[lld-link] diagnose undefined symbols before LTO when possible
Summary: This allows reporting undefined symbols before LTO codegen is run. Since LTO codegen can take a long time, this improves user experience by avoiding that time spend if the link is going to fail with undefined symbols anyway. Fixes PR32400. Reviewers: ruiu Reviewed By: ruiu Subscribers: mehdi_amini, steven_wu, dexonsmith, mstorsjo, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D62434 llvm-svn: 367136
This commit is contained in:
Bob Haarman
parent
2e040398f8
commit
51dcb292cc
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@ -1752,24 +1752,6 @@ void LinkerDriver::link(ArrayRef<const char *> argsArr) {
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addUndefined(mangle("_load_config_used"));
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} while (run());
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if (errorCount())
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return;
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// Do LTO by compiling bitcode input files to a set of native COFF files then
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// link those files (unless -thinlto-index-only was given, in which case we
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// resolve symbols and write indices, but don't generate native code or link).
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symtab->addCombinedLTOObjects();
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// If -thinlto-index-only is given, we should create only "index
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// files" and not object files. Index file creation is already done
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// in addCombinedLTOObject, so we are done if that's the case.
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if (config->thinLTOIndexOnly)
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return;
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// If we generated native object files from bitcode files, this resolves
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// references to the symbols we use from them.
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run();
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if (args.hasArg(OPT_include_optional)) {
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// Handle /includeoptional
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for (auto *arg : args.filtered(OPT_include_optional))
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@ -1796,8 +1778,32 @@ void LinkerDriver::link(ArrayRef<const char *> argsArr) {
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run();
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}
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// Make sure we have resolved all symbols.
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symtab->reportRemainingUndefines();
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// At this point, we should not have any symbols that cannot be resolved.
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// If we are going to do codegen for link-time optimization, check for
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// unresolvable symbols first, so we don't spend time generating code that
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// will fail to link anyway.
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if (!BitcodeFile::instances.empty() && !config->forceUnresolved)
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symtab->reportUnresolvable();
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if (errorCount())
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return;
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// Do LTO by compiling bitcode input files to a set of native COFF files then
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// link those files (unless -thinlto-index-only was given, in which case we
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// resolve symbols and write indices, but don't generate native code or link).
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symtab->addCombinedLTOObjects();
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// If -thinlto-index-only is given, we should create only "index
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// files" and not object files. Index file creation is already done
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// in addCombinedLTOObject, so we are done if that's the case.
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if (config->thinLTOIndexOnly)
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return;
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// If we generated native object files from bitcode files, this resolves
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// references to the symbols we use from them.
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run();
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// Resolve remaining undefined symbols and warn about imported locals.
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symtab->resolveRemainingUndefines();
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if (errorCount())
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return;
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@ -69,7 +69,8 @@ static Symbol *getSymbol(SectionChunk *sc, uint32_t addr) {
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for (Symbol *s : sc->file->getSymbols()) {
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auto *d = dyn_cast_or_null<DefinedRegular>(s);
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if (!d || !d->data || d->getChunk() != sc || d->getValue() > addr ||
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if (!d || !d->data || d->file != sc->file || d->getChunk() != sc ||
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d->getValue() > addr ||
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(candidate && d->getValue() < candidate->getValue()))
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continue;
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@ -79,6 +80,15 @@ static Symbol *getSymbol(SectionChunk *sc, uint32_t addr) {
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return candidate;
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}
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static std::vector<std::string> getSymbolLocations(BitcodeFile *file) {
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std::string res("\n>>> referenced by ");
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StringRef source = file->obj->getSourceFileName();
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if (!source.empty())
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res += source.str() + "\n>>> ";
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res += toString(file);
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return {res};
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}
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// Given a file and the index of a symbol in that file, returns a description
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// of all references to that symbol from that file. If no debug information is
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// available, returns just the name of the file, else one string per actual
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@ -123,13 +133,23 @@ std::vector<std::string> getSymbolLocations(ObjFile *file, uint32_t symIndex) {
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return symbolLocations;
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}
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std::vector<std::string> getSymbolLocations(InputFile *file,
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uint32_t symIndex) {
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if (auto *o = dyn_cast<ObjFile>(file))
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return getSymbolLocations(o, symIndex);
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if (auto *b = dyn_cast<BitcodeFile>(file))
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return getSymbolLocations(b);
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llvm_unreachable("unsupported file type passed to getSymbolLocations");
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return {};
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}
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// For an undefined symbol, stores all files referencing it and the index of
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// the undefined symbol in each file.
