REL_SLEB64:
case R_WASM_MEMORY_ADDR_I32:
case R_WASM_MEMORY_ADDR_I64:
case R_WASM_MEMORY_ADDR_TLS_SLEB:
case R_WASM_MEMORY_ADDR_TLS_SLEB64:
case R_WASM_FUNCTION_OFFSET_I32:
case R_WASM_FUNCTION_OFFSET_I64:
case R_WASM_MEMORY_ADDR_LOCREL_I32:
return reloc.Addend;
case R_WASM_SECTION_OFFSET_I32:
return getSectionSymbol(reloc.Index)->section->getOffset(reloc.Addend);
default:
llvm_unreachable("unexpected relocation type");
}
}
// Translate from the relocation's index into the final linked output value.
uint64_t ObjFile::calcNewValue(const WasmRelocation &reloc, uint64_t tombstone,
const InputChunk *chunk) const {
const Symbol* sym = nullptr;
if (reloc.Type != R_WASM_TYPE_INDEX_LEB) {
sym = symbols[reloc.Index];
// We can end up with relocations against non-live symbols. For example
// in debug sections. We return a tombstone value in debug symbol sections
// so this will not produce a valid range conflicting with ranges of actual
// code. In other sections we return reloc.Addend.
if (!isa<SectionSymbol>(sym) && !sym->isLive())
return tombstone ? tombstone : reloc.Addend;
}
switch (reloc.Type) {
case R_WASM_TABLE_INDEX_I32:
case R_WASM_TABLE_INDEX_I64:
case R_WASM_TABLE_INDEX_SLEB:
case R_WASM_TABLE_INDEX_SLEB64:
case R_WASM_TABLE_INDEX_REL_SLEB:
case R_WASM_TABLE_INDEX_REL_SLEB64: {
if (!getFunctionSymbol(reloc.Index)->hasTableIndex())
return 0;
uint32_t index = getFunctionSymbol(reloc.Index)->getTableIndex();
if (reloc.Type == R_WASM_TABLE_INDEX_REL_SLEB ||
reloc.Type == R_WASM_TABLE_INDEX_REL_SLEB64)
index -= config->tableBase;
return index;
}
case R_WASM_MEMORY_ADDR_LEB:
case R_WASM_MEMORY_ADDR_LEB64:
case R_WASM_MEMORY_ADDR_SLEB:
case R_WASM_MEMORY_ADDR_SLEB64:
case R_WASM_MEMORY_ADDR_REL_SLEB:
case R_WASM_MEMORY_ADDR_REL_SLEB64:
case R_WASM_MEMORY_ADDR_I32:
case R_WASM_MEMORY_ADDR_I64:
case R_WASM_MEMORY_ADDR_TLS_SLEB:
case R_WASM_MEMORY_ADDR_TLS_SLEB64:
case R_WASM_MEMORY_ADDR_LOCREL_I32: {
if (isa<UndefinedData>(sym) || sym->isUndefWeak())
return 0;
auto D = cast<DefinedData>(sym);
uint64_t value = D->getVA() + reloc.Addend;
if (reloc.Type == R_WASM_MEMORY_ADDR_LOCREL_I32) {
const auto *segment = cast<InputSegment>(chunk);
uint64_t p = segment->outputSeg->startVA + segment->outputSegmentOffset +
reloc.Offset - segment->getInputSectionOffset();
value -= p;
}
return value;
}
case R_WASM_TYPE_INDEX_LEB:
return typeMap[reloc.Index];
case R_WASM_FUNCTION_INDEX_LEB:
return getFunctionSymbol(reloc.Index)->getFunctionIndex();
case R_WASM_GLOBAL_INDEX_LEB:
case R_WASM_GLOBAL_INDEX_I32:
if (auto gs = dyn_cast<GlobalSymbol>(sym))
return gs->getGlobalIndex();
return sym->getGOTIndex();
case R_WASM_TAG_INDEX_LEB:
return getTagSymbol(reloc.Index)->getTagIndex();
case R_WASM_FUNCTION_OFFSET_I32:
case R_WASM_FUNCTION_OFFSET_I64: {
auto *f = cast<DefinedFunction>(sym);
return f->function->getOffset(f->function->getFunctionCodeOffset() +
reloc.Addend);
}
case R_WASM_SECTION_OFFSET_I32:
return getSectionSymbol(reloc.Index)->section->getOffset(reloc.Addend);
case R_WASM_TABLE_NUMBER_LEB:
return getTableSymbol(reloc.Index)->getTableNumber();
default:
llvm_unreachable("unknown relocation type");
}
}
template <class T>
static void setRelocs(const std::vector<T *> &chunks,
const WasmSection *section) {
if (!section)
return;
ArrayRef<WasmRelocation> relocs = section->Relocations;
assert(llvm::is_sorted(
relocs, [](const WasmRelocation &r1, const WasmRelocation &r2) {
return r1.Offset < r2.Offset;
}));
assert(llvm::is_sorted(chunks, [](InputChunk *c1, InputChunk *c2) {
return c1->getInputSectionOffset() < c2->getInputSectionOffset();
}));
auto relocsNext = relocs.begin();
auto relocsEnd = relocs.end();
auto relocLess = [](const WasmRelocation &r, uint32_t val) {
return r.Offset < val;
};
for (InputChunk *c : chunks) {
auto relocsStart = std::lower_bound(relocsNext, relocsEnd,
c->getInputSectionOffset(), relocLess);
relocsNext = std::lower_bound(
