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-rw-r--r--lld/wasm/Driver.cpp46
-rw-r--r--lld/wasm/SymbolTable.cpp275
-rw-r--r--lld/wasm/SymbolTable.h9
-rw-r--r--lld/wasm/Symbols.cpp8
-rw-r--r--lld/wasm/Symbols.h2
5 files changed, 267 insertions, 73 deletions
diff --git a/lld/wasm/Driver.cpp b/lld/wasm/Driver.cpp
index 40e88f2ac2a..d3286af258b 100644
--- a/lld/wasm/Driver.cpp
+++ b/lld/wasm/Driver.cpp
@@ -534,17 +534,6 @@ void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
for (auto *Arg : Args.filtered(OPT_undefined))
handleUndefined(Arg->getValue());
- // Handle the `--export <sym>` options
- // This works like --undefined but also exports the symbol if its found
- for (auto *Arg : Args.filtered(OPT_export)) {
- Symbol *Sym = handleUndefined(Arg->getValue());
- if (Sym && Sym->isDefined())
- Sym->ForceExport = true;
- else if (!Config->AllowUndefined)
- error(Twine("symbol exported via --export not found: ") +
- Arg->getValue());
- }
-
Symbol *EntrySym = nullptr;
if (!Config->Relocatable) {
if (!Config->Shared && !Config->Entry.empty()) {
@@ -555,26 +544,47 @@ void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
error("entry symbol not defined (pass --no-entry to supress): " +
Config->Entry);
}
-
- // Make sure we have resolved all symbols.
- if (!Config->AllowUndefined)
- Symtab->reportRemainingUndefines();
}
if (errorCount())
return;
+ // Handle the `--export <sym>` options
+ // This works like --undefined but also exports the symbol if its found
+ for (auto *Arg : Args.filtered(OPT_export))
+ handleUndefined(Arg->getValue());
+
// Do link-time optimization if given files are LLVM bitcode files.
// This compiles bitcode files into real object files.
Symtab->addCombinedLTOObject();
if (errorCount())
return;
- // Add synthetic dummies for weak undefined functions. Must happen
- // after LTO otherwise functions may not yet have signatures.
- if (!Config->Relocatable)
+ // Resolve any variant symbols that were created due to signature
+ // mismatchs.
+ Symtab->handleSymbolVariants();
+ if (errorCount())
+ return;
+
+ for (auto *Arg : Args.filtered(OPT_export)) {
+ Symbol *Sym = Symtab->find(Arg->getValue());
+ if (Sym && Sym->isDefined())
+ Sym->ForceExport = true;
+ else if (!Config->AllowUndefined)
+ error(Twine("symbol exported via --export not found: ") +
+ Arg->getValue());
+ }
+
+ if (!Config->Relocatable) {
+ // Add synthetic dummies for weak undefined functions. Must happen
+ // after LTO otherwise functions may not yet have signatures.
Symtab->handleWeakUndefines();
+ // Make sure we have resolved all symbols.
+ if (!Config->AllowUndefined)
+ Symtab->reportRemainingUndefines();
+ }
+
if (EntrySym)
EntrySym->setHidden(false);
diff --git a/lld/wasm/SymbolTable.cpp b/lld/wasm/SymbolTable.cpp
index 35ac2c5a6da..b196d5017c9 100644
--- a/lld/wasm/SymbolTable.cpp
+++ b/lld/wasm/SymbolTable.cpp
@@ -26,6 +26,38 @@ using namespace lld::wasm;
SymbolTable *lld::wasm::Symtab;
+static char encodeValType(ValType Type) {
+ switch (Type) {
+ case ValType::I32:
+ return 'i';
+ case ValType::I64:
+ return 'j';
+ case ValType::F32:
+ return 'f';
+ case ValType::F64:
+ return 'd';
+ case ValType::V128:
+ return 'V';
+ case ValType::EXCEPT_REF:
+ return 'e';
+ }
+ llvm_unreachable("invalid wasm type");
+}
+
+static std::string encodeSignature(const WasmSignature &Sig) {
+ std::string S = ":";
+ for (ValType Type : Sig.Returns)
+ S += encodeValType(Type);
+ S += ':';
+ for (ValType Type : Sig.Params)
+ S += encodeValType(Type);
+ return S;
+}
+
+static StringRef getVariantName(StringRef BaseName, const WasmSignature &Sig) {
+ return Saver.save(BaseName + encodeSignature(Sig));
+}
+
void SymbolTable::addFile(InputFile *File) {
log("Processing: " + toString(File));
if (Config->Trace)
@@ -81,6 +113,11 @@ Symbol *SymbolTable::find(StringRef Name) {
return SymVector[It->second];
}
+void SymbolTable::replace(StringRef Name, Symbol* Sym) {
+ auto It = SymMap.find(CachedHashStringRef(Name));
+ SymVector[It->second] = Sym;
+}
+
std::pair<Symbol *, bool> SymbolTable::insertName(StringRef Name) {
bool Trace = false;
auto P = SymMap.insert({CachedHashStringRef(Name), (int)SymVector.size()});
@@ -123,29 +160,19 @@ static void reportTypeError(const Symbol *Existing, const InputFile *File,
}
// Check the type of new symbol matches that of the symbol is replacing.
