[WebAssembly] Initial wasm linker implementation
This linker backend is still a work in progress but is
enough to link simple programs including linking against
library archives.
Differential Revision: https://reviews.llvm.org/D34851
llvm-svn: 318539
diff --git a/lld/wasm/SymbolTable.cpp b/lld/wasm/SymbolTable.cpp
new file mode 100644
index 0000000..492a809
--- /dev/null
+++ b/lld/wasm/SymbolTable.cpp
@@ -0,0 +1,191 @@
+//===- SymbolTable.cpp ----------------------------------------------------===//
+//
+// The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "SymbolTable.h"
+
+#include "Config.h"
+#include "Memory.h"
+#include "Strings.h"
+#include "lld/Common/ErrorHandler.h"
+
+#include <unordered_set>
+
+#define DEBUG_TYPE "lld"
+
+using namespace llvm;
+using namespace lld;
+using namespace lld::wasm;
+
+SymbolTable *lld::wasm::Symtab;
+
+void SymbolTable::addFile(InputFile *File) {
+ log("Processing: " + toString(File));
+ File->parse();
+
+ if (auto *F = dyn_cast<ObjFile>(File))
+ ObjectFiles.push_back(F);
+}
+
+void SymbolTable::reportRemainingUndefines() {
+ std::unordered_set<Symbol *> Undefs;
+ for (auto &I : Symtab) {
+ Symbol *Sym = I.second;
+ if (Sym->isUndefined() && !Sym->isWeak() &&
+ Config->AllowUndefinedSymbols.count(Sym->getName()) == 0) {
+ Undefs.insert(Sym);
+ }
+ }
+
+ if (Undefs.empty())
+ return;
+
+ for (ObjFile *File : ObjectFiles)
+ for (Symbol *Sym : File->getSymbols())
+ if (Undefs.count(Sym))
+ error(toString(File) + ": undefined symbol: " + toString(*Sym));
+
+ for (Symbol *Sym : Undefs)
+ if (!Sym->getFile())
+ error("undefined symbol: " + toString(*Sym));
+}
+
+Symbol *SymbolTable::find(StringRef Name) {
+ auto It = Symtab.find(CachedHashStringRef(Name));
+ if (It == Symtab.end())
+ return nullptr;
+ return It->second;
+}
+
+std::pair<Symbol *, bool> SymbolTable::insert(StringRef Name) {
+ Symbol *&Sym = Symtab[CachedHashStringRef(Name)];
+ if (Sym)
+ return {Sym, false};
+ Sym = make<Symbol>(Name, false);
+ return {Sym, true};
+}
+
+void SymbolTable::reportDuplicate(Symbol *Existing, InputFile *NewFile) {
+ error("duplicate symbol: " + toString(*Existing) + "\n>>> defined in " +
+ toString(Existing->getFile()) + "\n>>> defined in " +
+ (NewFile ? toString(NewFile) : "<internal>"));
+}
+
+static void checkSymbolTypes(Symbol *Existing, InputFile *F,
+ const WasmSymbol *New) {
+ if (Existing->isLazy())
+ return;
+
+ bool NewIsFunction = New->Type == WasmSymbol::SymbolType::FUNCTION_EXPORT ||
+ New->Type == WasmSymbol::SymbolType::FUNCTION_IMPORT;
+ if (Existing->isFunction() == NewIsFunction)
+ return;
+
+ std::string Filename = "<builtin>";
+ if (Existing->getFile())
+ Filename = toString(Existing->getFile());
+ error("symbol type mismatch: " + New->Name + "\n>>> defined as " +
+ (Existing->isFunction() ? "Function" : "Global") + " in " + Filename +
+ "\n>>> defined as " + (NewIsFunction ? "Function" : "Global") + " in " +
+ F->getName());
+}
+
+Symbol *SymbolTable::addDefinedGlobal(StringRef Name) {