relocsStart, relocsEnd, c->getInputSectionOffset() + c->getInputSize(),
relocLess);
c->setRelocations(ArrayRef<WasmRelocation>(relocsStart, relocsNext));
}
}
// An object file can have two approaches to tables. With the reference-types
// feature enabled, input files that define or use tables declare the tables
// using symbols, and record each use with a relocation. This way when the
// linker combines inputs, it can collate the tables used by the inputs,
// assigning them distinct table numbers, and renumber all the uses as
// appropriate. At the same time, the linker has special logic to build the
// indirect function table if it is needed.
//
// However, MVP object files (those that target WebAssembly 1.0, the "minimum
// viable product" version of WebAssembly) neither write table symbols nor
// record relocations. These files can have at most one table, the indirect
// function table used by call_indirect and which is the address space for
// function pointers. If this table is present, it is always an import. If we
// have a file with a table import but no table symbols, it is an MVP object
// file. synthesizeMVPIndirectFunctionTableSymbolIfNeeded serves as a shim when
// loading these input files, defining the missing symbol to allow the indirect
// function table to be built.
//
// As indirect function table table usage in MVP objects cannot be relocated,
// the linker must ensure that this table gets assigned index zero.
void ObjFile::addLegacyIndirectFunctionTableIfNeeded(
uint32_t tableSymbolCount) {
uint32_t tableCount = wasmObj->getNumImportedTables() + tables.size();
// If there are symbols for all tables, then all is good.
if (tableCount == tableSymbolCount)
return;
// It's possible for an input to define tables and also use the indirect
// function table, but forget to compile with -mattr=+reference-types.
// For these newer files, we require symbols for all tables, and
// relocations for all of their uses.
if (tableSymbolCount != 0) {
error(toString(this) +
": expected one symbol table entry for each of the " +
Twine(tableCount) + " table(s) present, but got " +
Twine(tableSymbolCount) + " symbol(s) instead.");
return;
}
// An MVP object file can have up to one table import, for the indirect
// function table, but will have no table definitions.
if (tables.size()) {
error(toString(this) +
": unexpected table definition(s) without corresponding "
"symbol-table entries.");
return;
}
// An MVP object file can have only one table import.
if (tableCount != 1) {
error(toString(this) +
": multiple table imports, but no corresponding symbol-table "
"entries.");
return;
}
const WasmImport *tableImport = nullptr;
for (const auto &import : wasmObj->imports()) {
if (import.Kind == WASM_EXTERNAL_TABLE) {
assert(!tableImport);
tableImport = &import;
}
}
assert(tableImport);
// We can only synthesize a symtab entry for the indirect function table; if
// it has an unexpected name or type, assume that it's not actually the
// indirect function table.
if (tableImport->Field != functionTableName ||
tableImport->Table.ElemType != uint8_t(ValType::FUNCREF)) {
error(toString(this) + ": table import " + Twine(tableImport->Field) +
" is missing a symbol table entry.");
return;
}
auto *info = make<WasmSymbolInfo>();
info->Name = tableImport->Field;
info->Kind = WASM_SYMBOL_TYPE_TABLE;
info->ImportModule = tableImport->Module;
info->ImportName = tableImport->Field;
info->Flags = WASM_SYMBOL_UNDEFINED;
info->Flags |= WASM_SYMBOL_NO_STRIP;
info->ElementIndex = 0;
LLVM_DEBUG(dbgs() << "Synthesizing symbol for table import: " << info->Name
<< "\n");
const WasmGlobalType *globalType = nullptr;
const WasmSignature *signature = nullptr;
auto *wasmSym =
make<WasmSymbol>(*info, globalType, &tableImport->Table, signature);
Symbol *sym = createUndefined(*wasmSym, false);
// We're only sure it's a TableSymbol if the createUndefined succeeded.