-// For functions this can also involve verifying that the signatures match.
-static void checkFunctionType(Symbol *Existing, const InputFile *File,
- const WasmSignature *NewSig) {
- auto ExistingFunction = dyn_cast<FunctionSymbol>(Existing);
- if (!ExistingFunction) {
- reportTypeError(Existing, File, WASM_SYMBOL_TYPE_FUNCTION);
- return;
- }
-
+// Returns true if the function types match, false is there is a singature
+// mismatch.
+bool signatureMatches(FunctionSymbol *Existing, const WasmSignature *NewSig) {
if (!NewSig)
- return;
+ return true;
- const WasmSignature *OldSig = ExistingFunction->Signature;
+ const WasmSignature *OldSig = Existing->Signature;
if (!OldSig) {
- ExistingFunction->Signature = NewSig;
- return;
+ Existing->Signature = NewSig;
+ return true;
}
- if (*NewSig != *OldSig)
- warn("function signature mismatch: " + Existing->getName() +
- "\n>>> defined as " + toString(*OldSig) + " in " +
- toString(Existing->getFile()) + "\n>>> defined as " +
- toString(*NewSig) + " in " + toString(File));
+ return *NewSig == *OldSig;
}
static void checkGlobalType(const Symbol *Existing, const InputFile *File,
@@ -255,26 +282,45 @@ Symbol *SymbolTable::addDefinedFunction(StringRef Name, uint32_t Flags,
bool WasInserted;
std::tie(S, WasInserted) = insert(Name, File);
+ auto Replace = [&](Symbol* Sym) {
+ // If the new defined function doesn't have signture (i.e. bitcode
+ // functions) but the old symbol does, then preserve the old signature
+ const WasmSignature *OldSig = S->getSignature();
+ auto* NewSym = replaceSymbol<DefinedFunction>(Sym, Name, Flags, File, Function);
+ if (!NewSym->Signature)
+ NewSym->Signature = OldSig;
+ };
+
if (WasInserted || S->isLazy()) {
- replaceSymbol<DefinedFunction>(S, Name, Flags, File, Function);
+ Replace(S);
return S;
}
- if (Function)
- checkFunctionType(S, File, &Function->Signature);
+ auto ExistingFunction = dyn_cast<FunctionSymbol>(S);
+ if (!ExistingFunction) {
+ reportTypeError(S, File, WASM_SYMBOL_TYPE_FUNCTION);
+ return S;
+ }
- if (shouldReplace(S, File, Flags)) {
- // If the new defined function doesn't have signture (i.e. bitcode
- // functions) but the old symbol does then preserve the old signature
- const WasmSignature *OldSig = nullptr;
- if (auto* F = dyn_cast<FunctionSymbol>(S))
- OldSig = F->Signature;
- if (auto *L = dyn_cast<LazySymbol>(S))
- OldSig = L->Signature;
- auto NewSym = replaceSymbol<DefinedFunction>(S, Name, Flags, File, Function);
- if (!NewSym->Signature)
- NewSym->Signature = OldSig;
+ if (Function && !signatureMatches(ExistingFunction, &Function->Signature)) {
+ Symbol* Variant;
+ if (getFunctionVariant(S, &Function->Signature, File, &Variant))
+ // New variant, always replace
+ Replace(Variant);
+ else if (shouldReplace(S, File, Flags))
+ // Variant already exists, replace it after checking shouldReplace
+ Replace(Variant);
+
+ // This variant we found take the place in the symbol table as the primary
+ // variant.