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struct UndefinedDiag {
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Symbol *sym;
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struct File {
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ObjFile *oFile;
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uint64_t symIndex;
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InputFile *file;
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uint32_t symIndex;
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};
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std::vector<File> files;
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};
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@ -143,7 +163,7 @@ static void reportUndefinedSymbol(const UndefinedDiag &undefDiag) {
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size_t i = 0, numRefs = 0;
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for (const UndefinedDiag::File &ref : undefDiag.files) {
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std::vector<std::string> symbolLocations =
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getSymbolLocations(ref.oFile, ref.symIndex);
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getSymbolLocations(ref.file, ref.symIndex);
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numRefs += symbolLocations.size();
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for (const std::string &s : symbolLocations) {
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if (i >= maxUndefReferences)
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@ -183,10 +203,14 @@ void SymbolTable::loadMinGWAutomaticImports() {
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}
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}
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bool SymbolTable::handleMinGWAutomaticImport(Symbol *sym, StringRef name) {
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Defined *SymbolTable::impSymbol(StringRef name) {
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if (name.startswith("__imp_"))
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return false;
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Defined *imp = dyn_cast_or_null<Defined>(find(("__imp_" + name).str()));
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return nullptr;
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return dyn_cast_or_null<Defined>(find(("__imp_" + name).str()));
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}
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bool SymbolTable::handleMinGWAutomaticImport(Symbol *sym, StringRef name) {
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Defined *imp = impSymbol(name);
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if (!imp)
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return false;
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@ -232,7 +256,97 @@ bool SymbolTable::handleMinGWAutomaticImport(Symbol *sym, StringRef name) {
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return true;
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}
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void SymbolTable::reportRemainingUndefines() {
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/// Helper function for reportUnresolvable and resolveRemainingUndefines.
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/// This function emits an "undefined symbol" diagnostic for each symbol in
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/// undefs. If localImports is not nullptr, it also emits a "locally
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/// defined symbol imported" diagnostic for symbols in localImports.
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/// objFiles and bitcodeFiles (if not nullptr) are used to report where
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/// undefined symbols are referenced.
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static void
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reportProblemSymbols(const SmallPtrSetImpl<Symbol *> &undefs,
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const DenseMap<Symbol *, Symbol *> *localImports,
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const std::vector<ObjFile *> objFiles,
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const std::vector<BitcodeFile *> *bitcodeFiles) {
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// Return early if there is nothing to report (which should be
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// the common case).
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if (undefs.empty() && (!localImports || localImports->empty()))
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return;
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for (Symbol *b : config->gcroot) {
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if (undefs.count(b))
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errorOrWarn("<root>: undefined symbol: " + toString(*b));
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if (localImports)
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if (Symbol *imp = localImports->lookup(b))
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warn("<root>: locally defined symbol imported: " + toString(*imp) +
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" (defined in " + toString(imp->getFile()) + ") [LNK4217]");
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}
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std::vector<UndefinedDiag> undefDiags;
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DenseMap<Symbol *, int> firstDiag;
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auto processFile = [&](InputFile *file, ArrayRef<Symbol *> symbols) {
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uint32_t symIndex = (uint32_t)-1;
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for (Symbol *sym : symbols) {
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++symIndex;
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if (!sym)
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continue;
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if (undefs.count(sym)) {
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auto it = firstDiag.find(sym);
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if (it == firstDiag.end()) {
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firstDiag[sym] = undefDiags.size();
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undefDiags.push_back({sym, {{file, symIndex}}});
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} else {
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undefDiags[it->second].files.push_back({file, symIndex});
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}
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}
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if (localImports)
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if (Symbol *imp = localImports->lookup(sym))
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warn(toString(file) +
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": locally defined symbol imported: " + toString(*imp) +
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" (defined in " + toString(imp->getFile()) + ") [LNK4217]");
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}
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};
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for (ObjFile *file : objFiles)
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processFile(file, file->getSymbols());
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if (bitcodeFiles)
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for (BitcodeFile *file : *bitcodeFiles)
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processFile(file, file->getSymbols());
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for (const UndefinedDiag &undefDiag : undefDiags)
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reportUndefinedSymbol(undefDiag);
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}
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void SymbolTable::reportUnresolvable() {
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SmallPtrSet<Symbol *, 8> undefs;
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for (auto &i : symMap) {
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Symbol *sym = i.second;
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auto *undef = dyn_cast<Undefined>(sym);
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if (!undef)
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continue;
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if (Defined *d = undef->getWeakAlias())
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continue;
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StringRef name = undef->getName();
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if (name.startswith("__imp_")) {
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Symbol *imp = find(name.substr(strlen("__imp_")));
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if (imp && isa<Defined>(imp))
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continue;
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}
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if (name.contains("_PchSym_"))
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continue;
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if (config->mingw && impSymbol(name))
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continue;
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undefs.insert(sym);
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}
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reportProblemSymbols(undefs,
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/* localImports */ nullptr, ObjFile::instances,
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&BitcodeFile::instances);
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}
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void SymbolTable::resolveRemainingUndefines() {
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SmallPtrSet<Symbol *, 8> undefs;