if (errorCount())
return;
symbols.push_back(sym);
// Because there are no TABLE_NUMBER relocs, we can't compute accurate
// liveness info; instead, just mark the symbol as always live.
sym->markLive();
// We assume that this compilation unit has unrelocatable references to
// this table.
config->legacyFunctionTable = true;
}
static bool shouldMerge(const WasmSection &sec) {
if (config->optimize == 0)
return false;
// Sadly we don't have section attributes yet for custom sections, so we
// currently go by the name alone.
// TODO(sbc): Add ability for wasm sections to carry flags so we don't
// need to use names here.
// For now, keep in sync with uses of wasm::WASM_SEG_FLAG_STRINGS in
// MCObjectFileInfo::initWasmMCObjectFileInfo which creates these custom
// sections.
return sec.Name == ".debug_str" || sec.Name == ".debug_str.dwo" ||
sec.Name == ".debug_line_str";
}
static bool shouldMerge(const WasmSegment &seg) {
// As of now we only support merging strings, and only with single byte
// alignment (2^0).
if (!(seg.Data.LinkingFlags & WASM_SEG_FLAG_STRINGS) ||
(seg.Data.Alignment != 0))
return false;
// On a regular link we don't merge sections if -O0 (default is -O1). This
// sometimes makes the linker significantly faster, although the output will
// be bigger.
if (config->optimize == 0)
return false;
// A mergeable section with size 0 is useless because they don't have
// any data to merge. A mergeable string section with size 0 can be
// argued as invalid because it doesn't end with a null character.
// We'll avoid a mess by handling them as if they were non-mergeable.
if (seg.Data.Content.size() == 0)
return false;
return true;
}
void ObjFile::parse(bool ignoreComdats) {
// Parse a memory buffer as a wasm file.
LLVM_DEBUG(dbgs() << "Parsing object: " << toString(this) << "\n");
std::unique_ptr<Binary> bin = CHECK(createBinary(mb), toString(this));
auto *obj = dyn_cast<WasmObjectFile>(bin.get());
if (!obj)
fatal(toString(this) + ": not a wasm file");
if (!obj->isRelocatableObject())
fatal(toString(this) + ": not a relocatable wasm file");
bin.release();
wasmObj.reset(obj);
checkArch(obj->getArch());
// Build up a map of function indices to table indices for use when
// verifying the existing table index relocations
uint32_t totalFunctions =
wasmObj->getNumImportedFunctions() + wasmObj->functions().size();
tableEntriesRel.resize(totalFunctions);
tableEntries.resize(totalFunctions);
for (const WasmElemSegment &seg : wasmObj->elements()) {
int64_t offset;
if (seg.Offset.Opcode == WASM_OPCODE_I32_CONST)
offset = seg.Offset.Value.Int32;
else if (seg.Offset.Opcode == WASM_OPCODE_I64_CONST)
offset = seg.Offset.Value.Int64;
else
fatal(toString(this) + ": invalid table elements");
for (size_t index = 0; index < seg.Functions.size(); index++) {
auto functionIndex = seg.Functions[index];
tableEntriesRel[functionIndex] = index;
tableEntries[functionIndex] = offset + index;
}
}
ArrayRef<StringRef> comdats = wasmObj->linkingData().Comdats;
for (StringRef comdat : comdats) {
bool isNew = ignoreComdats || symtab->addComdat(comdat);
keptComdats.push_back(isNew);
}
uint32_t sectionIndex = 0;
// Bool for each symbol, true if called directly. This allows us to implement
// a weaker form of signature checking where undefined functions that are not
// called directly (i.e. only address taken) don't have to match the defined
// function's signature. We cannot do this for directly called functions
// because those signatures are checked at validation times.