+ replace(Name, Variant);
+ return Variant;
}
+
+ // Existing function with matching signature.
+ if (shouldReplace(S, File, Flags))
+ Replace(S);
+
return S;
}
@@ -287,15 +333,19 @@ Symbol *SymbolTable::addDefinedData(StringRef Name, uint32_t Flags,
bool WasInserted;
std::tie(S, WasInserted) = insert(Name, File);
- if (WasInserted || S->isLazy()) {
+ auto Replace = [&]() {
replaceSymbol<DefinedData>(S, Name, Flags, File, Segment, Address, Size);
+ };
+
+ if (WasInserted || S->isLazy()) {
+ Replace();
return S;
}
checkDataType(S, File);
if (shouldReplace(S, File, Flags))
- replaceSymbol<DefinedData>(S, Name, Flags, File, Segment, Address, Size);
+ Replace();
return S;
}
@@ -307,15 +357,19 @@ Symbol *SymbolTable::addDefinedGlobal(StringRef Name, uint32_t Flags,
bool WasInserted;
std::tie(S, WasInserted) = insert(Name, File);
- if (WasInserted || S->isLazy()) {
+ auto Replace = [&]() {
replaceSymbol<DefinedGlobal>(S, Name, Flags, File, Global);
+ };
+
+ if (WasInserted || S->isLazy()) {
+ Replace();
return S;
}
checkGlobalType(S, File, &Global->getType());
if (shouldReplace(S, File, Flags))
- replaceSymbol<DefinedGlobal>(S, Name, Flags, File, Global);
+ Replace();
return S;
}
@@ -327,15 +381,19 @@ Symbol *SymbolTable::addDefinedEvent(StringRef Name, uint32_t Flags,
bool WasInserted;
std::tie(S, WasInserted) = insert(Name, File);
- if (WasInserted || S->isLazy()) {
+ auto Replace = [&]() {
replaceSymbol<DefinedEvent>(S, Name, Flags, File, Event);
+ };
+
+ if (WasInserted || S->isLazy()) {
+ Replace();
return S;
}
checkEventType(S, File, &Event->getType(), &Event->Signature);
if (shouldReplace(S, File, Flags))
- replaceSymbol<DefinedEvent>(S, Name, Flags, File, Event);
+ Replace();
return S;
}
@@ -350,13 +408,25 @@ Symbol *SymbolTable::addUndefinedFunction(StringRef Name, StringRef ImportName,
bool WasInserted;
std::tie(S, WasInserted) = insert(Name, File);
- if (WasInserted)
+ auto Replace = [&]() {
replaceSymbol<UndefinedFunction>(S, Name, ImportName, ImportModule, Flags,
File, Sig);
+ };
+
+ if (WasInserted)
+ Replace();
else if (auto *Lazy = dyn_cast<LazySymbol>(S))
Lazy->fetch();
- else
- checkFunctionType(S, File, Sig);
+ else {
+ auto ExistingFunction = dyn_cast<FunctionSymbol>(S);
+ if (!ExistingFunction) {
+ reportTypeError(S, File, WASM_SYMBOL_TYPE_FUNCTION);
+ return S;
+ }
+ if (!signatureMatches(ExistingFunction, Sig))
+ if (getFunctionVariant(S, Sig, File, &S))
+ Replace();
+ }
return S;
}
@@ -438,6 +508,44 @@ bool SymbolTable::addComdat(StringRef Name) {
return Comdats.insert(CachedHashStringRef(Name)).second;
}
+// The new signature doesn't match. Create a variant to the symbol with the
+// signature encoded in the name and return that instead. These symbols are
+// then unified later in handleSymbolVariants.
+bool SymbolTable::getFunctionVariant(Symbol* Sym, const WasmSignature *Sig,
+ const InputFile *File, Symbol **Out) {
+ StringRef NewName = getVariantName(Sym->getName(), *Sig);
+ LLVM_DEBUG(dbgs() << "getFunctionVariant: " << Sym->getName() << " -> " << NewName
+ << " " << toString(*Sig) << "\n");
+ Symbol *Variant = nullptr;
+
+ // Linear search through symbol variants. Should never be more than two
+ // or three entries here.