+ DEBUG(dbgs() << "addDefinedGlobal: " << Name << "\n");
+ Symbol *S;
+ bool WasInserted;
+ std::tie(S, WasInserted) = insert(Name);
+ if (WasInserted)
+ S->update(Symbol::DefinedGlobalKind);
+ else if (!S->isGlobal())
+ error("symbol type mismatch: " + Name);
+ return S;
+}
+
+Symbol *SymbolTable::addDefined(InputFile *F, const WasmSymbol *Sym,
+ const InputSegment *Segment) {
+ DEBUG(dbgs() << "addDefined: " << Sym->Name << "\n");
+ Symbol *S;
+ bool WasInserted;
+ Symbol::Kind Kind = Symbol::DefinedFunctionKind;
+ if (Sym->Type == WasmSymbol::SymbolType::GLOBAL_EXPORT)
+ Kind = Symbol::DefinedGlobalKind;
+
+ std::tie(S, WasInserted) = insert(Sym->Name);
+ if (WasInserted) {
+ S->update(Kind, F, Sym, Segment);
+ } else if (!S->isDefined()) {
+ // The existing symbol table entry is undefined. The new symbol replaces
+ // it
+ DEBUG(dbgs() << "resolving existing undefined symbol: " << Sym->Name
+ << "\n");
+ checkSymbolTypes(S, F, Sym);
+ S->update(Kind, F, Sym, Segment);
+ } else if (Sym->isWeak()) {
+ // the new symbol is weak we can ignore it
+ DEBUG(dbgs() << "existing symbol takes precensence\n");
+ } else if (S->isWeak()) {
+ // the new symbol is not weak and the existing symbol is, so we replace
+ // it
+ DEBUG(dbgs() << "replacing existing weak symbol\n");
+ S->update(Kind, F, Sym, Segment);
+ } else {
+ // niether symbol is week. They conflict.
+ reportDuplicate(S, F);
+ }
+ return S;
+}
+
+Symbol *SymbolTable::addUndefinedFunction(StringRef Name) {
+ Symbol *S;
+ bool WasInserted;
+ std::tie(S, WasInserted) = insert(Name);
+ if (WasInserted)
+ S->update(Symbol::UndefinedFunctionKind);
+ else if (!S->isFunction())
+ error("symbol type mismatch: " + Name);
+ return S;
+}
+
+Symbol *SymbolTable::addUndefined(InputFile *F, const WasmSymbol *Sym) {
+ DEBUG(dbgs() << "addUndefined: " << displayName(Sym->Name) << "\n");
+ Symbol *S;
+ bool WasInserted;
+ Symbol::Kind Kind = Symbol::UndefinedFunctionKind;
+ if (Sym->Type == WasmSymbol::SymbolType::GLOBAL_IMPORT)
+ Kind = Symbol::UndefinedGlobalKind;
+ std::tie(S, WasInserted) = insert(Sym->Name);
+ if (WasInserted) {
+ S->update(Kind, F, Sym);
+ } else if (S->isLazy()) {
+ DEBUG(dbgs() << "resolved by existing lazy\n");
+ auto *AF = cast<ArchiveFile>(S->getFile());
+ AF->addMember(&S->getArchiveSymbol());
+ } else if (S->isDefined()) {
+ DEBUG(dbgs() << "resolved by existing\n");
+ checkSymbolTypes(S, F, Sym);
+ }
+ return S;
+}
+
+void SymbolTable::addLazy(ArchiveFile *F, const Archive::Symbol *Sym) {
+ DEBUG(dbgs() << "addLazy: " << displayName(Sym->getName()) << "\n");
+ StringRef Name = Sym->getName();
+ Symbol *S;
+ bool WasInserted;
+ std::tie(S, WasInserted) = insert(Name);
+ if (WasInserted) {
+ S->update(Symbol::LazyKind, F);
+ S->setArchiveSymbol(*Sym);
+ } else if (S->isUndefined()) {
+ // There is an existing undefined symbol. The can load from the
+ // archive.
+ DEBUG(dbgs() << "replacing existing undefined\n");
+ F->addMember(Sym);
+ }
+}