[ELF] Merge exportDynamic/isExported and remove Symbol::includeInDynsym

Commit 3733ed6 introduced isExported to
cache includeInDynsym. If we don't unnecessarily set isExported for
undefined symbols, exportDynamic/includeInDynsym can be replaced with
isExported.

Author: MaskRay

lld/ELF/Driver.cpp

@@ -2554,7 +2554,8 @@ void LinkerDriver::compileBitcodeFiles(bool skipLinkedOutput) {
       for (Symbol *sym : obj->getGlobalSymbols()) {
         if (!sym->isDefined())
           continue;
-        if (ctx.hasDynsym && sym->includeInDynsym(ctx))
+        if (ctx.hasDynsym && ctx.arg.exportDynamic &&
+            sym->computeBinding(ctx) != STB_LOCAL)
           sym->isExported = true;
         if (sym->hasVersionSuffix)
           sym->parseSymbolVersion(ctx);

lld/ELF/InputFiles.cpp

@@ -1574,7 +1574,7 @@ template <class ELFT> void SharedFile::parse() {
       }
       Symbol *s = ctx.symtab->addSymbol(
           Undefined{this, name, sym.getBinding(), sym.st_other, sym.getType()});
-      s->exportDynamic = true;
+      s->isExported = true;
       if (sym.getBinding() != STB_WEAK &&
           ctx.arg.unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore)
         requiredSymbols.push_back(s);
@@ -1771,7 +1771,7 @@ static void createBitcodeSymbol(Ctx &ctx, Symbol *&sym,
                    nullptr);
     // The definition can be omitted if all bitcode definitions satisfy
     // `canBeOmittedFromSymbolTable()` and isUsedInRegularObj is false.
-    // The latter condition is tested in Symbol::includeInDynsym.
+    // The latter condition is tested in parseVersionAndComputeIsPreemptible.
     sym->ltoCanOmit = objSym.canBeOmittedFromSymbolTable() &&
                       (!sym->isDefined() || sym->ltoCanOmit);
     sym->resolve(ctx, newSym);

lld/ELF/SymbolTable.cpp

@@ -203,7 +203,7 @@ void SymbolTable::handleDynamicList() {
       syms = findByVersion(ver);
 
     for (Symbol *sym : syms)
-      sym->exportDynamic = sym->inDynamicList = true;
+      sym->isExported = sym->inDynamicList = true;
   }
 }
 
@@ -350,10 +350,8 @@ void SymbolTable::scanVersionScript() {
         assignAsterisk(pat, &v, true);
   }
 
-  // isPreemptible is false at this point. To correctly compute the binding of a
-  // Defined (which is used by includeInDynsym(ctx)), we need to know if it is
-  // VER_NDX_LOCAL or not. Compute symbol versions before handling
-  // --dynamic-list.
+  // Handle --dynamic-list. If a specified symbol is also matched by local: in a
+  // version script, the version script takes precedence.
   handleDynamicList();
 }
 

lld/ELF/Symbols.cpp

@@ -268,16 +268,6 @@ uint8_t Symbol::computeBinding(Ctx &ctx) const {
   return binding;
 }
 
-bool Symbol::includeInDynsym(Ctx &ctx) const {
-  if (computeBinding(ctx) == STB_LOCAL)
-    return false;
-  if (!isDefined() && !isCommon())
-    return true;
-
-  return exportDynamic ||
-         (ctx.arg.exportDynamic && (isUsedInRegularObj || !ltoCanOmit));
-}
-
 // Print out a log message for --trace-symbol.
 void elf::printTraceSymbol(const Symbol &sym, StringRef name) {
   std::string s;
@@ -374,9 +364,18 @@ void elf::parseVersionAndComputeIsPreemptible(Ctx &ctx) {
   for (Symbol *sym : ctx.symtab->getSymbols()) {
     if (sym->hasVersionSuffix)
       sym->parseSymbolVersion(ctx);
-    if (hasDynsym) {
-      sym->isExported = sym->includeInDynsym(ctx);
-      sym->isPreemptible = sym->isExported && computeIsPreemptible(ctx, *sym);
+    if (!hasDynsym)
+      continue;
+    if (sym->computeBinding(ctx) == STB_LOCAL) {
+      sym->isExported = false;
+      continue;
+    }
+    if (!sym->isDefined() && !sym->isCommon()) {
+      sym->isPreemptible = computeIsPreemptible(ctx, *sym);
+    } else if (ctx.arg.exportDynamic &&
+               (sym->isUsedInRegularObj || !sym->ltoCanOmit)) {
+      sym->isExported = true;
+      sym->isPreemptible = computeIsPreemptible(ctx, *sym);
     }
   }
 }
@@ -655,7 +654,7 @@ void Symbol::resolve(Ctx &ctx, const LazySymbol &other) {
 }
 
 void Symbol::resolve(Ctx &ctx, const SharedSymbol &other) {
-  exportDynamic = true;
+  isExported = true;
   if (isPlaceholder()) {
     other.overwrite(*this);
     return;

lld/ELF/Symbols.h

@@ -105,6 +105,9 @@ class Symbol {
   uint8_t partition;
 