// See https://bugs.llvm.org/show_bug.cgi?id=40412
std::vector<bool> isCalledDirectly(wasmObj->getNumberOfSymbols(), false);
for (const SectionRef &sec : wasmObj->sections()) {
const WasmSection &section = wasmObj->getWasmSection(sec);
// Wasm objects can have at most one code and one data section.
if (section.Type == WASM_SEC_CODE) {
assert(!codeSection);
codeSection = &section;
} else if (section.Type == WASM_SEC_DATA) {
assert(!dataSection);
dataSection = &section;
} else if (section.Type == WASM_SEC_CUSTOM) {
InputChunk *customSec;
if (shouldMerge(section))
customSec = make<MergeInputChunk>(section, this);
else
customSec = make<InputSection>(section, this);
customSec->discarded = isExcludedByComdat(customSec);
customSections.emplace_back(customSec);
customSections.back()->setRelocations(section.Relocations);
customSectionsByIndex[sectionIndex] = customSections.back();
}
sectionIndex++;
// Scans relocations to determine if a function symbol is called directly.
for (const WasmRelocation &reloc : section.Relocations)
if (reloc.Type == R_WASM_FUNCTION_INDEX_LEB)
isCalledDirectly[reloc.Index] = true;
}
typeMap.resize(getWasmObj()->types().size());
typeIsUsed.resize(getWasmObj()->types().size(), false);
// Populate `Segments`.
for (const WasmSegment &s : wasmObj->dataSegments()) {
InputChunk *seg;
if (shouldMerge(s)) {
seg = make<MergeInputChunk>(s, this);
} else
seg = make<InputSegment>(s, this);
seg->discarded = isExcludedByComdat(seg);
// Older object files did not include WASM_SEG_FLAG_TLS and instead
// relied on the naming convention. To maintain compat with such objects
// we still imply the TLS flag based on the name of the segment.
if (!seg->isTLS() &&
(seg->name.startswith(".tdata") || seg->name.startswith(".tbss"))) {
seg->flags |= WASM_SEG_FLAG_TLS;
seg->implicitTLS = true;
}
segments.emplace_back(seg);
}
setRelocs(segments, dataSection);
// Populate `Functions`.
ArrayRef<WasmFunction> funcs = wasmObj->functions();
ArrayRef<WasmSignature> types = wasmObj->types();
functions.reserve(funcs.size());
for (auto &f : funcs) {
auto *func = make<InputFunction>(types[f.SigIndex], &f, this);
func->discarded = isExcludedByComdat(func);
functions.emplace_back(func);
}
setRelocs(functions, codeSection);
// Populate `Tables`.
for (const WasmTable &t : wasmObj->tables())
tables.emplace_back(make<InputTable>(t, this));
// Populate `Globals`.
for (const WasmGlobal &g : wasmObj->globals())
globals.emplace_back(make<InputGlobal>(g, this));
// Populate `Tags`.
for (const WasmTag &t : wasmObj->tags())
tags.emplace_back(make<InputTag>(types[t.SigIndex], t, this));
// Populate `Symbols` based on the symbols in the object.
symbols.reserve(wasmObj->getNumberOfSymbols());
uint32_t tableSymbolCount = 0;
for (const SymbolRef &sym : wasmObj->symbols()) {
const WasmSymbol &wasmSym = wasmObj->getWasmSymbol(sym.getRawDataRefImpl());
if (wasmSym.isTypeTable())
tableSymbolCount++;
if (wasmSym.isDefined()) {
// createDefined may fail if the symbol is comdat excluded in which case
// we fall back to creating an undefined symbol
if (Symbol *d = createDefined(wasmSym)) {
symbols.push_back(d);
continue;
}
}
size_t idx = symbols.size();
symbols.push_back(createUndefined(wasmSym, isCalledDirectly[idx]));
}
addLegacyIndirectFunctionTableIfNeeded(tableSymbolCount);
}
bool ObjFile::isExcludedByComdat(const InputChunk *chunk) const {
uint32_t c = chunk->getComdat();
if (c == UINT32_MAX)
return false;
return !keptComdats[c];
}
FunctionSymbol *ObjFile::getFunctionSymbol(uint32_t index) const {
return cast<FunctionSymbol>(symbols[index]);
}
GlobalSymbol *ObjFile::getGlobalSymbol(uint32_t index) const {
return cast<GlobalSymbol>(symbols[index]);
}
TagSymbol *ObjFile::getTagSymbol(uint32_t index) const {
return cast<TagSymbol>(symbols[index]);
}
TableSymbol *ObjFile::getTableSymbol(uint32_t index) const {
