Commit fc5d815d authored by Fangrui Song's avatar Fangrui Song
Browse files

[ELF] Merge demoteSymbols and isPreemptible computation. NFC 

Remove one iteration of symtab and slightly improve the performance.
parent 3472d4d4

lld/ELF/Writer.cpp

+11 −13
Original line number Diff line number Diff line
@@ -255,17 +255,20 @@ void elf::addReservedSymbols() { 
// DT_NEEDED. If that happens, replace ShardSymbol with Undefined to avoid

// dangling references to an unneeded DSO. Use a weak binding to avoid

// --no-allow-shlib-undefined diagnostics. Similarly, demote lazy symbols.

static void demoteSymbols() {

static void demoteSymbolsAndComputeIsPreemptible() {

  llvm::TimeTraceScope timeScope("Demote symbols");

  for (Symbol *sym : symtab.getSymbols()) {

    auto *s = dyn_cast<SharedSymbol>(sym);

    if (!(s && !cast<SharedFile>(s->file)->isNeeded) && !sym->isLazy())

      continue;

    if (sym->isLazy() || (s && !cast<SharedFile>(s->file)->isNeeded)) {

      uint8_t binding = sym->isLazy() ? sym->binding : uint8_t(STB_WEAK);

      Undefined(nullptr, sym->getName(), binding, sym->stOther, sym->type)

          .overwrite(*sym);

      sym->versionId = VER_NDX_GLOBAL;

    }



    if (config->hasDynSymTab)

      sym->isPreemptible = computeIsPreemptible(*sym);

  }

}



// Fully static executables don't support MTE globals at this point in time, as
@@ -1954,12 +1957,7 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() { 
    }

  }



  demoteSymbols();

  if (config->hasDynSymTab) {

    parallelForEach(symtab.getSymbols(), [](Symbol *sym) {

      sym->isPreemptible = computeIsPreemptible(*sym);

    });

  }

  demoteSymbolsAndComputeIsPreemptible();



  // Change values of linker-script-defined symbols from placeholders (assigned

  // by declareSymbols) to actual definitions.