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DenseMap<Symbol *, Symbol *> localImports;
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@ -290,46 +404,9 @@ void SymbolTable::reportRemainingUndefines() {
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undefs.insert(sym);
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}
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if (undefs.empty() && localImports.empty())
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return;
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for (Symbol *b : config->gcroot) {
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if (undefs.count(b))
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errorOrWarn("<root>: undefined symbol: " + toString(*b));
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if (config->warnLocallyDefinedImported)
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if (Symbol *imp = localImports.lookup(b))
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warn("<root>: locally defined symbol imported: " + toString(*imp) +
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" (defined in " + toString(imp->getFile()) + ") [LNK4217]");
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}
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std::vector<UndefinedDiag> undefDiags;
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DenseMap<Symbol *, int> firstDiag;
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for (ObjFile *file : ObjFile::instances) {
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size_t symIndex = (size_t)-1;
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for (Symbol *sym : file->getSymbols()) {
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++symIndex;
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if (!sym)
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continue;
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if (undefs.count(sym)) {
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auto it = firstDiag.find(sym);
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if (it == firstDiag.end()) {
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firstDiag[sym] = undefDiags.size();
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undefDiags.push_back({sym, {{file, symIndex}}});
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} else {
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undefDiags[it->second].files.push_back({file, symIndex});
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}
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}
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if (config->warnLocallyDefinedImported)
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if (Symbol *imp = localImports.lookup(sym))
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warn(toString(file) +
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": locally defined symbol imported: " + toString(*imp) +
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" (defined in " + toString(imp->getFile()) + ") [LNK4217]");
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}
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}
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for (const UndefinedDiag& undefDiag : undefDiags)
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reportUndefinedSymbol(undefDiag);
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reportProblemSymbols(
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undefs, config->warnLocallyDefinedImported ? &localImports : nullptr,
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ObjFile::instances, /* bitcode files no longer needed */ nullptr);
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}
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std::pair<Symbol *, bool> SymbolTable::insert(StringRef name) {
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@ -49,10 +49,13 @@ class SymbolTable {
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public:
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void addFile(InputFile *file);
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// Emit errors for symbols that cannot be resolved.
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void reportUnresolvable();
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// Try to resolve any undefined symbols and update the symbol table
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// accordingly, then print an error message for any remaining undefined
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// symbols.
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void reportRemainingUndefines();
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// symbols and warn about imported local symbols.
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void resolveRemainingUndefines();
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void loadMinGWAutomaticImports();
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bool handleMinGWAutomaticImport(Symbol *sym, StringRef name);
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@ -110,6 +113,9 @@ public:
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}
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private:
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/// Given a name without "__imp_" prefix, returns a defined symbol
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/// with the "__imp_" prefix, if it exists.
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Defined *impSymbol(StringRef name);
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/// Inserts symbol if not already present.
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std::pair<Symbol *, bool> insert(StringRef name);
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/// Same as insert(Name), but also sets isUsedInRegularObj.
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@ -0,0 +1,30 @@
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; REQUIRES: x86
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; RUN: rm -fr %t
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; RUN: mkdir %t
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; RUN: opt -thinlto-bc -o %t/main.obj %s
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; RUN: opt -thinlto-bc -o %t/foo.obj %S/Inputs/lto-dep.ll
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; RUN: not lld-link -lldsavetemps -out:%t/main.exe -entry:main \
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; RUN: -subsystem:console %t/main.obj %t/foo.obj 2>&1 | FileCheck %s
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; RUN: ls %t | sort | FileCheck --check-prefix=FILE %s
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; RUN: ls %t | count 2
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; Check that the undefined symbol is reported, and that only the two
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; object files we created are present in the directory (indicating that
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; LTO did not run).
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; CHECK: undefined symbol: bar
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; CHECK: referenced by {{.*}}unresolved-lto-bitcode.ll
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; CHECK: >>> {{.*}}unresolved-lto-bitcode.ll.tmp/main.obj
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; FILE: foo.obj
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; FILE: main.obj
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target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-pc-windows-msvc"
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define i32 @main() {
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call void @foo()
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call void @bar()
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ret i32 0
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}
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declare void @bar()
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declare void @foo()
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@ -0,0 +1,29 @@
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; REQUIRES: x86
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; RUN: rm -fr %t
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; RUN: mkdir %t
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; RUN: llc -filetype=obj -o %t/main.obj %s
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; RUN: opt -thinlto-bc -o %t/foo.obj %S/Inputs/lto-dep.ll
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; RUN: not lld-link -lldsavetemps -out:%t/main.exe -entry:main \
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; RUN: -subsystem:console %t/main.obj %t/foo.obj 2>&1 | FileCheck %s
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; RUN: ls %t | sort | FileCheck --check-prefix=FILE %s
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; RUN: ls %t | count 2
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; Check that the undefined symbol is reported, and that only the two
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; object files we created are present in the directory (indicating that
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; LTO did not run).
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; CHECK: undefined symbol: bar
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; CHECK: referenced by {{.*}}main.obj
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; FILE: foo.obj
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; FILE: main.obj
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target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-pc-windows-msvc"
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define i32 @main() {
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call void @foo()
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call void @bar()
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ret i32 0
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}
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declare void @bar()
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declare void @foo()
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