   // True if this symbol is preemptible at load time.
+  //
+  // Primarily set in two locations, (a) parseVersionAndComputeIsPreemptible and
+  // (b) demoteSymbolsAndComputeIsPreemptible.
   LLVM_PREFERRED_TYPE(bool)
   uint8_t isPreemptible : 1;
 
@@ -131,16 +134,9 @@ class Symbol {
   // - If -shared or --export-dynamic is specified, any symbol in an object
   //   file/bitcode sets this property, unless suppressed by LTO
   //   canBeOmittedFromSymbolTable().
-  //
-  // Primarily set in two locations, (a) after parseSymbolVersion and
-  // (b) during demoteSymbols.
   LLVM_PREFERRED_TYPE(bool)
   uint8_t isExported : 1;
 
-  // Used to compute isExported. Set when defined or referenced by a SharedFile.
-  LLVM_PREFERRED_TYPE(bool)
-  uint8_t exportDynamic : 1;
-
   LLVM_PREFERRED_TYPE(bool)
   uint8_t ltoCanOmit : 1;
 
@@ -159,7 +155,6 @@ class Symbol {
     stOther = (stOther & ~3) | visibility;
   }
 
-  bool includeInDynsym(Ctx &) const;
   uint8_t computeBinding(Ctx &) const;
   bool isGlobal() const { return binding == llvm::ELF::STB_GLOBAL; }
   bool isWeak() const { return binding == llvm::ELF::STB_WEAK; }
@@ -247,8 +242,8 @@ class Symbol {
   Symbol(Kind k, InputFile *file, StringRef name, uint8_t binding,
          uint8_t stOther, uint8_t type)
       : file(file), nameData(name.data()), nameSize(name.size()), type(type),
-        binding(binding), stOther(stOther), symbolKind(k), exportDynamic(false),
-        ltoCanOmit(false), archSpecificBit(false) {}
+        binding(binding), stOther(stOther), symbolKind(k), ltoCanOmit(false),
+        archSpecificBit(false) {}
 
   void overwrite(Symbol &sym, Kind k) const {
     if (sym.traced)

lld/ELF/SyntheticSections.cpp

@@ -4776,8 +4776,8 @@ template <class ELFT> void elf::createSyntheticSections(Ctx &ctx) {
       add(*part.buildId);
     }
 
-    // dynSymTab is always present to simplify sym->includeInDynsym(ctx) in
-    // finalizeSections.
+    // dynSymTab is always present to simplify several finalizeSections
+    // functions.
     part.dynStrTab = std::make_unique<StringTableSection>(ctx, ".dynstr", true);
     part.dynSymTab =
         std::make_unique<SymbolTableSection<ELFT>>(ctx, *part.dynStrTab);

lld/ELF/Writer.cpp

@@ -296,13 +296,12 @@ static void demoteSymbolsAndComputeIsPreemptible(Ctx &ctx) {
                   sym->type)
             .overwrite(*sym);
         sym->versionId = VER_NDX_GLOBAL;
-        if (hasDynsym && sym->includeInDynsym(ctx))
-          sym->isExported = true;
       }
     }
 
     if (hasDynsym)
-      sym->isPreemptible = sym->isExported && computeIsPreemptible(ctx, *sym);
+      sym->isPreemptible = (sym->isUndefined() || sym->isExported) &&
+                           computeIsPreemptible(ctx, *sym);
   }
 }
 
@@ -1841,9 +1840,10 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
 
   // If the previous code block defines any non-hidden symbols (e.g.
   // __global_pointer$), they may be exported.
-  if (ctx.hasDynsym)
+  if (ctx.hasDynsym && ctx.arg.exportDynamic)
     for (Symbol *sym : ctx.synthesizedSymbols)
-      sym->isExported = sym->includeInDynsym(ctx);
+      if (sym->computeBinding(ctx) != STB_LOCAL)
+        sym->isExported = true;
 
   demoteSymbolsAndComputeIsPreemptible(ctx);
 
@@ -1931,7 +1931,8 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
 
       // computeBinding might localize a linker-synthesized hidden symbol
       // (e.g. __global_pointer$) that was considered exported.
-      if (sym->isExported && !sym->isLocal()) {
+      if (ctx.hasDynsym && (sym->isUndefined() || sym->isExported) &&
+          !sym->isLocal()) {
         ctx.partitions[sym->partition - 1].dynSymTab->addSymbol(sym);
         if (auto *file = dyn_cast<SharedFile>(sym->file))
           if (file->isNeeded && !sym->isUndefined())