+ auto &Variants = SymVariants[CachedHashStringRef(Sym->getName())];
+ if (Variants.size() == 0)
+ Variants.push_back(Sym);
+
+ for (Symbol* V : Variants) {
+ if (*V->getSignature() == *Sig) {
+ Variant = V;
+ break;
+ }
+ }
+
+ bool WasAdded = !Variant;
+ if (WasAdded) {
+ // Create a new variant;
+ LLVM_DEBUG(dbgs() << "added new variant\n");
+ Variant = reinterpret_cast<Symbol *>(make<SymbolUnion>());
+ Variants.push_back(Variant);
+ } else {
+ LLVM_DEBUG(dbgs() << "variant already exists: " << toString(*Variant) << "\n");
+ assert(*Variant->getSignature() == *Sig);
+ }
+
+ *Out = Variant;
+ return WasAdded;
+}
+
// Set a flag for --trace-symbol so that we can print out a log message
// if a new symbol with the same name is inserted into the symbol table.
void SymbolTable::trace(StringRef Name) {
@@ -451,14 +559,16 @@ static const uint8_t UnreachableFn[] = {
// Replace the given symbol body with an unreachable function.
// This is used by handleWeakUndefines in order to generate a callable
-// equivalent of an undefined function.
+// equivalent of an undefined function and also handleSymbolVariants for
+// undefined functions that don't match the signature of the definition.
InputFunction *SymbolTable::replaceWithUnreachable(Symbol *Sym,
const WasmSignature &Sig,
StringRef DebugName) {
auto *Func = make<SyntheticFunction>(Sig, Sym->getName(), DebugName);
Func->setBody(UnreachableFn);
SyntheticFunctions.emplace_back(Func);
- replaceSymbol<DefinedFunction>(Sym, Sym->getName(), Sym->getFlags(), nullptr, Func);
+ replaceSymbol<DefinedFunction>(Sym, Sym->getName(), Sym->getFlags(), nullptr,
+ Func);
return Func;
}
@@ -471,21 +581,15 @@ void SymbolTable::handleWeakUndefines() {
if (!Sym->isUndefWeak())
continue;
- const WasmSignature *Sig = nullptr;
-
- if (auto *FuncSym = dyn_cast<FunctionSymbol>(Sym)) {
+ const WasmSignature *Sig = Sym->getSignature();
+ if (!Sig) {
// It is possible for undefined functions not to have a signature (eg. if
// added via "--undefined"), but weak undefined ones do have a signature.
- assert(FuncSym->Signature);
- Sig = FuncSym->Signature;
- } else if (auto *LazySym = dyn_cast<LazySymbol>(Sym)) {
- // Lazy symbols may not be functions and therefore can have a null
- // signature.
- Sig = LazySym->Signature;
- }
-
- if (!Sig)
+ // Lazy symbols may not be functions and therefore Sig can still be null
+ // in some circumstantce.
+ assert(!isa<FunctionSymbol>(Sym));
continue;
+ }
// Add a synthetic dummy for weak undefined functions. These dummies will
// be GC'd if not used as the target of any "call" instructions.
@@ -498,3 +602,64 @@ void SymbolTable::handleWeakUndefines() {
Sym->setHidden(true);
}
}
+
+static void reportFunctionSignatureMismatch(StringRef SymName,
+ FunctionSymbol *A,
+ FunctionSymbol *B, bool Error) {
+ std::string msg = ("function signature mismatch: " + SymName +
+ "\n>>> defined as " + toString(*A->Signature) + " in " +
+ toString(A->getFile()) + "\n>>> defined as " +
+ toString(*B->Signature) + " in " + toString(B->getFile()))
+ .str();
+ if (Error)
+ error(msg);
+ else
+ warn(msg);
+}
+
+// Remove any variant symbols that were created due to function signature
+// mismatches.
+void SymbolTable::handleSymbolVariants() {
+ for (auto Pair : SymVariants) {
+ // Push the initial symbol onto the list of variants.
+ StringRef SymName = Pair.first.val();
+ std::vector<Symbol *> &Variants = Pair.second;
+
+#ifndef NDEBUG
+ dbgs() << "symbol with (" << Variants.size()
+ << ") variants: " << SymName << "\n";
+ for (auto *S: Variants) {
+ auto *F = cast<FunctionSymbol>(S);
+ dbgs() << " variant: " + F->getName() << " " << toString(*F->Signature) << "\n";
+ }
+#endif
+
+ // Find the one definition.