return cast<TableSymbol>(symbols[index]);
}
SectionSymbol *ObjFile::getSectionSymbol(uint32_t index) const {
return cast<SectionSymbol>(symbols[index]);
}
DataSymbol *ObjFile::getDataSymbol(uint32_t index) const {
return cast<DataSymbol>(symbols[index]);
}
Symbol *ObjFile::createDefined(const WasmSymbol &sym) {
StringRef name = sym.Info.Name;
uint32_t flags = sym.Info.Flags;
switch (sym.Info.Kind) {
case WASM_SYMBOL_TYPE_FUNCTION: {
InputFunction *func =
functions[sym.Info.ElementIndex - wasmObj->getNumImportedFunctions()];
if (sym.isBindingLocal())
return make<DefinedFunction>(name, flags, this, func);
if (func->discarded)
return nullptr;
return symtab->addDefinedFunction(name, flags, this, func);
}
case WASM_SYMBOL_TYPE_DATA: {
InputChunk *seg = segments[sym.Info.DataRef.Segment];
auto offset = sym.Info.DataRef.Offset;
auto size = sym.Info.DataRef.Size;
if (seg->implicitTLS) {
flags |= WASM_SYMBOL_TLS;
}
if (sym.isBindingLocal())
return make<DefinedData>(name, flags, this, seg, offset, size);
if (seg->discarded)
return nullptr;
return symtab->addDefinedData(name, flags, this, seg, offset, size);
}
case WASM_SYMBOL_TYPE_GLOBAL: {
InputGlobal *global =
globals[sym.Info.ElementIndex - wasmObj->getNumImportedGlobals()];
if (sym.isBindingLocal())
return make<DefinedGlobal>(name, flags, this, global);
return symtab->addDefinedGlobal(name, flags, this, global);
}
case WASM_SYMBOL_TYPE_SECTION: {
InputChunk *section = customSectionsByIndex[sym.Info.ElementIndex];
assert(sym.isBindingLocal());
// Need to return null if discarded here? data and func only do that when
// binding is not local.
if (section->discarded)
return nullptr;
return make<SectionSymbol>(flags, section, this);
}
case WASM_SYMBOL_TYPE_TAG: {
InputTag *tag = tags[sym.Info.ElementIndex - wasmObj->getNumImportedTags()];
if (sym.isBindingLocal())
return make<DefinedTag>(name, flags, this, tag);
return symtab->addDefinedTag(name, flags, this, tag);
}
case WASM_SYMBOL_TYPE_TABLE: {
InputTable *table =
tables[sym.Info.ElementIndex - wasmObj->getNumImportedTables()];
if (sym.isBindingLocal())
return make<DefinedTable>(name, flags, this, table);
return symtab->addDefinedTable(name, flags, this, table);
}
}
llvm_unreachable("unknown symbol kind");
}
Symbol *ObjFile::createUndefined(const WasmSymbol &sym, bool isCalledDirectly) {
StringRef name = sym.Info.Name;
uint32_t flags = sym.Info.Flags | WASM_SYMBOL_UNDEFINED;
switch (sym.Info.Kind) {
case WASM_SYMBOL_TYPE_FUNCTION:
if (sym.isBindingLocal())
return make<UndefinedFunction>(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.Signature, isCalledDirectly);
return symtab->addUndefinedFunction(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.Signature, isCalledDirectly);
case WASM_SYMBOL_TYPE_DATA:
if (sym.isBindingLocal())
return make<UndefinedData>(name, flags, this);
return symtab->addUndefinedData(name, flags, this);
case WASM_SYMBOL_TYPE_GLOBAL:
if (sym.isBindingLocal())
return make<UndefinedGlobal>(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.GlobalType);
return symtab->addUndefinedGlobal(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.GlobalType);
case WASM_SYMBOL_TYPE_TABLE:
if (sym.isBindingLocal())
return make<UndefinedTable>(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.TableType);
return symtab->addUndefinedTable(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.TableType);
case WASM_SYMBOL_TYPE_TAG:
if (sym.isBindingLocal())
return make<UndefinedTag>(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.Signature);
return symtab->addUndefinedTag(name, sym.Info.ImportName,
sym.Info.ImportModule, flags, this,
sym.Signature);
case WASM_SYMBOL_TYPE_SECTION:
llvm_unreachable("section symbols cannot be undefined");
}
llvm_unreachable("unknown symbol kind");
}
void ArchiveFile::parse() {
// Parse a MemoryBufferRef as an archive file.