+ DefinedFunction *Defined = nullptr;
+ for (auto *Symbol : Variants) {
+ if (auto F = dyn_cast<DefinedFunction>(Symbol)) {
+ Defined = F;
+ break;
+ }
+ }
+
+ // If there are no definitions, and the undefined symbols disagree on
+ // the signature, there is not we can do since we don't know which one
+ // to use as the signature on the import.
+ if (!Defined) {
+ reportFunctionSignatureMismatch(SymName,
+ cast<FunctionSymbol>(Variants[0]),
+ cast<FunctionSymbol>(Variants[1]), true);
+ return;
+ }
+
+ for (auto *Symbol : Variants) {
+ if (Symbol != Defined) {
+ auto *F = cast<FunctionSymbol>(Symbol);
+ reportFunctionSignatureMismatch(SymName, F, Defined, false);
+ StringRef DebugName = Saver.save("unreachable:" + toString(*F));
+ replaceWithUnreachable(F, *F->Signature, DebugName);
+ }
+ }
+ }
+}
diff --git a/lld/wasm/SymbolTable.h b/lld/wasm/SymbolTable.h
index f03980d7066..3d0529af41d 100644
--- a/lld/wasm/SymbolTable.h
+++ b/lld/wasm/SymbolTable.h
@@ -49,6 +49,8 @@ public:
Symbol *find(StringRef Name);
+ void replace(StringRef Name, Symbol* Sym);
+
void trace(StringRef Name);
Symbol *addDefinedFunction(StringRef Name, uint32_t Flags, InputFile *File,
@@ -79,12 +81,15 @@ public:
DefinedFunction *addSyntheticFunction(StringRef Name, uint32_t Flags,
InputFunction *Function);
+ void handleSymbolVariants();
void handleWeakUndefines();
private:
std::pair<Symbol *, bool> insert(StringRef Name, const InputFile *File);
std::pair<Symbol *, bool> insertName(StringRef Name);
+ bool getFunctionVariant(Symbol* Sym, const WasmSignature *Sig,
+ const InputFile *File, Symbol **Out);
InputFunction *replaceWithUnreachable(Symbol *Sym, const WasmSignature &Sig,
StringRef DebugName);
@@ -94,6 +99,10 @@ private:
llvm::DenseMap<llvm::CachedHashStringRef, int> SymMap;
std::vector<Symbol *> SymVector;
+ // For certain symbols types, e.g. function symbols, we allow for muliple
+ // variants of the same symbol with different signatures.
+ llvm::DenseMap<llvm::CachedHashStringRef, std::vector<Symbol *>> SymVariants;
+
llvm::DenseSet<llvm::CachedHashStringRef> Comdats;
// For LTO.
diff --git a/lld/wasm/Symbols.cpp b/lld/wasm/Symbols.cpp
index 60030bef3fa..f8ea47176a3 100644
--- a/lld/wasm/Symbols.cpp
+++ b/lld/wasm/Symbols.cpp
@@ -45,6 +45,14 @@ WasmSymbolType Symbol::getWasmType() const {
llvm_unreachable("invalid symbol kind");
}
+const WasmSignature *Symbol::getSignature() const {
+ if (auto* F = dyn_cast<FunctionSymbol>(this))
+ return F->Signature;
+ if (auto *L = dyn_cast<LazySymbol>(this))
+ return L->Signature;
+ return nullptr;
+}
+
InputChunk *Symbol::getChunk() const {
if (auto *F = dyn_cast<DefinedFunction>(this))
return F->Function;
diff --git a/lld/wasm/Symbols.h b/lld/wasm/Symbols.h
index fd501ed64cd..3ed9e7abf55 100644
--- a/lld/wasm/Symbols.h
+++ b/lld/wasm/Symbols.h
@@ -105,6 +105,8 @@ public:
// True if this symbol is specified by --trace-symbol option.
unsigned Traced : 1;
+ const WasmSignature* getSignature() const;
+
protected:
Symbol(StringRef Name, Kind K, uint32_t Flags, InputFile *F)
: IsUsedInRegularObj(false), ForceExport(false), Traced(false),
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