LLVM_DEBUG(dbgs() << "Parsing library: " << toString(this) << "\n");
file = CHECK(Archive::create(mb), toString(this));
// Read the symbol table to construct Lazy symbols.
int count = 0;
for (const Archive::Symbol &sym : file->symbols()) {
symtab->addLazy(this, &sym);
++count;
}
LLVM_DEBUG(dbgs() << "Read " << count << " symbols\n");
}
void ArchiveFile::addMember(const Archive::Symbol *sym) {
const Archive::Child &c =
CHECK(sym->getMember(),
"could not get the member for symbol " + sym->getName());
// Don't try to load the same member twice (this can happen when members
// mutually reference each other).
if (!seen.insert(c.getChildOffset()).second)
return;
LLVM_DEBUG(dbgs() << "loading lazy: " << sym->getName() << "\n");
LLVM_DEBUG(dbgs() << "from archive: " << toString(this) << "\n");
MemoryBufferRef mb =
CHECK(c.getMemoryBufferRef(),
"could not get the buffer for the member defining symbol " +
sym->getName());
InputFile *obj = createObjectFile(mb, getName(), c.getChildOffset());
symtab->addFile(obj);
}
static uint8_t mapVisibility(GlobalValue::VisibilityTypes gvVisibility) {
switch (gvVisibility) {
case GlobalValue::DefaultVisibility:
return WASM_SYMBOL_VISIBILITY_DEFAULT;
case GlobalValue::HiddenVisibility:
case GlobalValue::ProtectedVisibility:
return WASM_SYMBOL_VISIBILITY_HIDDEN;
}
llvm_unreachable("unknown visibility");
}
static Symbol *createBitcodeSymbol(const std::vector<bool> &keptComdats,
const lto::InputFile::Symbol &objSym,
BitcodeFile &f) {
StringRef name = saver.save(objSym.getName());
uint32_t flags = objSym.isWeak() ? WASM_SYMBOL_BINDING_WEAK : 0;
flags |= mapVisibility(objSym.getVisibility());
int c = objSym.getComdatIndex();
bool excludedByComdat = c != -1 && !keptComdats[c];
if (objSym.isUndefined() || excludedByComdat) {
flags |= WASM_SYMBOL_UNDEFINED;
if (objSym.isExecutable())
return symtab->addUndefinedFunction(name, None, None, flags, &f, nullptr,
true);
return symtab->addUndefinedData(name, flags, &f);
}
if (objSym.isExecutable())
return symtab->addDefinedFunction(name, flags, &f, nullptr);
return symtab->addDefinedData(name, flags, &f, nullptr, 0, 0);
}
BitcodeFile::BitcodeFile(MemoryBufferRef m, StringRef archiveName,
uint64_t offsetInArchive)
: InputFile(BitcodeKind, m) {
this->archiveName = std::string(archiveName);
std::string path = mb.getBufferIdentifier().str();
// ThinLTO assumes that all MemoryBufferRefs given to it have a unique
// name. If two archives define two members with the same name, this
// causes a collision which result in only one of the objects being taken
// into consideration at LTO time (which very likely causes undefined
// symbols later in the link stage). So we append file offset to make
// filename unique.
StringRef name = archiveName.empty()
? saver.save(path)
: saver.save(archiveName + "(" + path::filename(path) +
" at " + utostr(offsetInArchive) + ")");
MemoryBufferRef mbref(mb.getBuffer(), name);
obj = check(lto::InputFile::create(mbref));
// If this isn't part of an archive, it's eagerly linked, so mark it live.
if (archiveName.empty())
markLive();
}
bool BitcodeFile::doneLTO = false;
void BitcodeFile::parse() {
if (doneLTO) {
error(toString(this) + ": attempt to add bitcode file after LTO.");
return;
}
Triple t(obj->getTargetTriple());
if (!t.isWasm()) {
error(toString(this) + ": machine type must be wasm32 or wasm64");
return;
}
checkArch(t.getArch());
std::vector<bool> keptComdats;
// TODO Support nodeduplicate https://bugs.llvm.org/show_bug.cgi?id=50531
for (std::pair<StringRef, Comdat::SelectionKind> s : obj->getComdatTable())
keptComdats.push_back(symtab->addComdat(s.first));
for (const lto::InputFile::Symbol &objSym : obj->symbols())
symbols.push_back(createBitcodeSymbol(keptComdats, objSym, *this));
}
} // namespace wasm
} // namespace lld
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